Boric acid esters and oxetanes for stabilizing phosphite-free polycarbonates

A polycarbonate molding composition comprising a phosphite-free polycarbonate and a stabilizing additive selected from the group consisting of

• (i) a boric acid ester containing at least one oxetane group of the structural formulae I, IIIa, or IIIb ##STR14## wherein at least one of the radicals R.sub.1, R.sub.2 and R.sub.3 is the radical of a monoalcohol containing at least one oxetane group, while at most 2 of the radicals R.sub.1, R.sub.2 and R.sub.3 are radicals of primary, secondary or tertiary aliphatic or cycloaliphatic monoalcohols which are free from oxetane groups or monohydroxyaryl compounds which are free from oxetane groups,
• X is the radical of a dialcohol HO-X-OH containing at least one oxetane group, in which X is an organic radical, containing at least one oxetane group, with between about 5 and 20 C atoms,
• R.sub.5 is the radical of a monoalcohol which is free from oxetane groups or of a monohydroxyaryl compound which is free from oxetane groups and
• n is an integer from about 1 to 10,
• (ii) a mixture of a boric acid ester containing at least one oxetane group of the formulae I, IIIa or IIIb and a boron-free oxetane compound wherein the ratio of boron atoms to oxetane groups is between about 1:2 and 1:10 and
• (iii) a mixture of a boric acid ester which is free from oxetane groups and a boron-free oxetane compound wherein the ratio of boron atoms to oxetane groups is between about 1:2 and 1:10,
• characterized in that the stabilizing additive is present in amounts between about 0.01 and 1% by weight, relative to the weight of pure polycarbonate resin.