A method for purifying a mixture containing polyphenylene sulfide

Abstract

This invention discloses a method for purifying a mixture containing polyphenylene sulfide (PPS). The method comprises the following steps: S1, washing the PPS-containing mixture with an organic solvent to obtain a first intermediate product; the first washing is performed under microwave heating at a temperature of 60-150°C; S2, washing the first intermediate product with an aqueous acid solution to obtain a second intermediate product; S3, washing the second intermediate product with water to obtain a purified PPS product; the third washing is performed under microwave heating at a temperature of 60-150°C. The purification method for the PPS-containing mixture of this invention is highly efficient and low-cost, and the obtained purified PPS product has a yellowness of no more than 7 and a salt content of less than 0.3%.

Description

Technical Field

[0001] This invention relates to a method for purifying a mixture containing polyphenylene sulfide. Background Technology

[0002] Polyphenylene sulfide (PPS) is a semi-crystalline thermoplastic engineering plastic with a main chain composed of sulfur atoms and para-benzene rings. It possesses excellent mechanical properties, high-temperature stability, chemical resistance, flame retardancy, abrasion resistance, and processability. The relative density of this high-performance polymer is 1.36 g / cm³. 3 The crystallization temperature (Tc) is approximately 110-130℃, and the melting temperature (Tm) is approximately 285℃.

[0003] Conventionally, polyphenylene sulfide (PPS) particles obtained through polymerization contain encapsulated oligomers, salts, and unreacted monomers, necessitating a cleaning process. Currently, the cleaning process primarily involves mixing PPS with a solvent or water and electrically heating the mixture to over 100 degrees Celsius. This causes the PPS molecular chains to extend, releasing the encapsulated oligomers, salts, and unreacted monomers into the solvent or water. The cleaned PPS is then obtained through filtration. However, this method has low impurity removal efficiency, requires multiple repeated cleaning cycles, consumes large amounts of solvent and water, and increases production costs. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the shortcomings of existing methods for removing impurities from mixtures containing polyphenylene sulfide (PPS), which are characterized by low efficiency, complex operation, and high cost. This invention provides a method for purifying mixtures containing PPS. The purification method for PPS mixtures of this invention is highly efficient and low-cost, and the obtained purified PPS has a yellowness of no more than 7 and a salt content of less than 0.3%.

[0005] This invention provides a method for purifying a mixture containing polyphenylene sulfide, comprising the following steps:

[0006] S1. The mixture containing polyphenylene sulfide is first washed with an organic solvent to obtain a first intermediate product; the first washing is carried out under microwave heating at a temperature of 60-150°C.

[0007] S2. The first intermediate product is washed a second time with an aqueous acid solution to obtain a second intermediate product;

[0008] S3. The second intermediate product is washed with water to obtain a purified polyphenylene sulfide; the third washing is performed under microwave heating at a temperature of 60-150°C.

[0009] In this invention, preferably, the salt content of the polyphenylene sulfide-containing mixture is not less than 15%, for example, 20%.

[0010] The salt content is determined based on the ash content, and the ash content testing method includes the following steps: placing a porcelain crucible in a muffle furnace at a constant temperature of 200°C and firing it to a constant weight, then removing it and placing it in a desiccator to cool before weighing it, which is recorded as M0; placing a certain amount of sample in the crucible, weighing the total weight of the crucible and the sample, which is recorded as M1; then placing the crucible in a muffle furnace at a constant temperature of 800°C and firing it for 4 hours, removing it and placing it in a desiccator to cool before weighing it, which is recorded as M2; the ash content is (M2-M0) / (M1-M0)*100%.

[0011] In step S1 of the present invention, preferably, the microwave frequency of the microwave heating is 0.9-2.5 GHz, for example 2.1 GHz.

[0012] In step S1 of the present invention, preferably, the microwave power of the microwave heating is 1-10kW, for example 7kW.

[0013] In step S1 of the present invention, preferably, the microwave wavelength of the microwave heating is 0.33-0.12m, for example 0.14m.

[0014] In step S1 of the present invention, preferably, the temperature of the microwave heating is 60-100℃ or 150℃, for example, 60℃, 80℃ or 100℃.

[0015] In step S1 of the present invention, preferably, the microwave heating time is 20-300 min; preferably, the microwave heating time is 0.5-2 h, for example, 0.5 h or 1 h.

[0016] In step S3 of the present invention, preferably, the microwave frequency of the microwave heating is 0.9-2.5 GHz, for example 2.1 GHz.

[0017] In step S3 of the present invention, preferably, the microwave power of the microwave heating is 1-10kW, for example 7kW.

[0018] In step S3 of the present invention, preferably, the microwave wavelength of the microwave heating is 0.33-0.12m, for example 0.14m.

[0019] In step S3 of the present invention, preferably, the temperature of the microwave heating is 60-100℃ or 150℃, for example, 60℃, 80℃ or 100℃.

[0020] In step S3 of the present invention, preferably, the microwave heating time is 20-300 min; preferably, the microwave heating time is 0.5-2 h, for example, 0.5 h or 1 h.

[0021] In step S1 of the present invention, preferably, the organic solvent is selected from one or more of N-methyl-2-pyrrolidone, acetone, methanol, xylene, and ethylene glycol.

[0022] In step S1 of the present invention, preferably, the mass ratio of the organic solvent to the mixture containing polyphenylene sulfide is (0.5-2):1, for example 1:1.

[0023] In step S1 of the present invention, preferably, a filtration step is included after the first washing.

[0024] In step S2 of the present invention, preferably, the aqueous solution of the acid is an aqueous solution of hydrochloric acid and / or acetic acid.

[0025] In step S2 of the present invention, preferably, the mass percentage of the acid in the aqueous solution of the acid is 0.1%-10%, for example 6%.

[0026] In step S2 of the present invention, preferably, a filtration step is included after the second washing.

[0027] In step S3 of the present invention, preferably, the water is deionized water.

[0028] In step S3 of the present invention, preferably, the mass ratio of the water to the mixture containing polyphenylene sulfide is (1-5):1, for example 2:1.

[0029] In step S3 of the present invention, preferably, a filtration step is included after the third washing.

[0030] In this invention, preferably, in step S3, the third washing is repeated once or more, for example, twice or three times.

[0031] In this invention, preferably, step S3 further includes a drying step after the third washing.

[0032] In this invention, the mixture containing polyphenylene sulfide is generally a polyphenylene sulfide product prepared by a polyphenylene sulfide preparation method and without post-treatment.

[0033] In this invention, preferably, the method for preparing the mixture containing polyphenylene sulfide includes the following steps:

[0034] a. Sodium sulfide pentahydrate, an aqueous solution of alkali metal hydroxide, an auxiliary agent, and N-methyl-2-pyrrolidone are mixed, heated to 150-200°C for dehydration, and then cooled to 160-180°C; wherein the mixing container is a reaction vessel.

[0035] b. Add p-dichlorobenzene and N-methyl-2-pyrrolidone to the material obtained in step a, raise the temperature to start the polymerization reaction, gradually increase the internal pressure from atmospheric pressure to 0.5-2 MPa, and maintain the temperature and pressure for 2-5 hours.

[0036] c. After the polymerization reaction described in step b is completed, the temperature is lowered to 100-150℃ to obtain a polyphenylene sulfide reaction solution, which is then filtered to obtain a mixture containing polyphenylene sulfide.

[0037] In step a, preferably, the concentration of the alkali metal hydroxide in the aqueous solution of the alkali metal hydroxide is 40-55 wt%; and the molar amount of the alkali metal hydroxide is 0.01-0.25 mol, based on the molar amount of sulfur in the sodium sulfide pentahydrate being 1.0 mol.

[0038] In step a, preferably, the alkali metal hydroxide aqueous solution is a sodium hydroxide aqueous solution.

[0039] In step a, preferably, the auxiliary agent is an alkali metal salt and / or a fatty acid salt, and the molar amount of the auxiliary agent is 0-0.5 mol, based on the molar amount of sulfur in the sodium sulfide pentahydrate being 1.0 mol.

[0040] More preferably, the alkali metal salt is selected from one or more of lithium chloride, lithium phosphate, and sodium phosphate;

[0041] More preferably, the fatty acid salt is selected from one or more of lithium acetate, sodium acetate, sodium propionate, sodium butyrate, sodium hexanoate, sodium laurate, sodium decanoate, and tetrasodium iminodisuccinate.

[0042] In step a, preferably, with the molar amount of sulfur in the sodium sulfide pentahydrate being 1.0 mol, the molar amount of N-methyl-2-pyrrolidone is 1.5-4 mol, for example, 3.5 mol.

[0043] In step a, preferably, the endpoint of the dehydration is when the molar ratio of water to sulfur in the system is 0.1-3.5.

[0044] In step b, preferably, with a total sulfur molar amount of 1.0 mol in the system, the molar amount of p-dichlorobenzene is 0.99-1.05 mol.

[0045] In step b, preferably, with a total sulfur molar amount of 1.0 mol in the system, the molar amount of N-methyl-2-pyrrolidone is 1-2 mol, for example, 1.5 mol.

[0046] In step b, preferably, the temperature is increased to 240-280°C at a rate of 0.5-3°C / min, for example, the temperature of the reaction system is slowly increased from 170°C to 240-280°C within 2 hours.

[0047] In step c, preferably, the filtration is to filter the polyphenylene sulfide reaction solution through a 50-200 mesh sieve.

[0048] In step c, preferably, the filtration process further includes a drying step. The drying method is, for example, spin drying.

[0049] In this invention, preferably, the yellowness of the purified polyphenylene sulfide is not greater than 7, for example 6, 6.3, 6.5, 6.8 or 7.

[0050] In this invention, preferably, the salt content of the purified polyphenylene sulfide is less than 0.3%, for example, 0.10%, 0.14%, 0.15%, 0.19%, 0.23%, 0.25%, or 0.26%.

[0051] The present invention also provides a purified polyphenylene sulfide, which is obtained by the purification method of the polyphenylene sulfide-containing mixture described above.

[0052] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0053] The reagents and raw materials used in this invention are all commercially available.

[0054] The positive and progressive effects of this invention are as follows:

[0055] This invention provides a method for purifying mixtures containing polyphenylene sulfide (PPS), which employs microwave heating. Compared to conventional electric heating, microwaves promote intermolecular movement, enhancing the release of oligomers, salts, and unreacted monomers from PPS particles while achieving the desired heating effect. This results in a purified PPS product with a yellowness of no more than 7 and a salt content of less than 0.3%. Furthermore, this purification method improves impurity removal efficiency, reduces the number of washing cycles, and successfully lowers post-processing costs by more than 50%.

[0056] Furthermore, the purification method for polyphenylene sulfide mixtures of the present invention, compared with ultrasonic cleaning, does not require the addition of organic solvents other than NMP and water, thus reducing the difficulty and cost of solvent recovery. Detailed Implementation

[0057] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0058] Methods for testing salt content:

[0059] Salt content is determined based on ash content. A porcelain crucible is placed in a muffle furnace at 200℃ and fired until constant weight. It is then removed, cooled in a desiccator, and weighed, denoted as M0. A certain amount of sample is placed in the crucible, and the total weight of the crucible and sample is recorded as M1. The crucible is then placed in a muffle furnace at 800℃ and fired for 4 hours. It is then removed, cooled in a desiccator, and weighed, denoted as M2. The ash content is (M2-M0) / (M1-M0)*100%.

[0060] Methods for testing yellowness:

[0061] Yellowness was measured using an X-Rite CI7830 benchtop spectrophotometer.

[0062] The polyphenylene sulfide-containing mixtures used in the embodiments and comparative examples of this invention were all prepared by the following method:

[0063] In a 20L reactor, add 5254g (53.00mol) of N-methylpyrrolidone (hereinafter referred to as NMP), 136.51g (1.50mol) of 45% sodium hydroxide aqueous solution, 2547.29g (15.05mol) of sodium sulfide pentahydrate and 682.67g (4.97mol) of auxiliary agent. Under the stirring speed of 200rpm and nitrogen protection, heat to 190℃ to remove 1600g of aqueous solution. After dehydration, cool to 150℃.

[0064] 2324.79 g (15.79 mol) of p-dichlorobenzene (hereinafter referred to as PDCB) and 2206 g (22.25 mol) of NMP were added to the above-mentioned reaction vessel. The temperature was slowly raised to 270℃ and held for 4 hours; after the holding time was completed, the reaction system was cooled to 110℃. The material in the vessel was centrifuged and filtered through a 100-mesh sieve and dried to obtain a mixture containing polyphenylene sulfide with a salt content of 20%.

[0065] In the microwave heating described in the following embodiments and comparative examples of the present invention, the microwave frequency is 2.1 GHz, the power is 7 kW, and the wavelength is 0.14 m.

[0066] Example 1

[0067] Weigh 100g of the obtained polyphenylene sulfide-containing mixture, add an equal mass of NMP, and microwave-heat to 80℃ for a first wash of 0.5h. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave-heat to 80℃ for a third wash of 0.5h, then filter. Repeat this third wash twice, and dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide was found to have a salt content of 0.15% and a yellowness of 6.

[0068] Example 2

[0069] Weigh 100g of the obtained polyphenylene sulfide mixture, add an equal mass of acetone, and microwave to 60℃ for a first wash of 0.5h. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave to 60℃ for a third wash of 0.5h, then filter. Repeat this third wash twice, and dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide has a salt content of 0.23% and a yellowness of 6.3.

[0070] Example 3

[0071] Weigh 100g of the obtained polyphenylene sulfide-containing mixture, add an equal mass of NMP, and microwave-heat to 60℃ for a first wash of 0.5h. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave-heat to 60℃ for a third wash of 0.5h, then filter. Repeat the third wash twice, and dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide had a salt content of 0.26% and a yellowness of 6.5.

[0072] Example 4

[0073] Weigh 100g of the polyphenylene sulfide-containing mixture obtained above, add an equal mass of NMP, and microwave-heat to 100℃ for a first wash of 0.5h. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave-heat to 100℃ for a third wash of 0.5h, then filter. Repeat the third wash twice, and dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide had a salt content of 0.1% and a yellowness of 6.8.

[0074] Example 5

[0075] Weigh 100g of the polyphenylene sulfide-containing mixture obtained above, add an equal mass of NMP, and microwave-heat to 150℃ for a first wash of 0.5h. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave-heat to 150℃ for a third wash of 0.5h, then filter. Repeat the third wash twice, and dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide was found to have a salt content of 0.1% and a yellowness of 7.

[0076] Example 6

[0077] Weigh 100g of the above-obtained mixture containing polyphenylene sulfide, add an equal mass of NMP, and microwave to 80℃ for a first wash of 1 hour. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave to 80℃ for a third wash of 1 hour, then filter. Repeat this third wash twice, and dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide was found to have a salt content of 0.15% and a yellowness of 6.

[0078] Example 7

[0079] Weigh 100g of the obtained polyphenylene sulfide-containing mixture, add an equal mass of NMP, and microwave-heat to 80℃ for a first wash of 0.5h. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave-heat to 80℃ for a third wash of 0.5h, then filter. Repeat the third wash once, and dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide had a salt content of 0.19% and a yellowness of 7.

[0080] Example 8

[0081] Weigh 100g of the above-obtained mixture containing polyphenylene sulfide, add an equal mass of NMP, and microwave-heat to 80℃ for a first wash of 0.5h. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave-heat to 80℃ for a third wash of 0.5h, then filter. Repeat this third wash three times, and dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide was found to have a salt content of 0.14% and a yellowness of 6.

[0082] Example 9

[0083] Weigh 100g of the obtained polyphenylene sulfide (PPS) mixture, add an equal mass of NMP, and microwave-heat to 60°C for a first wash of 5 hours. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave-heat to 60°C for a third wash of 5 hours, then filter. Repeat this third wash twice, and dry to obtain the purified PPS. The purified PPS contained 0.25% salt and had a yellowness of 7.

[0084] Comparative Example 1

[0085] Weigh 100g of the polyphenylene sulfide-containing mixture obtained above, add an equal mass of NMP, and microwave-heat to 40℃ for a first wash of 0.5h. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave-heat to 40℃ for a third wash of 0.5h, then filter. Repeat the third wash twice, and dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide was found to have a salt content of 1.35% and a yellowness of 8.

[0086] Comparative Example 2

[0087] Weigh 100g of the above-obtained mixture containing polyphenylene sulfide, add an equal mass of NMP, and perform a first wash at 60℃ for 0.5h by electric heating. Filter to obtain the first intermediate product. Then, perform a second wash and filter the first intermediate product with 6% dilute hydrochloric acid solution to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and perform a third wash at 60℃ for 0.5h by electric heating. Filter. Repeat the third wash twice. Dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide has a salt content of 1.25% and a yellowness of 12.

[0088] Comparative Example 3

[0089] Weigh 100g of the above-obtained mixture containing polyphenylene sulfide, add an equal mass of NMP, and perform a first wash at 80℃ for 0.5h by electric heating. Filter to obtain the first intermediate product. Then, perform a second wash and filter the first intermediate product with 6% dilute hydrochloric acid solution to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and perform a third wash at 80℃ for 0.5h by electric heating. Filter. Repeat the third wash twice. Dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide has a salt content of 0.67% and a yellowness of 10.

[0090] Comparative Example 4

[0091] Weigh 100g of the polyphenylene sulfide-containing mixture obtained above, add an equal mass of NMP, heat to 80℃ while sonicating at 25kHz, perform a first wash for 0.5h, filter, and obtain the first intermediate product; then perform a second wash with 6% dilute hydrochloric acid solution, filter, and obtain the second intermediate product; finally, mix 200g of deionized water with the second intermediate product, heat to 80℃ while sonicating at 25kHz, perform a third wash for 0.5h, filter; repeat the third wash twice, dry, and obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide was found to have a salt content of 0.59% and a yellowness of 8.

[0092] Comparative Example 5

[0093] Weigh 100g of the above-obtained mixture containing polyphenylene sulfide, add an equal mass of NMP, and microwave-heat to 80℃ for a first wash of 15 min. Filter to obtain the first intermediate product. Then, wash the first intermediate product a second time with 6% dilute hydrochloric acid solution and filter to obtain the second intermediate product. Finally, mix 200g of deionized water with the second intermediate product and microwave-heat to 80℃ for a third wash of 15 min, then filter. Repeat this third wash twice, and dry to obtain the purified polyphenylene sulfide. The purified polyphenylene sulfide was found to have a salt content of 1.59% and a yellowness of 15.

Claims

1. A method for purifying a mixture containing polyphenylene sulfide, characterized in that, It includes the following steps: S1. The mixture containing polyphenylene sulfide is first washed with an organic solvent to obtain a first intermediate product; the first washing is carried out under microwave heating at a temperature of 60-150°C. S2. The first intermediate product is washed a second time with an aqueous acid solution to obtain a second intermediate product; S3. The second intermediate product is washed with water to obtain the purified polyphenylene sulfide. The third washing is performed under microwave heating at a temperature of 60-150°C.

2. The purification method for a mixture containing polyphenylene sulfide as described in claim 1, characterized in that, The salt content of the polyphenylene sulfide-containing mixture is not less than 15%, for example, 20%.

3. The purification method for a mixture containing polyphenylene sulfide as described in claim 1, characterized in that, It satisfies one or more of the following conditions: (1) In step S1, the microwave frequency of the microwave heating is 0.9-2.5GHz, for example 2.1GHz; (2) In step S1, the microwave power of the microwave heating is 1-10kW, for example 7kW; (3) In step S1, the microwave wavelength of the microwave heating is 0.33-0.12m, for example 0.14m; (4) In step S1, the temperature of microwave heating is 60-100℃ or 150℃, for example, 60℃, 80℃ or 100℃; (5) In step S1, the microwave heating time is 20-300 min; preferably, the microwave heating time is 0.5-2 h, for example 0.5 h or 1 h; (6) In step S3, the microwave frequency of the microwave heating is 0.9-2.5GHz, for example 2.1GHz; (7) In step S3, the microwave power of the microwave heating is 1-10kW, for example 7kW; (8) In step S3, the microwave wavelength of the microwave heating is 0.33-0.12m, for example 0.14m; (9) In step S3, the temperature of microwave heating is 60-100℃ or 150℃, for example, 60℃, 80℃ or 100℃; (10) In step S3, the microwave heating time is 20-300 min; preferably, the microwave heating time is 0.5-2 h, for example 0.5 h or 1 h.

4. The purification method for a mixture containing polyphenylene sulfide as described in claim 1, characterized in that, It satisfies one or more of the following conditions: (1) In step S1, the organic solvent is selected from one or more of N-methyl-2-pyrrolidone, acetone, methanol, xylene and ethylene glycol; (2) In step S1, the mass ratio of the organic solvent to the mixture containing polyphenylene sulfide is (0.5-2):1, for example 1:1; (3) In step S1, the first washing is followed by a filtration step.

5. The purification method for a mixture containing polyphenylene sulfide as described in claim 1, characterized in that, It satisfies one or more of the following conditions: (1) In step S2, the aqueous solution of the acid is an aqueous solution of hydrochloric acid and / or acetic acid; (2) In step S2, the mass percentage of the acid in the aqueous solution is 0.1%-10%, for example 6%; (3) In step S2, the second washing is followed by a filtration step.

6. The method for purifying a mixture containing polyphenylene sulfide as described in claim 1, characterized in that, It satisfies one or more of the following conditions: (1) In step S3, the water is deionized water; (2) In step S3, the mass ratio of the water to the mixture containing polyphenylene sulfide is (1-5):1, for example 2:1; (3) In step S3, the third washing is followed by a filtration step.

7. The method for purifying a mixture containing polyphenylene sulfide as described in claim 1, characterized in that, It satisfies conditions (1) and / or (2) below: (1) In step S3, the third washing is repeated once or more, for example, twice or three times. (2) In step S3, the third washing also includes a drying step.

8. The method for purifying a mixture containing polyphenylene sulfide as described in claim 1, characterized in that, The method for preparing the mixture containing polyphenylene sulfide includes the following steps: a. Sodium sulfide pentahydrate, an aqueous solution of alkali metal hydroxide, an auxiliary agent, and N-methyl-2-pyrrolidone are mixed, heated to 150-200°C for dehydration, and then cooled to 160-180°C; wherein the mixing container is a reaction vessel. b. Add p-dichlorobenzene and N-methyl-2-pyrrolidone to the material obtained in step a, raise the temperature to start the polymerization reaction, gradually increase the internal pressure from atmospheric pressure to 0.5-2 MPa, and maintain the temperature and pressure for 2-5 hours. c. After the polymerization reaction described in step b is completed, the temperature is lowered to 100-150℃ to obtain a polyphenylene sulfide reaction solution, which is then filtered to obtain a mixture containing polyphenylene sulfide.

9. The method for purifying a mixture containing polyphenylene sulfide as described in claim 1, characterized in that, It satisfies one of the following conditions (1) and / or (2): (1) The yellowness of the purified polyphenylene sulfide is not greater than 7, for example 6, 6.3, 6.5, 6.8 or 7; (2) The salt content of the purified polyphenylene sulfide is less than 0.3%, for example, 0.10%, 0.14%, 0.15%, 0.19%, 0.23%, 0.25% or 0.26%.

10. A purified polyphenylene sulfide, characterized in that, It is obtained by the purification method of the mixture containing polyphenylene sulfide as described in any one of claims 1-9.