Fluorine-containing copolymer and leather treatment composition

Abstract

To provide a fluorine-containing copolymer and a leather treatment composition which contain no perfluoroalkyl group having 8 or more carbon atoms and can impart high water repellency to an object to be treated containing moisture under high humidity conditions.SOLUTION: There is provided a fluorine-containing copolymer containing (A) a structural unit derived from a fluorine-containing monomer represented by a specific general formula and (B) a structural unit derived from a non-fluorine monomer, wherein the mass ratio ((A) / (B)) is 40 / 60 to 85 / 15. Here, (B) the structural unit derived from a non-fluorine monomer has (B-1) a structural unit derived from a (meth)acrylate monomer having a cyclic hydrocarbon group having 3 to 20 carbon atoms, (B-2) a structural unit derived from a (meth)acrylate monomer having a linear hydrocarbon group having 10 or more carbon atoms and (B-3) a structural unit derived from a (meth)acrylate monomer having an oxyethylene group represented by a specific general formula.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a fluorine-containing copolymer capable of imparting water repellency to an object to be treated. [Background technology]

[0002] Fluorine resins can impart water repellency to various objects to be treated. For example, by using a fluorine-containing copolymer having a perfluoroalkyl group, it is possible to impart water repellency to fibers, leather, paper, etc.

[0003] However, in recent years, the United States Environmental Protection Agency (US EPA) has proposed the total abolition of perfluorooctanoic acid (PFOA), which has a similar structure to perfluorooctyl sulfonic acid (PFOS), which has become a regulated substance due to its persistence and high accumulation, as well as similar substances and precursors. For this reason, efforts are being made to replace fluorine-containing monomers with perfluoroalkyl groups having a carbon number of 8 with fluorine-containing monomers with perfluoroalkyl groups having a carbon number of 6 or less.

[0004] The water repellency of the fluorine-containing copolymer having a perfluoroalkyl group is the best when the terminal trifluoromethyl group of the perfluoroalkyl group is arranged on the surface. However, when the carbon number of the perfluoroalkyl group is 6 or less, the crystallinity is low and the molecular mobility is high compared with a compound having a perfluoroalkyl group having a carbon number of 8. Therefore, there is a problem that the arrangement of the trifluoromethyl group is easily broken and water repellency is difficult to be expressed. When the fluorine-containing copolymer is used to impart water repellency, it is usually used as a coating composition dissolved in a solvent. In this case, taking into consideration the effect of the material of the object to be treated, a non-polar solvent may be used rather than a polar solvent.

[0005] In this context, Patent Document 1 discloses that a surface treatment composition containing a copolymer of a fluorine-containing (meth)acrylic acid ester monomer containing a perfluoroalkyl group having 6 or less carbon atoms, a (meth)acrylic acid ester monomer having a cyclic hydrocarbon group, and a (meth)acrylic acid ester monomer having a long-chain alkyl group is soluble in a hydrocarbon solvent, which is a non-polar solvent, and exhibits high water repellency. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-99077 A Summary of the Invention [Problem to be solved by the invention]

[0007] The fluorocopolymer disclosed in the above Patent Document 1 is expected to have high water repellency depending on the conditions of use. However, it has been found that the fluorocopolymer disclosed in Patent Document 1 is difficult to impart water repellency to a material to be treated that contains moisture under high humidity, even if the fluorocopolymer can impart water repellency to a material to be treated that is dried under low humidity.

[0008] In view of the above circumstances, an object of the present invention is to provide a fluorine-containing copolymer and a leather treatment composition which are soluble in hydrocarbon solvents, do not contain a perfluoroalkyl group having 8 or more carbon atoms, and can impart high water repellency to a treated object containing moisture under high humidity conditions. [Means for solving the problem]

[0009] The present invention relates to [1] and [2]. [1] A fluorine-containing copolymer comprising (A) a structural unit derived from a fluorine-containing monomer and (B) a structural unit derived from a non-fluorine-containing monomer, represented by the following formula (1): (B) The structural unit derived from a non-fluorinated monomer is (B-1) a structural unit derived from a (meth)acrylate monomer having a cyclic hydrocarbon group having 3 to 20 carbon atoms, (B-2) a structural unit derived from a (meth)acrylate monomer having a linear hydrocarbon group having 10 or more carbon atoms, and (B-3) A structural unit derived from a (meth)acrylate monomer having an oxyethylene group represented by the following formula (2): In the fluorine-containing copolymer, the mass ratio ((A) / (B)) of the constituent units derived from the fluorine-containing monomer (A) to the constituent units derived from the non-fluorine monomer (B) is 40 / 60 to 85 / 15; (B) When the total amount of structural units derived from non-fluorinated monomers is 100 parts by mass, A fluorine-containing copolymer, characterized in that the mass of the structural unit (B-1) is 30 to 70 parts by mass, the mass of the structural unit (B-2) is 25 to 60 parts by mass, and the mass of the structural unit derived from the structural unit (B-3) is 1 to 10 parts by mass. [ka] (In formula (1), R 1 represents a hydrogen atom or a methyl group, m is an integer from 0 to 4; n is an integer from 0 to 5. [ka] (In formula (2), R 2 and R 3 each independently represents a hydrogen atom or a methyl group, l is an integer between 10 and 25.

[0010] [2] A composition for treating leather, comprising: Aliphatic Hydrocarbons solvent , and A leather treatment composition comprising the fluorine-containing copolymer of [1]. Effect of the Invention

[0011] Effects of the Invention According to the present invention, there can be provided a fluorine-containing copolymer and a leather treatment composition which are soluble in hydrocarbon solvents and can impart excellent water repellency even to a treated object containing moisture under high humidity conditions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will now be described in further detail. [Fluorine-containing copolymer] The fluorine-containing copolymer according to this embodiment is a fluorine-containing copolymer containing a constituent unit derived from a fluorine-containing monomer (A) represented by formula (1) and a constituent unit derived from a non-fluorine monomer (B). The constituent unit derived from the non-fluorine monomer (B) is characterized by containing a constituent unit derived from a (meth)acrylate monomer (B-1) having a cyclic hydrocarbon group having 3 to 20 carbon atoms, a constituent unit derived from a (meth)acrylate monomer (B-2) having a linear hydrocarbon group having 10 or more carbon atoms, and a constituent unit derived from a (meth)acrylate monomer having an oxyethylene group represented by formula (2) (B-3).

[0013] <(A) Fluorine-containing monomer> The fluorine-containing monomer (A) is a fluorine-containing monomer represented by formula (1). In formula (1), R 1 represents a hydrogen atom or a methyl group, m is an integer of 0 to 4, and n is an integer of 0 to 5. Preferably, m is 1 or 2, and n is 3 to 5.

[0014] Specific examples of the compound represented by (A) fluorine-containing monomer include 2-(perfluorohexyl)ethyl (meth)acrylate, 2-(perfluorobutyl)ethyl (meth)acrylate, 3-(perfluorohexyl)propyl (meth)acrylate, 4-(perfluorohexyl)butyl (meth)acrylate, and 2,2,2 trifluoroethyl (meth)acrylate. 2-(perfluorohexyl)ethyl (meth)acrylate and 2-(perfluorobutyl)ethyl (meth)acrylate are preferred, with 2-(perfluorohexyl)ethyl methacrylate being more preferred from the viewpoint of enhancing the synovial properties of water droplets. The (A) fluorine-containing monomer may be used alone or in combination of two or more.

[0015] <(B-1) (Meth)acrylate Monomer Having a Cyclic Hydrocarbon Group> Examples of the cyclic hydrocarbon group include saturated or unsaturated monocyclic groups, polycyclic groups, bridged ring groups, etc. The number of carbon atoms in the cyclic hydrocarbon group is 3 to 20, preferably 6 or more, and more preferably 10 or less. Specific examples of (B-1) (meth)acrylate monomers having a cyclic hydrocarbon group having 3 to 20 carbon atoms include cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, adamantyl (meth)acrylate, and 2-methyl-2-adamantyl (meth)acrylate. Cyclohexyl (meth)acrylate and isobornyl (meth)acrylate are particularly preferred. The (B-1) cycloalkyl group-containing monomers may be used alone or in combination of two or more. When the fluorine-containing copolymer has a structural unit derived from these monomers, the molecular mobility of the fluorine-containing copolymer is suppressed, and a coating film having excellent water sliding properties and waterproofing properties can be formed.

[0016] <(B-2) (Meth)acrylate Monomer Having a Linear Hydrocarbon Group> The straight-chain hydrocarbon group has 10 or more carbon atoms, and preferably 12 or more carbon atoms. The straight-chain hydrocarbon group has 30 or less carbon atoms, and preferably 22 or less carbon atoms.

[0017] Specific examples of (B-2) (meth)acrylate monomers having linear hydrocarbon groups include decyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, and docosyl (meth)acrylate, among which octadecyl (meth)acrylate and docosyl (meth)acrylate are preferred from the viewpoint of solubility in hydrocarbon solvents. The (B-2) alkyl group-containing monomers may be used alone or in combination of two or more.

[0018] <(B-3) (Meth)acrylate Monomer Having an Oxyethylene Group> The (B-3) oxyethylene group-containing monomer is a (meth)acrylate monomer having an oxyethylene group represented by formula (2). In formula (2), R 2 and R 3 each independently represents a hydrogen atom or a methyl group, and 1 is an integer of 10 to 25.

[0019] The structural unit derived from the (meth)acrylate monomer having oxyethylene (B-3) in the fluorine-containing copolymer can form a coating having excellent water repellency even on wet surfaces. When l is smaller than 10, the water repellency on wet surfaces tends to decrease. On the other hand, when l is larger than 25, the hydrophilicity becomes too high, so that the water repellency and the solubility in hydrocarbon solvents tend to decrease. It is more preferable that l is 12 or more. It is also preferable that l is 23 or less, and more preferably 18 or less.

[0020] Specific examples of the compound represented by formula (2) include polyethylene glycol mono(meth)acrylate and methoxypolyethylene glycol (meth)acrylate, in which l is an integer of 10 to 25. Preferred are polyethylene glycol mono(meth)acrylate and methoxypolyethylene glycol (meth)acrylate, in which l is an integer of 12 to 23.

[0021] <Composition ratio> In the fluorine-containing copolymer, the mass ratio (A) / (B) of the constituent units derived from the fluorine-containing monomer (A) to the constituent units derived from the non-fluorine monomer (B) is in the range of 40 / 60 to 85 / 15, preferably 50 / 50 to 85 / 15. When the constituent units derived from the fluorine-containing monomer (A) are smaller than the range of 40 / 60, the water repellency decreases. On the other hand, when the constituent units derived from the fluorine-containing monomer (A) are larger than 85 / 15, the solubility of the fluorine-containing copolymer in hydrocarbon solvents tends to decrease significantly.

[0022] When the total amount of the structural units derived from the non-fluorine monomer (B) is 100 parts by mass, the structural units derived from the monomer (B-1) are 30 to 70 parts by mass, the structural units derived from the monomer (B-2) are 25 to 60 parts by mass, and the structural units derived from the monomer (B-3) are 1 to 10 parts by mass. However, from the viewpoint of enhancing the synovial properties of the water droplets, it is preferable that the structural units derived from the monomer (B-1) are 50 to 70 parts by mass, the structural units derived from the monomer (B-2) are 25 to 48 parts by mass, and the structural units derived from the monomer (B-3) are 2 to 7 parts by mass. It is more preferable that the structural units derived from the monomer (B-1) are 60 to 70 parts by mass, the structural units derived from the monomer (B-2) are 25 to 38 parts by mass, and the structural units derived from the monomer (B-3) are 2 to 7 parts by mass. When the content of the monomer (B-1)-derived structural unit is less than 30 parts by mass, the orientation of the perfluoroalkyl groups in the fluorocopolymer is difficult to maintain, and water repellency tends to decrease. When the content of the monomer (B-3)-derived structural unit is less than 1 part by mass, or when the content of the monomer (B-3)-derived structural unit is more than 10 parts by mass, water repellency tends to decrease and solubility in hydrocarbon solvents tends to decrease.

[0023] The fluorine-containing copolymer may contain (A) a structural unit derived from a fluorine-containing monomer, (B-1) a structural unit derived from a (meth)acrylate monomer having a cyclic hydrocarbon group having 3 to 20 carbon atoms, (B-2) a structural unit derived from a (meth)acrylate monomer having a linear hydrocarbon group having 10 or more carbon atoms, and (B-3) a structural unit derived from a (meth)acrylate monomer having an oxyethylene group represented by formula (2), and may also contain (C) a structural unit derived from other monomers, as long as the effect of the present invention is not impaired. The content of (C) other monomers in the fluorine-containing copolymer is 10 parts by mass or less, preferably 5 parts by mass or less, when the total amount of the monomers to be polymerized in the fluorine-containing copolymer is 100 parts by mass. (C) Other monomers may not be contained.

[0024] Specific examples of (C) other monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, (meth)acrylamide, N,N-dimethyl (meth)acrylamide, (meth)acrylic acid, (meth)acrylonitrile, vinyl acetate, and styrene.

[0025] <Weight average molecular weight> The fluorocopolymer of the present invention preferably has a weight average molecular weight in terms of polystyrene in the range of 10,000 to 300,000, and when the fluorocopolymer is dissolved in a solvent, taking into consideration the balance between solubility and water repellency, it is more preferably in the range of 10,000 to 200,000, and particularly preferably in the range of 10,000 to 100,000.

[0026] The fluorine-containing copolymer of the present invention can be used to impart water repellency to a treated object. Examples of treated objects to which the fluorine-containing copolymer can be applied include natural fibers such as cotton, hemp, wool, and silk, regenerated fibers such as rayon and cupra, semi-synthetic fibers such as acetate and triacetate, synthetic fibers such as polyamide, polyester, polyacrylonitrile, polypropylene, polyvinyl chloride, and polyvinyl alcohol, mixed fibers thereof, and fabrics, clothing, shoes, and other materials made of these fibers, glass fibers, glass, paper, wood, leather, fur, bricks, cement, metals, and plastics. Among these, the fluorine-containing copolymer is particularly effective on leather.

[0027] Specific examples of leather materials include cow, pig, horse, sheep, goat, crocodile, snake, etc. Furthermore, leather products made from these leather materials may be subjected to a nap-brushing process such as suede or nubuck.

[0028] <Polymerization method for fluorine-containing copolymer> The polymerization method for the above-mentioned fluorine-containing copolymer is not particularly limited, and known polymerization methods such as solution polymerization, suspension polymerization and emulsion polymerization can be used, but solution polymerization is preferably carried out.

[0029] In the polymerization method by solution polymerization, various monomers are dissolved in any solvent in the presence of a polymerization initiator, and after nitrogen substitution, the mixture is heated and stirred to polymerize the fluorine-containing copolymer.

[0030] In the fluorine-containing copolymer of the present invention, the arrangement of the above-mentioned (A) constituent units derived from a fluorine-containing monomer, (B) constituent units derived from a non-fluorine monomer, and (C) constituent units derived from other monomers is not particularly limited, and may be any of random, block, graft, etc.

[0031] The polymerization initiator may be an organic peroxide, an azo compound, a persulfate, etc. Specific examples of the polymerization initiator include tert-butyl peroxypivalate, tert-hexyl peroxyneodecanate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di-3,5,5-trimethylhexanoyl peroxide, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), ammonium persulfate, etc.

[0032] <Leather treatment composition> The obtained fluorine-containing copolymer can be used as a solution or dispersion in the solvent shown below, or as an emulsion dispersed in water with the addition of a surfactant, etc. It can also be used in the form of a fine powder.

[0033] The treatment with the fluorine-containing copolymer can be carried out by a general method such as spray coating, bar coating or dip coating.

[0034] When the fluorocopolymer is dissolved or dispersed in the solvent shown below, the content of the fluorocopolymer is preferably 0.1 to 10 parts by mass, and more preferably 1 to 10 parts by mass, based on 100 parts by mass of the fluorocopolymer solution. If the content of the fluorocopolymer is more than 10 parts by mass, the texture of the treated object tends to deteriorate and the appearance of the treated object tends to be poor.

[0035] The polymerization solvent and dilution solvent are not particularly limited as long as they are solvents capable of dissolving or dispersing the fluorine-containing copolymer, and examples thereof include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, butyl acetate, tetrahydrofuran, dimethylformaldehyde, toluene, xylene, n-hexane, isohexane, n-heptane, cyclopentane, cyclohexane, methylcyclohexane, isoparaffin solvents, etc. These solvents may be used alone or in combination of two or more.

[0036] In particular, when leather is subjected to a water-repellent treatment, the solvent for dissolving or dispersing the fluorine-containing copolymer is preferably an aliphatic hydrocarbon solvent, from the viewpoint of preventing deterioration of the texture of the leather product. Preferred examples include n-hexane, isohexane, n-heptane, cyclopentane, cyclohexane, and methylcyclohexane, with n-hexane, n-heptane, and cyclohexane being particularly preferred. EXAMPLES

[0037] Specific examples of the present invention will now be described. First, the production examples of the fluorine-containing copolymers according to Examples 1 to 8 will be described.

[0038] Example 1 First, 697 g of n-heptane, 120 g of 2-(perfluorohexyl)ethyl methacrylate (FMAC6), 117 g of cyclohexyl methacrylate (CHMA), 54 g of stearyl methacrylate (SMA), and 9 g of methoxypolyethylene glycol methacrylate (l=13) (PME550) were charged into a 2-L four-neck flask equipped with a thermometer, a stirrer, and a reflux condenser, and the mixture was heated to 70°C while blowing in nitrogen gas.

[0039] 3 g of 2,2'-azodiisobutyronitrile was added to the flask, and a polymerization reaction was carried out for 2 hours, followed by a further polymerization reaction for 5 hours at 80°C to obtain a fluorine-containing copolymer solution.

[0040] As shown in Table 1, the mass ratio ((A) / (B)) of the constituent units derived from the fluorine-containing monomer (A) to the constituent units derived from the non-fluorine monomer (B) in the fluorine-containing copolymer obtained in Example 1 was 40 / 60, and the mass ratio ((B-1) / (B-2) / (B-3)) of the constituent units derived from the monomer (B-1), the constituent units derived from the monomer (B-2), and the constituent units derived from the monomer (B-3) in a total of 100 parts by mass of the constituent units derived from the non-fluorine monomer (B) was 65 / 30 / 5.

[0041] (Examples 2 to 8) In Examples 2 to 8, fluorine-containing copolymers were produced in the same manner as in Example 1, except that the types or amounts of the monomers were changed to those shown in Table 1.

[0042] (Comparative Examples 1 to 8) In Comparative Examples 1 to 8, fluorine-containing copolymers were produced in the same manner as in Example 1, except that the types or amounts of the monomers were changed to those shown in Table 2.

[0043] The weight average molecular weights of the fluorocopolymers obtained in Examples 1 to 8 and Comparative Examples 1 to 8 were measured. Specifically, a TOSOH HLC-8320GPC was used as the GPC system, and two TOSOH TSKgel Super Multipore HZ-M columns and one TOSOH A single TSKgel Super H-RC was installed in series, the column temperature was set to 40°C, the standard substance was polystyrene, the developing solvent was tetrahydrofuran, the developing solvent was flowed at a flow rate of 1 ml / min, 0.1 ml of sample solution with a sample concentration of 0.1% by mass was injected, and the measurement was performed using the EcoSEC-Work Station GPC calculation program.

[0044] (Preparation of test specimens (dry) and (wet)) A test specimen (dry) and a test specimen (wet) were prepared. Specifically, cowhide leather measuring 50 mm x 50 mm x t4 mm that had been stored for 72 hours or more in a thermohygrostat at a temperature of 20°C and a relative humidity of 50% was used as a test piece (dry). In addition, a 50 mm x 50 mm x t4 mm piece of cowhide leather (moisture absorption 31 mg / cm) stored for 72 hours or more in a thermo-hygrostat at a temperature of 20°C and a relative humidity of 79% 3 ) was used as a test specimen (wet).

[0045] In addition, the solutions of the fluorocopolymers according to the above-mentioned respective Examples and Comparative Examples were diluted with n-heptane to prepare solutions (leather treatment compositions) with a concentration of 2.0 mass %. Each of the prepared fluorocopolymer solutions was applied to a test piece by spraying using a spray gun, and then the test piece was dried for 1 hour or more at the respective storage temperatures and humidity.

[0046] (Solubility of Fluorine-Containing Copolymer) The appearance of the solution adjusted to a concentration of 2.0% by mass was evaluated according to the following criteria. ○: No insoluble matter ×: Insoluble matter is present

[0047] (Measurement of water sliding angle) For the measurements, DMo-501 (manufactured by Kyowa Interface Science Co., Ltd.) was used. 40 μL of water was dropped onto the surface of the test piece, and the stage angle was changed at a tilt speed of 2° / sec. The angle at which the droplet began to slide down was taken as the sliding angle (unit: °). The target value for the sliding angle (unit: °) was set to 40° or less.

[0048] [Evaluation Results] Table 1 shows the evaluation results of Examples 1-8, and Table 2 shows the evaluation results of Comparative Examples 1-8.

[0049] [Table 1]

[0050] FMAC6: 2-(perfluorohexyl)ethyl methacrylate CHMA: Cyclohexyl methacrylate IBOMA: Isobornyl methacrylate SMA: Stearyl methacrylate LMA: Lauryl methacrylate PME550: Methoxypolyethyleneglycol methacrylate (l=13) PME1000: Methoxypolyethyleneglycol methacrylate (l=23)

[0051] [Table 2]

[0052] FMAC6: 2-(perfluorohexyl)ethyl methacrylate CHMA: Cyclohexyl methacrylate SMA: Stearyl methacrylate PME200: Methoxypolyethyleneglycol methacrylate (l=4) PME400: Methoxypolyethyleneglycol methacrylate (l=9) PME550: Methoxypolyethyleneglycol methacrylate (l=13)

[0053] As is clear from the results in Table 1, all of Examples 1 to 8 were excellent in solubility in hydrocarbon solvents and water repellency.

[0054] On the other hand, as is clear from Table 2, in Comparative Examples 1 to 8, the balance of these performances was insufficient.

[0055] Specifically, in Comparative Example 1, the number of moles of oxyethylene groups added to the monomer (B'-3) was too small, so that the test piece was inferior in water repellency when dry and in water repellency when wet.

[0056] In Comparative Examples 2 to 4, since the number of moles of oxyethylene groups added to the monomer (B'-3) was too small, the test pieces had excellent water repellency in the dry state but had poor water repellency in the wet state.

[0057] In Comparative Example 5, the ratio of the constituent units derived from the monomer (B-1) was too small and the ratio of the constituent units derived from the monomer (B-2) was too large, and therefore the water repellency was poor.

[0058] In Comparative Example 6, the ratio of the structural units derived from the monomer (B-3) was excessively large, and therefore the solubility in n-heptane was poor.

[0059] In Comparative Example 7, the ratio of the constitutional units derived from the monomer (A) was too small, and therefore the water repellency was poor.

[0060] In Comparative Example 8, the ratio of the constituent units derived from the monomer (A) was excessively large, and therefore the solubility in n-heptane was poor.

Claims

1. A fluorine-containing copolymer comprising (A) a structural unit derived from a fluorine-containing monomer and (B) a structural unit derived from a non-fluorine monomer, represented by the following formula (1): (B) the structural unit derived from a non-fluorine monomer is (B-1) a structural unit derived from a (meth)acrylate monomer having a cyclic hydrocarbon group having 3 to 20 carbon atoms, (B-2) a structural unit derived from a (meth)acrylate monomer having a linear hydrocarbon group having 10 or more carbon atoms, and (B-3) A structural unit derived from a (meth)acrylate monomer having an oxyethylene group represented by the following formula (2): In the fluorine-containing copolymer, the mass ratio ((A) / (B)) of the constitutional units derived from the fluorine-containing monomer (A) to the constitutional units derived from the non-fluorine monomer (B) is 40 / 60 to 85 / 15; (B) When the total amount of the structural units derived from the non-fluorinated monomer is 100 parts by mass, A fluorine-containing copolymer, characterized in that the mass of the structural unit (B-1) is 30 to 70 parts by mass, the mass of the structural unit (B-2) is 25 to 60 parts by mass, and the mass of the structural unit (B-3) is 1 to 10 parts by mass. 【Chemistry 1】 (In formula (1), R １ represents a hydrogen atom or a methyl group, m is an integer from 0 to 4; n is an integer from 0 to 5. 【Chemistry 2】 (In formula (2), R ２ and R ３ each independently represents a hydrogen atom or a methyl group, l is an integer from 10 to 25.

2. A composition for treating leather, comprising: Aliphatic hydrocarbon solvents, and A leather treatment composition comprising the fluorine-containing copolymer according to claim 1.

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