Surface-coating binders

Claim 1

A surface-coating binder which is substantially free from epoxide groups and water-dilutable by protonization with acids, said binder being a reaction product of (A) from 25 to 90 percent by weight of a Mannich base obtained from (a 1 ) a polyhydric phenol which contains two or more aromatic rings and is free from ether groups, and which can be partially replaced by (a 2 ) a monohydric or polyhydric phenol which contains two or more aromatic rings and contains an ether group, (b 1 ) a secondary amine which contains one or two hydroxy alkyl groups, mixed with (b 2 ) a secondary dialkylamine or dialkoxyalkylamine and (c) formaldehyde or a formaldehyde donor, the amount of (c) is at least one mole per mole of (b 1 +b 2 ), and (B) from 75 to 10 percent by weight of an epoxy resin, wherein (a 1 ) is a phenol of the general formula ##STR6## where X is a straight-chain or branched, divalent aliphatic radical of 1 to 3 carbon atoms or is SO 2 , SO, O or CH 2 --NR--CH 2 (where R is alkyl of 1 to 6 carbon atoms) and (a 2 ) is at least one further condensed phenol, which contains at least one phenolic hydroxyl group and in addition one or more ether groups in the molecule, having the general formula HO--B--[O--E--O].sub.n --H or HO--B--[O--E--O].sub.n --P where B is ##STR7## and X has the above meanings, E is a radical, containing hydroxyl groups, obtained by addition of an epoxy compound to a phenolic hydroxyl group, P is phenyl or alkylphenyl, and n is an integer from 1 to 3, (b 1 ) is a dialkanolamine of alcohols of 2 to 6 carbon atoms, (b 2 ) is a secondary dialkylamine having the general formula ##STR8## where R 1 and R 2 are identical or different and are a straight-chain or branched aliphatic radical of 2 to 10 carbon atoms, which may or may not contain alkoxy groups, the weight ratio of components (b 1 ) and (b 2 ) being from 1:10 to 1:0.1, at least a part of the hydroxyl groups bounded to aliphatic structures of the Mannich base (A) or of the epoxy resin (B) have been converted to urethane groups by reaction with a partially blocked polyisocyanate.