Abstract: A polyacetal resin composition suitable for providing a plate-shaped resin molded article that satisfies all of the following: high flatness, low shrinkage ratio anisotropy (high dimensional stability), high creep resistance, high impact strength, and excellent color stability during residence in the molding machine. The polyacetal resin composition for molding a plate-shaped molded article includes 100 mass parts of a polyacetal resin having a melt index (according to ASTM D1238, 190° C., 2.16 kgf) of 2.0 g/10 min to 4.0 g/10 min; 0.1 mass parts to 2 mass parts of a polyacetal copolymer that is a copolymer of (b1) trioxane, (b2) a compound having two to four cyclic ether units per one molecule, and (b3) a compound having one cyclic ether unit per one molecule, the polyacetal copolymer having a branched or crosslinked structure; and 0.1 mass parts to 1 mass part of a hindered phenol antioxidant.

Abstract: A polyacetal resin composition suitable for providing a plate-shaped resin molded article that satisfies all of the following: high flatness, low shrinkage ratio anisotropy (high dimensional stability), high creep resistance, high impact strength, and excellent color stability during residence in the molding machine. The polyacetal resin composition for molding a plate-shaped molded article includes 100 mass parts of a polyacetal resin having a melt index (according to ASTM D1238, 190° C., 2.16 kgf) of 2.0 g/10 min to 4.0 g/10 min; 0.1 mass parts to 2 mass parts of a polyacetal copolymer that is a copolymer of (b1) trioxane, (b2) a compound having two to four cyclic ether units per one molecule, and (b3) a compound having one cyclic ether unit per one molecule, the polyacetal copolymer having a branched or crosslinked structure; and 0.1 mass parts to 1 mass part of a hindered phenol antioxidant.

Abstract: A polyacetal resin composition which is suppressed low in formaldehyde generation, while having high stiffness and high toughness. The resin is produced by a method including blending from 0.1 part by weight to 2 parts by weight (inclusive) of a polyacetal copolymer having a branched or crosslinked structure, which is a copolymer of a trioxane, a compound having from 3 to 4 (inclusive) cyclic ether units in each molecule and a compound having one cyclic ether unit in each molecule, per 100 parts by weight of a linear polyacetal copolymer which contains an oxymethylene unit as a main constituent, while containing, as a comonomer unit, an oxyalkylene unit at a ratio of from 0.4% by mole to 0.9% by mole (inclusive) relative to the constituents of the linear polyacetal copolymer, the linear polyacetal copolymer being obtained by copolymerization wherein a heteropolyacid or the like is used as a polymerization catalyst.

Abstract: A polyacetal resin composition which is suppressed low in formaldehyde generation, while having high stiffness and high toughness. The resin is produced by a method including blending from 0.1 part by weight to 2 parts by weight (inclusive) of a polyacetal copolymer having a branched or crosslinked structure, which is a copolymer of a trioxane, a compound having from 3 to 4 (inclusive) cyclic ether units in each molecule and a compound having one cyclic ether unit in each molecule, per 100 parts by weight of a linear polyacetal copolymer which contains an oxymethylene unit as a main constituent, while containing, as a comonomer unit, an oxyalkylene unit at a ratio of from 0.4% by mole to 0.9% by mole (inclusive) relative to the constituents of the linear polyacetal copolymer, the linear polyacetal copolymer being obtained by copolymerization wherein a heteropolyacid or the like is used as a polymerization catalyst.

Abstract: A process for producing a polyacetal copolymer, the process making catalyst deactivation easy and efficient. Trioxane as a major monomer is copolymerized with one or more comonomers that are a cyclic ether and/or cyclic formal having at least one carbon-carbon bond, using a nonvolatile protonic acid as a polymerization catalyst at 100° C. or lower until the conversion reaches 50% and thereafter at a polymerization environment temperature of 115° C. to 140° C. This process includes: a crushing step in which a dry-process crusher is used to obtain a crude polyacetal copolymer crushed to such a degree that when the crude copolymer is screened with a sieve having an opening size of 11.2 mm, 90 parts by weight or more thereof passes therethrough; and a deactivation step in which a basic compound (e) is added to the crude copolymer and the mixture is melt-kneaded to thereby deactivate the polymerization catalyst.

Abstract: A production method for a polyacetal copolymer that makes deactivation of a catalyst simple and efficient and that achieves a high polymerization yield and high quality using equipment that does not require a cleaning step and a process that involves a simple operation technique. The production method for a polyacetal copolymer uses trioxane as a main monomer and a cyclic ether and/or a cyclic formal having at least one carbon-carbon bond as a comonomer. In the production method, a predetermined heteropoly acid is used as a polymerization catalyst to perform copolymerization, a predetermined salt is added to the reaction product, melt kneading processing is performed, and the polymerization catalyst is deactivated.

Abstract: A process for producing a polyacetal copolymer, the process making catalyst deactivation easy and efficient. Trioxane as a major monomer is copolymerized with one or more comonomers that are a cyclic ether and/or cyclic formal having at least one carbon-carbon bond, using a nonvolatile protonic acid as a polymerization catalyst at 100° C. or lower until the conversion reaches 50% and thereafter at a polymerization environment temperature of 115° C. to 140° C. This process includes: a crushing step in which a dry-process crusher is used to obtain a crude polyacetal copolymer crushed to such a degree that when the crude copolymer is screened with a sieve having an opening size of 11.2 mm, 90 parts by weight or more thereof passes therethrough; and a deactivation step in which a basic compound (e) is added to the crude copolymer and the mixture is melt-kneaded to thereby deactivate the polymerization catalyst.

Abstract: A production method for a polyacetal copolymer that makes deactivation of a catalyst simple and efficient and that achieves a high polymerization yield and high quality using equipment that does not require a cleaning step and a process that involves a simple operation technique. The production method for a polyacetal copolymer uses trioxane as a main monomer and a cyclic ether and/or a cyclic formal having at least one carbon-carbon bond as a comonomer. In the production method, a predetermined heteropoly acid is used as a polymerization catalyst to perform copolymerization, a predetermined salt is added to the reaction product, melt kneading processing is performed, and the polymerization catalyst is deactivated.