Aqueous-dispersing composition of synthetic resin and...

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

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C524S267000, C524S265000, C524S243000, C524S545000, C525S100000, C260S001000, C260S001000, C428S335000

Reexamination Certificate

active

06541552

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an aqueous-dispersing composition of synthetic resin which is excellent in stain-proofing property, weather resistance and storage stability and further is capable of forming a coating film having a high gloss, a coating composition comprising the aqueous-dispersing composition and a coated article coated with the coating composition.
BACKGROUND ART
An attempt to improve stain-proofing property and weather resistance by adding a silicate compound to an aqueous coating or paint has been already known.
For example, JP-A-5-170909, WO95/02462 and JP-A-8-259892 disclose coating compositions prepared by adding an alkylsilicate compound to an aqueous emulsion paint. The silicate compounds disclosed in those publications have an alkyl group having 1 to 10 carbon atoms, and when the number of carbon atoms is as small as 1 or 2, hydrolization speed is fast, and therefore an effect of stain-proofing property appears earlier and the effect itself is larger, but on the contrary, they have a drawback that storage stability is very poor in case of an aqueous paint. On the other hand, in order to inhibit hydrolization in water and improve storage stability, use of a silicate compound having an alkyl group having three or more carbon atoms has been proposed, but there was a problem that sufficient stain-proofing effect could not be obtained.
An object of the present invention is to provide an aqueous-dispersing composition of synthetic resin being capable of giving a coating composition for aqueous paint which assures very small adherence of outdoor stains, can form a coating film having a high gloss and is excellent in weather resistance and storage stability.
DISCLOSURE OF INVENTION
The present invention relates to the aqueous-dispersing composition of synthetic resin which comprises an aqueous dispersion of synthetic resin and a condensate of tetrafunctional silicate compound represented by the formula (I):
wherein R represents R
1
and R
2
, in which R
1
is methyl and/or ethyl and R
2
is at least one linear or branched alkyl having 3 to 10 carbon atoms, n is 2 to 15, and contains 1 to 100 parts by weight of the condensate of tetrafunctional silicate compound on the basis of 100 parts by weight of solid content in the aqueous dispersion of synthetic resin.
With respect to the condensate of tetrafunctional silicate compound represented by the formula (I) (hereinafter referred to as “silicate condensate (I)”), a proportion of R
1
to the whole R is preferably from 5 to 98% by mole. Further it is preferable that R
2
is propyl and/or butyl. Also it is preferable to use a fluorine-containing resin as a synthetic resin.
The above-mentioned aqueous-dispersing composition of synthetic resin can give a coating composition for an aqueous paint.
BEST MODE FOR CARRYING OUT THE INVENTION
The aqueous-dispersing composition of synthetic resin of the present invention comprises the aqueous dispersion of synthetic resin and the above-mentioned condensate (I) of tetrafunctional silicate compound.
The condensate (I) of tetrafunctional silicate compound functions to give a property for preventing adherence of stains and weather resistance to a coating film formed by using the aqueous-dispersing composition or coating composition of the present invention.
In the present invention, R in the silicate condensate (I) represents R
1
and R
2
. R
1
are methyl or ethyl or the both of them. From the viewpoint of stability in water, ethyl is preferred. R
2
is at least one alkyl having 3 to 10 carbon atoms, for example, propyl, isopropyl, buty, pentyl, hexyl and heptyl. Particularly propyl or butyl or the both of them are preferred from the viewpoint of good affinity for a synthetic resin, particularly a fluorine-containing resin. As the number of carbon atoms of an alkyl group R
2
increases, an affinity for a synthetic resin is lowered, thereby separating the aqueous-dispersing composition into two phases and causing cissing at coating.
R
1
solely contributes to hydrophilization of a coating film by hydrolization of —OR
1
, and exhibits an effect of preventing adherence of stains. However when R consists of R
1
, a large amount of hydrolization of silicate condensate (I) occurs in the aqueous-dispersing composition, which causes gelling and remarkably lowers storage stability of the aqueous-dispersing composition, and besides no —OR
1
group for preventing adherence of stains on a coating film remain in the composition. Particularly when pH of the aqueous dispersion deviates toward acid or alkali side, such a tendency appears remarkably.
R
2
functions to enhance storage stability in the aqueous dispersion of synthetic resin. However when R consists of R
2
, an affinity for a resin is lowered and dispersibility in the aqueous-dispersing composition becomes very poor, which causes separation of the composition into two phases or easily causes cissing at coating. Thus good appearance of a coating film is difficult to obtain. It is a matter of course that an ability of preventing adherence of stains is hardly exhibited.
Therefore in the present invention, R
1
is contained in the whole R of the silicate condensate (I) in an amount of 5 to 98% by mole (R
2
is from 95 to 2% by mole), preferably 50 to 98% by mole (R
2
is from 50 to 2% by mole). When R
1
is less than 5% by mole, an effect of improving stain-proofing property is not obtained, and when exceeding 98% by mole, a gloss of a coating film tends to be lowered.
An average degree of condensation n is from 2 to 15, preferably from 4 to 10. When n is less than 2, namely when an amount of silicate compound of n=1 is large, since the silicate compound is easily evaporated, it is evaporated when drying a coating film, and thus a desired ability of preventing adherence of stains cannot be obtained. On the other hand, when n exceeds 10, appearance of an obtained coating film is lowered.
Represented examples of a method for preparing the condensate (I) of tetrafunctional silicate compound are the following two methods.
{circle around (1)} A method for condensing tetramethoxysilane, tetraethoxysilane or a mixture thereof in the presence of an acid or a base and then substituting a part (2 to 95% by mole) of its alkyl (methyl and/or ethyl) with an alcohol having a linear or branched alkyl R
2
of C3 to C10 to introduce R
2
:
Examples of tetramethoxysilane are, for instance, METHYL SILICATE 39 available from Colcoat Co., Ltd., and the like, examples of tetraethoxysilane are ETHYL SILICATE 28 available from Colcoat Co., Ltd., and the like, examples of the acid are sulfuric acid, hydrochloric acid, and the like, examples of the base are triethanolamine, and the like, and examples of the alcohol of C3 to C10 are propanol, butanol, hexanol, octanol, 2-ethylhexyl alcohol, and the like.
METHYL SILICATE 51 (n=5) commercially available from Colcoat Co., Ltd. as the condensate of tetramethoxysilane, or ETHYL SILICATE 40 (n=4), ETHYL SILICATE 45 (n=8) or ETHYL SILICATE 48 (n≧10) commercially available from Colcoat Co., Ltd. as the condensate of tetraethoxysilane may be alkyl-substituted by reacting with the above-mentioned alcohol of C3 to C10.
The alkyl-substitution reaction with alcohol may be carried out at a temperature around a boiling point of alcohol in the presence of the above-mentioned acid or base.
{circle around (2)} A method for co-condensing by heating tetramethoxysilane, tetraethoxysilane or a mixture thereof and one or two or more of tetraalkoxysilane having a linear or branched alkyl R
2
of C3 to C10 in the presence of an acid or base:
Examples of tetramethoxysilane, tetraethoxysilane, acid and base are those used in {circle around (2)} above. Examples of tetraalkoxysilane of C3 to C10 are, for instance, propyl silicate and butyl silicate available from Colcoat Co., Ltd., and the like.
A proportion of R
1
to R
2
may be adjusted by an amount of tetraalkoxysilane to be used.
Non-restricted examples of the synthetic resin in the aqueous dispersion of synthetic resin to which the cond

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