Abstract: The present invention provides a polyacetal resin composition comprising (I) a polyacetal resin; and per 100 parts by weight thereof, (II) more than 5 parts by weight but less than 100 parts by weight of calcium carbonate, wherein the calcium carbonate has an average particle diameter of 0.1 to less than 1.5 ?m and an average aspect ratio (L/D) which is a ratio of average major axis (L) of particles to average minor axis (D) of particles (D) of 3 or less; (III) 0.005 to 10 parts by weight of an organic acid; and (IV) 0 to less than 0.05 part by weight of a fatty acid ester, wherein the amount of Na relative to Ca is 250 ppm or less while the amount of Sr relative to Ca is 500 to 2500 ppm.

Abstract: The present invention provides a polyacetal resin composition comprising (I) a polyacetal resin; and per 100 parts by weight thereof, (II) more than 5 parts by weight but less than 100 parts by weight of calcium carbonate, wherein the calcium carbonate has an average particle diameter of 0.1 to less than 1.5 ?m and an average aspect ratio (L/D) which is a ratio of average major axis (L) of particles to average minor axis (D) of particles (D) of 3 or less; (III) 0.005 to 10 parts by weight of an organic acid; and (IV) 0 to less than 0.05 part by weight of a fatty acid ester, wherein the amount of Na relative to Ca is 250 ppm or less while the amount of Sr relative to Ca is 500 to 2500 ppm.

Abstract: The present invention provides a polyacetal resin composition comprising (I) a polyacetal resin; and per 100 parts by weight thereof, (II) more than 5 parts by weight but less than 100 parts by weight of calcium carbonate, wherein the calcium carbonate has an average particle diameter of 0.1 to less than 1.5 ?m and an average aspect ratio (L/D) which is a ratio of average major axis (L) of particles to average minor axis (D) of particles (D) of 3 or less; (III) 0.00.5 to 10 parts by weight of an organic acid; and (IV) 0 to less than 0.05 part by weight of a fatty acid ester, wherein the amount of Na relative to Ca is 250 ppm or less while the amount of Sr relative to Ca is 500 to 2500 ppm.

Abstract: The present invention provides a polyacetal resin composition comprising (I) a polyacetal resin; and per 100 parts by weight thereof, (II) more than 5 parts by weight but less than 100 parts by weight of calcium carbonate, wherein the calcium carbonate has an average particle diameter of 0.1 to less than 1.5 ?m and an average aspect ratio (L/D) which is a ratio of average major axis (L) of particles to average minor axis (D) of particles (D) of 3 or less; (III) 0.00.5 to 10 parts by weight of an organic acid; and (IV) 0 to less than 0.05 part by weight of a fatty acid ester, wherein the amount of Na relative to Ca is 250 ppm or less while the amount of Sr relative to Ca is 500 to 2500 ppm.

Abstract: A polyoxymethylene copolymer having a melting point of 167° to 173° C. and containing a low molecular weight polyoxymethylene copolymer in an amount of not higher than 5000 ppm, and a composition thereof. The copolymer is obtainable by subjecting unstable terminal groups to heat treatment in the presence of 0.05 to 50 ppm by weight of a quaternary ammonium compound. Further, the above composition is used for working parts such as a gear and a cam; apparatuses for image, music and telecommunication; interior and exterior parts for an automobile; and the like.

Abstract: A polyacetal resin composition comprising 30-90% by weight of polyacetal copolymer (A) having a melt index of less than 1.0 g/10 min. and 70-10% by weight of polyacetal copolymer (B) having a melt index of 1.0-100 g/10 min., both melting points of (A) and (B) being 155°-162° C., or a difference in melting point between (A) and (B) being not less than 6° C., has distinguished toughness and creep resistance.

Abstract: Disclosed is a method for stabilizing a crude oxy-methylene copolymer having thermally unstable terminal groups, which comprises subjecting a crude oxymethylene copolymer to heat treatment in the presence of at least one quaternary ammonium compound represented by the following formula (1): [R1R2R3R4N+]nX−n  (1) wherein each of R1, R2, R3 and R4 independently represents an unsubstituted or substituted alkyl group, an aryl group, an aralkyl group which is an unsubstituted or substituted alkyl group substituted with at least one aryl group, or an alkylaryl group which is an aryl group substituted with at least one unsubstituted or substituted alkyl group; n is an integer of from 1 to 3; and X is a hydroxyl group or an acid residue. In this method, even by the addition of a very small amount of the quaternary ammonium compound, the decomposition rate of the unstable terminal groups can be remarkably increased, thereby facilitating the stabilization of the crude copolymer.

Abstract: A polyacetal resin composition comprising 30-90% by weight of polyacetal copolymer (A) having a melt index of less than 1.0 g/10 min. and 70-10% by weight of polyacetal copolymer (B) having a melt index of 1.0-100 g/10 min., both melting points of (A) and (B) being 155°-162° C., or a difference in melting point between (A) and (B) being not less than 6° C., has distinguished toughness and creep resistance.

Abstract: A polyoxymethylene copolymer prepared by copolymerizing a mixture comprising trioxane and 1,3-dioxolane in the presence of at least one polymerization catalyst selected from the group consisting of boron trifluoride, a boron trifluoride hydrate and a coordination complex compound of an organic compound containing an oxygen atom or a sulfur atom with boron trifluoride, wherein the 1,3-dioxolane has a 2-methyl-1,3-dioxolane content of not more than 500 ppm by weight and a 1,3-dioxolane peroxide content of not more than 15 ppm by weight in terms of hydrogen peroxide, and contains at least one hindered phenol in an amount of from 10 to 500 ppm by weight, each based on the weight of the 1,3-dioxolane.

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.