Title: Process for the preparation of cationically modified formaldehyde resins of prolonged stability

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Abstract: Cationic resins soluble in water and stable in solution, based upon melamine and formaldehyde, primary or secondary aliphatic amines, alkanolamines or a polyamine are prepared by reacting melamine with formaldehyde in a methylolation reaction in methanol in the presence of one or more of the aforementioned amines by heating for a period of fifteen minutes to two hours at an alkaline pH of 7.5 to 10 at a temperature of 60.degree. to 85.degree. C. The methylation-condensation reaction which follows is carried out at a pH of 5 to 6, preferably 5.4 to 5.7 until a viscosity is obtained which has a minimum of seventeen seconds measured at 20.degree. C. by an AFNOR No. 6 consistometric head. The methylation reaction is then terminated by the addition of aqueous formaldehyde and condensation is carried out for thirty minutes to two hours at 60.degree. to 90.degree. C. and a pH of 5.5 to 7, preferably a pH of 6 to 6.5. The product has longterm stability and can be used as a water-resisting or humidity-resistant coating or sizing for paper or as an adhesion promoting coating for solid supports to which a varnish is to be applied.


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