Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1998-03-10
2000-02-29
Sergent, Rabon
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523409, 523415, 523417, 524507, 524522, 524523, 524539, 524560, 524562, 524591, 524819, 524832, 524839, 524840, 525109, 525111, 525123, 525124, 525131, 525528, C08L 6302, C08L 6310, C09D16302, C09D16310, C09D17500
Patent
active
060310286
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a novel cationic electrodeposition coating composition.
BACKGROUND ART
Japanese Examined Patent Publication No. 71090/1992 discloses a cationic electrodeposition coating composition prepared by reacting an epoxy-containing acrylic polymer, a bisphenol compound and a bisphenol diglycidyl ether-type epoxy resin to produce an epoxy-containing resin, introducing thereinto cationic groups and adding a blocked polyisocyanate compound.
The above electrodeposition coating composition, however, is insufficient in curability and in corrosion resistance of the cured coating film. To improve these properties, a lead compound such as lead acetate, lead 2-ethyl hexanoate or lead silicate is generally added.
The lead compound, however, is toxic and causes environmental pollution. Therefore, a need exists for a lead compound-free cationic electrodeposition coating composition which is excellent in curability and in corrosion resistance of the cured coating film.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a cationic electrodeposition coating composition which is lead compound-free and is excellent in curability and in corrosion resistance of the cured coating film.
Further objects and characteristics of the present invention will be apparent from the following description.
The present invention provides a cationic electrodeposition coating composition comprising polymer, a bisphenol compound and a bisphenol diglycidyl ether-type epoxy resin to produce an epoxy-containing resin and introducing thereinto cationic groups and being crosslinked and cured by urethanation reaction with (C) an isocyanate crosslinking agent component.
The inventors of the present invention carried out extensive research to develop a cationic electrodeposition coating composition which is free of the above-mentioned drawbacks of the conventional electrodeposition coating composition. More specifically, they did research to develop a cationic electrodeposition coating composition which is lead-compound free but excellent in curability and in corrosion resistance of the cured coating film. The inventors of this invention finally found that this object can be achieved by adding to the above-mentioned component (A) a hydroxyl- and amino-containing acrylic resin (B). The invention has been accomplished based on this finding.
The component (A) of the composition of the invention is a resin prepared by introducing cationic groups into an epoxy-containing resin which is a reaction product of three components of an epoxy- or carboxyl-containing acrylic polymer (A-1), a bisphenol compound (A-2) and a bisphenol diglycidyl ether-type epoxy resin (A-3).
When an epoxy-containing acrylic polymer is used as the component (A-1), the component (A) has a graft structure in the molecule that the polymer (A-1) is linked to a bisphenol diglycidyl ether-type epoxy resin (A-3) via a bisphenol compound (A-2). When a carboxyl-containing acrylic polymer is used as the component (A-1), the component (A) has a graft structure in the molecule that the polymer (A-1) is linked to a bisphenol compound (A-2) via a bisphenol diglycidyl ether-type epoxy resin (A-3).
The component (A) before introduction of cationic groups contains epoxy groups, preferably epoxy groups and at least one hydroxyl group, in the molecule. For introduction of cationic groups, all or most of the epoxy groups are reacted with a cationizing agent, thus giving a cationized resin.
The epoxy- or carboxyl-containing acrylic polymer (A-1) is an acrylic polymer and contains at least one epoxy group or at least one carboxyl group in the molecule. The polymer (A-1) is prepared by polymerizing an epoxy- or carboxyl-containing polymerizable unsaturated compound alone or together with other polymerizable unsaturated compounds. It is essential that at least one of the polymerizable unsaturated compounds used be an acrylic compound. In view of facilitating crosslinking and curing reactions with an isocyanate crosslinking agent component, it is p
REFERENCES:
patent: 4616066 (1986-10-01), Tominaga
patent: 5164430 (1992-11-01), Hattori et al.
patent: 5283290 (1994-02-01), Jung et al.
patent: 5331050 (1994-07-01), Harper
patent: 5472999 (1995-12-01), Kudoh
Iino Yutaka
Kamikado Koji
Sugisaki Katsuhisa
Kansai Paint Company Limited
Sergent Rabon
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