Manufacturing method for nanostructures

Abstract

To provide a method for manufacturing nanostructures that allows for the production of nanostructures without changes in the dimensions or shape of the mold due to the influence of moisture from the time of mold creation to the formation of the coating layer. [Solution] A method for producing a nonwoven nanostructure, comprising the steps of: producing a mold made of polyvinyl butyral; forming a coating layer on the mold; and removing the mold to obtain a nanostructure.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing nanostructures. More specifically, the present invention relates to a method for manufacturing nanostructures that are not affected by water, such as moisture in the atmosphere or sweat emitted from the human body, by forming a coating layer on a mold made of polyvinyl butyral and then removing the mold.

Background Art

[0002] Metals, metal oxides, organic compounds, or composite materials composed of organic compounds and metals having nanostructures have attracted attention because they exhibit properties different from those of the corresponding bulk materials. Nanostructures are expected to be applied in various fields including separation technology, catalysis, and materials.

[0003] Conventionally, nanostructures have been manufactured using a mold made of polyvinyl alcohol. For example, a manufacturing method is known in which nanofibers made of polyvinyl alcohol are coated with a metal and then dissolved using water to dissolve and remove the nanofibers made of polyvinyl alcohol (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the mold made of polyvinyl alcohol is water-soluble, the dimensions and shape of the mold may change due to the influence of moisture from the time of mold production to the time of coating layer formation, and a coating layer with the expected shape may not be obtained. An object of the present invention is to provide a novel method for manufacturing nanostructures that avoids the above problems.

Means for Solving the Problems

[0006] To achieve the above objective, the inventors conducted diligent research. As a result, they discovered that by using polyvinyl butyral, which does not change in the dimensions or shape of the mold due to moisture in the environment, it is possible to manufacture a nonwoven fabric-like nanostructure made of metal nanotubes with slits without changing the dimensions or shape of the mold, leading to the conception of the present invention.

[0007] In other words, the present invention has the following configuration. [1] A method for producing nanostructures, comprising forming a coating layer on a mold made of polyvinyl butyral, and then removing the mold by dissolving it in a solvent. [2] The method for producing a nanostructure according to [1], wherein the shape of the material used as a template is a fiber. [3] The method for producing a nanostructure according to [2], wherein the diameter of the fiber shape of the mold is 1 to 1000 nm. [4] The method for producing a nanostructure according to any one of [1] to [3], wherein the coating layer is made of a metal or a metal oxide. [5] The method for manufacturing a nanostructure according to any one of [1] to [4], wherein the thickness of the coating layer is 1 to 1000 nm. [6] The method for producing a nanostructure according to any one of [1] to [5], wherein the solvent is methanol, ethanol, 2-propanol, 1-butanol, or a solvent comprising at least one of these. [Effects of the Invention]

[0008] According to the present invention, it is possible to manufacture a nonwoven nanostructure made of slit-type metal nanotubes without the dimensions or shape of the mold changing due to the influence of water, such as moisture in the air or sweat emitted from the human body. [Brief explanation of the drawing]

[0009] [Figure 1] This is a scanning electron microscope image of the polyvinyl butyral fiber used as a template. [Figure 2] This is a scanning electron microscope image of polyvinyl butyral fibers after contact with water. [Figure 3] This is a scanning electron microscope image of silver-coated polyvinyl butyral fibers. [Figure 4] This is a scanning electron microscope image of a nanostructure made of silver nanotubes obtained in Example 1 of the present invention. [Figure 5] This is a scanning electron microscope image of a nanostructure made of silver nanotubes obtained in Example 1 of the present invention. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below. However, the present invention is not limited to the embodiments described below.

[0011] <Method for manufacturing nanostructures> A method for manufacturing nanostructures will be described. The nanostructures according to this embodiment are manufactured mainly in the following three steps: (1) A step of manufacturing the fibers that will serve as the mold; (2) Step of forming a coating layer on the mold; (3) Step of removing the mold to obtain a nanostructure.

[0012] The following provides a detailed explanation of stages (1) through (3).

[0013] (1) Step of manufacturing the fibers that will serve as the mold. The method for manufacturing the template fibers is not particularly limited, but electrospinning is preferred. Electrospinning is preferred because it allows for a small and uniform average fiber diameter. The fiber diameter is not particularly limited, but 1 to 1000 nm is preferred.

[0014] Electrospinning is a method in which a spinning solution is ejected while an electric field is applied to fiberize the ejected spinning solution and obtain fibers with a very small fiber diameter on a collector. For example, methods include extruding a spinning solution from a nozzle while applying an electric field for spinning, foaming the spinning solution while applying an electric field for spinning, and guiding the spinning solution onto the surface of a cylindrical electrode while applying an electric field for spinning.

[0015] The spinning solution is not particularly limited as long as it has drawability. For example, those obtained by dispersing a fiber-forming polymer in a solvent, dissolving a fiber-forming polymer in a solvent, or melting a fiber-forming polymer by heat or laser irradiation can be used.

[0016] The fiber-forming polymer is not particularly limited as long as good drawability can be obtained. Examples include polyolefin resins such as polyethylene, polypropylene, or cyclic polyolefin, fluorine-based resins such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, or polytetrafluoroethylene, polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polyglycolic acid, polycaprolactone, or polybutylene succinate, polyamide-based resins such as nylon 6, nylon 6,6, or aromatic polyamide, polyvinyl acetal-based resins such as polyvinyl formal or polyvinyl butyral, polyurethane, polycarbonate, polystyrene, polysulfone, polyethersulfone, polyacrylonitrile, polymethyl methacrylate, cellulose, cellulose acetate, collagen, glucomannan derivative, chitin, chitosan, polylysine, polyamic acid, and polyimide. These fiber-forming polymers may be used alone or in combination of two or more, and can be appropriately set in view of the required drawability, dispersibility, and physical properties of the obtained fibers, fiber layers, etc.

[0017] The solvent for dispersing or dissolving the fiber-forming polymer is not particularly limited, and examples thereof include acetone, methanol, ethanol, 2-propanol, 1-butanol, 2-methylpropyl alcohol, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, triethyl phosphate, propylene glycol monomethyl ether, diethylene glycol ethyl methyl ether, toluene, xylene, pyridine, formic acid, acetic acid, tetrahydrofuran, dichloromethane, chloroform, 1,1,1,3,3,3-hexafluoroisopropanol. These solvents may be used alone or in combination of two or more. The mixing ratio when used in combination is not particularly limited and can be appropriately set in view of the drawability, dispersibility, and physical properties of the resulting fibers.

[0018] The concentration of the fiber-forming polymer in the spinning solution is not particularly limited, but is preferably 1 to 50% by weight, more preferably 2 to 40% by weight, and even more preferably 5 to 30% by weight. If the concentration of the fiber-forming polymer in the spinning solution is at least 1% by weight, it is preferable because good drawability and high productivity can be easily obtained. If it is 50% by weight or less, it is preferable because fibers with a small average fiber diameter can be easily obtained.

[0019] For the purpose of improving the stability and drawability of electrospinning, the spinning solution may further contain a surfactant. Examples of the surfactant include anionic surfactants such as sodium dodecyl sulfate, cationic surfactants such as tetrabutylammonium bromide, and nonionic surfactants such as polyoxyethylene sorbitan monolaurate. The concentration of the surfactant is not particularly limited, but is preferably 0.001 to 5% by weight with respect to the spinning solution because an effect commensurate with the use can be obtained.

[0020] Other components may be included in the spinning solution as long as they do not significantly impair the effects of the present invention. Examples of additives include antibacterial agents, deodorants, antistatic agents, conductive materials, fluorescent materials, smoothing agents, hydrophilic agents, water repellents, oil repellents, antioxidants, weather-resistant agents, and charge stabilizers.

[0021] The method for preparing the spinning solution is not particularly limited and may include methods such as stirring or ultrasonic treatment. The order of mixing is also not particularly limited; the components may be mixed simultaneously or sequentially. When preparing the spinning solution by stirring, the stirring time is not particularly limited as long as the fiber-forming polymer is uniformly dissolved or dispersed in the solvent. For example, stirring may be performed at -50 to 200°C for 1 to 24 hours.

[0022] The viscosity of the spinning solution is not particularly limited, but is preferably 10 to 10,000 cP, and more preferably 100 to 4,000 cP. A viscosity of 10 cP or higher is preferable because it provides good spinnability and stability during electrospinning, and a viscosity of 10,000 cP or lower is preferable because it facilitates the preparation of the spinning solution and the dispensing during electrospinning. The viscosity of the spinning solution can be adjusted by appropriately changing the molecular weight and concentration of the fiber-forming polymer, as well as the type and mixing ratio of the solvent.

[0023] The spinning solution may be spun at room temperature, or it may be heated or cooled to a temperature of, for example, 0 to 200°C. As for the method of dispensing the spinning solution, for example, a pump can be used to dispense the spinning solution, filled in a syringe, from a nozzle. The inner diameter of the nozzle is not particularly limited, but is preferably 0.1 to 1.5 mm, more preferably 0.2 to 0.8 mm, and even more preferably 0.3 to 0.6 mm. Furthermore, the single-hole discharge volume of the spinning solution is not particularly limited, but is preferably 0.1 to 50 ml / hr, more preferably 0.2 to 20 ml / hr, and even more preferably 0.5 to 10 ml / hr.

[0024] The method for applying the electric field is not particularly limited as long as it allows for stable electrospinning. For example, a high voltage may be applied to the nozzle or spinning solution to ground the collector. The applied voltage is not particularly limited as long as it allows for fiber formation and stable spinning, but examples include 5 to 100 kV. The distance between the nozzle and the collector is not particularly limited as long as the solvent evaporates sufficiently, but examples include 5 to 100 cm. The electric field strength is not particularly limited as long as it allows for stable spinning, but examples include 1 to 10 kV / cm. The material of the collector is not particularly limited as long as it can collect the electrospun fibers, but conductive materials such as metals can be suitably used. The shape of the collector is not particularly limited, but examples include a flat plate, a shaft, or a conveyor. If the collector is flat, a sheet-like laminate can be obtained, and if it is shaft-like, a tubular laminate can be obtained. If it is conveyor-like, a sheet-like laminate can be produced continuously.

[0025] (2) Step of forming a coating layer on the mold The method for forming a coating layer on a mold is not particularly limited, but examples include immersion method, coating method, spraying method, electrolytic plating method, electroless plating method, vacuum deposition method, sputtering method, ion plating method, chemical vapor deposition method, and atomic layer deposition method.

[0026] The coating layer is not particularly limited, but examples of metals include silver (Ag), gold (Au), aluminum (Al), platinum (Pt), titanium (Ti), zinc (Zn), scandium (Sc), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), indium (In), tin (Sn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), strontium (Sr), tungsten (W), cadmium (Cd), tantalum (Ta), or alloys and oxides thereof. The thickness of the coating layer is not particularly limited, but 1 to 500 nm is preferred. These coating layers may be used individually or in mixtures of two or more types.

[0027] (3) Step of removing the mold to obtain the nanostructure One example of a method for obtaining nanostructures by removing the template is a dissolution process.

[0028] The solvent used in the dissolution process is not particularly limited, but a solvent that dissolves the mold without dissolving the coating layer is preferred. Examples include acetone, methanol, ethanol, 2-propanol, 1-butanol, 2-methylpropyl alcohol, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, triethyl phosphate, propylene glycol monomethyl ether, diethylene glycol ethyl methyl ether, toluene, xylene, pyridine, formic acid, acetic acid, tetrahydrofuran, dichloromethane, chloroform, and 1,1,1,3,3,3-hexafluoroisopropanol. Preferred solvents are methanol, ethanol, 2-propanol, 1-butanol, or solvents containing at least one of these. These solvents may be used individually or as a mixture of two or more. When used as a mixture, the mixing ratio is not particularly limited and can be appropriately set considering the solubility of the mold and the physical properties of the resulting nanostructure. The solvent used in the dissolution process may be used at room temperature, or it may be heated or cooled to a temperature of, for example, 0 to 200°C. The amount of solvent is not particularly limited, as long as the solvent is able to dissolve the mold in proportion. [Examples]

[0029] The following examples are for illustrative purposes only. The scope of the present invention is not limited to these examples. The measurement methods and definitions of the physical properties shown in the examples are shown below. <Fiber diameter of the mold fiber> Using a scanning electron microscope (SU-8000) manufactured by Hitachi High-Tech Corporation, fibers were observed at magnifications of 100 to 500,000 times. Image analysis software was used to measure the diameter (fiber diameter) of 50 or more fibers, and the average value was defined as the average fiber diameter. [Examples]

[0030] (1) Step of manufacturing the fibers that will serve as the mold. A spinning solution was prepared consisting of 14 parts by weight of polyvinyl butyral (product name: S-Rec B, variety: BM-1) manufactured by Sekisui Chemical Co., Ltd., 29 parts by weight of ethanol, and 58 parts by weight of 1-butanol. The spinning solution was supplied at a rate of 1 ml / hr to a nozzle with an inner diameter of 0.3 mm using a syringe pump, and a voltage of 46 kV was applied between the nozzle and a grounded collector. Polyvinyl butyral fibers were produced on the collector by electrospinning. The spinning solution temperature during electrospinning was 25°C. The average fiber diameter was 510 nm, and the basis weight of the fiber layer was 3 g / m². 2 The obtained fibers were as follows. A scanning electron microscope image of the obtained fibers is shown in Figure 1. Next, the obtained fibers were brought into contact with water and their shape was observed using a scanning electron microscope. Even after contact with water, the average fiber diameter of the fibers was 510 nm, and there were no significant changes in dimensions or shape compared to before contact with water. A scanning electron microscope image of the obtained fibers after contact with water is shown in Figure 2.

[0031] (2) Step of forming a coating layer on the mold The polyvinyl butyral fibers were placed in a vacuum deposition apparatus. The polyvinyl butyral fibers were coated with silver by vacuum deposition. The silver film thickness was 150 nm. A scanning electron microscope image of the silver-coated fibers is shown in Figure 3.

[0032] (3) Step of removing the mold to obtain the nanostructure The polyvinyl butyral fibers coated with silver were removed from the aforementioned silver-coated polyvinyl butyral fibers by dissolution treatment to obtain a nonwoven fabric-like nanostructure made of slit-containing silver nanotubes. Ethanol was used as the solvent for the dissolution treatment. The solvent temperature was 25°C. Scanning electron microscope images of the nanostructure made of slit-containing silver nanotubes obtained in Example 1 of this application are shown in Figures 4 and 5. Figure 5 is an overall view of the nanostructure observed from the opposite direction to that in Figure 4. [Industrial applicability]

[0033] According to the present invention, it is possible to manufacture a nonwoven fabric-like nanostructure made of slit-type metal nanotubes without the dimensions or shape of the mold changing due to the influence of water, such as moisture in the air or sweat emitted from the human body. This structure can be suitably used as a filter material, catalyst, sound-absorbing material, waterproof and breathable membrane, battery separator, cell culture substrate, and the like.

Claims

1. A method for manufacturing nanostructures, comprising forming a coating layer on a mold made of polyvinyl butyral, and then removing the mold by dissolving it in a solvent.

2. The method for producing a nanostructure according to claim 1, wherein the shape of the material used as a template is a fiber.

3. The method for producing a nanostructure according to claim 2, wherein the diameter of the fiber shape of the mold is 1 to 1000 nm.

4. The method for producing a nanostructure according to any one of claims 1 to 3, wherein the coating layer is a metal or a metal oxide.

5. The method for manufacturing a nanostructure according to any one of claims 1 to 3, wherein the thickness of the coating layer is 1 to 1000 nm.

6. The method for producing a nanostructure according to any one of claims 1 to 3, wherein the solvent is methanol, ethanol, 2-propanol, 1-butanol, or a solvent comprising at least one of these.

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