Catalyst for bulk polymerization of polyoxymethylene and preparation method of polyoxymethylene copolymer

Abstract

The invention provides a catalyst for bulk polymerization of polyoxymethylene, comprising: 0.03-3 parts by mass of the first catalyst; 0.01-2 parts by mass of the second catalyst; 3-35 parts by mass of the first auxiliary agent; 65 parts by mass of the second auxiliary agent ~95 parts by mass; the first catalyst is selected from phosphomolybdic acid, phosphotungstic acid, phosphomolybdotungstic acid, phosphomolybdovanadic acid, phosphotungstovanadate, phosphomolybdotungstic vanadic acid, silicotungstic acid, silicomolybdic acid, silicon Molybdenum tungstic acid, phosphomolybdate, phosphotungstate, phosphomolybdotungstate, phosphomolybdovanadate, phosphotungstate vanadate, phosphomolybdotungtovanadate, silicotungstate, silicomolybdate and silicon One or more of molybdenum tungstates; the second catalyst is a protonic acid; the first auxiliary agent is selected from cyclic ethers, cyclic formals, compounds containing cyclic ether groups and cyclic formals One or more of the compounds of the group; the second auxiliary agent is an acetal compound. Under the premise of ensuring the conversion rate, the composite catalyst of the invention can still initiate the copolymerization reaction with a small dosage.

Description

technical field [0001] The invention relates to the technical field of polymer materials, in particular to a catalyst for bulk polymerization of polyoxymethylene copolymer. Background technique [0002] In the production of polyoxymethylene materials, paraformaldehyde is often used as the first monomer in industry, and cyclic ethers or cyclic formals with at least one carbon-carbon bond are used as comonomers. The production is carried out by bulk polymerization. The polymerization mechanism For cationic ring-opening polymerization, the catalyst is generally an acidic compound, and its quality and dosage can affect the polymerization rate, monomer conversion rate, and molecular weight of the polymer. [0003] The important component in the above reaction is the catalyst. The type and amount of the catalyst will have a certain impact on the reaction, so the selection of the catalyst is very important. Relevant studies have pointed out that the induction period of protonic ac...

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Problems solved by technology

Relevant studies have pointed out that the initiation and induction period of protonic acid initiators is very short, which not only makes the analysis and characterization of the initiation stage difficult, but also causes a large instantaneous heat release of the reaction and poor controllability of the reaction.

In addition, the vast majority of domestic manufacturers currently use Lewis acid BF3 and its ether / butyl ether complex as a catalyst for industrial applications. The temperature for initiating polymerization is moderate, from the appearance of polymerization "soft material" to complete reaction curing The interval time is longer, that is, the reaction rate is suitable, and the heat of reaction is effectively removed during continuous production, which ensures the stability of the production of the polymerizer. However, the characteristic of this type of boron-containing catalyst is that the polymerization conversion rate will be low if the amount is too small. , The polymer softens and the discharge is wet; if the amount is too much, the molecular weight of the produced polymer will decrease, the smell of formaldehyde will increase significantly, and it will be accompanied by depolymerization, post-processing is difficult, residues in the final product will lead to the occurrence of reverse polymerization, etc. , which greatly affects the quality of POM material

[0004] At present, with the increasing thermal stability requirements for the application of polyoxymethylene materials, under the premise of ensuring a high polymerization conversion rate, the boron trifluoride complex catalyst remaining in the material that is easy to cause depolymerization reverse reaction The less the dosage, the better, but directly reducing the content of this traditional catalyst will lead to lower polymerization conversion rate, wet discharge, and even affect the continuity of production

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