Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Patent
1994-09-22
1996-05-28
Hruskoci, Peter A.
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
209 5, 423121, 423122, 210733, B01D 2101
Patent
active
055208207
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to water soluble copolymers formed from ethylenically unsaturated dibasic carboxylic acids of formula (I): ##STR1## where R.sup.1 =H and R.sup.2 =COOH or R.sup.1 =COOH and R.sup.2 =H and the use of the copolymers as flocculating agents, especially in Bayer process liquors.
Water soluble anionic polymers formed from ethylenically unsaturated dibasic acids and ethylenically unsaturated monobasic acids are known to be useful as metal sequestrants, as builders for detergents, and as scale inhibitors. For instance U.S. Pat. No. 4,519,920 describes copolymers of maleic acid and (meth)acrylic acid having molecular weight up to 8,000, useful as scale inhibitors. The polymers are made by continuously feeding the (meth)acrylic acid during polymerisation to a solution of half-neutralised maleic acid. The aqueous solution of the polymeric product is subsequently neutralised by the use of alkali metal hydroxides or carbonates.
EP-A-0106111, EP-A-0106110, EP-A-076992 and EP-A-075820 all disclose copolymers of a monoethylenically unsaturated dicarboxylic acid derived compound with a monoethylenically unsaturated monocarboxylic acid derived compound. These copolymers are of low molecular weight and are useful as scale inhibitors in detergent compositions.
Higher molecular weight copolymers of ethylenically unsaturated dibasic carboxylic acids are known for use as coagulants or flocculants. For instance CN-A-1032925 describes the use of an acrylamide/maleic anhydride copolymer as a coagulant to assist the multi-stage flocculation process for washing hydrated titanium dioxide. SU-A-1,411,297 describes the use of a neutralised copolymer of acrylic acid and maleic anhydride having molecular weight about 1.times.10.sup.6 as a flocculant for the treatment of aqueous effluent, especially sewage effluent, flocculation. In SU-A-1,028,683 a terpolymer of ammonium maleate, (meth)acrylic acid and ammonium (meth)acrylate is used to flocculate suspended matter from aqueous wastes from galvanic processes. In SU-B-842,041 a copolymer of maleic acid and acrylamide is used to remove suspended matter from impure water. In JP-A-52085287 (1977) a copolymer of acrylamide and up to 5 wt. % ethylenically unsaturated dicarboxylic acid is used as a sedimentation aid and a flocculant. In SU-A-402,530 copolymers of acrylamide with either maleic acid or fumaric acid are used as flocculants. In JP-A-47020078 (1972) acrylic and maleic acid are copolymerised in aqueous solution to form flocculant polymer. There are also several disclosures by Asanov et al and from Dzhalilova et al describing the use of copolymers of maleic acid with either acrylic acid or acrylamide and their use as flocculants for various substrates, including bentonite, sulphur and in water purification. Florea et al in Bul. Univ. Galati, Fasc. 6, 3, 23- 32 (1980) and Chem. Abs. 96:102647, describe the use of copolymers of acrylic acid and maleic acid as flocculants for the treatment of sugarbeet juices and for clarifying wines.
U.S. Pat. No. 3,784,526 describes the use of terpolymers of itaconic acid with acrylamide and acrylic acid as a flocculant for various media, including dispersions of red mud from bauxite treatment in the Bayer process. The present inventors have found, however, that the use of itaconic acid can lead to difficulties in polymerisation.
In U.S. Pat. No. 4,608,237 the use of anionic polymers or copolymers of acrylic acid are described as crystal modifiers for addition to pregnant Bayer process liquors to minimise interference by sodium oxalate crystals. The polymer which can be provided in the form of a solution, water-in-oil emulsion, dry solid or gel form, may include comonomers, one less preferred example of which is maleic anhydride.
U.S. Pat. No. 4,845,192 describes a procedure for extruding and dissolving gel form flocculant polymers and copolymers prior to their use as flocculants. Examples of copolymers for which the process may be used are polyacrylamides and copolymers of acrylamide with, inter alia, maleic anhydride. The p
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Hunter Trevor K.
Moody Gillian M.
Allied Colloids Limited
Hruskoci Peter A.
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