Preparation method of polyphenylene sulfide resin

Abstract

The invention provides a polyphenylene sulfide resin and a preparation method thereof. The polyphenylene sulfide resin polymerization process comprises the steps of dehydration, first-stage polymerization, second-stage polymerization, third-stage polymerization and post-treatment. The preparation method of the polyphenylene sulfide resin is characterized in that a sulfur source, an alkali metal hydroxide and a dihalo aromatic compound are used as raw materials to be subjected to polymerization reaction in an organic polar solvent, and the organic solvent is added in a second-stage polymerization process to reduce the viscosity of the system and increase the DCB conversion rate; the organic solvent is removed in the three-stage polymerization process, so that the collision probability of the PPS oligomer is increased, the cyclization side reaction is inhibited, and the polyphenylene sulfide resin is prepared at high yield. According to the method, the generation amount of cyclic polyphenylene sulfide in the polyphenylene sulfide polymerization process can be remarkably reduced, and the purity of PPS is improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and specifically relates to a method for manufacturing polyphenylene sulfide resin. Background Technology

[0002] Polyphenylene sulfide (PPS), as a new type of high-performance thermoplastic resin material, occupies an important position in the field of materials science due to its excellent high temperature resistance, corrosion resistance, balanced mechanical properties and excellent dimensional stability. It is known as the world's sixth largest engineering plastic and is widely used in many fields such as the automotive industry, electronics and electrical appliances and environmental protection industry.

[0003] Phillips Petroleum Company pioneered the industrial and commercial production of PPS by polymerizing p-dichlorobenzene (p-DCB) with sodium sulfide in a polar aprotic solvent. However, the initial PPS product had limitations such as low molecular weight and high impurity content. To improve the quality of PPS products, subsequent research focused on improving the polymerization process and post-processing. For example, polymerization aids such as water (JP1988039926A) and alkali metal carboxylates (US5342654A) were added to promote the formation of high molecular weight PPS, and high-purity PPS products were obtained by washing with organic solvents such as ethylene glycol (JP1993032417B2) and acetone (JP1982205425A). Although adding polymerization aids and using organic solvents for multiple washing strategies can yield high-purity, high-molecular-weight PPS, their effect on improving polymerization yield is relatively limited. During the polymerization process, a large number of side reactions occur in the system, inevitably producing a large number of byproducts, such as cyclic phenyl sulfides (CPS). These byproducts have characteristics such as complex composition, difficulty in further polymerization, and extremely small particle size. These characteristics together lead to an extremely cumbersome post-processing procedure, which greatly affects production efficiency.

[0004] Several patented technologies aim to reduce side reactions and improve polymerization yield during polymerization. For example, US5744576A employs a two-stage polymerization method, controlling the polymerization temperature and heating rate to reduce side reactions, ultimately reducing the impurity (bis-4-chlorophenyl sulfide) content in the system to 100 ppm. However, the two-stage polymerization method results in a longer polymerization time, significantly reducing production efficiency. CN100355811C adds alkali metal hydroxides during polymerization to suppress side reactions and PPS decomposition, ultimately achieving a nitrogen content of less than 800 ppm in the final product. However, adding a large amount of alkali during polymerization can cause ring-opening and deterioration of the organic solvent in the system, introducing new impurities into the product.

[0005] In summary, a novel preparation technology is needed to significantly reduce the occurrence of side reactions during the polymerization of polyphenylene sulfide. Summary of the Invention

[0006] Previously, during the manufacturing process of PPS, cyclization side reactions occurred in the polymerization system, generating cyclic phenyl sulfides (CPS). These side reactions not only resulted in the waste of raw materials but also generated a large number of byproducts, requiring extremely tedious washing processes to obtain high-purity PPS. From the perspectives of productivity, economy, and efficiency, it is essential to reduce the amount of impurities generated in PPS and improve product purity.

[0007] This invention was made to solve this problem, and its main objective is to provide a method for manufacturing high-purity PPS that can suppress cyclization side reactions.

[0008] The technical solution of the present invention is as follows:

[0009] The PPS manufacturing process of this invention includes:

[0010] (1) Dehydration step: Prepare a mixture of organic polar solvent, sulfur source, water and alkali metal hydroxide, and gradually heat the mixture to remove some of the water from the system.

[0011] (2) One-stage polymerization: After dehydration, dihaloaromatic compounds and organic polar solvents are added to the system, the temperature is raised, and a polymerization reaction is carried out to generate a reaction mixture containing prepolymer.

[0012] (3) Two-stage polymerization: After the first-stage polymerization is completed, a certain amount of organic polar solvent is added and the reaction mixture is heated to generate PPS oligomers.

[0013] (4) Three-stage polymerization: After PPS oligomers are generated, a certain amount of organic polar solvent is evaporated, the temperature is raised to a certain temperature, a phase separation agent is added, and the reaction continues.

[0014] (5) Post-processing: The mixture obtained from polymerization is cooled, the reaction slurry is centrifuged, washed and filtered.

[0015] In the method for manufacturing PPS of the present invention, it is preferred that, in the dehydration step, the molar ratio of sulfur source to alkali metal hydroxide in the prepared mixture is 1:0.5 to 0.99, and the molar ratio of organic polar solvent to sulfur source is 0.2 to 3.0, more preferably 1.0 to 2.5.

[0016] In the PPS manufacturing method of the present invention, it is preferred that the polymerization temperature in a polymerization step is 200-240°C, more preferably 210-230°C.

[0017] In the PPS manufacturing method of the present invention, it is preferred that the polymerization temperature in the two-stage polymerization step is 230-250°C, more preferably 240-250°C.

[0018] In the manufacturing method of PPS of the present invention, it is preferred that, in the two-stage polymerization step, a portion of organic solvent is added to the system until the molar ratio of the organic polar solvent to the effective sulfur source (the effective sulfur source is the sulfur source in the system, which is equal to the total sulfur source added minus the sulfur source lost in the dehydration stage) is 2.0 to 6.0, more preferably 3.0 to 5.0.

[0019] In the PPS manufacturing method of the present invention, it is preferred that the polymerization temperature in the three-stage polymerization step is 250-280°C, more preferably 250-270°C.

[0020] In the method for manufacturing PPS of the present invention, it is preferred that, in the three-stage polymerization step, a portion of the organic solvent is removed from the system until the molar ratio of the organic polar solvent to the effective sulfur source is 2.0 to 4.0, more preferably 3.0 to 4.0.

[0021] In the PPS manufacturing method of the present invention, it is preferable that, in the three-stage polymerization step, a portion of the organic solvent is removed first, and then polymerization is carried out.

[0022] In the PPS manufacturing method of the present invention, it is preferred that, in the post-processing stage, the centrifuged particles are washed with an organic solvent and then washed with hot water.

[0023] According to the present invention, a method for manufacturing PPS that can suppress cyclization side reactions and produce high-purity PPS can be provided. Detailed Implementation

[0024] The following is a detailed description of each process.

[0025] (Dehydration process)

[0026] The dehydration process is a process that removes water-containing distillates from the reaction system during polymerization before the polymerization process.

[0027] The polymerization reaction of PPS is either promoted or hindered by the amount of water present in the polymerization system. Therefore, as long as the amount of water in the system during polymerization is not enough to hinder the polymerization reaction, a dehydration process is not necessary, but it is preferable to perform dehydration treatment before polymerization to reduce the amount of water in the system during polymerization.

[0028] In the dehydration process, heating dehydration is preferably carried out under an inert gas atmosphere. The total water volume in the system during the dehydration process refers to the bound water contained in each raw material input in the dehydration process, the free water added to the system, and the water produced as a byproduct of the reaction between the raw materials.

[0029] At the end of the dehydration process, the water content in the system is preferably 0 to 2 mol relative to 1 mol of effective sulfur source (the effective sulfur source is the sulfur source in the system = the total sulfur source added - the sulfur source lost in the dehydration stage), more preferably 0.5 to 2.0 mol.

[0030] It should be noted that the organic polar solvent used in the dehydration process can be selected from N-alkylpyrrolidone compounds, N-cycloalkylpyrrolidone compounds, N,N-dialkylimidazolinone compounds, tetraalkylurea compounds, and hexaalkylphosphotriamide compounds; among which, N-alkylpyrrolidone compounds are preferably N-methyl-2-pyrrolidone, etc.; N-cycloalkylpyrrolidone compounds are preferably N-cyclohexyl-2-pyrrolidone, etc.; N,N-dialkylimidazolinone compounds are preferably 1,3-dialkyl-2-imidazolinone, etc.; tetraalkylurea compounds are preferably tetramethylurea, etc.; hexaalkylphosphotriamide compounds are preferably hexamethylphosphotriamide, etc.; and more preferably N-methyl-2-pyrrolidone.

[0031] It should be noted that the sulfur source used in the dehydration process can be an alkali metal sulfide, an alkali metal hydrogen sulfide, or hydrogen sulfide, with sodium sulfide or sodium hydrosulfide being preferred.

[0032] It should be noted that the alkali metal hydroxide used in the dehydration process can be lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, or cesium hydroxide, with sodium hydroxide being the preferred choice.

[0033] (A polymerization process)

[0034] One polymerization step involves heating a mixture to initiate the polymerization reaction, producing a prepolymer with a dihaloaromatic compound conversion rate of over 50%. After dehydration, a mixture of the dihaloaromatic compound and an organic polar solvent is added, and the mixture is heated to a certain temperature to carry out the polymerization reaction, generating a reaction mixture containing the prepolymer.

[0035] The amount of dihaloaromatic compound used is 1 mol relative to the effective sulfur source in the system (the effective sulfur source in the system = total added sulfur source - sulfur source lost during the dehydration stage), typically 0.9–1.5 mol, more preferably 0.92–1.1 mol. Excessive use of dihaloaromatic compound makes it difficult to produce high molecular weight PPS. Insufficient use results in low sulfur source conversion, making stable polymerization difficult.

[0036] The amount of organic polar solvent added is 2.0 mol relative to the effective sulfur source in the system, usually 0.2 to 3.0 mol, more preferably 1.0 to 2.5 mol.

[0037] In a single-stage polymerization process, it is preferable to heat the system to a temperature of 200–240°C to initiate the polymerization reaction, producing a prepolymer with a conversion rate of more than 50% for dihaloaromatic compounds. From the viewpoint of suppressing side reactions and decomposition reactions, the polymerization temperature in the single-stage polymerization process is preferably selected from the range of 210–230°C.

[0038] To shorten the polymerization time, the conversion rate of the dihaloaromatic compound is preferably 50-98%, more preferably 60-90%, and even more preferably 65-85%.

[0039] It should be noted that the dihaloaromatic compounds used in the polymerization process can be selected from o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, dichlorotoluene, dichlorobiphenyl, dichlorobenzoic acid, dichlorodiphenyl ether, dichlorodiphenyl sulfone, dichlorodiphenyl sulfoxide, dichlorodiphenyl ketone, etc., with p-dichlorobenzene being preferred.

[0040] (Two-stage polymerization process)

[0041] The two-stage polymerization process involves heating the prepolymer to continue the polymerization reaction, generating PPS oligomers. After the first-stage polymerization is complete, a certain amount of organic polar solvent is added, and the temperature is further raised to a certain level to carry out the polymerization reaction and generate a reaction mixture containing PPS oligomers. Preferably, after the two-stage polymerization, the conversion rate of the dihaloaromatic compound is 80-99%, more preferably 85-95%.

[0042] Regarding the polymerization temperature in the two-stage polymerization process, it is preferable to heat to 230–250°C, more preferably to 240–250°C, to continue the polymerization reaction. The polymerization temperature can be maintained at a constant temperature, or it can be raised or lowered in stages as needed. From the viewpoint of controlling the polymerization reaction, maintaining a constant temperature is preferred.

[0043] In the two-stage polymerization process, the prepolymer polymerizes to form PPS oligomers, which increases the viscosity of the system and is not conducive to the polymerization reaction. The increase in viscosity can be suppressed by adding a certain amount of organic solvent to the system. The amount of organic solvent in the system is preferably 2.0 to 6.0 mol relative to 1 mol of effective sulfur source.

[0044] (Three-stage polymerization process)

[0045] The three-stage polymerization process involves heating the oligomers to continue the polymerization reaction. After the two-stage polymerization is complete, a portion of the organic solvent is removed from the system, and a phase-separating agent is added to continue the polymerization reaction.

[0046] In the three-stage polymerization process, the amount of organic solvent in the system affects the occurrence of cyclization side reactions. When the organic solvent content is greater than 4.0 mol (relative to 1 mol of effective sulfur source), the concentration of PPS oligomers in the system is low, and the PPS oligomers preferentially cyclize to form cyclic phenyl sulfides, increasing the mass of impurities in the system. When the organic solvent content is less than 2.0 mol, the system viscosity is too high, the polymerization reaction is incomplete, the product particle size distribution is large, the polymerization yield is reduced, and particle blockage of the pipeline is likely to occur. In the three-stage polymerization process, the amount of organic solvent in the system relative to 1 mol of effective sulfur source is preferably 2.0–4.0 mol, more preferably 3.0–4.0 mol.

[0047] Regarding the polymerization temperature in the three-stage polymerization process, it is preferable to heat to 250–280°C, and more preferably to heat to 250–270°C to continue the polymerization reaction.

[0048] It should be noted that the phase separating agent used in the three-stage polymerization process can be selected from organic carboxylic acid metal salts, organic sulfonic acid metal salts, alkali metal halides, alkaline earth metal halides, alkaline earth metal salts of aromatic carboxylic acids, alkali metal salts of phosphates, alcohols, paraffinic hydrocarbons, water, or a mixture of the above substances. Water, which is inexpensive and easy to treat, is preferred.

[0049] In three-stage polymerization, the amount of phase separating agent used is typically 2–8 mol relative to the effective sulfur source in 1 mol of the system, more preferably 2–5 mol. If the amount of phase separating agent added is too small, the phase separation effect will be unsatisfactory.

[0050] (Post-processing steps)

[0051] The post-processing step involves removing unwanted components from the slurry obtained from the polymerization process to obtain high-purity PPS. After polymerization, the reaction slurry is centrifuged, washed with an organic solvent, filtered, and then washed with hot water.

[0052] It should be noted that the organic solvents used in the post-treatment process can be selected from N-alkylpyrrolidone compounds, N-cycloalkylpyrrolidone compounds, N,N-dialkylimidazolinone compounds, tetraalkylurea compounds, and hexaalkylphosphotriamide compounds; among them, N-alkylpyrrolidone compounds are preferably N-methyl-2-pyrrolidone, etc.; N-cycloalkylpyrrolidone compounds are preferably N-cyclohexyl-2-pyrrolidone, etc.; N,N-dialkylimidazolinone compounds are preferably 1,3-dialkyl-2-imidazolinone, etc.; tetraalkylurea compounds are preferably tetramethylurea, etc.; hexaalkylphosphotriamide compounds are preferably hexamethylphosphotriamide, etc.; and N-methyl-2-pyrrolidone is preferred.

[0053] The present invention will be described below through specific embodiments.

[0054] [Conversion rate of p-dichlorobenzene]

[0055] The amount of p-dichlorobenzene remaining in the slurry after polymerization was determined by gas chromatography. Then, the conversion rate of p-dichlorobenzene was calculated based on the residual amount, the amount of p-dichlorobenzene fed, and the amount of sodium hydrosulfide fed.

[0056] [Aggregation Yield]

[0057] Assuming that all sodium hydrosulfide fed into the reactor is converted into PPS, the mass of PPS at this point (theoretical amount) is set as the baseline value. The ratio of the actual recovered mass of PPS (the material collected on a 100-mesh sieve) to this baseline value is calculated and defined as the polymerization yield (unit: wt.%).

[0058] [Cyclic phenyl sulfide content]

[0059] After drying the polymerized PPS, it was pulverized and extracted using a Soxhlet extractor with dichloromethane as the solvent. The extracted liquid phase was then precipitated with methanol, and the precipitated product was cyclic phenyl sulfide. The ratio of the mass of the extracted cyclic phenyl sulfide to the mass of the pulverized PPS was defined as the cyclic phenyl sulfide content (unit: %).

[0060] [Example 1]

[0061] 1. Dehydration stage:

[0062] In a 10L titanium reactor, 1218.76g (10.0mol) of a 46% NaSH aqueous solution, 759.94g (9.5mol) of a 50% NaOH aqueous solution, and 17.0mol (1685.26g) of NMP were added, with a NaOH / NaSH molar ratio of 0.95. The temperature was increased to 180℃ at a rate of 1.2℃ / min at 150 rpm, removing 1049.78g of the aqueous solution (88.1% water content). The sulfur (S) loss during the dehydration stage was 0.1mol. At this point, the remaining water content in the system had a H₂O / NaSH molar ratio of 1.65 and an NMP / NaSH molar ratio of 1.59. Dehydration was complete, and the material temperature was lowered to 150℃.

[0063] 2. A segment of aggregation:

[0064] p-DCB (1499.4 g, 10.2 mol) and NMP (893.19 g, 9.01 mol) were pumped into the reactor. The molar ratio of p-DCB / NaSH was 1.03, and the molar ratio of NMP / NaSH in the system was 2.5. The stirring speed of the reactor was increased to 200 rpm, and the temperature was increased to 230 °C over 90 minutes. The reaction was carried out at 230 °C for 1 hour to complete the first-stage polymerization. The conversion rate of p-DCB after the first-stage polymerization was 77%.

[0065] 3. Two-stage aggregation:

[0066] NMP (2453.54 g, 24.75 mol) was pumped into the reactor, with an NMP / NaSH molar ratio of 5.0. The stirring speed of the reactor was increased to 220 rpm, and the temperature was increased to 240 °C over 10 minutes. The reaction was carried out at 240 °C for 0.5 hours to complete the two-stage polymerization. After the two-stage polymerization, the conversion rate of p-DCB was 90%.

[0067] 4. Three-stage aggregation:

[0068] After the two-stage polymerization was completed, 981.42 g (9.9 mol) of NMP was removed from the system, and the molar ratio of NMP / NaSH was 4.0. The temperature was increased to 270 °C at a rate of 2 °C / min, and then water (356.70 g, 19.8 mol) was added to the system. The reaction was continued at 270 °C for 2 hours to complete the three-stage polymerization.

[0069] 5. Post-processing:

[0070] After polymerization, the material temperature was lowered to 120°C for 1 hour. The product was sieved using a 100-mesh sieve, and the residue was centrifuged and filtered. The filter cake was washed with NMP, filtered again, and then washed with boiling water to obtain granular PPS resin. The resin was dried at 120°C for 8 hours. The polymerization yield was 96.3%.

[0071] Take 100g of dry granular PPS resin, pulverize it, extract it with dichloromethane, precipitate it with methanol, filter it, and dry it to obtain cyclic phenyl sulfide.

[0072] [Example 2]

[0073] The feeding and polymerization operations were basically the same as in Example 1, except that NMP was added to the reactor during the two-stage polymerization until the molar ratio of NMP / NaSH in the system was 3.0. The stirring speed of the reactor was increased to 220 rpm, and the temperature was raised to 240°C over 10 minutes. The reaction was carried out at 240°C for 1 hour to complete the two-stage polymerization. The conversion rate of p-DCB after the two-stage polymerization was 87%.

[0074] The three-stage polymerization and post-processing operations were the same as in Example 1. The polymerization yield was 93.5%.

[0075] [Example 3]

[0076] The feeding and polymerization operations were basically the same as in Example 1, except that NMP was added to the reactor during the two-stage polymerization until the molar ratio of NMP / NaSH in the system was 4.0. The stirring speed of the reactor was increased to 240 rpm, and the temperature was raised to 250°C over 20 minutes. The reaction was carried out at 250°C for 1 hour to complete the two-stage polymerization. The conversion rate of p-DCB after the two-stage polymerization was 85%.

[0077] The three-stage polymerization and post-processing operations were the same as in Example 1. The polymerization yield was 94.7%.

[0078] [Example 4]

[0079] The feeding and polymerization operations were basically the same as in Example 1, except that NMP was added to the reactor during the two-stage polymerization until the molar ratio of NMP / NaSH in the system reached 6.0. The two-stage polymerization time was 0.25 h, and the conversion rate of p-DCB after the two-stage polymerization was 92%.

[0080] The three-stage polymerization and post-processing operations were the same as in Example 1. The polymerization yield was 96.5%.

[0081] [Example 5]

[0082] The feeding conditions, first-stage polymerization, and second-stage polymerization operations were basically the same as in Example 1, except that some NMP was removed from the reactor during the third-stage polymerization until the molar ratio of NMP / NaSH in the system was 2.0. The reaction was carried out at 260°C for 2 hours to complete the three-stage polymerization.

[0083] The post-processing was the same as in Example 1. The polymerization yield was 93.7%.

[0084] [Example 6]

[0085] The feeding conditions, first-stage polymerization, and second-stage polymerization operations were basically the same as in Example 1, except that some NMP was removed from the reactor during the third-stage polymerization until the molar ratio of NMP / NaSH in the system was 3.0. The reaction was carried out at 260°C for 3 hours to complete the three-stage polymerization.

[0086] The post-processing was the same as in Example 1. The polymerization yield was 94.2%.

[0087] [Comparative Example 1]

[0088] The preparation method of Comparative Example 1 is the same as that of Example 1, except that some NMP is not removed in the three-stage polymerization process.

[0089] The test data for each embodiment and comparative example are shown in Table 1.

[0090] Table 1 Test data for the examples and comparative examples

[0091]

[0092]

[0093] The data comparison above shows that the content of organic solvent in the three-stage polymerization has a significant impact on the cyclization side reaction. A lower organic solvent content increases the collision probability between PPS oligomers, making them more likely to undergo polymerization reactions, reducing the probability of cyclization reactions, and reducing the impurity content in the product.

Claims

1. A method for preparing polyphenylene sulfide resin, characterized in that, The preparation method includes the following steps: (1) Dehydration step: Prepare a mixture of organic polar solvent, sulfur source, water and alkali metal hydroxide, and gradually increase the temperature to remove part of the water in the system; (2) One-stage polymerization: After dehydration, dihaloaromatic compounds and organic polar solvents are added, the temperature is raised, and a polymerization reaction is carried out to generate a reaction mixture containing prepolymers; (3) Two-stage polymerization: After the first-stage polymerization is completed, a certain amount of organic polar solvent is added, and the reaction mixture is heated to generate PPS oligomers. (4) Three-stage polymerization: After PPS oligomers are generated, a certain amount of organic polar solvent is evaporated, the temperature is raised to a certain temperature, and a phase separation agent is added to allow the generated oligomers to react further. (5) Post-processing: The mixture obtained from polymerization is cooled, the reaction slurry is centrifuged, washed and filtered.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of sulfur source to alkali metal hydroxide in the prepared mixture is 1:0.5 to 0.99, and the molar ratio of organic polar solvent to sulfur source is preferably 0.2 to 3.0, more preferably 1.0 to 2.5; At the end of the dehydration process, the amount of water in the system relative to 1 mol of effective sulfur source is 0 to 2 mol, preferably 0.5 to 2.0 mol; Preferably, the organic polar solvent is selected from N-alkylpyrrolidone compounds, N-cycloalkylpyrrolidone compounds, N,N-dialkylimidazolinone compounds, tetraalkylurea compounds, and hexaalkylphosphotriamide compounds; wherein, the N-alkylpyrrolidone compound is preferably N-methyl-2-pyrrolidone; the N-cycloalkylpyrrolidone compound is preferably N-cyclohexyl-2-pyrrolidone; the N,N-dialkylimidazolinone compound is preferably 1,3-dialkyl-2-imidazolinone; the tetraalkylurea compound is preferably tetramethylurea; the hexaalkylphosphotriamide compound is preferably hexamethylphosphotriamide; and the organic polar solvent is more preferably N-methyl-2-pyrrolidone. Preferably, the sulfur source is selected from alkali metal sulfides, alkali metal hydrogen sulfides, or hydrogen sulfide, with sodium sulfide or sodium hydrosulfide being the most preferred. Preferably, the alkali metal hydroxide is selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide.

3. The method according to claim 1 or 2, characterized in that, In step (2), the polymerization temperature is 200-240°C, more preferably 210-230°C; The amount of dihaloaromatic compounds used is 0.9–1.5 mol relative to 1 mol of effective sulfur source; The amount of organic polar solvent used is 0.2 to 3.0 mol relative to 2.0 mol of effective sulfur source, more preferably 1.0 to 2.5 mol; Preferably, the conversion rate of the dihaloaromatic compound is 50-98%, more preferably 60-90%, and even more preferably 65-85%. Preferably, the dihaloaromatic compound is selected from o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, dichlorotoluene, dichlorobiphenyl, dichlorobenzoic acid, dichlorodiphenyl ether, dichlorodiphenyl sulfone, dichlorodiphenyl sulfoxide, and dichlorodiphenyl ketone.

4. The method according to any one of claims 1-3, characterized in that, In step (3), the two-stage polymerization temperature is 230-250°C, more preferably 240-250°C; Preferably, in the two-stage polymerization step, a portion of organic solvent is added to the system until the molar ratio of the organic polar solvent to the effective sulfur source is 2.0 to 6.0, more preferably 3.0 to 5.

0.

5. The method according to any one of claims 1-4, characterized in that, In step (4), the three-stage polymerization temperature is 250-280℃, more preferably 250-270℃; Remove a portion of the organic solvent from the system until the molar ratio of the organic polar solvent to the effective sulfur source is 2.0 to 4.0, more preferably 3.0 to 4.

0.

6. The method according to any one of claims 1-5, characterized in that, In step (4), the phase separating agent is selected from organic carboxylic acid metal salts, organic sulfonic acid metal salts, alkali metal halides, alkaline earth metal halides, alkaline earth metal salts of aromatic carboxylic acids, alkali metal salts of phosphates, alcohols, paraffinic hydrocarbons, and water. Preferably, the amount of phase separating agent used is 2 to 8 mol relative to the effective sulfur source in 1 mol of the system.

7. The method according to any one of claims 1-5, characterized in that, In step (5), the centrifuged particles are washed with an organic solvent and then with hot water.

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