Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
2002-09-18
2004-06-08
Tucker, Philip (Department: 1712)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S335000, C428S413000, C428S447000, C428S480000, C428S523000, C106S287160, C106S287220, C106S014050, C525S055000, C525S107000, C525S185000, C525S476000, C525S477000, C525S479000
Reexamination Certificate
active
06746763
ABSTRACT:
This invention relates to acid-epoxy-silane system clear paint compositions to be applied onto base-coated surfaces of object substrate. In particular, the invention relates to clear paint compositions capable of forming coating film of improved water repellency and oil repellency, without any deterioration in acid resistance thereof.
Conventionally, “2-coat-1-bake (2C1B) system” in which, for example, metallic paint and clear paint are applied wet-on-wet, and heated to be simultaneously cured to form a multi-layered top coating, has been widely adopted as a top coating method of exterior panels of automotive bodies. It is also known to use as the clear paint in said method an acid-epoxy-silane system clear paint whose chief ingredients are acrylic resin having hydroxyl groups and epoxy groups, high acid value polyester resin and alkoxysilyl-containing acrylic resin.
Multi-layered top coatings formed by this coating system excel in weatherability, acid resistance, etc., but have a defect that their water repellency and oil repellency are insufficient. Where water repellency of a coating is insufficient, it becomes necessary to apply wax frequently onto the coating to impart water repellency thereto, which is a quite complex operation. Whereas, when the coating has insufficient oil repellency, birds' droppings or dead insects adhere thereto, leaving spots of deteriorated gloss or leveling property on the coat surface after their removal and impairing the finished appearance.
We have conducted concentrative studies to solve the problems as above, and now discovered that the object could be accomplished by using, as the clear paint composition to be applied onto base-coated surfaces of an object substrate, an acid-epoxy-silane system paint which further contains an acrylic resin containing alkoxysilyl groups and dimethylpolysiloxane side chains, said paint forming a cured coating having a glass transition point of 100-120° C. The present invention is thus completed.
Thus, according to the present invention, a clear paint composition characterized by comprising
(a) a hydroxyl- and epoxy-containing acrylic resin,
(b) a high acid value polyester resin having an acid value of 120-200 mgKOH/g and a number-average molecular weight of 500-4,000,
(c) an alkoxysilyl-containing acrylic resin, and
(d) an acrylic resin containing alkoxysilyl groups and dimethylpolysiloxane side chains, and forming a coating which, after being cured, has a glass transition point within a range of 100-120° C.
Because the multi-layered coating formed by applying a clear paint composition of the present invention onto a base-coated surface excels in acid resistance, water repellency and oil repellency, it is particularly suitable for top coating on exterior or outer panels of automotive bodies for which these properties are strongly in demand. Specifically, it is preferred to apply a clear paint composition of the present invention on base-coated surface which is formed either directly on outer panels (coating object) of car bodies such as metallic or plastic automobiles, trucks, motorbikes, buses and the like, or through an undercoat such as of cationic electrodeposition paint and further optionally an intercoat applied on the undercoat and cured. In that occasion, said metallic coating object is preferably chemically treated in advance, with phosphate, chromate or the like. As said undercoating paint and intercoating paint, those known per se can be used.
The clear paint compositions of the invention are applied onto the base-coated surfaces of such coating objects as above-described.
The base coating preferably is sparkling and bright or iridescent, which can be formed, for example, by applying a base coating (A) comprising base resin, crosslinking agent, pigment (metallic or iridescent pigment) and organic solvent onto a coating object.
As examples of base resin, acrylic, polyester and alkyd resins having crosslinkable functional groups such as hydroxyl group; and as examples of crosslinking agent, those reactable with said functional groups, such as melamine resin and blocked polyisocyanate compounds, may be named. The blend ratio of the base resin and crosslinking agent adequately falls within a range of, based on the combined solid weight of the two components, 50-90%, in particular, 65-80%, of the former and 50-10%, in particular, 35-20%, of the latter.
As examples of the metallic pigment, aluminum flakes, aluminum oxide and vapor-deposited aluminum may be named, and as iridescent pigment, for example, titanium dioxide-covered mica may be named. In this specification these pigments are hereafter referred to as “metallic pigment, etc.”. Blend ratios of these metallic pigment, etc. may be optionally selected according to individual purpose, while generally it is within a range of 5-30 parts, in particular, 10-25 parts by weight, per 100 parts of combined solid weight of the base resin and crosslinking agent.
As organic solvent, conventional organic solvents for paints can be conveniently used. The base coating (A) may further contain, as individual occasions demand, extender, sedimetation-preventing agent, catalyst and the like.
Solid content of base coating (A) at application time preferably is within a range of 5-40% by weight, in particular, 10-30% by weight, and the hiding film thickness, within a range of 5-20 &mgr;m, in particular, 10-15 &mgr;m. Here “hiding film thickness” refers to: when a base coating (A) is applied onto a black-and-white checkered pattern painted on a coating object, the minimum film thickness (cured coating film) of the base coating (A) through which the black-and-white checkered pattern underneath is invisible. Less hiding film thickness signifies better hiding ability.
Base coating (A) can be applied onto such a coating object as earlier described, by ordinary coating means such as air spray, airless spray and electrostatic coating. Preferably its film thickness is at least same as the hiding film thickness. Thus, normally the film thickness preferably lies within a range of 5-20 &mgr;m, in particular, 10-15 &mgr;m, or may be even more, in terms of cured coating film.
According to the present invention, it is preferred to apply onto the base coating film formed by applying a base coating (A) onto a coating object, a clear paint composition (B), before the base coating film is cured, i. e. while the film is remaining in substantially uncured condition.
Clear paint composition (B) is a paint which forms a colorless transparent, or colored transparent, coating film. According to the present invention, a clear paint composition comprising:
(a) an acrylic resin having hydroxyl groups and epoxy groups,
(b) a high acid value polyester resin having an acid value of 120-200 mgKOH/g and a number-average molecular weight of 500-4,000,
(c) an alkoxysilyl-containing acrylic resin, and
(d) an acrylic resin having alkoxysilyl groups and dimethylpolysiloxane side chains, and forming a coating which, after being cured by heating at 140° C. for 30 minutes, has a glass transition point (Tg) within a range of 100-120° C. is used.
Hereafter the clear paint composition of the present invention is explained in further details.
Component (a): an acrylic resin having hydroxyl groups and epoxy groups
This is an acrylic resin containing at least one each of hydroxyl group and epoxy group per molecule. Such an acrylic resin can be obtained, for example, by copolymerizing a hydroxyl-containing polymerizable monomer, epoxy-containing polymerizable monomer, acrylic polymerizable monomer, and if necessary still other polymerizable monomer(s).
A hydroxyl-containing polymerizable monomer is a compound containing at least one each of hydroxyl group and polymerizable double bond per molecule, examples of which including 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate and hydroxyalkyl (meth)acrylates which are obtained by reacting the foregoing with lactones.
An epoxy-containing polymerizable monomer i
Ishihara Tatsuya
Matsuno Yoshizumi
Mizuno Tetsuji
Saito Goro
Yamanaka Masahiko
Feely Michael J
Nissan Motor Co,. Ltd.
Tucker Philip
Wenderoth , Lind & Ponack, L.L.P.
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