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CN-121991407-A - Cracking method of polysulfide polymer and application thereof

CN121991407ACN 121991407 ACN121991407 ACN 121991407ACN-121991407-A

Abstract

The invention provides a cracking method of polysulfide polymer and application thereof. The cracking method of the polysulfide polymer comprises the steps of contacting an organic solution containing the polysulfide polymer with an aqueous solution of a cracking agent for a cracking reaction to obtain a polysulfide polymer with low molecular weight, and evaporating at least part of the organic solvent during the cracking reaction. The cracking method can greatly save the operation time of post-cracking treatment, reduce the wastewater production, simultaneously clean the residual cracking agent and sodium thiosulfate as a by-product of the cracking reaction, avoid the risk of generating elemental sulfur by the reaction of sodium thiosulfate and acid in the post-acidification treatment, and improve the quality of polysulfide rubber products.

Inventors

  • HAN KAI

Assignees

  • 北京诺维新材科技有限公司

Dates

Publication Date
20260508
Application Date
20241030

Claims (10)

  1. 1. A method of cracking a polysulfide polymer, the method comprising: (1) Contacting an organic solution containing a polysulfide polymer with an aqueous solution of a cracking agent to carry out a cracking reaction to obtain a low molecular weight polysulfide polymer; characterized in that at least part of the organic solvent is distilled off during the cleavage reaction.
  2. 2. The method of cracking of claim 1, further comprising: (2) After the cracking reaction is finished, adding the organic solvent distilled out in the step (1) into a reaction system after the cracking reaction in the step (1), dissolving the low-molecular-weight polysulfide polymer in the organic solvent, and collecting an organic phase, namely an organic solution of the low-molecular-weight polysulfide polymer; Preferably, in the cleavage reaction, the volume of the organic solvent distilled off is 0% or more, preferably 50% or more of the volume of the organic solvent added in step (1).
  3. 3. The method of cracking of claim 1, wherein in step (1), the organic solution containing the polysulfide polymer is obtained by adding an aqueous emulsion of the polysulfide polymer to an organic solvent and layering to obtain the organic solution containing the polysulfide polymer.
  4. 4. A method of cracking according to claim 1 or 3, wherein the polysulfide polymer has a solubility parameter in organic solvents of greater than 10 (J/cm 3 ) 1/2 . Preferably, the organic solvent is selected from at least one of benzene, toluene, xylene and ethylbenzene or a mixture of two or more. Preferably, the solid content in the organic solution containing a polysulfide polymer is 10wt% or more.
  5. 5. The method according to any one of claims 1 to 4, wherein the step (1) comprises contacting the organic solution containing the polysulfide polymer with an aqueous solution of a cracking agent for a cracking reaction, wherein the cracking agent is a mixture of sodium hydrosulfide and sodium sulfite or sodium bisulphite.
  6. 6. The method according to any one of claims 1 to 5, wherein the organic solvent distilled off in the step (2) is added to the reaction system of the cleavage reaction to obtain an organic solution of the low molecular weight polysulfide polymer, and further water washing to neutrality is performed. Preferably, the solid content in the organic solution of the washed low molecular weight polysulfide polymer is more than 5 weight percent. Preferably, the low molecular weight polysulfide polymer has a number average molecular weight of 500 to 8000 in an organic solution of the low molecular weight polysulfide polymer.
  7. 7. An organic solution of a low molecular weight polysulfide polymer produced by the cleavage process of any one of claims 1-6.
  8. 8. Use of an organic solution of a low molecular weight polysulfide polymer of claim 7 in the preparation of polysulfide rubber.
  9. 9. A polysulfide rubber obtained by acidifying an organic solution of the low molecular weight polysulfide polymer of claim 8.
  10. 10. Use of the polysulfide rubber of claim 9 in the field of aircraft oil phase sealants, adhesives for rocket propellants, construction, automobiles, railways, hollow glass, watercraft.

Description

Cracking method of polysulfide polymer and application thereof Technical Field The invention belongs to the technical field of polymer cracking, and relates to a cracking method of a polysulfide polymer, a cracking product of the cracking method and application of the cracking product. Background The liquid polysulfide rubber is easy to glue, and the product after vulcanization and solidification has excellent oil resistance, ozone resistance and low temperature performance, so that the liquid polysulfide rubber is widely applied to the fields of aircraft oil phase sealants, adhesives of rocket propellants, buildings, automobiles, railways, hollow glass, ships and the like. The production method of the liquid polysulfide rubber comprises the steps of carrying out polycondensation reaction on a sodium polysulfide aqueous solution and a dichloro monomer in a water phase with a dispersing agent to obtain polysulfide polymer emulsion, washing the emulsion for 3-4 times, removing excessive inorganic salts such as sodium polysulfide and the like until the washed latex is neutral, reacting the washed polysulfide polymer with sodium hydrosulfide and sodium sulfite to obtain a cracking product, and acidifying the cracking product to obtain the liquid polysulfide rubber. The emulsion obtained by polycondensation reaction needs to be washed to remove unreacted inorganic salts such as sodium polysulfide and the like before the next reaction, and because the emulsion contains an emulsifying agent, particles of polysulfide polymer are tiny and about 50 mu m, water and latex phase separation is difficult after the emulsion is added with washing water, and the separated water phase is at the upper layer, the water content in the lower latex layer still exceeds 65wt% after standing for 12 hours by prolonging standing time, and meanwhile, the operation difficulty is increased in the production process of the upper layer by the separated water phase. The same problem also arises in the working-up of the cleavage products, the emulsion of the polysulfide polymer remaining in emulsion form after cleavage, and the emulsion also having to be washed to a pH of 7.5 or less before acidification to prepare the liquid polysulfide rubber. The existing industrial method is that emulsion washing, standing phase separation and long phase separation time exist, and the possibility that washing and desalting are incomplete exists, and the residual sodium sulfite, sodium hydrosulfide, sodium thiosulfate and other salts in the reaction liquid react with acid in the next acidification process to generate hydrogen sulfide and separate out elemental sulfur, so that the environment is polluted, the content of free sulfur in the product is increased, the quality of the liquid polysulfide rubber product is influenced, and the content of free sulfur in the liquid polysulfide rubber product with good application in the market is required to be controlled below 0.1 percent by weight. In summary, emulsion washing requires long standing for phase separation, and it is difficult to wash thoroughly. Disclosure of Invention In order to overcome the defects in the prior art, the invention provides a cracking method of a polysulfide polymer, which adopts an organic solution containing the polysulfide polymer as a cracking raw material, overcomes a plurality of problems existing in the prior art that an emulsion of the polysulfide polymer is adopted as the cracking raw material, and specifically provides the following technical scheme: a method of cracking a polysulfide polymer, the method comprising: (1) And (3) carrying out a cracking reaction on the organic solution containing the polysulfide polymer to obtain a low-molecular-weight polysulfide polymer, wherein the end group of the low-molecular-weight polysulfide polymer is sodium sulfide group and/or sulfhydryl group, and at least part of the organic solvent is distilled out during the cracking reaction. The inventor finds that in the cracking reaction, along with the evaporation of part of the organic solvent, the concentration of the polysulfide polymer and the cracking agent can be maintained within a certain range, so that the contact probability of the polysulfide polymer and the cracking agent is increased, the rate of the cracking reaction is increased, and the cracking reaction time is shortened. According to an embodiment of the invention, the cleavage method further comprises: (2) After the cracking reaction is finished, adding the organic solvent distilled out in the step (1) into a reaction system after the cracking reaction in the step (1), dissolving the low-molecular-weight polysulfide polymer in the organic solvent, and collecting an organic phase, namely the organic solution of the low-molecular-weight polysulfide polymer. According to an embodiment of the present invention, in step (1), the organic solution containing the polysulfide polymer is obtained by adding an aqueous emulsion of