Abstract: To provide a practical and economical process for producing trioxane from an aqueous formaldehyde solution in the presence of a solid acid catalyst, which permits a stable operation for a long period of time.A process for producing trioxane from an aqueous formaldehyde solution by using a production apparatus comprising two functional steps, i.e. the first functional step of conducting mainly the removal of metallic impurities from the aqueous formaldehyde solution with a substance having an ion-exchanging function and the second functional step of conducting mainly the synthesis of trioxane from the aqueous formaldehyde solution, from which metallic impurities have been removed, with a solid acid catalyst.

Abstract: Moldable polyacetal resin compositions include a polyacetal base resin and an impact resistant effective amount of a thermoplastic polyurethane resin melt-blended therewith. The polyacetal base resin is itself a mixture of (A.sub.1) a low hydroxyl-containing (LHC) polyacetal resin having less than 50 mmol/kg hydroxyl groups in its molecule, and (A.sub.2) a high hydroxyl-containing (HHC) polyacetal resin having greater than 50 mmol/kg hydroxyl groups in its molecule. The polyacetal resin compositions optionally may include a reactive compound having at least one reactive moiety to further enhance the desirable properties that are achieved by inclusion of the HHC polyacetal resin. The components are melt-blended and subjected to conditions (which typically occur during the melt-blending step) to allow the polyurethane resin to react with the HHC polyacetal resin.