GB960319A - A process for cross-linking of high molecular weight organic materials - Google Patents

Abstract

Polyaddition and polycondensation products are cross-linked by heating to 100 DEG to 220 DEG C. with a peroxide of the general formula: <FORM:0960319/C3/1> in which R is a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms and X is an aliphatic hydrocarbon radical, a cycloaliphatic radical or the group: <FORM:0960319/C3/2> Peroxides mentioned are mesityloxide-peroxide; 3-ethyl-peroxy-3, 5, 5-trimethyl-dioxolane-(1,2); and 3-tert-butyl-peroxy-3, 5, 5-trimethyl-dioxolane-(1, 2). These peroxides may be used in conjunction with other known peroxides e.g. di-tert-butyl peroxide. The amount of peroxide used is generally 0.5 to 10% by weight, calculated on the weight of polymer. Polyaddition products mentioned are polymers of a -olefines and copolymers thereof with vinyl esters; homopolymers of acrylic esters and copolymers thereof with vinyl esters or methacrylic esters; homopolymers of conjugated diolefines and copolymers thereof with a -olefines &c. Mixtures of ethylene-vinyl ester-copolymers and polyethers e.g. polytetrahydrofuran, polyethylene oxide and polypropylene oxide, may be cross-linked. Polycondensation products mentioned are unsaturated polyesters especially those based on a , b -unsaturated dicarboxylic acids and polyhydric alcohols; polyesters which have been lengthened with polyisocyanates e.g. reaction products of linear hydroxyl-group containing condensation and/or addition products with diisocyanates and glycols. In the cross-linking process, the peroxides and if desired other additives, are mixed into the high molecular weight compounds either in solution or in the solid state. In one embodiment of the invention copolymers of ethylene and vinyl esters or ethylene and propylene are cross-linked with the above peroxides in the presence of small quantities of compounds which contain several olefinically unsaturated bonds and which have at least two unconjugated polymerizable carbon-carbon double bonds, the prepared compounds containing three allyl groups; many other suitable compounds are mentioned, including olefinically unsaturated polyethene, polyurethanes of polyisocyanates and olefinically unsaturated alcohols, and unsaturated polyesters. In addition sulphur or compounds which split off sulphur may be present. The polymers to be cross-linked may contain fillers. The copolymers may be foamed before or during vulcanization, e.g. by adding a gas under pressure and subsequently releasing the pressure or by heating mixtures of these copolymers with easily volatile solvents. Alternatively blowing agents may be used e.g. alkali metal carbonates or organic compounds such as azodiisobutyric acid dinitrile, aromatic sulphohydrazides and nitroso compounds. Specifications 862,232, 935,044, 937,165, 937,166 and 940,713 are referred to.