JP7615523B2 - Fluorine-containing copolymer and leather treatment composition - Google Patents

Description

The present invention relates to a fluorocopolymer that can impart water repellency to a treated object.

Fluororesins can impart water repellency to a variety of objects. For example, by using a fluorine-containing copolymer with perfluoroalkyl groups, it is possible to impart water repellency to textiles, leather, paper, etc.

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 its analogous substances and precursors. For this reason, efforts are being made to replace fluorine-containing monomers having a perfluoroalkyl group with 8 carbon atoms with fluorine-containing monomers having a perfluoroalkyl group with 6 or less carbon atoms.

The water repellency of the fluorine-containing copolymer having perfluoroalkyl group is the best when the terminal trifluoromethyl group of perfluoroalkyl group is arranged on the surface.However, when the carbon number of perfluoroalkyl group is 6 or less, compared with the compound having the perfluoroalkyl group having the carbon number of 8, the crystallinity is low and the molecular mobility is high.Therefore, the arrangement of trifluoromethyl group is easily broken, and the 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.

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 dissolves in a hydrocarbon solvent, which is a non-polar solvent, and exhibits high water repellency.

JP 2011-99077 A

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

In view of the above circumstances, the object of the present invention is to provide a fluorine-containing copolymer and a leather treatment composition that are soluble in hydrocarbon solvents, do not contain perfluoroalkyl groups having 8 or more carbon atoms, and can impart high water repellency to treated objects that contain moisture under high humidity conditions.

（式（１）中、
Ｒ^１は水素原子またはメチル基を示し、
ｍは０～４の整数であり、
ｎは０～５の整数である。）

（式（２）中、
Ｒ^２およびＲ^３はそれぞれ独立して水素原子またはメチル基を示し、
ｌは１０～２５の整数である。） 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 monomer, represented by the following formula (1):
(B) the structural unit derived from a non-fluorine-containing 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 derived from the structural unit (B-3) is 1 to 10 parts by mass.

(In formula (1),
^R1 represents a hydrogen atom or a methyl group;
m is an integer from 0 to 4;
n is an integer from 0 to 5.

(In formula (2),
^R2 and ^R3 each independently represent a hydrogen atom or a methyl group;
l is an integer from 10 to 25.

[2] A composition for treating leather, comprising:
A leather treatment composition comprising an aliphatic hydrocarbon solvent and the fluorine-containing copolymer of [1].

The present invention provides a fluorine-containing copolymer and a leather treatment composition that are soluble in hydrocarbon solvents and can impart excellent water repellency to treated objects that contain moisture under high humidity conditions.

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 (B-1) a constituent unit derived from a (meth)acrylate monomer having a cyclic hydrocarbon group having 3 to 20 carbon atoms, (B-2) a constituent unit derived from a (meth)acrylate monomer having a linear hydrocarbon group having 10 or more carbon atoms, and (B-3) a constituent unit derived from a (meth)acrylate monomer having an oxyethylene group represented by formula (2).

<(A) Fluorine-containing monomer>
The fluorine-containing monomer (A) is a fluorine-containing monomer represented by formula (1). In formula (1), ^R1 represents a hydrogen atom or a methyl group, m represents an integer of 0 to 4, and n represents an integer of 0 to 5. Preferably, m is 1 to 2, and n is 3 to 5.

Specific examples of compounds 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 in terms of enhancing the synovial properties of water droplets. The (A) fluorine-containing monomer may be used alone or in combination of two or more kinds.

<(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 cycloalkyl group-containing monomers (B-1) may be used alone or in combination of two or more. When the fluorine-containing copolymer has structural units derived from these monomers, the molecular mobility of the fluorine-containing copolymer is suppressed, and a coating having excellent water sliding properties and waterproofing properties can be formed.

<(B-2) (Meth)acrylate Monomer Having a Linear Hydrocarbon Group>
The linear hydrocarbon group has a carbon number of 10 or more, and more preferably 12 or more. The linear hydrocarbon group has a carbon number of preferably 30 or less, and more preferably 22 or less.

Specific examples of (B-2) (meth)acrylate monomers having a linear hydrocarbon group 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. From the viewpoint of solubility in hydrocarbon solvents, octadecyl (meth)acrylate and docosyl (meth)acrylate are preferred. The (B-2) alkyl group-containing monomers may be used alone or in combination of two or more.

<(B-3) (Meth)acrylate Monomer Having an Oxyethylene Group>
The oxyethylene group-containing monomer (B-3) is a (meth)acrylate monomer having an oxyethylene group represented by formula (2), in which ^R2 and ^R3 each independently represent a hydrogen atom or a methyl group, and l is an integer of 10 to 25.

The structural unit (B-3) derived from the (meth)acrylate monomer having oxyethylene in the fluorine-containing copolymer can form a coating that has excellent water repellency even on wet surfaces. If l is smaller than 10, the water repellency on wet surfaces tends to decrease. On the other hand, if l is larger than 25, the hydrophilicity tends to be too high, which tends to result in a decrease in water repellency and a decrease in solubility in hydrocarbon solvents. 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.

Specific examples of compounds represented by formula (2) include polyethylene glycol mono(meth)acrylate and methoxypolyethylene glycol (meth)acrylate, where l is an integer from 10 to 25. Preferred are polyethylene glycol mono(meth)acrylate and methoxypolyethylene glycol (meth)acrylate, where l is an integer from 12 to 23.

<Composition ratio>
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 in the range of 40/60 to 85/15, preferably 50/50 to 85/15. When the constitutional 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 constitutional 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.

When the total amount of the structural units derived from the non-fluorine monomer (B) is taken as 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 further 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 amount of the constituent units derived from the monomer (B-1) 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 amount of the constituent units derived from the monomer (B-3) is less than 1 part by mass, or when the amount of the constituent units derived from the monomer (B-3) is more than 10 parts by mass, water repellency tends to decrease and solubility in hydrocarbon solvents tends to decrease.

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 (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.

(C) Specific examples of 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, styrene, etc.

<Weight average molecular weight>
The fluorine-containing copolymer of the present invention preferably has a weight average molecular weight in terms of polystyrene in the range of 10,000 to 300,000, but when the fluorine-containing copolymer 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. The range of 10,000 to 100,000 is particularly preferred.

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 from these fibers; glass fibers, glass, paper, wood, leather, fur, bricks, cement, metals, plastics, and the like. Among these, a particularly high effect is observed on leather.

Specific leather materials include cow, pig, horse, sheep, goat, crocodile, snake, etc. Furthermore, leather products made from these leather materials may be given a brushed finish such as suede or nubuck.

<Method for polymerizing fluorocopolymer>
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.

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

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 random, block, graft, or the like.

As the polymerization initiator, organic peroxides, azo compounds, persulfates, etc. can be used. 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.

<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.

Treatment with fluorine-containing copolymers can be carried out by common methods such as spray coating, bar coating, and dip coating.

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.

The polymerization solvent and dilution solvent are not particularly limited as long as they are 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.

In particular, when applying a water-repellent treatment to leather, the solvent for dissolving or dispersing the fluorine-containing copolymer is preferably an aliphatic hydrocarbon solvent, in order to prevent 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.

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.

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.

3 g of 2,2'-azodiisobutyronitrile was added to the flask and the polymerization reaction was carried out for 2 hours. The polymerization reaction was then carried out for an additional 5 hours at 80°C to obtain a fluorine-containing copolymer solution.

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 monomer (B-1), the constituent units derived from monomer (B-2), and the constituent units derived from 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.

(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.

(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.

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
One 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 a 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.

(Preparation of test specimens (dry) and (wet))
A test specimen (dry) and a test specimen (wet) were prepared.
That is, cowhide leather measuring 50 mm x 50 mm x 4 mm in thickness 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).
Also, a test piece (wet) was prepared by storing tanned cowhide leather (moisture absorption: 31 mg/cm ³ ) of 50 mm×50 mm×t4 mm in a thermohygrostat at a temperature of 20° C. and a relative humidity of 79% for 72 hours or more.

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% by mass. Each of the prepared fluorocopolymer solutions was applied by spraying onto the test pieces using a spray gun, and then the test pieces were dried for at least 1 hour at the respective storage temperatures and humidity.

(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

(Measurement of water sliding angle)
For the measurement, 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 started to fall was taken as the sliding angle (unit: °). The target value for the sliding angle (unit: °) was 40° or less.

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

FMAC6: 2-(perfluorohexyl)ethyl methacrylate CHMA: cyclohexyl methacrylate IBOMA: isobornyl methacrylate SMA: stearyl methacrylate LMA: lauryl methacrylate PME550: methoxypolyethylene glycol methacrylate (l=13)
PME1000: Methoxypolyethyleneglycol methacrylate (l=23)

FMAC6: 2-(perfluorohexyl)ethyl methacrylate CHMA: cyclohexyl methacrylate SMA: stearyl methacrylate PME200: methoxypolyethylene glycol methacrylate (l=4)
PME400: Methoxypolyethyleneglycol methacrylate (l=9)
PME550: Methoxypolyethyleneglycol methacrylate (l=13)

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

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

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

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

In Comparative Example 5, the ratio of the structural units derived from monomer (B-1) was too small and the ratio of the structural units derived from monomer (B-2) was too large, resulting in poor water repellency.

In Comparative Example 6, the proportion of structural units derived from monomer (B-3) was too high, and therefore the solubility in n-heptane was poor.

In Comparative Example 7, the proportion of structural units derived from monomer (A) was too small, and therefore the water repellency was poor.

In Comparative Example 8, the proportion of structural units derived from monomer (A) was too high, and therefore the solubility in n-heptane was poor.

Claims (2)

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-containing 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.

(In formula (1),
^R1 represents a hydrogen atom or a methyl group;
m is an integer from 0 to 4;
n is an integer from 0 to 5.

(In formula (2),
^R2 and ^R3 each independently represent a hydrogen atom or a methyl group;
l is an integer from 10 to 25.
A composition for treating leather, comprising:
A leather treatment composition comprising an aliphatic hydrocarbon solvent , and the fluorine-containing copolymer according to claim 1.