Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-10-10
2004-06-01
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S212000, C524S837000, C525S070000, C525S078000, C525S080000, C525S124000, C525S125000, C525S191000, C525S221000, C525S222000, C525S243000, C525S288000, C525S902000, C526S279000, C528S035000
Reexamination Certificate
active
06743834
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to anionic electrodeposition coating compositions which are capable of forming matte films having good film performance characteristics such as finish appearance, storage stability, adhesion, and hardness.
2. Description of the Background Art
It is desirable to coat substrates such as aluminum sash with anionic electrodeposition coating compositions to give a good film appearance. Examples of anionic electrodeposition coating compositions which have been previously used are described in Japanese Patent Publication No. 24519/87. That publication 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 amino resin as a curing agent.
The 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 hydrolyzed to form silanol on water solubilization or making water dispersion, 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.
For the reasons discussed above, these compositions are widely used in the art. However, in these coating compositions, it is difficult to control the gloss of the final film, and it would be desirable to improve the storage stability of the alkoxysilyl group-containing acrylic copolymer.
Other coating compositions are described in Japanese Laid-open Patent Application No. 139574/91 and Japanese Laid-open Patent Application No. 263296/93. These coating compositions comprise an acrylic copolymer and a crosslinked particle resin. With these compositions, it is possible to control the degree of matte and the electrodeposition film performance characteristics. However, when a low gloss film appearance is desired, a high concentration of the crosslinked particle is needed, and this can result in unsatisfactory adhesion and hardness.
SUMMARY OF THE INVENTION
The present invention to provides an anionic electrodeposition coating composition for forming matte film which exhibits good storage stability and forms a matte film having good adhesion and hardness.
Specifically the present invention provides an anionic electrodeposition coating composition comprising (a) about from 20 to 70% by weight of acrylic resin; (b) about from 5 to 40% by weight of emulsified polymer containing alkoxysilyl groups and produced by a multiple stage emulsion polymerization of unsaturated monomers, wherein about from 5 to 40% by weight of the unsaturated monomers used in the multiple stage emulsion polymerization contain alkoxysilyl groups, and the polymerization is carried out in the presence of water and emulsifier; and (c) about from 20 to 60% by weight of at least one crosslinking agent.
DETAILED DESCRIPTION OF THE INVENTION
The anionic electrodeposition coating composition for forming matte film used in the present invention contains acrylic resin, alkoxysilyl-group containing emulsified polymer, and at least one crosslinking agent.
Acrylic Resin
The acrylic resin used in the present invention is present in an amount of about from 20 to 70% by weight. The acrylic resin preferably has an acid value of about from 5 to 150 mg KOH/g, and especially about from 20 to 70 mg KOH/g, and a hydroxyl value of about from 5 to 150 mg KOH/g, preferably about from 30 to 100 mg KOH/g. When the acid value is less than about 5 mg KOH/g, water dispersibility is reduced. On the other hand, with more than about 150 mg KOH/g, resistance of the film is poor. When the hydroxyl value is less than about 5 mg KOH/g, curing properties are reduced, resulting in poor film hardness. On the other hand, when more than 150 mg KOH/g, a large amount of unreacted hydroxyl groups may remain in the film, resulting in poor durability.
The acrylic resin is prepared by radical polymerization of unsaturated monomers in organic solvent in the presence of radical polymerization catalyst. The monomers used can vary widely, and can be selected from the following groups of monomers:
Hydroxyl group-containing unsaturated monomers, for example, C2-C8 hydroxyalkylesters of (meth)acrylic acid, such as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate; other hydroxyl group-containing unsaturated monomers; such as caprolactone modified (meth)acrylic acid hydroxyesters, all marketed by Daicel Chemical Industries, Ltd. under the trade names Placcel FMI, Placcel FM2, Placcel FM3, Plac6el FA1, Placcel FA2, and Placcel FA3, N -methylolacrylamide, and the like. The above monomers can be used alone or in combination. The above monomers introduce hydroxy groups into the acrylic resin. These can react with the crosslinking agents mentioned below.
Carboxylic group- containing unsaturated monomers, for example, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, and the like. The above monomers introduce carboxyl groups into the acrylic resin, so that the acrylic resin can be dispersed in water by neutralization. The above monomers can be used alone or in combination.
Other unsaturated monomers such as C1-C24 alkyl or cycloalkyl esters of (meth)acrylic acid, such as methyl (meth)acrylate, ethyl(meth)acrylate, n, i-propyl(meth)acrylate, n-,i-,t-butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, cyclohexyl (meth) acrylate, and the like; aromatic vinyl monomers, such as styrene &agr;-methylstyrene, vinyltoluene; (meth)acrylamide, N-butoxymethylacrylamide, and the like. The above monomers can be used alone or in combination.
The acrylic resin can be prepared by copolymerizing two or more unsaturated monomers. Examples of such compounds having two or more unsaturated groups in the molecule include allyl(meth)acrylate, ethyleneglycoldi(meth)acrylate, diethyleneglycoldi-(meth)acrylate, triethyleneglycoldi(meth)acrylate, tetraethyleneglycoldi(meth)acrylate, butyleneglycoldi(meth)acrylate butyleneglycoldi(meth)acrylate, butanedioldi(meth)acrylate, glyceroltri(meth)acrylate, trimethyrolpropanedi(meth)acrylate, trimethyrolpropanetri-(meth)acrylate, pentaerythritoldi(meth)acrylate, pentaerythritoltri(meth)acrylate, pentaerythritoltetra(meth)acrylate, dipentaerythritolpenta(meth)acrylate, hydroxyisocyanuratetri(meth)acrylate, neopentylglycoldiacrylate, 1,6-hexanedioldiacrylate, glycerolallyloxydi(meth)acrylate, 1,1,1-tris(hydroxymethyl)ethanedi(meth)acrylate, 1,1,1-tris (hydroxymethyl)ethanetri(meth)acrylate, triallylisocyanurate, triallyltrimesate, diallylterephthalate, diallylphthalate, diallylisophthalate, pentaerythritoldiallylether, divinylbenzene, and the like.
Acrylic resin prepared by copolymerizing two or more unsaturated monomers exhibits the characteristics of a macromolecule and a multi divergence structure to some extent. This improves the dispersion ability of the acrylic resin with crosslinking agents as well as the storage stability of the final coating composition. In the present invention, when melamine resin is used as a crosslinking agent, it is preferable to use triallylisocyanurate as the compound in the preparation of the acrylic resin. This results in particularly good stability of the coating composition.
Alkoxysilyl group-containing unsaturated monomer can be copolymerized in the acrylic resin. The use of this monomer, however, can depreciate storage stability of the acrylic resin, and is accordingly not preferred.
The radical polymerization catalyst used in the preparation of the acrylic resin can vary widely, and can include azo compounds, peroxide compounds, sulfides, sulfines, diazo-compounds, nitroso-
Koji Kamikado
Yokoyama Tetsuya
Huntley & Associates LLC
Kansai Taint Co., Ltd.
Zimmer Marc S.
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