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US 2004/0071887 A1Published application
Coating compositions having improved "direct to metal" adhesion and method therefore
AssigneeBASF SE
InventorDavid L. Newton
Life of this patent
Estimating the term…
Abstract
The invention provides a coating composition for use with metallic substrates that provides desirable levels of adhesion to metal, sandability without the production of harmful dust, corrosion resistance, and recoatability. The coating composition of the invention comprises a polyurethane film-forming component, and a corrosion protection component present in the composition in an amount effective in minimizing corrosion and adhesion loss of the coating at the substrate. A cured film of the coating applied to metallic substrates, previously coated substrates, as well as plastic substrates has improved corrosion resistance following Salt Spray Cabinet exposure.
Claims18
A two component coating composition for preventing corrosion of a metallic substrate, the composition comprising:
- a) a film-forming component comprising a film-forming polymer and a crosslinking agent, wherein the film-forming polymer has functional groups selected from the group consisting of active hydrogen containing groups, epoxide groups, and mixtures thereof, and the crosslinking agent have functional groups selected from the group consisting of isocyanate groups and amine groups,
- b) a corrosion protection component consisting essentially of compounds selected from the group consisting of zinc oxide, zinc phosphate, basic zinc phosphate, zinc nitrophophthalate, zinc molybdate, basic zinc phosphate hydrate, basic zinc molybdate, zinc benzoate and zinc salt of an organic nitro compound such as those sold under the trademark Heucorin RZ, calcium molybdate, calcium metaborate, barium metaborate, calcium strontium phosphosilicate, aluminum triphosphate, aluminum zinc phosphate, and zinc calcium aluminum strontium polyphosphate silicate and strontium aluminum polyphosphate and mixtures thereof, and
- c) a component comprising (I) a first compound having an acid number of from 70 to 120 mg KOH/g, a hydroxyl number of from 200 to 400 mg KOH/g, a number average molecular weight of from 150 to 3000, and which is the reaction product of (a) at least one difunctional carboxylic acid, (b) at least one trifunctional polyol, (c) at least one chain stopper, and (d) phosphoric acid, and (II) a second compound comprising one or more carboxy phosphate esters having the formula:
- (R—O)X—P(O)—(OM)3-X
- wherein M is hydrogen, metal or ammonium, x is a number from 0 to 3, and R is a saturated or unsaturated C5-C40 aliphatic group in which one or more of the aliphatic carbon atoms can be substituted or replaced with a halogen atom (such as fluorine or chlorine), a C1-C6 alkyl group, a C1-C6 alkoxy group, a C6-C10 aromatic hydrocarbon group, preferably phenyl or naphthyl, or a C6-C10 aromatic hydrocarbon group that is substituted with one or more (preferably 1 to 3) C1-C6 alkyl groups or —COOR1 groups wherein R1 is H, metal, ammonium, C1-C6 alkyl, or C6-C10 aryl, or mixtures thereof, wherein said coating demonstrates at least a 20% reduction in salt spray corrosion over the same coating without components (b) and (c).
2 more elements
A composition as claimed in claim comprising from 0.10 to 1.00% by weight of the mixture of compounds (I) and (II), based on the total nonvolatile weight of the coating composition.
A method of improving corrosion resistance in a multilayer coating system, comprising
- applying a primer coating composition directly to a metal substrate, the primer coating composition comprising:
- a) a film-forming component comprising a film-forming polymer and a crosslinking agent, wherein the film-forming polymer has functional groups selected from the group consisting of active hydrogen containing groups, epoxide groups, and mixtures thereof, and the crosslinking agent have functional groups selected from the group consisting of isocyanate groups and amine groups, and
- b) a corrosion protection component consisting essentially of compounds selected from the group consisting of zinc oxide, zinc phosphate, basic zinc phosphate, zinc nitrophophthalate, zinc molybdate, basic zinc phosphate hydrate, basic zinc molybdate, zinc benzoate and zinc salt of an organic nitro compound such as those sold under the trademark Heucorin RZ, calcium molybdate, calcium metaborate, barium metaborate, calcium strontium phosphosilicate, aluminum triphosphate, aluminum zinc phosphate, and zinc calcium aluminum strontium polyphosphate silicate and strontium aluminum polyphosphate, calcium aluminum strontium polyphosphate silicate hydrate, a modified strontium aluminum polyphoshate hydrate, (2-benzothiozolythio)-succinic acid amine salt and mixtures thereof, present in the composition in an amount effective to prevent corrosion of the substrate, and
- c) a composition comprising (I) a first compound having an acid number of from 70 to 120 mg KOH/g, a hydroxyl number of from 200 to 400 mg KOH/g, a number average molecular weight of from 150 to 3000, and which is the reaction product of (a) at least one difunctional carboxylic acid, (b) at least one trifunctional polyol, (c) at least one chain stopper, and (d) phosphoric acid, and (II) a second compound comprising one or more carboxy phosphate esters having the formula:
- (R—O)X—P(O)—(OM)3-X wherein M is hydrogen, metal or ammonium, x is a number from 0 to 3, and R is a saturated or unsaturated C5-C40 aliphatic group in which one or more of the aliphatic carbon atoms can be substituted or replaced with a halogen atom (such as fluorine or chlorine), a C1-C6 alkyl group, a C1-C6 alkoxy group, a C6-C10 aromatic hydrocarbon group, preferably phenyl or naphthyl, or a C6-C10 aromatic hydrocarbon group that is substituted with one or more (preferably 1 to 3) C1-C6 alkyl groups or —COOR1 groups wherein R1 is H, metal, ammonium, C1-C6 alkyl, or C6-C10 aryl, or mixtures thereof, curing the coating to provide a primed metallic substrate, and applying to the primed metallic substrate one or more additional coating compositions, and curing the one or more additional coating compositions to provide a cured multilayer coating system, wherein said coating system demonstrates at least a 20% reduction in salt spray corrosion over the same coating without components (b) and (c).
2 more elements
Dependencies are inferred from the claim text.