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Abstract

N-substituted, N-(polysubstituted-4-piperidinyl)-.alpha.-(3,5-dialkyl-4-hydroxyphenyl)-.alpha., .alpha.-disubstituted acetamide ('3,5-DHPIPA') generates an exceptionally stable hindered acetamide aroxyl radical which is far more stable than the 'blue aroxyl radical' derived from 2,4,6-tri-tert-butyl-phenol, which radical was heretofore adjudged the standard of superior stability and resistance to degradation due to heat, oxygen and light, the compound having been specifically disclosed as a uv-stabilizer. The hindered aroxyl amide radical which is at least ten times more stable than the 'blue aroxyl radical' heretofore deemed stable, may be generated by 3,5-DHPIPA compounds prepared by a peculiarly effective synthesis known as the ketoform reaction. This ketoform reaction is unexpectedly well-adapted to produce the 3,5-DHPIPA compounds which we have been unable to produce by any other synthesis known to us. The stability of the hindered aroxyl amide radical inculcates an organic material in which a 3,5-DHPIPA compound is dispersed, with excellent stability. The use of a combination of 3,5-DHPIPA compounds, or a combination of a 3,5-DHPIPA compound with with known stabilizers, particularly the phosphites and benzophenones, in a small but stabilizing amount, provides especially effective stabilization in polyolefins and a host of other synthetic resinous materials.

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