Latent mercaptan stabilizers for improved weatherability of clear halogen-containing polymer compositions

A clear halogen-containing polymer composition stabilized against the deteriorative effects of heat, light and weathering, said composition being capable of producing substantially transparent articles, said composition comprising a halogenated polymer and, in an amount sufficient to stabilize said polymer against the deteriorative effects of heat, light and weathering, a stabilizer composition comprising the combination of:

• A) degradation products of a blocked mercaptan present during processing of the composition at an elevated temperature, said products including a free mercaptan;
• wherein said latent mercptan has the structure
• wherein a is 0 or 1, m and n are 0 or 1;
• y=1 to 4;
• when y=1, z is 1 to 4;
• and when y is more than 1, z is 1;
• R1 is a hydroxyalkyl, dihydroxyalkyl, hydroxy(polyalkoxy)alkyl, alkoxyalkyl, hydroxyalkoxyalkyl, alkoxy(hydroxyalkyl), alkoxy(acyloxyalkyl), alkoxy(polyalkoxy)alkyl, carboxyalkyl, acyloxyalkyl, acyloxy(hydroxyalkyl), acyloxyalkoxyalkyl, acyloxy(polyalkoxy)alkyl, benzoyloxy(polyalkoxy)alkyl, alkylenebis-(acyloxyalkyl), alkoxycarbonylalkyl, alkoxycarbonylalkylenyl, hydroxyalkoxycarbonylalkyl, hydroxy(polyalkoxy)carbonylalkyl, alkoxy(polyalkoxy)carbonylalkyl, mercaptoalkyl, mercaptoalkylenyl, mercaptoalkoxycarbonylalkyl, mercaptoalkoxycarbonylalkylenyl, alkoxycarbonyl(amido)alkyl, alkylcarbonyloxy(polyalkoxy)carbonylalkyl, tetrahydropyranyloxyalkyl, tetrahydopyranyloxy(polyalkoxy)carbonylalkyl, hydroxyaryl, mercaptoaryl or carboxyatyl radical having from 1 to 22 carbon atoms;
• R2, R3, R4, R5, R6, and R7 are independently hydrogen, a hydroxyl, mercapto, acyl, alkyl, alkylenyl, aryl, haloaryl alkaryl, aralkyl, hydroxyalkyl, mercaptoalkyl, hydroxyaryl, alkoxyaryl, alkoxyhydroxyaryl, hydroxyalkyl, mercaptoalkyl, mercaptoalkylenyl, mercaptoalkoxycarbonylalkylenyl, hydroxyaryl, arylcarbonyl, mercaptoaryl, carboxyalkyl, carboxyaryl, or acyl radical having from 1 to 22 carbon atoms;
• X is aryl, haloaryl, alkaryl, hydroxyaryl, dihydroxyaryl, aralkaryl, alkoxyaryl, arylcycloalkyl, or a heteroatom, with the option that when a is 1 and m is 0, one of the R3 and R5 radicals joins with R7 and X to form a heterocyclic moiety with X as a heteroatom selected from the group consisting of oxygen and sulfur, and with the further option that when m is 1, R6 and R7 form a heterocyclic moiety in conjunction with X as a nitrogen atom;
• with the proviso that when X is aralkaryl, R6 and R7 are hydroxyl, a is 1 and m is 1, then z is 1 or 2, and with the further proviso that when R6≠hydroxyl or mercapto, z is 1;
• and,
• B) in an amount sufficient to synergize the stabilization of the free mercaptan, a free phenyl salicylate compound.