JPH10168380A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous coating composition excellent in preservation stability and further capable of providing a coating film excellent in hardness, waterproof properties, etc., by adding a specific component to an acrylic resin emulsion containing a carbonyl based on a aldehyde or ketone and an organic hydrazine compound. SOLUTION: This aqueous coating composition includes (A) an aqueous emulsion comprising a polymer obtained by performing an emulsion polymerization of a radical-polymerizable vinyl compound and having carbonyl group based on aldehyde group or a keto group, (B) or organic hydrazine compound having two or more hydrazine residues (preferably, dihydrazine of adipic acid), and (C) colloidal silica surface-treated with a silane compound of the formula SiR<1> n+1 (OR<2> )3-n [R<1> is H or a 1-10C hydrocarbon; R<2> is H or a 1-10C hydrocarbon (including ether bond); (n) is 0-2], (preferably, trimethoxysilane). The solid content of the component C is 1-30 pts.wt. based on 100 pts.wt. polymer component in the component A. The average particle diameter of the component C is preferably 1-80nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition, and more particularly, to an aqueous coating composition which forms a film having excellent storage stability, hardness, water resistance, stain resistance and weather resistance. It relates to a composition.

[0002]

2. Description of the Related Art Conventionally, solvent-based paints have been mainly used as paints. However, solvent-based paints may cause inflammation and poisoning and may cause environmental pollution. The transition to paint is progressing rapidly. However, water-based paints have lower coating properties such as weather resistance and water resistance than solvent-based paints, and there are currently many problems to be solved.

[0003] A variety of aqueous paints have been developed to solve these problems. For example, as a resin for a water-based paint, an emulsion of an acrylic resin obtained by emulsion polymerization has been widely studied because it has a feature that the obtained coating film has relatively good weather resistance and the like. For example, JP-A-54-144432 proposes a resin composition comprising an emulsion of an acrylic resin containing a carbonyl group based on an aldehyde group or a keto group and an organic hydrazine compound having two or more hydrazine residues. It is possible to form a coating film at room temperature, and has the excellent feature that it can be used as a one-pack type, but has the problem that the water resistance of the obtained coating film is insufficient, Have a problem that when they are exposed outdoors, they are easily contaminated by dust, soot, sand and the like.

[0004]

On the other hand, as a means for improving the performance of the water-based paint, a method of containing an inorganic substance is known. For example, Japanese Patent Publication No. 41180/1989 proposes a coating composition containing colloidal silica in an aqueous emulsion obtained by copolymerizing vinyl silane and an acrylic monomer, and has heat resistance, water resistance, and adhesion of a coating film. It has the feature of being excellent. However, since this coating composition requires a relatively large amount of colloidal silica having a solid content of 500 to 20,000 parts by weight with respect to 100 parts by weight of the solid content of the aqueous emulsion, storage stability is poor. Have a point. On the other hand, when the colloidal silica solid content is less than 500 parts by weight, the storage stability tends to be improved, but there is a problem that the coating properties such as hardness are reduced.

It is an object of the present invention to provide an aqueous coating composition for coatings which forms a coating film having excellent storage stability and excellent hardness, water resistance, stain resistance and weather resistance.

[0006]

Means for Solving the Problems In view of the above-mentioned problems of the prior art, the present inventors have made intensive studies on an aqueous coating composition for paints, and as a result, have reached the present invention.

That is, the gist of the present invention is as follows.
Obtained by emulsion polymerization of a radically polymerizable vinyl compound,
Aqueous emulsion (A) comprising a polymer having a carbonyl group based on an aldehyde group or a keto group, an organic hydrazine compound (B) having two or more hydrazine residues, and a silane compound represented by the following general formula (I) The solid content of the colloidal silica (C) is 1 to 300 with respect to 100 parts by weight of the polymer component in the aqueous emulsion (A).
Water-based coating composition, characterized in that it is in parts by weight.

[0008]

Embedded image

(Wherein R ¹ is a hydrogen atom or a C ¹ -C 1)
0 hydrocarbon group, R ² represents a hydrocarbon group having 1 to 10 carbon atoms which may contain a hydrogen atom or an ether bond, n represents an integer of 0 to 2. )

[0010]

DETAILED DESCRIPTION OF THE INVENTION The aqueous coating composition of the present invention comprises an aqueous emulsion comprising a polymer having a carbonyl group based on an aldehyde group or a keto group, which is obtained by emulsion polymerization of a radically polymerizable vinyl compound. The organic hydrazine compound having the above hydrazine residue and colloidal silica are contained.

The aqueous emulsion (A) of the present invention can be obtained by using a vinyl monomer containing a carbonyl group based on an aldehyde group or a keto group as the radically polymerizable vinyl compound.

The amount of the vinyl monomer used is preferably in the range of 0.1 to 30 parts by weight based on 100 parts by weight of the radically polymerizable vinyl compound. If the amount is less than 0.1 part by weight, the hardness and solvent resistance of the obtained coating film tend to decrease, and if it exceeds 30 parts by weight, the effect of improving the coating film performance cannot be obtained any more. On the contrary, the water resistance tends to decrease. More preferably, it is in the range of 1 to 10 parts by weight.

Examples of the vinyl monomer having a carbonyl group based on an aldehyde group or a keto group used in the present invention include acrolein, diacetone acrylamide, formyl styrene, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, Examples thereof include diacetone acrylate, diacetone methacrylate, acetonyl acrylate, acryloxyalkylpropenal, and methacryloxyalkylpropenal.

Other radically polymerizable vinyl compounds used in the aqueous emulsion (A) of the present invention include:
Known radically polymerizable monomers can be used. For example, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, n-lauryl methacrylate, n-methacrylic acid
-Alkyl methacrylates such as stearyl and cyclohexyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, n-lauryl acrylate , N-stearyl acrylate, alkyl acrylates such as cyclohexyl acrylate, methacrylic acid, acrylic acid, crotonic acid,
Carboxyl group-containing vinyl monomers such as fumaric acid, maleic acid, itaconic acid and sorbic acid; acid anhydrides such as maleic anhydride and itaconic anhydride; N-phenylmaleimide;
Maleimide derivatives such as -cyclohexylmaleimide, N-butylmaleimide, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, acrylic acid Vinyl polymerizable monomers having a hydroxyalkyl group such as 2-hydroxyethyl, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, methacrylamide, acrylamide Group-containing vinyl monomers such as crotonamide, N-methylol acrylamide, etc., and epoxy group-containing vinyl such as allyl glycidyl ether, glycidyl acrylate and glycidyl methacrylate. Monomer, styrene, alpha-aromatic vinyl monomers methyl styrene, nitrile group-containing vinyl monomers such as acrylonitrile, olefinic monomers such as butadiene and the like. These components can be used alone or in combination of two or more as necessary. If necessary, a cross-linking agent such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl acrylate, allyl methacrylate, divinylbenzene, and trimethylolpropane triacrylate can be used.

The aqueous emulsion of the present invention (A)
By using an alkoxysilane compound,
The weather resistance of the coating film can be further improved. The alkoxysilane compound can be used by adding it to the aqueous emulsion (A). However, the dispersion of the colloidal silica is performed more uniformly, and the emulsion polymerization with the radical polymerizable vinyl compound is carried out. It is preferable to introduce an alkoxysilyl group and / or a silanol group into the constituting polymer.

The amount of the alkoxysilane compound used is preferably not more than 20 parts by weight based on 100 parts by weight of the radically polymerizable vinyl compound. This is because when the amount of the alkoxysilane compound exceeds 20 parts by weight, the storage stability of the obtained aqueous coating composition tends to decrease. More preferably, it is in the range of 0.05 to 10% by weight.

The alkoxysilane compounds used in the aqueous emulsion (A) of the present invention include those represented by the following general formulas (1) to (6).

[0018]

Embedded image

[0019]

Embedded image

[0020]

Embedded image

[0021]

Embedded image

[0022]

Embedded image

[0023]

Embedded image

(Wherein R ¹ is a hydrogen atom or a group having 1 to 1 carbon atoms)
10 hydrocarbon groups, R ² is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms which may contain an ether bond, R ³ is a hydrogen atom or a methyl group, n is an integer of 0 to 2, p is 1 to 10 Integer and q represent an integer of 0 to 10. Specific examples of the general formula (1) include γ-mercaptopropyltrimethoxysilane and γ-mercaptopropylmethyldimethoxysilane.

As a specific example of the general formula (2), γ-
Acryloyloxypropyltrimethoxysilane, γ-
Acryloyloxypropyltriethoxysilane, γ-
Acryloyloxypropylmethyldimethoxysilane,
γ-acryloyloxypropylmethyldiethoxysilane, γ-acryloyloxypropylethyldimethoxysilane, β-acryloyloxyethyltrimethoxysilane, β-acryloyloxyethylmethyldimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxy Propyltriethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, γ-methacryloyloxypropylmethyldiethoxysilane, γ-methacryloyloxypropylethyldimethoxysilane, γ-methacryloyloxypropyldimethylmethoxysilane, β-methacryloyloxyethyltrimethoxysilane And β-methacryloyloxyethylmethyldimethoxysilane.

Specific examples of the above general formula (3) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-n-butoxysilane, vinyltris (β-methoxyethoxy) silane, vinylmethyldimethoxysilane, and vinylmethyldiethoxysilane. Silane, vinylethyltrimethoxysilane, vinyldimethylmethoxysilane, isopropenyltrimethoxysilane, isopropenylmethyldimethoxysilane, allyltrimethoxysilane, 5-hexenyltrimethoxysilane, 9-decenyltrimethoxysilane, and the like can be given. .

As a specific example of the above general formula (4), p-
Vinylphenyltrimethoxysilane (p-trimethoxysilylstyrene), p-vinylphenyltriethoxysilane, p-vinylphenyltriisopropoxysilane,
p-vinylphenylmethyldimethoxysilane, p-vinylphenylmethyldiethoxysilane, p-vinylphenylethyldimethoxysilane, p-vinylphenylpropyldimethoxysilane, p-vinylphenylphenyldimethoxysilane, p-vinylphenyldimethylmethoxysilane, o -Vinylphenyltrimethoxysilane, o-vinylphenylmethyldimethoxysilane, m-vinylphenyltrimethoxysilane, o-vinylphenylmethyldimethoxysilane, p-isopropenylphenyltrimethoxysilane, p-isopropenylphenylmethyldimethoxysilane, m -Isopropenylphenyltrimethoxysilane, m-isopropenylphenylmethyldimethoxysilane and the like.

Specific examples of the general formula (5) include trimethoxysilylpropyl vinyl ether and methyldimethoxysilylpropyl vinyl ether.

As a specific example of the above general formula (6), 11
-Vinyl trimethoxysilylundecanoate.

Preferred among the above-mentioned alkoxysilane compounds are alkoxysilane compounds having a mercapto group and / or an ethylenically unsaturated group represented by the general formulas (1) to (3), and among them, γ-mercaptopropyl Particularly preferred are trimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, and vinyltrimethoxysilane. These components can be used alone or in combination of two or more as necessary.

The aqueous emulsion (A) of the present invention can be obtained by subjecting a mixture of the above radical polymerizable compounds to aqueous emulsion polymerization in the presence of a radical polymerization initiator. The polymerization temperature is 5 to 100C, preferably 40 to 95C.
And the polymerization time is in the range of 0.1 to 24 hours. In the step of emulsion polymerization, the mixture of the radically polymerizable compound may be added to the reactor in a lump, dividedly or continuously, or a combination thereof.

Examples of the radical polymerization initiator include, for example, t
-Oxidizing agent consisting of organic hydroperoxides such as -butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, sugar-containing iron pyrophosphate formulation, sulfoxylate formulation,
Redox initiators in combination with reducing agents such as a mixture of sugar-containing iron pyrophosphate formulation / sulfoxylate formulation, persulfates such as potassium persulfate and ammonium persulfate, azobisisobutyronitrile, azobisdimethyl Known compounds such as azo compounds such as valeronitrile and dimethyl-2,2'-azobisisobutyrate, and organic peroxides such as benzoyl peroxide and lauroyl peroxide can be used. The amount of the radical polymerization initiator used is usually about 0.01 to 5 parts by weight based on 100 parts by weight of the radical polymerizable compound.

In the emulsion polymerization, known emulsifiers and chain transfer agents can be used, if necessary. Examples of the emulsifier include sulfonate emulsifiers such as sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium diphenyl ether disulfonate, sodium dialkyl sulfosuccinate, sodium polyoxyethylene alkyl phenyl ether sulfate, and polyoxyethylene alkyl phenyl ether phosphate. Phosphate emulsifiers such as sodium salts, carboxylic acid emulsifiers such as potassium oleate, sodium N-lauroyl sarcosinate, sodium N-myristoyl sarcosinate, potassium alkenyl succinate, polyoxyethylene alkyl ester, polyoxyethylene alkylaryl Anionic emulsifiers such as nonionic emulsifiers such as ethers, sulfonate emulsifiers, phosphate emulsifiers, and carboxylate emulsifiers It is below. These emulsifiers may be used alone or in combination of two or more. In particular, the use of an anionic emulsifier is preferable because colloidal silica can be uniformly dispersed. The amount of these emulsifiers is usually 0.5 to 100 parts by weight of the vinyl polymerizable monomer.
It is about 10 parts by weight.

As the chain transfer agent, for example, t-
Dodecyl mercaptan, n-octyl mercaptan, n
-Mercaptans such as tetradecyl mercaptan and n-hexyl mercaptan; and halogen compounds such as carbon tetrachloride and ethylene bromide. The use amount of these chain transfer agents is usually 1 part by weight or less based on 100 parts by weight of the radical polymerizable compound.

Further, at the time of emulsion polymerization, various known electrolytes, pH adjusters and the like can be used as necessary.

The emulsion particle size of the present invention can be arbitrarily changed depending on the production conditions.
The thickness is preferably about 1 to 1 μm.

The aqueous coating composition of the present invention can be used as an emulsion for paints by including the above-mentioned aqueous emulsion (A) with an organic hydrazine compound (B) having two or more hydrazine residues. Becomes

The amount of the organic hydrazine compound (B) used in the present invention depends on the number of moles (i) of the carbonyl group based on the aldehyde group or keto group in the polymer and the number of moles of the hydrazine residue in the organic hydrazine compound ( ii)
It is preferable to set the range of 0.05 ≦ (ii) / (i) ≦ 5. When (ii) / (i) is less than 0.05,
The progress of the cross-linking reaction tends to be insufficient, and the water resistance and solvent resistance of the formed coating film tend to be insufficient. If it exceeds 5, the unreacted organic hydrazine compound (B) remains, This is because the appearance and water resistance of the coating film tend to be adversely affected. More preferably, 0.5 ≦ (ii) / (i)
≦ 2.

Specific examples of the organic hydrazine compound (B) include dicarboxylic dihydrazides containing 2 to 10, especially 4 to 6, carbon atoms, such as oxalic dihydrazide, malonic dihydrazide, succinic dihydrazide, and the like. Glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide and itaconic acid dihydrazide, and aliphatic water-soluble dihydrazine having 2 to 4 carbon atoms, such as ethylene-1,2- Dihydrazine,
Propylene-1,3-dihydrazine, butylene-1,4
-Dihydrazine and the like. Of these, adipic dihydrazide, isophthalic dihydrazide, sebacic dihydrazide and succinic dihydrazide are preferred. These may be used in combination of two or more.

The aqueous coating composition of the present invention uses a relatively small amount of colloidal silica (C) surface-treated with a specific silane compound to provide water resistance, stain resistance, hardness, and weather resistance. The coating film performance can be improved.

(C) in the aqueous coating composition of the present invention
It is necessary that the solid content of the component is in the range of 1 to 300 parts by weight with respect to 100 parts by weight of the polymer component constituting the aqueous emulsion. If the amount is less than 1 part by weight, the hardness, water resistance and stain resistance of the coating film tend to be insufficient, and if it exceeds 300 parts by weight, the storage stability of the aqueous coating composition tends to decrease. That's why. Preferably it is in the range of 1 to 150 parts by weight.

As the colloidal silica before surface treatment used in the present invention, various commercially available products using water as a dispersion medium can be used, but those having an average particle diameter of 300 nm or less are preferable. When the thickness exceeds 300 nm, the transparency, rigidity (elastic modulus) and heat resistance of the obtained coating film tend to be low, and more preferably 1 to 80 n.
m.

In the present invention, these colloidal silicas are subjected to a surface treatment with the silane compound represented by the above general formula (I).

Specific examples of the silane compound represented by the general formula (I) include trimethoxysilane, dimethoxymethylsilane, dimethoxydimethylsilane, methoxytrimethylsilane, triethoxysilane, diethoxymethylsilane, dimethylethoxysilane, phenyl Examples thereof include trimethoxysilane, dimethoxyphenylsilane, phenyltriethoxysilane, and diethoxyphenylsilane. These can be used alone or in combination of two or more, but trimethoxymethylsilane is particularly preferred.

As a method for surface-treating colloidal silica with a silane compound, colloidal silica and at least one silane compound selected from the above-mentioned silane compounds are added to the aqueous emulsion (A), and optionally at room temperature to 100 ° C. For a period of time.

As another method, at least one of colloidal silica and a silane compound is previously added at room temperature to 10 ° C.
Examples include a method of adding colloidal silica surface-treated with a silane compound obtained by stirring at a temperature of 0 ° C. for an arbitrary time to the aqueous emulsion (A), but the method is particularly limited to these methods. Not something.

The amount of the silane compound used in the surface treatment of the colloidal silica is preferably in the range of 1 to 60 parts by weight based on 100 parts by weight of the solid content of the colloidal silica. If the amount is less than 1 part by weight, the weather resistance of the obtained coating film tends to be insufficient, and if it exceeds 60 parts by weight, the storage stability of the aqueous coating composition and the water resistance and This is because the contamination tends to be insufficient. More preferably, it is in the range of 5 to 40 parts by weight.

The polymer component content of the aqueous coating composition of the present invention is preferably in the range of 20 to 70% by weight. When the content of the polymer component is less than 20% by weight, the thickness of the obtained coating film tends to be thin, and the coating workability tends to decrease. On the other hand, if it exceeds 70% by weight, the viscosity of the system tends to increase significantly, and it tends to be difficult to obtain a stable emulsion. More preferably, 3
It is in the range of 0 to 60% by weight.

In the aqueous coating composition of the present invention, the method of mixing the aqueous emulsion and colloidal silica is preferably a method of mixing a colloidal silica dispersion with an aqueous emulsion of a polymer obtained by emulsion polymerization. Further, a method of emulsion polymerization of a radically polymerizable compound in an aqueous medium containing colloidal silica to obtain an aqueous emulsion may be used, but in this method, although the production process is simplified, the polymerization stability tends to be low. It is in.

The aqueous coating composition of the present invention contains, if necessary, various additives such as a pigment, an ultraviolet absorber, an antioxidant, a heat resistance improver, a leveling agent, an anti-sagging agent and a matting agent. Or a mixture with another emulsion resin, a water-soluble resin, a viscosity control agent, and a commonly used curing agent such as melamines.

The resin composition of the present invention can be applied by a method such as brush coating, roll coating, spray coating, and the like, and can be cured by standing at room temperature or heating to 50 to 200 ° C.

[0052]

The present invention will be described in more detail with reference to the following examples. In the examples, “parts” are “parts by weight” and “%”.
Indicates "% by weight".

The evaluation of the performance in Examples and Comparative Examples was performed using the following method.

(1) Transparency A spot-like coating film was formed on a glass plate, and the transparency was visually judged. ○: Transparent △: Translucent ×: Cloudy (2) Hardness Using Mitsubishi Pencil Uni (45 ° angle) (3) Water resistance After dipping in hot water of 50 ° C. for 100 hours, the appearance of the coating film was visually judged. Furthermore, the 60-60 degree specular reflectance after immersion (hereinafter referred to as 60 ° gloss) is measured as a gloss value, and is divided by the 60 ° gloss (initial gloss value) immediately after the coating film formation to obtain a gloss retention rate (gloss value / gloss value). Retention) was calculated. ：: no change △: no change except slight swelling ×: remarkable swelling and gloss shrinkage (4) Stain resistance A carbon paste obtained by well mixing carbon black and water at a weight ratio of 20/80 is applied. Smear at 60 ° C for 30 minutes
After heating for minutes, it was washed with running water, and the state of adhesion of carbon was visually determined. ：: No change from before carbon paste application ：: Slight trace remains X: Marked trace remains (5) Storage stability The state of the aqueous coating composition after standing at room temperature for one month is visually judged 判定: No change × : Agglomeration, gelation (6) Weather resistance The 60 ° gloss immediately after the formation of the coating film was measured as the initial gloss,
Sunshine-type waza meter (Suga Test Machine Co., Ltd.)
(WEL-SUN-DC type) was used to perform an exposure test (rain cycle: 12 minutes / hour, black panel temperature: 63 ± 3 ° C.). Gloss value was measured by measuring the gloss at 60 degrees after exposure for 1000 hours, and the gloss retention was calculated.

[0055]

Example 1 Deionized water 113 was placed in a separable flask equipped with a condenser, a nitrogen inlet tube, a thermometer and a stirrer.
Part, dodecylbenzenesulfonic acid sodium salt (manufactured by Kao Corporation, trade name: Neoperex F-2) as an emulsifier
5) 2 parts and 0.6 part of potassium persulfate were added, and the temperature was raised to 70 ° C. while stirring. Thereto, a mixture of 42 parts of methyl methacrylate, 42 parts of n-butyl methacrylate, 11 parts of 2-ethylhexyl acrylate, 2 parts of methacrylic acid, and 3 parts of diacetone acrylamide was dropped over 4 hours. After completion of dropping, hold at 70 ° C for 1 hour, then 80 ° C
And kept for another hour. After cooling, the pH was adjusted to 8 to 9 with aqueous ammonia to obtain an aqueous emulsion of a copolymer.

Next, an aqueous dispersion of colloidal silica having an average particle diameter of 10 to 20 nm (silica content: 20% by weight, manufactured by Nissan Chemical Industries, Ltd., trade name: Snowtex O) 15
0 parts, 3.5 parts of methyltrimethoxysilane was added,
The aqueous dispersion of the surface-treated colloidal silica obtained by stirring at 0 ° C. for 1 hour was added to the above aqueous emulsion with stirring.

Thereafter, adipic dihydrazide 1.9 was obtained.
And 20 parts of butyl cellosolve were added with sufficient stirring to obtain an aqueous coating composition.

The aqueous coating composition was applied on a test steel plate using a bar coater # 40, left at room temperature for 30 minutes, and then cured at 70 ° C. for 3 hours. The resulting coating is smooth,
Transparent and tough, 60
° Gloss value was 85. Table 1 shows the evaluation results of the obtained coating films.

[0059]

Examples 2 to 5 An aqueous coating composition was prepared in the same manner as in Example 1 except that the composition was changed as shown in Table 1.
Further, a coating film was obtained using this. Table 1 shows the properties of the obtained aqueous coating composition.

[0060]

Example 6 Instead of Snowtex O as the colloidal silica to be used, Snowtex 30 (having an average particle size of 1) was used.
A coating film was obtained in the same manner as in Example 2 except that 0 to 20 nm, a silica content of 30% by weight, and Nissan Chemical Industry Co., Ltd.) were used and the addition amount was 100 parts. Table 1 shows the properties of the obtained aqueous coating composition.

[0061]

Comparative Examples 1 and 2 An aqueous coating composition was prepared in the same manner as in Example 1 except that the composition was changed as shown in Table 1.
Further, a coating film was obtained using this. As shown in Table 1, the properties of the obtained aqueous coating composition were inferior to those of the examples.

[0062]

Comparative Example 3 Deionized water 113 was placed in a separable flask equipped with a condenser, a nitrogen inlet tube, a thermometer and a stirrer.
, 2 parts of sodium dodecylbenzenesulfonate as an emulsifier and 0.6 part of potassium persulfate were added, and the temperature was raised to 70 ° C while stirring. There, 25 parts of methyl methacrylate, 29.5 parts of n-butyl methacrylate, 31 parts of 2-ethylhexyl acrylate, 11.5 parts of 2-hydroxyethyl methacrylate, 2 parts of methacrylic acid, and γ-methacryloxypropyltrimethoxysilane ( One part of a mixture of Shin-Etsu Chemical Co., Ltd., trade name: KBM503) was added dropwise over 4 hours. After completion of the dropwise addition, the temperature was maintained at 70 ° C. for 1 hour, then the temperature was raised to 80 ° C., and further maintained for 1 hour. After cooling, the pH was adjusted to 8 to 9 with aqueous ammonia to obtain an aqueous emulsion of a copolymer.

Next, 100 parts of Snowtex O
10 parts of methyltrimethoxysilane was added, and the aqueous dispersion of the surface-treated colloidal silica obtained by stirring at 60 ° C. for 1 hour was added to the aqueous emulsion with stirring.

Thereafter, a water-soluble melamine (Sumimar M-40W, Sumitomo Chemical Co., Ltd.) having a melamine solid content of 80% by weight was used.
And 30 parts of butyl cellosolve were added with stirring, and the mixture was further stirred for 30 minutes to obtain an aqueous coating composition.

The aqueous coating composition was applied on a test steel plate using a bar coater # 40, left at room temperature for 30 minutes, and then cured at 160 ° C. for 30 minutes. The obtained coating film was clouded as shown in Table 1.

[0066]

Comparative Example 4 Deionized water 51 was placed in a separable flask equipped with a condenser, a nitrogen inlet tube, a thermometer and a stirrer.
Parts, 2 parts of dodecylbenzenesulfonic acid sodium salt, 0.6 part of potassium persulfate, and 100 parts of Snowtex 30 as an emulsifier, and the mixture was heated to 70 ° C. while stirring. Thereto, a mixture of 42 parts of methyl methacrylate, 42 parts of n-butyl methacrylate, 11 parts of 2-ethylhexyl acrylate, 2 parts of methacrylic acid, and 3 parts of diacetone acrylamide was dropped over 4 hours. However, the system solidified during the dropping, and a desired aqueous coating composition could not be obtained.

[0067]

[Table 1]

1) Shin-Etsu Chemical Co., Ltd., γ-methacryloxypropyltrimethoxysilane 2) Shin-Etsu Chemical Co., Ltd., mercaptopropylmethyldimethoxysilane 3) Kao Corporation, Dodecylbenzenesulfonic acid sodium salt 4) Colloidal silica aqueous dispersion (solid content 20% by weight) manufactured by Nissan Chemical Industries, Ltd. 5) Colloidal silica aqueous dispersion (solid content 30% by weight) manufactured by Nissan Chemical Industries, Ltd. 6) Sumitomo Chemical Co., Ltd. , Water-soluble melamine (melamine solid content 80% by weight)

[0069]

Industrial Applicability The aqueous coating composition of the present invention has excellent storage stability, provides a coating excellent in weather resistance, hardness, water resistance and stain resistance, and is used in various coating applications as a resin for aqueous emulsion coatings. Can be very useful industrially.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 133/24 C09D 133/24

Claims (2)

[Claims] An aqueous emulsion (A) comprising a polymer having a carbonyl group based on an aldehyde group or a keto group, which is obtained by emulsion polymerization of a radically polymerizable vinyl compound (A).
And an organic hydrazine compound (B) having two or more hydrazine residues, and colloidal silica (C) surface-treated with a silane compound represented by the following general formula (I):
Wherein the solid content of the colloidal silica (C) is 1 to 300 parts by weight based on 100 parts by weight of the polymer component in the aqueous emulsion (A). Embedded image (Wherein, R ¹ represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, R ² represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms which may contain an ether bond, and n represents an integer of 0 to 2) .) 2. The aqueous coating composition according to claim 1, wherein the polymer constituting the aqueous emulsion (A) contains an alkoxysilyl group and / or a silanol group.