The present invention relates to a method for producing formaldehyde-alkylene carbonate copolymers comprising the step of reacting trimeric, oligomeric and/or polymeric formaldehyde with an alkylene carbonate in the presence of a catalyst. Said invention further relates to copolymers obtainable by this method and the reaction products thereof with polyisocyanates.

A polymer of an embodiment includes a repeating unit containing at least one bivalent group selected from the following formula (1) and the following formula (2). ##STR00001## In the formulas (1) and (2), R is hydrogen, fluorine, an alkyl group, an aryl group, a heteroaryl group, or the like. X and Y are each an alkanoyl group, an aminocarbonyl group, an alkylsulfonyl group, or the like. Ar is an aryl group or a heteroaryl group.

The present invention provides: a polyacetal resin composition that achieves a highly dispersed state of cellulose in a polyacetal resin, and that achieves, at a high level, both high temperature rigidity and toughness when being under a load; and a method for producing same. This polyacetal resin composition contains: 100 parts by mass of a polyacetal resin (a); 1-150 parts by mass of fine cellulose fibers (b) having a fiber diameter of 2-1000 nm; and 0.1-100 parts by mass of a polyethylene glycol (c). An ethylene ratio R (%) which is the ratio of the number of oxyethylene units in the polyacetal resin (a) with respect to the total number of oxymethylene units and oxyethylene units in the polyacetal resin (a), and an oxyethylene repeating unit number n of the polyethylene glycol (c) satisfy the relationship of formula: (R+0.5)/0.015n(R+10)/0.015.