Title of Invention

POLYETHYLENE TEREPHTHLATE, MOLDED OBJECT THEREOF, AND PROCESSES FOR PRODUCING THESE

Abstract A polyethylene terephthalate resin obtained by melt polymerization under a reduced pressure range 0.1 Pa-50,000 Pa or under an inert gas atmosphere and having the properties comprising: (A) an intrinsic viscosity [n] of 0.4 to 2.5 d1/g; (B) a content of carboxyl end groups of 30 meq/kg or less; (C) a content of acetaldehyde of 10 ppm or less; (D) a hue represented by the L value of 99 or greater and the b value of 0.4 or less, (E) said hue being measured by transmission of hexafluoroisopropanol solution; (F) Mw/Mn of 1.8 to 2.3; and a content of cyclic trimer of 5 wt% or less.
Full Text DESCRIPTION
POLYESTER RESIN, MOLDED OBJECT THEREOF, AND
PROCESSES FOR PRODUCING THESE
TECHNICAL FIELD
The present invention relates to a polyester
resin (particularly polyethylene terephthalate resin)
having a polymerization degree ranging from a low
polymerization degree ?-o a high polymerization degree,
having a reduced amount of carboxyl group on the
polymer terminal and a reduced content of impurities
such as acetaldehyde, generating a reduced amount of
aldehyde during processing, having a favorable hue,
having a narrow molecular weight distribution and
having high quality and excellent moldability, a
polyester resin pellets having a reduced amount of fine
powder, having a good handling characteristic and
giving a molded article having good quality, and a
preform and a hollow body formed by molding the high-
quality polyester resin described above.
BACKGROUND ART
Polyester resins represented by polyethylene
terephthalate resins (hereinafter abbreviated as "PET
resin" in some cases) has characteristics such as
excellent heat resistance, weather resistance,
mechanical properties, and transparency. Making use of

such characteristics, polyester resins have widely been
used not only for fiber or magnetic tapes, but also for
preforms used to produce beverage containers, injection
molded articles used for various purposes, or extrusion
molded articles such as wrapping films or sheets. In
particular, a hollow body produced by blow molding of a
preform has excellent characteristics in terms of light
weight, impact resistance, transparency, and the like.
Accordingly, such hollow bodies have increasingly been
used for containers for various types of beverages such
as carbonated drinks, juice, tea, or mineral water, or
containers for liquid condiments of foods such as soy
sauce, sauce, salad oil, cosmetics, or liquid
detergent. It is expected that the market will further
expand in the future. It is required that such
containers not affect the taste of the contents
thereof, as well as having excellent strength, impact
resistance, and transparency. Thus, it is required
that polyester resins used for the aforementioned
purposes be of high quality such that it has a high
polymerization degree, is not colored, and contains a
very small amount of impurities such as acetaldehyde.
In addition, it is strongly desired that such polyester
resins be able to be produced in an industrially stable
'manner and with good productivity at a low cost.
As a method of producing polyester resins
used for the aforementioned purposes, a lower alcohol
diester of PTA such as terephtalic acid (hereinafter

abbreviated as "PTA") or dimethyl terephthalate
(hereinafter abbreviated as "DMT") and alkylene glycol
such as ethylene glycol (hereinafter abbreviated as
"EG") are subjected to a transesterification or direct
esterification in the absence or presence of a catalyst
such as a metal carboxylate, so as to produce an
intermediate such as bis-p-hydroxyethyl terephthalate
(hereinafter abbreviated as "BHET") or its oligomer in
advance. Thereafter, the above intermediate or
oligomer, which is in a molten state, is heated under
reduced pressure in the presence of a polycondensation
reaction catalyst. While alkylene glycol generated as
a by-product is discharged from the reaction system,
melt polymerization is then carried out until the
desired polymerization degree is achieved, so as to
produce polyester resins.
Alternatively, a polymer pellet with a medium
polymerization degree is produced by the above
described melt polymerization, and it is then heated in
a solid state, under reduced pressure, or in an inert
gas current. Thereafter, solid phase polymerization is
carried out by discharging alkylene glycol generated as
a by-product from the reaction system for high
polymerization, so as to produce polyester resins (see
e.g. Patent Document 1).
In order to obtain a molded article by solid
phase polymerization, however, a polymer pellet with a
medium polymerization degree, which is solidified by

cooling after melt polymerization, is heated again to a
high temperature, and then dried, and crystallized.
Thereafter, it is subjected to solid phase polymerize-
tion for a long period of time, so as to obtain a
pellet with a high polymerization degree. Thereafter,
the obtained pellet is cooled again, transported, and
conserved. It is then heated and dried again to supply
to a melt molding machine, so that a final molded
article, or a preform used to produce a container, is
molded. Thus, complex processes are required for
production of polyester resins.
Although such complex processes have been
required, solid phase polymerization has conventionally
been carried out. That is because a low polymerization
temperature results in the low likelihood of a
pyrolysis reaction, and coloration or decomposition
products are thereby hardly generated. Moreover, since
volatile impurities are volatilized and eliminated from
a polymer during polymerization, a high-quality polymer
can be produced. However, this technique is
problematic in that it requires special and complex
equipment or methods as well as a long period of time.
Moreover, the technique is also problematic in that it
requires an enormous amount of energy for repeating
heating and cooling so many times. Furthermore, such
solid phase polymerization is also problematic in that
a large amount of powder polymer that is hardly melted
is generated during the polymerization, and in that the

thus generated polymer plays a role in foreign matter,
which might inhibit molding or might deteriorate the
quality of a molded article, such as in terms of
surface properties, resistance, or transparency. Still
further, the core portion and the surface portion of
the pellets have different molecular weights, and
therefore the molecular weight distribution is wide.
Therefore, a change in the molecular weight before and
after processing is so significant that it is difficult
to stabilize product quality. The surface portion of
the pellets has a high polymerization degree and an
extremely high crystallinity. Therefore, a large
amount of shear heat is generated during molding
processing, and a decrease in polymerization degree due
to cutting of molecular branches, the amount of
acetaldehyde produced as a byproduct and the degree of
coloring due to thermal degradation are significant.
To date, an attempt to obtain polyester
resins with a high polymerization degree only by melt
polymerization without performing solid phase
polymerization has also been carried out. Since an
equilibrium constant is very small in the
polycondensation reaction of polyester resins, a
polymerization degree can be increased only after
eliminating alkylene glycol generated as a by-product
from the reaction system. However, since high
polymerization brings on a high viscosity, it becomes
more difficult to eliminate alkylene glycol. Thus,

there has been a technique of using a horizontal
agitator, which enables surface renewal of a large and
sufficient surface area of a reaction solution in a
final polycondensation reaction vessel that causes a
high polymerization degree (see e.g. Patent Documents 2
and 3). Using such a technique, polyester resins with
a high polymerization degree can be obtained, but a
technique of using a polymerization apparatus having a
rotary drive portion in the main body thereof, such as
a horizontal agitator, has the following disadvantages.
When polymerization is carried out in a high
vacuum, since the rotary drive portion cannot be
completely sealed, inflow of a trace amount of air
cannot be prevented, and polymer coloration thereby
becomes inevitable. Even when a sealing solution is
used to prevent such inflow of air, mixing of the
sealing solution is inevitable, and thus, the quality
of a polymer is inevitably deteriorated. Moreover,
even when high sealing properties are kept at the
beginning of the operations, the sealing properties
might be decreased during long-term operations. Thus,
there is also a serious problem regarding maintenance.
Furthermore, it is also difficult to reduce
the content of impurities such as acetaldehyde, which
is emphasized especially in the field of beverage
containers. That is because acetaldehyde is likely to
be generated as a by-product due to inflow of the air,
and also because since an industrial-scale apparatus,

including a horizontal agitator, causes a great depth
of liquid, impurities such as acetaldehyde remain in a
polymer.
With regard to acetaldehyde, a technique of
compulsively removing acetaldehyde from PET obtained by
melt polymerization by a melt deaeration treatment or
the like, and directly molding a preform in a molten
state, has been recently proposed.
For example, a thermoplastic polyester
obtained by melt polymerization is subjected to a
deaeration treatment without substantial increase in an
intrinsic viscosity, so as to decrease the concentra-
tion of acetaldehyde, and thereafter, a preform is
molded (see Patent Document 4). In this technique,
however, since an extruder with a vent is used in
deaeration, a polyester with a high polymerization
degree has an excessively high viscosity, and
acetaldehyde cannot be sufficiently reduced. In
addition, a polymer locally has a high temperature due
to heating by shearing or a heater, strong coloration
occurs due to inflow of the air from an axial sealing
portion, as stated above, or a large amount of
decomposition products are generated. A technique of
adding a phosphate-containing compound to prevent
coloration has also been proposed, but it cannot
sufficiently enhance quality.
Moreover, there has been another technique
whereby inert gas is injected into a polyester molten

body with an intrinsic viscosity between 0.5 and 0.75
dl/g, and melt polymerization is then carried out in a
polymerization reactor at a temperature between 260°C
and 285°C under reduced pressure, so as to form a
polyester molten body containing low acetaldehyde with
an intrinsic viscosity between 0.75 and 0.95 dl/g,
followed by injection molding of the obtained polyester
molten body (see Patent Document 5). However,
according to the studies of the present inventors,
since a horizontal biaxial agitator-type reactor is
used as a polymerization reactor in this technique, a
long period of time is required for high polymerize-
tion. Further, inflow of the air from the axial
sealing portion causes significant coloration. In
addition, since an industrial-scale reactor causes a
great depth of liquid, high polymerization is further
difficult, and it also becomes impossible to reduce
acetaldehyde. It is also extremely difficult to
uniformly inject into a polyester molten body inert gas
in an amount sufficient for deaeration in a horizontal
reactor on an industrial scale.
Furthermore, there has been another technique
whereby a polyester polymerized in a reactor is
supplied to a mixer without solidifying it at midpoint,
acetaldehyde-eliminating agents such as nitrogen or
carbon monoxide are then injected into the mixer,
acetaldehyde is then eliminated in a flash tank, and
the residue is then transported to a molding machine,

so as to obtain a molded article (see Patent Document
6). In this technique, a polyester into which a
stripping agent is mixed is converted into a large
number of strands, filaments, or ribbons through a die,
and the thus obtained products are extruded into a
flash tank in a reduced-pressure atmosphere. The thus
extruded product is allowed to fall onto the bottom of
the flash tank, and then it is allowed to intensively
foam, so as to eliminate acetaldehyde. Regarding this
technique, the form of the polymerization reactor is
not described in detail. However, if a common
horizontal double axis agitator-type reactor was used
in this technique, a long period of time would be
required for high polymerization, and further, inflow
of the air from an axial sealing portion would cause
significant coloration. Further, since this technique
requires special auxiliary equipment such as a mixer or
flash tank as well as a reactor, the processes become
complicated. Furthermore, since such a mixer or flash
tank has a space where a polymer can remain for a long
time, pyrolysis locally progresses, and a depleted
polymer that is significantly colored is mixed into a
product.
Still further, there has been another
technique of transporting a resin in a molten state
from a polymerization machine to a molding machine and
then molding it (see Patent Document 7). However, a
horizontal agitating polymerization machine is used in

this method. Therefore, long-term polymerization is
required to achieve a high polymerization degree, and
inflow of the air from an axial sealing portion causes
significant coloration. A devolatilizer for
eliminating acetaldehyde, etc. is essential in this
method, but a polymer is required to remain in such a
devolatilizer for a further period of time, so that the
product is deteriorated in color and that the
production cost also increases.
Still further, there has been another
technique of adding an acetaldehyde scavenger as well
as a devolatilizer for eliminating acetaldehyde (see
Patent Document 8). However, the use of a large amount
of such an acetaldehyde scavenger causes problems such
as generation of odor and coloration derived from the
scavenger.
As stated above, the conventional melt
polymerization techniques can reduce volatile
impurities such as acetaldehyde, but they cannot
achieve a molded article of polyester resins, which has
a high polymerization degree and a good hue.
Other than the above described technique of
using a polymerization apparatus comprising a rotary
drive portion in the main body thereof, a method of
performing polymerization while allowing a prepolymer
to fall by gravitation from the upper part of a
polymerization reactor, so as to produce PET with a
high polymerization degree by melt polymerization, has

also been proposed from a long time ago.
For example, there has been a technique
whereby filamentary polyester is allowed to fall into a
vacuum space, so as to produce a polyester with a
desired molecular weight (see Patent Document 9). In
this technique, since recirculation of the fallen
polymer results in deterioration of the quality of the
produced polyester, polymerization is completed by one-
pass operation. However, since it is extremely
difficult to keep a sufficient polymerization time by
such a method, it is also extremely difficult to obtain
a polymer with a high polymerization degree. In
addition, filaments are easily cut off in a
polymerization reactor. This is problematic in that
the quality of the obtained polymer is drastically
fluctuated; and in that condensates with a low
molecular weight scattered from the filaments
contaminate the nozzle surface, and it becomes
difficult for the filaments to be injected directly
below from the nozzle due to such contamination, and as
a result, the filaments come into contact with one
another and are cut off, or they are gathered to become
a thick filament and it is then fallen, so that it
prevents the reaction.
In order to solve such inconveniences, as a
continuous polycondensation method of BHET as an
initial condensate of PET and/or an initial condensate
as an oligomer thereof, there has been proposed a

method involving polymerizing the above materials at a
reactor temperature of 340°C, while allowing the
materials to fall by gravitation along a linear object
that is vertically hung from a nozzle in an atmosphere
where inert gas is circulated (see Patent Document 10).
However, according to the studies of the present
inventors, EG generated as a by-product cannot be
eliminated from the reaction product at a sufficient
rate in such an atmosphere where inert gas is
circulated. Thus, a polymer with a high polymerization
degree required for beverage containers cannot be
obtained. Furthermore, pyrolysis significantly occurs
at a high temperature such as 340°C, and only a polymer
that is colored so as to become yellow can be obtained.
In addition to the above described methods,
as a method of producing a polyester and a polyamide,
there has also been a method of performing polymerize-
tion while allowing a polymer to fall by gravitation
along a linear support vertically disposed in a reactor
(see Patent Document 11). Moreover, as a method of
producing a polyester, there has also been a technique
whereby a PET oligomer with a mean degree of
polymerization between 8 and 12 (which corresponds to
an intrinsic viscosity of 0.1 dl/g or less) is supplied
at 285°C, the oligomer is allowed to fall by gravitation
along a cylindrical wire gauze vertically disposed in a
reactor, and at the same time, polymerization is
carried out under reduced pressure in the reactor (see

Patent Document 12). Furthermore, there has also been
proposed a method and an apparatus of allowing a PET
prepolymer with a melting viscosity of 0.5 Pa-s (which
corresponds to an intrinsic viscosity of 0.1 dl/g or
less) to absorb inert gas, allowing the prepolymer to
fall by gravitation along a guide under reduced
pressure, and at the same time, performing
polymerization (see Patent Document 13).
However, according to the studies of the
present inventors, a polymer with a polymerization
degree of interest cannot be obtained by directly
applying the above described method in industrial-scale
equipment. Moreover, a polymer discharged from a
perforated plate or the like intensively foams, and it
contaminates the wall of the reactor provided with the
support and the nozzle surface. Such contaminants are
decomposed, modified, or colored during long-term
operations, and these degradation products are mixed
into a polymer, so that the quality of a product
deteriorates.
Other than these methods, there has also been
proposed a polymerization method wherein the
temperature of a reaction product is continuously
decreased as the reaction product falls when bis-
hydroxyethyl terephthalate or an oligomer thereof is
supplied to a wetted-wall column followed by continuous
polymerization under reduced pressure, and at the same
time, vacuum aspiration is carried out from the lower

portion of the column (see Patent Document 14).
However, according to the studies of the present
inventors, a polymer with a high polymerization degree
cannot be obtained by applying the above method. When
the amount of a polymerization intermediate
(prepolymer) supplied is decreased to improve a
polymerization velocity, a drift (biased flow) of the
polymerization intermediate (prepolymer) occurs, and
thus, a high-quality polymer cannot be obtained.
Hence, the conventional gravity falling-type
melt polymerization techniques (Patent Documents 9 to
14) could not provide a method of industrially stably
producing high-quality polyester resins having a high
polymerization degree with good productivity, which can
be substituted for the solid phase polymerization
technique. In addition, these gravity falling-type
melt polymerization techniques give no suggestion
regarding a technique of obtaining a molded article
containing small quantities of low molecular weight
volatile substances such as acetaldehyde.
[Patent Document 1] JP-A-58-45228
[Patent Document 2] JP-A-48-102894
[Patent Document 3] JP-A-9-77857
[Patent Document 4] JP-A-2000-117819
— [Patent Document 5] Japanese Patent No. 3345250
[Patent Document 6] National Publication of
International Patent Application No. 2001-516389
[Patent Document 7] National Publication of

International Patent Application No. 2000-506199
[Patent Document 8] National Publication of
International Patent Application No. 2002-514239
[Patent Document 9] U.S. Patent No. 3110547
[Patent Document 10] JP-B-4-58806
[Patent Document 11] JP-A-53-17569
[Patent Document 12] JP-B-48-8355
[Patent Document 13] International Publication
WO99/65970 pamphlet
[Patent Document 14] JP-A-58-96627
It is an object of the present invention to
provide a polyester resin (particularly polyethylene
terephthalate resin) having a polymerization degree
ranging from a low polymerization degree to a high
polymerization degree, having a reduced amount of
carboxyl group on the polymer terminal and a reduced
content of impurities such as acetaldehyde, generating
a reduced amount of aldehyde during processing, having
a favorable hue, having a narrow molecular weight
distribution and having high quality and excellent
moldability; a polyester resin having a reduced
crystallinity and suffering a less degradation in
quality during processing in addition to the above-
mentioned excellent characteristics; a polyester resin
having a reduced content of cyclic trimer and having
excellent moldability; a polyester resin pellets having
a reduced amount of fine powder, having a good handling
characteristic and giving a molded article having good

quality; and a preform and a hollow body formed by
molding the high-quality polyester resin described
above.
DISCLOSURE OF THE INVENTION
As a result of conducting vigorous studies
for solving the above described problems, the present
inventors have found surprisingly that melt
polycondensation at a low temperature which could not
have been achieved at all by a previously publicly
known polymerization apparatus is made possible by
carrying out polymerization under specified conditions
in a polymerization reactor of a new principle in which
a polymerization intermediate (i.e., prepolymer) of a
polyester resin is continuously fed into a
polymerization reactor from a raw material feed opening
in a molten state, discharged through holes of a
perforated plate, and then polymerized while falling
along a support under a reduced pressure, and the melt
polycondensation is quite excellent in productivity,
leading to completion of the present invention.
Namely, the attributes of the present
invention are as follows.
(1) A polyethylene terephthalate resin obtained
by melt polymerization under a reduced pressure or
under an inert gas atmosphere and having the properties
comprising:
(A) an intrinsic viscosity [r\] of 0.4 to 2.5

dl/g;
(B) a content of carboxyl end groups of 30
meq/kg or less;
(C) a content of acetaldehyde of 10 ppm or
less;
(D) a hue represented by the L value of 99 or
greater and the b value of 0.4 or less,
the above described hue being measured by
transmission of hexafluoroisopropanol solution;
(E) Mw/Mn of 1.8 to 2.3; and
(F) a content of cyclic trimer of 5 wt% or
less.
(2) The polyethylene terephthalate resin
according to (1), wherein the crystallinity is 55% or
less.
(3) The polyethylene terephthalate resin
according to (1) or (2), wherein the content of cyclic
trimer is 0.8 wt% or less.
(4) A pellets obtained by pelletizing the
polyethylene terephthalate resin set out in any of (1)
to (3), wherein the content of a fine powder having a
particle size of 1 mm or less is 5 mg/kg or less.
(5) A preform, which is obtained by feeding the
polyethylene terephthalate resin set out in any of (1)
to (3) in a molten state in a polymerization reactor
into an injection molding machine via a feed pipe at a
temperature lower by 10°C or less, and higher by 60°C or
less than the crystalline melting point and then

injection-molding the polyethylene terephthalate resin,
and having the properties comprising:
(G) a content of carboxyl end groups of 30
meq/kg or less,
(H) a content of acetaldehyde of 10 ppm or
less, and
(I) a hue represented by the L value of 98 or
greater and the b value of 0.7 or less,
the above described hue being measured by
transmission of hexafluoroisopropanol solution.
(6) A polyethylene terephthalate hollow body
obtained by blow-molding the preform set out in (5) and
having the properties comprising:
(J) a content of carboxyl end groups of 30
meq/kg or less,
(K) a content of acetaldehyde of 10 ppm or
less, and
(L) a hue represented by the L value of 98 or
greater and the b value of 0.8 or less,
the above described hue being measured by
transmission of hexafluoroisopropanol solution.
(7) A preform, which is obtained by extruding the
polyethylene terephthalate resin set out in any of (1)
to (3) in a molten state in a polymerization reactor to
feed the polyethylene terephthalate resin into a
compression molding machine via a feed pipe at a
temperature lower by 10°C or less, and higher by 60°C or
less than the crystalline melting point and then

compression-molding the polyethylene terephthalate
resin, and having the properties comprising:
(G) a content of carboxyl end groups of 30
meq/kg or less,
(H) a content of acetaldehyde of 10 ppm or
less, and
(I) a hue represented by the L value of 98 or
greater and the b value of 0.7 or less,
the above described hue being measured by
transmission of hexafluoroisopropanol solution.
(8) A polyethylene terephthalate hollow body
obtained by blow-molding the preform set out in (7) and
having the properties comprising:
(J) a content of carboxyl end groups of 30
meq/kg or less,
(K) a content of acetaldehyde of 10 ppm or
less, and
(L) a hue represented by the L value of 98 or
greater and the b value of 0.8 or less,
the above described hue being measured by
transmission of hexafluoroisopropanol solution.
(9) A method for producing a polyester resin, in
which a polymerization intermediate of polyester having
an intrinsic viscosity [r|] of 0.2 to 2.0 dl/g is fed
into a polymerization reactor through a feed opening in
a molten state, then discharged through the holes of a
perforated plate, and subsequently polymerized under a
reduced pressure or under an inert gas atmosphere and a

reduced pressure at a temperature lower by 10°C or less,
and higher by 30°C or less than the crystalline melting
point of the polymerization intermediate under the
condition of the following formula (1) while falling
along an outer open surface(s) of a support(s), wherein
the polymerization intermediate contains at least one
polycondensation catalyst in an amount of 3 to 300 ppm
as a total amount of metal atoms, selected from an Sn
catalyst in an amount less than 50 ppm; a catalyst
selected from Ti, Ge, Al and Mg in an amount less than
100 ppm, respectively; and a catalyst selected from
metals of the IB group and II to VIII groups of the
periodic table other than the above metals in an amount
less than 300 ppm, respectively, in terms of metal
atoms,
and wherein:
S1/S2>1 ... (formula 1),
Si; surface area of the falling polyester
resin, and
S2; area in which the support and the
polyester resin is in contact with each other.
(10) The method for producing a polyester resin
according to (9), wherein at least one of alkali
compounds is made to coexist in the polymerization
intermediate.
(11) The method for producing a polyester resin
according to (9) or (10), wherein at least one of
phosphorous compounds is made to coexist in the

polymerization intermediate.
(12) A method for producing a polyethylene
terephthalate resin, comprising the steps of
providing as a raw material a solid state
polyethylene terephthalate resin having the properties
comprising:
(S) a crystallinity of 35% or less, and
(T) a content of acetaldehyde of 30 ppm or
less, and
subjecting the solid state polyethylene terephthalate
resin to at least one selected from heat treatment,
vacuum treatment and cleaning treatment to obtain a
polyethylene terephthalate resin having the properties
comprising:
(U) a crystallinity of 55% or less;
(V) Mw/Mn = 1.8 to 2.3; and
(W) a content of acetaldehyde of no more than
50% of its content in the raw polyethylene
terephthalate resin.
(13) The method for producing a polyethylene
terephthalate resin according to (12), wherein the
content of acetaldehyde in the raw polyethylene
terephthalate resin is 15 ppm or less.
(14) The method for producing a polyethylene
terephthalate resin according to (12) or (13), wherein
the raw polyethylene terephthalate resin is a
polyethylene terephthalate resin produced by feeding a
polymerization intermediate of polyethylene

terephthalate having an intrinsic viscosity [r\] of 0.2
to 2.0 dl/g into a polymerization reactor through a
feed opening in a molten state, then discharging the
polymerization intermediate through the holes of a
perforated plate, and subsequently polymerizing the
polymerization intermediate under a reduced pressure or
under an inert gas atmosphere and a reduced pressure at
a temperature lower by 10°C or less, and higher by 30°C
or less than the crystalline melting point of the
polymerization intermediate under the condition of the
following formula (1) while falling along an outer open
surface(s) of a support(s), wherein:
S1/S2>1 ... (formula 1),
SI; surface area of the falling polyethylene
terephthalate resin, and
S2; area in which the support and the
polyethylene terephthalate resin is in contact with
each other.
(15) The method for producing a polyethylene
terephthalate resin according to any of (12) to (14),
comprising subjecting the raw polyethylene
terephthalate resin to heat treatment at a temperature
of 140 to 220°C for 20 minutes to 10 hours, whereby the
polyethylene terephthalate resin has a content of
acetaldehyde of 3 ppm or less.
(16) A method for producing a polyethylene
terephthalate resin, wherein a polymerization
intermediate of a polyethylene terephthalate resin

having an intrinsic viscosity [r\] of 0.2 to 2.0 dl/g
and having a content of cyclic trimer of 0.8% by weight
or less is fed into a polymerization reactor through a
feed opening in a molten state, then discharged through
holes of a perforated plate, and subsequently
polymerized under a reduced pressure at a temperature
lower by 10°C or less, and higher by 30°C or less than
the crystalline melting point of the polymerization
intermediate while falling along a support(s) to
produce a polyethylene terephthalate resin having the
properties comprising:
(a) an intrinsic viscosity [r\] of 0.2 to 2.5
dl/g; and
(b) a content of cyclic trimer of 0.8% by
weight or less.
(17) A method for producing a polyethylene
terephthalate resin, wherein a polymerization
intermediate of polyethylene terephthalate resin having
an intrinsic viscosity [r\] of 0.2 to 2.0 dl/g is fed
into a polymerization reactor through a feed opening in
a molten state, then discharged through holes of a
perforated plate, and subsequently polymerized under a
reduced pressure at a temperature lower by 10°C or less,
and higher by 30°C or less than the crystalline melting
point of the polymerization intermediate while falling
along a support(s) to obtain a polyethylene
terephthalate resin, and further processing the
polyethylene terephthalate resin to remove a cyclic

triraer oligomer by an amount of 0.2% by weight or more
therefrom is carried out to produce a polyethylene
terephthalate resin having the properties comprising:
(c) an intrinsic viscosity [r\] of 0.20 to 2.5
dl/g; and
(d) a content of cyclic trimer of 0.8% by
weight or less.

(18) The method for producing a polyethylene
terephthalate resin according to (16) or (17),
comprising feeding a polymerization intermediate of
polyethylene terephthalate resin, which shows an
increase in content of cyclic trimer when the
polymerization intermediate is held in a molten state
at 275°C for 30 minutes is 0.2% by weight or less, into
the polymerization reactor to polymerize the
polymerization intermediate.
(19) A method for producing a polyester resin,
comprising pelletizing a polyester resin obtained by
feeding a polymerization intermediate of polyester
resin having an intrinsic viscosity [r|] of 0.2 to 2.0
dl/g into a polymerization reactor through a feed
opening in a molten state, then discharging the
polymerization intermediate through the holes of a
perforated plate, and subsequently polymerizing the
polymerization intermediate under a reduced pressure at
a temperature lower by 10°C or less, and higher by 30°C
or less than the crystalline melting point of the
polymerization intermediate while falling along a

support(s), and then introducing the resultant pellets
into a solid-state polycondensation reactor to further
subject the pellets to solid-state polycondensation at
a temperature of 190 to 230°C.
(20) A method for producing a polyester resin, in
which a polymerization intermediate of polyester resin
having a number average molecular weight of 6,000 to
80,000 and showing no crystalline melting point is fed
into a polymerization reactor through a feed opening in
a molten state, then discharged through the holes of a
perforated plate, and subsequently polymerized under a
reduced pressure or under an inert gas atmosphere and a
reduced pressure under the condition of the following
formula (1) while falling along an outer open
surface(s) of a support(s), the method comprising
polymerizing the polymerization intermediate at a
temperature in the range of the higher of 100°C or a
temperature at which a melt viscosity when the
polyester resin extracted from the polymerization
reactor is evaluated at a shear rate of 1000 (sec-1) is
100000 (poise) or greater, to 290°C:
S1/S2>1 ... (formula 1),
SI; surface area of the falling polyester
resin, and
S2; area in which the support and the
polyester resin is in contact with each other.
(21) The method for producing a polyester resin
according to any of (9) to (11), (19) and (20),

comprising making the polymerization intermediate
undergo a reaction with any amount of molecular weight
regulator in any step before feeding the polymerization
intermediate into the polymerization reactor.
(22) The method for producing a polyester resin
according to any of (9) to (11) and (19) to (21),
comprising making the polymerization intermediate in a
molten state pass through a polymer filter having a
filtration accuracy of 0.2 to 200 fim and controlled to
have a temperature in the range of a temperature lower
by 20°C than a crystalline melting point of the
polymerization intermediate to a temperature higher by
100°C than the crystalline melting point of the
polymerization intermediate; or in the range of the
higher of 100°C or a temperature at which a melt
viscosity when the polymerization intermediate is
evaluated at a shear rate of 1000 (sec-1) is 100000
(poise) or greater, to 350°C, and then feeding the
polymerization intermediate into the polymerization
reactor.
(23) The method for producing a polyethylene
terephthalate resin according to any of (12) to (18),
comprising making the polymerization intermediate
undergo a reaction with any amount of molecular weight
regulator in any step before feeding the polymerization
intermediate into the polymerization reactor.
(24) The method for producing a polyethylene
terephthalate resin according to any of (12) to (18),

comprising making the polymerization intermediate in a
molten state pass through a polymer filter having a
filtration accuracy of 0.2 to 200 ^m and controlled to
have a temperature in the range of a temperature lower
by 20°C than a crystalline melting point of the
polymerization intermediate to a temperature higher by
100°C than the crystalline melting point of the
polymerization intermediate; or in the range of the
higher of 100°C or a temperature at which a melt
viscosity when the polymerization intermediate is
evaluated at a shear rate of 1000 (sec-1) is 100000
(poise) or greater, to 350°C, and then feeding the
polymerization intermediate into the polymerization
reactor.
The hollow body of the present invention is a
high-quality polyester resin produced with stability
from an industrial point of view, with good
productivity and at a low cost, having a high
polymerization degree, having a reduced amount of
carboxyl group on the polymer terminal and a reduced
content of impurities such as acetaldehyde, generating
a reduced amount of aldehyde during processing, having
a favorable hue, having a narrow molecular weight
distribution and having high quality and excellent
moldability. Therefore, it is a high-quality beverage
container or the like having a low-cost production
characteristic, and an excellent strength, impact
resistance and transparency and having no influence on

the taste of contents.
According to the present invention, it is
possible to provide a polyester resin (particularly
polyethylene terephthalate resin) having a
polymerization degree ranging from a low polymerization
degree to a high polymerization degree, having a
reduced amount of carboxyl group on the polymer
terminal and a reduced content of impurities such as
acetaldehyde, generating a reduced amount of aldehyde
during processing, having a favorable hue, having a
narrow molecular weight distribution and having high
quality and excellent moldability. It is also possible
to provide a polyester resin having a reduced
crystallinity and suffering a less degradation in
quality during processing in addition to the above-
mentioned excellent characteristics, a polyester resin
having a reduced content of cyclic trimer and having
excellent moldability, a polyester resin pellets having
a reduced amount of fine powder, having a good handling
characteristic and giving a molded article having good
quality, and a preform and a hollow body formed by
molding the high-quality polyester resin described
above.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be described
specifically below.
The present invention uses a polymerization

reactor based on a new principle. Thus, (I) principle
of polymerization method of the present invention, (II)
explanation of polyester resin, (III) explanation of
polymerization reactor of the present invention, (IV)
explanation of polymerization method of the present
invention and (V) explanation of molding method and
molded material will be described specifically in this
order.
(I) Principle of polymerization method of the present
invention
A polymerization method of the present
invention is a method in which a polymerization
intermediate of a polyester resin capable of being
polymerized by a melt polycondensation reaction is fed
into a polymerization reactor from a raw material feed
opening in a molten state, discharged through holes of
a perforated plate, and then polymerized under a
reduced pressure or an inert gas atmosphere under a
reduced pressure while falling under gravity along a
support.
As described later, the characteristics of
the polymerization intermediate, the structure of the
polymerization reactor and the polymerization method
meet appropriate conditions. Consequently, the
polymerization intermediate falling along the support
contains a large amount of bubbles, and as
polymerization proceeds, the resin comes to have a
structure in a form of bubble agglomerates (mass) and

exhibits a behavior of falling toward the lower part of
the polymerization reactor.
As a result, an area of contact between the
resin and a gas phase and an effect of stirring the
resin dramatically increase. A byproduct of the
polycondensation reaction (ethylene glycol in the case
of the PET resin) and impurities generated by thermal
decomposition during polymerization (acetaldehyde and
the like in the case of the PET resin) can be
efficiently removed from the polymerization
intermediate. The polymerization velocity dramatically
increases compared with conventional melt
polymerization techniques. Further, there is an
advantage that a high-quality resin having an extremely
small amount of remaining impurities can be produced at
a low polymerization temperature which could not have
been achieved at all by a previously publicly known
polymerization apparatus, and with a quite excellent
productivity.
(II) Explanation of polyester resin
Polyester resins of the present invention
include aliphatic polyesters, aliphatic and aromatic
polyesters, aromatic polyesters and copolymers thereof.
The present invention is suitable for production of a
high-quality polyethylene terephthalate resin (PET
resin) having a high value in use among the polyester
resins described above.
(II-I) Explanation of polyethylene terephthalate resin

of the present invention
The polyethylene terephthalate resin of the
present invention is preferably composed of ethylene
terephthalate repeated units in an amount of 50 mol% or
more, and may contain one or more other copolymer
components in an amount less than 50 mol%.
Examples of copolymer components include
ester forming monomers such as 5-sodium
sulfoisophthalic acid, 3,5-dicarboxylic acid
benzenesulfonic acid tetramethyl phosphonium salts,
1,3-butanediol, 1,4-butanediol, neopentylglycol, 1,6-
hexamethyleneglycol, 1,4-cyclohexanediol, 1,4-
cyclohexanedimethanol, isophthalic acid, oxalic acid,
succinic acid, adipic acid, dodecanedioic acid, fumaric
acid, maleic acid, 1,4-naphthalenedicarboxylic acid,
2,6-naphthalenedicarboxylic acid and 1,4-
cyclohexanedicarboxylic acid, polyethylene glycol,
polypropylene glycol, polytetramethylene glycol and
copolymers thereof. They may be polyester amide
copolymers, polyester ether copolymers, copolymers with
polyalkylene glycols such as polyethylene glycol,
polypropylene glycol and polytetramethylene glycol,
polyester carbonate copolymers and the like in which
different bonds allowing copolymerization with a
polyester resin, such as amide bonds, ether bonds and
carbonate bonds, in addition to ester bonds.
In addition to the polyethylene terephthalate
resin, cyclic and linear oligomers, monomers such as

dimethyl terephthalate (hereinafter abbreviated as
DMT), terephthalic acid (hereinafter abbreviated as
TPA) and ethylene glycol (hereinafter abbreviated as EG
in some cases) and various kinds of additives may be
contained.
The polyethylene terephthalate resin of the
present invention is a high-quality polyethylene
terephthalate resin having the properties (A) to (F)
and being suitable for production of a beverage bottle
or the like:
(A) an intrinsic viscosity [t|] of 0.4 to 2.5
dl/g;
(B) a content of carboxyl end groups of 30
meq/kg or less;
(C) a content of acetaldehyde of 10 ppm or
less;
(D) a hue represented by the L value of 99 or
greater and the b value of 0.4 or less,
the above described hue being measured by
transmission of hexafluoroisopropanol solution;
(E) Mw/Mn of 1.8 to 2.3; and
(F) a content of cyclic trimer of 5 wt% or
less.
The method for producing a polyethylene
terephthalate resin having these properties is not
specifically limited, but most preferable is a method
using the above-mentioned polymerization reactor based
on the new principle of the present invention.

(A) The intrinsic viscosity [r|] is preferably
0.4 dl/g or greater in terms of mechanical properties
of a molded material produced from the polyethylene
terephthalate resin of the present invention, and
preferably 2.5 dl/g or less in terms of ease of
molding. It is more preferably in the range of 0.5 to
2.0 dl/g, further preferably in the range of 0.6 to 1.5
dl/g in terms of a purpose of production of films,
sheets, hollow bodies such as bottles and high-strength
fibers, and especially preferably in the range of 0.7
to 1.3 dl/g.
(B) The amount of carboxyl group on the
polymer terminal is preferably 30 meq/kg or less in
terms of an influence on thermal stability of the
resin, more preferably in the range of 25 meq/kg or
less, further preferably in the range of 20 meq/kg or
less, especially preferably in the range of 15 meq/kg
or less and most preferably in the range of 10 meq/kg
or less. The carboxyl group on the polymer terminal
not only accelerates decomposition of the resin but
also brings about production of diethylene glycol and
acetaldehyde as a byproduct during production of the
resin and during melt molding, thus causing a
degradation in resin quality. In the conventional melt
polymerization technique, a reaction at a higher
temperature and for a longer time is required when a
resin having a high polymerization degree is produced,
and therefore the amount of carboxyl group is extremely

large. In the solid-state polycondensation technique,
on the other hand, a raw material having a larger
amount of carboxyl group is prepared for the purpose of
promoting a polycondensation reaction when a resin
having a high polymerization degree is produced. As a
result, the amount of carboxyl group is extremely large
in the product as well.
(C) For the content of acetaldehyde, it is
desired to reduce the content because even a very small
amount of acetaldehyde gives discomfort to taste and
smell senses of human beings. Thus, the content of
acetaldehyde is preferably 10 ppm or less, more
preferably 8 ppm or less, further preferably 5 ppm or
less, especially preferably 3 ppm or less, and most
preferably 1 ppm or less.
The content of acetaldehyde in the present
invention was measured by the water extraction method.
As a method for quantitative determination of the
content of acetaldehyde, the ASTM method (head space GC
method) has been often used. However, this method is a
method in which the amount of acetaldehyde volatized by
heating in a head space is measured. Therefore,
acetaldehyde in the resin cannot be totally extracted,
and a measured value is lower than an actual level. In
the water extraction method used in the present
invention, acetaldehyde in the resin is totally
extracted, and therefore a measured value closer to an
actual level can be obtained. For the error of

measured values of these measurement methods, it is
known that a value obtained by the water extraction
method is higher by about 3 ppm in the order of several
ppm. Thus, it is important to compare a value in the
conventional literature with 3 ppm added to the value.
In the conventional melt polymerization
technique, a reaction at a high temperature and for a
long time is required compared with the polymerization
method of the present invention, and therefore the
content of acetaldehyde is vary high, and normally 50
ppm or greater. On the other hand, in the solid-state
polycondensation technique, the reaction is made to
proceed at a temperature of 200°C or greater for several
tens of hours, and therefore the content of
acetaldehyde can be reduced to about 5 ppm. However,
since the surface portion of a pellets produced by the
solid-state polycondensation has a high polymerization
degree and an extremely high crystallinity as described
previously, a large amount of shear heat is generated
during molding processing, and the amount of
acetaldehyde produced as a byproduct during processing
is extremely large. Therefore, the content of
acetaldehyde in the molded material is far greater than
10 ppm.
In contrast to this, according to the
production method of the present invention, the
polymerization temperature is low, i.e. close to a
crystalline melting point, in spite of the melt

polymerization technique. Moreover, a polyethylene
terephthalate resin having a reduced content of
impurities such as acetaldehyde can be produced owing
to unique bubbling and surface update behaviors of the
resin in the polymerization reactor. Moreover, the
temperature of the resin drawn out from the
polymerization reactor of the present invention is low,
and therefore the amount of acetaldehyde generated in a
drawing pipe until the resin is cooled into a solid is
small. Moreover, the amount of acetaldehyde generated
during molding processing is also small because the
crystalline of a pellets obtained by solidification of
the resin is low.
(D) For the hue measured by the method of
penetration of a hexafluoroisopropanol solution, it is
preferable that the L value is 99 or greater and the b
value is 0.4 or less, it is more preferably that the L
value is 99.2 or greater and the b value is 0.3 or
less, and it is especially preferable that the L value
is 99.4 or greater and the b value is 0.2 or less for
producing a molded material having an excellent
external appearance.
Evaluations of the hue in the present
invention are made by the penetration method for a
solution prepared by dissolving a polymer in an HFIP
solution in a concentration of 13% by weight. The
value is evaluated with the Hunter colorimetric system,
and the L value and the b value measured by a method

compliant with JIS Z8730 are expressed.
The color E has the following relation.

In view of the above relation, a color cannot
be specified unless a, b and L are expressed. A
transparent resin may take on a yellow tinge due to
coloring, and for reducing an apparently yellow tinge,
a small amount of blue dye or the like is often added.
Since the b value expresses a blue or yellow tinge,
addition of the blue dye or the like changes only the b
value, and has little influence on the a value
expressing a red or green tinge. Addition of a dye or
the like definitely causes a reduction in L value, and
therefore a color can be specified by expression of the
L value and the b value in a transparent resin. For
the hue of a transparent resin, a blue dye or the like
is often added to a resin having a yellow tinge to
reduce the b value (at this time, the L value is
certainly reduced). Therefore, expression of only the
b value is not sufficient, and a color can be specified
only by expressing both L and b values.
In the polymerization method according to the
present invention, thermal hysteresis is low compared
with the conventional melt polymerization method and
solid-state polycondensation technique, and moreover,
there is no rotational driving part in a main body of
the polymerization reactor. Therefore, neither leakage
of air nor heat generation by shearing occurs, and thus

a polyethylene terephthalate resin having an excellent
hue can be produced.
(E) The molecular weight distribution
expressed by Mw/Mn is important in control of quality
of a melt-processed product of the polyethylene
terephthalate resin of the present invention, and is
preferably in the range of 1.8 to 2.3. It is more
preferably in the range of 1.8 to 2.2, further
preferably in the range of 1.8 to 2.1, and especially
preferably in the range of 1.8 to 2.0. As described
above, for the polyethylene terephthalate resin
produced by the solid-state polycondensation technique,
a pellets having a low polymerization degree is used as
a raw material, and made to undergo a reaction for a
long time to increase the polymerization degree. At
this time, EG produced as a byproduct is harder to
escape from the core portion of the pellets than from
the surface portion of the pellets, and therefore a
nonuniform product in which the surface portion of the
pellets has a higher polymerization degree than that of
the core portion of the pellets is obtained, and its
molecular weight distribution is wide. Because of the
reaction in the pellets form, a fine powder tends to be
generated, but if the pellets forms into a fine powder,
the surface area increases, resulting in extreme
progress of polymerization. For such a nonuniform
resin, the molecular weight significantly changes
before and after processing, and it is thus difficult

to control quality of a molded material to be
stabilized. On the other hand, according to the method
of the present invention, a product of uniform quality
can be produced, and therefore it is easy to control
quality of a molded material.
(F) The content of cyclic trimer is
preferably 5 wt% or less in terms of mechanical
properties of a molded material, more preferably 2 wt%
or less, further preferably 1.2 wt% or less, especially
preferably 0.8 wt% or less, and most preferably 0.5 wt%
or less.
As described later, examples of methods for
producing a polyethylene terephthalate resin having a
content of cyclic trimer of 0.8 wt% or less include a
method in which a polymerization intermediate of a
polyethylene terephthalate resin having an intrinsic
viscosity [T|] of 0.2 to 2.0 dl/g and a content of
cyclic trimer of 0.8% by weight or less is polymerized
under a reduced pressure at a temperature in the range
of a temperature lower by 10°C than the crystalline
melting point of the polymerization intermediate to a
temperature higher by 30°C than the crystalline melting
point of the polymerization intermediate while falling
along a support in the polymerization reactor of the
present invention, and a method in which processing of
removing a cyclic trimer oligomer in an amount of 0.2%
by weight or more from a polyethylene terephthalate
resin produced by the polymerization method of the

present invention is carried out. If these methods for
reducing the content of cyclic trimer are carried out,
the polymerization intermediate is preferably adjusted
so that an increase in content of cyclic trimer when it
is held in a molten state at 275°C for 30 minutes is
0.2% by weight or less. These specific methods will be
described in order.
A polyethylene terephthalate resin having a
crystallinity of 55% or less in addition to the above
features of (A) to (F) requires only a low level of
heating for melt processing, and generates only a small
amount of sear heat during plasticization. Therefore,
a reduction in polymerization degree of the resin due
to thermal decomposition, a degradation in hue and the
amount of acetaldehyde produced as a byproduct are
insignificant. The crystallinity is more preferably
50% or less, further preferably 40% or less, especially
preferably 30% or less, most preferably 20% or less,
especially most preferably 10% or less. The
crystallinity of a polyethylene terephthalate resin
produced by the solid-state polycondensation technique
is normally 60% or greater, and particularly the
surface portion of the pellets and a fine powder mixed
in the pellets have a high crystallinity. Therefore,
the resin is not uniformly melted during molding
processing, and thus has many troubles in terms of
product quality leading to defects such as unevenness
of the thickness of a sheet molded material and

roughening (fisheye) of the surface of a molded
material. In contrast to this, if a polyethylene
terephthalate resin produced by the method of the
present invention is used, the resin is easily melted
uniformly during molding processing, whereby a molded
material having a good external appearance can be
obtained.
(II-2) Explanation of polymerization intermediate
A polymerization method using a
polymerization reactor based on a new principle of the
present invention, which is most suitable for
production of a polyester resin, particularly
polyethylene terephthalate resin of the present
invention will be described below. First, a
polymerization intermediate suitable for being fed into
the polymerization reactor of the present invention and
polymerized will be described.
The polymerization intermediate is a polymer
in an initially stage of polymerization having a
polymerization degree lower than that of a product
resin, and is formed into a product polyester resin by
further increasing the polymerization degree using a
polymerization apparatus of the present invention. The
polymerization intermediate may include an oligomer and
a monomer.
Methods for producing a polymerization
intermediate of a polyester resin represented by a
polyethylene terephthalate resin are broadly classified

into two types according to a difference in raw
material. The first method is a method in which for
example, a monomer having a lower alcohol ester of a
carboxyl group such as DMT and a monomer having a
hydroxyl group such as EG are made to undergo an ester
exchange reaction to obtain hydroxy ethylene
terephthalate (hereinafter abbreviated as "BHET") in
the case of the polyethylene terephthalate resin, and
then the BHET is made to undergo a polycondensation
reaction to produce a polymerization intermediate
(hereinafter abbreviated as "ester exchange method").
The second method is a method in which for example, a
monomer having a carboxyl group such as a terephthalic
acid and a monomer having a hydroxyl group such as EG
are made to undergo an esterification reaction to
obtain a BHET, and then the BHET is made to undergo a
polycondensation reaction to produce a polymerization
intermediate as in the first method (hereinafter
abbreviated as "direct esterification method").
For the method for producing a polymerization
intermediate, a broad division is made between the
batch polymerization method (also called a batch
method) in which a raw material and the like are all
introduced into a reaction apparatus and made to
undergo a reaction at a time to obtain a polymerization
intermediate and the continuous polymerization method
in which a raw material is continuously introduced into
a reaction apparatus to continuously obtain a

polymerization intermediate. For the polyester resin
of the present invention, most preferable is a method
in which a polymerization intermediate is obtained by
the continuous polymerization method and the
polymerization intermediate is continuously polymerized
by the production method described later.
A method for producing a polymerization
intermediate of a polyethylene terephthalate resin as a
representative of the polyester resin of the present
invention will be described in detail as an example.
In the ester exchange method, for example,
DMT and EG are subjected to ester exchange at a
temperature of 160 to 240°C under presence of an ester
exchange catalyst to obtain BHET. In the ester
exchange method, DMT or the like as a raw material has
a relatively high volatility, and therefore it is
preferable that the reaction vessel is divided into two
or more vessels and the temperature is changed
according to the reaction rate. BHET may include a
lower alcohol ester of unreacted TPA, EG and an
oligomer, but it is preferable that BHET or an oligomer
having a low molecular weight occupies 70% by weight or
more based on the total amount of reactants.
The molar ratio of DMT to EG during placement
is preferably in the range of 1:1.2 to 1:4, and more
preferably in the range of 1:1.4 to 1:2.5 for reducing
the reaction time and obtaining a polymer of good
quality.

The ester exchange method requires use of an
ester exchange catalyst. Preferable examples thereof
include titanium alkoxides represented by titanium
tetrabutoxide and titanium tetraisopropoxide, tin
compounds such as tin 2-ethylhexanoate, manganese
acetate, cobalt acetate, calcium acetate and zinc
acetate. Among them, manganese acetate and calcium
acetate are preferable because a polymer of good
quality can be obtained. The amount of ester exchange
catalyst is preferably in the range of 0.0005 to 0.5%
by weight, more preferably in the range of 0.0005 to
0.3% by weight and further preferably in the range of
0.0005 to 0.1% by weight based on the amount of DMT.
In the direct esterification method, for
example, TPA and EG can be made to undergo an
esterification reaction at a temperature of 150 to 240°C
to obtain BHET. The molar ratio of TPA to EG during
placement is preferably in the range of 1:1.01 to 1:3,
and more preferably in the range of 1:1.03 to 1:2. By
limiting the molar ratio to within this range, the
reaction time can be reduced.
In the direct esterification method, protons
isolated from TPA serve as a catalyst, and therefore an
esterification catalyst is not necessarily required,
but an esterification catalyst may be used for
enhancing a reaction velocity. Examples of catalysts
include titanium alkoxides represented by titanium
tetrabutoxide and titanium tetraisopropoxide and tin

compounds such as tin 2-ethylhexanoate. The amount of
the catalyst added is preferably in the range of 0.0005
to 1% by weight, more preferably in the range of 0.0005
to 0.5% by weight and further preferably in the range
of 0.0005 to 0.2% by weight based on the amount of TPA.
For making the esterification reaction
proceed smoothly, BHET is preferably added when the
reaction is started. In the batch method, TPA and EG
as raw materials and 5 to 80% by weight of BHET based
on the amount of TPA are placed at a time, and the
reaction is started. At the time of starting the
continuous polymerization method, 5 to 80% by weight of
BHET based on a predetermined level is placed in
advance in a reaction vessel in which a direct
esterification reaction is carried out, and melted, and
then a fixed amount of mixture of TPA and EG is
introduced thereinto while a fixed amount of reaction
product (BHET) is withdrawn to start the reaction.
Thereafter, the feeding of the raw material and the
withdrawal of the product can be continued to make a
transition to a steady state.
BHET produced by the by the direct
esterification method may include unreacted TPA, EG and
an oligomer, but it is preferable that BHET or an
oligomer having a low molecular weight occupies 70% by
weight or more based on the total amount of reactants.
BHET obtained by the method described above
is subsequently subjected to polycondensation to

produce a polymerization intermediate for use in the
present invention. BHET is made to undergo a
polycondensation reaction under a reduced pressure or
under an inert gas atmosphere while removing EG
produced as a byproduct. The temperature of the
polycondensation reaction is preferably set to 260 to
300°C. By setting the temperature 260°C or higher, a
situation in which the reactant is solidified or the
reaction time increases is prevented. By setting the
temperature to 300°C or lower, thermal decomposition can
be inhibited to obtain a resin having an excellent hue.
The temperature of the polycondensation reaction is
more preferably in the range of 260 to 290°C and further
preferably in the range of 260 to 280°C.
If the polycondensation reaction is carried
out under a reduced pressure, the degree of reduced
pressure is appropriately adjusted according to the
sublimation state and the reaction velocity of BHET and
polycondensation reactants. If the reaction is carried
out under an inert gas atmosphere, it is important to
sufficiently replace the inert gas as required so that
EG produced as a byproduct can be efficiently removed.
It is desirable to use a polycondensation
catalyst for polycondensation of BHET. Use of the
polycondensation catalyst can dramatically reduce the
polycondensation time. Preferable examples of the
polycondensation catalyst include germanium compounds
such as germanium dioxide, antimony compounds such as

diantimony trioxide and antimony acetate, aluminum
compounds represented by aluminum acetate, aluminum
isopropoxide and aluminum phosphate, tin compounds such
as tin 2-ethylhexanoate, titanium alkoxides represented
by titanium tetrabutoxide and titanium
tetraisopropoxide, titanium dioxide, and complex salts
of titanium dioxide and silicon dioxide.
Among them, the antimony compound has a high
reaction velocity and is advantageous in terms of the
cost of the catalyst. The germanium compound catalyst
is advantageous in terms of the hue of the resin. The
tin compound is advantageous in terms of the reaction
velocity. The aluminum compound and the titanium
compound catalyst are advantageous in terms of the cost
of the catalyst and influences on environments. Only
one of these catalysts may be used, or two or more
thereof may be used in combination.
The amount of polycondensation catalyst added
is preferably in the range of 0.0005 to 1% by weight,
more preferably in the range of 0.0005 to 0.5% by
weight and especially preferably in the range of 0.0005
to 0.2% by weight based on the weight of the
polymerization intermediate. If a compound acting also
as a polycondensation catalyst in a process of
production of BHET is used, the amount of the compound
should be included in the amount described above.
According to the polymerization method of the
present invention, a polyester resin of high quality

can be produced according to the above condition for
use of the catalyst, but the more preferable amount of
catalyst used is an amount close to the lower limit of
the above amount of catalyst used in terms of product
quality.
Specifically, the amount polycondensation
catalyst is preferably a used amount of at least one
catalyst in an amount of 3 to 300 ppm as a total amount
of metal atoms, selected from an Sn catalyst in an
amount less than 50 ppm; a catalyst selected from Ti,
Ge, Al and Mg in an amount less than 100 ppm,
respectively; and a catalyst selected from metals of
the IB group and II to VIII groups of the periodic
system other than the above metals in an amount less
than 300 ppm, respectively, in terms of metal atoms
based on the amount of polymerization intermediate.
For each type of catalyst described above,
the antimony compound and tin compound catalysts have
disadvantages of degradation of the hue of the resin,
precipitation of the catalyst, adverse effects on
environments and the like. The germanium compound
catalyst has a disadvantage of expensiveness. The
aluminum compound and titanium compound catalysts have
a disadvantage that the hue of the resin is much poor
than that of the antimony compound and the germanium
compound. For these problems, a method of reducing the
amount of catalyst used for the purpose of reduction of
catalyst cost and alleviation of adverse effects on

environments and degradation of the hue of the resin, a
method of adding a phosphorus compound or the like for
the purpose of inhibiting the activity of the
polymerization catalyst to prevent degradation of the
hue of the resin, and the like have been proposed.
However, if a sufficient effect is to be obtained by
these methods, the velocity of the polymerization
reaction significantly decreases, so that productivity
is degraded, much time is required for the reaction,
and it is necessary to increase the polymerization
temperature. As a result, the amount of byproduct
increases and the hue is degraded against the
intention, and it is thus impossible to obtain adequate
results.
In the polymerization method of the present
invention, surprisingly, even if the amount of these
catalysts used is considerably reduced, a reduction in
productivity is insignificant, and reduction of the
catalyst cost, alleviation of effects on environments,
improvement of the hue of the polymer and the like can
be adequately achieved. Even if a phosphorus compound
or the like is added, a reduction in productivity is
insignificant, thus making it possible to further
improve the hue of the resin. Moreover, the reduction
in hue and the amount of thermal decomposition
byproduct during the molding of a produced resin can be
alleviated.
Especially preferable as a polycondensation

catalyst is at least one metal-containing compound
selected from the group consisting of antimony
compounds, germanium compounds, titanium compounds and
aluminum compounds. For the antimony compound,
antimony pentaoxide, metal antimony and alkoxides
represented by antimony glycoxide and antimony
isopropoxide are preferable in addition to the
diantimony trioxide and antimony acetate described
above; for the germanium compound, germanium
tetrachloride, germanium acetate, metal germanium, and
alkoxides represented by germanium glycoxide and
germanium isopropoxide are preferable in addition to
the germanium dioxide described above; for the titanium
compound, hydrolysates obtained by hydrolyzing titanium
halides or titanium alkoxides, complexes prepared by
dehydrating and drying hydrolysates obtained by
hydrolyzing titanium halides or titanium alkoxides
under coexistence of a polyvalent alcohol, titanium
oxalate, titanium acetate, titanium benzoate, titanium
trimellitate, metal titanium, and reactants of any one
or more of the above titanium compounds and trimellitic
anhydrate are preferable in addition to the titanium
alkoxides represented by titanium tetrabutoxide,
titanium tetra n-propoxide, titanium tetraisopropoxide,
titanium tetra n-butoxide, titanium tetraisobutoxide,
titanium tetra t-butoxide, titanium tetracyclohexide,
tetraphenyl titanate and tetrabenzyl titanate, titanium
dioxide, and complex salts of titanium dioxide and

silicon dioxide described above; and for the aluminum
compound, there are metal aluminum, carboxylates such
as aluminum formate, basic aluminum acetate, aluminum
propionate, aluminum oxalate, aluminum acrylate,
aluminum laurate, aluminum stearate, aluminum benzoate,
aluminum trichloroacetate, aluminum lactate, aluminum
citrate, aluminum salicylate, inorganic acid salts such
as aluminum chloride, aluminum hydroxide, aluminum
chloride hydroxide, aluminum carbonate, aluminum
phosphate and aluminum phosphonate, aluminum alkoxides
such as aluminum methoxide, aluminum ethoxide, aluminum
n-propxide, aluminum iso-propoxide, aluminum n-butoxide
and aluminum t-butoxide, aluminum chelate compounds
such as aluminum acetylacetnate, aluminum
acetylacetate, aluminum ethylacetacetate and aluminum
ethylacetacetate diiso-propoxide, organic aluminum
compounds such as trimethyl aluminum and trimethyl
aluminum and partial hydrolysates thereof, and aluminum
oxide in addition to the aluminum acetate, aluminum
isopropoxide and aluminum phosphate described above.
Among them, carboxylates, inorganic acid salts and
chelate compounds are preferable and among them,
further, aluminum acetate, aluminum chloride, aluminum
hydroxide, aluminum chloride hydroxide and aluminum
acetylacetnate are especially preferable.
Further, catalysts containing at least one of
these aluminum compounds and phenol compounds are also
preferable. Phenol compounds are not specifically

limited as long as they are compounds having a phenol
structure, but they may include, for example, 1,3,5-
trimethyl 2,4,6-tris (3,5-di-t-butyl-4-
hydroxybenzyl)benzene, tetrakis-(methyl-3-(3',5'-di-t-
butyl-4-hydroxyphenyl)propionate)methane,
thiodiethylene-bis(3-(3,5-di-t-butyl-4-
hydroxyphenyl)propionate), 2,6-di-t-butyl-4-
methylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,6-
dicyclohexyl-4-methylphenol, 2,6-diisopropyl-4-
ethylphenol, 2,6 di-t-amyl-4-methylphenol, 2,6-di-t-
octyl-4-n-propylphenol, N,N'-hexamethylenebis(3,5-di-t-
butyl-4-hydroxy-hydrocinamide) , 1,3,5-tris(2,6-
dimethyl-3-hydroxy-4-tpbutylbenzyl)isocyanurate, 2-
cyclohexyl-4-n-butyl-6-isopropylphenol and 1,1,1-
tris(4-hydroxyphenyl)ethane.
Two or more of these compounds may be used in
combination. By adding these phenol compounds during
polymerization, the catalytic activity of the aluminum
compound is improved and the thermal stability of
polyester produced is improved. The amount of the
above described phenol compound added is preferably in
the range of 5> the range of l*icr4 to 0.5 mol% based on the number of
moles of all carboxylic acid components such as
dicarboxylic acid and polyvalent carboxylic acid in the
obtained polyester.
It is also preferable that in addition to the
compounds described above, metal compounds of sodium,

potassium, magnesium, calcium, iron, cobalt, copper,
tin, zirconium, hafnium and the like are used in
combination or one of these metal compounds is used as
a polycondensation catalyst. If the antimony
compounds, germanium compounds, titanium compounds and
aluminum compounds are used in combination, an
arbitrarily selected metal compound can be separately
added, but it is also preferable that a coprecipitate
is prepared by concurrent hydrolysis and added.
Coexistence at least one of alkali compounds
coexist in the polymerization intermediate as necessary
has an effect of inhibiting generation of foreign
matters and degradation of the hue, and is thud
preferable. The alkali compound for use in the present
invention is a generalized alkali, and refers to an
entire group consisting of hydroxides of alkali metals
and alkaline earth metals as well as alkali metal
carbonates, ammonia, amine and derivatives thereof.
More specifically, examples of alkali compounds of
nitrogen-containing alkali compounds include ammonia,
diethyl amine, trimethyl amine, ethylene diamine,
pyridine, quinoline, pyrroline, piperidine, pyrolidone
and tetramethylammonium hydroxide. These compounds may
be separately added to the polymerization intermediate,
or a method in which these compounds are added with the
compound in contact with the polycondensation catalyst
is preferable, and especially preferable when they are
used in combination with titanium compounds and

aluminum compounds.
Examples of alkali compounds of alkali metals
include lithium compounds, sodium compounds, potassium
compounds, rubidium compounds and cesium compounds.
Among them, sodium compounds and potassium compounds
are preferable. Examples of alkali compounds of
alkaline earth metals include calcium compounds,
magnesium compounds, strontium compounds and barium
compounds. Among them, calcium compounds and magnesium
compounds are preferable. Alkali metals and alkaline
earth metals are used in the form of salts such as
sulfates, carbonates, chlorides, acetates, formates and
benzoates. These compounds may be separately added to
the polymerization intermediate, or a method in which
these compounds are added with the compound in contact
with the polycondensation catalyst is preferable, and
especially preferable when they are used in combination
with titanium compounds and aluminum compounds because
the activity of the polymerization reaction is
improved.
If the alkali compound is added in the
present invention, the amount of alkali compound added
is preferably in the range of 50 to 5000 ppm based on
the amount of polyester resin obtained. However, it is
preferable that the total amount of metal-containing
components does not exceed 300 ppm. If the amount is
less than 50 ppm, an effect of inhibiting generation of
foreign matters is hard to be obtained. If the

compound is added in an amount greater than 5000 ppm,
the hue of the obtained polyester resin may be
degraded. The amount of the compound added is
preferably in the range of 60 to 3000 ppm, and
especially preferably in the range of 70 to 1000 ppm.
Coexistence of at least one of phosphorus
compounds in the polymerization intermediate as
necessary has an effect of inhibiting generation of
foreign matters and degradation of the hue, and is thus
preferable. The phosphorus compound is not
specifically limited, but is selected from, for
example, phosphoric acid, polyphosphoric acid,
tripolyphosphoric acid, phosphorous acid, trioctyl
phosphate, triphenyl phosphate, triphenyl phosphite,
hypophosphoric acid, methyl hypophosphite, trimethyl
hypophosphite, dimethyl esters, diethyl esters,
dipropyl esters and dibutyl esters of phosphonic acid
derivatives such as phenyl phosphonic acid, ethyl
phosphonic acid, propyl phosphonic acid, butyl
phosphonic acid, biphenyl phosphonic acid, naphthyl
phosphonic acid, 2-carboxyphenyl phosphonic acid, 2,6-
dicarboxyphenyl phosphonic acid, 2,3,4-tricarboxyphenyl
phosphonic acid, phenyl phosphinic acid, ethyl
phosphinic acid, propyl phosphinic acid, butyl
phosphinic acid, biphenyl phosphinic acid, diphenyl
phosphinic acid, diethyl phosphinic acid, dipropyl
phosphinic acid, dibutyl phosphinic acid, 2-
carboxyphenyl phosphinic acid, 2,-dicarboxyphenyl

phosphinic acid, 2,3,4-tricarboxyphenyl phosphinic
acid, 2,3,5-tricarboxyphenyl phosphinic acid, 2,3,6-
tricarboxyphenyl phosphinic acid, bis(2,4,6-
tricarboxyphenyl)phosphinic acid, carbomethoxymethane
phosphonic acid, carboethoxymethane phosphonic acid,
carbopropoxymethane phosphonic acid, carbobutoxymethane
phosphonic acid and carbomethoxyphenylmethane
phosphonic acid, phosphates such as lithium phosphate,
sodium phosphate, sodium dihydrogen phosphate, disodium
hydrogen phosphate, potassium phosphate, potassium
dihydrogen phosphate, dipotassium hydrogen phosphate,
strontium phosphate, zirconium phosphate, barium
phosphate and aluminum phosphate, phosphites such as
lithium phosphite, sodium phosphite, potassium
phosphite, zirconium phosphite, barium phosphite and
aluminum phosphite, and the like.
The phosphorus compound can be added directly
to the polymerization intermediate. A method in which
the phosphor compound is added with the phosphor
compound in direct contact with a metal compound as a
polycondensation catalyst, or added in a form of a
reaction product obtained by making the phosphor
compound undergo a reaction in water and/or an organic
solvent is also preferable.
If the phosphorus compound is added in the
present invention, the amount of phosphor compound
added is preferably in the range of 2 to 5000 ppm based
on the amount of polyester obtained. If the amount is

less than 2 ppm, an effect of inhibiting generation of
foreign matters is hard to be obtained, and if the
phosphor compound is added in an amount greater than
5000 ppm, the polycondensation reaction may be hard to
proceed. The amount of the compound added is more
preferably in the range of 5 to 2000 ppm, further
preferably in the range of 10 to 1000 ppm, especially
preferably in the range of 15 to 500 ppm, most
preferably in the range of 20 to 200 ppm, and
especially most preferably in the range of 20 to 100
ppm.
Addition of a cobalt compound together with
the above metal-containing organic compounds as
necessary is preferable because the hue of a polyester
resin produced is further improved in addition to the
action as a polycondensation catalyst. The type of
cobalt catalyst is not specifically limited, but
examples thereof include cobalt acetate, cobalt
nitrate, cobalt chloride, cobalt acetyl acetate and
cobalt naphthenate. The amount of cobalt compound
added may be arbitrarily selected according to
applications, but is usually preferably 100 ppm or less
and more preferably 50 ppm or less in the case of, for
example, applications of beverage containers.
The reason why in this way, a polyester resin
having a high polymerization degree and high quality
can be produced while reducing the amount of catalyst
used in the present invention is as follows. Namely,

in the polymerization reactor of the present invention,
the surface turnover of the polymerization intermediate
involved in a polymerization reaction is extremely
high, and the polymerization reaction easily proceeds;
the polymerization reactor has no stirring mechanism,
and therefore a resin having a high polymerization
degree is not subjected to a high shear force, and the
cutoff of a molecular chain does not occur during
polymerization; and in addition because the
polymerization reactor has no stirring mechanism,
polymerization can be carried out under a condition in
which the amount of oxygen mixed is small, and at a low
temperature, and therefore a reduction in catalyst
activity due to degeneration of the resin or catalyst
itself, agglomeration of the catalyst, influences of
degenerated matters and the like is hard to occur.
Examples of apparatuses carrying out
polycondensation include previously publicly known
vertical stirring polymerization reactors; horizontal
stirring reaction vessels having a uniaxial or biaxial
stirring vane; gravity flow type thin film
polymerization reactors having shelves; thin film
polymerization reactors in which a raw material flows
down under gravity along an inclined plane; tube type
polymerization reactors; wetted-wall columns; and
apparatuses discharging a raw material through holes of
a perforated plate and making the material undergo a
reaction while falling along a support, like the

polymerization reactor of the present invention
described in detail later. Of course, they may be used
in combination.
For the polycondensation reaction apparatus,
a single apparatus may be used from the start of
polycondensation of BHET to the production of a
polymerization intermediate in the batch polymerization
method, but of course, the reaction apparatus may be
divided into two or more reaction vessel. In the
continuous polymerization method, a single apparatus
may be used, but for making the reaction proceed
efficiently, the apparatus may be divided into two or
more reaction vessels where the temperature, the degree
of reduced pressure and the like are changed.
Time required for the reaction after
polycondensation of BHET is started until the
polymerization intermediate is produced is normally in
the range of 30 minutes to 20 hours. The reaction time
is preferably 30 minutes or more for producing a
polymerization intermediate having a polymerization
degree suitable for the polymerization reactor of the
present invention described later, and the reaction
time is preferably 20 hours or less for obtaining a
product excellent in quality such as a hue. The
reaction time is more preferably in the range of 35
minutes to 10 hours, further preferably in the range of
40 minutes to 5 hours, and especially preferably in the
range of 45 minutes to 3 hours.

The amount of carboxyl group on the terminal
of a polymerization intermediate produced by the ester
exchange method is preferably 50 meq/kg or less. More
preferable is 45 meq/kg or less, further preferable is
40 meq/kg or less, especially preferable is 35 meq/kg
or less, most preferable is 30 meq/kg or less, and
especially most preferable is 25 meq/kg or less.
The amount carboxyl group on the terminal of
a polymerization intermediate produced by the direct
esterification method is preferably 70 meq/kg or less.
Particularly if the intrinsic viscosity [r\] of the
polymerization intermediate is 0.4 dl/g or more, the
amount of carboxyl group is preferably 50 meq/kg or
less, more preferably 45 meq/kg or less, further
preferably 40 meq/kg or less, especially preferably 35
meq/kg or less, most preferably 30 meq/kg or less, and
especially most preferably 25 meq/kg or less. When the
intrinsic viscosity [r|] of the polymerization
intermediate is less than 0.4 dl/g, the amount of
carboxyl group is more preferably 60 meq/kg or less,
and further preferably 50 meq/kg or less.
If other conditions for the polymerization
intermediate are the same, conductivity in the
polymerization reactor of the present invention
improves as the amount of carboxyl group of the
polymerization intermediate decreases. Furthermore,
the quality of the product also improves.
The polymerization degree of a polymerization

intermediate suitable for the present invention can be
specified by a melt viscosity evaluated under the
condition of a shear rate of 1000 (sec-1) at a
temperature at which polymerization is carried out in
the polymerization reactor of the present invention,
and the polymerization degree is preferably in the
range of 60 to 100000 (poise). By setting the
polymerization degree to 60 (poise) or more, vigorous
bubbling and splashing of the polymerization
intermediate discharged through holes of the perforated
plate of the polymerization reactor can be inhibited.
By setting the polymerization degree to 100000 (poise)
or less, the reaction byproduct can be efficiently
removed to outside the system so that polymerization
swiftly proceeds. The polymerization degree is more
preferably in the range of 100 to 50000 (poise),
further preferably in the range of 200 to 10000
(poise), and especially preferably in the range of 300
to 5000 (poise). One reason why a polymerization
intermediate having a relatively high viscosity is thus
preferred in the present invention is that
polymerization is carried out with the resin containing
a large amount of bubbles as described previously and
as a result, the polymerization velocity dramatically
increases. For another reason, if the polymerization
intermediate discharged through holes of the perforated
plate vigorously bubbles and splashes, splashed matters
are deposited on, and smears, the nozzle surface and

wall surfaces of the perforated plate through which the
polymerization intermediate is discharged. The
deposited polymerization intermediate is thermally
decomposed into a colored low-molecular weight matters
and degenerated matters as it resides over a long time
period. If such matters find their way into a product,
quality is degraded such that a predetermined
polymerization degree is not achieved. For preventing
the splashing of the resin due to vigorous bubbling,
the polymerization degree of the polymerization
intermediate should be within the range described
above. For producing a polyester resin having a less
content of impurities such as acetaldehyde, the
polymerization intermediate preferably has a lower
polymerization degree. This is probably because the
amount of byproducts of the polycondensation reaction
such as EG increases, and therefore impurities are
efficiently removed with the impurities entrained in
these byproducts.
The polymerization degree of the
polymerization intermediate suitable for the present
invention is in the range of 6000 to 80000 if specified
as a number average molecular weight.
If the polymerization intermediate is a
polyethylene terephthalate resin, the polymerization
degree suitable for the present invention may also be
specified as an intrinsic viscosity [r\] . The intrinsic
viscosity [r\] of the polymerization intermediate of the

polyethylene terephthalate resin is in the range of 0.2
to 2.0 dl/g, preferably in the range of 0.25 to 1.5
dl/g, more preferably in the range of 0.3 to 1.2 dl/g,
further preferably in the range of 0.4 to 0.8 dl/g,
especially preferably in the range of 0.42 to 0.7 dl/g,
and most preferably in the range of 0.44 to 0.6 dl/g.
For a specific method for producing the
polymerization intermediate described above, a
reference may be made to, for example, "Polymer
Synthesis, vol.1, second edition," 1992 (issued by
Academic Press, Inc., U.S.).
In the method for producing the polyethylene
terephthalate resin of the present invention, one
method for producing a polyethylene terephthalate resin
having a content of cyclic trimer of 0.8 wt% or less is
the following method. Namely, it is a method in which
a polymerization intermediate of a polyethylene
terephthalate resin having an intrinsic viscosity [r|]
of 0.2 to 2.0 dl/g and a content of cyclic trimer of
0.8% by weight or less is polymerized under a reduced
pressure at a temperature in the range of a temperature
lower by 10°C than the crystalline melting point of the
polymerization intermediate to a temperature higher by
30°C than the crystalline melting point of the
polymerization intermediate while falling along a
support in the polymerization reactor of the present
invention.
Here, the method for producing a

polymerization intermediate of a polyethylene
terephthalate resin having a content of cyclic trimer
of 0.8% by weight or less is not specifically limited,
and a previously publicly known method may be used.
Examples of the method include a method in which the
cyclic trimer contained in the polymerization
intermediate is removed by extraction and/or
devolatilization; a method in which a polymerization
intermediate having a content of cyclic trimer of 0.8%
by weight or less is prepared by producing a
polymerization intermediate by the solid-state
polycondensation method; a method in which a
polyethylene terephthalate resin produced by the solid-
state polycondensation method and having a content of
cyclic trimer of 0.8% by weight or less is crushed, and
this crushed resin is directly used, or a material of
which the molecular weight is arbitrarily adjusted by
making the resin undergo a reaction with a molecular
weight regulator as necessary is adjusted so that the
content of cyclic trimer contained in the
polymerization intermediate is 0.8% by weight or less,
and used as part or all of the polymerization
intermediate; and a method in which a polymerization
intermediate having a content of cyclic trimer of 0.8%
by weight or less is produced using a polymerization
catalyst containing an element such as tin or titanium
having a capability of ring opening polymerization of a
cyclic trimer.

For further reducing the content of cyclic
trimer in the polyethylene terephthalate resin of the
product, the content of cyclic trimer in the
polymerization intermediate is preferably lower. More
preferable is 0.7% by weight or less, further
preferable is 0.6% by weight or less, especially
preferably is 0.5% by weight or less, most preferable
is 0.4% by weight or less, and especially most
preferable is 0.3% by weight or less.
A polymerization intermediate of which the
content of cyclic trimer increases by 0.2% by weight or
less when held in a molten state at 275°C for 30 minutes
is fed into the polymerization reactor of the present
invention and polymerized, whereby the rate of
generation of the cyclic trimer during polymerization
can be made further sluggish. Thus, a polyethylene
terephthalate resin having a lower content of cyclic
trimer can be obtained, and moreover the rate of
generation of the cyclic trimer by an equilibration
reaction when the produced resin is melt-molded can be
reduced. As a result, a molded article having a low
content of cyclic trimer can be produced.
Particularly, in the present invention, the produced
resin can be transferred to a molding machine in a
molten state and formed with high efficiency.
Therefore, it is preferable that an increase in content
of cyclic trimer during transfer is reduced to inhibit
the problem of mold deposit or the like impairing

molding efficiency.
The method for reducing to 0.20% by weight or
less an increase in content of cyclic trimer when the
polymerization intermediate is held in a molten state
at 275°C for 30 minutes is not specifically limited, and
a previously publicly known method may be used.
Examples of the method include a method in which water
or a compound containing an element such as phosphorus
is added to the polymerization intermediate to adjust
the activity of a polymerization catalyst involved in a
reaction producing a cyclic trimer as a byproduct; and
a method in which a hydroxyl group on the terminal of
the molecule of the polymerization intermediate serving
as an origin of a reaction producing a cyclic trimer is
replaced by a different functional group. In a usual
method for polymerization of polyester, if the above-
mentioned method is used for the polymerization
intermediate, the polymerization activity itself drops,
and therefore a polyethylene terephthalate resin having
a high polymerization degree cannot be produced with
good productivity. In contrast to this, in the
polymerization reactor of the present invention, a
polymerization reaction proceeds with high efficiency
compared with the conventional polymerization
apparatus, and therefore a resin having a high
polymerization degree can be produced with good
productivity.
For obtaining a sufficient effect for

reduction of the content of cyclic trimer in the
present invention, the increase in content of cyclic
trimer when the polymerization intermediate is held in
a molten state at 275°C for 30 minutes is preferably
0.20% by weight or less. The increase in content of
cyclic trimer when the polymerization intermediate is
held in a molten state at 275°C for 30 minutes is more
preferably 0.15% by weight or less, further preferably
0.10% by weight or less, especially preferably 0.05% by
weight or less, most preferably 0.03% by weight or
less, and especially most preferably 0.02% by weight or
less.
(Ill) Explanation of polymerization reactor of the
present invention
The polymerization reactor of the present
invention is an apparatus characterized in that the
above-mentioned polymerization intermediate is fed into
the polymerization reactor in a molten state,
discharged through holes of a perforated plate, and
then subjected to melt polycondensation under a reduced
pressure or under an inert gas atmosphere under a
reduced pressure while falling along a support.
(III-l) Perforated plate
The perforated plate is a plate having a
plurality of through-holes. By using the perforated
plate, a biased flow of the polymerization intermediate
is inhibited and local residence of the material in the
reaction vessel is prevented, thus making it possible

to produce a high-quality and homogenous resin.
For the structure of the perforated plate,
the thickness is not specifically limited, but is
usually in the range of 0.1 to 300 mm, preferably in
the range of 1 to 200 mm, and further preferably in the
range of 5 to 150 mm. The perforated plate is required
to have a strength for enduring a pressure of feeding
chamber for the melt polymerization intermediate, and
bearing the weights of the support and the falling
polymerization intermediate if the support of a
polymerization chamber is fixed to the perforated
plate. It is preferably reinforced with a rib or the
like.
The shape of the hole of the perforated plate
is usually selected from circular, elliptic,
triangular, slit, polygonal and star shapes and the
like. The cross-sectional area of the hole is usually
in the range of 0.01 to 100 cm2, preferably in the range
of 0.05 to 10 cm2, and especially preferably in the
range of 0.1 to 5 cm2. Provision of a nozzle or the
like connected to the hole is also included.
The distance between holes is usually in the
range of 1 to 500 mm, and preferably in the range of 10
to 100 mm in terms of a distance between the centers of
holes. The hole of the perforated plate may be a hole
perforating the perforated plate, or may be a hole of a
pipe attached to the perforated plate. It may be
tapered. It is preferable that the size and shape of

the hole are determined so that the pressure loss when
the polymerization intermediate passes through the
perforated plate is in the range of 0.1 to 50 kg/cm2.
The number of holes of the perforated plate
is not specifically limited, and varies depending on
conditions of the reaction temperature, pressure and
the like, the amount of catalyst, the range of
molecular weights for polymerization, and the like.
Normally, when a polymer is produced at a rate of, for
example, 100 kg/hr, 10 to 105 holes, more preferably 50
to 104 holes and further preferably 102 to 103 holes are
required.
Normally, the material of the perforated
plate is preferably metal materials made of stainless
steel, carbon steel, hastelloy, nickel, titanium,
chromium and other alloys.
Examples of the method for discharging the
polymerization intermediate through such a perforated
plate include a method in which the material is made to
fall by a liquid head or under its own weight, and a
method in which the material is squeezed out under
pressure using a pump or the like. It is preferable
that the polymerization intermediate is squeezed out
using a pump, such as a gear pump, having a metering
capability for inhibiting variations in the amount of
the falling polymerization intermediate.
A filter is preferably provided in a channel
on the upstream side from the perforated plate. By the

filter, foreign matters clogging holes of the
perforated plate can be removed. The type of filter is
appropriately selected so that foreign matters having a
size equal to or greater than that of the hole of the
perforated plate can be removed, and the filter is not
damaged by passage of the polymerization intermediate.
For the filter, for example, the filtration
accuracy is preferably in the range of 0.2 to 200 um.
The filtration accuracy is an index representing the
size of a particle of minimum size removable by the
filter. The filtration accuracy is preferable 0.2 |jm
or greater in terms of the frequency of replacement due
to the clogging of the filter, and is preferably 200 \im
or less in terms of the size of foreign matters
perceived by the human eye. The filtration accuracy of
the filter is more preferably in the range of 0.5 to
180 nm, further preferably in the range of 1 to 150 fim,
especially preferably in the range of 3 to 120 |im, most
preferably in the range of 5 to 100 {im, and especially
most preferably in the range of 10 to 80 um.
The temperature of the filter is preferably
in the range of a temperature lower by 20°C than the
crystalline melting point of the polymerization
intermediate made to pass through the filter to a
temperature higher by 100°C than the crystalline melting
point of the polymerization intermediate. If the
polymerization intermediate shows no crystalline
melting point, the filter temperature is preferably in

the range of the higher of 100°C or a temperature at
which the polymerization intermediate is evaluated at a
shear velocity of 1000 (sec-1) is 100000 (poise) or
greater, to 350°C. A temperature equal to or higher
than the lower limit of the ranged described above is
preferable in terms of prevention of adverse effects on
product quality and damage of the filter due to shear
heat generation occurring when the polymerization
intermediate passes through the filter. A temperature
equal to or lower than the upper limit of the range
described above is preferable in terms of prevention of
adverse effects on product quality due to the heating
of the polymerization intermediate in the filter. The
temperature of the filter is more preferably is in the
range of a temperature lower by 10°C than the
crystalline melting point of the polymerization
intermediate to a temperature higher by 90°C than the
crystalline melting point of the polymerization
intermediate. The temperature is further preferably in
the range of a temperature lower by 10°C than the
crystalline melting point of the polymerization
intermediate to a temperature higher by 80°C than the
crystalline melting point of the polymerization
intermediate, especially preferably in the range of a
temperature lower by 10°C than the crystalline melting
point of the polymerization intermediate to a
temperature higher by 70°C than the crystalline melting
point of the polymerization intermediate, and most

preferably in the range of a temperature lower by 10°C
than the crystalline melting point of the
polymerization intermediate to a temperature higher by
60°C than the crystalline melting point of the
polymerization intermediate.
Examples of the material of the polymer
filter may include wire nets, metallic powder sintered
bodies, metallic fiber sintered bodies and sintered
metal stacked wire nets. Among them, nonwoven sintered
bodies composed of stainless steel long fibers are
preferable. Examples of the shape of the filter
include a candle shape, a cylindrical shape, a
cylindrical shape with a pleat, a disc shape and a leaf
disc shape.
A filter may also be provided on extraction
side of the polymerization reactor of the present
invention, but the filtration accuracy of the filter
preferably exceeds 10 (xm. If the filtration accuracy
is less than 10 |im, the polymer is degenerated due to
shear heat generation. More preferable is 20 fxm or
greater, and further preferable is 30 jam or greater.
By making the polymerization intermediate
pass through the filter under the above conditions when
its viscosity is still low, very small foreign matters
can be removed without causing significant shear heat
generation to occur even if a filter with a relatively
low filtration accuracy (aperture) is used. In this
way, surface roughing such as fisheye can be prevented

when the obtained resin is molded into a bottle, sheet
or the like. The feed pressure for filtration can be
reduced, and the filtration area can be reduced.
Therefore, the structure is simplified, thus making it
possible to reduce the size.
By making the polymerization intermediate
pass through the filter when its viscosity is still low
in this way, control of the temperature of a filter
portion is facilitated. Further, degeneration of the
polymer due to shear generation (coloring of the
product, surface roughing of the product due to
occurrence of foreign matters, rise in pressure of the
resin due to occurrence of foreign matters, and the
like) is insignificant, and a rise in feed pressure is
low compared to an increase in degree of clocking of
the filter. Therefore, a stable operation can be
performed over a long time period.
In the polymerization reactor of the present
invention, polymerization can be carried out at a low
temperature close to the melting point of the resin,
and productivity is extremely high, and therefore no
fine foreign matters newly occur within the
polymerization reactor. Therefore, the filter should
be placed only in the upstream of the feed opening of
the polymerization reactor of the present invention,
and it is not necessary at all to provide a filter on
the extraction port side of the polymerization reactor.
It is not necessary to make a highly polymerized

polymer on the extraction port side of the
polymerization reactor pass through a polymer filter
having a small aperture. Therefore, a high-quality
resin and formed material having reduced degeneration
such as coloring due to shear heat generation and an
increase in content of acetaldehyde polymer after
extraction from the polymerization reactor can be
produced.
In contrast to this, in the conventional
polymerization reactor, the polymerization temperature
is higher and the residence time in the polymerization
reactor is longer, and therefore product quality is
inevitably degraded unless a polymer filter is provided
on the extraction port side of the polymerization
reactor.
(III-2) Support
The polymerization intermediate discharged
through holed of the perforated plate falls along a
support. Examples of the specific structure of the
support include "wire" shape; "chain shape" and
"lattice shape (wire net shape)" having a wire-shaped
material combined; "space lattice shape" having a wire-
shaped material coupled like so called a jungle gym;
"thin plate shape" being flat or curved; and
"perforated plate shape." In addition, it is
preferable for efficiently extracting reaction
byproducts, impurities generated by thermal
decomposition, and the like, the surface area of the

resin made to fall is increased, the resin is made to
fall along a support having irregularities (concavities
and convexities) along a direction in which the
polymerization intermediate falls to cause stirring and
surface update to actively occur. A support having a
structure hindering the resin from falling, such as
"wire shape having irregularities along the direction
in which the resin falls," is also preferable. These
supports may be used in combination.
The "wire shape" represents a material in
which the ratio of a length along a direction vertical
to a cross section to an average length of the outer
periphery of the cross section is very high. The area
of the cross section is not specifically limited, but
it is usually in the range of 10"3 to 102 cm2, preferably
in the range of 10~3 to 101 cm2, and especially
preferably in the range of 10~2 to 1 cm2. The shape of
the cross section is not specifically limited, and is
usually selected from shapes such as a circular shape,
an elliptic shape, a triangular shape, a rectangular
shape, a polygonal shape and a star shape. The shape
of the cross section is either fixed or varied along
the lengthwise direction. Wires include hollow wires.
The wire is either a single wire having a wiry shape or
the like or multiple wires combined by a method such as
stranding. Examples of the surface of the wire include
a flat surface, a surface having irregularities, a
surface having partially protrusions or the like.

The "chain shape" represents a material
having rings made of the above described wire material
coupled together. Examples of the shape of the ring
include a circular shape, an elliptic shape, a
rectangular shape and a quadrate form. The way of
coupling is any of one-dimensional coupling, two-
dimensional coupling and three-dimensional coupling.
The "lattice shape (wire net shape)
represents a material having the above-described wire-
shaped material combined into a lattice shape. The
wire to be combined is either linear or a curved, and
an angle of combination may be freely selected. The
ration of the area of the material to space when the
lattice-shaped (wire net-shaped) material is projected
onto the surface in a vertical direction is not
specifically limited, but it is usually in the range of
1:0.5 to 1:1000, preferably in the range of 1:1 to
1:500, and especially preferably in the range of 1:5 to
1:100. The ratio of the area is preferably 1:1 in a
horizontal direction, and is preferably 1:1 or such
that the ratio of space becomes greater in the lower
part in a vertical direction.
The "space lattice shape" represents a
material having the wire-shaped material combined
three-dimensionally into a space lattice shape like so
called a jungle gym. The wire to be combined is either
linear or curved, and an angle of combination may be
freely selected.

The "wire shape having irregularities along a
direction in which the polymer halls" represents a
material having a stick having a circular cross section
or polygonal cross section attached to the wire, or a
material having a disc or cylinder attached to the
wire. The step of irregularities is preferably 5 mm or
greater. Specific examples include a wire with discs
in which a wire extends through a disk having a size
larger by 5 mm or greater than the wire size and nor
larger than 100 mm and a thickness of 1 to 50 mm, and
the distance between the discs is in the range of 1 to
500 mm.
The volume ratio of the volume of the support
placed in the reaction vessel to space of the reaction
vessel is not specifically limited, but it is usually
in the range of 1:0.5 to 1:107, preferably in the range
of 1:10 to 1:106, and especially preferably in the range
of 1:50 to 1:105. The volume ratio of the volume of the
support to space of the reaction vessel is preferably
1:1 in a horizontal direction, and is preferably 1:1 or
such that the ratio of space of the reaction vessel
becomes greater in the lower part in a vertical
direction.
Provision of a single support or provision of
multiple supports may be appropriately selected
according to the shape. In the case of "wire shape"
and "chain shape," the number of supports is usually in
the range of 1 to 105, and preferably in the range of 3

to 104. In the case of "lattice shape," "two-
dimensional ly coupled chain shape," "thin plate shape"
and "perforated plate shape," the number of supports is
usually in the range of 1 to 104, and preferably in the
range of 2 to 103. In the case of "three-dimensionally
coupled chain shape" and "space lattice shape,"
providing a single support or dividing the support into
multiple supports may be appropriately selected
considering the size of the apparatus, installation
space and the like.
In the case of multiple supports, it is
preferable that a spacer or the like is appropriately
used so that supports are not in contact with one
another.
The material of the support is not
specifically limited, but it is usually selected from
stainless steel, carbon steel, hastelloy, titanium and
the like. The wire may be subjected to various surface
treatments such as plating, lining, passivation
processing and acid cleaning.
In the present invention, the polymerization
intermediate is usually fed through one or more hole of
the perforated plate for one support, but the number of
holes may be appropriately selected according to the
shape of the support. The polymerization intermediate
which has passed through one hole can be made to fall
along a plurality of supports.
The position of the support is not

specifically limited as long as it allows the
polymerization intermediate to fall along the support.
For the method for attaching the support to the
perforated plate, a method in which the hole of the
perforated plate is perorated to place the support or a
method in which the support is placed in the lower part
of the hole of the perforated plate without perforating
the hole may be appropriately selected.
The height at which the polymerization
intermediate which has passed through the hole falls
along the support is preferably in the range of 0.5 to
50 m, further preferably in the range of 1 to 20 m, and
more preferably in the range of 2 to 10 m.
(III-3) Heating apparatus
The polymerization temperature can be
appropriately set by controlling the temperature of a
heater or heat medium jacket placed on the surface of
the wall of the polymerization reactor covering the
support, or putting a heater or heat medium in the
interior of the support and controlling the temperature
thereof.
(III-4) Pressure reducing apparatus
The degree of a reduced pressure of the
polymerization reactor can be appropriately set by
connecting an evacuation port placed at any location in
the polymerization reactor to a vacuum line and
controlling the degree of the reduced pressure. From
the evacuation port, impurities produced by thermal

decomposition during polymerization, an inert gas
introduced into the polymerization reactor as
necessary, and the like are discharged.
(III-5) Inert gas feeding apparatus
If an inert gas is introduced directly into
the polymerization reactor for the purpose of carrying
out a reaction under an inert gas atmosphere under a
reduced pressure, the inert gas can be fed through an
inlet placed at any location in the polymerization
reactor. The position of the inert gas inlet is
preferably distant from the perforated plate, and close
to the extraction port for the resin. It is also
preferably away from the evacuation port.
Alternatively, the polymerization intermediate can be
made to absorb and/or contain an inert gas in advance.
In this case, an inert gas feeding apparatus is
additionally provided in the upstream in the
polymerization reactor.
The inert gas feeding apparatus uses, for
example, a method in which a publicly known absorption
apparatus such as a packed tower type absorption
apparatus, shelf type absorption apparatus or spray
tower type absorption apparatus described in Chemical
Apparatus Design/Operation Series No. 2, Revised Gas
Absorption, pp. 49-54 (issued by Kagaku Kogyo Ltd. at
March 15, 1981) is used, a method in which an inert gas
is injected into a pipe through which the
polymerization intermediate is transferred, or the

like. Most preferable is a method in which an
apparatus making the polymerization intermediate absorb
an inert gas while it falls along the support under an
inert gas atmosphere is used. In this method, an inert
gas having a pressure higher than that in the interior
of the polymerization reactor is introduced into an
apparatus absorbing the inert gas. The pressure at
this time is preferably in the range of 0.01 to 1 MPa,
more preferably in the range of 0.05 to 0.5 MPa, and
further preferably in the range of 0.1 to 0.2 MPa.
(IV) Explanation of the polymerization method
according to the present invention
The present inventors found the following:
surprisingly, when an intermediate for polymerization
having a polymerization degree in the above-mentioned
polymerization degree range is polymerized in the
above-mentioned polymerization reactor in the ranges of
polymerization temperature and degree of vacuum
described hereinafter, the deterioration in quality of
a resin by fouling of the nozzle surface and the wall
surfaces of the polymerization reactor can be
suppressed by preventing spattering of the intermediate
for polymerization caused by vigorous foaming just
under a perforated plate; and there is caused such a
phenomenon that the resin dropped along a support
contains a large amount of bubbles, resulting in
"extension of the surface area of the resin" and
"rolling-down of the resin in a form of bubble

agglomerates or in a form of bubble balls". At the
same time, the present inventors confirmed a marked
increase in the polymerization velocity and the
improvement of hue of the resin.
It is conjectured that the marked increase in
the polymerization velocity is due to the synergistic
effect of the extension of the surface area by the
incorporation of a large volume of water and the
surface renewal by the plasticizing effect of bubbles.
The plasticizing effect of bubbles has made it possible
to improve the hue of the resin by reducing the
residence time of the resin in the polymerization
reactor and take out the highly viscous resin with a
high polymerization degree easily from the
polymerization reactor.
A conventional gravity-type molten-thin-film
polymerization reactor such as a wetted-wall column is
designed to polymerize an intermediate for
polymerization obtained in the initial reaction and
having a low degree of coloring and a polymerization
degree much lower than that in the method according to
the present invention, at a higher temperature and a
shorter resistance time as compared with the method
according to the present invention, in order to obtain
a resin having a high polymerization degree and a high
quality. From a commonsense standpoint, it has been
considered that when an intermediate for polymerization
having a high polymerization degree and a high melt

viscosity as in the method according to the present
invention is continuously melt-polymerized, coloring
proceeds remarkably and moreover, the residence time
during dropping of a resin in a polymerization reactor
is extremely increased. Therefore, it has been not
conceivable at all that a resin with a high quality can
be produced.
On the other hand, in the present invention,
the range of the melt viscosity of an intermediate for
polymerization is set at a rather high melt viscosity
range in contrast to conventional common sense as
described above, and moreover, the polymerization
temperature is set at a low temperature in contrast to
conventional common sense. The present inventors found
that by employing these conditions, the following
surprising effects can be obtained: the foamed state of
a resin can be controlled, the polymerization velocity
can be greatly increased at a low temperature rather
than at a high temperature, and a resin having a high
polymerization degree can easily be taken out.
(IV-1) Polymerization temperature
The polycondensation reaction temperature is
preferably (the crystalline melting point of the
polyester resin - 10°C) or more and (the crystalline
melting point + 30°C) or less. The adjustment of the
reaction temperature to (the crystalline melting point
- 10°C) or more makes it possible to prevent the
solidification of reactants and the increase of the

reaction time. The adjustment of the reaction
temperature to (the crystalline melting point + 30°C) or
less makes it possible to suppress thermal
decomposition and produce a resin having an excellent
hue. The temperature is more preferably (the
crystalline melting point - 5°C) or more and (the
crystalline melting point + 25°C) or less, still more
preferably the crystalline melting point or more and
(the crystalline melting point + 20°C) or less. The
reason why such a relatively low reaction temperature
is preferable in the present invention is that it
easily allows the resin to contain a large amount of
bubbles and hence makes it possible to increase the
polymerization velocity greatly.
In general, polymer resins have a
temperature-drop crystallization temperature
considerably lower than their crystalline melting
point. It is known that particularly in the case of
slightly crystalline resins among them, the difference
between the temperature-drop crystallization
temperature and the crystalline melting point is as
large as tens degrees. Polyester resins and their
intermediates for polymerization also have a low
temperature-drop crystallization temperature and hence
can be handled even at a temperature 10°C lower than
their crystalline melting point.
Here, the term "crystalline melting point"
means the peak temperature of an endothermic peak due

to melting of crystals measured under the following
conditions with Pyris 1 DSC (an input compensation type
differential scanning colorimeter) manufactured by
Perkin-Elmer Corporation. The peak temperature was
determined by the use of attached analysis software.
Measuring temperature: 0 to 300°C.
Heating rate: 10°C/ min.
On the other hand, in the case of slightly
crystalline or non-crystalline polyester resins for
which no endothermic peak due to melting of crystals is
observed, polymerization is preferably carried out at a
temperature not higher than 290°C and not lower than the
higher of the following two temperatures: 100°C and a
temperature at which the melt viscosity of the
polyester resin taken out of the polymerization reactor
is 100,000 (poise) or more when the resin is evaluated
at a shear rate of 1,000 (sec-1). When the
polymerization temperature is within the above range,
the resin is satisfactorily foamed, so that
polymerization can be carried out while dropping the
resin at a short residence time. On the other hand,
the quality is hardly deteriorated by thermal
decomposition. The polymerization temperature is more
preferably not higher than 280°C and not lower than the
higher of the following two temperatures: 150°C and a
temperature at which the melt viscosity of the
polyester resin taken out of the polymerization reactor
is 100,000 (poise) or more when the resin is evaluated

at a shear rate of 1,000 (sec-1). The polymerization
temperature is still more preferably not higher than
270°C and not lower than the higher of the following two
temperatures: 190°C and a temperature at which the melt
viscosity of the polyester resin taken out of the
polymerization reactor is 100,000 (poise) or more when
the resin is evaluated at a shear rate of 1,000 (sec-1).
(IV-2) Polymerization pressure
The melt polycondensation reaction according
to the present invention should be carried out under
reduced pressure also for allowing a resin to contain a
large amount of bubbles. The degree of vacuum (i.e.,
the degree of a reduced pressure) is properly
controlled depending on the sublimed states of an
intermediate for polymerization and reactants for
polycondensation and the reaction rate. The degree of
vacuum is preferably 50,000 Pa or less, more preferably
10,000 Pa or less, still more preferably 1,000 Pa or
less, particularly preferably 500 Pa or less. Although
the lower limit of the degree of vacuum is not
prescribed, the degree of vacuum is preferably 0.1 Pa
or more from the viewpoint of, for example, the scale
of an equipment for evacuating the polymerization
reactor.
The following is also a preferable method: a
small amount of an inert gas having no undesirable
influence on the polycondensation reaction is
introduced into the polymerization reactor under

reduced pressure, and for example, polymerization by-
products and impurities produced by thermal
decomposition during the polymerization are removed in
company with the gas.
The introduction of an inert gas into a
polymerization reactor has been considered as an
operation for allowing the reaction to proceed
advantageously by reducing the partial pressure of
polymerization by-products to displace the equilibrium.
However, the amount of an inert gas introduced in the
present invention may be very small, and an effect of
increasing the polymerization velocity by the partial
pressure reduction is so small that it is hardly
expectable. Such a role of the inert gas cannot be
explained by the conventional way of understanding.
As a result of investigation by the present
inventors, the following was observed: surprisingly,
the foaming phenomenon of an intermediate for
polymerization dropping in a molten state along a
support is intensified by the introduction of the inert
gas into the polymerization reactor, so that the
surface area of the intermediate for polymerization is
greatly increased and that the surface renewal state of
the intermediate is extremely improved. Although the
principle of this fact is not clear, it can be
speculated that the change of the interior and surface
profile of the intermediate for polymerization causes a
marked increase in the polymerization velocity.

The inert gas introduced is preferably a gas
having no undesirable influence (e.g. coloring,
modification or decomposition) on the resin and
includes nitrogen, argon, helium, carbon dioxide, lower
hydrocarbon gases, and mixed gases thereof. As the
inert gas, nitrogen, argon, helium and carbon dioxide
are more preferable. Of these, nitrogen is especially
preferable because of its easy availability.
The amount of the gas introduced in the
present invention may be very small and is preferably
0.05 to 100 mg per g of a resin to be taken out of the
polymerization reactor. When the amount of the inert
gas is adjusted to 0.05 mg or more per g of the resin
to be taken out, foaming of resin becomes sufficient,
so that the improving effect on the polymerization
degree is enhanced. On the other hand, when the amount
of the inert gas is adjusted to 100 mg or less, it
becomes easy to attain a high degree of vacuum. The
amount of the inert gas is more preferably 0.1 to 50
mg, particularly preferably 0.2 to 10 mg, per g of the
resin to be taken out.
As a method for introducing the inert gas,
there can be exemplified a method of directly
introducing the inert gas into the polymerization
reactor; a method of previously allowing an
intermediate for polymerization to absorb and/or
contain the inert gas and releasing the absorbed and/or
contained gas from the intermediate for polymerization

under reduced pressure to introduce the inert gas into
the polymerization reactor; and a method comprising a
combination of the above two methods. Here, the term
"absorb" means the case where the inert gas is
dissolved in a resin and is not present as bubbles.
And the term "contain" means the case where the inert
gas is present as bubbles. When the inert gas is
present as bubbles, the bubbles are preferably as small
as possible. The average diameter of the bubbles is
preferably 5 mm or less, more preferably 2 mm or less.
(IV-3) Polymerization time
The polymerization time is the sum of a time
required for dropping a resin along a support and the
residence time of the resin in the bottom of the
polymerization reactor. The polymerization time ranges
preferably from 10 seconds to 100 hours, more
preferably from 1 minute to 10 hours, still more
preferably from 5 minutes to 5 hours, particularly
preferably from 20 minutes to 3 hours, most preferably
30 minutes to 2 hours.
As a process for producing the polyester
resin of the present invention, there can be
exemplified a process of continuously feeding an
intermediate for polymerization in a molten state into
the polymerization reactor through a material feed
opening, polymerizing the intermediate while dropping
the intermediate along a support from the holes of a
perforated plate, and continuously taking out the whole

of the dropped resin from the polymerization reactor;
and a process of recycling a portion of the dropped
polymer and subjecting it to polymerization while
dropping it along the support. The process of taking
out the whole of the dropped resin is preferable. When
a portion of the dropped polymer is recycled and then
subjected to polymerization while being dropped along
the support, it is preferable to reduce the residence
time in a liquid receiver, a recycling line and the
like and lower the temperature, in order to prevent
thermal decomposition from occurring in these places
after the dropping along the support. Also in the
process of taking out the whole of the dropped resin,
it is preferable to reduce the residence time in the
bottom of the polymerization reactor, a taking-out
piping and the like in order to prevent thermal
decomposition from occurring in these places.
(IV-4) Polymerization rate
The polymerization capability of the
polymerization rector according to the present
invention is characterized in that when wire-like
supports are used, the design of scale-up is easy
because the polymerization capability can be enhanced
in proportion to the number of the supports set in the
polymerization reactor.
In the case of the wire-like supports, the
flow rate of an intermediate for polymerization per
support is preferably 10~2 to 102 liters/hr. By

adjusting the flow rate to a value in this range, a
sufficient production capacity can be assured and the
polymerization velocity can be greatly increased. The
flow rate is more preferably 0.1 to 50 liters/hr.
In the case of a support obtained by braiding
wires, such as a lattice-like (wire-net-like) support,
the flow rate is preferably 10~2 to 102 liters/hr, more
preferably 0.1 to 50 liters/hr, per vertical wire
structure constituting the support.
In the case of a support having a structure
other than a structure formed by braiding wires, such
as a thin-plate-like support, the flow rate is
preferably 10~2 to 102 liters/hr, more preferably 0.1 to
50 liters/hr, per hole of a perforated plate for
feeding an intermediate for polymerization to the
support.
(IV-5) Molecular weight regulator
In the present invention, if necessary, an
intermediate for polymerization may be reacted with any
amount of a molecular weight regulator in any step
before the feed of the intermediate for polymerization
into the polymerization rector according to the present
invention. The present inventors found the following:
the rate of dropping of the intermediate for
polymerization along a support can be drastically
changed by changing the molecular weight of the
intermediate for polymerization to be fed into the
polymerization rector according to the present

invention; and by this dropping rate change, the
residence time in the polymerization reactor can be
controlled, so that the quality (e.g. polymerization
degree) and output of the polyester resin produced can
easily be controlled in wide ranges.
As the molecular weight regulator, a
molecular weight reducing agent or a molecular weight
increasing agent is used. In the present invention, by
using the molecular weight regulator, the quality (e.g.
polymerization degree) and output of the polyester
resin can be adjusted in such wide ranges that the
adjustment cannot be achieved in conventional
polymerization processes at all.
For example, when a molecular weight reducing
agent is used, the polymerization degree of the
polyester resin produced in the polymerization rector
according to the present invention can be greatly
reduced merely by adding a relatively small amount of
the molecular weight reducing agent. This is because
the molecular weight reducing agent has not only its
intrinsic effect but also the effect of reducing the
reaction time by increasing the rate of dropping of the
intermediate for polymerization along the support.
That the polymerization degree of the polyester resin
produced can be greatly reduced is synonymous with that
the output can be greatly reduced. On the other hand,
in conventional polymerization methods, only the effect
intrinsic to the molecular weight reducing agent is

obtained, so that the polymerization degree of the
polyester resin is reduced only to an extent
corresponding to the amount of the molecular weight
reducing agent added. Therefore, a large amount of the
molecular weight reducing agent should be added for
adjusting the molecular weight in a wide range, so that
the conventional polymerization methods are
disadvantageous also from the viewpoint of handling,
cost and product quality.
On the other hand, when a molecular weight
increasing agent is used, the polymerization degree of
the polyester resin produced in the polymerization
rector according to the present invention can be
greatly increased merely by adding a relatively small
amount of the molecular weight increasing agent. This
is because the molecular weight increasing agent has
not only its intrinsic effect but also the effect of
increasing the reaction time by reducing the rate of
dropping of the intermediate for polymerization along
the support. That the polymerization degree of the
polyester resin produced can be greatly increased is
synonymous with that the output can be greatly
increased. On the other hand, in conventional
polymerization methods, only the effect intrinsic to
the molecular weight increasing agent is obtained, so
that the polymerization degree of the polyester resin
is increased only to an extent corresponding to the
amount of the molecular weight increasing agent added.

Therefore, a large amount of the molecular weight
increasing agent should be added for adjusting the
molecular weight in a wide range, so that the
conventional polymerization methods are disadvantageous
also from the viewpoint of handling, cost and product
quality.
When the molecular weight of the intermediate
for polymerization fed from a step of producing the
intermediate for polymerization varies, the varied
state can be detected and on the basis of the detection
result, the molecular weight regulator can be added to
the intermediate for polymerization in a step prior to
the feed of the intermediate for polymerization into
the polymerization reactor. It is also possible to
absorb the variation of the molecular weight by the
addition of the regulator and introduce the
intermediate for polymerization varied little in
molecular weight, into the polymerization reactor.
The molecular weight regulator can be reacted
with the intermediate for polymerization in any step
prior to the feed of the intermediate for
polymerization into the polymerization reactor. This
reaction may be carried out in a reactor separately
provided. It is also possible to introduce the
molecular weight regulator into a piping for feeding
the intermediate for polymerization and carry out the
reaction in the piping. It is also preferable to adopt
a method in which the mixing and reaction of the

molecular weight regulator are accelerated by utilizing
a kneading apparatus having a driving portion (e.g. an
extruder) or a static mixer.
As the molecular weight reducing agent, known
molecular weight reducing agents used for the
depolymerization or molecular weight reduction of a
polyester resin may be properly used. It is also
preferable to utilize as the molecular weight reducing
agent the above-exemplified starting monomer, an
intermediate for polymerization with a lower molecular
weight collected in a step nearer to the starting
material, or a compound produced as a by-product by
polycondensation reaction.
There can be used, for example, one member or
a mixture of two or more members selected from the
group consisting of compounds formed by direct bonding
of one or two hydroxyl groups to an aliphatic
hydrocarbon group of 1 to 30 carbon atoms, such as
ethylene glycol, 1,3-propanediol, 1,4-propanediol,
neopentyl glycol, 1,6-hexamethylene glycol, 1,4-
cyclohexanediol, methanol, ethanol, propanol, butanol,
benzyl alcohol, etc.; alkylene glycols such as
diethylene glycol, triethylene glycol, tetraethylene
glycol, dipropylene glycol, tripropylene glycol, etc.,
water, and compounds formed by direct bonding of one or
two carboxyl groups to an aromatic hydrocarbon group of
6 to 30 carbon atoms, such as terephthalic acid,
isophthalic acid, naphthalenedicarboxylic acid, 5-

sodium sulfoisophthalate, tetramethylphosphonium
benzenesulfonate 3,5-dicarboxylate, etc.; compounds
formed by direct bonding of one or two carboxyl groups
to an aliphatic hydrocarbon group of 1 to 30 carbon
atoms, such as formic acid, acetic acid, propionic
acid, butanoic acid, oxalic acid, succinic acid, adipic
acid, dodecanedioic acid, fumaric acid, maleic acid,
1,4-cyclohexanedicarboxylic acid, etc.; and compounds
formed by direct bonding of a hydroxyl group and a
carboxyl group to an aliphatic hydrocarbon group of 1
to 30 carbon atoms, such as lactic acid, glycolic acid,
etc., and compounds formed by the esterification of the
carboxyl group of each of these compounds with a lower
alcohol.
In addition, the following methods may also
be adopted: a method in which the increase of the
molecular weight is suppressed by inhibiting
polycondensation reaction by the addition of a compound
capable of inhibiting the action of a polymerization
catalyst, such as water, trimethyl phosphate or the
like; a method in which not only the reduction of the
molecular weight but also the suppression of the
increase of the molecular weight are achieved by adding
a compound having a single functional group or a low
reactivity which can be used as a reactive-end-blocking
agent; and a method in which polycondensation reaction
is inhibited by lowering the temperature of the
intermediate for polymerization by adding intermediate

for polymerization of a lower temperature or mixing a
portion of intermediate for polymerization locally
adjusted to a lower temperature with the other portion.
The molecular weight increasing agent is not
particularly limited so long as it increases the
molecular weight of the intermediate for polymerization
when added. The molecular weight can be increased also
by exchange reaction by adding, for example, an
intermediate for polymerization with a higher molecular
weight collected in a step nearer to the product, a
high-molecular weight polyester resin as product, or a
high-molecular weight polyester resin produced by
another polymerization technique such as solid-state
polycondensation. More specifically, there can be
adopted one method or a combination of two or more
methods selected from the group consisting of, for
example, a method in which the molecular weight is
increased by partial crosslinking reaction by adding a
compound having three or more functional groups and
capable of undergoing condensation reaction, such as
glycerol, pentaerythritol, sorbitol, 1,2,4-
benzenetricarboxylic acid, citric acid or the like; a
method in which the molecular weight is increased by
accelerating polycondensation reaction by addition (or
addition in an amount larger than a usual adding
amount) of a compound capable of catalyzing
polymerization and containing titanium, germanium,
antimony, tin, aluminum or cobalt, such as titanium

oxide, titanium tetrabutoxide, titanium
tetraisopropoxide, a titanium halide, a hydrolyzate
obtained by hydrolysis of a titanium alkoxide,
germanium oxide, germanium isopropoxide, a hydrolyzate
obtained by hydrolysis of a germanium alkoxide,
antimony oxide, tin acetate, tin 2-ethylhexanoate,
aluminum acetate, aluminum propionate, aluminum
lactate, aluminum chloride, aluminum hydroxide,
aluminum carbonate, aluminum phosphate, aluminum
ethoxide, aluminum isopropoxide, aluminum
acetylacetonate, cobalt acetate or the like.; a method
in which the molecular weight is increased by
accelerating polycondensation reaction by raising the
temperature of the intermediate for polymerization by
adding intermediate for polymerization heated to a
higher temperature or mixing a portion of intermediate
for polymerization locally heated to a higher
temperature with the other portion.
(IV-6) Combination of the polymerization method
according to the present invention and a solid-state
polycondensation technique
A method comprising pelletizing the polyester
resin produced by the above-mentioned polymerization
method according to the present invention, introducing
the pellets into a solid-state polycondensation reactor
and then subjecting the pellets to solid-state
polycondensation at a temperature of 190°C to 230°C, is
also preferable for producing a polyester resin having

a high polymerization degree and a high quality.
Since pellets conventionally used as a
starting material in solid-state polycondensation are
produced by a conventional melt polymerization
technique, the intrinsic viscosity [n] of the starting
pellets has been at most 0.5 dl/g. The reason is as
follow: in the case of the conventional melt
polymerization technique, when an attempt is made to
increase the polymerization degree to a value higher
than the above value, polycondensation reaction and
thermal decomposition reaction proceed in parallel with
each other because of a high polymerization
temperature, so that the hue of the product is
extremely deteriorated. There has also been the
following problem: the amount of carboxyl group at the
end of the polymer is increased by the thermal
decomposition reaction, resulting in a deteriorated
productivity in a solid-state polycondensation step or
a deteriorated quality of the product.
As other problems in a combination of the
conventional melt polymerization technique and a solid-
state polycondensation technique, the following
problems can be exemplified: a problem that in the case
of the conventional melt polymerization technique, the
intrinsic viscosity [n] of the starting pellets is low
for the above-mentioned reason, so that the
crystallization degree of product pellets becomes very
high, resulting in marked quality deterioration during

melt processing; a problem that the molecular weight
distribution expressed as Mw/Mn becomes too wide, so
that only a nonuniform product can be obtained; a
problem that the amount of fine powder produced in a
solid-state polycondensation step is increased,
resulting in an increase in production process troubles
and troubles about product quality which produce
defects such as surface roughening (fish eye) of the
surface of a molded or shaped product; and a problem
that since the starting pellets has a high acetaldehyde
content, the acetaldehyde cannot be completely removed
during solid-state polycondensation, so that about 5
ppm of acetaldehyde remains in the product pellets.
On the other hand, in the case of a
combination of the polymerization technique according
to the present invention and a solid-state
polycondensation technique, starting pellets have a
high polymerization degree, a good hue and a small
amount of carboxyl group at the end of the polymer, so
that a high-quality polyester resin can be stably
produced at low cost by greatly improving the
productivity in a solid-state polycondensation step.
Moreover, since the intrinsic viscosity [n] of the
starting pellets can be increased, the crystallization
degree of product pellets does not exceed 55% and
quality deterioration is hardly caused during melt
processing. In addition, almost no fine powder is
produced, so that production process troubles and

troubles about product quality are hardly caused.
Because of a negligible amount of fine powder and the
high molecular weight of the starting material, a
uniform product having a narrow molecular weight
distribution expressed as Mw/Mn can be produced. Since
the acetaldehyde content of the starting pellets is
low, the acetaldehyde content of the product pellets is
very low. Furthermore, since a cyclic trimer is
incorporated into the main chain of the polymer as a
result of cyclic chain equilibration reaction, the
cyclic trimer content can be reduced. Thus, the above-
mentioned combination solves all the problems in the
method comprising a combination of a conventional melt
polymerization technique and a solid-state
polycondensation technique, to permit production of a
high-quality polyester resin, and hence is a preferable
method.
When the polymerization technique according
to the present invention is combined with a solid-state
polycondensation technique, the intrinsic viscosity [n]
of starting pellets produced by the polymerization
technique according to the present invention ranges
preferably from 0.4 to 1.5 dl/g, more preferably from
0.5 to 1.2 dl/g, still more preferably from 0.6 to 1
dl/g, particularly preferably from 0.7 to 0.9 dl/g. As
a pelletizing method, drying method, pre-
crystallization method, crystallization method and
solid-state polycondensation method for the starting

pellets, the methods described hereinafter and methods
based on a conventional solid-state polycondensation
technique can be adopted.
(IV-7) Process for producing a polyethylene
terephthalate resin having a reduced content of a
cyclic trimer
As described above, as a production process
of a polyethylene terephthalate resin with a cyclic
trimer content of 0.8 wt% or less as the production
process of a polyethylene terephthalate resin of the
present invention, there is a process in which an
intermediate of polyethylene terephthalate resin having
an intrinsic viscosity [n] of 0.2 to 2.0 dl/g and a
cyclic trimer content of 0.8 wt% or less is polymerized
under reduced pressure in the polymerization rector
according to the present invention while being dropped
along a support, at a temperature of (the crystalline
melting point of the intermediate for polymerization -
10°C) or more and (the crystalline melting point + 30°C)
or less. As another process, a process can be
exemplified in which a treatment is carried out for
reducing a cyclic trimer by 0.2% by weight or more in a
polyethylene terephthalate resin produced by the
polymerization method according to the present
invention. When either of these methods for reducing
the cyclic trimer content is practiced, the
intermediate for polymerization is preferably adjusted
so that the cyclic trimer content may be increased by

0.2% by weight or less when the intermediate is kept
melted at a temperature of 275°C for 30 minutes.
The reason why the cyclic trimer content of
the product can be reduced by the former method is as
follows. That is, in the polymerization method
according to the present invention, the polymerization
temperature is as low as near the crystalline melting
point. Therefore, although the equilibration reaction
of a cyclic trimer proceeds during polymerization, the
production rate of the cyclic trimer is slow and
moreover, the polymerization degree can be increased in
a short time. As a result, the cyclic trimer content
of the product is hardly increased. In addition, when
the polymerization method according to the present
invention is adopted, oligomers such as bis(p-
hydroxyethyl) terephthalate (BHET) can also be reduced
which accelerate the transfer of the cyclic trimer to a
mold and the surface of a molded or shaped product.
Therefore, a polyethylene terephthalate resin and its
molded or shaped product can desirably be produced
which hardly cause mold deposit and bleed out.
In the latter method, a method for the
treatment for reducing the cyclic trimer content of the
polyethylene terephthalate resin is not particularly
limited. As the treatment method, there can be
exemplified a method of removing the cyclic trimer
contained in the resin by extraction and/or volatile
elimination; a method of subjecting the resin produced

by the polymerization method according to the present
invention to solid-state polycondensation until the
cyclic trimer content is reduced to 0.8% by weight or
less; and a method of reacting the resin with a
compound containing an element such as tin or titanium,
which permits ring-opening polymerization of the cyclic
trimer, to reduce the cyclic trimer content to 0.8% by
weight or less.
The polyethylene terephthalate resin produced
by utilizing the polymerization reactor according to
the present invention has a high polymerization degree
and is excellent also in quality such as hue.
Therefore, this resin retains its polymerization degree
and quality even after being subjected to a procedure
for reducing the cyclic trimer, such as extraction, and
hence can be used in various articles such as vessels
for drinking. In addition, the resin has a low content
of oligomers such as bis ((3-hydroxyethyl) terephthalate
(BHET) which accelerate the transfer of the cyclic
trimer to a mold and the surface of a molded or shaped
products. Therefore, the resin is desirably
characterized in that it hardly causes problems such as
mold deposit and bleed out.
Since the problems such as mold deposit and
bleed out are further prevented by reducing the cyclic
trimer content of the resin, the cyclic trimer content
is preferably as low as possible. The cyclic trimer
content is preferably 0.7% by weight or less, more

preferably 0.6% by weight or less, particularly
preferably 0.5% by weight or less, most preferably 0.4%
by weight or less, in particular, 0.3% by weight or
less.
For further enhancing the effects of the
present invention, a method is preferable in which a
treatment is carried out for reducing a cyclic trimer
by 0.2% by weight or more in a polyethylene
terephthalate resin obtained by polymerizing an
intermediate for polymerization with a cyclic trimer
content of 0.8% by weight or less in the polymerization
reactor according to the present invention. Another
method is also preferable in which a treatment is
carried out for reducing a cyclic trimer by 0.2% by
weight or more in a polyethylene terephthalate resin
obtained by polymerizing, in the polymerization reactor
according to the present invention, an intermediate for
polymerization whose cyclic trimer content is increased
by 0.20% by weight or less when the intermediate is
kept melted at a temperature of 275°C for 30 minutes.
(IV-8) Method for further reducing acetaldehyde in a
polyethylene terephthalate resin produced by the
polymerization method according to the present
invention
In the present invention, a polyethylene
terephthalate resin satisfying the following
requirements at the same time is used as a starting
material: a crystallization degree of 35% or less and

an acetaldehyde content of 30 ppm or less, and this
resin is subjected to one or more treatments selected
from heat treatment, vacuum treatment and washing
treatment, whereby the treated polyethylene
terephthalate resin can be produced which has (U) a
crystallization degree of 55% or less, (V) a molecular
weight distribution expressed as Mw/Mn of 1.8 to 2.3,
and (W) an acetaldehyde content of 50% or less of the
acetaldehyde content of the starting polyethylene
terephthalate resin.
Here, the crystallization degree of the
starting polyethylene terephthalate resin is preferably
35% or less for reducing the acetaldehyde content more
easily (under easier conditions such as a lower
treatment temperature and a shorter treatment time).
The crystallization degree may be 0%, though when the
starting resin is in the form of pellets, its
crystallization degree is preferably 1% or more for
preventing the pellets from fusing together with one
another. The crystallization degree ranges more
preferably from 2 to 30%, particularly preferably from
2.3 to 25%, most preferably from 2.5 to 20%. When the
crystallization degree of the starting resin is more
than 35%, a high treatment temperature and a long
'treatment time are required for reducing acetaldehyde,
resulting in a high production cost. In addition, it
becomes difficult to reduce the acetaldehyde content to
5 ppm which is the same as the acetaldehyde content of

a solid-state polycondensation product. Moreover, the
treated polyethylene terephthalate resin has a high
crystallization degree and hence is undesirably liable
to be deteriorated in quality when molded or shaped.
The acetaldehyde content of the starting
polyethylene terephthalate resin is preferably 30 ppm
or less for reducing the acetaldehyde content under
easier conditions. The acetaldehyde content is more
preferably 25 ppm or less, still more preferably 20 ppm
or less, particularly preferably 15 ppm or less, most
preferably 10 ppm or less, in particular, 7 ppm or
less. Particularly when the acetaldehyde content of
the starting resin is 15 ppm or less, it becomes
possible surprisingly to reduce the acetaldehyde
content of the treated polyethylene terephthalate resin
to 2 ppm or less under easy conditions. Unexpectedly,
this value is lower than the acetaldehyde content of a
solid-state polycondensation product.
On the other hand, when the acetaldehyde
content of the starting resin is more than 30 ppm, a
high treatment temperature and a long treatment time
are required for reducing acetaldehyde. In addition,
it is difficult to reduce the acetaldehyde content to 5
ppm, which is the same as the acetaldehyde content of a
solid-state polycondensation product, even if the
treatment time is increased. Under such conditions,
the production cost is raised and moreover, the treated
polyethylene terephthalate resin has a high

crystallization degree and hence is undesirably liable
to be deteriorated in quality when molded or shaped.
Although the reason is not known in detail,
the following possibility is conjectured: when the
starting resin having a high acetaldehyde content of
more than 30 ppm is heat-treated, the resin is more
easily crystallized to a high degree and a site holding
acetaldehyde is formed in the resin, resulting in
difficult reduction of acetaldehyde.
On the other hand, the starting polyethylene
terephthalate resin used in the present invention has
an acetaldehyde content of as low as 30 ppm or less and
a crystallization degree of as low as 35% or less. It
can be speculated that since such a resin is used, a
site holding acetaldehyde is hardly formed in the resin
during the treatment, so that an acetaldehyde content
lower than that of a solid-state polycondensation
product can be attained under treatment conditions much
milder than solid-state polycondensation conditions.
A method for adjusting the crystallization
degree and acetaldehyde content of the starting
polyethylene terephthalate resin is not particularly
limited. From the viewpoint of resin quality and
production cost, it is most preferable to adopt a
method in which a polyethylene terephthalate resin
having an acetaldehyde content of 30 ppm or less in
spite of the adoption of a melt polymerization method
is produced in a polymerization reactor based on the

novel principle according to the present invention.
As to a method for further reducing
acetaldehyde in the polyethylene terephthalate resin
produced by the polymerization method according to the
present invention, the above-mentioned starting resin
is treated in a solid state by one or more methods
selected from heat treatment, vacuum treatment and
washing treatment.
For maintaining the solid state, the
treatment temperature should be lower than the
crystalline melting point of the resin. In addition,
for removing the acetaldehyde efficiently, the
treatment temperature is preferably higher than 21°C,
the boiling point of acetaldehyde. The treatment
temperature ranges more preferably from 30 to 220°C.
From the viewpoint of quality and cost, the treatment
temperature ranges further preferably from 140 to 220°C,
still more preferably from 140 to 200°C, particularly
preferably from 145 to 190°C, most preferably from 150
to 180°C.
The treatment temperature is preferably low
because the crystallization degree of the treated
polyethylene terephthalate resin is low, so that
acetaldehyde production and quality deterioration such
as hue deterioration can be suppressed during molding
or shaping. When the treatment is carried out at a
temperature of 200°C or lower, it is more advantageous
also in cost than solid-state polycondensation. The

treatment may be carried out at a constant temperature,
or with stepwise temperature rise or lowering, or with
repeated temperature rise or lowering, so long as the
treatment temperature is within the above range. When
the starting resin is in the form of pellets, it is
most preferable to adopt a method in which in order to
prevent the pellets from fusing together with one
another, the treatment temperature is gradually raised
and the treatment is completed finally in the range of
40 to 220°C, followed by cooling to ordinary
temperature.
The shape of the starting polyethylene
terephthalate resin at the time of the treatment for
reducing acetaldehyde is not particularly limited and
may be a definite shape, an indefinite shape, a powder
shape, a leaf shape or a pellet shape. It is
preferably a leaf shape in order to use the resin
produced according to the present invention, suitably
as a material for melt molding or melt shaping. The
shape of the pellets may be any shape, for example, a
cubic shape, a spherical shape, a cylindrical shape, a
flat cylindrical shape or a granular shape of go stone.
The size of the pellets is preferably
suitable for acetaldehyde-reducing treatment conditions
and molding or shaping conditions for the treated
resin. When the size is too small, the pellets are
liable to be nonuniform in size or are liable to fuse
together with one another during heating. On the other

hand, when the size is too large, the feed of the
pellets into a molding or shaping machine and the
treatment for reducing acetaldehyde become difficult.
When the pellets are cylindrical, the diameter and
height of the cylindrical pellets range preferably from
1 to 10 mm, more preferably from 1.5 to 8 mm, still
more preferably from 2 to 6 mm.
When the heat treatment is carried out, it
may be carried out in the above-mentioned temperature
range in an atmosphere of an inert gas (e.g. air or
nitrogen); or while introducing an inert gas (e.g. air
or nitrogen); or under pressure or reduced pressure in
an atmosphere of an inert gas (e.g. air or nitrogen).
In order to suppress quality deterioration such as
polymerization degree lowering during the treatment,
the heat treatment is preferably carried out in an
atmosphere of an inert gas (e.g. dry air or dried
nitrogen); or while introducing an inert gas (e.g. dry
air or dried nitrogen); or under pressure or reduced
pressure in an atmosphere of an inert gas (e.g. dry air
or dried nitrogen). The heat treatment is most
preferably carried out while introducing a dried inert
gas.
Although depending on the treatment
temperature, the heat treatment time is preferably 10
minutes or more for effective reduction of acetaldehyde
and is preferably 15 hours or less from the viewpoint
of production cost. The heat treatment time ranges

more preferably from 15 minutes to 10 hours,
particularly preferably from 20 minutes to 6 hours,
most preferably from 30 minutes to 4 hours. During the
treatment, the starting resin may be in a standing
state. Alternatively, the starting resin may be in a
stirred, suspended or flowing state in order to
suppress the fusion.
When the vacuum treatment is carried out, it
is preferable for effective reduction of acetaldehyde
to carry out the vacuum treatment in the above-
mentioned temperature range under a reduced pressure of
100,000 Pa or less in an atmosphere of an inert gas
such as air or nitrogen, preferably in an atmosphere of
an inert gas such as dry air or dried nitrogen.
Although depending on the scale, the treatment pressure
is preferably 5 Pa or more from the viewpoint of the
cost of equipment. The treatment pressure ranges more
preferably from 10 to 80,000 Pa, still more preferably
from 20 to 50,000 Pa, particularly preferably from 30
to 10,000 Pa, most preferably from 40 to 5,000 Pa, in
particular, from 50 to 2,000 Pa.
Although depending on other conditions, the
vacuum treatment time is preferably 10 minutes or more
for effective reduction of acetaldehyde and is
preferably 15 hours or less from the viewpoint of
production cost. The vacuum treatment time ranges more
preferably from 15 minutes to 10 hours, particularly
preferably from 20 minutes to 6 hours, most preferably

from 30 minutes to 4 hours. During the treatment, the
starting PET resin may be in a standing state.
Alternatively, the starting resin may be in a stirred,
suspended or flowing state in order to suppress the
fusion.
When the washing treatment is carried out,
the starting resin is brought into contact with a
washing agent selected from the group consisting of
water, alcohols, acetone, MEK, ethers, hexanes, halogen
compounds (e.g. chloroform), nitrogen, carbon dioxide
and the like. These washing agents may be liquid,
gaseous or supercritical.
Whichever treatment method is adopted, the
treated PET resin produced according to the present
invention should satisfy the following requirements at
the same time: (i) the crystallization degree is 55% or
less; (ii) the molecular weight distribution Mw/Mn
ranges from 1.8 to 2.3; and (iii) the acetaldehyde
content after the treatment is a reduced content of 50%
or less of the acetaldehyde content of the starting
resin.
(U) When the crystallization degree of the
treated polyethylene terephthalate resin is 55% or
less, acetaldehyde production and quality deterioration
such as hue deterioration by thermal decomposition can
be greatly suppressed during molding or shaping of the
treated resin, which is desirable. The crystallization
degree may be 0%, though when the resin is in the form

of pellets, the crystallization degree is preferably 1%
or more for preventing the pellets from fusing together
with one another. The crystallization degree ranges
more preferably from 2 to 52%, still more preferably
from 3 to 47%, particularly preferably from 4 to 45%,
most preferably from 5 to 43%, in particular, from 6 to
41%.
(V) When Mw/Mn of the treated polyethylene
terephthalate resin ranges from 1.8 to 2.3, the
nonuniformity of the molecular weight before and after
molding or shaping of the treated resin is slight, so
that the quality of the molded or shaped product can
easily be controlled to be constant, which is
desirable. Usually, Mw/Mn of a PET resin produced by
melt polymerization ranges from 1.8 to 2.1. However,
if this resin is treated in a solid state under
unsuitable treatment conditions, Mw/Mn exceeds 2.5 in
some cases because for example, when the PET resin is
in the form of pellets, the surfaces of the pellets are
locally decomposed or solid-state polycondensation
reaction proceeds nonuniformly. In the case of the
local decomposition, the polymer obtained has an
increased amount of a hydroxyethyl end group in some
cases, so that the amount of the acetaldehyde produced
during melt molding or shaping is increased. When the
solid-state polycondensation reaction proceeds
nonuniformly, the pellets become slightly meltable, so
that the increase of the amount of acetaldehyde

produced during melt molding or shaping and quality
deterioration are unavoidable. Mw/Mn of the treated
polyethylene terephthalate resin ranges more preferably
from 1.9 to 2.2 and has particularly preferably the
same value as in the case of the starting PET resin.
When all the requirements described above are
satisfied and moreover, (W) the acetaldehyde content of
the treated polyethylene terephthalate resin is a
reduced content of 50% or less of the acetaldehyde
content of the starting resin, a molded or shaped
product having a very low acetaldehyde content can
desirably be produced by the use of the treated resin.
If the acetaldehyde reduction is insufficient, no
effect corresponding to a production cost increase
required for the reducing treatment can be obtained.
Therefore, the insufficient reduction is uneconomical.
By the acetaldehyde-reducing treatment, the
acetaldehyde content is preferably reduced to 40% or
less, more preferably 30% or less, particularly
preferably 20% or less, of the acetaldehyde content of
the starting resin. The absolute value of the
acetaldehyde content after the acetaldehyde-reducing
treatment is preferably 15 ppm or less, more preferably
10 ppm or less, still more preferably 5 ppm or less
which is the same as in the case of a solid-state
polycondensation product, particularly preferably 3 ppm
or less, more particularly preferably 2 ppm or less,
most preferably 1 ppm or less, in particular, 0.5 ppm

or less.
Although the polymerization degree of the
starting resin and the resin subjected to the
acetaldehyde-reducing treatment is not particularly
limited, their intrinsic viscosity [n] is preferably
0.4 dl/g or more for sufficient exhibition of physical
properties of a molded or shaped product by the use the
resin as a molding or shaping material. The intrinsic
viscosity [n] is preferably 2.5 dl/g or less from the
viewpoint of ease of molding or shaping. The intrinsic
viscosity [n] ranges more preferably from 0.45 to 2.0
dl/g, still more preferably from 0.55 to 1.7 dl/g,
particularly preferably from 0.65 to 1.4 dl/g, most
preferably from 0.7 to 1.2 dl/g.
The difference in polymerization degree
between the starting resin and the resin subjected to
the acetaldehyde-reducing treatment is preferably 0.20
dl/g or less, more preferably 0.15 dl/g or less, still
more preferably 0.10 dl/g or less, particularly
preferably 0.05 dl/g or less, most preferably 0.02 dl/g
or less, for maintaining the quality of the product
stably.
(IV-9) Others
The present invention includes the case where
the following various additives are copolymerized or
mixed if necessary: for example, delustering agents,
heat stabilizers, flame reterdants, antistatic agents,
defoaming agents, orthochromatic agents, antioxidants,

ultraviolet absorbers, crystal nucleators, brightening
agents, and impurity scavengers. Such stabilizers and
various additives may be added in any stage before
molding or shaping.
Particularly in the present invention, a
suitable stabilizer is preferably added depending on a
polymer to be produced. For example, pentavalent
and/or trivalent phosphorus compounds and hindered
phenol type compounds are preferable. The amount of
the phosphorus compound added is preferably 2 to 500
ppm, more preferably 10 to 200 ppm, in terms of the
weight proportion of phosphorus element contained in
the polymer. Specific preferable examples of the
phosphorus compounds are trimethyl phosphite,
phosphoric acid and phosphorous acid. The phosphorus
compounds are preferable because they prevent coloring
of the polymer and are effective also as a crystal
nucleator.
The hindered phenol type compounds are phenol
type derivatives having a substituent capable of
causing steric hindrance, at a position adjacent to the
phenolic hydroxyl group, and are compounds having one
or more ester linkages in the molecule. As to the
amount of the hindered phenol type compound added, its
weight proportion relative to the polymer to be
obtained is preferably 0.001 to 1% by weight, more
preferably 0.01 to 0.2% by weight. Specific examples
of the hindered phenol type compounds are

pentaerythritol, tetrakis[3-(3,5-di-tert-butyl-4-
hydroxyphenyl)propionate] , 1,1,3-tris(2-methyl-4-
hydroxy-5-tert-butylphenyl)butane, octadecyl-3-(3,5-di-
tert-butyl-4-hydroxyphenyl)propionate and N,N'-
hexamethylenebis(3,5-tert-butyl-4-hydroxyhydro-
cinnamamide). Co-using these stabilizers is a
preferable method.
In the present invention, the addition of a
crystal nucleator is also preferable. Preferable
examples of the crystal nucleator are phosphorus
compounds, organic acid metal salts and resin powder of
a polyolefine or the like. The amount of the crystal
nucleator added is preferably 2 to 1,000 ppm, more
preferably 10 to 500 ppm, in the polymer. Specific
examples of the crystal nucleator are phosphates such
as sodium 2,2'-methylenebis(4,6-di-t-butylphenyl)
phosphate, sodium bis(4-t-butylphenyl) phosphate, etc.;
sorbitols such as bis(p-methylbenzylidene)sorbitor,
etc.; and metal-element- containing compounds such as
hydroxy aluminum bis(4-t-butylbenzoate), etc.
Particularly in a preform for PET bottle to be
subjected to thermal crystallization by heating of a
mouth portion, the crystal nucleator is preferably used
in order to accelerate the crystallization to lower the
thermal crystallization temperature.
In the present invention, the addition of a
scavenger for volatile impurities is also preferable
method. For example, in the case of a polyethylene

terephthalate resin, its impurity is acetaldehyde and a
scavenger for acetaldehyde includes, for example,
polymers and oligomers, such as polyamides, polyester
amides, etc.; and low-molecular weight compounds having
an amide group and an amine group, such as 2-
aminobenzamide, etc. Specific examples of the
scavenger are polyamides such as nylon 6.6, nylon 6,
nylon 4.6, etc.; polymers such as polyethylene imines,
etc.; a reaction product of N-phenylbenzenamine with
2,4,4-trimethylpentene; and Irganoxl098 and Irganox565
(trade names) manufactured by Ciba Speciality Chemical
Co., Ltd. These scavengers are preferably added after
the discharge of the resin from the polymerization
reactor and before the feed of the resin into a molding
or shaping machine.
(V) Description of the molding method and the molded
article
The polyester resin produced in the present
invention may be once formed as pellets and then
remelted for use in molding. Alternatively, the
polyester resin produced in the polymerization reactor
of the present invention may be transferred to a
molding machine for molding with the molten state
maintained without solidification to allow production
of a molded article of higher quality at low cost.
(V-l) Description of the production method of pellets
When the polyester resin is once formed as
pellets, it is desirable to achieve low loss and

uniform extrusion by an extruder. The methods of
pelletization are not particularly limited and include
a strand cut method in which molten strands are cooled
in water and palletized by a pelletizer, an underwater
cut method in which molten strands are directly
extruded into water and formed into pellets by a cutter
provided at the outlet, a direct cult method in which
strands are extruded with the molten state maintained
and cut by a cutter, and the like. When a coolant such
as water is used, the temperature of the coolant is
preferably 60 °C or lower, more preferably 50 °C or
lower, and more preferably 40 °C or lower. In view of
economics and handleability, water is preferable as the
coolant, and thus the temperature of the coolant is
preferably 0 °C or higher. The cutting for providing
the pellet form is preferably performed after the
cooling to 100 °C or lower within 120 seconds after the
extrusion of the resin.
The crystallinity of the pellet produced
according to the present invention is 55% or lower,
preferably 50% or lower, more preferably 40% or lower,
more preferably 30% or lower, particularly preferably
20% or lower, and most preferably 10% or lower.
Polyethylene terephthalate resin with the crystallinity
of 55% or lower reguires less heating for melt
processing and generates less shearing heat in
plasticization. Thus, that crystallinity is preferable
since it does not cause a great reduction in the degree

of polymerization of the resin due to thermal
decomposition, deteriorated hues, or a large amount of
acetaldehyde as a by-product. In addition, uniform
melting easily achieved in the melt molding can provide
a molded article with a favorable appearance.
On the other hand, polyethylene terephthalate
resin produced in the solid-state polycondensation
technique typically has a crystallinity of 60% or
higher. Particularly, the crystallinity is higher in a
surface portion of a pellet or in fine powder contained
in the pellet to cause nonuniform melting in molding,
resulting in many disadvantageous troubles in product
quality such as variations in thickness of a sheet-
shaped molded article and fish eyes on the surface of
the molded article. It also requires a large amount of
heat for crystal melting in melt molding of the pellet,
which leads to production of acetaldehyde due to
decomposition of the resin from excessive heat and an
increased amount of the carboxyl group at the end.
Besides, it easily causes clouding associated with
crystallization in blow molding.
The amount of fine powder with a diameter of
1 mm or lower contained in the pellet produced
according to the present invention is preferably 5
mg/kg or lower, more preferably 3 mg/kg or lower, more
preferably 2 mg/kg, and particularly preferably 1 mg/kg
or lower.
In contrast, in the solid-state

polycondensation technique, crystallization and
polymerization are performed in the form of pellets, so
that a great amount of fine powder is produced due to
fusion/solidification and grinding of the pellets.
Such fine powder causes process troubles such as stuck
pneumatic piping and operational troubles such as an
increased loss rate. In addition, since the degree of
polymerization and the crystallinity of the fine powder
of the polymer are significantly higher than those of
the product pellet, it is not melted uniformly in
molding to create many disadvantageous troubles in
product quality such as such variations in thickness of
a sheet-shaped molded article and fish eyes on the
surface of the molded article.
(V-2) Description of the method of transferring the
polyester resin produced in the polymerization reactor
of the present invention to a molding machine for
molding with the molten state maintained without
solidification
The polyester resin produced in the
polymerization reactor of the present invention may be
once solidified into pellets and then remelted for use
in molding as described above. However, the resin may
be transferred to a molding machine for use in molding
with the molten state maintained without
solidification. The molten state refers to the state
in which the resin is melted under heat and flows with
a viscosity of approximately 500,000 Pa-s or lower. In

this case, it is important to perform molding while
suppressing a reduction in the degree of polymerization
due to thermal decomposition of the polyester resin,
coloring, and production of a volatile impurity such as
acetaldehyde.
The temperature of transfer piping from the
polymerization reactor to the molding machine and the
temperature in molding according to the present
invention can be set to a temperature represented by
(the crystalline melting point - 10 °C) or higher to
achieve stable transfer and molding without
significantly increasing the viscosity or causing
solidification. On the other hand, the setting to a
temperature represented by (the crystalline melting
point + 60 °C) or lower can reduce coloring due to
thermal decomposition or production of a volatile
impurity such as acetaldehyde to easily provide a
molded article of high quality. The temperatures are
preferably in a range represented by (the crystalline
melting point + 0 to 50 °C) of the polymerization
intermediate, more preferably in a range represented by
(the crystalline melting point + 0 to 40 °C), more
preferably in a range represented by (the crystalline
melting point + 0 to 30 °C) , particularly preferably in
a range represented by (the crystalline melting point +
0 to 20 °C), and most preferably in a range represented
by (the crystalline melting point + 0 to 10 °C). On the
other hand, for the polyester resin which shows no

crystalline melting point, of the temperature of 100 °C
and the temperature at which the melting viscosity is
100,000 (poise) or higher when the polyester resin
extruded from the polymerization reactor is evaluated
at a shear rate of 1,000 (sec-1), the temperatures are
preferably in a range from the higher one of the two
temperatures to 290 °C. More preferably, of the
temperature of 150 °C or the temperature at which the
melting viscosity is 100,000 (poise) or higher when the
polyester resin extruded from the polymerization
reactor is evaluated at a shear rate of 1,000 (sec-1),
the temperatures are preferably in a range from the
higher one of the two temperatures to 280 °C. More
preferably, of the temperature of 190 °C or the
temperature at which the melting viscosity is 100,000
(poise) or higher when the polyester resin extruded
from the polymerization reactor is evaluated at a shear
rate of 1,000 (sec-1), the temperatures are preferably
in a range from the higher one of the two temperatures
to 270 °C. Such a temperature range can be achieved by
properly controlling the temperatures of the transfer
piping, the transfer pump, and the heater or jacket
which covers the molding machine.
The time period taken before the molding is
preferably 40 minutes or shorter, more preferably 20
minutes or shorter, and particularly preferably 10
minutes or shorter. Of course a shorter time period is
better. It should be noted that the time period taken

before the molding refers to the period from the time
when the molten resin comes out of the drainage pump of
the polymerization reactor to the time when it is
cooled equal to or lower than the crystalline melting
point or the temperature at which the viscosity of the
resin is 500,000 Pa-s or higher in the molding machine
or after it is removed out of the molding machine.
When the resin is moved continuously in the piping or
the like, the average time period calculated from the
volume and flow rate in the piping or the like can be
used. If the time period varies, it must be controlled
within the abovementioned time period.
In the present invention, the polyester resin
of high quality can be polymerized with the
abovementioned method. In addition, the resin
temperature is maintained at a low temperature close to
the crystalline melting point and the resin is
transferred to the molding machine for molding with a
short melting residence time and the quality
maintained, so that a high-quality molded article can
be created with excellent productivity, which is an
object of the present invention. As a result, no need
of the solid-state polycondensation can omit a series
of complicated steps typical of the solid-state
polycondensation such as cooling and solidification of
the resin of low polymerization degree produced in the
melt polymerization, pelletization, predrying,
crystallization, solid-state polycondensation, cooling

of the product, carrying of the product, heating and
drying before molding, and molding. Besides, energy
can be saved. In terms of quality, the solid-state
polycondensation technique requires a long time period
for polymerization over several tens of hours although
it is performed at the melting point or lower. In
addition, temperature rises and drops repeated many
times outside the polymerization system as described
above have effects such as moisture absorption of the
pellet or oxidation degradation. Furthermore, the
highly crystalline pellet requires heating at a high
temperature in the melt processing, and a large amount
of shearing heat generation tends to cause extreme
conditions to result in significantly reduced quality.
In contrast, the polyester resin and the molded article
produced in the polymerization method and the molding
method of the present invention involve a slight
quality reduction between before and after the melt
molding. It is contemplated that this is achieved for
the following reasons. Specifically, in the
polymerization method of the present invention, the
polymerization is typically completed within three
hours at a temperature close to the crystalline melting
point of the polyester resin, the polymerization
reactor body has no rotary driving part or no resin
residence part to produce little air leakage, cutting
of polymer molecular chains due to shearing, or
degradation of the resin due to melting residence, and

the supply of the molten resin to the molding machine
involves no moisture absorption, oxidation degradation,
or shearing heat generation. The abovementioned points
are presumed as the reasons.
Examples of the molded article formed in the
abovementioned method include a preform for molding of
a hollow body such as a beverage container, a hollow
body, a film, a sheet, a fiber for clothing or an
industrial material such as a tier cord, a strand, and
a pellet. It is possible that those molded articles
are formed by a single molding machine, molded articles
of the same type are simultaneously formed by two or
more molding machines, or molded articles of a
plurality of types are simultaneously formed by two or
more types of molding machines.
The intrinsic viscosity (r\) of the polyester
resin produced in the present invention is in a range
of 0.4 to 2.5 dl/g. For applications as a hollow body
such as a beverage bottle, the use of a resin of high
viscosity provides better blow-up during biaxial
stretching to improve spreading of the material,
thereby allowing a thinner wall of a bottle. The
viscosity can reduce the drawdown of the preform and is
advantageous in providing transparency. For
applications as a stretched film, the use of a resin of
high viscosity in film formation also facilitates a
film having a better stretching property and uniform
thickness and is suitable for production of thin films.

In addition, since slack and drawdown in stretching are
reduced, the viscosity is preferable for thick sheet
molding.
For molding a hollow body as an example of
the molded article, the following molding method
including the steps (a) to (h) is preferably selected.
The hollow body refers to a molded article which has
space inside a resin molded article, and a blow bottle
is an example thereof. An injection molding machine or
an extruder for molding the preform may be provided
separately from a blow molding machine for forming the
hollow body. It is also preferable to use a molding
machine which allows molding therein from a resin to a
hollow body through a preform since heating steps are
reduced. In addition, it is more preferable to perform
aseptic filling for conducting steps to content filling
in a sterile room after the blow molding since a high-
temperature sterilization step is not required. All
the molding methods preferably have biaxial stretching
after the blow molding since it can provide impact
resistance for the bottle. The stretching in the
vertical direction is suitably 1.0 to 5.0 times. The
resin temperature in the molding machine is preferably
230 to 330 °C, and more preferably 240 to 320 °C.
(a) The resin in the molten state is
transferred from the polymerization reactor to the
injection molding machine to mold a preform. After the
preform is completely solidified and then removed, the

preform is heated and melted, and blow-molded in a mold
to provide a hollow body (a cold parison method). The
bottle is preferably stretched in the vertical
direction during the blow molding in providing the
impact resistance for the bottle. The preform is
preferably heated externally when it is remelted.
On the other hand, it is also preferable that
the preform is removed with only its surface
solidified, the overall preform is again melted
resulting from the diffusion of the heat stored inside,
and then blow molding is performed to provide a hollow
body (a hot parison method). The bottle is preferably
stretched in the vertical direction in the blow-up.
(b) The resin in the molten state is
transferred from the polymerization reactor to the
injection molding machine to mold a preform. The
preform is removed with the molten state maintained and
is blow-molded in a mold to provide a hollow body. The
bottle is preferably stretched in the vertical
direction during the blow molding.
(c) The resin is once palletized, and the
resulting pellet is transferred to the injection
molding machine and formed into a molded article in the
same manner as in (a). The bottle is preferably
stretched in the vertical direction during the blow
molding.
(d) The resin is once palletized, and the
resulting pellet is transferred to the injection

molding machine and formed into a molded article in the
same manner as in (b). The bottle is preferably
stretched in the vertical direction during the blow
molding.
(e) The resin in the molten state is
transferred from the polymerization reactor to the
extruder, and the extruded resin mass is put in a mold
and subjected to compression molding to mold a preform.
After the preform is completely solidified and then
removed, the preform is heated and melted, and blow-
molded in a mold to provide a hollow body (the cold
parison method). The bottle is preferably stretched in
the vertical direction during the blow molding in
providing the impact resistance for the bottle. The
preform is preferably heated externally when it is
remelted.
On the other hand, it is also preferable that
the preform is removed with only its surface
solidified, the overall preform is again melted
resulting from the diffusion of the heat stored inside,
and then blow molding is performed to provide a hollow
body (the hot parison method). The bottle is
preferably stretched in the vertical direction during
the blow-up.
The method of producing the preform with the
compression molding is particularly suitable for
molding polyethylene terephthalate resin of high
polymerization degree and high viscosity as produced

according to the present invention.
(f) The resin in the molten state is
transferred from the polymerization reactor to the
extruder, the extruded resin mass is put to a mold and
subjected to compression molding, and it is removed
with the molten state maintained and then blow-molded
in a mold to provide a hollow body. The bottle is
preferably stretched in the vertical direction during
the blow molding.
(g) The resin is once palletized, and the
resulting pellet is transferred to the extruder and
formed into a molded article in the same manner as in
(e). The bottle is preferably stretched in the
vertical direction during the blow molding.
(h) The resin is once palletized, and the
resulting pellet is transferred to the extruder and
formed into a molded article in the same manner as in
(f). The bottle is preferably stretched in the
vertical direction during the blow molding.
A single or two or more molding machines
and/or a single or two or more extruders may be
connected to the polymerization reactor to supply the
resin. When a plurality of molding machines which
intermittently receive the resin such as injection
"molding machines are used, the plurality of molding
machines preferably operate in molding cycles with a
certain shift between them to average the flow rate in
order to maintain the flow rate constant without

residence of the resin drawn from the polymerization
reactor.
When the resin drawn continuously from the
polymerization reactor is supplied to the molding
machine which intermittently receives the resin, an
accumulator is preferably provided between them for
storing the resin. It is more preferable to
synchronize the molding machine with the accumulator to
reduce residence of the resin. It is also preferable
to provide an extruder separate from the molding
machine to allow pelletization simultaneously with the
molding.
A commercially available pellet molding
machine can be used as it is or with some modifications
as the molding machine. Particularly, in the present
invention, the resin in the molten state is supplied
from the polymerization reactor, which can simplify or
omit a plasticating mechanism for the pellet such as a
melt plasticating screw essential to the conventional
molding machine which uses a pellet as a material. In
this case, molding can be performed under less shearing
heat generation in the screw to allow production of the
molded article with higher quality.
(V-3) Description of the preform for producing a hollow
body and the hollow body in the present invention
The preform for producing the hollow body
suitable for producing a beverage bottle or the like in
the present invention is provided by supplying the

polyethylene terephthalate resin having the
abovementioned characteristics (A) to (F) to the
injection molding machine or the compression molding
machine from the polymerization reactor of the present
invention through pipes in a temperature range
represented by (the crystalline melting point - 10 °C)
or higher and (the crystalline melting point + 60 °C) or
lower and performing molding. The preform has the
following characteristics (G) to (I).
(G) The amount of the carboxyl group at the
end of the polymer; 30 meq/kg or lower,
(H) The amount of acetaldehyde contained; 10
ppm or lower, and
(I) The hue in a transmission method with a
hexafluoroisopropanol solution; an L value of 98 or
higher and a b value of 0.7 or lower.
The hollow body suitable for a beverage
bottle and the like in the present invention is
provided by performing blow molding of the preform for
producing the hollow body having the abovementioned
characteristics (G) to (I) and has the following
characteristics (J) to (L).
(J) The amount of the carboxyl group at the
end of the polymer; 30 meq/kg or lower,
(H) The amount of acetaldehyde contained; 10
ppm or lower, and
(I) The hue in the transmission method with
hexafluoroisopropanol solution; an L value of 98 or

higher and a b value of 0.8 or lower.
The amount of the carboxyl group at the end
of the polymer described in (G) and (J) is preferably
30 meq/kg or lower in terms of the influence upon the
thermal stability of the resin. It is more preferably
25 meq/kg or lower, more preferably 20 meq/kg or lower,
particularly preferably 15 meq/kg or lower, and most
preferably 10 meq/kg or lower. The carboxyl group at
the end of the polymer not only promotes decomposition
of the resin but also leads to acetaldehyde as a by-
product in producing the hollow body or deteriorated
hues, thereby reducing the quality of the resin.
The amount of acetaldehyde contained
described in (H) and (K) is desirably reduced since
even a slight amount thereof causes discomfort in
senses of taste and smell of humans and is preferably
10 ppm or lower. It is more preferably 8 ppm or lower,
and more preferably 7 ppm or lower, and particularly
preferably 5 ppm or lower.
According to the polymerization method of the
present invention, the polyethylene terephthalate resin
having a low content of acetaldehyde can be produced.
In addition, the resin can be transferred to the
molding machine for molding with the molten state
maintained at a low temperature close to the melting
point. Thus, no influence of heat generation due to
shearing allows the preform and the hollow body to be
produced with a low content of acetaldehyde. In

contrast, since the conventional melt polymerization
technique requires reaction at a higher temperature for
a longer time period than in the polymerization method
of the present invention, a significantly large amount
of acetaldehyde is contained. On the other hand, the
surface portion of the pellet produced in the solid-
state polycondensation technique is highly polymerized
and highly crystallized to generate much shearing heat
in the mold processing, thereby producing a large
amount of acetaldehyde as a by-product in processing.
Consequently, the acetaldehyde content in the molded
article greatly exceeds 10 ppm.
For the hue in the transmission method with
the hexafluoroisopropanol solution described in (I) and
(L), the L value of the preform is preferably 98 or
higher and the b value thereof is preferably 0.7 or
lower in order to produce a molded article with an
excellent appearance. The L value and b value are more
preferably 99 or higher and 0.6 or lower, respectively,
and the L value and b value are particularly preferably
99.2 or higher and 0.5 or lower, respectively. For the
hollow body, the L value and b value are preferably 98
or higher and 0.8 or lower, respectively. The L value
and b value are more particularly preferably 99 or
higher and 0.7 or lower, respectively, and the L value
and b value are particularly preferably 99.2 or higher
and 0.6 or lower, respectively.
According to the polymerization method of the

present invention, since the amount of thermal
hysteresis is small and the polymerization reactor body
has no rotary driving part as compared with the
conventional melt polymerization technique or solid-
state polycondensation technique, air leakage or heat
generation due to shearing are not created, and the
polyethylene terephthalate resin can be produced with
excellent hues. In addition, according to the method
of transferring the resin to the molding machine for
molding with the molten state maintained, the preform
and the hollow body can be produced with excellent hues
because of no influence of heat generation due to
shearing or no influence of contact with air or
moisture.
(Representative embodiment of the polymerization
reactor and the polymerization method in the present
invention)
Next, description will be made for examples
of a preferred polymerization reactor and a preferred
polymerization method used in the present invention
with reference to the drawings.
Fig. 1 shows a specific example of the
polymerization reactor suitable for producing the
polyester resin in the present invention. The
polymerization intermediate of the polyester resin is
supplied from a feed opening 2 to a polymerization
reactor 10 through a transfer pump 1, is introduced
into the polymerization reactor through a perforated

plate 3, and falls along a support 5. The inside of
the polymerization reactor is controlled to a
predetermined reduced pressure. EG produced from the
polymerization intermediate as a by-product, an inert
gas such as nitrogen introduced through an inert gas
feed port 6 as required and the like are discharged
from an evacuation port 7. The highly polymerized
polyester resin is discharged from a drainage port 9
with a drainage pump 8. When the pellet is produced,
the resin is pulled out from the drainage port 9 and
then immediately brought into contact with a coolant
such as water for cooling, followed by cutting into
pellets. The body or the like of the polymerization
reactor 10 is heated and heat retention is provided by
a heater or a jacket.
Fig. 2 shows a specific example of the
polymerization reactor suited for producing the
polyester resin of the present invention when an inert
gas absorption apparatus N10 is used. The
polymerization intermediate of the polyester resin is
supplied into the inert gas absorption apparatus N10
from a feed opening N2 through a transfer pump Nl, is
introduced into the inert gas absorption apparatus
through a perforated plate N3, and then falls along a
support N5. The inside of the inert gas absorption
apparatus is controlled to a predetermined reduced
pressure with an evacuation port N7. While falling,
the polymerization intermediate absorbs an inert gas

such as nitrogen introduced from an inert gas feed port
N6. The polymerization intermediate is supplied into a
polymerization reactor 10 from a feed opening 2 through
a drainage/transfer pump N8, is introduced into the
polymerization reactor through a perforated plate 3,
and falls along a support 5. The inside of the
polymerization reactor is controlled to a predetermined
reduce pressure. EG produced from the polymerization
intermediate as a by-product, an inert gas such as
nitrogen introduced through an inert gas feed port 6 as
required and the like are discharged from an evacuation
port 7. The highly polymerized polyester resin is
discharged from a drainage port 9 with a drainage pump
8. When the pellet is produced, the resin is pulled
out from the drainage port 9 and then is immediately
brought into contact with a coolant such as water for
cooling, followed by cutting into pellets. The body or
the like of the polymerization reactor 10 is heated and
heat retention is provided by a heater or a jacket.
Figs. 3 and 4 are schematic diagrams showing
an example of an apparatus which achieves the method of
the present invention. Fig. 3 shows an example of an
apparatus in which BHET, an intermediate of
polyethylene terephthalate resin, is provided from
direct esterification reaction, and polycondensation
reaction of the BHET is caused to produce a
polymerization intermediate which is then supplied to a
polymerization reactor 10 of the present invention for

polymerization. Fig.4 shows an example of an apparatus
in which BHET is provided from transesterification
reaction, and a polymerization intermediate is produced
by a combination of a stirred vessel polymerization
reactor with a horizontal stirred polymerization
reactor and then is supplied to a polymerization
reactor 10 of the present invention for polymerization.
In both methods, the resin falling along a
support reaches a lower portion of the polymerization
reactor and then pulled out from a drainage port with a
drainage pump. In this case, the smallest possible
amount of the resin is preferably stored as uniformly
as possible in the lower portion of the polymerization
reactor. This can easily suppress coloring due to
thermal decomposition or a reduction in the degree of
polymerization and reduce variations in quality of the
resin. The stored amount can be controlled by
monitoring the stored amount through a sight glass 4 or
monitoring the stored amount using a level meter of
capacitance type or the like to adjust the feed amount
by the transfer pump 1 and the drainage pump 8.
The polymerization reactor for use in the
present invention may has a stirrer or the like at the
bottom thereof, but it is not particularly necessary.
Thus, it is possible to eliminate a rotary driving part
in the polymerization reactor body and achieve
polymerization with favorable sealing under high
vacuum. Since the rotary driving part of the drainage

pump is covered with the resin to be discharged, the
sealing is much more excellent as compared with the
case where the polymerization reactor body has a rotary
driving part.
The method of producing the polyester resin
in the present invention may be performed by a single
polymerization reactor, but two or more polymerization
reactors may be used. Alternatively, a single
polymerization reactor may be divided vertically or
horizontally to provide a multistage polymerization
reactor.
In the present invention, it is possible to
perform the overall process of increasing the molecular
weight from the polymerization intermediate to the
intended polyester resin with a high degree of
polymerization while the resin is dropped along the
support from the holes in the perforated plate and
polymerized at the same time. In addition, the process
may be performed in combination with another
-polymerization method, for example, by using a stirred
vessel polymerization reactor, a horizontal stirred
polymerization reactor or the like.
The horizontal stirred polymerization reactor
includes a screw type, an independent blade type, a
uniaxial type, a biaxial type or the like, and for
example, a polymerization reactor described in Chapter
4 of "Research Report of Research Group of Reaction
Engineering: Reactive Processing Part 2" (The Society

of Polymer Science, 1992) .
As the stirred vessel polymerization reactor,
any of stirred vessels described, for example, in
Chapter 11 of Chemical Equipment Guide (The Society of
Chemical Engineers, 1989) can be used. The shape of
the vessel is not particularly limited, and a vertical
or horizontal cylindrical type is typically used. The
shape of the stirring blade is not particularly
limited, and a paddle type, an anchor type, a turbine
type, a screw type, a ribbon type, a double blade type
or the like is used.
The process of producing the polymerization
intermediate from a material such as monomer can be
performed in batches or continuously. It can be
performed in batches by supplying all of the material
and the reactant to the reactor for reaction over a
predetermined time period and then transferring all of
the reactant to the next reactor. On the other hand,
it can be performed continuously by supplying the
material and reactant continuously to each reactor and
discharging the reactant continuously. It is
preferably performed continuously to produce a large
amount of polyester resin with uniform quality.
The material of the polymerization reactor
for use in the present invention is not particularly
limited, and it is typically selected from stainless
steel, nickel, glass lining and the like.
Next, Figs. 5 and 6 show a preferable

combination when the polyester resin and the molded
article thereof are produced, but the present invention
is not limited thereto.
Fig. 5 is a schematic diagram showing an
example of the polymerization reactor and the molding
machine used in the present invention. The
polymerization intermediate is supplied to a
polymerization reactor 10 from a feed opening 2 through
a transfer pump 1, is introduced into the
polymerization reactor through a perforated plate 3,
and falls along a support 5. The inside of the
polymerization reactor is controlled to a predetermined
reduced pressure. EG produced from the polymerization
intermediate as a by-product, an inert gas such as
nitrogen introduced from an inert gas feed port 6 as
required and the like are discharged from an evacuation
port 7. The highly polymerized polyester resin is
discharged continuously from a drainage pump 8 and then
supplied to an 12 molding machine A, an 13 molding
machine B, and an 14 molding machine C with transfer
piping and a distributor II to perform molding. More
than three molding machines may be connected. The
transfer pump 1, the polymerization reactor 10, the
drainage pump 8, the transfer piping and the
distributor II and the like are heated by a heater or a
jacket and heat retention is provided.
Fig. 6 is a schematic diagram showing an
example of the inert gas absorption apparatus, the

polymerization reactor, and the molding machine used in
the present invention.
In all the methods, the highly polymerized
polyester resin falls to a lower portion of the
polymerization reactor and is discharged continuously
from the drainage pump 8, and then supplied to the 12
molding machine A, the 13 molding machine B, and the 14
molding machine C with the transfer piping and the
distributor II to perform molding.
In this case, the smallest possible amount of
the resin is preferably stored as uniformly as possible
in the lower portion of the polymerization reactor.
This can easily suppress coloring due to thermal
decomposition or a reduction in the degree of
polymerization and reduce variations in quality of the
resin. The stored amount can be controlled by
monitoring the stored amount through a sight glass 4 or
monitoring the stored amount using a level meter of
capacitance type or the like to adjust the feed amount
by the transfer pump 1 and the drainage pump 8.
The method of transferring the polymerized
resin to the molding machine is not particularly
limited, but a gear pump, an extruder and the like can
be used. The transfer to the molding machine includes
continuous transfer and intermittent transfer, but in
both cases, the transfer and molding must be performed
within the abovementioned time period. When the resin
is intermittently transferred, the discharge from the

polymerization reactor may be intermittently performed.
However, it is preferable as shown in Fig. 5 that the
resin is continuously discharged from the
polymerization reactor and is intermittently
transferred to two or more molding machines (three in
Fig. 5, and more than three molding machines may be
used) with sequential switching between them through
the transfer piping and the distributor II provided
between the polymerization reactor and the molding
machine. Alternatively, it is preferable to set a
known apparatus, for example an apparatus formed of a
reservoir and a piston, or to set an apparatus called
an accumulator which temporarily stores the resin.
The molding machine in the present invention
refers to an apparatus which forms the resin in the
molten state into a specific shape, and includes, for
example, an extruder, an injection molding machine, and
a blow molding machine. The molding machine performs
molding of a bottle or a preform of a bottle, a film, a
sheet, a tube, a rod, a fiber, injection molded
produces in various shapes. Of them, the present
invention is suited especially for producing a preform
of a beverage bottle. This is because it is highly
desirable that the beverage bottle has high strength
and transparency, includes a reduced amount of volatile
impurity of a low molecular weight which adversely
affects the taste or smell of the content, represented
by acetaldehyde in the polyethylene terephthalate

resin, and allows high productivity.
Fig. 7 shows a specific example of the
polymerization reactor suited for the polymerization
method which includes reaction with an arbitrary amount
of a molecular weight regulator at the step before the
polymerization intermediate is supplied to the
polymerization reactor in producing the polyester resin
of the present invention. In Fig. 7, the
polymerization intermediate is supplied to a
polymerization reactor 10 with a transfer pump 1
through piping after the polymerization intermediate
producing step. In the feed piping, the polymerization
intermediate is mixed and reacts with the molecular
weight regulator to change the molecular weight of the
polymerization intermediate. Next, the polymerization
intermediate is supplied to the polymerization reactor
10 from a feed opening 2 through the transfer pump 1,
is introduced into the polymerization reactor through a
perforated plate 3, and falls along a support 5. The
inside of the polymerization reactor is controlled to a
predetermined reduced pressure. EG produced from the
polymerization intermediate as a by-product, an inert
gas such as nitrogen introduced as required from an
inert gas feed port 6 and the like are discharged from
an evacuation port 7. The highly polymerized polyester
resin is discharged from a drainage port 9 with a
drainage pump 8. When the pellet is produced, the
resin is pulled out from the drainage port 9 and then

immediately brought into contact with a coolant such as
water for cooling, followed by cutting into pellets.
When the molded article is produced, the resin is
discharged continuously and then supplied to an 12
molding machine A, an 13 molding machine B, and an 14
molding machine C for molding through transfer piping
and a distributor II, similarly to the stages of the
drainage pump 8 or after in Fig. 5. More than three
molding machines may be connected.
Fig. 8 shows a specific example of the
polymerization reactor suited for the method which
includes supplying the polymerization intermediate to
the polymerization reactor for polymerization after it
is passed through a polymer filter in producing the
polyester resin of the present invention. In Fig. 8,
the polymerization intermediate is supplied to a
polymerization reactor 10 with a transfer pump 1
through piping after the polymerization intermediate
producing step. Then, the polymerization intermediate
passes through a polymer filter 11 which is set
immediately before a feed opening 2, has a filtering
accuracy of 0.2 to 200 fim, and is controlled in a
temperature range represented by (the crystalline
melting point - 20 °C) of the polymerization
intermediate or higher to (the crystalline melting
point + 100 °C) or lower. Then, the resin is supplied
to the polymerization reactor 10 from the feed opening
2, is introduced into the polymerization reactor

through a perforated plate 3, and falls along a support
5. The inside of the polymerization reactor is
controlled to a predetermined reduced pressure. EG
produced from the polymerization intermediate as a by-
product, an inert gas such as nitrogen introduced as
required from an inert gas feed port 6 and the like are
discharged from an evacuation port 7. The highly
polymerized polyester resin is discharged from a
drainage port 9 with a drainage pump 8. Fig. 8 shows
the example in which a polymer filter 12 is provided
after the drainage port 9, but the polymer filter 12
may not be provided. When the pellet is produced, the
resin is pulled out from the drainage port 9, passed
through the polymer filter 12 as required, and
immediately brought into contact with a coolant such as
water for cooling, followed by cutting into pellets.
When the molded article is produced, the resin is
discharged continuously, then passed through the
polymer filter 12 as required, and is supplied to an 12
molding machine A, an 13 molding machine B, and an 14
molding machine C for molding through transfer piping
and a distributor II, similarly to the stages of the
drainage pump 8 or after in Fig. 5. More than three or
more molding machines may be connected.
(Examples)
The present invention will be described on
the basis of Examples.
In Examples, principal measured values were

obtained in the following methods.
(1) Intrinsic Viscosity (TJ)
The intrinsic viscosity (TI) was calculated
with an Ostwald viscometer in accordance with the
following equation by extrapolating the ratio Tisp/C of a
specific viscosity t|sp in o-chlorophenol at a
temperature of 35 °C and a concentration C (g/100
milliliters) in the concentration zero.

(2) Crystalline melting point
The crystalline melting point was measured
with Pyris 1 DSC (a differential calorimeter of input
compensation type) manufactured by PerkinElmer, Inc.
under the following conditions, and the value of an
endothermic peak from the molten crystal was used as
the crystalline melting point. The peak value was
determined by using the accompanying analysis software.
Measurement temperature: 0 to 280 °C
Temperature rise rate: 10 °C/min
(3) Carboxyl group amount at the end of the polymer
A gram of sample was dissolved in 25 ml of
benzyl alcohol, and then 25 ml of chloroform was added
thereto. The resulting solution was subjected to
titration with 1/50 N of potassium hydroxide dissolved
in benzyl alcohol to make calculations from the
titration value VA (ml) and the blank value V0 when PET
is not present in accordance with the following
equation:

Carboxyl group amount at end of polymer
(meq/kg) = (VA- V0) x 20
(4) Hue (L value, b value)
1.5 g of sample was dissolved in 10 g of
1,1,1,3,3,3-hexafluoro-2-propanol, and analyzed in the
transmission method with UV-2500 PC (an ultraviolet-
visible spectrophotometer) manufactured by Simadzu
Corporation, and evaluated with the accompanying
analysis software in the method based on JIS Z8730.
(5) Rate of content of acetaldehyde (water extraction
method)
Finely cut sample pieces were frozen and
crushed for 3 to 10 minutes under cooling in liquid
nitrogen with 6700 freezer mill manufactured by SPEX
into powder with a particle size of 850 to 1000 fim. A
gram of the powder was put into a glass ampul together
with 2 ml of water for nitrogen substitution before
sealing. Then, it was heated at 130 °C for 90 minutes
to extract the impurity such as acetaldehyde. After
the ampul was cooled, it was opened to perform analysis
by GC-14B (a gas chromatograph) manufactured by Simadzu
Corporation in the following conditions:
Column: VOCOL (60 m x 0.25 mm0 x a thickness
of 1.5 urn);
Temperature conditions: maintained at 35 °C
for 10 minutes, then raised to 100 °C at 5 °C/min, and
then raised to 100 to 220 °C at 20 °C/min.
Temperature of intake port: 220 °C

Intake method: Split Method (split ratio =
1:30), intake of 1,5 (J.1
Measurement method: FID method
(6) Molecular weight distribution
The sample was dissolved in 1,1,1,3,3,3-
hexafluoro-2-propanol (5 mmol/1 of sodium
trifluoroacetate dissolved) at a concentration of 1.0
mg/ml. The resulting solution was analyzed with HLC-
8020GPC (a gel-permeation chromatograph) manufactured
by Tosoh Corporation in the following conditions and
evaluated with the accompanying analysis software.
Column: HFIP-606M and HFIP-603 manufactured
by Showa Denko K.K.
Column temperature: 40 °C
Intake Amount: 30 fj.1
Measurement Method: RI detector, PMMA
conversion
(7) Content of cyclic trimer
A g of the sample was completely dissolved in
a mixed solution of 10 g of 1,1,1,3,3,3-hexafluoro-2-
propanol and 5 g of chloroform, and then 15 g of
chloroform was also added to that solution for
dilution. While the diluted solution was stirred with
a magnetic stirrer, 100 g of tetrahydrofurane was
dropped thereto to reprecipitate the sample. This was
filtered to provide the solution from which any
precipitation is removed. The solvent was evaporated
by an evaporator from the solution to take oligomer as

a residue thereof. The resulting oligomer was
dissolved in 20 g of dimethylformamide and analyzed
with SCL-10A (a high-performance liquid chromatograph)
manufactured by Simadzu Corporation in the following
conditions:
Columns: Unisil Q C18 (4.6 mm in diameter and
250 mm in length)
Column Temperature: 40 °C
Intake amount: 20 \xl
Separation Solvent: solvent A (distilled
water containing 1 wt% of acetic acid)
solvent B (acetonitrile
containing 0.02 wt% of acetic acid)
A mixed solution of the solvent A and the
solvent B was flowed at a flow rate of 1.0 ml/min. The
mixing conditions of the solvents are such that the
percentage of the solvent B was linearly increased from
17 to 70% over 18 minutes in the early phase of the
analysis, linearly increased from 70 to 100% over the
next 22 minutes, and then to 100% over 20 minutes until
the end of the analysis.
Measurement method: a UV detector (254 nm)
was used to provide a calibration curve from the sample
of the cyclic trimer to calculate the amount of the
cyclic trimer contained in the polymer sample from the
amount of the cyclic trimer contained in the oligomer.
(8) Crystallinity
The crystallinity (crystallization degree)

was calculated in the following equation from the
density determined in a density gradient tube method
using a density gradient tube formed with carbon
tetrachloride and n-heptane based on JIS K7112D. The
measurement was performed at 10 points of the sample
and the average value thereof was used:

(9) Amount of fine powder
A commercially available adhesive tape is
spread over one surface of a 2-by-10 centimeter plate
with its adhesive surface facing upward to perform
precise weighing. Then, the above-mentioned plate and
300 g of resin pellet were put into a 28-by-40
centimeter plastic bag and they were shaken for one
minute. All the resin pellet attached to the adhesive
surface of the plate was removed with tweezers. The
weight of the fine powder of 1 mm or smaller remaining
on the adhesive surface was measured from the increase
in the weight of the plate.
The molding in Examples was performed in the
following conditions.
(I) Preform and bottle molding
Molding machine: SBIII-100H-15 manufactured
by Aoki Technical Laboratory, Inc. for bottle molding

with biaxial stretching
Cylinder temperature: 280 °C
Hot runner nozzle temperature: 290 °C
Injection pressure: 140 kg/cm2
Mold temperature: water cooling
Preform weight: 24 g
Bottle content: 500 ml
(II) Preform molding
Molding machine: SE280S manufactured by
Sumitomo Heavy Industries, Ltd.
Cylinder temperature: 285 °C
Injection rate: 100 mm/s
Mold temperature: 15 °C
(III) Molding of dumbbell molded article
MJEC-10 injection molding machine
manufactured by Modern Machinery Co. LTD
Cylinder temperature: 275 °C
Injection pressure: 55 kg/cm2
Mold temperature: 70 °C
Example 1
Using the apparatus shown in FIG. 3 and high-
purity terephthalic acid and EG as starting materials,
a PET resin was polymerized at a rate of 2.4 kg per
hour on the average by a continuous polymerization
method. Vertical stirring polymerization reactors
having paddle stirring blade (P2, P6, P10) were used as
the esterification reaction vessel (PI) and the first
and second stirring vessel type polymerization reactors

(P5, P9), and the materials were polymerized under a
reduced pressure by discharging them from the holes in
a perforated plate (3) and letting them fall down along
the supports (5) in a final polymerization reactor
(10). Polymerization was carried out under the
conditions shown in Table 1 and Table 3 by continuously
supplying a slurry-like 1 : 1.2 (by mole) mixture of
terephthalic acid and EG to the esterification reaction
vessel. The structure of the supports 1 used here is
described in Table 9.
In this operation, 0.04% by weight of
diantimony trioxide and 20 ppm of trimethyl phosphate
as phosphorus element were added continuously to the
polymerization intermediate obtained in the first
stirring vessel type polymerization reactor (P5).
Diantinony trioxide and trimethyl phosphate were each
added as a 2 wt% EG solution.
The properties of the polymerization
intermediate are shown in Table 1 and Table 3. The
polymerization intermediate supplied to the final
polymerization reactor had an intrinsic viscosity [ TJ ]
of 0.30 dl/g and a crystalline melting point of 255°C.
The polymerization intermediate of said PET
resin was supplied to the polymerization reactor (10)
from a feed opening (2) by a transfer pump (1) and
discharged from the holes in the perforated plate (3)
in a 260°C molten state at a rate of 10 g/min per hole.
Then, the intermediate was polymerized under a reduced

pressure of 65 Pa by letting it fall down along the
supports (5) at an ambient temperature same as the
discharge temperature, and discharged by a drainage
pump (8), and then palletized. The perforated plate
(3) was 50 mm thick and had 4 holes, each being 1 mm in
diameter, arranged linearly at intervals of 25 mm.
The supports (5) (supports 1 in Table 9)
comprised the 2 mm diameter and 8 m long wires, each
being suspended vertically and positioned close to a
hole, and the 2 mm diameter and 100 mm long wires
disposed at intervals of 15 mm to cross the above-said
wires at right angles to constitute a latticework. The
supports (5) were made of stainless steel.
The prepolymer in the polymerization reactor
(10) was foamed moderately, and there took place no
fouling of the polymerization reactor due to vehement
foaming. The resin falling down along the supports
contained a large volume of bubbles and was observed
rolling down along the supports in a form of bubble
balls.
The drainage pump (8) was operated while
watching the inside of the polymerization reactor (10)
from a sight glass (4) to check against accumulation of
the resin at the bottom of the reactor (10). The
residence time in the polymerization reactor in this
operation was 40 minutes. The residence time was
determined by using the value given by dividing the
amount of the resin staying in the reactor (10) by the

feed of the resin.
The polymerized PET resin was discharged out
continuously from the polymerization reactor by a
drainage pump (8) and drawn out in a form of strand
from the outlet (9). The obtained strand was cooled
and solidified in a 20°C running-water bath and
palletized continuously by a pelletizer.
The properties of the obtained resin and
pellets are shown in Table 1 and Table 2. Analysis of
the obtained cylindrical transparent pellets showed
that their intrinsic viscosity [ ri ] was 0.49 dl/g, the
amount of the carboxyl groups at the polymer terminal
was 28 meq/kg, the acetaldehyde content was 5.0 ppm,
the crystallization degree was 2.7%, and Mw/Mn = 2.1.
These pellets also had an excellent hue. The grain
size of the pellets was 3.0 mm in circle diameter and
2.0 mm in cylinder height on the average. The pellets
contained no fine particles (dust-size particles) with
a size of 1 mm or less.
Example 2
By following the same procedure as Example 1,
a PET resin was polymerized at a rate of 5.5 kg per
hour on the average by a continuous polymerization
method under the conditions shown in Table 1 and Table
4.
The perforated plate (3) was 50 mm thick and
had 7 holes, 1 mm in diameter, arranged linearly at
intervals of 10 mm in two parallel rows with a spacing

of 70 mm.
The supports (5) (supports 2 in Table 9)
comprised the seven 2 mm diameter and 8 m long wires,
each being suspended vertically and positioned close to
a hole, and the 2 mm diameter and 100 mm long wires
disposed at intervals of 100 mm to cross the above-said
group of seven wires at right angles to constitute a
wire gauze. Two sheets of such wire gauze were used
(Table 9).
The properties of the polymerization
intermediate are shown in Table 1 and Table 4. 10 kg
of the polymerized pellets were put into a vat and
subjected to a 10-hour heat treatment in a 130°C hot-air
dryer, and the heat treated pellets were further
subjected to biaxially oriented blow molding by an
injection molding machine. SB111-100H-15 manufactured
by Aoki Technical Laboratory, Inc. was used as the
biaxially oriented blow molding machine. The
properties of the obtained resin and pellets are shown
in Table 1 and Table 2.
The untreated pellets had the following
properties: intrinsic viscosity [ i) ] = 0.80 dl.g, amount
of carboxyl end groups of the polymer = 16 meq/kg,
acetaldyhyde content =5.4 ppm, crystallization degree
= 2.7%, Mw/Mn =2.1. They also had an excellent hue.
The grain size of the pellets was 3.0 mm in circle
diameter and 2.0 mm in cylinder height on the average.
The pellets were free of fine powders with a size of 1

mm or smaller.
The treated pellets have advanced in
crystallization and assumed a milky white color. These
pellets had an intrinsic viscosity [77] of 0.80 dl.g, a
carboxyl end group amount of 16 meq/kg and an
acetaldehyde content of 2.8 ppm. These values were
equal to or lower than those of the PET resins produced
by the conventional solid-state polycondensation
techniques. On the other hand, the crystallization
degree of the said pellets was relatively low at 25%
and Mw/Mn was 2.1, indicating a limited distribution of
molecular weight. These pellets also excelled in hue
and contained no fine particles with a size of 1 mm or
smaller.
The preform and hollow body produced by
injection molding the treated pellets had an intrinsic
viscosity [77] of 0.78 dl/g and were limited in
reduction of viscosity during molding. The
acetaldehyde content was also low: 9.0 ppm in preform
and 7.2 ppm in hollow body. They also had an excellent
hue.
Example 3
A polymerization intermediate was produced by
using the apparatus of FIG. 3. The process steps after
the transfer pump (1) operation, viz. polymerization
and molding, were carried out using the apparatus of
FIG. 5.
Polymerization was carried out in the same

way as in Example 1 by polymerizing a PET resin by a
continuous polymerization method under the conditions
shown in Table 1 and Table 5 at a rate of 4 0 kg per
hour on the average.
The perforated plate (3) was 50 mm thick and
had 15 holes, 1 mm in diameter, arranged linearly at
intervals of 10 mm in three parallel rows spaced 70 mm
from each other.
The supports (5) (supports 3 in Table 9)
comprised 15 pieces of 2-mm diameter and 8 m long wire,
each being suspended vertically and positioned close to
a hole, and the 2-mm diameter and 150 mm long wires
disposed at intervals of 100 mm to cross the above-said
group of 15 wires at right angles to constitute a wire
gauze. Three sheets of such wire gauze were used.
The properties of the polymerization
intermediate are shown in Table 1 and Table 5. The
polymerization intermediate supplied to the final
polymerization reactor had an intrinsic viscosity [ 77 ]
of 0.50 dl/g and a crystalline melting point of 255°C.
Polymerization was carried out using the
final polymerization reactor (10) shown in FIG. 5 and a
molding machine under the conditions of Table 1 to
obtain a PET resin having an intrinsic viscosity of
0.80 dl/g, and this resin was passed as it was through
transfer piping (II) and led into an injection molding
machine A for conducting biaxially oriented blow
molding. Here, one set of SB111-100H-15 manufactured

by Aoki Technical Laboratory, Inc. was used as the
biaxially oriented blow molding machine, and the
molding operations from preform molding to hollow body
molding were conducted successively under the
conditions of: resin temperature = 280°C, injection time
= 7 seconds, cooling time = 3 seconds and cycling time
= 18 seconds. Other molding machines B and C shown in
FIG. 5 were not used, and instead a discharge nozzle
was provided to allow discharge of the surplus resin.
First, the resin was drawn out in a form of
strand from the discharge nozzle, palletized
continuously in the same way as in Examples 1 and 2,
then heat treated and injection molded to produce a
preform and a hollow body.
Then 30 g of molten resin was extruded from
the discharge nozzle into a compression mold and
compressed to produce a preform. After 10 seconds of
compression molding, the preform female die was
replaced by a blow molding male die and compressed air
was blown into the mold from a compressed air nozzle
provided in the preform male die to produce a hollow
body.
The properties of the obtained resin and
pellets are shown in Table 1 and Table 2. The obtained
PET resin pellets and moldings before and after the
treatment were the high-quality ones having a high
polymerization degree, an excellent hue and a low
acetaldehyde content.

Comparative Example 1
3y following the same procedure as Example 1
except for nonuse of the final polymerization reactor
(10) in the apparatus of FIG. 3, PET was polymerized by
a continuous polymerization method under the conditions
shown in Table 1 and Table 6 at a rate of 2.4 kg per
hour on the average.
There was obtained a PET resin having an
intrinsic viscosity [ r\ ] of 0.57 dl/g. The properties
of the obtained resin and pellets are shown in Table 1,
Table 2 and Table 6. As seen from these tables, the
acetaldehyde content was high and hue of the products
was also bad.
Comparative Example 2
A polymerization intermediate having an
intrinsic viscosity of 0.49 dl/g obtained according to
Example 2 was extruded into water from a discharge
nozzle and made into pellets by a cutter. The obtained
pellets were vacuum dried (under a reduced pressure of
13.3 Pa or less at 80°C for 12 hours) and successively
subjected to a crystallization treatment (under a
reduced pressure of 13.3 Pa or less at 130°C for 3
hours, followed by additional 3-hour treatment at
160°C) . After allowed to cool by standing, the pellets
were put into a tumbler type solid-state
polycondensation reactor to conduct solid-state
polycondensation while maintaining the inside of the
system under a reduced pressure of 13.3 Pa or less and

at 215°C.
The produced pellets had a crystallization
degree of as high as 58.8% and a large Mw/Mn ratio of
2.4, and contained a large volume of fine particles.
The pellets were further subjected to a heat treatment
under the same conditions as in Example 2, but the
acetaldehyde content was not reduced.
Injection molding and biaxially oriented blow
molding were conducted with these pellets under the
same conditions as used in Example 2. Also, these
pellets were melted by an extruder and the melt was
extruded and compression molded under the same
conditions as in Example 3.
The properties of the polymerization
intermediate and the obtained resin and pellets are
shown in Table 1 and Table 2. The pellets produced by
solid-state polycondensation were greater in reduction
of polymerization degree in the molding work and also
higher in amount of acetaldehyde as a by-product
generated than those of the Examples.
Comparative Examples 3 to 5
Using a polymerization intermediate having an
intrinsic viscosity of 0.45 dl/g and a carboxyl end
group amount of 0.30 meq/kg, polymerization was carried
out under the conditions shown in Table 1. The
properties of the polymerization intermediate and the
obtained resin are shown in Table 1. In the case of
Comparative Example 3, vehement bubbling took place due

to too high discharge temperature and polymerization
temperature to cause fouling of the nozzle surface and
wall surfaces. Also, the obtained polymer was
discolored to yellow and non-uniform in hue.
In the case of Comparative Example 4, because
of too low setting of both discharge temperature and
polymerization temperature, the polymerization
intermediate was solidified and incapable of discharge
from the holes in the perforated plate.
In the case of Comparative Example 5, because
the interior of the polymerization reactor was set at
normal pressure, the falling polymer did not contain a
large amount of bubbles, so that its polymerization
degree did not rise up but was rather reduced as a
result of thermal decomposition.
Comparative Example 6
Using the apparatus shown in FIG. 1, a high
polymerization degree PET was produced from a
polymerization intermediate having an intrinsic
viscosity [ r\ ] of 0.45 dl/g, a carboxyl end group amount
of 30 meq/kg and a crystalline melting point of 255°C.
The residence time in this operation was 60 minutes.
There took place little vehement bubbling of the
prepolymer discharged from the perforated plate (3) in
the polymerization operation, and therefore fouling of
the nozzle surface and wall surfaces by such bubbling
was strikingly reduced. On the other hand, the falling
resin contained a large volume of bubbles, and there

was observed the behavior of the resin rolling down in
a form of bubble balls along the supports. The
obtained polymer had a high polymerization degree and a
good hue but its acetaldehyde content was as high as 40
ppm. The properties of the polymerization intermediate
and the obtained resin are shown in Table 1.
Examples 4 to 6
Using a polymerization intermediate having an
intrinsic viscosity of 0.45 dl/g and a carboxyl end
group amount of 0.30 meq/kg, a prepolymer was
discharged out form a perforated plate having 4 holes
arranged lattice-wise under the conditions of Table 1
at a rate of 10 g/min per hole, and polymerization was
carried out using the supports of a structure
described later. The supports, in Example 4, were a
cubic latticework (supports 4) comprising the 3 mm
diameter wires combined with each other at intervals of
30 mm vertically and 50 mm transversely. Used as the
supports in Example 5 were chains of ellipsoids
measuring 3 mm in linear diameter, 50 mm in length and
20 mm$ in curvature (supports 5), and the supports used
in Example 6 were the wires having a round section with
a diameter of 5 mm (supports 6). The properties of the
polymerization intermediate and the obtained resin are
shown in Table 1. In each case, vehement bubbling of
the prepolymer discharged from the perforated plate and
fouling of the nozzle surface, etc., caused thereby
were minimized, and the falling resin contained a large

volume of bubbles. The obtained polymer was a
homogeneous high-quality PET having a high
polymerization degree, an excellent hue and a low
acetaldehyde content. Of the supports used in these
Examples, those having a structure hindering the fall
of the polymer, such as cubic latticework or chain
type, could provide a polymer with a higher
polymerization degree under the same conditions.
Example 7
Using the apparatus of FIG. 4 and using DMT
and EG as starting materials, a PET resin was
polymerized by a continuous polymerization method at a
rate of 2.4 kg per hour on average. A vertical
polymerization reactor having a turbine stirring blade
was used as the first and second ester exchange
reaction vessels (El, E2), and a vertical stirring
polymerization reactor having a paddle stirring blade
(E10) was used as the first stirring vessel type
reactor (E9). There was also used a horizontal
stirring polymerization reactor (E13) having a single-
screw disc stirring blade. The final polymerization
reactor (10) was the same as used in Example 1.
Polymerization was carried out under the
conditions shown in Table 1 and Table 7 by continuously
supplying DMT and an EG solution at a molar ratio of
1 : 2 to an esterification reactor, said EG solution
being prepared by adding manganese acetate in an amount
of 0.05% by weight based on DMT. In this operation,

trimethyl phosphate of an amount of 100 ppm as the
weight ratio of phosphorus element and 0.04% by weight
of diantimony trioxide were added continuously to the
polymer obtained from the line between the second ester
exchange reaction vessel (E5) and the first stirring
vessel type polymerization reactor (E9). Diantimony
trioxide and trimethyl phosphate were both added as an
EG solution with a concentration of 2% by weight.
The properties of the polymerization
intermediate and the obtained resin are shown in Table
1. The polymerization intermediate supplied to the
final polymerization reactor (10) is embraced within
the scope of the present invention. Vehement bubbling
of the polymerization intermediate discharged from the
perforate plate and fouling of the nozzle surface,
etc., caused by such bubbling were minimized. The
falling resin contained a large volume of bubbles, and
the obtained polymer was a homogeneous high-quality PET
resin having a high polymerization degree, an excellent
hue and a low acetaldehyde content.
Example 8
Polymerization was carried out under the
conditions shown in Table 1 and Table 7 in the same way
as in Example 7 except that nitrogen of the amount
shown in Table 1 was introduced from an inert gas
feeding port (6) of the polymerization reactor (10).
The properties of the polymerization intermediate and
the obtained resin are shown in Table 1.

The polymerization intermediate supplied to
the final polymerization reactor falls within the scope
of the present invention. Vehement bubbling of the
polymerization intermediate discharged from the
perforated plate (3) and fouling of the nozzle surface,
etc., caused thereby were minimized. The falling resin
contained a large volume of bubbles, and the obtained
polymer had a high polymerization degree, a good hue
and a low acetaldehyde content and was confirmed to be
a homogeneous high-quality PET resin.
Comparative Example 7
Following the same procedure as in Example 7
except for the decrease of polymerization rate to 1.2
kg per hour and nonuse of the polymerization reactor
(10), polymerization was carried out under the
conditions of Table 1 and Table 8 using the apparatus
shown in FIG. 4. The properties of the polymerization
intermediate and the obtained resin are shown in Table
1. The obtained polymer could not be increased in
polymerization degree to a satisfactory level, and it
also assumed a yellowish discoloration and had a high
acetaldehyde content.
Example 9
Polymerization was carried out in the same
way as in Example 2 except for use of a polymerization
apparatus in which an inert gas is introduced into the
polymerization reactor (10) by an inert gas absorption
apparatus (N10) and use of the conditions shown in

Table 1. The perforated plate (N3) of the inert gas
absorption apparatus (N10) had nine 1-mm diameter holes
arranged in lattice form, and the supports (N5)
(supports 6 in Table 9) comprised the 5 mm diameter and
8 m long stainless steel wires having a circular
sectional shape. One support (N5) was provided for
each of the holes of the perforated plate (N3) .
Nitrogen gas was supplied into the absorption apparatus
for maintaining the inside thereof under a pressure of
.0.11 MPa, causing the polymerization intermediate
falling down along the supports (N5) to absorb and
contain nitrogen.
The transfer pump (Nl) was operated while
watching the inside of the inert gas absorption
apparatus (N10) from a sight glass to make sure that
the polymer would not substantially be accumulated at
the bottom of the absorption apparatus. There existed
a certain amount of bubbles in the polymer transferred
from the absorption apparatus. Also, when the change
of gas pressure was examined by stopping the supply of
nitrogen gas to the absorption apparatus, there was
noted a change of pressure corresponding to 0.5 mg of
gas per gram of polymer. This amount is considered as
the quantity of nitrogen gas absorbed and contained in
_ the polymerization intermediate. Supposing that the
whole amount of feed gas has been introduced into the
polymerization reactor, the quantity of nitrogen
introduced into the polymerization reactor was

determined.
The properties of the polymerization
intermediate and the obtained resin are shown in Table
1. Observation from the sight glass (4) confirmed that
the falling polymer was in a foamed state and contained
a large volume of bubbles. The polymerization
intermediate supplied to the final polymerization
reactor (10) is embraced within the scope of the
present invention. There took place little vehement
bubbling of the polymerization intermediate discharged
from the perforated plate (3), and so fouling of the
nozzle surface, etc., caused thereby was minimized.
The obtained polymer had a high polymerization degree,
a good hue and a low acetaldehyde content and proved to
be a homogeneous high-quality PET resin.
Example 10
Using the apparatus shown in FIG. 1, the
polymerization intermediate of a PET resin having an
intrinsic viscosity [77] of 0.52 dl/g, a carboxyl end
group amount of 30 meq/kg and a crystalline melting
point of 256°C was supplied continuously to the
polymerization reactor (10) from the feed opening (2)
by the transfer pump (1), and the 255°C melt thereof was
discharged out from the holes of the perforated plate
(3) at a rate of 10 g/min per hole. Then the
discharged material was polymerized under a reduced
pressure of 60 Pa by letting it fall along the supports
at an ambient temperature same as the discharge

temperature.
The perforated plate of the polymerization
reactor was 50 mm thick and had 7 holes, 1 mm in
diameter, arranged linearly at intervals of 10 mm. The
supports comprised the 2-mm diameter and 8 m long
wires, each being hanged down vertically and positioned
close to a hole, and the 2-mm diameter and 100 mm long
wires disposed at intervals of 100 mm to cross the
above-said wires at right angles to constitute a
latticework. Stainless steel was used as the support
material.
The residence time in the polymerization
reactor in the polymerization operation was 55 minutes.
The residence time was determined by using the value
obtained by dividing the amount of the polymer
remaining in the polymerization reactor by the feed of
the resin. In this polymerization operation, vehement
bubbling of the PET resin polymerization intermediate
discharged from the perforated plate and fouling of the
nozzle surface and wall surfaces caused thereby were
minimized. On the other hand, the falling PET resin
contained a large volume of bubbles and was observed
rolling down along the support in a form of bubble
balls.
The polymerized PET resin was discharged
continuously from the polymerization reactor by the
drainage pump (8) and drawn out as a strand from the
outlet (9). This strand was cooled and solidified in a

20°C running-water bath and palletized continuously by a
pelletizer.
Analyzing the obtained cylindrical
transparent pellets, it was found that the intrinsic
viscosity [77] of the pellets was 0.81 dl/g, the amount
of the carboxyl groups at the molecular terminal of the
polymer was 28 meq/kg, the acetaldehyde content was 4.8
ppm, the crystallization degree was 2.7%, and Mw/Mn =
1.9. The grain size of the pellets was 3.0 mm in
diameter and 2.0 mm in cylinder height on the average.
When 10 kg of these pellets were put into a
vat and heat treated by a 140°C hot-air dryer for 8
hours, the pellets were crystallized and became milky
white. Analysis of the pellets after the treatment
showed that their intrinsic viscosity [ r? ] was 0,81
dl/g, the amount of the carboxyl end groups was 28
meq/kg, and the acetaldehyde content was as low as 1.2
ppm. Also, the crystallization degree was relatively
low 39.5% and Mw/Mn was as small as 1.9, indicating
homogeneity of the produced resin.
These heat treated pellets were further
subjected to the molding operations from preform
molding to hollow body molding at a molding temperature
of 280°C using a biaxially oriented blow molding machine
(SB111-100H-15 manufactured by Aoki Technical
Laboratory, Inc.).
Analyzing the produced preform, it was found
that this preform was low in acetaldehyde content (7.1

ppm) and also had a good hue. Reduction of
polymerization degree after molding was also limited.
The evaluation results are shown in Table 10 along with
the properties of the PET resin used as starting
material, etc.
Comparative Example 8
Analysis of the commercially available flat
cylindrical highly crystallized PET resin pellets
produced by solid-state polycondensation showed that
their intrinsic viscosity [ rj ] was 0.80 dl/g, the amount
of the carboxyl end groups of the polymer was 30
meq/kg, the acetaldehyde content was 3.6 ppm, the
crystallization degree was 59.6%, and Mw/Mn = 2.4. The
grain size of the pellets was 3 mm and 1.5 mm in major
diameter and minor diameter, respectively, of the
circle, and 3.0 mm in cylinder height on the average.
10 kg of these pellets were put into a vat as
in Example 10 and subjected to an 8-hour heat treatment
by a 140°C hot-air dryer. Analysis of the resultant
milky white pellets showed that their intrinsic
viscosity [77] was 0.80 dl/g, the amount of the carboxyl
end groups was 30 meq/kg, and the acetaldehyde content
was 3.6 ppm, which were all unchanged from those before
the heat treatment. Also, the crystallization degree
was 59.6% and Mw/Mn =2.4.
Further, using the pellets after the heat
treatment, the molding operations were continued from
preform molding to hollow body molding at a molding

temperature of 280°C according to Example 10.
Analysis of the produced preform showed a
high acetaldehyde content of 17.6 ppm. Reduction of
polymerization degree after molding was also relatively
large. The evaluation results are shown in Table 10
along with the properties of the PET resin used as
starting material, etc.
Comparative Example 9
Analysis of the commercially available flat
^cylindrical transparent PET resin pellets produced by
melt polymerization showed that these pellets had an
intrinsic viscosity [ TJ ] of 0.58 dl/g, the amount of
carboxyl groups at the molecular terminal of the
polymer was 40 meq/kg, the acetaldehyde content of
these pellets was 41.3 ppm, their crystallization
degree was 2.7%, and Mw/Mn = 2.0. The grain size of
these pellets was 3 mm and 1.6 mm in major diameter and
minor diameter, respectively, of the circle, and 3.1 mm
in cylinder height on the average.
10 kg of these pellets were put into a vat
and heat treated by a 140°C hot-air dryer for 8 hours as
in Example 10. Analysis of the pellets after the heat
treatment showed: intrinsic viscosity [77] = 0.58 dl/g,
amount of carboxyl end groups = 40 meq/kg, acetaldehyde
content = 14.3 ppm, crystallization degree = 44.1%, and
Mw/Mn =2.0.
Further, using these pellets after the heat
treatment, the molding operations were conducted from

preform molding to hollow body molding at a molding
temperature of 280°C in the same way as in Example 10.
Analyzing the produced preform, it was found
that its acetaldehyde content was as high as 24.6 ppm.
The evaluation results are shown in Table 10 along with
the properties of the starting PET resin, etc.
Example 11
Polymerization, heat treatment and molding
were carried out under the same conditions as used in
Example 10 except that the heat treatment was conducted
at 160°C for 6 hours. Analysis of the pellets after the
treatment gave the following results: intrinsic
viscosity [ TJ } = 0.81 dl/g, amount of carboxyl end
groups = 28 meq/kg, acetaldehyde content = 0.5 ppm,
crystallization degree = 42.9%, and Mw/Mn = 1.9.
Analyzing the produced preform, it was found that its
acetaldehyde content was as low as 6.6 ppm and it also
had a good hue. The evaluation results are shown in
Table 10 along with the properties of the starting PET
resin, etc.
Comparative Example 10
Polymerization, heat treatment and molding
were carried out under the same conditions as used in
Example 10 except that the heat treatment was conducted
at 240°C for 15 hours. Analysis of the pellets after
the treatment gave: intrinsic viscosity [77] = 0.88
dl/g, amount of carboxyl end groups = 38 meq/kg,
acetaldehyde content = 1.3 ppm, crystallization degree

= 57.4%, and Mw/Mn =2.1. The produced preform was
found on analysis to have a high acetaldehyde content
of 15.3 ppm. This is considered attributable to high-
degree crystallization of the pellets after the
treatment. Also, reduction of polymerization degree
after molding was large, and the hue was deteriorated
in comparison with Examples 10 and 11. The evaluation
results are shown in Table 10 along with the properties
of the starting PET resin, etc.
Examples 12 and 13
Polymerization, heat treatment and molding
were carried out under the same conditions as used in
Example 10 except for a change of the polymerization
conditions and a change of the properties of the PET
resin before the heat treatment. The evaluation
results are shown in Table 10 along with the properties
of the starting PET resin, etc. The lower the
crystallization degree or the lower the acetaldehyde
content of the PET resin before the treatment, the less
the acetaldehyde content after the treatment can be
made.
Example 14
Using the apparatus shown in FIG. 1, a
polymerization intermediate (of a polyethylene
terephthalate-isophthalate copolymer) having an
intrinsic viscosity [ rj ] of 0.50 dl/g, a carboxyl end
group amount of 32 meq/kg, a terephthalic acid moiety
to isophthalic acid moiety ratio in the polymer

skeleton of 98 : 2 and a crystalline melting point of
245°C, was polymerized and palletized under the same
conditions as used in Example 10. There were obtained
the transparent pellets having an intrinsic viscosity
[ j] ] of 0.82 dl/g, a carboxyl end group amount of 28
meq/kg, an acetaldehyde content of 4.6 ppm, a
crystallization degree of 2.8% and Mw/Mn = 2.0.
These pellets were subjected to a heat
treatment and molding under the same conditions as used
in Example 10 except that the heat treatment was
conducted at 190°C for 4 hours. Analysis of the
resultant pellets showed: intrinsic viscosity [77] =
0.82 dl/g, amount of carboxyl end group = 28 meq/kg,
acetaldehyde content = 0.4 ppm, crystallization degree
= 45.0%, and Mw/Mn = 2.0. Also, the produced perform
was found on analysis to have a low acetaldehyde
content of 6.3 ppm and a good hue. The evaluation
results are shown in Table 10 along with the properties
of the staring PET resin, etc.
Example 15
Polymerization, heat treatment and molding
were carried out under the same conditions as used in
Example 14 except that the heat treatment was conducted
at 200°C for 4 hours. Analysis of the obtained pellets
after the treatment showed: intrinsic viscosity [ 77 ] =
0.83 dl/g, carboxyl end group = 28 meq/kg, acetaldehyde
content = 0.5 ppm, crystallization degree = 49.3%, and
Mw/Mn = 2.0. Also, analysis of the produced preform

confirmed a low acetaldehyde content of 7.6 ppm and a
good hue of the product. The evaluation results are
shown in Table 10 along with the properties of the
starting PET resin, etc.
Example 16
Polymerization, heat treatment and molding
were carried out under the same conditions as used in
Example 10 except that the heat treatment was conducted
in an inert oven in a stream of nitrogen. The
evaluation results are shown in Table 10 along with the
properties of the starting PET resin, etc. Working in
a stream of nitrogen contributed to the reduction of
acetaldehyde content and an improvement of hue of the
molded product.
Example 17
Polymerization, heat treatment and molding
were carried out under the same conditions as used in
Example 10 except that the heat treatment was conducted
using a vacuum heating dryer evacuated to 80 Pa. The
evaluation results are shown in Table 10 along with the
properties of the starting PET resin, etc. Operations
under vacuum promoted the reduction of acetaldehyde
content and also improved hue of the molded product.
Comparative Example 11
Polymerization, heat treatment and molding
were carried out under the same conditions as used in
Example 17 except for use of the solid-state
polycondensed pellets employed in Comparative Example

8. The evaluation results are shown in Table 10 along
with the properties of the starting PET resin, etc. No
reduction of acetaldehyde content was observed although
the operations were conducted under vacuum.
Example 18
Polymerization, acetaldehyde removal
treatment and molding were carried out under the same
conditions as used in Example 10 except that instead of
conducting the heat treatment, there was conducted a
carbon dioxide cleaning treatment in which 2 kg of the
transparent pellets obtained by polymerization are
supplied to a 5-litre stainless steel autoclave, then
carbon dioxide of 5.0 MPa is injected into the
autoclave and left at room temperature for one hour,
causing the pellets to absorb carbon dioxide, and then
the pellets are led into and left in a vacuum
desiccator at room temperature under 80 Pa for one hour
to thereby remove carbon dioxide and acetaldehyde from
the pellets. The evaluation results are shown in Table
10 along with the properties of the starting PET resin,
etc. Application of the carbon dioxide cleaning
treatment realized a remarkable reduction of
acetaldehyde content of the pellets as well as a
lowering of crystallization degree, making it possible
to produce the excellent moldings.
Comparative Example 12
Polymerization, acetaldehyde removal
treatment and molding were carried out under the same

conditions as used in Example 18 except for use of the
solid-state polycondensed pellets used in Comparative
Example 8. The evaluation results are shown in Table
10 along with the properties of the starting PET resin,
etc.
No reduction of acetaldehyde was observed
despise the exercise of the carbon dioxide cleaning
treatment.
Comparative Example 13
The prepolymer (of a polyethylene
terephthalate-isophthalate copolymer) used in Example
14 - the one having an intrinsic viscosity [77] of 0.50
dl/g, a carboxyl end group amount of 36 meq/kg, an
acetaldehyde content of 66.4 ppm, a terephthalic acid
moiety to isophthalic acid moiety ratio in the polymer
skeleton of 98 : 2 and acrystalline melting point of
245°C - was palletized as it was to produce the
cylindrical pellets having a grain size of 3.0 mm in
circle diameter and 2.0 mm in cylinder height on the
average. These pellets were subjected to
polymerization, heat treatment and molding under the
same conditions as used in Example 14 except that the
heat treatment was conducted at 200°C for 4 hours.
Analysis of the obtained pellets after the treatment
gave the following findings: intrinsic viscosity [ rj ] =
0.55 dl/g, carboxyl end group = 35 meq/kg, acetaldehyde
content = relatively high 11.2 ppm, crystallization
degree = high 59.2%, and Mw/Mn =2.2. Also, analysis

of the produced preform showed a high acetaldehyde
content of 26.6 ppm. The evaluation results are shown
in Table 10 along with the properties of the starting
PET resin, etc.
Production Example 1
A titanium compound catalyst was prepared as
described below.
One litre of an ethanol solution containing
100 g of titanium (IV) tetraisoproxide was mixed with 1
• litre of an ethanol solution containing 120 g of
distilled water, then the precipitated solids of
titanium hydroxide were washed 5 times with deionized
water and dried in vacuo at 50°C, and the obtained solid
titanium compound was pulverized to the fine particles
of about 50 jum.
Production Example 2
A polymerization intermediate was produced as
described below.
A slurry-like 1 : 1.2 (by mole) mixture of
high-purity terephthalic acid and EG was supplied
continuously to an esterification reaction vessel to
carry out an esterification reaction with stirring at a
polymerization temperature of 250°C in a nitrogen
atmosphere. The average residence time in the
esterification reaction vessel was 220 minutes, and a
low-order condensate having an average molecular weight
of 1,200 was obtained. Then this low-order condensate
was supplied continuously to a stirring vessel type

melt polycondensation reactor along with the solid
titanium compound catalyst (equivalent to 50 ppm as
titanium atoms based on the terephthalic acid unit in
the low-order condensate) prepared in Production
Example 1 to carry out a polycondensation reaction
under the conditions of: polymerization temperature =
280°C, degree of vacuum = 300 Pa, average residence time
= 100 minutes, to produce a prepolymer having an
intrinsic viscosity [77] of 0.46 dl/g, a carboxyl end
group amount of 31 meq/kg and a crystalline melting
point of 256°C. The titanium content in this
intermediate product was 35 ppm.
Production Example 3
A polymerization intermediate was produced
under the same conditions as in Production Example 2
except that at the stage of polycondensation reaction,
magnesium carbonate (equivalent to 50 ppm as magnesium
atoms based on the terephthalic acid unit in the low-
order condensate) was supplied together with the solid
titanium compound catalyst. The obtained
polymerization intermediate had an intrinsic viscosity
[77] of 0.49 dl/g, a carboxyl end group amount of 30
meq/kg and a crystalline melting point of 256°C, and the
titanium content and the magnesium content in the
, intermediate were both 36 ppm.
Production Example 4
A polymerization intermediate was produced
under the same conditions as in Production Example 2

except that at the stage of polycondensation reaction,
tributyl phosphate (equivalent to 200 ppm based on the
terephthalic acid unit in the low-order condensate) was
supplied together with the solid titanium compound
catalyst. The obtained polymerization intermediate had
an intrinsic viscosity [ r\ ] of 0.50 dl/g, a carboxyl end
group amount of 28 meq/kg and a crystalline melting
point of 256°C, and the titanium content in the
intermediate was 36 ppm.
Production Example 5
A polymerization intermediate was produced
under the same conditions as in Production Example 2
except that at the stage of polycondensation reaction,
an ethylene glycol solution of aluminum acetylacetonate
(equivalent to 50 ppm as aluminum atoms based on the
terephthalic acid unit in the low-order condensate),
dimethyl phenylphosphonate (equivalent to 50 ppm based
on the terephthalic acid unit in the low-order
condensate) and lithium acetate dihydrate (equivalent
to 50 ppm as lithium atoms based on the terephthalic
acid unit in the low-order condensate) was supplied in
place of the solid titanium compound catalyst. The
obtained polymerization intermediate had an intrinsic
viscosity [ y ] of 0.49 dl/g, a carboxyl end group amount
of 30 meq/kg and a crystalline melting point of 256°C,
and the aluminum content and the lithium content in
this product were 37 ppm and 36 ppm, respectively.
Production Example 6

A polymerization intermediate was produced
under the same conditions as in Production Example 2
except that at the stage of polycondensation reaction,
an ethylene glycol solution of diantimony trioxide
(equivalent to 180 ppm as antimony atoms based on the
terephthalic acid unit in the low-order condensate),
trimethyl phosphate (equivalent to 50 ppm based on the
terphthalic acid unit in the low-order condensate) and
cobalt acetate (equivalent to 50 ppm as cobalt atoms
based on the terephthalic acid unit in the low-order
condensate) was supplied in place of the solid titanium
compound catalyst. The obtained polymerization
intermediate had an intrinsic viscosity [7?] of 0.52
dl/g, a carboxyl end group amount of 33 meq/kg and a
crystalline melting point of 256°C, and the antimony
content and the cobalt content in the product were 152
ppm and 35 ppm, respectively.
Example 19
Using the apparatus shown in FIG. 1, the
polymerization intermediate obtained in Production
Example 2 was supplied continuously to the
polymerization reactor (10) from the feed opening (2)
by the transfer pump (1), and the 255°C melt thereof was
discharged from the holes of the perforate plate (3) at
a rate of 10 g/min per hole and polymerized in a vacuum
of 50 Pa by letting it fall down along the supports at
an ambient temperature same as the discharge
temperature.

The perforated plate of the polymerization
reactor was 50 mm thick and had seven 1-mm diameter
holes arranged linearly at intervals of 10 mm. The
supports comprised the 2 mm diameter and 8 m long
wires, each being suspended vertically and positioned
close to a hole, and the 2 mm diameter and 100 mm long
wires provided at intervals of 100 mm to cross the
above-said wires at right angles to constitute a
latticework. Stainless steel was used as the support
material.
The residence time in the polymerization
reactor in the polymerization operation was 65 minutes.
The residence time was determined by using the value
given by dividing the amount of the polymer staying in
the reactor by the feed of the resin. Vehement
bubbling of the polymerization intermediate of PET
resin let out from the perforated plate in the
polymerization and fouling of the nozzle surface and
wall surfaces caused thereby were minimized. On the
^ other hand, the falling PET resin contained a large
volume of bubbles and was observed rolling down along
the supports in a form of bubble balls.
The polymerized PET resin was discharged
continuously from the polymerization reactor by the
drainage pump (8) and drawn out in a form of strand
from the outlet port (9). This strand was cooled and
solidified in a 20°C running-water bath and palletized
continuously by a pelletizer.

Analysis of the obtained cylindrical
transparent pellets showed that the intrinsic viscosity
[ ri ] of these pellets was 0.84 dl/g, the amount of the
carboxyl groups at the polymer terminal was 26 meq/kg,
and the acetaldehyde content was 4.9 ppm. The L value
and the b value of color difference determined by the
solution method were 99.8 and 0.17, respectively.
Using these pellets, the molding operations
were carried out continuously from preform molding to
hollow body molding at a molding temperature of 280°C by
a biaxially oriented blow molding machine (SBIII-100H-
15 manufactured by Aoki Technical Laboratory, Inc).
The obtained preform was found on analysis to
have an acetaldehyde content of 9.9 ppm and a good hue.
Example 20
Pellets were produced in the same way as in
Example 19 except that the polymerization intermediate
obtained in Production Example 3 was used in place of
the polymerization intermediate obtained in Production
Example 2.
Analyzing the produced pellets, it was found
that these pellets had an intrinsic viscosity [ r\ ] of
0.87 dl/g, a carboxyl end group amount of 30 meq/kg and
an acetaldehyde content of 5.0 ppm. The color
difference of the pellets determined by the solution
method was 99.8 in L value and 0.12 in b value.
Example 21
Pellets were produced in the same way as in

Example 19 except that the polymerization intermediate
obtained in Production Example 4 was used in place of
the polymerization intermediate obtained in Production
Example 2.
Analyzing the produced pellets, it was found
that these pellets had an intrinsic viscosity [ r\ ] of
0.85 dl/g, a carboxyl end group amount of 28 meq/kg and
an acetaldehyde content of 5.0 ppm. The color
difference of the pellets determined by the solution
method was 99.7 in L value and 0.11 in b value.
Example 22
Pellets were produced in the same way as in
Example 19 except that the polymerization intermediate
obtained in Production Example 5 was used in place of
the polymerization intermediate obtained in Production
Example 2.
Analysis of the produced pellets confirmed
that these pellets had an intrinsic viscosity [ r\ ] of
0.87 dl/g, a carboxyl end group amount of 29 meq/kg and
an acetaldehyde content of 5.1 ppm, and their color
difference determined by the solution method was 99.8
in L value and 0.13 in b value.
Example 23
Pellets were produced in the same way as in
Example 19 except for use of the polymerization
intermediate obtained in Production Example 6 in place
of the one obtained in Production Example 2.
Analysis of the produced pellets showed that

these pellets had an intrinsic viscosity [n ] of 0.88
dl/g, a carboxyl end group amount of 33 meq/kg and an
acetaldehyde content of 5.4 ppm. These pellets assumed
a slightly bluish discoloration, and their color
difference determined by the solution method was 99.3
in L value and -0.02 in b value.
Comparative Example 14
Using the polymerization intermediate product
obtained in Production Example 2, a PET resin was
- polymerized by 120-minute batch polymerization by a
conventional stirring vessel type melt polymerization
apparatus under the conditions of 255°C polymerization
temperature and 50 Pa vacuum, and the pellets were made
therefrom. Intrinsic viscosity [ t] ] of these pellets
reached the ceiling and never topped 0.60 dl/g, and it
was impossible to obtain PET with a desired molecular
weight. Also the pellets were light yellow in hue.
Comparative Example 15
Pellets were produced under the same
conditions as used in Comparative Example 14 except
that the polymerization temperature was raised to 275°C.
Intrinsic viscosity [ 77 ] of these pellets reached the
ceiling and never topped 0.70 dl/g, and it was
impossible to obtain PET with a desired molecular
weight. Also the pellets had a yellow hue.
Comparative Examples 16 to 19
Pellets were made from a PET resin
polymerized under the same conditions as in Comparative

Example 15 except for use of the polymerization
intermediates obtained in Production Examples 3 to 6 in
place of the polymerization intermediate obtained in
Production Example 2. In each case, intrinsic
viscosity [ TJ ] reached the ceiling and never topped 0.70
dl/g, and it was impossible to obtain PET with a
desired molecular weight. Also, the pellets were
yellowish in hue.
Example 24
Using the apparatus shown in FIG. 8 having a
polymer filter (11) which is a tube type filter with a
filter area of 0.0188 m2 and a filter precision of 30 n
m (mfd. by Nippon Seisen Co., Ltd.), and providing an
extruder upstream of the transfer pump (1), the
commercially available PET resin pellets having an
intrinsic viscosity [77] of 0.58 dl/g, a carboxyl end
group amount of 40 meq/kg, an acetaldehyde content of
41.3 ppm and Mw/Mn =2.0 were supplied as the
polymerization intermediate at a rate of 2.0 kg per
hour from the pellet hopper of the extruder, and they
were polymerized at a polymerization temperature of
255°C under a reduced pressure of 65 Pa by discharging
the melt from the holes of the perforated plate (3) and
letting it fall down along the supports (5) in the
polymerization reactor (10). A heating medium was
passed through the outside jacket of the line to keep
the resin temperature in the polymer filter section at
265°C. The perforated plate (3) was 50 mm thick and had

4 holes, 1 mm in diameter, arranged linearly at
intervals of 25 mm.
The supports (5) comprised the 2 mm diameter
and 8 m long wires, each being suspended vertically and
positioned close to a hole, and the 2 mm diameter and
100 mm long wires disposed at intervals of 15 mm to
cross the above-said wires at right angles to
constitute a wire gauze. Stainless steel was used as
the support material.
The polymerization intermediate in the
polymerization reactor (10) was foamed to a proper
degree, and there took place no fouling of the reactor
due to vehement bubbling. On the other hand, the resin
falling down along the supports contained a volume of
bubbles and was observed rolling down in a form of
bubble balls.
The obtained polymer was a high-quality PET
resin having the following properties: intrinsic
viscosity [77] = 0.77 dl/g, carboxyl end group = 29
meq/kg, acetaldehyde content = 6.3 ppm, Mw/Mn = 2.0,
and color difference determined by the solution method,
L = 99.6 and b = 0.36.
The polymerization was conducted for 15 days
continuously under the above conditions, but the
polymer quality remained stable throughout the period.
Also, the polymer was checked for extraneous matter
every 5 days from the 5th day after start of
polymerization, but there was seen no extraneous matter

with a size exceeding 30 nm in the polymer.
Example 25
Polymerization was carried out for 15 days
continuously under the same conditions as in Example 24
except that a mixture of 5% by weight of the cleaned
flakes of recovered PET bottles and 95% by weight of
PET resin pellets having an intrinsic viscosity [ 73 ] of
0.58 dl/g, a carboxyl end group amount of 40 meq/kg, an
acetaldehyde content of 41.3 ppm and Mw/Mn =2.0 was
used as the polymerization intermediate of PET resin.
The obtained polymer was a high-quality PET
resin having an intrinsic viscosity [77] of 0.78 dl/g, a
carboxyl end group amount of 30 meq/kg, an acetaldehyde
content of 6.5 ppm, and Mw/Mn = 2.0, with its color
difference determined by the solution method being L =
99.2 and b = 0.38. The polymer remained stable
throughout the period of polymerization. The polymer
was also checked for extraneous matter periodically, or
every 5 days from the 5th day after start of
polymerization, but there was observed no extraneous
matter with a size exceeding 30 /zm in the polymer.
Comparative Examples 20 and 21
Polymerization and examination for the
presence or absence of extraneous matter were conducted
under the same conditions as in Example 24 and Example
25, respectively, except for nonuse of the polymer
filter (11). The obtained polymer contained 5 to 18
pieces of black extraneous matter with a size of 100 to

200 fim per 300 g of the PET resin. The black
extraneous matter is considered to have been produced
as the polymerization intermediate was decomposed in
the extruder by the action of oxygen contained in the
pellets or recovered flakes of polymerization
intermediate or the infiltration of air in the extruder
used for melting the polymerization intermediate.
Example 26
Using the apparatus shown in FIG. 1, the
polymerization intermediate of a PET resin having an
intrinsic viscosity [ TJ ] of 0.43 dl/g, a carboxyl end
group amount of 30 meq/kg and a crystalline melting
point of 255°C was supplied continuously to the
polymerization reactor (10) from the feed opening (2)
by the transfer pump (1) , and the 255°C melt thereof was
discharged from the holes of the perforated plate (3)
at a rate of 10 g/min and polymerized by letting it
fall along the supports at an ambient temperature same
as the discharge temperature.
The perforated plate (3) of the
polymerization reactor (10) was 50 mm thick and had 7
holes, 1 mm in diameter, arranged linearly at intervals
of 10 mm. The supports (5) comprised the 2 mm diameter
and 8 mm long wires, each being suspended vertically
and positioned close to a hole, and the 2 mm diameter
and 100 mm long wires disposed at intervals of 100 mm
to cross the above-said wires at right angles to
constitute a latticework. Stainless steel was used as

the support material.
The residence time in the polymerization
reactor in the polymerization operation was 60 minutes.
This resistance time was determined by using the value
given by dividing the amount of the polymer staying in
the polymerization reactor by the feed of the resin.
Vehement bubbling of the polymerization intermediate of
PET resin discharged from the perforated plate in
polymerization and fouling of the nozzle surface and
wall surfaces caused thereby were minimized. On the
other hand, the falling PET resin contained a large
volume of bubbles and was observed rolling down along
the supports in a form of bubble balls.
The polymerized PET resin was discharged
continuously from the polymerization reactor (10) by
the drainage pump (8) and drawn out as a strand from
the outlet (9). This strand was cooled and solidified
in a 20°C running-water bath and palletized continuously
by a pelletizer. Intrinsic viscosity [ 77 ] of the
pellets was 0.82 dl/g. The pellets were heat treated
in a vacuum dryer at 130°C for 10 hours and crystallized
simultaneously with drying. The crystallized pellets
were solid-state polycondensed by a tumbler type solid-
state polycondensation reactor under a reduced pressure
of 50 Pa at 210°C for 12 hours to obtain a high quality
PET resin having an intrinsic viscosity [ 77 ] of as high
as 1.32 dl/g and a good hue and also, quite
surprisingly, very low in acetaldehyde content.

Further, the amount of fine powder generated by rubbing
of the pellets during solid-state polycondensation was
minimized to provide an economical advantage. The
properties of the pellets obtained from the solid-phase
polymerization are shown in Table 11.
Comparative Example 22
The pellets of a PET resin having an
intrinsic viscosity [ r? ] of 0.44 dl/g, a carboxyl end
group amount of 32 meq/kg and a crystalline melting
point of 255°C were heat treated in a vacuum dryer at
130°C for 12 hours and crystallized simultaneously with
drying. The crystallized pellets were subjected to
solid-state polycondensation by a tumbler type solid-
state polycondensation reactor under a reduced pressure
of 50 Pa at 210°C for 10 hours. The obtained pellets
had a low intrinsic viscosity [ rj ] of 0.58 dl/g, and
also there was produced fine powder in bulk to cause an
economical loss. The properties of the pellets
obtained from the above solid-state polycondensation
are shown in Table 11.
Comparative Example 23
Polymerization was carried out under the same
conditions as applied in Comparative Example 22 except
that the solid-state polycondensation time was
prolonged to 48 hours. The obtained pellets were still
low in intrinsic viscosity [77], which was 0.85 dl/g.
Further, the hue of the pellets was aggravated and
there was formed a greater volume of fine powder than

in Comparative Example 22 to suffer an economical loss.
The properties of these pellets are shown in Table 11.
Example 27
Using the apparatus shown in FIG. 1, a pellet
of a polymerization intermediate of a PET resin having
an intrinsic viscosity [ 7j ] of 0.49 dl/g, a carboxyl end
group amount of 32 meq/kg, a crystalline melting point
of 250°C and a cyclic trimer content of 0.40% by weight
was melted using an extruder placed upsteam of the
transfer pump (1) and was supplied continuously to the
polymerization reactor (10) from the feed opening (2)
by the transfer pump (1). And, the 255°C melt thereof
was discharged from the holes of the perforated plate
(3) at a rate of 10 g/min per hole and then polymerized
under a reduced pressure of 60 Pa by letting the melt
fall down along the supports at an ambient temperature
same as the discharge temperature.
Used as a polymerization intermediate here
was one prepared by immersing a pellet of the
polymerization intermediate in chloroform, removing a
part of a cyclic trimer included in the pellet by
extraction and drying the treated pellet. Thereto
added was 100 ppm of trimethyl phosphate at the time of
re-melting for the purpose of inhibiting the increase
of cyclic trimer content in the melt. A part of the
polymerization intermediate was sampled out, put into a
sample tube and, after sealing the tube, left in a
molten state at 275°C for 30 minutes in a nitrogen

atmosphere, and the increment of cyclic trimer content
after this melt-holding period was measured. It was as
low as 0.08% by weight.
The perforated plate of the polymerization
reactor was 50 mm thick and had 7 holes, each being 1
mm in diameter, arranged linearly at intervals of 10
mm. The supports comprised the 2-mm diameter and 8 m
long wires, each being suspended vertically and
positioned close to a hole, and the 2 mm diameter and
100 mm long wires disposed at intervals of 100 mm to
cross the above-said wires at right angles to
constitute a latticework. Stainless steel was used as
the support material.
The residence time in the polymerization
reactor in the polymerization operation was 65 minutes.
For the determination of residence time, there was used
the value given by dividing the amount of the polymer
staying in the polymerization reactor by the feed of
the resin. Vehement bubbling of the PET resin
polymerization intermediate discharged from the
perforated plate during polymerization and fouling of
the nozzle surface and wall surfaces caused thereby
were minimized. On the other hand, the falling PET
resin contained abundant bubbles and was observed
rolling down along the supports in a form of bubble
balls.
The polymerized PET resin was discharged
continuously from the polymerization reactor by the

drainage pump (8) and drawn out in a form of strand
from the outlet (9). This strand was cooled and
solidified in a 20°C running-water bath and palletized
continuously by a pelletizer.
The obtained cylindrical transparent pallets
were analytically determined to have an intrinsic
viscosity [n ] of 0.82 dl/g, a carboxyl end group amount
of 28 meq/kg, an acetaldehyde content of 5.2 ppm and a
cyclic trimer content of as low as 0.48% by weight. It
was found that the pellet was excellent one having
L=99.4 and b=0.36 of color difference determined by the
solution method.
Using these pellets, the molding operations
were carried out continuously from preform molding to
hollow body molding at a molding temperature of 280°C by
using a biaxially oriented blow molding machine (SBIII-
100H-15 mfd. by Aoki Technical Laboratory, Inc.).
On analysis, the produced perform was found
to have a low acetaldehyde content of 11.3 ppm, also a
low cyclic trimer content of 0.50% by weight and a good
hue.
Example 28
Pellets were produced by carrying out
polymerization in the same way as in Example 27 except
that trimethyl phosphate was not added when re-melting
the intermediate. A part of the polymerization
intermediate was sampled out, put into a sample tube,
and after sealing the tube, left in a molten state at

275°C for 30 minutes in a nitrogen atmosphere, and the
increment of cyclic trimer content after the melt
holding operation was measured. It was 0.22% by weight.
The obtained cylindrical transparent pellets
were found on analysis to have an intrinsic viscosity
[77] of 0.87 dl/g, a carboxyl end group amount of 28
meq/lg. an acetaldehyde content of 5.1 ppm and a cyclic
trimer content of as low as 0.63% by weight. It was
found that the pellet was excellent one having L=99.4
and b=0.39 of color difference determined by the
solution method.
Example 29
Pellets were produced by carrying out
polymerization in the same way as in Example 27 except
that a PET resin polymerization intermediate having an
intrinsic viscosity [ TJ ] of 0.49 dl/g, a carboxyl end
group amount of 30 meq/kg, a crystalline melting point
of 250°C and a cyclic trimer content of 1.2% by weight
was used as starting material.
The polymerization intermediate used here was
the one produced by a conventional melt polymerization
method. A part of this polymerization intermediate was
sampled out and kept in a sealed sample tube in a
molten state at 275°C for 30 minutes in a nitrogen
atmosphere, and the increment of cyclic trimer content
after the melt holding operation was measured. It was
as high as 0.38% by weight.
The obtained cylindrical transparent pellets

were analyzed to find: intrinsic viscosity [77] =0.86
dI/g; carboxyl end group = 28 meq/kg; acetaldehyde
content = 5.4 ppm; color difference determined by the
solution method, L = 99.3 and b = 0.37; and cyclic
trimer content = 0.82% by weight.
Example 30
When the pellets obtained in Example 29 were
extracted with chloroform at normal temperature for 10
hours, the cyclic trimer content could be decreased to
0.16% by weight. Using these pellets, the molding
operations were carried out continuously from preform
molding to hollow body molding according to the
procedure of Example 27. The produced preform was
found on analysis to have an intrinsic viscosity [ r\ ] of
0.80 dl/g, an acetaldehyde content of 0.7 ppm, a
carboxyl end group of 28 meq/kg and a cyclic trimer
content of as low as 0.22% by weight. It was an
excellent pellet having L=99.3 and b=0.38 of color
difference determined by the solution method.
Comparative Example 24
The polymerization intermediate same as used
in Example 27 was polymerized by a conventional
stirring vessel type melt polymerization reactor at a
polymerization temperature of 255°C under a reduced
pressure of 55 Pa by setting the polymerization time at
2 hours. There were obtained the pellets discolored to
light yellow, with its intrinsic viscosity [ 77 ] never

exceeding 0.50 dl/g. When the similar polymerization
was conducted at a polymerization temperature of 275°C
under a reduced pressure of 55 Pa by setting the
polymerization time at 2 hours, there were obtained the
yellow-tinted pellets whose cyclic trimer content
increased to 0.84% by weight, with their intrinsic
viscosity [ µ ] never exceeding 0.55 dl/g.
Comparative Example 25
The same polymerization intermediate as used
in Example 29 was polymerized by a conventional
stirring vessel type melt polymerization reactor at a
polymerization temperature of 255°C under a reduced
pressure of 55 Pa by setting the polymerization time at
2 hours. There were obtained the yellow-discolored
pellets with an intrinsic viscosity [ r\ ] not exceeding
0.52 dl/g. When the similar polymerization was carried
out at a polymerization temperature of 275°C under a
reduced pressure of 55 Pa by setting the polymerization
time at 2 hours, there were obtained the yellow-
discolored pellets having an intrinsic viscosity [ r\ ] of
0.59 dl/g (never exceeding 0.60 dl/g).
Extraction of the obtained pellets with
chloroform in the same manner as in Example 30 could
decrease the cyclic trimer content to 0.23% by weight.
Using these pellets, the molding operations were
conducted continuously from preform molding to hollow
body molding according to the procedure of Example 27,
but the molding ruptured during hollow body molding

succeeding preform molding because of the low
polymerization degree of the polymer, and it was
impossible to produce a desired hollow body.
The produced preform was found on analysis to
have an intrinsic viscosity [77] of 0.52 dl/g and a
cyclic trimer content of 0.37% by weight. The preform
was also discolored to in yellow.
Production Example 7
Using the apparatus shown in FIG. 1, a
polymerization intermediate of a PET resin having an
intrinsic viscosity [77] of 0.50 dl/g, a carboxyl end
group amount of 28 meq/kg and a crystalline melting
point of 252°C was supplied continuously to the
polymerization reactor (10) from the feed opening (2)
by the transfer pump (1), and the 265°C melt thereof was
discharged from the holes of the perforated plate (3)
at a rate of 10 g/min per hole and let fall down along
the supports at an ambient temperature same as the
discharge temperature to exercise polymerization under
a reduced pressure of 60 Pa.
The perforated plate of the polymerization
reactor was 50 mm thick and had 7 holes, each being 1
mm in diameter, arranged linearly at intervals of 10
mm. The supports comprised the 2-mm diameter and 8 m
long wires, each being suspended vertically and
positioned close to a hole, and the 2-mm diameter and
100 mm long wires disposed at intervals of 100 mm to
cross the above-said wires at right angles to

constitute a latticework. Stainless steel was used as
support material.
The residence time in the polymerization
reactor in the polymerization operation was 70 minutes.
The residence time was determined by using the value
given by dividing the amount of the polymer staying in
the polymerization reactor by the feed of the resin.
Severe bubbling of the PET polymerization intermediate
discharged from the perforated plate in the
polymerization operation and fouling of the nozzle
surface and wall surfaces caused thereby were
minimized. On the other hand, the falling PET resin
contained abundant bubbles and was observed rolling
down along the supports in a form of bubble balls.
The polymerized PET resin was discharged
continuously from the polymerization reactor by the
drainage pump (8) and drawn out in a form of strand
from the outlet (9). This strand was cooled and
solidified in a 20°C running-water bath and palletized
continuously by a pelletizer.
The obtained cylindrical transparent pellets
were found on analysis to have an intrinsic viscosity
[ 7] ] of 0.80 dl/g, a carboxyl end group amount of 29
meq/kg and an acetaldehyde content of 4.8 ppm.
Example 31
Pellets were produced by carrying out
polymerization in succession to Production Example 7
under the same conditions as used in Production Example

7 except that after producing the pellets under the
conditions of Production Example 7, ethylene glycol was
introduced continuously as a molecular weight reducing
agent into the transfer line of the polymerization
intermediate to adjust the intrinsic viscosity [n ] of
the prepolymer to 0.45 dl/g in the line, and supplying
this prepolymer continuously to the polymerization
reactor (10) from the feed opening (2) by the transfer
pump (1).
The obtained cylindrical transparent pellets
were analytically determined to have an intrinsic
viscosity [77] of 0.69 dl/g, a great variation from that
of the polymerization intermediate. It was also found
that the amount of carboxyl end groups was 2 9 meq/kg
and the acetaldehyde content 4.2 ppm. The properties
of the produced pellet were shown in Table 12.
Example 32
Pellets were produced by carrying out
polymerization in succession to Production Example 7
under the same conditions as used in Production Example
7 except that after producing the pellets under the
conditions of Production Example 7, glycerin was
introduced continuously as a molecular weight
increasing agent into the transfer line of the
polymerization intermediate to adjust intrinsic
viscosity [77] of the polymerization intermediate to
0.55 dl/g in the line, and supplying this intermediate
continuously to the polymerization reactor (10) from

the feed opening (2) by the transfer pump (1).
The obtained cylindrical transparent pellets
were analytically determined to have an intrinsic
viscosity [77] of 0.92 dl/g, a great variation from that
of the polymerization intermediate. It was also found
that the amount of carboxyl end groups was 30 meq/kg
and the acetaldehyde content 5.2 ppm. The properties
of the produced pellet were shown in Table 12.
Production Example 8
The same polymerization intermediate as used
in Production Example 7 was polymerized in a 270°C
molten state by a conventional stirring vessel type
polymerization reactor under the conditions of reduced
pressure of 60 Pa and polymerization time of 100
minutes to produce the pellets.
The obtained pellets were found on analysis
to have an intrinsic viscosity [77] of 0.58 dl/g, a
carboxyl end group amount of 36 meq/kg and an
acetaldehyde content of 54.3 ppm. The pellets also had
a light yellowish discoloration.
Comparative Example 26
Pellets were produced by carrying out
polymerization in succession to Production Example 8
under the same conditions as used in Production Example
8 except that after producing the pellets under the
conditions of Production Example 8, ethylene glycol was
introduced continuously as a molecular weight reducing
agent into the transfer line of the polymerization

intermediate to adjust intrinsic viscosity [ rj ] of the
polymerization intermediate to 0.45 dl/g in the line,
and this intermediate was supplied continuously to the
polymerization reactor. The properties of the produced
pellet were shown in Table 12.
Analysis of the obtained pellets showed that
their intrinsic viscosity [77] was 0.53 dl/g, which
indicated that the variation of intrinsic viscosity was
of the same degree as that of the polymerization
intermediate. Also, the amount of the carboxyl end
groups was 36 meq/kg and the acetaldehyde content 55.3
ppm, and the pellets were discolored to yellow.
Comparative Example 27
Pellets were produced by carrying out
polymerization in succession to Production Example 8
under the same conditions as used in Production Example
8 except that after producing the pellets under the
conditions of Production Example 8, glycerin was
introduced continuously as a molecular weight
increasing agent into the transfer line of the
polymerization intermediate to adjust intrinsic
viscosity [ 77 ] of the polymerization intermediate to
0.55 dl/g in the line, and then this intermediate was
supplied continuously to the polymerization reactor.
Analysis of the obtained pellets showed that
intrinsic viscosity [77] thereof was 0.61 dl/g, which
indicated that the variation of intrinsic viscosity was
of the same degree as or smaller than that of the

polymerization intermediate. Also, the amount of the
carboxyl end groups was 37 meq/kg and the acetaldehyde
content 56.2 pprn, and the pellets were discolored to
yellow. The properties of the produced pellet were
shown in Table 12.

























Industrial Applicability
The polyester resin according to the present
invention contains a small amount of the carboxyl group
at the end of the polymer and a small amount of
impurity such as acetaldehyde, involves a reduced
amount of acetaldehyde produced in the processing, and
has excellent hues with narrow molecular weight
distribution and high quality and moldability from a
low polymerization degree to a high polymerization
degree. More specifically, the polyester resin
according to the present invention is characterized by
low crystallinity and a small reduction in quality in
the processing or a small rate of content of cyclic
trimer and excellent workability in addition to the
abovementioned favorable characteristics. Furthermore,
the present invention provides the polyethylene
terephthalate resin pellet with a small amount of fine
powder, high handleability, and high quality of the
molded article formed therefrom, and the preform and
the hollow body formed by molding the high-quality
polyethylene terephthalate resin as described above.
They are suited for a material of a container of
drinking water or the like.
Brief Description of the Accompnying Drawings
Fig. 1 is a schematic diagram showing an
example of a polymerization reactor for producing
polyester resin according to the present invention.

Fig. 2 is a schematic diagram showing an
inert gas absorption apparatus and a polymerization
reactor for producing the polyester resin according to
the present invention.
Fig. 3 is a schematic diagram showing an
example of an apparatus for producing the polyester
resin according to the present invention.
Fig. 4 is a schematic diagram showing an
example of an apparatus for producing the polyester
resin according to the present invention.
Fig. 5 is a schematic diagram showing an
example of a polymerization reactor and a molding
machine for producing the polyester resin according to
the present invention.
Fig. 6 is a schematic diagram showing an
example of an inert gas absorbing apparatus, a
polymerization reactor, and a molding machine for
producing the polyester resin according to the present
invention.
Fig. 7 is a schematic diagram showing an
example of a polymerization reactor for producing the
polyester resin according to the present invention.
Fig. 8 is a schematic diagram showing an
example of a polymerization reactor for producing the
polyester resin according to the present invention.
Explanation of references
1 Transfer pump

2 Feed opening
3 Perforated plate
4 Sight glass
5 Support and Falling polymer
6 Inert gas feeding port
7 Evacuation port
8 Drainage pump
9 Outlet
10 Polymerization reactor
11 Polymer filter
12 Polymer filter
Nl Transfer pump
N2 Feed opening
N3 Perforated plate
N5 Support and Falling polymer
N6 Inert gas inlet
N7 Evacuation port
N8 Drainage/transfer pump
N10 Inert gas absorption apparatus
P1 Esterification reaction vessel
P2 Stirring blade
P3 Evacuation port
P4 Transfer pump
P5 First stirring vessel type polymerization
reactor
P6 Stirring blade
P7 Evaluation port
P8 Transfer pump

P9 Second stirring vessel type polymerization
reactor
P10 Stirring blade
P11 Evaluation port
E1 First ester exchange reaction vessel
E2 Stirring blade
E3 Evaluation port
E4 Transfer pump
E5 Second ester exchange reaction veseel
E6 Stirring blade
E7 Evaluation port
E8 Transfer pump
E9 First stirring vessel type polymerization
reactor
E10 Stirring blade
Ell Evaluation port
E12 Transfer pump
E13 Horizontal stirring polymerization reactor
E14 Stirring blade
E15 Evaluation port
I1 Transfer piping and distributor
I2 Molding machine A
I3 Molding machine B
I4 Molding machine C


WE CLAIM:
1. A polyethylene terephthalate resin obtained by melt polymerization under
a reduced pressure range 0.1 Pa-50,000 Pa or under an inert gas
atmosphere and having the properties comprising:
(A) an intrinsic viscosity [n] of 0.4 to 2.5 d1/g;
(B) a content of carboxyl end groups of 30 meq/kg or less;
(C) a content of acetaldehyde of 10 ppm or less;
(D) a hue represented by the L value of 99 or greater and the b value
of 0.4 or less,
said hue being measured by transmission of hexafluoroisopropanol
solution;
(E) Mw/Mn of 1.8 to 2.3; and
(F) a content of cyclic trimer of 5 wt% or less.
2. The polyethylene terephthalate resin as claimed in claim 1, wherein the
crystallinity is 55% or less.
3. The polyethylene terephthalate resin as claimed in claim 1 or 2, wherein
the content of cyclic trimer is 0.8 wt% or less.


4. A pellets obtained by pelletizing the polyethylene terephthalate resin as
claimed in any one of claims 1 to 3, wherein the content of a fine powder
having a particle size of 1 mm or less is 5 mg/kg or less.
5. A preform, which is obtained by feeding the polyethylene terephthalate
resin as claimed in any one of claims 1 to 3 in a molten state in a
polymerization reactor into an injection molding machine via a feed pipe at
a temperature lower by 10°C or less, and higher by 60°C or less than the
crystalline melting point and then injection-molding the polyethylene
terephthalate resin, and having the properties comprising:
(G) a content of carboxyl end groups of 30 meq/kg or less,
(H) a content of acetaldehyde of 10 ppm or less, and
(I) a hue represented by the L value of 98 or greater and the b value of
0.7 or less,
said hue being measured by transmission of hexafluoroisopropanol
solution.
6. A polyethylene terephthalate hollow body obtained by blow-molding the
preform as claimed in claim 5 and having the properties comprising:
(J) a content of carboxyl end groups of 30 meq/kg or less,
(K) a content of acetaldehyde of 10 ppm or less, and

(L) a hue represented by the L value of 98 or greater and the b value of
0.8 or less,
said hue being measured by transmission of hexafluoroisopropanol
solution.
7. A preform, which is obtained by extruding the polyethylene terephthalate
resin as claimed in any one of claims 1 to 3 in a molten state in a
polymerization reactor to feed the polyethylene terephthalate resin into a
compression molding machine via a feed pipe at a temperature lower by
10°C or less, and higher by 60°C or less than the crystalline melting point
and then compression-molding the polyethylene terephthalate resin, and
having the properties comprising:
(G) a content of carboxyl end groups of 30 meq/kg or less,
(H) a content of acetaldehyde of 10 ppm or less, and
(I) a hue represented by the L value of 98 or greater and the b value of
0.7 or less,
said hue being measured by transmission of hexafluoroisopropanol
solution.

8. A polyethylene terephthalate hollow body obtained by blow-molding the
preform as claimed in claim 7, and having the properties comprising:
(J) a content of carboxyl end groups of 30 meq/kg or less,
(K) a content of acetaldehyde of 10 ppm or less, and
(L) a hue represented by the L value of 98 or greater and the b value of
0.8 or less,
said hue being measured by transmission of hexafluoroisopropanol
solution.
9. A method for producing a polyethylene terephthalate, in which a
polymerization intermediate of polyester having an intrinsic viscosity [n] of
0.2 to 2.0 dl/g is fed into a polymerization reactor through a feed opening
in a molten state, then discharged through the holes of a perforated plate,
and subsequently polymerized under a reduced pressure range 0.1 Pa -
50,000 pa or under an inert gas atmosphere and a reduced pressure at a
temperature lower by 10°C or less, and higher by 30°C or less than the
crystalline melting point of the polymerization intermediate under the
condition of the following formula (1) while falling along an outer open
surface(s) of a support(s), wherein the polymerization intermediate
contains at least one polycondensation catalyst in an amount of 3 to 300
ppm as a total amount of metal atoms, selected from an Sn catalyst in an
amount less than 50 ppm; a catalyst selected from Ti, Ge, Al and Mg in an

amount less than 100 ppm, respectively; and a catalyst selected from
metals of the IB group and II to VIII groups of the periodic table other than
the above metals in an amount less than 300 ppm, respectively, in terms
of metal atoms,
and wherein:
S1/S2>1 ... (formula 1),
S1; surface area of the falling polyethylene terephthalate
and,
S2; area in which the support and the polyethylene
terephthalate is in contact with each other.
10. The method for producing a polyethylene terephthalate as claimed in
claim 9, wherein at least one of alkali compounds is made to coexist in the
polymerization intermediate.
11. The method for producing a polyethylene terephthalate as claimed in
claim 9 or 10, wherein at least one of phosphorous compounds is made to
coexist in the polymerization intermediate.
12. A method for producing a polyethylene terephthalate resin, comprising the
steps of

providing as a raw material a solid state polyethylene terephthalate resin
having the properties comprising:
(S) a crystallinity of 35% or less; and
(T) a content of acetaldehyde of 30 ppm or less, and subjecting the solid
state polyethylene terephthalate resin to at least one selected from heat
treatment at a temperature of 30°C-220°C for 10 minutes to 15 hours,
vacuum treatment at 5 Pa-100, 000 Pa and a temperature of 30 °C-220 °C
for 10 minutes to 15 hours, and cleaning treatment using a washing agent
selected from the group consisting of water, alcohols, acetone, MEK,
ethers, hexanes, halogen compounds (e.g. chloroform), nitrogen, and
carbon dioxide to obtain a polyethylene terephthalate resin having the
properties comprising:
(U) a crystallinity of 55% or less;
(V)Mw/Mn = 1.8 to 2.3;and
(W) a content of acetaldehyde of no more than 50% of its content in the
raw polyethylene terephthalate resin.
13. The method for producing a polyethylene terephthalate resin as claimed in
claim 12, wherein the content of acetaldehyde in the raw polyethylene
terephthalate resin is 15 ppm or less.

14.The method for producing a polyethylene terephthalate resin as claimed in
claim 12 or 13, wherein the raw polyethylene terephthalate resin is a
polyethylene terephthalate resin produced by feeding a polymerization
intermediate of polyethylene terephthalate having an intrinsic viscosity [n]
of 0.2 to 2.0 dl/g into a polymerization reactor through a feed opening in a
molten state, then discharging the polymerization intermediate through
the holes of a perforated plate, and subsequently polymerizing the
polymerization intermediate under a reduced pressure or under an inert
gas atmosphere and a reduced pressure at a temperature lower by 10°C
or less, and higher by 30°C or less than the crystalline melting point of the
polymerization intermediate under the condition of the following formula
(1) while falling along an outer open surface(s) of a support(s), wherein:
S1/S2>1 ... (formula 1),
S1; surface area of the falling polyethylene terephthalate resin, and
S2; area in which the support and the polyethylene terephthalate
resin is in contact with each other.
15. The method for producing a polyethylene terephthalate resin as claimed in
any one of claims 12 to 14, comprising subjecting the raw polyethylene
terephthalate resin to heat treatment at a temperature of 140 to 220°C for
20 minutes to 10 hours, whereby the polyethylene terephthalate resin has
a content of acetaldehyde of 3 ppm or less.

16. A method for producing a polyethylene terephthalate resin, wherein a
polymerization intermediate of a polyethylene terephthalate resin having
an intrinsic viscosity [n] of 0.2 to 2.0 dl/g and a content of cyclic trimer of
0.8% by weight or less is fed into a polymerization reactor through a feed
opening in a molten state, then discharged through holes of a perforated
plate, and subsequently polymerized under a reduced pressure at a
temperature lower by 10°C or less, and higher by 30°C or less than the
crystalline melting point of the polymerization intermediate while falling
along a support(s) to produce a polyethylene terephthalate resin having
the properties comprising:
(a) an intrinsic viscosity [n] of 0.2 to 2.5 dl/g; and
(b) a content of cyclic trimer of 0.8% by weight or less.
17.A method for producing a polyethylene terephthalate resin, wherein a
polymerization intermediate of polyethylene terephthalate resin having an
intrinsic viscosity [n] of 0.2 to 2.0 dl/g is fed into a polymerization reactor
through a feed opening in a molten state, then discharged through holes
of a perforated plate, and subsequently polymerized under a reduced
pressure at a temperature lower by 10°C or less, and higher by 30°C or
less .than the crystalline melting point of the polymerization intermediate
while falling along a support(s) to obtain a polyethylene terephthalate
resin, and further processing the polyethylene terephthalate resin to

remove a cyclic trimer oligomer by an amount of 0.2% by weight or more
therefrom is carried out to produce a polyethylene terephthalate resin
having the properties comprising:
(c) an intrinsic viscosity [n] of 0.20 to 2.5 dl/g; and
(d) a content of cyclic trimer of 0.8% by weight or less.
18. The method for producing a polyethylene terephthalate resin as claimed in
claim 16 or 17, comprising feeding a polymerization intermediate of
polyethylene terephthalate resin, which shows an increase in content of
cyclic trimer when said polymerization intermediate is held in a molten
state at 275°C for 30 minutes is 0.2% by weight or less, into the
polymerization reactor to polymerize said polymerization intermediate.
19. A method for producing a polyethylene terephthalate, comprising
pelletizing a polyethylene terephthalate obtained by feeding a
polymerization intermediate of polyethylene terephthalate having an
intrinsic viscosity [n] of 0.2 to 2.0 dl/g into a polymerization reactor through
a feed opening in a molten state, then discharging the polymerization
intermediate through the holes of a perforated plate, and subsequently
polymerizing the polymerization intermediate under a reduced pressure at
a temperature lower by 10°C or less, and higher by 30°C or less than the
crystalline melting point of the polymerization intermediate while falling

along a support(s), and then introducing the resultant pellets into a solid-
state polycondensation reactor to further subject the pellets to solid-state
polycondensation at a temperature of 190 to 230°C.
20. A method for producing a polyethylene terephthalate, in which a
polymerization intermediate of polyethylene terephthalate having a
number average molecular weight of 6,000 to 80,000 and showing no
crystalline melting point is fed into a polymerization reactor through a feed
opening, then discharged through the holes of a perforated plate, and
subsequently polymerized under a reduced pressure or under an inert gas
atmosphere and a reduced pressure under the condition of the following
formula (1) while falling along an outer open surface(s) of a support(s),
said method comprising polymerizing the polymerization intermediate at a
temperature in the range of the higher of 100°C or a temperature at which
a melt viscosity when the polyethylene terephthalate extracted from the
polymerization reactor is evaluated at a shear rate of 1000 (sec-1) is
100000 (poise) or greater, to 290oC:
S1/S2>1 ... (formula 1),
S1; surface area of the falling polyethylene terephthalate, and
. S2; area in which the support and the polyethylene terephthalate is
in contact with each other.

21.The method for producing a polyethylene terephthalate as claimed in any
one of claims 9 to 11, 19 and 20, comprising making the polymerization
intermediate undergo a reaction with any amount of molecular weight
regulator in any step before feeding the polymerization intermediate into
the polymerization reactor.
22.The method for producing a polyethylene terephthalate as claimed in any
one of claims 9 to 11 and 19 to 21, comprising making the polymerization
intermediate in a molten state pass through a polymer filter having a
filtration accuracy of 0.2 to 200 µm and controlled to have a temperature in
the range of a temperature lower by 20°C than a crystalline melting point
of the polymerization intermediate to a temperature higher by 100°C than
the crystalline melting point of the polymerization intermediate; or in the
range of the higher of 100°C or a temperature at which a melt viscosity
when the polymerization intermediate is evaluated at a shear rate of 1000
(sec-1) is 100000 (poise) or greater, to 350oC, and then feeding the
polymerization intermediate into the polymerization reactor.
23. The method for producing a polyethylene terephthalate resin as claimed in
any one of claims 12 to 18, comprising making the polymerization
intermediate undergo a reaction with any amount of molecular weight
regulator in any step before feeding the polymerization intermediate into
the polymerization reactor.

24.The method for producing a polyethylene terephthalate resin as claimed in
any one of claims 12 to 18, comprising making the polymerization
intermediate in a molten state pass through a polymer filter having a
filtration accuracy of 0.2 to 200 µm and controlled to have a temperature in
the range of a temperature lower by 20°C than a crystalline melting point
of the polymerization intermediate to a temperature higher by 100°C than
the crystalline melting point of the polymerization intermediate; or in the
range of the higher of 100°C or a temperature at which a melt viscosity
when the polymerization intermediate is evaluated at a shear rate of 1000
(sec-1) is 100000 (poise) or greater, to 350°C, and then feeding the
polymerization intermediate into the polymerization reactor.


A polyethylene terephthalate resin obtained by melt polymerization under a
reduced pressure range 0.1 Pa-50,000 Pa or under an inert gas atmosphere and
having the properties comprising: (A) an intrinsic viscosity [n] of 0.4 to 2.5 d1/g;
(B) a content of carboxyl end groups of 30 meq/kg or less; (C) a content of
acetaldehyde of 10 ppm or less; (D) a hue represented by the L value of 99 or
greater and the b value of 0.4 or less, (E) said hue being measured by
transmission of hexafluoroisopropanol solution; (F) Mw/Mn of 1.8 to 2.3; and
a content of cyclic trimer of 5 wt% or less.

Documents:

01386-kolnp-2007-abstract.pdf

01386-kolnp-2007-claims.pdf

01386-kolnp-2007-correspondence others 1.1.pdf

01386-kolnp-2007-correspondence others 1.2.pdf

01386-kolnp-2007-correspondence others 1.3.pdf

01386-kolnp-2007-correspondence others.pdf

01386-kolnp-2007-description complete.pdf

01386-kolnp-2007-drawings.pdf

01386-kolnp-2007-form 1.pdf

01386-kolnp-2007-form 18.pdf

01386-kolnp-2007-form 2.pdf

01386-kolnp-2007-form 3.pdf

01386-kolnp-2007-form 5.pdf

01386-kolnp-2007-gpa.pdf

01386-kolnp-2007-international publication.pdf

01386-kolnp-2007-international search report.pdf

01386-kolnp-2007-priority document 1.1.pdf

01386-kolnp-2007-priority document.pdf

1386-kolnp-2007-correspondence.pdf

1386-kolnp-2007-examination report.pdf

1386-kolnp-2007-form 13.pdf

1386-kolnp-2007-form 3.pdf

1386-kolnp-2007-form 5.pdf

1386-KOLNP-2007-FORM-27.pdf

1386-kolnp-2007-gpa.pdf

1386-kolnp-2007-granted-abstract.pdf

1386-kolnp-2007-granted-claims.pdf

1386-kolnp-2007-granted-description (complete).pdf

1386-kolnp-2007-granted-drawings.pdf

1386-kolnp-2007-granted-form 1.pdf

1386-kolnp-2007-granted-form 2.pdf

1386-kolnp-2007-granted-specification.pdf

1386-kolnp-2007-intenational publication.pdf

1386-KOLNP-2007-OTHER PATENT DOCUMENT.pdf

1386-kolnp-2007-others.pdf

1386-kolnp-2007-reply to examination report.pdf

abstract-01386-kolnp-2007.jpg


Patent Number 246522
Indian Patent Application Number 1386/KOLNP/2007
PG Journal Number 09/2011
Publication Date 04-Mar-2011
Grant Date 02-Mar-2011
Date of Filing 19-Apr-2007
Name of Patentee ASAHI KASEI CHEMICALS CORPORATION
Applicant Address 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO
Inventors:
# Inventor's Name Inventor's Address
1 YOKOYAMA, HIROSHI C/O. ASAHI KASEI KABUSHIKI KAISHI 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO, 100-8440
2 AMINAKA, MUNEAKI C/O. ASAHI KASEI KABUSHIKI KAISHI 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO, 100-8440
3 HIROSHIGE OKAMOTO C/O. ASAHI KASEI KABUSHIKI KAISHI 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO, 100-8440
PCT International Classification Number C08G 63/183
PCT International Application Number PCT/JP2005/021893
PCT International Filing date 2005-11-29
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2005-109937 2005-04-06 Japan
2 2005-235817 2005-08-16 Japan
3 2004-345242 2004-11-30 Japan
4 2004-345240 2004-11-30 Japan
5 2005-119627 2005-04-18 Japan