Abstract: A polyoxymethylene resin composition comprising (A) 100 parts by weight of a polyoxymethylene resin and (B) 0.01 to 10 parts by weight of a vinyl compound having a primary acid amide group and an acid imide group is provided. The composition is excellent in heat stability in molding and weatherability and suited for use as a molding material for electric and electronic parts and automotive parts.

Abstract: Disclosed is an oxymethylene copolymer resin composition comprising (A) 100 parts by weight of an oxymethylene copolymer resin comprising a plurality of oxymethylene copolymer chains, each comprising recurring oxymethylene monomer units and oxyalkylene monomer units inserted therein, wherein the oxyalkylene monomer units, each having at least 2 carbon atoms, are present in the oxymethylene copolymer resin in an amount of from 0.05 to 0.5 mol %, based on the oxymethylene monomer units, the plurality of oxymethylene copolymer chains collectively having, as terminal groups, alkoxyl groups each having at least one carbon atom, hydroxyalkyl groups each having at least 2 carbon atoms, and formate groups; (B) 0.01 to 3.0 parts by weight of a poly-.beta.-alanine having an average particle diameter of 6 .mu.m or less; and (C) from 0.001 to 0.6 part by weight of an alkaline earth metal salt of a fatty acid, an amino-substituted triazine or a hydrotalcite.

Abstract: Disclosed is a method for producing an acetal copolymer, which comprises copolymerizing trioxane with a cyclic ether in the presence of a cation-active catalyst, wherein the cyclic ether is obtained by adding to a fresh cyclic ether containing a peroxide derived therefrom in an amount of 15 ppm by weight or less in terms of hydrogen peroxide at least one sterically hindered phenol in an amount of from 10 to 500 ppm by weight, based on the weight of said fresh cyclic ether. By the method of the present invention, it has become possible not only to stably and efficiently produce an acetal copolymer having high thermal stability, but also to stably conduct a post-treatment of the obtained acetal copolymer for deactivating the remaining catalyst and changing the unstable terminals to stable terminals, so that an ultimate acetal copolymer having high thermal stability can be stably obtained.