Kontinuierliches Verfahren zur Herstellung von Polymerdispersionen

1,234,395. Continuous preparation of polymer dispersions. IMPERIAL CHEMICAL INDUSTRIES Ltd. 20 June, 1968 [30 June, 1967], No. 30353/67. Headings C3G and C3P. A continuous process for preparing stabilized dispersions of polymer in organic liquid, which does not dissolve the dispersed polymer but which does dissolve the monomer from which the polymer is derived, comprises feeding ethylenically unsaturated monomer, dispersion stabilizer and organic liquid into a reaction vessel, whose working capacity occupied by the dispersion is of greater height than average width, and which contains a dispersion of the desired polymer in the desired organic liquid, the monomer being fed diffusely (i.e. the monomer feed is rapidly diluted by the dispersion in the region of the point of addition so as to prevent a localized high concentration of monomer) into the uppermost portion of the dispersion, and a corresponding amount of polymer dispersion being drawn off at the bottom of the vessel, while avoiding mixing of the upper and lower portions of the contents of the vessel. A diffuse feed of monomer is suitably effected by introducing the monomer in one or more thin streams or as a spray. The controlled manner of feeding enables a density gradient to be established, extending from the upper part of the dispersion to the lower part. In order to avoid turbulence when the contents are stirred to prevent sedimentation, the reaction vessel preferably has a circular cross-section, being generally cylindrical or conical in shape. Preferably, the height of the working capacity in the vessel is at least twice the average width. The process is particularly suitable for forming dispersed polymers of esters and nitriles of acrylic or methacrylic acid, and of vinyl esters. The following monomers are used in illustrated preparations (a) methyl methacrylate optionally with a minor proportion of other monomers, e.g. (meth)acrylate esters, (meth)acrylonitrile, butoxymethyl acrylamide, (meth)acrylic acid, itaconic acid, citraconic acid, maleic acid or anhydride, vinyl sulphonic acid and vinylidene chloride, (b) vinyl acetate optionally with vinyl propionate, (c) vinyl chloride, (d) acrylonitrile with vinyl acetate, (e) maleic anhydride with styrene or olefins (unspecified), and (f) methyl methacrylate in the presence of preformed polyethyl acrylate (seed polymer); the preparations being effected in aliphatic hydrocarbons as organic liquid, and the stabilizer being (i) methyl methacrylate-m