| 摘要 |
524,350. Urea - aldehyde condensation products. BRITISH INDUSTRIAL PLASTICS, Ltd., and BROOKES, A. Jan. 27, 1939, No. 2945. [Class 2 (iii)] The hardening of urea-aldehyde condensates is accelerated by the addition of diaminodiazines or -1:3: 5-triazines or their salts. or mixtures of these materials. These may be added to urea-aldehyde glues or moulding powders in addition to, or in substitution for all or part of, the conventional acid hardener. Materials specified are melamine, its sulphate, oxalate, formate, acetate, and hydrochloride. the mixture, comprising mainly melamine : melam, melem, mellon, obtained by heating dicyandiamide ; crude melam thiocyanate, obtained by heating ammonium thiocyanate ; 1: 4-diaminophthalazine ; 4 : 6-diaminopyrimidine; and 2 : 4-diaminoquinazoline. The glues may be used in manufacturing composite materials, e.g. plywood. In examples : melamine or its formate is added to a neutral ureaformaldehyde glue and the product applied to laminae which are hot-pressed to form plywood or to paper to form a film glue ; to a ureaformaldehyde glue is added crude melam thiocyanate or tartaric acid and the product obtained by fusing dicyandiamide : to a ureaformaldehyde moulding powder is added melamine formate or acetate, melamine, or melamine and its hydrochloride, formate or acetate. |
