Preparation method of polyphenylene sulfide

Abstract

The invention relates to a preparation method of high-yield and high-purity polyphenylene sulfide, and belongs to the field of oxidative polymerization. The technical problem to be solved by the invention is to provide a production method of polyphenylene sulfide with mild reaction conditions, high yield and high purity. According to the method, diphenyl disulfide is taken as a raw material, thionyl chloride is taken as a solvent, oxygen is taken as an oxidizing agent, a vanadium-based Lewis acid complex is taken as a catalyst, and the main technological process comprises the steps of feeding, synergistic action of the catalyst and the oxygen, polymerization, filtration, washing, drying and oxidative polymerization at normal temperature and normal pressure to obtain the high-yield and high-purity polyphenylene sulfide. The method is simple in process flow and mild in condition, does not need to introduce other polymerization additives, avoids the influence of metal sodium salt and other by-products generated by many preparation methods on the toughness of the product, and has the yield of almost 100% and high product purity.

Description

Technical Field

[0001] The invention belongs to the technical field of oxidative polymerization, and further relates to a method for preparing high-yield and high-purity polyphenylene sulfide. Background Art

[0002] Polyphenylene sulfide (PPS), also known as polyphenylene sulfide and polyphenylene sulfide, is the most important and widely used thermoplastic resin with high crystallinity (up to 75%) among polyarylene sulfides. PPS is known as "plastic gold" and has now evolved from the first category of special engineering plastics to the sixth largest general engineering plastic after polyamide (PA), polycarbonate (PC), polyoxymethylene (POM), modified ether (MPPO) and thermoplastic polybutylene terephthalate (PBT), and is also one of the eight major aerospace materials. PPS is formed by sulfur atoms and phenylene rings in a para-substitution mode, and has strong chain regularity; the molecular structure contains highly stable chemical bonds, forming a crystal lattice with thermal stability, which makes it have high molecular stability against thermal degradation and chemical reactions; the rigid structure of benzene rings and the flexible structure of sulfide bonds make it have certain unique properties in addition to the properties of general engineering plastics, such as excellent heat resistance, chemical corrosion resistance, flame retardancy, outstanding electrical properties, high rigidity, dimensional stability, good melt fluidity, etc. According to the molecular weight, PPS resin can be divided into high molecular weight, medium molecular weight and low molecular weight resins; according to the structural composition, it can be divided into linear, branched and modified resins (copolymer, block, cross-linked, grafted, etc.); from the use, it can be divided into coating type (average molecular weight Mw = ~ 22600), injection molding type (Mw = ~ 48000), fiber type (Mw = ~ 52000), etc.

[0003] The main methods for synthesizing PPS are: sodium sulfide method, sulfur method, oxidative polymerization method, para-halogenated benzenethiophenol salt melt or solution self-condensation polymerization method, hydrogen sulfide method, ring-opening polymerization of cyclic benzene sulfide oligomers, etc. From the perspective of synthesis mechanism, PPS synthesis is mainly divided into four pathways, namely nucleophilic substitution, electrophilic substitution, free radical polymerization and single electron transfer. Nucleophilic substitution reaction pathway is mostly used in industrial production. Catalysts are the key to synthesizing PPS, including sulfonates, phosphates, carboxylates, halides and other systems, and metal ions are mainly sodium salts, lithium salts, calcium salts, etc. The co-catalyst is generally an alkali metal salt of an inorganic acid or organic acid (sodium phosphate, sodium benzoate, sodium acetate or a mixture thereof). The solvents used in the synthesis are mainly organic amide polar solvents, such as N-methylpyrrolidone (NMP), N-methylcaprolactam (NMC), N,N-dimethylformamide (DMF), hexamethylphosphoric triamide (HMPA), etc. However, the disadvantages of the sodium sulfide method are that the production process is long, the raw material refining is difficult, and PPS contains trace amounts of Na +ions, which reduce the moisture resistance, electrical properties and molding performance of the product; the disadvantages of the sulfur method are that the technology is difficult and the by-products are not easy to remove; the disadvantages of the halogenated benzenethiophenol melt or solution self-condensation polymerization method are that the preparation process of the monomer is relatively complicated, the cost is high, and some monomers are highly toxic, and the side reaction easily generates cyclic PPS, which hinders the growth of relative molecular mass; the disadvantages of the hydrogen sulfide method are that the reaction rate is too fast and hydrogen sulfide is highly corrosive, the production equipment requirements are high, and the reaction process is also long. Summary of the invention

[0004] The invention provides a method for preparing high-yield and high-purity polyphenylene sulfide, which uses diphenyl disulfide as a raw material, thionyl chloride as a solvent, oxygen as an oxidant, and a vanadium-based Lewis acid complex as a catalyst (the catalyst preparation method is: 1 mole fraction of vanadium pentoxide and 0.8-3 mole fraction of sodium metavanadate are ball-milled at 200 rpm for 2 hours, and then heated to room temperature under N 2 The temperature is raised to 800-900°C in a tube furnace at 2-5°C / min for activation calcination for 2-8h under an atmosphere of 2-5°C / min. The molar fractions of the components involved in the reaction are: 2.0-3.2 diphenyl disulfide, 0.05-0.15 vanadium-based Lewis acid complex, the molar fraction of the amount of solvent thionyl chloride added to the amount of raw material input is 5-10, and the raw materials, solvents, and catalysts are added dropwise to the reaction system at room temperature and pressure. The specific process flow of its production includes the following steps:

[0005] (1) Adding materials: Adding diphenyl disulfide and vanadium-based Lewis acid complex catalyst into a reaction kettle in sequence, then adding thionyl chloride, and assembling and sealing the reaction kettle;

[0006] (2) Synergistic effect of catalyst and oxygen: oxygen is introduced into the reactor to enable the catalyst and oxygen to act synergistically on the surface of the raw materials;

[0007] (3) Polymerization: Stirring is started to uniformly mix the raw materials and solvent added in step (1) in the reactor, and reacting for 12-18 hours under the synergistic effect of the catalyst and oxygen. After the reaction is completed, the mixture in the reactor is placed in an automatic filtering centrifuge to separate the polyphenylene sulfide particles by centrifugation;

[0008] (4) Centrifugal filtration, washing and drying to obtain polyphenylene sulfide product.

[0009] Preferably, the molar fractions of the materials added in step (1) are:

[0010] 2.0-3.2 of diphenyl disulfide, 0.05-0.15 of vanadium-based Lewis acid complex catalyst, and the molar fraction of the added amount of thionyl chloride solvent to the input amount of raw materials 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 specifically performed as follows:

[0014] 1) Centrifugal filtration: The slurry after the reaction is placed in an automatic filtering centrifuge for centrifugal filtration, the filtrate is recycled in a recovery device, and the filter cake is kept for the next step;

[0015] 2) Washing: The filter cake obtained by filtration is moved to a water washing tank, and washing water is pumped into the tank for 20-30 minutes. Then, the washing water and filter cake are recovered by an automatic filtering centrifuge and this step is repeated 5-6 times.

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

[0017] The method uses diphenyl disulfide as a raw material, thionyl chloride as a solvent, oxygen as an oxidant, and a vanadium-based Lewis acid complex as a catalyst. The main process flow includes feeding, synergistic action of the catalyst and oxygen, polymerization, filtration, washing, and drying. The high-yield and high-purity polyphenylene sulfide is obtained by oxidative polymerization at normal temperature and pressure. The process flow of the invention is simple, the conditions are mild, no other polymerization aids are required, and the influence of byproducts such as metal sodium salts produced by many preparation methods on the toughness of the product is avoided. The yield can reach almost 100%, and the product purity is high.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The high-efficiency synthesis method of polyphenylene sulfide of the present invention has a yield of more than 99%, which is higher than other existing technologies.

[0020] (2) The highly efficient synthesis method of polyphenylene sulfide of the present invention has high product purity, simple process flow, convenient operation, and the automatic filtering centrifuge used greatly saves manpower.

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

[0022] Preparation method of vanadium-based Lewis acid complex catalyst: 1 mole fraction of vanadium pentoxide and 1 mole fraction of sodium metavanadate were ball milled at 200 rpm for 2 h, and then heated to 400 °C in N2 The temperature was raised to 800°C at 5°C / min in a tube furnace under atmosphere for activation calcination for 4 hours, and the obtained black powder was the desired catalyst.

[0023] Example 1

[0024] (1) Adding materials: 2 mol of diphenyl disulfide and 0.05 (in terms of vanadium, the same below) of a vanadium-based Lewis acid complex catalyst are sequentially added into a reactor, and then 5 mol of thionyl chloride is added, and the reactor is assembled and sealed;

[0025] (2) Synergistic effect of catalyst and oxygen: oxygen with a flow rate of 5 m / s is introduced into the reactor (into the solution) to enable the catalyst and oxygen to achieve synergistic effect on the surface of the raw material;

[0026] (3) Polymerization: Stirring is started to uniformly mix the raw materials and solvent added in step (1) in the reactor, and reacting for 12 hours under the synergistic action of the catalyst and oxygen. After the reaction is completed, the mixture in the reactor is placed in an automatic filtering centrifuge to separate the polyphenylene sulfide particles by centrifugation;

[0027] (4) Centrifugal filtration: The slurry after the reaction is placed in an automatic filtering centrifuge for centrifugal filtration, the filtrate is recovered in a recovery device, and the filter cake is retained for the next step of processing;

[0028] (5) Washing: The filter cake obtained by filtration is transferred to a water washing tank, and water is pumped into the tank for washing for 20-30 min (28 min in this case). The washing water and filter cake are then recovered by an automatic filtering centrifuge and this step is repeated 5-6 times (5 times in this case).

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

[0030] The obtained white powder is a polyphenylene sulfide product with a particle size of 200 meshes and a purity of more than 97%.

[0031] Example 2

[0032] According to the operating steps of Example 1, the process and conditions are the same as those of Example 1, except that the molar fractions of the feed materials are changed to 2.2 of diphenyl disulfide, 0.05 of vanadium-based Lewis acid complex catalyst, and 5 of dichlorothionyl. The reaction time is 14 h, and the obtained white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of more than 97%.

[0033] Example 3

[0034] According to the operating steps of Example 1, the process and conditions are the same as those of Example 1, except that the molar fractions of the feed materials are changed to 2.4 of diphenyl disulfide, 0.1 of vanadium-based Lewis acid complex catalyst, and 5 of dichlorothionyl. The reaction time is 15 h, and the obtained white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of more than 97%.

[0035] Example 4

[0036] According to the operating steps of Example 1, the process and conditions are the same as those of Example 1, except that the molar fractions of the feed materials are changed to 2.6 of diphenyl disulfide, 0.1 of vanadium-based Lewis acid complex catalyst, and 8 of dichlorothionyl. The reaction time is 15 h, and the obtained white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of more than 97%.

[0037] Example 5

[0038] According to the operating steps of Example 1, the process and conditions are the same as those of Example 1, except that the molar fractions of the feed materials are changed to 2.8 of diphenyl disulfide, 0.15 of vanadium-based Lewis acid complex catalyst, and 8 of dichlorothionyl. The reaction time is 16 h, and the obtained white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of more than 97%.

[0039] Example 6

[0040] According to the operating steps of Example 1, the process and conditions are the same as those of Example 1, except that the molar fractions of the feed materials are changed to 3.0 of diphenyl disulfide, 0.15 of vanadium-based Lewis acid complex catalyst, 10 of dichlorothionyl, and the reaction time is 16 h. The obtained white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of more than 97%.

[0041] Example 7

[0042] According to the operating steps of Example 1, the process and conditions are the same as those of Example 1, except that the molar fractions of the feed materials are changed to 3.2 of diphenyl disulfide, 0.15 of vanadium-based Lewis acid complex catalyst, 10 of dichlorothionyl, and the reaction time is 16 h. The obtained white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of more than 97%.

[0043] Example 8

[0044] According to the operating steps of Example 1, the process and conditions are the same as those of Example 1, except that the molar fractions of the feed materials are changed to 3.2 of diphenyl disulfide, 0.15 of vanadium-based Lewis acid complex catalyst, 10 of dichlorothionyl, and the reaction time is 18 h. The obtained white powder is a polyphenylene sulfide product with a particle size of 200 mesh and a purity of more than 97%.

[0045] The physical properties (whiteness, density) and yield of the polyphenylene sulfide prepared in Examples 1-8 and the conditions in the reactor after the reaction were tested, and the obtained data are shown in Table 1 (wherein the whiteness test standard is GB2913-1982, and the yield is determined by gas chromatography internal standard method for diphenyl disulfide.)

[0046] Table 1 is a comparison of the properties of polyphenylene sulfide in different embodiments

[0047]

[0048] It can be seen from the above examples that the polyphenylene sulfide preparation method used in the present invention has a simple process, mild reaction conditions, high cost performance, a product yield of nearly 100%, a high product purity, and great industrial application value.

[0049] Compared with the existing technology, the oxidative polymerization technology of the present invention has the advantages of mild reaction conditions (normal temperature and pressure), simple operation ("one-pot method"), economical materials, high product yield, and has the prospect of industrial production.

Claims

1. A method for preparing polyphenylene sulfide, characterized in that: Diphenyl disulfide is used as a raw material, thionyl chloride is used as a solvent, oxygen is used as an oxidant, and a vanadium-based Lewis complex is used as a catalyst. The molar fractions of the components involved in the reaction are: 2.0-3.2 of diphenyl disulfide, 0.05-0.15 of the vanadium-based Lewis acid complex, and 5-10 of the solvent thionyl chloride. The raw material, the solvent, and the catalyst are added into a reaction kettle at a time at normal temperature and pressure, and oxygen is introduced to react.

2. The preparation method according to claim 1, characterized in that: The specific production process includes the following steps: (1) Adding materials: Adding diphenyl disulfide and vanadium-based Lewis acid complex catalyst into a reactor in sequence, then adding thionyl chloride, and sealing the reactor; (2) Synergistic effect of catalyst and oxygen: oxygen is introduced into the reactor to enable the catalyst and oxygen to act synergistically on the surface of the raw materials; (3) Polymerization: Stirring is started to mix the input materials in the reactor evenly, and the mixture is reacted for 12-18 hours under the synergistic effect of the catalyst and oxygen. After the reaction is completed, the mixture in the reactor is introduced into a filtering centrifuge to separate the polyphenylene sulfide particles by centrifugation; (4) The polyphenylene sulfide particles are washed and dried to obtain a polyphenylene sulfide product.

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 conventional oxidative polymerization catalyst for producing polyphenylene sulfide, is used as a catalyst; The oxidative polymerization method was used to synthesize polyphenylene sulfide products in one pot; The yield of synthesized polyphenylene sulfide is 99.5%, close to 100%, achieving high yield; No other additives are used, so no byproducts or impurities such as metal sodium salts are produced, so that the obtained polyphenylene sulfide product has high purity.

4. The preparation method according to feature 1, characterized in that: The specific operations of step (4) are as follows: (1) Centrifugal filtration: The slurry after the reaction is placed in an automatic filtering centrifuge for centrifugal filtration, the filtrate is recycled in a recovery device, and the polyphenylene sulfide particle filter cake is retained for the next step of treatment; (2) Washing: The polyphenylene sulfide particle cake obtained by filtration is transferred to a water washing tank, and water is pumped into the tank for washing for 20-30 minutes, and then the washing water and filter cake are recovered by an automatic filtering centrifuge, and this step is repeated 5-6 times; (3) Drying: The filter cake after filtration and washing is dried in a vacuum dryer.

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