Coating for EMI shielding and method for making

Claim 1

An electrically conductive water based, air dried, paint comprising: metallic particulate selected from a group consisting of copper, silver, iron phosphide, gold, nickel, mixtures thereof, and substrates coated therewith, the particles having dimensions not greater than passable through a spray nozzle intended for applying the paint; polymeric latex, the polymer having a molecular weight of at least about 90,000, a backbone, and pendant acidic functional moieties in the backbone in sufficient quantity to provide the polymer with an acid number of at least about 7 but not more than about 195, the latex being capable of withstanding heating to at least 50° C. for a period of at least 1 hour, the latex being present in the paint in a ratio of about 15% by weight to about 100% by weight (polymer basis) of the metallic flake present in the paint; an air drying, co-solvent having a boiling point greater than water and being capable of agglomerating particles of the latex polymer to form a coherent coating upon a surface being painted in a quantity of at least 2% by weight and 40% by weight of polymer in the latex; a pH adjusting compound in a quantity sufficient to adjust the pH of the paint to between about 5 and 11; and at least one non-silicone, non-silicate based film forming enhancer in a quantity of between about 1% by weight and 5% by weight of the metallic particulate present in the paint.

Claim 18

A method for forming a paint having therein suspending metal particulates selected from a group consisting of copper, silver, iron phosphide, gold, nickel, mixtures thereof and substrates coated therewith, 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 greater than water and capable of agglomerating particles of the latex to form a coherent coating upon a surface being painted, the co-solvent and 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 and 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 particles having a dimension not greater than passable through a spray nozzle intended for applying the paint and continuing agitation for a time period sufficient to suspend the metal particles; providing the latex on a 100% 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 40%; about 1% to about 5%; Applying heat to the resultant paint and maintaining the same for at least 1 hour at at least 50° C.; and filtering the resulting mixture.

Claim 19

A method for forming a paint having therein suspending metal particulates selected from a group consisting of copper, silver, iron phosphide, gold, nickel, mixtures thereof and substrates coated therewith, 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 greater than water and capable of agglomerating particles of the latex to form a coherent coating upon a surface being painted, the co-solvent and 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 and 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 particles having a dimension not greater than passable through a spray nozzle intended for applying the paint and continuing agitation for a time period sufficient to suspend the metal particles; providing the latex on a 100% 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 40%; about 1% to about 5%; Applying heat to the resultant paint and maintaining the same for at least 1 hour at at least 50° C.; and filtering the resulting mixture.

Claim 24

The method of any one of claims 16-20 including the step of providing a pH adjusting compound selected from a group consisting of primary, secondary, and tertiary amines of C 1 -C 5 and ammonia.

Claim 25

The method of any one of claims 13-18, the latex being a copolymer of at least two monomers selected from a group consisting of: an unsaturated carboxylic acid containing monomer, 0.5-0.15% by weight; styrene 0.5-65% by weight; acrylate or methacrylate esters, 35-90% by weight; acrylonitrile or methacrylonitrile, 0-20% by weight; an acrylamide or N-substituted acrylamide, 0-15% by weight; and a multi-functional acrylate selected from a group consisting of ethylene glycol, dimethylacrylate, trimethyl propane, and trimethylacrylate, 0-5% by weight, with at least one of the monomers being an acid.