Patent ID: 9546241
Date: 2017-01-17
CPC Classifications: C08G,C08L

Claim:
1. A method for producing a polyacetal copolymer. comprising: supplying a raw material comprising trioxane, a comonomer which copolymerizes with the trioxane, and a non-volatile protonic acid to a continuous stirring mixer type reaction device having two parallel shafts which rotate in the same or in opposite directions, a plurality of paddles mounted on each shaft, and a barrel which comes close to an outer circumference of the paddles, wherein a long axis end of a paddle periodically comes close to a short axis end of a companion side, wherein the raw material is charged from an introduction opening provided at one end in an axial direction, and a reaction mixture and an unreacted monomer are obtained from a plurality of removal openings provided at the other end; carrying out a polymerization reaction of the raw material, and obtaining a reaction mixture; vaporizing and separating an unreacted monomer from the reaction mixture at an environmental temperature of at least 115° C. and less than 140° C.; supplying the unreacted monomer to the raw material supply; and recovering the polyacetal copolymer from the reaction mixture, wherein the polymerization reaction is carried out at a polymerization environmental temperature set to no more than 100° C. until a weight ratio D/C of the polyacetal copolymer D with respect to a total supplied monomer C which is defined as a sum of a monomer A which is newly supplied to the reaction device and a monomer B which is recovered from the reaction device and re-supplied, becomes 0.5, and then carrying out further polymerization; wherein the D/C is no less than 0.7; and a weight ratio D/A of the polyacetal copolymer D with respect to the monomer A which is newly supplied to the reaction device is no less than 0.85.