The present invention addresses the problem of providing a polyacetal resin composition which can minimize degradation of a molded product produced from the acetal resin composition, when the molded product is in contact with an acidic cleaner. Said problem is solved by a polyacetal resin composition, comprising: polyacetal copolymer (A) in an amount of 100 parts by mass, wherein said polyacetal copolymer (A) has a hemiformal terminal group content of 0.8 mmol/kg or less; hindered phenol-based antioxidant (B) in an amount of 0.1 to 1.0 part by mass; and at least one selected from an oxide of magnesium or zinc or a hydroxide of magnesium or zinc (C) in an amount more than 2.0 parts by mass and 30 parts by mass or less.

The present invention addresses the problem of providing a method for producing an oxymethylene copolymer, which is capable of producing an oxymethylene copolymer having a high molecular weight with high yield and high economic efficiency. This problem is able to be solved by a method for producing an oxymethylene copolymer, in which a copolymer starting material containing a trioxane and a comonomer is subjected to a polymerization reaction in the presence of a polymerization initiator that contains an acidic compound (A), and wherein: the copolymer starting material contains a basic compound (B); an acidic compound (C) that is different from the acidic compound (A) is added into the copolymer starting material before performing the polymerization reaction, thereby causing a reaction between the basic compound (B) and the acidic compound (C) in advance; and the polymerization reaction is carried out by means of melt polymerization.

A process for making an oxymethylene polymer comprising polymerizing at least one compound capable of forming CH.sub.2O repeat units (monomer) in the presence of at least one ester of the general formula I (ester): R.sup.1COOR.sup.2 (I) wherein R.sup.1 can be hydrogen, wherein R.sup.1 and R.sup.2 are independently of each other linear or branched C.sub.1 to C.sub.10 alkyl C.sub.5 to C.sub.7 cycloalkyl [R.sup.3-0-].sub.nR.sup.4 wherein R.sup.3 is a linear or branched C.sub.2 to C.sub.5 alkylen and R.sup.4 is a linear of branched C.sub.1 to C.sub.5 alkyl and n is an integer of from 1 to 5. and in the presence of at least one Lewis acid.

A process for making an oxymethylene polymer comprising polymerizing at least one compound capable of forming CH.sub.2O repeat units (monomer) in the presence of at least one ester of the general formula I (ester): R.sup.1COOR.sup.2 (I) wherein R.sup.1 can be hydrogen, wherein R.sup.1 and R.sup.2 are independently of each other linear or branched C.sub.1 to C.sub.10 alkyl C.sub.5 to C.sub.7 cycloalkyl [R.sup.3-0-].sub.nR.sup.4 wherein R.sup.3 is a linear or branched C.sub.2 to C.sub.5 alkylen and R.sup.4 is a linear of branched C.sub.1 to C.sub.5 alkyl and n is an integer of from 1 to 5. and in the presence of at least one Lewis acid.

A polyacetal resin composition contains a polyacetal copolymer (A) in an amount of 100 parts by mass, the polyacetal copolymer resin having a hemiformal terminal group amount of 0.8 mmol/kg or less, an antioxidant (B) in an amount of 0.5 to 3.0 parts by mass, at least one of zinc oxide or magnesium oxide (C) having an average particle diameter of 5 m or less in an amount of more than 2.0 parts by mass and 12 parts by mass or less, carbon black (D) having a BET specific surface area of 300 to 400 m.sup.2/g in an amount of 5.0 to 16 parts by mass, and polyalkylene glycol (E) in an amount of 0.5 to 3.0 parts by mass.

An oxymethylene-copolymer manufacturing method includes: polymerizing a polymerization raw material containing trioxane and a comonomer in the presence of an acid catalyst in a quantity that is 1.0?10.sup.?8 moles to 5.0?10.sup.?6 moles with respect to 1 mole of trioxane; adding a hydroxylamine compound represented by general formula (1) (in the formula, R.sup.1 and R.sup.2 are, independently of each other, a hydrogen atom or an organic group having 1-20 carbon atoms) to a reaction product obtained during the polymerizing of the polymerization raw material at 50-5000 times the quantity of the acid catalyst, in terms of the molar quantity, and mixing the hydroxylamine compound with the reaction product; and subjecting the mixture of the reaction product and the hydroxylamine compound, which is obtained during the adding of the hydroxylamine compound, to an additional melt-kneading. ##STR00001##

A photochromic polyurethane laminate wherein the photochromic polyurethane layer of the laminate has been crosslinked with an isocyanate-active prepolymer using a crosslinking agent. The crosslinking agent is formulated to have at least three functional groups that are reactive with functional groups of the polyurethane or of the isocyanate-active prepolymer. A method of making the photochromic polyurethane laminate includes steps of causing the crosslinking.

A photochromic polyurethane laminate wherein the photochromic polyurethane layer of the laminate has been crosslinked with an isocyanate-active prepolymer using a crosslinking agent. The crosslinking agent is formulated to have at least three functional groups that are reactive with functional groups of the polyurethane or of the isocyanate-active prepolymer. A method of making the photochromic polyurethane laminate includes steps of causing the crosslinking.

A photochromic polyurethane laminate wherein the photochromic polyurethane layer of the laminate has been crosslinked with an isocyanate-active prepolymer using a crosslinking agent. The crosslinking agent is formulated to have at least three functional groups that are reactive with functional groups of the polyurethane or of the isocyanate-active prepolymer. A method of making the photochromic polyurethane laminate includes steps of causing the crosslinking.

Polyoxymethylene, where a ratio of a low molecular weight component having a molecular weight of 10,000 or less in a molecular weight distribution is 7.0% or less of the total, and the molecular weight distribution is obtained by measurement by gel permeation chromatography (GPC) using polymethyl methacrylate (PMMA) as a standard substance.