Abstract: The binder serves to produce foundry moulds and comprises a solution (preferably an aqueous solution) of aldehyde reactive phenol substances and gaseous acetals (preferably dimethyl formal) as reaction partners and strong acids, e.g. sulphuric acid and sulphonic acids as a catalyst. The acetal is in this system hydrolysed by the acid, the basic aldehyde being formed, which will react with the aldehyde reactive phenol substance accompanied by cross-linking. The acid serves thereby simultaneously as a cross-linking catalyst. In principle, it is possible to regard as "aldehyde reactive phenol substances" any phenolic compounds which can in the acid range cross-link more or less spontaneously with aldehydes. Preferably, these are resorcinol or resorcinol products, e.g. resorcinol pitch or precondensates formed with a shortfall of aldehyde, e.g. based on resorcinol formaldehyde, phenol resorcinol formaldehyde or resorcinol melamine formaldehyde.To produce foundry moulds, a granular basic moulding material, e.g.

Abstract: This relates to a bonding agent which is used for the production of molded foundry parts and which is composed of two basic components which harden out cold in the mixture of the molded material in the presence of a catalyst under the formation of polyurethane. One basic component is a polyol in the form of a solution of a co-condensate containing an OH group consisting of phenol, aldehyde and an alkyl phenyl siloxane with a contents of at least 3% by weight in free OH groups, if applicable in mixture with a phenol aldehyde condensate containing an OH group, and the second basic component is a polyisocyanate likewise dissolved under normal conditions. Appropriately the solvent has a content in vegetable oils, preferably castor oil.

Abstract: A cold setting molding material which includes sand and a polyurethane binder with the polyol portion of the polyurethane reaction mixture containing a tertiary amino group and phenolic hydroxyl groups.