Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2002-12-23
2004-03-16
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C427S386000
Reexamination Certificate
active
06706328
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a metal sheet material that has at least one of superior corrosion resistance, paintability, fingerprint resistance, and workability and that is used in consumer electrical and electronic products, building materials, and the like.
Metal sheet materials such as steel sheets, aluminum-plated steel sheets, zinc-plated steel sheets, and aluminum sheets are commonly used in a wide range of fields related to automobiles, building materials, and consumer electrical and electronic products. Zinc and aluminum, however, corrode in the atmosphere and generate corrosion products (known as white rust), which mar the appearance of the metal material and also adversely affect the paintability of the material. Furthermore, the material is susceptible to fingerprints and other soiling when handled by workers in the course of the various steps of manufacturing the finished product at the user's plant; such soiling can markedly lower the commercial value of the product. Also, oils and the like are used as lubricants in pressing and other such working of the material, and this oil has to be removed after forming.
In view of this, in order to improve the corrosion resistance, paintability, fingerprint resistance, and workability of the above-mentioned metal material surfaces, the surface of a metal sheet material has been subjected to a chromate treatment using a treatment solution composed primarily of chromic acid, dichromic acid, or a salt thereof, after which the upper layer is coated with a polyolefin resin having carboxyl groups and containing colloidal silica and a wax or the like, or with a coating agent comprising a resin containing a lubricating component such as a wax (rather than imparting workability with an oil or the like), and these metal sheet materials have been used in press molding and other such applications.
Due to heightened awareness about environmental protection in recent years, however, there has been a move away from chromate treatments because the hexavalent chromium in the chromate treatment solutions used to treat metal material surfaces has a direct and adverse effect on humans. Wastewater containing hexavalent chromium also requires special treatment as set forth in various laws and regulations, and this leads to a considerable Increase in the overall cost. Also, a metal material that has undergone a chromate treatment becomes an industrial waste containing chromium, which is a serious drawback because such material cannot be recycled, and this poses problems for society.
Another well-known surface treatment method other than using a chromate involves the use of tannic acid and/or another polyvalent phenol carboxylic add. When a metal material is treated with an aqueous solution of tannic acid, the protective film formed by a reaction between the tannic acid and the metal material becomes a barrier to the infiltration of corrosive substances, so that the corrosion resistance of the metal material is believed to be improved.
Still, the need for ever higher quality in products today makes it necessary for the protective film itself to have high corrosion resistance, and the use of tannic acid by itself, or along with an inorganic component in the cover film, has not afforded sufficient corrosion resistance, and practical use is therefore impossible at the present time.
In view of this, a method in which a metal surface is coated with an aqueous solution composed of water-dispersible silica, an alkyd resin, and a trialkoxysilane compound has been disclosed in Japanese Laid-Open Patent Application S53-121034 as a treatment method that improves the corrosion resistance of a metal material.
A surface treatment method aimed at imparting corrosion resistance to a metal material by using a water-soluble resin composed of a hydroxypyrrone derivative and a method in which corrosion resistance is imparted by using a water-soluble or water-dispersible polymer of a hydroxystyrene compound have been disclosed in Japanese Patent Publication S57-44751, Japanese Laid-Open Patent Application H1-177380, and elsewhere.
Unfortunately, none of the above methods has allowed the formation of a film capable of imparting corrosion resistance good enough to replace a chromate film on a metal material surface, so the current problems discussed above have not been solved. At present, therefore, there is yet to be found a non chromium-based surface treatment agent or method for a metal material with excellent corrosion resistance.
The present invention is intended to solve the above problems encountered with prior art, and it is an object of the invention to provide a chromium free surface treated metal material with at least one, more preferably more than one, or most preferably all, of superior corrosion resistance, paintability, fingerprint resistance, and workability.
BRIEF SUMMARY OF THE INVENTION
There has been discovered a metal sheet material with superior corrosion resistance, paintability, fingerprint resistance, and workability, and a method for manufacturing this material, which is accomplished by coating the surface of a metal sheet material with a composition composed of a silane coupling agent component, a polymer component having a specific chemical structure, and a wax component.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
A coating composition according to the invention comprises, preferably consists essentially of, or more preferably consists of, the following components:
(A) a silane coupling agent component comprised of at least one type of silane coupling compound having one or more reactive functional moieties selected from among active hydrogen-containing amino moieties, epoxy moieties, vinyl moieties, mercapto moieties, and methacryloxy moieties;
(B) a polymer component comprising at least one type of polymer that: conforms to the following General Formula 1:
where, independently for each instance of General Formula 1 in the polymer:
Y
1
represents a hydrogen atom or a “Z” moiety that conforms to one of the following General Formulas, 3 or 4:
where each of R
3
, R
4
, R
5
, R
6
, and R
7
independently represents a hydrogen atom, a C
1
to C
10
alkyl moiety, or a C
1
to C
10
hydroxyalkyl moiety; and
X represents a hydrogen atom, a hydroxyl moiety, a C
1
to C
5
alkyl moiety, a C
1
to C
5
hydroxyalkyl moiety, a C
6
to C
12
aryl moiety, a benzyl moiety, a benzal moiety, an unsaturated hydrocarbon moiety forming a naphthalene ring by condensation with the benzene ring to which the general formula shows X is bonded, or a moiety conforming to the following General Formula 2:
where:
each of R
1
and R
2
independently represents a hydrogen atom, a hydroxyl moiety, a C
1
to C
5
alkyl moiety, or C
1
to C
10
hydroxyalkyl moiety (if these moieties have eleven or more carbons, there will be a drop in the film formability of the resulting coating composition, so that corrosion resistance, paintability, fingerprint resistance, and/or workability may be inadequate); and
Y
2
represents a hydrogen atom or a “Z” moiety as described above;
has an average degree of polymerization (i.e., number of units as represented by General Formula 1 per molecule of the polymer, the degree of polymerization may hereinafter be designated as “n”) of 2 to 50; and
has a number of Z moieties that has a ratio to the number of benzene rings that is from 0.2 to 1.0 (if this average number of Z moiety substitutions is less than 0.2, the resulting polymer may not adhere well to the metal material and paintability may be poor; while the resulting polymer will be more hydrophilic if this number is over 1.0, the resulting metal sheet material may have insufficient corrosion resistance); and
(C) a wax component.
The weight ratio of the silane coupling agent component (A) to the polymer component (B) preferably is from: 1:10 to 10:1, a range of 1:1 to 5:1 being more preferred. If this weight ratio is less than 1:10, that is, if the proportion of the silane coupling agent component (A) is too low, there will be a d
Kawakami Katsuyuki
Nakamura Mitsuru
Ogino Takao
Cameron Erma
Cameron Mary K.
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
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