GRAFTING ANTIOXIDANTS .8. ANTIOXIDANT ACTIVITY AND GRAFTING OF SOME N-(ARYL)-2,6-DI-TERT-BUTYLQUINONEIMINES

Several 2,6-di-tert-butyl-N-aryl-p-quinoneimines Ia-Id and N-isopropyl -N'-phenyl-p-quinonediimines were synthesized and tested as rubber ant ioxidants. Quinoneimines containing an N-p-hydroxyphenyl and an N-p-am inophenyl substituent have a high antioxidant efficiency in IR, SBR, E PR and EPDM rubbers because they add to the allylic -CH of the polymer giving active adducts. These adducts contain two groups which can tra p peroxy radicals. Quinoneimines and quinonediimine also assure a good protection of the vulcanizates even after water extraction. The reten tion of the protective activity after extraction indicates the graftin g of these compounds during thermal or mechanical processing of rubber . A reaction mechanism is proposed to explain the antioxidant activity and the grafting ability of these compounds. The quite significant ac tivity of compound Ic as an antiozonant in rubber vulcanizates must al so be mentioned.