Patent ID: 7691952

Claim:
A method for inhibiting and retarding the premature polymerization and the polymer growth of styrene monomer comprising adding to said styrene monomer an effective amount of at least one inhibitor that is a sulfonated nitrophenol of the formula: wherein: R 1 , R 2 , and R 3 are independently selected from the group consisting of hydrocarbyl, NO 2 and SO 3 H, provided that one of R 1 , R 2 , and R 3 is NO 2 , one of R 1 , R 2 , and R 3 is hydrocarbyl, and one of R 1 , R 2 , and R 3 is SO 3 H; and the total inhibitor concentration is in the range of from about 1 to about 2000 ppm versus the styrene monomer being inhibited.