Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-05-06
2002-09-24
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S261000, C524S502000, C524S588000, C524S730000
Reexamination Certificate
active
06455629
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to an aqueous matte coating composition.
(2) Description of the Background Art
An aqueous coating composition has widely been used, because it uses water as a medium and is free of troubles about working atmosphere, danger of fire, and so forth. However, recent diversification in user's need shows a tendency to lose interest in feeling of metallic luster and highly demands matte coating film which provides grave feeling.
Particularly, user's needs in recent years highly demand to provide an aqueous matte coating composition capable of forming a coating film showing difficulties in forming mars during transportation and showing high mar resistance.
Japanese Patent Publication No.24519/87 discloses a process for forming a matte coating film by use of an anionic electrodeposition coating composition comprising an alkoxysilyl group-containing vinyl copolymer as a base resin and an amino resin as a curing agent.
The aqueous matte coating composition used in the above process is such that the acrylic copolymer used as the base resin has alkoxysilyl group on its side chain and the alkoxysilyl group is gradually hydrolized on water solubilization or making water dispersion to form silanol, and further condensation between the silanols forms siloxane linkage, resulting in forming fine dispersion particles having an interparticle gel structure. As the result, when the fine dispersion particles are subjected to anionic electrodeposition coating, a film having a fine coarse surface is formed and even if heat-cured, the film keeps the coarse surface without forming a complete melt flow to form a good matte coating film, resulting in being widely used in the art.
However, use of the above aqueous matte coating composition makes it impossible to satisfy user's needs of providing a coating film having high mar resistance, too. On the one hand, attempts to improve the mar resistance have been made, for example, by heat curing the coating film at high temperatures. On the other hand, developments of materials capable of drastically improve mar resistance have been demanded from the standpoint of the coating composition.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an aqueous matte coating composition which is capable of forming a matte coating film by use of conventional coating methods.
It is another object of the present invention to provide an aqueous mar-resistant matte coating composition which is capable of showing good storage stability, and capable of forming a coating film showing improved properties in mar resistance and durability.
That is, the present invention in a first embodiment provides an aqueous matte coating composition containing an aqueous dispersion (I) prepared by dispersing into water (B) a water-dispersible vinyl copolymer prepared by subjecting a monomer mixture of radically polymerizable unsaturated monomers including an unsaturated monomer having a polymerizable unsaturated double bond and an alkoxysilyl group in one molecule to radical polymerization in the presence of (A) a silicate compound consisting of an organosilicate represented by the general formula (1):
where R is same or different and is hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carton atoms, and/or its condensate, having an alkoxysilyl group, an acid value of 15 to 150 mg KOH/g and a hydroxyl value of 30 to 200 mg KOH/g, and including the silicate compound (A), and (C) a melamine resin not having complete compatibility with the vinyl copolymer (B).
The present invention in a second embodiment provides an aqueous matte coating composition containing an aqueous dispersion (II) prepared by dispersing into water (A) a silicate compound as claimed in claim
1
, (D) a water-dispersible vinyl copolymer having an alkoxysilyl group, an acid value of 15 to 150 mg KOH/g and a hydroxyl value of 30 to 200 mg KOH/g, and (C) a melamine resin not having complete compatibility with the vinyl copolymer (D).
DETAILED DESCRIPTION OF THE INVENTION
The silicate compound (A) used in the first and second embodiments of the present invention includes ones represented by the above general formula (1), in which R is same or different and is hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms and its condensates. Use of such an organosilicate as to have a carbon number more than 10 in R results in reducing a speed of hydrolysis and in making poor the pollution resistance and durability of the film.
Examples of the monovalent hydrocarbon group having 1 to 10 carbon atoms in the above general formula may include alkyl group, aryl group and the like.
The above “alkyl group” may include straight-chain ones and branched ones, for example, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, neopentyl, n-hexyl, iso-hexyl, n-octyl and the like. Of these, lower alkyl groups having 1 to 4 carbon atoms are preferred. The “aryl group” may include monocyclic and polycyclic ones, for example, phenyl group, toluyl group, xylyl group, naphtyl group and the like, phenyl group being preferred.
Preferable examples of the organosilicate used in the present invention may include tetrahydroxysilane, tetrame thoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraphenoxysilane, dimethoxydiethoxysilane and the like. These may be used alone or in combination.
The condensate of organosilicate may include branched or straight-chain condensates between organosilicates represented by the above generai formula (1) and preferably includes condensates having a degree of condensation of 2 to 100 and represented by the general formula (2).
where R is defined as above, n is an integer of 2 to 100, preferably 2-8.
In the above general formula, when n is more than 100, effect of pollution resistance is undesirably reduced.
The organosilicate used in the present invention may preferably include such ones that R in the general formula is a lower alkyl group having 1 to 4 carbon atoms, and the condensate thereof may particularly include such ones that R in the general formula is a lower alkyl group having 1 to 4 carbon atoms and that the degree of condensation is in the range of 2 to 15 preferably 2-8.
The first embodiment of the present invention is explained more in detail hereinafter.
The aqueous matte coating composition in the first embodiment of the present invention consists of an aqueous dispersion (I) containing a water-dispersible vinyl copolymer (B) and a melamine resin (C). The aqueous dispersion (I) is prepared by a process which comprises subjecting a monomer mixture of radically polymerizable unsaturated monomers including an unsaturated monomer having a polymerizable unsaturated double bond and an alkoxysilyl group in one molecule to radical polymerization in the presence of the silicate compound (A) to prepare a water-dispersible vinyl copolymer (B) having an alkoxysilyl group, an acid value of 15 to 150 mg KOH/g and a hydroxyl value of 30 to 200 mg KOH/g, and including the silicate compound (A), followed by adding (C) a melamine resin not having complete compatibility with the vinyl copolymer (B) prior to or after adding a neutralizing agent, adding a neutralizing agent if no neutralizing agent is previously added, and by dispersing into water.
An advantageous process for preparing the water-dispersible vinyl copolymer (B) having alkoxysilyl group is a method of copolymerizing a monomer mixture of an alkoxysilyl group-containing unsaturated monomer with other monomers. The above monomer mixture may include (1) an unsaturated monomer having a polymerizable unsaturated double bond and an alkoxysilyl group in one molecule, (2) &agr;, &bgr;-ethylenically unsaturated carboxylic acid, (3) a hydroxyl group-containing acrylic monomer, and (4) a radically polymerizable unsaturated monomer other than the above monomers (1), (2) and (3).
The unsaturated monomer (1) having the polymerizable unsaturated double bond and alkoxysilyl group
Aoki Kenji
Harakawa Hiromi
Kondo Masahiro
Yokoyama Tetsuya
Fisher Christen & Sabol
Kansai Paint Co. Ltd.
Reddick Judy M.
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