Solvent recycling technology adopted in polyphenylene sulfide production

Abstract

The invention relates to a solvent recycling technology adopted in polyphenylene sulfide production. According to the technology, sodium sulfide and paradichlorobenzene which contain a certain amount of crystallization water are adopted as raw materials, lithium chloride is adopted as cosolvent, and N-methyl pyrrolidone is adopted as solvent, so that polyphenylene sulfide resin is synthecized; after a polycondensation reaction is completed, the solvent for synthesizing and producing the polyphenylene sulfide resin is recycled, meanwhile, a certain amount of fresh NMP solvent and oxygen-free deionized water need to be added to a polycondensation reaction system to dissolve the cosolvent and a by-product (sodium chloride) generated in the synthesis technological process, thereby a mixture system containing the polyphenylene sulfide resin, NMP, the cosolvent, the by-product and organic impurities is formed, and immediately the mixture system is input into a centrifugal machine for solid-liquid separation. According to the solvent recycling technology, the high boiling point solvent and the oxygen-free deionized water are adopted as diluent of the polycondensation reaction system, and the solvent recycling technology aims at lowering the viscosity of the polycondensation reaction system, raising the velocity of solid-liquid separation, further raising the production rate of the polyphenylene sulfide resin, lowering production cost of whole polyphenylene sulfide resin, shortening the washing process flow at the same time and reducing equipment investment of the washing process flow.

Description

technical field [0001] The invention relates to the improvement of the production process of polyphenylene sulfide. Background technique [0002] Using sodium sulfide and p-dichlorobenzene (P-DCB) as raw materials, in the process of polycondensation production of polyphenylene sulfide (PPS) resin under the action of alkali metal co-solvent, alkali metal NMP (N-formaldehyde) is required in the polymerization stage base pyrrolidone) solution to complete the catalysis, compared with the cost of other raw materials, NMP and alkali metal co-solvent occupy a considerable price proportion, but in the production process of PPS, solvent NMP and co-solvent are not consumed in theory, therefore, can Whether to recover the still and co-solvent with a higher recovery rate is the key to reduce the production cost of PPS. [0003] After the polymerization reaction is completed, 65-70% of NMP can be recovered by conventional methods, but the remaining 25-30% is combined with a co-solvent a...

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Problems solved by technology

[0003] After the polymerization reaction is completed, 65-70% of NMP can be recovered by conventional methods, but the remaining 25-30% is combined with co-solvent and remains in the residue, which is similar to complex Solid solution, boiling point 150-160°C, extremely difficult to separate, even under vacuum conditions, this part of NMP cannot be recovered

[0004] In Chinese patent applications CN001161423 and 201110229729.2, a kind of solvent or / and co-solvent recovery technology in the production of polyphenylene sulfide is introduced, but it is puzzling that carbonate is used to recover the so-called catalyst, but in fact this catalyst The recovery rate is so low that it is not flattering, the catalyst recovery is very low, generally between 5-10%wt, and the recovered co-solvent cannot be reused at all

[0005] Introduce the recovery technology of the solvent that polyphenylene sulfide resin is produced in U.S. Patent US5711873, although this technology adopts low-boiling point solvent as the diluent of reaction system, although adding low-boiling point organic solvent in reaction system helps the filtration of reaction mixture, And low-boiling point solvents are also easy to recover and purify. However, the requirements for the material of the polymerization reactor are relatively high. If it is added in the later stage of the reaction system, the pressure of the reactor will be increased. At the same time, it is necessary to always pay attention to the pressure of the reactor beyond the design. accidentally causing a serious accident

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