Water-dilutable printing ink binder system and use thereof as printing ink

Water-dilutable printing ink binder system based on a binder in the form of a clear, dilute, ammoniacal or amine-containing solution, the binder being a product of reacting a natural resin acid and formaldehyde in at least one stage, the amount of (100% strength) formaldehyde being 1 to 25% by weight, based on the natural resin acid, and the reaction having been carried out under atmospheric or superatmospheric pressure in the absence or in the presence of 0.1 to 2% by weight of a Lewis catalyst. A variant comprises partially esterifying the natural resin acid/formaldehyde reaction product with at least one polycarboxylic acid unit of the group (a) an ethylenically unsaturated dicarboxylic acid and/or the anhydride thereof and (b) a hydroxycarboxylic acid. The binder system has added to it as solubilizers monohydric and/or polyhydric alcohols, and the pH value is preferably set to 7.5 to 10. The binder systems are used as printing varnishes or in combination with carbon black or colored pigments and if desired further customary additives as printing inks, in particular for flexographic printing, letterpress printing and offset printing.