Verfahren zur Herstellung von wasserloeslichen Pfropfmischpolymerisaten

摘要

Water-soluble graft polymers are obtained by polymerizing an ethylenically unsaturated compound having the structure: wherein X is a hydrogen atom or a methyl or ethyl group and Y is a carboxyl group, a carboxylic salt group, a nitrile group or an acid amide group in the presence of water-soluble polymeric material, other than a protein, containing a C-H bond having a molecular weight greater than 1000, and, if necessary to impart water-solubility, hydrolysing the polymerization product, the amount of the preformed polymeric substance present in the graft polymer being between 5% and 50% by weight. Water-soluble preformed polymers specified are polyvinyl alcohol, polyvinyl pyridine, polyacrylic and polymethacrylic acids and amides, starch, starch ethers, e.g. isopropylated starch, dextrins, cellulose ethers and polyethylene oxide. Monomers specified are acrylonitrile and acrylamide. Polymerization may be carried out in an aqueous medium with the assistance of catalysts, e.g. peroxides and persulphates, or mixtures of persulphates with reducing agents. The hydrolysis of the polymerization products, when carried out, may be partial or complete and may be effected by means of acid or alkaline hydrolysing agents. Specification 715,194 is referred to.ALSO:The settlement and filtration of aqueous suspensions of ores and waste waters is assisted by the addition thereto of water-soluble graft polymers made by the polymerization of an ethylenically unsaturated compound in the presence of a water-soluble preformed polymeric substance (see Group IV(a)). Examples describe the addition of graft polymers to coal talings and to the precipitates obtained in successive acid and alkaline treatments of scheelite. Specification 715,194 is referred to.ALSO:The settlement and filtration of aqueous suspensions of ores is assisted by the addition thereto of water-soluble graft polymers made by the polymerization of an ethylenically unsaturated compound in the presence of a water-soluble preformed polymeric substance (see Group IV(a)). In an Example (9) scheelite is treated with concentrated hydrochloric acid to form a colloidal precipitate of tungstic acid and other insoluble substances the flocculation and settling of which is assisted by the addition of a hydrolysed acrylonitrile/starch ether graft polymer, the ore precipitate is then dissolved in ammonium hydroxide to form a precipitate of silica, the flocculation and settling of which is assisted by the graft polymer remaining from the first stage of the process. Specification 715,194 is referred to.