JP2001323211A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous coating composition having excellent storage stability and forming a coating film having excellent weather resistance, transparency, adhesion and the like. SOLUTION: The weight average particle diameter obtained by co-condensing an organosiloxane and a graft crosslinking agent is 5 to 100 nm.
In the presence of an aqueous dispersion containing a polyorganosiloxane polymer having a solubility in water of 20.degree.
5% by mass or less of an oil-soluble radical polymerization initiator,
An aqueous coating composition containing a copolymer obtained by radical polymerization of an ethylenically unsaturated monomer having a solubility in water at 20 ° C of 0.1 to 10% by mass in the presence of an emulsifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an aqueous coating composition having excellent weather resistance. In particular, the present invention is to form a coating film having excellent weather resistance over a long period of time, that is, having excellent gloss retention, yellowing resistance, water resistance and substrate adhesion, and also having excellent transparency. And a water-based coating composition which can be widely used for various water-based paints.

[0002]

2. Description of the Related Art In recent years, from the viewpoints of environmental protection and safety and health, there has been a shift from organic solvent type paints to aqueous type paints, especially aqueous emulsion type paints. For this reason, applications of the water-based paint have been expanded, and accordingly, the required performance of the water-based paint has become higher. Among such required performances, the importance of improving the appearance, weather resistance, storage stability and the like of the coating film has always been pointed out.

[0003] In response to these requirements, Japanese Patent Application Laid-Open No. 58-1805
No. 63 proposes to use a mixture of an acrylic polymer emulsion and a silicone polymer emulsion as a main component of a paint. In addition, Japanese Patent Application Laid-Open
JP-A-261454 reports an acrylic monomer copolymerized in the presence of a silicone polymer emulsion. However, when such a composition is used, the compatibility between the acrylic copolymer and the silicone polymer is poor, and the refractive index is also different, so that the transparency of the coating film is impaired or the coating film is damaged. When formed, the acrylic component and the silicone component are separated from each other, resulting in a drawback that sufficient water resistance and coating strength cannot be obtained.

[0004] In order to solve the above problems, Japanese Patent Laid-Open No.
In JP-A-12311, an aqueous dispersion of a low-molecular-weight silicone polymer and a radical polymerizable monomer is copolymerized by using an oil-soluble initiator or a reactive emulsifier. I have. However, in this case, since the polymerization stability is impaired when a high molecular weight silicone polymer is used, only a low molecular weight silicone polymer can be used. is there.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides an aqueous solution which is excellent in storage stability and forms a coating film excellent in weather resistance, transparency, adhesion and the like. It is intended to provide a coating composition.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that an aqueous dispersion of a polyorganosiloxane polymer having a weight-average particle diameter in a specific range can be obtained. Excellent weather resistance by radical polymerization using an ethylenically unsaturated monomer having a specific range of water solubility and an oil-soluble radical polymerization initiator having a specific range of water solubility. The present inventors have found that an aqueous coating composition having excellent properties such as transparency, adhesion, and storage stability can be obtained, thereby completing the present invention.

That is, the aqueous coating composition of the present invention is obtained by co-condensing an organosiloxane (I) with a graft-linking agent (II) and having an average particle diameter of 5 to 100 nm. (III) In the presence of 1 to 50% by mass (solid content) of an aqueous dispersion, (a) an oil-soluble radical polymerization initiator (IV) having a solubility in water at 20 ° C of 0.5% by mass or less. (B) 1 to 99% by mass of an ethylenically unsaturated monomer (V) having a solubility in water at 20 ° C of 0.1 to 10% by mass.
And (c) other ethylenically unsaturated monomers (VI) from 0 to 98% by mass ((III) + (V) + (VI) = 100% by mass); (d) 100% by mass of the obtained copolymer 0.5 to
It is characterized by containing a copolymer (A) obtained by radical polymerization in the presence of 10% by mass (solid content) of an emulsifier.

Here, it is preferable that the copolymer (A) contains an ethylenically unsaturated carboxylic acid monomer unit in an amount of 0.1 to 10% by mass. Further, the emulsifier used for polymerizing the copolymer (A) is preferably a so-called reactive emulsifier having a radically polymerizable ethylenically unsaturated group in the molecule.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Organoshiro used in the present invention
Xan (I) is, for example, of the general formula R¹ _mSIO
_{(4-m) / 2}(Where R¹Is a substituted or unsubstituted monovalent hydrocarbon
And m represents an integer of 0 to 3).
Having a linear, branched or cyclic structure.
It has a structure. This organosiloxane (I)
As a substituted or unsubstituted monovalent hydrocarbon group possessed by
For example, methyl group, ethyl group, propyl group, vinyl group,
Phenyl groups and their hydrogen atoms are replaced by halogen or
Examples include a substituted hydrocarbon group substituted with an ano group.
You.

[0010] Specific examples of the organosiloxane (I) include:
Other than cyclic compounds such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and trimethyltriphenylcyclotrisiloxane, linear or branched organosiloxanes may be mentioned. Can be. The organosiloxane (I)
May be a pre-polymerized polyorganosiloxane. In this case, the terminal of the molecular chain may be blocked with a hydroxyl group, an alkoxy group, a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, a methyldiphenylsilyl group, or the like.

[0011] The graft crosslinking agent (II) used in the present invention comprises:
For example, one or more hydrolyzable silyl groups may be
Those containing two or more ethylenically unsaturated groups or mercapto groups can be mentioned. As the hydrolyzable silyl group, an alkoxysilyl group is preferable in terms of polymerization reactivity, ease of handling, and the like. Specific examples of the graft crosslinking agent include vinylsilanes such as vinylmethyldimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane, and 3- (meth) acryloxypropyltrimethoxysilane and 3- (meth) acryloxypropylmethyldimethoxysilane. (Meth) acryloxyalkylsilanes such as 3- (meth) acryloxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane,
And mercaptoalkylsilanes such as mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropylmethyldiethoxysilane. These components can be used alone or in combination of two or more as necessary.

[0012] The proportion of the graft crosslinking agent (II) used is 0.1 to 30% by mass, preferably 0.5 to 20% by mass, based on the total amount of the components (I) and (II). Often,
By using 0.1% by mass or more of a graft crosslinking agent, a high molecular weight polyorganosiloxane polymer (III)
Graft polymerization of the ethylenically unsaturated monomer component and the ethylenically unsaturated monomer component is efficiently performed, and the weather resistance and water resistance of the coating film can be improved. Further, by using 30% by mass or less of the grafting agent, the weather resistance of the coating film can be effectively improved.

[0013] The weight average particle diameter of the polyorganosiloxane polymer (III) obtained by co-condensing the organosiloxane (I) and the graft crosslinking agent (II) must be in the range of 5 to 100 nm. This means that the weight average particle diameter is 5 nm.
Because less than less water resistance of the obtained coating film,
This is because if the weight average particle size exceeds 100 nm, the transparency of the coating film obtained is poor. Preferably it is in the range of 5 to 50 nm.

The polyorganosiloxane polymer (III) is polymerized by forcibly emulsifying and dispersing the organosiloxane (I) and the graft-linking agent (II) in water by using a homomixer or a pressure homogenizer. It can be produced by adding an acid such as alkylbenzene sulfonic acid as an agent and subjecting it to polycondensation. After this polycondensation, the acid component can be neutralized with an alkali component to be used as an emulsifier.

[0015] The amount of the polycondensation initiator used is preferably in the range of 0.1 to 30% by mass based on the total amount of the components (I) and (II). This is because the use of the polycondensation initiator in this range tends to make it easier to design the weight average particle size of the polyorganosiloxane polymer (III) in the range of 5 to 100 nm. Preferably it is in the range of 1 to 20% by mass.

Also, a polyorganosiloxane polymer (III)
Has a weight average molecular weight of 10,000 or more, preferably 50,000 or more. By using such a relatively high molecular weight polyorganosiloxane copolymer (III), the weather resistance of the coating film can be improved.

[0017] The copolymer (A) used in the aqueous coating composition of the present invention is prepared by adding a radical polymerization initiator in the presence of the aqueous dispersion of the polyorganosiloxane polymer (III) obtained as described above. It is obtained by adding an ethylenically unsaturated monomer (V) containing (IV) to start polymerization, and then further adding an ethylenically unsaturated monomer (VI) and polymerizing.

The radical polymerization initiator (IV) used for the graft polymerization of the polyorganosiloxane polymer (III) with the ethylenically unsaturated monomers (V) and (VI) has a solubility in water at 20 ° C. Is not particularly limited as long as it is 0.5% by mass or less, and a known material can be used. By using a radical polymerization initiator having a solubility in water at 20 ° C. of 0.5% by mass or less, the permeation of the initiator into the polyorganosiloxane polymer (III) can be efficiently performed, and thus, it is obtained. In the aqueous dispersion particles of the copolymer (A), the compatibility between the polyorganosiloxane component and the polymer component comprising an ethylenically unsaturated monomer is improved, and a coating film having excellent weather resistance can be obtained. .

Conversely, when an initiator having a solubility in water at 20 ° C. of more than 0.5% by mass is used, the grafting of the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomer (V) is performed. The transparency and weather resistance of the coating film obtained from the aqueous coating composition containing the copolymer (A) obtained by polymerization are reduced.

Specific examples of the radical polymerization initiator having a solubility in water at 20 ° C. of 0.5% by mass or less include azobisisobutyronitrile and 2,2-azobis (2,4-dimethylvaleronitrile). Azo compounds such as 2,2-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, benzoyl peroxide, cumene hydropar Organic peroxides such as oxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate and the like can be mentioned. These initiators can be used alone, or two or more initiators can be used in combination. In addition, as long as it does not affect the water resistance, it can be used as a redox type in combination with a reducing agent such as ferrous sulfate / dextrose or sodium hydrogen sulfite.

The ethylenically unsaturated monomer component (V) used in the copolymer (A) constituting the aqueous coating composition of the present invention has a solubility in water at 20 ° C. of 0.1 to 10%. It is necessary to use a compound having a solubility of 1 to 10% by mass, and more preferably a compound having a solubility of 1 to 10% by mass. By using an ethylenically unsaturated monomer having a solubility in water at 20 ° C. of 0.1% by mass or more, the oil-soluble radical polymerization initiator (IV) can be efficiently used in the polyorganosiloxane polymer (III). It can penetrate well and enables highly efficient graft polymerization between the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomer (V). On the contrary, the solubility in water at 20 ° C. is 10 mass. % Or less, the weather resistance of the coating film can be improved.

Conversely, the solubility in water at 20 ° C. is 0.1%
When less than the ethylenically unsaturated monomer is used, the radical polymerization initiator (IV) does not sufficiently penetrate into the polyorganosiloxane polymer (III), so that the polyorganosiloxane polymer (III) )) And the ethylenically unsaturated monomer (V), which is not preferable because the polymerization becomes unstable and a large amount of aggregates are formed.

When an ethylenically unsaturated monomer having a solubility in water at 20 ° C. of more than 10% by mass is used, the hydrophilicity of the coating film increases, and the water resistance of the coating film deteriorates. The weather resistance will also be reduced.

The amount of the ethylenically unsaturated monomer (V) used is 1
It is in the range of ~ 99 mass%, preferably 5-79 mass%. Within this range, the permeation of the radical polymerization initiator (IV) into the polyorganosiloxane polymer (III) is sufficiently performed, so that the polyorganosiloxane polymer (III)
Obtained from the aqueous coating composition of the present invention comprising a copolymer (A) obtained by the radical polymerization of ethylenically unsaturated monomer (V) and the subsequent ethylenically unsaturated monomer. The transparency and weather resistance of the coating film are improved. If the amount of the ethylenically unsaturated monomer (V) is less than 1% by mass, the polymerization of the polyorganosiloxane polymer (III) with the ethylenically unsaturated monomers (V) and (VI) does not proceed sufficiently. result,
The transparency of the coating film obtained from the aqueous coating composition of the present invention decreases.

[0025] Specific examples of the ethylenically unsaturated monomer (V) used include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl acrylate, and i-acrylate.
-Butyl, t-butyl acrylate, glycidyl (meth) acrylate, tetrafurfuryl (meth) acrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, ethylene glycol dimethacrylate, triethylene dimethacrylate (Meth) acrylic acid esters such as glycol, 2-methacryloyloxyethyl succinate, 2-methacryloyloxyethyl maleate, hexahydrophthalic acid-methacryloyloxyethyl, diethylaminoethyl methacrylate, and acrylonitrile and methacrylonitrile. Vinyl cyanide compounds, furthermore, various aromatic vinyl compounds and ethylenically unsaturated carboxylic acid vinyl ester compounds and mixtures thereof, and have a solubility in water at 20 ° C. of 0.1 to 10
It is not limited to the above as long as it is in mass%.

The other ethylenically unsaturated monomers (V) used in the copolymer (A) contained in the aqueous coating composition of the present invention
Examples of I) include n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and (meth) acrylic. (Meth) acrylic acid alkyl ester compounds such as cyclohexyl acid; aromatic vinyl compounds such as styrene and vinyltoluene; and conjugated diene compounds such as 1,3-butadiene, isoprene, and 2-chloro-1,3-butadiene. Is not limited to these as long as they are radically polymerizable.

The copolymer (A) contained in the aqueous coating composition of the present invention contains the above-mentioned ethylenically unsaturated monomer as a monomer unit derived from the ethylenically unsaturated monomer (VI). It is preferable that, in addition to the units derived from the monomer, a unit from an ethylenically unsaturated carboxylic acid monomer unit is contained, and the amount of such a monomer unit is based on the copolymer (A). 0.
It is preferably from 5 to 10% by mass, more preferably from 1 to 8% by mass. The copolymer (A) has an ethylenically unsaturated carboxylic acid monomer unit of 0.5% by mass or more, so that the adhesion to various base materials and the dispersion stability during storage and blending into a paint are effectively achieved. Conversely, by having 10% by mass or less of an ethylenically unsaturated carboxylic acid monomer unit, the copolymer (A) can be easily polymerized without impairing the stability during polymerization. be able to.

Specific examples of the ethylenically unsaturated carboxylic acid monomer contained in the copolymer (A) contained in the aqueous coating composition of the present invention include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itacone Acid, 2-methacryloxyethyl succinic acid, 2-methacryloxyethyl phthalic acid, 2-methacryloxyethyl hexahydrophthalic acid, and the like.

In the process of polymerizing the copolymer (A) contained in the aqueous coating composition of the present invention, the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomers (V) and (V)
As the emulsifier used in the polymerization with I), various known emulsifiers such as anionic, cationic and nonionic types used in general emulsion polymerization can be used. It is preferred to use anionic emulsifiers such as sodium, potassium or ammonium salts.

Further, in the present invention, it is more preferable to use a so-called reactive emulsifier having a radically polymerizable ethylenically unsaturated group in order to improve the storage stability of the emulsion and the water resistance of the coating film. . Examples of such reactive emulsifiers include Eleminol (trademark) JS-2 manufactured by Sanyo Chemical Co., Ltd. and Latemul (trademark) manufactured by Kao Corporation.
S-120, S-180, S-180A, Adeka Riasoap (trademark) SE-10N manufactured by Asahi Denka Kogyo KK, Aqualon HS series manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and the like.

The emulsifier used for preparing the copolymer (A) may be used alone or in combination of two or more, and the amount of the emulsifier used is 100% of the copolymer (A). It is 0.5 to 10% by mass (solid content), preferably 0.5 to 5% by mass (solid content). By adding the emulsifier in an amount of 0.5% by mass or more to adjust the copolymer (A), the dispersion stability can be improved, and conversely, the copolymer may be added in an amount of 10% by mass or less. By adjusting (A), a copolymer (A) having excellent dispersion stability can be obtained without reducing the water resistance of the coating film.

The composition charged when polymerizing the ethylenically unsaturated monomers (V) and (VI) in the presence of the aqueous dispersion of the polyorganosiloxane polymer (III) is as follows: , The component (III) is 1 to 50% by mass, and the component (V) is 1 to 50% by mass based on the total amount of the components (V) and (VI).
99% by mass, component (VI) is 0 to 98% by mass, preferably 5 to 75% by mass of component (V) and 20 to 50% by mass of component (III). 90% by mass. When the aqueous coating composition of the present invention is used, the solid concentration of the polyorganosiloxane emulsion is usually from 20 to 70% by mass, preferably from 30 to 60% by mass.
% By mass.

In the present invention, the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomers (V) and (VI)
And more preferably, as a procedure for efficiently proceeding the copolymerization with a reactive emulsifier, a method in which a radical polymerization initiator (IV) is dissolved in part or all of an ethylenically unsaturated monomer (V) Polyorganosiloxane polymer (III)
And then the remaining ethylenically unsaturated monomers (V) and (VI) and a reactive emulsifier are added and impregnated to form a batch polymerization, or radical polymerization to the polyorganosiloxane polymer (III) After the initiator (IV) is dissolved and impregnated with one part or all of the ethylenically unsaturated monomer (V) and polymerized, the remaining ethylenically unsaturated monomer (V) and ( VI), and a divided drop polymerization method in which a reactive emulsifier is added dropwise to carry out polymerization.

[0034] The aqueous coating composition of the present invention may optionally contain a film-forming aid in order to improve the film-forming properties. Specific examples of such a film-forming auxiliary include:
Methanol, ethanol, 2-propanol, ethylene glycol, propylene glycol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, ethyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol mono n-butyl ether, etc. Is mentioned. Further, the aqueous coating composition of the present invention contains various additives such as known pigments and ultraviolet absorbers, antioxidants, heat resistance improvers, leveling agents, anti-sagging agents, matting agents, and the like, if necessary. It may be used in combination with another emulsion resin, a water-soluble resin, a viscosity controlling agent, and the like.

[0035]

The present invention will be described below in more detail with reference to examples. All “parts” in the examples are parts by mass. The evaluation of the performance in Examples and Comparative Examples was performed using the following method.

[0036] The solubility in water at 20 ° C in the text is expressed as solubility mass% (= mass of solute [kg] / solvent (20 ° C
Water) (mass [kg] x 100) [wt%].

(1) Residue after heating 3 g of an aqueous dispersion of the polyorganosiloxane polymer (III) was weighed on an aluminum dish, and the weight change after drying for 4 hours in a thermostat (150 ° C.) (weight after drying / drying) Weight before (wt
%)).

(2) Particle size Dynamic light scattering particle size DLS-600 [manufactured by Otsuka Electronics Co., Ltd.]
The resin particle size (weight-average particle size) in the aqueous dispersion of the polyorganosiloxane polymer (III) was measured in the above.

(3) Weather resistance test Taipaque R-930 (manufactured by Ishihara Sangyo Co., Ltd., titanium oxide sulfate method) 196.3 g, OROTAN SG (manufactured by Rohm & Haas Co., pigment dispersant) 2.1 g, Surfynol DF- 58 (made by Air Products, defoamer) 0.0
8 g, propylene glycol 29.4 g, deionized water 3
After sufficiently mixing 4.3 g and 1.8 g of a 28% aqueous ammonia solution, glass beads were added, the pigment was dispersed with a high-speed disperser for 30 minutes, and the glass beads were filtered off with a 300 mesh nylon gauze for evaluation. Mill base. Then, 120 g of the aqueous coating composition (emulsion) (based on a solid content of 45%) was added to the above mill base 55 for evaluation.
g, Kyowanol M (Kyowa Hakko Co., Ltd., plasticizer)
6.4 g and 1.5 g of RHEOLATE 350 (manufactured by RHEOX, a thickener) were added in order, and after sufficient stirring, the mixture was adjusted by adding deionized water with a Ford cup # 4 so as to be about 100 seconds to 140 seconds. .

After the adjustment, filtration was performed again using a 300 mesh nylon gauze to prepare a white enamel aqueous paint for a weather resistance test. This water-based paint was applied to a zinc phosphate-treated steel sheet of 150 mm × 70 mm using a bar coater # 40, and was coated at 20 ° C. ×
After setting in an environment of 65% Rh for 30 minutes, the coating was dried in a dryer at 80 ° C. for 1 hour to prepare a coated plate for a weather resistance test.

After applying a polyester tape to the painted surface of the painted plate to prevent water droplets and the like from being attached to the place other than the painted surface during the weather resistance test, the irradiance was reduced to 30.
W / m ² Irradiation temperature 70 ° C., wet temperature 50 ° C., 1 cycle 12 hours (irradiation time 8 hours, wet time 4 hours) DuPanel light control weather meter DPWL-5 manufactured by Suga Test Instruments Co., Ltd. And the weather resistance test was performed using the retention rate of 60 ° gloss after 1000 hours and the color difference (ΔE value) as indices.

(4) Transparency test 20% by weight (based on solids) of butylcellosolve as a plasticizer and RH as a thickener were added to the aqueous coating composition (emulsion).
3 wt% (relative to solid content) of RHEOLATE 350 manufactured by EOX was added, and the mixture was sufficiently stirred and filtered with a 300 mesh nylon gauze to prepare an aqueous paint.

[0043] This water-based paint was coated with transparent Pyrex (registered trademark).
Paint on a glass plate with a bar coater # 40, 20 ° C x 65
After setting for 30 minutes in an environment of% Rh, 8
After drying in a dryer at 0 ° C. for 1 hour, the transparency of the coating film was visually confirmed and evaluated according to the following criteria.

A: The coating film is glossy, and slight whitening and coloring are not observed. ：: The coating film is glossy, but very slight whitening is observed. Δ: The coating film is slightly whitened or in a matte state. X: A clear whitening or matting state is confirmed in the coating film.

(5) Water Resistance Test Butylcellosolve as a plasticizer was added to the aqueous coating composition (emulsion) at 20 wt% (based on solid content) as a thickener RH.
3 wt% (relative to solid content) of RHEOLATE 350 manufactured by EOX was added, and the mixture was sufficiently stirred and filtered with a 300 mesh nylon gauze to prepare an aqueous paint.

This water-based paint was coated on a zinc phosphate-treated steel sheet of 150 mm × 70 mm with a bar coater # 40, and was coated at 20 ° C. ×
After setting in an environment of 65% Rh for 30 minutes, it was dried in a dryer at 80 ° C. for 1 hour to prepare a coated plate for a water resistance test. After attaching a polyester tape to the painted surface of the painted plate to prevent water droplets and the like from being applied during the water resistance test from adhering to places other than the painted surface,
The film was immersed in warm water at ℃ and left for 7 days, then taken out. The coating film immediately after being taken out was visually checked for whitening and blisters, and evaluated according to the following criteria.

◎: No boundary between a portion immersed in warm water and a portion not immersed in the coating film was observed, and neither whitening nor blistering of the coating film was observed. ：: A portion immersed in hot water and a portion not immersed in the coating film. , But no whitening or blistering of the coating film Δ: slight whitening or blistering in the coating film X: clear whitening or blistering in the coating film

(6) Storage stability The storage stability was evaluated according to the following criteria by checking changes in viscosity, pH, etc. after immersion in a constant temperature water bath at 50 ° C. for 168 hours.

：: No generation of aggregates, change in viscosity and pH
Less than 0.5 and change in viscosity is less than 5% of the initial value Δ: Change in viscosity and pH is less than 1.0 and change in viscosity is less than 10% of the initial value ×: It is considered to be aggregates That could not be used as a coating material due to the occurrence of gelation, etc.

<Preparation of Polyorganosiloxane Polymer> (Silicone Polymerization Example 1) 98 parts of a mixture of cyclic dimethylsiloxane oligomer trimers to heptamers, which is the compound of the formula (I) defined in the present invention, are similarly described in claim 1. A composition comprising 2 parts of the compound (II) shown, γ-methacryloxypropylmethyldimethoxysilane, 310 parts of water and 0.67 parts of sodium dodecylbenzenesulfonate is premixed with a homomixer, and then mixed with a pressure homogenizer. 20
Forced emulsification was performed at a pressure of 0 kg / cm2 to obtain a silicone raw material emulsion.

Next, 90 parts of water and 10 parts of dodecylbenzenesulfonic acid were charged into a flask equipped with a stirrer, a condenser, a heating jacket and a dropping pump, and the mixture was stirred for 4 hours while maintaining the temperature inside the flask at 85 ° C. The above silicone raw material emulsion was dropped. After completion of the dropwise addition, the polymerization was further allowed to proceed for 1 hour, and then cooled, and sodium hydroxide in an equimolar amount to dodecylbenzenesulfonic acid was added to obtain a polyorganosiloxane polymer (III-1). Table 1 shows the characteristic values.

(Silicone Polymerization Example 2) By the same polymerization method as in Silicone Polymerization Example 1, a polyorganosiloxane polymer emulsion (III-2) having the composition shown in Table 1 was obtained. Table 1 shows the characteristic values.

(Silicone Polymerization Example 3) Similarly, 98 parts of a mixture of cyclic dimethylsiloxane oligomer 3 to 7-mer, 2 parts of γ-methacryloxypropylmethyltrimethoxysilane,
A composition consisting of 200 parts of water, 0.67 parts of dodecylbenzenesulfonic acid and 0.67 parts of sodium dodecylbenzenesulfonate was premixed with a homomixer, and then emulsified by a pressure homogenizer at a pressure of 200 kg / cm2 to form silicone. A raw material emulsion was obtained.

This silicone raw material emulsion was charged all at once into a flask equipped with a stirrer, a condenser, a heating jacket and a dropping pump, heated to 80 ° C., reacted under stirring for 6 hours, and then cooled to dodecylbenzenesulfonic acid. And an equimolar amount of sodium hydroxide were added to obtain a polyorganosiloxane polymer (III-3). Table 1 shows the characteristic values.

Example 1 A part of the obtained polyorganosiloxane polymer (III-1) was added to 2,2-azobis (2,4-
5 parts of methyl methacrylate (MMA) in which 0.15 parts of (dimethylvaleronitrile) are dissolved are mixed with stirring, and the mixture is stirred at room temperature under a nitrogen atmosphere for 40 minutes. Thereafter, 62 parts of water are charged and added all at once to a flask which has been heated to 80 ° C. and provided with a stirrer, a condenser, a temperature controller, a dropping pump and a nitrogen inlet tube. After the flask was maintained at 80 ° C. for 5 minutes with stirring, the temperature was changed to 32 parts of t-butyl methacrylate, 25 parts of n-butyl methacrylate, and 2 parts of acrylic acid.
35 parts of ethylhexyl, 2 parts of acrylic acid, 55 parts of Neoperex F-255, and 0.1 part of a 28% aqueous ammonia solution, which had been previously emulsified and dispersed in 40 parts of water, were added dropwise over 2 hours to carry out polymerization. After the completion of dropping, the temperature was raised to 90 ° C.
After keeping for a period of time, 0.125 parts of t-butylperoxy-2-ethylhexanoate was added, and the mixture was kept for another 2 hours. After the reaction solution was cooled to room temperature, it was neutralized with a 28% aqueous ammonia solution to obtain a polyorganosiloxane-based emulsion (aqueous coating composition). Table 2 shows the composition and characteristic values of the polyorganosiloxane-based emulsion of Example 1, and Table 4 shows the performance evaluation results of the coating film.

(Examples 2 to 6) By the same polymerization method as in Example 1, polyorganosiloxane-based emulsions having the compositions shown in Table 1 were prepared. Table 2 shows the composition and characteristic values of the polyorganosiloxane emulsions of these examples.
Table 4 shows the evaluation results of the coating films.

Comparative Examples 1 to 7 Polyorganosiloxane emulsions having the compositions shown in Table 2 were prepared in the same manner as in Example 1. In Comparative Example 2, the polyorganosiloxane polymer (III-3) was used as it was.
In Comparative Example 3, the radical polymerization initiator (IV) was dissolved in cyclohexyl methacrylate, which is the compound of (VI), instead of the ethylenically unsaturated monomer (V). Used in formulation. Table 3 shows the compositions and characteristic values of the polyorganosiloxane emulsions of these comparative examples, and Table 4 shows the evaluation results of the coating films.

However, in Comparative Example 3, a remarkably large amount of cullet was generated during polymerization, and in Comparative Example 5, an ethylenically unsaturated monomer (VI) in which a radical polymerization initiator (IV) was dissolved was used as a polyorganosiloxane polymer. It was difficult to continue the polymerization because the polyorganosiloxane polymer was aggregated at the stage of addition to the aqueous dispersion of the coalescence (III), and the polymerization was stopped. Therefore, the coating film could not be evaluated.

[0059]

【table 1】

[0060]

[Table 2]

(Note) Neoperex F-25 (solid content 25% by mass) and Latemul S-180A (solid content 50% by mass)
Is an anionic emulsifier made by Kao Corporation ABEX 23S (solid content: 60% by mass) is an anionic emulsifier made by Rhodia Co., Ltd. Adecaria Soap SE-10N (solid content: 100% by mass)
Is an anionic emulsifier manufactured by Asahi Denka Co., Ltd.

[0062]

[Table 3]

(Note) Neoperex F-25 (solid content 25% by mass) and Latemul S-180A (solid content 50% by mass)
Is an anionic emulsifier made by Kao Corporation ABEX 23S (solid content: 60% by mass) is an anionic emulsifier made by Rhodia Co., Ltd. Adecaria Soap SE-10N (solid content: 100% by mass)
Is an anionic emulsifier manufactured by Asahi Denka Co., Ltd.

[0064]

[Table 4]

(Note) Comprehensive evaluation was performed according to the following criteria: ◎: Gloss retention of 90% or more, ΔE5 or less, transparency, water resistance, storage stability of 以上 or more ：: Gloss retention of 85% or more, Δ Less than E7, transparency and water resistance, storage stability both ○ or more △: Gloss retention 80% or more, ΔE10 less than transparency, water resistance, storage stability 以上 or more ×: Gloss retention less than 80%, or , ΔE10 or more, or less than transparency ○ level, less than water resistance ○ level, or less than storage stability ○ level

[0066]

Industrial Applicability The present invention provides an aqueous coating composition which is excellent in storage stability and forms a coating film excellent in weather resistance, transparency, adhesion and the like, and is industrially very useful. Things.

Claims (3)

[Claims] A weight average particle diameter of 5 obtained by co-condensing an organosiloxane (I) and a graft crosslinking agent (II).
In the presence of an aqueous dispersion containing 1 to 50% by mass (solid content) of a polyorganosiloxane polymer (III) having a range of from 100 to 100 nm, (a) the solubility in water at 20 ° C. is 0.5% by mass. (B) an ethylenically unsaturated monomer (V) having a solubility in water at 20 ° C. of 0.1 to 10% by mass (V) 1 to 99% by mass using the following oil-soluble radical polymerization initiator (IV) %
And (c) other ethylenically unsaturated monomers (VI) from 0 to 98% by mass ((III) + (V) + (VI) = 100% by mass); (d) 100% by mass of the obtained copolymer For 0.5
An aqueous coating composition containing a copolymer (A) obtained by radical polymerization in the presence of 10 to 10% by mass of an emulsifier. 2. The aqueous coating composition according to claim 1, wherein the ethylenically unsaturated carboxylic acid monomer unit is contained in the copolymer (A) in an amount of 0.1 to 10% by mass. 3. The aqueous coating composition according to claim 1, wherein the emulsifier is a reactive emulsifier.