GB803670A - Surface finishing agent for paper and cardboard - Google Patents

Abstract

A cellulose composition for application to paper and cardboard comprises a mixture of (a) a water-soluble cellulose derivative, e.g. methyl cellulose or an alkali metal compound of carboxy-methyl cellulose or a cellulose ether sulphonic acid, which becomes difficulty soluble in contact with multivalent metal ions; (b) a difficulty soluble polar compound having a multivalent metal cation, e.g. the hydroxides of aluminium, zinc, tin, copper, or less suitably those of iron, chromium, calcium and magnesium; (c) a soluble polar compound having a monovalent cation, e.g. an alkali metal or ammonium salt, particularly sulphate or chloride, the cation being exchanged for the cation of (b) when the water content of the mixture is reduced, particularly by heating, after application to the paper; and (d) not less than 10 per cent water referred to the weight of (b). Components (a) to (d) may be mixed together, in which case (a) and/or (c) are added as aqueous solutions, but preferably (b) and (c) are formed during the production of the mixture by first steeping the cellulose derivative with a solution of a soluble salt of the multivalent metal, e.g. aluminium sulphate, and then adding a polar compound containing a monovalent cation, e.g. ammonium hydroxide produced by passing in ammonia gas. Zinc or aluminium powder may be added to the mixture as catalysts for the ion-exchange reactions referred to under (a) and (c). Colouring pigments and a paraffin oil suspension can also be added.ALSO:A surface finishing agent for application to paper and cardboard comprises a mixture of (a) a water soluble cellulose derivative, e.g. methyl cellulose or an alkali metal compound of carboxymethyl cellulose or a cellulose ether sulphonic acid, which becomes difficultly soluble in contact with multivalent metal ions; (b) a difficulty soluble polar compound having a multivalent metal cation, e.g. the hydroxides of aluminium, zinc, tin, copper, or, less suitably, those of iron, chromium, calcium and magnesium; (c) a soluble polar compound having a monovalent cation, e.g. an alkali metal or ammonium salt, particularly sulphate or chloride, the cation being exchanged for the cation of (b) when the water content of the mixture is reduced, particularly by heating, after application to the paper; and (d) not less than 10 per cent. water referred to the weight of (b). Components (a) to (d) may be mixed together, in which case (a) and/or (c) are added as aqueous solutions, but preferably (b) and (c) are formed during the production of the mixture by first steeping the cellulose derivative with a solution of a soluble salt of the multivalent metal e.g. aluminium sulphate, and then adding a polar compound containing a monovalent cation, e.g. ammonium hydroxide produced by passing in ammonia gas. Zinc or aluminium powder may be added to the mixture as catalysts for the ion-exchange reactions referred to under (a) and (c). Colouring pigments and a paraffin oil suspension can also be added.