Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-12-01
2002-10-15
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C524S548000, C524S560000, C526S273000, C526S279000
Reexamination Certificate
active
06465589
ABSTRACT:
The present invention relates to a paint composition excellent in weatherability and coating gloss.
Recently, from the standpoint of elimination of the need of maintenance, there has been an increasing demand for highly durable materials, and it has been required that paint resins also possess higher weatherability. As of now, fluororesins comprised of a fluoroolefin-vinyl ether-series copolymer, acrylic silicon resins, and others have been known as paint resins with excellent weatherability. However, the fluororesins have problems that they are insufficient in recoatability and coating gloss, and when used as thermosetting paints smoothness of the resulting coatings is unsatisfactory, and the resulting coatings turn yellow. Moreover, acrylic silicone resins require humidity at their curing and therefore there arise the problems that airing in winter may result in inadequate curing and that they are not cured only by application of heat. In addition, acrylic silicone resins are still insufficient in weatherability and their coating gloss and adhesion to substrates are also below satisfactory levels. For solving such problems, epoxy group-containing (meth)acrylic copolymers, which are heat-set using a dibasic acid or an acid group-containing resin as a curing agent, have been in wide use as powder paints or acid rain-resistant paints, yet these paints are also unsatisfactory in weatherability.
It is an object of the present invention to provide a paint composition which is curable at ordinary temperature or under application of heat, unsusceptible to external environment upon curing, excellent in coating gloss, and capable of providing a coating with high weatherability, and which is further excellent in adhesion and does not turn yellow.
The inventors of the present invention have made intensive studies to solve the aforementioned problems and finally found that the problem is solved by a paint composition containing a copolymer which comprises, as constitutional units,
(A) an acrylic or methacrylic ester monomer unit having a straight-chain, branched-chain, or cyclic alkyl group;
(B) at least one monomer unit selected from the group consisting of a monomer unit having an unsaturated double bond and a hydroxyalkyl group, a monomer unit having an unsaturated double bond and an epoxy group, and a monomer unit having an unsaturated double bond and an alkoxysilyl group; and
(C) a monomer unit having an unsaturated double bond and a maleimide group.
That is, the present invention is a paint composition composed of a (meth)acrylic copolymer containing the aforementioned constitutional units (A), (B), and (C) as essential components. In this specification, “(meth)acrylic” means “acrylic or methacrylic”, and “(meth)acrylate” means “acrylate or methacrylate”.
Hereinafter, the present invention will be described in further detail.
The (meth)acrylic ester monomer as the constitutional unit (A) in the present invention has a straight-chain, branched-chain, or cyclic alkyl group, and the alkyl group may contain a phenyl group, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, and others.
Examples of the (meth)acrylic ester having a straight-chain alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate. The monomer may be one having an aromatic ring, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, or others in its alkyl group, examples of which include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethylcarbitol (meth)acrylate, ethoxypolyethylene glycol 400 (meth)acrylate, aminoethyl (meth)acrylate, chloroethyl (meth)acrylate, trifluoroethyl (meth)acrylate, and heptadecafluorooctylethyl (meth)acrylate.
Examples of the (meth)acrylic ester having a branched-chain alkyl group include isopropyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, neopentyl (meth)acrylate, ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, and isostearyl (meth)acrylate. The monomer may be one having an aromatic ring, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, or others in its alkyl group, examples of which include 3-methoxybutyl (meth)acrylate, methoxytripropylene glycol (meth)acrylate, and hexafluoropropyl (meth)acrylate.
Examples of the (meth)acrylic ester having a cyclic alkyl group include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and tricyclodecynyl (meth)acrylate. The monomer may be one having an aromatic ring, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, or others in its alkyl group, examples of which include tetrahydrofurfuryl (meth)acrylate and morpholinoethyl (meth)acrylate.
These (meth)acrylic esters can be used singly or in combination.
Among the (meth)acrylic esters exemplified above, from the viewpoint of hardness of coatings and weatherability, those having an alkyl group of 1 to 20 carbon atoms are preferred, and those having an alkyl group of 1 to 8 carbon atoms are particularly preferred. Examples of such monomers include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.
When hardness of coatings is of particular importance, monomers having an alkyl group of 1 to 7 carbon atoms are preferred. Examples of such monomers include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, and cyclohexyl (meth)acrylate.
If prevention of lifting phenomenon described later is of particular importance, it is preferred that a monomer having an alkyl group of 8 to 20 carbon atoms is used. Examples of such monomer include octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, palmitoyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, octadecanoyl (meth)acrylate, oleyl (meth)acrylate, icosanoyl (meth)acrylate, and isobornyl (meth)acrylate.
The constitutional unit (B) in the present invention can be selected from the group consisting of a monomer unit having an unsaturated double bond and a hydroxyalkyl group, a monomer unit having an unsaturated double bond and an epoxy group, and a monomer unit having an unsaturated double bond and an alkoxysilyl group.
Examples of the monomer having an unsaturated double bond and a hydroxyalkyl group are hydroxyalkyl group-containing ethylenically unsaturated monomers including hydroxyl group-containing monomers such as hydroxybutyl vinyl ether, hydroxyethyl allyl ether, and hydroxyethyl crotonate besides (meth)acrylic esters such as hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, 2-hydroxychloropropyl (meth)acrylate and commercial products available under the tradename “Placcel F” product family (i.e., lactone-modified hydroxyethyl-modified (meth)acrylic ester) manufactured by Daicel Chemical Industries, Ltd. Of these, monomers having a primary hydroxyl group are preferred because they easily react with curing agents such as isocyanates and melamine. Examples of such monomers include hydroxyethyl (meth)acrylate, hydroxybutyl (meth)acrylate, and the aforementioned commercial products “Placcel F”.
Examples of the monomer having an unsaturated double bond and an epoxy group are epoxy group-containing ethylenically unsaturated monomers including glycidyl (meth)acrylate, single terminal (meth)acrylic acid adducts of bisphenol A diglycidyl ether, allyl glycidyl ether, and glycidyl vinyl ether. Of these, glycidyl (meth)acrylate is preferred due to its copolymerizability with other monomers. This monomer unit is particularly useful in producing a thermosetting paint. The thermosetting paint is a paint which
Iida Akihito
Inukai Hiroshi
Mizutani Kunihiko
Okazaki Eiichi
Fitch Even Tabin & Flannery
Toagosei Co. Ltd.
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