Cathodic electrocoating compositions containing hydroxyl-carbonate blocked polyisocyanate crosslinking agent
AssigneeE. I. Du Pont de Nemours and Company
InventorAllisa Gam
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Abstract
An improved aqueous cathodic electrocoating composition having a binder of an epoxy-amine adduct and a blocked polyisocyanate crosslinking agent; wherein the improvement is the use of a hydoxyl-carbonate blocked polyisocyanate crosslinking agent. Electrodeposited finishes are formed that have reduced weight loss when heated to cure.
Claims10
An improved aqueous cathodic electrocoating composition comprising a binder of an epoxy-amine adduct, a blocked polyisocyanate crosslinking agent and an organic or inorganic acid as a neutralizing agent for the epoxy-amine adduct;
- wherein the improvement is the incorporation of a blocked polyisocyanate crosslinking agent that has at least one isocyanate group blocked with a hydroxy-functional cyclic carbonate compound.
An improved method of preparing a cathodic electrocoating composition comprising the following steps in any workable order:
- preparing an epoxy amine adduct of an epoxy resin extended with a dihydric phenol and reacted with an amine;
- preparing a blocked polyisocyanate crosslinking agent;
- blending the epoxy amine adduct with the blocked polyisocyanate crosslinking agent;
- neutralizing the epoxy amine adduct with an organic or inorganic acid to form a neutralized emulsion;
- forming a pigment dispersion and blending the pigment dispersion with the neutralized emulsion;
- wherein the improvement consist of using in step (b) a blocked polyisocyanate crosslinking agent having at least one isocyanate group blocked with a hydroxy functional cyclic carbonate compound.
Dependencies are inferred from the claim text.