System and method for producing polystyrene and application of system and method

Abstract

The invention discloses a polystyrene production system and method and application thereof, the system comprises a prepolymerization unit, a polymerization unit, a devolatilization unit and a monomer recovery unit which are connected in series, the prepolymerization unit comprises two stages of prepolymerization kettles, the polymerization unit comprises three stages of polymerization reactors, and the monomer recovery unit is a rectifying tower. The system can be applied to preparation of high-impact polystyrene, universal polystyrene, styrene copolymers and the like. According to the polystyrene production system and method disclosed by the invention, a two-stage pre-polymerization and three-stage polymerization series form is adopted, so that the conversion rate of the system is effectively improved, and residues are few; and the batching unit is arranged, so that monomer feeding can be realized, and different types of high-quality products can be produced.

Description

Technical Field

[0001] The present invention belongs to the field of polymers, and in particular relates to the production of polystyrene, and specifically, to a system and method for producing polystyrene and applications thereof. Background Art

[0002] Polystyrene refers to a polymer synthesized from styrene monomers through free radical addition polymerization, including high impact polystyrene (HIPS), general purpose polystyrene (GPPS) and styrene-methyl methacrylate copolymer (MS) and other types. Polystyrene is a colorless and transparent thermoplastic with a glass transition temperature above 100°C, so it is often used to make various disposable containers. Ordinary polystyrene resin is an amorphous polymer, and the side groups of its macromolecular chains are benzene rings. The random arrangement of large-volume side groups of benzene rings determines the physical and chemical properties of polystyrene, such as high transparency, high rigidity, high glass transition temperature, brittleness, etc. Polystyrene is widely used.

[0003] However, most existing polystyrene production devices can only produce a single type of polystyrene, and cannot accurately control various parameters in the production process. The conversion rate is low, the quality of the products produced is poor, and the energy consumption is high, which pollutes the environment. Summary of the invention

[0004] In order to overcome the problems existing in the prior art, the present invention provides a system and method for producing polystyrene and its application, which effectively improves the conversion rate by adopting a two-stage prepolymerization and a three-stage polymerization in series, and can produce different types of high-quality products with less residue.

[0005] On one hand, the present invention provides a system for producing polystyrene, the system comprising a prepolymerization unit, a polymerization unit, a devolatilization unit and a monomer recovery unit connected in series, wherein the prepolymerization unit comprises a two-stage prepolymerization kettle, the polymerization unit comprises a three-stage polymerization reactor, and the monomer recovery unit is a distillation tower.

[0006] In the system of the present invention, the prepolymerization unit comprises a first prepolymerization kettle and a second prepolymerization kettle connected in series. Preferably, a stirrer is independently provided in the first prepolymerization kettle and the second prepolymerization kettle.

[0007] In the system described in the present invention, the polymerization unit comprises a first polymerization reactor, a second polymerization reactor and a third polymerization reactor connected in series; preferably, a feed port is arranged at the top of the first polymerization reactor, the bottom of the first polymerization reactor is connected to the bottom of the second reactor, the top of the second reactor is connected to the top of the third reactor, and a crude product discharge port is arranged at the bottom of the third reactor; more preferably, a plurality of temperature zones are independently arranged in the first polymerization reactor, the second polymerization reactor and the third reactor, preferably 2 to 5 temperature zones are independently arranged in each of them.

[0008] In the system described in the present invention, the devolatilization unit comprises a first devolatilizer and a second devolatilizer connected in series, and feed ports are independently provided at the tops of the first devolatilizer and the second devolatilizer; preferably, a first devolatilization preheater is provided at the feed port of the first devolatilizer, and a second devolatilization preheater is provided at the feed port of the second devolatilizer.

[0009] In the system of the present invention, the devolatilization unit further comprises a condenser I, a condenser II, and a condenser III, wherein the condenser I, the condenser II, and the condenser III are each independently provided with a volatile component inlet, a non-condensable gas outlet, and a condensate outlet;

[0010] Preferably, the volatile component inlet of the condenser I is connected to the upper part or top of the first devolatilizer, the non-condensable gas outlet of the condenser I is connected to the volatile component inlet of the condenser II, and the volatile component inlet of the condenser III is connected to the upper part or top of the second devolatilizer;

[0011] More preferably, the condensate outlet of the condenser I and the condensate outlet of the condenser III are both connected to the feed inlet of the distillation tower, and the top of the distillation tower and the condensate outlet of the condenser II obtain the recovered monomer.

[0012] In the system of the present invention, a mixer is arranged between the bottom of the first devolatilizer and the feed inlet of the second devolatilizer, and a desalted water input pipeline is further arranged on the mixer.

[0013] In the system described in the present invention, the system further includes a batching unit; preferably, the batching unit includes a rubber dissolving device and a TBC removal device arranged in parallel, wherein the rubber dissolving device includes a rubber dissolving tank and a rubber solution tank connected in series, and the TBC removal device includes at least two TBC removal towers arranged in parallel; more preferably, the discharge port of the rubber dissolving device and the discharge port of the TBC removal device are each independently connected to the prepolymerization unit.

[0014] The second aspect of the present invention is to provide the use of the system of the present invention in the preparation of high impact polystyrene, general-purpose polystyrene and styrene copolymers.

[0015] The third aspect of the present invention is to provide a method for producing styrene polymers, which is carried out using the system described in the first aspect of the present invention.

[0016] In the method of the present invention, the temperature of the first prepolymerization kettle is controlled to be 100-115°C, preferably 105-110°C; and / or the temperature of the second prepolymerization kettle is controlled to be 115-130°C, preferably 125-130°C.

[0017] In the method described in the present invention, the temperature of the first polymerization reactor is controlled to be 120-140°C, and the temperatures of each temperature zone gradually increase from top to bottom; preferably, the temperature of the first polymerization reactor is controlled as follows: from top to bottom, the temperature of the first temperature zone is 121-127°C, the temperature of the second temperature zone is 128-134°C, and the temperature of the third temperature zone is 135-140°C.

[0018] In the method described in the present invention, the temperature of the second polymerization reactor is controlled at 140-155°C, and the temperatures of each temperature zone gradually increase from bottom to top; preferably, the temperature of the second polymerization reactor is controlled as follows: from bottom to top, the temperature of the first temperature zone is 140-143°C, the temperature of the second temperature zone is 144-147°C, and the temperature of the third temperature zone is 148-152°C.

[0019] In the method described in the present invention, the temperature of the third polymerization reactor is controlled to be 150-170°C, and the temperatures of each temperature zone gradually increase from top to bottom; preferably, the temperature of the third polymerization reactor is controlled as follows: from top to bottom, the temperature of the first temperature zone is 152-160°C, and the temperature of the second temperature zone is 161-170°C.

[0020] In the method of the present invention, the temperature of the first devolatilizer is controlled to be 235-245°C; and / or the temperature of the second devolatilizer is controlled to be 235-245°C.

[0021] In the method of the present invention, the bottom material of the first devolatilizer is mixed with desalted water and then preheated to enter the second devolatilizer; preferably, the weight ratio of the desalted water to the bottom material of the first devolatilizer is (0.015-0.025):1.

[0022] The endpoints and any values ​​of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, the endpoint values ​​of each scope, the endpoint values ​​of each scope and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The polystyrene production system and method of the present invention effectively improves the conversion rate of the system and reduces the residue by adopting a two-stage prepolymerization and a three-stage polymerization in series; and by providing a batching unit, monomer addition can be achieved, thereby producing different types of high-quality products;

[0025] The polystyrene obtained by using the system and method of the present invention has the advantages of high tensile strength, low melt index, high heat deformation temperature and cantilever beam impact strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of the system of the present invention is shown.

[0027] Figure numerals: dosing unit 1; prepolymerization unit 2; polymerization unit 3; devolatilization unit 4; monomer recovery unit 5; rubber dissolution tank 6; agitator 7; rubber solution tank 8; TBC removal tower 9; first prepolymerization kettle 10; first prepolymerization kettle condenser 11; first kettle bottom pump 12; second prepolymerization kettle 13; second kettle bottom pump 14; second prepolymerization kettle condenser 15; first polymerization reactor 16; second polymerization reactor 17; third polymerization reactor 18; first devolatilizer 19; first devolatilizer preheater 20; first devolatilizer bottom pump 21; second devolatilizer 22; second devolatilizer preheater 23; second devolatilizer bottom pump 24; condenser I 25; condenser II 26; condenser III 27; distillation tower 28.

[0028] Figure 2 A schematic diagram of the specific structure of the first temperature zone of the first polymerization reactor from top to bottom is shown. It can be seen that it includes two sections of inner coils arranged vertically, and an agitator is arranged between the two sections of inner coils. DETAILED DESCRIPTION

[0029] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0030] One of the objects of the present invention is to provide a system for producing polystyrene, the system comprising a prepolymerization unit, a polymerization unit, a devolatilization unit and a monomer recovery unit connected in series, wherein the prepolymerization unit comprises a two-stage prepolymerization kettle, the polymerization unit comprises a three-stage polymerization reactor, and the monomer recovery unit is a distillation tower.

[0031] In a preferred embodiment, the prepolymerization unit comprises a first prepolymerization kettle and a second prepolymerization kettle connected in series. Preferably, an agitator is independently provided in the first prepolymerization kettle and the second prepolymerization kettle; more preferably, a paddle-type agitator (single-blade or multi-blade) or a ribbon-type agitator is provided in the first prepolymerization kettle, and a ribbon-type agitator is provided in the second prepolymerization kettle.

[0032] Wherein, the paddle-type agitator and the ribbon-type agitator are both frequency-controlled. Preferably, a lotus root heating oil jacket is independently provided on the outside of the first prepolymerization kettle and the second prepolymerization kettle. The inventor has found through experiments that the ribbon-type agitator provided in the second prepolymerization kettle can fully stir the material in both radial and axial directions, and the material temperature is uniform.

[0033] In a further preferred embodiment, a circulation loop I and a first prepolymerization kettle condenser arranged on the circulation loop I are arranged on the upper part of the first prepolymerization kettle; and / or a circulation loop II and a second prepolymerization kettle condenser arranged on the circulation loop II are arranged on the upper part of the second prepolymerization kettle.

[0034] In a further preferred embodiment, a bottom pump is independently provided at the bottom of the first prepolymerization kettle and the second prepolymerization kettle.

[0035] In a preferred embodiment, a feed port is provided at the top of the first prepolymerization kettle, the bottom of the first prepolymerization kettle is connected to the top of the second prepolymerization kettle, and the bottom of the second prepolymerization kettle is connected to the polymerization unit.

[0036] In the present invention, the prepolymerization unit comprises: a first prepolymerization kettle, a first prepolymerization kettle condenser connected to the top (gas phase outlet) of the first prepolymerization kettle, a first kettle bottom pump connected to the bottom of the first prepolymerization kettle at its input end, a second prepolymerization kettle connected to the first kettle bottom pump at its input end, a second prepolymerization kettle condenser connected to the top (gas phase outlet) of the second prepolymerization kettle, and a second kettle bottom pump connected to the bottom of the second prepolymerization kettle at its input end.

[0037] In a preferred embodiment, the polymerization unit comprises a first polymerization reactor, a second polymerization reactor and a third polymerization reactor connected in series, a feed port is arranged at the top of the first polymerization reactor (preferably connected to the bottom of the second prepolymerization reactor), the bottom of the first polymerization reactor is connected to the bottom of the second reactor, the top of the second reactor is connected to the top of the third reactor, and a crude product discharge port is arranged at the bottom of the third reactor.

[0038] In the present invention, the polymerization unit comprises: a first polymerization reactor having an input end connected to the second prepolymerization reactor bottom pump, a second polymerization reactor having an input end connected to the bottom of the first polymerization reactor, and a third polymerization reactor having an input end connected to the top of the second polymerization reactor.

[0039] In a further preferred embodiment, a plurality of temperature zones are independently provided in the first polymerization reactor, the second polymerization reactor and the third reactor, preferably 2 to 5 temperature zones are independently provided in each reactor, for example 2, 3, 4 or 5. More preferably, 3 temperature zones are independently provided in each of the first polymerization reactor and the second polymerization reactor, and 2 temperature zones are provided in the third reactor.

[0040] Among them, the inventors found through a large number of experiments that it is preferred to independently set 3 to 5 temperature zones (for example 3) in the first polymerization reactor and the second polymerization reactor. This is because if there are too few temperature zones, the temperature difference in each temperature zone increases, resulting in the inability to smoothly heat up the reactants, uneven temperature in the temperature zones, and an increase in oligomeric products, which affects product quality.

[0041] The polymerization reactor of the present invention may be a vertical plug flow reactor.

[0042] In a preferred embodiment, each temperature zone of the first polymerization reactor, the second polymerization reactor and the third reactor independently includes two to four sections of inner coils arranged in sequence from top to bottom. Preferably, the tubes of the inner coils are staggered in space to form a Chinese knot-like structure.

[0043] The coil inside the structure exerts a shear force on the melt, and the melt is subjected to uniform force in the radial direction, which can further improve the reaction efficiency and obtain a high molecular weight polymer.

[0044] In a preferred embodiment, an agitator is provided in the first polymerization reactor, and preferably an agitator is provided in any temperature zone or between any two sections of the coils in the first polymerization reactor.

[0045] In a further preferred embodiment, an agitator is provided in the middle of the temperature zone at the top of the first polymerization reactor (i.e., the first temperature zone at the top). The inventors have found through experiments that the effect is better when an agitator is provided in the temperature zone at the top of the first polymerization reactor.

[0046] For example, two sections of inner coils are arranged in the temperature zone at the top of the first polymerization reactor, and the agitator is arranged between the two sections of inner coils.

[0047] Among them, after a large number of experiments, the inventors found that setting an agitator in the middle of the temperature zone at the top of the first polymerization reactor can improve the grafting efficiency and the molecular weight of the product, thereby ensuring that the melt index, bending strength and other performance of the product meet the standards.

[0048] In a preferred embodiment, the devolatilization unit comprises a first devolatilizer and a second devolatilizer connected in series, and feed ports are independently provided at the tops of the first devolatilizer and the second devolatilizer.

[0049] In a further preferred embodiment, a first devolatilizer preheater is provided at the feed inlet of the first devolatilizer, and a second devolatilizer preheater is provided at the feed inlet of the second devolatilizer.

[0050] Among them, the inventors found through a large number of experiments that setting a preheater at the feed inlet of the second devolatilizer can greatly improve the devolatilization effect and obtain a high-purity product.

[0051] In a preferred embodiment, the devolatilization unit further comprises a condenser I, a condenser II, and a condenser III, wherein the condenser I, the condenser II, and the condenser III are each independently provided with a volatile component inlet, a non-condensable gas outlet, and a condensate outlet.

[0052] In a further preferred embodiment, the volatile component inlet of the condenser I is connected to the upper part or top (its gas phase outlet) of the first devolatilizer, the non-condensable gas outlet of the condenser I is connected to the volatile component inlet of the condenser II, and the volatile component inlet of the condenser III is connected to the upper part or top (its gas phase outlet) of the second devolatilizer.

[0053] In a further preferred embodiment, the condensate outlet of the condenser I and the condensate outlet of the condenser III are both connected to the feed port of the distillation tower, and the top of the distillation tower and the condensate outlet of the condenser II obtain recovered monomers for reuse (for example, connected to a dosing unit).

[0054] In the present invention, the devolatilization unit comprises: a first devolatilization preheater having an input end connected to the third polymerization reactor (bottom) or the output end of the polymerization unit, a first devolatilizer having an input end connected to the output end of the first devolatilization preheater, a condenser I and a condenser II connected to the upper part or top of the first devolatilizer (outside its gas phase outlet), a first devolatilization bottom pump having an input end connected to the bottom of the first devolatilizer (its liquid phase outlet), a second devolatilization preheater having an input end connected to the output end of the first devolatilization bottom pump, a second devolatilizer having an input end connected to the output end of the second devolatilization preheater, a condenser III connected to the upper part or top of the second devolatilizer (outside its gas phase outlet), and a second devolatilization bottom pump having an input end connected to the bottom of the second devolatilizer (its liquid phase outlet). Further, the devolatilization unit includes: a first devolatilization preheater having an input end connected to the output end of the third polymerization reactor, a first devolatilizer having an input end connected to the output end of the first devolatilization preheater, a condenser I and a condenser II arranged outside the gas phase outlet of the first devolatilizer, a first devolatilization bottom pump having an input end connected to the liquid phase outlet of the first devolatilizer, a second devolatilization preheater having an input end connected to the output end of the first devolatilization bottom pump, a second devolatilizer having an input end connected to the output end of the second devolatilization preheater, a static mixer arranged at the input end of the second devolatilizer, a condenser III arranged at the gas phase outlet of the second devolatilizer, and a second devolatilization bottom pump having an input end connected to the liquid phase outlet of the second devolatilizer; wherein the condensate outlet of the condenser I is connected to the distillation tower, the gas phase outlet of the second devolatilization condenser is provided with a vacuum pump, the condensate outlet of the condenser III is connected to the distillation tower, and the output end of the second devolatilization bottom pump is connected to a pelletizer.

[0055] In a preferred embodiment, a mixer is provided between the bottom of the first devolatilizer and the feed inlet of the second devolatilizer, and a desalted water input pipeline is further provided on the mixer.

[0056] Among them, the inventors have found through a large number of experimental studies that the first devolatilizer discharge is mixed with deionized water before entering the second devolatilizer, which can significantly improve the devolatilization efficiency of the second devolatilizer and obtain a product with high purity or low residual monomer. The deionized water of the present invention can be deionized water, etc.

[0057] In a preferred embodiment, the system further comprises a dosing unit.

[0058] In a further preferred embodiment, the batching unit comprises a rubber dissolving device and a TBC removal device arranged in parallel, wherein the rubber dissolving device comprises a rubber dissolving tank and a rubber solution tank connected in series, and the TBC removal device comprises at least two TBC removal towers arranged in parallel. The TBC in the present invention refers to an inhibitor.

[0059] Among them, one of the at least two parallel-connected TBC removal towers is in working state, and the others are in standby state or regeneration state. In the present invention, when preparing HIPS, the required rubber is metered and ground by a rubber cutter, and falls into a rubber dissolution tank, and additives (such as antioxidants) are added in proportion; after the rubber is dissolved, a glue liquid is formed, which is sent to a rubber solution tank for storage by a glue liquid delivery pump, and the next batch of sol operation is started. The glue liquid in the rubber solution tank is continuously delivered by a glue liquid feed pump, and the undissolved rubber and large gel are filtered out by a filter. When the product has a high requirement for the inhibitor content, the monomer is first processed through the TBC removal tower to remove most of the inhibitors in the monomer.

[0060] In a further preferred embodiment, the discharge port of the rubber dissolving device and the discharge port of the TBC removal device are independently connected to the prepolymerization unit, preferably connected to the feed port of the first prepolymerization kettle.

[0061] In the present invention, the dosing unit comprises: a rubber dissolving tank, an agitator arranged inside the rubber dissolving tank, a rubber solution tank whose input end is connected to the output end of the rubber dissolving tank, and a TBC removal tower whose output end is combined with the output end of the rubber solution tank; preferably, a raw material tank and a dosing unit are arranged at the input end of the rubber dissolving tank.

[0062] Preferably, a feed line for raw material I is provided at the upper part of the rubber dissolution tank, and the raw material I includes styrene, rubber and additives (such as antioxidants), etc.; a feed line for raw material II is provided at the bottom of the TBC removal tower, and the raw material II includes styrene, other comonomers (such as acrylic ester monomers, such as methyl methacrylate), etc.

[0063] In the present invention, the external pipelines of the batching unit, the prepolymerization unit, the prepolymerization unit, the polymerization unit and the monomer recovery unit are connected with a temperature control mechanism and an exhaust gas treatment mechanism. The system is also provided with an exhaust gas treatment mechanism (such as a commonly used CO furnace, RO furnace, etc.), which can centrally treat the discharged exhaust gas, effectively reducing the pollution of the system.

[0064] In the present invention, the input end refers to the feed end, and the output end refers to the discharge end. Unless otherwise specified, the "connection" in the present invention refers to connection through a pipeline or a pipeline.

[0065] The second object of the present invention is to provide the use of the system described in the first object of the present invention in the preparation of high impact polystyrene (HIPS), general purpose polystyrene (GPPS) and styrene copolymers (such as styrene-methyl methacrylate copolymers).

[0066] The third object of the present invention is to provide a method for producing styrene polymers, which is carried out using the system described in one of the objects of the present invention.

[0067] In a preferred implementation manner, the temperature of the first prepolymerization kettle is controlled to be 100-115°C, preferably 105-110°C; and / or the temperature of the second prepolymerization kettle is controlled to be 115-130°C, preferably 125-130°C.

[0068] For example, the temperature of the first prepolymerization kettle is controlled to be 100°C, 105°C, 110°C or 115°C; and / or the temperature of the second prepolymerization kettle is controlled to be 115°C, 120°C, 125°C or 130°C.

[0069] In a further preferred embodiment, the temperature of the second prepolymerization kettle is higher than the temperature of the first prepolymerization kettle.

[0070] In a further preferred embodiment, the pressure of the first prepolymerization kettle is controlled to be 20-40 kPaA (for example, 20 kPaA, 25 kPaA, 30 kPaA, 35 kPaA or 40 kPaA), preferably 30 kPaA; and / or the pressure of the second prepolymerization kettle is controlled to be 40-60 kPaA (for example, 40 kPaA, 45 kPaA, 50 kPaA, 55 kPaA or 60 kPaA), preferably 50 kPaA.

[0071] Preferably, the pressure of the second prepolymerization kettle is controlled to be higher than the pressure of the first prepolymerization kettle.

[0072] In a preferred embodiment, the residence time of the material in the first prepolymerization kettle is controlled to be 50 to 95 minutes, and / or the residence time of the material in the second prepolymerization kettle is controlled to be 150 to 267 minutes.

[0073] In a preferred embodiment, the temperature of the first polymerization reactor is controlled to be 120-140°C (for example, 120°C, 125°C, 130°C, 135°C or 140°C), and the temperature of each temperature zone increases gradually from top to bottom.

[0074] In a further preferred embodiment, the temperature of the first polymerization reactor is controlled as follows: from top to bottom, the temperature of the first temperature zone is 121-127°C, the temperature of the second temperature zone is 128-134°C, and the temperature of the third temperature zone is 135-140°C; preferably, the temperature of the first temperature zone is 123-125°C, the temperature of the second temperature zone is 130-132°C, and the temperature of the third temperature zone is 137-138°C.

[0075] For example, the temperature of the first polymerization reactor is controlled as follows: from top to bottom, the temperature of the first temperature zone is 121°C, 122°C, 123°C, 124°C, 125°C, 126°C or 127°C, the temperature of the second temperature zone is 128°C, 129°C, 130°C, 131°C, 132°C, 133°C or 134°C, and the temperature of the third temperature zone is 135°C, 136°C, 137°C, 138°C, 139°C or 140°C.

[0076] In a preferred embodiment, the pressure of the first polymerization reactor is controlled to be 0.1-10 MPa, preferably 1-5 MPa, for example 2-3 MPa, and the pressure of each temperature zone decreases gradually from top to bottom.

[0077] In a preferred embodiment, the residence time of the material in the first polymerization reactor is controlled to be 20 to 60 min, for example, 20 min, 30 min, 40 min, 50 min or 60 min.

[0078] In a preferred embodiment, the temperature of the second polymerization reactor is controlled to be 140-152°C (for example, 140°C, 142°C, 144°C, 146°C, 148°C, 150°C or 152°C), and the temperature of each temperature zone gradually increases from bottom to top.

[0079] In a further preferred embodiment, the temperature of the second polymerization reactor is controlled as follows: from bottom to top, the temperature of the first temperature zone is 140-143°C, the temperature of the second temperature zone is 144-147°C, and the temperature of the third temperature zone is 148-152°C; preferably, the temperature of the first temperature zone is 141-142°C, the temperature of the second temperature zone is 145-146°C, and the temperature of the third temperature zone is 149-151°C.

[0080] For example, the temperature of the second polymerization reactor is controlled as follows: from bottom to top, the temperature of the first temperature zone is 140°C, 141°C, 142°C or 143°C, the temperature of the second temperature zone is 144°C, 145°C, 146°C or 147°C, and the temperature of the third temperature zone is 148°C, 149°C, 150°C, 151°C or 152°C.

[0081] In a preferred embodiment, the pressure of the second polymerization reactor is controlled to be 0.1-10 MPa, preferably 1-5 MPa, for example 1-3 MPa, more preferably 1.4-2 MPa, and the pressure of each temperature zone decreases gradually from bottom to top.

[0082] In a preferred embodiment, the residence time of the material in the second polymerization reactor is controlled to be 60 to 220 min, for example, 60 min, 100 min, 120 min, 150 min, 180 min, 200 min or 220 min.

[0083] In a preferred embodiment, the temperature of the third polymerization reactor is controlled to be 152-170°C (for example, 152°C, 154°C, 156°C, 158°C, 160°C, 162°C, 164°C, 166°C, 168°C or 170°C), and the temperatures of each temperature zone gradually increase from top to bottom.

[0084] In a further preferred embodiment, the temperature of the third polymerization reactor is controlled as follows: from top to bottom, the temperature of the first temperature zone is 152-160°C, and the temperature of the second temperature zone is 161-170°C; preferably, the temperature of the first temperature zone is 155-157°C, and the temperature of the second temperature zone is 164-167°C.

[0085] In a preferred embodiment, the pressure of the third polymerization reactor is controlled to be 0.1-10 MPa, preferably 0.2-5 MPa, such as 0.5-3 MPa, more such as 0.8-1.4 MPa, and the pressure of each temperature zone decreases gradually from bottom to top.

[0086] In a preferred embodiment, the residence time of the material in the third polymerization reactor is controlled to be 68-125 min, for example, 68 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min or 125 min.

[0087] In a preferred embodiment, the temperature of the first devolatilizer is controlled to be 235-245°C (for example, 235°C, 236°C, 238°C, 240°C, 242°C, 244°C or 245°C); and / or the pressure of the first devolatilizer is controlled to be 0.5-10 kPaA, preferably 1.8-5 kPaA.

[0088] Wherein, the first devolatilizer preheater preheats the material temperature to the control temperature of the first devolatilizer.

[0089] In a preferred embodiment, the temperature of the second devolatilizer is controlled to be 235-245°C (for example, 235°C, 236°C, 238°C, 240°C, 242°C, 244°C or 245°C); and / or the pressure of the second devolatilizer is controlled to be 0.1-5 kPaA, preferably 0.2-1.5 kPaA.

[0090] Wherein, the second devolatilizer preheater preheats the material temperature to the control temperature of the second devolatilizer.

[0091] In a preferred embodiment, the bottoms of the first devolatilizer are mixed with desalted water and then preheated before entering the second devolatilizer. Preferably, the desalted water is heated desalted water having a temperature of 135-145°C, for example, 135°C, 136°C, 138°C, 140°C, 142°C, 144°C or 145°C.

[0092] In a further preferred embodiment, the weight ratio of the desalted water to the bottoms of the first devolatilizer is (0.015-0.025):1, for example, 0.015:1, 0.016:1, 0.018:1, 0.02:1, 0.022:1, 0.024:1 or 0.025:1.

[0093] In a preferred embodiment, the conditions of the distillation tower include: pressure of 4.6-5.1 kPaA, tower top temperature of 50-55°C, and tower bottom temperature of 88-92°C.

[0094] For example, the conditions of the distillation tower include: a pressure of 4.6 kPaA, 4.7 kPaA, 4.8 kPaA, 4.9 kPaA, 5.0 kPaA or 5.1 kPaA, a top temperature of 50°C, 51°C, 52°C, 53°C, 54°C or 55°C, and a bottom temperature of 88°C, 89°C, 90°C, 91°C or 92°C.

[0095] Example

[0096] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0097] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0098] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0099] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0100] [Example 1]

[0101] like Figure 1 As shown, a polystyrene production system comprises: a batching unit 1, a prepolymerization unit 2 whose input end is connected to the output end of the batching unit, a polymerization unit 3 whose input end is connected to the output end of the prepolymerization unit 2, a devolatilization unit 4 whose input end is connected to the output end of the polymerization unit 3, and a monomer recovery unit 5 whose input end is connected to the devolatilization unit 4.

[0102] The batching unit 1 comprises: a rubber dissolving tank 6, an agitator 7 arranged inside the rubber dissolving tank 6, a rubber solution tank 8 whose input end is connected to the output end of the rubber dissolving tank 6, and a TBC removal tower 9 whose output end is combined and connected to the output end of the rubber solution tank 8; wherein the input end of the rubber dissolving tank 6 is provided with a raw material tank and a dosing unit;

[0103] The prepolymerization unit 2 comprises: a first prepolymerization kettle 10 whose input ends are respectively connected to the output ends of the rubber solution tank 8 and the output end of the TBC removal tower 9, a first prepolymerization kettle condenser 11 connected to the top (gas phase outlet) of the first prepolymerization kettle 10, a first kettle bottom pump 12 whose input end is connected to the output end of the first prepolymerization kettle 10, a second prepolymerization kettle 13 whose input end is connected to the output end of the first kettle bottom pump 12, a second prepolymerization kettle condenser 15 connected to the top (gas phase outlet) of the second prepolymerization kettle 13, and a second kettle bottom pump 14 whose input end is connected to the bottom of the second prepolymerization kettle 13; wherein the agitator of the first prepolymerization kettle 10 is a paddle-type agitator, the agitator of the second prepolymerization kettle 13 is a ribbon-type agitator, the agitator of the first prepolymerization kettle 10 and the agitator of the second prepolymerization kettle 13 are both frequency-controlled, and the first prepolymerization kettle 10 and the second prepolymerization kettle 13 are both provided with hot oil jackets on their exteriors;

[0104] The polymerization unit 3 includes: a first polymerization reactor 16 whose input end is connected to the output end of the second kettle bottom pump 14, a second polymerization reactor 17 whose input end is connected to the output end of the first polymerization reactor 16, and a third polymerization reactor 18 whose input end is connected to the output end of the second polymerization reactor 17; wherein the first polymerization reactor 16, the second polymerization reactor 17 and the third polymerization reactor 18 are all vertical plug flow reactors; the first polymerization reactor 16 is provided with three temperature zones, namely the first temperature zone, the second temperature zone and the third temperature zone from top to bottom, wherein the first temperature zone includes two sections of inner coils arranged up and down, the second temperature zone includes four sections of inner coils arranged up and down in sequence, and the third temperature zone includes four sections of inner coils arranged up and down in sequence, and the pipes of each section of the inner coils are staggered in space to form a structure similar to a Chinese knot. A stirrer is arranged between two sections of inner coils in the first temperature zone of the first polymerization reactor; the second polymerization reactor 17 is provided with three temperature zones, each of which independently includes four sections of inner coils arranged in sequence up and down, and the pipes of each section of the inner coil are staggered in space to form a structure similar to a Chinese knot; the third polymerization reactor 18 is provided with two temperature zones, each of which independently includes four sections of inner coils arranged in sequence up and down, and the pipes of each section of the inner coil are staggered in space to form a structure similar to a Chinese knot;

[0105] The devolatilization unit 4 includes: a first devolatilization preheater 20 having an input end connected to the output end of the third polymerization reactor 18, a first devolatilizer 19 having an input end connected to the output end of the first devolatilization preheater 20, a condenser I 25 and a condenser II 26 arranged outside the top (gas phase outlet) of the first devolatilizer 19, a first devolatilization bottom pump 21 having an input end connected to the liquid phase outlet of the first devolatilizer 19, a second devolatilization preheater 23 having an input end connected to the output end of the first devolatilization bottom pump 21, a second devolatilizer 22 having an input end connected to the output end of the second devolatilization preheater 23, a second devolatilization condenser 27 arranged at the top (gas phase outlet) of the second devolatilizer 22, and a second devolatilization bottom pump 24 having an input end connected to the liquid phase outlet of the second devolatilizer 22; wherein the condensed phase outlet of the condenser I 25 is connected to the monomer recovery unit 5, the non-condensable gas outlet of the second devolatilization condenser 27 is provided with a vacuum pump, and the condenser III The condensate phase outlet of 27 is connected to the monomer recovery unit 5, and the output end of the second devolatilization bottom pump 24 is connected to the pelletizer;

[0106] The monomer recovery unit 5 comprises: a distillation tower 28, and the liquid phase outlets of the condenser I 25 and the condenser III 27 are connected to the input end of the distillation tower 28; the external pipelines of the dosing unit 1, the prepolymerization unit 2, the prepolymerization unit 3, the polymerization unit 4 and the monomer recovery unit 5 are connected to a temperature control mechanism and a waste gas treatment mechanism.

[0107] [Example 2]

[0108] A polystyrene production method comprising:

[0109] S1. According to the type of product to be produced, the required raw material ratio is set, and the raw materials are processed by the batching unit. When the product has a high requirement for the inhibitor content, the monomer sent from the tank area is first passed through the TBC removal tower to remove most of the inhibitors in the raw materials and then sent to the prepolymerization unit; when rubber is used, the agitator of the rubber dissolving tank is started, and the required rubber is measured and ground by the rubber cutting machine and falls into the rubber dissolving tank, and auxiliary agents (such as antioxidants) are added in proportion; after the rubber is dissolved, a glue liquid is formed, which is sent to the rubber solution tank for storage through a glue liquid delivery pump, and the next batch of sol operation is started. The glue liquid in the rubber solution tank is continuously sent out by the glue liquid feed pump, and the undissolved rubber and large gel are filtered out by the filter;

[0110] Specifically, the raw material for producing HIPS is a solution of rubber in styrene, which is prepared in an intermittent manner; the styrene monomer and mineral oil are fed into a rubber dissolving tank after being measured, and the agitator is started. The required rubber is measured, ground and crushed by a rubber cutter, and falls into the rubber dissolving tank, and an antioxidant is added in proportion; the rubber is dissolved to form a glue liquid, which is fed into a rubber solution tank for storage through a glue liquid delivery pump, and the next batch of sol operation is started; the glue liquid in the rubber solution tank is continuously fed out by a feed pump, and after being filtered out by a filter to remove undissolved rubber and large gel, it is fed to the first prepolymerization kettle to start polymerization reaction; the glue liquid in the rubber solution tank is circulated through a glue liquid circulation pump and a glue liquid circulation cooler to control the storage temperature of the rubber solution tank;

[0111] Specifically, the raw material for producing GPPS is styrene. The styrene sent from the tank area first passes through a TBC removal tower to remove most of the inhibitors in the raw material through an adsorbent, and then enters the first prepolymerization kettle after filtration to start the polymerization reaction. The TBC removal tower is one in operation and one in standby;

[0112] Specifically, the raw material for producing MS is a mixture of styrene and MMA. The MMA and styrene from the tank area are mixed in a certain proportion, passed through a TBC removal tower to remove most of the inhibitor, and then filtered into the first prepolymerization kettle to start the polymerization reaction.

[0113] S2. The raw materials from the batching unit are first filtered to remove impurities, and then preheated to a certain temperature before entering the first prepolymerization kettle. The hot oil jacket heats the materials in the kettle to reach the required temperature for the prepolymerization reaction. During normal operation, the jacket temperature is set to be consistent with the temperature of the materials in the kettle. The heat released by the polymerization reaction is removed through evaporation, condensation and reflux of the raw materials in the kettle. The discharge from the first prepolymerization kettle is pumped to the second prepolymerization kettle through the bottom pump of the first kettle, and the conversion rate is further improved in the second prepolymerization kettle, and then pumped to the first polymerization reactor by the bottom pump of the second kettle.

[0114] S3, the polymer material is mixed with optional auxiliary agents (such as lubricants and / or additives) before entering the first polymerization reactor. After static mixing, it flows through three polymerization reactors in sequence, the first polymerization reactor is top-in and bottom-out, the second polymerization reactor is bottom-in and top-out, and the third polymerization reactor is top-in and bottom-out. The discharge of the third polymerization reactor enters the first devolatilization preheater of the devolatilization unit.

[0115] Among them, the lubricant is selected from mineral oil, which can reduce the friction inside the molecule, improve the fluidity of the molecule, and has the effect of internal filling and plasticization; the additive is selected from a release agent and / or a transparent agent, the release agent is beneficial to the user's processing and molding on the extruder, and the transparent agent can increase the transparency of GPPS; the release agent can be zinc stearate, and the transparent agent can be a blue material commonly used in the field.

[0116] S4, the polymer material enters the first devolatilizer preheater and is heated, and then enters the first devolatilizer, wherein unreacted monomers, optional solvents, part of oligomers and other volatiles are discharged from the gas phase port, and are divided into two stages of condensation and enter condenser I and condenser II respectively, the condensate of condenser I is sent to the monomer recovery unit, and the condensate of condenser II is recovered, the liquid phase discharge of the first devolatilizer is mixed with a certain proportion of heated desalted water through the first devolatilizer bottom pump, and enters the second devolatilizer preheater, after heating, the oligomers are further removed in the second devolatilizer, and the addition of desalted water is beneficial to reducing the volatile content in the final polymer, the gas phase of the second devolatilizer is condensed through the condenser III, the liquid phase is sent to the monomer recovery unit, and the non-condensable gas is extracted through the vacuum pump; the liquid phase discharge of the second devolatilizer is a finished polymer product, which is sent to a granulator for shredding through the second devolatilizer bottom pump.

[0117] S5. The polymer from the second devolatilizer enters the pelletizer to form polystyrene particles, which are inspected by pneumatic conveying and then sent to off-site packaging or further processing according to the sampling and analysis results.

[0118] S6. The condensate from the first devolatilization condenser I is mixed with the condensate from the condenser III and enters the middle part of the distillation tower. The tower bottom is heated by warm oil and the tower top is cooled by chilled water. The tower bottom contains oligomers, which are temporarily stored in a storage tank and then sent out of the boundary area. The tower top contains styrene monomer, ethylbenzene, etc., which are sent for recycling and reuse.

[0119] S7. The temperature control mechanism uses heat transfer oil to control the system temperature. Through the hot oil main pipe, warm oil main pipe and cold oil main pipe, the hot oil, warm oil and cold oil required for heating and cooling are provided to the system.

[0120] S8. The waste gas generated by the system is collected and sent to the waste gas treatment mechanism for treatment by catalytic oxidation or thermal oxidation.

[0121] [Example 3] Production of HIPS-1 products

[0122] HIPS-1 was produced by using the system of Example 1 and the method of Example 2. The raw materials of this process were styrene and butadiene rubber, with a ratio of about 90wt% and 7wt%. The remaining 3wt% was auxiliary materials of mineral oil and zinc stearate (wherein, mineral oil was 2.2wt% and zinc stearate was 0.8wt%). The production conditions were controlled as shown in Tables 1 to 3 below. The properties of the obtained product are shown in Table 13.

[0123] Table 1 Prepolymerization

[0124]

[0125]

[0126] Table 2 Polymerization reaction

[0127]

[0128] Table 3 Devolatilization treatment

[0129] Operating conditions First Devolatilizer Second Devolatilizer Operating pressure(kPaA) 5 1.5 Operating temperature(℃) 240 235 <![CDATA[Discharge density (kg / m 3 )]]> 1046 1039 Discharge viscosity (cp) 2000000 2000000

[0130] The weight ratio of 140° C. desalted water to the bottom material of the first devolatilizer was 0.02:1.

[0131] The operating conditions of the distillation tower include: a tower top temperature of 53.4° C., a tower bottom temperature of 90° C., a tower top pressure of 4.6 kPaA, and a tower bottom pressure of 5.1 kPaA.

[0132] [Example 4] Production of HIPS-2 products

[0133] HIPS-2 was produced by using the system of Example 1 and the method of Example 2. The raw materials of this process were styrene and butadiene rubber, with a ratio of about 90wt% and 8wt%. The remaining 2wt% was auxiliary materials of mineral oil and zinc stearate (wherein, mineral oil was 1.5wt% and zinc stearate was 0.5wt%). The production conditions were controlled as shown in Tables 4 to 6 below. The properties of the obtained products are shown in Table 13.

[0134] Table 4 Prepolymerization

[0135] Operating conditions The first prepolymerization kettle The second prepolymerization kettle Operating pressure(kPaA) 32 52 Operating temperature(℃) 108 128 Residence time (min) 54 162 Reactor Type CSTR CSTR Agitator type Paddle Screw Ribbon

[0136] Table 5 Polymerization reaction

[0137]

[0138] Table 6 Devolatilization treatment

[0139] Operating conditions First Devolatilizer Second Devolatilizer Operating pressure(kPaA) 4.8 1.3 Operating temperature(℃) 240 235

[0140] The operating conditions of the distillation tower include: a tower top temperature of 53° C., a tower bottom temperature of 91° C., a tower top pressure of 4.7 kPaA, and a tower bottom pressure of 5 kPaA.

[0141] [Example 5] Production of GPPS-1 product

[0142] GPPS-1 was produced by using the system of Example 1 and the method of Example 2. The raw material of this process was styrene, with a ratio of about 98wt%. The remaining 2wt% was auxiliary materials of mineral oil, zinc stearate, and blueing agent (wherein mineral oil was 1wt%, zinc stearate was 0.8wt%, and blueing agent was 0.2wt%, where blueing agent was a dye). The conditions were controlled as shown in Tables 7 to 9 below. The properties of the obtained product are shown in Table 13.

[0143] Table 7 Prepolymerization

[0144] Operating conditions The first prepolymerization kettle The second prepolymerization kettle Operating pressure(kPaA) 35 55 Operating temperature(℃) 108 128 Residence time (min) 54 162 Reactor Type CSTR CSTR Agitator type Paddle Screw Ribbon

[0145] Table 8 Polymerization reaction

[0146]

[0147]

[0148] Table 9 Devolatilization treatment

[0149] Operating conditions First Devolatilizer Second Devolatilizer Operating pressure 4.6kPaA 1.1kPaA Operating temperature(℃) 240 235

[0150] The operating conditions of the distillation tower include: a tower top temperature of 54° C., a tower bottom temperature of 92° C., a tower top pressure of 4.7 kPaA, and a tower bottom pressure of 5.1 kPaA.

[0151] [Example 6] Production of GPPS-2 product

[0152] GPPS-2 was produced by using the system of Example 1 and the method of Example 2. The raw material of this process was styrene, with a ratio of about 97wt%. The remaining 3wt% was auxiliary materials of mineral oil, zinc stearate, and blueing agent (wherein mineral oil was 1.2wt%, zinc stearate was 1.2wt%, and blueing agent was 0.6wt%, where blueing agent was a dye). The conditions were controlled as shown in Tables 10 to 12 below. The properties of the obtained product are shown in Table 13.

[0153] Table 10 Prepolymerization

[0154] Operating conditions The first prepolymerization kettle The second prepolymerization kettle Operating pressure(kPaA) 36 56 Operating temperature(℃) 108 128 Residence time (min) 54 162 Reactor Type CSTR CSTR Agitator type Paddle Screw Ribbon

[0155] Table 11 Polymerization reaction

[0156]

[0157]

[0158] Table 12 Devolatilization treatment

[0159] Operating conditions First Devolatilizer Second Devolatilizer Operating pressure(kPaA) 4.4 0.9 Operating temperature(℃) 240 235

[0160] The operating conditions of the distillation tower include: a tower top temperature of 52° C., a tower bottom temperature of 90° C., a tower top pressure of 4.6 kPaA, and a tower bottom pressure of 5.0 kPaA.

[0161] Table 13 Polystyrene products

[0162]

[0163] Among them, overhang refers to the strength of notched cantilever beam, and full overhang refers to the strength of unnotched cantilever beam.

[0164] In summary, the polystyrene production system and method of the present invention effectively improves the conversion rate of the system and reduces the residue by adopting the two-stage prepolymerization and three-stage polymerization in series; and by providing the batching unit 1, different monomers can be added to produce different types of high-quality products. In addition, the polystyrene products obtained by the system and method of the present invention have a low melt index, a high heat deformation temperature and a high Izod impact strength.

[0165] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A system for producing polystyrene, the system comprising a prepolymerization unit, a polymerization unit, a devolatilization unit and a monomer recovery unit connected in series, wherein: The prepolymerization unit includes a two-stage prepolymerization kettle, the polymerization unit includes a three-stage polymerization reactor, and the monomer recovery unit is a distillation tower.

2. The system according to claim 1, characterized in that The prepolymerization unit comprises a first prepolymerization kettle and a second prepolymerization kettle connected in series. Preferably, a stirrer is independently provided in the first prepolymerization kettle and the second prepolymerization kettle.

3. The system according to claim 1, characterized in that The polymerization unit comprises a first polymerization reactor, a second polymerization reactor and a third polymerization reactor connected in series; preferably, a feed port is arranged at the top of the first polymerization reactor, the bottom of the first polymerization reactor is connected to the bottom of the second reactor, the top of the second reactor is connected to the top of the third reactor, and a crude product discharge port is arranged at the bottom of the third reactor; more preferably, a plurality of temperature zones are independently arranged in the first polymerization reactor, the second polymerization reactor and the third reactor, preferably 2 to 5 temperature zones are independently arranged in each of them.

4. The system according to claim 1, characterized in that The devolatilization unit comprises a first devolatilizer and a second devolatilizer connected in series, and feed ports are independently arranged at the tops of the first devolatilizer and the second devolatilizer; preferably, a first devolatilization preheater is arranged at the feed port of the first devolatilizer, and a second devolatilization preheater is arranged at the feed port of the second devolatilizer.

5. The system according to claim 4, characterized in that The devolatilization unit further comprises a condenser I, a condenser II, and a condenser III, wherein the condenser I, the condenser II, and the condenser III are each independently provided with a volatile component inlet, a non-condensable gas outlet, and a condensate outlet; Preferably, the volatile component inlet of the condenser I is connected to the upper part or top of the first devolatilizer, the non-condensable gas outlet of the condenser I is connected to the volatile component inlet of the condenser II, and the volatile component inlet of the condenser III is connected to the upper part or top of the second devolatilizer; More preferably, the condensate outlet of the condenser I and the condensate outlet of the condenser III are both connected to the feed inlet of the distillation tower, and the top of the distillation tower and the condensate outlet of the condenser II obtain the recovered monomer.

6. The system according to claim 4, characterized in that A mixer is arranged between the bottom of the first devolatilizer and the feed inlet of the second devolatilizer, and a desalted water input pipeline is further arranged on the mixer.

7. The system according to any one of claims 1 to 6, characterized in that: The system further includes a batching unit; preferably, the batching unit includes a rubber dissolving device and a TBC removal device arranged in parallel, wherein the rubber dissolving device includes a rubber dissolving tank and a rubber solution tank connected in series, and the TBC removal device includes at least two TBC removal towers arranged in parallel; more preferably, the discharge port of the rubber dissolving device and the discharge port of the TBC removal device are each independently connected to the prepolymerization unit.

8. Use of the system according to any one of claims 1 to 7 in the preparation of high impact polystyrene, general purpose polystyrene and styrene copolymers.

9. A method for producing styrene polymers, using the system according to any one of claims 1 to 8.

10. The method according to claim 9, characterized in that The temperature of the first prepolymerization kettle is controlled to be 100-115°C, preferably 105-110°C; and / or the temperature of the second prepolymerization kettle is controlled to be 115-130°C, preferably 125-130°C.

11. The method according to claim 9, characterized in that The temperature of the first polymerization reactor is controlled to be 120-140°C, and the temperatures of each temperature zone are gradually increased from top to bottom; preferably, the temperature of the first polymerization reactor is controlled as follows: from top to bottom, the temperature of the first temperature zone is 121-127°C, the temperature of the second temperature zone is 128-134°C, and the temperature of the third temperature zone is 135-140°C; and / or, The temperature of the second polymerization reactor is controlled to be 140-152° C., and the temperatures of each temperature zone are gradually increased from bottom to top; preferably, the temperature of the second polymerization reactor is controlled as follows: from bottom to top, the temperature of the first temperature zone is 140-143° C., the temperature of the second temperature zone is 144-147° C., and the temperature of the third temperature zone is 148-152° C.; and / or, The temperature of the third polymerization reactor is controlled at 152-170°C, and the temperatures of each temperature zone gradually increase from top to bottom; preferably, the temperature of the third polymerization reactor is controlled as follows: from top to bottom, the temperature of the first temperature zone is 152-160°C, and the temperature of the second temperature zone is 161-170°C.

12. The method according to any one of claims 9 to 11, characterized in that: Controlling the temperature of the first devolatilizer to 235-245° C.; and / or controlling the temperature of the second devolatilizer to 235-245° C.; and / or, The bottom material of the first devolatilizer is mixed with desalted water and then preheated to enter the second devolatilizer; preferably, the weight ratio of the desalted water to the bottom material of the first devolatilizer is (0.015-0.025):1.

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