Solution Polymerization Process

Abstract

Disclosed herein is a system for solution polymerization, the system including: a reactor system operative to receive a anti-solvent, a monomer, and a solvent and react the monomer to form a polymer, wherein the anti-solvent is not a solvent for the polymer and acts to lower the lower critical solution temperature; a plurality of devolatilization vessels located downstream of the reactor system, each devolatilization vessel operating at a lower pressure than the previous devolatilization vessel, the plurality of devolatilization vessels receiving the polymer solution from the reactor system; and a liquid-liquid separator operative to receive the polymer solution from the reactor system and to facilitate separation between the polymer and volatiles by reducing the pressure and temperature of the polymer solution in the liquid-liquid separator.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Application No. 62 / 779,589, filed December 14, 2018, the entirety of which is incorporated herein by reference. [Background technology]

[0002] The present disclosure relates to a solution polymerization process. In particular, the present disclosure relates to a solution polymerization process integrated with an upstream ethylene plant that uses a mixture of a solvent and a non-solvent.

[0003] Polymer solutions can exhibit the phenomenon of lower critical solution temperature (LCST), whereby a homogeneous polymer solution separates into a polymer-rich liquid phase and a solvent-rich phase above a certain temperature. This temperature is a function of the solvent type, polymer stream composition, and pressure. Any of these variables can be manipulated to induce liquid-liquid separation. This separation has a very small heat load associated with it, especially compared to the vaporization of an equivalent amount of solvent. Commercial solution polymerization requires increased efficiency and reduced costs associated with the solvent removal process.

[0004] U.S. Patent No. 6,881,800 to Friedersdorf is directed to a process and plant for continuous solution polymerization. The plant includes a pressure source, a polymerization reactor downstream of the pressure source, a pressure reducer located downstream of the polymerization reactor, and a separator downstream of the pressure reducer. The pressure source is disclosed as being sufficient to provide pressure to the reaction mixture during polymerization to produce a single-phase liquid reaction mixture in the reactor and a two-phase liquid-liquid reaction mixture in the separator in the absence of an additional pressure source between the reactor and the separator. The process discloses using a heater to heat the reactor outlet stream prior to inducing liquid-liquid phase separation. Because the solution coming out of the reactor has more solvent per pound of polymer than the solution coming out of the separator, heating prior to the separator significantly increases the heat load per pound of polymer.

[0005] International Publication No. WO 2008 / 076589 to Friedersdorf et al. discloses a process for polymerizing olefins in a dense fluid homogeneous polymerization system. The process includes: (a) contacting in one or more reactors olefin monomers having three or more carbon atoms present at 30 weight percent or greater with 1) one or more catalyst compounds; 2) one or more activators; 3) 0 to 50 mole percent of a comonomer; and 4) 0 to 40 weight percent of a diluent or solvent; (b) forming a reactor effluent comprising a polymer-monomer mixture; (c) optionally heating the polymer-monomer mixture of (b) after it exits the reactor and before or after the pressure is reduced in step (e); (d) collecting the polymer-monomer mixture of (b) in a separation vessel; and (e) reducing the pressure of the reactor effluent comprising the polymer-monomer mixture of (b) below the cloud point pressure either before or after collecting the polymer-monomer mixture in the separation vessel to form a two-phase mixture comprising a polymer-rich phase and a monomer-rich phase. The pressure in the reactor is 7-100 MPa higher than the pressure in the separation vessel, and the temperature in the separation vessel is above the higher of the crystallization temperature of the polymer, or above 80°C if the polymer does not have a crystallization temperature. The monomer-rich phase is separated from the polymer-rich phase and recycled to the reactor or reactors. The patent discloses high reactor pressures (up to 200 MPa) used to run the process with less than 40 weight percent solvent to ensure a supercritical polymerization medium. The high pressures make the reactor difficult to operate and necessitate the use of thick-walled reactors, reducing capital and energy efficiency.

[0006] U.S. Patent No. 6,255,410 to Shigekauzu et al. discloses a process for producing polyolefins in a two-phase system at substantially lower pressures than conventional high pressure conditions. The process includes (a) continuously feeding an olefin monomer and a catalyst system of metallocene and cocatalyst, (b) continuously polymerizing the monomer feed to result in a monomer-polymer mixture, and (c) continuously fixing the two-phase mixture to a continuous molten polymer phase and a continuous monomer vapor, the latter of which can optionally be at least partially recycled to (a). In (b), the mixture is at a pressure below the cloud point pressure to result in a polymer-rich phase and a monomer-rich phase at a temperature above the melting point of the polymer. The polymerization is carried out at a temperature and pressure that exceeds the productivity of the catalyst system at that temperature and at twice the pressure above the cloud point. The patent discloses only a small amount of solvent required for the catalyst support and does not have the advantage of using the lower temperatures and pressures associated with solution polymerization processes.

[0007] The polymerization processes described in the above references are typically energy intensive, requiring heat exchange between the polymerization reactor and a separator, supercritical polymerization conditions, and / or additional polymer-solvent separation means. There is a need to develop new polymerization processes that use less energy, increase efficiency, and reduce costs through the use of solvent separation means. There is also a need to eliminate auxiliary, energy intensive equipment, thereby reducing capital and operating costs. Summary of the Invention

[0008] Disclosed herein is a system for solution polymerization, the system including: a reactor system operative to receive a anti-solvent, a monomer, and a solvent and react the monomer to form a polymer, where the anti-solvent is not a solvent for the polymer and acts to lower the lower critical solution temperature; a plurality of devolatilization vessels located downstream of the reactor system, where each devolatilization vessel operates at a lower pressure than the previous devolatilization vessel, where the plurality of devolatilization vessels receive the polymer solution from the reactor system; and a liquid-liquid separator, where the liquid-liquid separator receives the polymer solution from the reactor system and operates to facilitate separation between the polymer and volatiles by reducing the pressure and temperature of the polymer solution in the liquid-liquid separator, where the polymer is in a polymer-rich phase and the volatiles are in a solvent-rich phase.

[0009] Also disclosed herein is a method that includes charging a reactor system with a feed stream that includes a anti-solvent, a monomer, and a solvent, where the anti-solvent is not a solvent for the polymer and operates to lower a lower critical solution temperature of the polymer solution; reacting the monomer to form a polymer, where the polymer is included in the polymer solution; transferring the polymer solution phase to a liquid-liquid separator; reducing the pressure of the polymer solution in the liquid-liquid separator to separate the polymer-rich phase from the solvent-rich phase in the liquid-liquid separator; transferring the polymer-rich phase to a plurality of devolatilization vessels located downstream of the liquid-liquid separator, where each devolatilization vessel operates at a lower pressure than the previous devolatilization vessel; and separating the polymer from volatiles present in the polymer-rich phase. [Brief description of the drawings]

[0010] [Figure 1] 1 illustrates an exemplary embodiment of a system used for solution polymerization of a monomer in a solution that includes a poor solvent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] As used herein, the term "continuously stirred tank reactor" or "CSTR" refers to a tank reactor into which reactants are continuously fed and products are continuously withdrawn. CSTRs are mechanically agitated such that near complete backmixing exists.

[0012] The term "boiling reactor" as used herein refers to a reactor operated under conditions such that both liquid and gas phases are present. At least a portion of the solvent and monomers introduced into the reactor as liquids are evaporated and leave the reactor as vapors, thereby removing a portion of the heat of polymerization, resulting in a higher polymer concentration in the liquid stream exiting the reactor compared to an adiabatic reactor. The vapor stream exiting the reactor is cooled and recycled to the reactor. Liquids condensed in this cooling process are also recycled to the reactor. These reactors are generally well mixed, and mixing can be achieved simply by introducing a vapor recycle stream, although mixing can be enhanced by mechanical agitation. The boiling reactor can be used by itself or in combination with other boiling reactors, CSTRs, loop reactors, or any other reactors for making polyolefins, and can be a single or multi-stage reactor.

[0013] A variation of the CSTR is the loop reactor, which includes a conduit through which the process fluids are recirculated. Often the loop reactor also includes one or more heat exchangers, a recirculation pump, and injection equipment for the reactants and catalyst. The heat exchangers in the loop reactor can be shell-and-tube, shell-and-tube with mixing element inserts, plate-and-frame, or flat plate heat exchangers.

[0014] The term "tubular reactor" is intended to denote a reactor in the shape of a simple tube. The tubular reactor of the present invention has a length / diameter (L / D) ratio of at least 10 / 1. The tubular reactor may be stirred or unstirred. The tubular reactor may be operated adiabatically or isothermally. When operated adiabatically, as the polymerization proceeds, more and more of the remaining comonomer is consumed and the temperature of the solution increases (both of which improve the efficiency of separating the remaining comonomer from the polymer solution). It is particularly preferred that the increase in temperature along the length of the tubular reactor is greater than 3°C (i.e. the discharge temperature from the tubular reactor is at least 3°C ​​higher than the discharge temperature from the reactor feeding the tubular reactor).

[0015] The tubular reactor used in the present disclosure may have feed ports for additional ethylene, hydrogen, and solvent. The feeds may be "tempered", i.e., the temperature of the additional ethylene, hydrogen, and / or solvent is heated above ambient temperature (preferably to about 100°C), but below the discharge temperature of the tubular reactor. In one embodiment, the ethylene is tempered to 100-200°C. It is also desirable to add the ethylene and hydrogen together with the solvent. The amount of solvent (expressed as a weight ratio based on ethylene) is preferably 10 / 1 to 0.1 / 1, in particular 5 / 1 to 1 / 1.

[0016] As used herein, the term "adiabatically flashed" refers to a flashing step in which no heat is added to the polymer solution between the reactor(s) and the flashing vessel.

[0017] By "substantially uniform" as used with respect to a dimension (such as width or height) or cross-sectional area of ​​a zone within a heating channel, it is meant that the same does not converge or diverge at all, or converges and / or diverges by no more than 10% of the average of its dimensions.

[0018] The term "solids content" refers to the amount of polymer in a polymer solution. The term "polymer concentration" is used synonymously with "solids content" when referring to the concentration of polymer in a polymer solution.

[0019] "Polymer" refers to a compound prepared by polymerizing monomers, whether of the same or different types. The general term "polymer" encompasses the terms "oligomer," "homopolymer," "copolymer," "terpolymer," and "interpolymer."

[0020] "Interpolymer" refers to a polymer prepared by polymerization of at least two different types of monomers. The general term "interpolymer" includes the term "copolymer" (usually used to refer to a polymer prepared from two different monomers) and the term "terpolymer" (usually used to refer to a polymer prepared from three different types of monomers). It also encompasses polymers made by polymerizing four or more types of monomers.

[0021] "Oligomer" refers to a polymer molecule consisting of only a few monomeric units, such as dimers, trimers, tetramers, or polymers having less than 20 carbon atoms in the chain.

[0022] Alpha olefins (or α-olefins) have the chemical formula C x H 2x Alkenes (also called olefins) are a family of organic compounds that are distinguished by having a double bond in the primary or alpha (α) position.

[0023] "Bubbling pressure" means the pressure at which the first gas bubbles form at a given temperature.

[0024] "Polymer solution" means a solution containing dissolved polymer and volatile materials in a single phase (liquid phase).

[0025] The viscosity of the solutions is measured using an AntonPaar MCR102 rheometer manufactured by Anton Paar Germany GmbH. The rheometer is equipped with a C-ETD300 electric heating system. The cup-and-bob system (a combination of concentric cylinders) comprises a cup with a diameter of 27 mm and a bob with a diameter of 25 mm, leaving a gap of 1 mm between them. The bob is pressurized at 150 bar (approximately 153 kgf / cm 2 ) pressure cell in rotational mode. Viscosity measurements are performed at 30 bar (approximately 31 kgf / cm 2 The range of pressures (obtained in a nitrogen atmosphere), temperatures (150 to 250 °C), polymer concentrations (20 to 90 weight percent), and shear rates (0.1 to >100 reciprocal seconds (s -1 )), and a range of polymer molecular weights (15,000-200,000 g / mol). The solvent in all cases was ISOPAR™ E by ExxonMobil. Viscosity measurements obtained ranged from 100 to over 2,000,000 centipoise.

[0026] Disclosed herein is a process for the solution polymerization of α-olefins. The process involves the homogeneous polymerization of α-olefins in a hydrocarbon solvent using one or two high-pressure stirred adiabatic reactors to produce engineered polyethylene and elastomer products. The reactors are operated at low conversion conditions and use a mixture of monomer and anti-solvent to lower the lower critical solution temperature (LCST) of the system. In a preferred embodiment, the monomer is ethylene. The anti-solvent is a liquid in which the polymer (e.g., polyolefin) is poorly soluble, more preferably in which the polymer is insoluble.

[0027] This combined ethane and ethylene feed stream helps eliminate the costly "de-ethanization" step in ethylene plants (hydrocarbon plants) to separate ethylene from ethane. This process can be used to make olefin-based polymers such as ethylene homopolymers, or interpolymers (e.g., copolymers or terpolymers) with other alkenes, and, optionally, dienes (e.g., EPDM terpolymers).

[0028] Also disclosed herein is a system in which solution polymerization of α-olefins is carried out. The system includes one or more reactors in which α-olefins are polymerized in a solvent system comprising a poor solvent (e.g., ethane). In one embodiment, the system includes multiple reactors in series with one another, which are used for solution polymerization of one or more monomers to produce a polymer-solvent solution (hereinafter referred to as polymer solution). At least one of the reactors promotes polymerization under adiabatic conditions. The reactors are in fluid communication with a liquid-liquid separator and a devolatilization system, which includes at least one devolatilization vessel, preferably at least two devolatilization vessels. Each successive devolatilization vessel operates at a lower pressure than the previous vessel. This arrangement increases the solids content in the polymer stream to at least 92% by weight before pelletization, granulation and coagulation.

[0029] The figure is a schematic diagram of an exemplary solution polymerization system 100 (hereinafter system 100) that may be used to polymerize a monomer (or monomers) to produce a polymer or copolymer. System 100 includes a reactor system 103, which may include one or more reactor units in fluid communication with one another (arranged either in series or in parallel). An example of such a reactor system is provided in U.S. Pat. Nos. 4,616,937, 4,753,535, and 4,808,007, the entire contents of which are incorporated herein by reference.

[0030] The reactor system 103 is operable to receive monomers, comonomers, hydrogen, catalysts, initiators, solvents, etc. In an embodiment, the reactors in the reactor system may be continuous stirred tank reactors (CSTRs), loop reactors (e.g., single loop reactors, dual loop reactors), boiling reactors, and may be single or multi-stage reactors. In an embodiment, the process may use multiple catalysts in one or more reactors.

[0031] In one embodiment, when a reactor system employs multiple reactors, the reactors may all be of the same type (e.g., all of the reactors may be loop reactors or all of the reactors may be continuous stirred tank reactors). In another embodiment, the reactors may be different reactor types (e.g., one reactor may be a loop reactor and the other reactor may be a continuous stirred tank reactor) or a combination thereof. In one embodiment, at least one of the reactors is an adiabatic reactor, i.e., no heat is supplied to the reactor during the reaction.

[0032] Referring again to the figure, reactor system 103 includes two reactors, a first reactor 102 and a second reactor 104, in series with each other. In a preferred embodiment, both first reactor 102 and second reactor 104 are continuous stirred tank reactors. Both reactors are operated under adiabatic conditions. Details of the reactor operation are detailed below.

[0033] Located downstream of the reactor system 103 are a plurality of devolatilization vessels in series, a first devolatilization vessel 110, and a second devolatilization vessel 112, in fluid communication with the reactor system and with each other. Disposed between the reactor system 102 and the first devolatilization vessel 108 is a liquid-liquid separator 106 that operates to separate the solvent and a portion of the unreacted monomer from the polymer. The liquid-liquid separator 106 increases the polymer concentration by vaporizing the solvent and a portion of the unreacted monomer and discharging it into the reactor system 103 via stream 212.

[0034] A positive displacement pump is disposed downstream of each devolatilization vessel to facilitate movement of the polymer solution from the devolatilization vessels. A first positive displacement pump 110 is disposed downstream of first devolatilization vessel 110 and a second positive displacement pump 114 is disposed downstream of second devolatilization vessel 112.

[0035] In one embodiment, both pumps 110 and 114 are screw pumps. In another embodiment, both pumps 110 and 114 are gear pumps. The polymer solution discharged from the second pump 114 is charged to an extruder 116 where the substantially solvent-free polymer solution is pelletized. The solvent and unreacted monomer extracted in the extruder are recycled and charged to the reactor system 103 via condensers 120 and 122.

[0036] In one embodiment, in one mode of utilizing system 100 to produce olefin polymers, α-olefin monomer is charged to reactor system 103 along with catalyst, initiator, solvent, and hydrogen. Reactants such as α-olefin monomer along with ethane are introduced into reaction system 103 via stream 302, while hydrogen is simultaneously introduced into reaction system 103 via stream 304.

[0037] In one embodiment, the α-olefin monomer may include only ethylene. In another embodiment, the α-olefin monomer may include ethylene with an α-olefin comonomer having 3 to 12 carbon atoms. Illustrative examples of such α-olefin monomers include one or more of propylene, 1-butene, 1-pentene, 1-hexane, 1-octene, and 1-decene. 1-octene is preferred.

[0038] In addition to solubilizing the polymer, the feed solvent acts as a heat sink to absorb the heat of reaction. Examples of inert hydrocarbon solvents include C 5~12Hydrocarbons, whether unsubstituted or C, such as pentane, methylpentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, hydrogenated naphtha, etc. 1~4 The solvent may be substituted with an alkyl group, an alkyl group, or a combination thereof. The preferred solvent is methylcyclohexane.

[0039] The weight ratio of solvent to monomer in stream 202 (which feeds the reactants to reactor system 103) is 5 to 10. In a preferred embodiment, the weight ratio of solvent to monomer in stream 202 is 6 to 8.

[0040] In one embodiment, the solvent comprises a poor solvent (i.e., the solvent comprises two or more fluids, one of which is incompatible with the polymer being produced). The poor solvent is an alkane. The poor solvent is preferably ethane. Other poor solvent alkanes, such as propane, butane, hexane, may also be used in place of or in combination with ethane. In a preferred embodiment, the process utilizes a feed stream from a hydrocarbon plant that "naturally" has ethane and ethylene. The presence of ethane facilitates the lowering of the lower critical solution temperature (LCST) of the system. The advantage of combining ethane with the α-olefin feed in stream 302 is that it (the ethane) facilitates the separation of ethylene from the ethane by reacting the ethylene in the ethane / ethylene stream, thus reducing the capital and operational costs of the upstream ethylene plant. Ethane acts as a poor solvent by lowering the LCST of the solution, thus facilitating effective liquid-liquid separation without the need to preheat the reactor effluent stream.

[0041] The weight ratio of anti-solvent to solvent in stream 202 is 1 to 10. In a preferred embodiment, the weight ratio of anti-solvent to solvent in stream 202 is 1 to 5.

[0042] The monomers are mixed with hydrogen and dissolved / dispersed in a solvent before being fed to the reactor system 103. Before mixing, the solvent and monomers (sometimes referred to as "feed") are typically purified to remove potential catalyst poisons such as water, oxygen, or other polar impurities. Feed purification may use molecular sieves, alumina beds, or oxygen removal catalysts. Solvents may also be purified in a similar manner. The feed to the reactor system 103 is typically cooled to a temperature below 40°C, preferably below 20°C. Cooling the feed can facilitate a reduction in the size of heat exchangers in the reactor system. Cooling can occur within the reactor system or prior to entering the reactor system. In a preferred embodiment, cooling of the feed can be performed prior to entering the reactor system.

[0043] In one embodiment, the catalyst may be premixed in a solvent for the reaction or may be fed as separate streams to one or more reactors in reactor system 103. In one embodiment, some or all of the catalyst may be introduced into first reactor 102 via stream 203, while additional catalyst may be added to second reactor 104 via stream 205. The catalyst used may be a Ziegler-Natta catalyst, a bismetallocene catalyst, a constrained geometry catalyst, a polyaryloxyether complex, a phosphinimine, or a combination thereof.

[0044] In one embodiment, the first reactor 102 has a pressure of 90 kgf / cm 2 Pressure of 95kgf / cm or more, preferably 95kgf / cm 2 More preferably, 100kgf / cm 2 In one embodiment, the first reactor 102 operates at a pressure of 200 kgf / cm or more. 2 Pressure below 195kgf / cm 2 Less than or equal to 180kgf / cm 2 In a preferred embodiment, the first reactor 102 operates at a pressure of 145 kgf / cm 2 ~165kgf / cm 2In one embodiment, the reactor system 102 operates at a temperature in the range of 120-230° C. In one embodiment, the polymer solution exiting the first reactor 102 may be at a temperature of 130-240° C., preferably 150-170° C.

[0045] The polymer (solids) is present in the polymer solution at the outlet of the first reactor 102 in an amount of 8-16 wt%, preferably 9-15 wt%, more preferably 11-13 wt%. The weight percentage (wt%) is based on the total weight of the polymer stream. The melt index I2 (or I2) and I 10 (or I10) are measured according to ASTM D-1238 (Method B) at 190°C and 2.16 kg and 10 kg loads, respectively. The values ​​are reported in g / 10 min. Melt Index Ratio (also called Melt Flow Ratio) I 10 / I2 is the ratio of two values ​​and is dimensionless. The melt index ratio of the polymers at the outlet of the first reactor 102 can range from 0.1 to 1,500.

[0046] In one embodiment, the viscosity of the polymer solution exiting the first reactor 102 is between 50 and 6,000 centipoise, measured as described above. Samples for density measurements are prepared according to ASTM D4703. Measurements are made during a 1 hour sample press according to ASTM D792, Method B.

[0047] In an exemplary embodiment, the product exiting the first reactor 102 has a density of 0.865 to 0.920 g / cm 3 Density of 0.25 to 210.0, melt index I2 of 0.25 to 210.0, and melt flow ratio I of 6.0 to 8.5 10 At a reactor temperature of 160° C. and a polymer concentration of 12 wt %, the solution viscosity at the reactor system outlet, measured as detailed above, is expected to be in excess of 350 centipoise.

[0048] The second reactor 104 operates at a higher temperature than the first reactor 102. In one embodiment, the second reactor operates at a lower pressure than the first reactor 102. The second reactor 104 operates to increase the solids content in the polymer stream by more than 10 wt%, preferably more than 15 wt%, preferably more than 20 wt%, more preferably more than 25 wt%, compared to the solids content of the polymer stream originating from the first reactor 102. In one embodiment, the solids content originating from the second reactor 104 is 12-20 wt%, preferably 14-18 wt%, more preferably 15-17 wt%, based on the total weight of the polymer stream.

[0049] In one embodiment, the second reactor 104 operates at a lower pressure than the first reactor 102. The second reactor 104 operates at a lower pressure than the first reactor 102. 2 Pressure of 85kgf / cm or more, preferably 85kgf / cm 2 More preferably, 90kgf / cm 2 In one embodiment, the second reactor 104 operates at a pressure of 180 kgf / cm or more. 2 Pressure below 175kgf / cm 2 Less than or equal to 170kgf / cm 2 In a preferred embodiment, the second reactor 102 operates at a pressure of 130 kgf / cm 2 ~143kgf / cm 2 It operates at a pressure of

[0050] The second reactor 104 operates at a higher temperature than the first reactor. The second reactor has a temperature at least 25% higher, preferably at least 30% higher, more preferably at least 35% higher than the temperature of the first reactor 102. In one embodiment, the second reactor 104 operates at a temperature in the range of 190-250°C. In one embodiment, the polymer solution exiting the second reactor 102 may have a temperature of 200-240°C, preferably 210-230°C, more preferably 218-224°C.

[0051] In one embodiment (not shown), the activity of the polymer solution is substantially terminated or reduced by adding a catalyst neutralizer (sometimes referred to as a hydrolysis agent) to the polymer solution at a port (not shown) located in stream 206 (located downstream of reactor system 103). The catalyst neutralizer functions to reduce the catalyst activity to as close to zero as possible. Examples of catalyst neutralizers include water or alcohol, which are added to the polymer solution in amounts of 10-100 ppm based on the total weight of polymer in the solution.

[0052] The polymer solution is then transferred from the reactor system 103 to a liquid-liquid separator 106. The pressure of the polymer solution from the second reactor is adjusted to the outlet pressure of the second reactor 104 (130 kgf / cm 2 ~143kgf / cm 2 ) to 92kgf / cm in the liquid-liquid separator 2 The presence of ethane, a component of the feed stream to reactor system 103, effectively reduces the lower critical solution temperature (LCST) of the system to about 193° C., the minimum temperature for inducing liquid-liquid separation.

[0053] The liquid-liquid separator facilitates the separation of the polymer from the volatile materials by reducing the pressure, temperature, or both pressure and temperature of the polymer solution. In other words, the use of ethane facilitates the separation of the polymer from the volatile materials without consuming energy. In other words, the temperature and pressure of the polymer solution is not increased as it is transferred from the reactor system to the liquid-liquid separator.

[0054] The second reactor is operated at at least 220°C and the reactor effluent (i.e., polymer solution) is above the lower critical solution temperature of the system at which liquid-liquid separation can be induced without additional energy input. The polymer solution moves into the liquid-liquid region but is still below the system's bubble point pressure (approximately 70 kgf / cm 2 Since the pressure in the liquid-liquid separator remains above 92 kgf / cm 2Lowering the temperature below the critical solution temperature promotes liquid-liquid separation. The displacement of the polymer solution below the lower critical solution temperature promotes separation of the polymer solution into a solvent-rich phase and a polymer-rich phase. The polymer-rich phase separates into the bottom of the liquid-liquid separator and the solvent-rich phase above the polymer-rich phase. The polymer-rich phase is removed from the bottom of the liquid-liquid separator and transferred to the first devolatilization vessel 108 via stream 210. In one embodiment, stream 210 resulting from the liquid-liquid separator has at least 25% more solids than stream 206 resulting from the second reactor 104. Stream 210 contains 20-24% solids by weight based on the total weight of the polymer solution removed from the bottom of the separator.

[0055] The solvent-rich phase is removed via stream 212 and recycled to the reactor system 103 via stream 208. In one embodiment, the solvent-rich phase is recycled to the second reactor 104. Because no polar compounds are introduced into the polymer stream prior to the liquid-liquid separator, the solvent-rich stream exiting the liquid-liquid separator can be sent directly back to the reactor feed section without having to go through an additional purification step.

[0056] In one embodiment, the reactivity of the resulting polymer-rich stream 210 is terminated using a heater 209 located downstream of the liquid-liquid separator and upstream of the first devolatilization vessel 108. Heater 209 (located along stream 210) raises the temperature of the polymer stream to at least 215° C., and preferably at least 220° C. In addition to terminating the reaction within system 100, this increase in temperature facilitates flashing of solvent from the polymer solution when the solution is introduced into a devolatilization system described below.

[0057] The polymer solution is then discharged into a devolatilization system that includes a series of devolatilization vessels, a first devolatilization vessel 108, and a second devolatilization vessel 112, in series and in fluid communication with one another. The first devolatilization vessel 108 is located upstream of the second devolatilization vessel 112. Each devolatilization vessel in the series operates at a lower pressure than the previous vessel, and each devolatilization vessel promotes adiabatic flashing of solvent from the polymer solution, leaving the polymer solution with a higher polymer concentration than before the flash.

[0058] The polymer solution contains about 20-24% solids by weight, preferably 21-23% solids by weight upon entering the first devolatilization vessel 108. In the first devolatilization vessel 108, the polymer solution undergoes a flash in which at least 60% by weight of the solvent is removed such that the polymer solution is concentrated to at least 60% polymer by weight, preferably 65% ​​polymer by weight, based on the total weight of the polymer solution. In one embodiment, the flashing is performed adiabatically.

[0059] In one embodiment, the first devolatilization vessel 108 operates adiabatically to facilitate solvent removal from the polymer solution. In one embodiment, the pressure in the first devolatilization vessel is between 6 and 12 kgf / cm 2 , preferably 8 to 10 kgf / cm 2 216, thus allowing the solvent to be flashed off and the polymer content in the polymer solution to be increased to 45-90 wt. %, preferably 50-70 wt. %, based on the total weight of the polymer solution leaving the first devolatilization vessel via stream 214. In one embodiment, at least 50 wt. %, preferably at least 55 wt. %, of the solvent present in the polymer solution (at the time of entering the first devolatilization vessel 108) is flashed off. The flashed solvent is transferred from the first devolatilization vessel 108 via line 216 to the condensation tank 122, from where it is recycled to the reactor system 103 via streams 226 and 228.

[0060] The temperature of the polymer solution discharged from the first devolatilization vessel 108 is 170°C to 220°C, and the pressure is 2 to 12 kgf / cm.2 The polymer solution exiting first devolatilization vessel 108 contains an amount of polymer between 50-90 wt %, based on the total weight of the polymer solution exiting first devolatilization vessel 108. In one embodiment, the solids content increases to at least 60 wt % polymer, preferably at least 65 wt %, based on the total weight of the polymer solution exiting first devolatilization vessel 108.

[0061] The polymer solution is then discharged from the first devolatilization vessel 108 via stream 214 to the optional first positive displacement pump 110. The optional first positive displacement pump 110 facilitates an increase in the pressure of the polymer solution. This pressure increase (provided by the first optional positive displacement pump 110) further promotes devolatilization of volatiles (e.g., solvent and unreacted monomers) from the polymer solution as it is adiabatically flashed in the second devolatilization vessel 112 to increase the solids concentration to an amount of 90 wt. % or more, preferably 92 wt. % or more, and more preferably 95 wt. % or more, based on the total weight of the polymer solution exiting the second devolatilization vessel 112.

[0062] The second devolatilizer vessel 112 may also be operated adiabatically to facilitate solvent removal from the polymer solution. In one embodiment, the polymer solution entering the second devolatilizer vessel 112 (see figure) is at a temperature of 210-260°C, preferably 220-240°C. In one embodiment, the pressure in the second devolatilizer vessel is 0.5-1 kgf / cm 2 The second devolatilization vessel 112 is maintained at a constant temperature to allow the solvent to flash off and increase the solids content in the polymer solution to 90-97% by weight, preferably 92-95% by weight, based on the total weight of the polymer solution at the outlet of the second devolatilization vessel 112. The temperature of the polymer solution leaving the second devolatilization vessel 112 is 180°C to 240°C, preferably 190-230°C.

[0063] Volatiles removed from the flash (of polymer solution) in second devolatilization vessel 112 are transferred via stream 219 to condensation vessel 122 from where they are recycled to reactor system 103 via solvent recovery vessel 124. Streams 226 and 228 facilitate the transfer of volatiles to reaction system 103. Heat exchanger 126 and pump 128 are used to increase the temperature and pressure of the volatile streams, respectively.

[0064] A second positive displacement pump 114 facilitates the charging of the polymer solution (less than 6% by weight, preferably less than 5% by weight solvent content) via stream 218 to a granulation and coagulation device such as a pelletizer 116 where the polymer is pelletized and packaged for transport.

[0065] Volatiles produced in the two devolatilizer vessels 108 and 112, as well as volatiles produced in the pelletizer, are transferred to a solvent recovery vessel 124 from which they are recycled to the reactor system 103. Volatiles from the first devolatilizer vessel 108 are transferred to the solvent recovery vessel 124 via stream 216 and condenser vessel 122. Volatiles from the second devolatilizer vessel 112 are transferred to the solvent recovery vessel 124 via stream 219 and condenser vessel 122. Volatiles from the pelletizer 116 are transferred to the solvent recovery vessel 124 via streams 220, 222, 224, 226, and 228 from which they are recycled to the reactor system 103.

[0066] The recycled volatiles are then fed to reactor system 103 via stream 202 along with a feed comprising ethylene and ethane (see stream 302) and hydrogen (see stream 304). The reaction in reactor system 103 proceeds as described above.

[0067] The system disclosed herein is advantageous in that the addition of ethane as an anti-solvent reduces the lower critical solution temperature to a value sufficient to induce liquid-liquid separation without the need for additional energy. There is no need to preheat the reactor effluent stream to facilitate liquid-liquid separation. Therefore, this is a cost-effective and energy-efficient method. The invention as originally claimed in the present application is set forth below. [1] A system for solution polymerization comprising: a reactor system operative to receive a anti-solvent, a monomer, and a solvent and to react said monomer to form a polymer, said anti-solvent being a non-solvent for said polymer and acting to reduce a lower critical solution temperature; a plurality of devolatilization vessels located downstream of the reactor system, each devolatilization vessel operating at a lower pressure than the preceding devolatilization vessel, the plurality of devolatilization vessels receiving the polymer solution from the reactor system; a liquid-liquid separator that receives a polymer solution from the reactor system and operates to facilitate separation between the polymer and volatiles by reducing the pressure and temperature of the polymer solution in the liquid-liquid separator, wherein the polymer is present in a polymer-rich phase and the volatiles are present in a solvent-rich phase. [2] The system described in [1], wherein the anti-solvent is ethane, the monomer is an α-olefin, and the solvent is methylcyclohexane. [3] The reactor system has a temperature of 120°C to 230°C and a pressure of 90 kgf / cm 2 More than ~200kgf / cm 2 13. The system of claim 1, comprising a first reactor operating at a pressure: [4] The system described in [3], wherein the solid content in the polymer solution is present in an amount of 8 to 16 weight % based on the total weight of the polymer solution at the outlet of the first reactor. [5] The system of [3], wherein the reactor system further includes a second reactor operating at a higher temperature and lower pressure than the first reactor. [6] The second reactor has a pressure of 80 kgf / cm 2 More than ~180kgf / cm 2 The system described in [5] operates at a pressure of 200 to 240°C and at a temperature of 200 to 240°C. [7] The system of [6], wherein the solids in the polymer solution are present in an amount of 12 to 20 weight percent, based on the total weight of the polymer solution at the outlet of the second reactor. [8] The system of [1], wherein the pressure in the liquid-liquid separator is above the boiling point of the polymer solution. [9] The pressure of the polymer solution in the liquid-liquid separator is 180 kgf / cm 2 from 92kgf / cm 2 and the solids content of the polymer solution emerging from the liquid-liquid separator is 20-24 wt.%.

[10] The system of [1], wherein the plurality of devolatilization vessels includes a first devolatilization vessel, the first devolatilization vessel operative to increase the solids content in the polymer stream to at least 60 wt. % polymer, based on a total weight of the polymer solution exiting the first devolatilization vessel.

[11] The system of

[10] , wherein the plurality of devolatilization vessels further includes a second devolatilization vessel, the second devolatilization vessel operative to increase the solids content in the polymer stream to at least 90 wt. % polymer, based on a total weight of the polymer solution exiting the second devolatilization vessel.

[12] The system of [1], wherein the volatile materials produced in the plurality of devolatilization vessels are recycled to the reactor system.

[13] A method comprising: charging a reactor system with a feedstream comprising a poor solvent, a monomer, and a solvent, wherein the poor solvent is not a solvent for the polymer and acts to lower the lower critical solution temperature of a polymer solution; reacting the monomers to form a polymer, the polymer being contained in a polymer solution; transferring the polymer solution phase to a liquid-liquid separator; reducing the pressure of the polymer solution in the liquid-liquid separator to separate a polymer-rich phase from a solvent-rich phase in the liquid-liquid separator; transferring the polymer-rich phase to a plurality of devolatilization vessels located downstream of the liquid-liquid separator, each devolatilization vessel operating at a lower pressure than the previous devolatilization vessel; separating said polymer from volatile materials present in said polymer-rich phase; The method includes:

[14] The method of

[13] , further comprising pelletizing the polymer.

[15] The method of

[13] , further comprising recycling volatile materials to the reactor system.

Claims

1. 1. A system for solution polymerization comprising: a reactor system operative to receive a poor solvent, a monomer, and a solvent and react said monomer to form a polymer, said poor solvent being a non-solvent for said polymer and acting to lower a lower critical solution temperature, said reactor system including a first reactor and a second reactor; said second reactor operating at a higher temperature and lower pressure than said first reactor; a liquid-liquid separator operable to receive a polymer solution from the reactor system and to facilitate separation between the polymer and volatile materials, including solvent and unreacted monomers, by reducing the pressure and temperature of the polymer solution in the liquid-liquid separator, such that the polymer is present in a polymer-rich phase and the volatile materials are present in a solvent-rich phase; a plurality of devolatilization vessels downstream of the liquid-liquid separator, each devolatilization vessel operating at a lower pressure than the preceding devolatilization vessel, the plurality of devolatilization vessels receiving the polymer-rich phase from the liquid-liquid separator; Including, the poor solvent is ethane, the monomer is an α-olefin, and the solvent is methylcyclohexane; The liquid-liquid separator is located between the reactor system and the first devolatilization vessel and has a pressure of 70 kgf / cm ２ Higher, 92 kgf / cm ２ and at a temperature that causes separation between the polymer and the volatile material. system.

2. The reactor system is operated at a temperature of 120°C to 230°C and 90 kgf / cm ２ More than ~200kgf / cm ２ 10. The system of claim 1 comprising a first reactor operating at a pressure of:

3. 3. The system of claim 2, wherein the solids in the polymer solution are present in an amount of 8 to 16 wt. %, based on the total weight of the polymer solution at the outlet of the first reactor.

4. The second reactor has a pressure of 80 kgf / cm ２ Above ~180kgf / cm ２ 2. The system of claim 1, which operates at a pressure of 200 to 240° C.

5. 5. The system of claim 4, wherein the solids in the polymer solution are present in an amount of 12 to 20 wt. %, based on the total weight of the polymer solution at the outlet of the second reactor.

6. The system of claim 1 , wherein the pressure in the liquid-liquid separator is above the boiling point of the polymer solution.

7. The pressure of the polymer solution in the liquid-liquid separator is 180 kgf / cm ２ From 70kgf / cm2 higher to 92kgf / cm ２ 2. The system of claim 1, wherein the pressure is reduced to less than 2000 psi and the polymer solution exiting the liquid-liquid separator has a solids content of 20-24 wt %.

8. 2. The system of claim 1, wherein the plurality of devolatilizer vessels includes a first devolatilizer vessel, the first devolatilizer vessel operative to increase the solids content in the polymer stream to at least 60 weight percent polymer, based on the total weight of the polymer solution exiting the first devolatilizer vessel.

9. 9. The system of claim 8, wherein the plurality of devolatilizer vessels further includes a second devolatilizer vessel, the second devolatilizer vessel operative to increase the solids content in the polymer stream to at least 90 weight percent polymer, based on a total weight of the polymer solution exiting the second devolatilizer vessel.

10. 10. The system of claim 1, wherein the volatile materials produced in the plurality of devolatilization vessels are recycled to the reactor system.

11. 1. A method comprising: charging a reactor system with a feedstream comprising a poor solvent, a monomer, and a solvent, wherein the poor solvent is not a solvent for the polymer and acts to lower a lower critical solution temperature of the polymer solution, wherein the reactor system comprises a first reactor and a second reactor; the second reactor operating at a higher temperature and lower pressure than the first reactor; reacting the monomers to form a polymer, the polymer being included in a polymer solution; transferring the polymer solution phase to a liquid-liquid separator; reducing the pressure of the polymer solution in the liquid-liquid separator to separate a polymer-rich phase from a solvent-rich phase in the liquid-liquid separator; transferring the polymer-rich phase to a plurality of devolatilization vessels located downstream of the liquid-liquid separator, each devolatilization vessel operating at a lower pressure than the preceding devolatilization vessel; separating said polymer from volatile materials, including solvent and unreacted monomer, present in said polymer-rich phase; Including, the poor solvent is ethane, the monomer is an α-olefin, and the solvent is methylcyclohexane; The liquid-liquid separator is located between the reactor system and the first devolatilization vessel and has a pressure of 70 kgf / cm ２ Higher, 92 kgf / cm ２ and at a temperature that causes separation between the polymer and the volatile material. method.

12. The method of claim 11 further comprising pelletizing the polymer.

13. The method of claim 11, further comprising recycling the volatile material to the reactor system.

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