The present invention discloses a process for stabilizing polyolefin compositions against the deleterious effects of melt processing, heat aging and exposure to combustion products of natural gas, which process comprises incorporating or applying to a polyolefin an effective stabilizing amount of a tris-(mono-alkyl)phenyl phosphite ester of the formula I, ##STR00001## or a mixture of phosphite esters of formula I, where each R is the same or different and is straight or branched chain alkyl of from 1 to 8 carbon atoms, and where said phosphite ester or phosphite ester mixture is in the liquid state at 25.degree. C. and 1 atm of pressure. Also disclosed is a stabilized composition comprising polyolefin and a present phosphite ester or phosphite ester mixture as well as certain mixtures of tris-(mono-alkyl)phenyl phosphite. The present liquid phosphite ester stabilizers are especially compatible with low density polyethylene.
This application claims benefit under 35 USC 119(e) of U.S. provisional application No. 60/701,279, filed Jul. 21, 2005, the contents of which are hereby incorporated by reference.
