Poly(vinyl chloride) stabilisation with organo-tin compounds: Part V—Model studies of epoxy—Tin synergism

Abstract

Organo-tin chlorides are able to catalyse the reaction of epoxy compounds with allylic chlorine atoms. Three main reactions are observed: nucleophilic substitution of the epoxy compound which leads to the formation of a β-chloroether, elimination which gives a diene compound, and cationic polymerisation of the epoxy. Increasing the Lewis acidity of the tin chlorides strongly favours the substitution reaction which is actually a stabilisation reaction for the PVC. On the other hand, the most basic epoxy compounds are very prone to the polymerisation. The details of the kinetics can be explained in terms of a concerted mechanism inside the co-ordination sphere of the tin atom, after initial coordination of the epoxy compound for which there is NMR spectroscopic evidence. Two other side reactions are observed: consumption of the ionic chlorides through the termination reaction of the polymerisation and acidolysis of the ether by excess HCl, but that reaction may take place only when there is an excess of allylic chloride with respect to epoxy, or upon addition of HCl.