Synthesis of antimony tris(mercaptoethyl carboxylates) as thermal stabilizer for polyvinyl chloride

A novel type of thermal stabilizers-antimony tris(mercaptoethyl carboxylates) (Sb(SCH 2CH 2OOCR) 3), was synthesized from carboxylic acid, antimony trioxide and 2-mercaptoethanol in two steps. The experimental results show that the molar ratio of carboxylic acid to antimony tris(2-hydroxyethyl mercaptide) is 1.2, when adding 0.6% tetra-n-butyl titanate as catalyst and xylene as isotropic solvent, heating and refluxing for about 2～4 h. The thermal stability was measured by heat-aging oven test. The thermal stability time is about 8～40 min(at 200 ℃) when adding 2% tetra-n-butyl titanate in polyvinyl chloride(PVC). Among these stabilizers, antimony tris(mercaptoethyl stearate) has best thermal stability. Its thermal stability is better than that of Ca-Zn complex and basic lead stabilizers, and equal to that of organotin. In addition, the stabilization mechanism of this kind of stabilizers for PVC was discussed briefly.