Coating with fluoroethylene resins

Claim 1

A method for coating with a fluoroethylene resin which comprises (a) coating, directly on the surface of a metal substrate, an aqueous fluoroethylene resin dispersion paint consisting essentially of a particulate fluoroethylene resin having a particle size of about 0.03-2μ, an inorganic solid powder which is substantially water-insoluble and has a geometric average particle size of about 0.03-100μ, and an aqueous medium, the particulate resin and inorganic powder being employed in a volume ratio of about 40-80/60-20, said aqueous medium being an aqueous solution containing about 0.1-10% by weight of a water soluble high-molecular suspension agent which functions to prevent the subsequently dried coating from peeling off the substrate by means of friction, the solid content in the paint being about 10-60% by weight, with the proviso that no organic liquid is employed in said dispersion paint, (b) drying the paint coating, (c) heating the thus coated surface of the substrate to a temperature not lower than the fusion temperature of the fluoroethylene resin, thereby thermally decomposing and carbonizing the water soluble high-molecular suspension agent and forming a primer layer about 10-500μ thick on the substrate, said primer layer having a void volume of 10-40%, (d) coating the primer layer, which is in a molten state, with a fluoroethylene resin powder having a particle size of about 10-300μ, which can undergo deposition on the primer layer, and (e) heating the resin layer powder coating to a temperature not lower than the fusion temperature of the resin powder to form a surface coating layer about 50-3000μ thick.

Claim 2

A method for coating with a fluoroethylene resin which comprises (a) coating, directly on the surface of a metal substrate, an aqueous fluoroethylene resin dispersion paint consisting essentially of a particulate fluoroethylene resin having a particle size of about 0.03-2μ, an inorganic solid powder which is substantially water-insoluble and has a geometric average particle size of about 0.03-100μ, and an aqueous medium, the particulate resin and inorganic powder being employed in a volume ratio of about 40-80/60-20, said aqueous medium being an aqueous solution containing about 0.1-10% by weight of a water soluble high-molecular suspension agent which functions to prevent the subsequently dried coating from peeling off the substrate by means of friction, the solid content in the paint being about 10-60% by weight, with the proviso that no organic liquid is employed in said dispersion paint, (b) drying the paint coating, (c) heating the thus coated surface of the substrate to a temperature not lower than the fusion temperature of the fluoroethylene resin, thereby thermally decomposing and carbonizing the water soluble high-molecular suspension agent and forming a primer layer about 10-500μ thick on the substrate, said primer layer having a void volume of 10-40%, (d) coating the primer layer, which is in a molten state, with a fluoroethylene resin powder having a particle size of about 10-300μ, which can undergo deposition on the primer layer, and (e) heating the resin layer powder coating to a temperature not lower than the fusion temperature of the resin powder to form a surface coating layer about 50-3000μ thick.