GB750233A - Improvements in modified phenol-aldehyde resins - Google Patents

Abstract

Oil-soluble and oil-reactive phenolic resins are obtained by reacting a monohydric phenol substituted with a hydrocarbon substituent in the para position with an aldehyde, preferably formaldehyde, in presence of an acid catalyst, to produce a resin reaction mixture free from aldehyde, dehydrating the reaction mixture, and heating the dehydrated resin in presence of an etherification catalyst and in the presence of free monohydric phenol to temperatures between 50 DEG and 175 DEG C. The dehydration catalyst is sulphuric acid, alkyl or aryl sulphonic acid or a low alkyl sulphate. Phenol itself may be used in the initial reaction provided a substituted phenol is used in the etherification stage. Acid catalysts specified for the first stage are hydrochloric, sulphuric, oxalic, or phosphoric acid. Thus when sulphuric acid is used the same catalyst may be used in both stages and the reaction may be carried out without further addition of materials after the first stage by employing excess phenol, reacting until all the formaldehyde has been removed, dehydrating, and then raising the temperature to that required for the etherification reaction. In a modification the novolak resin obtained in the first stage is further heated with styrene, coumarone, or indene, in presence of an acid catalyst. The reaction of the resinous product with conjugated unsaturated vegetable oils takes place over a limited range of temperature, e.g. from 110-170 DEG C., the optimum temperature being about 150 DEG C. Oil reactivity of the resin is destroyed by reaction with a base, e.g. NaOH, triethanolamine, morpholine, hexamine or metallic oxides, e.g. oxides of zinc, calcium and lead. Gelation of the resin-oil mixtures may be retarded by addition of a hydroxyl containing solvent, e.g. alcohols. The oil-resin products are alkali resistant and can be thinned with hydrocarbon solvent to give varnishes; they can be emulsified in water and used as an adhesive in the manufacture of sand cores, brake linings, etc; also in the production of linoleum and like floor coverings. In examples: (1) 100 parts xylenol are mixed with 80 parts 40 per cent formalin, 0.5 parts sulphuric acid in 1.5 parts water being added. The mixture is refluxed for 30 hours when the mixture contains 20 per cent free xylenol and no formaldehyde; 50 parts xylol are added and the mixture dehydrated azeotropically the xylol being finally distilled off until the temperature rises to 140 DEG C. as evidenced by a sudden drop in viscosity; (2) 500 parts of a cresol novolak resin containing 15 per cent free cresols are dissolved in 215 parts xylol at 130 DEG C.; 5 parts toluene sulphuric acid are added and the mixture refluxed until a minimum viscosity is obtained. The xylol is distilled off and the heating is continued until the temperature rises to 150 DEG C.; a resin of m.p. 70 DEG C. soluble in wood oil is obtained; (3) 20 parts p-octyl phenol are melted and mixed with 2 parts of a catalyst mixture consisting of 20 per cent sulphuric acid and 80 per cent diethyl sulphate; the mixture is heated to 130 DEG C., mixed with 100 parts of the novolak of Example 2, and heated for 15 minutes at 140-150 DEG C.; a dark resin of m.p. 85-90 DEG C. is obtained; (4) a varnish is prepared by dissolving 200 parts of the resin in 100 parts xylol and then adding 200 parts wood oil and heating for 15 minutes at 140 DEG C.; 50 parts blown linseed oil, 300 parts coumarone naphtha and 50 parts butanol are then added to give a varnish of 340 c.s. viscosity which with the addition of driers gives a stoving varnish which dries in air in 6 hours; (5) 100 parts of the resin and 200 parts wood oil are heated to 140 DEG C. and the reaction checked by addition of 300 parts xylol giving a varnish of 380 c.s. viscosity; (6) by heating 100 parts of the resin with 200 parts wood oil to 140 DEG C. and then chilling viscous product is obtained which gels in 15 minutes when heated to 150 DEG C. and can be used as a filling composition.