Liquid-repellent structure, method for manufacturing liquid-repellent structure, and packaging material

Abstract

This liquid-repellant structure is provided with a surface for imparting liquid repellency, and a liquid-repellant layer that is formed on the surface, wherein: the liquid-repellant layer contains a binder resin that includes a fluorine-containing resin, and a filler that is dispersed in the binder resin; the filler contains a first filler that has a BET specific surface area M of 100–400 m2 / g; and the ratio M / F of the BET specific surface area M of the first filler to the amount F (mass%) of the fluorine-containing resin, based on the entire amount of the liquid-repellant layer, is 1.5–4.0.

Description

[Technical Field]

[0001] The present disclosure relates to a liquid-repellent structure, a method for producing a liquid-repellent structure, a coating liquid for forming a liquid-repellent layer, and a packaging material. [Background technology]

[0002] Various embodiments of water-repellent structures are known. For example, Patent Document 1 discloses a single-layer water-repellent heat-sealable film containing a thermoplastic resin and hydrophobic particles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-155183 Summary of the Invention [Problem to be solved by the invention]

[0004] In the invention described in Patent Document 1, water repellency is evaluated based on the contact angle with a water droplet, etc. However, in the invention described in this document, it is unclear whether water repellency is maintained over a long period of time.

[0005] The present disclosure aims to provide a liquid-repellent structure that has excellent water repellency for a long period of time, a method for producing the liquid-repellent structure, a coating liquid for forming a liquid-repellent layer, and a packaging material having the liquid-repellent structure on the side that comes into contact with an article. [Means for solving the problem]

[0006] The liquid-repellent structure according to the present disclosure comprises a surface to be imparted with liquid repellency (hereinafter sometimes referred to as a "treated surface") and a liquid-repellent layer formed on the surface, the liquid-repellent layer containing a binder resin including a fluorine-containing resin and a filler dispersed in the binder resin. In the liquid-repellent layer, the filler has a BET specific surface area M of 100 to 400 m 2 / g of a first filler, and the ratio M / F of the BET specific surface area M of the first filler to the amount F (mass %) of the fluorine-containing resin based on the total amount of the liquid-repellent layer is 1.5 to 4.0.

[0007] The liquid-repellent layer provided in the liquid-repellent structure has excellent liquid-repellency against water and oil, and can maintain liquid-repellency, particularly against water, for a long period of time. The inventors believe that the reason for this effect is as follows: In other words, in order to achieve liquid-repellency against liquids with high surface tension such as water, it is necessary to form strong fine irregularities by the first filler. The shape and strength of the fine irregularities are determined by the ratio (M / F) of the BET specific surface area of ​​the first filler to the amount of the fluorine-containing resin. When M / F is within the above range, strong fine irregularities can be efficiently formed, and not only excellent liquid-repellency but also liquid-repellency can be maintained for a long period of time.

[0008] In the liquid-repellent structure, the first filler may have a structure in which a plurality of primary particles are linked together in a beaded shape. The beaded structure of the beaded filler is easy to impart flexibility to the liquid-repellent layer due to its three-dimensional structure, and the liquid-repellent property can be maintained for a longer period of time.

[0009] In the liquid-repellent structure, the fluorine-containing resin may contain a fluorine-acrylic copolymer, which allows the liquid repellency to be maintained for a longer period of time.

[0010] In the liquid-repellent structure, the filler may include a scaly filler. By including the scaly filler in the liquid-repellent layer, unevenness is more efficiently formed on the surface, making it easier to maintain liquid repellency against water for a longer period of time.

[0011] The liquid-repellent structure may further include a base layer between the surface and the liquid-repellent layer, and the base layer may contain a binder resin and a third filler having an average primary particle diameter of 5 to 60 μm. This allows for the formation of large irregularities in the liquid-repellent structure. The large irregularities facilitate point contact between the liquid-repellent layer and the contents, thereby further suppressing a decrease in liquid repellency.

[0012] The liquid-repellent structure may have a surface roughness Sa of 1.5 to 15.0 μm so that the effect of holding the contents in point contact can be easily obtained.

[0013] The present disclosure provides a packaging material having the above-described liquid-repellent structure on the side that comes into contact with an article. As described above, the liquid-repellent layer provided in the liquid-repellent structure has excellent water repellency for a long period of time. Therefore, this packaging material can be used for articles that contain moisture.

[0014] The present disclosure provides a method for producing a liquid-repellent structure. The liquid-repellent structure is produced through a step of forming a liquid-repellent layer as follows. That is, the method for producing the liquid-repellent structure includes the steps of preparing a coating liquid containing a binder resin including a fluorine-containing resin and a filler, forming a coating film of the coating liquid on a surface to be imparted with liquid repellency, and drying and curing the coating film to form a liquid-repellent layer. In the coating liquid used in the production method, the filler has a BET specific surface area M of 100 to 400 m 2 / g of a first filler, and the ratio M / F of the BET specific surface area M of the first filler to the amount F (mass %) of the fluorine-containing resin based on the total amount of solids contained in the coating liquid is 1.5 to 4.0. By the above method, it is possible to produce a liquid-repellent structure of the present disclosure that exhibits the above-mentioned effects.

[0015] The present disclosure provides a coating liquid for forming a liquid-repellent layer, which is used in the method for producing the liquid-repellent structure. That is, the coating liquid for forming a liquid-repellent layer contains a binder resin containing a fluorine-containing resin and a filler, and the filler has a BET specific surface area M of 100 to 400 m 2 / g of a first filler, and the ratio M / F of the BET specific surface area M of the first filler to the amount F (mass %) of the fluorine-containing resin based on the total amount of solids contained in the coating liquid is 1.5 to 4.0. By using the coating liquid, it is possible to produce a liquid repellent structure of the present disclosure that exhibits the above-mentioned effects. [Effects of the Invention]

[0016] The present disclosure provides a liquid-repellent structure that has excellent water repellency for a long period of time. The present disclosure also provides a method for producing the liquid-repellent structure, a coating liquid for forming a liquid-repellent layer, and a packaging material having the liquid-repellent structure on the side that comes into contact with an article. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating one embodiment of a liquid-repellent structure according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view schematically showing another embodiment of the liquid-repellent structure according to the present disclosure. [Figure 3] FIG. 3 is a cross-sectional view schematically showing another embodiment of the liquid repellent structure according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same elements or elements having the same functions will be denoted by the same reference numerals, and redundant description will be omitted.

[0019] <Liquid repellent structure> Fig. 1 is a cross-sectional view schematically illustrating one embodiment of a liquid-repellent structure according to the present disclosure. As shown in Fig. 1, the liquid-repellent structure 10A includes a substrate 1 having a treatment surface 1a (a surface to be imparted with liquid repellency) and a liquid-repellent layer 3A formed on the treatment surface 1a.

[0020] (base material) The substrate 1 is not particularly limited as long as it has a surface to be imparted with liquid repellency and can serve as a support, and may be, for example, a film (thickness: about 10 to 200 μm) or a plate (thickness: about 1 to 10 mm). Examples of film-shaped substrates include paper, resin film, and metal foil. By using the inner surface of a film packaging material made of these materials as the treated surface 1a and forming a liquid-repellent layer 3 on this, a packaging bag to which the contents do not easily adhere can be obtained. Examples of plate-shaped substrates include paper, resin, metal, and glass. By using the inner surface of a container molded from these materials as the treated surface 1a and forming a liquid-repellent layer 3 on this, a container to which the contents do not easily adhere can be obtained.

[0021] Examples of paper include fine paper, special fine paper, coated paper, art paper, cast-coated paper, construction paper, and kraft paper. Examples of resin include polyolefin, acid-modified polyolefin, polyester (e.g., polyethylene terephthalate (PET)), polyethylene (PE), polypropylene (PP), polyamide (PA), polyvinyl chloride (PVC), cellulose acetate, and cellophane resin. Examples of metal include aluminum and nickel.

[0022] When the substrate 1 is in the form of a film, it is preferable that the substrate 1 has heat-sealing properties with the liquid-repellent layer 3. Furthermore, when an underlayer is interposed between the substrate 1 and the liquid-repellent layer 3 as described below, it is preferable that the substrate 1 has heat-sealing properties with the underlayer. The melting point of the substrate 1 is preferably 170°C or lower. This strengthens the adhesion between the substrate 1 and the liquid-repellent layer 3 when forming a packaging bag by heat sealing, thereby further improving the heat-sealing properties. From this perspective, it is more preferable that the melting point of the substrate 1 is 150°C or lower. The melting point of the substrate 1 can be measured by differential scanning calorimetry.

[0023] (liquid repellent layer) The liquid-repellent layer 3A is a liquid-repellent layer and contains a first filler 5f and a binder resin 5b. The liquid-repellent layer 3A is formed to cover part or all of the surface of the substrate 1. Liquid repellency encompasses both water repellency and oil repellency, specifically, the property of repelling water-based or oil-based materials in liquid, semi-solid, or gel form. Examples of water-based or oil-based materials include water, oil (salad oil, etc.), yogurt, curry, fresh cream, jelly, pudding, syrup, porridge, soup, and other foods; detergents (hand soap, body soap, shampoo, conditioner, etc.); cosmetics (hand cream, lotion, etc.); pharmaceuticals; and chemicals. The liquid-repellent layer 3A forms the innermost or outermost layer of the liquid-repellent structure 10 so as to be in direct contact with these materials. The liquid-repellent layer according to this embodiment can maintain its liquid-repellent properties (liquid-repellent durability), particularly against water, for a long period of time.

[0024] As shown in FIG. 1, the liquid-repellent layer 3A contains first fillers 5f. The first fillers 5f are, for example, spherical, and their average primary particle diameter is preferably 3 to 1,000 nm, and may be 5 to 100 nm or 5 to 20 nm. When the average primary particle diameter of the first fillers 5f is 3 nm or more, the first fillers tend to be less embedded in the fluorine-containing resin and more likely to form fine irregularities. When the average primary particle diameter is 1,000 nm or less, the fluorine-containing resin and the first fillers tend to more likely to form dense irregularities. The average primary particle diameter of the first filler refers to the average value obtained by measuring the major axis and minor axis of any 10 first fillers in the field of view of the SEM or TEM and dividing the sum by 2.

[0025] Examples of materials that can form the first filler 5f include silica, titanium oxide, aluminum oxide, mica, talc, calcium carbonate, barium sulfate, zinc oxide, smectite, zeolite, and acrylic resin.

[0026] The first filler 5f may be a beaded filler having a structure in which a plurality of primary particles are linked in a beaded shape. The beaded structure of the beaded filler may have a branched structure in which spherical particles are linked in a chain shape in addition to a structure in which spherical particles are linked in a beaded shape. The beaded structure is easy to impart flexibility to the liquid-repellent layer due to its three-dimensional structure. By using a beaded filler, the liquid-repellent layer can easily maintain its liquid-repellent properties not only against water but also against liquids containing water for a long period of time. The beaded filler can also be called a pearl necklace-type filler.

[0027] The average particle diameter (average secondary particle diameter) of the beaded filler is preferably 50 to 1,000 nm, and may be 100 to 400 nm or 100 to 200 nm. When the average particle diameter of the beaded filler is 50 nm or more, the flexibility of the beaded filler tends to be easily imparted to the liquid-repellent layer, and when it is 1,000 nm or less, the beaded filler tends to easily form fine irregularities. The average particle diameter of the beaded filler means the average value obtained by measuring the major axis and minor axis lengths of a total of 10 arbitrary beaded fillers within the field of view of the TEM and dividing the sum by 2.

[0028] The BET specific surface area M of the first filler 5f is 100 to 400 m 2 / g. The BET specific surface area M is 100m 2 / g or more, it is possible to form fine irregularities sufficient to obtain liquid repellency, and 2 / g or less, the first filler is not buried in the fluorine-containing resin, and fine irregularities can be formed. From this viewpoint, the BET specific surface area M of the first filler 5f is 130 to 300 m 2 / g, and 200 to 300m 2 / g The BET specific surface area of ​​the filler is measured by the BET method.

[0029] The content of the first filler 5f in the liquid-repellent layer 3A may be, for example, 20 to 80 mass %, 30 to 75 mass %, or 30 to 50 mass % based on the total mass of the liquid-repellent layer. When the content of the first filler 5f is within the above range, it is easy to prevent the first filler 5f from falling off and it is possible to impart sufficient unevenness to the liquid-repellent layer 3A, so that excellent liquid repellency attributable to the first filler 5f is easily obtained.

[0030] Commercially available products can be used as the first filler 5f. Commercially available silica fillers include, for example, Aerosil (AEROSIL 130, 200, 300, 380, etc.) manufactured by Nippon Aerosil, Reolosil (QS-10, 20, 40) manufactured by Tokuyama Corporation, spherical silica microparticles QSG manufactured by Shin-Etsu Silicone, and the Snowtex series (Snowtex ST-30, etc.) manufactured by Nissan Chemical Industries, Ltd. Commercially available aluminum oxide fillers include, for example, AEROXIDE Alu manufactured by Evonik Degussa. Commercially available beaded fillers include, for example, the HDK series (HDK V15, N20, T30, T40, etc.) manufactured by Asahi Kasei Wacker Silicone Co., Ltd. and the Snowtex series (Snowtex PS-S-PO, etc.) manufactured by Nissan Chemical Industries, Ltd.

[0031] FIG. 2 is a cross-sectional view schematically illustrating another embodiment of a liquid-repellent structure according to the present disclosure. As shown in FIG. 2, the liquid-repellent structure 10B includes a substrate 1 having a surface to be treated 1a and a liquid-repellent layer 3B formed on the surface to be treated 1a. As shown in FIG. 2, the liquid-repellent layer 3B may further include a second filler 6f in addition to a first filler 5f and a binder resin 5b. The second filler 6f is flaky (plate-like) and can be referred to as a flaky (plate-like) filler. When the filler includes the second filler 6f, the liquid-repellent layer 3B may include an aggregate F of the first filler 5f and the second filler 6f. The first filler 5f, the second filler 6f, and the aggregate F form unevenness on the surface of the liquid-repellent layer 3B. The aggregate F is composed of the first filler 5f, the second filler 6f, and the binder resin 5b covering them. The liquid-repellent layer 3B having such a configuration has more efficiently formed irregularities on its surface, which makes it easier to maintain its liquid-repellent (water-repellent) properties against water for a long period of time. Furthermore, the liquid-repellent layer 3B also makes it easier to maintain its liquid-repellent properties against not only water but also liquids containing water for a long period of time. The liquid-repellent layer 3B also makes it easier to maintain its liquid-repellent properties against products containing alcohol in addition to water, such as lotions, for a long period of time.

[0032] The second filler 6f can exist in the form of primary particles, secondary aggregates, or tertiary aggregates. Secondary aggregates are formed by multiple overlapping layers of parallel-oriented primary particles of the second filler 6f. Tertiary aggregates of the second filler 6f are formed by crystal growth in various directions due to the irregular overlapping of primary particles or secondary aggregates.

[0033] The average particle size of the second filler 6f is preferably 0.1 to 6 μm, and may be 0.1 to 4 μm or 4 to 6 μm. When the average particle size of the second filler 6f is 0.1 μm or more, aggregates F are easily formed, while when it is 6 μm or less, the liquid repellency resulting from the complex and fine shape of the second filler 6f is fully exhibited. The average particle size of the second filler means the average value of the values ​​obtained by measuring the major axis and minor axis lengths of any 10 second fillers in the field of view of the SEM and dividing the sum by 2.

[0034] Examples of materials constituting the second filler 6f include silica, mica, aluminum oxide, talc, titanium oxide, calcium carbonate, barium sulfate, zinc oxide, smectite, and zeolite. An example of a commercially available scaly silica product is Sun Lovely manufactured by AGC Si-Tech Co., Ltd. An example of a commercially available scaly mica product is Repco Mica manufactured by Repco Corporation. An example of a commercially available scaly aluminum oxide product is Cerasure manufactured by Kawai Lime Industry Co., Ltd. The second filler 6f may not have been subjected to a hydrophobic or liquid-repellent treatment.

[0035] The content of the second filler 6f in the liquid-repellent layer 3B may be, for example, 5 to 100 parts by mass, 5 to 75 parts by mass, or 5 to 50 parts by mass per 100 parts by mass of the first filler 5f. When the content of the second filler 6f is within the above range, it becomes easier to prevent the primary particles of the second filler 6f from stacking (aggregating) excessively to form excessively large aggregates, and it becomes easier to obtain excellent liquid repellency due to the first filler 5f and the second filler 6f.

[0036] The aggregates F may be spaced apart from one another in the liquid-repellent layer 3B. That is, the aggregates F may be arranged in an island pattern. Alternatively, a large number of aggregates F may be continuously formed, forming a porous layer made of the aggregates F in the liquid-repellent layer 3B. The aggregates F have a complex shape resulting from the complex and fine shape of the second filler 6f. That is, the aggregates F are formed by aggregating a plurality of primary particles of the second filler 6f (e.g., particles with an average primary particle diameter of 0.1 to 6 μm) in a randomly arranged state, and thus have a pleated surface and voids formed by the pleats. According to the inventors' investigations, when the size ((major axis + minor axis) / 2) of one aggregate F is 4 μm or more, the aggregates F significantly contribute to improving the liquid repellency of the liquid-repellent layer.

[0037] The binder resin 5b contains at least a fluorine-containing resin. The binder resin 5b may further contain one or both of a thermoplastic resin and a crosslinking agent. When the binder resin 5b contains a crosslinking agent, the binder resin 5b in the liquid-repellent layer 3 may have a crosslinked structure in which the fluorine-containing resin and the thermoplastic resin are crosslinked via the crosslinking agent.

[0038] The fluorine-containing resin is not particularly limited, and resins having a structure such as perfluoroalkyl, perfluoroalkenyl, or perfluoropolyether can be used as appropriate. From the viewpoint of further improving the liquid repellency of the liquid-repellent layer 3, the fluorine-containing resin preferably contains a fluorine-acrylic copolymer. The fluorine-acrylic copolymer is a copolymer composed of a fluorine-containing monomer and an acrylic monomer. The fluorine-acrylic copolymer may be a block copolymer or a random copolymer. By using a fluorine-acrylic copolymer, the weather resistance, water resistance, chemical resistance, and film-forming properties of the liquid-repellent layer 3 can also be improved.

[0039] The fluorine content in the fluorine-containing resin is, for example, 30 to 60 mass %, or may be 40 to 50 mass %. The fluorine content means the ratio of the mass of fluorine atoms to the total mass of atoms constituting the fluorine-containing resin.

[0040] As the fluorine-containing resin, commercially available fluorine-based paints can be used, such as Asahi Guard manufactured by Asahi Glass Co., Ltd., SF Coat manufactured by AGC Seimi Chemical Co., Ltd., Ftergent manufactured by Neos Co., Ltd., Fluorolink manufactured by Solvay, Unidyne manufactured by Daikin Industries, Ltd., H-3539 series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., and Modiper F series manufactured by NOF Corporation.

[0041] The use of a fluorine-containing resin can improve liquid repellency not only against water but also against oil or liquids containing oil, and highly viscous liquids containing surfactants and the like (e.g., emulsions, hand soaps, body soaps, shampoos, and conditioners). From this perspective, the fluorine-containing resin may not contain a structural unit derived from pyrrolidone or a derivative thereof (pyrrolidones). Examples of pyrrolidones include N-vinyl-2-pyrrolidone, N-vinyl-3-methyl-2-pyrrolidone, N-vinyl-5-methyl-2-pyrrolidone, and N-vinyl-3,3-dimethyl-2-pyrrolidone. Examples of fluorine-containing resins that do not contain a structural unit derived from pyrrolidones include Asahiguard AG-E060, AG-E070, AG-E082, and AG-E090 manufactured by Asahi Glass Co., Ltd., and Unidyne TG-8111 manufactured by Daikin Industries, Ltd.

[0042] The thermoplastic resin is not particularly limited, and examples thereof include low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-α-olefin copolymer, homo-, block-, or random polypropylene, propylene-α-olefin copolymer, and ethylene-vinyl acetate copolymer. For example, an ethylene-α-olefin copolymer can be referred to as a block copolymer or random copolymer of propylene and an α-olefin. Examples of the α-olefin component include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene.

[0043] The melting point of the thermoplastic resin is, for example, 50 to 135°C. A melting point of 135°C or lower facilitates bleeding of the fluorine-containing resin onto the surface of the liquid-repellent layer. Bleeding of the fluorine-containing resin onto the surface reduces the surface free energy, thereby enabling the liquid-repellent layer to exhibit excellent liquid repellency. While high-temperature drying can be used to promote bleeding of the fluorine-containing resin, if the melting point of the thermoplastic resin is too high, a correspondingly high temperature is required, which may cause problems such as deformation of the substrate 1. On the other hand, a melting point of 50°C or higher ensures a certain degree of crystallinity, thereby suppressing the occurrence of blocking due to softening. From this perspective, a melting point of the thermoplastic resin is more preferably 60 to 120°C.

[0044] The thermoplastic resin may be a modified polyolefin modified with a specific acid. The modified polyolefin can be obtained by graft-modifying a polyolefin with an unsaturated carboxylic acid derivative component derived from, for example, an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, or an ester of an unsaturated carboxylic acid. Alternatively, modified polyolefins such as hydroxyl-modified polyolefins and acrylic-modified polyolefins can also be used. Examples of modified polyolefin resins include Auroren manufactured by Nippon Paper Industries Co., Ltd., Zaixen manufactured by Sumitomo Seika Chemicals Co., Ltd., Unistall manufactured by Mitsui Chemicals, Inc., and Arrowbase manufactured by Unitika Ltd.

[0045] The modified polyolefin is also preferred from the viewpoint that it has an introduced functional group, which easily reacts with a crosslinking agent to form a crosslinked structure. Examples of the functional group include a carboxyl group, a hydroxyl group, a (meth)acryloyl group, and an amino group. By using a modified polyolefin having such a functional group together with a crosslinking agent described below, a crosslinked structure consisting of a thermoplastic resin, a fluorine-containing resin, and a crosslinking agent is formed in the liquid-repellent layer 3, thereby imparting greater durability to the liquid-repellent layer 3.

[0046] The crosslinking agent preferably has a functional group that reacts with the fluorine-containing resin. Examples of such crosslinking agents that can be used include crosslinking agents having functional groups such as an aziridine group, an isocyanate group, a carbodiimide group, and an amino group. Examples of commercially available crosslinking agents include Chemitite manufactured by Nippon Shokubai Co., Ltd., Takenate manufactured by Mitsui Chemicals, Inc., Carbodilite manufactured by Nisshinbo Chemical Inc., Meikanate manufactured by Meisei Chemical Industry Co., Ltd., and Cymel manufactured by Cytec Industries.

[0047] Fluorine-containing resins are generally used as aqueous dispersions in which they are dispersed in water. Therefore, many fluorine-containing resins have hydrophilic groups, such as hydroxyl groups or amino groups, to enhance their affinity with water. By using a crosslinking agent having functional groups reactive with the fluorine-containing resin, these functional groups in the fluorine-containing resin react with the functional groups in the crosslinking agent, forming a crosslinked structure in the liquid-repellent layer. Furthermore, these functional groups in the fluorine-containing resin are reduced by the reaction with the crosslinking agent, thereby reducing the number of functional groups remaining in the liquid-repellent layer. Therefore, even if the liquid-repellent layer is in contact with a liquid for a long period of time, the decrease in liquid repellency can be suppressed, and excellent liquid repellency can be maintained for a long period of time. When the fluorine-containing resin is used as a dispersion in a solvent other than water, the fluorine-containing resin may have a structure (e.g., a hydrocarbon chain) to enhance its affinity with the solvent used.

[0048] As described above, the BET specific surface area M of the first filler 5f is set to 100 to 400 m 2 / g, the ratio M / F of the BET specific surface area M of the first filler 5f to the amount F (mass %) of the fluorine-containing resin based on the total amount of the liquid-repellent layer is 1.5 to 4.0. The inventors have found that in order to form a liquid-repellent layer that maintains water repellency for a long period of time, it is not sufficient to focus solely on the amount of the first filler and the amount of the fluorine-containing resin, but it is important to adjust the amount of the fluorine-containing resin according to the BET specific surface area of ​​the first filler. When the M / F value is within the above range, water repellency (water repellency) can be maintained for a long period of time. From this perspective, M / F is preferably 2.0 to 4.0, and more preferably 3.0 to 4.0.

[0049] The content of the fluorine-containing resin in the binder resin 5b (based on the mass of the binder resin 5b) is, for example, 5% by mass or more, and may be 15% by mass or more, or 50% by mass or more. The content of the fluorine-containing resin in the binder resin 5b may be 100% by mass, but when the binder resin 5b contains a thermoplastic resin and a crosslinking agent, the content of the fluorine-containing resin may be 99% by mass or less, or may be 75% by mass or less. When the content of the fluorine-containing resin in the binder resin 5b is 5% by mass or more, the liquid-repellent layer is likely to exhibit excellent liquid repellency. On the other hand, when the content is 99% by mass or less, the content of the thermoplastic resin and the crosslinking agent can be sufficiently ensured, which can sufficiently prevent the filler from falling off from the liquid-repellent layer and sufficiently increase the durability of the liquid-repellent layer.

[0050] The content of the thermoplastic resin in binder resin 5b (based on the mass of binder resin 5b) is, for example, 5 to 90 mass %, or may be 10 to 50 mass %, or 20 to 30 mass %. When the content of the thermoplastic resin in binder resin 5b is 5 mass % or more, it is possible to sufficiently prevent the filler from falling off from the liquid-repellent layer, while when it is 90 mass % or less, it is possible to ensure a sufficient content of the fluorine-containing resin and crosslinking agent, and the liquid-repellent layer is likely to exhibit excellent liquid repellency and durability.

[0051] Mass W of the crosslinking agent contained in the binder resin 5b Cand the mass W of the fluorine-containing resin contained in the binder resin 5b J Relative to W C / W J is, for example, 0.01 to 0.5, and may be 0.05 to 0.3 or 0.1 to 0.2. C / W J When the ratio W is 0.01 or more, the filler can be sufficiently prevented from falling off from the liquid-repellent layer, and the durability of the liquid-repellent layer can be sufficiently increased. C / W J When the ratio is 0.5 or less, the content of the fluorine-containing resin can be sufficiently ensured, and the fluorine-containing resin can be sufficiently bled out onto the surface of the liquid-repellent layer, thereby achieving good liquid repellency.

[0052] Mass W of binder resin 5b contained in the liquid-repellent layer B and the mass of the filler W S Relative to W B / W S may be 0.1 to 5, 0.2 to 2, or 0.3 to 1. Here, the mass W of the binder resin 5b B is the mass of the fluorine-containing resin W J , and the mass W of the thermoplastic resin optionally contained P , and the mass of the crosslinker W C The above ratio W B / W S By being within the above range, the filler is entirely covered with the binder resin 5b, and yet the filler is likely to form an uneven structure on the surface of the liquid-repellent layer. This prevents the filler from falling off the liquid-repellent layer, and allows the liquid-repellent properties of both the filler and the fluorine-containing resin contained in the binder resin 5b to be enjoyed. Note that even if the liquid-repellent layer 3 is burned, the mass W of the filler S Since there is no substantial change in the above ratio W B / W S The value of can be calculated from the measured value by measuring the change in mass due to the burning of the liquid-repellent layer.

[0053] The mass per unit area of ​​the liquid-repellent layer is, for example, 0.3 to 10.0 g / m 2 and 1.0 to 3.0 g / m 2 or 1.5 to 2.5 g / m 2 The mass per unit area of ​​the liquid-repellent layer may be 0.3 g / m 2 On the other hand, when the mass per unit area of ​​the liquid-repellent layer is 10.0 g / m or more, excellent liquid repellency can be achieved by the fluorine-containing resin. 2 By satisfying the condition below, it is possible to efficiently obtain the liquid repellent effect of the uneven structure and the fluorine-containing resin.

[0054] The liquid-repellent layer may contain other additives as needed, to the extent that the liquid-repellent function is not impaired, such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier.

[0055] From the viewpoint of further improving the liquid repellency against liquids containing surfactants and having high viscosity, the liquid-repellent layer may not contain structural units derived from pyrrolidones. That is, structural units derived from pyrrolidones may not only be absent from the fluorine-containing resin, but also from any of the other components constituting the liquid-repellent layer. The presence or absence of structural units derived from pyrrolidones in the liquid-repellent layer can be determined by infrared spectroscopy, nuclear magnetic resonance spectroscopy, pyrolysis GC-MS, etc.

[0056] In the above embodiment, the liquid-repellent layer is formed in direct contact with the surface 1a to be treated of the substrate 1, but an underlayer may be formed on the surface 1a to be treated of the substrate 1, and the liquid-repellent layer may be formed on the underlayer. The underlayer is a layer disposed between the substrate 1 and the liquid-repellent layer, and can be formed so as to cover part or all of the surface (surface 1a to be treated) of the substrate 1. By interposing the underlayer between the substrate 1 and the liquid-repellent layer, the adhesion between the substrate 1 and the liquid-repellent layer can be improved. Furthermore, by providing the underlayer, the liquid repellency of the liquid-repellent structure can be further improved.

[0057] FIG. 3 is a cross-sectional view schematically illustrating another embodiment of a liquid-repellent structure according to the present disclosure. As shown in FIG. 3, the liquid-repellent structure 10C includes a substrate 1 having a surface to be treated 1a, a base layer 2 formed on the surface to be treated 1a, and a liquid-repellent layer 3C on the base layer 2. The base layer includes a binder resin 7b and a third filler 7f. The liquid-repellent layer 3C may include a first filler 5f and a binder resin 5b as shown in FIG. 1, or may include a second filler 6f in addition to the first filler 5f and the binder resin 5b as shown in FIG. 2. FIG. 3 shows the former embodiment as an example. By providing the base layer 2 below the liquid-repellent layer 3C, unevenness is more efficiently formed on the surface, making it easier to maintain liquid repellency for a long period of time. The liquid-repellent layer 3C makes it easier to maintain liquid repellency against products, such as lotions containing alcohol in addition to water, for a long period of time.

[0058] (base layer) The underlayer contains a binder resin. The underlayer can be formed from the same resin as the thermoplastic resin used in the liquid-repellent layer. Specific embodiments of the thermoplastic resin are as described above. The underlayer may be formed from a thermosetting resin. Examples of thermosetting resins include urethane resin, epoxy resin, and phenolic resin. The use of a thermosetting resin makes it easier to obtain stronger adhesion between the substrate and the liquid-repellent layer. Examples of urethane resins include Burnock manufactured by DIC Corporation, Takelac and Takenate manufactured by Mitsui Chemicals, Inc., and examples of epoxy resins include EPICLON manufactured by DIC Corporation.

[0059] The underlayer may contain a third filler having an average primary particle diameter of 5 to 60 μm. Examples of materials for the third filler include inorganic materials such as silica, talc, mica, titanium oxide, calcium carbonate, barium sulfate, zinc oxide, smectite, zeolite, and aluminum oxide, and resin materials such as silicone, acrylic resin, urethane resin, and polyolefin resin (polypropylene, polyethylene). By incorporating the third filler, rough irregularities can be formed on the surface of the underlayer, and by providing a liquid-repellent layer thereon, rough and complex irregularities can be formed by the liquid-repellent structure. As a result, the liquid repellency can be further improved. From this perspective, the average primary particle diameter of the third filler may be 10 to 50 μm, or may be 20 to 50 μm. The primary particle diameter of the third filler may be 5 to 30 μm.

[0060] Examples of the third filler include Sunsphere (silica) manufactured by AGC Si-Tech Co., Ltd., Silicone Powder KMP series (silicone) manufactured by Shin-Etsu Chemical Co., Ltd., Ganz Pearl (acrylic resin) manufactured by Aica Kogyo Co., Ltd., Art Pearl (acrylic resin) manufactured by Negami Chemical Industrial Co., Ltd., Art Pearl (urethane resin) manufactured by Negami Chemical Industrial Co., Ltd., Flow Beads (polyethylene resin) manufactured by Sumitomo Seika Chemical Co., Ltd., Flow Beads (polypropylene resin) manufactured by Sumitomo Seika Chemical Co., Ltd., and Mipelon (ultra-high molecular weight polyethylene) manufactured by Mitsui Chemicals, Inc.

[0061] The underlayer can impart coarse irregularities to the liquid-repellent structure. The coarse irregularities facilitate point contact between the liquid-repellent layer and the contents, thereby further suppressing a decrease in liquid repellency. The surface roughness Sa of the liquid-repellent structure may be 1.5 to 15.0 μm, 2.0 to 14.0 μm, or 5.0 to 14.0 μm, from the viewpoints of easily achieving a sufficient point contact effect and making it difficult for the contents to become trapped in the recesses.

[0062] Mass W of binder resin contained in the base layer BU and the mass of the third filler W SU Relative to W BU / W SUThe ratio W may be 0.1 to 1, or may be 0.2 to 0.5. BU / W SU When the ratio W is within the above range, the third filler particles are prevented from being detached, and a coarse uneven structure is easily formed by the third filler particles. BU / W SU The value of can be easily adjusted by changing the amount of paint used. BU / W SU The value of can also be calculated from the measured value by measuring the change in mass due to combustion of the base layer.

[0063] The mass per unit area of ​​the undercoat layer is, for example, 1.0 to 20.0 g / m 2 and 3.0 to 10.0 g / m 2 The mass per unit area of ​​the underlayer may be 1.0 g / m 2 On the other hand, when the mass per unit area of ​​the undercoat layer is 20.0 g / m or more, excellent liquid repellency can be easily achieved. 2 By satisfying the condition of 0.1 mm or less, it becomes easier to obtain the effect of point contact sufficiently.

[0064] <Method for manufacturing liquid-repellent structure> A method for producing a liquid-repellent structure will now be described. The production method according to this embodiment includes the steps of preparing a coating liquid for forming a liquid-repellent layer, forming a coating film of the coating liquid on the surface to be treated of the substrate, and drying and curing the coating film to form the liquid-repellent layer. Each step will be described below.

[0065] First, a coating liquid containing a filler, a fluorine-containing resin, a solvent, and optionally a thermoplastic resin and optionally a crosslinking agent is prepared. In this case, the filler is a fluorine-containing resin having a BET specific surface area M of 100 to 400 m. 2The coating solution contains a first filler having a BET specific surface area of ​​1.5 to 4.0. Examples of the solvent include water, alcohol, and organic solvent. The amount (solid content) of each component in the coating solution may be adjusted appropriately so that the content of each component in the liquid-repellent layer is as described above. The coating solution is prepared so that the ratio M / F of the BET specific surface area M of the first filler to the amount F (mass %) of the fluorine-containing resin based on the total amount of solids contained in the coating solution is 1.5 to 4.0. The thermoplastic resin may be in the form of an emulsion dispersed in water, alcohol, or the like. Such a polyolefin emulsion may be prepared by emulsifying a polymer produced by the polymerization reaction of the corresponding monomer, or may be prepared by emulsion polymerization of the corresponding monomer.

[0066] The resulting coating liquid is applied to a substrate. Any known method can be used for the application without any particular limitation, including immersion (dipping) and methods using a spray, coater, printer, brush, etc. Examples of the types of coaters and printers used in these methods and their coating methods include gravure coaters such as direct gravure, reverse gravure, kiss reverse gravure, and offset gravure, reverse roll coaters, microgravure coaters, chamber doctor combined coaters, air knife coaters, dip coaters, bar coaters, comma coaters, and die coaters. The amount of coating liquid applied can be appropriately adjusted so as to obtain the mass per unit area of ​​the liquid-repellent layer described above.

[0067] The coating film formed on the substrate is dried and cured by heating. This allows for the production of a liquid-repellent structure comprising a substrate and a liquid-repellent layer formed on the substrate. When the coating liquid contains a crosslinking agent, a crosslinked structure consisting of a fluorine-containing resin, a thermoplastic resin used as needed, and the crosslinking agent is formed in the liquid-repellent layer. There are no limitations on the heating conditions as long as they can volatilize the solvent and cause a crosslinking reaction, but heating conditions can be, for example, 60 to 100°C for 0.5 to 5 minutes.

[0068] When the liquid-repellent structure further includes an underlayer, the manufacturing method according to this embodiment includes the steps of preparing a coating liquid for forming the underlayer and a coating liquid for forming the liquid-repellent layer, forming a coating film of the coating liquid for forming the underlayer on the surface to be treated of the substrate, drying and curing the coating film to form the underlayer, forming a coating film of the coating liquid for forming the liquid-repellent layer, and drying and curing the coating film to form the liquid-repellent layer. The preparation and application of the coating liquid for forming the underlayer, and the drying and curing of the coating film can be carried out in accordance with the description of the preparation and application of the coating liquid for forming the liquid-repellent layer, and the drying and curing of the coating film.

[0069] <Coating liquid for forming liquid-repellent layer> The liquid-repellent layer-forming coating liquid is prepared in the step of preparing the liquid-repellent layer-forming coating liquid described above. That is, the liquid-repellent layer-forming coating liquid contains a binder resin containing a fluorine-containing resin and a filler, and the filler has a BET specific surface area M of 100 to 400 m 2 / g of a first filler, and the ratio M / F of the BET specific surface area M of the first filler to the amount F (mass %) of the fluorine-containing resin based on the total amount of solids contained in the coating liquid is 1.5 to 4.0.

[0070] <Packaging material> The packaging material according to this embodiment has a liquid-repellent structure on the side that comes into contact with the product. The packaging material according to this embodiment can be applied to products containing moisture (e.g., water, beverages, yogurt, lotion) and oil (e.g., salad oil, curry, fresh cream), as well as to products containing surfactants, such as emulsions, hand soaps, body soaps, shampoos, and conditioners. The packaging material according to this embodiment can maintain its liquid-repellent properties, particularly against water, for a long period of time. Specific examples of packaging materials include retort pouches for curry or pasta sauce, containers and lids for yogurt or pudding, containers or refill pouches for toiletries such as hand soap, shampoo, and conditioner, and tubes for toothpaste or medicines. [Example]

[0071] The present disclosure will be explained in more detail by the following experimental examples, but the present disclosure is not limited to these examples.

[0072] In order to fabricate the liquid-repellent structure according to the experimental example, the following materials were prepared. (base material) Polyethylene terephthalate (PET) film (Fluorine-containing resin) Asahiguard AG-E060 (product name, manufactured by Asahi Glass Co., Ltd., a fluorine-acrylic copolymer that does not contain structural units derived from pyrrolidones, a cationic water-based material) Asahiguard AG-E070 (product name, manufactured by Asahi Glass Co., Ltd., a fluorine-acrylic copolymer that does not contain structural units derived from pyrrolidones, a cationic water-based material) Asahiguard AG-E082 (product name, manufactured by Asahi Glass Co., Ltd., a fluorine-acrylic copolymer that does not contain structural units derived from pyrrolidones, a cationic water-based material) Asahiguard AG-E090 (product name, manufactured by Asahi Glass Co., Ltd., a fluorine-acrylic copolymer that does not contain structural units derived from pyrrolidones, an anionic water-based material) (First Filler) AEROSIL50 (product name, manufactured by Nippon Aerosil Co., Ltd.) AEROSIL90G (product name, manufactured by Nippon Aerosil Co., Ltd.) AEROSIL130 (product name, manufactured by Nippon Aerosil Co., Ltd.) AEROSIL200 (product name, manufactured by Nippon Aerosil Co., Ltd.) AEROSIL300 (product name, manufactured by Nippon Aerosil Co., Ltd.) AEROSIL380 (product name, manufactured by Nippon Aerosil Co., Ltd.) Snowtex ST-30 (product name, manufactured by Nissan Chemical Co., Ltd.) Snowtex ST-XS (product name, manufactured by Nissan Chemical Co., Ltd.) 530 (product name, Fuji Silysia Chemical Ltd.) HDK V15 (product name, Wacker Asahi Kasei Silicone Co., Ltd., beaded filler) HDK N20 (product name, Wacker Asahi Kasei Silicone Co., Ltd., beaded filler) HDK T30 (product name, Wacker Asahi Kasei Silicone Co., Ltd., beaded filler) HDK T40 (product name, Wacker Asahi Kasei Silicone Co., Ltd., beaded filler) Snowtex PS-S-PO (product name, Nissan Chemical Co., Ltd., beaded filler) (Second filler) Sun Lovely (product name, manufactured by AGC Si-Tech Co., Ltd., scale-like filler, average particle size 4-6 μm) (Third filler) Art Pearl SE-010T (product name, manufactured by Negami Chemical Industrial Co., Ltd., cross-linked acrylic resin particles) Art Pearl SE-020T (product name, manufactured by Negami Chemical Industrial Co., Ltd., cross-linked acrylic resin particles) Art Pearl SE-030T (product name, manufactured by Negami Chemical Industrial Co., Ltd., cross-linked acrylic resin particles) Art Pearl SE-050T (product name, manufactured by Negami Chemical Industrial Co., Ltd., cross-linked acrylic resin particles) (binder resin) Arrowbase SB5230N (product name, Unitika Ltd., modified polyolefin resin (thermoplastic resin)) Takelac A525 / Takenate A52 (product name, manufactured by Mitsui Chemicals, Inc., urethane resin (thermosetting resin)) (solvent) Alcohol-based solvents (2-propanol) Ester solvents (ethyl acetate)

[0073] <Fabrication of liquid-repellent structure (without underlayer)> Each component was added to an alcohol-based solvent so that the liquid-repellent layer would have the composition shown in Tables 1 to 5. This was thoroughly stirred to prepare a coating liquid for forming a liquid-repellent layer, which was then applied to a PET film substrate using a bar coater. The applied coating liquid was then heated at 80°C for 1 minute to dry and harden, forming a liquid-repellent layer on the substrate. The mass per unit area of ​​the liquid-repellent layer was 1.8 g / m 2The F / Si ratio in the table is the ratio of the mass F (mass%) of the fluorine-containing resin to the mass Si (mass%) of the silica filler, based on the total amount of the liquid-repellent layer, and the above-mentioned ratio W B / W S corresponds to the value of

[0074] (surface roughness) The arithmetic mean height (Sa) of the contour curved surface was measured as described in JIS B0681-2 Geometric Product Specifications (GPS) - Surface Texture: Three-Dimensional - Part 2: Terms, Definitions and Surface Texture Parameters, item 4.1.7. If the sample was tilted, surface correction (tilt correction) was performed and then Sa was measured by three-dimensional measurement. Measurements were taken at any three points on the liquid-repellent structure, and the average value was taken as the surface roughness Sa. Measuring equipment: Olympus OLS4000 (laser microscope) Measurement magnification:x20 Measurement mode: Multi-layer

[0075] [Table 1]

[0076] [Table 2]

[0077] [Table 3]

[0078] However, the compounding ratio of the first filler and the second filler was as follows.

[0079] [Table 4]

[0080] [Table 5]

[0081] <Fabrication of liquid-repellent structure (with underlayer)> Each component was added to an alcohol-based solvent or an ester-based solvent (an ester-based solvent was used when A525 / A52 was used) so that the underlayer would have the composition shown in Table 6. This was thoroughly stirred to prepare a coating solution for forming the underlayer, which was then applied to a PET film substrate using a bar coater. The applied coating solution was then heated at 80°C for 1 minute to dry and harden, forming an underlayer on the substrate. The mass per unit area of ​​the underlayer was 5.00 g / m 2 The amount of the binder resin contained in the underlayer was adjusted to be W BU and the mass of the third filler W SU Relative to W BU / W SU was set to 0.2. Then, a liquid-repellent layer was formed on the underlayer in the same manner as in the case where no underlayer was used. When the liquid-repellent layer contained the first filler and the second filler, the compounding ratio Ws2 / Ws1 of the first filler to the second filler was set to 0.5 (50 parts by mass of the second filler relative to 100 parts by mass of the first filler).

[0082] [Table 6]

[0083] <Evaluation of liquid-repellent structures> The liquid-repellent structures were evaluated from the following viewpoints. The evaluation results are shown in Tables 7 to 11.

[0084] (Liquid repellency evaluation) The liquid-repellent structure was placed flat with the liquid-repellent layer side facing up, and 2 μL of the following liquid was dropped onto the liquid-repellent layer using a dropper. The liquid-repellent structure was then placed upright and left to stand for 30 seconds, after which the state of the dropped liquid was visually observed. The liquid repellency was evaluated based on the observation results and on the following evaluation criteria. An evaluation result of 2 to 5 can be said to be satisfactory for practical use. An evaluation result of 3 to 5 is desirable. [Liquid used] pure water Yogurt: Meiji Bulgaria Yogurt L81 Low Sugar (Meiji) Salad oil: Nissin salad oil (Nissin Oillio) Curry (room temperature): Bon Curry Gold, medium spicy (Otsuka Foods) Emulsion: Emulsion containing soy milk isoflavones (Tokiwa Pharmaceutical Co., Ltd.) Toner: Toner containing soy milk isoflavones (Tokiwa Pharmaceutical Co., Ltd.) [Evaluation criteria] 5: The droplets became round and rolled off the liquid-repellent layer, or peeled off. 4: The liquid ran off the liquid-repellent layer, leaving no trace. 3: The liquid flowed down from the liquid-repellent layer, but traces of the flow remained in small spots. 2: The liquid flowed down from the liquid-repellent layer, but a line-shaped trace remained. 1: The substance remained on the liquid-repellent layer and did not move, or soaked into the liquid-repellent layer.

[0085] (Durability evaluation) The liquid-repellent structure was cut into a size of 50 mm wide and 100 mm long to prepare a test specimen. 150 ml of some of the liquids used in the liquid-repellency evaluation was poured into a 200 ml beaker, and the test specimen was immersed in the liquid up to half its length and left at room temperature (25°C) for 5 days. After leaving the test specimen, it was removed from the liquid, and the state of adhesion of each liquid to the surface of the immersed portion of the liquid-repellent structure on the side where the liquid-repellent layer was formed was visually observed. Durability (liquid repellency after long-term contact with each liquid) was evaluated based on the following evaluation criteria. [Evaluation criteria] 5: No liquid was observed on the immersed area. 4: Liquid adhesion was observed over less than 10% of the immersed area. 3: Liquid adhesion was observed over 10% or more but less than 30% of the immersed area. 2: Liquid adhesion was observed over 30% or more but less than 70% of the immersed area. 1: Liquid adhesion was observed over 70% or more of the immersed area.

[0086] [Table 7]

[0087] [Table 8]

[0088] [Table 9]

[0089] [Table 10]

[0090] [Table 11]

[0091] It was found that the liquid-repellent structures of Experimental Examples 3 to 8, 13 to 15, 23 to 24, 38, 42 to 45, 50 to 52, 60 to 61, 73 to 75, 80 to 82, 87 to 89, and 97 to 112 having the configuration of the present disclosure had excellent liquid repellency against water or liquids containing water for a long period of time. [Explanation of symbols]

[0092] 1...substrate, 1a...treated surface (surface to be imparted with liquid repellency), 2...undercoat layer, 3A, 3B, 3C...liquid repellent layer, 5b...binder resin, 5f...first filler, 6f...second filler, 7b...binder resin, 7f...third filler, F...aggregate, 10A, 10B, 10C...liquid repellent structure.

Claims

1. A liquid-repellent structure comprising a surface to which liquid repellency is to be imparted, an underlayer formed on the surface, and a liquid-repellent layer formed on the underlayer, the liquid-repellent layer contains a binder resin including a fluorine-containing resin and a filler dispersed in the binder resin; The filler has a BET specific surface area M of 100 to 400 m ２ / g of a first filler, the first filler having a structure in which a plurality of primary particles are linked together in a beaded shape, a ratio M / F of a BET specific surface area M of the first filler to an amount F (mass%) of the fluorine-containing resin based on the total amount of the liquid-repellent layer is 1.5 to 4.0, The liquid-repellent structure, wherein the underlayer contains a binder resin (excluding polyvinyl chloride resin) and a third filler having an average primary particle size of 5 to 60 μm.

2. The liquid-repellent structure according to claim 1, wherein the BET specific surface area M is 200 to 300 m 2 / g, and the ratio M / F is 3.0 to 4.

0.

3. 3. The liquid-repellent structure according to claim 1, wherein the fluorine-containing resin comprises a fluorine-acrylic copolymer.

4. The liquid-repellent structure according to any one of claims 1 to 3, wherein the filler includes a second filler in the form of a scale.

5. 5. The liquid-repellent structure according to claim 1, wherein the third filler has an average primary particle size of 10 to 50 μm.

6. 6. The liquid-repellent structure according to claim 5, wherein the surface roughness Sa is 1.5 to 15.0 μm.

7. A packaging material having the liquid-repellent structure according to any one of claims 1 to 6 on the side that comes into contact with an article.

8. The packaging material of claim 7 wherein the product contains moisture.

9. preparing a coating liquid for forming an underlayer, which contains a binder resin (excluding polyvinyl chloride resins) and a third filler having an average primary particle size of 5 to 60 μm, and a coating liquid for forming a liquid-repellent layer, which contains a binder resin containing a fluorine-containing resin and a filler; forming a coating film of the underlayer-forming coating liquid on a surface to be imparted with liquid repellency; a step of forming an underlayer by drying and curing a coating film of the underlayer-forming coating liquid; forming a coating film of the liquid-repellent layer-forming coating liquid on the underlayer; and forming a liquid-repellent layer by drying and curing the coating film of the liquid-repellent layer-forming coating liquid, The filler has a BET specific surface area M of 100 to 400 m ２ / g of a first filler, the first filler having a structure in which a plurality of primary particles are linked together in a beaded shape, a ratio M / F of a BET specific surface area M of the first filler to an amount F (mass %) of the fluorine-containing resin based on the total amount of solids contained in the liquid-repellent layer-forming coating liquid is 1.5 to 4.

0.

10. The method according to claim 9, wherein the third filler has an average primary particle size of 10 to 50 μm.

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