Solution Polymerization Process

Abstract

Also disclosed herein is a process that includes charging a feed stream that includes a catalyst, a monomer, and a solvent; reacting the monomer to form a polymer, wherein the polymer is contained in a single-phase polymer solution; transferring the polymer solution to a preheater to increase the temperature of the polymer solution; charging the polymer solution to a liquid-liquid separator; reducing the pressure of the polymer solution in the liquid-liquid separator; separating 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 disposed downstream of the liquid-liquid separator, each devolatilization vessel operating at a lower pressure than the preceding devolatilization vessel; and separating the polymer from volatiles present in the polymer-rich phase.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Application No. 62 / 779,595, 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 using a high pressure reactor in combination with thermal activation and a liquid-liquid separator.

[0003] Polymer solutions may 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 type of solvent, the composition of the polymer stream, and the pressure. Manipulation of any of these variables can induce liquid-liquid separation. This separation has a very small heat load associated with it, especially compared to the vaporization of the same amount of solvent. In commercial solution polymerization, there is a need to increase the efficiency and reduce the costs associated with the solvent removal process.

[0004] Friedersdorf's U.S. Patent No. 6,881,800 relates to a process and plant for continuous solution polymerization. The plant includes a pressure source, a polymerization reactor downstream of said pressure source, a pressure drop device disposed downstream of the polymerization reactor, and a separator disposed downstream of the pressure drop device. A pressure source 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 is disclosed. 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] Friedersdorf et al., International Publication No. WO 2008 / 076589, 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 3 or more carbon atoms present at 30 weight percent or more 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 reducing the pressure 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) to below a cloud point pressure to form a two-phase mixture comprising a polymer-rich phase and a monomer-rich phase either before or after collecting the polymer-monomer mixture in the separation vessel. The pressure in the reactor is 7-100 MPa higher than the pressure in the separation vessel, and the temperature in the separation vessel exceeds the higher of the crystallization temperature of the polymer or exceeds 80°C if the polymer has no crystallization temperature. The monomer-rich phase is separated from the polymer-rich phase and recycled to one or more reactors. The patent discloses that high reactor pressures (up to 200 MPa) are used to run this process with less than 40 weight percent solvent to ensure a supercritical polymerization medium. This high pressure necessitates the use of thick-walled reactors, which make the reactor operation difficult and reduces capital and energy efficiency.

[0006] Shigekauzu et al., U.S. Patent No. 6,255,410, discloses a process for producing polyolefins in a two-phase system at pressures substantially below conventional high pressure conditions. The process includes (a) continuously feeding an olefin monomer and a catalyst system of a metallocene and a cocatalyst; (b) continuously polymerizing the monomer feed to provide a monomer-polymer mixture; and (c) continuously fixing the two-phase mixture in a continuous molten polymer phase and a continuous monomer vapor, the latter of which can be optionally at least partially recycled to (a). In (b), the mixture is at a pressure below the cloud point pressure and at a temperature above the melting point of the polymer to provide a polymer-rich phase and a monomer-rich phase, and the polymerization is carried out at a temperature and pressure where the productivity of the catalyst system exceeds the productivity obtained at twice the pressure above the cloud point at that temperature. The patent discloses only less than half the amount of solvent required as a 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 utilize less energy and use solvent separation means that are more efficient and less costly. There is also a need to eliminate auxiliary, energy intensive devices, thereby reducing capital and operating costs. Summary of the Invention

[0008] Disclosed herein is a system for solution polymerization comprising a reactor system operative to receive monomer, catalyst, and solvent and react the monomer to form a polymer; a preheater disposed downstream of the reactor system, the preheater operative to receive a polymer solution from the reactor system and heat the polymer solution to a temperature above its lower critical solution temperature; a liquid-liquid separator operative to receive the polymer solution from the preheater and facilitate separation between the polymer and volatiles by reducing the pressure and / or temperature of the polymer solution below the lower critical solution temperature of the polymer solution, where the polymer is present in a polymer-rich phase and the volatiles are present in a solvent-rich phase; and a plurality of devolatilization vessels disposed downstream of the reactor system, where each devolatilization vessel operates at a lower pressure than the preceding devolatilization vessel, where the plurality of devolatilization vessels receive the polymer-rich phase from the reactor system and separate the polymer from the volatiles.

[0009] Also disclosed herein is a process that includes charging a feed stream that includes a catalyst, a monomer, and a solvent; reacting the monomer to form a polymer, the polymer being contained in a single-phase polymer solution; transferring the polymer solution to a preheater to increase the temperature of the polymer solution; charging the polymer solution to a liquid-liquid separator; reducing the pressure of the polymer solution in the liquid-liquid separator; separating 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 disposed downstream of the liquid-liquid separator, each devolatilization vessel operating at a lower pressure than the preceding 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 to solution polymerize monomers to form a polymer. [Diagram 2]1 shows a pressure-temperature graph illustrating the effect of a preheater on system properties. 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 perfect 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). In particular, it is preferred that the temperature increase along the length of the tubular reactor is more 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 that feeds the tubular reactor).

[0015] The tubular reactor used in this 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 between 100 and 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) are compounds with the chemical formula C x H 2x A family of organic compounds that are alkenes (also known as olefins) having the formula:

[0023] "Bubble point pressure" means the pressure at which the first gas bubble forms 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 Anton Paar MCR102 rheometer from 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 taken at a pressure of 30 bar (approximately 31 kgf / cm 2 -obtained in nitrogen atmosphere), and a range of temperatures (150 to 250 °C), polymer concentrations (20 to 90 weight percent), and shear rates (0.1 to >100 inverse 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 homogeneous polymerization of α-olefins in a hydrocarbon solvent using one or two high-pressure stirred adiabatic reactors to make engineered polyethylene and elastomer products. The reactors are operated at low ethylene conversion conditions. The process involves heating the reactor effluent (hereinafter "polymer solution") to a high temperature to deactivate the catalyst without the use of polar compounds to kill the catalyst. To accomplish this, the system utilizes a preheater (located upstream of the liquid-liquid separator and downstream of the reactor system) to raise the reactor effluent temperature to a value above the lower critical solution temperature of the system. At this temperature, the catalyst is deactivated.

[0027] Both the high unreacted ethylene concentration and preheating of the reactor effluent facilitated liquid-liquid separation, resulting in the removal of over 33 wt.% of the total solvent.

[0028] A system for carrying out solution polymerization of α-olefins is also disclosed herein. The system includes one or more reactors in which α-olefins are polymerized. In one embodiment, the system includes multiple reactors in series with each other, which are used for solution polymerization of one or more monomers to produce a polymer-solvent solution (also referred to as reactor effluent, hereinafter referred to as "polymer solution"). At least one of the reactors facilitates polymerization under adiabatic conditions. The reactor is in fluid communication with a devolatilization system including a preheater, a liquid-liquid separator, and at least one devolatilization vessel, preferably at least two devolatilization vessels. Each successive devolatilization vessel operates at a lower pressure than the previous vessel. The preheater heats the temperature of the polymer solution to a temperature above the lower solution critical temperature. The temperature of the polymer solution is reduced in the liquid-liquid separator to facilitate separation of the polymer from the volatiles. The polymer separates into a polymer-rich phase, and the volatiles separate into a solvent-rich phase. In this arrangement, no antisolvent is used to precipitate the polymer from the volatiles. This arrangement increases the solids content in the polymer stream to at least 92% by weight prior to pelletizing, granulation, and solidification.

[0029] 1 is a schematic diagram of an exemplary solution polymerization system 100 (hereinafter, system 100) that can be used to polymerize a monomer (or monomers) to produce a polymer or copolymer. System 100 includes a reactor system 103 that can include one or more reactor units (arranged either in series or parallel) in fluid communication with one another. Examples of such reactor systems are provided in U.S. Patent 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 one embodiment, the reactors in the reactor system can be continuous stirred tank reactors (CSTRs), loop reactors (e.g., single loop reactors, dual loop reactors), boiling type reactors, and can be single or multi-stage reactors. In one embodiment, the process may use multiple catalysts in one or more reactors.

[0031] In one embodiment, when a reactor system uses multiple reactors, the reactors can all be of the same type (e.g., all of the reactors can be loop reactors or all of the reactors can be continuous stirred tank reactors). In another embodiment, the reactors can be different reactor types (e.g., one reactor can be a loop reactor and the other reactor can 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 Figure 1, reactor system 103 is comprised of two reactors in series with one another, namely, first reactor 102 and second reactor 104. In a preferred embodiment, first reactor 102 and second reactor 104 are both continuous stirred tank reactors. Both reactors are operated under adiabatic conditions. Details of the reactor operation are detailed below.

[0033] Downstream of the reactor system 103 are disposed in series with one another, a first volatilization vessel 110 and a second volatilization vessel 112, in fluid communication with the reactor system and with one another. Disposed between the reactor system 102 and the first volatilization vessel 108 is a preheater 107 and a liquid-liquid separator 106 that operates to separate the solvent and a portion of the unreacted monomers from the polymer.

[0034] The preheater 107 heats the polymer solution exiting the reactor system 103 to a temperature above the lower critical solution temperature. The temperature of the polymer solution is reduced below the lower critical solution temperature in the liquid-liquid separator 106, thus promoting the precipitation of the polymer from the volatiles. A polymer-rich phase is removed from the bottom of the liquid-liquid separator 106, while a solvent-rich phase is removed from the top of the liquid-liquid separator.

[0035] A positive displacement pump is disposed downstream of each devolatilization vessel to facilitate transfer 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.

[0036] In one embodiment, pumps 110 and 114 are both screw pumps. In another embodiment, pumps 110 and 114 are both 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 monomers extracted in the extruder are recycled and charged to the reactor system 103 via condensers 120 and 122.

[0037] In one embodiment, in one method of producing olefin polymers utilizing system 100, α-olefin monomer is charged to reactor system 103 along with catalyst, initiator, solvent, and hydrogen. Reactants such as α-olefin monomer along with solvent are introduced into reaction system 103 via stream 302, and hydrogen is simultaneously introduced into reaction system 103 via stream 304.

[0038] In one embodiment, the α-olefin monomer may include only ethylene. In another embodiment, the α-olefin monomer may include ethylene along with an α-olefin comonomer having 3 to 12 carbon atoms. Illustrative examples of such alpha-olefin comonomers are one or more of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 1-decene. 1-octene is preferred.

[0039] In addition to solubilizing the polymer, the feed solvent serves as a heat sink to absorb the heat of reaction. Examples of inert hydrocarbon solvents include C pentane, methylpentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, hydrogenated naphtha, or combinations thereof, which may be unsubstituted or may be substituted. 1~4 C optionally substituted with an alkyl group 5~12 A preferred solvent is methylcyclohexane.

[0040] The weight ratio of solvent to monomer in stream 202 (which feeds the reactants to reactor system 103) is between 5 and 10. In a preferred embodiment, the weight ratio of solvent to monomer in stream 202 is between 6 and 8.

[0041] 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 heat exchanger size within 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.

[0042] 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 is introduced into first reactor 102 via stream 203, while additional catalyst can be added to second reactor 104 via stream 205. The catalyst used can be a Ziegler-Natta catalyst, a bismetallocene catalyst, a constrained geometry catalyst, a polyaryloxyether complex, a phosphinimine, or a combination thereof.

[0043] In one embodiment, the first reactor 102 has a pressure of 105 kgf / cm 2 More than 110kgf / cm 2 More preferably, 115kgf / cm 2 In one embodiment, the first reactor 102 operates at a pressure of 200 kgf / cm or more. 2 Less than 195kgf / cm 2 Less than or equal to 180kgf / cm 2 In a preferred embodiment, the first reactor 102 operates at a pressure of 130 kgf / cm 2 ~155kgf / cm 2 In one embodiment, the first reactor 102 operates at a temperature in the range of 120-230° C. In one embodiment, the polymer solution exiting the first reactor 102 can have a temperature of 130-240° C., preferably 150-170° C.

[0044] 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 percentages (wt%) are based on the total weight of the polymer stream. The melt indexes I2 (or I2) and I 10(or I10) are measured according to ASTM D-1238 (Method B) at 190°C and loads of 2.16 kg and 10 kg, 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, it is dimensionless. The melt index ratio of the polymers at the outlet of the first reactor 102 can range from 0.1 to 1500.

[0045] In one embodiment, the viscosity of the polymer solution exiting the first reactor 102 is between 50 and 11,000 centipoise, measured as detailed 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.

[0046] In an exemplary embodiment, the product exiting the first reactor 102 has a mercury content of 0.865 to 0.920 g / cm 3 Density of 0.25 to 210.0 g / 10 min, melt index I2 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 outlet of the reactor system is expected to be at least 350 centipoise, measured as detailed above.

[0047] 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% by weight, preferably more than 15% by weight, preferably more than 20% by weight, and more preferably more than 25% by weight relative to the solids content of the polymer stream emanating from the first reactor 102.

[0048] In one embodiment, the monomer content in the polymer stream fed to the liquid-liquid separator is greater than at least 5 wt. % based on the total weight of the polymer solution stream entering the liquid-liquid separator. The presence of at least 5 wt. % monomer in the liquid-liquid separator feed stream (i.e., the polymer solution stream) facilitates phase separation of the polymer from the solvent when the polymer solution is at a temperature below the lower critical solution temperature. As noted above, the monomer comprises an α-olefin. In a preferred embodiment (as described below), the α-olefin monomer present in the polymer stream fed to the liquid-liquid separator is ethylene.

[0049] In one embodiment, the ethylene content (reflecting the ethylene concentration in the stream feeding the liquid-liquid separator) is greater than at least 5 wt.% based on the total weight of the polymer solution stream entering the liquid-liquid separator. The presence of at least 5 wt.% ethylene in the liquid-liquid separator feed stream facilitates phase separation of the polymer from the solvent when the polymer solution is at a temperature below the lower critical solution temperature.

[0050] In one embodiment, the solids content exiting the second reactor 104 is between 12 and 20 wt %, preferably between 14 and 18 wt %, more preferably between 15 and 17 wt %, based on the total weight of the polymer stream.

[0051] The second reactor 104 has a pressure of 100 kgf / cm 2 More than 105kgf / cm, preferably 105kgf / cm 2 More preferably, 110kgf / cm 2 In one embodiment, the second reactor 104 operates at a pressure of 180 kgf / cm or more. 2 Less than 175kgf / cm 2 Less than or equal to 155kgf / cm 2 In a preferred embodiment, the second reactor 102 operates at a pressure of 120 kgf / cm 2 ~135kgf / cm 2 It operates at a pressure of

[0052] 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 180-250°C. In one embodiment, the polymer solution exiting the second reactor 102 can have a temperature of 190-230°C, preferably 200-220°C, more preferably 208-214°C.

[0053] The polymer solution is then transferred from the reactor system 103 to a preheater 107. The preheater heats the polymer solution to a temperature above the lower critical solution temperature of the polymer solution. In one embodiment, the preheater heats the polymer solution to a temperature of about 250° C. or higher, preferably about 255° C. or higher. In one embodiment, the preheater heats the polymer solution to a temperature of 260° C.

[0054] The polymer solution leaving the preheater 107 is then charged into the 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 (which is 120 kgf / cm 2 ~135kgf / cm 2 ) to 70kgf / cm for liquid-liquid separators 2 FIG. 2 shows a pressure-temperature graph illustrating the effect of the preheater on the system properties. The operating point of the second reactor is at a temperature of 200° C. and a pressure of 1800 pounds per square inch (126 kgf / cm 2 ). 2 The preheater raises the temperature of the polymer solution, so that the system temperature rises to about 250°C (see preheater operating point in Figure 2). When the polymer solution is charged into the liquid-liquid separator, the pressure is about 930 psi (about 65 kgf / cm 2 The operating point of the liquid-liquid separator is below the lower critical solution temperature, so that the polymer solution separates into a polymer-rich phase and a solvent-rich phase, which is described in more detail below.

[0055] 2 shows that the pressure drop brings the polymer solution to a temperature below the lower critical solution temperature, but in some cases, a decrease in temperature, or alternatively a decrease in both pressure and temperature, can bring the system to a temperature below the lower critical solution temperature. In short, a decrease in pressure, temperature, or both temperature and pressure can facilitate bringing the polymer solution to a temperature below the lower critical solution temperature, and the single-phase solution separates into a two-phase system of a polymer-rich phase and a solvent-rich phase.

[0056] The liquid-liquid separator facilitates the separation of the polymer from the volatiles by reducing the pressure, temperature, or both the pressure and temperature of the polymer solution. In one embodiment, the pressure is 65 kgf / cm in the liquid-liquid separator 106. 2 Less than 60kgf / cm, preferably 60kgf / cm 2 The pressure drop in the liquid-liquid separator 106 facilitates driving the polymer solution below the lower critical solution temperature, and the polymer solution separates into a polymer-rich phase and a solvent-rich phase.

[0057] When the second reactor is operated at at least 250°C, the reactor effluent (i.e., polymer solution) is above the lower critical solution temperature of the system where liquid-liquid separation can be induced without any additional energy input. The pressure of the liquid-liquid separator is set to 60 kgf / cm 2 By lowering the temperature below the bubble point pressure of the system (approximately 56 kgf / cm 2(which is 0.25° C.), liquid-liquid separation is promoted. Displacing 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 at the bottom of the liquid-liquid separator, and the solvent-rich phase resides 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 exiting the liquid-liquid separator has at least 25% more solids than stream 206 exiting 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.

[0058] 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. The use of a liquid-liquid separator removes at least 33% of the volatiles (solvent and monomers) from the polymer solution in the liquid-liquid separator. 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 does not have to go through an additional purification step and can be sent directly back to the reactor feed section.

[0059] The polymer solution (polymer-rich stream) is then discharged into a devolatilization system that includes a series of devolatilization vessels, namely, a first devolatilization vessel 108 and a second devolatilization vessel 112, both of which are in series fluid communication with one another. The first devolatilization vessel 108 is disposed upstream of the second devolatilization vessel 112. Each devolatilization vessel in the series operates at a lower pressure than the previous vessel, with each devolatilization vessel facilitating adiabatic flashing of solvent from the polymer solution, leaving the polymer solution with a higher polymer concentration than before the flash.

[0060] The polymer solution contains about 20-24 wt. % solids, preferably 21-23 wt. % solids, at the point of entry into the first devolatilization vessel 108. In the first devolatilization vessel 108, the polymer solution is subjected to a flash to remove at least 60 wt. % of the solvent, thereby concentrating the solution to at least 60 wt. % polymer, preferably at least 65 wt. % polymer, based on the total weight of the polymer solution. In one embodiment, the flashing is performed adiabatically.

[0061] In one embodiment, the first devolatilizer vessel 108 operates adiabatically to facilitate solvent removal from the polymer solution. In one embodiment, the pressure in the first devolatilizer vessel is between 6 and 12 kgf / cm 2 , preferably 8 to 10 kgf / cm 2 214, thus the solvent is flashed off and the polymer content in the polymer solution is increased to 45-90 wt.%, preferably 50-70 wt.%, based on the total weight of the polymer solution exiting 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 (as it enters the first devolatilization vessel 108) is flashed off. The flashed solvent is removed from the first devolatilization vessel 108 via line 216 to condensation tank 122, from where it is recycled back to reactor system 103 via streams 226 and 228.

[0062] The temperature of the polymer solution discharged from the first volatilization vessel 108 is 170°C to 220°C, and the pressure is 2 to 12 kgf / cm. 2 The polymer solution exiting the first devolatilizer vessel 108 contains an amount of polymer between 50 and 90 weight percent based on the total weight of the polymer solution exiting the first devolatilizer vessel 108. In one embodiment, the solids content increases to at least 60 weight percent polymer, and preferably at least 65 weight percent polymer, based on the total weight of the polymer solution exiting the first devolatilizer vessel 108.

[0063] 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 increase in pressure (provided by the first optional positive displacement pump 110) facilitates further devolatilization of volatiles (e.g., solvent and unreacted monomers) from the polymer solution as the volatiles are adiabatically flashed in the second devolatilization vessel 112 to increase the solids concentration to greater than 90 wt. %, preferably greater than 92 wt. %, and more preferably greater than 95 wt. %, based on the total weight of the polymer solution exiting the second devolatilization vessel 112.

[0064] The second devolatilizer vessel 112 can 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 FIG. 1) is at a temperature of 210-260° C., preferably 220-240° C.

[0065] In one embodiment, the pressure in the second volatilization vessel is 0.5 to 1 kgf / cm 2 The temperature of the polymer solution exiting the second devolatilization vessel 112 is 180°C to 240°C, preferably 190°C to 230°C, and the solvent is flashed off to increase the solids content in the polymer solution to 90 to 97% by weight, preferably 92 to 95% by weight, based on the total weight of the polymer solution at the outlet of the second devolatilization vessel 112.

[0066] 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, respectively, of the volatiles stream.

[0067] A second positive displacement pump 114 facilitates the loading of the polymer solution (having a solvent content of less than 6% by weight, preferably less than 5% by weight) via stream 218 into a granulation and solidification device, such as a pelletizer 116, where the polymer is pelletized and packaged for shipment.

[0068] Volatiles generated in the two devolatilizer vessels 108 and 112, as well as volatiles generated 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.

[0069] The recycled volatiles are then fed to reactor system 103 via stream 202 along with a feed comprising ethylene and solvent (see stream 302) and hydrogen (see stream 304). The reaction in reactor system 103 proceeds as described above.

[0070] The system disclosed herein is advantageous in that liquid-liquid separation is achieved by using low ethylene conversion conditions, together with a preheater that thermally deactivates the catalyst, and by raising the system above the lower critical solution temperature of the system. Liquid-liquid separation is achieved by reducing the pressure. This is achieved without the use of an anti-solvent. The advantage of applying thermal deactivation without adding a catalyst-killing compound (which would neutralize the catalyst and stop further reaction) is that the solvent-rich stream leaving the liquid-liquid separator remains a "clean" stream, free of polar compounds, and can be sent directly back to the reactor without additional purification steps. 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 monomers, a catalyst, and a solvent and to react the monomers to form a polymer; a preheater disposed downstream of the reactor system, the preheater operative to receive the polymer solution from the reactor system and to heat the polymer solution to a temperature above its lower critical solution temperature; a liquid-liquid separator that receives the polymer solution from the preheater and operates to facilitate separation between the polymer and volatiles by reducing the pressure and / or temperature of the polymer solution below a lower critical solution temperature of the polymer solution, wherein the monomer content in the polymer solution entering the liquid-liquid separator is greater than 5 weight percent of a total weight of the polymer solution, the polymer being present in a polymer-rich phase and volatiles being present in a solvent-rich phase; a plurality of devolatilizer vessels disposed downstream of the reactor system, each devolatilizer vessel operating at a lower pressure than the preceding devolatilizer vessel, the plurality of devolatilizer vessels receiving the polymer-rich phase from the reactor system and separating the polymer from the volatiles. [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 13. The system described in [1], comprising a first reactor operating at a pressure of: [3] The system described in [2], wherein the solid content in the polymer solution is present in an amount of 8 to 16% by weight based on the total weight of the polymer solution at the outlet of the first reactor. [4] The system of [2], wherein the reactor system further comprises a second reactor operating at a higher temperature and lower pressure than the first reactor. [5] The second reactor has a pressure of 80 kgf / cm 2 More than ~180kgf / cm 2 The system described in [4] operates at the following pressures and temperatures: 190-230°C. [6] The system described in [5], wherein the solid content in the polymer solution is present in an amount of 12 to 20% by weight, based on the total weight of the polymer solution at the outlet of the second reactor. [7] The system of [1], wherein the pressure and / or temperature in the liquid-liquid separator remains above the bubble point of the polymer solution. [8] The pressure of the polymer solution in the liquid-liquid separator is 180 kgf / cm 2 From 65kgf / cm 2 and the solids content of the polymer solution discharged from the liquid-liquid separator is 20-24 wt. %. [9] The system of [1], wherein the plurality of devolatilizers includes a first devolatilizer, the first devolatilizer operative to increase the solids content in the polymer stream to at least 60 wt.% polymer, based on a total weight of the polymer-rich phase exiting the first devolatilizer.

[10] The system of [1], wherein the plurality of devolatilizers further includes a second devolatilizer, the second devolatilizer operative to increase the solids content in the polymer stream to at least 90 wt.% polymer, based on a total weight of the polymer-rich phase exiting the second devolatilizer.

[11] The system of [1], wherein the volatile materials generated in the plurality of devolatilizer vessels are recycled back to the reactor system.

[12] The system described in [1], wherein the monomer is an α-olefin.

[13] The system described in

[12] , wherein the α-olefin is ethylene.

[14] A method comprising: charging a feed stream comprising a catalyst, a monomer, and a solvent; reacting the monomers to form a polymer, the polymer being contained in a single-phase polymer solution; transferring the polymer solution to a preheater to increase the temperature of the polymer solution; Filling a liquid-liquid separator with the polymer solution; 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 disposed downstream of the liquid-liquid separator, each devolatilization vessel operating at a lower pressure than the preceding devolatilization vessel; and separating said polymer from volatile materials present in said polymer-rich phase.

[15] The method of

[14] , further comprising pelletizing the polymer.

[16] The method of

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

Claims

1. 1. A system for solution polymerization comprising: a reactor system operative to receive monomers, a catalyst, and a solvent and to react the monomers to form a polymer; a preheater disposed downstream of the reactor system, the preheater operative to receive the polymer solution from the reactor system and to heat the polymer solution to a temperature above a lower critical solution temperature to deactivate a catalyst without the use of polar compounds; a liquid-liquid separator that receives a polymer solution from the preheater and operates to reduce the pressure and / or temperature of the polymer solution below a lower critical solution temperature of the polymer solution to facilitate separation between (i) the polymer and (ii) the solvent and the monomer, wherein the monomer content in the polymer solution entering the liquid-liquid separator is greater than 5 weight percent of the total weight of the polymer solution, the polymer being present in a polymer-rich phase and the solvent and the monomer being present in a solvent-rich phase; a plurality of devolatilizer vessels disposed downstream of the reactor system, each devolatilizer vessel operating at a lower pressure than a preceding devolatilizer vessel, the plurality of devolatilizer vessels receiving the polymer-rich phase from the reactor system and separating polymer from the solvent and the monomer; The monomer is an α-olefin. A system for solution polymerization.

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 2. The system of claim 1 comprising a first reactor operating at a pressure:

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

4. 3. The system of claim 2, wherein the reactor system further comprises a second reactor operating at a higher temperature and lower pressure than the first reactor.

5. The second reactor has a pressure of 80 kgf / cm ２ Above ~180kgf / cm ２ 5. The system of claim 4, which operates at a pressure of 190 to 230° C.

6. 6. The system of claim 5, 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.

7. The system of claim 1 , wherein the pressure and / or temperature in the liquid-liquid separator is maintained above the bubble point of the polymer solution.

8. The pressure of the polymer solution in the liquid-liquid separator is 180 kgf / cm ２ From 65 kgf / cm ２ 2. The system of claim 1, wherein the solids content of the polymer solution discharged from the liquid-liquid separator is between 20 and 24 weight percent.

9. 2. The system of claim 1, wherein the plurality of devolatilizers includes a first devolatilizer, the first devolatilizer 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-rich phase exiting the first devolatilizer.

10. 2. The system of claim 1, wherein the plurality of devolatilizing vessels further comprises a second devolatilizing vessel, the second devolatilizing vessel operative to increase the solids content in the polymer stream to at least 90 weight percent polymer, based on the total weight of the polymer-rich phase exiting the second devolatilizing vessel.

11. 10. The system of claim 1 , wherein the solvent and the monomer generated in the multiple devolatilizers are recycled back to the reactor system.

12. The system of claim 1, wherein the α-olefin is ethylene.

13. 1. A method comprising: charging a feed stream comprising a catalyst, a monomer, and a solvent; reacting the monomers to form a polymer, the polymer being contained in a single-phase polymer solution; transferring the polymer solution to a preheater to increase the temperature of the polymer solution and deactivate the catalyst without using a polar compound; Filling a liquid-liquid separator with the polymer solution; separating a polymer-rich phase from a solvent-rich phase in the liquid-liquid separator by reducing the pressure and / or temperature of the polymer solution in the liquid-liquid separator to below a lower critical solution temperature of the polymer solution, wherein the monomer content in the polymer solution entering the liquid-liquid separator is greater than 5 wt. % of the total weight of the polymer solution, the polymer being present in the polymer-rich phase, and the solvent and the monomer being present in the solvent-rich phase; transferring the polymer-rich phase to a plurality of devolatilization vessels disposed downstream of the liquid-liquid separator, each devolatilization vessel operating at a lower pressure than the preceding devolatilization vessel; and separating the polymer from the solvent and the monomers present in the polymer-rich phase; The monomer is an α-olefin. method.

14. The method of claim 13 further comprising pelletizing the polymer.

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