JP3448529B2 - Aqueous coating composition - Google Patents

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 forms a coating containing a polyorganosiloxane emulsion and having excellent weather resistance for a long period of time, that is, excellent gloss retention, yellowing resistance, water resistance, transparency and substrate adhesion. The present invention relates to an aqueous coating composition that can be applied to various aqueous paints.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of environmental protection and safety and hygiene, the organic solvent type of paint has been changed to an aqueous type, particularly an aqueous emulsion type. Therefore, the applications of water-based paints are expanding, and the performance required for water-based paints is becoming higher accordingly. In particular, as such performance, it is always pointed out that the appearance, weather resistance, storage stability, etc. of the coating film should be improved.

To meet these requirements, Japanese Patent Laid-Open No. 58-18
No. 0563 proposes that an acrylic polymer emulsion blended with a silicone polymer emulsion is used as a paint main component. In addition, JP-A-4
No. 261,454 proposes a copolymer of an acrylic monomer in the presence of a silicone polymer emulsion. However, when such a composition is used, the acrylic copolymer and the silicone polymer have poor compatibility and also have different refractive indexes, so that the transparency of the coating film is impaired and the coating film is When they are formed, they are separated from each other, and there is a drawback that sufficient water resistance and coating strength cannot be obtained.

In order to solve the above problems, JP-A-11-12311 uses an aqueous dispersion of a low molecular weight silicone polymer and a monomer, and an oil-soluble initiator or a reactive emulsifier. Therefore, a copolymerized product has 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, and there is a drawback that sufficient coating strength cannot be obtained. is there.

[0005]

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

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that the solubility of water in a specific range in the presence of an aqueous dispersion of a polyorganosiloxane polymer It has excellent weather resistance, transparency and adhesion by radical polymerization using an ethylenically unsaturated monomer having an and an oil-soluble radical polymerization initiator having solubility in a specific range of water. It was found that an aqueous coating composition having excellent properties such as storage stability can be obtained, and the present invention has been completed.

That is, the aqueous coating composition of the present invention is obtained by co-condensing an organosiloxane (I) and a graft crossing agent (II) and has a polyorganosiloxane polymer having an average molecular weight of 50,000 or more. (A) an oil-soluble radical polymerization initiator (IV) having a solubility in water at 20 ° C. of 0.5% by mass or less in the presence of an aqueous dispersion of 1 to 50% by mass (solid content) of the combination (III). (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) 0 to 98% by mass of other ethylenically unsaturated monomer (VI) ((III) + (V) + (VI) = 100% by mass)
(D) 0.5 to 100 parts by mass of the obtained copolymer.
It contains a copolymer (A) obtained by radical polymerization in the presence of 5 parts by mass 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 copolymer (A)
The emulsifier used when polymerizing 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 is linear or branched. Alternatively, it has a cyclic structure. Examples of the substituted or unsubstituted monovalent hydrocarbon group contained in the organosiloxane (I) include a methyl group, an ethyl group, a propyl group, a vinyl group, a phenyl group and a hydrogen atom thereof or a cyano group. The substituted hydrocarbon group etc. which were substituted can be mentioned.
Specific examples of the organosiloxane (I) include cyclic compounds such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and trimethyltriphenylcyclotrisiloxane, as well as direct compounds. A chain or branched organosiloxane can be mentioned. The organosiloxane (I) may be a prepolymerized polyorganosiloxane. In this case, the molecular chain terminal 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 crossing agent (I
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 from the viewpoints of polymerization reactivity, easy handling, and the like. Specific examples of the graft crossing agent include vinylmethyldimethoxysilane,
Vinylsilanes such as vinyltrimethoxysilane and vinyltriethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, etc. (Meth) acryloxyalkylsilanes, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltriethoxysilane,
Examples thereof include mercaptoalkylsilanes such as 3-mercaptopropylmethyldiethoxysilane. These components can be used alone or in combination of two or more as required.

The proportion of the graft crossing agent (II) used is 0.1 based on the total mass of the components (I) and (II).
-30% by mass, preferably 0.5-20% by mass, and by using 0.1% by mass or more of the graft crossing agent, the high molecular weight polyorganosiloxane polymer (III) and ethylenic 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 30% by mass or less of the graft crossing agent, 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 obtained by forcibly emulsifying and dispersing the organosiloxane (I) and the graft crossing agent (II) in water with a homomixer, a pressure homogenizer or the like, and adding an acid such as alkylbenzene sulfonic acid as a polycondensation initiator. It can also be used as an emulsifier by neutralizing the acid component with an alkali component after the polycondensation. The amount of the polycondensation initiator used is not particularly limited and can be arbitrarily set depending on the polymerization conditions such as the molecular weight of the target polyorganosiloxane polymer, the solid content and the polymerization temperature. In order to make it proceed rapidly, it is desirable to use it in an amount of 0.5% by mass or more based on the total amount of the organosiloxane (I) component and the graft crossing agent (II) component.

The polyorganosiloxane polymer (III) thus obtained has an average molecular weight of 50,0.
It is preferably 00 or more. 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 ethylene containing a radical polymerization initiator (IV) in an aqueous dispersion of the polyorganosiloxane polymer (III) obtained as described above. Of the unsaturated unsaturated monomer (V), (IV) and (V) are permeated into (III), polymerization is started, and then an ethylenically unsaturated monomer (VI) and an emulsifier are added. It is obtained by adding and polymerizing.

Polyorganosiloxane polymer (III)
The radical polymerization initiator (IV) used in the graft polymerization of ethylene with the ethylenically unsaturated monomer (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 ones can be used. By using a radically polymerizable initiator having a solubility in water at 20 ° C. of 0.5% by mass or less, the initiator can be efficiently permeated into the polyorganosiloxane polymer (III), and therefore, ethylene can be effectively used. Unsaturated monomer (V)
In the copolymerization with (VI) and (VI), a graft ratio and compatibility are improved, and a coating film having excellent weather resistance can be obtained.

On the contrary, the solubility in water at 20 ° C. is 0.
When an initiator exceeding 5% by mass is used, 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 Weather resistance decreases. Specific examples of the radical polymerization initiator whose solubility in water at 20 ° C. is 0.5% by mass or less include azobisisobutyronitrile,
Slightly 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- Examples thereof include organic peroxides such as butyl peroxy-2-ethyl hexanoate and t-butyl peroxyisobutyrate. These initiators can be used alone or 2
One or more initiators may be used in combination. Further, it can be used also as a redox type in combination with a reducing agent such as ferrous sulfate / dextrose or sodium bisulfite, as long as it does not affect the water resistance.

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 one having a mass%, and it is preferable to use one 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 at 20 ° C. of 0.1% by mass or more, the oil-soluble radical polymerization initiator (IV) is added to the polyorganosiloxane polymer (I
II) can be efficiently permeated into the polymer, and highly efficient graft polymerization of the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomer (V) becomes possible, and conversely to water at 20 ° C. By using an ethylenically unsaturated monomer having a solubility of 10% by mass or less, it is possible to prevent the coating film from absorbing water easily and improve the weather resistance of the coating film.

On the contrary, 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 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.

Further, 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, resulting in poor water resistance and weather resistance. Will be reduced. The amount of the ethylenically unsaturated monomer (V) used is 1 to 99% by mass, preferably 5 to 79% by mass.
Is the range. Within this range, the radical polymerization initiator (IV) is sufficiently permeated into the polyorganosiloxane polymer (III), and as a result, the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomer (V ) And subsequent graft polymerization with ethylenically unsaturated monomers (VI) gives high grafting rates.
The amount of the ethylenically unsaturated monomer (V) used is 1% by mass.
If it is less than the above range, the polymerization of the polyorganosiloxane polymer (III) and the ethylenically unsaturated monomers (V) and (VI) will not proceed sufficiently, resulting in an insufficient graft ratio.

Ethylenically unsaturated monomer (V) used
As 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
-Ethoxyethyl, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 2-methacryloyloxyethyl succinate, 2-methacryloyloxyethyl maleate, methacryloyloxyethyl hexahydrophthalate, diethylaminoethyl methacrylate, etc. ) Acrylic esters, vinyl cyanide compounds such as acrylonitrile, methacrylonitrile, and various aromatic vinyl compounds, ethylenically unsaturated carboxylic acid vinyl ester compounds, and mixtures thereof. Has a solubility of 0.1
The content is not limited to the above as long as it is 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 acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, vinyltoluene Aromatic vinyl compounds such as 1,3-butadiene, isoprene, 2-
Examples thereof include conjugated diene compounds such as chloro-1,3-butadiene, but not limited to these as long as radical polymerization is possible.

Further, 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 0.1 to 10% by mass, more preferably 1 to 8% by mass based on the copolymer (A). Since the copolymer (A) has 0.1% by mass or more of the ethylenically unsaturated carboxylic acid monomer unit, the adhesion to various base materials and the dispersion stability during storage and formulation into a paint are effective. Can be improved to 10 mass%
By having the following ethylenically unsaturated carboxylic acid monomer unit, 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 and itacone. Acid, 2-methacryloxyethyl succinic acid, 2-methacryloxyethyl phthalic acid, 2-
Methacryloxyethyl hexahydrophthalic acid and the like can be mentioned.

Polymerization of the polyorganosiloxane polymer (III) with the ethylenically unsaturated monomers (V) and (VI) in the process of polymerizing the copolymer (A) contained in the aqueous coating composition of the present invention. As the emulsifier used at that time,
Although various known emulsifiers such as anionic, cationic, nonionic, etc. used for general emulsion polymerization can be used, anionic properties such as sodium, potassium and ammonium salts of sulfonic acid group or sulfuric acid ester group can be used. It is preferable to use the 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 preferred to use so-called reactive emulsifiers having radically polymerizable ethylenically unsaturated groups. Examples of such reactive emulsifiers include Eleminol (trademark) JS-2 manufactured by Sanyo Kasei Co., Ltd., and Latemur (trademark) S-120, S-180, S-180A manufactured by Kao Co., Ltd., Asahi. Adeka Riasoap (trademark) SE-1 manufactured by Denka Kogyo Co., Ltd.
0N, Aqualon HS series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., and the like.

The emulsifier used when preparing the copolymer (A) may be used alone or in combination of two or more kinds, and the amount thereof is 100% of the copolymer (A).
It is 0.5 to 5 parts by mass with respect to parts by mass, and dispersion stability can be improved by adding 0.5 part by mass or more of an emulsifier to prepare the copolymer (A). On the contrary, by preparing the copolymer (A) with an amount of the emulsifier 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
And (VI), the composition charged is 1-50 mass% of (III) component, (V) based on the total amount of (III) component, (V) component and (VI) component in terms of solid content. )
1 to 99 mass% of component, 0 to 98 mass% of (VI) component
And preferably 5 to 50 mass% of the (III) component, 5 to 75 mass% of the (V) component and 2 of the (VI) component.
It is 0 to 90 mass%. When using the aqueous coating composition of the present invention, the solid content concentration of the polyorganosiloxane emulsion is usually 20 to 70% by mass, preferably 30 to 60% by mass.

In the present invention, the procedure for efficiently advancing the copolymerization of the polyorganosiloxane polymer (III), the ethylenically unsaturated monomers (V) and (VI), and more preferably the reactive emulsifier, is as follows. The polyorganosiloxane polymer (III) is first impregnated with a radical polymerization initiator (IV) dissolved in a part or all of the ethylenically unsaturated monomer (V), and then the remaining ethylenically unsaturated monomer (V). Polymers (V) and (VI) and a reactive emulsifier are added and impregnated to carry out batch polymerization, or a radical polymerization initiator (IV) is added to the polyorganosiloxane polymer (III) as an ethylenically unsaturated monomer. After impregnating a part or all of the body (V) dissolved therein and polymerizing it, the remaining ethylenically unsaturated monomers (V) and (VI),
Then, a divided drop polymerization method in which a reactive emulsifier is added dropwise to carry out polymerization is mentioned.

Further, a film-forming aid may be added to the aqueous coating composition of the present invention, if necessary, in order to improve the film-forming property. 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 can be mentioned. Furthermore, the aqueous coating composition of the present invention, if necessary, known pigments and ultraviolet absorbers, antioxidants, heat resistance improvers, leveling agents,
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 resin, water-soluble resin, viscosity control agent and the like.

[0029]

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

(1) Weather resistance test Taipaque R-930 (sulfuric acid titanium oxide manufactured by Ishihara Sangyo Co., Ltd.) 196.3 g, OROTAN SG (ROHM &
Haas Co. pigment dispersant) 2.1 g, Surfynol
DF-58 (Anti-foaming agent manufactured by Air Products) 0.08
g, propylene glycol 29.4 g, deionized water 3
After thoroughly mixing 4.3 g and 1.8 g of 28% aqueous ammonia solution, glass beads were added and the pigment was dispersed for 30 minutes with a high speed disperser, and the glass beads were filtered with a 300 mesh nylon gauze for evaluation. It was a mill base.
Next, to 120 g of the aqueous coating composition (emulsion) (based on solid content of 45%), the above evaluation mill base 55 was used.
g, Kyowanol M (plasticizer manufactured by Kyowa Hakko Co., Ltd.)
6.4 g and 1.5 g of RHEOLATE 350 (thickener manufactured by RHEOX) were added in order, and after sufficiently stirring, deionized water was added to the Ford cup # 4 for about 100 seconds to 140 seconds for adjustment. .

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

Polyester tape was attached to the surface other than the coated surface of this coated plate to prevent water drops and the like from being adhered to places other than the coated surface during the weather resistance test, and then the irradiance was 30 W / m ² and the irradiation temperature was 70 ° C. , Wet temperature 50 ℃,
A painted plate was placed in the DPWL-5 model of Dew Panel Light Control Weatherometer manufactured by Suga Test Instruments Co., Ltd., which was set to 12 hours (irradiation time: 8 hours, wetting time: 4 hours), and after 1000 hours, A weather resistance test was carried out using the 60 ° gloss retention rate and the color difference (ΔE value) as indexes.

(2) Water resistance test 20 wt% of butyl cellosolve (as a solid content) as a plasticizer and 3 wt% of RHEOLATE 350 made by RHEOX Co. as a thickening agent in an aqueous coating composition (emulsion).
(To solid content) was added, and after sufficiently stirring, filtration was performed with a 300 mesh nylon gauze to prepare an aqueous paint.

This water-based paint was applied to a zinc phosphate-treated steel plate of 150 mm × 70 mm with a bar coater # 40, and 20
After setting for 30 minutes in an environment of ° C x 65% Rh, it was dried in an oven at 80 ° C for 1 hour to prepare a coated plate for a water resistance test. After applying a polyester tape to the surface other than the coated surface of this coated plate to prevent water droplets etc. that are applied during the water resistance test from adhering to other than the coated surface, soak it in warm water at 40 ° C and leave it for 7 days before taking it out. The whitening of the coating film immediately after taking it out and the presence or absence of blisters were visually confirmed, and evaluated according to the following criteria.

⊚ No boundary between the part soaked in warm water and the part not soaked in the coating film is not seen, and there is no whitening or blistering of the coating film. ○ There is a slight boundary between the part that was dipped in hot water and the part that was not dipped in the paint film, but there is no whitening or blistering of the paint film. △ There is slight whitening or blistering in the coating film.

× There are clear whitening and blister in the coating film. (3) Storage stability The storage stability was evaluated by the following criteria by checking changes in viscosity, pH, etc. after immersion for 168 hours in a constant temperature water bath at 50 ° C. ○ No agglomerates are generated, the change in viscosity and pH is less than 0.5 and the change in viscosity is less than 5% of the initial value. △ The change in viscosity and pH is less than 1.0 and the change in viscosity is initial. Less than 10% of the value x those which seem to be aggregates or which are in a state where they cannot be used as a coating material due to gelation, etc. <Preparation of polyorganosiloxane polymer> Defined in the present invention (I) 98 parts of a mixture of cyclic dimethylsiloxane oligomer 3 to 7 mer which is the compound of 2), 2 parts of γ-methacryloxypropylmethyldimethoxysilane which is the compound of (II) defined in the present invention, 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 silicone To obtain a 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 temperature in the flask was kept at 85 ° C. under stirring for 4 hours. The above silicone raw material emulsion was dropped. After completion of the dropwise addition, the polymerization was allowed to proceed for an additional 1 hour, then cooled and added with sodium hydroxide in an equimolar amount to dodecylbenzan sulfonic acid to give a polyorganosiloxane polymer (III-
1) was obtained.

The polystyrene reduced mass average molecular weight of the obtained polymer was 168,000. Similarly, 98 parts of a cyclic dimethylsiloxane oligomer 3-7 mer mixture,
γ-methacryloxypropylmethyltrimethoxysilane 2 parts, water 200 parts and dodecylbenzene sulfonic acid 0.
67 parts and sodium dodecylbenzene sulfonate 0.6
After premixing the composition consisting of 7 parts with a homomixer,
A silicone raw material emulsion was obtained by forced emulsification with a pressure homogenizer at a pressure of 200 kg / cm ² .

This silicone raw material emulsion was placed in a flask equipped with a stirrer, a condenser, a heating jacket and a dropping pump all at once, heated to 80 ° C., reacted for 6 hours under stirring, and then cooled to give dodecylbenzenesulfonic acid. An equimolar amount of sodium hydroxide was added to obtain a polyorganosiloxane polymer (III-2). The polystyrene reduced weight average molecular weight of the obtained polymer was 323.
It was 000.

Example 1 Obtained polyorganosiloxane polymer (III-1)
5 parts of methyl methacrylate (hereinafter referred to as MMA), in which 0.15 parts of 2,2-azobis (2,4-dimethylvaleronitrile) was dissolved in 1 part, were mixed with stirring for 40 minutes at room temperature under a nitrogen atmosphere. Stir with. Then, 62 parts of water is charged and added all at once to a flask equipped with a stirrer, a condenser, a temperature control device, a dropping pump and a nitrogen introduction tube, which has been heated to 80 ° C. After maintaining the flask temperature at 80 ° C. for 5 minutes with stirring, t-butyl methacrylate 32 parts, n-butyl methacrylate 25 parts, 2-ethylhexyl acrylate 35 parts, acrylic acid 2 parts and Neoperex F-25.
What was preliminarily emulsified and dispersed in 5 parts and 0.1 part of 28% aqueous ammonia solution in 40 parts of water was added dropwise over 2 hours to carry out polymerization. After the dropping was completed, the temperature was raised to 90 ° C. and maintained for 1 hour, 0.125 parts of 1-butylperoxy-2-ethylhexanoate was added, and the temperature was maintained for another 2 hours. The reaction solution was cooled to room temperature and then neutralized with a 28% aqueous ammonia solution to obtain a polyorganosiloxane emulsion (aqueous coating composition) A.

The composition and characteristic values of the polyorganosiloxane emulsion of Example 1 are shown in Table 1, and the performance evaluation results of the coating film are shown in Table 3. 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 composition and characteristic values of the polyorganosiloxane emulsions of these Examples are shown in Table 1, and the evaluation results of the coating film are shown in Table 3. Comparative Examples 1 to 6 By the same polymerization method as in Example 1, polyorganosiloxane emulsions having the compositions shown in Table 2 were prepared. In addition,
In Comparative Example 3, the radical polymerization initiator (IV) was dissolved in cyclohexyl methacrylate which is a compound of (VI) instead of the ethylenically unsaturated monomer (V), and the same polymerization formulation as in Example 1 was used. Using.

The composition and characteristic values of the polyorganosiloxane emulsions of these comparative examples are shown in Table 2, and the evaluation results of the coating film are shown in Table 3. However, in Comparative Example 3, remarkable cullet was generated during the polymerization, and in Comparative Example 5, the ethylenically unsaturated monomer (VI) in which the radical polymerizable initiator (IV) was dissolved was added to the polyorganosiloxane polymer (III). Since it was difficult to continue the polymerization because the polyorganosiloxane polymer aggregated at the stage of addition to the aqueous dispersion, the coating film could not be evaluated because the polymerization was stopped.

[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 water-based coatings in various coating applications, and is industrially very useful. It is something.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsushi Fukuzumi 4-chome, Sunadabashi, Higashi-ku, Nagoya, Aichi Prefecture, 60-1 Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor, Yukihiro Ikegami 4-chome, Sunadabashi, Higashi-ku, Aichi No. 1-60 Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Kazuhiko Hotta No. 1-60 Sunadabashi, Higashi-ku, Aichi Prefecture Nagoya City Mitsubishi Rayon Co., Ltd. Product Development Laboratory (56) Reference Japanese Patent Laid-Open No. 11 -12311 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09D 151 / 08,5 / 00,183 / 06

Claims (3)

(57) [Claims] 1. An average molecular weight of 5 obtained by co-condensing an organosiloxane (I) and a graft crossing agent (II).
Over 10,000 polyorganosiloxane polymers (II
I) In the presence of an aqueous dispersion containing 1 to 50 mass% (solid content), (a) an oil-soluble radical polymerization initiator (IV) having a solubility in water at 20 ° C. of 0.5 mass% or less. (B) 1 to 99% by mass of an ethylenically unsaturated monomer (V) whose solubility in water at 20 ° C. is 0.1 to 10% by mass.
And (c) 0 to 98% by mass of other ethylenically unsaturated monomer (VI) ((III) + (V) + (VI) = 100% by mass)
(D) 0.5 to 100 parts by mass of the obtained 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 copolymer (A) contains an ethylenically unsaturated carboxylic acid monomer unit in an amount of 0.1 to 10% by mass. 3. The emulsifier is a reactive emulsifier.
Or the aqueous coating composition according to 2.