Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-11-26
2004-10-26
Sellers, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C523S414000, C525S065000, C525S118000, C525S407000, C525S454000, C525S463000, C525S502000, C525S525000, C525S528000, C525S529000, C525S531000
Reexamination Certificate
active
06809160
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a resin composition which can suitably be used in a cationic electrodeposition coating and, more particularly, to a resin composition which, when used in a cationic electrodeposition coating, gives electrodeposited coating films excellent in flexibility and, further, in impact resistance, chipping resistance and so forth and to a cationic electrodeposition coating composition using such resin composition.
BACKGROUND ART
Cationic electrodeposition coating technology has been generally used as an undercoating method of articles to be coated which are large and complicated in shape and are required to have high rust prevention, such as car bodies, since even details of those articles complicated in shape can be coated in an automated and continuous manner by that technology. As compared with other coating methods, the technology is highly efficient from the viewpoint of coating consumption, hence economical, and has come into wide use as an industrial coating method.
Cationic electrodeposition coating is carried out by immersing an article to be coated, which is to serve as a cathode, in a cationic electrodeposition coating composition and applying a voltage. The deposition of a coat in the process of this coating is based on an electrochemical reaction. The coat deposited on the surface of the article to be coated upon voltage application has an insulating property, so that as the film thickness of the deposited coat increases with proceeding of the deposition of the coat in the process of coating, the electric resistance of the coat increases proportionally to the increase in film thickness. As a result, the deposition of the coating on that site decreases and, instead, coat deposition starts on a site where any coat has not yet been deposited. In this manner, coating emulsion particles deposit on undeposited sites successively to thereby complete coating. In the present specification, such successive formation of a coat on undeposited sites of an article to be coated is referred to as “throwing power”.
Such cationic electrodeposition coating is generally employed in undercoating mainly for the purpose of rust prevention and, therefore, it is required that even in the case of an article to be coated having a complicated structure, the film thickness of a coat is not less than a certain predetermined value at every site. Accordingly, it is required that a sufficient level of throwing power be secured.
As a cationic electrodeposition coating excellent in throwing power, for example, WO 98/03701 discloses a cationic electrodeposition coating composition which comprises a fundamental resin containing a triple bond, such as an ethynyl or nitrile group, within the molecule.
On the other hand, the coating films formed on articles to be coated as car bodies are required to be sufficiently protected from damaging due to collision with grains of sand, pebbles or the like during driving. It is thus essential to strive for improving the so-called impact resistance. For improving the impact resistance, it has been a general practice to improve the physical properties of the topcoat coating film and intermediate coating film. By such means alone, however, it is not always possible to improve the impact resistance to a satisfactory extent. Generally, a coating film is constituted of a plurality of multilayer coating films and, therefore, it is necessary to strive to improve the impact resistance of the coating film as a whole. If, in particular, the physical properties of an electrodeposited coating film can be improved and the impact resistance of the coating film as a whole can be thereby improved, there will arise the possibility of markedly improving the impact resistance of coating films by using the new technology in combination with the prior art impact resistance related technology.
Japanese Kokai Publication 2000-38527 discloses a resin composition for use in cationic electrodeposition coatings which comprises a resin having an epoxy resin skeleton and containing a sulfonium group, an aliphatic hydrocarbon group of 8 to 24 carbon atoms containing an unsaturated double bond within the chain thereof and a propargyl group. It is for the purpose of improving the impact resistance that the resin contains an aliphatic hydrocarbon group of 8 to 24 carbon atoms containing an unsaturated double bond within the chain thereof, such as one derived from linseed oil or a like hydrocarbon compound.
However, while a cresol novolak-based epoxy resin or the like, which has a rigid structure and excellent in strength and corrosion resistance, can be used as the skeleton-forming epoxy resin, this causes the coating films obtained to be lacking in flexibility, hence in impact resistance. Further, although the epoxy group-derived hydroxy group moieties in the epoxy resin have excellent adhesiveness and the propargyl group is an excellent nonvolatile functional group for curability, these increase hydrophilicity of coating films, decrease waterproof property, and cause lack in corrosion resistance.
Thus, the above composition is unsatisfactory from the viewpoint of simultaneous attainment of impact resistance and corrosion prevention of coating films obtained.
In view of the above-mentioned state of the art, it is an object of the present invention to provide a resin composition excellent in throwing power and capable of providing coating films excellent in corrosion prevention as well as in impact resistance, and a cationic electrodeposition coating composition containing this resin composition.
SUMMARY OF THE INVENTION
The present inventors found that when a resin (A) having a flexible and hydrophobic structure is used as a core and a resin (B) containing a sulfonium group and a propargyl group, which are excellent in throwing power, is used as a shell, the impact resistance and chipping resistance of coating films can be improved while maintaining the excellent throwing power and corrosion prevention of coating films. Based on such findings, they have now completed the present invention.
It was further found that the oil repellency, corrosion prevention, curability, workability and adhesiveness and so forth, can also be further improved depending on the performance characteristics of the main chain of the resin (A) to be used as the core. Thus, the resin (A) to be used as the core can be selected according to the required purpose.
The present invention thus provides a resin composition
which comprises a resin (A) and a resin (B) as constituents,
said resin (A) having a number average molecular weight of 1,000 to 35,000 and,
being at least one member selected from the group consisting of following (A1) and (A2):
(A1) a polyester polyol, a polyether polyol, a polycarbonate polyol, a polyurethane polyol, a polyolefin polyol and an acrylic polyol,
(A2) a polymer obtained by reacting said (A1) with a compound having at least one functional group selected from the group consisting of isocyanato, carboxyl and epoxy groups within the molecule thereof, a dialkyl carbonate, a cyclic carbonate, an alcohol, or a mixture of these, and
said resin (B) having a sulfonium group and a propargyl group within the molecule thereof.
The invention also provides a cationic electrodeposition coating composition which comprises the above resin composition.
DETAILED DESCRIPTION OF THE INVENTION
In the following the present invention is described in detail.
The resin composition according to the invention comprises a resin (A) and a resin (B) as constituents.
In the resin composition of the invention, said resin (A) serves as a core component and has a flexible and hydrophobic structure. Since the resin (A) is structurally flexible, the coating films obtained can be improved in impact resistance and chipping resistance. Further, since the resin is hydrophobic, the corrosion prevention can be improved. It can form a core/shell structure with the resin (B) to give a stable emulsion.
The above resin (A) is at least one member selected from the group consisting of the above-mentioned (
Fujii Motoki
Kawakami Ichiro
Kokubun Takayuki
Sakamoto Hiroyuki
Tsuboniwa Noriyuki
Nippon Paint Co. Ltd.
Sellers Robert
Sughrue & Mion, PLLC
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