Cellulose nanofiber dispersed aqueous resin reinforced material

Abstract

To provide a cellulose nanofiber-dispersed aqueous resin reinforced material that is lightweight and excellent in elastic modulus.SOLUTION: A cellulose nanofiber-dispersed aqueous resin reinforced material has a cellulose nanofiber-dispersed aqueous resin in which cellulose nanofibers and an aqueous resin are impregnated into at least one substrate selected from the group consisting of a woven fabric, a nonwoven fabric, bamboo, paper, and wood (where, when the substrate is a woven fabric and / or a nonwoven fabric, the aqueous resin is not a thermoplastic resin).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a cellulose nanofiber-dispersed aqueous resin-reinforced material. [Background technology]

[0002] Carbon fiber reinforced polymer (CFRP) is increasingly being used in products requiring both lightness and strength, from components for automobiles and aircraft to sporting goods. For example, in sporting goods, there is a demand for "lighter and stronger materials," leading to the increased use of lightweight and high-strength CFRP. However, in the case of baseball bats, for instance, repeated impacts with the ball cause cracks to form on the surface and inside the CFRP, so the CFRP layer is thickened to increase its static and impact strength. In these products, a 20% improvement in the static and impact strength of CFRP would allow for thinner layers and a 15-30% weight reduction, resulting in a significantly lighter and more agile swing for the user. However, further improvements in the static and impact strength of CFRP are difficult.

[0003] Incidentally, cellulose nanofiber (CNF) is an environmentally friendly nanofiber that can be refined from wood and other materials, and is both lightweight and strong. However, controlling the dispersion of CNF in the base resin is extremely difficult, and hydrophobic modification techniques and the use of organic solvents are generally being considered. For this reason, it is generally considered difficult to apply CNF to CFRP without hydrophobic treatment.

[0004] Therefore, Patent Document 1 shows that by forming a cellulose nanofiber layer on at least one side of a carbon fiber reinforced plastic layer, that is, by forming the carbon fiber reinforced plastic and cellulose nanofiber as separate layers, it is possible to achieve a lightweight material with excellent impact strength. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2019 / 221155 [Overview of the project] [Problems that the invention aims to solve]

[0006] Patent Document 1 describes reinforcement by providing a cellulose nanofiber layer, but if carbon fiber reinforced plastic and cellulose nanofibers are made into separate layers, lamination is time-consuming, and the need to create separate layers increases working time and costs.

[0007] This invention was made to solve the above-mentioned problems, and aims to provide a lightweight, highly elastic, aqueous resin-reinforced cellulose nanofiber-dispersed material in a simple and low-cost manner. [Means for solving the problem]

[0008] In light of the above objectives, and after diligent research, we have discovered that, unlike conventional methods, by impregnating cellulose nanofibers and thermoplastic resin into the interior of woven fabrics, nonwoven fabrics, bamboo materials, paper materials, wood, etc., it is possible to produce aqueous resin-reinforced materials with dispersed cellulose nanofibers simply and at low cost, without having to create separate layers of carbon fiber-reinforced plastic and cellulose nanofibers. This material is lightweight and also has a high elastic modulus. Based on these findings, the inventors have conducted further research and completed the present invention. That is, the present invention encompasses the following configuration.

[0009] Item 1. A cellulose nanofiber-dispersed aqueous resin-reinforced material having a cellulose nanofiber-dispersed aqueous resin layer in which cellulose nanofibers and an aqueous resin are impregnated inside at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood (however, if the substrate is a textile and / or nonwoven fabric, the aqueous resin is not a thermoplastic resin).

[0010] Item 2. The cellulose nanofiber dispersed aqueous resin reinforced material according to Item 1, wherein the bamboo material is at least one selected from the group consisting of Moso bamboo, Japanese bamboo, and Sasa bamboo.

[0011] Item 3. The cellulose nanofiber dispersed aqueous resin reinforced material according to Item 1 or 2, wherein the paper material is at least one selected from the group consisting of Japanese paper, Western paper, processed paper, synthetic paper, and filter paper.

[0012] Item 4. A cellulose nanofiber dispersed aqueous resin reinforced material according to any one of items 1 to 3, wherein the wood is at least one selected from the group consisting of Japanese cypress, Japanese cypress, pine, Japanese cedar, Japanese red pine, Japanese larch, Ezo spruce, fir, birch, elm, beech, poplar, European spruce, European red pine, radiata pine, Douglas fir, Western hemlock, and North Pacific larch.

[0013] Item 5. A cellulose nanofiber dispersed aqueous resin reinforced material according to any one of items 1 to 4, wherein the fibers constituting the fabric are at least one selected from the group consisting of carbon fibers, glass fibers, mineral fibers, artificial mineral fibers, metal fibers, synthetic fibers, regenerated fibers, plant fibers, and animal fibers.

[0014] Item 6. The cellulose nanofiber dispersed aqueous resin reinforced material according to any one of items 1 to 5, wherein the fibers constituting the nonwoven fabric are at least one selected from the group consisting of carbon fibers, glass fibers, mineral fibers, artificial mineral fibers, metal fibers, synthetic fibers, regenerated fibers, plant fibers, and animal fibers.

[0015] Item 7. The cellulose nanofiber-dispersed aqueous resin-reinforced material according to any one of items 1 to 6, wherein the aqueous resin is at least one selected from the group consisting of thermoplastic resins, thermosetting resins, and photocurable resins.

[0016] Item 8. The cellulose nanofiber-dispersed aqueous resin reinforced material according to any one of items 1 to 7, wherein at least one side of the cellulose nanofiber-dispersed aqueous resin layer is separately provided with a carbon fiber-reinforced plastic layer.

[0017] Item 9. A method for producing a cellulose nanofiber-dispersed aqueous resin reinforcing material according to any one of Items 1 to 8, comprising: (1A) A step of immersing at least one base material selected from the group consisting of the fabric, non-woven fabric, bamboo material, paper material, and wood material in the dispersion liquid of the cellulose nanofiber and the aqueous resin, or (1B) After immersing at least one base material selected from the group consisting of the fabric, non-woven fabric, bamboo material, paper material, and wood material in the dispersion liquid of the cellulose nanofiber, impregnating at least one base material selected from the group consisting of the fabric, non-woven fabric, bamboo material, paper material, and wood material in the emulsion of the aqueous resin. A production method comprising the above.

[0018] Item 10. The production method according to Item 9, wherein in the immersion in the dispersion liquid in the step (1A) or the immersion in the emulsion in the step (1B), a roller treatment is performed.

[0019] Item 11. The production method according to Item 9 or 10, wherein in the step (1A) or (1B), the addition amount of the cellulose nanofiber is 0.1 to 100 parts by mass with respect to 100 parts by mass of at least one base material selected from the group consisting of the fabric, non-woven fabric, bamboo material, paper material, and wood material.

[0020] Item 12. The production method according to any one of Items 9 to 11, wherein in the step (1A) or (1B), the addition amount of the aqueous resin is 50 to 900 parts by mass with respect to 100 parts by mass of at least one base material selected from the group consisting of the fabric, non-woven fabric, bamboo material, paper material, and wood material.

[0021] Item 13. After the step (1A) or (1B), (2) A step of heating the cellulose nanofiber-dispersed aqueous resin reinforcing material obtained in the step (1) to remove moisture. The production method according to any one of Items 9 to 12, comprising the above.

[0022] Item 14. After the step (2), (3) A process of heating and molding the obtained cellulose nanofiber dispersed aqueous resin reinforced material under pressure. The manufacturing method according to item 13, comprising:

[0023] Item 15. The manufacturing method according to Item 14, wherein the molding pressure in step (3) is 5 MPa or more. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide a lightweight cellulose nanofiber-dispersed aqueous resin-reinforced material with excellent elastic modulus without the need for hydrophobic treatment. [Brief explanation of the drawing]

[0025] [Figure 1] The appearance of the test specimen obtained in Example 1 is shown. [Figure 2] The results of Test Example 1 are shown below. [Figure 3] The appearance of the test specimen obtained in Example 2 is shown. [Figure 4] The appearance of the test specimen obtained in Example 3 is shown. [Figure 5] The results of Test Example 3 are shown below. [Modes for carrying out the invention]

[0026] In this specification, "contains" is a concept that encompasses all of the following: "contains," "consist essentially of," and "consist of."

[0027] Furthermore, in this specification, when a numerical range is indicated as "A to B", it means A or greater and B or less.

[0028] 1. Cellulose nanofiber dispersed aqueous resin reinforced material The cellulose nanofiber-dispersed aqueous resin-reinforced material of the present invention has a cellulose nanofiber-dispersed aqueous resin in which cellulose nanofibers and an aqueous resin are impregnated inside at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood.

[0029] With this configuration, the presence of aqueous resin allows cellulose nanofibers to efficiently impregnate at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood, and also improves the elastic modulus through capillary action. This enables the production of aqueous resin-reinforced materials with dispersed cellulose nanofibers, resulting in materials that are both lightweight and highly elastic. Conversely, this makes it possible to reduce the amount of carbon fiber-reinforced plastic previously required to achieve the desired elastic modulus, leading to resource conservation. Furthermore, because cellulose nanofibers are lighter than carbon fiber-reinforced plastics, this can also contribute to the weight reduction of products.

[0030] (1-1) Cellulose nanofiber dispersed aqueous resin layer Base material The base material can be woven fabric, nonwoven fabric, bamboo, paper, wood, etc.

[0031] The fibers that make up the fabric are not particularly limited, and a wide range of inorganic fibers can be used, such as carbon fibers (PAN-based carbon fibers, pitch-based carbon fibers, carbon nanotubes, etc.), glass fibers (glass wool, glass fiber, etc.), mineral fibers (hot asbestos, white asbestos, blue asbestos, brown asbestos, orthophthalmic asbestos, tremolite asbestos, sunflower asbestos, etc.), artificial mineral fibers (rock wool, ceramic fiber, etc.), and metal fibers (stainless steel fibers, aluminum fibers, iron fibers, nickel fibers, copper fibers, etc.); synthetic fibers (nylon fibers, polyester fibers, acrylic fibers, vinylon fibers, polyolefin fibers, polyethylene fibers, polypropylene fibers, polyurethane fibers, etc.), regenerated fibers (rayon, polynosic, cupro, lyocell, acetate, etc.), plant fibers (cotton fibers, hemp fibers, flax fibers, etc.), and animal fibers (wool, silk, wild silk, mohair, cashmere, camel, llama, alpaca, vicuña, angora, spider silk, etc.). These fibers can be used individually or in combination of two or more types. Among these, inorganic fiber fabrics are preferred from the viewpoint of lightness and elastic modulus, carbon fiber fabrics, glass fiber fabrics, mineral fiber fabrics, artificial mineral fiber fabrics, metal fiber fabrics, etc. are more preferred, and carbon fiber fabrics are even more preferred.

[0032] The fiber form can be any of the following: continuous long fibers, short fibers obtained by cutting continuous long fibers, or milled yarn obtained by grinding into a powder.

[0033] The thickness of the fabric may vary depending on the type of fiber and is not particularly limited. From the viewpoint of lightness, elastic modulus, etc., the thickness of the fabric can be, for example, 50 μm to 30 mm, preferably 100 μm to 10 mm.

[0034] The basis weight of the fabric is not particularly limited, but from the viewpoint of lightness, elastic modulus, etc., for example, 5 to 300 g / m 2 Preferably 10-200 g / m² 2 It can be done this way.

[0035] The filament diameter of the fibers constituting the yarn in a woven fabric is not particularly limited, but from the viewpoint of lightness, elastic modulus, etc., it can be, for example, 5 to 20 μm, preferably 5 to 10 μm.

[0036] The yarns that make up the fabric can also be in the form of fiber bundles. From the viewpoint of lightness, elastic modulus, etc., the fiber bundles are preferably made up of, for example, 500 to 8000 filaments (yarns), and more preferably 1000 to 6000 filaments (yarns).

[0037] The above fibers may have known finishing agents attached to them, such as flame retardants, water absorbents, water repellents, softeners, heat storage agents, ultraviolet shielding agents, antistatic agents, antibacterial agents, deodorizers, insect repellents, mosquito repellents, phosphorescent agents, retroreflective agents, and sizing agents.

[0038] The fibers that make up the nonwoven fabric are not particularly limited, and a wide range of inorganic fibers can be used, such as carbon fibers (PAN-based carbon fibers, pitch-based carbon fibers, carbon nanotubes, etc.), glass fibers (glass wool, glass fiber, etc.), mineral fibers (hot asbestos, white asbestos, blue asbestos, brown asbestos, orthophthalmic asbestos, tremolite asbestos, sunflower asbestos, etc.), artificial mineral fibers (rock wool, ceramic fiber, etc.), and metal fibers (stainless steel fibers, aluminum fibers, iron fibers, nickel fibers, copper fibers, etc.); synthetic fibers (nylon fibers, polyester fibers, acrylic fibers, vinylon fibers, polyolefin fibers, polyethylene fibers, polypropylene fibers, polyurethane fibers, etc.), regenerated fibers (rayon, polynosic, cupro, lyocell, acetate, etc.), plant fibers (cotton fibers, hemp fibers, flax fibers, etc.), and animal fibers (wool, silk, wild silk, mohair, cashmere, camel, llama, alpaca, vicuña, angora, spider silk, etc.). These fibers can be used individually or in combination of two or more types. Among these, nonwoven fabrics using inorganic fibers are preferred from the viewpoint of lightness and elastic modulus, nonwoven fabrics using carbon fiber fabrics, glass fiber fabrics, mineral fiber fabrics, artificial mineral fiber fabrics, metal fiber fabrics, etc. are more preferred, and carbon nonwoven fabrics using carbon fiber fabrics are even more preferred.

[0039] The fiber form can be any of the following: continuous long fibers, short fibers obtained by cutting continuous long fibers, or milled yarn obtained by grinding into a powder.

[0040] The thickness of the nonwoven fabric may vary depending on the type of fiber and is not particularly limited. From the viewpoint of lightness, elastic modulus, etc., the thickness of the nonwoven fabric can be, for example, 50 μm to 30 mm, preferably 100 μm to 10 mm.

[0041] The basis weight of the nonwoven fabric is not particularly limited, but from the viewpoint of lightness, elastic modulus, etc., for example, 10 to 500 g / m² is suitable. 2 Preferably 20-200 g / m 2 It can be done this way.

[0042] The above fibers may have known finishing agents attached to them, such as flame retardants, water absorbents, water repellents, softeners, heat storage agents, ultraviolet shielding agents, antistatic agents, antibacterial agents, deodorizers, insect repellents, mosquito repellents, phosphorescent agents, retroreflective agents, and sizing agents.

[0043] While there are no particular restrictions on the type of bamboo used, various types of bamboo, such as Moso bamboo, Japanese bamboo, and Sasa bamboo, can be employed. These bamboo types can be used individually or in combination of two or more. Among these, Moso bamboo is preferred from the viewpoint of lightness and elastic modulus.

[0044] These bamboo materials can be used as is after felling, or they can be crushed into smaller pieces. Alternatively, the felled bamboo can be processed into flat sheets using conventional methods.

[0045] The thickness of the bamboo material may vary depending on the type of bamboo and is not particularly limited. From the viewpoint of lightness, elastic modulus, etc., the thickness of the bamboo material can be, for example, 300 μm to 10 mm, preferably 500 μm to 5 mm.

[0046] While there are no particular restrictions on the type of paper used, various types of paper can be employed, such as Japanese paper (washi), Western paper (yoto paper), processed paper, synthetic paper, and filter paper. Furthermore, papers conventionally used for other purposes, such as newsprint, printing paper (including high-quality paper), writing paper, drawing paper, packaging paper, tissue paper, and miscellaneous paper, can be used unprocessed or processed. When using tissue paper, examples include thin imitation paper, Indian paper, rice paper, glassine paper, tissue paper, and toilet paper. These paper materials are preferably those that have not undergone hydrophobic treatment such as hydrophobic coating. These paper materials can be used individually or in combination of two or more types. Among these, Japanese paper (washi), tissue paper (thin imitation paper, Indian paper, rice paper, glassine paper, tissue paper, toilet paper, etc.), and filter paper are preferred from the viewpoint of lightness and elastic modulus.

[0047] The thickness of the paper material is not particularly limited. From the viewpoint of lightness, elastic modulus, etc., the thickness of the paper material can be, for example, 10 μm to 3 mm, preferably 100 μm to 2 mm.

[0048] While there are no particular restrictions on the type of wood used, various types of wood can be employed, including Japanese cypress (sawara), hinoki cypress (hinoki), pine (matsu), cedar (sugi), Japanese red pine (akamatsu), Japanese larch (karamatsu), Ezo spruce (ezo pine), fir (tozo), birch (kaba), elm (nier), beech (funa), poplar (poplar), European spruce (suede), European red pine (suzume), radiata pine (radiata pine), Douglas fir (shiga), Western hemlock (tsuga), and North Pacific larch (karamatsu). These woods can be used individually or in combination of two or more types. Among these, Japanese cypress (sawara) and cedar (sugi) are preferred from the viewpoint of lightness and elastic modulus (modulus of elasticity).

[0049] These timbers can be used as they are after being felled, or they can be crushed into smaller pieces.

[0050] The thickness of the wood can vary depending on the type of wood and is not particularly limited. From the viewpoint of lightness, elastic modulus, etc., the thickness of the wood can be, for example, 300 μm to 10 mm, preferably 500 μm to 5 mm.

[0051] Cellulose nanofibers A wide range of known cellulose nanofibers can be used, and there are no particular limitations. Furthermore, any of the cellulose constituting the cellulose nanofibers—plant-derived cellulose, animal-derived cellulose, or bacterial-derived cellulose—can be suitably used. These may be used individually or in combination of two or more.

[0052] Plant-derived cellulose can be selected from, for example, broadleaf tree cellulose (eucalyptus, poplar, etc.), coniferous tree cellulose (pine, fir, cedar, cypress, etc.), herbaceous plant cellulose (straw, bagasse, reed, kenaf, abaca, sisal, etc.), and seed hair fibers (cotton, etc.). The pulp used as raw material may be mechanically processed wood chips (mechanically produced pulp), chemically processed wood chips (chemically produced pulp from which non-cellulose components have been chemically removed), or dissolved pulp refined by further removal of non-cellulose components.

[0053] In addition, animal-derived cellulose such as that found in sea squirts, and bacterial-derived cellulose such as that found in nata de coco, can also be used. Furthermore, such cellulose does not necessarily have to consist solely of pure cellulose components; it may contain non-cellulose components as an adjunct to the main cellulose component. Of course, it may also consist solely of pure cellulose components.

[0054] There are no particular limitations on the main non-cellulose components associated with cellulose nanofibers, and they can be appropriately selected depending on the application. For example, hemicellulose and lignin can be mentioned.

[0055] Furthermore, the ratio of pure cellulose components in cellulose nanofibers can be appropriately set according to the application. For example, the ratio of pure cellulose components is preferably 70% by mass or more, and more preferably 80% by mass or more, per 100% by mass of cellulose nanofibers. The upper limit for the ratio of pure cellulose components can be 100% by mass. In this specification, the cellulose ratio is the ratio of pure cellulose components, in which β-glucose molecules are polymerized linearly by glycosidic bonds, to 100% by mass of the total mass of cellulose nanofibers.

[0056] The degree of polymerization of the pure cellulose component contained in cellulose nanofibers can also be set appropriately depending on the application. For example, cellulose components with a degree of polymerization of 500 or higher, especially 600 or higher, can be used. There is no particular upper limit on the degree of polymerization of the cellulose component, but it can be set to, for example, 100,000.

[0057] There are no particular restrictions on the crystallinity of the pure cellulose component contained in the cellulose nanofibers, but 60% or more is preferred, and 70% or more is more preferred. There are no particular upper limits on the crystallinity of cellulose, but for example, it can be 99%. The crystalline structure of the cellulose component can be type I, type II, type III, and type IV.

[0058] There are no particular restrictions on the size of the cellulose nanofibers. However, when employing the manufacturing method of the present invention described later, a diameter of 10 to 500 nm and a length of 100 nm or more are preferred from the viewpoints of dispersibility, lightness, and elastic modulus. In this specification, the diameter of the cellulose nanofiber is the median diameter obtained by observing 50 or more randomly extracted cellulose nanofibers with a scanning electron microscope (SEM).

[0059] Water-based resin There are no particular restrictions on the water-based resin; for example, thermoplastic resins, thermosetting resins, photocurable resins, etc., can be used.

[0060] There are no particular restrictions on the thermoplastic resin, and examples include urethane resin, polyolefin resin (polyethylene resin, polypropylene resin, etc.), polyester resin, polyamide resin, polystyrene resin, vinyl resin (polyvinyl chloride resin, polyvinyl acetate resin, polyvinylidene chloride resin, etc.), polyvinyl alcohol resin, polycarbonate resin, polyacetal resin, ethylene vinyl acetate copolymer resin, acrylonitrile butadiene styrene copolymer resin (ABS resin), etc.

[0061] There are no particular limitations on the thermosetting resin, and examples include epoxy resins, phenolic resins (novolac resins, etc.), acrylic resins, nylon resins, vinyl resins, polyamide resins, polyimide resins, polyamide-imide resins, polystyrene resins, polycarbonate resins, polyolefin resins, polyesters, polyethylene terephthalate, polyethylene naphthalate, and polyethersulfone.

[0062] There are no particular restrictions on the photocurable resin, but UV-curable resins are preferred, such as methacrylate, acrylate (especially urethane acrylate, epoxy acrylate, acrylic acrylate), unsaturated polyester, epoxy resin, oxetane resin, etc.

[0063] These aqueous resins can be used individually or in combination of two or more. These aqueous resins are suitable for impregnation into at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood. From the viewpoint of lightness, elastic modulus, etc., thermoplastic resins such as urethane resins, polyolefin resins, polyester resins, and polyamide resins are preferred; thermosetting resins such as epoxy resins, phenolic resins (novolac resins, etc.), and acrylic resins are preferred; and photocurable resins such as methacrylate and acrylate are preferred. However, in this invention, when the substrate is a woven fabric and / or nonwoven fabric, the aqueous resin is not a thermoplastic resin, but rather a thermosetting resin and / or a photocurable resin.

[0064] Cellulose nanofiber dispersed aqueous resin layer As described above, the cellulose nanofiber-dispersed aqueous resin layer has cellulose nanofibers and an aqueous resin impregnated into the interior of at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood. Unlike conventional methods where the cellulose nanofiber layer is separate from the carbon fiber-reinforced plastic layer, the cellulose nanofibers and thermoplastic resin are impregnated into the interior of at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood. In other words, conventionally, reinforcement was achieved by providing a distinct cellulose nanofiber layer, but in the present invention, by impregnating cellulose nanofiber-dispersed thermoplastic resin into woven fabrics, nonwoven fabrics, bamboo, paper, wood, etc., a lightweight cellulose nanofiber-dispersed thermoplastic resin-reinforced material with excellent elastic modulus can be obtained without providing a distinct cellulose nanofiber layer. This eliminates the distinct interface with the CFRP layer that would occur if a distinct cellulose nanofiber layer were provided, and improves strength.

[0065] In the cellulose nanofiber-dispersed aqueous resin-reinforced material of the present invention, according to the manufacturing method described later, at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood is immersed in a dispersion of cellulose nanofibers and the aqueous resin, or at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood is immersed in a dispersion of cellulose nanofibers, and then at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood is impregnated with an emulsion of aqueous resin. Therefore, it is difficult to precisely specify the content of various components in the cellulose nanofiber-dispersed aqueous resin layer. However, from the viewpoint of lightness, elastic modulus, etc., the content of cellulose nanofibers is preferably 0.1 to 100 parts by mass, and more preferably 0.5 to 20 parts by mass, per 100 parts by mass of at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood.

[0066] In the cellulose nanofiber-dispersed aqueous resin-reinforced material of the present invention, according to the manufacturing method described later, at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood is immersed in a dispersion of cellulose nanofibers and the aqueous resin, or at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood is immersed in a dispersion of cellulose nanofibers, and then at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood is impregnated with an emulsion of aqueous resin. Therefore, it is difficult to precisely specify the content of various components in the cellulose nanofiber-dispersed aqueous resin layer. However, from the viewpoint of lightness, elastic modulus, etc., the content of the aqueous resin is preferably 50 to 900 parts by mass, and more preferably 100 to 300 parts by mass, per 100 parts by mass of at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood.

[0067] (1-2) Carbon fiber reinforced plastic layer The cellulose nanofiber-dispersed aqueous resin reinforced material of the present invention may consist solely of the above-mentioned cellulose nanofiber-dispersed aqueous resin layer, but it may also be provided with a carbon fiber-reinforced plastic layer on at least one side of the above-mentioned cellulose nanofiber-dispersed aqueous resin layer. In this invention, the carbon fiber-reinforced plastic layer is a layer containing carbon fiber-reinforced plastic.

[0068] This carbon fiber reinforced plastic typically employs a layer in which carbon fibers are impregnated with an aqueous resin. In other words, it has a structure in which carbon fibers are dispersed in an aqueous resin matrix.

[0069] In this case, the carbon fiber material is not particularly limited as long as it is a structure made of carbon fibers (especially a structure made of conductive carbon fibers). Examples include planar carbon fiber sheets, pipe-shaped carbon fiber sheets, wing-shaped carbon fiber sheets, L-shaped carbon fiber sheets, H-shaped carbon fiber sheets, etc. In particular, not only carbon fiber materials in which carbon fibers are arranged in a straight line, but also carbon fiber materials with complex three-dimensional shapes can be used. From the viewpoint of lightness, elastic modulus, etc., the fiber diameter of a single carbon fiber constituting such a carbon fiber material is preferably 0.001 to 50 μm on average. Known or commercially available carbon fiber materials can be used for such materials.

[0070] There are no particular restrictions on the water-based resin; for example, thermoplastic resins, thermosetting resins, photocurable resins, etc., can be used.

[0071] There are no particular restrictions on the thermoplastic resin, and examples include urethane resin, polyolefin resin (polyethylene resin, polypropylene resin, etc.), polyester resin, polyamide resin, polystyrene resin, vinyl resin (polyvinyl chloride resin, polyvinyl acetate resin, polyvinylidene chloride resin, etc.), polyvinyl alcohol resin, polycarbonate resin, polyacetal resin, ethylene vinyl acetate copolymer resin, acrylonitrile butadiene styrene copolymer resin (ABS resin), etc.

[0072] There are no particular limitations on the thermosetting resin, and examples include epoxy resins, phenolic resins (novolac resins, etc.), acrylic resins, nylon resins, vinyl resins, polyamide resins, polyimide resins, polyamide-imide resins, polystyrene resins, polycarbonate resins, polyolefin resins, polyesters, polyethylene terephthalate, polyethylene naphthalate, and polyethersulfone.

[0073] There are no particular restrictions on the photocurable resin, but UV-curable resins are preferred, such as methacrylate, acrylate (especially urethane acrylate, epoxy acrylate, acrylic acrylate), unsaturated polyester, epoxy resin, oxetane resin, etc.

[0074] These aqueous resins can be used individually or in combination of two or more. From the viewpoint of lightness, elastic modulus, etc., preferred aqueous resins include thermoplastic resins such as urethane resins, polyolefin resins, polyester resins, and polyamide resins; preferred thermosetting resins such as epoxy resins, phenolic resins (novolac resins, etc.), and acrylic resins; and preferred photocurable resins such as methacrylates and acrylates.

[0075] The thickness of such a carbon fiber reinforced plastic layer is preferably 10 to 500 μm, and more preferably 50 to 200 μm, from the viewpoint of lightness, elastic modulus, etc.

[0076] Since the carbon fiber reinforced plastic layer employs a layer in which carbon fibers are impregnated with thermoplastic resin, it is difficult to precisely determine the content of various components. However, from the viewpoint of lightness, elastic modulus, etc., the content of aqueous resin is preferably 50 to 900 parts by mass, and more preferably 100 to 300 parts by mass, per 100 parts by mass of carbon fiber.

[0077] (1-3) Cellulose nanofiber dispersed aqueous resin reinforced material As described above, the cellulose nanofiber-dispersed aqueous resin-reinforced material of the present invention has at least a cellulose nanofiber-dispersed aqueous resin layer, and may optionally include a carbon fiber-reinforced plastic layer.

[0078] The structure of the cellulose nanofiber-dispersed aqueous resin reinforced material of the present invention is not particularly limited as long as it has a cellulose nanofiber-dispersed aqueous resin layer. It is also possible to adopt a configuration in which at least one cellulose nanofiber-dispersed aqueous resin layer is arranged between two carbon fiber-reinforced plastic layers, or a configuration in which carbon fiber-reinforced plastic layers and cellulose nanofiber-dispersed aqueous resin layers are arranged alternately.

[0079] According to the present invention, a lightweight cellulose nanofiber-dispersed aqueous resin-reinforced material with excellent elastic modulus can be obtained, making it possible to manufacture lightweight sports equipment that could not be achieved with conventional technology. Specifically, it is expected to be put into practical use in golf clubs (entire body), tennis rackets (frame, shaft, etc.), baseball / softball bats (entire body), badminton rackets (frame, shaft, etc.), shoes (sole and internal plate), flower vases, tea ceremony utensils, tea ceremony tools (tea scoop, ladle, whisk, fan, etc.), landscaping materials, paper products, leather, etc.

[0080] For example, in baseball and softball bats, repeated hitting of the ball can cause fractures in the surface and carbon fiber layers, so the carbon fiber layer is made thicker to increase durability. According to the present invention, a cellulose nanofiber dispersed aqueous resin reinforced material with excellent elastic modulus can be obtained, making it possible to reduce the carbon fiber layer and thus reduce weight.

[0081] Furthermore, while badminton rackets and similar equipment do not break in the frame or shaft simply from hitting the shuttlecock, they are often accidentally hit with objects other than the shuttlecock, so it is necessary to ensure a certain modulus of elasticity in the product. In addition, high-modulus carbon fiber is sometimes used to reduce the weight of the shaft, but in that case, the modulus of elasticity tends to be low, so the carbon fiber layer is made thicker to improve durability. According to the present invention, a cellulose nanofiber dispersed aqueous resin reinforced material with excellent modulus of elasticity can be obtained, making it possible to reduce the carbon fiber layer and thus reduce weight.

[0082] Carbon fiber reinforced plastic materials, which have become popular in the sports market, are very often being expanded into aerospace and industrial applications. Therefore, in addition to the aforementioned applications in sports equipment, they can also be applied to automobile bodies and parts, aircraft bodies and parts, and highway ETC gate bars, where further weight reduction is being pursued.

[0083] Furthermore, in Japan, where the aging of society is accelerating, maintaining the health of the elderly is a major challenge. As the elderly gradually experience a decline in physical strength and muscle mass, mobility becomes increasingly difficult. By using the cellulose nanofiber dispersed aqueous resin reinforced material of the present invention, it becomes possible to develop lightweight and highly durable products for clothing, shoes, and orthotics that support walking for the elderly, making them useful for products aimed at the elderly.

[0084] 2. Method for producing a cellulose nanofiber-dispersed aqueous resin-reinforced material The method for producing the cellulose nanofiber-dispersed aqueous resin-reinforced material of the present invention is not particularly limited, (1A) A step of immersing at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood in a dispersion of cellulose nanofibers and the aqueous resin, or (1B) A step of immersing at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood in a dispersion of cellulose nanofibers, and then impregnating at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood with an emulsion of aqueous resin. It is equipped with.

[0085] By employing this method, even without hydrophobic treatment of the cellulose nanofibers in step (1A) or (1B), the presence of the aqueous resin allows the cellulose nanofibers to efficiently impregnate into at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood, and also improves the elastic modulus through capillary action.

[0086] Furthermore, by adopting this method, it is possible to improve the elastic modulus by using cellulose nanofibers. Conversely, this also makes it possible to reduce the amount of carbon fiber reinforced plastic that was conventionally required to achieve the desired elastic modulus, which can lead to resource conservation. In addition, since cellulose nanofibers are lighter than carbon fiber reinforced plastics, this can lead to lighter products, and especially improved fuel efficiency in mobile devices (automobiles, aircraft, etc.).

[0087] (2-1) Process (1A) As the substrate, at least one selected from the group consisting of cellulose nanofibers, aqueous resins, and textiles, nonwoven fabrics, bamboo, paper, and wood, the one described in "(1-1) Cellulose nanofiber dispersed aqueous resin layer" above can be used. The preferred embodiments are also the same. In addition, a microgel can be used as the aqueous resin.

[0088] The dispersion of cellulose nanofibers and aqueous resin further contains a solvent (such as monoalcohols like methanol, ethanol, propanol, isopropanol, and butanol). Examples of polyhydric alcohols include ethylenediols such as ethylene glycol, diethylene glycol, thiodiethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol; propanediols such as 2-methyl-1,3-propanediol, 2-ethyl-1,3-propanediol, and 3-methoxy-1,2-propanediol; butanediols such as 2-butene-1,4-diol, 1,3-butanediol, and 2-methyl-1,4-butanediol; 2-methyl-2,4-pentanediol, 1,5-pentanediol, 1,4-pentanediol, and 3-methyl-1,3-pentanediol. Pentanediols such as pentanediol and 2,4-diethyl-1,5-pentanediol; hexanediols such as 1,2-hexanediol; heptanediols such as 1,2,6-trimethyl-1,7-heptanediol and 2,4,6-triethyl-1,7-heptanediol; octanediols such as 3,6-dithia-1,8-octanediol; other alkylenediols such as propylene glycol, dipropylene glycol, polypropylene glycol, and butylene glycol; polyols such as glycerin, hexanetriol, thiodiglycol, and trimethylolpropane; acetylene alcohol, etc. Examples of glycol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, triethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether, propylene glycol monopropyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether, etc. Examples of amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine, etc. Other polar solvents may include, for example, formamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 3-methylsulfolane, 3-sulfolene, bis(2-hydroxyethyl)sulfone, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-pyrrolidone-5-carboxylic acid, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone, diacetone alcohol, 4-picoline, etc., as well as pigments (carbon, titanium dioxide, lead silicate, aluminum phosphate, bismuth hydroxide, yttrium hydroxide, aluminum silicate, talc, etc.), functional agents (microgels, etc.), acids (acetic acid, lactic acid, formic acid, propionic acid, sulfamic acid, etc.).

[0089] Thus, by immersing at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood in a dispersion of cellulose nanofibers and aqueous resin, the cellulose nanofibers and aqueous resin can be impregnated into the interior of at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood.

[0090] The amount of each component used (amount added) is not particularly limited, but the amount of cellulose nanofiber and aqueous resin used (amount added) can be adjusted so that it falls within the above-mentioned content range. However, according to the manufacturing method of the present invention, when at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood is immersed in a dispersion of cellulose nanofiber and aqueous resin, it is also possible to use more cellulose nanofiber and aqueous resin than the above-mentioned content, assuming that only a portion of the cellulose nanofiber and aqueous resin may be impregnated into the interior of the at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood. For this reason, the amount of cellulose nanofiber used (amount added) is preferably 0.1 to 100 parts by mass, and more preferably 0.5 to 20 parts by mass, per 100 parts by mass of the at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood. Furthermore, the amount of thermoplastic resin used (amount added) is preferably 50 to 900 parts by mass, and more preferably 100 to 300 parts by mass, per 100 parts by mass of woven fabric and / or nonwoven fabric.

[0091] In the manufacturing method of the present invention, in a dispersion of cellulose nanofibers and aqueous resin, the aqueous resin (particularly the microgel of the aqueous resin) is thought to penetrate the network structure (=mesh-like) of the cellulose nanofibers, and, in conjunction with the action of polymer functional groups, is uniformly dispersed. When at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood is immersed in the dispersion in this state, the cellulose nanofibers, along with the aqueous resin that has penetrated their network structure, can be impregnated into the interior of at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood.

[0092] In the manufacturing method of the present invention, there are no restrictions on the temperature at which at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood is immersed in a dispersion of cellulose nanofibers and aqueous resin. However, from the viewpoint of easily impregnating the cellulose nanofibers and aqueous resin into the interior of at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood, a temperature of 10 to 90°C is preferred, and 20 to 70°C is more preferred.

[0093] In the manufacturing method of the present invention, there is no limit to the time for immersing at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood in a dispersion of cellulose nanofibers and aqueous resin. However, from the viewpoint of easily impregnating the cellulose nanofibers and aqueous resin into the interior of at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood, 0.5 to 48 hours is preferred, and 2 to 6 hours is more preferred.

[0094] As described above, it is also possible to perform roller treatment after step (1A). By performing roller treatment, the gaps between the cellulose nanofibers and aqueous resin can be reduced, making it easier to further impregnate the cellulose nanofibers and aqueous resin into the interior of at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood.

[0095] While there are no particular limitations on the roller treatment method, it can be carried out according to conventional procedures.

[0096] In the method for producing a cellulose nanofiber-dispersed aqueous resin-reinforced material of the present invention, the above step (1A) can be repeated multiple times (especially 2 to 3 times). This makes it easier to further impregnate the cellulose nanofibers and aqueous resin into at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood.

[0097] (2-2) Process (1B) As the substrate, at least one selected from the group consisting of cellulose nanofibers, aqueous resins, and textiles, nonwoven fabrics, bamboo, paper, and wood, the one described in "(1-1) Cellulose nanofiber dispersed aqueous resin layer" above can be used. The preferred embodiments are also the same. In addition, a microgel can be used as the aqueous resin.

[0098] The dispersion of cellulose nanofibers further contains a solvent (such as monoalcohols like methanol, ethanol, propanol, isopropanol, and butanol). Examples of polyhydric alcohols include ethylenediols such as ethylene glycol, diethylene glycol, thiodiethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol; propanediols such as 2-methyl-1,3-propanediol, 2-ethyl-1,3-propanediol, and 3-methoxy-1,2-propanediol; butanediols such as 2-butene-1,4-diol, 1,3-butanediol, and 2-methyl-1,4-butanediol; 2-methyl-2,4-pentanediol, 1,5-pentanediol, 1,4-pentanediol, and 3-methyl-1,3-pentanediol. Pentanediols such as pentanediol and 2,4-diethyl-1,5-pentanediol; hexanediols such as 1,2-hexanediol; heptanediols such as 1,2,6-trimethyl-1,7-heptanediol and 2,4,6-triethyl-1,7-heptanediol; octanediols such as 3,6-dithia-1,8-octanediol; other alkylenediols such as propylene glycol, dipropylene glycol, polypropylene glycol, and butylene glycol; polyols such as glycerin, hexanetriol, thiodiglycol, and trimethylolpropane; acetylene alcohol, etc. Examples of glycol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, triethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether, propylene glycol monopropyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether, etc. Examples of amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine, etc. Other polar solvents may include, for example, formamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 3-methylsulfolane, 3-sulfolene, bis(2-hydroxyethyl)sulfone, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-pyrrolidone-5-carboxylic acid, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone, diacetone alcohol, 4-picoline, etc., pigments (carbon, titanium dioxide, lead silicate, aluminum phosphate, bismuth hydroxide, yttrium hydroxide, aluminum silicate, talc, etc.), functional agents (microgels, etc.), acids (acetic acid, lactic acid, formic acid, propionic acid, sulfamic acid, etc.).

[0099] Water-based resin emulsions also contain solvents (such as monoalcohols like methanol, ethanol, propanol, isopropanol, and butanol). Examples of polyhydric alcohols include ethylenediols such as ethylene glycol, diethylene glycol, thiodiethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol; propanediols such as 2-methyl-1,3-propanediol, 2-ethyl-1,3-propanediol, and 3-methoxy-1,2-propanediol; butanediols such as 2-butene-1,4-diol, 1,3-butanediol, and 2-methyl-1,4-butanediol; 2-methyl-2,4-pentanediol, 1,5-pentanediol, 1,4-pentanediol, and 3-methyl-1,3-pentanediol. Pentanediols such as pentanediol and 2,4-diethyl-1,5-pentanediol; hexanediols such as 1,2-hexanediol; heptanediols such as 1,2,6-trimethyl-1,7-heptanediol and 2,4,6-triethyl-1,7-heptanediol; octanediols such as 3,6-dithia-1,8-octanediol; other alkylenediols such as propylene glycol, dipropylene glycol, polypropylene glycol, and butylene glycol; polyols such as glycerin, hexanetriol, thiodiglycol, and trimethylolpropane; acetylene alcohol, etc. Examples of glycol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, triethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether, propylene glycol monopropyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether, etc. Examples of amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine, etc. Other polar solvents may include, for example, formamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 3-methylsulfolane, 3-sulfolene, bis(2-hydroxyethyl)sulfone, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-pyrrolidone-5-carboxylic acid, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone, diacetone alcohol, 4-picoline, etc., as well as pigments (carbon, titanium dioxide, lead silicate, aluminum phosphate, bismuth hydroxide, yttrium hydroxide, aluminum silicate, talc, etc.), functional agents (microgels, etc.), acids (acetic acid, lactic acid, formic acid, propionic acid, sulfamic acid, etc.).

[0100] Thus, by immersing at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood in a dispersion of cellulose nanofibers, and then immersing the substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood after immersion in the cellulose nanofiber dispersion, the interior of the at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood can be impregnated with cellulose nanofibers and aqueous resin.

[0101] The amount of each component used (amount added) is not particularly limited, but the amount of cellulose nanofibers and aqueous resin used (amount added) can be adjusted so that they fall within the above-mentioned content range. However, according to the manufacturing method of the present invention, when at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood is immersed in a dispersion of cellulose nanofibers, only a portion of the cellulose nanofibers may be impregnated into the interior of the at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood, or when at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood after being immersed in a dispersion of cellulose nanofibers is immersed in an emulsion of aqueous resin, only a portion of the aqueous resin may be impregnated into the interior of the at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood, and in this case, the amount of cellulose nanofibers and aqueous resin used (amount added) can be greater than the above-mentioned content. Therefore, the amount of cellulose nanofiber used (filling amount) is preferably 0.1 to 100 parts by mass, and more preferably 0.5 to 20 parts by mass, per 100 parts by mass of at least one base material selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood. Furthermore, the amount of thermoplastic resin used (filling amount) is preferably 50 to 900 parts by mass, and more preferably 100 to 300 parts by mass, per 100 parts by mass of woven fabric and / or nonwoven fabric.

[0102] In the manufacturing method of the present invention, after immersing at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood in a dispersion of cellulose nanofibers, the at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood after immersion in the dispersion of cellulose nanofibers is immersed in an emulsion of aqueous resin. At this time, the aqueous resin (particularly the microgel of the aqueous resin) penetrates the network structure (=mesh-like) of the cellulose nanofibers, and in conjunction with the action of polymer functional groups, it is uniformly dispersed, and the cellulose nanofibers, along with the aqueous resin in which they have penetrated the network structure, can be impregnated into the interior of the at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood.

[0103] In the manufacturing method of the present invention, the temperature at which at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood is immersed in the dispersion of cellulose nanofibers and the emulsion of aqueous resin is not limited, but from the viewpoint of easily impregnating the cellulose nanofibers and aqueous resin into the interior of at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood, 10 to 90°C is preferred, and 20 to 70°C is more preferred.

[0104] In the manufacturing method of the present invention, there is no limit to the time for immersing at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood in a dispersion of cellulose nanofibers and an emulsion of aqueous resin. However, from the viewpoint of easily impregnating the cellulose nanofibers and aqueous resin into the interior of at least one substrate selected from the group consisting of textiles, nonwoven fabrics, bamboo, paper, and wood, 0.5 to 48 hours is preferred, and 2 to 6 hours is more preferred.

[0105] As described above, it is also possible to perform roller treatment after step (1A). By performing roller treatment, the gaps between the cellulose nanofibers and aqueous resin can be reduced, making it easier to further impregnate the cellulose nanofibers and aqueous resin into the interior of at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood.

[0106] While there are no particular limitations on the roller treatment method, it can be carried out according to conventional procedures.

[0107] In the method for producing a cellulose nanofiber-dispersed aqueous resin-reinforced material of the present invention, the above step (1A) can be repeated multiple times (especially 2 to 3 times). This makes it easier to further impregnate the cellulose nanofibers and aqueous resin into at least one substrate selected from the group consisting of woven fabrics, nonwoven fabrics, bamboo, paper, and wood.

[0108] (2-3) Process (2) In the method for producing a cellulose nanofiber-dispersed aqueous resin-reinforced material of the present invention, after step (1A) or (1B) above, (2) A step of heating the cellulose nanofiber dispersed aqueous resin reinforced material obtained in step (1) to remove moisture. It can also be equipped with this feature.

[0109] This makes it possible to remove excess water present in the cellulose nanofiber-dispersed aqueous resin-reinforced material of the present invention.

[0110] In the manufacturing method of the present invention, the temperature at which the cellulose nanofiber-dispersed aqueous resin-reinforced material is heated to remove moisture is not limited, but from the viewpoint of lightness, elastic modulus, etc., 10 to 90°C is preferred, and 20 to 70°C is more preferred.

[0111] In the manufacturing method of the present invention, there is no limit to the time for heating the cellulose nanofiber-dispersed aqueous resin-reinforced material to remove moisture, but from the viewpoint of lightness, elastic modulus, etc., 0.5 to 48 hours is preferred, and 2 to 6 hours is more preferred.

[0112] (2-4) Process (3) In the method for producing a cellulose nanofiber dispersed aqueous resin reinforced material of the present invention, after step (2) above, (3) A process of heating and molding the obtained cellulose nanofiber dispersed aqueous resin reinforced material under pressure. It can also be equipped with this feature.

[0113] By applying pressure molding, the gaps between cellulose nanofibers and aqueous resins can be further reduced.

[0114] In the manufacturing method of the present invention, the temperature at which the cellulose nanofiber-dispersed aqueous resin-reinforced material is heated and molded is not limited, but from the viewpoint of lightness, elastic modulus, etc., 10 to 90°C is preferred, and 20 to 70°C is more preferred.

[0115] In the manufacturing method of the present invention, there are no restrictions on the temperature at which the cellulose nanofiber-dispersed aqueous resin-reinforced material is heated and molded, but from the viewpoint of lightness, elastic modulus, etc., 0.5 to 48 hours is preferred, and 2 to 6 hours is more preferred.

[0116] In the manufacturing method of the present invention, the pressure used when heating and molding the cellulose nanofiber-dispersed aqueous resin-reinforced material is not limited, but from the viewpoint of lightness, elastic modulus, etc., 5 MPa or higher is preferred, 10 to 60 MPa is more preferred, and 20 to 30 MPa is even more preferred. [Examples]

[0117] The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0118] In the following examples and comparative examples, Elecoat UC-4H (manufactured by Shimizu Co., Ltd.), a water-based ultraviolet-curable resin emulsion, was used as the photocurable resin; solid content 60% by mass.

[0119] In the following examples and comparative examples, cellulose nanofibers manufactured by Daio Paper Corporation (average fiber diameter 900 nm, average fiber length 2 μm) were used.

[0120] [Example 1: Bamboo] After drying the bamboo material (Moso bamboo from Takano Bamboo Crafts Co., Ltd.; 10g) in a tray, 5.5g (3.3g solids) of Elecoat UC-4H (manufactured by Shimizu Co., Ltd.), a water-based UV-curable resin emulsion, and 110g (3.3g solids) of cellulose nanofiber mixture (manufactured by Daio Paper Corporation) were mixed and applied at 20°C, impregnating the paper material with cellulose nanofibers and water-based UV-curable resin. Subsequently, ultraviolet light was irradiated for 5 minutes using a UV irradiation device (i-Grandage mini, manufactured by i-Graphics Co., Ltd.). The appearance of the test piece obtained in Example 1 is shown in Figure 1.

[0121] [Comparative Example 1: Bamboo] Bamboo material (Moso bamboo manufactured by Takano Bamboo Crafts Co., Ltd.; 10g) was used as the test specimen for Comparative Example 1.

[0122] [Comparative Example 2: Bamboo] Without using the cellulose nanofiber mixture (manufactured by Daio Paper Corporation), 5.5 g (3.3 g solids) of Elecoat UC-4H (manufactured by Shimizu Co., Ltd.), a water-based UV-curing resin emulsion, was applied. The test specimens for Comparative Example 2 were obtained in the same manner as in Example 1.

[0123] [Test Example 1: Three-point bending test of bamboo] The elastic modulus (stiffness) and maximum bending stress were evaluated in accordance with JIS K7171:2016 "Plastics - Method for determining bending properties".

[0124] The results are shown in Figure 2. As a result, in Comparative Example 1, which used bamboo material as is, the elastic modulus (rigidity) was 965 × 10⁻⁶. 3N / mm 2 , the maximum bending stress was 38 MPa. On the other hand, as in Comparative Example 2, even when an aqueous ultraviolet-curable resin was added, the elastic modulus (rigidity) was 1060×10 3 N / mm 2 , the maximum bending stress was 38 MPa, and even though the elastic modulus was improved, the maximum bending stress did not improve. In contrast, as in Example 1, by adding and impregnating cellulose nanofibers and an aqueous ultraviolet-curable resin, the elastic modulus (rigidity) was 1160×10 3 N / mm 2 , the maximum bending stress became 40 MPa, and it was possible to improve both the elastic modulus and the maximum bending stress.

[0125] [Example 2: Paper] In the tray, after drying the paper material (filter paper, circular quantitative filter paper No. 7 manufactured by Toyo Roshi Kaisha, Ltd.; 0.1 g), at 20°C, 5.5 (solid content 3.3 g) of Erecote UC-4H (manufactured by Shimizu Corporation), an aqueous ultraviolet-curable resin emulsion, and 110 g (solid content 3.3 g) of a cellulose nanofiber mixed solution (manufactured by Daio Paper Corporation) were mixed and applied to impregnate the paper material with cellulose nanofibers and an aqueous ultraviolet-curable resin. Then, it was irradiated with ultraviolet rays for 5 minutes using a UV irradiation device (Eye Graphic's Eye Glantage mini).

[0126] [Comparative Example 3: Paper] The paper material (filter paper, circular quantitative filter paper No. 7 manufactured by Toyo Roshi Kaisha, Ltd.; 0.1 g) was used as it was as the test piece of Comparative Example 3.

[0127] [Comparative Example 4: Paper] Without using the cellulose nanofiber mixed solution (manufactured by Daio Paper Corporation), 5.5 g (solid content 3.3 g) of Erecote UC-4H (manufactured by Shimizu Corporation), an aqueous ultraviolet-curable resin emulsion, was applied. Otherwise, the test piece of Comparative Example 4 was obtained in the same manner as in Example 1.

[0128] [Test Example 2: Maximum Stress] The sample was mounted on an A&D Corporation Force Tester MCT-2150 desktop tensile and compression testing machine, and tested at a test speed of 10 mm / s.

[0129] As a result, while the maximum stress was 8.3 MPa in Comparative Example 3, which used the paper material as is, the maximum stress improved to 28 MPa when a water-based UV-curable resin was added, as in Comparative Example 4. However, as in Example 2, by adding and impregnating cellulose nanofibers with a water-based UV-curable resin, it was possible to further improve the maximum stress to 33 MPa.

[0130] [Example 3: Wood] After drying the wood (Japanese cypress; 5g) in a tray, a mixture of 5.5g (3.3g solids) of Elecoat UC-4H (manufactured by Shimizu Co., Ltd.), a water-based UV-curable resin emulsion, and 110g (3.3g solids) of cellulose nanofiber mixture (manufactured by Daio Paper Corporation) was applied at 20°C, impregnating the wood with cellulose nanofibers and the water-based UV-curable resin. Subsequently, the wood was irradiated with ultraviolet light for 5 minutes using a UV irradiation device (i-Grandage mini, manufactured by iGraphics Co., Ltd.). The appearance of the test piece obtained in Example 3 is shown in Figure 4.

[0131] [Comparative Example 5: Wood] Wood (Japanese cypress; 5g) was used as the test specimen for Comparative Example 5.

[0132] [Comparative Example 6: Wood] Without using the cellulose nanofiber mixture (manufactured by Daio Paper Corporation), 5.5 g (3.3 g solids) of Elecoat UC-4H (manufactured by Shimizu Co., Ltd.), a water-based UV-curing resin emulsion, was applied. The test specimens for Comparative Example 6 were obtained in the same manner as in Example 3.

[0133] [Test Example 3: Flexural Modulus] The bending modulus (stiffness) and maximum bending stress were evaluated in accordance with JIS K7171:2016 "Plastics - Method for determining bending properties".

[0134] The results are shown in Figure 5. As a result, in Comparative Example 3, where wood was used as is, the flexural modulus was 4.3 GPa and the maximum bending stress was 29 MPa. In contrast, as in Comparative Example 4, when a water-based UV-curable resin was added, the flexural modulus (stiffness) was 5.0 GPa and the maximum bending stress was 38 MPa. This shows that it is possible to improve both the flexural modulus and the maximum bending stress. Furthermore, as in Example 3, by adding and impregnating cellulose nanofibers with a water-based UV-curable resin, the flexural modulus became 5.4 GPa and the maximum bending stress became 48 MPa, demonstrating that it is possible to further improve both the flexural modulus and the maximum bending stress.

Claims

1. The substrate, selected from the group consisting of bamboo and paper, has a cellulose nanofiber-dispersed aqueous resin layer in which cellulose nanofibers and aqueous resin are impregnated inside. A cellulose nanofiber-dispersed aqueous resin-reinforced material wherein the aqueous resin is at least one selected from the group consisting of thermoplastic resins, thermosetting resins, and photocurable resins.

2. The cellulose nanofiber dispersed aqueous resin reinforced material according to claim 1, wherein the bamboo material is at least one selected from the group consisting of Moso bamboo, Japanese bamboo, and Sasa bamboo.

3. The cellulose nanofiber dispersed aqueous resin reinforced material according to claim 1, wherein the paper material is at least one selected from the group consisting of Japanese paper, Western paper, processed paper, synthetic paper, and filter paper.

4. The cellulose nanofiber-dispersed aqueous resin reinforced material according to claim 1, wherein at least one side of the cellulose nanofiber-dispersed aqueous resin layer is separately provided with a carbon fiber-reinforced plastic layer.

5. A method for producing a cellulose nanofiber dispersed aqueous resin reinforced material according to any one of claims 1 to 4, (1A) A step of immersing at least one substrate selected from the group consisting of bamboo material and paper material in a dispersion of cellulose nanofiber and aqueous resin, or (1B) A step of immersing at least one substrate selected from the group consisting of bamboo and paper materials in the dispersion of cellulose nanofibers, and then impregnating at least one substrate selected from the group consisting of bamboo and paper materials in the aqueous resin emulsion. A manufacturing method that includes the following features.

6. The manufacturing method according to claim 5, wherein a roller treatment is performed in the immersion in the dispersion in step (1A) or in the immersion in the emulsion in step (1B).

7. The manufacturing method according to claim 5, wherein in step (1A) or (1B), the amount of cellulose nanofiber added is 0.1 to 100 parts by mass per 100 parts by mass of at least one base material selected from the group consisting of bamboo and paper.

8. The manufacturing method according to claim 5, wherein in step (1A) or (1B), the amount of aqueous resin added is 50 to 900 parts by mass per 100 parts by mass of at least one base material selected from the group consisting of bamboo and paper.

9. After the above step (1A) or (1B), (2) A step of heating the cellulose nanofiber dispersed aqueous resin reinforced material obtained in step (1) to remove moisture. The manufacturing method according to claim 5, comprising:

10. After step (2) above, (3) A process of heating and molding the obtained cellulose nanofiber dispersed aqueous resin reinforced material under pressure. The manufacturing method according to claim 9, comprising:

11. The manufacturing method according to claim 10, wherein the molding pressure in step (3) is 5 MPa or more.

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