Sterically hindered oxime color improvers for polyolefin processing

Claim 1

A polyolefin composition stabilized against discoloration during processing at elevated temperature which consists essentially of (a) polyethylene or polypropylene, and (b) an effective stabilizing amount of a compound of formula I ##STR2## wherein R 1 is a tert-alkyl group of 4 to 18 carbon atoms, aryl of 6 to 10 carbon atoms or said aryl substituted by one or two alkyl of 1 to 4 carbon atoms or by one or two alkoxy of 1 to 4 carbon atoms, R 2 and R 3 are independently alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, phenylalkyl of 7 to 9 carbon atoms, aryl of 6 to 10 carbon atoms, or said aryl or said phenylalkyl substituted on the phenyl ring by one or two alkyl of 1 to 4 carbon atoms or by one or two alkoxy of 1 to 4 carbon atoms; or R 2 and R 3 together are a straight or branched chain alkylene of 4 to 10 carbon atoms, n is an integer from 1 to 4, when n is 1, T is alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, phenylalkyl of 7 to 9 carbon atoms, aryl of 6 to 10 carbon atoms, or said aryl or said phenylalkyl substituted on the phenyl ring by one or two alkyl of 1 to 4 carbon atoms or by one or two alkoxy of 1 to 4 carbon atoms, when n is 2, T is alkylene of 2 to 12 carbon atoms, xylylene, arylene of 6 to 10 carbon atoms or said arylene substituted by one or two alkyl of 1 to 4 carbon atoms or by one or two alkoxy of 1 to 4 carbon atoms, and when n is 3 or 4, T is alkanetriyl of 3 to 10 carbon atoms, or alkanetetrayl of 4 to 10 carbon atoms.