Water-borne coating composition made from epoxy resin, first polymeric acid, tertiary amine and second polymeric acid
AssigneeE. I. Du Pont de Nemours and Company
InventorsLee R. Harper, Judith E. Obetz, William H. Steinmetz
Life of this patent
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Abstract
Water-borne reaction products of (a) carboxyl-functional polymers; (b) polyepoxides; and (c) tertiary amines are blended with (d) carboxyl-functional polymers having an acid number dissimilar to that of (a). The resulting products are useful as film-forming components of coating compositions which can be spray-, flow-, dip-, roller-, or electro-coated and are especially useful for spray coating the inside of two-piece tin-plated steel cans of beverages and food. The coating compositions are useful as such or can be crosslinked with crosslinking agents such as a nitrogen resin.
Claims39
A water-borne coating composition consisting essentially of liquid carrier and a second reaction product made by blending a second carboxyl-functional polymer with a first reaction product, wherein said first reaction product is the product of the reaction in an organic media of:
- (A) 50-90% by weight, based on the weight of (A) plus (B), of an epoxy resin containing, on the average, about 11/2 to 2 terminal 1,2-epoxy groups per molecule and having an epoxy equivalent weight of 750-5000;
- (B) a first carboxyl-functional polymer in an amount sufficient to provide at least 1.25 equivalents of carboxyl groups, when the source of the carboxyl group is a mono-protic acid, and at least 2.0 equivalents of carboxyl groups, when the source of such groups is a diprotic acid, per equivalent of 1,2-epoxy groups in the epoxy resin, said polymer having a weight average molecular weight (determined by light scattering) of about 10000-160000 and an acid number of 100-500;
- (C) at least 1.25 equivalents of a tertiary amine per equivalent of 1,2-epoxy groups in the epoxy resin, said tertiary amine being selected from the group consisting of R.sub.1 R.sub.2 R.sub.3 N, pyridine, N-methylpyrrole, N-methyl piperidine, N-methyl pyrrolidine, N-methyl morpholine, and mixtures thereof and wherein R.sub.1 and R.sub.2 are substituted or unsubstituted monovalent alkyl groups containing one or two carbon atoms in the alkyl portion and R.sub.3 is a substituted or unsubstituted monovalent alkyl group containing 1-4 carbon atoms;
- (D) optionally, 10-90% of the amount required for stoichiometric reaction with the carboxyl-functional polymer of (B) of at least one primary, secondary or tertiary amine or monofunctional quaternary ammonium hydroxide;
- wherein for increasing ratios of carboxyl groups to 1,2-epoxy groups, the amount of amine is increased to keep the carboxyl-functional polymer water dispersible;
- (E) said second carboxyl-functional polymer being blended in an amount of 5 to 200 parts by weight per 100 parts by weight of (A) plus (B) and having a weight average molecular weight (determined by light scattering) of about 10,000-160,000 and an acid number of 50-500, said acid number being at least 50 units different than the acid number of said first carboxyl-functional polymer, said second reaction product containing not less than 30% by weight of epoxy resin (A) based on the total of (A), (B) and (E).
Dependencies are inferred from the claim text.