Method for recycling additive lithium chloride in polyphenylene sulfide resin production process

Abstract

The invention relates to a method for recycling additive lithium chloride in polyphenylene sulfide resin production process. The method includes steps of dissolving waterish sodium sulfide in NMP and removing water in the waterish sodium sulfide in inert gas shielding under the catalytic function of lithium chloride and caustic soda flakes, adding DCB and NMP solution to polymerize, and synthesizing to obtain polyphenylene sulfide resin mixture pulp; separating solid of the polyphenylene sulfide resin from liquid to obtain polyphenylene sulfide resin product containing low polymer, bi-product salt and NMP solution containing lithium chloride respectively; filtering and purifying the NMP solution containing lithium chloride to obtain NMP solution containing 75-85% of lithium chloride; inversely soaking and rinsing the polyphenylene sulfide resin product containing low polymer and the bi-product salt to obtain polyphenylene sulfide resin product containing low polymer, bi-product salt and rinsing liquid respectively; depressurizing, distilling and separating rinsing liquid to obtain NMP salt solution; desalinating the NMP salt solution to obtain NMP solution containing 10-20% of lithium chloride. The method is simple and efficient.

Description

technical field [0001] The invention relates to the technical field of recovery and recycling of organic auxiliary agents, in particular to a method for recycling the auxiliary agent lithium chloride used in the production process of polyphenylene sulfide resin. Background technique [0002] Using sodium sulfide (Na 2 S·H 2 O) 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 and lithium salt additives, alkali metal and lithium salt are required in the polymerization stage NMP (N-methylpyrrolidone) solution completes the catalysis. Compared with the cost of other raw materials, NMP and lithium salt solvent occupy a considerable price proportion, but the solvent NMP and additives are theoretically not consumed in the production process of PPS , Therefore, whether the solvent NMP and additives can be recovered with a higher recovery rate is the key to reducing th...

AI Technical Summary

Problems solved by technology

[0006] In Chinese patent CN001161423, a solvent and co-solvent recovery technology in the production of polyphenylene sulfide is introduced. This technology uses carbonate to recover the so-called catalyst. The catalyst The recovery is very low, generally between 5~10%wt, and the recovered additives cannot be reused at all

[0007]Due to the serious loss of solvent NMP in the traditional production process of polyphenylene sulfide, it is difficult to realize the industrialization of additive recovery technology, which doubles the cost of producing PPS, and this It is a serious real problem faced by most enterprises