Coating for EMI shielding

Claim 1

A method for suspending metal flakes selected from a group consisting of copper, silver, iron phosphide, gold, nickel, mixtures thereof and substrates coated therewith, to produce a metallic paint having a cured surface resistivity of less than about 10 Ω/square comprising the steps of: agitating a partially crosslinked polymer latex, the polymer having a molecular weight of at least about 90,000, a backbone, and pendant acidic function moieties therefrom in sufficient quantity to provide the polymer with an acid value of at least about 7 but not more than about 195; adding under agitation an air drying, co-solvent having a boiling point greter than water and capable of agglomerting particles of the latex to form a coherent coating upon a surface being painted, the co-solvent being first diluted with a quantity of water at least twice and not more than twelve times the weight of co-solvent; adding under agitation a quantity of a pH adjusting compound sufficient to adjust the pH of the resulting mixture to between about 5 and about 11. adding under agitation film forming enhancer diluted with a quantity of water at least about twice and not more than about ten times the weight of the fatty acid; adding under agitation a quantity of the metal flakes having a thickness of not more than aobut 3 microns and a long dimension of at least about 10 microns but not greater than passable through a spray nozzle intended for applying the paint and continuing agitation for a time period sufficient to suspend the flakes; providing the latex on a polymer basis and the co-solvent and the film forming enhancer on an undiluted basis in a weight ratio to the metal flakes respectively of: about 15% to about 100%; about 2% to about 20%; about 1% to abotu 5%; and filtering the resulting mixture.

Claim 2

A method for suspending metal flakes selected from a group consisting of copper, silver, iron phosphide, gold, nickel, mixtures thereof and substrates coated therewith, to produce a metallic paint having a cured surface resistivity of less than about 10 Ω/square comprising the steps of: agitating a partially crosslinked polymer latex, the polymer having a molecular weight of at least about 90,000, a backbone, and pendant acidic function moieties therefrom in sufficient quantity to provide the polymer with an acid value of at least about 7 but not more than about 195; adding under agitation an air drying, co-solvent having a boiling point greter than water and capable of agglomerting particles of the latex to form a coherent coating upon a surface being painted, the co-solvent being first diluted with a quantity of water at least twice and not more than twelve times the weight of co-solvent; adding under agitation a quantity of a pH adjusting compound sufficient to adjust the pH of the resulting mixture to between about 5 and about 11. adding under agitation film forming enhancer diluted with a quantity of water at least about twice and not more than about ten times the weight of the fatty acid; adding under agitation a quantity of the metal flakes having a thickness of not more than aobut 3 microns and a long dimension of at least about 10 microns but not greater than passable through a spray nozzle intended for applying the paint and continuing agitation for a time period sufficient to suspend the flakes; providing the latex on a polymer basis and the co-solvent and the film forming enhancer on an undiluted basis in a weight ratio to the metal flakes respectively of: about 15% to about 100%; about 2% to about 20%; about 1% to abotu 5%; and filtering the resulting mixture.

Claim 8

The method of claims 6, the latex being a co-polymer of at least two monomers selected from a group consisting of: an unsaturated carboxylic acid containing monomer, 0.50-15% by weight; styrene 0.5-65% by weight; acrylate or methyacrylate esters, 35-90% by weight; acryloitrile or methacrylonitrile, 0-20% by weight; an acyrlamide or N-substituted acyrlamide, 0-15% by weight; and a multi-functional acrylate or methacrylate, 0-5% by weight with at least one of the monomers being mono or dicarboxylic acid.