Patent ID: 6331647
Filing Date: 2001-12-18
Classification: C07C

Abstract:
A process for the preparation of a purified monomer comprising the steps of reacting a substantially aqueous solution of an impure monomer ##STR12##wherein R.sup.1 and R.sup.2 are independently hydrogen or alkyl groups containing from 1 to about 6 carbon atoms, with(B) a substantially aqueous solution of an oxide or hydroxide of the structure MO or MOH wherein M is a Group IA or Group IIA metal, or an amine of the structure NR.sup.3 R.sup.4 R.sup.5 wherein R.sup.3, R.sup.4 and R.sup.5 are independently hydrogen or alkyl, alkanol or alkoxy groups containing from 1 to about 12 carbon atoms,wherein the molar ratio of (A):(B) is from about 1:1-2 for Group IA metals, 2:1-2 for Group IIA metals or ratio of moles of (A) to nitrogens of (B) is from about 1:1-2 nitrogens to form a salt, wherein in order to prevent polymerization of (A), the purified monomer or both or to prevent undesired side reactions, the reaction of (A) and (B) occurs at a temperature of between about -20 to 75.degree. C. and at a pH between 7 to 12.5, andrecovering a purified salt by crystallization in the presence of an oxygen bearing gas stream either by removing water from the aqueous solution by subjecting the aqueous solution to an increase in temperature and/or a decrease in pressure or by decreasing the solubility of the salt in the aqueous solution by subjecting the aqueous solution to a decrease in temperature.