Process for the production of polyoxymethylene block copolymers

A polyoxymethylene block copolymer comprising the catalytic addition product of one or more alkylene oxides and optionally additional comonomers onto at least one polymeric formaldehyde starter compound having at least one terminal hydroxyl group, in the presence of a double metal cyanide (DMC) catalyst, wherein (i) the DMC catalyst is activated in the presence of the polymeric formaldehyde starter compound, in which activation of the DMC catalyst is accomplished by adding a portion, based on the totality of the amount of alkylene oxides used in the activation and polymerization, of one or more alkylene oxides, (ii) one or more alkylene oxides and optionally additional comonomers are added to the mixture from (i), in which the alkylene oxides used in (ii) may be the same as or different than the alkylene oxides used in (i), and (iii) the activation of the DMC catalyst in (i) is effected at an activation temperature (Tact) of 20 to 120° C.