GB673634A - Process for preparing an aqueous colloidal solution of condensation products, and the application of such a solution to various uses - Google Patents

Abstract

A process of preparing a stable aqueous colloidal solution of aldehyde-phenolic condensation products, such products being obtained by reaction of a phenolic compound and an aqueous solution of an aldehyde, includes the step of adding a tannin to the reaction mixture not later than the time of formation of the aqueous solution representing the immediate result (first form) of the condensation of the reactants, the tannin preventing the transformation to the second form as long as the temperature remains lower than a certain limiting temperature which is higher than the temperature applied at the time of the production of the first form of the condensation product. The forms are said to correspond to the stages of condensation described in U.S.A. Specification 942,699. "Tannin" includes tannic acid and natural tannins. The products may be admixed with wood flour, colouring materials and pigments to form moulding compositions. Adhesive films may be obtained by impregnating a carrier, e.g. cellulosic material with the solution and drying, a suitable apparatus for this process being described (see Group VIII). Examples describe the preparation of "resinous fluids" by heating crude cresol (mixed o-, m-, and p-) or phenol, with formalin, hexamethylene tetramine and ammonia to 63 DEG C., and then cooling (the reaction is exothermic) to keep the temperature below 96 DEG C. When the reaction subsides, the mixture is heated to 91 DEG C. and tannin is added. In a further example, crude guaiacol from wood distillation is used as phenolic component, the upper limit then being 98 DEG C. The products above 96 DEG and 98 DEG C. turn into the second form. The Specification as open to inspection under Sect. 91 includes any stabilizing agent which will prevent transformation from the first stage to the second. This subject-matter does not appear in the Specification as accepted.ALSO:Stable aqueous colloidal solutions of aldehydephenolic condensation products, obtained by reaction of a phenolic compound and an aqueous solution of an aldehyde, are prepared by a process which includes adding a tannin to the reaction mixture not later than the time of formation of the aqueous solution representing the first form of the condensation products, the tannin preventing the transformation to the second form as long as the temperature remains lower than the temperature applied in the production of the first form of the condensation product. The forms are said to correspond to the stages of condensation described in U.S.A. Specification 942,699. "Tannin" includes tannic acid and natural tannins. The products may be used in the preparation of moulding compositions and adhesive films (see Groups IV (a) and VIII). Examples describe the preparation of "resinous fluids" by heating crude cresol (o-, m- and p-) or phenol with formalin, hexamethylene tetramine, and ammonia to 63 DEG C., cooling to keep the exothermic reaction temperature below 96 DEG C., and then adding tannin at 91 DEG C. In another example crude guaiacol is used, the upper limit being 98 DEG C.