Abstract: Disclosed are mixtures of oxyalkylene bridged bis- and tris-phosphite esters of formulae I and II where R is hydrogen or methyl, n and n? are independently an integer from 1 to 45 and R1, R2 and R3 are each independently hydrogen, straight or branched chain alkyl of 1 to 12 carbon atoms, phenylalkyl of 7 to 9 carbon atoms, phenylalkyl of 7 to 9 carbon atoms substituted on the phenyl ring by one to three straight or branched chain alkyl of 1 to 12 carbon atoms or R1, R2 and R3 are each independently —(CH2)k—COOR4 where k is 0, 1 or 2 and R4 is hydrogen or straight or branched chain alkyl of 1 to 20 carbon atoms. The mixtures of formula I and II are liquid at ambient conditions and are effective stabilizers for polyolefins.

Abstract: Disclosed are mixtures of oxyalkylene bridged bis- and tris-phosphite esters of formulae I and II where R is hydrogen or methyl, n and n? are independently an integer from 1 to 45 and R1, R2 and R3 are each independently hydrogen, straight or branched chain alkyl of 1 to 12 carbon atoms, phenylalkyl of 7 to 9 carbon atoms, phenylalkyl of 7 to 9 carbon atoms substituted on the phenyl ring by one to three straight or branched chain alkyl of 1 to 12 carbon atoms or R1, R2 and R3 are each independently —(CH2)k—COOR4 where k is 0, 1 or 2 and R4 is hydrogen or straight or branched chain alkyl of 1 to 20 carbon atoms. The mixtures of formula I and II are liquid at ambient conditions and are effective stabilizers for polyolefins.

Abstract: 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, 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° 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.