Method for preparing linear high molecular weight polyphenylene sulfide by utilizing pre-desalting method

Abstract

The invention relates to a method for preparing linear high molecular weight polyphenylene sulfide by utilizing a pre-desalting method. The method comprises the steps of adding sodium sulfhydrate into NMP (N-methyl-2-pyrrolidone) dissolved with lithium chloride under the inert gas shielding, separating solid sodium chloride after reacting under the heating condition of 70-110 DEG C, obtaining an NMP solution of lithium hydrogen sulfide, continuing to heat to 150-190 DEG C till no hydrogen sulphide escapes, obtaining an NMP suspension of lithium sulfide, adding p-dichlorobenzene and a catalyzing amount of lithium hydroxide at a molar ratio of (0.95-1.1):1, performing and accomplishing polymerization reaction for generating a target product at 190-280 DEG C and 0.1-0.5 MPa, and collecting a precipitation product after cooling. The product is 284-289 DEG C in melting point, 50000-52000 in weight-average molecular weight, 2-3 in molecular weight distribution index, and less than 300ppm in chloride ion content. Since a great deal of sodium chloride is removed before the polymerization reaction, the method solves the problems that a product produced by the traditional method is high in sodium chloride content, and sodium chloride is difficult to remove to result in low quality of the product.

Description

technical field [0001] The invention relates to an improvement to the preparation method of linear high molecular weight polyphenylene sulfide. Background technique [0002] Polyphenylene sulfide (PPS) is polyphenylene sulfide, also known as polyphenylene sulfide, which is an important chemical engineering plastic, following polyoxymethylene (POM), polycarbonate (PC), polyamide (PA ), polybutylene terephthalate (PBT), and the sixth largest engineering plastic after modified polyphenylene oxide (MPPO), with excellent high temperature resistance, corrosion resistance, radiation resistance, flame retardancy, and balanced physical machinery Performance and excellent dimensional stability and excellent electrical properties, etc., are widely used as structural polymer materials, widely used as special engineering plastics after filling and modification, and can also be made into various functional films, Coatings and composite materials have been successfully applied in the fie...

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Problems solved by technology

The main problems of this method are: firstly, the controllability and reproducibility of the process is poor, and the product quality is unstable, so it can only be classified by subsequent analysis; secondly, the quality of the product is poor, and the molecular weight distribution is wide, so it is difficult to meet high-demand applications The third is that polyphenylene sulfide wraps the inorganic salt impurities in the reaction system during the polymerization process, especially the large amount of sodium chloride precipitated, which makes it difficult to remove these impurities, resulting in its presence in polyphenylene sulfide products. The content of sodium chloride is high, which causes serious corrosion of equipment in the subsequent processing of the product; the fourth is that the environmental protection of the production process is not up to standard, and a large amount of by-product sodium chloride is produced in the production process, which is difficult to refine, difficult to use after separation, and low added value , low recycling rate of catalysts and solvents, etc.

Although U.S. Patent No. 5,235,032 reports a polyphenylene sulfide with low impurity content prepared using sodium hydrosulfide and p-dichlorobenzene as raw materials, NMP as a solvent, and a titanium reactor as a container, the method not only has high cost, but also requires sodium The content of ions is still high, and deep purification is still needed

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