JP2000239331A - Preparation of aqueous emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preparative method for aqueous emulsion excellent in storage stability and capable of obtaining coating film excellent in contamination resistance for a long period. SOLUTION: This preparation method for aqueous emulsion comprises following two processes, the first process: heating a radial-polymerizable monomer including a hydrolysable silyl group and a silane compound in the presence of water to condense the silane compound to the hydrolysable silyl group of the monomer obtaining (a) a radial-polymerizable condensate of the silane compound. The second process: copolymerizing the component (a) with a radical- polymerizable monomer (b) copolymerizable with the component (a) in an aqueous medium in the presence of a surfactant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aqueous emulsion capable of forming a coating film having excellent stain resistance over a long period of time, and relates to a technical field such as a coating material utilizing the emulsion. It can be awarded.

[0002]

2. Description of the Related Art Conventionally, acrylic emulsion-based paints based on acrylic polymers have been used as paints for outdoor painting. However, due to the low hardness of the coating film compared with the organic solvent-based coating, the coating material may cause contaminants due to automobile exhaust gas, sand dust, iron powder, and the like to accumulate on the coating film surface, The problem that the aesthetic appearance is impaired due to the attachment of dirt, that is, the problem of stain resistance, has become apparent, and a material having excellent stain resistance has been demanded.

[0003] As a method of improving the stain resistance of an organic solvent-based paint, an alkyl silicate or a partial hydrolyzate thereof is incorporated into the paint to impart hydrophilicity and oil repellency in water to the surface of the resulting paint film. A method of removing dirt by a so-called rolling-up mechanism in which a coating film is wetted with rainwater and then contaminants flow down with the rainwater has been proposed (Japanese Patent Application Laid-Open No. Hei 6-248237).

[0004]

However, when the same stain resistance improvement measures as those of the above-mentioned organic solvent-based paints are applied to emulsion-based paints, hydrolyzable compounds such as alkyl silicates are stably produced in water. Since it is difficult to maintain, it is difficult to improve the contamination by this method.

[0005] The present inventors can stably retain the compound in an emulsion even when an alkyl silicate or the like is used, and make the resulting coating film excellent in stain resistance. As a method for producing an emulsion, an aqueous emulsion dispersion obtained by emulsifying and dispersing a polymerizable monomer such as a silane-based monomer, an oil-soluble polymerization initiator, and an alkyl silicate in an aqueous medium in the presence of a surfactant. A method has been found in which a polymer is added to a heated aqueous medium and polymerized (Japanese Patent Application No. 10-216510). However, the emulsion obtained by this method is insufficient for applications requiring long-term stain resistance.

The inventors of the present invention have conducted intensive studies on a method for producing an aqueous emulsion having excellent storage stability and a resulting coating film having excellent stain resistance over a long period of time.

[0007]

As a result of various studies, the present inventors have produced a monomer obtained by condensing a silane compound with a silane-based monomer, It has been found that a production method in which the emulsion is obtained has excellent storage stability and the coating film has excellent long-term stain resistance, and has completed the present invention. Hereinafter, the present invention will be described in detail.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises the following steps 1 and 2
And a method for producing an aqueous emulsion comprising: Hereinafter, each step will be described.

1. Step 1 In the step 1, the hydrolyzable silyl group-containing radical polymerizable monomer and a specific silane compound are heated in the presence of moisture, so that the hydrolyzable silyl group of the radical polymerizable monomer is In this step, (a) a condensate of a silane compound having radical polymerizability is produced by condensing a silane compound. Hereinafter, each component and step 1 will be described.

1-1. Silane compound The silane compound in the present invention is a monomer, dimer, trimer or oligomer of the compound represented by the following general formula (1) (hereinafter these are simply referred to as silane compounds). It is.

[0011]

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Here, n is an integer of 0, 1, or 2,
Preferably it is 0 or 1. R ¹ is a stable hydrophobic group, for example, a hydrocarbon-based substituent such as an alkyl group and a phenyl group. R ² is a hydrolyzable group, and includes an alkoxy group such as a methoxy group and an ethoxy group, a hydroxyl group,
Examples include a halogen atom and an acetoxy group. In the present invention, an alkoxy group is preferable from the viewpoint of storage stability and ease of handling. When there are a plurality of R ¹ and R ² , they may be the same or different.

Specific examples of the silane compound useful in the present invention include the following. In the above general formula, examples of the compound where n = 0 include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and the like.
Examples of the compound where n = 1 include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriisopropoxysilane ,
Examples include cyclohexyltrimethoxysilane, benzyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, and the like. Examples of the compound where n = 2 include dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, and the like. Further, as the silane compound, these dimers, trimers or oligomers,
And mixtures thereof.

In the present invention, as the silane compound,
In the above general formula, n is an integer of 0 or 1, and R ¹
Is an alkyl group, and a compound in which R ² is an alkoxy group is preferred because the coating film has excellent stain resistance. Specific examples of these compounds include, as examples of the compound where n = 0,
Examples include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Examples of the compound where n = 1 include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, and octyltriisopropoxysilane. And the like, more preferably tetraalkoxysilane and methyltriethoxysilane. Two or more silane compounds can be used in combination.

1-2. Hydrolyzable silyl group-containing radical polymerizable monomer The hydrolyzable silyl group-containing radical polymerizable monomer (hereinafter referred to as a hydrolyzable silyl monomer) used in the present invention includes: There are various compounds, and a compound represented by the following formula (2) is preferable.

[0016]

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(Wherein R ³ is a monovalent hydrocarbon group selected from alkyl, aryl and aralkyl groups having 1 to 10 carbon atoms, R ⁴ is a radical polymerizable group, X is a hydrolyzable group, a Is an integer from 0 to 2. When each of X and R ³ bonded to Si is two or more, they may be the same or different groups.) R ³ has 1 carbon atom. To 10 alkyl groups, aryl groups and aralkyl groups. Examples of the aryl group include a phenyl group, and examples of the aralkyl group include a benzyl group. R ³ is preferably an alkyl group having 1 to 10 carbon atoms. As the radical polymerizable group for R ⁴ , an ethylenically unsaturated group is preferable, and a functional group having high radical polymerizability such as a (meth) acryloyl group, a styryl group, a vinyl ester group, and a vinyl ether group is more preferable. Examples of the hydrolyzable group for X include an alkoxy group, a hydroxyl group, a halogen atom, and an acetoxy group. Specific examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentanoxy group and a hexanoxy group. From the balance between reactivity and stability, X is preferably an alkoxy group having 4 or less carbon atoms.

Specific examples of the hydrolyzable silyl monomer include vinyltrimethoxysilane, vinylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, and vinyltriethoxysilane. Methyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, vinyltripropoxysilane, vinylmethyldipropoxysilane, γ-methacryloxypropyltripropoxysilane and γ-methacryloxypropylmethyl And dipropoxysilane. The monomers may be used in combination of two or more.

1-3. Step 1 In step 1, a silane compound is added to the hydrolyzable silyl group of the monomer by heating the hydrolyzable silyl monomer and the silane compound in the presence of water. It is to be hydrolyzed and condensed.

The ratio of the hydrolyzable silyl monomer to the silane compound is as follows: hydrolyzable silyl monomer: silane compound = 1:
It is preferably from 99 to 80:20 (weight ratio), more preferably from 10:90 to 50:50. If the proportion of the hydrolyzable silyl monomer is less than 1, the resulting emulsion may have insufficient stain resistance after long-term exposure, while if the proportion of the hydrolyzable silyl monomer exceeds 80, The resulting emulsion may have insufficient stain resistance.

The water added in the condensation reaction is preferably in the range of 0.05 to 0.45 mol based on the total number of mols of the hydrolyzable silyl monomer and the alkoxy group present in the silane compound. More preferably, it is in the range of 0.1 to 0.2 mol. If the amount of water added is less than 0.05, the hydrolysis reaction may be insufficient, and the long-term stain resistance of the resulting emulsion may be insufficient. If the amount exceeds 0.45 mol, gelation may occur during the condensation reaction. In some cases.

Step 1 is preferably performed in the presence of a catalyst. The catalyst is preferably an acidic catalyst, and examples thereof include organic acids such as paratoluenesulfonic acid and inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid. As the amount of catalyst used,
The content is preferably 0.05 to 10% by weight based on the added water.
The reaction temperature may be appropriately set according to the purpose,
It is preferably room temperature to 80 ° C.

Since the mixture of the hydrolyzable silyl monomer and the silane compound is difficult to mix with water, the reaction is preferably performed in an organic solvent that dissolves water. Examples of the organic solvent include methanol, ethanol, isopropyl alcohol, methyl ethyl ketone, ethylene glycol monobutyl ether, and ethylene glycol monomethyl ether.

2. Step 2 Step 2 is a step of copolymerizing a radical polymerizable monomer copolymerizable with the components (a) and (b) and the component (a) in an aqueous medium in the presence of a surfactant. Hereinafter, the component (b) and the step 2 will be described.

2-1. (B) Radical polymerizable monomer copolymerizable with component (a) As the component (b) in the present invention, various radical polymerizable monomers can be used. And compounds having an ethylenically unsaturated double bond such as a group or a (meth) acryloyl group. Specifically, (meth) acrylates, vinyl carboxylate such as vinyl acetate and vinyl propionate, ethylenically unsaturated group-containing aromatic compounds such as styrene and α-methylstyrene, (meth) acrylic acid,
Examples include compounds containing a carboxyl group and an ethylenically unsaturated group, such as itaconic acid and maleic acid. Examples of the (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, and n- (meth) acrylate.
-Butyl, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, alkyl (meth) acrylates such as lauryl (meth) acrylate and stearyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate And hydroxylalkyl (meth) acrylates such as 2-hydroxypropyl (meth) acrylate,
Perfluoroalkyl (meth) acrylate, glycidyl (meth) acrylate, and N (meth) acrylate
N-diethylaminoethyl and the like. These monomers can be used alone, but it is usually preferable to select a plurality of components so as to balance the properties of the coating film.

The component (b) is excellent in copolymerizability and the resulting copolymer has excellent properties such as a coating film.
Alkyl (meth) acrylate having -8 alkyl groups, styrene, hydroxyalkyl (meth) acrylate having 2-3 alkyl hydroxyalkyl groups, and glycidyl (meth) acrylate are preferred. In order to maintain the coating properties such as weather resistance, strength and heat resistance at a high level,
It is preferable to use at least 50 parts by weight of (meth) acrylate based on 100 parts by weight of the total amount of component (b).

The preferred copolymerization ratios of component (a) and component (b) are (a) 0.5 to 50% by weight and (b) 99.5 to 50% by weight, and more preferably (a). 3 to 30% by weight and
(b) 97 to 70% by weight. When the proportion of the component (a) is less than 0.5, the effect of using the component (a) as a component is not exhibited, while when it exceeds 50% by weight, the stability of the emulsion tends to be reduced.

2-2. Step 2 Step 2 of the present invention is a step of copolymerizing the components (a) and (b) in an aqueous medium in the presence of a surfactant.

2-2-1. Surfactant As the surfactant, various surfactants commonly used in ordinary emulsion polymerization, such as anionic, nonionic and cationic surfactants, can be used. Is preferable, and a radically polymerizable surfactant is preferably used because the film has excellent water resistance and weather resistance.

The radically polymerizable surfactant includes:
Those containing a polyoxyalkylene group represented by the following general formula (3) and an ion-dissociable group are preferred.

[0031]

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(Wherein, Z is an organic group having a radical polymerizable double bond copolymerizable with the component (a), AO is an oxyalkylene group, n is an integer of 2 or more, and Y is an ion dissociable group. The preferred Z in the general formula (3) is a radical polymerizable double bond with a hydrophobic group such as an aromatic hydrocarbon group, an alkyl-substituted aromatic hydrocarbon group, a higher alkyl group or an alicyclic hydrocarbon group. A structural unit in which a bond is combined. Furthermore, Z
Is preferably a (meth) allyl group, a propenyl group or a butenyl group.

The preferred ionicity of the polymerizable surfactant is an anion. Therefore, Y is a salt in which a group (AO) n can be bonded to an anionic group and a cation is ionically bonded to the anionic group. Is preferred. Specific examples of the preferred _{Y, -SO 3 Na, -SO 3} NH 4, -COO
_{Na, -COONH 4, -PO 3 Na} 2 , and -PO ₃ (NH
_{4) 2} and the like, more preferably from -SO ₃ Na or -SO ₃ NH _4. N in the group (AO) n is an integer of 2 or more. When n is 1, the hydrolyzable silyl group in the monomer (a) becomes unstable and easily decomposed. Preferred n is 300 or less, more preferably 5 to 50. When n is less than 5, the stability of the hydrolyzable silyl group in the monomer (a) tends to be insufficient, and when n exceeds 300, it is formed from a curable emulsion obtained. In some cases, the physical properties of the coating film tend to decrease. The unit A in the group (AO) n, that is, the alkylene group, is preferably an ethylene group or a propylene group.

Preferred specific examples of the polymerizable surfactant include compounds represented by the following formulas (4) to (6). In the formulas (4) and (5), R ⁵ and R ⁶ are preferably a linear or branched alkyl group having 6 to 18 carbon atoms. In the formula (6), R ⁷ is a hydrogen atom or a methyl group, and R ⁸ is a group having 8 to 24 carbon atoms.
Are preferred. In the formulas (4) to (6), A ¹ , A ² and A ^{3 each} represent an alkylene group, and in any of the compounds, n is an integer of 2 or more. In the formulas (4) to (6), Y ¹ , Y ² and Y ^{3 each} represent an ionic dissociative group, and specific examples thereof include the same as those described above for Y.

[0035]

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[0036]

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[0037]

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The preferred amount of the surfactant used is (a)
0.5 to 100 parts by weight of the total amount of the component and the component (b)
20 parts by weight, more preferably 1 to 5 parts by weight.

2-2-2. Microsuspension polymerization The polymerization method of the component (a) and the component (b) includes, for example, heating and stirring in an aqueous medium in the presence of a surfactant and a radical polymerizable initiator. It is good to follow the usual law. In the present invention, among various polymerization methods, particularly in the presence of a surfactant, (a)
Step [A] of emulsifying and dispersing the component, the component (b) and the oil-soluble radical polymerization initiator in an aqueous medium, and dropping the aqueous emulsified dispersion obtained in the step [A] into a heated aqueous medium. A production method comprising a step [B] of copolymerizing the component (a) and the component (b) is preferable. In this production method, since the oil-soluble radical polymerization initiator is contained in the emulsified and dispersed particles of the component (a) and the component (b), polymerization occurs in each dispersed fine particle. A polymerization method for polymerizing a monomer in such hydrophobic particles is generally called microsuspension polymerization, and according to the polymerization method, a single monomer is formed in a micelle forming an emulsifier with a water-soluble initiator. Compared with the emulsion polymerization method of polymerizing the monomer, the component (a) can be confined in each particle, the resulting emulsion is stable, and the coating film has excellent weather resistance. Hereinafter, the polymerization method will be described.

2-2-2-1. Oil-soluble radical polymerization initiator As the oil-soluble radical polymerization initiator in the present invention, various oil-soluble radical polymerization initiators can be used as long as they are oil-soluble, and their solubility in water at 20 ° C. Is preferably 10% by weight or less, and those which dissolve in the monomer mixture at the reaction temperature are preferred. For example, 2,2′-azobisisobutyronitrile,
2,2′-azobis-2,4 dimethylvaleronitrile,
Azo initiators such as 1-azobis-1-cyclohexanecarbonitrile and dimethyl-2,2'-azobisisobutyrate, lauroyl peroxide, benzoyl peroxide, dicumyl peroxide, cyclohexanone peroxide di-n-propyl Organic peroxides such as peroxydicarbonate and t-butylperoxypivalate are preferably used. The amount of these polymerization initiators is preferably from 0.1 to 10% by weight, more preferably from 0.2 to 3% by weight, based on the total amount of the components (a) and (b). .

2-2-2. Microsuspension polymerization method In microsuspension polymerization, the components (a) and (b) and the oil-soluble radical polymerization initiator are added to an aqueous solution in the presence of a surfactant. Step [A] of emulsifying and dispersing in a medium is performed. (a) component,
The mixture comprising the component (b) and the oil-soluble radical polymerization initiator can be obtained by dissolving the oil-soluble radical polymerization initiator in a mixture of the component (a) and the component (b). As a method of emulsifying and dispersing the mixture in an aqueous medium, a method of stirring the mixture of the mixture and the aqueous medium by a normal rotary homomixer or the like, or a method of adding the mixture to the aqueous medium is sufficient. Can be emulsified and dispersed. Even if the surfactant is mixed with the mixture of the components (a) and (b),
It may be added to an aqueous medium. The emulsified dispersion composed of the component (a), the component (b), the oil-soluble radical polymerization initiator, the surfactant and water is preferably fine particles, and the preferable particle size is 0.02 to 2 μm, more preferably. Is 0.1 to 1.0 μm. By making the aqueous emulsion dispersion having such a particle size, the particle size of the aqueous emulsion obtained after the polymerization can be reduced, the composition of each of the obtained polymers becomes uniform, and the coating film has solvent resistance and water resistance. It will have excellent properties. To achieve such a particle size,
After the treatment with a rotary homomixer, it is desirable to reduce the particle size using a high-pressure type emulsifying disperser (homogenizer), a dispersing device having a high shear energy such as a turbine type mixer.

The preferred ratio of the total amount of the component (a) and the component (b) to the aqueous medium is 100% of the total amount of the component (a) and the component (b).
The aqueous medium is 20 to 150 parts by weight per part by weight.

In the present invention, it is preferable to add a pH buffer for stabilizing the hydrolyzable silyl group in the component (a). The formulation of the pH buffer may be performed by dispersing the components (a) and (b) in an aqueous medium in advance in the aqueous medium, or the components (a) and (b) may be dissolved in advance. They may be added together in an aqueous medium. As the pH buffering agent, a buffering agent suitable for maintaining the pH of the aqueous medium at 6 to 10 is preferable, and examples thereof include organic acids, inorganic acids, bases and salts thereof. Examples include sodium, sodium carbonate, ammonium carbonate, sodium borate, sodium phosphate, sodium sulfate, sodium acetate, ammonium acetate, mono-, di- or triethanolamine, aniline, and sodium silicate. Among them, sodium hydrogencarbonate is most preferable in terms of safety, low cost, and the like. The buffers may be used alone or in combination of two or more. In general, the amount used is preferably from 0.01 to 5% by weight in the aqueous emulsion dispersion.

Next, a step [B] of dropping the aqueous emulsion obtained in the step [A] into a heated aqueous medium and copolymerizing the components (a) and (b) is performed. Specifically, the aqueous emulsified dispersion obtained in the step [A] is dropped into a stirred reactor in which a small amount of an aqueous medium is charged and which is heated to a temperature not lower than the decomposition temperature of the polymerization initiator. The preferred amount of the aqueous medium charged into the reactor is the amount of the aqueous emulsified dispersion 1 dropped into the reactor.
It is about 10 to 50 parts by weight per 00 parts by weight. The aqueous dispersion is preferably gradually dropped into the reactor from a dropping funnel, and the polymerization temperature is usually preferably from 40 to 100 ° C.

3. Other Ingredients The aqueous emulsion obtained in the present invention contains various additives commonly used for paints, coatings, binders for fibers and nonwoven fabrics, adhesives and rust inhibitors, for example, Fillers such as clay, talc, calcium carbonate and titanium white, pigments, dyes, film-forming aids, plasticizers, various surfactants used for wetting, dispersing, defoaming, etc., antistatic agents, thickeners, thixotropic If necessary, a property imparting agent, an antifreezing agent, various crosslinking agents, an antifogging agent, a lubricant, a metal powder, an antioxidant, an ultraviolet ray inhibitor, an antibacterial agent, an antifungal agent, a tackifier, and a rust inhibitor, etc. An appropriate amount can be added. In the present invention,
It is preferable to incorporate a film-forming aid used in an aqueous paint. Examples of the film forming aid include cellosolve such as butyl cellosolve, carbitol and tripropylene glycol-n.
And glycol ethers such as butyl ether.

4. Method of Use The aqueous emulsion obtained in the present invention can be applied to various substrates and a coating film can be obtained by evaporating water at ordinary temperature or under heating. The coating film is crosslinked by a reaction of a hydrolyzable silyl group or silanol group derived from the component (a). The crosslinking reaction proceeds even at room temperature, but if it is desired to further promote crosslinking, a curing catalyst may be added. As curing catalysts, for example, organic titanate compounds such as isopropyl triisostearoyl titanate and isopropyl tri (dioctyl pyrophosphate) titanate, organic tin compounds such as tin dioctylate, dibutyltin dilaurate and dibutyltin malate, and organic compounds such as paratoluenesulfonic acid Acid catalysts may be mentioned.

5. Use The aqueous emulsion obtained by the present invention is suitable as a coating material. Applicable substrates include, for example, glass, slate, metal, wood, plastic, concrete and the like. To show the use of the coating agent more specifically, paint, acid rain resistant paint, antifouling paint and water repellent for civil engineering and construction, moisture-proof coating agent for electric and electronic parts,
Examples include magnetic tape back coat agents, and other uses include sealing agents, fiber treatment agents, binders for fibers and nonwoven fabrics, binders for inks, and pressure-sensitive adhesives. Therefore, outdoor paint applications are most preferred.

[0048]

The present invention will now be described more specifically with reference to examples and comparative examples. In addition, "parts" in each example means parts by weight. The surfactant “AQUALON HS20” (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) used in the examples is a radical polymerizable surfactant represented by the following (7).

[0049]

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Example 1 (Step 1) The components shown in Table 1 were used in the proportions shown in Table 1. The hydrolyzable silyl monomer, silane compound and isopropyl alcohol were mixed in the amounts shown in Table 1 and charged into a flask equipped with a stirrer, thermometer and cooler. Liquid temperature 60
After the temperature was raised to 0 ° C, water in which the catalyst was dissolved was slowly dropped over about 30 minutes while stirring. After the completion of the dropwise addition, the reaction was maintained for another 1 hour to complete the reaction. In this case, it is calculated that about half of the hydrolyzable silyl group has been hydrolyzed and condensed. Thereafter, the reaction solution was distilled to remove isopropyl alcohol used as a solvent and ethanol generated by hydrolysis. The obtained liquid condensate (hereinafter referred to as condensate 1) was transparent and did not increase in viscosity even after long-term storage.

[0051]

[Table 1]

Example 2 (Step 1) The reaction was carried out in the same manner as in Example 1 except that the components and proportions shown in Table 1 were changed to produce the component (a). The resulting liquid condensate of component (a) (hereinafter referred to as condensate 2)
It was transparent and the viscosity did not increase even after long-term storage.

Example 3 (Step 2) (1) Production process of aqueous emulsified dispersion (Step [A]) Components (a) and (b), an oil-soluble radical polymerization initiator and pH buffer shown in Table 2 Agent, radical polymerizable surfactant and water,
The components were mixed in the amounts shown in Table 2 and emulsified and dispersed using a homomixer to prepare an aqueous emulsified dispersion. The particle size of the dispersion composed of the components (a) and (b) is approximately 0.2 μm.
m.

[0054]

[Table 2]

(2) Polymerization Step (Step [B]) A flask equipped with a stirrer, a thermometer and a cooler was charged with 70 parts of deionized water as an aqueous medium, the liquid temperature was raised to 85 ° C., and then the mixture was stirred. The above aqueous emulsified dispersion was added dropwise over 3 hours. After completion of the dropping, the temperature of the internal solution was raised to 90 ° C.
The time was maintained to complete the polymerization. No liquid separation and blocking occurred during the polymerization, and the polymerization was carried out stably. In the obtained aqueous emulsion, the average particle size of the copolymer was 0.1.
It was 23 μm. 10 parts of tripropylene glycol-n-butyl ether (hereinafter abbreviated as TPNB) is blended with 100 parts of the solid content of the obtained aqueous emulsion,
An aqueous composition was prepared. The following evaluation was performed using the obtained aqueous composition. Table 3 shows the results.

○ Evaluation Ethanol generation ratio The amount of alcohol produced by decomposition of the alkoxysilyl group was analyzed by gas chromatography for a sample in which the aqueous composition was kept at a temperature of 60 ° C. for one month immediately after the production or in a sealed container for one month. did. Assuming that the charged monomer (a) and the alkoxysilyl of the silane compound were all hydrolyzed, the ratio of the alcohol to the alcohol amount was calculated, and the ratio was defined as the ethanol generation ratio (% by weight).
In addition, it is presumed that the condensation reaction proceeds in a sample having a high ethanol generation rate, and the development of contamination resistance cannot be expected.

Stain resistance A 0.6-mm thick aluminum plate was coated with a white fluorine-based paint (CFC 900, manufactured by Kawakami Paint Co., Ltd.), and the resulting aqueous composition was applied using a bar coater. (Dry film thickness: about 30 μm) and dried at normal temperature for 1 week. The obtained coating film was subjected to an exposure test at an angle of 45 ° in a southern industrial zone in Nagoya City, and ΔL, which is a change in L value before and after the test, was measured. The smaller the absolute value of the ΔL value, the better the stain resistance. The value after 6 months of exposure is the stain resistance ΔL, 12
The value after exposure for months was indicated as stain resistance ΔL.

Example 4 (Step 2) An aqueous emulsion was produced under the same conditions as in Example 3 except that 20 parts of condensate 1 and 10 parts of n-butyl methacrylate were used. . Using the obtained aqueous emulsion, a composition was prepared by blending TPNB in the same manner as in Example 3, and evaluated in the same manner as in Example 3. Table 3 shows the results.

Example 5 (Step 2) An aqueous emulsion was produced under the same conditions as in Example 3 except that condensate 1 was replaced by condensate 2. Using the obtained aqueous emulsion, a composition was prepared by blending TPNB in the same manner as in Example 3, and evaluated in the same manner as in Example 3. Table 3 shows the results.

Comparative Example 1 An aqueous emulsion was produced under the same conditions as in Example 3 except that 30 parts of n-butyl methacrylate was used without using the condensate 1. Using the obtained aqueous emulsion, TPNB was obtained in the same manner as in Example 3.
Was prepared to prepare a composition, which was evaluated in the same manner as in Example 3. Table 3 shows the results.

Comparative Example 2 3.7 parts of γ-methacryloxypropyltriethoxysilane and 1 part of tetraethoxysilane were used without using the condensate 1.
An aqueous emulsion was produced under the same conditions as in Example 3 except that 3.3 parts were used and all other components and operations were the same. Using the obtained aqueous emulsion, a composition was prepared by blending TPNB in the same manner as in Example 3, and evaluated in the same manner as in Example 3. Table 3 shows the results.

Comparative Example 3 An aqueous emulsion dispersion was prepared in Example 3 without using an oil-soluble polymerization initiator. That is, an aqueous emulsified dispersion was dropped into an aqueous medium to which 1 part of ammonium persulfate as a polymerization initiator was added, and emulsion polymerization was carried out in the same manner as in Example 3 under other conditions. Using the obtained aqueous emulsion, TPNB was blended in the same manner as in Example 3 to produce a composition,
Evaluation was performed in the same manner as in Example 3. Table 3 shows the results.

[0063]

[Table 3]

[0064]

The aqueous emulsion obtained by the production method of the present invention has excellent storage stability, and the resulting coating film has excellent stain resistance over a long period of time. It is extremely useful for various uses such as coating agents.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C09D 183/00 C09D 183/00 F-term (reference) 4J011 AA05 JA13 JB14 JB26 JB29 SA76 SA79 4J027 AF03 AF05 BA02 BA04 BA05 BA06 BA07 CB03 CB09 CC02 CD08 4J038 CL001 KA09 MA08 MA10 4J100 AB02Q AB03Q AB07R AE18R AG02Q AG04Q AJ02Q AJ08Q AJ09Q AL03Q AL04Q AL05Q AL08P AL08Q AL09Q AL10Q AP16P BA04R BA08R BA17R BA18R BA18R BA17R BA18R BA17R BA17R BA18R

Claims (4)

[Claims] 1. A method for producing an aqueous emulsion comprising the following steps 1 and 2. Step 1: By heating the hydrolyzable silyl group-containing radical polymerizable monomer and the following silane compound in the presence of water, the silane compound is condensed with the hydrolyzable silyl group of the radical polymerizable monomer. (A) producing a condensate of a silane compound having radical polymerizability. ○ Silane compound; General formula R ¹ _n Si (R ² ) _4-n (1) (where n is an integer of 0, 1 or 2, R ¹ is a stable hydrophobic group, R ² is a hydrolyzable group), a monomer, dimer, trimer and / or oligomer of the compound represented by the formula: Step 2: a step of copolymerizing a radical polymerizable monomer copolymerizable with the above components (a) and (b) (a) in an aqueous medium in the presence of a surfactant. 2. The method according to claim 1, wherein the surfactant has the general formula Z- (AO) n
-Y (wherein, Z is an organic group having a radical polymerizable double bond, AO is an oxyalkylene group, n is an integer of 2 or more, Y
The method for producing an aqueous emulsion according to claim 1, wherein the surfactant is a radically polymerizable surfactant represented by the following formula: 3. The silane compound according to claim 1, wherein in the general formula (1), n is an integer of 0 or 1, R ¹ is an alkyl group, and R ² is an alkoxy group. A method for producing the aqueous emulsion according to claim 2. 4. The method for producing an aqueous emulsion according to claim 1, wherein the step 2 further comprises the following steps [A] and [B]. Step [A]: The component (a) and the component (b) in the presence of a surfactant
A step of emulsifying and dispersing the components and the oil-soluble radical polymerization initiator in an aqueous medium. Step [B]: a step of dropping the aqueous emulsified dispersion obtained in Step [A] into a heated aqueous medium to copolymerize the components (a) and (b).