Polyoxymethylene multi-block copolymers, their production and use

A composition comprising homo- and/or copolyoxymethylenes and multiblock copolymers containing the structural unit of formula I

• -A-O—R1—O—CO—X-D-X—CO—X— (I),
• where A is a radical derived from a homo- or copolyoxymethylene and the structural elements of —X—CO—X— derives from diesters of carbonic acid,
• R1 is an alkylene radical having at least two carbon atoms, or a cycloalkylene radical,
• X is selected from —O—, —S—, or —NH—, and
• D is a divalent radical B which is a radical of a hydroxy-terminated, mercaptan-terminated, or amino-terminated polymer which derives from polyalkylene glycols, polyvinyl ethers, polyvinyl ether copolymers with alkenes, polyvinyl esters, polyvinyl ester copolymers with alkenes, polyvinyl alcohols, polyvinyl alcohol-alkene copolymers, polyvinylaromatics, polyacrylates, polymethacrylates, polyacetals which have from 0 to 50 mol % of oxymethylene units, polycarbonates, polyesters, polyamides, polyimines, polyetherester elastomers (PEEs), polyetheramide elastomers (PEAs), polyalkadienes which may, where appropriate, have been hydrogenated, polyurethanes, polyureas, polysiloxanes, or is a hydroxyterminated triblock copolymer radical -PAO-B-PAO-, where B assumes one of the above meanings and PAO is a polyalkylene oxide radical.