Patent ID: 7812110

Claim:
A process for preparation of oxymethylene copolymers containing the structural units of the formula II and III, and also end groups of the formula IV or containing the structural units of the formula II and V, and optionally formula IV, and also end groups of the formula IV in which R 1 is an alkyl radical, m is a whole number from 1 to 1000, o is a whole number from 2 to 6, p is a whole number from 3 to 6, and R 3 is a p-valent organic radical encompassing the following measures: i) heterogeneous polymerization of a monomer which forms —CH 2 —O— units and simultaneously of a monomer which forms —O—C o H 2o — units, in the presence of an acetal of formaldehyde and of an initiator for cationic polymerization, or heterogeneous polymerization of a monomer which forms —CH 2 —O— units and simultaneously of a monomer which forms —O—(R 3 —O) p — units and, optionally simultaneously of a monomer which forms —O—C o H 2o — units, in the presence of an acetal of formaldehyde and of an initiator for cationic polymerization, wherein the heterogeneous polymerization is a precipitation polymerization conducted at a temperature from 70 to 120° C. and a pressure from 0 to 10 bar, and ii) deactivation of the initiator and/or of the active polymer chains by using an aprotic solvent which is basic and/or which comprises a dissolved base, the aprotic solvent added in an amount of at least 10% by weight, for treatment in a homogeneous phase of the polymer prepared in step i), wherein deactivation is conducted at a temperature from 130 to 160° C.