Abstract: Highly concentrated aqueous solutions of low viscosity of melamine/aldehyde resins are obtained by reacting to a precondensate in a first step melamine and an aldehyde in an alkaline medium and in the presence of water together with at least one compound (I), selected from the group, consisting of an alkali sulfite, an alkaline earth sulfite, an amino sulfonic acid, an amino carboxylic acid, a hydroxycarboxylic acid, a hydroxycarboxylic acid lactone, and a polyhydroxy carboxylic acid lactone, reacting then the thus obtained mixture in a second step with at least one compound (II), selected from the group, consisting of an amino carboxylic acid, a carboxylic acid, a hydroxy carboxylic acid, a hydroxy carboxylic acid lactone, a sulfamic acid, an amino sulfonic acid, a polyhydroxy carboxylic acid and a polyhydroxy carboxylic acid lactone, and then making alkaline the obtained resin solution by adding at least one basic compound (III).

Abstract: The invention provides a polycondensation product of(a) sulfamic acid (H.sub.2 N--SO.sub.3 H) and/or at least one N-substituted organic derivative of the sulfamic acid as such or in the form of their salts,(b) formaldehyde and/or glyoxal(c) melamine and/or at least one phenolic compound.This polycondensation product may be used as at least one component in a material for construction.

Abstract: Highly concentrated aqueous solutions of low viscosity of melamine/aldehyde resins are obtained by reacting to a precondensate in a first step melamine and an aldehyde in an alkaline medium and in the presence of water together with at least one compound (I), selected from the group, consisting of an alkali sulfite, an alkaline earth sulfite, an amino sulfonic acid, an amino carboxylic acid, a hydroxycarboxylic acid, a hydroxycarboxylic acid lactone, and a polyhydroxy carboxylic acid lactone, reacting then the thus obtained mixture in a second step with at least one compound (II), selected from the group, consisting of an amino carboxylic acid, a carboxylic acid, a hydroxy carboxylic acid, a hydroxy carboxylic acid lactone, a sulfamic acid, an amino sulfonic acid, a polyhydroxy carboxylic acid and a polyhydroxy carboxylic acid lactone, and then making alkaline the obtained resin solution by adding at least one basic compound (III).