Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2001-02-27
2003-06-03
Barr, Michael (Department: 1762)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C427S337000, C427S344000, C427S376100, C427S404000, C427S419100
Reexamination Certificate
active
06572983
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for surface treatment of metals, particularly metal-coated steel panels such as zinc-plated, aluminum-plated or tin-plated steel panels.
PRIOR ART
As the metallic surface treating agent, a chromium-containing surface treating agent such as a chromate system or a phosphate-chromate system has heretofore been used broadly and still in use today. However, in view of the recent trend toward more stringent regulatory control for environmental protection, it is likely that the use of such coating systems will be restricted for fear of the toxicity, particularly carcinogenicity, of chromium. Therefore, development of a rust-preventing agent not containing chromium and yet as effective as the chromating agent in imparting corrosion resistance has been awaited. As disclosed in Japanese Kokai Publication Hei-11-29724, the inventors of the present invention previously developed a nonchromate rust-preventing agent comprising an aqueous resin and, as incorporated therein, a thiocarbonyl group-containing compound, a phosphate ion, and water-dispersible silica. Regrettably, however, this system was found to be deficient in storage stability and somewhat poor in corrosion resistance at thin coating thickness. Meanwhile, with regard to silane coupling agents, an acidic surface treating agent containing two dissimilar silane coupling agents is disclosed in Japanese Kokai Publication Hei-8-73775. However, this system is intended to improve finger-print resistance and overcoat adhesion and is quite deficient in corrosion resistance for use in applications where high corrosion resistance and good processability are required after such metallic surface treatment as in the present invention. Moreover, Japanese Kokai Hei-10-60315 discloses a steel structure surface treating agent, which contains a silane coupling agent having a certain functional group reactive with an aqueous emulsion, but the corrosion resistance required here is only that of a degree satisfying comparatively mild test requirements such as those of wet tests and as far as corrosion resistance is concerned, the system is a far cry from a rust-preventing agent system as provided by the present invention. With the above state of the art by way of background, there has been a standing demand for development of a rust-preventing agent expressing sufficient corrosion resistance and overcoat adhesion at thin coating thickness.
SUMMARY OF THE INVENTION
The present invention has for its object to provide a method of treating a metallic surface which is suited for application to metals, particularly zinc-plated steel panels, and despite the absence of chromium therein, is capable of imparting high processability and corrosion resistance to steel panels, and a treated steel panel obtainable by said method.
The method of treating a metallic surface according to the present invention comprises
treating a metal-coated steel panel with a nonchromate metallic surface treating agent containing, in each liter thereof,
(a-1) a silane coupling agent and/or a hydrolytic condensation product thereof in an amount of 0.01 to 100 g/l,
(a-2) water-dispersible silica in a proportion of 0.05 to 100 g/l (solids), and
(a-3) a zirconium compound in an amount of 0.01 to 50 g/l in terms of zirconium ion and/or a titanium compound in an amount of 0.01 to 50 g/l in terms of titanium ion,
drying the treated steel panel and
coating it with an anticorrosion coating agent containing, in each liter of an aqueous resin solution or dispersion,
(b-1) a silane coupling agent and/or a hydrolytic condensation product thereof in an amount of 0.1 to 50 g/l,
(b-2) water-dispersible silica in an amount of 10 to 500 g/l (solids) and
(b-3) at least one phosphorus-containing ion selected from among phosphate ion, phosphite ion and hypophosphite ion in an amount of 0.1 to 10 g/l.
The nonchromate metallic surface treating agent for use in the present invention further contains one or more members selected from among sulfide ion, thiosulfate ion, persulfate ion and a triazinethiol compound in an amount of 0.01 to 100 g/l.
In an alternative mode of practicing the method of treating a metallic surface according to the present invention, said anticorrosion coating agent further contains one or more members selected from among sulfide ion, thiosulfate ion, persulfate ion and a triazinethiol compound in an amount of 0.01 to 100 g/l.
The present invention is further directed to a method of treating a metallic surface
which comprises using an anticorrosion coating agent obtainable by adding said components (b-1) and (b-2) to said aqueous resin solution or dispersion and reacting them at a temperature not less than 50° C. and not more than the boiling temperature of the resin composition. This method is most suited for surface treatment of zinc-coated steel panels.
The present invention is further directed to a nonchromate-treated steel panel as obtainable by any of the above methods.
DETAILED DESCRIPTION OF THE INVENTION
The metallic surface treating agent, which is used in the first place in the present invention, contains a silane coupling agent and/or a hydrolytic condensation product thereof as one of its essential components silane compounds. The hydrolytic condensation product of a silane coupling agent means an oligomer obtainable by hydrolytic polymerization of the silane coupling agent.
The silane coupling agent which can be used as above in the present invention is not particularly restricted but includes the following, among others: vinylmethoxysilane, vinyltrimethoxysilane, vinylethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N,N′-bis[3-(trimethoxysilyl)propyl]ethylenediamine, N-(.-aminoethyl)-.-aminopropylmethyldimethoxysilane, N-(.-aminoethyl)-.-aminopropyltrimethoxysilane, .-aminopropyltrimethoxysilane, .-aminopropyltriethoxysilane, . -glycidoxypropyltrimethoxysilane, .-glycidoxy-propyltriethoxysilane, .-glycidoxypropylmethyl-dimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl-trimethoxysilane, .-methacryloxypropyltrimethoxysilane, .-methacryloxypropyltriethoxysilane, .-mercaptopropyltrimethoxysilane, .-mercaptopropyl-triethoxysilane and N-[2-(vinylbenzyl-amino)ethyl]-3-aminopropyltrimethoxysilane.
The particularly preferred silane coupling agent includes vinylmethoxysilane, vinylethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyl-trimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine and N,N′-bis[3-(trimethoxysilyl)propyl]ethylenediamine. These silane coupling agents can be used each alone or in a suitable combination.
In the present invention, said silane compound is caused to be present in a concentration of 0.01 to 100 g/l, preferably 0.5 to 25 g/l, in [each liter of] the metallic surface treating agent. If the concentration of the silane coupling compound is less than 0.01 g/l, the corrosion resistance- and adhesion-enhancing effect of the nonchromate rust-preventive coating agent will be deficient. If the use of the silane coupling compound exceeds 100 g/l, the corrosion resistance-enhancing effect will not be improved any further but rather a cost disadvantage will result.
The metallic surface treating agent of the present invention contains water-dispersible silica. The water-dispersible silica which can be used in the present invention is not particularly restricted but is preferably spherical silica, chainlike silica or aluminum-modified silica, which is lean in sodium and other impurities and weakly basic. The spherical silica includes colloidal silicas such as “SnowtexN” and “Snowtex UP” (both manufactured by Nissan Chemical) and fumed silica such as “Aerosil” (Japan Aerosil); the chain like silica includes silica gel such as “Snowtex PS”, (Nissan Chemical); and the alumi
Sasaki Motohiro
Shimakura Toshiaki
Yamasoe Katsuyoshi
Barr Michael
Nippon Paint Co. Ltd.
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