GB585577A - Improved water-soluble phenolic adhesive resin - Google Patents

Abstract

Resin adhesives are made by refluxing together a mixture of a phenol, formaldehyde and alkali in the proportions of 2-3.5 molecules of formaldehyde and 0.2 to 1.0 molecules of caustic soda, caustic potash, or sodium carbonate, for each mol. of phenol, and continuing the refluxing until the mixture on cooling has a viscosity of 230 to 46,000 centipoises. The phenol may be p pure phenol or a phenolic material having a distillation range 180-220 DEG C. and having not more than 15 per cent of orthocresol, xylenol, or mixtures thereof. The resin may be mixed with 5-40 per cent wood flour, and the water content may be between 40 per cent and 75 per cent. If the proportion of caustic soda or potash is between .55 and .85 mols. per mol. of phenol and is increased progressively as the amount of formaldehyde is increased from 2-3.5 mols., continued refluxing eliminates free formaldehyde by a secondary reaction. The aqueous product may be dried to a powdered adhesive. In examples 1-5, phenol is reacted with varying proportions of formalin and caustic soda, and the products are mixed with wood flour and used in the manufacture of plywood; in example 4, the product is spray-dried before mixing with wood flour. In examples 6 and 7, metaparacresol (i.e. 53 per cent metacresol distilled within range 199-205 DEG C.), and metacresol were treated similarly.