Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2000-12-22
2003-01-07
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S414000, C428S415000, C428S416000, C428S417000, C428S418000, C525S423000, C525S438000, C528S111000, C528S114000, C528S121000, C528S291000, C528S341000, C528S361000, C528S407000, C523S417000, C523S420000
Reexamination Certificate
active
06503629
ABSTRACT:
The present invention relates to a cationic coating composition, more specifically to a cationic coating composition capable of forming a cured coating film which is excellent in a corrosion resistance and a rust preventive steel plate aptitude.
A cationic coating composition is used mainly as an 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 coating composition is, for example, a coating composition having an 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, for example, a lead compound or a chromium compound such as polyamide, polyester and polyether and blended is a rust preventive pigment 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 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.
An object of the present invention is to provide a cationic coating composition 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 using as a vehicle component in a cationic coating composition, a polyol-modified, amino group-containing epoxy resin prepared by reacting an epoxy resin with a polyol compound obtained by adding caprolactone to a compound having plural active hydrogen groups and an amino group-containing compound, and they have come to complete the present invention.
Thus, the present invention provides a cationic coating composition comprising as a vehicle component, a polyol-modified, amino group-containing epoxy resin prepared by reacting an epoxy resin (A) having an epoxy equivalent of 180 to 2500 with a polyol compound (B) obtained by adding caprolactone to a compound having plural active hydrogen groups and an amino group-containing compound (C).
The cationic coating composition of the present invention shall be explained below in further details.
Epoxy Resin (A)
An epoxy resin obtained by the reaction of a polyphenol compound with epihalohydrin, for example, epichlorohydrin is particularly suited as an epoxy resin used as a starting material in the production of the modified epoxy resin used as the vehicle component in the coating composition of the present invention from a corrosion resistance of the coating film.
The 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 the epoxy resin obtained by the reaction of a polyphenol compound with epihalohydrin is a compound derived from bisphenol A, which is represented by the following formula:
wherein n is 1 to 3.
The epoxy resin (A) can have an epoxy equivalent falling in a range of usually 180 to 2500, preferably 200 to 2000 and more preferably 400 to 1500. Further, it has suitably a number average molecular weight falling in a range of usually at least 200, particularly 400 to 4000 and more particularly 800 to 2000.
Commercially available products of such epoxy resin include, for example, products which are marketed from Oil Shell Epoxy Co., Ltd. in the trade names of Epikote 828EL, ditto 1002, ditto 1004 and ditto 1007.
Polyol Compound (B)
In the present invention, the polyol compound (B) is used for internally plasticizing (modifying) the epoxy resin (A) described above and is produced by adding caprolactone (b) to a compound (a) having plural active hydrogen groups.
An active hydrogen group means an atomic group containing at least one active hydrogen and includes, for example, an alcoholic hydroxyl group, a primary amino group and a secondary amino group. The compound (a) having plural groups of such active hydrogen group in a molecule includes, for example:
(i) low molecular weight polyols,
(ii) linear or branched polyetherpolyols,
(iii) linear or branched polyesterpolyols,
(iv) amine compounds having a primary amino group and/or a secondary amino group or hydroxylamine compounds having a primary amino group and/or a secondary amino group in combination with a hydroxyl group.
These active hydrogen group-containing compounds (a) can have a number average molecular weight falling in a range of usually 62 to 5,000, preferably 62 to 4,000 and more preferably 62 to 1,500. The active hydrogen group-containing compound (a) is suitably a compound having at least two groups and less than 30 groups, particularly 2 to 10 groups of the active hydrogen groups per molecule on the average.
The low molecular weight polyol (i) described above is a compound having at least two alcoholic hydroxyl groups in a molecule, and to be specific, it includes, for example, diols such as ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, cyclohexane-1,4-dimethylol, neopentyl glycol triethylene glycol and hydrogenated bisphenol A; triols such as glycerin, trimethylolethane and trimethylolpropane; tetrols such as pentaerythritol and &agr;-methylglycoside; hexols such as sorbitol and dipentaerythritol; and octols such as sucrose.
The linear or branched polyetherpolyol (ii) described above can have a number average molecular weight falling in a range of usually 62 to 10,000, preferably 62 to 2,000, and to be specific, it includes, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly(ethylene.propylene) glycol, bisphenol A ethylene glycol ether and bisphenol A propylene glycol ether which are produced by ring-opening reaction of alkylene oxides (e.g., ethylene oxide, propylene oxide, butylene oxide and tetrahydrofuran).
The linear or branched polyesterpolyol (iii) described above can have a number average molecular weight falling in a range of usually 200 to 10,000, preferably 200 to 3,000, and to be specific, it includes, for example, compounds obtained by polycondensation reaction of organic dicarboxylic acids or anhydrides thereof w
Hiraki Tadayoshi
Kamikado Koji
Nishiguchi Shigeo
Tominaga Akira
Kansai Paint Co. Ltd.
Kiliman Leszek
Wenderoth , Lind & Ponack, L.L.P.
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