GB551404A - Improvements in adhesives and coating compositions - Google Patents

Abstract

551,404. Improved adhesive and coating compositions. DEARING, W. C. July 23, 1941, No. 9282. Convention date, July 18, 1940.. [Class 2 (iii)] A. stable dry mixture adapted to form on addition of water an adhesive or coating composition comprises a urea-formaldehyde resin and an ammonium salt of a non-volatile acid, a 1 per cent. solution of which acid has a pH not greater than 4. Specified ammonium salts are the sulphate, dihydrogen phosphate, oxalate and diammonium hydrogen phosphate. In preparing a dry mixture for use as a water paint the pigment may be mixed with the resin by grinding but preferably is dispersed in an aqueous solution of the resin which is then dried, e.g. in a spray or vacuum drum drier. Before evaporation a plasticizer, e.g. ethylene glycol, may be added. The mixture may be prepared simply by mixing fine crystals of the ammonium salt with the resin. The proportion of salt is that which will cause the resin to harden with the desired rapidity after the addition of water. A suitable resin is obtained by heating one mol. of urea with 2 mols. of formaldehyde (37 per cent.) which has been brought to pH 4.5-5.5 with caustic soda. In examples, an adhesive is made by mixing 1 part of dry ammonium sulphate with 100 parts of the dried urea-formaldehyde reaction product, and a paint by evaporating a dispersion of 100 parts titanium oxide pigment and 1 part of ethylene glycol in an aqueous solution of 100 parts of urea-formaldehyde reaction product and mixing 1 part of ammonium sulphate with 200 parts of the spray-dried product.