Olefin solution polymerization method and device

Abstract

The invention belongs to the technical field of olefin polymerization, and discloses an olefin solution polymerization method and device, and the method comprises the following steps: 1) in the presence of a solvent, polymerizing at least one olefin monomer to obtain a polymer solution; (2) carrying out heat treatment on the polymer solution to enable the temperature of the polymer solution to reach the range of critical solution temperature + / -50 DEG C and the pressure of the polymer solution to be 10-50bar; (3) the polymer solution subjected to heat treatment exchanges heat with a heat-conducting medium through a jacketed pipe, the flowing Reynolds coefficient of the polymer solution is not lower than 30, and the temperature of the heat-conducting medium is lower than the heat treatment temperature by 5-20 DEG C; 4) the polymer solution after heat exchange enters a phase separation container for liquid-liquid phase separation; and 5) feeding the separated supernatant to the upstream of the polymerization reactor, and treating the lower concentrated phase in devolatilization equipment to obtain the polymer. The method is good in phase splitting effect, and polymer entrainment in a supernatant phase can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of olefin polymerization, and in particular, relates to an olefin solution polymerization method and device. Background Art

[0002] Solution polymerization plays an important role in olefin polymerization. However, polymer separation in the polymer solution generated by solution polymerization is more complicated than other processes. Generally, the solution leaving the polymerization reactor has a relatively low polymer concentration, such as 3-30 wt%. It is necessary to separate the polymer from the unreacted monomer and solvent, and to recycle the separated monomer and solvent back to the reactor for recycling.

[0003] The polymer solution can exhibit the phenomenon of Lower Critical Solution Temperature (LCST), in which the polymer solution separates into a polymer-rich dense phase and a polymer-free clear phase at a specific temperature and pressure interval. In the specific temperature and pressure interval, the polymer solution forms a liquid-liquid phase separation, the upper clear phase can be directly returned to the reactor, and the lower dense phase will be sent to the downstream equipment for further separation. Compared with evaporating the same amount of solvent, the required heat load is significantly reduced.

[0004] Typically, the phase separation method involves heating a polymer solution under high pressure and then reducing the pressure to a temperature and pressure range that can form phase separation. Patent document CN107614541A discloses a method for continuous solution polymerization, which can heat or cool a polymer solution to a temperature within 50°C of the critical temperature of the solvent; then the polymer solution is allowed to enter a liquid-liquid separator through a pressure relief valve, and the pressure of the polymer solution is reduced or increased to a pressure within 50 psig of the critical pressure to induce the polymer solution to separate into two liquid phases, with only a very small amount of polymer in the upper lean phase and the polymer enriched in the lower dense phase, thereby reducing the energy required for subsequent solvent separation. In this method, in order to ensure sufficient pressure before the pressure is released to enter the liquid-liquid separator, the polymerization reaction is carried out under conditions of 100-130 bar. This high pressure makes the reactor operation challenging, and the related equipment, instruments, and pipelines will require higher-grade materials and sealing means. Patent document CN113164898A promotes phase separation by reducing the monomer conversion rate and reduces the reactor operating pressure, but the operating pressure of the reactor is still greater than or equal to 90kgf / cm 2 (about 88bar).

[0005] Patent document CN112724281A conducts polymerization reaction under relatively low pressure and achieves phase separation condition by direct heating, and phase separation occurs in the coil heat exchanger used for heating. This method can avoid high pressure reaction, but it takes a long time to form a stable phase interface in this way, and long-term high temperature can easily lead to polymer degradation.

[0006] Therefore, it is still necessary to explore new phase separation methods to reduce equipment investment and operating costs. Summary of the invention

[0007] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide an olefin solution polymerization method and apparatus, which is conducive to promoting the phase separation of the polymer solution, overcoming the limitations of the prior art in performing polymer liquid-liquid phase separation from the polymer solution, as well as the defects of high energy consumption and high cost.

[0008] A first aspect of the present invention provides an olefin solution polymerization method, the method comprising:

[0009] 1) polymerizing at least one olefin monomer in the presence of a solvent to obtain a polymer solution;

[0010] 2) heat treating the polymer solution so that the temperature of the polymer solution reaches the range of the critical solution temperature ±50°C and the pressure of the polymer solution is 10 to 50 bar;

[0011] 3) the heat-treated polymer solution is subjected to heat exchange with a heat-conducting medium through a jacketed tube, the Reynolds coefficient of the polymer solution flow is not less than 30, and the temperature of the heat-conducting medium is 5 to 20° C. lower than the heat treatment temperature;

[0012] 4) The polymer solution after heat exchange enters a phase separation container for liquid-liquid phase separation;

[0013] 5) The separated upper clear liquid is sent to the upstream of the polymerization reactor, and the lower dense phase enters the devolatilization equipment for treatment to obtain a polymer.

[0014] The second aspect of the present invention provides an apparatus for use in the above-mentioned olefin solution polymerization method, the apparatus comprising: a polymerization reactor, a heating treatment device, a jacketed tube, a phase separation container, a devolatilization device, a granulation system and a separation system;

[0015] The discharge port of the polymerization reactor is connected to the feed port of the phase separation container via the heating treatment equipment and the jacketed pipe in sequence, the upper clear liquid outlet of the phase separation container is connected to the polymerization reactor, the lower dense phase outlet of the phase separation container is connected to the devolatilization equipment, the polymer outlet of the devolatilization equipment is connected to the granulation system, the volatile outlet of the devolatilization equipment is connected to the separation system, and the separation system is connected to the polymerization reactor.

[0016] The present invention heat treats the polymer solution to raise the temperature of the polymer solution to near the critical solution temperature, then cools it by contacting a medium with a temperature lower than the raised temperature, and then performs liquid-liquid phase separation, which helps to improve the phase separation effect and reduce polymer entrainment in the upper clear phase.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the process of olefin solution polymerization. DETAILED DESCRIPTION

[0019] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0020] According to a first aspect of the present invention, the present invention provides an olefin solution polymerization method, the method comprising:

[0021] 1) polymerizing at least one olefin monomer in the presence of a solvent to obtain a polymer solution;

[0022] 2) heat treating the polymer solution so that the temperature of the polymer solution reaches the range of the critical solution temperature ±50°C and the pressure of the polymer solution is 10 to 50 bar;

[0023] 3) the heat-treated polymer solution is subjected to heat exchange with a heat-conducting medium through a jacketed tube, the Reynolds coefficient of the polymer solution flow is not less than 30, and the temperature of the heat-conducting medium is 5 to 20° C. lower than the heat treatment temperature;

[0024] 4) The polymer solution after heat exchange enters a phase separation container for liquid-liquid phase separation;

[0025] 5) The separated upper clear liquid is sent to the upstream of the polymerization reactor, and the lower dense phase enters the devolatilization equipment for treatment to obtain a polymer.

[0026] In the present invention, the solvent may be selected from one or more of C5-C10 straight-chain or branched alkyls, C5-C10 cycloalkanes and C6-C20 aromatic hydrocarbons.

[0027] Preferably, the solvent is selected from one or more of n-pentane, isopentane, n-hexane, cyclohexane, benzene, toluene and xylene.

[0028] According to the present invention, the polymer solution can be various olefin polymer solutions commonly used in the art for heat treatment of phase separation. For example, the polymer solution can be an olefin polymer solution obtained by solution polymerization, such as a homogeneous liquid polymerization system contained in a reactor; or it can be a polymer solution obtained by dissolving a polymer in a liquid polymerization system, such as an inert solvent or one or more monomers or a blend thereof, preferably a polymer solution obtained by solution polymerization.

[0029] Specifically, the solution polymerization method is a "polymerization reaction in which a monomer is dissolved in a suitable solvent and an initiator (or catalyst) is added to the solution state" commonly used in the art. For example, a Ziegler-Natta catalyst, a transition metal single-center or multi-center catalyst, a rare earth metal catalyst, etc. can be used. The catalyst can be dissolved in a solvent or suspended in a solvent. In some embodiments, the catalyst can be used in combination with an electron donor. In other embodiments, the catalyst needs to be used in combination with a co-catalyst such as a boron-containing compound and / or an alkyl aluminum and / or methylaluminoxane.

[0030] The solution polymerization temperature can vary in a wide range, preferably between 45-200° C. The solution polymerization pressure can vary in a wide range, preferably between 0.5-15 MPa. The solution polymerization process can be batch, semi-continuous or continuous.

[0031] In the present invention, the polymer in the polymer solution may be at least one selected from the group consisting of plastics, rubbers and thermoplastic elastomers.

[0032] Specifically, the plastic may be selected from at least one of polyethylene, polypropylene, polybutene, a copolymer of ethylene and one or more α-olefins, and a copolymer of propylene and one or more α-olefins.

[0033] Specifically, the rubber may be at least one selected from butadiene-styrene rubber, butadiene rubber, isoprene rubber, and styrene-isoprene rubber.

[0034] Specifically, the thermoplastic elastomer can be selected from at least one of copolymers of ethylene and one or more α-olefins, copolymers of propylene and one or more α-olefins, copolymers of ethylene and one or more cyclic olefins, copolymers of ethylene and α-olefins and one or more cyclic olefins, copolymers of ethylene and α-olefins and optional non-conjugated dienes, butene-ethylene copolymers, styrene-butadiene-styrene block copolymers and hydrogenated styrene-butadiene-styrene block copolymers.

[0035] The copolymer of ethylene and one or more α-olefins refers to an ethylene-based copolymer having a density in the range of about 0.85-0.915 g / cm 3(Measured according to ASTM D4703 method B and ASTM D1505). The ethylene-based copolymers of the present invention contain copolymers of at least about 50 wt% ethylene-derived units and higher α-olefin-derived units (such as propylene, 1-butene, 1-hexene and 1-octene). In a preferred embodiment of the present invention, the copolymer of ethylene and one or more α-olefins is EPR, ethylene-1-butene copolymer elastomer or ethylene-1-octene copolymer elastomer.

[0036] Copolymers of propylene and one or more α-olefins are referred to as propylene-based copolymers. The propylene-based copolymers of the present invention contain copolymers of at least about 50 wt% propylene-derived units and ethylene or higher α-olefin-derived units (such as 1-butene, 1-hexene and 1-octene).

[0037] According to the present invention, the concentration of the polymer in the polymer solution can vary within a wide range. Preferably, the concentration of the polymer in the polymer solution is 5-20 wt %; more preferably, the concentration of the polymer in the polymer solution is 6-15 wt %.

[0038] According to some preferred embodiments of the present invention, a metallocene catalyst and a boron-containing compound and / or a methylaluminoxane compound are used as a catalyst system, and an alkyl aluminum is optionally used as a scavenger to carry out solution polymerization in an alkane such as isopentane, n-pentane, n-hexane, cyclohexane, and isohexane to prepare a polymer solution in which the polymer is an ethylene-α-olefin copolymer, a propylene-α-olefin copolymer, and an ethylene-propylene and optional non-conjugated diene copolymer. In some more preferred embodiments, a metallocene catalyst and a boron-containing compound are used as a catalyst system, and an alkyl aluminum is used as a scavenger to carry out solution polymerization in an alkane such as isopentane, n-pentane or n-hexane to prepare a polymer solution in which the polymer is an ethylene-α-olefin copolymer. In other more preferred embodiments, a metallocene catalyst and a boron-containing compound are used as a catalyst system, and an alkyl aluminum is used as a scavenger to carry out solution polymerization in an alkane such as isopentane, n-pentane or n-hexane to prepare a polymer solution in which the polymer is a propylene-α-olefin copolymer.

[0039] According to some preferred embodiments of the present invention, a non-metallocene catalyst and a boron-containing compound and / or a methylaluminoxane compound are used as a catalyst system, and an alkyl aluminum is optionally used as a scavenger, and a solution polymerization reaction is carried out in an alkane such as isopentane, n-pentane, n-hexane, cyclohexane, and isohexane to prepare a polymer solution in which the polymer is an ethylene-α-olefin copolymer, a propylene-α-olefin copolymer, or an ethylene-propylene and optional non-conjugated diene copolymer. In a more preferred embodiment, a non-metallocene catalyst and a boron-containing compound and methylaluminoxane are used as a catalyst system, and a solution polymerization reaction is carried out in an alkane such as isopentane, n-pentane, and n-hexane to prepare a polymer solution in which the polymer is an ethylene-propylene and non-conjugated diene copolymer.

[0040] According to a preferred embodiment of the present invention, the polymer in the polymer solution is a polyolefin elastomer, and the solvent in the polymer solution is a mixture of cyclohexane and n-hexane.

[0041] According to a preferred embodiment of the present invention, the polymer in the polymer solution is a polyolefin elastomer, and the solvent in the polymer solution is n-pentane.

[0042] According to a preferred embodiment of the present invention, the polymer in the polymer solution is a polyolefin elastomer, and the solvent in the polymer solution is isopentane.

[0043] According to a preferred embodiment of the present invention, the polymer in the polymer solution is a propylene-based elastomer, and the solvent in the polymer solution is n-pentane.

[0044] According to a preferred embodiment of the present invention, the polymer in the polymer solution is a propylene-based elastomer, and the solvent in the polymer solution is isopentane.

[0045] According to a preferred embodiment of the present invention, the polymer in the polymer solution is polybutadiene rubber, and the solvent in the polymer solution is a mixture of cyclohexane and n-hexane.

[0046] According to a preferred embodiment of the present invention, the polymer in the polymer solution is ethylene propylene rubber, and the solvent in the polymer solution is a mixture of cyclohexane and n-hexane.

[0047] In the present invention, the heat treatment can be carried out by using a heating device commonly used in the art, as long as the temperature requirement can be met, for example, a heat exchanger or a phase separation tank capable of heat treatment can be used.

[0048] Preferably, the heat treatment is carried out at a temperature lower than the lower critical solution temperature of the polymer solution, that is, the heat treatment temperature is within 50°C lower than the lower critical solution temperature of the polymer solution, more preferably within 30°C lower, and further preferably within 20°C lower.

[0049] As described above, the heat treatment temperature and pressure can be selected according to the lower critical solution temperature of the polymer solution, but usually, the heat treatment temperature can be 100-300°C, preferably 120-200°C, and the heat treatment pressure is preferably 20-50 bar.

[0050] According to the present invention, a phase separation agent can be added before heat treatment. The phase separation agent can be a silicone oil type phase separation agent or one or more selected from any C1-C4 straight chain or branched alkane with a substituent and any C2-C4 straight chain or branched olefin with a substituent. The substituent is preferably a halogen, more preferably chlorine.

[0051] Preferably, the phase separation aid is one or more of methane, ethane, propane, butane, ethylene, propylene, butene, dichloromethane, chloroform and chloropropane.

[0052] In the present invention, based on the weight of the polymer solution, the amount of the phase separation agent may be 0.3-5wt%, preferably 0.5-3wt%, and more preferably 1-2.5wt%.

[0053] When the polymer solution passes through the jacketed tube in the present invention, the polymer solution flows in the inner tube of the jacketed tube and performs heat exchange with the heat-conducting medium in the outer tube. After the polymer solution is slightly cooled, it is passed into the phase separation container for liquid-liquid phase separation, which helps to improve the phase separation effect and reduce the polymer entrainment in the upper clear phase.

[0054] According to the present invention, the concentration of the polymer in the upper clear liquid is less than 1wt%; the concentration of the polymer in the lower dense phase is 8-50wt%. Preferably, the concentration of the polymer in the lower dense phase is more than 1.35 times the concentration of the polymer in the polymer solution, preferably more than 1.8 times, and more preferably more than 2.0 times.

[0055] According to a second aspect of the present invention, the present invention provides an apparatus for use in the above-mentioned olefin solution polymerization method, the apparatus comprising: a polymerization reactor, a heating treatment device, a jacketed tube, a phase separation container, a devolatilization device, a granulation system and a separation system;

[0056] The discharge port of the polymerization reactor is connected to the feed port of the phase separation container via the heating treatment equipment and the jacketed pipe in sequence, the upper clear liquid outlet of the phase separation container is connected to the polymerization reactor, the lower dense phase outlet of the phase separation container is connected to the devolatilization equipment, the polymer outlet of the devolatilization equipment is connected to the granulation system, the volatile outlet of the devolatilization equipment is connected to the separation system, and the separation system is connected to the polymerization reactor.

[0057] Preferably, the pressure inside the polymerization reactor is not higher than 50 bar.

[0058] Depending on whether it is necessary to increase the pressure, a pressure-boosting device may be provided to increase the pressure of the system to achieve phase separation conditions. Preferably, a pressure-boosting device is provided between the discharge port of the polymerization reactor and the heating treatment device.

[0059] According to the present invention, there may be one or more polymerization reactors, which can be arranged as required.

[0060] In the present invention, at least two devolatilization devices can be provided, and the latter devolatilization device operates at a lower pressure and a higher temperature than the former devolatilization device, so as to separate the polymer from the volatile matter, and has a better separation effect. For example, the operating temperature of the devolatilization device can be 160-200°C, and the operating pressure can be 2-30bar. Specifically, when two devolatilization devices are included, the operating temperature of the former devolatilization device can be 170°C, and the operating pressure can be 20bar; the operating temperature of the latter devolatilization device can be 190°C, and the operating pressure can be 5bar. The operating temperature of the former devolatilization device can be 180°C, and the operating pressure can be 15bar, and the operating temperature of the latter devolatilization device can be 200°C, and the operating pressure can be 3bar.

[0061] The substances, parameters and equipment not limited in the present invention can be selected according to the existing technology and belong to the conventional technical means in the field. Unless otherwise specified, the operations and processing methods involved in the present invention belong to the conventional methods in the field, the equipment used is the conventional equipment in the field, and the various raw materials used are commercially available.

[0062] The present invention will be further described below with reference to the following examples, but is not limited to these examples.

[0063] In the following examples and comparative examples, the relevant raw materials and data were obtained by the following method:

[0064] 1. (tert-Butylamido)dimethyl(1,2,3,4,5-η)-1,5,6,7-tetrahydro-2-methylindenylsilanetitanium(II)1,3-pentadiene metal complex: prepared according to patent document US5965756.

[0065] 2. Dimethylsilylbis(5,6,7,8-tetrahydro-2,5,5,8,8-pentamethylbenzoindenyl)hafnium dimethyl: prepared according to patent document US60586465.

[0066] 3. Triphenylcarbonium tetrakis(pentafluorophenyl)borane: purchased from Beijing Bailingwei Technology Co., Ltd.

[0067] 4. Tris(pentafluorophenyl)borane: purchased from Beijing Bailingwei Technology Co., Ltd.

[0068] 5. Polymer solution concentration: Pour the taken out polymer solution into three times the amount of ethanol, take out the precipitated polymer, bake it at 80°C for 24 hours, weigh it, and calculate the polymer solution concentration.

[0069] 6. The Reynolds coefficient of polymer solution flow is calculated by the formula Re = ρvd / μ, where ρ is the density of the polymer solution (in kg / m 3 ), v is the flow rate of the polymer solution (in m / s), d is the inner diameter of the inner tube of the jacket tube (in m), and μ is the viscosity of the polymer solution (in Pa·s).

[0070] Examples 1-4

[0071] like Figure 1 As shown, the apparatus used in the olefin solution polymerization method includes: a polymerization reactor 110, a heating treatment device 112, a jacketed tube 113, a phase separation container 120, devolatilization devices 130 and 140, a granulation system 210 and a separation system 310;

[0072] The discharge port of the polymerization reactor 110 is connected to the feed port of the phase separation container 120 via the heating treatment device 112 and the jacket pipe 113 in sequence, the upper clear liquid outlet of the phase separation container 120 is connected to the polymerization reactor 110, the lower dense phase outlet of the phase separation container 120 is connected to the devolatilization device 130, the polymer outlet of the devolatilization device 140 is connected to the granulation system 210, the volatile outlets of the devolatilization devices 130 and 140 are connected to the separation system 310, and the separation system 310 is connected to the polymerization reactor 110. A booster device (gear pump, not shown) is provided between the discharge port of the polymerization reactor and the heating treatment device.

[0073] The polymerization reactor 110 is a 1.8L polymerization kettle equipped with a mechanical stirrer. The temperature of the polymerization kettle can be regulated by controlling the jacket temperature through an oil bath. The polymerization kettle is connected to an ethylene pipeline, a propylene pipeline, an octene pipeline, a hexane pipeline and a catalyst injection pipeline. The solvent and monomer feed entering the reactor are measured by a mass-flow controller, and the material flow rate and pressure are controlled by a variable speed diaphragm pump.

[0074] Propylene, ethylene, hexane, dimethylsilylbis(5,6,7,8-tetrahydro-2,5,5,8,8-pentamethylbenzindenyl)hafnium dimethyl toluene solution (concentration of 0.81 μmol / mL, abbreviated as C1), triphenylcarbonium tetrakis(pentafluorophenyl)boron toluene solution (concentration of 0.625 mg / mL, abbreviated as C2) and triisobutylaluminum hexane solution (concentration of 0.23 wt%, abbreviated as TIBA) were introduced into polymerization reactor 110 via pipeline 101, and polymerization reaction was carried out under the conditions of 80°C temperature and 30 bar pressure, and the obtained polymer solution containing solvent, polymer and unreacted monomer flowed out of the reactor via pipeline 111. The feed amount of each substance is shown in Table 1. Sampling and analysis were carried out at the sampling port on pipeline 110 to obtain the concentration of the polymer solution, as shown in Table 1.

[0075] The polymer solution flowing out of the polymerization kettle is pressurized to 40 bar by a gear pump, and then heated to 190°C by a heating treatment device (preheater) 112. The polymer solution then flows through a 0.5m long straight jacketed pipe, the inner diameter of the inner pipe of the jacketed pipe is 0.05m, and the inner diameter of the outer pipe is 0.1m. The polymer solution flows in the inner pipe of the jacketed pipe, and the calculation results of its Reynolds coefficient are shown in Table 1. 180°C heat transfer oil is passed into the jacket of the jacketed pipe. After that, the polymer solution enters the phase separation container (phase separation tank) 120 for liquid-liquid phase separation; the upper clear liquid obtained after phase separation is sent back to the upstream of the polymerization reactor via pipeline 125, and the lower polymer-rich dense phase enters the downstream devolatilization equipment 130, 140 via pipeline 121. Sampling and analysis are performed at the sampling ports on pipelines 125 and 121, respectively, and the concentration of the polymer solution is shown in Table 1. The operating temperature of the devolatilization device 130 is 170°C and the operating pressure is 20 bar. The operating temperature of the devolatilization device 140 is 190°C and the operating pressure is 5 bar, and the polymer is separated from the volatiles; the polymer enters the granulation system 210 through the pipeline 141 to obtain a granular product; the solvent and unreacted monomer removed in the devolatilization device enter the separation system 310 through the pipeline 135 and the pipeline 145, and are recycled to the polymerization reaction after separation.

[0076] Table 1

[0077]

[0078]

[0079] Embodiment 5-8

[0080] The apparatus used in the olefin solution polymerization method is the same as that in Example 1.

[0081] Ethylene, octene, hexane, (tert-butylamido) dimethyl (1,2,3,4,5-η) -1,5,6,7-tetrahydro-2-methylindenylsilane titanium (II) 1,3-pentadiene metal complex (concentration of 0.5 μmol / mL, abbreviated as C3), toluene solution of tri(pentafluorophenyl) borane (concentration of 0.3688 mg / mL, abbreviated as C4) and TIBA (concentration of 0.23 wt%) were introduced into polymerization reactor 110 via pipeline 101, and polymerization reaction was carried out under the conditions of 70°C temperature and 20 bar pressure, and the obtained polymer solution containing solvent, polymer and unreacted monomer flowed out of the reactor via pipeline 111. The feed amount of each substance is shown in Table 2. Sampling and analysis were performed at the sampling port on pipeline 110 to obtain the concentration of the polymer solution, as shown in Table 2.

[0082] The polymer solution flowing out of the polymerization kettle is pressurized to 40 bar by a gear pump, and then heated to 185°C by a heating treatment device (preheater) 112. The polymer solution then flows through a 0.5m long straight jacketed pipe, the inner diameter of the inner pipe of the jacketed pipe is 0.08m, and the inner diameter of the outer pipe is 0.15m. The polymer solution flows in the inner pipe of the jacketed pipe, and the calculation results of its Reynolds coefficient are shown in Table 2. 175°C heat transfer oil is passed into the jacket of the jacketed pipe. After that, the polymer solution enters the phase separation container (phase separation tank) 120 for liquid-liquid phase separation; the upper clear liquid obtained after phase separation is sent back to the upstream of the polymerization reactor via pipeline 125, and the lower polymer-rich dense phase enters the downstream devolatilization equipment 130, 140 via pipeline 121. Sampling and analysis are performed at the sampling ports on pipelines 125 and 121, respectively, and the concentration of the polymer solution is shown in Table 2. The operating temperature of the devolatilization device 130 is 180°C and the operating pressure is 15 bar. The operating temperature of the devolatilization device 140 is 200°C and the operating pressure is 3 bar, and the polymer is separated from the volatiles; the polymer enters the granulation system 210 through the pipeline 141 to obtain a granular product; the solvent and unreacted monomer removed in the devolatilization device enter the separation system 310 through the pipeline 135 and the pipeline 145, and are recycled to the polymerization reaction after separation.

[0083] Table 2

[0084] Example 5 Example 6 Example 7 Example 8 Hexane flow rate (g / h) 1250 1200 1450 1500 Ethylene flow rate (g / h) 80 100 160 200 Octene flow rate (g / h) 100 120 180 225 C3 solution flow rate (mL / h) 1 1 2 2 C4 solution flow rate (mL / h) 1.5 1.5 3 3 TIBA solution flow rate (mL / h) 300 300 300 300 Concentration of polymer solution in line 101 (wt%) 8.5 10.9 12.8 15.2 Reynolds coefficient of polymer solution flowing in jacketed tube 285 242 67 33 Concentration of polymer solution in line 125 (wt%) 0.05 0.06 0.11 0.16 Concentration of polymer solution in line 121 (wt%) 19.1 23.2 26.2 28.5

[0085] Comparative Example 1

[0086] After the polymer solution was heated to 190° C., it directly entered the phase separation container 120 without passing through the jacket tube, and other operations were the same as those in Example 1. The results are shown in Table 3.

[0087] Comparative Example 2

[0088] After the polymer solution was heated to 190° C., it directly entered the phase separation container 120 without passing through the jacket tube, and other operations were the same as those in Example 3. The results are shown in Table 3.

[0089] Comparative Example 3

[0090] After the polymer solution was heated to 190° C., it flowed through a 0.5 m long jacket tube in which the heat transfer oil temperature was 195° C., and other operations were the same as in Example 1. The results are shown in Table 3.

[0091] Comparative Example 4

[0092] After the polymer solution was heated to 185° C., it directly entered the phase separation container 120 without passing through the jacket tube, and other operations were the same as those in Example 5. The results are shown in Table 3.

[0093] Comparative Example 5

[0094] After the polymer solution was heated to 185° C., it directly entered the phase separation container 120 without passing through the jacket tube, and other operations were the same as those in Example 7. The results are shown in Table 3.

[0095] Comparative Example 6

[0096] After the polymer solution was heated to 185° C., it flowed through a 0.5 m long jacket tube in which the heat transfer oil temperature was 190° C., and other operations were the same as those in Example 5. The results are shown in Table 3.

[0097] Table 3

[0098]

[0099] As can be seen from Tables 1-3, by using the method of the present invention, raising the temperature of the polymer solution to near the lower critical temperature and then contacting it with a medium at a temperature lower than the raised temperature, it helps to improve the phase separation effect and reduce polymer entrainment in the upper clear phase.

[0100] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. An olefin solution polymerization method, characterized in that: The method includes: 1) polymerizing at least one olefin monomer in the presence of a solvent to obtain a polymer solution; 2) heat treating the polymer solution so that the temperature of the polymer solution reaches the range of the critical solution temperature ±50°C and the pressure of the polymer solution is 10 to 50 bar; 3) the heat-treated polymer solution is subjected to heat exchange with a heat-conducting medium through a jacketed tube, the Reynolds coefficient of the polymer solution flow is not less than 30, and the temperature of the heat-conducting medium is 5 to 20° C. lower than the heat treatment temperature; 4) The polymer solution after heat exchange enters a phase separation container for liquid-liquid phase separation; 5) The separated upper clear liquid is sent to the upstream of the polymerization reactor, and the lower dense phase enters the devolatilization equipment for treatment to obtain a polymer.

2. The olefin solution polymerization method according to claim 1, wherein The solvent is selected from one or more of C5-C10 straight-chain or branched alkyl, C5-C10 cycloalkane and C6-C20 aromatic hydrocarbon; The solvent is preferably selected from one or more of n-pentane, isopentane, n-hexane, cyclohexane, benzene, toluene and xylene.

3. The olefin solution polymerization method according to claim 1, wherein The polymer in the polymer solution is selected from at least one of plastic, rubber and thermoplastic elastomer; Preferably, the plastic is selected from at least one of polyethylene, polypropylene, polybutene, copolymers of ethylene and one or more α-olefins, and copolymers of propylene and one or more α-olefins; Preferably, the rubber is selected from at least one of butadiene-styrene rubber, butadiene rubber, isoprene rubber and styrene-isoprene rubber; Preferably, the thermoplastic elastomer is selected from at least one of copolymers of ethylene and one or more α-olefins, copolymers of propylene and one or more α-olefins, copolymers of ethylene and one or more cyclic olefins, copolymers of ethylene and α-olefins and one or more cyclic olefins, copolymers of ethylene and α-olefins and optionally non-conjugated dienes, butene-ethylene copolymers, styrene-butadiene-styrene block copolymers and hydrogenated styrene-butadiene-styrene block copolymers.

4. The olefin solution polymerization method according to claim 1, wherein The concentration of the polymer in the polymer solution is 5-20 wt %, preferably 6-15 wt %.

5. The olefin solution polymerization method according to claim 1, wherein The heat treatment temperature is within 50° C. lower than the lower critical solution temperature of the polymer solution, preferably within 30° C. lower, and more preferably within 20° C. lower.

6. The olefin solution polymerization method according to claim 1, wherein The temperature of the heat treatment is 100-300°C, preferably 120-200°C, and the pressure of the heat treatment is 20-50 bar.

7. The olefin solution polymerization method according to claim 1, wherein Before the heat treatment, a phase separation agent is added, wherein the phase separation agent is a silicone oil-type phase separation agent or one or more selected from any C1-C4 straight-chain or branched alkane with a substituent and any C2-C4 straight-chain or branched olefin with a substituent, wherein the substituent is preferably a halogen, and more preferably chlorine; Preferably, the phase separation aid is one or more of methane, ethane, propane, butane, ethylene, propylene, butene, dichloromethane, chloroform and chloropropane.

8. The olefin solution polymerization method according to claim 7, wherein: Based on the weight of the polymer solution, the amount of the phase separation agent is 0.3-5wt%, preferably 0.5-3wt%, and more preferably 1-2.5wt%.

9. The olefin solution polymerization method according to claim 1, wherein The concentration of the polymer in the supernatant is less than 1 wt %; the concentration of the polymer in the lower dense phase is 1.35 times or more, preferably 1.8 times or more, and more preferably 2.0 times or more of the polymer concentration in the polymer solution.

10. The device used in the olefin solution polymerization method according to any one of claims 1 to 9, characterized in that: The device comprises: a polymerization reactor, a heating treatment device, a jacketed pipe, a phase separation container, a devolatilization device, a granulation system and a separation system; The discharge port of the polymerization reactor is connected to the feed port of the phase separation container via the heating treatment device and the jacket pipe in sequence, the upper clear liquid outlet of the phase separation container is connected to the polymerization reactor, the lower dense phase outlet of the phase separation container is connected to the devolatilization device, the polymer outlet of the devolatilization device is connected to the granulation system, the volatile outlet of the devolatilization device is connected to the separation system, and the separation system is connected to the polymerization reactor; Preferably, the pressure in the polymerization reactor is not higher than 50 bar; Preferably, a pressurizing device is provided between the discharge port of the polymerization reactor and the heating treatment device. Preferably, at least two devolatilization devices are provided, and the latter devolatilization device is operated at a lower pressure and a higher temperature than the former devolatilization device.

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