| 摘要 |
In a method of controlling the amount of acetaldehyde and acetone in recovered monomers of a terminated copolymerization reaction of monomers having aliphatic carbon to carbon double bonds in the presence of a redox catalyst system in which the activator comprises a water-soluble, oxidizable, sulphoxy compound in which the valence of a sulphur atom does not exceed 4, an aqueous filtrate of the terminated copolymerization reaction is subjected to a first distillation, then to a decantation, then to a second distillation of the aqueous phase, and a decantation of the second distillate. Preferably the method comprises heating the aqueous filtrate in a distillation column, condensing the distillate and passing same overhead to a decanter where the condensate is allowed to separate into a monomer phase and an aqueous phase, returning the monomer phase to the copolymerization reaction system, the aqueous being divided into two parts, one being returned to the distillation column as reflux and the other being fed to a second distillation column, distilled and passed to a decanter where it is allowed to separate into a monomer and an aqueous phase, the former being recycled to the feed of the first distillation column, and the latter being divided into a large part which is returned to the column as reflux and a small part which is purged to waste. The monomers preferably comprise at least one vinyl carboxylate, e.g. vinyl acetate, butyrate, valerate, pelargonate, stearate or laurate and one or more other monomers such as styrene and substituted styrenes acrylic and substituted acrylic acids, esters, amides and nitriles, maleic and fumaric esters, vinyl heterocyclics, vinyl acetylene, methyl isopropenyl ketone, methyl vinyl ether, vinyl ethinyl carbinols, and vinyl and vinylidene halides. The catalyst may comprise perborates, perchlorates, persulphates, persulphuric acid and perdisulphates together with sulphur dioxide, sodium bisulphite, sodium metabisulphite, sodium hydrosulphite, sodium thiosulphate, dialkyl sulphites, p-toluene sulphinic acid and formamidine sulphinic acid. The copolymerization may be effected batchwise or continuously in aqueous emulsion or dispersion, if desired in the presence of an emulsifying agent. An example describes the treatment of an aqueous stream resulting from the copolymerization of vinyl acetate and acrylonitrile. |
