Abstract: A polyacetal resin composition comprising (A) 100 parts by mass of polyacetal resin generating formaldehyde in an amount of not more than 100 ppm when heated at a temperature of 200° C. for 50 minutes under the nitrogen atmosphere and (B) 0.01 to 5 parts by mass of a hydrazide compound can provide an article which is remarkably reduced in an emission amount of formaldehyde even though molded either at a higher temperature or under molding conditions wherein the resin temperature rises partially. Therefore, the polyacetal resin composition can be molded according to various molding methods and under a wide range of molding conditions. The article molded from the resin composition has succeeded in reducing the emission amount of formaldehyde, measured according to VDA275 method, to not more than 1 mg/kg, the level never achieved before, and therefore is usable for various applications where a reduced VOC is required.

Abstract: A polyacetal resin composition comprising (A) 100 parts by mass of polyacetal resin generating formaldehyde in an amount of not more than 100 ppm when heated at a temperature of 200° C. for 50 minutes under the nitrogen atmosphere and (B) 0.01 to 5 parts by mass of a hydrazide compound can provide an article which is remarkably reduced in an emission amount of formaldehyde even though molded either at a higher temperature or under molding conditions (or according to a molding method) wherein the resin temperature rises partially. Therefore, the polyacetal resin composition can be molded according to various molding methods and under a wide range of molding conditions. The article molded from the resin composition has succeeded in reducing the emission amount of formaldehyde, measured according to VDA275 method, to not more than 1 mg/kg, the level never achieved before, and therefore is usable for various applications where a reduced VOC is required.

Abstract: The present invention relates to a polyacetal ABA type block copolymer having a liquid hydrogenated polybutadiene block hydroxyalkylated at both end having a specific monomer structure in the main chain and a polyacetal resin composition comprising the block copolymer and a specific polymer compound or an inorganic filler. The block copolymer and the resin composition can satisfy 4 characteristics necessary for materials for large-diameter gears, i.e. (1) high cycle capability (high productivity), (2) high roundness, (3) distinguished dimensional stability and (4) distinguished durability at the same time and provide useful materials for large-diameter gears having a pitch circle diameter of 60 mm or more.

Abstract: The present invention relates to a polyacetal ABA type block copolymer having a liquid hydrogenated polybutadiene block hydroxyalkylated at both end having a specific monomer structure in the main chain and a polyacetal resin composition comprising the block copolymer and a specific polymer compound or an inorganic filler. The block copolymer and the resin composition can satisfy 4 characteristics necessary for materials for large-diameter gears, i.e. (1) high cycle capability (high productivity), (2) high roundness, (3) distinguished dimensional stability and (4) distinguished durability at the same time and provide useful materials for large-diameter gears having a pitch circle diameter of 60 mm or more.

Abstract: The present invention provides a method for producing an oxymethylene copolymer, which comprises:copolymerizing trioxane and a cyclic ether and/or a cyclic formal in the presence of at least one selected from the group consisting of boron trifluoride, boron trifluoride hydrate, and a coordination compound of an organic compound having an oxygen or a sulphur atom with boron trifluoride,volatilizing the residual polymerization catalyst to decrease its amount, by heating the obtained oxymethylene copolymer in an atmosphere of inert gas at or below its melting point, and/or reducing the pressure, without conducting any operation of deactivating the residual polymerization catalyst before volatilizing the residual polymerization catalyst, andstabilizing terminal moities of the oxymethylene copolymer after deactivating residual catalyst or stabilizing terminal moieties of the oxymethylene copolymer directly.