Patent GB-750990-A (GB)
Title: Sterile, biologically absorbable powdered starch derivative, and a process of making same
IPC: C08B31/00
Filed: 1954-03-23
Abstract: A sterile, biologically absorbable powder base material is produced by reacting native starch in acid suspension with formaldehyde, separating the formaldehyde-treated starch from the suspension, and reacting with a halohydrin in excess alkali and subsequently with a salt of a metal of the second or third group of the periodic system in alkaline medium.  The reactions with formaldehyde and with halohydrin may be effected in the presence of a water-miscible solvent, and the reactants may be added portionwise.  Preferably 30 to 70 mol. per cent of formaldehyde and 4 to 10 mol. per cent of halohydrin per starch unit are used and during the treatment with the metal salt, preferably 0.1 to 0.5 mol. per cent of alkali is present. The reaction products may also be (a) bailed with water until the birefringence of the starch particles disappears, (b) subjected to a further treatment with formaldehyde and/or (c) impregnated with a fatty material, such as stearic or palmitic acid, preferably in an amount of at least 0.1 per cent by weight of the product.  The products may be isolated, e.g. by filtration, and dried at moderate temperatures. The formaldehyde treatment may be carried out using formaldehyde vapours in the presence of acid vapours at temperatures preferably not exceeding 40 DEG  C.  Chloro- and bromohydrins of ethylene, propylene and butylene glycols and glycerol are suitable halohydrins.  Beryllium, magnesium, calcium, strontium, barium, zinc, cadmium, chlorides, bromides, iodides, nitrates, aluminium sulphate, chloride, fluoride, nitrate, the various alums, and mercury chloride are specified as suitable salts.  In examples: (1) corn starch is suspended in methanol and stirred with aqueous formaldehyde and HCl for 30 hours at 40 DEG  C.; wheat, rye, potato or rice starches and sulphuric, phosphoric or other acids may also be used; formaldehyde-treated starch thus obtained and (2) monochlorohydrin or (3) b -chloroethanol are added to an ethanol solution of sodium hydroxide and stirred while boiling under reflux for 7-10 hours, magnesium or aluminium sulphate is then added and the product is filtered, washed and dried; (4) to an aqueous solution of formaldehyde-treated starch obtained as in (1), epichlorohydrin and sodium hydroxide in water are added portionwise with stirring over 10 hours; after further stirring for 14 hours, magnesium or aluminium sulphate is added and the product is filtered, washed and dried; (5) the product of (2), (3) or (4) is suspended in water and further treated with aqueous formaldehyde; (6) a modified starch of Examples 2 to 5 is impregnated with an ethanol solution of stearic or palmitic acid and the mixture is dried.ALSO:A sterile, biologically absorbable powder base material is produced by reacting native starch in acid suspension with formaldehyde, separating the formaldehyde-treated starch from the suspension, and reacting with a halohydrin in excess alkali and subsequently with a salt of a metal of the second or third group of the periodic system in alkaline medium.  Suitable metal salts are beryllium, magnesium, calcium, strontium, barium, aluminium, zinc, cadmium and mercury halides, nitrates and sulphates. The material may also be (a) boiled with water until the birefringence of the starch particles disappears, (b) subjected to a further treatment with formaldehyde to increase the resistance to swelling and gelatinization on boiling with water, and/or (c) impregnated with a fatty material, such as stearic or palmitic acid, preferably in an amount of at least 0,1 per cent by weight of the material, to render it water-repellant.