The method for preparing a soluble, fusible phenol-resorcinol-formaldehyde resin solution, a resin solution and an adhesive mixture containing it

摘要

A phenol-resorcinol-formaldehyde resin and a method for making the same. In this method phenol and formaldehyde at an initial pH of 8.5 to 9.2 are reacted in the presence of a sodium sulfite catalyst. The reaction mixture is heated and refluxed until it has a viscosity of u-v on the Gardner bubble test. Additional resorcinol is added to the mixture and refluxing is continued until it has a viscosity of 30 to 100 Garner sections. The reaction mixture is diluted with a water miscible solvent to obtain a resin solution having a solids content of about 40 to 60 percent by weight and a viscosity of 2.0 to 3.5 poise. An alkali metal carbonate material in the amount of 4 to 8 percent by weight of the resin is added to make adhesives including this resin fast curing. Fumed silica is also added to the resin solution by means of high shear apparatus to make the solution thixotropic.