Ortho-substituted phenyl phosphite additive composition

In an additive composition for improving the color stability upon heating at 175.degree. C. of a vinyl chloride polymer composition stabilized with environmentally acceptable stabilizers only.

• said stabilizers comprising at least one salt of a non-nitrogenous mono-carboxylic acid having 6 to 24 carbon atoms or a phenol having 6 to 36 carbon atoms with at least one of the metals lithium, sodium, potassium, zinc, barium, calcium, magnesium, and strontium, and said additive composition comprising a 1,3-diketone represented by the formula ##STR18## in which R is a hydrocarbon group, a halohydrocarbon group, an alkoxyhydrocarbon group, or an alkylenedioxyhydrocarbon group having 1 to 18 carbon atoms;
• R' is a hydrogen atom, an acyl group ##STR19## where R"' is alkyl or a hydrocarbon group having 1 to 18 carbon atoms;
• R" is a hydrogen atom or a hydrocarbon group, a halohydrocarbon group, an alkoxyhydrocarbon group, or an alkylenedioxyhydrocarbon group, having 1 to 18 carbon atoms;
• M' is hydrogen or a metal selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, strontium, barium, and zinc;
• and n is an integer from 1 to 3 depending on the valence of M';
• and an organic phosphite, the improvement in which the organic phosphite has the formula:
• ##STR20## in which R.sub.1 is a t-butyl, t-amyl, phenyl or cycloalkyl group having 5 to 8 carbon atoms;
• each of R.sub.2 and R.sub.3 independently is a hydrogen atom, a phenyl group, an alkyl group having 1 to 5 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms;
• R.sub.4 is a hydrogen atom or a methyl group, and each of R.sub.5 and R.sub.6 independently is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 5 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 12 carbon atoms, an alkaryl group having 7 to 18 carbon atoms, or an ether-substituted group having 3 to about 80 carbon atoms and 1 to about 40 ether oxygen atoms.