procedure for the manufacture of tvaerbundne shaped subjects paabasis of tvaerbindingsdygtige olefinpolymere or vinylchloridpolymere materials

摘要

1489580 Cross-linking polymers with organic peroxides NORDISKE KABEL-OG TRAADFABRIKER AS 3 Oct 1974 [15 Oct 1973] 47993/73 Heading C3P Moulded objects, e.g. tubes or slabs, formed from cross-linkable polymers, e.g. polyethylene or PVC, are cross-linked by (a) heating the object in the presence of a liquid medium containing one or more peroxides which penetrate into the object, and (b) heating the impregnated object at an increased temperature whilst immersed in a liquid. The peroxide is chosen so as to be stable at the temperature of step (a) and to cleave into free radicals at the temperature of step (b). Suitable peroxides include di - t - butyl peroxide, 1,1 - bis - (tbutylperoxy) - 3,3,5 - trimethylcyclohexane, and a mixture of the latter with 2,5-dimethyl- 2,5-di-(t-butylperoxy)hexane. Additional crosslinking agents may be present, e.g. sorbic acid, ethylene glycol dimethacrylate and triallyl cyanurate. The liquid medium for step (a) is suitably an aqueous emulsion containing the peroxide, and the same medium may be retained for step (b). Alternatively, a different medium may be provided for step (b), e.g. an aqueous solution of sodium sulphite. In either case the medium for step (b) preferably has the same density as the object.