Title of Invention

"PROCESS OF INCREASING THE MOLECULAR WEIGHT OF POLYMER GRANULES"

Abstract A PROCESS OF INCREASING THE MOLECULAR WEIGHT OF POTYNER GRANUTES WHIC COME FROM A POLYONDNSTION PKLAQNT ARE AT LEAST PARTRY CRYSTELIZED,AND IN A POSTCONDEBNSATION ARE BROUGHT IN DIRECT CORTC WITH A NITROGEN-CONTALNING TRETMENT GAS,WHERE IN THE POLYMER GRANULE IS INCRESSE T175 to 250 0c as acomnopared top tEMPERATURY OF THE PLOYMER GRUNDULES COMING FROM THE PLOLYCOPNDENSATION PLNT HARCTERIZED ONTAINING EXHAUST GAS FRO THE POLYONDENSATION VLNYONING ECJJSIDY HSD GTP, YJRPOLYVONFRNDSYION PLSNF ID SFMXED TO THE TREATMENT GA IN A VOLUME RATIO 0F 1:1: TO100
Full Text Process of Increasing the Molecular Weight of
Polymer Granules
This invention relates to a process of increasing the molecular
weight of polymer granules which come from a polycondensation
plant, are at least partly crystallized, and in a
postcondensation are brought in direct contact with a nitrogen-containing
treatment gas, where in the postcondensation
the temperature of the polymer granules is increased to 175
to 250°C as compared to the temperature of the granules coming
from the polycondensation plant. As polymer, there can be
used polyesters such as polyethylene terephthalate (PETB),
polybutylene terephthalate (PBTP), polypropylene terephthalate
(PTTP) or mixed polymeres such as polyamides (PA). These
polymers in pure or doped form are preferably used for producing
packaging materials such as for instance films and
bottles or e.g. for producing highly viscous yarns or fibers.
The polycondensation of all kinds of monomers and the increase
of the molecular weight by postcondensation is known.
Details are described for instance in EP 0 685 502 B1, in
Rompp "Chemie-Lexikon", 10th edition, page 1316, and in
Houben-Weyl, "Methoden der Organischen Chemie", 4th edition,
vol. E20, part 1, "Festphasen-Polykondensation (Nachreaktion
in fester Phase)" (solid-phase polycondensation - secondary
reaction in solid phase). Polycondensation plants are described
in Ullmanns Encyklopädie der technischen Chemie, 4th
edition, vol. 19, pp. 117 - 119.
It is the object underlying the invention to further improve
the above-mentioned process and thereby find an inexpensive
solution. In accordance with the invention this is achieved
in that nitrogen-containing exhaust gas from the polycondensation
plant is admixed to the treatment gas in a volume ratio
of 1:1 to 1:1000, before it is introduced into the postcondensation.
Due to the postcondensation, the chain length
of the molecules is usually increased by at least 20 % and
preferably by at least 50 %. As a result, polyester granules
are produced, for example, which can preferably be used for
instance for bottles or films. With the chain length of the
molecules the viscosity (intrinsic viscosity) of the polymer
is also increased in a manner known per se.
By using nitrogen-containing exhaust gas from the polycondensation
plant, the addition of fresh nitrogen from outside, in
order to compensate leakages, can be reduced or be omitted
completely. The nitrogen-containing exhaust gas from the
polycondensation plant can also contain hydrocarbons, and advantageously
it is then first of all charged into a cleaning
stage together with recirculated treatment gas, in which cleaning stage hydrocarbons are removed by oxidation. The
treatment gas which is then introduced into the postcondensation
is virtually free from O2 and is dried expediently, before
it enters the postcondensation.
In the postcondensation, the treatment gas effects a levelling
of the temperature and the removal of the byproducts
formed by chemical reactions. Expediently, the degree of
crystallization of the polymer granules should be increased
before the postcondensation, e.g. in fluidized-bed crystallizers.
Since the treatment gas is passed through a cleaning stage
before it enters the postcondensation, the nitrogen supplied
to the gas circuit for compensating losses need not be of
high purity. It is enough to add fresh gas rich in nitrogen
with an N2 content of 80 to 99 vol-% to the treatment gas.
This means a remarkable saving of costs also at this point.
Embodiments of the process will be explained with reference
to the drawing which shows a flow diagram of the process.
To a polycondensation plant (1) known per se, starting chemicals,
i.e. chiefly alcohols and acids in the case of the production
of polyester, are supplied through line (2), and inert
gas rich in nitrogen is supplied through line (3). As
product, polymer granules are obtained, which via line (4)
are supplied to a first crystallization stage (5). A first
exhaust gas comes from line (6), it is rich in O2, poor in
hydrocarbons, and not suited for the further utilization in
the process. A second exhaust gas poor in O2 is withdrawn
via line (7). This second exhaust gas consists of N2 for
about 70 to 99 vol-%, it is relatively poor in O2 and contains
less than 10 vol-% O2; in addition, the second exhaust
gas can also contain hydrocarbons, e.g. 1 to 50 vol-% hydrocarbons .
To avoid agglutinations, the polymer granules coming from
line (4) are crystallized in two stages, and in the first
stage (5), e.g. in the fluidized bed, they are fluidized by
means of fluidizing gas rich in nitrogen from line (8) and
are brought to an elevated temperature. The temperature in
the fluidized bed lies in the range from 100 to 250°C and
preferably is at least 150°C. The polymer granules are then
passed through line (9) to the second crystallization stage
(10), which for instance constitutes a paddle mixer, where
the granules are heated indirectly.
The two-stage crystallization, mostly with an increase in
temperature in each stage, already effects an increase in the
degree of crystallization, but not a sufficient increase in
the molecular weight of the polymer. For the further increase
of the molecular weight and hence the viscosity, the postcondensation
reactor (12) is provided, to which the granules are
supplied through line (11). Dry treatment gas virtually free
from O2, whose main component is nitrogen, is supplied to
the reactor (12) through line (13a). The treatment gas is
passed upwards through the fixed bed disposed in the reactor,
the temperature being levelled and reaction products being
withdrawn. The dwell times of the granules in the reactor
(12) usually lie in the range from 8 to 22 hours. Polymer
granules with an increased molecular weight are withdrawn
from the reactor (12) via line (14) and are expediently supplied
to a cooling and dedusting not represented here.
Used treatment gas is withdrawn from the postcondensation reactor
(12) via line (15) and mixed with the gases of lines
(5a) and (7). Via line (16), the gas mixture formed is passed
through a cyclone (17) for dedusting purposes, and dedusted
gas is sucked off through line (18) by means of the blowers
(19) and (21a) and distributed over lines (20) and (21). Via
the heater (22) and line (8), the gas of line (20) flows back
to the first crystallization stage (5).
After a fine cleaning, the gas stream of line (21) is recirculated
as treatment gas to the reactor (12). First of all,
fresh gas rich in nitrogen is added to the gas of line (21)
through line (23), in order to compensate gas losses. A first
heating is effected in the indirect heat exchanger (24), and
the gas is then supplied through line (25) to an electric
heater (26), so that in line (25a) the desired inlet tempera-
ture for the oxidation reactor (27) is reached. The oxidation
reactor (27) includes for instance a fixed bed of a granular
oxidation catalyst (for instance on the basis of platinum or
palladium), in order to remove hydrocarbons by oxidation. If
necessary, oxygen is supplied for instance in the form of air
through line (28). The gas leaving the reactor (27) via line
(29) has an elevated temperature, which can be close to
400°C. The gas dissipates part of its sensible heat in the
heat exchanger (24) and then flows through line (30) to another
heat exchanger (31), before it is supplied through line
(32) to a drying (33). The drying may operate for instance by
adsorption in a manner known per se. The dried gas flows
through line (13) to the heat exchanger (31) and via line
(13a) flows into the reactor (12) as treatment gas. This
treatment gas preferably has a carbon monoxide content of 10
to 500 mg/Nm3.
Example:
In a conventional polycondensation plant (1), polyethylene
terephthalate (PETP) is produced from terephthalic acid,
isophthalic acid and ethylene glycol, which polyethylene
terephthalate is treated further as shown in the drawing. The
change of the polycondensation state of the PETP granules is
shown in Table I:
A fluidized-bed crystallizer (5) is operated at 160°C and a
paddle crystallizer (10) is operated at 205°C, the dwell time
in the fluidized-bed crystallizer is 15 minutes and in the
paddle crystallizer 60 minutes. In the reactor (12), the
granules are provided in a fixed bed. At a temperature of
205°C, the dwell time is 11 hours. Furthermore, there is used
an electric heater (26) and an absorption drying (33) by
means of a molecular sieve. 7532 kg/h PETP granules of 60°C
are supplied to the fluidized-bed crystallizer (5), and air
is supplied through line (28). Gas. flow rates (kg/h) and temperatures
(°C) are shown in Table II:
Gas compositions are indicated in Table III (in kg/h),
wherein OC = organic components.
WE CLAIM
1. A process of increasing the molecular weight of poymer grandee which
come from a polycondensestion plant, are at least partly crystalized, and in
a protocondensation are brought in direct contect with a nitrogen-
conteaining treatmen gas, where in the postcondensation the temperature
of the polymer granules is increased 175to 250oC as compared to the
tempertatuer of the granules coming from the polycondensation plant,
characterized in that nitrogen-containing method gas from the
polycondensation plant is a method to the teatment gas bin a volume ratio
of 1:1 to 1:1000, before it is introduced into the poolecondensation
2. The process as claimed in claim 1 wherein the nitrogen-containing
about gas from the poolecondensation plant contains hydrocarbons and
together with the tratment gas is passed through a cleaning stage for the
oxidathe rimoval of hydrocarbons before it is introduced into the postcondensation

3 the process as claimed in claim 1 or 2, wherein fesh gas gas rich in nitrogen
with an N2 content of 90 to 99 vol% is added to the treatment gas.

4. The process as claimed in dclaim 1 or any of the proceding claims, wherein
the cleaning stage for the adative removal of hydrocarbons includes an oxidation catalyst.
5. The process as claimed in calim 1 or any of the proceding claims, wherein
from nitrgen-containing about gas from the polycondensation plant,
treatment gas from the postcondensation, and from gas withdrawn from
the orycitalimation a gas misure is produced, which is at least partly used
as treatment gas.
A process of increasing the molecular weighy of polymer granules which come
from a polycondensation plant, are at least partly crystalized, and in a poolcondensations are broughy in direct contact with a nitrogen-containing
treatment gfas, where in the postcondesation the temperature of the polymer
granrles coming from the polycondensation plant, characterized in that nitrogen-
containing aboout gas from the polycondensation plant is admined to the
treatment gfas in a volume rtario of 1:1 to 1:1000, before it is intoduced into the
poolcondensation.

Documents:

162-kolnp-2003-granted-abstract.pdf

162-kolnp-2003-granted-claims.pdf

162-kolnp-2003-granted-correspondence.pdf

162-kolnp-2003-granted-description (complete).pdf

162-kolnp-2003-granted-drawings.pdf

162-kolnp-2003-granted-examination report.pdf

162-kolnp-2003-granted-form 1.pdf

162-kolnp-2003-granted-form 18.pdf

162-kolnp-2003-granted-form 2.pdf

162-kolnp-2003-granted-form 26.pdf

162-kolnp-2003-granted-form 3.pdf

162-kolnp-2003-granted-form 5.pdf

162-kolnp-2003-granted-letter patent.pdf

162-kolnp-2003-granted-priority document.pdf

162-kolnp-2003-granted-reply to examination report.pdf

162-kolnp-2003-granted-specification.pdf

162-kolnp-2003-granted-translated copy of priority document.pdf


Patent Number 214985
Indian Patent Application Number 00162/KOLNP/2003
PG Journal Number 08/2008
Publication Date 22-Feb-2008
Grant Date 20-Feb-2008
Date of Filing 10-Feb-2003
Name of Patentee ZIMMER AKTIENGESELLSCHAFT,
Applicant Address BORSIGALLEE 1, 60388 FRANKFURT AM MAIN, GERMANY
Inventors:
# Inventor's Name Inventor's Address
1 KIRSGTEN KLAUS. GUSTAVSBURGER WEG 22,55130 MAINZ, GERMANY
PCT International Classification Number B/61 22/00
PCT International Application Number PCT/EP01/10096
PCT International Filing date 2001-09-01
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 100 43 277.8 2000-09-02 Germany