block copolymer

Abstract

To provide a block copolymer which can constitute a water-based coating material, and enables formation of a film that has high water-repellent and oil-repellent properties and is comparatively flexible.SOLUTION: There is provided a block copolymer of a resin part (A) composed of a copolymer of three or more kinds of a (meth)acrylate-based monomer, and a functional part (B) composed of a (meth)acrylate-based monomer having a fluoroalkyl group having 6 or less carbon atoms, wherein the (meth)acrylate-based monomer constituting the resin part (A) has a (meth)acrylate-based monomer, a (meth)acrylate-based monomer having a crosslinkable group, and a (meth)acrylate-based monomer having a hydrophilic group, and the content of the (meth)acrylate-based monomer having the hydrophilic group is 7 mol% or more and 20 mol% or less when the total block copolymer is 100 mol%, and the hydrophilic group has a polyoxyalkylene group having the number of repeating units of 9 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a block copolymer, and in particular to a block copolymer suitable for use in a water-based surface treatment agent. [Background technology]

[0002] For example, in office automation equipment using electrophotography, such as copiers, printers, and facsimiles, various rolls, such as a charging roll, a developing roll, a transfer roll, and a toner supply roll, are arranged around a photosensitive drum. These rolls have a shaft and an elastic layer made of conductive rubber or the like arranged around the shaft, and a surface layer is formed on the outer periphery of the elastic layer to impart desired properties such as antifouling properties. Solvent-based paints, in which a composition containing a polymer, a binder, and the like is dissolved in an organic solvent, are used as surface treatment agents for forming the surface layer. However, from the perspective of environmental protection, it is desirable to change the surface treatment agent to a water-based paint that uses water as the solvent.

[0003] For example, Patent Document 1 describes a fluorine-containing block copolymer having a fluorine-containing portion (A) and a non-fluorine-containing portion (B) containing units derived from a non-fluorine-based monomer having a glass transition temperature of 30°C or higher as a material capable of forming a coating having water-repellent, oil-repellent, etc. Patent Document 2 describes a block copolymer having a hydrophilic portion-hydrophobic portion structure containing a fluorine atom as a hydrophilic surface-modifying material. Patent Document 3 describes a hydrophilic and oil-repellent agent containing a copolymer obtained by polymerizing monomers containing a (meth)acrylate compound (a1) having a fluoroalkyl group and a (meth)acrylate compound (a2) having a polyoxyalkylene group. Patent Document 4 describes a water-based paint containing a fluorine-containing non-block copolymer (polymer A) containing units derived from a fluoroolefin and units containing a hydrophilic group, a fluorine-containing block copolymer (polymer B) having a fluorine-containing segment containing units derived from a monomer having a perfluoroalkyl group and a non-fluorine segment containing no fluorine atoms, an anionic surfactant, and water. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 027679 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-75780 [Patent Document 3] International Publication No. 2019 / 198425 [Patent Document 4] International Publication No. 2019 / 069821 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the fluorine-containing block copolymer described in Patent Document 1, the non-fluorine-containing monomer constituting the non-fluorine portion (B) is hydrophobic. Therefore, the fluorine-containing block copolymer is poorly soluble in water, making its use in water-based paints difficult. The block copolymer described in Patent Document 2 is a material for modifying hydrophilic surfaces to hydrophobic surfaces. Although the block copolymer has a hydrophilic portion containing functional groups such as hydroxyl groups and carboxyl groups, the presence of these functional groups alone does not provide sufficient water solubility, making its use in water-based paints difficult. The copolymer constituting the hydrophilic oil repellent described in Patent Document 3 contains a (meth)acrylate compound (a2) having a polyoxyalkylene group as a monomer. While this copolymer may be usable in water-based paints due to its hydrophilic properties, paragraph

[0024] of the same document states that the number of repeating units of the oxyalkylene group should be 8 to 150, with a lower limit of 15 or more, and the polyoxyalkylene group is relatively long. In this case, not only does water repellency decrease, but the glass transition temperature increases, resulting in reduced flexibility. As a result, the formed film does not have the desired water repellency, and problems such as surface cracking are likely to occur. The water-based paint described in Patent Document 4 contains a fluorine-containing non-block copolymer (polymer A) and a fluorine-containing block copolymer (polymer B). This water-based paint is designed to form a film with excellent hydrophilicity, and therefore has low water repellency. Furthermore, since two types of polymers must be mixed, the manufacturing process becomes complicated and expensive. Furthermore, none of the copolymers described in Patent Documents 1 to 4 above contain a crosslinking component. The crosslinking component affects the physical properties of the film and also plays a role in improving adhesion to the treated member. Therefore, in the case of conventional copolymers, a separate binder or the like must be added to obtain the desired properties.

[0006] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a block copolymer that can be used to form a water-based paint and that can form a coating film that is highly water- and oil-repellent and relatively flexible. [Means for solving the problem]

[0007] In order to solve the above problems, the block copolymer of the present disclosure is a block copolymer of a resin part (A) consisting of a copolymer of three or more types of (meth)acrylate monomers, and a functional part (B) consisting of a (meth)acrylate monomer having a fluoroalkyl group having 6 or less carbon atoms, wherein the (meth)acrylate monomers constituting the resin part (A) include a (meth)acrylate monomer, a (meth)acrylate monomer having a crosslinkable group, and a (meth)acrylate monomer having a hydrophilic group, and the content of the (meth)acrylate monomer having the hydrophilic group is 7 mol % or more and 20 mol % or less when the entire block copolymer is taken as 100 mol %, and the hydrophilic group has a polyoxyalkylene group having 9 or less repeating units. [Effects of the Invention]

[0008] In the block copolymer of the present disclosure, the resin portion (A) and the functional portion (B) are arranged separately, so that the monomers are less likely to interfere with each other, and the properties of the monomers constituting each portion are more likely to be exhibited. Therefore, compared to the case of a random copolymer, for example, the water and oil repellency due to the functional portion (B) is more likely to be exhibited.

[0009] The resin portion (A) is composed of a copolymer of at least three types of (meth)acrylate monomers. In this disclosure, "(meth)acrylate" refers to acrylate or methacrylate. The (meth)acrylate monomer, which is the first monomer, improves film-forming properties and adjusts the glass transition temperature. The (meth)acrylate monomer having a crosslinkable group, which is the second monomer, forms a crosslinked structure during film formation, thereby improving physical properties such as the mechanical strength of the film and enhancing adhesion to the substrate. This allows the formation of a film with good adhesion to the substrate when used as a water-based paint without the need for a separate binder. The (meth)acrylate monomer having a hydrophilic group, which is the third monomer, has a polyoxyalkylene group as the hydrophilic group. This makes the block copolymer soluble in water and allows it to be used as a water-based paint.

[0010] Here, the number of repeating units of the polyoxyalkylene group, which is the hydrophilic group, is 9 or less. The larger the number of repeating units of the polyoxyalkylene group, in other words, the longer the polyoxyalkylene group, the higher the solubility in water, but the lower the water and oil repellency. Furthermore, the glass transition temperature of the resin portion (A) increases, and the flexibility of the block copolymer decreases. Therefore, in the block copolymer of the present disclosure, the polyoxyalkylene group is made relatively short and the content of the third monomer is adjusted to achieve both water solubility and the flexibility and water and oil repellency of the film formed. Thus, the block copolymer of the present disclosure, which has as its resin portion (A) a second monomer having a crosslinkable group and a third monomer having a hydrophilic group, can be used as a water-based paint and can form a flexible film that is less prone to surface cracking.

[0011] The functional part (B) is composed of a (meth)acrylate monomer having a fluoroalkyl group with 6 or less carbon atoms. The block copolymer of the present disclosure has the functional part (B), which allows the formation of a coating with excellent water and oil repellency and high stain resistance. It is believed that the greater the carbon number of the fluoroalkyl group, the higher the water repellency. However, fluoroalkyl groups with 7 or more carbon atoms are likely to have adverse effects on the environment and living organisms. Therefore, in the block copolymer of the present disclosure, the number of carbon atoms in the fluoroalkyl group is set to 6 or less. DETAILED DESCRIPTION OF THE INVENTION

[0012] The block copolymer of the present disclosure is described in detail below. The block copolymer of the present disclosure is not limited to the following forms, and can be embodied in various forms including modifications and improvements that can be made by those skilled in the art, without departing from the gist of the present disclosure.

[0013] <Block copolymer> The block copolymer of the present disclosure has two parts, a resin part (A) and a functional part (B), and in each part, the monomers that make up that part are continuously bonded. Because the resin part (A) and the functional part (B) are separated, the monomers are less likely to interfere with each other, and the characteristics of the monomers in each part are more likely to be exhibited. The block copolymer of the present disclosure preferably has an AB type structure (A represents the resin part (A) and B represents the functional part (B)).

[0014] The number-average molecular weight (Mn) of the block copolymer of the present disclosure is not particularly limited, but is preferably 10,000 or more in consideration of film-forming properties and the mechanical strength of the film. On the other hand, as the molecular weight increases, the viscosity of the coating increases. Therefore, in consideration of coatability, it is preferably 100,000 or less. The number-average molecular weight may be measured using a gel permeation chromatography (GPC) device.

[0015] [Resin part (A)] The resin portion (A) is composed of a copolymer of three or more types of (meth)acrylate monomers. "(Meth)acrylate monomer" means a monomer having a (meth)acryloyl group. "(Meth)acryloyl group" means an acryloyl group or a methacryloyl group. The resin portion (A) may be a random copolymer in which different (meth)acrylate monomers are randomly copolymerized. The (meth)acrylate monomer contains at least a (meth)acrylate monomer (hereinafter sometimes referred to as a "first monomer"), a (meth)acrylate monomer having a crosslinkable group (hereinafter sometimes referred to as a "second monomer"), and a (meth)acrylate monomer having a hydrophilic group (hereinafter sometimes referred to as a "third monomer").

[0016] (1) First Monomer Unlike the second and third monomers, the (meth)acrylate monomer is a monomer that does not have a crosslinkable group or a hydrophilic group. The (meth)acrylate monomer mainly contributes to film-forming properties and adjusting the glass transition temperature (Tg). Alkyl (meth)acrylates are suitable as the (meth)acrylate monomer. Examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, dodecyl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, and octadecyl (meth)acrylate.

[0017] When using alkyl (meth)acrylate, the alkyl group desirably has 1 to 8 carbon atoms, and 4 or less is even better. As the number of carbon atoms increases, the alkyl group becomes longer and larger. As a result, steric hindrance can cause deterioration in polymerization, and increased crystallinity can raise the glass transition temperature of the resin, reducing flexibility.

[0018] (2) Second Monomer (Meth)acrylate monomers with crosslinkable groups form crosslinked structures during film formation, primarily contributing to improved mechanical strength of the coating and adhesion to the substrate. Examples of crosslinkable groups include isocyanate groups, carboxy groups, hydroxy groups, amino groups, epoxy groups, and alkoxysilyl groups. Among these, isocyanate groups are preferred because of their high reactivity with rubber or resin substrates. The isocyanate groups are preferably blocked isocyanate groups protected with a blocking agent such as pyrazole or methyl ethyl ketone oxime (MEK oxime) because this makes it easier to control the progress of the reaction.

[0019] (3) the third monomer The (meth)acrylate monomer having a hydrophilic group mainly contributes to adjusting the solubility in water and the glass transition temperature. The hydrophilic group has a polyoxyalkylene group having 9 or less repeating units. The hydrophilic group can be represented by the following general formula (i): -(XO) n -OR (i) In formula (i), R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and X is an alkylene group. n is an integer of 2 to 9. From the viewpoint of achieving both water-solubilization of the block copolymer and water and oil repellency of the coating, the alkylene group is desirably a linear alkylene group having 1 to 3 carbon atoms. For example, a methylene group, an ethylene group, a propylene group, a butylene group, etc. are suitable.

[0020] Suitable examples of (meth)acrylate monomers having a hydrophilic group include methoxypolyethylene glycol acrylate, methoxypolyethylene glycol methacrylate, diethylene glycol monoethyl ether acrylate, 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate, and diethylene glycol monomethyl ether methacrylate. The content of the (meth)acrylate monomer having a hydrophilic group is 7 mol% or more and 20 mol% or less, assuming that the entire block copolymer is 100 mol%. If the content is less than 7 mol%, the solubility in water decreases. In addition, the glass transition temperature of the resin portion (A) increases, reducing the flexibility of the block copolymer. If the content is more than 20 mol%, the film-forming properties and water and oil repellency decrease.

[0021] (4) Other Monomers The (meth)acrylate-based monomer constituting the resin portion (A) may further contain another monomer in addition to the first to third monomers. For example, it is desirable to have an acrylamide-based monomer as a fourth monomer. Since the acrylamide-based monomer has an amino group, it can adjust the electrical resistance value of the block copolymer. Therefore, the incorporation of an acrylamide-based monomer is suitable when the block copolymer is applied to components that require controlled conductivity, such as various rolls used in office automation equipment. In addition, the acrylamide-based monomer is also effective for adjusting the hydrophilicity, molecular weight, etc. of the block copolymer.

[0022] Examples of acrylamide-based monomers include N-(3-dimethylaminopropyl)acrylamide (DMAPAA), acrylamide, and N,N-dimethylacrylamide. The content of the acrylamide-based monomer is preferably 1 mol % or more, where the entire block copolymer is taken as 100 mol %, from the viewpoint of controlling the electrical conductivity. Furthermore, the content is preferably 5 mol % or less, from the viewpoint of adjusting the hydrophilicity and molecular weight of the block copolymer.

[0023] (5) Glass transition temperature From the viewpoint of making the block copolymer flexible and suppressing surface cracking of the formed coating, the glass transition point of the resin part (A) is desirably 40° C. or lower, more desirably 30° C. or lower, and even more desirably 25° C. or lower. The glass transition point may be measured using a differential scanning calorimeter (DSC).

[0024] Functional section (B) The functional part (B) is composed of a (meth)acrylate monomer having a fluoroalkyl group with 6 or less carbon atoms. A fluoroalkyl group is a group in which one or more hydrogen atoms of an alkyl group are substituted with a fluorine atom. The (meth)acrylate monomer having a fluoroalkyl group can be represented by the following general formula (ii): CH2=CH-CO-OY-Rf (ii) In formula (ii), Y is an alkylene group, and Rf is a fluoroalkyl group having 6 or less carbon atoms.

[0025] The alkylene group is preferably a linear alkylene group having 1 to 2 carbon atoms, from the viewpoint of improving the water and oil repellency of the coating. Suitable examples include a methylene group, an ethylene group, a propylene group, and a butylene group. The fluoroalkyl group is preferably a fluoroalkyl group having 4 to 6 carbon atoms, from the viewpoint of improving the water and oil repellency of the coating. Examples include -CF2CF2CF2CF3, -CF2CF(CF3)2, -C(CF3)3, -(CF2)4CF3, -(CF2)2CF(CF3)2, -CF2C(CF3)3, -CF(CF3)CF2CF2CF3, -(CF2)5CF3, and -(CF2)3CF(CF3)2. Specific examples of (meth)acrylate monomers having a fluoroalkyl group having 6 or less carbon atoms include 1H,1H,5H-octafluoropentyl acrylate, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate, 1H,1H,2H,2H-nonafluorohexyl acrylate, 1H,1H,2H,2H-tridecafluorooctyl acrylate, 1H,1H,5H-octafluoropentyl methacrylate, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl methacrylate, 1H,1H,2H,2H-nonafluorohexyl methacrylate, and 1H,1H,2H,2H-tridecafluorooctyl methacrylate.

[0026] <Method of producing block copolymer> The block copolymer of the present disclosure can be produced, for example, by a living radical polymerization method. Among these, it is desirable to employ RAFT (Reversible Addition-Fragmentation Chain Transfer Polymerization) polymerization using a RAFT agent (reversible addition-fragmentation chain transfer agent) from the viewpoint of a simple polymerization process and high productivity. RAFT polymerization, for example, includes the following two steps: (1) A step of polymerizing three or more types of (meth)acrylate monomers in the presence of a RAFT agent to obtain a copolymer corresponding to the resin portion (A). (2) A step of polymerizing the copolymer obtained in the previous step (1) with a (meth)acrylate monomer having a fluoroalkyl group having 6 or less carbon atoms in the presence of a RAFT agent to obtain a block copolymer.

[0027] The RAFT agent may be a trithiocarbonate-type RAFT agent such as 2-cyano-2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propane. The RAFT agent may be used in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the monomer. The radical polymerization initiator may be an azo compound such as 1,1'azobis(methyl cyclohexylcarboxylate) or α,α'-azobisisobutyronitrile (AIBN). The radical polymerization initiator may be used in an amount of 0.01 to 2 parts by mass per 100 parts by mass of the monomer. The polymerization solvent may be toluene, methyl isobutyl ketone (MIBK), or the like. The polymerization temperature is preferably 40 to 100°C.

[0028] <Surface treatment agent> The block copolymer of the present disclosure may be used as a surface treatment agent as is, or may be dissolved in a solvent such as water to form a surface treatment agent. The surface treatment agent may contain, in addition to the block copolymer, a solvent, and, as necessary, various additives such as a surfactant, carbon black, and an ionic conductive agent. One or more types of block copolymers may be used. The content of the block copolymer in the surface treatment agent may be adjusted appropriately depending on the application, but may be, for example, 3 to 100% by mass, where the total mass of the surface treatment agent is 100% by mass. The solvent may be water (including pure water, tap water, etc.) alone, or a mixture of water and an organic solvent. Examples of organic solvents include methanol, ethanol, and isopropyl alcohol. In the case of a mixture, the organic solvent should be 40 parts by mass or less per 100 parts by mass of water from the standpoint of environmental protection. [Example]

[0029] Next, the present disclosure will be described more specifically with reference to examples.

[0030] <Preparation of copolymer samples> (1) Block copolymer samples were produced by the following three steps. The produced block copolymer samples correspond to Copolymers 1 to 5, 7, and 8 in Tables 1 and 2 below.

[0031] [RAFT agent synthesis process] The reaction scheme for this step is shown in formula (1). As shown in formula (1), first, 8.41 g (0.015 mol) of a RAFT agent precursor (bis(dodecylsulfanylthiocarbonyl)disulfide) and 6.59 g (0.015 mol) of an azo initiator (1,1'azobis(methyl cyclohexylcarboxylate), Fujifilm Wako Pure Chemical Industries, Ltd., "VE-073") were placed in a three-neck flask and dissolved in 85 g of toluene. Next, nitrogen bubbling was performed at room temperature for 15 minutes, and then the temperature was raised to 80°C and heated and stirred in a nitrogen atmosphere for 6 hours. After the reaction was completed, the mixture was cooled to obtain a RAFT agent solution. [ka]

[0032] [Resin part synthesis process] The reaction scheme for this step is shown in formula (2). As shown in formula (2), first, methyl methacrylate (MMA), blocked isocyanate monomer (2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate), DMAPAA, methoxypolyethylene glycol acrylate, RAFT agent solution, and azo initiator (same as above) were placed in a three-neck flask and dissolved in 25 g of toluene. Next, nitrogen bubbling was performed at room temperature for 15 minutes, and then the temperature was raised to 80°C and heated and stirred in a nitrogen atmosphere for 6 hours. After the reaction was completed, the reaction solution was reprecipitated in hexane to obtain copolymer a, which corresponds to the resin portion (A). The glass transition temperature (Tg) of copolymer a was measured using DSC. [ka]

[0033] [Copolymer synthesis process] The reaction scheme for this step is shown in formula (3). As shown in formula (3), copolymer a obtained in the previous step, 1H,1H,2H,2H-tridecafluorooctyl acrylate, and the azo initiator (same as above) were placed in a three-neck flask and dissolved in 15 g of MIBK. Next, nitrogen bubbling was performed at room temperature for 15 minutes, and then the temperature was raised to 80°C and heated and stirred in a nitrogen atmosphere for 6 hours. After the reaction was completed, the reaction solution was reprecipitated in hexane to obtain a copolymer having a resin portion (A) and a functional portion (B). The obtained copolymer was analyzed using a nuclear magnetic resonance (NMR) device and confirmed to be an AB-type block copolymer. The number-average molecular weight of the obtained copolymer was measured using a GPC device (the same was true for the random copolymers described below). [ka]

[0034] (2) A random copolymer sample was produced by the following two steps: The produced random copolymer sample corresponds to Copolymer 6 in Tables 1 and 2 below.

[0035] [RAFT agent synthesis process] The RAFT agent solution was prepared similarly to the preparation of the block copolymer samples.

[0036] [Copolymer synthesis process] First, MMA, blocked isocyanate monomer, DMAPAA, methoxypolyethylene glycol acrylate, 1H,1H,2H,2H-tridecafluorooctyl acrylate, RAFT agent solution, and azo initiator (same as above) were placed in a three-neck flask and dissolved in 25 g of MIBK. Next, nitrogen bubbling was performed at room temperature for 15 minutes, followed by heating to 80°C and stirring under a nitrogen atmosphere for 6 hours. After the reaction was completed, the reaction solution was reprecipitated in hexane to obtain a copolymer. The resulting copolymer was analyzed by NMR and confirmed to be a random copolymer.

[0037] <Evaluation of copolymer samples> [Applicability to water-based paints] 1 g of the produced copolymer was dissolved in 10 g of a mixed liquid of water and methanol in a mass ratio of 8:2. If it dissolved, it was evaluated as being applicable to water-based paints (indicated by a circle in Table 2), and if it did not dissolve, it was evaluated as being inapplicable to water-based paints (indicated by an x ​​in the same table).

[0038] [Flexibility] The produced copolymer was added to a mixture of water and methanol in a mass ratio of 8:2 to prepare a paint with a solids concentration of 20% by mass. Copolymers 4 and 5, which were insoluble in the mixture and could not be used as water-based paints, were dissolved in MEK solvent to prepare a paint with a solids concentration of 20% by mass. The prepared paint was applied to a polyethylene terephthalate (PET) film using a bar coating method and dried at 150°C for 30 minutes to form a film. The formed film was visually observed, and if no cracks were observed after one day, it was evaluated as having good flexibility (indicated by a circle in Table 2). If cracks were observed within one day of formation, it was evaluated as having poor flexibility (indicated by an x ​​in the same table).

[0039] [Static water and oil repellency] (1) Water repellency A film was formed in the same manner as in the evaluation of flexibility, and the water contact angle was measured. 2 μL of pure water was dropped onto the surface of the film in an environment of 23°C temperature and 40% humidity, and the contact angle was measured using an automatic contact angle meter (Kyowa Interface Science Co., Ltd., "DM-500"). Measurements were performed five times, and the average value was used as the water contact angle of the copolymer. A water contact angle of 90° or more was evaluated as good static water repellency (indicated by a circle in Table 2), and a water contact angle of less than 90° was evaluated as poor static water repellency (indicated by an x ​​in the same table).

[0040] (2)Oil repellency The contact angle of n-dodecane was measured in the same manner as for water, except that n-dodecane was used instead of pure water. An n-dodecane contact angle of 60° or more was evaluated as having good static oil repellency (indicated by a circle in Table 2), and an n-dodecane contact angle of less than 60° was evaluated as having poor static oil repellency (indicated by an x ​​in Table 2).

[0041] [Dynamic water and oil repellency] (1) Water repellency The water sliding angle of the coatings evaluated for static water repellency was measured. Under conditions of 23°C and 40% humidity, 2 μL of pure water was dropped onto the surface of the coating. Using an automatic contact angle meter (same as above), the coating was tilted from 0 to 90° at a rate of 2° / sec to measure the angle at which the water droplet slid off. Measurements were performed three times, and the average value was used as the water sliding angle of the copolymer. A water sliding angle of 40° or less was evaluated as having good dynamic water repellency (indicated by a circle in Table 2). A water sliding angle of more than 40°, or one in which the water droplet did not slide off even when tilted to 90°, was evaluated as having poor dynamic water repellency (indicated by an x ​​in Table 2).

[0042] (2)Oil repellency The sliding angle of n-dodecane was measured in the same manner as for water, except that n-dodecane was used instead of pure water. An n-dodecane sliding angle of 40° or less was evaluated as having good dynamic oil repellency (indicated by a circle in Table 2), and an n-dodecane sliding angle of more than 40° or one in which the oil droplet did not slide off even when tilted up to 90° was evaluated as having poor dynamic oil repellency (indicated by an x ​​in the same table).

[0043] Table 1 shows the blending amounts of materials used in the synthesis of the copolymers. Table 2 summarizes the compositions and evaluation results of the produced copolymer samples. Copolymers 1 to 3 are included in the concept of block copolymers of the present disclosure. For the third monomer, methoxypolyethylene glycol acrylate, the following three types were used, each differing in the number of repeating units n of the polyoxyethylene group. n=9: "AM-90G" manufactured by Shin-Nakamura Chemical Industry Co., Ltd. n=13: “AM-130G” manufactured by the company. n=23: "AM-230G" manufactured by the company. [Table 1] [Table 2]

[0044] As shown in Table 2, copolymers 1 to 3 are AB-type block copolymers consisting of a resin portion (A) and a functional portion (B). The resin portion (A) is a copolymer of a methacrylate monomer containing a second monomer, which is a crosslinkable component, and a third monomer, which is a hydrophilic component. The third monomer constituting copolymers 1 to 3 has a polyoxyethylene group with nine repeating units, and the content of the third monomer is 7.5 mol or more and 20 mol or less. Therefore, copolymers 1 to 3 can be used as water-based paints, and it has been confirmed that they have excellent film-forming properties, and the formed films have excellent flexibility, static water- and oil-repellency, and dynamic water- and oil-repellency. In contrast, copolymers 4 and 5, which do not contain the third monomer or contain a third monomer content of less than 7 mol, are insoluble in water and have a high Tg of the resin portion (A). In particular, copolymer 4, which does not contain the third monomer, formed a film when dissolved in a paint, but the film cracked. Furthermore, copolymer 6, a random copolymer, contains C6F 13 The water and oil repellency due to the group (fluorine component) was less likely to be expressed, and static oil repellency and dynamic water and oil repellency were reduced. Furthermore, in copolymers 7 and 8, which used a monomer having a polyoxyethylene group with 13 or 23 repeating units as the third monomer, the Tg of the resin portion (A) was higher and static oil repellency and dynamic water and oil repellency were reduced compared to copolymer 3, which had 9 repeating units of the polyoxyethylene group. In copolymer 8, the flexibility of the film was reduced and cracks occurred in the film. [Industrial Applicability]

[0045] The block copolymer of the present disclosure can be used in a liquid surface treatment agent to impart desired properties to the surface of a rubber or resin member, and is particularly suitable for a surface treatment agent that uses water as a solvent.

Claims

1. A block copolymer comprising a resin part (A) made of a copolymer of three or more kinds of (meth)acrylate monomers and a functional part (B) made of a (meth)acrylate monomer having a fluoroalkyl group having 6 or less carbon atoms, The (meth)acrylate-based monomer constituting the resin portion (A) includes a first monomer, a second monomer having a blocked isocyanate group as a crosslinkable group, and a third monomer having a polyoxyalkylene group having 9 or less repeating units as a hydrophilic group, the first monomer is at least one selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, and isooctyl (meth)acrylate; the third monomer is at least one selected from the group consisting of methoxypolyethylene glycol acrylate, methoxypolyethylene glycol methacrylate, diethylene glycol monoethyl ether acrylate, 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate, and diethylene glycol monomethyl ether methacrylate; the content of the third monomer is 7 mol % or more and 20 mol % or less, when the entire block copolymer is taken as 100 mol %, a block copolymer, wherein the (meth)acrylate monomer constituting the functional part (B) is at least one selected from the group consisting of 1H,1H,5H-octafluoropentyl acrylate, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate, 1H,1H,2H,2H-nonafluorohexyl acrylate, 1H,1H,2H,2H-tridecafluorooctyl acrylate, 1H,1H,5H-octafluoropentyl methacrylate, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl methacrylate, 1H,1H,2H,2H-nonafluorohexyl methacrylate, and 1H,1H,2H,2H-tridecafluorooctyl methacrylate.

2. The block copolymer according to claim 1 , wherein the (meth)acrylate-based monomer constituting the resin portion (A) further contains an acrylamide-based monomer.

3. 3. The block copolymer according to claim 2, wherein the content of the acrylamide-based monomer is 1 mol % or more and 5 mol % or less, when the entire block copolymer is taken as 100 mol %.

4. 4. The block copolymer according to claim 1, wherein the resin portion (A) has a glass transition temperature of 40° C. or lower.

5. 5. The block copolymer according to claim 1, wherein the number average molecular weight is 10,000 or more and 100,000 or less.

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