GB521653A - Improvement in urea formaldehyde resin adhesives - Google Patents

Abstract

521,653. Urea-aldehyde condensation products. RESINOUS PRODUCTS & CHEMICAL CO. Nov. 24, 1938, No. 34166. Convention date, Dec. 28, 1937. [Class 2 (iii)] A stable aqueous solution of a urea-formaldehyde intermediate condensate, suitable as a heat-hardenable adhesive, is obtained by heating a neutral aqueous solution of urea and formaldehyde in the presence of an amount of alkaline earth chloride chemically equivalent to 3-25 per cent. of calcium chloride, based upon the weight of urea, until the reaction mixture attains a viscosity of from 0.08 to 0.21 poises, and then cooling the mixture to stop the reaction. Urea may be partly replaced by thiourea, i.e., 5-20, preferably 10 per cent. from 1-2.5, preferably 1.7-2 mols of formaldehyde are employed per mol of urea. In an example, 5-10 per cent..of calcium chloride is added to a neutralized mixture of 1 mol of urea and 1.8-2 mols of aqueous formaldehyde and the solution heated to 85-90‹C. until the desired viscosity is attained, after which the mixture is cooled to 30-40‹C. and concentrated under vacuum to about 60-80 per cent. solids. Other examples are given, including thiourea and chlorides of calcium, magnesium, barium and strontium. The resin composition may be used for plywood, abrasives, laminated paper and textile finishing and may be mixed with plasticizers, e.g , polyhydric alcohols, sulphonamides, formaldehyde reaction products of carbamates and other resins for plywood, the solution is applied to the laminae by brushing, spraying or molten coating and the laminae pressed together and heated ; the hardening of the resin may be accelerated by applying to the laminae or adding to the resin solution an acidic condensing agent, e.g., diammonium phosphate. Commercial grade fertilizer urea may be employed.