STABILIZER FOR CHLORINE-CONTAINING POLYMER AND ITS PRODUCTION

PURPOSE:To provide the titled stabilizer composed of a specific basic lead maleate sulfate, and having remarkably improved thermal stability and improved insulation property. CONSTITUTION:The objective stabilizer is composed of a basic lead maleate sulfate of formula nPbO.PbMx(SO4)y.mH2O (n is 1.5-3.3; M is maleic acid residue; x is 0.05-0.7; y is 0.95-0.3; x+y=1; m is =I12.1/I10.0>=0.1 and 2>=I9.02/I12.1>=0 (I12.1, I10.0 and I9.02 are relative intensities of the X-ray diffraction pattern corresponding to the spacings of 12.1Angstrom , 10.0Angstrom and 9.02Angstrom , respectively). The compound can be produced by reacting maleic acid (anhydride) with an aqueous slurry containing lead monoxide and a catalytic amount of a monobasic acid or its ammonium salt, and reacting the reaction product with sulfuric acid keeping the molar ratio of [maleic acid (anhydride)]:(sulfuric acid) to 1:19-7:3, and that of (lead monoxide):(sum of the acids) to (2.5-4.3):1.