Patent ID: 7291669

Claim:
A polyolefin composition of improved discoloration resistance comprising a polyolefin which has incorporated therein a stabilizer system sufficient to attenuate the deleterious effects of melt processing, long term heat aging, and exposure to combustion products of natural gas, said stabilizer system comprising i) at least one hindered phenolic antioxidant selected from the group consisting of tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene and the calcium salt of the monoethyl ester of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid, ii) at least one compound selected from the group consisting of oligomeric sterically hindered amine light stabilizers having a molecular weight above about 1000 g/mole, iii) dioctadecyl methyl amine oxide, and optionally, iv) at least one compound selected from the group consisting of the organic phosphorus stabilizers, where the phenolic antioxidants i) are incorporated from about 0.01% to about 5% by weight, the oligomeric sterically hindered amine stabilizers ii) are incorporated from about 0.05% to about 5% by weight, the dioctadecyl methyl amine oxide iii) is incorporated from about 0.0005% to about 2% by weight, and optionally the organic phosphorus stabilizers iv) are incorporated from about 0.01% to about 5% by weight, each based on the weight of the polyolefin.