GB608940A - Improvements in or relating to resin products and preparations thereof - Google Patents

Abstract

A water-soluble resin is made by reacting one mol. of phenol with 1.3-2.5 mols. of formaldehyde at a pH of 7.5-8.5 in presence of a nonvolatile alkali catalyst until the reaction product contains less than 2 per cent free formaldehyde and tolerates the addition of from 0.1 to 5 volumes of water without causing the resulting solution to become cloudy at 70 DEG F., and reacting the resulting product of said first reaction with 10-150 parts by weight of an unsubstituted mononuclear dihydric phenol for each 100 parts phenol until the condensation product has a viscosity in aqueous media of A to G on the Gardner scale. The product may be vacuum distilled until it has a viscosity of 120-135 revolutions per minute at 70 DEG F. in a Stormer viscometer using a 500-gram weight. Further alkali (which may be volatile) may be added with the dihydric phenol according to the pH required in the final product. A part of the dihydric phenol, up to 10 per cent by weight of the phenol, may be added to the phenol-formaldehyde mixture before the preliminary condensation. The percentage of free formaldehyde at the end of the preliminary condensation is preferably less than 0.75 per cent, and the preferred proportion of formaldehyde used is 1.5-2.0 mols. per mol. of phenol. Cresols or xylenols may replace up to 10 per cent of the phenol. Alkaline catalysts specified are caustic soda and potash, sodium carbonate and trisodium phosphate. The amount of resorcinol added is preferably 75-150 parts per 100 parts phenol. The products may be used as glues or casting resins. Examples described the mixing and refluxing of phenol, 37 per cent formaldehyde solution, and caustic soda solution, followed by the addition of resorcinol and more caustic soda solution and heating to 80-90 DEG C., and vacuum distillation. Examples also describe the use of the products as casting resins, using hypophosphorous acid as catalyst, and acids specified as suitable for casting are formic, acetic, lactic, monochloracetic and monochlorpropionic.