CN1345892A

CN1345892A - Technology for recovering dissolvent and catalyst in producing polyphenyl-thioether

Info

Publication number: CN1345892A
Application number: CN00116142A
Authority: CN
Inventors: 蒋岳
Original assignee: SICHUAN HUATUO INDUSTRY DEVELOPMENT Co Ltd
Current assignee: SICHUAN HUATUO INDUSTRY DEVELOPMENT Co Ltd
Priority date: 2000-09-30
Filing date: 2000-09-30
Publication date: 2002-04-24

Abstract

The present invention relates to a technique for recovering solent and catalyst in the course of production of polyphenyl thioether and is characterized by that said invention includes the following steps: using polyhydrate sodium sulfide and p-xylene as raw material, through the processes of dehydration and polycondensation, to produce polyphenyl thioether monomer, metal halide is used as catalyst, after polycondensation reaction is completed, firstly, using carbonate to soake the filtered-out reaction residuum to make the reaction residuum undergo the process of double decomposition to obtain carbonate deposit matter and soluble salt solution, then filtering, making the filtrating richly containing NMP return to raw material treatment, and recovering the filter cake, and under the acid condition obtaining original metal halide catalyst. The recovery rate of NMP can be up to 93%, and recovery rate of the catalyst and be up to 95%.

Description

Solvent and catalyst recovery technology in polyphenylene sulfide production

The invention relates to an improvement of a production process of polyphenylene sulfide.

In the process of Producing Polyphenylene Sulfide (PPS) monomer by polycondensation under the action of alkali metal catalyst by using sodium sulfide and P-dichlorobenzene (P-DCB) as raw materials, NMP (N-methyl pyrrolidone) solution of alkali metal is needed to complete catalysis in the polymerization stage, compared with the cost of other raw materials, NMP and the alkali metal catalyst occupy equivalent price proportion, but NMP and the catalyst are not consumed theoretically in the production process of PPS, so that the key of reducing the production cost of PPS is whether the catalyst can be recovered at a higher recovery rate or not.

After the polymerization is completed, 65-70% of NMP can be recovered by a conventional method, but the remaining 25-30% combined with the catalyst remains in a residue which is a solid solution like a complex, has a boiling point of 150-160, is extremely difficult to separate, and even under vacuum conditions, this portion of NMP cannot be recovered.

In view of the above disadvantages of the prior art, the present invention is directed to a new method for recovering solvent and catalyst in the production of polyphenylene sulfide, so as to recover the portion of NMP and catalyst remaining in solid solution, thereby reducing the production cost of PPS.

The object of the present invention is achieved by the following method.

The solvent and catalyst recovering technology for producing polyphenyl thioether adopts sodium sulfide and p-xylene as material and produces polyphenyl thioether monomer through dewatering, polycondensation and other technological steps. Using metal halide salt as catalyst, after finishing polycondensation reaction: firstly, soaking the filtered reaction residue by carbonate to ensure that the residue is subjected to double decomposition to form carbonate precipitate and soluble salt solution; then filtering, and returning the filter liquor rich in NMP to the raw material for treatment; and recovering the filtered filter cake under an acidic condition to obtain the original metal halide salt catalyst.

The catalyst and the process method selected by the invention can decompose and recover the NMP and the catalyst viscous solid solution during polycondensation to respectively obtain the NMP and the corresponding catalyst, wherein the recovery rate of the NMP can reach 93 percent, the raw material is saved, and the production cost of the PPS is reduced.

In practice, LiCl and CaCl are used as metal halides as catalyst₂、MgCl₂(ii) a The carbonate is Na₂CO₃、K2CO₃、MgCO₃Soaking the residue in an aqueous solution of the compound, and carrying out double decomposition on the catalyst LiCl combined with the NMP and NaCl to generate LiCO which is insoluble in both water and NMP₃Precipitation, the reaction equation of which is as follows (to use LiCl and Na)₂CO₃The reaction system is as an example):

the filtrate obtained after filtration mainly contains NMP and NACL, and the filtrate is recovered by rectification under vacuum condition like NMP of other discharged liquid in the process.

The filter cake obtained after filtration, namely LI2CO3, is reacted with HCL

And recovering to obtain LiCl.

Example 1

600g LiCl and 12Kg NMP solution were added in the polymerization reaction, and after the polycondensation reaction was completed, the solvent and catalyst were recovered to obtain 11.16Kg NMP and 570g LiCl, with recovery rates of 93% and 95%, respectively.

Example 2 polymerization with 700g CaCl₂And NMP solution 14Kg, after the polycondensation reaction is completed, the solvent and catalyst are recovered, and NMP 12.95Kg and CaCl are recovered₂672g, and the recovery rates are respectively 92.5 percent and 96 percent.

Claims

1. The solvent and catalyst recovery technology in polyphenylene sulfide production adopts sodium sulfide dihydrate and p-dichlorobenzene as raw materials, and produces polyphenylene sulfide monomer through the process steps of dehydration, polycondensation and the like, and is characterized in that metal halide salt is used as a catalyst, and after the polycondensation reaction is finished:

1) soaking the filtered reaction residue in carbonate to double decompose the residue into carbonate precipitate

Starch and soluble salt solution.

2) Filtering on the basis of 1), and returning the filtrate rich in NMP to raw material treatment; filtered filter

Recovering the cake under acidic condition to obtain the original metal halide salt catalyst.

2. The solvent and catalyst recovery technique in polyphenylene sulfide production as claimed in claim 1, wherein said metal halide salt as catalyst is LiCl, CaCl₂、MgCl₂Any one of the above.

3. The method as claimed in claim 2, wherein the carbonate is Na₂CO₃K2CO₃、MgCO₃Any one of the above.

4. The solvent and catalyst recovery technique in polyphenylene sulfide production as claimed in claim 1 or 2, wherein the acidic substance added to the filter cake is HCl.