Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2001-11-28
2004-01-20
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C205S316000, C205S317000, C525S528000
Reexamination Certificate
active
06680122
ABSTRACT:
The present invention relates to a cationic paint composition. More specifically, it relates to a cationic electrodeposition paint composition capable of forming a cured coating film which is excellent in performances such as throwing power, electrodeposition coating aptitude for rust preventive steel plate, and corrosion resistance.
Cationic electrodeposition paint composition has been used mainly as an electrodeposition paint for a wide range of uses such as undercoating of a car body. Products having various properties have been developed up to now. For example, there has been proposed a cationic electrodeposition paint composition excellent in corrosion resistance and in electrodeposition coating aptitude for rust preventive steel plate and further in adhesion, which contains, as a base resin, an epoxy resin which contains amino group and/or quaternary ammonium group as water-soluble group, and which has been internally plasticized with a plasticizer such as polyamide, polyester, polyether etc. In such a cationic electrodeposition paint composition, there are compounded, as anticorrosive pigment, lead compounds or chromium compounds, for example, lead chromate, basic lead silicate, strontium chromate, etc. Recently, however, the use of such harmful compounds as lead compounds or chromium compounds is restricted in terms of pollution problems, and the development of a cationic paint composition, excellent in corrosion resistance and containing neither lead compounds nor chromium compounds, has been strongly desired.
Since an epoxy resin which is internally plasticized with a plasticizer tends to deteriorate the corrosion resistance of a coating film, it may be considered to improve the corrosion resistance by using, as base resin, an epoxy resin containing no plasticizing modifier. There is, however, a problem that a paint composition using a non-plasticized epoxy resin has a lower electrocoating aptitude for rust preventive steel plate.
Moreover, it has been proposed to compound in an epoxy resin a plasticizer which does not deteriorate the corrosion resistance of a coating film, for example, polyol resin such as polyester polyol polyether polyol polyurethane polyol, acrylpolyol etc.; polyolefin such as polybutadiene, polyethylene, etc. There are problems, however, that these materials are not compatible enough with epoxy resin, and are not only poorly effective to improve the electrocoating aptitude for rust preventive steel plate but also deteriorate, if compounded much, the corrosion resistance of a coating film.
The inventors of the present invention have made assiduous study with a view to resolving the above-mentioned problems, and, as a result, have found out that, when a certain kind of specific amino group-containing epoxy resin is compounded, there is obtained a cationic electrodeposition paint composition which is excellent in all of throwing power, electrocoating aptitude for rust preventive steel plate and corrosion resistance in a well-balanced manner, and, thus, have completed the present invention.
Thus, according to the present invention, there is provided a cationic paint composition containing, as resin component, an amino group-containing epoxy resin obtained by the reaction of:
(A) an epoxy resin with an epoxy equivalent of 300-2,500, with
(B) a hydroxyl group-containing carboxylic acid which is obtained by making hydroxy monocarboxylic acid (b
1
) react with caprolactone (b
2
), and
(C) an amino group-containing compound.
In the following, the cationic paint composition provided by the present invention is described in more detail.
(A) Epoxy Resin
Epoxy resin (A) to be the main skeleton of the amino group-containing epoxy resin according to the present invention has suitably an epoxy equivalent in the range of 300-2,500, preferably 350-2,000, and more desirably 400-1,500, and a number-average molecular weight of generally at least 500, preferably in the range of 500-5,000, and more desirably 800-3,000. If the epoxy equivalent of the epoxy resin is less than 300, the corrosion resistance and throwing power of the formed cationic paint composition becomes poor. If, on the other hand, it is more than 2,500, electrocoating aptitude for the rust preventive steel plate (zinc-plated steel plate) is deteriorated.
As such an epoxy resin (A), a product obtained by a reaction of a polyphenol compound with an epihalohydrin, for example, epichlorohydrin, is preferable from a viewpoint of corrosion resistance etc. of coating film.
As a polyphenol compound usable for the formation of said polyepoxide compound, there can be mentioned, for example, bis(4-hydroxyphenyl)-2,2-propane (bisphenol A), 4,4-dihydroxy-benzophenone, bis(4-hydroxyphenyl)methane (bisphenol F), bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)-1,1-iso-butane, bis(4-hydroxy-tert-butyl-phenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, tetra(4-hydroxyphenyl)-1,1,2,2-ethane, 4,4-dihydroxydiphenylsulfone, phenol novolac, cresol novolac, etc.
As an epoxy resin obtained by the reaction of polyphenol compound and epichlorohydrin, a product derived from bisphenol A which is illustrated by the following formula:
wherein n=0-8
is preferable in particular.
As such an epoxy resin available on the market, there can be mentioned, for example, products sold by Japan Epoxy Resin Co., Ltd., under the trade name of Epicote 828EL, 1002, 1004 and 1007.
(B) Hydroxyl Group-Containing Carboxylic Acid
Hydroxyl group-containing carboxylic acid which is to be made to react with the above-mentioned epoxy resin (A) in accordance with the present invention is useful for the internal plasticization of said epoxy resin, and is obtained by making hydroxy monocarboxylic acid (b
1
) react with caprolactone (b
2
).
Hydroxy monocarboxylic acid (b
1
) is a compound which contains, in a molecule, at least one, preferably one or two, hydroxyl groups and a carboxylic acid. Concrete examples include glycolic acid, hydroxy pivalic acid, dimethylol propionic acid, dimethylol butanoic acid, lactic acid, glyceric acid, etc., among which glycolic acid, hydroxy pivalic acid, dimethylol propionic acid and dimethylol butanoic acid are in particular preferable.
As caprolactone (b
2
) which is to be made to react with the above-mentioned hydroxy monocarboxylic acid (b
1
), there can be mentioned &ggr;-caprolactone, &egr;-caprolactone and &dgr;-caprolactone, among which &egr;-caprolactone is especially suitable.
The above-mentioned reaction between hydroxy monocarboxylic acid (b
1
) and caprolactone (b
2
) may be carried out by any known method. Concretely, for instance, said reaction can be conducted by heating hydroxy monocarboxylic acid (b
1
) and caprolactone (b
2
) at a temperature of about 100 to about 250° C. for about one to about 15 hours in the presence of a catalyst such as titanium compound like tetrabutoxy titanium or tetrapopoxy titanium; organotin compound like tin octylate, dibutyl tin oxide or dibutyl tin laurate; and metal compound like stannous chloride.
The above-mentioned catalyst may be used in an amount of 0.5 to 1,000 ppm on the basis of the total amount of hydroxy monocarboxylic acid (b
1
) and caprolactone (b
2
). Caprolactone (b
2
) may be used generally in a range of 1.5 to 15 moles, preferably 1.5 to 13 moles, more desirably 1.7 to 12 moles, per equivalent of hydroxyl group (i.e., per one hydroxyl group) of hydroxy monocarboxylic acid (b
1
).
(C) Amino Group-Containing Compound
An amino group-containing compound (C) to be made to react with the aforementioned epoxy resin (A) in the present invention is a component to give the cationicity to cationize said epoxy resin by introducing amino group to epoxy resin substrate. There is used a compound containing at least one active hydrogen which reacts with an epoxy group.
As an amino group-containing compound used for such a purpose, there can be mentioned, for example, mono- or di-alkylamines such as monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, trilsopropylamine, monobutylamine, dibutylamine, etc.; alkanola
Koji Kamikado
Shigeo Nishiguchi
Dawson Robert
Feely Michael
Kansai Paint Co. Ltd.
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