| 摘要 |
A process for preparing an aqueous thermosetting resinous composition comprises heating melamine, sucrose and formaldehyde in an aqueous alkaline medium having a pH value of 7 to 11 until a water-dilutability point of 15 to 35% is attained, the sucrose constituting 10 to 35% by weight of the total weight of reactants and the formaldehyde being present in an amount of 2 to 4 mols. per mol. of melamine. Part of the melamine may be replaced by toluene sulphonamides or by thiourea. In a modification the sucrose and formaldehyde are first condensed in a neutral or slightly acid medium and the product is then reacted with the melamine (and toluene sulphonamides and urea when used) under alkaline conditions. For use in laminating syrups 40 to 60% by weight of thermosetting resinous condensation product should be dissolved in 60 to 40% by weight of water or a mixture of a major amount of water and a minor amount of an acyclic alcohol containing 1 to 4 carbon atoms, e.g. methanol, ethanol, ethylene glycol, glycerine or propylene glycol. Specifications 486,519 and 486,577 are referred to. |
