Discoloration prevention of phenolic antioxidants

Claim 1

In a process of preparing phenolic antioxidants which comprises (1) reacting one mole of at least one phenolic reactant having the following structural formula: wherein R is selected from the group consisting of hydrogen, alkyl radicals having from 1 to 20 carbon atoms, cycloalkyl radicals having from 6 to 20 carbon atoms, and aralkyl radicals having from 6 to 20 carbon atoms, with (2) at least one tertiary olefin having from 4 to 9 carbon atoms at a temperature of from 50°C. to 150°C. in the presence of a catalyst; then (3) the catalyst is neutralized with an aqueous solution and (4) the reaction mixture is heated under vacuum to remove volatiles and filtered hot; the improvement is characterized in that (A) 0.01 to 5 percent by weight of at least one disubstituted hydroxylamine of general formula (I) and/or (II): wherein R 1 and R 2 are the same or different radicals selected from the group consisting of alkyl radicals of 1 to 18 carbon atoms; and R 3 , R 4 and R 5 are the same or different radicals selected from the group consisting of hydrogen and alkyl radicals of 1 to 8 carbon atoms; is added to the solution used to neutralize the catalyst and (B) prior to filtration 0.01 to 5 percent by weight of a substituted oxime of the structural formula (III): wherein R 1 and R 2 are defined as above is added to the reaction mixture together with an additional 0.01 to 5.0 percent by weight of a substituted hydroxylamine of formula (I) and/or (II); to yield a phenolic antioxidant with improved color and color stability.