POLYACETAL BLOCK COPOLYMER

PROBLEM TO BE SOLVED: To provide an AB-type polyacetal block copolymer that can suppress a production amount of formaldehyde gas and is excellent in welding characteristics and sliding property.SOLUTION: The AB-type polyacetal block copolymer comprises a polyacetal segment (A) containing a specified oxymethylene unit (i) and a specified oxyalkylene unit (ii) expressed by general formula (II), and a single-end hydroxyalkyl segment (B). An insertion amount of the oxyalkylene unit (ii) in the polyacetal segment (A) is 0.05 to 1.0 mol with respect to 100 mol of the oxymethylene unit (i). In the specified oxyalkylene unit (ii), a proportion of the oxyalkylene unit when y=1 is 95 mol% or more in the whole oxyalkylene units, and when y≥2, the proportion of the oxyalkylene unit is 5 mol% or less of the whole oxyalkylene units.