Polyplastics Co., Ltd.

Akira Nakai

Kaoru Yamamoto

Eiji Masuda

Hiroyuki Kanai

To economically produce a polyacetal copolymer excellent in properties including thermal stability by copolymerizing trioxane as the main monomer through simple steps, a polyacetal copolymer is produced by copolymerizing trioxane as the main monomer using a nonvolatile protonic acid catalyst as a polymerization catalyst until the conversion reaches at least 60% (based on all monomers), and then vaporizing unreacted monomers to separate, remove, and recover the same from the polymerization system to thereby reduce the residual monomer content of the polymerization system to 5% by weight or lower.

Process for producing polyacetal copolymer

A process for producing a polyacetal copolymer, which is extremely heat-stable and is extremely reduced in the quantity of unstable terminals even in a high polymerization yield in which trioxane as the principal monomer, comprises copolymerization of trioxane as the principal monomer with a cyclic ether or cyclic formal having at least one carbon-to-carbon bond as the comonomer by using a specific heteropoly-acid or acid salt thereof as a polymerization catalyst until the content of the remaining monomers is lowered to at most 10% by weight based on all the monomers fed, adding 0.01 to 10% by weight, based on the resulting crude polymer, of a solution containing a catalyst deactivator, or contacting a basic gas as the deactivator to deactivate the catalyst, and subjecting the crude polymer as such to heat melting treatment without washing thereof.

Process for preparing polyacetal copolymer

The present invention provides a process for preparing a thermally very stable polyacetal copolymer having very small unstable terminals even at a high polymerization yield, by the copolymerization of trioxane as the principal monomer with a comonomer copolymerizable therewith, wherein an isopolyacid or an acidic salt thereof is used as a polymerization catalyst; the catalyst can simply be deactivated in a small amount of a deactivator solution after the polymerization; and a washing step is not required. The copolymerization is effected with an isopolyacid or an acidic salt thereof used as a polymerization catalyst until the remaining monomers account for at most 10% by weight of all the fed monomers, and a solution containing a deactivator for the above catalyst is added in an amount of 0.01 to 10% by weight based on the resulting crude polymer to deactivate the catalyst, followed by subjecting the crude polymer intact to a heat-melting treatment without washing it.

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Shizuoka, Japan

Akira Nakai