Weldable coating compositions
AssigneeThe Dow Chemical Company
InventorsWilliam J. Elms, Steven A. Weitzel
Life of this patent
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Abstract
An improvement in a weldable coating for metallic substrates containing a high molecular weight epoxy or phenoxy resin, an electroconductive pigment such as zinc and a diluent such as a glycol ether wherein the improvement resides in replacing at least about 70 weight percent of said resin with a composition containing a low molecular weight epoxy resin such as the diglycidyl ether of bisphenol A, a phenolic hydroxyl-containing compound such as a phenolic hydroxyl terminated adduct of a diglycidyl ether of a diphenolic compound such as bisphenol A and a catalyst for effecting the reaction between the epoxy resin and the adduct.
Claims27
In a weldable coating composition for metallic substrates which comprises in admixture a high molecular weight epoxy or phenoxy resin, an electroconductive pigment and an diluent;
- the improvement which comprises replacing at least about epoxy or phenoxy resin with a composition consisting essentially of:
- (A) a low molecular weight epoxy resin or mixture of epoxy resins having an average of more than one vicinal epoxy group per molecule;
- (B) a hydroxyl-containing or thiol-containing material or mixture of such materials which is (1) a polyhydric phenolic or thiophenolic compound or (2) the product of reacting (a) a low molecular weight epoxy resin having an average of more than one vicinal epoxy group per molecule with (b) a polyhydric phenolic or thiophenolic compound wherein the phenolic hydroxyl or thiol to epoxy equivalent ratio is from about 2:1 to about 12:1;
- (C) a catalytic quantity of a catalyst for effecting the reaction between (A) and (B);
- wherein (A) and (B) are present in quantities such that the hydroxyl or thiol to epoxy equivalent ratio is from about 0.5:1 to about 1.1:1.
A weldable coating composition comprising:
- (A) a low molecular weight epoxy resin or mixtures of thereof having an average of more than one vicinal epoxy group per molecule;
- (B) a hydroxyl-containing or thiol-containing material or mixture of such materials which is (1) a polyhydric phenolic or thiophenolic compound or (2) the product of reacting (a) a low molecular weight epoxy resin having an average of more than one vicinal epoxy group per molecule with (b) a polyhydric phenolic or thiophenolic compound wherein the phenolic hydroxyl or thiol to epoxy equivalent ratio is from about 2:1 to about 12:1;
- (C) a catalytic quantity of a catalyst for effecting the reaction between (A) and (B);
- (D) an electroconductive pigment and;
- wherein the equivalent ratio of phenolic hydroxyl or thiol groups in (B) to epoxy groups in (A) is from about 0.5:1 to about 1.1:1;
- and
- (E) a diluent or solvent in an amount of from about 2% to about 40% by weight of the total composition.
Dependencies are inferred from the claim text.