PROBLEM TO BE SOLVED: To provide a quaternary ammonium compound for obtaining a polyacetal resin composition of high purity, where the quaternary ammonium compound prevents the occurrence of formaldehyde, acetaldehyde and acrolein even when subjected to a heating treatment such as heat melting.SOLUTION: The present invention provides a quaternary ammonium compound represented by formula (1): [(R1)m(R2)4-mN+]nXn- (R1s independently represent a C1-30 unsubstituted/substituted alkyl group, a C6-20 aryl group or the like R2s independently represent a group represented by the following formula -(RO) k-H, the group having 2-60 carbon atoms and 2-30 oxygen atoms R is a substituted/unsubstituted alkylene group k is a natural number of 2 or more m and n are each an integer of 1-3 X is a hydroxy group or an acid residue of a compound selected from C1-20 monocarboxylic acid, hydrogen acid, oxo acid, inorganic thio acid or C1-20 organic thio acid, representing a group free of N).SELECTED DRAWING: NoneCOPYRIGHT: (C)2018,JPO&INPIT【課題】加熱溶融等の加熱処理をしてもホルムアルデヒドとアセトアルデヒドとアクロレインの発生を抑制した、純度の高いポリアセタール樹脂組成物を得るための第4級アンモニウム化合物の提供。【解決手段】式(1)で表わされる第4級アンモニウム化合物。[(R1)m(R2)4-mN+]nXn-(1)(R1は各々独立してC1~30の非置換/置換アルキル基、C6~20のアリール基等;R2は各々独立してC2~60、酸素数が2~30である、次式で表される基-(RO)k―H;Rは置換/非置換のアルキレン基;kは2以上の自然数;m及びnは、1~3の整数;Xは水酸基又はC1~20のモノカルボン酸、水素酸、オキソ酸、無機チオ酸或いはC1~20の有機チオ酸から選ばれる化合物の酸残基、Nを含まない基)。【選択図】なし
