Title of Invention

PROCESS FOR CO-POLYMERIZATION OF ETHYLENE MONOMER AND AN OLEFIN CO-MONOMER IN A POLYMERIZATION LOOP REACTOR AND POLYMERIZATION LOOP REACTOR THEREFOR

Abstract There is disclosed a process for the co-polymerization of ethylene monomer and an olefin co-monomer, such as herein described, in a polymerization loop reactor comprising the steps of - feeding monomer, an olefin co-monomer, diluents and optionally hydrogen into the loop reactor, - feeding at least one polymerization catalyst, such as herein described, into the reactor, - co-polymerizing said monomer and said co-monomer to produce a polymer slurry comprising essentially liquid diluent and solid olefin co-polymer particles, - allowing said polymer slurry to settle into one or more settling legs connected to the reactor, and - sequentially discharging the settled polymer slurry from said one or more settling legs out of the reactor, characterized in that said process involves the step of controlling the co-monomer/monomer ratio along the path of the reactor by multiple, spatially separated, feeding of monomer along the path of the loop reactor and wherein the process is applied to the first loop of a double loop reactor.
Full Text Field of the invention
The present invention relates to the field of olefin polymerization. In particular, the present
invention relates to a process for improving the polymerization of a monomer and an olefin
co-monomer in a polymerization loop reactor. In another aspect, the present invention relates
to a polymerization reactor suitable for the polymerization process of a monomer and an
olefin co-monomer.
Background
Polyethylene (PE) is synthesized via polymerizing ethylene (CH2=CH2) monomers. Because
PE is cheap, safe, stable to most environments and easy to be processed polyethylene
polymers are useful in many applications. According to the properties polyethylene
can be classified into several types, such as but not limited to LDPE (Low Density
Polyethylene), LLDPE (Linear Low Density Polyethylene), and HDPE (High Density
Polyethylene). Each type of polyethylene has different properties and characteristics.
Polyethylene polymerizations are frequently carried out using monomer, diluent and catalyst
and optionally co-monomers and hydrogen in a loop reactor. The polymerization is usually
performed under slurry conditions, wherein the product usually consists of solid particles and
is in suspension in a diluent. The slurry contents of the reactor are circulated continuously
with a pump to maintain efficient suspension of the polymer solid particles in the liquid
diluent. The product is discharged by means of settling legs, which operate on a batch
principle to recover the product. Settling in the legs is used to increase the solids concentration
of the slurry finally recovered as product slurry. The product is further discharged to a flash
tank, through flash lines, where most of the diluent and unreacted monomers are flashed off
and recycled. The polymer particles are dried, additives can be added and finally the polymer
is extruded and pelletized.
Ethylene co-polymerization is the process wherein ethylene is polymerized with an olefin co-
monomer, such as e.g. propylene, butene, hexene, etc.. A major problem in such co-
polymerisation process is that the control of reaction parameters is very difficult. In particular,
the ratio of co-monomer to monomer (ethylene) differs at different points in the reactor.


As a result of the variation in the co-monomer/ethylene ratio throughout the reactor, reaction
conditions will vary along the path of the polymerization reactor. As the monomer (ethylene)
is depleted faster than the co-monomer in the reactor, fluctuations in reaction temperatures and
fluctuations in monomer concentration along the reactor occur. In addition, due to varying
reaction conditions in the reactor, the polymerization reaction is sub-optimal and polymer
particles will be obtained during the polymerization process, which have varying properties
and have a non-homogenous composition. In certain cases, due to the variation in the co-
monomer/ethylene ratio throughout the reactor, polyethylene is produced having a too low
density, which could induce "swelling" of the polymer particles. Swelling refers to the process
whereby formed polymer particles are dissolved in diluent, giving rise to polymer slurry
which is more viscous, which has undesired properties, and which may block the
polymerization reactor.
In view hereof, it is a need in the art to provide a process for improving the co-polymerization
reaction of ethylene with an olefin co-monomer, such that the co-polymerization process is
optimized and that more homogenous polymer end products are obtained.
It is therefore an object of the present invention to provide a process for improving the co-
polymerization of ethylene and an olefin co-monomer. It is in particular an object of the
invention to provide a process for controlling the co-monomer/ethylene ratio in a
polymerization reactor. The present invention aims to provide a process for obtaining a co-
polymer end product having improved compositional homogeneity and improved quality.
Summary
The present invention relates, in a first aspect, to a process for the co-polymerization of
ethylene monomer and an olefin co-monomer, such as herein described, in a polymerization
loop reactor comprising the steps of
- feeding monomer, an olefin co-monomer, diluents and optionally hydrogen into the
loop reactor,
- feeding at least one polymerization catalyst, such as herein described, into the reactor,
co-polymerizing said monomer and said co-monomer to produce a polymer slurry
comprising essentially liquid diluent and solid olefin co-polymer particles,


- allowing said polymer slurry to settle into one or more settling legs connected to the
reactor, and
- sequentially discharging the settled polymer slurry from said one or more settling legs
out of the reactor,
characterized in that said process involves the step of controlling the co-monomer/monomer
ratio along the path of the reactor by multiple, spatially separated, feeding of monomer along
the path of the loop reactor and wherein the process is applied to the first loop of a double
loop reactor.
The terms "path" and "flow path" of the reactor are used herein as synonyms and are defined
as the internal route followed by the reactant stream and the formed polymer slurry in the
reactor.
According to the present invention the co-monomer/ethylene ratio can be adequately
controlled in the polymerization reactor. Therefore, the invention provides a process
comprising controlling the co-monomer/monomer ratio by multiple, spatially separated,
feeding of monomer along the path of the loop reactor. Additional monomer (ethylene) is fed
into the reactor at multiple entries along the path of the reactor. The multiplied entries for
feeding additional monomer are in particular positioned spatially separated from each other on
the reactor.
In another preferred embodiment, the co-monomer/ethylene ratio can be adequately controlled
in the polymerization reactor by multiple, spatially separated, feeding of monomer in
conjunction with a diluent.
In yet another particularly preferred embodiment, the present process further comprises
separately controlling the flow rate of each, spatially separated, monomer feed along the path
of the loop reactor. Therefore, each additional ethylene feeding line is provided with a separate
flow controlling means for controlling the flow rate of ethylene injection in the reactor.
The present invention has the major advantages of providing optimal control of the co-
monomer/ethylene ratio in a polymerization reactor such that ethylene co-polymers can be
produced having homogenous properties throughout the flow path of the reactor.


Furthermore, the present process enables to optimize the polymerization reaction in the
reactor. In particular, optimal and adequate control of co-monomer/ethylene ratio in the
polymerization reactor permits to optimize and reduce fluctuations in reaction temperatures
and fluctuations in monomer concentration in the reactor. A stable composition along the
reactor, and a constant production rate can be obtained and thus less temperature oscillations
are observed. Fluctuating temperature conditions throughout the reactor are absolutely
detrimental with respect to homogeneity of composition of the prepared co-polymers.
Adequate control of the co-monomer/ethylene ratio according to the present invention enables
to minimize fluctuations in reaction temperatures and as a consequence to improve
homogeneity of composition of the prepared polymers.
The present invention permits to prepare co-polymers having homogenous densities
throughout the reactor. Furthermore, since according to the present invention co-polymers
may be obtained that have desired and relatively constant densities, the risk of obtaining co-
polymer particles having too low densities, which might induce "swelling" is considerably
reduced. Swelling refers to the process whereby formed polymer particles are 'swelled' by a
diluent, giving rise to polymer slurry which is more viscous, which perturbs the reactor flow
and may lead to a blockage of the reactor. Control of the co-monomer/monomer ratio
according to the invention thus enables to reduce the risk for swelling in the reactor.
Alternatively it allows to produce lower density resins without increasing the risk for swelling.
The present invention will be further disclosed in detail hereunder. The description is only
given by way of example and does not limit the invention. The reference numbers relate to the
hereto-annexed figures.
Detailed description of the accompanying drawings, wherein:
Figure 1 is a schematic representation of a double loop polymerization reactor wherein
multiple ethylene feed points are provided on one reactor.
Figure 2 is a detailed representation of a loop reactor having multiple feed points for feeding
monomer into the reactor.
Figure 3 is a schematic representation of a double loop polymerization reactor.


Detailed description of the invention
The present invention is especially applicable to the co-polymerization process of ethylene
and an olefin co-monomer in a polymerisation loop reactor. The term "ethylene co-
polymerization" includes co-polymerization of ethylene and an olefin co-monomer. Ethylene
polymerization comprises feeding to a reactor the reactants including the monomer ethylene, a
light hydrocarbon diluent, a catalyst, a co-monomer and optionally a co-catalyst and a
terminating agent such as hydrogen. The term "co-polymer" refers to a polymer, which is
made by linking two different types of in the same polymer chain.
Olefin co-monomers which are suitable for being used in accordance with the present
invention may comprise but are not limited to aliphatic C3-C20 alpha-olefms. Examples of
suitable aliphatic C3-C20 alpha-olefins include propylene, 1-butene, 4-methyl-l-pentene, 1-
hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and
1-eicosene. The present invention has in particular been described with reference to the co-
polymerization of ethylene with the co-monomer hexene in a loop reactor. However, it should
be clear from the present invention that other co-monomers may as well be applied according
to the present invention.
Diluents which are suitable for being used in accordance with the present invention may
comprise but are not limited to hydrocarbon diluents such as aliphatic, cycloaliphatic and
aromatic hydrocarbon solvents, or halogenated versions of such solvents. The preferred
solvents are C12 or lower, straight chain or branched chain, saturated hydrocarbons, C5 to C9
saturated alicyclic or aromatic hydrocarbons or C2 to C6 halogenated hydrocarbons.
Nonlimiting illustrative examples of solvents are butane, isobutane, pentane, hexane,
heptane, cyclopentane, cyclohexane, cycloheptane, methyl cyclopentane, methyl cyclohexane,
isooctane, benzene, toluene, xylene, chloroform, chlorobenzenes, tetrachloroethylene,
dichloroethane and trichloroethane. In a preferred embodiment of the present invention, said
diluent is isobutane. However, it should be clear from the present invention that other diluents
may as well be applied according to the present invention.


The co-polymerization reaction may utilize highly sophisticated catalyst systems that initiate
polymerization and propagate the reaction. According to the present invention the term
"catalyst" is defined herein as a substance that causes a change in the rate of a co-
polymerization reaction without itself being consumed in the reaction. According to an
embodiment said catalyst may be a Ziegler-Natta catalyst. Other suitable catalysts may
comprise a metallocene catalyst or a chromium catalyst. The term "co-catalyst" as used herein
refers to materials that can be used in conjunction with a catalyst in order to improve the
activity of the catalyst during the polymerization reaction.
The "Ziegler-Natta catalyst" is preferably of the general formula MXn wherein M is a
transition metal compound selected from group IV to VII, wherein X is a halogen, and
wherein n is the valence of the metal. Preferably, M is a group IV, group V or group VI metal,
more preferably titanium, chromium or vanadium and most preferably titanium. Preferably, X
is chlorine or bromine, and most preferably, chlorine. Illustrative examples of the transition
metal compounds comprise but are not limited to TiCl3, TiCl4.
The term "metallocene catalyst" is used herein to describe any transition metal complexes
consisting of metal atoms bonded to one or two ligands. In a preferred embodiment, the
metallocene catalyst has a general formula MX, wherein M is a transition metal compound
selected from group IV and wherein X is a ligand composed of one or two groups of
cyclopentadienyl (Cp), indenyl, fluorenyl or their derivatives. Illustrative examples of
metallocene catalysts comprise but are not limited to Cp2ZrCl2, Cp2TiCl2 or Cp2HfCl2.
The term "chromium catalysts" refers to catalysts obtained by deposition of chromium oxyde
on a support, e.g. a silica or aluminum support. Illustrative examples of chromium catalysts
comprise but are not limited to CrSiO2 or CrAl2O3.


It is known in the art that the ratio of co-monomer to monomer (ethylene) differs at different
points in the reactor and is difficult to control during the polymerization reaction. In has been
shown that just after its injection point in the reactor ethylene is preferentially polymerized.
However, the concentration of ethylene changes in favor of co-monomer along the reactor as
ethylene is depleted. As a result co-polymer chains are formed that are higher in ethylene
concentration in the chain segments grown near the reactor inlet (as defined at the point at
which the polymerization reaction commences), and higher in hexene concentration in the
chain segments formed near the reactor outlet.
In particular, due to the difference in monomer concentration throughout the reactor, the ratio
of hexene to ethylene will vary in the polymerization reactor. A maximal difference in co-
monomer/ethylene ratio will generally be observed when comparing the co-monomer/ethylene
ratio at the point at which the polymerization reaction commences, i.e. at the reactor inlet of
ethylene and co-monomer, with the co-monomer/ethylene ratio at the point downstream the
reactor at which the path of the reactor has been completely passed through.
In addition, the longer the reactors, the more important this difference in ratio between the
two above-mentioned points will be. According to a preferred embodiment of the present
invention, the process comprises reducing the variation in the co-monomer/monomer ratio by
providing multiple injection of monomer along the reactor path. Preferably, the variation in
ratio will be reduced in order to be lower than 40 %, preferably lower than 30 %, more
preferably below 20 % and even more preferably lower than 10 %. It is clear that the
reduction in variation may depend on the reactor size.
The following table 1 illustrates the difference in co-monomer/monomer ratio that may occur
in a reactor of 60m3 provided with only one injection point. A variation in co-
monomer/monomer ratio of more than 30% may be observed.



From the tables 1 and 2 it is clear that the use of three monomer injection points allows to
reduce the variation in co-monomer/monomer ratio to about 10 %, whereas in reactors having
only one injection point variations in co-monomer/monomer ratios of up to 30% may be
observed.
The following table 3 illustrates the difference in co-monomer/monomer ratio that may occur
in a reactor of 60m3 provided with only one injection point and illustrates the swelling
problems that occurs in a reactor provided with only one injection point, upon increasing the
reactor temperature from 84 °C to 88 °C.



From tables 3 and 4, it is clear that the use of three monomer injection points allows the
temperature in the reactor to be increased when compared with the case of single injection
wherein swelling is observed at 88°C. In the case of a single injection point the temperature
had to be reduced to avoid the swelling phenomena. With three injection points, the
temperature can be higher, while producing the polymer with a suitable final density and with
a higher productivity.
A major disadvantage of a non-optimal control of the co-monomer/monomer ratio in a
polymerization reactor is that co-polymers will be produced having varying and thus non-


homogenous properties throughout the reactor, and that the polymerization reaction in the
reactor will not be optimal. In addition, due to these varying co-monomer/monomer ratios
reaction temperatures will vary throughout the reactor. The polymerization reaction is
exothermic. Due to the consumption of ethylene monomer in the loop reactor, the reaction
temperature will differ throughout the reactor flow path. In parts of the loops where less
ethylene monomer is present, the polymerization rate will be reduced and the reaction
temperature will decrease. Fluctuating temperature conditions throughout the reactor are
absolutely detrimental with respect to homogeneity of composition of the prepared polymers.
Furthermore, as a consequence of these varying ratios in the loop reactor, co-polymers will be
produced having varying densities throughout the reactor.
Swelling refers to the process whereby formed polymer particles are 'swelled' by a diluent,
giving rise to polymer slurry which is more viscous and which has undesired properties.
Temperature and slurry densities must be well controlled in order to avoid the solubility of the
lightest polymer fractions in the diluent. Solubility may occur at temperatures and particular
polymer slurry densities, which depend on the quantity of co-monomer present in the diluent.
For a given polymer density there is a maximum operating temperature. In certain cases, when
the operation conditions are not well controlled, the risk for swelling is considerable. As a
result of the variation in co-monomer/monomer ratio, varying reaction temperatures and
depletion of monomer in the reactor may occur which can induce too low polymer densities,
and may lead to swelling. The present invention enables to effectively reduce the risk for this
swelling phenomenon by adequately controlling the co-monomer/monomer ratio, the
concentration of monomer in the reactor and the reaction temperatures.
The present invention now provides a solution to the above-cited problems by providing
additional monomer feed along the path of the reactor. Preferably the co-monomer/monomer
ratio is controlled by providing at least two, preferably at least three spatially separated,
feeding entries of monomer along the path of the loop reactor.
The application of additional monomer feeds along the path of the reactor has been described
in EP 0 891 990. However, this document does not specify where or why these additional
monomer feeds are provided on the reactor.


In another preferred embodiment, the invention provides a process for determining suitable
positions for multiple, spatially separated, feeding entries of monomer along the path of the
loop reactor in order to control the co-monomer/monomer ratio along the path of the reactor.
In particular, the feeding entries of additional monomer may be positioned equidistantly along
the reactor path in order to keep the co-monomer/monomer ratio substantially constant along
the complete path of the reactor. Alternatively, additional monomer feed entries may be
provided at non-equidistant positions on the reactor. Particular suitable positioning sites for
additional monomer feeding may be chosen in function of reaction parameters, such as
reaction temperature, co-monomer/monomer ratio, reactor pump activity, distribution of solids
in the reactors, reactant flow in the reactor, etc.. Preferably, the injection feeds are positioned
close to bottom elbows of the reactor, as illustrated in Fig. 2.
It is also preferred according to the invention to control the co-monomer/monomer ratio by
multiple, spatially separated, feeding of monomer in conjunction with a diluent. Preferably,
the monomer/diluent ratio is lower than 5/1, and for instance 3/1. Ethylene is a gas. The
reactor is preferably operated as full of liquid. Therefore it is preferred to inject ethylene
together with diluent so that part of the ethylene is already dissolved in the diluent. The feed
thus either comprises a liquid or a liquid with bubbles of ethylene.
The process according to the present invention is applied in a double loop polymerisation
reactor consisting of two liquid full loop reactors, comprising a first and a second reactor
connected in series by one or more settling legs of the first reactor connected for discharge of
slurry from the first reactor to said second reactor. Such double loop reactor is illustrated on
FIG. 3.
FIG. 3 represents two single loop reactors 100, 116, which are interconnected in series. Both
reactors 100, 116 consist of a plurality of interconnected pipes 104. The vertical sections of
the pipe segments 104 are preferably provided with heat jackets 105. Reactants are introduced
into the reactors 100 by line 107. Catalyst, optionally in conjunction with a co-catalyst or
activation agent, may be injected in one or both reactors 100 and 116 by means of conduct
106. The polymerization slurry is directionally circulated throughout the loop reactors 100,


116 as illustrated by the arrows 108 by one or more pumps, such as axial flow pump 101. The
pumps may be powered by an electric motor 102. The pumps may be provided with a set of
rotating impellers 103. The reactors 100, 116 are further provided with one or more settling
legs 109 connected to the pipes 104 of the reactors 100, 116. The settling legs 109 are
preferably provided with an isolation valve 110. Further the settling legs can be provided with
product take off or discharge valves 111 or can be in direct communication with the
downstream section. Downstream the exit of the settling leg 109 of reactor 100, a transfer line
112 is provided which allows to transfer polymer slurry settled in the settling legs 109 to the
other reactor 116 through a piston valve 115. Along transfer line 112, a three-way valve 114
may divert the flow to a product recovery zone if the multiple loop reactor has to be used in a
parallel configuration. Polymer slurry settled in the settling legs 109 of reactor 116 can be
removed by means of one or more product recovery lines 113, e.g. to a product recovery zone.
In series connected reactors are particularly suitable for the preparation of bimodal
polyethylene (PE). "Bimodal PE" refers to PE that is manufactured using two reactors, which
are connected to each other in series. Polymerization reactors, which are connected in series,
may in particular be used to prepare polyolefin polymers having different properties in the
different reactors.
In an example, such polymerization double loop reactor, consisting of two interconnected
loop reactors, whereby the reaction conditions are different in each of said loop reactors may
be used to produce high molecular weight ethylene co-polymers in a first reactor and a low
molecular weight ethylene co-polymers in a second reactor. Reactants fed to the first reactor
may comprise ethylene, hexene, isobutane diluent, and hydrogen. Concentration of reactants
in the first reactor may then for instance comprise 1% w/v ethylene, 3% w/v hexene, and a
low concentration of hydrogen. The reaction temperature may comprise around 83 to 88°C
and polyethylene co-polymers having a density comprised around 0.925 g/cm3 may be
obtained. Polymer slurry may be transferred to the second reactor, wherein further ethylene is
fed, preferably to obtain a concentration of 4 % w/v in the reactor and hydrogen is added,


preferably to obtain a concentration of 2 vol % in the reactor. Preferably, no additional
catalyst is added in the second reactor. Also, preferably no hexene co-monomer is added in
the second reactor and co-monomer concentrations in the second reactor result from the
transfer of co-monomer together with polymer slurry from the first reactor. Generally
residence time of the slurry in the reactor is higher in the first reactor than in the second
reactor.
When the hexene/ethylene ratio is not adequately controlled in the first reactor of a double
loop system, polymer particles having undesired and non-homogenous properties will be
transferred from the first reactor to the second reactor. In addition, due to an inadequate
control of the hexene/ethylene ratio in the first reactor, also the transfer of hexene together
with polymer slurry from the first reactor to the second reactor, wherein it is used for further
co-polymerization is inefficiently controlled. As a result thereof, the polymerization reaction
in the second reactor may be sub-optimal and co-polymers having non-homogenous and
undesired properties are prepared in the second reactor.
In order to overcome at least some of the above-cited problems associated with co-
polymerization in a double loop reactor, the invention further provides a process for
improving the co-polymerization of monomer and an olefin co-monomer in a polymerization
loop reactor, said reactor being interconnected with a first loop reactor, comprising the steps
of:
- sequentially transferring polymer slurry comprising essentially liquid diluent and solid
olefin co-polymer particles from the first reactor to the second reactor,
- feeding reactants comprising monomer, diluents and optionally hydrogen,
polymerization catalyst and additional co-monomer into the loop reactor,
- further co-polymerizing said reactants in said reactor to produce a polymer slurry
comprising essentially liquid diluent and solid olefin co-polymer particles;
- allowing said polymer slurry to settle into two or more settling legs connected to the
reactor, and


- sequentially discharging the settled polymer slurry from said two or more settling legs
out of the reactor,
characterized in that said process comprises the step of controlling the amount of co-monomer
transferred from said first reactor to the reactor.
The process further comprises the step of controlling the amount of co-monomer transferred
from said first reactor to the reactor by controlling the co-monomer/monomer ratio along the
path in the first reactor.
Controlling correctly the ratio along the path flow allows to improve the productivity of the
catalyst and to minimize the concentration of co-monomer in the first reactor. Consequently
less co-monomer is transferred to the second reactor.
The amount of co-monomer transferred from said first reactor to the reactor is controlled by
controlling the co-monomer/monomer ratio and thus by multiple, spatially separated, feeding
of monomer along the path of the first reactor. Preferably, the amount of co-monomer
transferred from said first reactor to the reactor is controlled by controlling the co-
monomer/monomer ratio and thus by providing at least two, preferably at least three spatially
separated, feeding entries of monomer along the path of the loop reactor. The multiple
injection allows to optimize the working conditions of the first reactor and the consequence is
that less co-monomer is transferred to the second reactor.
The co-monomer/monomer ratio along the path in the first reactor can be further controlled by
multiple, spatially separated, feeding of monomer in conjunction with a diluent in said first
reactor and by separately controlling the flow rate of each spatially separated monomer feed
along the path of the first reactor.
The present process is particularly relevant in polymerization processes wherein low
concentrations of monomer, preferably ethylene, are obtained in the polymerization reactor,
and wherein concentrations of monomer are obtained in the polymerization reactor which are
preferably below 4% w/v, or below 3% w/v, or below 2% w/v or below 1% w/v.


The present process can also advantageously be applied in polymerization processes, carried
out in a double loop reactor, wherein low concentrations of monomer, preferably ethylene, are
obtained in the first loop reactor, and more in particular wherein concentrations of monomer
are obtained in the first loop reactor which are preferably below 4% w/v, or below 3% w/v, or
below 2% w/v or below 1% w/v.
In another embodiment, the invention relates to a polymerization loop reactor suitable for the
co-polymerization process of ethylene and an olefin co-monomer, preferably hexene. Such a
reactor comprises a double loop reactor. Referring now to FIG. 1, a double loop
polymerisation reactor according to the invention is illustrated which is in particular
characterized in that said reactor comprises multiple additional means for feeding monomer,
which are positioned spatially separated along the path of the loop reactor. In particular, the
present reactor comprises at least two, preferably at least three additional means for feeding
monomer, which are positioned spatially separated along the path of the loop reactor.
A first reactor 1 comprises a plurality of interconnected pipes 6 defining a flow path 8 for
polymer slurry, said slurry consisting essentially of ethylene, hexene, a polymerization
catalyst, liquid diluent, preferably isobutane, and solid olefin polymer particles. Each loop
reactor 1, 2 consists of a plurality of interconnected pipes 6, such as a plurality of vertical pipe
segments, a plurality of upper lateral pipe segments, a plurality of lower lateral pipe segments,
wherein each of said vertical pipe segments is connected at an upper end thereof to one of said
upper lateral pipe segments and is connected at a lower end thereof to one of said lower lateral
pipe segments through elbow shaped connecting segments, thus, defining a continuous flow
path 11 for a polymer slurry. It will be understood that while the loop reactor 1 and 2 are
illustrated with four vertical pipes, said loop reactors 1,2 may be equipped with less or more
pipes, such as 4 or more pipes, for example between 4 and 20 vertical pipes. The vertical
sections of the pipe segments are preferably provided with heat jackets 7. Polymerization heat
can be extracted by means of cooling water circulating in these jackets of the reactor. Said
reactors preferably operate in a liquid full mode.


The reactants including ethylene, isobutane, hexene and optionally hydrogen are introduced
into the reactor 2 by means 9. At least one reactor 1 is also fed with catalyst, optionally in
conjunction with a co-catalyst or activation agent, by means of the conduct 8. In a preferred
embodiment, catalysts are introduced upstream from the circulation pump 3 via line 8, while
diluent, monomer, co-monomers and reaction additives are preferably introduced downstream
of the circulation pump 3 via line 9.
The first reactor 1 further comprises at least one means 10 for additionally feeding ethylene in
said reactor. In FIG.1 three additional ethylene feeding means 10 are illustrated.
In addition, the reactor according to the invention further comprises flow controlling means.
The flow controlling means can be multiple and spatially separated, or they can be centralized
and close to each other in space. In an embodiment, there can be one control per inlet or
feeding means. In another embodiment, the control can be spatially separated from the inlet.
In an embodiment of the present invention, the number of flow controlling means corresponds
to the number of additional means for feeding monomer, which are positioned spatially
separated along the path of the loop reactor. Referring to FIG. 2 there is further illustrated that
each means 10 for separately feeding additional ethylene to the reactor is provided with a flow
controlling means 19.
The polymerization slurry is maintained in circulation in the loop reactors. As illustrated in
FIG. 1. The polymerization slurry is directionally circulated throughout the loop reactor 1, 2
as illustrated by the arrows 11 by one or more pumps, such as axial flow pumps 3. The pump
may be powered by an electric motor 4. As used herein the term "pump" includes any device
from compressing driving, raising the pressure of a fluid, by means for example of a piston or
set of rotating impellers 5. According to the present invention, the pump is preferably of axial
type.


Each loop reactor 1, 2 is further provided with one or more settling legs 12 connected to the
pipes 6 of the reactor 1, 2. Intermediate polymer slurry or polymer product may be removed
from the loop reactors, by continuous or periodical discharge through one or more settling legs
12 along with some diluent. In the settling legs 12, the solid content is increased with respect
to its concentration in the body of the loop reactor. As illustrated in FIG. 1, polymer slurry
settled in the settling legs 12 of reactor 1 may be removed by means of a three-way valve 17
to another reactor 2, to which it is transferred by means of one or more transfer lines 15, while
polymer slurry settled in the settling legs 12 of reactor 2 may be removed to a product
recovery zone, for instance by means of conduit 16. As used herein "product recovery zone"
includes but is not limited to heated or not heated flash lines, flash tank, cyclones, filters and
the associated vapor recovery and solids recovery systems or transfer lines to a following
reactor and said following reactor when several reactors are connected in series.
The settling legs can be located on any segment or any elbow of said loop reactor. In said
settling legs the polymerization slurry decants so that the slurry exiting the reactor is more
concentrated in solid than the circulating slurry. This permits to limit the quantity of diluent
that has to be treated and re-fed to the reactor. It will be understood that the discharge of said
settling legs may be operated in a continuous or discontinuous mode, but preferably in a
continuous mode.
The settling legs 12 are preferably provided with an isolation valve 13. These valves 13 may
for example be ball valves. Under normal conditions these valves are open. These valves can
be closed for example to isolate a settling leg from operation. Said valves 13 can be closed
when the reactor pressure falls below a chosen value.
Further the settling legs can be provided with product take off or discharge valves 14.
Discharging is performed in such a way that the volume discharged from a settling leg
substantially corresponds to the volume of polymer slurry settled in said settling leg since its


previous discharge. The discharge valve 14 may be any type of valve, which can permit
continuous or periodical discharge of polymer slurry, when it is fully open. The type and
structure of the discharge valve can be selected by those skilled in the art as required.
According an embodiment of the present invention the totality of settled slurry is discharged at
each opening of the discharge valve. When a plurality of legs are employed, the discharge of
the settled polymer slurry may be discharged in sequence on a rotating basis for more uniform
discharging to a subsequent reactor or to a product recovery zone.
Downstream the valve 14, at the exit of the settling leg 12, a three-way valve 17 is provided
which allows to transfer polymer slurry settled in the settling legs, for instance to another
reactor by means of the transfer line 15. The transfer line 15 connects the three-way valve 17,
provided at the exit of the settling leg 12 of one reactor 1, with the entry in the other reactor 2,
where a piston valve 18 is provided.
For reasons of brevity and clarity, conventional auxiliary equipment such as pumps, additional
valves, and other process equipment have not been included in this description and the
accompanying drawings as they play no part in the explanation of the invention, also
additional measurement and control devices which would typically be used on a
polymerization process have not been illustrated.
In a preferred embodiment, it is to be understood that all lines or conduits applied in
accordance with the present invention for feeding reactants may be provided, where necessary
with flow measuring means.
It should be clear from the present description that concentrations of the different reactants in
the co-polymerization reaction relate to the size of the polymerization reactors and the
characteristics of the co-polymer end products and can be changed if desired, e.g. in function
of the reactor sizes.


WE CLAIM:
1. Process for the co-polymerization of ethylene monomer and an olefin co-monomer, such as
herein described, in a polymerization loop reactor comprising the steps of
- feeding monomer, an olefin co-monomer, diluents and optionally hydrogen into the
loop reactor,
- feeding at least one polymerization catalyst, such as herein described, into the reactor,
- co-polymerizing said monomer and said co-monomer to produce a polymer slurry
comprising essentially liquid diluent and solid olefin co-polymer particles,
- allowing said polymer slurry to settle into one or more settling legs connected to the
reactor, and
- sequentially discharging the settled polymer slurry from said one or more settling legs
out of the reactor,
characterized in that said process involves the step of controlling the co-monomer/monomer
ratio along the path of the reactor by multiple, spatially separated, feeding of monomer along
the path of the loop reactor and wherein the process is applied to the first loop of a double
loop reactor.
2. Process as claimed in claim 1, wherein the variation in the co-monomer/monomer ratio is
reduced to a variation which is lower than 30 %, more preferably below 20 % and even more
preferably lower than 10 % by controlling the co-monomer/monomer ratio by providing at
least two, preferably at least three spatially separated, feeding entries of monomer along the
path of the loop reactor.
3. Process as claimed in claim 1 or 2, wherein suitable positions for multiple, spatially
separated, feeding entries of monomer are determined along the path of the loop reactor in
order to control the co-monomer/monomer ratio along the path of the reactor.
4. Process as claimed in any of claims 1 to 3, wherein the step of controlling the co-monomer/
monomer ratio by multiple, spatially separated, feeding of monomer is done in conjunction
with a diluent.


5. Process as claimed in claim 4, whereby said monomer/diluent ratio is lower than 5/1.
6. Process as claimed in any of claims 1 to 5, wherein the flow rate of each, spatially
separated, monomer feed along the path of the loop reactor is separately controlled.
7. Process as claimed in any of claims 1 to 6, wherein said co-monomer is 1-hexene.
8. Polymerization loop reactor suitable for the co-polymerization process of a monomer, such
as herein described, preferably ethylene and an olefin co-monomer, such as herein described,
preferably hexene, said loop reactor comprising:

- a plurality of interconnected pipes defining a flow path for a polymer slurry, said slurry
consisting essentially of ethylene, a co-monomer, a polymerization catalyst, liquid
diluent and solid olefin co-polymer particles,
- means for feeding monomer, a co-monomer, diluent and optionally hydrogen in the
reactor,
- means for feeding the polymerization catalyst in the reactor,
- a pump suitable for maintaining the polymer slurry in circulation in said reactor,
- one or more settling legs connected to the pipes of said reactor for settling of polymer
slurry, and
one or more lines for discharging settled polymer slurry out of the reactor
characterized in that said reactor comprises multiple means for feeding monomer, which are
positioned spatially separated along the path of the loop reactor, whereby said reactor
corresponds to the first reactor of a double loop polymerization reactor, said first reactor being
interconnected with the second loop reactor of said double loop polymerization reactor.
9. Polymerization reactor as claimed in claim 8, which has multiple, spatially separated
additional means for the feeding of monomer in conjunction with a diluent into said first
reactor.

10. Polymerization reactor as claimed in claim 8 or 9, which has at least two, preferably at
least three additional means for feeding monomer, which are positioned spatially separated
along the path of the loop reactor.
11. Polymerization reactor as claimed in claim 10, having a number of flow controlling
means, whereby the number of flow controlling means corresponds to the number of
additional means for feeding monomer, which are positioned spatially separated along the
path of the loop reactor.
12. Polymerization reactor as claimed in claim 10, having a number of flow controlling
means, whereby the number of flow controlling means corresponds to the number of
additional means for feeding monomer, which are centralized.


There is disclosed a process for the co-polymerization of ethylene monomer and an
olefin co-monomer, such as herein described, in a polymerization loop reactor comprising the
steps of
- feeding monomer, an olefin co-monomer, diluents and optionally hydrogen into the
loop reactor,
- feeding at least one polymerization catalyst, such as herein described, into the reactor,
- co-polymerizing said monomer and said co-monomer to produce a polymer slurry
comprising essentially liquid diluent and solid olefin co-polymer particles,
- allowing said polymer slurry to settle into one or more settling legs connected to the
reactor, and
- sequentially discharging the settled polymer slurry from said one or more settling legs
out of the reactor,
characterized in that said process involves the step of controlling the co-monomer/monomer
ratio along the path of the reactor by multiple, spatially separated, feeding of monomer along
the path of the loop reactor and wherein the process is applied to the first loop of a double
loop reactor.

Documents:

01968-kolnp-2006-abstract.pdf

01968-kolnp-2006-asignment.pdf

01968-kolnp-2006-assignment-1.1.pdf

01968-kolnp-2006-claims.pdf

01968-kolnp-2006-correspondence other.pdf

01968-kolnp-2006-correspondence others-1.1.pdf

01968-kolnp-2006-description (complete).pdf

01968-kolnp-2006-drawings.pdf

01968-kolnp-2006-form-1.pdf

01968-kolnp-2006-form-3.pdf

01968-kolnp-2006-form-5.pdf

01968-kolnp-2006-international publication.pdf

01968-kolnp-2006-international search report.pdf

01968-kolnp-2006-pct form.pdf

01968-kolnp-2006-priority document.pdf

1968-KOLNP-2006-ABSTRACT 1.1.pdf

1968-KOLNP-2006-AMANDED CLAIMS.pdf

1968-kolnp-2006-assignment.pdf

1968-KOLNP-2006-CORRESPONDENCE.pdf

1968-kolnp-2006-correspondence1.1.pdf

1968-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

1968-KOLNP-2006-DRAWINGS 1.1.pdf

1968-KOLNP-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

1968-kolnp-2006-examination report.pdf

1968-KOLNP-2006-FORM 1 1.1.pdf

1968-kolnp-2006-form 13.1.pdf

1968-KOLNP-2006-FORM 13.pdf

1968-kolnp-2006-form 18.pdf

1968-KOLNP-2006-FORM 2.pdf

1968-KOLNP-2006-FORM 3 1.1.pdf

1968-kolnp-2006-form 3.pdf

1968-kolnp-2006-form 5.pdf

1968-KOLNP-2006-FORM-27.pdf

1968-kolnp-2006-gpa.pdf

1968-kolnp-2006-granted-abstract.pdf

1968-kolnp-2006-granted-claims.pdf

1968-kolnp-2006-granted-description (complete).pdf

1968-kolnp-2006-granted-drawings.pdf

1968-kolnp-2006-granted-form 1.pdf

1968-kolnp-2006-granted-form 2.pdf

1968-kolnp-2006-granted-specification.pdf

1968-KOLNP-2006-OTHERS.pdf

1968-kolnp-2006-others1.1.pdf

1968-KOLNP-2006-PETITION UNDER RULR 137.pdf

1968-kolnp-2006-reply to examination report.pdf


Patent Number 248220
Indian Patent Application Number 1968/KOLNP/2006
PG Journal Number 26/2011
Publication Date 01-Jul-2011
Grant Date 28-Jun-2011
Date of Filing 13-Jul-2006
Name of Patentee TOTAL PETROCHEMICALS RESEARCH FELUY
Applicant Address ZONE INDUSTRIELLE C, B-7181 SENEFFE (FELUY)
Inventors:
# Inventor's Name Inventor's Address
1 DAMME ERIC CHAUSSEE DE MONSTREUX, 7, B-7181 ARQUENNES
PCT International Classification Number C08F 210/02
PCT International Application Number PCT/EP2005/050624
PCT International Filing date 2005-02-14
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 04100568.7 2004-02-13 EUROPEAN UNION