Patent ID: 6210536
Filing Date: 2001-04-03
Classification: C07C,Y10S

Abstract:
A method for inhibiting the polymerization of an acrylic or methacrylic acid or ester during distillation of the acrylic or methacrylic acid or ester, which comprises conducting the distillation in the presence of an effective amount of a polymerization inhibitor composition consisting essentially of:(a) at least one N,N'-dinitroso phenylenediamine compound having the structure: ##STR4##wherein R is C.sub.1 -C.sub.12 alkyl or C.sub.6 -C.sub.10 aryl; R.sup.1 is C.sub.1 -C.sub.12 alkyl, C.sub.6 -C.sub.10 aryl, C.sub.7 -C.sub.11 aralkyl, or C.sub.7 -C.sub.16 alkaryl; and(b) at least one phenothiazine having the structure: ##STR5##wherein R.sup.2 is hydrogen or C.sub.1 -C.sub.12 alkyl; and R.sup.3 and R.sup.4 are each independently selected from the group consisting of hydrogen, C.sub.6 -C.sub.10 aryl, C.sub.7 -C.sub.11 aralkyl, C.sub.7 -C.sub.16 alkaryl and C.sub.1 -C.sub.12 alkyl;(c) optionally a hydroquinone or hydroquinone monomethyl ether; and(d) optionally a phenylenediamine compound having the following structure ##STR6##wherein R.sup.6 is C.sub.1 -C.sub.12 alkyl, C.sub.6 -C.sub.10 aryl or C.sub.7 -C.sub.16 alkaryl; and R.sup.7, R.sup.8 and R.sup.9 are independently selected from the group consisting of hydrogen, C.sub.1 -C.sub.12 alkyl, C.sub.3 -C.sub.12 cycloalkyl, C.sub.7 -C.sub.11 aralkyl and C.sub.7 -C.sub.16 alkaryl.