A method for manufacturing cross-linked polyphenylene sulfide

Abstract

This invention discloses a method for manufacturing cross-linked polyphenylene sulfide (PPS). In the later stage of the polymerization reaction for preparing linear PPS, a specific cross-linking accelerator is added to the system. After continued heating, flash evaporation is performed. This allows the specific cross-linking accelerator to not only be uniformly dispersed in the PPS resin particles, but also to be partially encapsulated by the PPS, making it less susceptible to removal during subsequent purification processes such as washing. In particular, the specific cross-linking accelerator of this invention has a high boiling point and is not easily soluble in water, thus being fully retained in the product. This significantly improves the thermo-oxidative treatment efficiency of the PPS particles, enabling the desired degree of cross-linking to be achieved in a shorter time, and resulting in a product with low gel content.

Description

Technical Field

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

[0002] Polyphenylene sulfide (PPS) is a thermoplastic resin with phenylene sulfide groups in its molecular backbone. It is a crystalline polymer. PPS is a high-performance engineering plastic widely used in various electronic and electrical components, mechanical parts, and automotive components. Currently, commercially available PPS resins can be mainly divided into two categories based on their chain structure: linear PPS resins and cross-linked PPS resins. Linear PPS resins are obtained directly through high-temperature, high-pressure polymerization followed by separation and purification. Cross-linked PPS resins are produced by further treating linear PPS resins with solid-state thermo-oxidative processes. As the thermo-oxidative cross-linking proceeds, the melt flowability of the resin continuously decreases until the target value is reached, at which point the material is discharged. In this production method, excessively long thermo-oxidative treatment times significantly reduce production efficiency.

[0003] Adding crosslinking accelerators is a widely reported method in patents to increase the thermo-oxidative crosslinking rate of PPS resin. Types of crosslinking accelerators include: R-SH (US Patent No. 3,386,950), mixtures of sulfur, thiuram polysulfides, and organic peroxides (US Patent No. 3,699,087), hexamethoxymethyl melamine (US Patent No. 3,998,767), and aromatic compounds (JP1,999,246,761A). However, all these methods suffer from the problem of uneven mixing and residue of the crosslinking accelerator, which can negatively impact product quality.

[0004] Patent JP1989240529A reports a high-pressure acid washing treatment of PPS resin during the post-processing of PPS after polymerization. Compared with high-pressure water washing, the crosslinking of PPS raw powder is significantly accelerated, but acid washing reduces the thermal stability of the resin and produces more gel in the crosslinked product.

[0005] Patent JP1987325279 (or EP1988312268) reported that PPS was dissolved in NMP, sodium hydroxide was added to the solution, and the mixture was kept at a certain temperature for a period of time before separation and purification. The crosslinking speed of the PPS resin after treatment was significantly increased. However, this method would make the post-processing of the product more complicated and increase solvent and energy consumption.

[0006] Patent JP2020084132A reports that mixing a small amount of ozone (<1200ppm) into the nitrogen-oxygen mixture used in thermo-oxidative crosslinking can shorten the time required for thermo-oxidative crosslinking. However, the introduction of ozone will make the production process and equipment more complicated, and the introduction of ozone will also bring more safety risks.

[0007] In summary, the existing methods for preparing cross-linked PPS mainly shorten the cross-linking time by adding cross-linking accelerators during thermo-oxidative cross-linking. However, the cross-linking accelerators and PPS particles are difficult to mix evenly, resulting in excessively fast local cross-linking speed and deep cross-linking degree, uneven product, and excessively high gel content in the product. Summary of the Invention

[0008] The purpose of this invention is to overcome one or more shortcomings in the prior art and provide an improved method for manufacturing cross-linked polyphenylene sulfide. This method can achieve the desired degree of cross-linking in a shorter time, shorten the thermo-oxidative treatment time, improve production efficiency, and produce products with stable and high quality and relatively low gel content.

[0009] To achieve the above objectives, the present invention provides a technical solution: a method for manufacturing cross-linked polyphenylene sulfide, the method comprising:

[0010] (1) The sulfur source, polycondensation aid and first polar organic solvent are mixed and dehydrated to obtain a dehydrated liquid. The dehydrated liquid, dihaloaromatic compound and second polar organic solvent are mixed and polymerized to obtain a reaction mixture.

[0011] (2) The crosslinking accelerator is added to the reaction mixture, kept warm under a protective atmosphere, flash evaporated after the reaction is completed, and then dried under a protective atmosphere to obtain a crude product; wherein the crosslinking accelerator is selected from at least one of the compounds shown in formula (I): In equation (Ⅰ), R1 and R2 are independently selected from -Cl and -O. - M + -S - M + Alkyl mono- or di-substituted amino groups, -NR3R4, where R3 is -R5COOM, and R4 and R5 are independently selected from C 1-6 Alkyl group, M is sodium, potassium or lithium, and n is selected from 1, 2, 3, 4 or 5;

[0012] (3) The crude product is washed with water, acid washed, dried, and then subjected to thermal oxygen treatment in a crosslinking atmosphere to obtain crosslinked polyphenylene sulfide.

[0013] According to some preferred aspects of the present invention, a method for preparing the crosslinking accelerator includes: reacting the compound represented by formula (II) with a modifier to generate the crosslinking accelerator;

[0014] In equation (II), R ’ R ’’ Independently selected from -SH, -OH, -NH2, -Cl;

[0015] When R ’ R’’ When -SH and / or -OH are present, the modifier includes at least one selected from sodium hydroxide, potassium hydroxide, and lithium hydroxide;

[0016] When R ’ R ’’ When -NH2 is present, the modifier includes a haloalkyl group;

[0017] When R ’ R ’’ When -Cl is present, the modifier includes In equation (Ⅲ), R4 is selected from C 1-6 Alkyl group, n is selected from 1, 2, 3, 4 or 5, R6 is C 1-6 Alkyl group, and the reaction is carried out in an aqueous solution of sodium hydroxide, potassium hydroxide, or lithium hydroxide.

[0018] In some embodiments of the present invention, the haloalkyl group may be selected from chlorinated, brominated, etc., and may be monosubstituted or polysubstituted. Further, the haloalkyl group may include, but is not limited to, bromomethane, bromoethane, bromopropane, chloroethane, chloromethane, etc.

[0019] In this invention, C 1-6 Alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, etc.

[0020] Furthermore, the alkyl mono- or di-substituted amino group can be C 1-20 Alkyl mono- or di-substituted amino groups. C 1-20 Alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, nonyl, etc.

[0021] According to some preferred and specific aspects of the present invention, the crosslinking accelerator is selected from sodium 4,4'-dithiophenol phenyl sulfide (structural formula: ), 4,4'-diphenol sodium phenyl sulfide (structural formula: ), 4,4'-(1,4-phenylene di(thio))-N,N-diethyl-diphenylamine (structural formula: Sodium N,N-methyl-(4'-chlorophenyl sulfide)butyrate (structural formula: One or more combinations of )

[0022] According to some preferred aspects of the present invention, the molar ratio of the added crosslinking accelerator to the added sulfur source is 0.0002-0.01:1.

[0023] According to some preferred aspects of the present invention, in step (2), the drying process is controlled until the material temperature reaches 230-240°C.

[0024] According to some preferred aspects of the present invention, in step (2), the heat preservation time is 1-20 min, preferably 5-15 min.

[0025] According to some preferred aspects of the present invention, in step (3), the pickling is carried out using an aqueous acetic acid solution, and further, the mass concentration of the aqueous acetic acid solution is 0.01wt.%-0.5wt.%.

[0026] In this invention, in step (3), the first water washing (e.g., atmospheric pressure water washing) mainly removes highly water-soluble byproducts such as sodium chloride. However, in practice, the accelerator uniformly coated in the product particles may be washed away during high-temperature water washing. This invention reduces or even avoids the removal of crosslinking accelerators during high-temperature water washing by adding a small amount of acetic acid in the form of an aqueous acetic acid solution during high-temperature washing. According to some preferred aspects of this invention, in step (3), the temperature of the thermal oxygen treatment is 200-230°C, and the oxygen content of the crosslinking atmosphere is 8%-21%.

[0027] In some embodiments of the present invention, in step (1), the molar ratio of the added polycondensation aid to the added sulfur source is 0.97-1.01:1.

[0028] In some embodiments of the present invention, in step (1), the molar ratio of water to sulfur in the dehydration liquid is 1.0:1-1.3:1.

[0029] In some embodiments of the present invention, in step (1), the sulfur source is selected from sodium hydrosulfide and / or potassium hydrosulfide. Further, the sulfur source can be added in the form of an aqueous solution.

[0030] In some embodiments of the present invention, in step (1), the polycondensation aid includes at least an alkali metal hydroxide, further comprising sodium hydroxide and / or potassium hydroxide, and even further comprising the polycondensation aid added in the form of an aqueous solution.

[0031] Furthermore, in some embodiments of the present invention, in step (1), the polycondensation aid further includes other aids, which are at least one selected from sodium acetate, sodium benzoate, and sodium C5-C6 fatty acids. Preferably, the molar ratio of the other aids to the sulfur source is 0.01-0.1:1.

[0032] In some embodiments of the present invention, in step (1), the dihaloaromatic compound is selected from at least one of p-dichlorobenzene, dichloronaphthalene, dichlorofluorene, and dichlorocarbazole; further, the molar ratio of the dihaloaromatic compound to the sulfur source is 1.03-1.06:1.

[0033] In some embodiments of the present invention, in step (1), the first polar organic solvent and the second polar organic solvent are both selected from organic amides. Further, the organic amide is at least one selected from N-methylpyrrolidone, triammonium hexamethylphosphate, and N-methyl-ε-caprolactam.

[0034] In some embodiments of the present invention, in step (1), the polymerization reaction is carried out in an oxygen-free atmosphere.

[0035] In this invention, based on the above-mentioned raw materials, the linear polyphenylene sulfide contained in the crude product prepared by this invention may contain end groups such as chlorine end groups and sodium thiolate end groups;

[0036] When chlorine is selected in R1 or R2, it may be attached to the linear polyphenylene sulfide via a terminal sodium thiolate contained in the linear polyphenylene sulfide and by a substitution reaction.

[0037] When -O is selected in R1 or R2 - M + -S - M + At that time, it may be attached to the linear polyphenylene sulfide via the terminal chlorine contained in the linear polyphenylene sulfide and through a substitution reaction.

[0038] Another technical solution provided by the present invention: a cross-linked polyphenylene sulfide produced by the above-described method for manufacturing cross-linked polyphenylene sulfide.

[0039] Another technical solution provided by the present invention is the application of the above-described cross-linked polyphenylene sulfide in the preparation of electronic and electrical components, mechanical components or automotive components.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects:

[0041] This invention addresses the shortcomings of existing cross-linked polyphenylene sulfide (PPS) preparation processes, such as long thermo-oxidative treatment times, excessively rapid local cross-linking leading to uneven product quality, high gel content, and complex equipment or processes. It innovatively provides an improved manufacturing method. This method involves adding a specific cross-linking accelerator to the system in the later stages of the polymerization reaction, followed by continued heat preservation and flash evaporation. This allows the specific cross-linking accelerator to not only be uniformly dispersed in the PPS resin particles but also to be partially encapsulated by the PPS, making it less susceptible to removal during subsequent purification processes such as washing. In particular, the specific cross-linking accelerator of this invention has a high boiling point and is not easily soluble in water, thus being fully retained in the product. This significantly improves the thermo-oxidative treatment efficiency of the PPS particles, achieving the desired degree of cross-linking in a shorter time, and resulting in a product with low gel content. Detailed Implementation

[0042] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0043] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0044] The following describes the melt flow rate (MFR) test: Following the national standard GB / T3682-2000, the melt flowability of PPS resin was tested using a German GOTTFERTMI-2.2 instrument at a test temperature of 315.6℃. 8g of dried sample was weighed and quickly added to the barrel, compacted with the injection rod, and a piston rod and 5kg load weight were added. The mixture was preheated for 5 minutes, then the lower ejector pin was removed, allowing the sample to flow naturally. When the lower mark on the piston rod just disappeared from view, it was cut with scissors, and the outflow was collected in a bowl while a stopwatch was started. When the upper mark on the piston rod disappeared from view, it was cut again with scissors, and the timing was stopped. The bowl was removed. The mass M (g) of the sample was weighed using a balance, and the stopwatch recording time t (s) was read. Therefore, MFR (g / 10min) = M*600 / t.

[0045] The following describes the gel content test for the product: Weigh 20g of the crosslinking agent, add 200ml of α-chloronaphthalene, heat to 240℃ to fully dissolve, filter while hot using glass fiber filter paper, then remove the filter paper and the above components together, add to 100ml of α-chloronaphthalene, heat again to dissolve, then filter again and dry under vacuum. Finally, remove both filter papers and the gel on them together, vacuum dry, and weigh. The weight is recorded as W. g The weight of the two glass fiber filter papers weighed beforehand is W.F Then the gel content △W g = (W g -W F ) / 20◊100%, where W is the weight of the initial sample.

[0046] In the following, the volatile matter content △W r = (W1-W2) / W1◊100%, where W1 is the weight of the sample after drying at 120℃ for 1 hour, and W2 is the weight of the sample after drying at 320℃ for another hour.

[0047] In the following description, the crosslinking atmosphere is a mixture of nitrogen and oxygen. The oxygen content is by volume percentage.

[0048] Example 1:

[0049] In a 100L reactor, add 19.8 kg (200.0 mol) of N-methylpyrrolidone, 10.0 kg (100.0 mol) of a 40% sodium hydroxide aqueous solution, and 14.02 kg (100.0 mol) of a 40% sodium hydrosulfide aqueous solution. Heat to 210℃ and continuously remove water during the heating process until 14.0 kg of the aqueous solution (98.0% water content) is removed. Then cool down to 160℃.

[0050] 15 kg (102.0 mol) of p-dichlorobenzene and 13.17 kg (133 mol) of NMP were added to the above-mentioned reactor. The temperature was increased to 260°C at a rate of 0.5°C / min and held for 2 hours. Then, 58.8 g (0.2 mol) of sodium 4,4'-dithiol phenyl sulfide was added. The reaction was continued for 10 minutes under a nitrogen atmosphere before flash evaporation was started. After flash evaporation, the product was dried under a nitrogen atmosphere until the material temperature reached 235°C, yielding 20.9 kg of crude product. The sodium 4,4'-dithiol phenyl sulfide was prepared as follows: 274 g (1 mol) of 4,4'-dithiol phenyl sulfide and 250 mL of NMP. 8 mol / L sodium hydroxide aqueous solution and 1 L acetonitrile were added to a glass bottle equipped with a stirrer, heated to 70°C and stirred for 1 hour. Acetonitrile was removed by rotary evaporation, and then 1 L acetone was added. After filtration, the filter cake was washed three times with water at room temperature and then dried to obtain 4,4'-dithiol sodium phenyl sulfide.

[0051] Add 50 kg of deionized water to the dried flash-evaporated crude product, stir and wash thoroughly at 65°C, then filter and rinse. Add another 50 kg of 0.05 wt.% acetic acid aqueous solution to the filter cake, heat to 150°C, hold for half an hour, then cool, filter, rinse, and dry to obtain linear PPS product with an MFR of 5000 g / 10 min. Place the dried PPS in a crosslinker equipped with a stirrer, dust removal bag, and heat transfer oil jacket. The heat transfer oil jacket temperature is 220°C, and crosslinking gas with an oxygen content of 16% and a temperature of 220°C is introduced for 12 hours to obtain PPS crosslinked product CPPS-1 with an MFR of 280 g / 10 min, volatile matter of 0.52 wt.%, and gel content of 0.42 wt.%.

[0052] Example 2:

[0053] The only difference between this example and Example 1 is that after holding the temperature for 2 hours, 87.2g of 4,4'-(1,4-phenylene di(sulfide))-N,N-diethyl-diphenylamine (0.2mol) was added to the reactor, and the reaction was continued for 10 minutes under a nitrogen atmosphere before the material was discharged and flash evaporated.

[0054] 4,4'-(1,4-phenylene di(sulfide))-N,N-diethyl-diphenylamine was prepared as follows: 324 g (1 mol) of 4,4'-(1,4-phenylene di(sulfide))-diphenylamine, 1.5 kg of dichloromethane, 528 g (4.4 mol) of bromoethane, and 445 g (4.4 mol) of triethylamine were added to a reaction vessel, sealed, heated to 50°C, kept at that temperature for 12 hours, and then cooled to room temperature. The precipitated salt was removed by filtration, and then the solvent, residual bromoethane, and triethylamine were removed by rotary evaporation to obtain the crude product. The crude product was purified by column chromatography to obtain 4,4'-(1,4-phenylene di(sulfide))-N,N-diethyl-diphenylamine.

[0055] The reaction formula for preparing 4,4'-(1,4-phenylene di(thio))-N,N-diethyl-diphenylamine is as follows:

[0056] .

[0057] Finally, PPS crosslinked product CPPS-2 was obtained, with an MFR of 340 g / 10 min, volatile matter of 0.58 wt.%, and gel content of 0.4 wt.%.

[0058] Example 3:

[0059] The only difference between this example and Example 1 is that after holding the temperature for 2 hours, 71.5g of sodium N,N-methyl-(4'-chlorophenyl sulfide)butyrate (0.2mol) was added to the reactor, and the reaction was continued for 10 minutes under a nitrogen atmosphere before the material was discharged and flash evaporated.

[0060] Sodium N,N-methyl-(4'-chlorophenyl sulfide)butyrate was prepared as follows: 255 g (1 mol) of 4,4'-dichlorophenyl sulfide, 80 g of sodium hydroxide (2 mol), 100 g of water and 2 kg of N-methylpyrrolidone were added to a reaction vessel, heated to 250°C, kept at that temperature for 2 hours, and then cooled to room temperature. Part of the solvent was removed by vacuum distillation to concentrate the reaction solution. Then, acetone was added to precipitate the solution. After filtration, the filter cake was washed twice with methanol and dried to obtain sodium N,N-methyl-(4'-chlorophenyl sulfide)butyrate.

[0061] The reaction formula for preparing sodium N,N-methyl-(4'-chlorophenyl sulfide)butyrate is:

[0062] .

[0063] Finally, PPS crosslinked product CPPS-3 was obtained, with an MFR of 305 g / 10 min, volatile matter of 0.52 wt.%, and gel content of 0.4 wt.%.

[0064] Example 4:

[0065] The only difference between this example and Example 1 is that after holding the mixture at room temperature for 2 hours, 5.9 g of 4,4'-dithiol sodium phenyl sulfide (0.02 mol) was added to the reactor. The reaction was continued for 10 minutes under a nitrogen atmosphere before flash evaporation was initiated. The final cross-linked product CPPS-4 was obtained, with an MFR of 420 g / 10 min, a volatile matter content of 0.50 wt.%, and a gel content of 0.4 wt.%.

[0066] Example 5:

[0067] The only difference between this example and Example 1 is that after holding the mixture at room temperature for 2 hours, 294g of 4,4'-dithiol sodium phenyl sulfide (1mol) was added to the reactor. The reaction was continued for 10 minutes under a nitrogen atmosphere before flash evaporation was initiated. The final cross-linked product CPPS-5 was obtained, with an MFR of 160g / 10min, a volatile matter content of 0.59wt.%, and a gel content of 0.48wt.%.

[0068] Comparative Example 1:

[0069] In a 100L reactor, add 19.8 kg (200.0 mol) of N-methylpyrrolidone, 10.0 kg (100.0 mol) of a 40% sodium hydroxide aqueous solution, and 14.02 kg (100.0 mol) of a 40% sodium hydrosulfide aqueous solution. Heat to 210℃ and continuously remove water during the heating process until 14.0 kg of the aqueous solution (98.0% water content) is removed. Then cool down to 160℃.

[0070] 15 kg (102.0 mol) of p-dichlorobenzene and 13.17 kg (133 mol) of NMP were added to the above reaction vessel. The temperature was increased to 260°C at a rate of 0.5°C / min and held at that temperature for 2 hours. The product was then flash-evaporated into a flash tank. After flash evaporation, the product was dried under a nitrogen atmosphere until the material temperature reached 235°C, yielding 20.9 kg of crude product.

[0071] Add 50 kg of deionized water to the dried flash-evaporated crude product, stir and wash thoroughly at 65°C, then filter and rinse. Add another 50 kg of deionized water to the filter cake, heat to 150°C, hold for half an hour, then cool, filter, rinse, and dry to obtain linear PPS product with an MFR of 3500 g / 10 min. Place the dried PPS in a crosslinker equipped with a stirrer, dust removal bag, and heat transfer oil jacket. The heat transfer oil jacket temperature is 220°C, and crosslinking gas with an oxygen content of 16% and a temperature of 220°C is introduced for 12 hours to obtain PPS crosslinked product CPPS-6 with an MFR of 540 g / 10 min, volatile matter of 0.5 wt.%, and gel content of 0.4 wt.%.

[0072] Comparative Example 1 shows that when the crosslinking accelerator of the present invention is not added and the acid washing process is omitted in the post-treatment process, the crosslinking rate decreases significantly within the same time under the same thermo-oxidative treatment conditions, resulting in a slower rate of decrease in MFR.

[0073] Comparative Example 2:

[0074] Compared with Example 1, the only difference in this example is that 50 kg of deionized water was added to the dried flash-evaporated crude product, and after thorough stirring and washing at 65°C, the mixture was filtered and rinsed. Another 50 kg of deionized water was added to the filter cake, the temperature was raised to 150°C, and held for half an hour. Then, the mixture was cooled, filtered, rinsed, and dried to obtain a linear PPS product with an MFR of 3500 g / 10 min. The dried PPS was placed in a crosslinker equipped with a stirrer, a dust removal bag, and a heat-conducting oil jacket. The heat-conducting oil jacket temperature was 220°C, and a crosslinking gas with an oxygen content of 16% and a temperature of 220°C was introduced for treatment for 12 hours to obtain the PPS crosslinked product CPPS-7 with an MFR of 440 g / 10 min, a volatile matter content of 0.54 wt.%, and a gel content of 0.42 wt.%.

[0075] Comparative Example 2 shows that when pickling is omitted in the post-treatment process, the crosslinking rate decreases significantly within the same time frame under the same thermo-oxidative treatment conditions, resulting in a slower rate of decrease in MFR.

[0076] Comparative Example 3:

[0077] The only difference between this example and Example 3 is that no crosslinking accelerator is added during the polymerization process. The obtained linear PPS is then thoroughly mixed with 71.5g of N,N-methyl-(4'-chlorophenyl sulfide)sodium butyrate (0.2mol) powder, and then placed in a crosslinker equipped with a stirrer, a dust removal bag, and a heat transfer oil jacket. The heat transfer oil jacket temperature is 220°C, and a crosslinking gas with an oxygen content of 16% and a temperature of 220°C is introduced for 12 hours to obtain the PPS crosslinked product CPPS-8, with an MFR of 380g / 10min, a volatile content of 0.56wt.%, and a gel content of 0.76wt.%.

[0078] Comparative Example 3 shows that when the crosslinking accelerator is mixed with linear PPS in powder form, the crosslinking rate decreases significantly within the same time frame, resulting in a slower decrease in MFR and a significant increase in gel content in the final crosslinked product.

[0079] Comparative Example 4:

[0080] Compared with Example 1, the only difference in this example is that after holding at a certain temperature for 2 hours, 50g of 4,4'-dithiol phenyl sulfide (0.2mol) was added to the reactor, and the reaction was continued for 10 minutes under a nitrogen atmosphere before flash evaporation was started. Linear PPS was obtained after post-treatment, with an MFR of 8500g / 10min. The dried PPS was placed in a crosslinker equipped with a stirrer, a dust removal bag, and a heat transfer oil jacket. The heat transfer oil jacket temperature was 220°C, and a crosslinking gas with an oxygen content of 16% and a temperature of 220°C was introduced for 12 hours to obtain the crosslinked PPS product CPPS-9, with an MFR of 400g / 10min, a volatile matter content of 0.60wt.%, and a gel content of 0.42wt.%.

[0081] Comparative Example 4 shows that the addition of dithiol phenyl sulfide during polymerization makes the polymerization system less stable, resulting in a significant increase in the MFR of linear PPS. Under the same thermo-oxidative treatment conditions and within the same time period, the MFR and volatile matter of the final crosslinked product are increased.

[0082] Comparative Example 5:

[0083] Compared with Example 3, the only difference in this example is that after holding the mixture at room temperature for 2 hours, a crosslinking accelerator was added to the reactor, and then flash evaporation was started immediately. The final product obtained was PPS crosslinked product CPPS-10, with an MFR of 350 g / 10 min, a volatile content of 0.55 wt.%, and a gel content of 0.4 wt.%.

[0084] Comparative Example 5 shows that flash evaporation immediately after adding the crosslinking accelerator during polymerization will cause a slight decrease in the crosslinking rate within the same time frame under the same heat and oxygen treatment conditions, resulting in a slower rate of decrease in MFR and an increase in the volatile matter content in the final crosslinked product.

[0085] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0086] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for producing a crosslinked polyphenylene sulfide, characterized by, The manufacturing method includes: (1) The sulfur source, polycondensation aid and first polar organic solvent are mixed and dehydrated to obtain a dehydrated liquid. The dehydrated liquid, dihaloaromatic compound and second polar organic solvent are mixed and polymerized to obtain a reaction mixture. (2) Add the crosslinking accelerator to the reaction mixture, keep it warm under a protective atmosphere, flash evaporate it after the reaction, and continue to dry it under a protective atmosphere to obtain the crude product; wherein the crosslinking accelerator is one or a combination of 4,4'-dimercaptosodium phenyl sulfide, 4,4'-(1,4-phenylene di(sulfide))-N,N-diethyl-diphenylamine, and N,N-methyl-(4'-chlorophenyl sulfide)butyrate sodium; the holding time is 5-20 min; (3) The crude product is washed with water, acid washed, dried, and then subjected to thermal oxygen treatment in a crosslinking atmosphere to obtain crosslinked polyphenylene sulfide.

2. The method for producing cross-linked polyphenylene sulfide according to claim 1, characterized by, The ratio of the molar amount of the crosslinking accelerator to the molar amount of the sulfur source is 0.0002-0.01:

1.

3. The method for producing cross-linked polyphenylene sulfide according to claim 1, characterized by, In step (2), the drying process is controlled until the material temperature reaches 230-240℃; and / or, in step (2), the heat preservation time is 5-15 minutes.

4. The method for producing cross-linked polyphenylene sulfide according to claim 1, characterized by, In step (3), the pickling is performed using an aqueous acetic acid solution.

5. The method for manufacturing cross-linked polyphenylene sulfide according to claim 4, characterized in that, The mass concentration of the acetic acid aqueous solution is 0.01 wt.% to 0.5 wt.%.

6. The method for manufacturing cross-linked polyphenylene sulfide according to claim 1, characterized in that, In step (3), the temperature of the thermal oxidation treatment is 200-230℃, and the oxygen content of the crosslinking atmosphere is 8%-21%.

7. The method for manufacturing cross-linked polyphenylene sulfide according to claim 1, characterized in that, In step (1), the molar ratio of the added polycondensation aid to the added sulfur source is 0.97-1.01:1; and / or, in step (1), the molar ratio of water to sulfur in the dehydration liquid is 1.0:1-1.3:

1.

8. The method for manufacturing cross-linked polyphenylene sulfide according to claim 1, characterized in that, In step (1), the sulfur source is selected from sodium hydrosulfide and / or potassium hydrosulfide.

9. The method for manufacturing cross-linked polyphenylene sulfide according to claim 1, characterized in that, In step (1), the polycondensation aid includes at least an alkali metal hydroxide.

10. The method for manufacturing cross-linked polyphenylene sulfide according to claim 9, characterized in that, The alkali metal hydroxides include sodium hydroxide and / or potassium hydroxide.

11. The method for manufacturing cross-linked polyphenylene sulfide according to claim 9 or 10, characterized in that, The polycondensation aid is added in the form of an aqueous solution.

12. The method for manufacturing cross-linked polyphenylene sulfide according to claim 9, characterized in that, The polycondensation aid also includes other aids, which are at least one selected from sodium acetate, sodium benzoate, and sodium C5-C6 fatty acids.

13. The method for manufacturing cross-linked polyphenylene sulfide according to claim 12, characterized in that, The molar ratio of the other additives to the sulfur source is 0.01-0.1:

1.

14. The method for manufacturing cross-linked polyphenylene sulfide according to claim 1, characterized in that, In step (1), the dihaloaromatic compound is p-dichlorobenzene.

15. The method for manufacturing cross-linked polyphenylene sulfide according to claim 1 or 14, characterized in that, The molar ratio of the dihaloaromatic compound to the sulfur source is 1.03-1.06:

1.

16. The method for manufacturing cross-linked polyphenylene sulfide according to claim 1, characterized in that, In step (1), the first polar organic solvent is at least one selected from N-methylpyrrolidone, hexamethyltriamine phosphate, and N-methyl-ε-caprolactam, and the second polar organic solvent is at least one selected from N-methylpyrrolidone, hexamethyltriamine phosphate, and N-methyl-ε-caprolactam.