JP2015174888A - Fluorine-containing aqueous dispersion and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorine-containing dispersion which has excellent uniformity of a formed coating film even after long-term storage.SOLUTION: A fluorine-containing aqueous dispersion contains a fluorine-containing copolymer (I) having a structural unit (A) based on a fluoroolefin and a structural unit (B) based on a monomer having cross-linking group and has a pH of 8.2-11.5. A method of producing the fluorine-containing aqueous dispersion includes a first step of emulsion-polymerizing a fluoroolefin (a) and a monomer (b) having a cross-linking group in the presence of an aqueous medium and a polymerization initiator and a second step of adjusting the pH to 8.2-11.5 by adding an alkali compound after the first step.

Description

  The present invention relates to a fluorine-containing aqueous dispersion and a method for producing the same.

  A fluorine-containing aqueous dispersion containing a fluorine-containing copolymer obtained by polymerizing tetrafluoroethylene or chlorotrifluoroethylene, a monomer having a crosslinkable group, vinylidene fluoride, or the like has a weather resistance, a water resistance, A coating film excellent in chemical resistance and heat resistance can be formed.

  For example, Patent Document 1 discloses a polymerized unit based on a fluoroolefin, a polymerized unit based on a macromonomer having a hydrophilic site, and a general formula: XYZ (where X is a radically polymerizable unsaturated group, Y is an essential constituent of a polymerized unit based on a hydroxyl group-containing monomer represented by a divalent linking group containing an alkylene group having a straight chain, branched chain or alicyclic structure having 5 or more carbon atoms, and Z is a hydroxyl group). A fluorine-containing aqueous dispersion containing a fluorine-containing copolymer as a component is disclosed.

JP-A-7-179809

The present inventors have found that a fluorine-containing aqueous dispersion containing a fluorine-containing copolymer causes a decrease in pH due to decomposition of a remaining polymerization initiator or the like when stored for a long period of time. In addition, it was found that when the coating film was formed using a fluorine-containing aqueous dispersion having a pH lowered to 6 or less, the curing rate during curing increased, and the uniformity of the coating film decreased.
Therefore, an object of the present invention is to provide a fluorine-containing aqueous dispersion composition that is excellent in the uniformity of a coating film to be formed even after long-term storage.

The present invention is a fluorine-containing aqueous dispersion having the following constitutions [1] to [4] and a method for producing the same.
[1] A fluorine-containing copolymer (I) having a structural unit (A) based on a fluoroolefin and a structural unit (B) based on a monomer having a crosslinkable group, and having a pH of 8.2 to 11.5 A fluorine-containing aqueous dispersion.
[2] The fluorinated aqueous dispersion according to [1], wherein the monomer having a crosslinkable group is a macromonomer having a hydrophilic portion.
[3] A first step of emulsion polymerization of the fluoroolefin (a) and the monomer (b) having a crosslinkable group in the presence of an aqueous medium and a polymerization initiator, and the alkali compound after the first step In addition, the manufacturing method of the fluorine-containing aqueous dispersion which has a 2nd process which adjusts pH to 8.2-11.5.
[4] The method for producing a fluorinated aqueous dispersion according to [3], wherein the monomer (b) having a crosslinkable group is a macromonomer having a hydrophilic portion.

  According to the present invention, it is possible to provide a fluorine-containing aqueous dispersion excellent in the uniformity of a coating film to be formed even after long-term storage.

In the present specification, the “structural unit” means a unit derived from a monomer formed by polymerization of the monomer. It may be a unit directly formed by a polymerization reaction, or may be a unit in which a part of the unit is converted into another structure by treating the polymer.
The “crosslinkable group” means a group capable of forming a crosslinked structure by reacting with a curing agent, or a group capable of forming a crosslinked structure by reacting with each other. The “curing agent” means a compound having two or more groups capable of reacting with the “crosslinkable group” and capable of forming a crosslinked structure by reacting with the crosslinkable group.

<Fluorine-containing aqueous dispersion>
The fluorine-containing aqueous dispersion of the present invention comprises a structural unit (A) based on a fluoroolefin (hereinafter simply referred to as “structural unit (A)”) and a structural unit (B) based on a monomer having a crosslinkable group ( Hereinafter, it includes a fluorine-containing copolymer (I) having simply “structural unit (B)”, and has a pH of 8.2 to 11.5.

[Fluoropolymer (I)]
The fluorine-containing copolymer (I) of the present invention has a structural unit (A) and a structural unit (B).
(Structural unit (A))
The structural unit (A) is a structural unit based on a fluoroolefin.
Examples of the fluoroolefin include fluoroolefins having about 2 to 4 carbon atoms such as vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, pentafluoropropylene, and hexafluoropropylene. Among these, chlorotrifluoroethylene and tetrafluoroethylene are preferable from the viewpoint of weather resistance, and chlorotrifluoroethylene is more preferable.

(Structural unit (B))
The structural unit (B) is a structural unit based on a monomer having a crosslinkable group.
The crosslinkable group is not particularly limited. For example, in addition to a hydroxyl group, an alkoxysilyl group, a carboxy group, an amino group, an isocyanate group, an epoxy group, etc., a vinyl group, an allyl group, a propenyl group, an isopropenyl group, an acryloyl group, and a methacryloyl group. And radical polymerizable unsaturated groups such as a group.
Among these, a hydroxyl group, a carboxy group, an amino group, and an epoxy group are preferable, and a hydroxyl group is particularly preferable because the mechanical and chemical stability of the fluorine-containing aqueous dispersion becomes good and the crosslinkability is also excellent.

Of the hydroxyl groups, a group represented by the following formula (1) is preferable.
XYZ [(X is a radically polymerizable unsaturated group, Y is an n-nonylene group or cyclohexane-1,4-dimethylene group, Z is a hydroxyl group] (1)
Here, examples of X include a vinyl group, an allyl group, a propenyl group, an isopropenyl group, an acryloyl group, and a methacryloyl group. The bond connecting X and Y is preferably an ether bond.
As specific examples of the monomer having a group represented by the formula (1),
_{(1) CH 2 = CHOCH 2} -cycloC 6 H 10 -CH 2 OH,
_{(2) CH 2 = CHCH 2} OCH 2 -cycloC 6 H 10 -CH 2 OH,
(3) CH ₂ = CHOC ₉ H ₁₈ OH,
_{(4) CH 2 = CHCH 2} OC 9 H 18 OH , and the like.
Among them, those having a vinyl ether type structure are preferable because they are excellent in alternating copolymerization with fluoroolefin and have good weather resistance of the coating film.

Macromonomer with hydrophilic moiety:
Preferable examples of the monomer having a hydroxyl group as a crosslinkable group include a macromonomer having a hydrophilic portion.
In this specification, the macromonomer means a low molecular weight polymer having a radically polymerizable unsaturated group at one end. That is, it is a compound having a radically polymerizable unsaturated group at one end and having at least two repeating units such as the following oxyethylene units. The number of repeating units is preferably 100 or less in terms of polymerizability and water resistance.
The hydrophilic portion represents a portion having a hydrophilic group, a portion having a hydrophilic bond or a combination thereof. Examples of hydrophilic groups include ionic, nonionic, amphoteric and combinations thereof.
From the viewpoint of the chemical stability of the fluorine-containing aqueous dispersion, a part having a nonionic or amphoteric hydrophilic group and a part having another hydrophilic group are combined, or a part having a hydrophilic group and a hydrophilic group are hydrophilic. It is preferable to combine with the site | part which has sex bond.

As a macromonomer having a specific hydrophilic portion, for example, (1) CH ₂ ═CHO (CH ₂ ) _a [O (CH ₂ ) _b ] _c OR ¹ (a is 1 to 10, b is 1 to 4, c is an integer of 2 to 20, R ¹ is a hydrogen atom or a lower alkyl group.), (2) CH ₂ ═CHCH ₂ O (CH ₂ ) _d [O (CH ₂ ) _e ] _f OR ² (d is 1 to 10, e is 1 to 4, f is an integer of 2 to 20, R ² is a hydrogen atom or a lower alkyl group.), (3) CH ₂ ═CHO (CH ₂ ) _g (OCH ₂ CH ₂ ) _h (OCH ₂ CH (CH ₃ )) _k OR ³ (g is 1 to 10, h is 2 to 20, k is an integer of 0 to 20, R ³ is a hydrogen atom or a lower alkyl group, an oxyethylene unit and Oxypropylene units may be arranged in either block or random form _{There.), (4) CH 2} = CHCH 2 O (CH 2) m (OCH 2 CH 2) n (OCH 2 CH (CH 3)) p OR 4 (m is 1 to 10, n is 2-20, p is an integer of 0 to 20, R ⁴ is a hydrogen atom or a lower alkyl group, and the oxyethylene unit and the oxypropylene unit may be arranged in any of a block type and a random type), or (5) CH _{2 = CHO (CH 2) q} O (CO (CH 2) r O) s H (q is 1 to 10, r is 1 to 10, s is from 1 to 30 integer), and the like.

Among these, one having a vinyl ether type structure at one end is preferable because of excellent copolymerizability with a fluoroolefin. In particular, it is preferable that the polyether chain portion is composed of an oxyethylene unit or an oxyethylene unit and an oxypropylene unit because of excellent hydrophilicity.
Moreover, if there are two or more oxyethylene units, various properties such as stability are improved. On the other hand, if the number of oxyalkylene units is too large, the water resistance and weather resistance of the coating film will deteriorate.
Such a macromonomer having a hydrophilic moiety can be produced by a method such as polymerizing formaldehyde or diol with a vinyl ether or allyl ether having a hydroxyl group, or ring-opening polymerization of a compound having an alkylene oxide or a lactone ring.

The macromonomer having a hydrophilic portion is a macromonomer having a chain obtained by radical polymerization of a hydrophilic ethylenically unsaturated monomer and having a radical polymerizable unsaturated group such as a vinyloxy group or an allyloxy group at the terminal. There may be.
Macromonomers having such a hydrophilic moiety are described by Yamashita et al. In Polym. Bull. , 5.335 (1981). That is, first, a polymer having a condensable functional group by radical polymerization of an ethylenically unsaturated monomer having a hydrophilic group in the presence of a polymerization initiator having a condensable functional group and a chain transfer agent. Manufacturing. Next, the functional group of this polymer is reacted with a compound such as glycidyl vinyl ether or glycidyl allyl ether to introduce a radical polymerizable unsaturated group at the terminal.
Examples of the ethylenically unsaturated monomer to be radically polymerized include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, 2-methoxyethyl acrylate, 2-methoxyethyl methacrylate, diacetone acrylamide, hydroxyethyl acrylate, hydroxy Examples include propyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, acrylic acid ester of polyhydric alcohol, methacrylic acid ester of polyhydric alcohol, and vinylpyrrolidone.
The structural unit (B) in the fluorinated copolymer (I) may be one type or two or more types.

(Combination ratio of structural unit (A) and structural unit (B))
0.5-800 are preferable and, as for the mixture ratio (A / B) of a structural unit (A) and a structural unit (B), 1.5-300 are more preferable.
If A / B is not less than the lower limit, the weather resistance and water resistance of the coating film will be better, while if not more than the upper limit, water dispersibility will be better.

(Structural unit (C) based on monomer (c))
The fluorine-containing copolymer (I) of the present invention may have a structural unit (C) based on the monomer (c) in addition to the structural unit (A) and the structural unit (B).
The monomer (c) is not particularly limited, and examples thereof include olefins such as ethylene and propylene, vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, and cyclohexyl vinyl ether, butanoic acid vinyl ester, octanoic acid vinyl ester, and the like. Vinyl esters, allyl ethers such as ethyl allyl ether, allyl esters such as ethyl allyl ester, aromatic vinyl compounds such as styrene and vinyl toluene, (meth) acrylic acid esters such as butyl acrylate and ethyl methacrylate And the like. Of these, olefins, vinyl ethers, vinyl esters, allyl ethers, and allyl esters are preferable. Further, olefins preferably have about 2 to 10 carbon atoms, and vinyl ethers, vinyl esters, allyl ethers, and allyl esters are linear, branched or fatty acids having about 2 to 15 carbon atoms. Those having a cyclic alkyl group are preferred.
The ratio (C / (A + B)) of the number of moles of the structural unit (C) to the total number of moles of the structural unit (A) and the structural unit (B) is preferably 0.01 to 1.

[Aqueous medium]
In the fluorine-containing aqueous dispersion of the present invention, the fluorine-containing copolymer (I) is dispersed in an aqueous medium.
Examples of the aqueous medium include water, a mixture of water and a water-soluble organic solvent, and the like.
Examples of the water-soluble organic solvent include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol.
1-40 mass parts is preferable with respect to 100 mass parts of water, and, as for content of a water-soluble organic solvent, 3-30 mass parts is more preferable.

[Optional ingredients]
The fluorine-containing aqueous dispersion may contain an emulsifier, another polymer, a colorant, a curing agent, and other additives in addition to the above-mentioned fluorine-containing copolymer (I).

(emulsifier)
The fluorine-containing aqueous dispersion of the present invention may or may not contain an emulsifier. In the case where emulsion polymerization cannot be performed only with other raw materials, it is preferable to include an emulsifier.
Examples of the emulsifier include an anionic emulsifier, a nonionic emulsifier, and a cationic emulsifier. Among these, nonionic emulsifiers and anionic emulsifiers are preferable.
Nonionic emulsifiers include alkylphenol ethylene oxide adducts, higher alcohol ethylene oxide adducts, block copolymers of ethylene oxide and propylene oxide, and the like.
Examples of the anionic emulsifier include alkyl benzene sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, alkyl sulfate ester salt, alkyl ether sulfate ester salt, and phosphate ester salt.
Although content of an emulsifier is not specifically limited, 0.01-10 mass parts is preferable with respect to 100 mass parts of total amounts of a fluorine-containing aqueous dispersion.

(Other polymers)
The fluorine-containing aqueous dispersion of the present invention may have another polymer other than the above-mentioned fluorine-containing copolymer (I).
The other polymer is not particularly limited, and examples thereof include an acrylic polymer and a polyester polymer.
Although content of another polymer is not specifically limited, 0-200 mass parts is preferable with respect to 100 mass parts of fluorine-containing copolymers (I).

(Coloring agent)
The fluorinated aqueous dispersion of the present invention may contain a colorant when used as a paint.
Examples of the colorant include dyes, organic pigments, and inorganic pigments.
Although content of a coloring agent is not specifically limited, 0-100 mass parts is preferable with respect to 100 mass parts of total amounts of a fluorine-containing aqueous dispersion.

(Curing agent)
The fluorine-containing aqueous dispersion may contain a curing agent in order to further improve the weather resistance, water resistance, chemical resistance, heat resistance and the like. The fluorine-containing aqueous dispersion of the present invention may be a one-component type or a two-component type. However, when a curing agent is included, a two-component type is used, and both solutions are mixed immediately before use. Is preferred.
Examples of the curing agent include blocked isocyanates such as hexamethylene isocyanate trimer or emulsion dispersions thereof, melamine resins such as methylated melamine, methylolated melamine, and butyrololized melamine, and urea resins such as methylated urea and butylated urea. Etc.
Although content of a hardening | curing agent is not specifically limited, 0.1-20 mass parts is preferable with respect to 100 mass parts of fluorine-containing copolymers (I).

(Other additives)
The fluorine-containing aqueous dispersion may contain other additives such as a component derived from an alkali compound, a plasticizer, an ultraviolet absorber, a leveling agent, a repellency inhibitor and an anti-burr agent.
The component derived from an alkali compound means that, in addition to an alkali compound used for adjusting the pH described later, ions derived from the alkali compound when the alkali compound forms a salt with other components.

[PH]
The pH of the fluorine-containing aqueous dispersion of the present invention is 8.2 to 11.5. The pH is preferably 8.3 to 11.0, more preferably 8.5 to 10.5, and most preferably 8.9 to 10.0.
If the pH is at least the lower limit, the stability of the fluorine-containing aqueous dispersion is good. On the other hand, if the pH is not more than the upper limit, the pigment dispersibility is good when the pigment is dispersed by coating. become.
The pH of the fluorinated aqueous dispersion is adjusted so as to be within the above range using an alkali compound that will be described later in the method for producing a fluorinated aqueous dispersion.

<Method for producing fluorine-containing aqueous dispersion>
The method for producing a fluorine-containing aqueous dispersion of the present invention includes a first step of emulsion polymerization of a fluoroolefin (a) and a monomer (b) having a crosslinkable group in the presence of an aqueous medium and a polymerization initiator, and And a second step of adjusting the pH to 8.2 to 11.5 by adding an alkali compound after the first step.

[First step]
The first step is a step of obtaining a fluorine-containing copolymer dispersion by emulsion polymerization of the fluoroolefin (a) and the monomer (b) having a crosslinkable group in the presence of an aqueous medium and a polymerization initiator. is there.
Here, the kind of fluoroolefin (a) is the same as that of what was demonstrated by said structural unit (A). The kind of the monomer (b) having a crosslinkable group is the same as that described in the structural unit (B).
In the emulsion polymerization, the other monomer (c) is also used as necessary, and the fluoroolefin (a), the monomer (b) having a crosslinkable group, and the other monomer (c). May be copolymerized.
In addition, when emulsion polymerization can be performed only with other raw materials, an emulsifier may not be used and may be used. The type of emulsifier is the same as that described above.
The aqueous medium is the same as described above. In addition, when an aqueous medium contains a water-soluble organic solvent, the dispersibility of a monomer and the dispersibility of the produced | generated polymer can be improved, and productivity can be improved. Further, the content of the water-soluble organic solvent is the same as that described above.

(Polymerization initiator)
The kind of polymerization initiator will not be specifically limited if it is a well-known radical polymerization initiator used in superposition | polymerization of a fluorine-containing copolymer. As the polymerization initiator, for example, a persulfate such as ammonium persulfate; a redox initiator composed of a combination of hydrogen peroxide and sodium bisulfite; an inorganic initiator such as ferrous salt and silver nitrate was mixed. Examples thereof include dibasic acid peroxides such as disuccinic acid peroxide and diglutaric acid peroxide; and organic initiators such as azobisbutyronitrile.
Although the usage-amount of a polymerization initiator is not specifically limited, For example, 0.01-5 mass parts is preferable with respect to 100 mass parts of total amounts of the monomer to be used.

(Chain transfer agent)
In the polymerization in the first step, a chain transfer agent may be used. By using a chain transfer agent, the degree of polymerization (molecular weight) of the fluorinated copolymer (I) can be adjusted. Also, the total concentration of monomers in the aqueous medium can be increased.
Examples of the chain transfer agent include alkyl mercaptans such as tert-dodecyl mercaptan, n-dodecyl mercaptan, stearyl mercaptan; aminoethanethiol, mercaptoethanol, 3-mercaptopropionic acid, 2-mercaptopropionic acid, thiomalic acid, thioglycolic acid. 3,3′-dithio-dipropionic acid, 2-ethylhexyl thioglycolate, n-butyl thioglycolate, methoxybutyl thioglycolate, ethyl thioglycolate, 2,4-diphenyl-4-methyl-1-pentene And carbon tetrachloride.
Although the usage-amount of a chain transfer agent is not specifically limited, For example, 0-2 mass parts is preferable with respect to 100 mass parts of total amounts of the monomer to be used.

(Emulsion polymerization)
The polymerization in the first step is performed by emulsion polymerization.
Examples of the reactor include a stainless steel autoclave with a stirrer (manufactured by Pressure Glass Industrial Co., Ltd.).
The method of emulsion polymerization is not particularly limited, and examples thereof include batch polymerization, monomer dropping polymerization, emulsion monomer dropping polymerization, and the like.
The conditions for emulsion polymerization are not particularly limited. For example, the polymerization initiation temperature is preferably 0 to 100 ° C, more preferably 10 to 90 ° C. Further, the reaction pressure is preferably 0.1 to 10 MPa, and more preferably 0.2 to 5 MPa.

[Second step]
The second step is a step of adjusting the pH to 8.2 to 11.5 by adding an alkali compound to the fluorine-containing copolymer dispersion obtained in the first step after the polymerization. The pH is preferably 8.3 to 11.0, more preferably 8.5 to 10.5, and most preferably 8.9 to 10.0. The significance of these numerical ranges is the same as described above for pH.

(Alkali compounds)
Examples of the alkali compound used for adjusting the pH include potassium hydroxide, sodium hydroxide, potassium carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, and ammonia. Among these, potassium hydrogen carbonate, sodium hydrogen carbonate, and potassium carbonate are preferable from the viewpoint of the stability of the fluorine-containing aqueous dispersion.
The shape of the alkali compound added to the fluorine-containing copolymer dispersion may be a powder or may be a liquid dissolved in a solvent such as water. From the point of adjusting pH, it is preferably liquid and more preferably an aqueous solution using water as a solvent.
The concentration of the alkali compound in the aqueous solution is preferably 0.1 to 50% by mass.

<Operational effects of the present invention>
According to the fluorine-containing aqueous dispersion of the present invention, the pH does not decrease to 6 or less even when stored for a long period of time, so that the curing rate does not become too fast when forming a coating film. Therefore, according to the fluorine-containing aqueous dispersion of the present invention, a highly uniform coating film can be formed even after long-term storage.
Moreover, since the fluorine-containing aqueous dispersion of the present invention contains the fluorine-containing copolymer (I) having the structural unit (A) and the structural unit (B), weather resistance, water resistance, chemical resistance, heat resistance, etc. An excellent coating film can be formed.

The present invention will be specifically described by the following examples, but the present invention is not limited to these examples.
(material)
CHVE: cyclohexyl vinyl ether (manufactured by BASF)
2-EHVE: 2-ethylhexyl vinyl ether (BASF)
_{EOVE: CH 2 = CHOCH 2 -cycloC} 6 H 10 -CH 2 O (CH 2 CH 2 O) n H, average molecular weight 830 (hydrophilic macromonomer) (Nippon Emulsifier Co., Ltd.)
_{HCVE: CH 2 = CHOCH 2 -cycloC} 6 H 10 -CH 2 OH ( hydroxyl group-containing monomer) (manufactured by BASF)
SLS: Sodium lauryl sulfate (anionic emulsifier) (manufactured by Nikko Chemicals)
CTFE: Chlorotrifluoroethylene (Asahi Glass Co., Ltd.)
TFE: Tetrafluoroethylene (Asahi Glass Co., Ltd.)

(Evaluation of appearance of coating film)
210 parts by mass of titanium oxide (Tipure (registered trademark) R-706 manufactured by Dupont), pigment dispersant Disperbyk (registered trademark) 190 (manufactured by BYK Chemie, copolymer having affinity for pigment, acid value of 10 mgKOH / g) 21 parts by mass, 4.5 parts by mass of antifoaming agent Dehydran (registered trademark) 1620 (manufactured by Cognis), 64.5 parts by mass of ion-exchanged water, and 300 parts by mass of glass beads were mixed, and a disperser was used. After dispersion, the glass beads were removed by filtration to obtain a pigment composition.
To 55 g of the pigment composition, 193 g of the fluorine-containing aqueous dispersion of each example or each comparative example, 0.5 g of the thickener Vermodol 2150 (manufactured by Akzo Nobel), 10 g of dipropylene glycol mono n-butyl ether Then, 15 g of water-dispersed isocyanate curing agent Bihijoule (registered trademark) 3100 (manufactured by Sumika Bayer) was added and mixed to obtain a coating composition.
The obtained coating composition was applied to one side of a chromate-treated aluminum plate so as to have a film thickness of 20 μm and dried at 80 ° C. for 1 hour. After drying, the appearance of the obtained coating film was evaluated. Appearance was evaluated as ◯ when the 60 ° gloss measured with an IG-410 handy gloss meter manufactured by HORIBA, Ltd. was 70 degrees or more, and x when it was 69 degrees or less.

(Production example)
In an autoclave with a stainless steel stirrer with an internal volume of 2500 mL (manufactured by Pressure Glass Industrial Co., Ltd.), 330 g of CHVE, 183.5 g of 2-EHVE, 16.6 g of EOVE, 27.1 g of HCVE, ion-exchanged water 1020 g, 2.5 g of potassium carbonate (K ₂ CO ₃ ), 0.7 g of ammonium persulfate (APS), 51 g of nonionic emulsifier (Newcol (registered trademark) -1110: manufactured by Nippon Emulsifier Co., Ltd.), 0 of SLS .1 g is charged and cooled with ice, and nitrogen gas is pressurized to 0.7 MPa and degassed. This pressure degassing was repeated twice, and after degassing to 0.01 MPa to remove dissolved air, 470 g of CTFE and TFE were charged, and a polymerization reaction was carried out at 50 ° C. for 24 hours. After the polymerization reaction, unreacted monomers were removed to obtain a fluorinated copolymer dispersion A.

Example 1
To 250 g of the fluorinated copolymer dispersion A, 0.32 g of a 10 mass% potassium carbonate (K ₂ CO ₃ ) aqueous solution as an aqueous solution containing an alkali compound was added to obtain a fluorinated aqueous dispersion.
The pH of the fluorine-containing aqueous dispersion was measured immediately after the addition and after storage for 2 weeks at 50 ° C. Moreover, the external appearance of the coating film formed using this fluorine-containing aqueous dispersion after storing for 2 weeks on 50 degreeC conditions was evaluated.

(Example 2)
A fluorine-containing aqueous dispersion is obtained in the same manner as in Example 1 except that 0.68 g of a 10% by mass K ₂ CO ₃ aqueous solution is added as an aqueous solution containing an alkali compound, and the pH is measured. evaluated.

(Example 3)
A fluorine-containing aqueous dispersion was obtained in the same manner as in Example 1 except that 0.32 g of a 14.5 mass% potassium hydrogen carbonate (KHCO ₃ ) aqueous solution was added as an aqueous solution containing an alkali compound, and the pH was measured. The appearance of the coating film was evaluated.

Example 4
A fluorine-containing aqueous dispersion was obtained in the same manner as in Example 1 except that 0.68 g of a 14.5 mass% KHCO ₃ aqueous solution was added as an aqueous solution containing an alkali compound, the pH was measured, and the appearance of the coating film was observed. evaluated.

(Example 5)
Other than using 250 g of a fluorinated copolymer dispersion “Zeffle (registered trademark) SE310” (solid content concentration 50 mass%) (hereinafter referred to as “fluorinated copolymer dispersion B”) manufactured by Daikin Industries, Ltd. Obtained the fluorine-containing aqueous dispersion similarly to Example 2, measured pH, and evaluated the external appearance of the coating film.

(Comparative Example 1)
Without adding an aqueous solution containing an alkali compound, the pH of the fluorinated copolymer dispersion A was measured immediately after production and after storage for 2 weeks at 50 ° C., and the appearance of the coating film was evaluated.

(Comparative Example 2)
Without adding an aqueous solution containing an alkali compound, the pH of the fluorocopolymer dispersion B was measured immediately after product purchase and after storage for 2 weeks at 50 ° C., and the appearance of the coating film was evaluated. .

  In Table 1 below, the types and blending amounts of the fluorine-containing copolymer dispersions used in Examples 1 to 5 and Comparative Examples 1 and 2 above, the types of alkali compounds, and the concentrations and additions of aqueous solutions containing alkali compounds The amount, the measurement result of pH immediately after production and after storage, and the glossiness are shown.

As a result, the fluorine-containing aqueous dispersions of Comparative Examples 1 and 2 in which the alkali compound was not added and the pH was not adjusted had pHs of 8.1 and 7.0 immediately after production, respectively. The pH after storage for 2 weeks under the conditions dropped to 5.4 and 5.1, respectively.
Moreover, the glossiness of the coating films of Comparative Examples 1 and 2 formed using the fluorine-containing aqueous dispersion after being stored for 2 weeks at 50 ° C. was low.
On the other hand, the fluorine-containing aqueous dispersions of Examples 1 to 5, which were adjusted to pH 9.1, 9.5, 8.4, 8.9, and 8.3 by adding an alkali compound, The pH was maintained at 6.5 or higher after 2 weeks storage under the conditions. In particular, the fluorine-containing aqueous dispersions of Examples 1, 2, and 4 adjusted to pH 9.1, 9.5, and 8.9, respectively, had a pH of 7. after being stored at 50 ° C. for 2 weeks. It was maintained at 1 or more.
Moreover, the coating films of Examples 1 to 5 formed using the fluorine-containing aqueous dispersion after being stored for 2 weeks at 50 ° C. had high gloss.

  The fluorine-containing aqueous dispersion of the present invention can be used for coating wood or concrete used in construction or the like, metal used in equipment or the like.

Claims (4)

  Including a fluorine-containing copolymer (I) having a structural unit (A) based on a fluoroolefin and a structural unit (B) based on a monomer having a crosslinkable group, and having a pH of 8.2 to 11.5. Fluorine-containing aqueous dispersion.   The fluorine-containing aqueous dispersion according to claim 1, wherein the monomer having a crosslinkable group is a macromonomer having a hydrophilic portion.   First step of emulsion polymerization of fluoroolefin (a) and monomer (b) having a crosslinkable group in the presence of an aqueous medium and a polymerization initiator, and after the first step, an alkali compound is added to adjust the pH. The manufacturing method of a fluorine-containing aqueous dispersion which has a 2nd process of adjusting to 8.2-11.5.   The method for producing a fluorine-containing aqueous dispersion according to claim 3, wherein the monomer (b) having a crosslinkable group is a macromonomer having a hydrophilic portion.