Patent ID: 8013083

Claim:
A method for inhibiting the premature polymerization of styrenic monomers comprising adding to said monomers a combination of: (A) from about 0.5 percent by weight to about 3 percent by weight of at least one sulfonic acid compound selected from the group consisting of toluenesulfonic acid, xylenesulfonic acid, cumenesulfonic acid, dodecylbenzenesulfonic acid, pentadecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid; and (B ) about 0.25 to about 0.5 molar equivalents per molar equivalent of said sulfonic acid compound of at least one amine selected from the group consisting of pyridine, 2,6-dimethyl-4-aminopyridine, 2,6-lutidine, N-(1,4-dimethylpentyl)aniline, and methyl aniline; and, (C) at least one inhibitor selected from the group consisting of a nitrophenol, a nitroxyl compound, and a nitrosoaniline whereby an uncontrolled exothermic reaction of styrenic monomer will be prevented.