Compositions: coating or plastic – Coating or plastic compositions – Heavy metal compound containing
Reexamination Certificate
2003-01-14
2004-05-18
Brunsman, David (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Heavy metal compound containing
C106S287100
Reexamination Certificate
active
06736890
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel coating composition for forming a titanium oxide film, process for forming a titanium oxide film, and use of the coating composition.
BACKGROUND ART
Metal substrates such as steel sheets, aluminum and aluminum alloys are usually subjected to various types of surface treatment (undercoating) to improve the corrosion resistance, coating adhesion, processability, etc.
In recent years, surface-treated steel sheets are required to have higher corrosion resistance, and therefore zinc-based metal plated steel sheets are frequently used as metal substrates replacing cold rolled steel sheets.
Conventionally, chromate treatment or phosphate treatment is employed for surface treatment of zinc-based metal plated steel sheets.
Chromate treatment have problems with inherent toxicity of chromium compounds. In particular, hexavalent chromium compounds are extremely harmful substances designated human carcinogens by IARC (International Agency for Research on Cancer Review) and many other public organizations. Specifically stated, chromate treatment has problems with chromate fumes produced during the treatment process, extremely high cost required for waste water disposal equipment, chromic acid dissolved out from chromate treatment coats, and the like.
Phosphate treatment using zinc phosphate, iron phosphate or like phosphate is usually followed by chromate post-treatment, and thus involves the problems with toxicity of chromium compounds. Moreover, phosphate treatment has problems with disposal of waster water which contains reaction accelerators, metal ions and the like owing to phosphate treatment agents, and sludge disposal necessitated by metal ions dissolved out from treated metals.
As another post-treating agent for phosphate treatment coats than chromate, Japanese Examined Patent Publication No. 1995-42423 proposes a post-treating composition containing metal ions such as titanium ions or zirconium ions and polyalkenyl phenol. However, when the proposed post-treating composition is used for post-treatment of a phosphate treatment coat on a zinc-based metal plated steel sheet, the composition does not sufficiently inhibit white rusting and thus hardly improves the corrosion resistance.
Japanese Unexamined Patent Publications No. 1983-224174, No. 1985-50179 and No. 1985-50180 disclose coated steel sheets comprising a zinc-based metal plated steel sheet substrate, a chromate coat formed on the substrate and an organic silicate coat formed on the chromate coat. The disclosed coated steel sheets are excellent in corrosion resistance and processability, but have the problems with toxicity of chromium compounds owing to the chromate coat. Without the chromate coat, the coated steel sheets have insufficient corrosion resistance.
Aluminum or aluminum alloy substrates are also subjected to various types of surface treatment (undercoating) in many cases, to improve the corrosion resistance, coating adhesion and other properties.
Generally, fins in heat exchangers for air conditioners are made of aluminum or aluminum alloy substrates which are light in weight and excellent in processability and thermal conductivity. In air conditioner heat exchangers, water condenses into droplets and forms water bridges between the fins during cooling operation. The bridges narrow the passageway for air and increase the resistance to air passage, thus causing problems such as power loss, noise, water splashing, etc.
To solve these problems, surfaces of the aluminum or aluminum alloy fins are subjected to boehmite treatment, water glass coating, aqueous polymer coating or like hydrophilizing treatment for preventing bridge formation. However, in a highly corrosive environment, the hydrophilized aluminum or aluminum alloy fins are corroded within a few months or so, partly because of the hydrophilicity of the treatment coat.
To prevent corrosion of the fins, chromate treatment is often employed for undercoating of aluminum or aluminum alloy substrates, since chromate treatment has the advantages of providing good corrosion resistance with low cost. However, chromate treatment is accompanied by the problems with toxicity of chromium compounds as described above.
As chromate-free undercoating materials and undercoating processes, Japanese Unexamined Patent Publication No. 1979-24232 discloses treatment of an aluminum surface with an acid solution comprising a titanium salt, hydrogen peroxide and condensed phosphoric acid; Japanese Unexamined Patent Publication No. 1979-160527 discloses treatment of an aluminum surface with an aqueous alkaline solution containing titanium ions and a complexing agent, followed by water washing and treatment with an aqueous solution of an acid such as phosphoric acid; Japanese Unexamined Patent Publication No. 1997-20984 discloses an aluminum surface treating agent comprising phosphoric acid ions, a titanium compound and a fluoride; and Japanese Unexamined Patent Publication No. 1997-143752 discloses an aluminum-based metal surface treating agent comprising condensed phosphate, a titanium salt, a fluoride and phosphite.
However, these undercoating materials and processes utilizing titanium compounds have the problems such as insufficient stability of the undercoating materials, lower corrosion resistance of the coat than a chromate treatment coat, insufficient hydrophilicity and insufficient durability of the coat.
In view of the above state of the art, there are demands for an inorganic film-forming material which is useful as an undercoating material for metal substrates such as steel sheets, aluminum, aluminum alloys or the like, or as a post-treating agent for phosphate undercoats, and which is capable of forming a film excellent in corrosion resistance and other properties without causing toxicity problems.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a novel coating composition and process for forming a titanium oxide film, which are capable of forming, on a metal substrate, an undercoat excellent in corrosion resistance, processability and coating adhesion.
Another object of the invention is to provide an undercoating material for a metal substrate, which is capable of forming a film excellent in corrosion resistance, processability and coating adhesion.
A further object of the invention is to provide a post-treating agent for phosphate undercoats on metal substrates, which is capable of forming a film excellent in corrosion resistance, processability and coating adhesion.
Other objects and features of the present invention will become apparent from the following description.
The invention provides the following novel coating compositions for forming a titanium oxide film, processes for forming a titanium oxide film, and use of the coating compositions:
1. A coating composition for forming a titanium oxide film, comprising (A) a titanium-containing aqueous liquid obtained by mixing at least one titanium compound selected from the group consisting of hydrolyzable titanium compounds, low condensates of hydrolyzable titanium compounds, titanium hydroxide and low condensates of titanium hydroxide with aqueous hydrogen peroxide, and (B) at least one halide selected from the group consisting of titanium halides, titanium halide salts, zirconium halides, zirconium halide salts, silicon halides and silicon halide salts.
2. A coating composition according to item 1, wherein the titanium-containing aqueous liquid (A) is an aqueous peroxo titanic acid solution obtained by mixing a hydrolyzable titanium compound and/or its low condensate with aqueous hydrogen peroxide.
3. A coating composition according to item 2, wherein the hydrolyzable titanium compound is a tetraalkoxytitanium represented by the formula
Ti(OR)
4
(1)
wherein Rs may be the same or different and each represent C
1
to C
5
alkyl.
4. A coating composition according to item 2, wherein the low condensate of a hydrolyzable titanium compound is a compound having a condensation degree of 2 to 30 and obtained by self-condensatio
Akui Jun
Haruta Yasuhiko
Isozaki Osamu
Armstrong Kratz Quintos Hanson & Brooks, LLP
Brunsman David
LandOfFree
Coating material for forming titanium oxide film, method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coating material for forming titanium oxide film, method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coating material for forming titanium oxide film, method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3253862