JP2570827B2 - Method for producing aqueous dispersion and aqueous coating composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an aqueous dispersion and an aqueous coating composition.

[Prior Art] Conventionally, as a conventional method for producing a dispersion, a method of performing emulsion polymerization in the presence of an emulsifier is generally known. However, since the aqueous dispersion obtained by this method contains a large amount of an emulsifier which is a water-soluble substance, the film has poor water resistance when the film is formed, and the emulsifier is easily decomposed, so that the weather resistance of the film is low. There was a problem that sex was bad.

Recently, an emulsion polymerization method using a graft copolymer having a fluorine-containing side chain and a hydrophilic side chain as a dispersion stabilizer has been proposed (JP-A-63-10611). However, although the aqueous dispersion obtained by this method can provide a film having good water resistance, improvement of weather resistance has not been sufficient.

A method is also known in which a vinyl monomer is employed in an organic liquid in the presence of a fluorine-containing copolymer soluble in the organic liquid, and then water is added to distill off the organic liquid. 62−2436
03). According to this method, an aqueous dispersion capable of forming a filter having excellent weather resistance can be obtained, but there is a problem in that the process is complicated and the use of a large amount of the organic liquid is dangerous.

[Problems to be Solved by the Invention] The present invention is intended to solve the above-mentioned problems of the prior art, and is intended to provide an aqueous dispersion which gives a film having excellent water resistance and weather resistance. It is another object of the present invention to provide a water-based coating composition which can be easily and easily produced, and has excellent water resistance and weather resistance.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and has a fluorine-containing compound having a fluorine atom directly bonded to the main chain and having a hydrophilic side chain. Emulsion polymerization of fluoroolefins having 2 to 4 carbon atoms in an aqueous medium in the presence of a polymer, or emulsion polymerization of a fluoroolefin having 2 to 4 carbon atoms and an emulsion-polymerizable monomer. A method for producing an aqueous dispersion, characterized by comprising, and an aqueous coating composition comprising a mixture of at least two aqueous dispersions,
Emulsion polymerization of a monomer in an aqueous medium in the presence of a fluorine-containing copolymer having at least one aqueous dispersion having a fluorine atom directly bonded to a main chain and having a hydrophilic side chain. The present invention provides an aqueous coating composition which is an aqueous dispersion obtained by the method.

In the production method of the present invention, it is important that emulsion polymerization is performed in the presence of a fluorine-containing copolymer having a fluorine atom directly bonded to the main chain and having a hydrophilic side chain. As such a fluorine-containing copolymer, those containing a fluorine atom bonded to the main chain at a ratio of 10% by weight or more are preferably employed because they give a film having particularly excellent weather resistance. As a method for obtaining a fluorine-containing copolymer having a fluorine atom bonded to the main chain, a method in which a fluoroolefin and another copolymerizable monomer are copolymerized is usually employed. As the fluoroolefin, a fluoroolefin having about 2 to 4 carbon atoms such as vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, pentafluoropropylene, and hexafluoropropylene is preferably employed. In the fluorinated copolymer, the unit based on the fluoroolefin is 20 to 80 mol%, preferably 30 to 70 mol%.
It is preferred to be mol%. If the amount of the fluoroolefin-based unit is too small, sufficient weather resistance will not be exhibited, and if it is too large, the solubility in water will be extremely low, and emulsion polymerization will be substantially difficult, which is not preferable.

In the present invention, the fluorinated copolymer has a hydrophilic side chain. Examples of the hydrophilic side chain include a hydrophilic side chain such as a polyoxyethylene chain and a side chain having a hydrophilic group such as a carboxylic acid group or a derivative thereof.
As the hydrophilic group, a side chain having a hydrophilic group is preferably employed from the viewpoint of easy production. Further, it is effective and preferable that the hydrophilic group is at the terminal of the side chain. Such hydrophilic _{groups, -COOM, -SO 3 M, -PO} 3 M ( where M hydrogen, alkali metal, quaternary ammonium groups or quaternary phosphonium groups,), an amide group and the like . The hydrophilic side chain preferably contains 0.1 to 80 mol% of a repeating unit having a hydrophilic side chain in the fluorinated copolymer. If the amount of the hydrophilic group is too small, it will not be dispersed or dissolved in water, and emulsion polymerization will be substantially difficult. On the other hand, if the proportion of the hydrophilic side chain is too large, gelation may occur, which is not preferable. In particular, a repeating unit having a hydrophilic side chain is 1 to 20.
A fluorine-containing copolymer containing at a mole percentage is preferably employed.

Examples of the method for introducing a hydrophilic side chain into the fluorinated copolymer include the following methods. First, a method of copolymerizing a monomer having a hydrophilic chain or a hydrophilic group. Second, a method in which a hydrophilic chain or a compound providing a hydrophilic group is reacted with a fluorine-containing copolymer having a reactive group by a polymer reaction to introduce a hydrophilic side chain. Third, a method of forming a hydrophilic side chain by hydrolysis or the like of a fluorinated copolymer obtained by previously polymerizing a monomer capable of forming a hydrophilic group by hydrolysis or the like. Such a method can be exemplified. In the first method, as the monomer having a hydrophilic chain or a hydrophilic group, a compound having an ethylenically unsaturated group is preferably employed from the viewpoint of copolymerizability with a fluoroolefin. Examples of the compound having an ethylenically unsaturated group include a vinyl compound, an allyl compound, an acryloyl compound, and a methacryloyl compound. As the hydrophilic chain, polyethylene oxide or the like is used, and as the hydrophilic group, as described above, a carboxylic acid group, a carboxylic acid group, a sulfonic acid group, a sulfonic acid group,
Examples include a phosphonic acid group, a phosphonate group, and an amide group. Further, a monomer having a hydrophilic chain or a hydrophilic group,
Some or all of the hydrogen bonded to carbon may be replaced by fluorine. Specific examples of such a monomer having a hydrophilic chain or a hydrophilic group include CH ₂ CHOCHOCH ₂ CH ₂ CH ₂ (OCH ₂ CH ₂ ) _n OH and CH ₂ CHCHCH ₂ OCH ₂ CH ₂ (OCH ₂ CH ₂ ) _n OH, CH ₂ CHCHCOOM, CH ₂ ＣC (CH ₃ ) COOM, , CF ₂ = CFOCF ₂ CF ₂ COOM, (M is the same hydrogen, alkali metal, quaternary ammonium group or quaternary phosphonium group as described above).

In the method using the second polymer reaction, the following fluorine-containing copolymer having a reactive group is employed. Examples of the reactive group include an active hydrogen-containing group such as a hydroxyl group, a carboxylic acid group, an amino group, an acid amide group, and a mercapto group, an epoxy group, an active halogen-containing group, and a double bond. Such a reactive group can be introduced into a fluorinated copolymer by copolymerizing a monomer having a reactive group with a fluoroolefin.
Here, as the monomer having a reactive group, hydroxyalkyl vinyl ether, hydroxyalkyl allyl ether, hydroxyalkyl vinyl ether or hydroxyalkyl allyl ether, a reaction product of a lacto compound or a reaction product of dicarboxylic anhydride, or glycidyl vinyl ether Or a reaction product of glycidyl allyl ether and phenol, glycidyl vinyl ether, glycidyl allyl ether, aminoalkyl vinyl ether, acrylamide, a reaction product of hydroxyalkyl vinyl ether and isocyanate alkyl methacrylate, allyl vinyl ether, and the like.

In the second method, a compound having a hydrophilic chain or a hydrophilic group is reacted with a fluorine-containing copolymer having a reactive group obtained by the above-described method by a polymer reaction. Examples of the compound that provides a hydrophilic chain include compounds having a hydrophilic chain such as isocyanate-terminated polyoxyethylene and a group capable of reacting with a reactive group of the above-mentioned fluorinated copolymer, and the like. And a compound capable of forming a hydrophilic chain such as ethylene oxide, for example, by introducing an ethylene oxide to the hydroxyl group of the above to introduce a polyoxyethylene chain. Examples of the compound that provides a hydrophilic group include polycarboxylic acids such as succinic acid, polysulfonic acids, polyphosphonic acids, acrylamide, methacrylamide, methacrylic acid, and acrylic acid. Examples thereof include compounds having a group capable of reacting with a reactive group of the fluorinated copolymer. Further, a compound that generates a hydrophilic group by reacting with a reactive group of a fluorine-containing copolymer such as a polyvalent carboxylic anhydride can also be used. When the hydrophilic group is an acid group, it is preferable that the hydrophilic group is neutralized by an ionic compound because the hydrophilicity is effectively exhibited. Here, the neutralization with the ionic compound may be performed either before or after the reaction with the fluorine-containing copolymer. Further, from the relationship with the curing reactive site described below, in the second method, a compound that provides a hydrophilic chain or a hydrophilic group to all of the reactive groups of the fluorocopolymer may be reacted, Some of the reactive groups of the fluorinated copolymer may remain. The presence or absence of the reactive group in the fluorinated copolymer can be achieved by appropriately selecting the type and amount of the hydrophilic chain or the compound providing the hydrophilic group to be reacted.

The third method is a method in which a compound that generates a hydrophilic group by hydrolysis or the like during the production of the fluorinated copolymer is copolymerized in advance, and after polymerization, the compound is hydrolyzed to generate a hydrophilic group. Here, examples of the compound that forms a hydrophilic group by hydrolysis or the like that is previously copolymerized include unsaturated carboxylic esters such as acrylic esters and unsaturated sulfonic esters.

The fluorinated copolymer may contain units based on monomers copolymerizable therewith, in addition to the aforementioned units based on fluoroolefins and the repeating units having a hydrophilic side chain. Examples of such monomers include olefins, vinyl ethers, vinyl esters, allyl ethers, allyl esters, acrylic esters, methacrylic esters, and the like. If these monomers are copolymerized in an excessively large amount, weather resistance is undesirably reduced. When such a monomer is copolymerized, it is preferable that the amount is 70 mol% or less. In addition, when these monomers are copolymerized, advantages such as excellent dispersibility of the pigment and gloss of the film, and good compatibility with the monomers during the emulsion polymerization described below are obtained, which is preferable. As this monomer, in particular,
Olefins, vinyl ethers, vinyl esters,
Allyl ethers and allyl esters are preferably employed. Here, the olefins preferably have about 2 to 10 carbon atoms, and the vinyl ethers, vinyl esters, allyl ethers, and allyl esters include linear, branched or fatty acids having about 2 to 15 carbon atoms. Those having a cyclic alkyl group are preferably employed.

Further, the fluorine-containing copolymer having a curing reactive site is preferable since a tough coating film can be obtained. Such a curing reactive site is a site that reacts with a curing agent or curing reactive sites to give a cured product. Specifically, the same groups as those described above as the reactive group of the fluorinated copolymer can be employed. Examples thereof include active hydrogen-containing groups such as a hydroxyl group, a carboxylic acid group, an amino acid, an acid amide group, and a mercapto group, an epoxy group-active halogen-containing group, and a double bond. In addition, the method for introducing a curing reactive site into the fluorinated copolymer was described as a method for introducing a reactive group in the second method of introducing a hydrophilic side chain into the fluorinated copolymer. Examples of the method include a method of copolymerizing a monomer having a curing reaction site. The curing reactive site preferably has about 0 to 35 mol% of repeating units containing the curing reactive site in the fluorinated copolymer.

In the present invention, the molecular weight of the fluorinated copolymer is not particularly limited. However, if it is too large, the viscosity of the aqueous medium becomes too high, and it is difficult to form good micelles in the aqueous medium. Too small is not preferable because of water resistance. Usually, the number average molecular weight is 1,000
About 500,000, especially about 3,000 to 400,000 is preferred.

In the production method of the present invention, emulsion polymerization is performed in the presence of the above-mentioned fluorine-containing copolymer. At this time, as the medium, water may be used alone, or a mixed solution of water and an organic liquid may be used. When an organic liquid is mixed, a stable dispersion may be obtained. Further, the aqueous dispersion obtained by the method of the present invention can be used as an aqueous coating as it is. Here, examples of the organic liquid include alcohols such as mer alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, Teat-butyl alcohol, sec-butyl alcohol, amyl alcohol, pentanol, octyl alcohol, and methyl cellosolve. And ethyl alcohol such as ethyl cellosolve, isopropyl cellosolve, butyl cellosolve, and diethylene glycol monobutyl ether; and fluorine-based solvents such as trichlorotrifluoroethane. Also,
These organic liquids may be used alone or as a mixture of two or more.

In the present invention, the monomer to be emulsion-polymerized is not particularly limited as long as it is usually a monomer that can be emulsion-polymerized.
Emulsion-polymerizable monomers include olefins such as ethyne and propylene, vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether and cyclohexyl vinyl ether; vinyl esters such as butyl vinyl ester and octyl vinyl ester; Vinyl compounds such as aromatic vinyl compounds such as vinyl toluene, allyl compounds such as allyl ethers such as ethyl allyl ether and allyl esters such as butyl allyl ester, acryloyl compounds such as butyl acrylate, and ethyl methacrylate A methacryloyl compound or the like, or a compound in which part or all of hydrogen bonded to carbon is substituted with a halogen atom, or the like is used. Examples of the compound substituted with a halogen atom include halogenated olefins such as vinyl chloride, vinyl bromide, vinylidene chloride, vinylidene fluoride, chlorotrifluoroethylene, tetrafluoroethylene, and hexafluoropropylene, and perfluoro (propyl vinyl ether). Examples thereof include a halogenated vinyl compound, fluoroacrylate, and fluoromethacrylate. Further, a monomer having a reactive group such as hydroxyalkyl vinyl ether and chrysidyl allyl ether may be used. In addition, such a monomer may be a single type of homopolymer or a copolymer of two or more types. Among them, fluoroolefins having about 2 to 4 carbon atoms such as hexafluoropropylene, pentafluoropropylene, tetrafluoroethylene, chlorotrifluoroethylene, trifluoroethylene, and vinylidene fluoride, and vinyl compounds, allyl compounds or fluorinated compounds It is preferable to carry out emulsion polymerization using the vinyl or allyl compound thus obtained as a monomer, since an aqueous dispersion giving a coating film having particularly excellent weather resistance is obtained.

In the present invention, the amount of the above-mentioned fluorine-containing copolymer can be appropriately adopted in the range of about 0.1 to 99 parts by weight based on 100 parts by weight of the above-mentioned emulsion-polymerized monomer. If the amount of the fluorinated copolymer is less than 0.1 part by weight per 100 parts by weight of the monomer to be emulsion-polymerized, the stability of the obtained aqueous dispersion may decrease, which is not preferable. Further, when the polymer obtained by emulsion polymerization does not show good weather resistance, for example, when the emulsion polymer does not contain fluorine or has a very low fluorine content, an aqueous dispersion which gives a coating film having sufficient weather resistance is used. In order to obtain a liquid, it is preferable to use 10 parts by weight or more of the fluorine-containing copolymer per 100 parts by weight of the monomer to be subjected to emulsion polymerization.

In the method of the present invention, a pH adjuster may be used for the purpose of increasing the pH of the emulsion. Examples of such a pH adjuster include inorganic bases such as sodium carbonate, potassium carbonate, sodium o-hydrogen phosphate, sodium thiosulfate, and sodium tetraborate, and organic bases such as triethylamine and triethanolamine. The amount of the pH adjuster is usually 0.05 to 100 parts by weight of the emulsion polymerization medium.
It is about 5 parts by weight, preferably about 0.1 to 1 part by weight.

Further, in the production method of the present invention, the initiation of emulsion polymerization is carried out by adding a polymerization initiator in the same manner as in the start of ordinary emulsion polymerization. As such a polymerization initiator, a water-soluble initiator is preferably adopted. Specifically, a water-soluble initiator such as a persulfate such as ammonium persulfate, hydrogen peroxide or a combination thereof with a reducing agent such as sodium hydrogen sulfite or sodium thiosulfate is used. Redox initiators, and furthermore, a small amount of these iron, ferrous salts, inorganic initiators in the presence of silver sulfate and the like, or dispersic acid peroxide, dibasic acid peroxides such as diglutaric acid peroxide, azo Organic initiators such as bisisobutylamidine dihydrochloride and azobisbutyronitrile are exemplified. The amount of polymerization initiator used is
Kind, emulsion polymerization, can be appropriately changed depending on the conditions, but usually per 100 parts by weight of the monomer to be emulsion-polymerized,
0.005 to 5 parts by weight, particularly about 0.05 to 0.5 parts by weight is preferably employed.

Also, the emulsion polymerization initiation temperature is appropriately selected optimally mainly depending on the type of polymerization initiator, usually, 0 ~ 100 ℃,
Particularly, about 10 to 90 ° C. is preferably employed. The reaction pressure can be appropriately selected, but is usually 1 to 100 kg / cm ² ,
In particular, it is desirable to employ about ² to 50 kg / cm ² .

Further, in the production method of the present invention, the addition of the monomer,
After the polymerization reaction has progressed, a method of additionally adding may be adopted. In the case of this additional addition, a monomer having the same composition as the initially charged monomer composition may be added, or a monomer having a different composition may be added.

Furthermore, the present invention provides an aqueous coating composition containing the aqueous dispersion obtained by the above method as a main component. Such an aqueous coating composition provides a coating film having extremely excellent water resistance, weather resistance, and the like.

The aqueous coating composition can be used as it is with the aqueous dispersion obtained by the above method, but if necessary, a coloring agent, a plasticizer, an ultraviolet absorber, a leveling agent,
An anti-cissing agent, an anti-burr agent, a curing agent and the like may be mixed. Examples of the coloring agent include dyes, organic pigments, and inorganic pigments. Examples of the plasticizer include conventionally known plasticizers, for example, low molecular weight plasticizers such as dimethyl phthalate and dioctyl phthalate, and high molecular weight plasticizers such as a vinyl polymer plasticizer and a polyester plasticizer. Examples of the ultraviolet absorber include organic ultraviolet absorbers such as benzophenone, benzotriazole and phenyl salicylate, and inorganic ultraviolet absorbers such as titanium oxide. As the curing agent, for example, blocked isocyanates such as hexamethylene isocyanate trimer, melamine resins such as methylated melamine, methylolated melamine and butylolated melamine, amino resins such as benzoguanamine, and urea resins such as methylated urea and butylated urea And the like.

Further, in the aqueous coating composition, it is preferable that each of the components is mixed as much as possible with an aqueous dispersion. Compared to the case where a solid or liquid composition is mixed with the aqueous dispersion, the composition can be microscopically dispersed when the aqueous dispersions are mixed with each other, and thus each of the components can be uniformly dispersed in the coating film. Can be demonstrated. For example, when two or more polymers are blended, uniform dispersion is easy,
A highly transparent coating film can be obtained. In addition, when an aqueous dispersion of a polymer having a high glass transition point (hereinafter, sometimes abbreviated as Tg) and an aqueous dispersion of a polymer having a low Tg are blended, high hardness, workability and flexibility are obtained. It is possible to obtain a coating film which is high and has improved scratch resistance. In addition, a fluorine-free polymer aqueous dispersion, an inorganic substance (for example, conductive carbon) aqueous dispersion is blended, and contamination of the coating film, chargeability,
Hardness and the like can be improved.

[Examples] Hereinafter, the present invention will be described specifically with reference to Synthesis Examples and Examples, but the present invention is not limited to these Examples and the like. The parts in the following Synthesis Examples, Examples and Comparative Examples are parts by weight unless otherwise specified.

[Synthesis Example (Synthesis of Fluorinated Copolymer Aqueous Solution)] Synthesis Example 1 35 parts of chlorotrifluoroethylene was placed in a 200 ml stainless steel autoclave with a stirrer (withstand pressure of 50 kg / cm ² ).
11 parts of cyclohexyl vinyl ether, 43 parts of ethyl vinyl ether, 15 parts of ω-hydroxybutyl vinyl ether,
98 parts of xylene, 28 parts of ethanol, 0.5 parts of azobisisobutyronitrile, and 1.5 parts of anhydrous potassium carbonate were charged, and cooled with liquid nitrogen to remove dissolved air by solidification and deaeration. Then, a hydroxyl group-containing fluorinated copolymer was obtained.

The obtained copolymer had a solid viscosity of 0.11 dl / g measured at 30 ° C. in tetrahydrofuran.

The obtained hydroxyl-containing fluorine-containing copolymer (having a hydroxyl value of about
An about 60% xylene solution of 120 mg KOH / g-resin) was heated to 50 ° C., and 3.6 parts of succinic anhydride and 10 parts of acetone were added to 100 parts of the polymer, and 0.2 part of triethylamine was further added. The reaction was performed for 2 hours.

When the infrared spectrum of the reaction solution was measured, the characteristic absorptions (1850 cm ^-1 and 1780 cm ^-1 ) of the anhydrous acid observed before the reaction disappeared after the reaction, and the carboxylic acid (1710 cm ^-1 ) and the ester ( An absorption of 1735 cm ^-1 ) was observed.

Thus, the acid value of the fluorinated copolymer having a carboxyl group introduced therein is 20 mg KOH / g-resin, and the hydroxyl value is 100 mg KOH / g.
-Resin.

The obtained fluorinated copolymer was once evaporated with a solvent to isolate the solid content of the copolymer, and then newly dissolved with ethyl alcohol to obtain an approximately 60% ethyl alcohol solution.

135 parts of this ethyl alcohol solution was placed in a reaction vessel equipped with a stirrer and a reflux condenser, 4 parts of triethanolamine was added, and 150 parts of deionized water was added to prepare an aqueous solution of a fluorine-containing copolymer.

Synthesis Examples 2 to 6 The monomers shown in Table 1 were polymerized using the same formulation as in Synthesis Example 1 to synthesize a xylene solution of a hydroxyl group-containing fluorinated copolymer.

Next, the obtained copolymer solution was reacted with succinic anhydride in the amount shown in Table 1 in the same manner as in Synthesis Example 1 to obtain a fluorine-containing copolymer containing a carboxyl group and a hydroxyl group. A polymer was synthesized.

The acid value and hydroxyl value of each fluorine-containing copolymer were as shown in Table 1.

An aqueous solution of each fluorine-containing copolymer was prepared in the same manner as in Synthesis Example 1.

Synthesis Example 7 In a 200 ml stainless steel autoclave with a stirrer, 35 parts of chlorotrifluoroethylene 11 parts of cyclohexyl vinyl ether 4.3 parts of ethyl vinyl ether 7.5 parts of ω-hydroxybutyl vinyl ether Xylene 98 parts Ethanol 28 parts Azobisisobutyronitrile 0.5 parts Anhydrous potassium carbonate 1.3 parts were charged, cooled with liquid nitrogen, solidified and degassed to remove dissolved air, and then reacted at 65 ° C for 16 hours. A fluorine-containing copolymer was obtained.

The obtained copolymer was precipitated in ethanol and dried. 40 g of the dried polymer is placed in a 10% aqueous KOH solution at 90 ° C. 15
After immersion for a period of time, after the hydrolysis, the mixture was further ion-exchanged to a sulfonic acid type with a 1N HCl aqueous solution. The sulfonic acid group-containing fluorinated copolymer thus obtained was once dried and then dissolved in ethyl alcohol to obtain an approximately 60% ethyl alcohol solution.

50 parts of this ethyl alcohol solution was charged into a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser, 2.32 parts of triethanolamine was added, and 76 parts of deionized water was added to prepare a fluorine-containing copolymer aqueous solution.

Synthesis Example 8 50 parts of 2-perfluorobutylethyl methacrylate 55 parts of 2-hydroxyethyl methacrylate 50 parts of a dispersant obtained by copolymerizing 5 parts of acrylic acid was neutralized with triethanolamine, dissolved in 50 parts of ethanol, and deionized. Water 100 was added to prepare an aqueous dispersant liquid.

Example 1 A 200 ml stainless steel autoclave with a stirrer (withstand pressure of 50 kg / cm ² ) was used. 41.5 parts of chlorotrifluoroethylene 13.5 parts of cyclohexyl vinyl ether 15.4 parts of ethyl vinyl ether 3.6 parts of ω-hydroxybutyl vinyl ether 3.6 parts of the fluorine-containing copolymer prepared in Synthesis Example 1 Add 29 parts of aqueous polymer solution and add 98.2 parts of ion-exchanged water.0.16 parts of ammonium persulfate. The reaction was performed. The resulting aqueous polymer dispersion was stable.

Examples 2 to 3 Polymerization was carried out in the same manner as in Example 1 except that the fluorine-containing copolymer aqueous solution having the composition shown in Synthesis Examples 2 and 3 in Table 1 was used. A polymer dispersion was obtained.

Synthesis Example 9 80 parts of a fluorine-containing copolymer aqueous liquid having the composition shown in Synthesis Example 4 in Table 1 70 parts of n-butyl methacrylate 0.56 parts of ammonium persulfate 10 parts of 2-hydroxyethyl methacrylate 94.5 parts of ion-exchanged water The mixture was charged in a 300 ml autoclave equipped with a stirrer, cooled with liquid nitrogen, and solidified and deaerated to remove dissolved oxygen, followed by polymerization at 600 ° C. for 2 hours. The resulting aqueous dispersion was stable.

Example 4 Aqueous solution of fluorine-containing copolymer having the composition shown in Synthesis Example 6 in Table 1 30 parts Veovar 10 (vinyl ester manufactured by Shell Petrochemical Co., Ltd.) 45 parts ω-hydroxybutyl vinyl ether 6.8 parts chlorotrifluoro 33.6 parts of ethylene 90 parts of ion-exchanged water 0.16 parts of ammonium persulfate were charged into a 300 ml-volume stainless steel autoclave equipped with a stirrer, cooled with liquid nitrogen to remove dissolved oxygen during solidification and degassing, and then polymerized at 65 ° C for 16 hours. Done. The resulting aqueous polymer dispersion was stable.

Example 5 Emulsion polymerization was carried out in the same manner as in Example 1, except that the aqueous solution of the fluorinated copolymer obtained in Synthesis Example 7 was used. The resulting aqueous dispersion was stable.

Comparative Example 1 Emulsion polymerization was carried out in the same manner as in Synthesis Example 9 except that the aqueous solution of the fluorinated copolymer obtained in Synthesis Example 8 was used. The resulting aqueous dispersion was stable.

Evaluation of weather resistance of coating film Using the aqueous dispersions obtained in Examples 1 to 5 and Comparative Example 1, aqueous coating materials having the compositions shown in Table 2 were prepared. This water-based paint is dried on an aluminum plate that has been treated with arosin.
After drying, the coating was dried at 170 ° C. for 30 minutes.
Table 2 shows the evaluation results of the weather resistance of the obtained coating films. In addition, each of the obtained coated articles had excellent bending workability.

Example 6 The aqueous dispersions obtained in Examples 1 to 5 were applied on a slate plate and dried at 120 ° C. for 1 hour to obtain each test piece. When each test piece was subjected to a repeated heating / cooling test and a water permeability test in accordance with JIS A 6910, good results were obtained in each case.

Example 7 An aqueous coating composition obtained by mixing 70 parts of the aqueous dispersion obtained in Example 1 and 30 parts of the aqueous dispersion obtained in Synthesis Example 9 was applied on a glass plate and dried. The obtained coating film had improved charging characteristics as compared with the coating film obtained by applying and drying the aqueous dispersion obtained in Example 1 alone.

[Effects of the Invention] According to the present invention, a film having excellent weather resistance can be obtained, and an aqueous dispersion can be produced safely and easily. Further, the water-based coating composition obtained by the present invention is extremely useful as a weather-resistant water-resistant coating, and can be applied to ceramics-like coatings, slate-based roofing coatings, electric coatings, household coatings, and the like. Further, the aqueous dispersion obtained by the production method of the present invention can provide a dispersion having a high molecular weight and a high concentration as compared with those obtained by solution polymerization or the like. Therefore, the aqueous dispersion obtained according to the present invention is useful not only as a coating material used in a field where the flexibility of a coating film is required, for example, a precoated metal field, etc., but also has high durability against fibers, fabrics and the like. It is also useful as a water repellent oil agent.

Claims (6)

(57) [Claims] 1. An emulsion polymerization of a fluoroolefin having 2 to 4 carbon atoms in an aqueous medium in the presence of a fluorine-containing copolymer having a fluorine atom directly bonded to a main chain and having a hydrophilic side chain. Or a method for producing an aqueous dispersion, comprising subjecting a fluoroolefin having 2 to 4 carbon atoms to another emulsion-polymerizable monomer. 2. The process according to claim 1, wherein the fluorocopolymer contains 30 to 70 mol% of units based on fluoroolefin. 3. The method according to claim 1, wherein the fluorinated copolymer has a curing reactive site. 4. An aqueous coating composition comprising, as a main component, an aqueous dispersion obtained by the production method according to claim 1. 5. The aqueous coating composition according to claim 4, further comprising a curing agent. 6. An aqueous coating composition comprising a mixture of at least two aqueous dispersions, wherein at least one of the aqueous dispersions is an aqueous coating composition.
An aqueous dispersion obtained by emulsion-polymerizing a monomer in an aqueous medium in the presence of a fluorine-containing copolymer having a fluorine atom whose species is directly bonded to a main chain and having a hydrophilic side chain A water-based coating composition.