GB1360419A - Removal of polymerisation inhibitors from ethylenically 'nsatu rated monomers - Google Patents

Abstract

1360419 Purification of ethylenically unsaturated monomers A A GELLON and V M RIETTI 1 Oct 1971 [14 Oct 1970] 45845/71 Heading C2C [Also in Division C5] Polymerization inhibitors, e.g. tertiary butyl catechol, hydroquinone and hydroquinone monoethylether, and other impurity that reacts with alkali metal hydroxide are removed from ethylenically unsaturated monomers, e.g. acrylonitrile and methylmethacrylate, by intimately contacting the latter with an alkali metal hydroxide solution of at least 4N and separating the alkaline phase from the monomer, the monomer phase having dissolved therein at least 0À02% by weight water and the alkaline phase having, throughout the process, a concentration of at least 4N. The monomer phase preferably has a water content between 0À02% by weight and the saturation value. If the process is carried out batchwise, the amount of alkali metal hydroxide solution may be less than 1% by weight of the monomer. Intimate contact may be achieved simply by vigorous stirring together of the monomer and alkali metal hydroxide solution. Alternatively the latter may be mixed with a minor proportion of the monomer to be purified and this mixture then mixed with the remainder of the monomer, or the hydroxide may be emulsified in an organic liquid and the emulsion then mixed with the monomer. A particulate adsorbent carrying the hydroxide solution may be used to promote intimate contact between the latter and the monomer. The purification may also be carried out continuously by passing the monomer over the alkali metal hydroxide solution which is carried on a support, e.g. a bed of particulate or fibrous material held in a vessel. Solvents specified for the alkali metal hydroxide solution are H 2 O, CH 3 OH, C 2 H 5 OH and mixtures thereof.