CHROME-FREE COATING COMPOSITIONS FOR SURFACE-TREATING STEEL SHEET INCLUDING CARBON NANOTUBE, METHODS FOR SURFACE-TREATING STEEL SHEET AND SURFACE-TREATED STEEL SHEETS USING THE SAME

• US 20100272991A1
• Filed: 12/23/2008
• Published: 10/28/2010
• Est. Priority Date: 12/27/2007
• Status: Abandoned Application

• Current Assignee: Posco Holdings Incorporated
• Original Assignee: Posco Holdings Incorporated
• Inventors: Park, Young-Jun, Cheong, Hoon, Kim, Gab-Yong
• Application Number:
  US12/810,340
• Publication Number:
  US 20100272991A1
• Time in Patent Office: Days
• US Class Current: 428/341
• CPC Class Codes: C08K 3/041 Carbon nanotubes
• CPC Class Codes: C08L 29/04 Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
• CPC Class Codes: C08L 33/12 Homopolymers or copolymers of methyl methacrylate
• CPC Class Codes: C08L 63/00 Compositions of epoxy resins; Compositions of derivatives of epoxy resins
• CPC Class Codes: C08L 65/02 Polyphenylenes
• CPC Class Codes: C09D 123/0869 Acids or derivatives thereof
• CPC Class Codes: C09D 163/00 Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
• CPC Class Codes: C09D 171/00 Coating compositions based on polyethers obtained by reactions forming an ether link in the main chain based on polyacetals C09D159/00; based on epoxy resins C09D163/00; based on polythioether-ethers C09D181/02; based on polyethersulfones C09D181/06; Coating compositions based on derivatives of such polymers
• CPC Class Codes: C09D 5/084 Inorganic compounds
• CPC Class Codes: C09D 5/24 Electrically-conducting paints conductive materials H01B1/00
• CPC Class Codes: C09D 7/48 Stabilisers against degradation by oxygen, light or heat
• CPC Class Codes: C09D 7/61 inorganic
• CPC Class Codes: C09D 7/70 characterised by shape, e.g. fibres, flakes or microspheres
• CPC Class Codes: C23C 2/26 After-treatment C23C2/14 takes precedence
• CPC Class Codes: Y10T 428/273 of coating

Abstract

A chrome-free coating composition for surface-treating a hot-dip galvanized steel sheet that includes carbon nanotubes and has excellent electric conductivity, comprising, based on the total solid weight of the composition: (a) 40 to 60 parts by weight of a water-soluble or water-borne organic resin; (b) 20 to 40 parts by weight of an inorganic metallic sol; (c) 2 to 5 parts by weight of a carbon nanotube paste including carbon nanotube (CNT); (d) 2 to 5 parts by weight of a metal oxide/phosphate-based anti-corrosion agent; (e) 5 to 15 parts by weight of an organic metal complex; (f) 3 to 7 parts by weight of a carbodimide cross-linking agent; and (g) the balance of water, ethanol or a mixture thereof. The steel sheet surface-treated with the composition may be useful to secure corrosion resistance without including a chrome component and shows its electric conductivity even when the coating composition is used at a coating amount of 1000 mg/m² or more.

Claims

1. A chrome-free coating composition for surface-treating a hot-dip galvanized steel sheet having excellent electric conductivity, comprising, based on the total solid weight of the composition:

(a) 40 to 60 parts by weight of a water-soluble or water-borne organic resin as a base resin;

(b) 20 to 40 parts by weight of an inorganic metallic sol;

(c) 2 to 5 parts by weight of a carbon nanotube paste including carbon nanotube (CNT);

(d) 2 to 5 parts by weight of a metal oxide/phosphate-based anti-corrosion agent;

(e) 5 to 15 parts by weight of an organic metal complex; and

(f) 3 to 7 parts by weight of a cross-linking agent.

2. The chronic-free coating composition of claim 1, comprising water or alcohol as a solvent so that the total solid content in the composition is in a range of 5 to 25% by weight.

3. The chrome-free coating composition of claim 1, wherein the water-soluble organic resin is selected from the group consisting of a water-dispersible urethane resin having a carboxy or hydroxyl group, an acrylic resin having a carboxy or hydroxyl group, an acryl or vinyl-modified water-dispersible urethane resin, an olefin resin such as poly(ethylene-co-acrylic acid) and poly (ethylene-co-methacrylic acid), a phenoxy resin including bisphenol A, and mixtures thereof.

4. The chrome-free coating composition of claim 1, wherein the inorganic metallic sol is selected from the group consisting of a silica sol, an alumina sol, a titania sol, a zirconia sol and mixtures thereof.

5. The chrome-free coating composition of claim 1, wherein the inorganic metallic sol has a metal particle size of 5 to 30 nm.

6. The chrome-free coating composition of claim 1, wherein the carbon nanotube paste is prepared by dispersing carbon nanotube in a resin selected from the group consisting of a water-dispersible urethane resin;

a copolymer such as poly(p-phenylenevinylene) (PPV), poly(p-phenylenevinylene-co-2,5-dioctoxy-m-phenylenevinylene) (PMPV) and polyaryleneethylene;

a water-soluble polymer such as poly(vinylalcohol), poly(ethyleneoxide) and polysaccharide; and

a surfactant such as sodium dodecyl sulfate, lithium dodecyl sulfate and cetyltrimethylammonium chloride.

7. The chrome-free coating composition of claim 1, wherein the corrosion resistance rust inhibitor is an aqueous solution including one selected from the group consisting of vanadium, zirconium, titanium, molybdenum, tungsten, manganese, cerium and mixtures thereof, or an aqueous phosphate solution of phosphate or hexaammonium heptamolybdate tetrahydrate including one selected from the group consisting of aluminum, aluminum diphosphate, zinc, molybdenum, fluorine and mixtures thereof.

8. The chrome-free coating composition of claim 1, wherein the organic metal complex is selected from the group consisting of a silane-based coupling agent, a titanium-based coupling agent, a zirconium-based coupling agent and mixtures thereof.

9. The chrome-free coating composition of claim 1, wherein the cross-linking agent is carbodimide cross-linking agent.

10. The chrome-free coating composition of claim 1, further comprising an alkoxy silane compound, wherein an organic/inorganic composite resin is formed by reaction of the water-soluble organic resin and inorganic metallic sol and the alkoxy silane compound.

11. The chrome-free coating composition of claim 10, wherein the alkoxy silane compound is present at a content of 1 to 10 parts by weight, based on 100 parts by weight of the sum of the solid weights of the water-soluble organic resin and the inorganic metal sol.

12. The chrome-free coating composition of claim 10, wherein the alkoxy silane compound comprises epoxysilane such as (3-glycidoxypropyl)trimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane and 3-glycidoxypropyltriethoxysilane, or aminosilane such as N-2(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propyl amine, N-phenyl-3-aminopropyltrimethoxysilane and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride.

13. A surface-treated steel sheet having excellent electric conductivity, comprising a hot-dip galvanized layer and a surface-treated layer, wherein the surface-treated layer is formed from the coating composition for surface-treating a steel sheet defined in claim 1, and a coating amount of the surface-treated layer is in a range of 600 to 2000 mg/m².

14. A surface-treated steel sheet having excellent electric conductivity, comprising a hot-dip galvanized layer and a surface-treated layer, wherein the surface-treated layer is formed from the coating composition for surface-treating a steel sheet defined in claim 10, and a coating amount of the surface-treated layer is in a range of 600 to 2000 mg/m².

15. The chrome-free coating composition of claim 2, further comprising an alkoxy silane compound, wherein an organic/inorganic composite resin is formed by reaction of the water-soluble organic resin and inorganic metallic sol and the alkoxy silane compound.

16. The chrome-free coating composition of claim 3, further comprising an alkoxy silane compound, wherein an organic/inorganic composite resin is formed by reaction of the water-soluble organic resin and inorganic metallic sol and the alkoxy silane compound.

17. The chrome-free coating composition of claim 4, further comprising an alkoxy silane compound, wherein an organic/inorganic composite resin is formed by reaction of the water-soluble organic resin and inorganic metallic sol and the alkoxy silane compound.

18. The chrome-free coating composition of claim 6, further comprising an alkoxy silane compound, wherein an organic/inorganic composite resin is formed by reaction of the water-soluble organic resin and inorganic metallic sol and the alkoxy silane compound.

19. The chrome-free coating composition of claim 7, further comprising an alkoxy silane compound, wherein an organic/inorganic composite resin is formed by reaction of the water-soluble organic resin and inorganic metallic sol and the alkoxy silane compound.

20. The chrome-free coating composition of claim 8, further comprising an alkoxy silane compound, wherein an organic/inorganic composite resin is formed by reaction of the water-soluble organic resin and inorganic metallic sol and the alkoxy silane compound.