Properties and role of benzoquinone imines in polymer stabilization

Abstract

Quinone imines are formed from aromatic amine antidegradants as a consequence of chemical transformations of the latter during the stabilization of hydrocarbon polymers. Quinone imines are deep coloured compounds and contribute to the antidegradant activity of the parent amines. The main interest is devoted to benzoquinone diimines (BQDI), generated from N,N '‐disubstituted 1,4‐phenylenediamines (PD). BQDI are antioxidants in unsaturated hydrocarbons, undergo hydrolytic deamination, addition and cyclization reactions, react with 2,6‐dialkylphenols, thiols and C‐centered radicals. PD are regenerated from BQDI in redox reactions. The active role of BQDI in antifatigue processes in rubbers has been explained using product analysis. BQDI account for staining and discoloring properties of PD but are not harmful to the polymer stability.

Antioxidants and stabilizers. XLV. Oxidation of halogenated dihydric phenols with oxygen and its comparison with antioxidative activity

“…We also found that halogenated hydroxy-l,4-benzoquinones were formed in a mixture with other compounds during the oxidation of trihalogenated pyrocatechols. Accordingly, 4-chloroand 4,5-dichloropyrocatechol yielded 2,5-dihydroxy-l,4-benzoquinone [ 141 , that is, the same product as that arising during the oxidation of pyrocatechol alone in an alkaline medium [15,16]. Besides quinoid compounds which are also the product of a reaction between tetrahalogenated pyrocatechols and tert-butylhydroperoxide, deeper oxidation leads to the formation, in a small amount, of the cleavage products of the aromatic ring; oxalic acid was identified here.…”