Process for chain stopping of PVC polymerization

A process for chain stopping vinyl chloride polymerization, which process comprises

• adding to a vinyl chloride polymerization reaction system
• a stable free nitroxyl radical of formula (I), (II), (III), (IV), (V), (VI), (VII), (VIII) or (IX)
• wherein
• G1, G2, G3, G4 are independently alkyl of 1 to 4 carbon atoms or G1 and G2 or G3 and G4, or G1 and G2 and G3 and G4 together are pentamethylene, with the proviso that if G1-G4 are C1-C4alkyl at least one is ethyl, propyl or butyl;
• G5, G6 are independently hydrogen or C1-C4alkyl;
• R, if m is 1, is hydrogen, C1-C18alkyl which is uninterrupted or C2-C18alkyl interrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic carboxylic acid having 2 to 18 carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or an α,β-unsaturated carboxylic acid having 3 to 5 carbon atoms or of an aromatic carboxylic acid having 7 to 15 carbon atoms;
• or R is a monovalent radical of a carbamic acid or phosphorous containing acid or a monovalent silyl radical;
• R, if m is 2, is C2-C12alkylene, C4-C12alkenylene, xylylene, a divalent radical of an aliphatic dicarboxylic acid having 2 to 36 carbon atoms, or a cycloaliphatic or aromatic dicarboxylic acid having 8-14 carbon atoms or of an aliphatic, cycloaliphatic or aromatic dicarbamic acid having 8-14 carbon atoms;
• or
• R is a divalent radical of a phosphorus-containing acid or a divalent silyl radical;
• R, if m is 3, is a trivalent radical of an aliphatic, cycloaliphatic or aromatic tricarboxylic acid;
• R, if m is 4, is a tetravalent radical of an aliphatic, cycloaliphatic or aromatic tetracarboxylic acid;
• p is 1;
• R1 is C1-C12alkyl, C5-C7cycloalkyl or benzoyl;
• R2 is C1-C12alkyl, C5-C7cycloalkyl or a group of the formula —CO-Z wherein Z is hydrogen, methyl or phenyl;
• R5, R6 and R7 independently are hydrogen, C1-C18alkyl or C6-C10aryl;
• R8 is hydrogen, OH, C1-C18alkyl, C3-C18alkenyl, C3-C18alkinyl, C1-C18alkyl, C3-C18alkenyl, C3-C8alkinyl which are substituted by one or more OH, halogen or a group —O—C(O)—R5, C2-C18alkyl which is interrupted by at least one O atom and/or NR5 group, C3-C12cycloalkyl or C6-C10aryl, C7-C9-phenylalkyl, C5-C10heteroaryl, —C(O)—C1-C18alkyl, —O—C1-C18alkyl or —COOC1-C18alkyl;
• and
• R9, R10, R11 and R12 are independently hydrogen, phenyl or C1-C18alkyl,
• wherein the reaction system comprises initial unreacted vinyl chloride monomer or unreacted vinyl chloride monomer and partially polymerized vinyl chloride monomer.