Importance

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Abstract

Disclosed herein is a method for inhibiting the premature polymerization of ethylenically unsaturated monomers comprising adding to said monomers an effective amount of a mixture comprising: A) at least one stable hindered nitroxyl compound having the structural formula: ##STR1## wherein R.sub.1 and R.sub.4 are independently selected from the group consisting of hydrogen, alkyl, and heteroatom-substituted alkyl and R.sub.2 and R.sub.3 are independently selected from the group consisting of alkyl and heteroatom-substituted alkyl; and X.sub.1 and X.sub.2 (1) are independently selected from the group consisting of halogen, cyano, COOR.sub.7, --S--COR.sub.7, --OCOR.sub.7, (wherein R.sub.7 is alkyl or aryl), amido, --S--C.sub.6 H.sub.5, carbonyl, alkenyl, or alkyl of 1 to 15 carbon atoms, or (2) taken together, form a ring structure with the nitrogen; and B) at least one inhibitor selected from the group consisting of ortho-quinone, ortho-hydroquinone, para-quinone, para-hydroquinone, and derivatives of the foregoing.

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First Claim