Patent GB-456342-A (GB)
Title: Improved manufacture of alginates
Filed: 1935-05-03
Abstract: Seaweed is demineralized by extraction in the cold with dilute acid, preferably sulphuric acid, and the residue is digested in the cold with sodium carbonate solution.  The mixture is then diluted and separated from cellulose, suitably by centrifuging, and the sodium alginate solution so obtained is treated in the cold with dilute sulphuric acid to precipitate alginic acid.  The acid is dehydrated, by compression or evaporation, until it contains about 90 per cent by weight of water, and is finally converted into an ammonium or metal alginate by reaction in the cold with ammonia or a suitable metal salt; a preservative, e.g. formaldehyde or an essential oil, is preferably added at the same time.  A sodium alginate solution so obtained may be clarified by treatment with Eau de Javel, or other alginates may be prepared therefrom by reaction with alkaline-earth bases or metal salts such as calcium oxide, calcium chloride, zinc chloride or sulphate, barium chloride, aluminium chloride or sulphate, alums, or a salt of copper, tin, iron or lead.  The alginates, particularly sodium alginate, may be used (a) for stiffening fibrous materials, such as paper or fabrics; (b) as mordants in dyeing cotton and wool; (c) as emulsifying or dispersing agents for oils, bitumen, and mineral substances such as talc, kaolin or chalk; (d) in the manufacture of adhesives; aluminium alginate is stated to be useful for waterproofing fabrics.  Some of the insoluble alginates are analogous to horn and can be compressed or stamped. The cellulose separated from the crude sodium alginate solution as described above may be bleached by means of calcium or sodium hypochlorite and used in the manufacture of paper or nitro-cellulose. The liquors from the original lixiviation of the seaweed may be concentrated, clarified by treatment in the warm with sodium carbonate, and then treated in the cold with sodium bisulphite and cupric chloride, or with copper sulphate and copper shavings, to obtain a precipitate of cuprous iodide.  The Specification as open to inspection under Sect. 91 states that the alginates, particularly sodium alginate, may be used for "thickening" or "clarifying" fabrics and for protecting them against acids.  It refers also to the manufacture of compositions comprising insoluble alginates and fillers.  This subject-matter does not appear in the Specification as accepted.ALSO:A sodium alginate solution, prepared from seaweed which has been demineralized by extraction in the cold with dilute acid, preferably sulphuric acid, is treated with metal salts such as zinc chloride or sulphate, aluminium chloride or sulphate, alums, or a salt of copper, tin, iron or lead, whereby the corresponding metal alginates are obtained.  The alginates, particularly sodium alginate, may be used as emulsifying or dispersing agents for oils, bitumen, and mineral substances such as talc, kaolin or chalk.  The liquors from the original lixiviation of the seaweed may be concentrated, clarified by treatment in the warm with sodium carbonate, and then treated in the cold with sodium bisulphite and cupric chloride, or with copper sulphate and copper shavings, to obtain a precipitate of cuprous iodide.ALSO:Alginates, particularly sodium alginate, may be used in the manufacture of adhesives.  Some of the water-insoluble alginates are analogous to horn and can be compressed or stamped. The Specification as open to inspection under Sect. 91 refers to the manufacture of compositions comprising water-insoluble alginates and fillers.  This subject-matter does not appear in the Specification as accepted.