Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
1999-12-30
2002-05-07
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S446000, C428S450000, C525S100000, C525S105000, C525S106000, C528S033000, C528S034000
Reexamination Certificate
active
06383648
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a curable composition for top coating. More particularly, the invention relates to a curable composition for top coating which can be successfully applied to structures, household electric appliances, industrial equipment and the like of metal, ceramics, glass, cement, molded ceramics, inorganic boards, plastics, wood, paper, fiber and/or other material and to an article coated with said curable composition for top coating.
BACKGROUND ART
So far, the appearance, corrosion resistance, weather resistance and other properties of buildings, industrial products such as architectural members and the like made of a ceramic composition, concrete, steel or the like have been improved by surface coating using a paint such as a fluororesin paint, an acryl-urethane resin paint or an acryl-silicone resin paint. In addition, with the increased awareness of recent aggravation of the environment and increased consciousness of the need for conservation of landscaping in urban communities, coating compositions provided with stain resistance have been developed and marketed.
Among such paints, an acryl-silicone paint, however, is still unsatisfactory in adhesion to substrates because of its mode of crosslinking as compared with the other two types of paints. Thus, shrinking may occur when a plurality of coats are applied or, because of poor solvent resistance, shrinking may occur when they are used in combination with epoxy type coatings. The impact resistance may also be insufficient when steel sheets are coated.
SUMMARY OF THE INVENTION
In view of the above state of the art, the present inventors made intensive investigations and, as a result, found that a composition which comprises an acrylic copolymer containing a specific reactive silyl group and a hydroxyl group as essential constituents, a specific silicon-containing compound, a polyfunctional isocyanate compound and a specific curing catalyst in specific proportions is curable at ordinary temperature or under heating and that the coat obtained from said composition shows the same excellent weather resistance as that exhibited by the coats formed from the acryl-silicone resin coating compositions and, yet, is improved in stain resistance, adhesiveness, solvent resistance and impact resistance.
In the case of the conventional one-component compositions prepared by incorporating a curing catalyst in advance, the viscosity thereof increases in a short time so that its pot life is limited.
Thus, in the prior art, when isocyanate compounds are used, it is difficult to prepare a one-component composition by using a curing catalyst. However, by selecting the curing catalyst of the present invention, it has become possible to provide a one-component composition.
The present invention thus provides a curable composition for top coating which comprises an acrylic copolymer (A) containing a reactive silyl group bound to a carbon atom as represented by the following general formula (1)
(wherein R
1
represents a hydrogen atom or an alkyl group containing 1 to 10 carbon atoms, R
2
represents a hydrogen atom or a univalent hydrocarbon group selected from among alkyl groups containing 1 to 10 carbon atoms, aryl groups and aralkyl groups and a represents an integer of 0 to 2), together with a hydroxyl group, 2 to 70 parts by weight, per 100 parts by weight of said acrylic copolymer (A), of a silicon compound represented by the general formula (2)
(wherein R
3
represents a univalent hydrocarbon group selected from among alkyl groups containing 1 to 10 carbon atoms, aryl groups and aralkyl groups, R
4
represents a univalent hydrocarbon group selected from among alkyl groups containing 1 to 10 carbon atoms, aryl groups and aralkyl groups and b represents 0 or 1), and/or a partial hydrolyzate condensate (B) thereof and 0.1 to 50 parts by weight of a compound (C) containing two or more isocyanate groups which serves as a crosslinking agent.
Said acrylic copolymer (A) is preferably a copolymer which contains 3 to 90% by weight of monomer units comprising the carbon-bound reactive silyl group as represented by general formula (1) within the molecule thereof. Such acrylic copolymer (A) is preferably a copolymer containing a n-butyl methacrylate unit as a polymer-constituting unit.
In another aspect, the present invention provides a curable composition for top coating which comprises 0 to 20 parts by weight of an organometallic compound (D) incorporated as a curing catalyst in the above-mentioned curable composition for top coating. Said organometallic compound (D) is preferably an organotin compound. Further, said organometallic compound (D) is preferably an organotin compound. Said organometallic compound (D) is preferably a compound containing a sulfur atom within the molecule thereof. It is also preferred that said organometallic compound (D) be an aluminum chelate compound.
It is preferred that the above-mentioned curable composition for top coating further comprises a mercapto-containing hydrocarbon and/or a mercaptosilane (E) incorporated.
In a further aspect, the present invention provides a coated article which is coated with the above-mentioned curable composition for top coating.
In a still further aspect, the present invention provides a coated article which is coated with a metallic powder- and/or color pigment-containing coating composition and further with a top coat clear coating composition thereon, wherein said clear top coat composition contains the above-mentioned curable composition for top coating as a main component thereof.
In a further aspect, the present invention provides a coated article which is coated with a coating composition comprising a dispersion of the above-mentioned curable composition for top coating and a pigment as main components thereof.
DETAILED DESCRIPTION OF THE INVENTION
The curable composition for top coating according to the present invention contains, as a base resin which is curable at room temperature in the presence of moisture, the acrylic copolymer (A) having a reactive silyl group bound to a carbon atom as represented by the general formula (1):
(wherein R
1
represents a hydrogen atom or an alkyl group containing 1 to 10 carbon atoms, R
2
represents a hydrogen atom or a univalent hydrocarbon group selected from among alkyl groups containing 1 to 10 carbon atoms, aryl groups and aralkyl groups and a represents an integer of 0 to 2), together with a hydroxyl group.
Since said acrylic copolymer (A) is a copolymer the main chain of which is substantially a main chain resulting from copolymerization of an acrylic monomer (main chain such main chain is hereinafter referred to also as “main chain substantially comprises an acrylic copolymer chain”), it becomes possible for the coatings formed from the curable composition for top coating according to the present invention to have excellent weather resistance and excellent chemical resistance, among others.
By saying that the main chain of said acrylic copolymer (A) substantially comprises an acrylic copolymer chain, it is meant that not less than 50%, preferably not less than 70%, of those units which constitute the main chain of said acrylic copolymer (A) are acrylic monomer units. Since the acrylic copolymer (A) contains a reactive silyl group in a form bound to a carbon atom, it also becomes possible to be excellent in water resistance, alkali resistance and acid resistance, among others.
In the acrylic copolymer (A), the number of carbon-bound reactive silyl groups of general formula (1) is preferably two or more, more preferably three or more, so that the coatings formed from the composition of the present invention may have good durability, typically good weather resistance and good solvent resistance.
The reactive silyl group represented by the above general formula (1) may be bound to the main chain of the acrylic copolymer (A) either at a terminal group or at a side chain thereof, or may be bound to such silyl groups at both a terminal group(s) and a side chain(s) of the main chain.
In the above gen
Inoue Masaharu
Tamai Hitoshi
Jackson Monique R.
Kaneka Corporation
Thibodeau Paul
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