JP7639699B2 - Fluorine-containing polymer, its production method, water- and oil-repellent composition, and article - Google Patents

Description

The present invention relates to a fluorine-containing polymer, a method for producing the same, a water- and oil-repellent composition, and an article.

As a method for imparting water and oil repellency to the surface of an article (such as a textile product), a method is known in which the article is treated with a water and oil repellent composition containing a fluorine-containing polymer having units based on (meth)acrylate having a perfluoroalkyl group. However, the ester bonds in the units based on (meth)acrylate are easily cleaved by hydrolysis with an alkali or the like. As a result, the perfluoroalkyl group is lost from the fluorine-containing polymer, which can reduce the water and oil repellency of the article.

As a water/oil repellent composition that can produce an article whose water/oil repellency is not likely to decrease even after exposure to alkaline conditions, a water/oil repellent composition containing a fluoropolymer that does not have units based on (meth)acrylate having a perfluoroalkyl group is known. As a fluoropolymer that does not have units based on (meth)acrylate having a perfluoroalkyl group, a fluoropolymer that has units based on (perfluoroalkyl)ethylene is known (Patent Document 1).

WO 2019/138680

However, articles treated with the water- and oil-repellent composition containing the fluorine-containing polymer described in Patent Document 1 have insufficient dynamic water repellency, specifically water repellency against water (rainfall) falling from a high place. Furthermore, the article has low resistance to repeated water immersion, and when the article is repeatedly immersed in water, the water- and oil-repellent coating formed on the article may crack or peel off.

The present invention provides a fluoropolymer and a method for producing the same which can provide an article having excellent dynamic water repellency, a water/oil repellent composition which can provide an article having excellent dynamic water repellency, and an article having excellent dynamic water repellency. Furthermore, with the fluoropolymer and water/oil repellent composition of the present invention, an article can be obtained whose water/oil repellency is unlikely to decrease even after exposure to alkaline conditions, etc.

The present invention has the following aspects.
[1] A fluorine-containing polymer comprising units based on the following monomer (a) and units based on the following monomer (b):
Monomer (a): A compound represented by CH ₂ ═CX— ^Rf .
In the above formula, X is a halogen atom, and ^Rf is a perfluoroalkyl group having 1 to 8 carbon atoms.
Monomer (b): A monomer copolymerizable with the monomer (a).
[2] The fluorine-containing polymer according to [1], wherein R ^f is a perfluoroalkyl group having 4 to 6 carbon atoms.
[3] The fluorine-containing polymer according to [1] or [2], wherein X is a chlorine atom.
[4] The fluorine-containing polymer according to any of [1] to [3], wherein the proportion of units based on said monomer (a) to all units constituting said fluorine-containing polymer is 20 to 60 mol %.
[5] The fluorine-containing polymer according to any one of [1] to [4], wherein at least a part of the units based on the monomer (b) is a unit based on the following monomer (b1):
Monomer (b1): A compound represented by CH ₂ ═CH-Q or CH ₂ ═CHCH ₂ -Q.
Here, Q is a halogen atom, or an organic group in which the bonding terminal atom is an oxygen atom, a nitrogen atom, or a sulfur atom.

[6] A method for producing a fluorine-containing polymer, comprising polymerizing a monomer component containing the following monomer (a) and the following monomer (b) in the presence of a polymerization initiator:
Monomer (a): A compound represented by CH ₂ ═CX— ^Rf .
In the above formula, X is a halogen atom, and ^Rf is a perfluoroalkyl group having 1 to 8 carbon atoms.
Monomer (b): A monomer copolymerizable with the monomer (a).
[7] The production method according to [6], wherein the proportion of the monomer (a) relative to the total monomer components is 20 to 60 mol %.
[8] The production method according to [6] or [7], wherein at least a part of the units based on the monomer (b) is a unit based on the following monomer (b1):
Monomer (b1): A compound represented by CH ₂ ═CH-Q or CH ₂ ═CHCH ₂ -Q.
Here, Q is a halogen atom, or an organic group in which the bonding terminal atom is an oxygen atom, a nitrogen atom, or a sulfur atom.
[9] The method according to any one of [6] to [8], wherein the monomer components are polymerized in an aqueous medium.
[10] The production method according to [9], comprising emulsion-polymerizing the monomer components in an aqueous medium containing a surfactant and the polymerization initiator.

[11] A fluoropolymer dispersion comprising the fluoropolymer of any of [1] to [5] above, and an aqueous medium in which the fluoropolymer is dispersed.
[12] The fluoropolymer dispersion according to [11], further comprising a surfactant.
[13] A water/oil repellent composition comprising the fluorine-containing polymer according to any one of [1] to [5] above.
[14] The water/oil repellent composition according to [13], which comprises an aqueous medium and the fluorine-containing polymer dispersed in the aqueous medium.
[15] An article in which at least a part of the surface of a substrate is treated with the water/oil repellent composition according to [13] or [14].

The fluoropolymer of the present invention can provide articles which are excellent in water and oil repellency, particularly in dynamic water repellency, and which are resistant to deterioration in water and oil repellency even after exposure to alkaline conditions.
According to the process for producing a fluoropolymer of the present invention, it is possible to produce a fluoropolymer which provides an article having excellent water and oil repellency, particularly dynamic water repellency, which is resistant to deterioration in water and oil repellency even after exposure to alkaline conditions, etc.
The water/oil repellent composition of the present invention can provide an article which is excellent in water/oil repellency, particularly in dynamic water repellency, and which is resistant to deterioration in water/oil repellency even after exposure to alkaline conditions.
The article of the present invention has excellent water and oil repellency, particularly dynamic water repellency, and the water and oil repellency is unlikely to decrease even after exposure to alkaline conditions.

The meanings and definitions of terms used in the present invention are as follows.
The term "unit based on a monomer" is a general term for an atomic group formed directly by polymerization of one monomer molecule, and an atomic group obtained by chemically converting a part of the atomic group.
"(Meth)acrylate" is a general term for acrylate and methacrylate. Similarly, "(meth)acryloyloxy group" is a general term for acryloyloxy group and methacryloyloxy group.
The number average molecular weight (hereinafter also referred to as "Mn") and the mass average molecular weight (hereinafter also referred to as "Mw") of the polymer are polymethyl methacrylate-equivalent molecular weights obtained by measuring by gel permeation chromatography (hereinafter also referred to as "GPC") using a calibration curve prepared using standard polymethyl methacrylate samples.

[Fluorine-containing polymer]
A fluorine-containing polymer according to one embodiment of the present invention (hereinafter also referred to as "polymer A") contains units based on monomer (a) (hereinafter also referred to as "units (a)") and units based on monomer (b) (hereinafter also referred to as "units (b)").
Monomer (a): A compound represented by CH ₂ ═CX— ^Rf .
In the above formula, X is a halogen atom, and ^Rf is a perfluoroalkyl group having 1 to 8 carbon atoms.
Monomer (b): A monomer copolymerizable with the monomer (a).

In the monomer (a), X may be a chlorine atom, a fluorine atom, a bromine atom or an iodine atom. Of these, a chlorine atom is preferred from the viewpoints of better adhesion between the water/oil repellent coating film formed from the water/oil repellent composition and the substrate, and of easy availability of raw materials.
The number of carbon atoms in ^Rf is preferably 1 to 6 from the viewpoints that the conversion rate to polymer A is likely to be good and that raw materials are easily available and easy to handle, and from the viewpoints of water and oil repellency, the number of carbon atoms is more preferably 4 to 6, and particularly preferably 6.
^Rf is preferably linear.

Examples of the monomer (a) include CH ₂ =CX-CF ₃ , CH ₂ =CX-CF ₂ CF ₃ , CH ₂ =CX-CF ₂ CF ₂ CF ₃ , CH ₂ =CX-CF(CF ₃ ) ₂ , CH ₂ =CX-(CF ₂ ) ₃ CF ₃ , _CH2 =CX- _CF2CF ( _CF3 ) ₂ , _CH2 =CX-C( _CF3 ) ₃ , _CH2 =CX-( _CF2 ) _{4CF3 , CH2} =CX- _CF2CF2CF ( _CF3 ) _{2 , CH2} =CX-(CF ₂ ) ₅ CF ₃ , CH ₂ Examples include ═CX-(CF ₂ ) ₅ CF(CF ₃ ) ₂ and CH ₂ ═CX-(CF ₂ ) ₇ CF ₃ .
As the monomer (a), CH ₂ ═CX-CF ₃ , CH ₂ ═CX-CF ₂ CF ₃ , CH ₂ ═CX-CF(CF ₃ ) ₂ , CH ₂ ═CX-(CF ₂ ) ₃ CF ₃ and CH ₂ ═CX-(CF ₂ ) ₅ CF ₃ are preferred, CH ₂ ═CX-CF ₃ , CH ₂ ═CX-CF ₂ CF ₃ , CH ₂ ═CX-(CF ₂ ) ₃ CF ₃ and CH ₂ ═CX-(CF ₂ ) ₅ CF ₃ are more preferred, CH ₂ ═CX-(CF ₂ ) ₃ CF ₃ and CH ₂ ═CX-(CF ₂ ) ₅ CF ₃ are even more preferred, and CH ₂ =CCl-( _CF2 ) _{3CF3 and CH2} =CCl-( _CF2 ) _{5CF3 are} particularly preferred.
The monomer (a) may be used in combination of two or more kinds.

The monomer (b) may be any monomer capable of copolymerizing with the monomer (a), but it is preferred that at least a part of the monomer (b) is a monomer (b1) in view of ease of copolymerization with the monomer (a). Note that units based on the monomer (b1) are hereinafter also referred to as "units (b1)".
Monomer (b1): A compound represented by CH ₂ ═CH-Q or CH ₂ ═CHCH ₂ -Q.
Here, Q is a halogen atom, or an organic group in which the bonding terminal atom is an oxygen atom, a nitrogen atom, or a sulfur atom.
Examples of organic groups in which the bonding end atom is an oxygen atom, nitrogen atom, or sulfur atom include -OR ⁴ , -OC(═O)R ⁴ , -NHR ⁴ , -NR ⁴ R ⁵ , -SR ⁴ , and nitrogen-containing heterocyclic groups in which a nitrogen atom constituting the ring is the bonding end atom. Here, R ⁴ and R ⁵ are each independently an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group. The number of carbon atoms in the alkyl group is, for example, 1 to 22. The number of carbon atoms forming the ring of the cycloalkyl group is, for example, 3 to 8.
The organic group in Q may have a reactive group such as a hydroxy group, a carboxy group, an amino group, or an alkylamino group, or a halogen atom, and may also have a linking group such as an ether oxygen atom, a carbonyloxy group, or a carbonyl group at a portion other than the bond terminal. Furthermore, it may have a polymerizable carbon-carbon double bond. The reactive group is preferably a hydroxy group. It is preferable that the organic group in Q does not have a polymerizable carbon-carbon double bond.
As Q, from the viewpoints of ease of copolymerization with the monomer (a) and good adhesion to the substrate, a halogen atom, -OR ⁴ or -OC(=O)R ⁴ is preferred, and a fluorine atom, a chlorine atom or -OC(=O)R ⁴ is more preferred. R ⁴ is the same as above.

The compound represented by CH ₂ ═CH-Q is preferably a vinyl carboxylate, a vinyl ether, or a vinyl halide. As the vinyl ether, an alkyl vinyl ether or a hydroxyalkyl vinyl ether is preferable.
The compound represented by CH ₂ ═CHCH ₂ -Q is preferably a carboxylic acid allyl ester, an allyl ether, or an allyl halide. As the allyl ether, an alkyl allyl ether or a hydroxyalkyl allyl ether is preferable.
The number of carbon atoms in the acyl group in the vinyl carboxylate or allyl carboxylate is preferably 24 or less, more preferably 2 to 6. It is also preferable to use a vinyl carboxylate or allyl carboxylate having an acyl group with 2 to 6 carbon atoms in combination with a vinyl carboxylate or allyl carboxylate having an acyl group with 10 to 22 carbon atoms.
The alkyl or hydroxyalkyl in the alkyl vinyl ether, hydroxyalkyl vinyl ether, alkyl allyl ether and hydroxyalkyl allyl ether preferably has 2 to 6 carbon atoms.

Examples of vinyl carboxylates include vinyl acetate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl chloroacetate, and divinyl adipate. Of the vinyl carboxylates, vinyl acetate is particularly preferred because it provides articles with excellent oil and alcohol repellency.

Examples of vinyl ethers include methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, iso-butyl vinyl ether, tert-butyl vinyl ether, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, stearyl vinyl ether, chloromethyl vinyl ether, 2-chloroethyl vinyl ether, chloropropyl vinyl ether, cyclohexyl vinyl ether, ethylene glycol monovinyl ether, and diethylene glycol monovinyl ether.

Examples of the allyl carboxylate include allyl acetate and diallyl adipate.
Examples of allyl ethers include allyl ethyl ether, diallyl ether, 1,3-diallyloxy-2-propanol, and ethylene glycol monoallyl ether.

Examples of the vinyl halides include vinyl chloride and vinyl fluoride.
The allyl halide includes, for example, allyl chloride and allyl fluoride.
Other examples of the compound represented by CH ₂ ═CH-Q or CH ₂ ═CHCH ₂ -Q include N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and ethyl vinyl sulfide.

As the monomer (b1), from the viewpoints of good copolymerizability with the monomer (a) and of obtaining articles having excellent oil repellency and alcohol repellency, vinyl carboxylates, allyl carboxylates, alkyl vinyl ethers, alkyl allyl ethers, hydroxyalkyl vinyl ethers, hydroxyalkyl allyl ethers, vinyl halides and allyl halides are preferred, and vinyl carboxylates and vinyl halides are more preferred.
Specific examples of the monomer (b1) that can give articles having excellent oil repellency and alcohol repellency include vinyl acetate, vinyl butyrate, vinyl pivalate, vinyl caprylate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl chloroacetate, ethyl vinyl ether, tert-butyl vinyl ether, 4-hydroxybutyl vinyl ether, ethylene glycol monoallyl ether, vinyl chloride, and vinyl fluoride, and vinyl acetate is more preferred.

In polymer A, at least a part of the units (b) may be units based on a monomer (b) other than the monomer (b1). The monomer (b) other than the monomer (b1) is hereinafter referred to as "monomer (b2)", and the units based on the monomer (b2) are hereinafter also referred to as "units (b2)".
As the polymer A, a polymer in which at least a part of the units (b) is the unit (b1) is preferable. Examples of the polymer in which at least a part of the units (b) is the unit (b1) include a polymer having only the unit (b1) as the unit (b) and a polymer having the unit (b1) and the unit (b2).
The polymer A may have two or more kinds of units (b1). When the polymer A has units (b2), it may have two or more kinds of units (b2).

Examples of the monomer (b2) include olefins, halogenated olefins other than vinyl halides, alkyl (meth)acrylates, hydroxyalkyl (meth)acrylates, fluoroalkyl (meth)acrylates, and perfluoro(alkyl vinyl ethers). Specifically, ethylene, propylene, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, a compound represented by CH ₂ ═CH-R ^f , methyl (meth)acrylate, ethyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, isobornyl (meth)acrylate _, 2-hydroxyethyl (meth)acrylate, 2-[(3,5-dimethylpyrazolyl)carbonylamino _] ethyl (meth)acrylate _, N _- methylol acrylamide, _{2 -} perfluorohexylethyl ₍ meth)acrylate _, CF ₂ ═CFOCF ₃ , _{CF 2 ═CFOCF 2 ...} ═CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ CF _3. In the compound represented by CH ₂ ═CH—R ^f , R ^f is the same as R ^f in the monomer (a).

As the monomer (b2), a (meth)acrylate is preferred. However, since it is possible to obtain an article whose water and oil repellency is less likely to decrease even after exposure to alkaline conditions, it is preferred that the polymer A does not have a unit based on a (meth)acrylate having a perfluoroalkyl group. Therefore, as the monomer (b2), a (meth)acrylate that does not contain a fluorine atom is preferred. Examples of (meth)acrylates that do not contain a fluorine atom include methyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate. n-Butyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate are preferred because they tend to lower the Tg of polymer A and provide good film-forming properties, and lauryl (meth)acrylate, stearyl (meth)acrylate and behenyl (meth)acrylate are preferred because they tend to provide good feel and improve water repellency when the article is a textile product.

The proportion of unit (a) relative to all units constituting polymer A (i.e., the total of units including unit (a) and unit (b)) is preferably in the range of 20 to 60 mol %, more preferably 30 to 50 mol %. If the proportion of unit (a) is equal to or greater than the lower limit, the article treated with polymer A will have better water and oil repellency, dynamic water repellency, and resistance to repeated immersion in water. If the proportion of unit (a) is equal to or less than the upper limit, the conversion rate in the polymerization reaction of polymer A is likely to be higher.

When at least a portion of the units (b) are units (b1), the ratio of units (b1) to all units constituting polymer A is preferably in the range of 40 to 80 mol%, more preferably 50 to 70 mol%. If the ratio of units (b1) is equal to or greater than the lower limit, the conversion rate in the polymerization reaction of polymer A tends to be higher. If the ratio of units (b1) is equal to or less than the upper limit, the water/oil repellency, dynamic water repellency, and resistance to repeated immersion in water of an article treated with polymer A are superior.

When at least a portion of the units (b1) are units based on vinyl halide, the ratio of the units based on vinyl halide to the total units of the units (b) is preferably 1 to 60 mol%, more preferably 5 to 50 mol%, and even more preferably 10 to 40 mol%. If the ratio of the units (b1) is equal to or greater than the lower limit, the conversion rate in the polymerization reaction of polymer A tends to be higher. If the ratio of the units (b1) is equal to or less than the upper limit, the water and oil repellency, dynamic water repellency, and repeated water immersion resistance of the article treated with polymer A are superior.

The proportion of units (b2) relative to the total units constituting polymer A is preferably less than 20% by mass, more preferably less than 10% by mass, and may be 0% by mass. If the proportion of units (b2) is equal to or less than the upper limit, an article can be obtained in which the water and oil repellency is further resistant to deterioration even after exposure to alkaline conditions.

The total ratio of the units (a) and (b1) to all units constituting polymer A is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass. If the total ratio is equal to or more than the lower limit, an article can be obtained whose water and oil repellency is further less likely to decrease even after exposure to alkaline conditions.

The proportion of each unit can be calculated from the reaction rate of each monomer component by ^1H -NMR and gas chromatography. When the conversion rate of the monomer components to the polymer A is high (e.g., 90% or more) during the production of the polymer A, the proportion of each unit may be calculated based on the amount of the monomer components charged.
The conversion rate is calculated from the theoretical mass of polymer A calculated from the amounts of raw materials charged during the production of polymer A and the actual mass of the produced polymer A by calculating the actual mass/theoretical mass×100.

The Mn of polymer A is preferably 10,000 or more, more preferably 11,000 or more, and even more preferably 12,000 or more. The Mn of polymer A is preferably 100,000 or less, more preferably 70,000 or less, and even more preferably 50,000 or less. If the Mn of polymer A is equal to or greater than the lower limit, the water and oil repellency, dynamic water repellency, and repeated water immersion resistance of the article treated with polymer A are even more excellent. If the Mn of polymer A is equal to or less than the upper limit, the water dispersibility of polymer A is even more excellent.

The Mw of polymer A is preferably 10,000 or more, more preferably 20,000 or more, and even more preferably 30,000 or more. The Mw of polymer A is preferably 150,000 or less, more preferably 120,000 or less, and even more preferably 100,000 or less. If the Mw of polymer A is equal to or greater than the lower limit, the water and oil repellency, dynamic water repellency, and repeated water immersion resistance of the article treated with polymer A are even more excellent. If the Mw of polymer A is equal to or less than the upper limit, the water dispersibility of polymer A is even more excellent.

The molecular weight distribution (Mw/Mn) of polymer A is preferably 1.0 or more, more preferably 1.3 or more, and even more preferably 1.6 or more. The Mw/Mn of polymer A is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.0 or less. If the Mw/Mn of polymer A is equal to or greater than the lower limit, the water/oil repellency, dynamic water repellency, and repeated water immersion resistance of the article treated with polymer A are even more excellent. If the Mw/Mn of polymer A is equal to or less than the upper limit, the water dispersibility of polymer A is even more excellent.

The glass transition temperature (hereinafter, referred to as "Tg") of polymer A is preferably 0 to 80°C, more preferably 5 to 70°C. When Tg is equal to or higher than the lower limit, the polymer has better resistance to repeated water immersion. When Tg is equal to or lower than the upper limit, the polymer has better film-forming properties of the water- and oil-repellent coating and better substrate covering properties.
Tg is the midpoint glass transition temperature determined by differential scanning calorimetry (DSC) according to JIS K 7121:1987.

(Mechanism of action)
The polymer A described above contains the unit (a), and since the unit (a) has X at the α-position, an article treated with a composition containing the polymer A has excellent dynamic water repellency or resistance to repeated immersion in water. The polymer A can also provide an article having excellent dynamic water repellency and resistance to repeated immersion in water. In addition, the water and oil repellency of an article treated with a composition containing the polymer A is unlikely to decrease even after being exposed to conditions such as an alkali. In addition,

[Method for producing fluoropolymer]
In a method for producing a fluorinated polymer according to one embodiment of the present invention, a monomer component containing monomer (a) and monomer (b) is polymerized in the presence of a polymerization initiator.

The monomer (a) and the monomer (b) are as described above.
The monomer (a) and the monomer (b) may be produced by a known production method. Commercially available monomers may be used.
Monomer (a) can be produced, for example, by adding X ₂ (a halogen such as Cl ₂ ) to a compound represented by CH ₂ ═CH—R ^f to obtain a compound represented by CH ₂ X—CHX—R ^f (Step A), and then removing HX from the compound represented by CH ₂ X—CHX—R ^f (Step B).

In step A, for example, a compound represented by CH ₂ ═CH—R ^f is contacted with gaseous X ₂ in the presence of a halogenation catalyst.
Examples of halogenation catalysts include tertiary amines (trimethylamine, triethylamine, tripropylamine, tributylamine, etc.) and their salts (hydrochlorides, etc.), N-substituted amides (dimethylformamide, etc.), and aromatic nitrogen-containing compounds (pyridine, methylpyridine, etc.). The amount of the halogenation catalyst used is, for example, 0.01 to 10 parts by mass relative to 100 parts by mass of the compound represented by CH ₂ ═CH-R ^f .
To bring the compound represented by CH ₂ ═CH-R ^f into contact with gaseous X ₂ , for example, a gas containing X ₂ may be blown into a solution of the compound represented by CH ₂ ═CH-R ^f under stirring. The amount of X ₂ blown in is, for example, 1 to 1.2 moles per mole of the compound represented by CH ₂ ═CH-R ^f . The time for blowing in X ₂ is, for example, 0.5 to 24 hours.
The reaction temperature in step A is, for example, 30 to 100° C. The reaction time is, for example, 0.5 to 24 hours. Step A is preferably carried out in the dark.
The reaction product in step A may be directly subjected to step B.

In step B, for example, a compound represented by CH ₂ X--CHX--R ^f is subjected to dehydrogenation in the presence of a dehydrogenation catalyst.
Examples of the dehydrogenation catalyst include amines such as tertiary amines, and aromatic nitrogen-containing compounds such as aromatic nitrogen-containing heterocyclic compounds. Examples of the amines include trimethylamine, triethylamine, tripropylamine, tributylamine, triethanolamine, and salts thereof (e.g., hydrochlorides). Examples of the aromatic nitrogen-containing compounds include pyridine and methylpyridine. The amount of the dehydrogenation catalyst used is, for example, 0.001 to 0.5 moles per mole of the compound represented by CH ₂ X-CHX-R ^f . When a tertiary amine or an aromatic nitrogen-containing compound is used as the halogenation catalyst, the halogenation catalyst used in step A can be used as it is as the dehydrogenation catalyst.
The reaction temperature in step B is, for example, −10 to 50° C. The reaction time is, for example, 0.5 to 12 hours.
It is preferable that step B is carried out in the presence of a polymerization inhibitor to prevent polymerization of the resulting monomer (a). Examples of the polymerization inhibitor include t-butylcatechol, hydroquinone, hydroquinone monomethyl ether, and phenothiazine. The amount of the polymerization inhibitor used is, for example, 0.003 to 0.1 parts by mass relative to 100 parts by mass of the compound represented by CH ₂ X-CHX-R ^f .
After the dehydrogenation, the monomer (a) is usually recovered from the resulting reaction mixture. To recover the monomer (a), for example, an acid is added to the reaction mixture to adjust the pH to 7 or less, and the mixture is allowed to stand. When the pH-adjusted reaction mixture is allowed to stand, the reaction mixture separates into an oil phase containing the monomer (a) and an aqueous phase. A conventionally known method can be used to purify the monomer (a).

The proportion of monomer (a) relative to the total monomer components (i.e., the sum of all monomers including monomer (a) and monomer (b)) is preferably in the range of 20 to 60 mol%, more preferably 30 to 50 mol%. If the proportion of monomer (a) is equal to or greater than the lower limit, the article treated with polymer A will have better water and oil repellency, dynamic water repellency, and resistance to repeated immersion in water. If the proportion of monomer (a) is equal to or less than the upper limit, the conversion rate in the polymerization reaction of polymer A is likely to be higher.

The proportion of monomer (b) relative to the total monomer components is preferably in the range of 40 to 80 mol%, more preferably 50 to 70 mol%. If the proportion of monomer (b) is equal to or greater than the lower limit, the conversion rate in the polymerization reaction is likely to be higher. If the proportion of monomer (b) is equal to or less than the upper limit, the article treated with polymer A has better water and oil repellency, dynamic water repellency, and resistance to repeated water immersion.

When at least a portion of monomer (b) is monomer (b1), the range of the proportion of monomer (b1) relative to the entire monomer component is preferably 40 to 80 mol%, and more preferably 50 to 70 mol%. If the proportion of monomer (b1) is equal to or greater than the lower limit, the conversion rate in the polymerization reaction tends to be higher. If the proportion of monomer (b1) is equal to or less than the upper limit, the article treated with polymer A has better water and oil repellency, dynamic water repellency, and resistance to repeated water immersion.

When at least a portion of monomer (b1) is a vinyl halide, the proportion of vinyl halide relative to the total monomer (b) is preferably in the range of 1 to 60 mol%, more preferably 5 to 50 mol%, and even more preferably 10 to 40 mol%. If the proportion of monomer (b1) is equal to or greater than the lower limit, the conversion rate in the polymerization reaction of polymer A tends to be higher. If the proportion of monomer (b1) is equal to or less than the upper limit, the water/oil repellency, dynamic water repellency, and resistance to repeated water immersion of an article treated with polymer A are more excellent.

The proportion of monomer (b2) in the total monomer components is preferably less than 20% by mass, more preferably less than 10% by mass, and may be 0% by mass. If the proportion of monomer (b2) is equal to or less than the upper limit, an article can be obtained whose water and oil repellency is less likely to decrease even after exposure to alkaline conditions.

The total proportion of monomer (a) and monomer (b1) relative to the total monomer components is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass. If the total proportion is equal to or more than the lower limit, an article can be obtained in which the water and oil repellency is further resistant to deterioration even after exposure to alkaline conditions.

Examples of the polymerization initiator include a thermal polymerization initiator, a photopolymerization initiator, a radiation polymerization initiator, a radical polymerization initiator, and an ionic polymerization initiator, with a radical polymerization initiator being preferred. Examples of the radical polymerization initiator include an azo-based polymerization initiator, a peroxide-based polymerization initiator, and a redox-based initiator, which are used depending on the polymerization temperature. Examples of the radical polymerization initiator include an azo-based compound, and more preferably a salt of an azo-based compound. The polymerization temperature is preferably 20 to 150°C.
The amount of the polymerization initiator added is preferably 0.1 to 5 parts by mass, and more preferably 0.1 to 3 parts by mass, based on 100 parts by mass of the monomer component.

When polymerizing the monomer components, a molecular weight regulator may be used. Examples of the molecular weight regulator include aromatic compounds, mercaptoalcohols, mercaptocarboxylic acids, and alkyl mercaptans, and more preferably mercaptocarboxylic acids or alkyl mercaptans. Examples of the molecular weight regulator include mercaptoethanol, mercaptopropionic acid, n-octyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan, stearyl mercaptan, and α-methylstyrene dimer (CH ₂ ═C(Ph)CH ₂ C(CH ₃ ) ₂ Ph, where Ph is a phenyl group).
The amount of the molecular weight modifier added is preferably 5 parts by mass or less, more preferably 2 parts by mass or less, and may be 0 parts by mass, based on 100 parts by mass of the monomer component.

Methods for polymerizing the monomer components include emulsion polymerization, solution polymerization, suspension polymerization, bulk polymerization, etc. Among these, emulsion polymerization is preferred. By polymerizing the monomer components by emulsion polymerization, it is possible to improve the conversion rate of the monomer components to polymer A and increase the molecular weight (Mn, Mw) of polymer A without using a solvent other than the aqueous medium.

In the emulsion polymerization method, for example, the monomer components are polymerized in an emulsion containing an aqueous medium, a monomer component, and a polymerization initiator. The emulsion may contain a surfactant, if necessary.
Examples of the aqueous medium include the same aqueous medium as in the water/oil repellent composition described below.
Examples of the surfactant include the same surfactants as those in the water/oil repellent composition described below.

The emulsion can be prepared by mixing an aqueous medium, a monomer component, and, if necessary, a surfactant, dispersing the mixture using a homogenizer, a high-pressure emulsifier, or the like, and then adding a polymerization initiator.
The concentration of the monomer component in the emulsion is preferably 20 to 60% by mass, more preferably 30 to 50% by mass. When the concentration of the monomer component in the emulsion is within the above range, the conversion rate of the monomer component to polymer A during polymerization of the monomer component can be improved, and the molecular weight of polymer A can be sufficiently increased.

The content of the surfactant in the emulsion is preferably 1 to 6 parts by mass per 100 parts by mass of the monomer component. If the content of the surfactant is equal to or greater than the lower limit, the dispersion stability of the emulsion is excellent. If the content of the surfactant is equal to or less than the upper limit, the adverse effect of the surfactant on the water and oil repellency of an article treated with a composition containing polymer A can be reduced.

The conversion rate of the monomer component to polymer A at the end of polymerization is preferably 80% or more, more preferably 90% or more. By increasing the conversion rate, the molecular weight of polymer A also increases, and water/oil repellency, dynamic water repellency, and resistance to repeated immersion in water also become good. In addition, by achieving a high conversion rate, the performance degradation due to the remaining monomer is suppressed and the amount of fluorine atoms contained in polymer A increases, so that water/oil repellency, dynamic water repellency, and resistance to repeated immersion in water become good.
In order to achieve a conversion rate of 80% or more, it is preferable to optimize the emulsion composition and the polymerization time.

By polymerizing the monomer components in the emulsion, a dispersion of polymer A is obtained.
In the dispersion, polymer A is dispersed as emulsified particles in an aqueous medium.
In the dispersion, the average particle size of the emulsion particles of polymer A is preferably 20 to 200 nm, more preferably 40 to 190 nm, and even more preferably 60 to 180 nm. When the average particle size is equal to or less than the upper limit, the water repellency of an article treated with the emulsion particles of polymer A and the dispersibility of the emulsion particles of polymer A are superior. When the average particle size is equal to or more than the lower limit, the emulsion particles of polymer A are more stable against mechanical shear.
The average particle size of the emulsion particles of polymer A is calculated by cumulant analysis from the autocorrelation function obtained by dynamic light scattering of a sample prepared by diluting the dispersion of polymer A with water to a solid content concentration of 1% by mass.

After the monomer components are polymerized in the emulsion, polymer A is recovered from the resulting dispersion as necessary. The dispersion may be directly used for the production of a water/oil repellent composition, etc.

(Mechanism of action)
In the above-described method for producing a fluorine-containing polymer, since a monomer component containing the monomer (a) is polymerized, it is possible to produce a polymer A from which an article having excellent dynamic water repellency or resistance to repeated immersion in water can be produced. Also, it is possible to produce a polymer A from which an article having water and oil repellency that is not easily reduced even after exposure to alkaline conditions can be produced.

[Water/Oil Repellent Composition]
The water/oil repellent composition according to one embodiment of the present invention (hereinafter also referred to as “the composition”) contains polymer A.
The composition typically contains polymer A and a medium. Examples of the medium include an aqueous medium and an organic solvent, and an aqueous medium is preferred.
The composition may optionally contain a surfactant.
The composition may optionally contain other ingredients.
The present composition is preferably a fluoropolymer dispersion containing polymer A, an aqueous medium, and a surfactant. The fluoropolymer dispersion includes the dispersion obtained by the above-mentioned method for producing polymer A, and the dispersion further diluted with any aqueous medium for treating articles.
The present composition may be a fluoropolymer solution containing polymer A and an organic solvent but not containing a surfactant.

(Aqueous medium)
Aqueous media include water and water containing a water-soluble organic solvent.
The water-soluble organic solvent is an organic solvent that can be mixed with water at any ratio. As the water-soluble organic solvent, at least one selected from the group consisting of alcohols (excluding ether alcohols), ether alcohols, and aprotic polar solvents is preferable. As the alcohol, for example, t-butanol and propylene glycol can be mentioned. As the ether alcohol, for example, 3-methoxymethylbutanol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol can be mentioned. As the aprotic polar solvent, for example, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran (hereinafter also referred to as "THF"), acetonitrile, acetone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, 3-methoxy-3-methyl-1-butanol, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether can be mentioned. When the liquid medium is an aqueous medium, the water-soluble organic solvent is preferably an ether alcohol, and more preferably dipropylene glycol, tripropylene glycol, or dipropylene glycol monomethyl ether, from the viewpoint of improving the compatibility between the polymer A and the aqueous medium and facilitating the formation of a uniform film on the article.
When the aqueous medium is water containing a water-soluble organic solvent, the content of the water-soluble organic solvent is preferably from 1 to 80 parts by mass, and more preferably from 5 to 60 parts by mass, per 100 parts by mass of water.

(Surfactant)
The surfactant is preferably a surfactant that does not contain a fluorine atom.
The surfactant may, for example, be an anionic surfactant, a nonionic surfactant, a cationic surfactant, or an amphoteric surfactant.
As the surfactant, from the viewpoint of excellent dispersion stability of the aqueous dispersion containing polymer A, it is preferable to use a nonionic surfactant alone, a nonionic surfactant in combination with a cationic surfactant or an amphoteric surfactant, or an anionic surfactant alone, and it is more preferable to use a nonionic surfactant in combination with a cationic surfactant.
The ratio of the nonionic surfactant to the cationic surfactant (nonionic surfactant/cationic surfactant) is preferably from 100/0 to 40/60 (mass ratio), and more preferably from 97/3 to 40/60 (mass ratio).
In certain combinations of a nonionic surfactant and a cationic surfactant, the total amount of surfactants per 100 parts by mass of polymer A can be made 5 parts by mass or less, thereby reducing the adverse effects of the surfactants on the water and oil repellency of articles treated with the composition.

Examples of the nonionic surfactant include surfactants s ¹ to s ⁶ described in paragraphs [0067] to [0095] of JP-A-2009-215370.
As surfactant ^s1 , polyoxyethylene alkyl ethers are preferred.
As the surfactant ^s2 , an acetylene glycol ethylene oxide adduct is preferred.
As surfactant ^s3 , polyoxyethylene polyoxypropylene glycol is preferred.
Two or more types of nonionic surfactants may be used in combination.

An example of the cationic surfactant is surfactant ^s7 described in paragraphs [0096] to [0100] of JP-A-2009-215370.
As the surfactant ^s7 , an ammonium salt in which one or more hydrogen atoms bonded to a nitrogen atom are substituted with an alkyl group, an alkenyl group, or a polyoxyalkylene chain terminated with a hydroxyl group is preferred, and a compound ^s71 represented by the following formula ^s71 is more preferred.
[(R ²¹ ) ₄ N ⁺ ]・X ⁻ s ⁷¹
R ²¹ is a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, a fluoroalkyl group having 1 to 9 carbon atoms, or a polyoxyalkylene chain having a hydroxyl group at the end. The four R ²¹ may be the same or different, but all four R ²¹ are not hydrogen atoms at the same time. X ^- is a counter ion.
X ⁻ is preferably a chloride ion, an ethyl sulfate ion, or an acetate ion.
Examples of compound s ⁷¹ include monostearyl trimethyl ammonium chloride, monostearyl dimethyl monoethyl ammonium ethyl sulfate, mono(stearyl) monomethyl di(polyethylene glycol) ammonium chloride, monofluorohexyl trimethyl ammonium chloride, di(tallow alkyl) dimethyl ammonium chloride, and dimethyl mono coconut amine acetate.
Two or more kinds of cationic surfactants may be used in combination.

Examples of the amphoteric surfactant include surfactant ^s8 described in paragraphs [0101] to [0102] of JP-A-2009-215370. These surfactants may be used alone or in combination of two or more.

As the combination of surfactants, from the viewpoint of having little adverse effect on the water and oil repellency of an article treated with the present composition and of having excellent dispersion stability of a dispersion containing polymer A, a combination of surfactants ^s1 , ^s2 and ^s7 , or a combination of surfactants ^s1 , ^s3 and ^s7 , or a combination of surfactants s1, ^s2 , ^{s3 and s7} is preferred, and the above combination in which surfactant ^s7 is compound ^s71 is more preferred.

(Other ingredients)
Examples of other components include fluorine-containing polymers other than polymer A, non-fluorine-based polymers, non-fluorine-based water- and oil-repellents, water-soluble polymer resins (e.g., hydrophilic polyesters and derivatives thereof, hydrophilic polyethylene glycols and derivatives thereof, hydrophilic polyamines and derivatives thereof), crosslinking agents, penetrating agents (e.g., nonionic surfactants having an acetylene group at the center and a symmetrical structure, such as the Dispanol (registered trademark) series manufactured by NOF Corp.), colloidal silica (e.g., the Snowtex (registered trademark) series manufactured by Nissan Chemical Industries, Ltd. and the Adelight series manufactured by ADEKA Corporation), defoaming agents (e.g., the Olfine (registered trademark) series manufactured by Nissin Chemical Industries, Ltd. and the FS Antifoam series manufactured by Dow Corning Toray Co., Ltd.), film-forming assistants, insect repellents, mildewproofing agents, preservatives, flame retardants, antistatic agents (e.g., the Directol series manufactured by Meisei Chemical Industries, Ltd.), wrinkle-proofing agents, softening agents (e.g., silicone emulsions, polyethylene wax emulsions), and pH adjusters (e.g., diethanolamine, triethanolamine, acetic acid, citric acid).

When the present composition contains a crosslinking agent, the adhesion to an article tends to be improved.
As the crosslinking agent, an isocyanate-based crosslinking agent, a methylol-based crosslinking agent, a carbodiimide-based crosslinking agent, and an oxazoline-based crosslinking agent are preferable.

Examples of isocyanate-based crosslinking agents include aromatic block type isocyanate-based crosslinking agents, aliphatic block type isocyanate-based crosslinking agents, aromatic unblocked type isocyanate-based crosslinking agents, and aliphatic unblocked type isocyanate-based crosslinking agents. The isocyanate-based crosslinking agent is preferably a water-dispersed type emulsified with a surfactant, or a self-water-dispersed type having a hydrophilic group.

Examples of methylol-based crosslinking agents include condensates or pre-condensates of urea or melamine with formaldehyde, methylol-dihydroxyethylene-urea and its derivatives, methylol-ethylene-urea, methylol-propylene-urea, methylol-triazone, dicyandiamide-formaldehyde condensates, methylol-carbamate, methylol-(meth)acrylamide, and polymers of these.

The carbodiimide crosslinking agent is a polymer having a carbodiimide group in the molecule, and is a crosslinking agent that exhibits excellent reactivity with carboxy groups, amino groups, and active hydrogen groups of articles and the like.
The oxazoline-based crosslinking agent is a polymer having an oxazoline group in the molecule, and is a crosslinking agent that exhibits excellent reactivity with carboxy groups of articles and the like.

Other crosslinking agents include, for example, divinyl sulfone, polyamides and their cationic derivatives, polyamines and their cationic derivatives, epoxy derivatives such as diglycidyl glycerol, halide derivatives such as (epoxy-2,3-propyl)trimethylammonium chloride and N-methyl-N-(epoxy-2,3-propyl)morpholinium chloride, pyridinium salts of chloromethyl ether of ethylene glycol, polyamine-polyamide-epichlorohydrin resins, polyvinyl alcohol or its derivatives, polyacrylamide or its derivatives, and glyoxal resin-based wrinkle inhibitors.

When the present composition contains a methylol-based crosslinking agent or a glyoxal resin-based wrinkle-preventive agent, it is preferable to contain a catalyst as an additive. Preferred catalysts include, for example, inorganic amine salts and organic amine salts. Examples of inorganic amine salts include ammonium chloride. Examples of organic amine salts include amino alcohol hydrochloride and semicarbazide hydrochloride. Examples of amino alcohol hydrochloride include monoethanolamine hydrochloride, diethanolamine hydrochloride, triethanolamine hydrochloride, and 2-amino-2-methylpropanol hydrochloride.

(Proportion of each ingredient)
When the present composition contains an aqueous medium, the content of the aqueous medium can be appropriately selected depending on the desired solids concentration of the present composition.
When the composition contains a surfactant, the content of the surfactant is preferably 1 to 6 parts by mass per 100 parts by mass of polymer A. When the content of the surfactant is equal to or more than the lower limit, the dispersion stability of the composition is excellent. When the content of the surfactant is equal to or less than the upper limit, adverse effects of the surfactant on the water/oil repellency and dynamic water repellency of an article treated with the composition can be reduced.
When the present composition contains a crosslinking agent, the content of the crosslinking agent is preferably 1 to 50 parts by mass per 100 parts by mass of Polymer A.

The solid content concentration of the present composition immediately after production of the present composition is preferably from 20 to 70% by mass, and more preferably from 30 to 60% by mass.
When the present composition is used to treat an article, the solids concentration of the present composition is preferably from 0.1 to 7% by mass, and more preferably from 0.2 to 5% by mass.
The solids concentration is calculated by (solids mass/sample mass)×100, where the mass of the sample before heating is the sample mass and the mass of the sample after drying for 4 hours in a convection dryer at 120° C. is the solids mass.

The method for producing the composition is not particularly limited.
For example, when the present composition is a fluoropolymer dispersion, a dispersion of polymer A is obtained by the above-mentioned emulsion polymerization method, and the obtained dispersion may be used as the present composition as it is, or it may be used as the present composition after diluting with an aqueous medium to adjust the solid content concentration. Other components may be further added to the present composition.

(Mechanism of action)
In the present composition described above, since polymer A contains unit (a) and said unit (a) has X at the α-position, an article treated with the present composition has excellent dynamic water repellency or resistance to repeated immersion in water. It is also possible to obtain an article having excellent dynamic water repellency and resistance to repeated immersion in water. In addition, since polymer A contains unit (a), the water and oil repellency of an article treated with the present composition is unlikely to decrease even after it is exposed to conditions such as an alkali. In addition,

[Goods]
An article according to one embodiment of the present invention is a substrate having at least a portion of its surface treated with the composition.
Examples of substrates to be treated with the composition include fibers, fiber fabrics (woven fiber fabrics, knitted fiber fabrics, nonwoven fabrics, raised fabrics, etc.), fiber products with fiber fabrics (key wear, rain wear, coats, blousons, windbreakers, down jackets, sportswear, work clothes, uniforms, protective clothing, backpacks, backpacks, bags, tents, tents, etc.), glass, paper, wood, leather, artificial leather, stone, concrete, ceramics, metals, metal oxides, ceramic products, resin molded products, porous resins, and porous fibers. Porous resins are used, for example, as filters. Examples of materials for porous resins include polypropylene, polyethylene terephthalate, and polytetrafluoroethylene. Examples of materials for porous fibers include glass fibers, cellulose nanofibers, carbon fibers, and cellulose acetate.

The substrate is preferably a fiber, a fiber fabric, or a fiber product comprising a fiber fabric.
The type of fiber is not particularly limited, and examples thereof include natural fibers such as cotton, wool, silk, and cellulose, synthetic fibers such as polyester, polyamide, acrylic, and aramid, chemical fibers such as rayon, viscose rayon, and lyocell, blended fibers of natural fibers and synthetic fibers, and blended fibers of natural fibers and chemical fibers. When the fiber substrate is a nonwoven fabric, examples of the fiber include polyethylene, polypropylene, polyolefin, polyethylene terephthalate, polytetrafluoroethylene, glass, and rayon.

The treatment method may be any method that can attach the composition to the article to be treated. For example, when the composition is liquid, the composition is applied to the substrate by a known coating method such as coating, impregnation, immersion, spraying, brushing, padding, size press, roller, etc., and then dried. When the substrate is a paper substrate, the composition is applied or impregnated to the paper substrate (external addition), and a pulp slurry containing the composition is made into paper (internal addition).
The amount of the present composition to be applied to a substrate is not particularly limited. For example, in the case of a fiber fabric, the amount of the present composition per unit mass of the fiber fabric is preferably 0.001 to 0.07 g/g, and more preferably 0.001 to 0.05 g/g, in terms of solid content.
Drying may be performed at room temperature or with heating, preferably with heating. When heating is performed, the heating temperature is preferably 40 to 200° C. Furthermore, when the present composition contains a crosslinking agent, it is preferable to cure the composition by heating to a crosslinking temperature of the crosslinking agent or higher, if necessary.

(Mechanism of action)
The articles of the present invention described above have been treated with the composition, and therefore have excellent dynamic water repellency or resistance to repeated immersion in water, and the water and oil repellency is not easily reduced even after exposure to alkaline conditions, etc.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these.
Examples 1 to 6 are working examples, and Examples 7 to 12 are comparative examples.

(Proportion of each unit)
After removing the surfactant and solvent from the fluoropolymer dispersion obtained in each example, the ratio (mol %) of each unit to all units constituting the fluoropolymer was calculated from the reaction rate of each monomer by ¹ H-NMR and gas chromatography of the fluoropolymer dispersion obtained in each example.

(Solid content concentration)
The solids concentration of the fluoropolymer dispersion was calculated by (solids mass/sample mass)×100, where the mass of the sample before heating is the sample mass and the mass of the sample after drying for 4 hours in a convection dryer at 120° C. is the solids mass.

(Conversion rate)
From the theoretical value of the solids concentration of the fluoropolymer dispersion calculated from the charged amounts of the raw materials and the actual measured value of the solids concentration of the fluoropolymer dispersion, the conversion rate of the monomer component to the fluoropolymer was calculated by dividing the actual value by the theoretical value x 100. A conversion rate of 90% or more was rated as ○ (good), 80% or more but less than 90% was rated as △ (passable), and less than 80% was rated as × (unacceptable).

(Average Molecular Weight)
<Recovery of Fluorine-Containing Polymer>
6 g of the fluoropolymer dispersion obtained in each example was dropped into 60 g of a mixed liquid of 6 g of hexane and 54 g of 2-butanol, and the mixture was stirred to precipitate a solid. After centrifugation at 3000 rpm for 5 minutes, the obtained solid was separated. 30 g of isopropyl alcohol (hereinafter also referred to as "IPA") denatured alcohol (manufactured by Imazu Corporation, product name: 95% IPA denatured alcohol) and 30 g of ion-exchanged water were added to the separated solid, and the mixture was thoroughly stirred. After centrifugation at 3000 rpm for 5 minutes, the obtained solid was separated from the supernatant and vacuum-dried at 35°C overnight to obtain a fluoropolymer.

<Measurement of Mn and Mw>
The recovered fluoropolymer was dissolved in a mixed solvent of fluorine-containing solvent (AK-225, manufactured by AGC)/tetrahydrofuran (hereinafter referred to as "THF") = 6/4 (volume ratio) to obtain a solution with a solid content concentration of 0.5 mass%, which was passed through a 0.2 μm filter to obtain an analysis sample. The Mn and Mw of the analysis sample were measured by GPC measurement. The measurement conditions were as follows.
Apparatus: Tosoh Corporation, HLC-8320GPC;
Column: Polymer Laboratories, MIXED-C Length: 300 mm, outer diameter: 7.5 mm Film thickness: 5 μm
Mobile phase: AK-225/THF=6/4 (volume ratio),
Flow rate: 1.0 mL/min,
Oven temperature: 37°C,
Sample concentration: 1.0% by mass
Injection volume: 50 μL,
Detector: RI,
Molecular weight standards: Polymethyl methacrylate (Mp=2136000, 955000, 569000, 332800, 121600, 67400, 31110, 13300, 7360, 1950, 1010, and 550).

(Tg)
About 10 mg of the recovered fluoropolymer was weighed out in a dedicated aluminum pan and used as an analysis sample. The analysis sample was measured for Tg by DSC measurement. The measurement conditions were as follows:
Apparatus: TA Instruments, Q2000,
Temperature program: -20°C to 180°C, 10°C/min, 2 cycles,
Measurement: Tg was calculated from the change in heat observed during the second heating.

(Water receding contact angle)
The receding contact angle of the surface of the article to water was measured at 25° C. by the Wilhelmy method using DCAT21 (manufactured by DataPhysics). The receding contact angle to water is an indicator of the dynamic water repellency of the article. The larger the receding contact angle to water, the better the dynamic water repellency.

(n-HD static contact angle)
In accordance with JIS R 3257:1999 "Test method for wettability of glass substrate surface", droplets of n-hexadecane (hereinafter referred to as "n-HD") were placed at five locations on the surface of an article, and the contact angle of n-HD was measured for each droplet by the sessile drop method. The droplets were approximately 2 μL/droplet, and the measurements were performed at 20° C. The contact angle of n-HD is shown as the average value of the measurements at the five locations. The contact angle of n-HD is an indicator of the oil repellency of an article.

(Repeated water immersion resistance)
The article was repeatedly immersed in ion-exchanged water by reciprocating five times at a speed of 0.5 mm/sec using a dip coater (device name: F225, manufactured by Asumi Giken Co., Ltd.). Thereafter, the shape of the surface of the article was visually observed and evaluated according to the following criteria.
◯: No change in appearance of the article surface.
△: Cracks and peeling were observed on some parts of the surface of the article.
x: Cracks and peeling are observed over the entire surface of the article.

(Monomer (a))
αCl-C6OLF: CH ₂ ═CCl-(CF ₂ ) ₅ CF ₃ (manufactured by Synquest).
αCl-C4OLF: CH ₂ ═CCl-(CF ₂ ) ₃ CF ₃ (manufactured by Synquest).
(Monomer (b))
C6OLF: CH ₂ ═CH—(CF ₂ ) ₅ CF ₃ (manufactured by Tokyo Chemical Industry Co., Ltd.).
C4OLF: CH ₂ ═CH—(CF ₂ ) ₃ CF ₃ (manufactured by Tokyo Chemical Industry Co., Ltd.).
AcV: vinyl acetate (Tokyo Chemical Industry Co., Ltd.).
PiV: vinyl pivalate (Tokyo Chemical Industry Co., Ltd.).
StV: vinyl stearate (Tokyo Chemical Industry Co., Ltd.).
VCM: CH ₂ ═CHCl (manufactured by Yokohama Chemical Co., Ltd.).

(Surfactant)
<Cationic Surfactant>
LC18-63: 63% by mass solution of alkyl chloride (carbon number: 16 to 18) trimethylammonium chloride in water and isopropyl alcohol (manufactured by Lion Specialty Chemicals, Lipocard 18-63).
<Nonionic Surfactant>
PEO-30: 10% by mass aqueous solution of polyoxyethylene oleyl ether (approximately 30 moles of ethylene oxide adduct, manufactured by Kao Corporation, Emulgen 430).
P204: Ethylene oxide-propylene oxide polymer (average molecular weight 3,330, containing 40 mass% ethylene oxide, NOF Corporation product name, Pronon #204).

(Medium)
Water: Ion-exchanged water.
DPG: dipropylene glycol.
(Polymerization initiator)
VA-061A: 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (VA-061, Fujifilm Wako Pure Chemical Industries, Ltd.) was mixed with acetic acid at a mass of 0.8, giving a mass of 1, to obtain a 20 mass% aqueous solution of acetate of VA061.

(Examples 1 to 12)
A mixture was obtained by stirring in a 1-liter autoclave equipped with a stirrer, where monomers other than AcV and VCM, a medium, and a surfactant were charged in the amounts (parts by mass) shown in Tables 1 and 2. The mixture was then placed in a high-pressure homogenizer and pre-emulsified at a pressure of 10 MPa, and then high-pressure emulsified and dispersed at a pressure of 40 MPa to obtain an emulsion.
The emulsion was placed in a stainless steel autoclave, and a polymerization initiator was added in the number of parts charged shown in Tables 1 and 2. The inside of the autoclave was replaced with nitrogen five times at a pressure of 0.5 MPa, AcV and VCM were added, and the temperature was raised to 45°C, and the monomer components were polymerized for 72 hours to obtain a fluoropolymer dispersion. Tables 1 and 2 show the solid content concentration of the fluoropolymer dispersion, the conversion rate, and the Mw, Mn, Mw/Mn and Tg of the fluoropolymer in the fluoropolymer. In Tables 1 and 2, the number of parts charged of the surfactant and polymerization initiator is the total amount including the mass of the solvent.

The fluoropolymer dispersion was diluted with distilled water to adjust the solid content concentration to 1.0 mass % to obtain a water/oil repellent composition.
The water/oil repellent composition was applied to the surface of a glass substrate (ASLAB, SUPER GRADE MICROSCOPE SLIDES; product name of THICK Corporation, length: 25 mm, width: 75 mm, thickness: 1.0-1.2 mm) using a dip coater (device name: F255) by reciprocating three times at a speed of 0.5 mm/sec, and then dried at 200° C. for 10 minutes to prepare an article for evaluation. The article was evaluated for water receding contact angle, n-HD static contact angle, and repeated water immersion resistance. The results are shown in Tables 1 and 2.

The articles treated with the water/oil repellent compositions of Examples 1 to 6 containing a fluoropolymer having units (a) were excellent in dynamic water repellency, oil repellency and resistance to repeated immersion in water. In addition, since an ^Rf group is introduced into the fluoropolymer by the units (a), it can be judged that these properties are unlikely to deteriorate even when exposed to alkaline conditions, etc.
The water/oil repellent compositions of Examples 7 to 12 were similar to the water/oil repellent compositions of Examples 1 to 6 except that the chlorine atom at the α-position of unit (a) was replaced with a hydrogen atom, but the articles were inferior to those of Examples 1 to 6 in dynamic water repellency, oil repellency and repeated water immersion resistance.
In addition, the entire contents of the specification, claims and abstract of Japanese Patent Application No. 2019-236897 filed on December 26, 2019 are hereby incorporated by reference as the disclosure of the specification of the present invention.

Claims (13)

A fluorine-containing polymer comprising units based on the following monomer (a) and units based on the following monomer (b):
Monomer (a): A compound represented by CH ₂ ═CX— ^Rf .
In the formula, X is a chlorine atom, and ^Rf is a perfluoroalkyl group having 4 to 6 carbon atoms.
Monomer (b): A monomer copolymerizable with the monomer (a). 2. The fluoropolymer according to claim 1 , wherein the proportion of units based on said monomer (a) to all units constituting said fluoropolymer is 20 to 60 mol %. 3. The fluorine-containing polymer according to claim 1, wherein at least a part of the units based on the monomer (b) is a unit based on the following monomer (b1):
Monomer (b1): A compound represented by CH ₂ ═CH-Q or CH ₂ ═CHCH ₂ -Q.
Here, Q is a halogen atom, or an organic group in which the bonding terminal atom is an oxygen atom, a nitrogen atom, or a sulfur atom. A process for producing a fluorine-containing polymer, comprising polymerizing a monomer component containing the following monomer (a) and monomer (b) in the presence of a polymerization initiator:
Monomer (a): A compound represented by CH ₂ ═CX— ^Rf .
In the formula, X is a chlorine atom, and ^Rf is a perfluoroalkyl group having 4 to 6 carbon atoms.
Monomer (b): A monomer copolymerizable with the monomer (a). The method according to claim 4 , wherein the proportion of the monomer (a) in the entire monomer components is 20 to 60 mol %. The method according to claim 4 or 5 , wherein at least a portion of the units based on the monomer (b) are units based on the following monomer (b1):
Monomer (b1): A compound represented by CH ₂ ═CH-Q or CH ₂ ═CHCH ₂ -Q.
Here, Q is a halogen atom, or an organic group in which the bonding terminal atom is an oxygen atom, a nitrogen atom, or a sulfur atom. The method according to any one of claims 4 to 6 , wherein the monomer components are polymerized in an aqueous medium. The method according to claim 7 , wherein the monomer components are emulsion-polymerized in an aqueous medium containing a surfactant and the polymerization initiator. A fluoropolymer dispersion comprising the fluoropolymer according to any one of claims 1 to 3 and an aqueous medium in which the fluoropolymer is dispersed. The fluoropolymer dispersion according to claim 9 , further comprising a surfactant. A water/oil repellent composition comprising the fluorine-containing polymer according to any one of claims 1 to 3 . The water/oil repellent composition according to claim 11 , comprising an aqueous medium and the fluorine-containing polymer dispersed in the aqueous medium. 13. An article, comprising a substrate, at least a portion of the surface of which is treated with the water/oil repellent composition according to claim 11 or 12 .