GB385658A - Process for the production of hard masses having a certain elasticity - Google Patents

Abstract

A process for the production from plaster of Paris, or other substances which set with water, e.g. cement and zinc or magnesium oxychloride, of a composition, adapted, when brought into contact with water, to set to a hard mass possessing some elasticity, consists in mixing the plaster of Paris &c. with a solution in a substantially anhydrous solvent of a binding medium which is also capable of rapidly dissolving or swelling in water, and then removing the solvent. The mass may then be hardened by subsequently bringing it into contact with water, or it may be repowdered and mixed with water in the usual manner to form a plastic mass capable of being moulded or otherwise shaped. The process is specially applicable to the production of plaster surgical and like bandages. Examples of suitable binding media are: alkali metal compounds with the higher fatty acids dissolved in alcohol or benzene, water soluble or swellable artificial resins, e.g. partially saponified polymerization products of vinyl acetates, polyvinyl alcohol or derivatives thereof, polyacrylic acid and condensation products of phthalic acid and glycerine &c., in a low state of polymerization; water-swellable cellulose esters, e.g. powerfully hydrolyzed cellulose acetate dissolved in an alcoholic solution of calcium chloride; water soluble or swellable cellulose ethers, e.g. viscose monoethyl ether, mixed cellulose esters, e.g. phospho-acetates or sulpho-acetates; and organic derivatives of starch such as are obtained by the action of ethylene oxide on starch. Additional substances may be added to increase or decrease the sensitivity of the media to water. In an example, 100 grams of the gummy product obtained by the action of ethylene oxide on wheat starch is dissolved in a hot mixture of 700 gms. of alcohol and 200 gms. of ethyl acetate, and mixed when cold with 1350 gms. of plaster of Paris. The mass is thinned with another 500 gms of alcohol, spread thinly on a muslin strip or bandage and dried. On being wetted with water, the bandage softens in a few seconds and sets in a few minutes.ALSO:A process specially applicable to the production of plaster surgical and like bandages, from compositions of plaster of paris, or other substances which set with water, e.g. cement and zinc or magnesium oxychloride, of which compositions are adapted, when brought into contact with water, to set to a hard mass possessing some elasticity, consists in mixing the plaster of paris &c., with a solution in a substantially anhydrous solvent of a binding medium which is also capable of rapidly dissolving or swelling in water, and then removing the solvent. The mass may then be hardened by subsequently bringing it into contact with water, or it may be re-powdered and mixed with water in the usual manner to form a plastic mass capable of being moulded or otherwise shaped. Examples of suitable binding media are:-alkali metal compounds with the higher fatty acids dissolved in alcohol or benzene; water soluble or swellable artificial resins, e.g. partially saponified polymerization products of vinyl acetates, polyvinyl alcohol or derivatives thereof, polyacrylic acid and condensation products of phthalic acid and glycerine, &c., in a low state of polymerization; water-swellable cellulose esters, e.g. powerfully hydrolysed cellulose acetate dissolved in an alcoholic solution of calcium chloride; water soluble or swellable cellulose ethers, e.g., viscose monoethyl ether, mixed cellulose esters, e.g. phospho-acetates or sulpho-acetates; and organic derivatives of starch such as are obtained by the action of ethylene oxide on starch. Additional substances may be added to increase or decrease the sensitivity of the media to water. In an example, 100 grams of the gummy product obtained by the action of ethylene oxide on wheat starch is dissolved in a hot mixture of 700 gms. of alcohol and 200 gms. of ethyl acetate, and mixed when cold with 1350 gms. of plaster of paris. The mass is thinned with another 500 gms. of alcohol, spread thinly on a muslim strip or bandage and dried. On being wetted with water, the bandage softens in a few seconds and sets in a few minutes.