Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Reexamination Certificate
1999-08-13
2001-10-30
Sheehan, John (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C148S255000, C148S270000, C148S279000, C106S014120, C252S389200
Reexamination Certificate
active
06309477
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to pretreatment chemicals for metal materials to be painted. The metal materials include a steel plated with a metal (referred to as a metal-plated steel hereinafter), a non-plated steel or a metal other than steel. The present invention particularly relates to non-chromium pretreatment chemicals for metal materials to be painted, a metal-plated steel or a non-plated steel used as building materials or electrical household appliances in which a severe processing such as press or bending is needed after being painted, a method for pretreatment and a metal material treated thereby.
As the pretreatment chemicals used in the pretreatment for painting mentioned above, a reaction type or a coating type chromate-containing treating agent have been usually used. For example, a treating method where after the chromate treating agents are coated, an aqueous solution of an organic polymer resin is applied is disclosed in Japanese Patent Application KOKAI No.202084/1987. But considering the nowadays tendency of environmental regulation, there is the possibility such chromate-containing anticorrosive agent is restricted in use because of the high toxicity and the carcinogenicity. In this situation, Japanese Publication No.31593/1984 discloses a method of treating a metal surface without chromium. This method basically relates to a formation of phosphoric acid conversion film, which is insufficient for achieving a high adhesion of the painted film in the use of tough bending processing. An anticorrosive agent disclosed in Japanese Patent Application No.195244/1993 is not a perfect pollution-free treating agent, as it contains fluorine ion and heavy metal, and it is far from an ideal non-chromium treating agent in view of the high load in waste water treatment.
SUMMARY OF THE INVENTION
The present invention relates to pretreatment chemicals for metal materials to be painted with paints and a pretreatment using the same, by which an excellent adhesion between the painted film and the undersurface of the metal materials (this adhesion of the painted film is expressed by term “formability”), especially high resistance against bending and scratching can be achieved.
The present invention relates to pretreatment chemicals for metal materials to be painted, which comprise at least one of sulfur-containing compounds and at least one of phosphorus ion-containing compounds (phosphorus ion means acid ions containing at least one of a phosphorus atom) in water.
Further, the present invention relates to an anticorrosive treatment comprising treating metal materials with said pretreatment chemicals.
Additionally the present invention relates to metal materials treated with said pretreatment chemicals.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to pretreatment chemicals for metal materials to be painted (simply referred to as “pretreatment chemicals” hereinafter) which comprises at least one of sulfur-containing compounds and at least one of phosphorus ion-containing compounds in water.
In the present specification the term “metal materials” means a sheet, a plate, a processed product or the like which is made of metal such as steel, zinc, aluminum, copper and the like; steel plated with metal such as Zn, Al, Ni, Cr, Sn, Pb, Fe, Co, Mg, Mn, Ti and the like; alloys made of at least two kinds of metals; steel alloyed with at least one of the above metals and in some cases hetero atoms or other impurities on the surface; metals such as steel in which an oxide such as silica, titania, alumina and the like or other elements such as carbon, silicon and the like are dispersed; non-plated metal such as non-plated steel and the like.
Typical examples of the metal materials are zinc-plated steel, aluminum-plated steel or non-plated steel, particularly zinc-plated steel.
The term “plating” or “plated” includes an electro-galvanizing, a fused metal plating, a deposition, an injection and the like.
The metal materials are treated with an aqueous solution comprising one or more sulfur-containing compounds selected from the group consisting of sulfides, triazinethiols, thiocarbonyl group-containing compounds, thiosulfuric acid, thiosulfates, persulfuric acid, and persulfates in the amount of 0.1 g-50 g and one or more compounds containing phosphorus ions (referred to as “phosphorus ion-containing compounds” hereinafter) which contain ions selected from the group consisting of phosphate ion, phosphite ion, hypophosphite ion, condensed phosphate ions, phytate ion, phosphonate ion in the amount of 0.1 g-50 g per one liter of the total amount of the pretreatment chemicals.
In the present invention, the working mechanism of the sulfur-containing compounds and phosphorus ion-containing compounds has not been clarified, but it is inferred as follows.
A sulfide ion reacts with a metal surface to form a metal sulfide. For example, zinc sulfide is one of the most stable compounds among the zinc compounds as is clear from the last that zinc sulfide naturally exists as sphalerite. Therefore, it is considered the corrosion resistance and formability of the paint are improved by the formation of the film of zinc sulfide on the zinc-plated surface. At this moment as there are phosphorus ion-containing compounds, the corrosion resistance and formability of the paint is further improved as multiplier effect but the reason is not clear.
In the case of the other sulfur-containing compounds, an absorbed layer of the sulfur-containing compounds are also formed owing to easy absorbency of a sulfur atom to metal materials, especially zinc surface, and therefore the corrosion resistance and the formability of a paint are improved. At this moment if there is a phosphorus ion-containing compound, the corrosion resistance and the formability of paint are further improved as multiplier effect but the reason is not clear. Sulfur-containing compounds or phosphorus ion-containing compounds can lower only cathode current of metal materials, but when both of them exist at the same time, both of the anode current and the cathode current lower so as to improve the corrosion resistance and the formability of paint.
Examples of the sulfur-containing compounds useful in the present invention include sulfides, triazinethiol compounds, thiocarbonyl group-containing compounds, thiosulfuric acid, thiosulfates, persulfuric acid persulfates.
Any sulfides which can release a sulfide ion in an aqueous solution may be used. Examples of such sulfides include sodium sulfide, ammonium sulfide, manganese sulfide, molybdenum sulfide, iron sulfide, barium sulfide and like. Sulfide ion is formed in pretreatment chemicals by the addition of the sulfides which can release a sulfide ion in an aqueous solution.
The examples of triazinethiol compounds include 2,4,6-trimercapto-S-triazine, 2-dibutylamino-4,6-dimercapto-S-triazine, monosodium 2,4,6-trimercapto-S-triazine, trisodium 2,4,6-trimercapto-S-triazine, 2-anilino-4,6-dimercapto-S-triazine, monosodium 2-anilino-4,6-dimercapto-S-triazine.
Examples of the thiocarbonyl group-containing compounds include thiourea, dimethylthiourea, 1,3-diethylthiourea, dipropylthiourea, dibutylthiourea, 1,3-diphenyl-2-thiourea, 2,2-ditolylthiourea, thioacetamide, sodium dimethyldithiocarbamate, tetramethylthiuram monosulfide, tetrabutylthiuram disulfide, zinc N-ethyl-N-phenyl-dithiocarbamate, zinc dimethylthiocarbamate, piperidine pentamethylenedithiocarbamate, zinc diethyldithiocarbamate, sodium diethyldithiocarbamate, zinc isopropylxanthate, ethylene thiourea, dimethylxanthatedisulfide, dithiooxamide and like. They should only be the compounds having at least one thiocarbonyl group.
A thiosulfate ion can be formed in pretreatment chemicals by adding a compound which can release thiosulfate ion in an aqueous solution. Such compounds should only be ones which can release thiosulfate ion in an aqueous solution and examples of such compounds include thiosulfuric acid, ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate and the like.
A persulfate ion c
Fukuoka Takayuki
Shimakura Toshiaki
Wada Yutaka
Nippon Paint Co. Ltd.
Oltmans Andrew L.
Sheehan John
Wenderoth , Lind & Ponack, L.L.P.
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