GB1177003A - Method of improving Operational Efficiency of White-Water-Recovery Systems - Google Patents

Abstract

1,177,003. Papermaking. NALCO CHEMICAL CO. 24 Jan., 1967 [9 March, 1966], No. 3538/67. Heading D2A. [Also in Division C1] Finely-divided solids are separated from paper-mill white water by adding a cationic polymer, introducing air bubbles into the white water to form a froth and adding an anionic polymer to the froth. Preferably air is dissolved in the white water under pressure, the cationic polymer added, the pressure released so that the air comes out of solution as bubbles and the anionic polymer added just below the surface. The cationic polymer may be: a condensation product of a polyamine and an epihalohydrin; a condensation product of an alkylene dihalide and an amine, such as ammonia, ethylene diamine, diethylene triamine, tetraethylene pentamine or triethylene pentamine; a cationic melamine-aldehyde or melamine-urea-aldehyde resin; a polyimine, polyvinylpyridine or polyvinylpyrrolidone; a polymer of a vinyl-benzylquaternary-ammonium salt or a copolymer of this with acrylamide or methacrylamide; a homopolymer of aminoethyl acrylate hydrochloride, amino-ethyl methacrylate hydrochloride, a substituted ammonium-alkyl acrylate or methacrylate or a copolymer of this with acrylamide, methacrylamide, acrylonitrile, a lower alkyl ester of acrylic or methacrylic acid or vinyl methyl ether; or a cationic starch or gum. The anionic polymer may be a copolymer of a carboxylic acid or its anhydride, e.g. maleic anhydride, acrylic acid, maleic acid, fumaric acid, itaconic acid, aconitic acid, or citraconic acid, with an amide or alkali-metal, alkaline-earth-metal or ammonium salt of one of these acids, their half-esters, the salts of their half-esters or their substituted amides, styrene, alphamethylstyrene, vinyltoluene, chlorostyrene, vinyl acetate, vinyl chloride, vinyl formate, a vinyl alkyl ether, an alkyl acrylate, an alkyl methacrylate, ethylene, propylene or isobutylene; the sodium salt of hydrolysed polyacrylonitrile, sodium carboxymethylcellulose, sodium salt of a starch ester, sodium salt of sulphonated polystyrene, a phosphorylated starch or an anionic polysaccharide; an after-sulphonated polymer of a vinyl-aromatic hydrocarbon; a copolymer of sodium acrylate and acrylamide; a polymer of acrylic acid, methacrylic acid, sulphoethyl acrylate or carboxyethyl acrylate, a salt thereof, or a copolymer thereof with acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, an alkyl acrylate or a vinyl alkyl ether.