JP2001131466A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous coating composition which is excellent in weatherability, transparency, adhesiveness, storage stability. SOLUTION: The composition comprises a copolymer obtained by radical polymerization by use of an ethylenically unsaturated monomer having a solubility in water within a specified range and an oil-soluble radical polymerization initiator having a solubility in water within a specified range in the presence of an aqueous dispersion of a polyorganosiloxane.

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 comprises a polyorganosiloxane emulsion and forms a coating having excellent weather resistance over a long period of time, that is, excellent gloss retention, yellowing resistance, water resistance, transparency and substrate adhesion. 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 health and safety, there has been an increasing 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. In particular, as such performance, the appearance, weather resistance, storage stability, and the like of the coating film are always pointed out by the importance of improvement.

In response to these requirements, Japanese Patent Application Laid-Open No. 58-18 / 1983
No. 0563 proposes to use a mixture of an acrylic polymer emulsion and a silicone polymer emulsion as a main component of the paint. In addition, Japanese Unexamined Patent Application Publication No.
No. 261454 proposes 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, they are separated from each other, resulting in a drawback that sufficient water resistance and coating film strength cannot be obtained.

In order to solve the above problems, Japanese Patent Application Laid-Open No. 11-12311 discloses that an aqueous dispersion of a low molecular weight silicone polymer and a monomer is used with an oil-soluble initiator or a reactive emulsifier. Accordingly, copolymerized products have been proposed. 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]

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art as described above, and provides weather resistance, transparency, adhesion, and the like.
An object is to provide an aqueous coating composition having excellent storage stability and the like.

[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, it has been found that, in the presence of an aqueous dispersion of a polyorganosiloxane polymer, the solubility in a specific range of water is reduced. It has excellent weather resistance, transparency and adhesion by radical polymerization using an ethylenically unsaturated monomer having an oil-soluble radical polymerization initiator having a specific range of water solubility. It has been found that an aqueous coating composition having excellent performance in storage stability and the like can be obtained, and the present invention has been completed.

That is, the aqueous coating composition of the present invention comprises 1 to 50% by mass (solid content) of a polyorganosiloxane polymer (III) obtained by co-condensing an organosiloxane (I) and a graft-linking agent (II). (A) using an oil-soluble radical polymerization initiator (IV) having a solubility in water of 0.5% by mass or less at 20 ° C. in the presence of the aqueous dispersion of (b), Solubility of 0.1 to 10
1 to 99% by mass of the ethylenically unsaturated monomer (V), which is 1% by mass, and (c) 0 other ethylenically unsaturated monomer (VI).
９８98% by mass ((III) + (V) + (VI) = 100
(D) contains (A) a copolymer (A) obtained by radical polymerization in the presence of 0.5 to 5 parts by mass of an emulsifier with respect to 100 parts by mass of the obtained copolymer. .

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

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The organosiloxane (I) used in the present invention has, for example, the general formula R ¹ _m SiO _{(4-m) / 2}
(Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group, and m represents an integer of 0 to 3), and has a linear or branched structure. Or it has a cyclic structure. Examples of the substituted or unsubstituted monovalent hydrocarbon group possessed by the organosiloxane (I) include a methyl group, an ethyl group, a propyl group, a vinyl group, a phenyl group and a hydrogen atom of such a group represented by a halogen atom or a cyano group. Examples thereof include a substituted substituted hydrocarbon group.
Specific examples of the organosiloxane (I) include, in addition to cyclic compounds such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and trimethyltriphenylcyclotrisiloxane, A chain or branched organosiloxane can be mentioned. In addition, this organosiloxane (I) may be a polyorganosiloxane previously polymerized. 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.

The graft crosslinking agent (I) used in the present invention
Examples of I) include those containing one or more hydrolyzable silyl groups and one or more ethylenically unsaturated groups or mercapto groups in the molecule. 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 vinylmethyldimethoxysilane,
Vinylsilanes such as vinyltrimethoxysilane and vinyltriethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, and 3- (meth) acryloxypropyltriethoxysilane (Meth) acryloxyalkylsilanes, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltriethoxysilane,
And mercaptoalkylsilanes such as 3-mercaptopropylmethyldiethoxysilane. These components can be used alone or in combination of two or more as necessary.

The use ratio of the above grafting agent (II) is 0.1% with respect to the total mass of the components (I) and (II).
The amount is preferably from 30 to 30% by mass, preferably from 0.5 to 20% by mass, and by using a graft-linking agent of 0.1% by mass or more, the high molecular weight polyorganosiloxane polymer (III) and Graft polymerization of the unsaturated monomer component is efficiently performed, and the weather resistance and water resistance of the coating film can be effectively improved. Further, by using a graft crosslinking agent of 30% by mass or less, the graft ratio can be improved without lowering the molecular weight of the polyorganosiloxane (III), and the weather resistance of the coating film can be effectively improved.

Polyorganosiloxane polymer (III)
Is a method in which an acid such as alkylbenzene sulfonic acid is added as a polycondensation initiator to a product obtained by forcibly emulsifying and dispersing the organosiloxane (I) and the graft-linking agent (II) in water using a homomixer or a pressure homogenizer. It can be used as an emulsifier by neutralizing the acid component with an alkali component after the polycondensation. The amount of the polycondensation initiator to be used is not particularly limited, and can be arbitrarily set according to polymerization conditions such as a molecular weight, a solid content, and a polymerization temperature of a target polyorganosiloxane polymer. For rapid progress, it is desirable to use an amount of 0.5% by mass or more based on the total amount of the organosiloxane (I) component and the graft crosslinking agent (II) component.

The polyorganosiloxane polymer (III) thus obtained has an average molecular weight of 10,0.
It is preferably at least 00, more preferably at least 50,000. By using such a relatively high molecular weight polyorganosiloxane copolymer (III), it becomes possible to particularly improve the weather resistance of the coating film. The copolymer (A) used in the aqueous coating composition of the present invention is prepared by adding a radical polymerization initiator (I) to the aqueous dispersion of the polyorganosiloxane polymer (III) obtained as described above.
V) containing an ethylenically unsaturated monomer (V),
After infiltration of (IV) and (V) into (III), the polymerization is initiated and then further ethylenically unsaturated monomers (V
It is obtained by adding I) and an emulsifier and polymerizing.

Polyorganosiloxane polymer (III)
The radical polymerization initiator (IV) used for the graft polymerization of ethylenically unsaturated monomers (V) and (VI) is 2
There is no particular limitation as long as the solubility in water at 0 ° C. is 0.5% by mass or less, and known compounds can be used. By using a radically polymerizable initiator having a solubility in water of 0.5% by mass or less at 20 ° C., the permeation of the initiator into the polyorganosiloxane polymer (III) is efficiently carried out. Unsaturated monomer (V)
In the copolymerization with (VI) and (VI), the graft ratio and compatibility are improved, and a coating film having excellent weather resistance can be obtained.

Conversely, the solubility in water at 20 ° C. is 0.
When the initiator exceeds 5% by mass, a high graft ratio cannot be obtained in the graft polymerization of the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomer (V), and the transparency of the coating film and the The weather resistance decreases. Specific examples of the radical polymerization initiator having a solubility in water at 20 ° C. of 0.5% by mass or less include azobisisobutyronitrile,
Poorly water-soluble azo compounds such as 2,2-azobis (2,4-dimethylvaleronitrile) and 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, benzoyl peroxide, cumene hydroperoxide, t- Organic peroxides such as butylperoxy-2-ethylhexanoate and t-butylperoxyisobutyrate are exemplified. These initiators can be used alone, or 2
More than one initiator may 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
May have a solubility in water at 20 ° C. of 0.1 to 10
It is necessary to use a compound having a solubility in the range of 1 to 10% by mass, more preferably 1 to 9% by mass.
By using an ethylenically unsaturated monomer having a solubility in water of 20 ° C. of 0.1% by mass or more, the oil-soluble radical polymerization initiator (IV) can be converted to a polyorganosiloxane polymer (I
II), it is possible to efficiently infiltrate the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomer (V) with high efficiency. By using an ethylenically unsaturated monomer having a solubility of 10% by mass or less, the coating film can be prevented from easily absorbing water, and the weather resistance of the coating film can be improved.

Conversely, the solubility in water at 20 ° C. is 0.
When less than 1% of 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 is not used. In the graft polymerization of (III) and the ethylenically unsaturated monomer (V), a high graft ratio cannot be obtained, the polymerization becomes unstable, and a large amount of aggregates are generated.

The solubility in water at 20 ° C. is 10%.
When an ethylenically unsaturated monomer in excess of mass% is used, the hydrophilicity of the coating film increases, and water easily penetrates into the coating film, so that the water resistance of the coating film deteriorates and the weather resistance also decreases. Will decrease. The amount of the ethylenically unsaturated monomer (V) used is 1 to 99% by mass, preferably 5 to 79% by mass.
Range. Within this range, the radical polymerization initiator (IV) sufficiently penetrates into the polyorganosiloxane polymer (III), so that the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomer (V ) And subsequently with the ethylenically unsaturated monomer (VI), a high degree of grafting is obtained.
The amount of the ethylenically unsaturated monomer (V) used is 1% by mass.
If it is less than 3, polymerization of the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomers (V) and (VI) does not proceed sufficiently, resulting in an insufficient graft ratio.

Ethylenically unsaturated monomer (V) used
Specific examples of methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, glycidyl (meth) acrylate, (meth) acrylic acid Tetrafurfuryl, 2-methoxyethyl methacrylate, methacrylic acid 2
(Meth) such as ethoxyethyl, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 2-methacryloyloxyethyl succinate, 2-methacryloyloxyethyl maleate, hexahydrophthalic acid-methacryloyloxyethyl, diethylaminoethyl methacrylate, etc. ) Acrylic esters, vinyl cyanide compounds such as acrylonitrile and methacrylonitrile, as well as various aromatic vinyl compounds, ethylenically unsaturated carboxylic acid vinyl ester compounds, and mixtures thereof. Has a solubility of 0.1
It is not limited to the above as long as it is 10 to 10% by mass.

Other ethylenically unsaturated monomers (VI) used in the copolymer (A) contained in the aqueous coating composition of the present invention include n-butyl methacrylate, i-butyl methacrylate, and methacrylic acid. (Meth) acrylic acid alkyl ester compounds such as t-butyl acid, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene and vinyltoluene Aromatic vinyl compounds such as 1,3-butadiene, isoprene, 2-
Examples thereof include conjugated diene compounds such as chloro-1,3-butadiene, but are not limited thereto as long as they are capable of radical polymerization.

The copolymer (A) contained in the aqueous coating composition of the present invention preferably contains a unit derived from an ethylenically unsaturated monomer. The amount of the unit is preferably from 0.1 to 10% by mass, more preferably from 1 to 8% by mass, based on the copolymer (A). The copolymer (A) has 0.1% by mass or more of an ethylenically unsaturated carboxylic acid monomer unit, so that the adhesion to various substrates and the dispersion stability during storage and blending into a coating can be effectively achieved. 10% by mass
By having the following ethylenically unsaturated carboxylic acid monomer units, the copolymer (A) can be easily polymerized without impairing the stability during polymerization.

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 course of polymerizing the copolymer (A) contained in the aqueous coating composition of the present invention, polymerization of the polyorganosiloxane polymer (III) with the ethylenically unsaturated monomers (V) and (VI) The emulsifier used for
Various known emulsifiers such as anionic, cationic, nonionic and the like used in general emulsion polymerization can be used, and anionic salts such as sodium, potassium, and ammonium salts of a sulfonic acid group or a sulfate group can be used. It is preferable to use an emulsifier of

Further, in the present invention, in order to improve the storage stability of the emulsion and the water resistance of the coating film,
It is more preferable to use a so-called reactive emulsifier having a radically polymerizable ethylenically unsaturated group. Examples of such a reactive emulsifier include Eleminol (trademark) JS-2 manufactured by Sanyo Kasei Co., Ltd., Latemul (trademark) S-120, S-180, S-180A manufactured by Kao Corporation, and Asahi. Adecaria Soap (trademark) SE-1 manufactured by Denka Kogyo Co., Ltd.
0N, Aqualon HS series manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

The emulsifier used for preparing the copolymer (A) may be used alone, or two or more kinds may be used in combination.
It is 0.5 to 5 parts by mass with respect to parts by mass, and the dispersion stability can be improved by adding the emulsifier in an amount of 0.5 part by mass or more to prepare the copolymer (A). Conversely, by preparing the copolymer (A) with an emulsifier in an amount of 5 parts by mass or less, without lowering the water resistance of the coating film,
A copolymer (A) having excellent dispersion stability can be obtained.

Polyorganosiloxane polymer (III)
Ethylenically unsaturated monomer (V) in the presence of an aqueous dispersion of
When the polymerization composition of (VI) and (VI) is polymerized, the component (III) is 1 to 50% by mass based on the total amount of the component (III), the component (V) and the component (VI) in terms of solid content, )
Component is 1 to 99% by mass, component (VI) is 0 to 98% by mass.
Preferably, the component (V) is 5 to 75% by mass and the component (VI) is 2 to 5 to 50% by mass with respect to the component (III).
0 to 90% by mass. When using the aqueous coating composition of the present invention, the solid content concentration of the polyorganosiloxane-based emulsion is usually in the range of 20 to 70% by mass, preferably 30 to 60% by mass.

In the present invention, the procedure for efficiently proceeding the copolymerization of the polyorganosiloxane polymer (III) with the ethylenically unsaturated monomers (V) and (VI), and more preferably with the reactive emulsifier, is as follows. A radical polymerization initiator (IV) dissolved in part or all of the ethylenically unsaturated monomer (V) is first impregnated into the polyorganosiloxane polymer (III), and then the remaining ethylenically unsaturated monomer (V) is dissolved. A method in which the monomers (V) and (VI) and a reactive emulsifier are added and impregnated and polymerized at once, or a radical polymerization initiator (IV) is added to the polyorganosiloxane polymer (III) by an ethylenically unsaturated monomer. After impregnating and polymerizing a substance dissolved in part or all of the body (V), the remaining ethylenically unsaturated monomers (V) and (VI) are further added.
Then, a split dropping polymerization system in which a reactive emulsifier is added dropwise to carry out polymerization is exemplified.

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 aid 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, and the like. Furthermore, the aqueous coating composition of the present invention is a known pigment or ultraviolet absorber, an antioxidant, a heat resistance improver, a leveling agent, if necessary.
It may contain various additives such as an anti-sagging agent and a matting agent, and may be used as a mixture with other emulsion resins, water-soluble resins, viscosity control agents and the like.

[0029]

EXAMPLES The present invention will be further described below with reference to examples.
All "parts" in the examples are indicated by parts by mass. The evaluation of the performance in Examples and Comparative Examples was performed using the following method. The solubility in water at 20 ° C. in the text is represented by the solubility mass% [(mass of solute [kg] / solvent (20
C. of water) [kg]) × 100] [wt%].

(1) Weather resistance test Taipaque R-930 (sulfuric acid method titanium oxide manufactured by Ishihara Sangyo Co., Ltd.) 196.3 g, OROTAN SG (ROHM &
2.1 g of a pigment dispersant manufactured by Haas Co., Ltd., Surfynol
DF-58 (Antifoamer manufactured by Air Products) 0.08
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 and the like were filtered off with a 300 mesh nylon gauze for evaluation. Mill base.
Next, with respect to 120 g of the aqueous coating composition (emulsion) (based on a solid content of 45%), the above mill base 55
g, Kyowanol M (plasticizer manufactured by Kyowa Hakko Co., Ltd.)
6.4 g and RHEOLATE 350 (a thickener manufactured by RHEOX) 1.5 g were sequentially added, and after sufficient stirring, deionized water was added using Ford cup # 4 so as to be about 100 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.
After setting for 30 minutes in an environment of 65 ° C. × 65% Rh, drying was performed 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 coated surface of the coated plate to prevent water droplets and the like from being attached to the portions other than the coated surface during the weather resistance test, the irradiance is 30 W / m ² , and the irradiation temperature is 70 ° C. , Wet temperature 50 ° C,
The coated plate prepared in a Suga Test Instruments Co., Ltd. DuPanel light control weatherometer DPWL-5 type set for 12 hours per cycle (irradiation time 8 hours, wet time 4 hours) was placed, and after 1000 hours had passed. A 60% gloss retention and color difference (ΔE value) were used as indices to conduct a weather resistance test.

(2) Water resistance test In the aqueous coating composition (emulsion), 20 wt% of butyl cellosolve (based on solid content) as a plasticizer and 3 wt% of RHEOLATE 350 manufactured by RHEOX as a thickener were used.
(To solid content), and after sufficient stirring, filtration was performed with a 300 mesh nylon gauze to prepare an aqueous paint.

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

◎ No boundary between the portion immersed in warm water and the portion not immersed in the coating film was not observed, and there was neither whitening nor blistering of the coating film. ○ The boundary between the part immersed in the warm water and the part not immersed in the paint film is slightly seen, but there is no whitening or blister of the paint film. △ The coating film is slightly whitened or blistered.

× The coating film has clear whitening and blisters. (3) Storage Stability The storage stability was evaluated based on 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 change in viscosity and pH of less than 0.5 and no change in viscosity of less than 5% of the initial value △ No change in viscosity and pH less than 1.0 and initial change in viscosity Less than 10% of the value x What seems to be agglomerates, gelled, etc., and could not be used as a coating material <Preparation of polyorganosiloxane polymer> (I) specified in the present invention 98 parts of a cyclic dimethylsiloxane oligomer tri- to 7-mer mixture which is a compound of the formula (II), 2 parts of γ-methacryloxypropylmethyldimethoxysilane which is also a compound of the formula (II), 310 parts of water and dodecylbenzenesulfone after a composition comprising sodium 0.67 parts were premixed by a homomixer, and forced emulsification at a pressure of 200 kg / cm ² by pressure homogenizer silico To obtain a down raw materials 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 the completion of the dropwise addition, the polymerization was further allowed to proceed for 1 hour, followed by cooling and adding an equimolar amount of sodium hydroxide to dodecylbenzanesulfonic acid to obtain a polyorganosiloxane polymer (III-
1) was obtained.

The obtained polymer had a weight average molecular weight in terms of polystyrene of 168,000. Similarly, 98 parts of a cyclic dimethylsiloxane oligomer tri- to 7-mer mixture,
2 parts of γ-methacryloxypropylmethyltrimethoxysilane, 200 parts of water and 0.1 part of dodecylbenzenesulfonic acid.
67 parts and sodium dodecylbenzenesulfonate 0.6
After premixing the composition consisting of 7 parts with a homomixer,
The emulsion was forcibly emulsified with a pressure homogenizer at a pressure of 200 kg / cm ² to obtain a silicone raw material emulsion.

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, cooled, and cooled to dodecylbenzenesulfonic acid. Then, an equimolar amount of sodium hydroxide was added to obtain a polyorganosiloxane polymer (III-2). The weight average molecular weight of the obtained polymer in terms of polystyrene was 323,
000.

Example 1 Polyorganosiloxane polymer (III-1) obtained
To 1 part, 5 parts of methyl methacrylate (hereinafter referred to as MMA) in which 0.15 part of 2,2-azobis (2,4-dimethylvaleronitrile) was dissolved was mixed with stirring, and the mixture was stirred at room temperature under a nitrogen atmosphere for 40 minutes. And stir. 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 maintaining the temperature in the flask at 80 ° C. for 5 minutes with stirring, 32 parts of t-butyl methacrylate, 25 parts of n-butyl methacrylate, 35 parts of 2-ethylhexyl acrylate, 2 parts of acrylic acid, and Neoperex F-25
A solution obtained by emulsifying and dispersing 5 parts and 0.1 part of a 28% aqueous ammonia solution in 40 parts of water in advance was added dropwise over 2 hours to carry out polymerization. After completion of the dropwise addition, the temperature was raised to 90 ° C. and maintained for 1 hour. Then, 0.125 parts of 1-butylperoxy-2-ethylhexanoate was added, and the temperature was further maintained for 2 hours. After the reaction solution was cooled to room temperature, it was neutralized with a 28% aqueous ammonia solution to obtain a polyorganosiloxane emulsion (aqueous coating composition) A.

Table 1 shows the composition and characteristic values of the polyorganosiloxane emulsion of Example 1, and Table 3 shows the results of evaluating the performance of the coating film. Examples 2 to 8 By the same polymerization method as in Example 1, polyorganosiloxane emulsions having the compositions shown in Table 1 were prepared.

The compositions and characteristic values of the polyorganosiloxane emulsions of these examples are shown in Table 1, and the evaluation results of the coating films are shown in Table 3. Comparative Examples 1 to 6 Polyorganosiloxane emulsions having the compositions shown in Table 2 were prepared by the same polymerization method as in Example 1. In addition,
In Comparative Example 3, the radical polymerization initiator (IV) was dissolved in cyclohexyl methacrylate, which is the compound of (VI), in place of the ethylenically unsaturated monomer (V). Using.

Table 2 shows the compositions and characteristic values of the polyorganosiloxane-based emulsions of these comparative examples, and Table 3 shows the evaluation results of the coating films. However, in Comparative Example 3, significant cullet was generated during the polymerization, and in Comparative Example 5, the ethylenically unsaturated monomer (VI) in which the radically polymerizable initiator (IV) was dissolved was used as the polyorganosiloxane polymer (III). The polymerization was difficult to continue because the polyorganosiloxane polymer aggregated at the stage of addition to the aqueous dispersion, and the polymerization was stopped. Therefore, the coating film could not be evaluated.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

Industrial Applicability The aqueous coating composition of the present invention provides a coating film having excellent water resistance and durability and can be used as a resin for aqueous coatings in various coating applications, and is very useful in industry. It is something.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsushi Fukuzumi 4-160 Sunadabashi, Higashi-ku, Nagoya, Aichi Prefecture Inside Mitsubishi Rayon Co., Ltd. (72) Inventor Yukihiro Ikegami 4-1-1 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Prefecture No.60 Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Kazuhiko Hotta 4-160 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Laboratory F-term (reference) 4J038 CP091 GA06 JA66 JB23 JC09 JC14 KA03 KA09 MA10 NA01 NA03 NA04 NA12 NA26

Claims (3)

[Claims] 1. An aqueous dispersion containing 1 to 50% by mass (solid content) of a polyorganosiloxane polymer (III) obtained by co-condensing an organosiloxane (I) and a graft-linking agent (II). (A) using an oil-soluble radical polymerization initiator (IV) having a solubility in water at 20 ° C of 0.5% by mass or less, and (b) a solubility in water at 20 ° C of 0.1 to 1 to 99% by mass of an ethylenically unsaturated monomer (V) which is 10% by mass
And (c) 0 to 98% by mass of the other ethylenically unsaturated monomer (VI) ((III) + (V) + (VI) = 100% by mass)
From 0.5 to 100 parts by mass of the resulting copolymer.
An aqueous coating composition containing a copolymer (A) obtained by radical polymerization in the presence of 5 parts 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 method of claim 1, wherein the emulsifier is a reactive emulsifier.
Or the aqueous coating composition according to 2.