JPH09165533A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous coating composition for a coating material having excellent storage stability and capable of forming a coating film excellent in hardness, water resistance, stain resistance and weather resistance. SOLUTION: This composition comprises an aqueous emulsion consisting of a polymer having carbonyl groups originating from an aldehyde group or a ketone group and obtained by the emulsion polymerization of a radically polymerizable vinyl compound, an organic hydrazine compound having two or more hydrazine residues and a colloidal silica. The solid content of the colloidal silica is 1-300 pts.wt. based on 100 pts.wt. polymer component in the aqueous emulsion.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aqueous coating composition, and more specifically to an aqueous coating which is excellent in storage stability and forms a film having excellent hardness, water resistance, stain resistance, weather 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.

Various developments of water-based paints aimed at solving these problems have been made. 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 discloses 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. The coating film can be formed at room temperature, and has an excellent feature that it can be used as a one-pack type, but it has a drawback that the water resistance of the obtained coating film is insufficient. When exposed outdoors, it has the drawback of being 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 Examined Patent Publication (Kokoku) No. 1-41180 discloses a coating composition in which colloidal silica is contained in an aqueous emulsion obtained by copolymerizing vinylsilane and an acrylic monomer, and the coating film has heat resistance, water resistance, and adhesion. 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.

The object of the present invention is to provide an aqueous coating composition for a coating which forms a coating having excellent storage stability, hardness, water resistance, stain resistance, and weather resistance, an aqueous emulsion used therefor, and its production. Is to provide a method.

[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,
An aqueous emulsion composed of a polymer having a carbonyl group based on an aldehyde group or a keto group, an organic hydrazine compound having two or more hydrazine residues, and colloidal silica are contained, and the solid content of the colloidal silica is in the aqueous emulsion. 1 to 100 parts by weight of the polymer component of
˜300 parts by weight.

[0008]

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 of the present invention can be obtained by using a vinyl monomer having a carbonyl group based on an aldehyde group or a keto group as a radically polymerizable vinyl compound.

The amount of the vinyl monomer used is preferably 0.1 to 30 parts by weight with respect to 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.

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

Used in the aqueous emulsion of the present invention,
As other radically polymerizable vinyl compounds, 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-stearyl methacrylate, cyclohexyl methacrylate, etc. Methacrylic acid alkyl ester, 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 Carboxylic group-containing vinyl monomers such as acids, crotonic acid, fumaric acid, maleic acid, itaconic acid, sorbic acid, maleic anhydride, acid anhydrides such as itaconic anhydride, N-phenylmaleimide, N-cyclohexylmaleimide, N -Maleimide derivatives such as butyl maleimide, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-methacrylic acid
Hydroxypropyl, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 6-hydroxy acrylate Vinyl polymerizable monomer having hydroxyalkyl group such as hexyl, amide group-containing vinyl monomer such as methacrylamide, acrylamide, crotonamide and N-methylol acrylamide, epoxy group such as allyl glycidyl ether, glycidyl acrylate and glycidyl methacrylate Examples of the vinyl monomers include aromatic vinyl monomers such as styrene and α-methylstyrene, nitrile group-containing vinyl monomers such as acrylonitrile, and olefin monomers such as butadiene. These components can be used alone or in combination of two or more as necessary.
If necessary, ethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl acrylate, allyl methacrylate, divinylbenzene,
Crosslinking agents such as trimethylolpropane triacrylate can be used.

By using an alkoxysilane compound in the aqueous emulsion of the present invention, the weather resistance of the coating film can be further improved. The alkoxysilane compound can also be used by adding it to the aqueous emulsion, but in that the colloidal silica is more uniformly dispersed, it is emulsion-polymerized with the radical-polymerizable vinyl compound to form an aqueous emulsion. It is preferable to introduce an alkoxysilyl group and / or a silanol group.

The amount of the alkoxysilane compound used is preferably 20 parts by weight or less 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 compound used in the aqueous emulsion of the present invention has the following general formulas (1) to (1).
Examples shown in (7) can be given.

[0016]

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[0017]

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[0018]

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[0019]

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[0020]

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[0021]

[Chemical 6]

[0022]

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(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.

A specific example of the general formula (2) is 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 , Β-methacryloyloxyethylmethyldimethoxysilane can be mentioned.

Specific examples of the general formula (3) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-n-butoxysilane, vinyltris (β-methoxyethoxy) silane, vinylmethyldimethoxysilane and vinylmethyldiethoxy. Examples thereof include silane, vinylethyltrimethoxysilane, vinyldimethylmethoxysilane, isopropenyltrimethoxysilane, isopropenylmethyldimethoxysilane, allyltrimethoxysilane, 5-hexenyltrimethoxysilane, and 9-decenyltrimethoxysilane.

A specific example of the general formula (4) is 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 and m-isopropenylphenylmethyldimethoxysilane can be mentioned.

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
Mention may be made of vinyl trimethoxysilyl undecanoate.

Specific examples of the general formula (7) include trimethoxysilane, dimethoxymethylsilane, dimethoxydimethylsilane, methoxytrimethylsilane, triethoxysilane, diethoxymethylsilane, dimethylethoxysilane, phenyltrimethoxysilane, dimethoxy. Examples thereof include phenylsilane, phenyltriethoxysilane, and diethoxyphenylsilane.

Among the above-mentioned alkoxysilane compounds, preferred are alkoxysilane compounds having a mercapto group and / or an ethylenically unsaturated group of (1) to (3), among which γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane,
γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane and vinyltrimethoxysilane are particularly preferred.
These components can be used alone or in combination of two or more as necessary.

The aqueous emulsion of the present invention can be obtained by subjecting a mixture of the above radically polymerizable compounds to aqueous emulsion polymerization in the presence of a radical polymerization initiator. The polymerization temperature is in the range of 5 to 100 ° C, preferably 40 to 95 ° C, 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 alkylphenyl ether sulfate, and polyoxyethylene alkylphenyl ether phosphate. Phosphate emulsifiers such as sodium salts, potassium oleate, sodium N-lauroyl sarcosinate, sodium N-myristoyl sarcosinate, carboxylic acid emulsifiers such as potassium alkenyl succinate, polyoxyethylene alkyl ester, polyoxyethylene alkylaryl Examples include nonionic emulsifiers such as ether, sulfonate emulsifiers, phosphate emulsifiers, carboxylate emulsifiers. The preferred anionic emulsifier. These may be used in combination of two or more. By using an anionic emulsifier, colloidal silica, which is an essential component of the present invention, can be uniformly dispersed. The amount of these emulsifiers used is usually about 0.5 to 10 parts by weight with respect to 100 parts by weight of the radically polymerizable compound.

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 according to the production conditions, but the usual average particle size is 0.0
It is about 1 to 1 μm.

The aqueous coating composition of the present invention can be used as a coating emulsion by incorporating the above-mentioned aqueous emulsion with an organic hydrazine compound having two or more hydrazine residues. Further, the addition of a relatively small amount of colloidal silica is characterized in that the coating properties such as water resistance and stain resistance are further improved.

The amount of the organic hydrazine compound used in the present invention depends on the number of moles of the carbonyl group based on the aldehyde group or keto group in the polymer (i) and the number of moles of the hydrazine residue in the organic hydrazine compound (ii). The ratio is 0.05 ≦
It is preferable that (ii) / (i) ≦ 5. (Ii)
When / (i) is less than 0.05, the progress of the crosslinking reaction tends to be insufficient, and the water resistance and solvent resistance of the coating film formed tend to be insufficient. The reason is that the residual unreacted organic hydrazine compound tends to adversely affect the appearance and water resistance of the coating film. More preferably, the range is 0.5 ≦ (ii) / (i) ≦ 2.

Specific examples of the above organic hydrazine compound include dicarboxylic acid dihydrazides containing 2 to 10 carbon atoms, particularly 4 to 6 carbon atoms, for example, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide. , Adipic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide and itaconic acid dihydrazide, 2 to
An aliphatic water-soluble dihydrazine having 4 carbon atoms,
For example, ethylene-1,2-dihydrazine, propylene-1,3-dihydrazine, butylene-1,4-dihydrazine and the like can be mentioned. 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 contains colloidal silica as an essential component, and is obtained by mixing the above aqueous emulsion and colloidal silica aqueous dispersion.

As the colloidal silica used in the present invention, various commercially available products having water as a dispersion medium can be used, but those having an average particle diameter of 300 nm or less are preferable. 300n
This is because the transparency and hardness of the resulting coating film tend to be low when a material having a thickness exceeding m is used. The colloidal silica used in the present invention may be surface-treated with a silane compound or the like.

The solid content of colloidal silica in the aqueous coating composition of the present invention needs to be in the range of 1 to 300 parts by weight based on 100 parts by weight of the polymer component constituting the above aqueous emulsion. If less than 1 part by weight,
The hardness, water resistance and stain resistance of the coating film tend to be insufficient, and when it exceeds 300 parts by weight, the storage stability of the aqueous coating composition tends to decrease. More preferably 1-150
It is in the range of parts by weight.

The content of the polymer component in 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 the colloidal silica is preferably a method of mixing the aqueous colloidal silica dispersion with the aqueous emulsion of the polymer obtained by emulsion polymerization. Other methods include, for example, a method of obtaining an aqueous emulsion by emulsion polymerization of a radically polymerizable compound in an aqueous medium containing colloidal silica,
Although this method simplifies the manufacturing process, it tends to lower the polymerization stability.

The aqueous coating composition of the present invention optionally contains various additives such as pigments, ultraviolet absorbers, antioxidants, heat resistance improvers, leveling agents, anti-sagging agents and matting agents. Alternatively, it may be mixed with another emulsion resin, a water-soluble resin, a viscosity control agent, or 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 or spray coating, and can be cured by leaving it at room temperature or by heating it at 50 to 200 ° C.

[0047]

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 the examples and comparative examples was carried out by the method described below.

(1) Transparency A spot-shaped coating film is formed on a glass plate and its transparency is visually evaluated. ◯: Transparent Δ: Semi-transparent ×: White turbid The hardness is measured by scratching the coating film with (3) Water resistance After 100 hours of immersion in warm water of 50 ° C., 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 Δ: No change except that there is slight swelling ×: Swelling and glossing are noticeable (5) Contamination resistance A carbon paste in which carbon black and water are mixed well at a weight ratio of 20/80 is applied. Apply it to the membrane, 30 at 60 ℃
After heating for minutes, it was washed with running water, and the state of adhesion of carbon was visually determined.

◯: No change from before application of carbon paste Δ: Some traces are left ×: Remarkably traces are left (6) Storage stability The state after standing the aqueous coating composition at room temperature for 1 month is visually evaluated ◯: No change x: Aggregation, gelation

[0051]

Example 1 A separable flask equipped with a condenser, a nitrogen introducing tube, a thermometer and a stirrer was charged with deionized water 121.
Part, sodium dodecylbenzene sulfonate as an emulsifier (Kao Corporation, trade name: Neoperex F-25)
Add 2 parts and 0.6 parts of potassium persulfate, and mix with stirring 7
The temperature was raised to 0 ° C. There, methyl methacrylate 42
Part, n-butyl methacrylate 42 parts, 2-ethylhexyl acrylate 11 parts, methacrylic acid 2 parts, and diacetone acrylamide 3 parts were 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, p with ammonia water
H was adjusted to 8 to 9 to obtain an aqueous copolymer emulsion.

Next, the average particle diameter is 10 to 20n.
m colloidal silica aqueous dispersion (silica content 30% by weight, manufactured by Nissan Chemical Industries, Ltd., trade name: Snowtex 3
0) 100 parts was added with stirring, and the mixture was kept at 80 ° C. for 1 hour.

Thereafter, adipic acid dihydrazide 1.9 was obtained.
Parts and 20 parts of butyl cellosolve were added with stirring, and the mixture was further stirred for 30 minutes to obtain an aqueous coating composition.

This aqueous coating composition was applied onto 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
The gross value was 88. The evaluation results of the obtained coating film are shown in Table 1.

[0055]

Example 2 A separable flask equipped with a condenser, a nitrogen introducing tube, a thermometer and a stirrer was charged with 122 deionized water.
Part, sodium dodecylbenzene sulfonate as an emulsifier (Kao Corporation, trade name: Neoperex F-25)
Add 2 parts and 0.6 parts of potassium persulfate, and mix with stirring 7
The temperature was raised to 0 ° C. There, methyl methacrylate 42
Parts, n-butyl methacrylate 42 parts, 2-ethylhexyl acrylate 11 parts, methacrylic acid 2 parts, and diacetone acrylamide 3 parts, γ-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: K
A mixture of 1 part of BM503) 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, adjust the pH to 8 with ammonia water.
Adjustment to 9 gave an aqueous copolymer emulsion. Then, 100 parts of Snowtex 30 was added thereto with stirring, and the mixture was kept at 80 ° C. for 1 hour.

Thereafter, adipic acid dihydrazide 1.9 was obtained.
Parts and 20 parts of butyl cellosolve were added with stirring, and the mixture was further stirred for 30 minutes to obtain an aqueous coating composition.

This aqueous coating composition was applied onto 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
The gross value was 86. The evaluation results of the obtained coating film are shown in Table 1.

[0058]

Example 3 γ-Mercaptopropylmethyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KBM80) instead of γ-methacryloxypropyltrimethoxysilane.
2) A coating film was obtained in the same manner as in Example 2 except that 1 part was used. The 60 ° gloss value of the coating film was 86. The evaluation results of the obtained coating film are shown in Table 1.

[0059]

Example 4 Instead of Snowtex 30 as the colloidal silica used, Snowtex O (average particle size 1
A coating film was obtained in the same manner as in Example 2 except that 0 to 20 nm, silica content 20% by weight, manufactured by Nissan Chemical Industries, Ltd. were used, and the addition amount was 150 parts. The 60 ° gloss value of the coating film was 86. The evaluation results of the obtained coating film are shown in Table 1.

[0060]

Comparative Examples 1 to 3 An aqueous coating composition was produced in the same manner as in Example 1 except that the composition was changed as shown in Table 1, and a coating film was obtained using the aqueous coating composition. As shown in Table 1, the properties of the obtained aqueous coating composition were inferior to those of the examples.

[0061]

[Comparative Example 4] 122 deionized water was placed in a separable flask equipped with a condenser, a nitrogen introducing tube, a thermometer and a stirrer.
Parts, 2 parts of sodium dodecylbenzenesulfonate as an emulsifier and 0.6 parts of potassium persulfate were added, and the temperature was raised to 70 ° C. with stirring. There, methyl methacrylate 2
5 parts, n-butyl methacrylate 29.5 parts, 2-ethylhexyl acrylate 32 parts, 2-hydroxyethyl methacrylate 11.5 parts, methacrylic acid 2 parts, and 1
A mixture of parts of 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, adjust the pH to 8 with ammonia water.
Adjustment to 9 gave an aqueous copolymer emulsion.

Then, 100 parts of Snowtex 30 was added thereto with stirring, and the mixture was kept at 80 ° C. for 1 hour.

After that, water-soluble melamine having a solid content of melamine of 80% by weight (Sumimar M-40W, Sumitomo Chemical Co., Ltd.)
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.

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

[0065]

Comparative Example 5 An aqueous coating composition was produced in the same manner as in Comparative Example 4 except that the composition was changed as shown in Table 1, and a coating film was obtained by using the composition. As shown in Table 1, the properties of the obtained aqueous coating composition were inferior to those of the examples.

[0066]

[Comparative Example 6] Deionized water 51 was placed in a separable flask equipped with a condenser, a nitrogen introducing tube, a thermometer and a stirrer.
Parts, 2 parts of sodium dodecylbenzenesulfonate as an emulsifier, 0.6 parts of potassium persulfate, and 100 parts of Snowtex 30 were added, and the temperature was raised to 70 ° C. with 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 the desired aqueous coating composition could not be obtained.

[0067]

[Table 1]

[0068]

EFFECT OF THE INVENTION The aqueous coating composition of the present invention provides a film having excellent storage stability, hardness, water resistance, stain resistance and weather resistance, and is used as a resin for aqueous emulsion paints in various paint applications. It is possible to do, and it is very useful industrially.

Claims (2)

[Claims] 1. 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, and an organic hydrazine compound having two or more hydrazine residues.
And a colloidal silica, wherein the solid content of the colloidal silica is 1 to 300 parts by weight based on 100 parts by weight of the polymer component in the aqueous emulsion. 2. A polymer which constitutes an aqueous emulsion,
The aqueous coating composition according to claim 1, which contains an alkoxysilyl group and / or a silanol group.