A method for producing a polyphenylene sulfide

Abstract

This invention relates to a method for preparing high-yield and high-purity polyphenylene sulfide (PPS), belonging to the field of oxidative polymerization. The technical problem solved by this invention is to provide a method for producing PPS with mild reaction conditions and high yield and high purity. This method uses diphenyl disulfide as a raw material, sulfoxide as a solvent, oxygen as an oxidant, and a vanadium-based Lewis acid complex as a catalyst. The main process flow includes feeding, synergistic effect of the catalyst and oxygen, polymerization, filtration, washing, and drying. High-yield and high-purity PPS is obtained through oxidative polymerization at room temperature and pressure. This invention features a simple process flow, mild conditions, and does not require the use of other polymerization aids. It avoids the impact of byproducts such as sodium metal salts generated in many preparation methods on the toughness of the product, and the yield can reach almost 100%, with high product purity.

Description

Technical Field

[0001] This invention belongs to the field of oxidative polymerization technology, and more specifically relates to a method for preparing high-yield and high-purity polyphenylene sulfide. Background Technology

[0002] Polyphenylene sulfide (PPS), also known as polyphenylene sulfate or polyphenylene sulfide, is the most important and widely used high-crystallinity (up to 75%) thermoplastic resin among polyaryl sulfides. PPS is often referred to as "plastic gold" and has evolved from a first-class specialty engineering plastic to the sixth major general-purpose engineering plastic after polyamide (PA), polycarbonate (PC), polyoxymethylene (POM), modified ether (MPPO), and thermoplastic polybutylene terephthalate (PBT). It is also one of the eight major aerospace materials. PPS is formed by the para-substitution of sulfur atoms and phenylene rings, exhibiting strong chain regularity. Its molecular structure contains highly stable chemical bonds, forming a thermally stable crystal lattice, giving it high molecular stability against thermal degradation and chemical reactions. The rigid benzene ring and flexible thioether bonds give it not only the properties of general engineering plastics but also unique properties such as excellent heat resistance, chemical corrosion resistance, flame retardancy, outstanding electrical properties, high rigidity, dimensional stability, and good melt flowability. Based on molecular weight, PPS resin can be classified into high molecular weight, medium molecular weight, and low molecular weight resins; according to structural composition, it can be classified into linear, branched, and modified resins (copolymer, block, crosslinked, grafted, etc.); and based on application, it can be classified into coating type (average molecular weight Mw = ~22600), injection molding type (Mw = ~48000), and fiber type (Mw = ~52000), etc.

[0003] The main methods for synthesizing PPS include: sodium sulfide method, sulfur method, oxidative polymerization method, melt or solution self-condensation polymerization of p-halothiophene salts, hydrogen sulfide method, and ring-opening polymerization of cyclic phenyl sulfide oligomers. From a mechanistic perspective, PPS synthesis mainly follows four pathways: nucleophilic substitution, electrophilic substitution, free radical polymerization, and single-electron transfer. Industrial production mostly employs the nucleophilic substitution reaction pathway. Catalysts are crucial for PPS synthesis, including sulfonates, phosphates, carboxylates, and halides. Metal ions are primarily sodium, lithium, and calcium salts. Co-catalysts are generally alkali metal salts of inorganic or organic acids (sodium phosphate, sodium benzoate, sodium acetate, or mixtures thereof). The solvents used in synthesis are mainly polar organic amide solvents, such as N-methylpyrrolidone (NMP), N-methylcaprolactam (NMC), N,N-dimethylformamide (DMF), and hexamethylphosphoric triamine (HMPA). However, the sodium sulfide method has disadvantages such as a long production process, difficulty in raw material refining, and the presence of trace amounts of sodium in PPS. +Ions reduce the product's moisture resistance, electrical properties, and molding performance; the sulfur method is technically difficult and byproducts are not easy to remove; the halogenated thiophene salt melt or solution autocondensation method has the disadvantages of complex monomer preparation process, high cost, and some monomers are highly toxic, and side reactions can easily generate cyclic PPS, which hinders the increase of relative molecular mass; the hydrogen sulfide method has the disadvantages of too fast reaction rate and strong corrosiveness of hydrogen sulfide, high requirements for production equipment, and long reaction process. Summary of the Invention

[0004] This invention provides a method for preparing high-yield, high-purity polyphenylene sulfide (PPS), using diphenyl disulfide as raw material, sulfoxide as solvent, oxygen as oxidant, and a vanadium-based Lewis acid complex as catalyst (catalyst preparation method: 1 molar amount of vanadium pentoxide and 0.8-3 molar amount of sodium metavanadate are ball-milled at 200 rpm for 2 hours, and then activated and calcined in a tube furnace under N2 atmosphere at 800-900℃ at 2-5℃ / min for 2-8 hours). The molar proportions of each component participating in the reaction are: diphenyl disulfide 2.0-3.2, vanadium-based Lewis acid complex 0.05-0.15, and the molar ratio of sulfoxide to raw material is 5-10. The raw material, solvent, and catalyst are added dropwise to the reaction system at room temperature and pressure. The specific production process includes the following steps:

[0005] (1) Feeding: Diphenyl disulfide and vanadium-based Lewis acid complex catalyst are sequentially added to the reactor, followed by the addition of thionyl chloride. The reactor is then assembled and sealed.

[0006] (2) Synergistic effect of catalyst and oxygen: oxygen is introduced into the reactor so that the catalyst and oxygen can work synergistically on the surface of the raw materials;

[0007] (3) Polymerization: Turn on the stirring to mix the raw materials and solvents added in step (1) evenly in the reactor and react for 12-18 hours under the combined synergistic effect of catalyst and oxygen. After the reaction is completed, the mixture in the reactor is put into an automatic filter centrifuge to separate the polyphenylene sulfide particles by centrifugation.

[0008] (4) Centrifugation, filtration, washing and drying are performed to obtain polyphenylene sulfide products.

[0009] Preferably, the molar proportions of each material added in step (1) are as follows:

[0010] Diphenyl disulfide 2.0-3.2, vanadium-based Lewis acid complex catalyst 0.05-0.15, and the molar ratio of solvent sulfoxide to raw material input is 5-10;

[0011] Preferably, the oxygen flow rate in step (2) is 2-6 m / s;

[0012] Preferably, the stirring rate of the reactor in step (3) is 750-800 r / min, and the reaction time is 18-24 h;

[0013] Preferably, step (4) is performed as follows:

[0014] 1) Centrifugal filtration: The reacted slurry is fed into an automatic centrifugal separator for centrifugal filtration. The filtrate is recovered in a recovery unit, and the filter cake is reserved for the next step of processing.

[0015] 2) Washing: Transfer the filter cake obtained from filtration to a water washing tank, and use a water pump to introduce washing water for 20-30 minutes of washing. Then, use an automatic filter centrifuge to recover the washing water and filter cake. Repeat this step 5-6 times.

[0016] 3) Drying: The filter cake after filtration and washing is dried in a vacuum dryer and stored.

[0017] This method uses diphenyl disulfide as raw material, sulfoxide as solvent, oxygen as oxidant, and vanadium-based Lewis acid complex as catalyst. The main process flow includes feeding, synergistic effect of catalyst and oxygen, polymerization, filtration, washing, and drying. High-yield, high-purity polyphenylene sulfide is obtained through oxidative polymerization at room temperature and pressure. This invention features a simple process flow, mild conditions, and does not require other polymerization aids. It avoids the impact of byproducts such as sodium metal salts generated in many preparation methods on the toughness of the product, and the yield can reach almost 100%, with high product purity.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] (1) The efficient synthesis method of polyphenylene sulfide of the present invention has a yield of over 99%, which is an improvement over other existing technologies.

[0020] (2) The efficient synthesis method of polyphenylene sulfide of the present invention has a high product purity, and the process is simple and easy to operate. The automatic filtration centrifuge used greatly saves manpower.

[0021] (3) The efficient synthesis method of polyphenylene sulfide of the present invention uses a vanadium-based Lewis acid complex catalyst, which is different from traditional catalysts, which greatly improves the production efficiency and is cheaper and more cost-effective than the lithium chloride and other catalysts used in other technologies. Detailed Implementation

[0022] Preparation method of vanadium-based Lewis acid complex catalyst: 1 mole of vanadium pentoxide and 1 mole of sodium metavanadate are ball-milled at 200 rpm for 2 h, and then activated and calcined in a tube furnace at 5 °C / min to 800 °C for 4 h under N2 atmosphere. The resulting black powder is the desired catalyst.

[0023] Example 1

[0024] (1) Feeding: 2 moles of diphenyl disulfide and 0.05 moles of vanadium-based Lewis acid complex catalyst are sequentially added to the reactor, followed by 5 moles of thionyl chloride. The reactor is then assembled and sealed.

[0025] (2) Synergistic effect of catalyst and oxygen: oxygen at a flow rate of 5 m / s is introduced into the reactor (into the solution) so that the catalyst and oxygen can work synergistically on the surface of the raw materials.

[0026] (3) Polymerization: Turn on the stirring to mix the raw materials and solvents added in step (1) evenly in the reactor and react for 12 hours under the combined synergistic effect of catalyst and oxygen. After the reaction is completed, the mixture in the reactor is put into an automatic filter centrifuge to separate the polyphenylene sulfide particles by centrifugation.

[0027] (4) Centrifugal filtration: The reacted slurry is put into an automatic centrifugal separator for centrifugal filtration. The filtrate is recycled into a recovery unit, and the filter cake is left for the next step of processing.

[0028] (5) Washing: The filter cake obtained by filtration is transferred to the water washing tank and water is pumped in for 20-30 minutes (28 minutes in this case) for washing. Then the washing liquid and filter cake are recovered again by an automatic filter centrifuge. This step is repeated 5-6 times (5 times in this case).

[0029] (6) Drying: The filter cake after filtration and washing is dried by a vacuum dryer and stored.

[0030] The resulting white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of over 97%.

[0031] Example 2

[0032] The operation steps, process and conditions are the same as in Example 1, except that the molar proportions of the feed are changed to 2.2% diphenyl disulfide, 0.05% vanadium-based Lewis acid complex catalyst, and 5% sulfoxide, and the reaction time is 14 hours. The resulting white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of over 97%.

[0033] Example 3

[0034] The operation steps, process and conditions are the same as in Example 1, except that the molar proportions of the feed are changed to 2.4% diphenyl disulfide, 0.1% vanadium-based Lewis acid complex catalyst, and 5% sulfoxide, and the reaction time is 15 hours. The resulting white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of over 97%.

[0035] Example 4

[0036] The operation steps, process and conditions are the same as in Example 1, except that the molar proportions of the feed are changed to 2.6% diphenyl disulfide, 0.1% vanadium-based Lewis acid complex catalyst, and 8% sulfoxide, and the reaction time is 15 hours. The resulting white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of over 97%.

[0037] Example 5

[0038] The operation steps, process and conditions are the same as in Example 1, except that the molar proportions of the feed are changed to 2.8% diphenyl disulfide, 0.15% vanadium-based Lewis acid complex catalyst, and 8% sulfoxide, and the reaction time is 16 hours. The resulting white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of over 97%.

[0039] Example 6

[0040] The operation steps, process and conditions are the same as in Example 1, except that the molar proportions of the feed are changed to 3.0 of diphenyl disulfide, 0.15 of vanadium-based Lewis acid complex catalyst, and 10 of sulfoxide, and the reaction time is 16 hours. The resulting white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of over 97%.

[0041] Example 7

[0042] The operation steps, process and conditions are the same as in Example 1, except that the molar proportions of the feed are changed to 3.2% diphenyl disulfide, 0.15% vanadium-based Lewis acid complex catalyst, and 10% sulfoxide, and the reaction time is 16 hours. The resulting white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of over 97%.

[0043] Example 8

[0044] The operation steps, process and conditions are the same as in Example 1, except that the molar proportions of the feed are changed to 3.2% diphenyl disulfide, 0.15% vanadium-based Lewis acid complex catalyst, and 10% sulfoxide, and the reaction time is 18 hours. The resulting white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of over 97%.

[0045] The physical properties (whiteness, density) and yield of the polyphenylene sulfide prepared in Examples 1-8, as well as the conditions inside the reactor after the reaction, were tested. The data are shown in Table 1. (The whiteness was measured according to GB2913-1982, and the yield was determined by gas chromatography with internal standard method for diphenyl disulfide.)

[0046] Table 1 compares the properties of polyphenylene sulfide in different embodiments.

[0047]

[0048] As can be seen from the above embodiments, the polyphenylene sulfide preparation method used in this invention has a simple process, mild reaction conditions, high cost performance, a product yield close to 100%, and high product purity, and has great industrial application value.

[0049] Compared with existing technologies, the oxidative polymerization technology described in this invention has the advantages of mild reaction conditions (room temperature and pressure), simple operation ("one-pot method"), economical use of materials, high product yield, and promising prospects for industrial production.

Claims

1. A method for preparing polyphenylene sulfide, characterized in that: Using diphenyl disulfide as raw material, sulfoxide as solvent, oxygen as oxidant, and vanadium-based Lewis complex as catalyst, the molar proportions of each component participating in the reaction are as follows: diphenyl disulfide 2.0-3.2, vanadium-based Lewis acid complex 0.05-0.15, and sulfoxide solvent 5-10. The raw material, solvent, and catalyst are added to the reactor at room temperature and pressure, and oxygen is introduced to carry out the reaction. The preparation method of vanadium-based Lewis acid complex catalyst is as follows: 1 molar part of vanadium pentoxide and 1 molar part of sodium metavanadate are ball-milled at 200 rpm for 2 h, and then activated and calcined in a tube furnace at 5 °C / min to 800 °C for 4 h under N2 atmosphere. The resulting black powder is the desired catalyst.

2. The preparation method according to claim 1, characterized in that: The specific production process includes the following steps: (1) Feeding: Diphenyl disulfide and vanadium-based Lewis acid complex catalyst are added to the reactor in sequence, followed by the addition of thionyl chloride, and the reactor is then sealed. (2) Synergistic effect of catalyst and oxygen: oxygen is introduced into the reactor so that the catalyst and oxygen can work synergistically on the surface of the raw materials; (3) Polymerization: Turn on the stirring to mix the added materials evenly in the reactor and react for 12-18 hours under the combined effect of catalyst and oxygen. After the reaction is completed, the mixture in the reactor is introduced into a filter centrifuge to separate polyphenylene sulfide particles by centrifugation. The polyphenylene sulfide particles are washed and dried to obtain polyphenylene sulfide products.

3. The preparation method according to claim 1, characterized in that: A vanadium-based Lewis acid complex with higher oxidative polymerization efficiency, which is different from the traditional catalyst for the production of polyphenylene sulfide, was used as the catalyst. The oxidative polymerization method was used to synthesize polyphenylene sulfide products in a "one-pot" process; the yield of synthesized polyphenylene sulfide was over 99%, achieving high production volume. No other additives are used, thus avoiding the generation of sodium metal salt byproducts or impurities, resulting in high purity polyphenylene sulfide products.

4. The preparation method according to claim 2, characterized in that, Step (3) is performed as follows: (1) Centrifugal filtration: The slurry after reaction is put into an automatic centrifugal separator for centrifugal filtration. The filtrate is recycled into a recovery unit, and the polyphenylene sulfide granular filter cake is left for the next step of processing. (2) Washing: The polyphenylene sulfide granular filter cake obtained by filtration is transferred to a water washing tank and water is pumped in for 20-30 minutes for washing. Then, the washing liquid and filter cake are recovered again by an automatic filter centrifuge. This step is repeated 5-6 times. (3) Drying: The filter cake after filtration and washing is dried by a vacuum dryer.

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