Patent GB-725460-A (GB)
Title: Improvements relating to the process of facilitating the dewatering of aqueous suspensions of finely-divided minerals
IPC: C09K23/52
Filed: 1953-04-07
Abstract: The de-watering of aqueous suspensions of finely-divided minerals is facilitated by subjecting them to the action of one or more synthetic linear polymers or polymer salts having at least three carboxylic acid groups per molecule in an amount of 0.01 to 10 lbs. per ton of minerals in the suspension.  The preferred polymers are those formed of from about 100 to 6,000 units of monomer.  Examples are polymers of unsaturated aliphatic monocarboxylic acids such as acrylic acid, methacrylic acid, and vinyl acetic acid, and salts thereof; of these, a hydrolyzed polymer of acrylonitrile or its sodium salt is preferred.  This polymer may be a homopolymer or the acrylonitrile may be copolymerized with small amounts of vinyl pyridine, acrylic esters and the like.  The above acids may be polymerized by themselves to form homopolymers or they may be copolymerized with compounds such as vinyl pyridine, vinyl acetate, styrene, vinyl esthers, vinyl halides, or even unsaturated hydrocarbons such as isobutylene.  Polymers of polybasic unsaturated acids may also be used, though in that case it is difficult to obtain a homopolymer. For example, maleic anhydride, which itself will not polymerize, copolymerizes readily with such materials as styrene, vinyl acetate, acrylates and the like.  The linear polymer is water-soluble or water-dispersible.  Sufficient must be used to obtain the desired degree and quickness of flocculation, but where the concentration is much above the upper limit given, the polymer tends to act as a deflocculating agent.  It may be added to the suspension at any time prior to or during settling, thickening or filtration operations; in the latter case it acts as a filter aid. Several examples illustrating increased settling or filtration rates are given.  In some cases the supernatant liquid is suitable for recycling, or may be discharged without creating a pollution hazard.ALSO:The dewatering of aqueous suspension of finely-divided minerals is facilitated by subjecting them to the action of one or more synthetic linear polymers or polymer salts having at least three carboxylic acid groups per molecule in an amount of 0.01 to 10 lbs. per ton of minerals in the suspension.  The preferred polymers are those formed of from about 100 to 6,000 units of monomer.  Examples are polymers of unsaturated aliphatic monocarboxylic acids such as acrylic acid, methacrylic acid, and vinyl acetic acid, and salts thereof: of these a hydrolyzed polymer of acrylonitrile or its sodium salt is preferred.  This polymer may be a homopolymer or the acrylonitrile may be copolymerized with small amounts of vinyl pyridine, acrylic esters and the like.  The above acids may be polymerized by themselves to form homopolymers or they may be copolymerized with compounds such as vinyl pyridine, vinyl acetate, styrene, vinyl ethers, vinyl halides, or even unsaturated hydrocarbons such as isobutylene.  Polymers of polybasic unsaturated acids may also be used, though in that case it is difficult to obtain a homopolymer. For example, maleic anhydride, which itself will not polymerize, copolymerizes readily with such materials as styrene, vinyl acetate, acrylates and the like.  The linear polymer is water-soluble or water-dispersible.  Sufficient must be used to obtain the desired degree and quickness of flocculation, but where the concentration is much above the upper limit given the polymer tends to act as a deflocculating agent.  It may be added to the suspension at any time prior to or during settling, thickening or filtration operations: in the latter case it acts as a filter aid. Several examples illustrating increased settling or filtration rates are given.  In some cases the supernatant liquid is suitable for recycling or may be discharged without creating a pollution hazard.ALSO:The dewatering of aqueous suspensions of finely-divided minerals is facilitated by subjecting them to the action of one or more synthetic linear polymers or polymer salts having at least three carboxylic acid groups per molecule in an amount of 0.01 to 10 lbs. per ton of minerals in the suspension.  The preferred polymers are those formed of from about 100 to 6000 units of monomer.  Examples are polymers of unsaturated aliphatic monocarboxylic acids such as acrylic acid, methacrylic acid, and vinyl acetic acid, and salts thereof; of these a hydrolysed polymer of acrylonitrile or its sodium salt is preferred.  This polymer may be a homopolymer or the acrylonitrile may be copolymerized with small amounts of vinyl pyridine, acrylic esters and the like.  The above acids may be polymerized by themselves to form homopolymers or they may be copolymerized with compounds such as vinyl pyridine, vinyl acetate, styrene, vinyl ethers, vinyl halides, or even unsaturated hydrocarbons such as isobutylene. Polymers of polybasic unsaturated acids may also be used, though in that case it is difficult to obtain a homopolymer. For example, maleic anhydride, which itself will not polymerize, copolymerizes readily with such materials as styrene, vinyl acetate, acrylates and the like.  The linear polymer is water-soluble or water-dispersible.  Sufficient must be used to obtain the desired degree and quickness of flocculation, but where the concentration is much above the upper limit given the polymer tends to act as a deflocculating agent.  It may be added to the suspension at any time prior to or during settling, thickening or filtration operations; in the latter case it acts as a filter aid. Several examples illustrating increased settling or filtration rates are given.  In some cases the supernatant liquid is suitable for recycling or may be discharged without creating a pollution hazard.