JPH04325509A - Aqueous dispersion of fluoropolymer - Google Patents

Abstract

PURPOSE:To obtain the title dispersion improved in film-forming properties, adhesion to a substrate, etc., by emulsion-polymerizing an alpha,beta-unsaturated carboxylic acid with a specified alkyl (meth)acrylate in the presence of vinylidene fluoride polymer particles. CONSTITUTION:30-90wt.% vinylidene fluoride is emulsion-copolymerized with 50-9wt.% tetrafluoroethylene and 20-1wt.% hexafluoropropylene to obtain vinylidene fluoride polymer particles (A) of a particle side of 0.05-3.0mum. 10-70wt.% alpha,beta-unsaturated carboxylic acid is mixed with 5-80wt. % alkyl (1-5C) (meth) acrylate and 0-85wt.% other ethylenically unsaturated compounds copolymerizable therewith to obtain a monomer (B). 10-900 pts. wt. component B is emulsion-polymerized at 30-100 deg.C for 1-30hr in the presence of 100 pts. wt. component A in an aqueous medium containing an emulsifier, a polymerization initiator, a pH adjusting agent, a solvent, etc.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an aqueous dispersion of a fluoropolymer, and more specifically, the present invention relates to an aqueous dispersion of a fluoropolymer. The present invention relates to an aqueous dispersion of a fluoropolymer that can be formed.

0002

[Prior Art] Fluororesins have excellent chemical resistance and solvent resistance, as well as heat resistance, weather resistance, gas impermeability, and
It also has good radiation resistance, electrical insulation, etc. For this reason, fluororesins are used as lining materials, corrosion-resistant materials, porous materials (e.g. asbestos sheets, glass sheets, felt sheets,
impregnated processed materials (paper, etc.), packing materials, coating materials, acid-resistant,
Spraying materials, baking paints, laminated film materials, etc. on the surface of materials that require alkali resistance or electrical insulation.
It is widely being considered for use as a non-tackifying material for fibers, water repellent material, coating material for floors, etc.

By the way, in recent years, from the viewpoint of environmental hygiene to prevent air pollution and adverse effects on the human body caused by organic solvents, as well as from the viewpoint of resource conservation, dispersion media have been changed from the conventionally commonly used solution-based solvent-based fluororesin. Converting to water-based fluororesin using water is being actively studied.

However, compared to solvent-based fluororesins, water-based fluororesins do not have sufficient film-forming properties and are inferior in adhesion to substrates. As a result, coatings formed from water-based fluororesins do not have sufficient durability, are prone to coating defects such as pinholes, and have poor mechanical strength.

[0005] This is thought to be mainly due to the following reasons. In other words, in water-based fluororesins, since the polymer is in a dispersed state and has the form of particles, there is insufficient fusion between the particles during film formation, making it difficult to form a homogeneous film, resulting in the above disadvantages. .

On the other hand, in solvent-based fluororesins, the polymer is in a solution state and does not have a particle form.
As a result of forming a film at the molecular level, the film formability and adhesion to the substrate are much better than those of the water-based fluororesin.

[0007] In order to alleviate these drawbacks of water-based fluororesins, optimization of the monomer composition of water-based fluororesins, reduction of particle size, composite of particles with core/shell structure, and use of water-soluble solvents in water media have been developed. Attempts have been made to improve it through techniques such as adding it to the water, but the reality is that it has not yet been sufficiently improved.

[0008]

[Problems to be Solved by the Invention] The present invention was made against the background of the above-mentioned problems of the prior art, and its purpose is to provide an aqueous dispersion with particularly improved film-forming properties and adhesion to a substrate. An object of the present invention is to provide an aqueous dispersion of a fluoropolymer.

[0009]

[Means for Solving the Problems] The above object is achieved by: (a) α,β-unsaturated carboxylic acid in the presence of 100 parts by weight of vinylidene fluoride polymer particles as seed particles;
10 to 70% by weight, (b) 5 to 80% by weight of an acrylic ester in which the alkyl group has 1 to 5 carbon atoms and/or a methacrylic ester in which the alkyl group has 1 to 5 carbon atoms, (c
) Other ethylenically unsaturated compounds copolymerizable with these monomers (a) and (b)

This is achieved by an aqueous dispersion of a fluoropolymer, which is obtained by emulsion polymerizing 10 to 900 parts by weight of a monomer consisting of 0 to 85% by weight in an aqueous medium.

0010

[Function] In the present invention, by using a relatively large amount of α,β-unsaturated carboxylic acid as a monomer in a specific ratio, the so-called Alkali solubility can be imparted. By simply adjusting the aqueous dispersion of the fluoropolymer obtained by emulsion polymerization to alkalinity, the particle shape of the polymer can be eliminated and the polymer can be dissolved (
(including an amorphous swollen state that is close to the dissolved state but not completely dissolved), the film is formed in almost the same state as the solvent-based one. As a result, although it is an aqueous dispersion, the drawbacks of conventional water-based fluororesins can be significantly improved, particularly in terms of film formability, adhesion, and the occurrence of film defects. (Structure) The present invention will be explained in detail below.

Vinylidene Fluoride Polymer Vinylidene fluoride polymers used as seed particles in the present invention include vinylidene fluoride homopolymers, vinylidene fluoride and trifluorochloroethylene copolymerizable therewith; Fluorine-containing ethylenically unsaturated compounds such as hexafluoropropylene, tetrafluoroethylene, vinyl fluoride, hexafluoroisobutylene, perfluoroacrylic acid, fluorine-free ethylenically unsaturated compounds such as cyclohexyl vinyl ether and hydroxyethyl vinyl ether, butadiene, Examples include copolymers with fluorine-free diene compounds such as isoprene and chloroprene. The proportion of vinylidene fluoride used in the vinylidene fluoride polymer is usually 30% by weight or more of the polymer. Among these, vinylidene fluoride homopolymer, vinylidene fluoride/ethylene tetrafluoride copolymer,
Vinylidene fluoride/ethylene tetrafluoride/propylene hexafluoride copolymers are preferred, especially vinylidene fluoride/ethylene tetrafluoride/propylene hexafluoride copolymers.
Ethylene tetrafluoride/propylene hexafluoride copolymer is preferably used, and the copolymerization ratio is usually 30 to 90% by weight of vinylidene fluoride, 50 to 9% by weight of ethylene tetrafluoride, and 20 to 20% by weight of propylene hexafluoride. It is 1% by weight.

The vinylidene fluoride polymer described above can be obtained by various methods, but in the present invention, a vinylidene fluoride polymer obtained by emulsion polymerization is particularly preferably used.

The vinylidene fluoride polymer may be added in any state as long as it is dispersed as particles in an aqueous medium, but as mentioned above, in the present invention, vinylidene fluoride polymer obtained by emulsion polymerization is used. Polymers are preferred;
In this case, since it is produced as an aqueous dispersion, it is convenient to use the aqueous dispersion as it is for emulsion polymerization. Such an aqueous dispersion of a vinylidene fluoride polymer can be prepared by a normal emulsion polymerization method, for example, by adding an emulsifier, a polymerization initiator, a pH
It can be produced by emulsion polymerization in the presence of a regulator or the like.

The particle size of the vinylidene fluoride polymer particles varies depending on the particle size of the polymer particles in the target fluoropolymer aqueous dispersion, but is usually 0.05 to 3.0.
Preferably, it is in the μm range.

Monomer (a) component As the monomer to be emulsion polymerized in the presence of the vinylidene fluoride polymer particles, the α,β-unsaturated carboxylic acid of the component (a) is, for example, acrylic acid. , methacrylic acid, itaconic acid, fumaric acid, crotonic acid, etc. Among these, methacrylic acid is preferred.

Monomer (b) component (b) As the acrylic acid alkyl ester whose alkyl group has 1 to 5 carbon atoms, examples thereof include methyl acrylate, ethyl acrylate, propyl acrylate, and n-butyl acrylate. , isobutyl acrylate, amyl acrylate, and isoamyl acrylate. Among these, acrylic acid alkyl esters in which the alkyl group has 1 to 3 carbon atoms, especially acrylic acid alkyl esters in which the alkyl group has 1 or 2 carbon atoms.
Acrylic acid alkyl esters of are preferably used.

The alkyl group of component (b) has 1 to 5 carbon atoms.
Examples of the methacrylic acid alkyl ester include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, amyl methacrylate, and isoamyl methacrylate. Among these, methacrylic acid alkyl esters in which the alkyl group has 1 to 3 carbon atoms, particularly methacrylic acid alkyl esters in which the alkyl group has 1 or 2 carbon atoms, are preferably used.

Monomer (c) component Other ethylenically unsaturated compounds copolymerizable with the above components (a) and (b) of component (c) include (a) and (
Vinyl compounds other than component b) can be mentioned.

Component (c) includes vinyl compounds such as vinyl acetate, acrylamide, methacrylamide, N-
Methylacrylamide, N-methylmethacrylamide,
Amide compounds such as N-methylol acrylamide, N-methylol methacrylamide, N-alkylacrylamide, N-alkyl methacrylamide, N,N-dialkyl acrylamide, N,N-dialkyl methacrylamide, 2-hydroxyethyl acrylate, acrylic acid N-dialkylaminoethyl, glycidyl acrylate,
Acrylic acid esters such as fluoroalkyl acrylate, diacylaminoethyl methacrylate, fluoroalkyl methacrylate, 2-hydroxyethyl methacrylate,
Methacrylic acid esters such as glycidyl methacrylate and ethylene glycol dimethacrylate, vinyl ether compounds such as allyl glycidyl ether, conjugated dienes such as 1,3-butadiene and isoprene, styrene, α-
Examples include aromatic vinyl compounds such as methylstyrene and halogenated styrene, divinyl compounds such as divinylbenzene, and vinyl cyanides such as acrylonitrile and methacrylonitrile. Among these, N-methylol acrylamide, N-methylol methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, allyl glycidyl ether, 1
, 3-butadiene, styrene, acrylonitrile, etc. are preferably used.

[0020] The above (a) α,β-unsaturated carboxylic acid, (b) acrylic acid alkyl ester and methacrylic acid alkyl ester, and (c) ethylenically unsaturated compound used as necessary are any of the following: Also, the monomers exemplified above can be used alone or in a mixture of two or more.

When using an acrylic acid alkyl ester and a methacrylic acid alkyl ester together as component (b), there is no particular restriction on the ratio of the two, and it is determined as appropriate depending on the properties of the intended fluoropolymer. be able to.

Proportion of monomers The amount of α,β-unsaturated carboxylic acid used as component (a) is 10 to 70% by weight, preferably 20% by weight based on the total monomers.
~60% by weight, most preferably 30-60% by weight. If the content of component (a) is less than 10% by weight, the resulting polymer will not have sufficient alkali solubility, and film-forming properties and adhesion to the substrate will be impaired. On the other hand, if the content of component (a) exceeds 70% by weight, the weather resistance and chemical resistance of the coating will decrease, and the polymerization stability will also decrease.

The amount of (meth)acrylic acid alkyl ester used as component (b) is 5 to 80% by weight based on the total monomers.
, preferably 10 to 60% by weight. (b) component is 5
If the amount is less than 80% by weight or more than 80% by weight, the resulting polymer will not have sufficient alkali solubility, resulting in poor film-forming properties and poor adhesion to the substrate.

The amount of component (c) used is 0 based on the total monomers.
-85% by weight, preferably 0-70% by weight. If component (c) exceeds 85% by weight, the alkali solubility of the polymer will be insufficient, which is not preferable.

The aqueous dispersion of the fluoropolymer of the present invention is
Vinylidene fluoride polymer particles 10 as seed particles
(a), (b) and (c) above in the presence of 0 parts by weight.
10 to 900 parts by weight, preferably 40 to 400 parts by weight, more preferably 70 to 400 parts by weight of the monomer consisting of component
By polymerizing at a ratio of parts by weight, the monomer is polymerized in a state where it is absorbed or adsorbed onto the vinylidene fluoride polymer particles, preferably in an absorbed state.

If the amount of the monomer used is less than 10 parts by weight, the alkali solubility of the polymer will be insufficient, resulting in poor film formability and poor adhesion to the substrate. On the other hand, if the amount of the monomer used exceeds 900 parts by weight, the weather resistance and chemical resistance of the coating will decrease, which is not preferable.

The above emulsion polymerization can be carried out under normal emulsion polymerization conditions. For example, an emulsifier, a polymerization initiator, a pH adjuster, a solvent, etc. are added to an aqueous medium, and a temperature of 30 to 1
The reaction is carried out at about 00°C for about 1 to 30 hours.

Emulsifier As the emulsifier, an anionic, nonionic or anionic-nonionic combination is used, and in some cases, an amphoteric surfactant or a cationic surfactant can also be used.

Examples of the anionic emulsifier include higher alcohol sulfate sodium salts, alkylbenzenesulfonic acid sodium salts, succinic acid dialkyl ester sulfonic acid sodium salts, and alkyldiphenyl ether disulfonic acid sodium salts. Among these, dodecylbenzenesulfonic acid sodium salt, lauryl sulfate sodium salt, polyoxyethylene alkyl (or alkylphenyl) ether sulfate, and the like are preferably used.

Examples of the nonionic emulsifier include polyoxyethylene alkyl ether and polyoxyethylene alkyl allyl ether. Generally, polyoxyethylene nonylphenyl ether,
Polyoxyethylene octylphenyl ether and the like are used.

[0031] As the amphoteric emulsifier, lauryl betaine and the like are suitable.

As the cationic surfactant, alkylpyridinium chloride, alkylammonium chloride, etc. can be used.

Furthermore, so-called reactive emulsifiers that can be copolymerized with the above monomers, such as sodium styrene sulfonate and sodium allylalkylsulfonate, may also be used as emulsifiers.

The amount of emulsifier used is usually 0 per 100 parts by weight of the vinylidene fluoride polymer particles and the monomer.
．． The amount is approximately 0.05 to 5 parts by weight.

Polymerization Initiator As the polymerization initiator, for example, water-soluble persulfates, hydrogen peroxide, etc. can be used, and depending on the case, they can be used in combination with a reducing agent. Examples of the reducing agent include sodium pyrobisulfite, sodium hydrogensulfite, sodium thiosulfate, L-ascorbic acid and its salts, and sodium formaldehyde sulfoxylate.

[0036] Also, oil-soluble polymerization initiators, such as 2,2
-Azobis-(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis-2,4-dimethylvaleronitrile, 1,1'-azobis-cyclohexane-
1-carbonitrile, benzoyl peroxide, dibutyl peroxide, cumene hydroperoxide, etc. can be used as a monomer or dissolved in a solvent. Preferred oil-soluble polymerization initiators include cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, azobisisobutyronitrile,
Examples include benzoyl peroxide, t-butyl hydroperoxide, 3,5,5-trimethylhexanol peroxide, and t-butyl peroxide (2-ethylhexanoate). The amount of polymerization initiator used is
The amount is about 0.1 to 3 parts by weight per 100 parts by weight of the total monomers.

Chain Transfer Agent Chain transfer agents include halogenated hydrocarbons (eg, carbon tetrachloride, chloroform, bromoform, etc.), mercaptans (eg, n-dodecylmercaptan, t
-dodecylmercaptan, n-octylmercaptan, etc.), xanthogens (eg, dimethylxanthogen disulfide, diisopropylxanthogen disulfide, etc.), and terpenes (eg, dipentene, terpinolene, etc.). The amount of chain transfer agent used is about 0 to 10 parts by weight per 100 parts by weight of the total monomers.

Other Additives Examples of chelating agents include glycine, alanine, and ethylenediaminetetraacetic acid, and examples of pH adjusters include sodium carbonate, potassium carbonate, and sodium hydrogen carbonate. The amount of chelating agent and pH adjuster used was 100% of total monomer, respectively.
They are about 0 to 0.1 parts by weight and 0 to 3 parts by weight per part by weight.

As the solvent, small amounts of methyl ethyl ketone, acetone, trichlorotrifluoroethane, methyl isobutyl ketone, dimethyl sulfoxide, toluene, and dibutyl can be used within a range that does not impair workability, disaster prevention safety, environmental safety, and manufacturing safety. Phthalates, methylpyrrolidone, ethyl acetate, etc. may also be used. The amount of the solvent used is about 0 to 20 parts by weight per 100 parts by weight of the total monomers.

Polymerization method The emulsion polymerization using the vinylidene fluoride polymer as seed particles can be carried out by a known method, for example, a method in which the entire monomer is charged into the reaction system in the presence of the vinylidene fluoride polymer particles. , a method in which a part of the monomer is charged and reacted, and then the remaining monomer is charged continuously or in parts; a method in which the entire amount of the monomer is charged continuously; a method in which vinylidene fluoride is added while reacting the monomer This can be carried out by adding the polymer particles in portions or continuously.

[0041] The average particle diameter of the polymer particles in the aqueous dispersion of the fluoropolymer of the present invention is usually 0.05 to 1.
It is about 0 μm.

The average particle diameter of the fluoropolymer particles can be adjusted by appropriately selecting the size of the vinylidene fluoride polymer particles.

[0043] The aqueous dispersion of fluoropolymer has excellent film-forming properties and adhesion to the substrate, and also forms a film with excellent weather resistance, transparency, chemical resistance, mechanical strength, etc.
In addition to baking or air-drying paints, cationic electrodeposition paints, fiber treatment agents, paper processing agents, floor coating agents, carpet backing agents, packing agents, non-adhesive treatment agents, sealants, laminating agents, water and oil repellent treatment agents. It can also be used as For example, after adjusting the fluoropolymer aqueous dispersion of the present invention to pH 7 or higher, preferably pH 7 to 9 to dissolve the polymer,
1 to 30 at a temperature of 100 to 200℃ after applying to the object to be coated
After baking for a few minutes, a coating with excellent durability, chemical resistance, and weather resistance can be obtained.

The fluoropolymer of the present invention is alkaline,
Although it is possible to prepare an aqueous solution with a concentration of 90% by weight or more, the concentration is usually 50 to 60% by weight when used as a coating composition.

In the present invention, compounds used to prepare the fluoropolymer dispersion include sodium hydroxide, potassium hydroxide, ammonium hydroxide, calcium hydroxide, boranex, amine, etc., and preferably ammonium hydroxide is used.

The aqueous dispersion of the fluoropolymer of the present invention may also contain fillers, polycarboxylic acid dispersants, thickeners,
Antifreeze agent, antifoaming agent, fuvolac resin, N-methylolmelamine resin, alkylated N-methylolmelamine resin, water-soluble acrylic resin, urethane resin, epoxy resin,
Polyester resins, water-based nylon resins, alkyd resins, urea resins, maleated polybutadiene, maleated oils, etc., preferably N-methylolmelamine resins, alkylated N-methylolmelamine resins, water-soluble acrylic resins, etc. can also be added. .

The fluoropolymer dispersion of the present invention usually contains
It can be coated in a film thickness of 1 to 30 μm, and when a filler or the like is added to form a coating composition, it can be coated in a film thickness of about 5 to 200 μm.

[0048]

[Examples] The present invention will be explained in more detail below with reference to Examples. Note that both "parts" and "%" are based on weight.

Example 1 (Production of an aqueous dispersion of a fluoropolymer) In a nitrogen atmosphere, a vinylidene fluoride resin having an average particle size of 0.25 μm was placed in a separable flask with a capacity of 7 liters as shown in Table 1. Polymer (vinylidene fluoride/tetrafluoroethylene/propylene hexafluoride copolymer, trade name: KYNER9)
031 (manufactured by Atochem) and stirred.
The temperature was raised to 5°C. Methyl methacrylate 35 in a separate container
A mixture of 20 parts of ethyl acrylate, 10 parts of butyl acrylate, 15 parts of styrene, 20 parts of methacrylic acid, 50 parts of water, and 1.0 part of sodium alkylbenzenesulfonate as an emulsifier was placed in the above separable flask. The addition was continued over a period of 3 hours. After this addition was completed, the mixture was further aged at 85 to 95° C. for 2 hours, and then cooled to obtain an aqueous dispersion of an alkali-soluble fluoropolymer.

[0050] Furthermore, the obtained aqueous dispersion of the fluoropolymer was adjusted to alkaline pH 9.0 with aqueous ammonia,
The particles were dissolved by a neutralization reaction of the carboxyl groups of the polymer.

When the alkaline solution of the fluoropolymer obtained was checked, it was found that the liquid was clear and the polymer was completely dissolved. The results are shown in Table 1.

[0052] The dissolution state of the alkali-soluble polymer was confirmed by taking the solution into a beaker and visually observing it in the following three stages.

○: Transparent (particles are completely dissolved) △: Slightly opaque (some particles do not dissolve) ×: Cloudy (significant particles remain)

[0054]

[Table 1] (Preparation of coating composition and evaluation thereof) Furthermore, Example 1
100 parts (solid content) of the aqueous dispersion of the fluoropolymer obtained in step 1 was added with titanium oxide (trade name, Taipei R9) as a filler.
30, manufactured by Ishihara Sangyo Co., Ltd.)

5
0 parts, polycarboxylic acid sodium salt (as a dispersant)
Product name: SN-DISPERSANT5044, manufactured by San Nopco Co., Ltd.)
Part 2, ethylene glycol as antifreeze agent
1 part, preservative (trade name, SN-215, manufactured by Sannopco)
0.05 part, antifoaming agent (trade name, FOAMAST
ER-AP, manufactured by San Nopco) 0.5 part, and 2-amino-2-methyl-1-propanol
After adjusting the solid content to 60% with water, add hydroxyethyl cellulose (trade name, A-5) as a thickener.
000, manufactured by Fuji Chemical Co., Ltd.), and the paint viscosity was 400.
Adjusted to 0cps. The mixture was thoroughly mixed using a disper stirrer, and then transferred to a vacuum defoaming machine for defoaming.

[0055] The obtained paint was degreased with xylene and an alkaline detergent on an iron plate (JIS-G3141, SPCC).
It was applied to a plate (0.8 x 70 x 150 mm) using an airless spray gun so that the coating film after drying was 200 μm. The coated iron plate was dried at 150° C. for 15 minutes.

[0056] Using the above-mentioned coated iron plate, tests were conducted on the following properties. ■Gloss retention rate (%) of the initial gloss value after being placed in a weather resistant fade meter (manufactured by Suga Test Instruments Co., Ltd.) for 1000 hours
The weather resistance was evaluated based on the following criteria.

Gloss retention ○: 100-80 △: 79-40 ×: 39 or less ■Adhesion After cross-cutting the coating surface (10 x 10 squares of 2 mm), adhesive tape (manufactured by Nichiban Co., Ltd.) was applied. A peel test was conducted using Adhesion was evaluated according to the following criteria.

Number of particles remaining on cut surface ○: 100-80 △: 79-40 Drying was performed to obtain a coating film. Judgment was made visually in the following three stages.

○: No cracks in the paint film due to cracks △: Cracks occurred in some areas ×: Cracks occurred throughout ■ Alkali resistance Tested using 5% sodium carbonate solution according to JIS-K5400 (40°C ± 2°C, 24 hours). (2) Volatile oil resistance Tested using No. 2 volatile oil according to JIS-K5400. (2) Acid resistance A test was conducted using a 1% sulfuric acid solution (20±1° C., 8 hours) according to JIS-K5400, and changes in the coating film were visually determined. ■Durability: Pass the nut (M-6) through the vinyl pipe from a height of 2m.
) was dropped onto the coating film at an angle of 60 degrees, the weight of the nut when the iron plate was exposed was determined, and the durability was evaluated according to the following criteria.

[0060] ○: 30kg or more △: 11kg or more - less than 30kg ×: 10kg or less ■Pencil hardness Measured according to JIS-K5400, 6-14.

Examples 2 to 4 Aqueous dispersions of fluoropolymer were prepared in the same manner as in Example 1, except that the type and amount of monomers were changed to the compositions shown in Table 1. . Further, a coating composition was prepared in the same manner as in Example 1, and tested for each of the above characteristics. The results are shown in Table 1.

Comparative Examples 1 and 2 An aqueous dispersion of a fluoropolymer was obtained in the same manner as in Example 1 except that the monomers shown in Table 1 were used, and the properties of the coating composition were evaluated. The evaluation results are shown in Table 1.

Comparative Example 1 is an example in which the amount of unsaturated carboxylic acid (methacrylic acid) used is smaller than the range of the present invention, and the alkali solubility of the polymer is insufficient, resulting in poor film-forming properties and adhesion.

Comparative Example 2 is an example in which the amount of unsaturated carboxylic acid (methacrylic acid) used exceeded the range of the present invention, and the polymerization stability was poor, making it impossible to obtain an aqueous dispersion of a polymer that could be evaluated. .

Examples 5 to 7 Using the polymerization components shown in Table 2, an aqueous dispersion of a fluoropolymer was prepared in the same manner as in Example 1, and further in Example 1.
The physical properties of the coating composition were evaluated in the same manner as described above. The results are shown in Table 2.

[0066]

[Table 2] Comparative Examples 3 and 4 Using the polymerization recipe shown in Table 2, an aqueous dispersion of a fluoropolymer was obtained in the same manner as in Example 1, and the physical properties of the coating composition were evaluated. The results are shown in Table 2.

Comparative Example 3 is an example in which the amount of monomer used is smaller than the range of the present invention, and the alkali solubility of the polymer is insufficient, resulting in poor film forming properties, adhesion, weather resistance, alkali resistance, and resistance. It is inferior in all properties such as volatile oil properties and durability. It should be noted that the pencil hardness could not be measured due to the significant occurrence of cracks.

Comparative Example 4 is an example in which the amount of monomer used exceeds the range of the present invention, and is inferior in film forming property, adhesion, weather resistance, alkali resistance, volatile oil resistance, and durability.

Examples 8 and 9 In Example 8, vinylidene fluoride homopolymer (trade name Kynar 500) was used as the vinylidene fluoride polymer.
An aqueous dispersion of a fluoropolymer was prepared in the same manner as in Example 1, except for using Atochem Co., Ltd.), and the physical properties of the coating composition were evaluated in the same manner as in Example 1. The results are shown in Table 2.

In Example 9, vinylidene fluoride/ethylene tetrafluoride copolymer (
An aqueous dispersion of a fluoropolymer was prepared in the same manner as in Example 1, except that Kynar SL (trade name, manufactured by Atochem) was used, and the physical properties of the coating composition were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0071]

[Effects of the Invention] The aqueous dispersion of the fluoropolymer of the present invention has alkali solubility, so even though an aqueous medium is used, it has excellent properties comparable to solvent-based fluoropolymers. Because it forms a film that has film formability and adhesion to the substrate, and also has the excellent transparency, weather resistance, chemical resistance, and mechanical strength inherent to fluoropolymers,
In addition to various paints, it can be used as electrodeposition coating, fiber processing material, paper processing material, floor coating material, etc.

Claims (1)

[Claims] Claim 1: In the presence of 100 parts by weight of vinylidene fluoride polymer particles as seed particles, (a) an α,β-unsaturated carboxylic acid;
10 to 70% by weight, (b) 5 to 80% by weight of an acrylic ester in which the alkyl group has 1 to 5 carbon atoms and/or a methacrylic ester in which the alkyl group has 1 to 5 carbon atoms, (c
) Other ethylenically unsaturated compounds copolymerizable with these monomers (a) and (b)

An aqueous dispersion of a fluoropolymer, characterized in that it is obtained by emulsion polymerization of 10 to 900 parts by weight of a monomer comprising 0 to 85% by weight in an aqueous medium.