Polyacetal resin composition and preparation process thereof

A polyacetal resin composition obtained by a process comprising mixing a polyacetal resin with a mixture of a first hydrazine derivative and a compound for lowering the melting point of the first hydrazine derivative,

• wherein the mixture of the first hydrazine derivative and the compound for lowering the melting point of the first hydrazine derivative satisfies the conditions represented by the following formulas (1) and (2):
• T1<T2 (1)
• T1<T3 (2)
• wherein T1 is a temperature (° C.) showing an apex of an endothermic peak of the mixture having a maximum endothermic capacity, among endothermic peaks obtained by, with a differential scanning calorimeter, heating and cooling the mixture in accordance with a predetermined temperature program and then heating at a rate of 2.5° C./min until the mixture fuses, T2 is a temperature (° C.) showing an apex of an endothermic peak of the first hydrazine derivative having a maximum endothermic capacity, among endothermic peaks obtained by, with the differential scanning calorimeter, heating and cooling the first hydrazine derivative in accordance with a predetermined temperature program and then heating at a rate of 2.5° C./min, and T3 is a temperature (° C.) showing an apex of an endothermic peak of the polyacetal resin having a maximum endothermic capacity, among endothermic peaks obtained by, with the differential scanning calorimeter, heating and cooling the polyacetal resin in accordance with a predetermined temperature program and then heating at a rate of 2.5° C./min, and
• wherein the first hydrazine derivative and the compound for lowering the melting point of the first hydrazine derivative respectively contain carboxylic acid dihydrazides selected from the group consisting of adipic acid dihydrazide and sebacic acid dihydrazide, but different from each other.