| 摘要 |
<p>1. Binder for foundry moulding mixtures and containing a phenol-aldehyde condensation product and a polyisocyanate in a solution and which, with a hardening catalyst, hardens out cold forming urethane, the phenol-aldehyde condensation product having been obtained by condensation of a phenol component with an aldehyde, preferably formaldehyde, in the presence of a condensation catalyst, characterized in that the phenol-aldehyde condensation product is condensed with a mixture comprising 85 to 60 % by weight of unsubstituted phenol and 15 to 50 % by weight of a p-substituted phenol as a phenol component with a molar ratio of total phenol to aldehyde in the range from 1:1.0 to 1:1.5 in the presence of 0.01 to 0.1 % by weight, in relation to the total phenol component, of a metal salt of a higher carboxylic acid with multivalent metals as the condensation catalyst, and in a water-containing medium at a temperature of up to 100 degrees C at the beginning and with slow removal of water at a temperature of up to 125 degrees C at the end, and, after removal of the water, is dissolved in a non-polar solvent.</p> |
