GB590321A - Improved process of preparing phenolic resin compositions and product thereof - Google Patents

Abstract

Glue compositions are prepared by heating a monohydric phenol with not more than 25. mols. of formaldehyde in aqueous alkaline solution having a pH of 9 or higher until a low polymer is formed which is still soluble in the reaction mixture, adding a dihydric phenol together with sufficient alkaline material capable of forming a salt with a phenol to keep the reaction product in solution, to dissolve the dihydric phenol, and to maintain a pH of 9 or higher, and further condensing the resulting product, but only to such an extent as to obtain a product that is completely miscible with water. Dihydric phenols specified are resorcinol, catechol, hydroquinone. The resorcinol may be mixed with the monohydric phenol at the beginning of the reaction in the proportion of not more than 4 parts by weight resorcinol to 10 parts monohydric phenol. The solution should be cooled below 75 DEG C., preferably 40-75 DEG C., before adding the dihydric phenol. The proportion of dihydric phenol is preferably 2.5-10 parts for each 10 parts of monohydric phenol. Paraformaldehyde and hexamethylene tetramine may be added just before curing, and the proportion of formaldehyde used initially may be 1.5-2.5 mols. per mol. phenol. Alkalies which may be used are caustic soda or potash or lime. Examples describe the reaction according to the foregoing of phenol, resorcinol, and caustic soda. The resins may be mixed with fillers such as wood flour and walnut-shell flour, and the glues may be spray-dried and reconstituted with water. Curing takes place at 120-240 DEG F. The glues are used in the manufacture of plywood and are bonding agents for paper, rockwool, cork, sand and compregnated wood, i.e. board prepared by laminating phenolic resin impregnated veneers.