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.

The present invention is to provide a process for producing an oxymethylene copolymer, in which deteriorate due to oxidation hardly occurs, an amount of formaldehyde generated from the product when stored for a long time under environment of high temperature and high humidity is reduced, and occurrence of mold deposit during molding is small. A process for producing an oxymethylene copolymer includes Step 1 of polymerizing polymer raw materials containing trioxane and a comonomer in the presence of a specific amount of an acid catalyst, Step 2 of adding a hydroxylamine compound represented by the following general formula (1):

##STR00001## to a product obtained in the Step 1 in an amount of 1 to 20-fold mol based on an amount of the acid catalyst and mixing these, and Step 3 of further melting and kneading a mixture of the product and the hydroxylamine compound obtained in the Step 2.

The present invention is to provide a process for producing an oxymethylene copolymer, in which deteriorate due to oxidation hardly occurs, an amount of formaldehyde generated from the product when stored for a long time under environment of high temperature and high humidity is reduced, and occurrence of mold deposit during molding is small. A process for producing an oxymethylene copolymer includes Step 1 of polymerizing polymer raw materials containing trioxane and a comonomer in the presence of a specific amount of an acid catalyst, Step 2 of adding a hydroxylamine compound represented by the following general formula (1):

##STR00001## to a product obtained in the Step 1 in an amount of 1 to 20-fold mol based on an amount of the acid catalyst and mixing these, and Step 3 of further melting and kneading a mixture of the product and the hydroxylamine compound obtained in the Step 2.

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.

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.

The invention provides an antimicrobial fiber which exhibits excellent antimicrobial properties even without the addition of antimicrobial agents and can remain antimicrobial even after repeated washing. The antimicrobial fiber comprises a fiber having on a surface thereof a polyacetal copolymer (X) containing oxyalkylene groups, the molar amount of oxyalkylene groups in the polyacetal copolymer (X) being 0.2 to 5 mol % relative to the total of the molar amount of oxymethylene groups and the molar amount of oxyalkylene groups.

An oxymethylene copolymer resin composition, which includes (i) an oxymethylene copolymer, (ii) a derivative of an aryl boron fluoride compound, and (iii) a layered double hydroxide; and a method for producing the same.

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.

A method of producing dimethoxymethane oligomers (DMMn), the method comprising: reacting a formaldehyde source and dimethoxymethane monomer (DMM1) in the presence of an acidic catalyst to produce a reaction effluent comprising DMMn and unreacted DMM1; and separating, from the reaction effluent, DMM1-2 including unreacted DMM1 and DMMn having a chain length n equal to 2 (DMM2), dimethoxymethane oligomers having a chain length n in the range of from 2-5 (DMM2-5), dimethoxymethane oligomers having a chain length n of 5 (DMM5+), or a combination thereof, wherein the separating comprises distillation in the presence of at least one alcohol, a distillate fuel, or both.

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.