COATING, COATING COMPOSITION AND METHOD FOR IMPROVING ADHESION OF THE COATING

摘要

The invention relates to a coating composition demonstrating improved adhesion and method for improving adhesion of a coating composition to metal. The coating and method of the invention provide improved adhesion of a coating when coating is applied directly over metal substrates, especially untreated metal substrates such as galvanized steel, unsanded aluminum and unsanded cold-rolled steel. More particularly, the invention provides a composition comprising (I) an effective amount of a first compound having an acid number of from 70 to 120 mg KOH/g, a hydroxyl number of from 200 to 400 mg KOH/g, a number average molecular weight of from 300 to 700, and which is the reaction product of (a) at least one difunctional carboxylic acid, (b) at least one trifunctional polyol, (c) at least one chain stopper, and (d) phosphoric acid, (II) an effective amount of a second compound comprising a carboxy phosphate ester having the formula (I), wherein R is an C5-C40 aliphatic group in which one or more aliphatic carbon atoms are substituted with lateral or terminal -COOR1 groups, wherein R1 is H, metal, ammonium, C1-C6 alkyl, or C6-C10 aryl, M is hydrogen, metal or ammonium and x is a number from 0 to 3, and (III) a compound providing low surface tension and promoting surface wetting of a substrate.