| abstract |
1439057 Bayer process; flocculating agent ALLIED COLLOIDS Ltd 2 Oct 1974 [10 Oct 1973] 47321/73 Heading C1A [Also in Division C3] In the production of alumina by digestion of bauxite with aqueous sodium hydroxide to give a solution of sodium aluminate containing suspended red mud, the red mud is settled by use of a water-soluble copolymer having a M.W. of at least 0À5 Î 10<SP>6</SP> and containing units of formula in which R 1 , R 2 and R 3 are each H or CH 3 ; R 4 is OH, OM or NHR 5 SO 3 M, where M is a cation and R 5 is -(CH 2 ) m , and m is 1-6; and x, y and z are the mole percentages of the respective units based on x+y+z being 100, x being 2-40. Up to 10 mol. per cent of other units may be present, based on x+y+z. Suitable polymers are those prepared by reacting (1) acrylamide/sodium acrylate copolymer with formalin, (2) polyacrylamide with both formalin and sodium bisulphite, and (3) acrylamide/ sodium 2-acrylamide-2-methylpropane sulphonate copolymer with formalin. |