Process for producing polyoxymethylene copolymer having reduced amount

Abstract

Processes for producing a polyoxymethylene copolymer includes forming a crude polyoxymethylene copolymer by subjecting a reaction system containing trioxane, a cyclic ether or cyclic formal comonomer, and a catalyst (e.g., boron trifluoride or a coordination compound thereof) to copolymerization reaction conditions. During copolymerization, both the total content of impurities and catalyst in the copolymerization reaction system are adjusted. In this regard, the impurities content (i.e., those compounds which form unstable end groups in the polyoxymethylene copolymer and/or those compounds having a chain-terminating or chain-transfer function) in the copolymerization reaction system is adjusted to 1.times.10.sup.-2 mole percent or less based on the total monomer amount, while the the content of the catalyst in the copolymerization reaction system to between 1.times.10.sup.-3 to 1.times.10.sup.-2 mole percent based on the total monomer amount. Immediately after copolymerization has been completed, the crude polyoxymethylene copolymer is quenched to a temperature of 45.degree. C. or less within 30 seconds after completion of copolymerization. Quenching of the crude polyoxymethylene copolymer is preferably simultaneously accompanied by deactivation of the catalyst by bringing the crude polyoxymethylene copolymer immediately following completion of copolymerization into contact with a cold liquid which contains a catalyst deactivator.