Polyoxymethylene moulding compositions with improved heat stability and stability against discoloration

摘要

Polyoxymethylene moulding compositions of the invention comprise;(i) at least one polyoxymethylene homo- and/or copolymer,;(ii) at least one conventional additive and;(iii) at least one polymeric plastics material as an additive for improving the heat stability,;and are distinguished in that;(iii) is a copolymer which is obtainable by polymerization in bulk of a mixture of;A) 60-90 parts of one or more (meth)acrylates,;B) 10-40 parts of one or more (meth)acrylamides,;C) per 100 parts of A)B), 0.2 to 5 parts of molecular weight regulator and;D) per 100 parts of A)B), up to 2 parts of lipophilic free radical polymerization initiators,;and in that;the moulding composition comprises (iii) in an amount of 0.01 to 2 parts, based on the sum of (i)(ii) where all the amounts relate to parts by weight (wt/wt) and A) and B) together must give 100 parts.;By the use of relatively highly regulated bulk co- or terpolymerization for stabilizing POM moulding compositions, advantages over the use of emulsion or suspension bead polymerization result in the heat stability, in the stability against discoloration and/or in the residual monomer contents of POM moulding compositions and shaped articles and shaped films produced therefrom.