Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2001-05-31
2002-12-10
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C204S505000, C523S403000, C523S404000, C523S410000, C523S423000, C523S424000, C525S526000, C525S528000, C525S533000
Reexamination Certificate
active
06492027
ABSTRACT:
The present invention relates to a cationic resin composition, more specifically to a cationic resin composition capable of forming a cured coating film which is excellent in both corrosion resistance and an aptitude for the cationic electrodepositable coating of a rust preventive steel plate.
A cationic resin composition is used mainly as a cationic electrodepositable coating composition for wide-ranged uses including an undercoating composition for car bodies, and those having various characteristics have so far been developed. Proposed as a conventional cationic resin composition is, for example, a coating composition having excellent corrosion resistance and improved in an electrodepositable coating aptitude and an adhesive property toward a rust preventive steel plate, in which used as a vehicle component is a modified epoxy resin obtained by internally plasticizing an epoxy resin having an amino group and/or a quaternary ammonium salt group as a hydrophilic group with a plasticizer such as polyamide, polyester and polyether and blended is a rust preventive pigment, for example, a lead compound or a chromium compound such as lead chromate, basic lead silicate and strontium chromate. In recent years, however, hazardous compounds such as lead compounds and chromium compounds are restricted in use thereof from a viewpoint of pollution problems, and techniques which can improve a corrosion resistance of the coating film without blending such hazardous compounds are expected to be developed.
On the other hand, an epoxy resin which is internally plasticized with a plasticizer such as polyamide, polyester and polyether tends to reduce a corrosion resistance of the coating film, and therefore it is considered to use an epoxy resin containing no plasticizing modifier to thereby elevate the corrosion resistance. However, this provides the problem that the electrodepositable coating aptitude against a rust preventive steel plate is reduced. In order to solve such problems, it is proposed that added as a plasticizer for an epoxy resin are, for example, polyol resins such as polyesterpolyols, polyetherpolyols, polyurethanepolyols and acrylpolyols; and polymers including polyolefins such as polybutadiene and polyethylene. Involved therein, however, is the problem that these materials not only do not have a sufficiently high compatibility with epoxy resins and are not effective so much for elevating a rust preventive steel plate aptitude but also reduce a corrosion resistance of the coating film by adding in a large amount.
A main object of the present invention is to provide a cationic resin composition useful in particular as a cationic electrodepositable coating, comprising an epoxy resin as a base material and capable of forming a coating film which is excellent both in a corrosion resistance and a rust preventive steel plate aptitude without using hazardous compounds such as lead compounds and chromium compounds.
Intensive researches repeated by the present inventors have resulted in finding that the object described above can be achieved by combining, as a vehicle component in a cationic resin composition, a certain kind of amino group-containing epoxy resin with a specific polyol-modified amino group-containing epoxy resin and a blocked polyisocyanate curing agent.
Thus, the present invention provides a cationic resin composition comprising the following components:
(A) an amino group-containing epoxy resin which is prepared by adding an amino group-containing compound (a-2) to an epoxy resin (a-1) having an epoxy equivalent of 400 to 3000,
(B) a polyol-modified amino group-containing epoxy resin which is prepared by making an epoxy resin (b-1) having an epoxy equivalent of 180 to 2500 react with an amino group-containing compound (b-2) and with a polyol compound (b-3) obtained by adding caprolactone to a compound having plural active hydrogen groups, and
(C) a blocked polyisocyanate curing agent, component (A) being 40 to 70% by weight, component (B) being 4 to 40% by weight, and component (C) being 10 to 40% by weight, based on the total solid contents of (A), (B) and (C).
The cationic resin composition of the present invention shall be explained below in further details.
Amino Group-containing Epoxy Resin (A)
Amino group-containing epoxy resin which is used as component (A) in the cationic resin composition of the present invention is prepared by adding an amino group-containing compound (a-2) to an epoxy resin (a-1). Said epoxy resin (a-1) can have an epoxy equivalent falling in a range of 400 to 3000, preferably 450 to 2500, and more desirably 500 to 2200. Further, it has suitably a number average molecular weight falling in a range of usually 500 to 5000, particularly 600 to 4500, and more particularly 800 to 4000. An epoxy resin obtained by the reaction of a polyphenol compound with epihalohydrin, for example epichlorohydrin, is particularly suited as an epoxy resin (a-1) from the viewpoint of corrosion resistance of coating film.
Polyphenol compounds which can be used for producing the above epoxy resin include, for example, bis(4-hydroxyphenyl)-2,2-propane (bisphenol A), 4,4-dihydroxybenzophenone, bis(4-hydroxyphenyl)methane (bisphenol F), bis(4-hydroxyphenyl)-1,1 -ethane, bis(4-hydroxyphenyl)-1,1-isobutane, bis(4-hydroxy-tert-butyl-phenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, tetra(4-hydroxyphenyl)-1,1,2,2-ethane, 4,4-dihydroxy-diphenylsulfone (bisphenol S), phenol novolak and cresol novolak.
Particularly suited as an epoxy resin obtained by the reaction of a polyphenol compound with epichlorohydrin is a compound which is derived from bisphenol A, and which is represented by the following formula:
wherein n is 1 to 10.
Commercially available products of such epoxy resin include, for example, products which are marketed from Japan Epoxy Resin Co., Ltd. in the trade names of Epikote 828EL, ditto 1002, ditto 1004 and ditto 1007.
For the amino group-containing compound (a-2) as a cationic property-providing component with which to introduce an amino group into the above-mentioned epoxy resin (a-1) and to thereby cationize said epoxy resin, there are suitably used amine compounds having at least one active hydrogen which performs an addition reaction with an epoxy group of epoxy resin (a-1), for instance amine compounds which have at least one primary or secondary amino group in molecule. Concrete examples of such compounds include mono- or di-alkylamines such as monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine and dibutylamine; alkanolamines such as monoethanolamine, diethanolamine, mono(2-hydroxypropyl)amine, di(2-hydroxypropyl)amine, tri(2-hydroxypropyl)amine, monomethylaminoethanol and monoethylaminoethanol; alkylenepolyamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, tetraethylenepentamine, pentaethylenehexamine, diethylaminopropylamine, diethyelenetriamine and triethylenetetramine, and ketimine-reduced compounds of these polyamines; alkyleneimines such as ethyleneimine and propyleneimine; and cyclic amines such as piperazine, morpholine and pyrazine.
The above-mentioned addition reaction between epoxy resin (a-1) and amino group-containing compound (a-2) may be conducted by a known method. For instance, epoxy resin (a-1) and amino group-containing compound (a-2) are allowed to react with each other in an organic solvent like hydrocarbon type solvent such as heptane, toluene, xylene, octane and mineral spirits; ester type solvent such as ethyl acetate, n-butyl acetate, isobutyl acetate, ethyleneglycol monomethylether acetate and ethyleneglycol monobutylether acetate; ketone type solvent such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone and cyclohexane; alcohols such as methanol, ethanol, iso-propanol, n-butanol, sec-butanol and isobutanol; and ether type solvent such as n-butylether, dioxane, ethyleneglycol monomethylether and ethyleneglycol monoethylether, at a temperature of about 80 to about 130° C. The proportion
Hiraki Tadayoshi
Kamikado Koji
Nishiguchi Shigeo
Tominaga Akira
Aylward D.
Dawson Robert
Kansai Paint Co. Ltd.
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