JPH107940A - Coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating compsn. which is excellent in storage stability and can form a coating film having a high hardness and excellent flexibility, weatherability, durability, stain resistance, adhesion to a substrate, etc., by compounding colloidal silica, a synthetic resin emulsion, and a specific oligomer. SOLUTION: This compsn. contains colloidal silica in an amt. (solid basis) of pref. 5-60wt.%, dispersed in water, and pref. having a particle size of about 7-90nm, a solid content of 20-50wt.%, a pH of about 2-11, and a specific gravity of 1.10-1.40, a synthetic resin emulsion (e.g. one obtd. by the emulsion polymn. of butyl acrylate, methyl methacrylate, styrene, acrylamide. and sodium styrenesulfonate) in an amt. (solid basis) of pref. 20-94wt.%, and a tetramethoxysilane oligomer having a degree of polymn. of 4-5 and in an amt. (solid basis) of pref. 0.05-20wt.%, the sum of the amts. (solid basis) of those three ingredients being 100wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition, and more particularly, to a coating composition having excellent adhesion to various substrates and excellent durability. The present invention relates to an aqueous coating composition useful as a primer paint, a top paint and the like which can be used.

[0002]

2. Description of the Related Art In recent years, attempts have been made in the field of paints to switch from organic solvent type paints to water-based paints containing a water-soluble resin, a water-dispersible resin or the like as a resin component in view of measures against pollution.
However, among these, the water-dispersible resin is affected by the surfactant, which is indispensable when preparing by emulsion polymerization,
The formed coating film has a disadvantage that it is inferior in weather resistance, water resistance, stain resistance and the like.

Various methods have been studied to improve this drawback. For example, a silane compound is introduced at the time of emulsion polymerization of an acrylic resin to form a water-dispersed silicon-modified acrylic resin, whereby a coating film is formed. Attempts have been made to improve the characteristics.

[0004] However, such silicone-modified acrylic resins often have poor storage stability and do not provide satisfactory performance in terms of stain resistance.

[0005]

SUMMARY OF THE INVENTION The main object of the present invention is to:
An object of the present invention is to provide a water-based coating composition having excellent storage stability and capable of forming a coating film having various physical properties such as weather resistance, durability, and stain resistance.

[0006]

Means for Solving the Problems The present inventor has made intensive studies to solve the above-mentioned problems. as a result,
According to a composition containing a synthetic resin emulsion and a composition containing colloidal silica, and further, a tetramethoxysilane oligomer, tetramethoxysilane oligomer is present between colloidal silica as an inorganic component and a synthetic resin emulsion as an organic component. Intermediately, these components are chemically bonded, and the properties such as weather resistance, high hardness, and stain resistance that colloidal silica has mainly, and the flexibility, substrate adhesion, and water resistance that synthetic resin emulsions mainly have Characteristics, such as cohesiveness, and the drawback of using colloidal silica alone is that the coating film is hard and brittle, easily peels off from the base material due to cracks and poor adhesion, and uses a synthetic resin emulsion alone. The disadvantages of long-term weather resistance, hardness, etc., which are drawbacks when used in, are improved, and a coating film with excellent properties is formed. It is, moreover found that becomes excellent in storage stability, and have completed the present invention herein.

That is, the present invention relates to a coating composition containing colloidal silica, a synthetic resin emulsion, and a tetramethoxysilane oligomer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The components of colloidal silica, synthetic resin emulsion, and tetramethoxysilane oligomer which are contained as effective components in the coating composition of the present invention will be described in detail below.

(I) Colloidal Silica In the composition of the present invention, colloidal silica mainly contains abrasion resistance, heat resistance, antistatic property,
It functions to improve the stain resistance and the like. The colloidal silica used in the present invention are those negatively charged amorphous silica particles form a colloidal dispersed in water, SiOH on the particle surface, OH ^- electric double by alkali ions ions are present An overlay is formed and stabilized by repulsion between the particles, and the shape of the particles is usually spherical. In the present invention, the colloidal silica has a particle size of about 7 to 90 nm, a solid content of about 20 to 50% by weight,
It is preferable to use colloidal silica dispersed in water having a pH of about 2 to 11 and a specific gravity of about 1.10 to 1.40.

(Ii) Synthetic resin emulsion In the present invention, the synthetic resin emulsion mainly contributes to the flexibility of the film to be formed, the adhesion to the substrate, the water resistance, and the like. An aqueous synthetic resin emulsion obtained by a polymerization method can be used. The resin component of the synthetic resin emulsion is not particularly limited, for example, acrylic resin, acrylic-styrene copolymer resin, vinyl acetate resin, vinyl acetate-acrylic copolymer resin, ethylene-vinyl acetate copolymer resin, olefin resin, Vinyl chloride resin, vinylidene chloride resin,
Examples thereof include a vinyl chloride / acrylic copolymer resin, a styrene / butadiene copolymer resin, a urethane resin, and a polyester resin.

The monomer components that can be used for emulsion polymerization of synthetic resin emulsions include acrylates, methacrylates, styrene or derivatives thereof, acrylonitrile, vinyl acetate, other vinyl monomers, butadiene, chloroprene, isoprene and the like. One or two or more diene monomers can be selected and used.

Specific examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate and octyl acrylate. Specific examples include methyl methacrylate, ethyl methacrylate, and n-methacrylic acid.
Butyl, t-butyl methacrylate, iso-methacrylate
Butyl, 2-ethylhexyl memethacrylate and the like.

Examples of styrene derivatives include styrene,
α-methylstyrene, vinyltoluene and the like.

Examples of other vinyl monomers include acrylonitrile, methoxyethyl methacrylate, methoxyethyl acrylate, glycidyl methacrylate, glycidyl acrylate, butoxyethyl methacrylate, butoxyethyl acrylate, vinyl acetate, vinyl propionate, and versatic. Vinyl acid, vinyl chloride and the like.

When these monomers are emulsion-polymerized,
In order to stabilize the formed emulsion particles, a radical polymerizable monomer having a hydrophilic group is usually copolymerized.

As the radical polymerizable monomer having such a hydrophilic group, an anionic, cationic, nonionic or zwitterionic monomer can be used.

As the anionic monomer, a monomer having a carboxyl group in the molecule includes maleic acid, fumaric acid, crotonic acid, itaconic acid, acrylic acid, methacrylic acid and the like. Similarly, as anionic monomers having a sulfone group in the molecule, vinyl sulfonic acid, allyl sulfone test, methacrylsulfonic acid, styrene sulfonic acid, 2-ethylsulfonic acid acrylate, 2-ethylsulfonic acid methacrylate, 2-methylsulfonic acrylamide Acids and the like. Similarly, examples of the anionic monomer having a phosphoric acid group in the molecule include acrylic acid 2-hydroxyethyl phosphate and methacrylic acid 2-hydroxyethyl phosphate. These anionic monomers can also be used as salts of organic amines such as ammonia, trimethylamine and monoethanolamine, and alkali metals such as sodium and potassium.

Examples of cationic monomers include dimethylaminoethyl acrylate, dimethylethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, acrylamidodimethylaminopropyl, methacrylamidodimethylaminopropyl, acrylamidopropyltrimethylammonium chloride, methacryl Amidopropyltrimethylammonium chloride, diallyldimethylammonium chloride, p-vinylbenzylammonium chloride and the like can be mentioned.

Examples of the nonionic monomer include acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide,
Acryloyl morpholine, diacetone acrylamide,
Vinylpyrrolidone, vinyloxazolidone, hydroxypropyl acrylate and the like.

If the amount of the radical polymerizable monomer having a hydrophilic group is too small, the stability of the emulsion is reduced. If the amount is too large, the water resistance of the dried film is deteriorated. It is used in the range of about 5 to 10% by weight, preferably about 1 to 5% by weight.

The emulsion polymerization reaction is carried out in the presence of an emulsifier,
It is carried out by supplying the monomer and the polymerization initiator all at once or continuously at a predetermined temperature while stirring in an aqueous medium.

The emulsifier is used in an amount of usually 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on the total amount of the polymerized monomers. Specific examples of the emulsifier include cationic emulsifiers such as stearylamine hydrochloride, lauryltrimethylammonium chloride, trimethyloctadecylammonium chloride, potassium oleate, sodium laurate, sodium dodecylbenzenesulfonate, sodium alkanesulfonate, and sodium alkylnaphthalenesulfonate. Anionic emulsifiers such as sodium dialkyl sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl allyl ether sulfate, polyoxyethylene alkyl allyl phosphate, polyoxyethylene alkyl allyl phosphate, polyoxyethylene alkyl ether, poly Oxyethylene alkyl allyl ether, polyoxyethylene oxypropyl Kkuporima, polyethylene glycol fatty acid esters, nonionic emulsifiers such as polyoxyethylene sorbitan fatty acid esters, lauryl betaine, amphoteric emulsifiers such as such as lauryl dimethyl amine oxide.

In addition, a water-soluble polymer such as polyvinyl alcohol, hydroxyethyl cellulose, a water-soluble acrylic copolymer, a copolymer of sodium styrenesulfonate and the like can be used alone or in combination with the above-mentioned emulsifier.

The monomer concentration during the polymerization is usually 30 to 70
The polymerization initiator may be a commonly used radical polymerization initiator, for example, persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate; Azo-based polymerization initiators such as 2'-azobisisobutylnitrile and 2,2'-azobis (2,4-dimethylvaleronitrile) and peroxide-based polymerization initiators such as benzoyl peroxide and lauryl peroxide are used. be able to.

The amount of the radical polymerization initiator used may be about 0.1 to 10% by weight, preferably about 0.3 to 5% by weight, based on the total amount of the polymerization monomers.

The reaction time may be generally about 2 to 16 hours, and the temperature during the polymerization may be usually about 60 to 100 ° C.

(Iii) Tetramethoxysilane Oligomer The tetramethoxysilane oligomer used in the present invention is a partially hydrolyzed condensate of tetramethoxysilane.
About 5 to 5 are preferable. Tetramethoxysilane monomers are highly toxic and have too high an activity, which may cause heat generation or bumping during operation. However, tetramethoxysilane oligomers do not have such problems, and toxicity is reduced. It also has excellent workability during liquid application, and can be suitably blended into a coating composition. In addition, the tetramethoxysilane oligomer is more active and more reactive than other oligomers such as a tetramethoxysilane oligomer, and the cured product has a higher hardness. The base intervenes between the colloidal silica and the synthetic resin emulsion through the interposition of the groups, and the high hardness, weather resistance, stain resistance, etc., which are the properties of colloidal silica as an inorganic substance, and the base material, which is the properties of the synthetic resin emulsion as an organic substance Properties such as adhesion, flexibility, and water permeability are exhibited in a well-balanced manner, and the storage stability is also excellent.

The tetramethoxysilane used to obtain the tetramethoxysilane oligomer has the chemical formula: Si (O
CH ₃ ) _4, which can be obtained by a method such as a reaction between silicon tetrachloride and methanol, a reaction between metal silicon and methanol, and the like. Since there is no problem of equipment corrosion because hydrochloric acid can not be produced as a by-product and hydrochloric acid is not produced, tetramethoxysilane obtained by reacting metal silicon and methanol is used especially for applications that need to remove impurities. It is desirable.

The hydrolysis-condensation reaction itself for obtaining the tetramethoxysilane oligomer may be carried out by a known method. For example, a predetermined amount of water is added to a tetramethoxysilane monomer to form a by-product in the presence of an acid catalyst. The reaction is usually carried out at room temperature to about 100 ° C. while distilling off the alcohol to be formed. In this reaction, an alcohol such as methanol may be used as a solvent. By this reaction, tetramethoxysilane is hydrolyzed, and furthermore, a liquid tetramethoxysilane oligomer having a number of hydroxyl groups of 1 or less (usually an average degree of polymerization of about 2 to 10, mostly 3 to 4) by a condensation reaction.
7) is obtained as a partially hydrolyzed condensate. The degree of hydrolysis can be appropriately adjusted depending on the amount of water used, and the amount of water necessary to hydrolyze and condense all hydrolyzable groups of tetramethoxysilane, that is, Is expressed as a percentage of the actual amount added to 1/2 of the number of moles of the group of water. In the present invention, the degree of hydrolysis of the tetramethoxysilane oligomer is usually about 20 to 80%, preferably 30 to 60%.
Selected from degree. If it is less than 20%, the residual ratio of the monomer is high and the productivity is low. On the other hand, if it is more than 80%, the obtained composition tends to gel, which is not preferable.

The partially hydrolyzed condensate thus obtained generally contains about 2 to 10% by weight of a monomer. When this monomer is contained, it is highly toxic, has high activity and is difficult to handle, so that the monomer content is 1% by weight or less,
The monomer is preferably removed so as to be preferably 0.3% by weight or less. This monomer removal can be performed by flash distillation, vacuum distillation, blowing of inert gas, or the like.

Coating Composition The coating composition of the present invention is prepared by using the above-mentioned colloidal silica, synthetic resin emulsion,
And a tetramethoxysilane oligomer. By blending such three components, each component is united and effectively acts to improve weather resistance, durability, stain resistance, substrate adhesion and the like. An excellent film is formed, and the storage stability is also good.

In particular, according to the coating composition in which colloidal silica and tetramethoxysilane oligomer are previously condensed and combined with a synthetic resin emulsion, active silanol groups increase due to tetramethoxysilane condensed with colloidal silica. As a result, the active silanol group works effectively, the reactivity is further improved, and the thermosetting property becomes more excellent. In addition, the reactivity between the functional group of the synthetic resin emulsion and the silanol group of the colloidal silica is further improved, and the integration of the colloidal silica and the synthetic resin emulsion is further advanced, and the curability, water resistance, warm water resistance, etc. are further improved. As a result, a film having excellent physical properties can be formed.

As a method for obtaining a coating composition in which a condensate of colloidal silica and a tetramethoxysilane oligomer is combined with a synthetic resin emulsion, a tetramethoxysilane oligomer is added to an aqueous solution containing colloidal silica to condense the two. After that, there is a method of mixing this with a synthetic resin emulsion, a method of adding a tetramethoxysilane oligomer to an aqueous solution containing colloidal silica and a synthetic resin emulsion, and condensing the colloidal silica and the tetramethoxysilane oligomer.

As a method for adding a tetramethoxysilane oligomer to an aqueous solution containing colloidal silica for condensation, for example, the concentration of colloidal silica in the aqueous solution is set to a solid content of about 5 to 45% by weight, preferably 15 to 35% by weight. % By weight, and the liquid temperature is about 0 to 80 ° C., preferably about 0 to 50 ° C., and a necessary amount of tetramethoxysilane oligomer is added thereto to carry out the condensation reaction. At this time, if the tetramethoxysilane oligomer is added at once, it is instantaneously condensed with colloidal silica and easily gelled. Therefore, it is preferable to gradually drop the tetramethoxysilane oligomer usually over a period of about 10 minutes to 1 hour.

The pH of the system at the time of the condensation reaction may be about pH 2 to 11, but the pH of the system is preferably about 9 to 11 since the condensation reaction of the silanol group is faster in the alkaline region.

The reaction may be carried out usually for about 0.5 to 8 hours, preferably for about 2 to 5 hours. Since the tetramethoxysilane oligomer tends to separate from water, the point at which the separated oil component disappears from the aqueous solution. May be used as the end point of the reaction.

In the method of adding and condensing a tetramethoxysilane oligomer to an aqueous solution containing colloidal silica and a synthetic resin emulsion, the concentration of colloidal silica and other reaction conditions may be the same as those described above.

In the coating composition of the present invention, the mixing ratio of each component is not limited to the case where the colloidal silica and the tetramethoxysilane oligomer are used as they are without being condensed and the case where they are used after being condensed in advance. The range may be the same, usually, colloidal silica,
Based on the total solid content of the three components of the synthetic resin emulsion and the tetramethoxysilane oligomer, 5 to 60% by weight of the colloidal silica, 20 to 94% by weight of the synthetic resin emulsion, and 0. The amount may be about 0.5 to 20% by weight, preferably 30 to 60% colloidal silica.
%, About 30 to 60% by weight of a synthetic resin emulsion, and about 1 to 10% by weight of a tetramethoxysilane oligomer. In the coating composition of the present invention, when the mixing ratio of each component is in the above-mentioned range, each component acts in a well-balanced manner and can exhibit excellent performance. If the blending ratio of colloidal silica is too small,
The properties of colloidal silica such as abrasion resistance, heat resistance, antistatic property and stain resistance are not sufficiently exhibited. On the other hand, if the amount is too large, a good coating film is not formed, and after drying, powder It is not preferable because it tends to be If the mixing ratio of the tetramethoxysilane oligomer is too large, the storage stability of the coating composition tends to be unstable. If the mixing ratio is too small, the effect of mixing the tetramethoxysilane oligomer is not sufficiently exhibited, which is not preferable.

The solid concentration of the coating composition of the present invention is not particularly limited, but is usually 5 to 5 with water as a medium.
Prepared at about 5% by weight, and when used, 10-60% by weight
Is appropriate. In particular, in the case of industrial production, it is preferable to increase the solid content within an allowable range.

The coating composition of the present invention may be used by adjusting the solid content to an appropriate amount using water as a medium according to the intended use, and, if necessary, adjusting the pH of aqueous ammonia, sodium hydroxide or the like. Agents, viscosity modifiers, water repellents, ultraviolet absorbers, crosslinking agents, film-forming aids, penetrants, pigments, fillers,
A paint may be added by adding a dye or the like according to a conventional method. The amount of the pigment and the filler used is 300 per 100 parts by weight of the total solid content of the three components of the above-mentioned colloidal silica, synthetic resin emulsion, and tetramethoxysilane oligomer.
It is preferable that the content is not more than about parts by weight.

When the coating composition of the present invention is used as a primer, the viscosity is preferably low in terms of permeability to the substrate, and the solid content is preferably about 10 to 30% by weight. . In addition, when used as a top coating, the viscosity is preferably high, and considering that the drying speed should be high, the solid content is high and the solid content is preferably about 30 to 60% by weight.

The coating composition of the present invention can be applied by various known methods.
It is also possible to perform multiple coatings. For example, it can be applied by line coating such as roll coater coating, curtain coater coating or spray coating, or as a field application, a spray gun can be used to spray-coat a coating composition that has been previously coated at room temperature. . The amount of application is not particularly limited and may be appropriately determined according to the purpose.
What is necessary is just to make it about 150 g / m < ² >.

The coating composition of the present invention has good curability and can form a coating film at room temperature of about 0 to 35 ° C. However, heating can further promote the formation of the coating film. .

The object to be coated with the coating composition of the present invention is not particularly limited. For example, iron, stainless steel, aluminum and other metals, plastics, glass, wood, cement and other substrates, granules, linear bodies, etc. Can be used for the purpose of forming a film on various products.
For example, as an example when used as a top paint,
It can be applied to sealer-coated surfaces such as slate boards and mortar.

[0045]

The coating composition of the present invention contains colloidal silica as an inorganic component and a synthetic resin emulsion as an organic component, and these are integrated by a tetraethoxysilane oligomer. At the same time, each disadvantage is eliminated, and as a result, a film with high hardness, excellent flexibility, excellent weather resistance, durability, stain resistance, substrate adhesion, water permeability resistance, etc. can be formed. In particular, when the colloidal silica and the tetramethoxysilane oligomer are pre-condensed and used in combination with a synthetic resin emulsion, the curability is further improved, and the water resistance is improved. And various film properties such as warm water resistance are improved.

[0046]

The present invention will be described below in more detail with reference to Reference Examples and Examples.

Reference Example 1 (Synthesis of Aqueous Synthetic Resin Emulsion) A 2-liter four-necked flask equipped with a stirrer, a temperature controller, a thermometer, a reflux condenser, a dropping funnel and a nitrogen gas inlet tube was prepared. 2.0 parts by weight of sodium dodecylbenzenesulfonate and 120 parts by weight of water were charged, and the temperature was raised to 65 ° C. while introducing nitrogen gas.
After the addition of 1.2 parts by weight of sodium hyposulfite, 220 parts by weight of butyl acrylate, 100 parts by weight of methyl methacrylate, 60 parts by weight of styrene, 12 parts by weight of acrylamide, 12 parts by weight of sodium styrenesulfonate, polyethylene oxide A monomer emulsion obtained by stirring and mixing 2 parts by weight of nonylphenyl ether (addition of 20 mol of ethylene oxide) and 340 parts by weight of water was dropped from a dropping funnel over 3 hours, and polymerization was carried out at 65 to 70 ° C. After dropping, add ammonium persulfate 0.8
A part by weight was dissolved in and added to 20 parts by weight of water, the mixture was aged at 80 ° C. for 3 hours, and then cooled to obtain an aqueous synthetic resin emulsion.

The emulsion obtained had a non-volatile content of 45.
It was a milky white dispersion having a pH of 5%, a pH of 2.2 and a viscosity of 1300 cP.

Example 1 The synthetic resin emulsion obtained in Reference Example 1, colloidal silica (trade name: Snowtex CM, Nissan Chemical Industries, Ltd.)
Manufactured, particle size 10-20 nm, pH 8.9-9.0, solid content 30-31%) and tetramethoxysilane oligomer (trade name: MS-51, Mitsubishi Chemical Corporation, degree of polymerization 4-)
Using 5) as a raw material, each component was blended at the ratio (% by weight in solid content) shown in Table 1 below to obtain a coating composition. Using this, the following tests were conducted for the stability of standing and the performance of the coating film. The results are shown in Table 1 below.

For the adhesion test, a primer composition adjusted to a solid content of 15% using tap water was used, and for the other tests, a white paint having the following composition was used.

White paint formulation Coating composition (solid content 30% by weight) 150 parts by weight Deionized water 40 parts by weight Titanium oxide (rutile type) 60 parts by weight Anionic surfactant * 1) 2 parts by weight Defoamer * 2) 0.3 parts by weight butyl cellosolve 10 parts by weight * 1) Trademark: Demol EP, manufactured by Kao Corporation, special carboxylic acid type polymer surfactant, solid content 25% aqueous solution * 2) Trademark: Nopco 8034, San Nopco Solid content 100%, manufactured by Co., Ltd. <Test method>-Stability after storage After the white paint was prepared, it was left at 50 ° C for 1 month, and the stability of the liquid was visually evaluated. Those in which separation and solidification did not occur are indicated by a circle.

Adhesion The primer composition adjusted to a solid content of 15% was applied to each of a slate plate and a glass plate at 100 g / m ² ,
After leaving at 0 ° C. for 10 hours, 2 mm at intervals of 4 mm × 4 mm
Five gobangs were inserted with a cutter knife until they reached the base material, a cellophane tape was stuck thereon, and peeled off at a stretch to determine the number of squares in which the coating film remained on the base material surface. A mark of 25/25 means that the coating film was completely left on the substrate, and 0/25 means that the coating film was completely peeled off.

Water resistance The above-mentioned white paint was spray-coated on a flexible board so as to form a coating having a dry film thickness of about 80 μm, and dried at 20 ° C. for 2 days to obtain a test piece.

After this test piece was immersed in normal temperature water for one week, the state of the coating film was visually observed and evaluated in the following three grades.

○ No appearance abnormality △ Whitening occurred × Whitening and blister occurred ・ Alkali resistance 5% using the same test piece as that used in the water resistance test
After being immersed in an aqueous solution of sodium carbonate at 40 ° C. for 24 hours, the state of the coating film was visually observed and evaluated according to the following three grades.

○ No appearance abnormality △ Whitening occurred × Whitening and blister occurred ・ Pencil hardness Using a test piece similar to that used in the water resistance test, JI
It measured according to S-K5400, 6-14.

Stain resistance The above-mentioned white paint is spray-coated on a flexible board so as to form a coating film having a dry film thickness of about 80 μm.
A test piece was dried under a RH condition of 65% for 7 days, and a paste-like mixture in which carbon powder and glycerin were mixed at a weight ratio of 1: 2 was uniformly coated on the surface of the coating film and left at room temperature for 24 hours. After that, the coating film was washed with water, the degree of dirt was visually examined, and evaluated according to the following criteria.

◎ No contamination ○ Slightly colored △ Light but clearly colored × Significantly colored ・ Accelerated weather resistance test Using a test piece similar to the one used in the water resistance test, a sunshine weather tester (Atlas Co., CI35W, manufactured by Atlas Co., Ltd.) )
The state of the coating film after the accelerated weathering test for 2000 hours was visually observed, and evaluated in the following three stages.

○ Good △ Some defects were found on the coating film × Significant discoloration Example 2 Colloidal silica (trade name: Snowtex O, Nissan Chemical Co., Ltd.) was placed in a flask equipped with a stirrer, a reflux condenser, a dropping funnel and a material inlet. Industrial Co., Ltd., particle size 10-20n
m, pH 2-4, solid content 20-21%) 450 g and water 5
Then, while stirring, the internal temperature was kept at 50 ° C., and stirring was continued, a tetramethoxysilane oligomer (trade name: MS-51, Mitsubishi Chemical Corporation) was added from the dropping funnel.
10 g of a polymer having a degree of polymerization of 4 to 5) was gradually added dropwise over 30 minutes, and the liquid temperature was maintained at 50 ° C., stirring was further continued, and colloidal silica and tetramethoxysilane oligomer were condensed over 3 hours. Then, cool to room temperature and remove
A clear aqueous solution having a weight of 0%, a pH of 4.8 and a viscosity of 10 cP was obtained.

To the transparent aqueous solution, the synthetic resin emulsion obtained in Reference Example 1 was blended so that the ratio of synthetic resin emulsion / the transparent aqueous solution (solid content ratio) = 90/10, and tap water was added thereto to form a coating composition. I got This coating composition has a solid content of 40% by weight, a pH of 7.8, and a viscosity of 10c.
It was a milky emulsion of P. Using this, a test of standing stability and coating film performance was performed in the same manner as in Example 1. The results are shown in Table 1 below.

Examples 3 to 6 and Comparative Examples 1 to 5 In the same manner as in Example 1, coating compositions were prepared in the proportions shown in Tables 1 and 2 below and tested for shelf stability and coating film performance. Was performed. The results are shown in Tables 1 and 2 below.

In each example, as the tetramethoxysilane oligomer, trade name: MS-51 (Mitsubishi Chemical Corporation, degree of polymerization of tetramethoxysilane 4 to 5) or trade name: MS-56 (Mitsubishi Chemical Co., Ltd., an oligomer having a degree of polymerization of tetramethoxysilane of 8 to 10), and as a silane coupling agent, a trade name: A187 (manufactured by Nippon Unicar Co., Ltd .; chemical formula: CH ₂ CHCH ₂ OC ₃ H ₆ Si (O
CH ₃ ) ₃ ) using a silane coupling agent, as a colloidal silica, a trademark: Snowtex CM (manufactured by Nissan Chemical Industries, Ltd., particle diameter 10-20 nm, pH 8.9-
9.0, solid content 30 to 31%) or trademark: Snowtex O (manufactured by Nissan Chemical Industries, Ltd., particle size 10 to 20 nm)
pH 2-4, solids 20-21%).

[0063]

[Table 1]

[0064]

[Table 2]

Claims (3)

[Claims] 1. A coating composition comprising colloidal silica, a synthetic resin emulsion, and a tetramethoxysilane oligomer. 2. A method according to claim 1, wherein said colloidal silica and said tetramethoxysilane oligomer are condensed with each other.
A coating composition according to claim 1. 3. A colloidal silica, a synthetic resin emulsion, and a tetramethoxysilane oligomer, wherein the total solid content of the three components is 5 to 60% by weight of the colloidal silica, 20 to 94% by weight of the synthetic resin emulsion, and a tetramethoxysilane oligomer. 3. The coating composition according to claim 1, comprising 0.05 to 20% by weight.