| abstract |
A method for foaming a vinyl chloride polymer comprises heating a mixture of a polymer, a blowing agent and at least one stabiliser. The stabiliser is selected from an organotin mercaptide of a mercaptoalkyl carboxylate of formula (I) or a sulphide of (I): R1(4-y)Sn[SR2OC(O)R3]y (I) R1 = 1-8C alkyl, R2 = 2-18C alkylene radical, R3 = H, (hydroxy)hydrocarbyl or R4C(O)OR5, R4 = (CH2)2, phenylene or -CH=CH-, R5 = hydrocarbyl radical, p = an integer from 0-8, y = 1-3. The stabiliser optionally further contains at least one organotin salt of formula (II): R'(4-x)SnXx (II) R' = 1-18C alkyl, X = chloride or carboxylate ion and x = 1-3; with the proviso that when (II) is not present, the composition is free from an organotin mercaptoalkyl carboxylate sulphide containing >80 wt.% of a monoorganotin bis(mercaptoalkylcarboxylate)sulphide. |