THERMAL DEHYDROCHLORINATION AND STABILIZATION OF POLYVINYL-CHLORIDE IN SOLUTION .10. DIALKYLTIN THIOGLYCOLATES

The basic mechanisms already established from model compound studies t o explain the high efficiency of organotin thioester stabilizers for P VC have been confirmed by the study of PVC stabilized in solution at 1 94-degrees-C: the main reaction is substitution of thioglycolate group s either directly or through the thioesters resulting from the reactio n of stabilizers with HCl, which are added to the double bonds of the degraded PVC. A new observation is that this addition reaction does no t take place in the absence of HCI; it is suggested that HCI is first added, followed by a substitution reaction. These mechanisms are valid whether the stabilization, is carried out in air or argon.