| 摘要 |
<p>A resinous composition suitable for impregnating decorative overlays comprises a soluble, thermosetting condensate of from 1 to 3 mols. of an aldehyde per mol. of either melamine or benzoguanamine and from 1 to 5% by weight, based on the weight of the condensate, of a hydrolysed product of polyvinyl acetate having a hydroxyl content of at least 50%. Such amidogens as urea and dicyandiamide can be used in combination with the melamine or benzoguanamine in the production of the condensates. A dry single package system can be formed by mixing the condensate, polyvinyl alcohol, hexamethylene tetramine and an acid catalyst, such as a carboxylic acid having a dissociation constant of at least 2,1 X 10-4, e.g. fumaric or oxalic acid or maleic, phthalic or tetrachlorophthalic anhydride. The composition is dissolved by the moulder or laminator in water or a water-alcohol system and the solution is used to impregnate decorative overlays. The condensate is prepared preferably at pH 6,5 to 9,5 and at 60 DEG to 105 DEG C. Formaldehyde, paraformaldehyde, hexamethylene tetramine, acetaldehyde, propionaldehyde, butyraldehyde, acrolein, benzaldehyde and furfural are specified aldehydes. The hydrolysed polyvinyl acetate preferably has a hydroxyl content of at least 80% and this may be 100%. In examples the impregnation of alpha cellulose paper is effected with (1) a water-isopropyl alcohol solution of melamine-formaldehyde condensate, hydrolysed polyvinyl acetate containing 88% polyvinyl alcohol, hexa and phthalic anhydride; (2) an ethanol/ethylene glycol monoethyl ether solution of benzoguanamine-formaldehyde condensate and hydrolysed polyvinyl acetate containing 60% of the polyvinyl alcohol.</p> |
