Patent GB-1091087-A (GB)
Title: Flocculant composition and method of flocculating
IPC: C02F1/52
Filed: 1965-07-29
Abstract: A free-flowing solid flocculant composition comprises a high molecular weight water-soluble polymer of an ethylenically unsaturated amide, from 0.1 to 1 mole, per molar equivalent of amide in the polymer, of a solid water-soluble dialkyl ammonium salt wherein each alkyl group contains from 1 to 2 carbon atoms and from 0.1 to 1 mole, per molar equivalent of amide in the polymer, of formaldehyde in the form of paraformaldehyde.  In a modification, the salt and aldehyde may be pre-reacted on a 1:1 molar basis.  When the composition is dissolved in water and the pH is adjusted to at least 9.5, the polymeric amide is converted to a cationic derivative. Suitable polymers include those of acrylamide, methacrylamide, N-isopropyl-acrylamide, crotonamide and maleic and fumaric acid amides.  They may comprise up to 50 mole per cent of other monomer components, e.g. acrylic, methacrylic, styrenesulphonic, vinylbenzoic or maleic acid and their alkali metal and ammonium salts, acrylonitrile, methacrylonitrile, allyl alcohol, N-vinyl-heterocyclic compounds, vinyl benzyl quaternary ammonium compounds, alkyl acrylates and methacrylates, 2-aminoethyl acrylates, styrene, alpha-methyl styrene, vinyl acetate, chloride or formate, and vinyl alkyl ethers.  Polyacrylamide is exemplified; such polymer may have up to 40% of its carboxamide groups hydrolysed to carboxylate groups. Dialkyl ammonium salts specified are dimethyl ammoium chloride, bromide, sulphate, borate, oxalate, benzoate and succinate; diethyl ammonium chloride, acetate and formate; and methyl ethyl ammonium chloride.  The compositions are suitable for flocculating aqueous suspensions of clay, silica, coal-fines and organic matter including polysaccharides, e.g. cellulose fibres; an example illustrates the flocculation of a starch dispersion.ALSO:A method for flocculating an aqueous suspension of finely divided solids with a cationic polymeric flocculant comprises dissolving in water a free-flowing solid composition comprising (a) a high molecular weight water-soluble polymer of an ethylenically unsaturated amide; (b)0.1 to 1 mole, per molar equivalent of amide in the polymer (a), of a solid water-soluble dialkyl ammonium salt wherein each alkyl group has 1 or 2 carbon atoms; and (c) 0.1 to 1 mole, per molar equivalent of amide in the polymer (a), of formaldehyde in the form of paraformaldehyde, so as to provide a solids concentration from 0.01 to 20% by weight, adjusting the pH of the solution to at least 9.5 and then after agitating the solution for at least 15 minutes adding it to the aqueous suspension of finely divided solids.  Separation of the floc may be achieved by allowing the floc to settle out; means such as filtration, centrifugation or floatation may also be employed Components (b) and (c) of the flocculant composition may be prereacted before being admixed with the polymeric component; component (a) is preferably polyacrylamide or a partially hydrolysed derivative thereof.  Suspensions which may be treated include those of suspended phase clays, silica, coal-fines, cellulose fibres and an aqueous starch dispersion.