Preparation method of polyphenylene sulfide resin

Abstract

The invention discloses a preparation method of polyphenylene sulfide resin, which comprises the following steps: taking a sulfur-containing compound and p-dichlorobenzene as raw materials, carrying out condensation polymerization in a polar organic solvent in an alkaline environment, after the reaction is finished, cooling and separating to obtain the polyphenylene sulfide resin, and when the temperature is reduced to a preset temperature of 243-248 DEG C in the cooling process, carrying out condensation polymerization in the polar organic solvent to obtain the polyphenylene sulfide resin. Adding polyphenylene sulfide particles with a particle size of 700-900 [mu] m or a slurry prepared from the polyphenylene sulfide particles into the system, and carrying out heat preservation; the adding mass of the polyphenylene sulfide particles with the particle size of 700-900 microns is 1-5% of the total mass of the polyphenylene sulfide calculated by the total sulfur of the system; according to the invention, the amount of PPS ultrafine powder generated by polymerization reaction can be reduced, the particle size of the ultrafine powder PPS is increased, so that the ultrafine powder PPS becomes a PPS main product, the post-treatment vibration separation efficiency is further improved, the yield of the PPS main product is improved, the ash content and oligomer content can be kept relatively low, and the particle size distribution can be optimized to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, and specifically to a method for preparing polyphenylene sulfide resin. Background Technology

[0002] Polyphenylene sulfide resin, also known as PPS resin, possesses excellent thermal stability, flame retardancy, solvent resistance, chemical corrosion resistance, electrical insulation, radiation resistance, good mechanical properties and dimensional stability, good flowability, molding processability, creep resistance, and fatigue resistance due to the rigid structure of the benzene ring in its molecular backbone and the lone pair electrons on the sulfur atoms. Through filler modification, processing using various molding methods, and precision molding, PPS resin can be made into various tubes, sheets, filaments, films, fabrics, and parts, earning it the title of "plastic gold." It has been widely used in textiles, automobiles, electronics, machinery, petrochemical equipment, defense, aerospace, and home appliances, demonstrating promising application prospects and economic value.

[0003] Currently, the main industrial production route for PPS resin is the sodium sulfide method, which involves the direct polycondensation of dichlorobenzene and sodium sulfide in a polar organic solvent to synthesize linear PPS resin. However, in actual industrial production of PPS, it has been found that after the polymerization reaction, the polymerization slurry contains 10% to 15% PPS ultrafine powder (D... 50 The micro-powder produced by this polymerization reaction (<50μm) has such a small particle size that the mother liquor viscosity of the polymer slurry is too high. This makes solid-liquid separation difficult in subsequent vibration separation and centrifugation processes, resulting in excessive entrainment of mother liquor. Consequently, the solid content of the filter cake decreases, while the salt content and oligomer content increase. After purification and washing, the resin generally has high ash content, volatile matter, and oligomer content, ultimately leading to a series of application quality problems for PPS resin in fiber extrusion and injection molding, such as fiber breakage, short scraper cycle, and fiber floating during injection molding. Furthermore, the large amount of polymerized micro-powder PPS entering the waste system after vibration separation and centrifugation significantly increases waste, generating a substantial increase in industrial hazardous waste and posing safety risks. The excessive amount of fine PPS powder also significantly reduces the yield of the finished PPS product, thereby increasing production costs.

[0004] Currently, many in the industry are dedicated to researching ways to reduce the amount of micronized PPS generated during polymerization reactions and to optimize PPS particle size to improve yield. For example, patent CN119842077A proposes that when the conversion rate of dihaloaromatic compounds is greater than 50%, i.e., the first-stage prepolymerization reaction ends, the material passing through the external circulation pipe is placed in a turbulent state to enhance the mixing effect of the polymerization system, reduce the generation of oligomer ultrafine powder waste, and improve the polymerization yield. However, because the reaction is carried out at high temperature and pressure, and the material is in a strongly alkaline environment, the requirements for the temperature and pressure resistance and airtightness of the circulation pump are very high, greatly increasing equipment investment. At the same time, adding an external circulation system to the polymerization reactor will increase additional pipe interfaces, and improper operation can easily lead to material leakage. In addition, since the temperature and pressure of the polymerization reaction need to be maintained, circulating the material through the external circulation pump can easily disrupt the pressure balance inside the reactor, making it difficult to maintain the reaction temperature. This can easily cause local pressure accumulation, overheating, and thus lead to exothermic failure of the reaction, resulting in depolymerization or an inability to increase the molecular weight.

[0005] It should be noted that the information disclosed in the background section above is only for understanding the background of this application. Therefore, the background section of this invention may include background information about the problems or environment of this invention, and is not necessarily a description of the prior art. Thus, the content included in the background section does not constitute an admission of the prior art by the applicant. Summary of the Invention

[0006] The purpose of this invention is to overcome one or more shortcomings in the prior art and provide an improved method for preparing polyphenylene sulfide resin.

[0007] The inventors of this invention, through in-depth research on the PPS polymerization process, discovered that during the cooling process after the PPS reaction at its highest temperature, feedback from the stirring current showed a significant increase in the stirring current when the polymerization temperature dropped to between 243°C and 248°C, and this increase was maintained for approximately 15-40 minutes. After further reducing the polymerization reactor temperature, the current returned to normal. Simultaneously, the study found that the solid-liquid transition temperature in the PPS polymerization reaction is precisely between 243°C and 248°C. Furthermore, it was found that the transformation of PPS from a liquid phase to a solid phase during the polymerization reaction and cooling process is irreversible; that is, once PPS has transformed from a liquid to a solid phase, it is difficult to dissolve even with high-temperature heating. Therefore, the inventors innovatively propose that during the liquid-solid phase transition of PPS during the polymerization cooling stage, 1%-5% of the theoretically synthesized PPS particles with a particle size of 700-900 μm are pumped in (a pressure pump, such as a high-pressure pump, can be selected) to act as a nucleating agent. Due to the high surface energy barrier of the ultrafine powdered PPS produced by polymerization, the newly introduced PPS particles can induce the agglomeration of fine powder with D50 < 50 μm, resulting in increased particle size precipitation. This transforms the original ultrafine powdered PPS into larger PPS particles, thereby effectively reducing the viscosity of the slurry mother liquor, improving the vibration separation effect, increasing purification efficiency, and enhancing the purity of the PPS product. The original ultrafine powdered PPS produced by polymerization also enters the main production line due to the increased particle size, thereby increasing PPS production and improving product yield. It should be noted that although PPS particles are added during the solid-liquid transition stage of PPS polymerization and cooling, there are specific requirements for their particle size. Selecting PPS with a particle size of 700~900μm not only has a beneficial impact on the physical properties of the product, but also has advantages such as easy preparation of the liquid, reduced dust, and the prepared liquid is less likely to clog the pump chamber of the high-pressure pump.

[0008] Based on this, the technical solution adopted by the present invention is: A method for preparing polyphenylene sulfide resin, the method comprising: using a sulfur-containing compound and p-dichlorobenzene as raw materials, undergoing a polycondensation reaction in an alkaline environment and a polar organic solvent; after the reaction is completed, cooling and separation to obtain polyphenylene sulfide resin; particularly, the method further comprising: during the cooling process, when the temperature drops to a preset temperature, adding polyphenylene sulfide particles with a particle size of 700-900 μm or a slurry thereof to the system, and maintaining the temperature; The preset temperature is 243-248℃, and the added mass of the 700-900μm polyphenylene sulfide particles is 1%-5% of the total mass of polyphenylene sulfide calculated from the total sulfur in the system.

[0009] In some embodiments of the present invention, the preset temperature is 244-246°C. Further, the preset temperature is 244.5-245.5°C.

[0010] In some embodiments of the present invention, the preset temperature is 243℃, 243.2℃, 243.5℃, 243.8℃, 244℃, 244.2℃, 244.5℃, 244.8℃, 245℃, 245.2℃, 245.5℃, 245.8℃, 246℃, 246.2℃, 246.5℃, 246.8℃, 247℃, 247.2℃, 247.5℃, 247.8℃, 248℃, etc.

[0011] In some embodiments of the present invention, the added mass of the 700-900 μm polyphenylene sulfide particles is 2%-4% of the total mass of polyphenylene sulfide calculated from the total sulfur in the system. Further, the added mass of the 700-900 μm polyphenylene sulfide particles is 2.5%-3.5% of the total mass of polyphenylene sulfide calculated from the total sulfur in the system.

[0012] In some embodiments of the present invention, the added mass of the 700-900μm polyphenylene sulfide particles is 1%, 1.2%, 1.5%, 1.8%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, etc., of the total mass of polyphenylene sulfide calculated from the total sulfur in the system.

[0013] In this invention, the total mass of polyphenylene sulfide calculated from the total sulfur in the system refers to the total mass calculated by taking the total molar amount of sulfur in the system as a basis, calculating the corresponding molar amount of polyphenylene sulfide, and then calculating the total mass. For example, if the total molar amount of sulfur in the system is 1000 mol, then the corresponding total mass of polyphenylene sulfide is approximately 1000 mol × 10⁶ g / mol = 10⁶ kg.

[0014] In some embodiments of the present invention, the particle size of the polyphenylene sulfide particles is 720-880 μm, and more specifically 750-850 μm.

[0015] In some embodiments of the present invention, the particle size of the polyphenylene sulfide particles is 700μm, 710μm, 720μm, 730μm, 740μm, 750μm, 760μm, 770μm, 780μm, 790μm, 800μm, 810μm, 820μm, 830μm, 840μm, 850μm, 860μm, 870μm, 880μm, 890μm, 900μm, etc.

[0016] In some embodiments of the present invention, when polyphenylene sulfide particle slurry is added to the system, the mass concentration of the polyphenylene sulfide particle slurry is controlled to be 10%-40%, further to 15%-25%, and even further, the polyphenylene sulfide particle slurry is obtained by dispersing polyphenylene sulfide particles in N-methylpyrrolidone.

[0017] In some embodiments of the present invention, the control system is kept at the preset temperature for 0.5-3 hours after cooling down, for example, 0.5 hours, 1.0 hours, 1.5 hours, 2.0 hours, 2.5 hours, 3.0 hours, etc.

[0018] In some embodiments of the present invention, the cooling rate to the preset temperature is controlled to be 0.1-5℃ / min, and more specifically 0.5-1.5℃ / min.

[0019] In some embodiments of the present invention, during the cooling process, after the preset temperature holding period ends, the temperature continues to drop to 100-120°C. Further, the cooling rate is 0.1-5°C / min, even more so 0.2-2°C / min, for example 0.3-1°C / min, or 0.3-0.8°C / min.

[0020] In some embodiments of the present invention, the polycondensation reaction includes a prepolymerization stage and a final polymerization stage, wherein the temperature of the prepolymerization stage is controlled at 220-240°C and the temperature of the final polymerization stage is controlled at 255-270°C.

[0021] According to some specific aspects of the present invention, the polycondensation reaction includes a prepolymerization stage and a final polymerization stage, wherein the temperature of the prepolymerization stage is controlled at 225-235°C and the temperature of the final polymerization stage is controlled at 255-265°C.

[0022] Furthermore, the heating rate is controlled to reach the temperature of the prepolymerization reaction stage within 1-2 hours.

[0023] Furthermore, the heat is controlled to be maintained for 2-5 hours during the prepolymerization reaction stage, for example, 2.0 hours, 2.5 hours, 3.0 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, etc.

[0024] Further, the temperature is increased to the final polymerization stage temperature at a heating rate of 0.1-3℃ / min. Even further, the temperature is increased to the final polymerization stage temperature at a heating rate of 0.1-1.5℃ / min.

[0025] Furthermore, the temperature is controlled to be maintained for 1-4 hours during the final polymerization reaction stage, for example, 1.0 hour, 1.5 hours, 2.0 hours, 2.5 hours, 3.0 hours, 3.5 hours, 4 hours, etc.

[0026] Furthermore, after the prepolymerization reaction stage ends and before the final polymerization reaction stage begins, water is added to the system as a phase separating agent to promote a decrease in system viscosity, improve stirring effect, make PPS easier to disperse, and also provide a high-pressure environment for the system. However, too much water will cause small molecule impurities generated in the prepolymerization reaction to precipitate into the polymer dense phase. Preferably, the amount of water added is based on the total molar amount of sulfur-containing compounds in the system before the start of the prepolymerization reaction stage, with 2.2-4 mol of water added for every 1 mol of sulfur-containing compounds.

[0027] In some embodiments of the present invention, a method for preparing the polyphenylene sulfide resin includes: The mixture comprising water, the sulfur-containing compound, the alkaline substance, and the polar organic solvent is dehydrated under heating conditions; After dehydration, the p-dichlorobenzene is added to initiate a polycondensation reaction; After the reaction is completed, the temperature is lowered to the preset temperature, and then polyphenylene sulfide particles with a particle size of 700-900 μm or their prepared slurry are added to the system and kept at the temperature. After the temperature is kept at the temperature, the temperature is lowered again, and then the slurry is separated by sieve, washed, centrifuged, and dried to obtain polyphenylene sulfide resin.

[0028] In some embodiments of the present invention, the dehydration process is carried out under a protective atmosphere; further, the protective atmosphere is formed by introducing nitrogen and / or an inert gas. The inert gas includes, but is not limited to, argon, helium, etc.

[0029] In some embodiments of the present invention, the temperature of the dehydration is controlled to be 180-200°C.

[0030] In some embodiments of the present invention, the ratio of the molar amount of water to the molar amount of total sulfur in the dehydrated system is controlled to be less than or equal to 1.5, more specifically 0.01-1.5, or 0.1-1.5, or 0.5-1.5.

[0031] In some embodiments of the present invention, after the dehydration is completed, when the system temperature cools to 160-180°C, water is added to the system, and p-dichlorobenzene is added to carry out a condensation reaction. Further, the amount of water added depends on the amount of water removed after dehydration. Specifically, after dehydration, the actual water-to-sulfur ratio in the system is calculated by testing the water content and sulfur loss in the effluent and absorbent, and then water is added in accordance with the theoretically required water-to-sulfur ratio.

[0032] In some embodiments of the present invention, the sulfur-containing compound comprises sodium sulfide and / or sodium hydrosulfide.

[0033] In some embodiments of the present invention, the alkaline environment is formed by adding an alkaline hydroxide, which comprises sodium hydroxide and / or potassium hydroxide.

[0034] In some embodiments of the present invention, the polar organic solvent comprises N-methylpyrrolidone (NMP).

[0035] In some embodiments of the invention, the polycondensation reaction is carried out in the presence of an auxiliary agent, which includes sodium valerate.

[0036] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: This invention can reduce the amount of ultrafine PPS powder (D50 < 50 μm) produced by the polymerization reaction, increase the particle size of the ultrafine PPS powder, making it the main PPS product, thereby improving the efficiency of post-processing vibration separation and thus increasing the yield of the main PPS product. At the same time, the method of this invention does not significantly increase the ash and oligomer content, keeping them within industry standard ranges, and even reducing them to some extent under certain conditions. The particle size distribution can also be optimized to a certain extent, and there is no significant change in viscosity.

[0037] In summary, the method of the present invention can improve the yield of PPS main product while keeping other physical properties such as ash content, oligomer content and fine powder content of plate and frame at a relatively low level, thus avoiding the problem of sacrificing one aspect for another. Attached Figure Description

[0038] Figure 1 The particle size distribution diagrams are for the polyphenylene sulfide resins obtained in Examples 1-7 and Comparative Examples 1-10 of the present invention. Detailed Implementation

[0039] 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.

[0040] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0041] The methods for determining PPS particle size distribution, melt viscosity, oligomer content, and ash content are as follows: (1) PPS particle size distribution test: Weigh all the sieves (8 mesh, 10 mesh, 18 mesh, 35 mesh, 100 mesh) (W1, W2, W3, ...), stack them from top to bottom in order of increasing mesh size, and place the sieves at the bottom of the stack. Weigh approximately 300g ± 0.1g of the dry material and pour it into the top sieve. Cover the screen with a lid and place the entire device on the vibrator; Place the screen device on the vibrating screen and secure it. Set the vibrator amplitude to 60Hz; Closure interval; Set the time to 30 minutes and click the start button; After 30 minutes, remove the vibrating screen from the vibrator; Weigh the mass of each sieve layer (W1', W2', W3', ...), record the data in a table, and calculate the mass of each layer of material. For example, (W1'-W1) is the mass of the first layer of material. Calculate the percentage of each particle size content (%) = ((mass of product and standard sieves of each layer Wn' - mass of standard sieves of each layer Wn) / sum of mass of each layer of material m) × 100% (n=1, 2, 3...). Product yield calculation: The weight of polyphenylene sulfide resin obtained after washing and drying is W (unit: kg), the total sulfur calculated from the actual feed amount is S (mol), and the sulfur loss caused by the dehydration reaction is [S]. Therefore, the yield Q is: ; (2) Method for determining melt viscosity: The melt viscosity of PPS was determined using an LCR7001 capillary rheometer manufactured by Dynisco. The temperature was set to 310℃. The polymer sample was introduced into the device and held for 5 minutes, then the melt viscosity was measured at a shear rate of 1216 sec. -1 The melt viscosity was measured.

[0042] (3) Oligomer content test: Test instruments: Soxhlet extractor, water bath, drying oven Test conditions: 5g of sample and 150mL of dichloromethane were added to the extract and refluxed in a 70℃ water bath for 6 hours.

[0043] Test principle: A certain amount of PPS is extracted in dichloromethane using the Soxhlet extraction method, and the percentage of PPS mass loss after 6 hours of extraction is recorded.

[0044] (4) Method for determining ash content: Accurately weigh 1.50 g of PPS and place it in a crucible, recording the precise mass as G0. Calcine in a muffle furnace at 750℃ for 2 hours, then turn off the furnace for 0.5 hours. Remove and cool in a desiccator for 30 minutes. Add 5 mL of nitric acid, slowly dripping it along the inner wall of the crucible using a pipette, ensuring no sample residue remains and that the nitric acid completely covers the sample. Place the crucible in an electric heating furnace for carbonization for 45 minutes, heating until no smoke is emitted. Calcine the carbonized crucible in a muffle furnace at 750℃ for 3 hours, cool for 0.5 hours, remove, confirm complete calcination, and place in a sealed desiccator for 1.5 hours. Weigh the sample and record the weight as G1. The ash content is calculated as: [Ash Content] = G1 / G0 × 100%.

[0045] Example 1: This example provides a method for preparing polyphenylene sulfide resin, the method comprising: Dehydration process: In a 1000L reactor, add 327.4 kg of N-methylpyrrolidone (NMP), 129.6 kg of a 47.5 wt.% sodium hydrosulfide aqueous solution (the molar amount of sodium hydrosulfide is approximately 1100 mol), 91.9 kg of a 48.6 wt.% sodium hydroxide aqueous solution, and 22 kg of a 40.0 wt.% sodium valerate aqueous solution (the molar amount of sodium valerate is approximately 70.95 mol). After purging the reactor with nitrogen, heat the reactor at a stirring speed of 80 rpm and a rate of 1.0 °C / min. When the liquid phase temperature reaches 199 °C, dehydration is stopped when the water content in the reaction system is less than 1.5 mol / mol (relative to total sulfur). At this point, 115 kg of solution (containing approximately 95.0 wt.% water) has been removed from the reactor. The calculated hydrogen sulfide loss is 21.35 mol, the sulfur source in the reactor is 1078.6 mol, and the water / sulfur molar ratio is 1.25.

[0046] Polymerization process: After the dehydrated mixture cools to 170℃, add 3kg of pure water and 165.003kg of p-dichlorobenzene (PDCB) (the molar amount of p-dichlorobenzene is approximately 1122mol), and 79.659kg of NMP to the reactor. Then, raise the temperature from 170℃ to 230℃ within 1.5h and hold for 3h. Next, add 28kg of pure water to the polymerization reactor through a metering pump, and continue to raise the temperature to 260℃ at a rate of 0.5℃ / min and hold for 2h. After the heat preservation period, the temperature was lowered to the preset temperature of 245℃ at a rate of 1℃ / min. Simultaneously, 5.8 kg of PPS slurry (prepared by thoroughly mixing 800 μm PPS particles with NMP at 40℃ to a concentration of 0.2 g / g, with the PPS particles added approximately 1% of the total mass of polyphenylene sulfide calculated from the total sulfur content) was pumped into the polymerization reactor and kept at this temperature for 2 hours. Then, the temperature was lowered to 110℃ at a rate of 0.5℃ / min. The polymerization slurry was separated by vibration through a 100-mesh sieve. The mother liquor was filtered through a plate and frame filter press to obtain fine powder. The granular PPS resin was washed with acetone, 0.3% dilute hydrochloric acid, and pure water, respectively, centrifuged, and finally dried and weighed. The obtained polyphenylene sulfide resin was tested; detailed physical property data are shown in Tables 1 and 3, and particle size distribution is shown in... Figure 1 .

[0047] Example 2: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 1, except that the amount of PPS particles added is approximately 3% of the total mass of polyphenylene sulfide calculated from the total sulfur in the system, i.e., the amount of PPS slurry added is 17.4 kg. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 1 and 3. Particle size distribution is shown in... Figure 1 .

[0048] Example 3: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 1, except that the amount of PPS particles added is approximately 5% of the total mass of polyphenylene sulfide calculated from the total sulfur in the system, i.e., the amount of PPS slurry added is 29 kg. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 1 and 3. Particle size distribution is shown in... Figure 1 .

[0049] Example 4: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that the preset temperature is 243℃. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 1 and 3. Particle size distribution is shown in... Figure 1 .

[0050] Example 5: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that the preset temperature is 248℃. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 1 and 3. Particle size distribution is shown in... Figure 1 .

[0051] Example 6: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that PPS particles with a particle size of 700 μm are used when preparing the PPS slurry. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 1 and 3. The particle size distribution is shown in... Figure 1 .

[0052] Example 7: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that PPS particles with a particle size of 900 μm are used when preparing the PPS slurry. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 1 and 3. The particle size distribution is shown in... Figure 1 .

[0053] Comparative Example 1: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that PPS slurry is not added. The obtained polyphenylene sulfide resin was tested; detailed physical property data are shown in Tables 2 and 4, and particle size distribution is shown in... Figure 1 .

[0054] Comparative Example 2: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that PPS particles with a particle size of 300 μm are used when preparing the PPS slurry. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 2 and 4. The particle size distribution is shown in... Figure 1 .

[0055] Comparative Example 3: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that PPS particles with a particle size of 500 μm are used when preparing the PPS slurry. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 2 and 4. The particle size distribution is shown in... Figure 1 .

[0056] Comparative Example 4: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that PPS particles with a particle size of 1100 μm are used when preparing the PPS slurry. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 2 and 4. The particle size distribution is shown in... Figure 1 .

[0057] Comparative Example 5: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that PPS particles with a particle size of 1300 μm are used when preparing the PPS slurry. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 2 and 4. The particle size distribution is shown in... Figure 1 .

[0058] Comparative Example 6: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that the preset temperature is 240℃. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 2 and 4. Particle size distribution is shown in... Figure 1 .

[0059] Comparative Example 7: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that the preset temperature is 250℃. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 2 and 4. Particle size distribution is shown in... Figure 1 .

[0060] Comparative Example 8: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 1, except that the amount of PPS particles added is approximately 10% of the total mass of polyphenylene sulfide calculated from the total sulfur in the system, i.e., the amount of PPS slurry added is 58 kg. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 2 and 4. Particle size distribution is shown in... Figure 1 .

[0061] Comparative Example 9: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 1, except that the amount of PPS particles added is approximately 0.5% of the total mass of polyphenylene sulfide calculated from the total sulfur in the system, i.e., the amount of PPS slurry added is 2.9 kg. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 2 and 4. Particle size distribution is shown in... Figure 1 .

[0062] Comparative Example 10: This example provides a method for preparing polyphenylene sulfide resin, which is basically the same as in Example 2, except that the preset temperature is 255℃. The obtained polyphenylene sulfide resin was tested, and detailed physical property data are shown in Tables 2 to 4. Particle size distribution is shown in... Figure 1 .

[0063] Table 1

[0064] Table 2

[0065] Table 3

[0066] Table 4

[0067] As described above, the method of this invention can reduce the amount of PPS ultrafine powder (D50 < 50 μm) produced by the polymerization reaction, increase the particle size of the ultrafine PPS powder, making it the main PPS product, thereby improving the efficiency of post-processing vibration separation and increasing the yield of the main PPS product. At the same time, the method of this invention does not significantly increase the ash and oligomer content, keeping them within industry standard ranges, and even reducing them to some extent under certain conditions. The particle size distribution can also be optimized to a certain extent.

[0068] The reason why the average particle size of Examples 4 and 5 is relatively large may be that the addition temperature of PPS slurry, 243℃ and 248℃, is close to the solid-liquid transition temperature discovered in this invention. The addition of additional slurry does not have a full effect, but only a partial effect, inducing fine powder agglomeration and precipitation. There is still a lot of fine powder remaining in the mother liquor. The finished product obtained by vibration separation contains fewer PPS products in the middle particle size range and larger PPS products. Compared with the finished product obtained when all the added slurry has a full effect, which contains more PPS products in the middle particle size range and larger PPS products, the average particle size of the former finished product will be larger.

[0069] 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.

[0070] 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 preparing a polyphenylene sulfide resin, the method comprising: Using sulfur-containing compounds and p-dichlorobenzene as raw materials, a polycondensation reaction is carried out in an alkaline environment and in a polar organic solvent. After the reaction is completed, the mixture is cooled and separated to obtain polyphenylene sulfide resin. The preparation method is characterized by further comprising: during the cooling process, when the temperature drops to a preset temperature, adding polyphenylene sulfide particles with a particle size of 700-900 μm or a slurry thereof to the system and keeping it at the temperature. The preset temperature is 243-248℃, and the added mass of the 700-900μm polyphenylene sulfide particles is 1%-5% of the total mass of polyphenylene sulfide calculated from the total sulfur in the system.

2. The method for preparing polyphenylene sulfide resin according to claim 1, characterized in that, The preset temperature is 244-246℃; and / or, the added mass of the 700-900μm polyphenylene sulfide particles is 2%-4% of the total mass of polyphenylene sulfide calculated from the total sulfur in the system.

3. The method for preparing polyphenylene sulfide resin according to claim 2, characterized in that, The preset temperature is 244.5-245.5℃; and / or, the added mass of the 700-900μm polyphenylene sulfide particles is 2.5%-3.5% of the total mass of polyphenylene sulfide calculated from the total sulfur in the system.

4. The method for preparing polyphenylene sulfide resin according to claim 1, characterized in that, The polyphenylene sulfide particles have a particle size of 720-880 μm, more specifically 750-850 μm; and / or, When polyphenylene sulfide granule slurry is added to the system, the mass concentration of the polyphenylene sulfide granule slurry is controlled to be 10%-40%, further to 15%-25%, and even further, the polyphenylene sulfide granule slurry is obtained by dispersing polyphenylene sulfide granules in N-methylpyrrolidone.

5. The method for preparing polyphenylene sulfide resin according to claim 1, characterized in that, After the control system cools down to the preset temperature, it is kept at that temperature for 0.5-3 hours; and / or, the cooling rate to the preset temperature is controlled to be 0.1-5℃ / min, and further to be 0.5-1.5℃ / min.

6. The method for preparing polyphenylene sulfide resin according to claim 1 or 5, characterized in that, During the cooling process, after the preset temperature holding period ends, the temperature continues to drop to 100-120℃. Furthermore, the cooling rate is 0.1-5℃ / min, and even more specifically, 0.2-2℃ / min.

7. The method for preparing polyphenylene sulfide resin according to claim 1, characterized in that, The polycondensation reaction includes a prepolymerization stage and a final polymerization stage, wherein the temperature of the prepolymerization stage is controlled at 220-240℃ and the temperature of the final polymerization stage is controlled at 255-270℃. Furthermore, the heating rate is controlled to reach the temperature of the prepolymerization reaction stage within 1-2 hours; and / or, the temperature is controlled to be maintained at the prepolymerization reaction stage for 2-5 hours; Further, the temperature is increased to the final polymerization stage temperature at a heating rate of 0.1-3℃ / min; and / or, the temperature is controlled to be maintained at the final polymerization stage for 1-4 hours; Furthermore, after the prepolymerization reaction stage ends and before the final polymerization reaction stage begins, water is added to the system. The amount of water added is based on the total molar amount of sulfur-containing compounds in the system before the start of the prepolymerization reaction stage, with 2.2-4 mol of water added for every 1 mol of sulfur-containing compounds.

8. The method for preparing polyphenylene sulfide resin according to claim 1, characterized in that, The method for preparing the polyphenylene sulfide resin includes: The mixture comprising water, the sulfur-containing compound, the alkaline substance, and the polar organic solvent is dehydrated under heating conditions; After dehydration, the p-dichlorobenzene is added to initiate a polycondensation reaction; After the reaction is completed, the temperature is lowered to the preset temperature, and then polyphenylene sulfide particles with a particle size of 700-900 μm or their prepared slurry are added to the system and kept at the temperature. After the temperature is kept at the temperature, the temperature is lowered again, and then the slurry is separated by sieve, washed, centrifuged, and dried to obtain polyphenylene sulfide resin.

9. The method for preparing polyphenylene sulfide resin according to claim 8, characterized in that, The dehydration process is carried out under a protective atmosphere; further, the protective atmosphere is formed by introducing nitrogen and / or an inert gas; and / or, The dehydration temperature is controlled at 180-200℃; and / or, The ratio of the molar amount of water to the molar amount of total sulfur in the dehydrated system is controlled to be less than or equal to 1.5, more specifically 0.01-1.5, or 0.1-1.5, or 0.5-1.

5.

10. The method for preparing polyphenylene sulfide resin according to claim 1, characterized in that, The sulfur-containing compound comprises sodium sulfide and / or sodium hydrosulfide; and / or, the alkaline environment is formed by adding an alkaline hydroxide comprising sodium hydroxide and / or potassium hydroxide; and / or, the polar organic solvent comprises N-methylpyrrolidone; and / or, the polycondensation reaction is carried out in the presence of an auxiliary comprising sodium valerate.

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