process for the production of solutions of melamine formaldehyde resin and a fibrous material impregnated with the product obtained with such solutions

摘要

1406771 Silicate-modified melamine-formaldehyde resins STAMICARBON BV 31 Jan 1973 [5 Feb 1972 28 July 1972] 4847/73 Heading C3R [Also in Division B5] A modified melamine-formaldehyde resin is prepared by reaction of melamine with formaldehyde in alkaline solution, a water soluble inorganic or quaternary ammonium silicate being incorporated before, during, or after the condensation, in amounts giving at most 1-5 wt. per cent SiO 2 in the product solution. When added before or during condensation, as pH adjuster, the silicate preferably provides up to 0À15 wt. per cent SiO 2 (from sodium silicate) or 0À1 wt. per cent (from tetraethanolammonium silicate). When added after the condensation the silicate preferably contains 10-20 wt. per cent SiO 2 and the resin solution is below pH 10; a stabilized silicate solution suitable for addition to the'resin solution contains 2-15 wt. per cent SiO 2 , acid to give a pH of 0À5-3, and 10-50 wt. per cent of a C 1-15 alcohol, a C 2-12 polyol or C 1-6 alkyl ether thereof, an N,N-di-(C 1-4 )alkyl C 1-4 carboxylic amide, a di-(C 1-4 ) alkyl sulphoxide or a C 4-7 lactam. In preparations 1-4 stable silicate solutions are prepared by adding 18% water glass (Na 2 O : SiO 2 1 : 3À3) to 25% aqueous toluenesulphonic acid, followed by triethylene glycol monoethyl ether, caprolactam, dimethyl formamide, or dimethylsulphoxide. In Examples I and II water glass is added both during and after the condensation of melamine with formaldehyde to give a pH of 9À7 and SiO 2 content of 0À08%; in Example III it is added during the condensation of melamine with formaldehyde and minor amounts of caprolactam, toluenesulphonamide and sugar; in Example IV the solution from Preparation 1 is added to a preformed MF resin solution followed by untreated water glass. The resin solutions are used to impregnate paper for laminating to chipboard.