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
2001-06-28
2002-11-19
Moore, Margaret G. (Department: 1712)
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...
C524S837000, C524S838000, C524S827000, C524S831000, C524S816000, C524S819000, C524S820000, C525S100000, C523S409000, C523S410000, C523S411000
Reexamination Certificate
active
06482890
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel aqueous curable resin composition which is suited for use as an aqueous coating composition. More particularly, the present invention relates to an aqueous curable resin composition the cured article of which is superior in the water resistance and weather resistance, and which is also suited for use as an aqueous normal temperature-curable coating composition, the aqueous curable resin composition comprising an aqueous dispersion, as a main agent, containing gel-like resin dispersed particles having a functional group selected from a salt of a tertiary amino group or a salt of an acid group dispersed in an aqueous medium, and a compound having both an epoxy group and a hydrolyzable silyl group, as a curing agent.
2. Description of the Related Art
Based on the recent requirements such as protection of the environment and improvement of working environments on a global scale, it has become necessary to replace conventional coating compositions containing organic solvents with coating compositions from which organic solvent is less likely to volatilize into the atmosphere. Also, resins for coating compositions capable of curing at normal temperature are required in view of energy saving.
In view of the environment and energy savings, technologies using an aqueous emulsion composition as an organic solvent-free coating resin composition have been studied and put into practical use.
However, this aqueous emulsion composition has the fatal problem for a coating composition that the cured article has poor water resistance because emulsifiers or surfactants must be used. Therefore, its uses are limited. That is, at present, the performance of the coating film is still inferior to that of an organic solvent based coating composition.
As an organic solvent-free aqueous normal temperature-curable resin coating composition which neither contains an emulsifier nor a surfactant, for example, Japanese Patent Application, First Publication No. Hei 8-104846 discloses an aqueous normal temperature-curable resin composition wherein the water resistance and especially the weather resistance of the coating film is improved by using an aqueous compound, which is obtained by dispersing or dissolving a vinyl polymer having a tertiary amino group and/or an acid group neutralized with an acidic compound, or a vinyl polymer having an acid group and/or a tertiary amino group neutralized with a basic compound, in combination with a compound having both an epoxy group and a hydrolyzable silyl group.
However, the aqueous normal temperature-curable resin composition described in Japanese Patent Application, First Publication No. Hei 8-104846, as before, cannot attain satisfactory water resistance and weather resistance of the cured coating film and the performance of the coating film is inferior to an organic solvent based coating composition.
It is, therefore, an object of the present invention to remarkably improve the water resistance and weather resistance of the cured coating film in the aqueous curable resin composition.
SUMMARY OF THE INVENTION
The present inventors have carried out intensive studies in order to solve the problems described above and found that an excellent cured coating film, which is equivalent to that obtained with organic solvent based coating compositions can be obtained by using an aqueous dispersion as a main agent, which contains, as essential components, gel-like resin dispersed particles having a functional group selected from a salt of a tertiary amino group or a salt of an acid group and an aqueous medium, and using a compound having both an epoxy group and a hydrolyzable silyl group, as a curing agent. Thus, the present invention has been completed.
That is, the present invention relates to a two-pack aqueous curable resin composition comprising a combination of (I) an aqueous resin dispersion containing, as essential components, gel-like resin dispersed particles having a functional group selected from a salt of a tertiary amino group and a salt of an acid group, and an aqueous medium; and (II) a compound having both an epoxy group and a hydrolyzable silyl group.
DETAILED DESCRIPTION OF THE INVENTION
The gel-like resin dispersed particles used in the present invention have a functional group selected from a salt of a tertiary amino group and a salt of an acid group, thereby exerting self-dispersion properties in the aqueous medium. According to the present invention, by using self-dispersing gel-like resin dispersed particles and using a compound having both an epoxy group and a hydrolyzable silyl group as a curing agent, a uniformly crosslinked cured coating film is formed and the water resistance and light resistance are remarkably improved, and thus obtaining a normal temperature-curable coating composition which is very suited for practical use.
Specifically, the degree of gelation of the gel-like resin dispersed particles, which exist in the aqueous dispersion (I), is preferably within such a range that the aqueous dispersion (I) preferably has a light transmittance of 95% or less when it is made into a tetrahydrofuran solution having a solid content of 5% by weight (prepared by dissolving in tetrahydrofuran an aqueous dispersion having a solid content of 35% by weight).
The light transmittance when the aqueous dispersion (I) is made into a tetrahydrofuran solution having a solid content of 5% by weight (prepared by dissolving in tetrahydrofuran an aqueous dispersion having a solid content of 35% by weight) is the light transmittance obtained using a spectrophotometer to measure the light transmittance of a sample obtained by dissolving in tetrahydrofuran an aqueous dispersion (I) having a solid content of 35% by weight, to thereby reduce the solid content to 5% by weight. More specifically, it is the light transmittance obtained by measuring the light transmittance of the sample using a rectangular cell made of glass having an optical path length of 10 mm in the presence of a light source having a wavelength of 640 nm. Examples of the spectrophotometer include “Shimadzu Spectrophotometer UV-1200” manufactured by Shimadzu Corp.
The light transmittance (%) can be determined by the following equation. (Light transmittance (%))=(Measured value (%) of light transmittance of sample)/(Measured value (%) of light transmittance of tetrahydrofuran)×100
The aqueous dispersion (I) shows the light transmittance (%) of 95% or less. To remarkably reduce adhesion of the coating surface at high temperatures when forcibly drying, the light transmittance is preferably reduced to 80% or less
Examples of the gel-like resin dispersed particles having a functional group selected from a salt of a tertiary amino group and a salt of an acid group include (1) crosslinked urethane urea resin particles formed from a self-dispersing resin, a polyisocyanate compound and a polyfunctional amine described in Japanese Patent Application, First Publication No. Hei 4-249517, (2) gel-like resin dispersed particles obtained by the crosslinking reaction of a vinyl polymer having a functional group selected from a salt of a tertiary amino group and a salt of an acid group, and a hydrolyzable group or hydroxyl group-containing polysiloxane segment, (3) gel-like resin dispersed particles obtained by crosslinking a vinyl polymer (A-1) having a functional group selected from a salt of a tertiary amino group and a salt of an acid group, and a hydrolyzable silyl group, and (4) gel-like resin dispersed particles obtained by crosslinking a vinyl polymer (A-2) having a functional group selected from a salt of a tertiary amino group and a salt of an acid group, or the functional group and a hydroxyl group or an epoxy group with a compound (B) having a molecular weight of 500 or less, the compound (B) having both a functional group, which has reactivity with a group selected from salt of tertiary amino group, salt of acid group, hydroxyl group and epoxy group, which exist in the vinyl polymer (A-2), and a hy
Kiyohara Teruki
Kuwamura Shin'ichi
Armstrong Westerman & Hattori, LLP
Dainippon Ink and Chemical Inc.
Moore Margaret G.
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