GB1185594A - Moisture-Resistant Plaster of Paris Bandages Containing Water-Swellable Gums - Google Patents

Abstract

1,185,594. Plaster of paris bandages. CONTINENTAL CHEMICAL CO. Inc. 6 May, 1968, No. 21288/68. Heading A5R. A plaster of Paris bandage comprises a porous, flexible backing material impregnated with powdered plaster of Paris having admixed therewith a small amount of water swellable hydroxyethyl ethyl cellulose, preferably with a degree of substitution of hydroxyethyl and ethyl groups in the range 0.5 and 1 and a viscosity between 50 and 4000 c.p.s. in 2 weight per cent aqueous solution at 20‹C. According to an example 18.5 parts by weight of steam cooked aqueous starch solution containing 1.3 parts starch, 29.4 parts 29-30% aqueous ammonia and 6.06 parts of water are thoroughly mixed together. These are added to the mixture: (1) 0.033 part sodium alkyl naphthyl sulphonate (or sodium lauryl sulphate); (2) a solution obtained by wetting 0.123 parts acid casein (or borate) in 2.94 parts water and dissolving up the wet casein by addition of 1.54 parts 29-30% aqua ammonia; (3) 2 parts of potassium or zinc sulphate set accelerator ground to 100 mesh U.S. standard screen size or finer; and (4) a mixture of 0.25 parts hydroxyethyl ethyl cellulose (degree of substitution of hydroxyethyl 0.8 and of ethyl 0.9) with 100 parts plaster of Paris. The resulting slurry is coated upon 32 x 28 mesh surgical gauze at a rate to yield a dry bandage weighing 230-240 grams per 5 sq. ft. and the coated gauze is dried in air at 250‹F to the point (but not substantially beyond) where a roll of the dried product after standing protected from moisture for a few hours does not show any gritty feel when wet and formed into a cast. The dried web is cut and rolled into rolls 4 inch wide by 5 yards long. According to a further example, a solution of 11.3 g. of the hydroxyethyl ethyl cellulose in 805 g. water is added with stirring to 1879 g. of methanol (or ethanol, propanol, isopropanol or acetone) and 1.5 g. sodium alkyl naphthyl sulphonate. There are then added 45.4 g. zein, 45.4 g. powdered potassium sulphate and 10.6 1bs. plaster of Paris. The resulting slurry is then coated on gauze and dried as in the previous example. Binders mentioned: methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl ethyl cellulose, polyvinyl acetate emulsion solids, dextrin and cooked starch.