Curing resin composition

Abstract

The resin composition for curing contains at least a thermosetting resin and a composite powder, and the composite powder contains cellulose nanofibers and a silicon-based porous material. On the basis of mass, the content ratio of the cellulose nanofibers to the silicon-based porous material is (1: 5)-(1: 20), in the composite powder, the cellulose nanofibers are at least attached to the surface of the silicon-based porous material or at least enter holes of the silicon-based porous material, and the silicon-based porous material is prepared. The content of the composite powder is 0.1-10 parts by mass per 100 parts by mass of the thermosetting resin.

Description

Technical Field

[0001] The present invention relates to a resin composition for curing rubber, resin, and carbon fiber reinforced plastic (hereinafter sometimes referred to as "CFRP"). Background Art

[0002] Sports goods require "lighter and stronger materials", so many products using carbon fiber reinforced plastic have been manufactured. For example, golf clubs and badminton rackets have a high demand for CFRP with high impact resistance, and the potential demand is also large. Therefore, research on matrix resin modification and addition of fillers with excellent strength is actively underway.

[0003] Here, although CFRP is lightweight and has high strength, since it uses a resin with low impact strength as the base material, there is a problem of insufficient impact strength in practical use. Thus, hitherto, as a method for improving the impact strength of CFRP, a method of improving the impact strength of CFRP by mixing cellulose nanofibers (hereinafter sometimes referred to as "CNF") in the matrix resin has been developed.

[0004] In addition, there is also a need for rubber and resin to be "stronger materials", and rubber and resin are used in various products such as the outsoles and midsoles of shoes, and golf balls. Taking rubber as an example, a method of strengthening with carbon black, in particular, for the purpose of improving wear resistance and mechanical strength is well known, or inorganic fillers such as silica are also widely used as strengthening materials. In addition, rubber and resin are generally organic substances. In order to improve their interaction with silica as an inorganic substance and further improve the strengthening effect, silane coupling agents are also widely used, which is also well known.

[0005] Thus, extensive research has been conducted on whether an equivalent or higher strengthening effect can be obtained in the following cases: using cellulose nanofibers as a substitute for the above carbon black and silica and reducing the addition amount of the cellulose nanofibers. However, since cellulose nanofibers have good compatibility with water, there is a problem that they are not easily directly dispersed in rubber and resin.

[0006] Thus, various methods for dispersing cellulose nanofibers in the matrix resin have been proposed. For example, the following method has been proposed: alcohol substitution is performed on cellulose nanofibers containing moisture to remove the moisture contained in the cellulose nanofibers, the alcohol-substituted cellulose nanofibers are dispersed in an epoxy resin, and then the alcohol is removed (evaporated). In addition, instead of the above alcohol substitution method, the following method has also been proposed: freeze-drying treatment (or spray drying treatment) is performed on cellulose nanofibers containing moisture to remove the moisture contained in the cellulose nanofibers, and the freeze-dried (or spray-dried) cellulose nanofibers are dispersed in an epoxy resin (for example, refer to Patent Document 1).

[0007] In addition, the following method has also been proposed: Chemically pulped paper, which is the raw material of nanofibers, is put into the base resin in a dry state, and kneading is performed using a pressure kneader or a twin-screw extrusion kneader, thereby fibrillating the pulp and dispersing it in the base resin (for example, refer to Patent Document 2).

[0008] Patent Document 1: Japanese Patent No. 5341787 Gazette

[0009] Patent Document 2: Japanese Patent No. 6471377 Gazette Summary of the Invention

[0010] -Technical Problem to be Solved by the Invention-

[0011] Here, in the alcohol displacement method described in the above Patent Document 1, alcohol displacement is performed to remove the moisture contained in the microfibrillated cellulose, and alcohol must be removed after being dispersed in the epoxy resin. Therefore, there is a problem that the treatment for dispersing the cellulose nanofibers requires too much time. In addition, in the case where the moisture removal is incomplete, during the heating treatment (100 °C or higher) when the resin is cured, the residual moisture will vaporize to form voids, so there is a problem of a decrease in the strength of the resin.

[0012] In addition, in the freeze-drying method (or spray-drying method) described in the above Patent Document 1, dedicated equipment must be installed. In addition, since the morphology of the obtained cellulose nanofibers is in the form of an aerogel or powder, there is a problem that the cellulose nanofibers aggregate and it is difficult to disperse the cellulose nanofibers into the epoxy resin.

[0013] In addition, in the method described in the above Patent Document 2, there is a problem that a dedicated twin-screw extrusion kneader must be installed.

[0014] Therefore, the present invention has been completed to solve the above problems, and its object is to provide a resin composition for curing, which can uniformly disperse cellulose nanofibers in a thermosetting resin by a simple method and can reliably improve the strength while maintaining the impregnation property for reinforcing fibers such as carbon fibers.

[0015] -Technical Solution for Solving the Technical Problem-

[0016] In order to achieve the above object, the resin composition for curing of the present invention contains at least a thermosetting resin and a composite powder. The composite powder contains cellulose nanofibers and a silicon-based porous material. Based on mass, the content ratio of cellulose nanofibers to the silicon-based porous material is cellulose nanofibers:silicon-based porous material = 1:5 to 1:20. In the composite powder, the cellulose nanofibers are at least attached to the surface of the silicon-based porous material or at least enter the pores of the silicon-based porous material. The content of the composite powder relative to 100 parts by mass of the thermosetting resin is 0.1 to 10 parts by mass.

[0017] - Effects of the Invention -

[0018] According to the present invention, it is possible to provide a resin composition for curing that can uniformly disperse cellulose nanofibers in a thermosetting resin by a simple method and can reliably improve the strength while maintaining the impregnation property with respect to reinforcing fibers such as carbon fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a graph showing the relationship between the content X (in parts by mass) of the silicon-based porous material contained in the dispersion liquid and the concentration Y (in mass %) of cellulose nanofibers;

[0020] Figure 2 is a scanning electron microscope (SEM) photograph showing the state of the composite powder of Example 1;

[0021] Figure 3 is a graph showing carbon atoms derived from cellulose nanofibers in the composite powder of Example 1 by Energy Dispersive X-ray Spectroscopy (EDS);

[0022] Figure 4 is a schematic diagram for explaining the strength evaluation in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, preferred embodiments of the present invention will be described.

[0024] The resin composition for curing of the present invention contains at least a thermosetting resin and a composite powder, and the composite powder contains cellulose nanofibers and a silicon-based porous material.

[0025] (Thermosetting Resin)

[0026] As the thermosetting resin of the present invention, there is no particular limitation as long as it is a thermosetting resin for fiber-reinforced plastics. For example, epoxy resins, unsaturated polyester resins, polyamide resins, phenolic resins, etc. can be cited. It should be noted that these materials can be used alone or in combination of two or more.

[0027] In addition, among these thermosetting resins, the epoxy resin has higher adhesion performance and elastic modulus than other resins. Therefore, from the viewpoint of firmly holding fibers to each other in a fiber-reinforced composite material for good stress transfer, it is preferable to use an epoxy resin.

[0028] In addition, as the epoxy resin, from the viewpoints of high mechanical strength, excellent dimensional stability, heat resistance, and chemical resistance, for example, bisphenol A type, bisphenol F type, bisphenol A / F type mixed epoxy resin, bisphenol S type and other bisphenol type epoxy resins, 1,3-bis(aminomethyl)cyclohexane type, diaminodiphenylmethane type, diaminodiphenylsulfone type, glycidyl aniline type, aminophenol type, m-xylenediamine type and other glycidylamine type epoxy resins, naphthalene type epoxy resins, alicyclic epoxy resins, trihydroxyphenylmethane type, phenol novolac type, isocyanurate type, o-cresol novolac type, dicyclopentadiene novolac type, hydantoin type, biphenyl type, tetraphenylethane type, and polyfunctional epoxy resins can be used. It should be noted that these materials can be used alone or in combination of two or more.

[0029] It should be noted that as these epoxy resins, commercially available products can also be used. For example, bisphenol A type epoxy resin "JER828" manufactured by Mitsubishi Chemical Corporation, polyfunctional epoxy resin "JER604" manufactured by Mitsubishi Chemical Corporation, bisphenol A / F type mixed epoxy resin "DENATOOL XNR6809" manufactured by Nagase ChemteX Corporation, and in addition, jER630 (manufactured by Mitsubishi Chemical Corporation), jER807 (manufactured by Mitsubishi Chemical Corporation), jER152 (manufactured by Mitsubishi Chemical Corporation), HP4032 (manufactured by DIC Corporation), EXA-4580-1000 (manufactured by DIC Corporation), EX-201 (manufactured by Nagase ChemteX Corporation), CELLOXIDE 2081 (manufactured by Daicel Corporation), CELLOXIDE 3000 (manufactured by Daicel Corporation), MY-0500 (manufactured by Huntsman Corporation), MY-0600 (manufactured by Huntsman Corporation), TETRAD-X (manufactured by Mitsubishi Gas Chemical Company, Inc.), GAN (manufactured by Nippon Kayaku Co., Ltd.), SR-HHPA (manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.), and 1500NP (manufactured by Kyoeisha Chemical Co., Ltd.) etc. can be used.

[0030] (Curing agent)

[0031] In addition, the resin composition for curing of the present invention contains a curing agent (resin for curing) for curing the above-mentioned thermosetting resin. As such a curing agent, for example, when an epoxy resin is used as the thermosetting resin, as long as it is a curing agent having an active group that reacts with an epoxy group, there is no particular limitation, and amine curing agents such as aliphatic amines and aromatic amines, acid anhydride curing agents such as polyphenols, imidazoles, carboxylic acids, and carboxylic anhydrides, carboxylic acid amides, thiols, and Lewis acids such as boron amine complex halides can be used. It should be noted that these kinds of materials can be used alone or in combination of two or more.

[0032] As the amine curing agent, for example, a modified aromatic amine-based curing agent such as diethyltoluenediamine can be used; as the acid anhydride curing agent, for example, a modified alicyclic acid anhydride such as tetrahydrophthalic anhydride can be used.

[0033] In addition, the addition ratio of the curing agent relative to the thermosetting resin can be appropriately set according to the types of the thermosetting resin and the curing agent used. From the viewpoint of reliably curing the resin composition for curing, the content of the curing agent relative to 100 parts by mass of the thermosetting resin is preferably 25 to 95 parts by mass.

[0034] (Composite powder)

[0035] The composite powder of the present invention contains cellulose nanofibers and a silicon-based porous material, and by dispersing the composite powder in the above-mentioned thermosetting resin that is the base material of CFRP, the strength of the resin composition for curing of the present invention is improved in terms of stretchability and elasticity.

[0036] <Cellulose nanofibers>

[0037] As the cellulose nanofibers, there is no particular limitation, and publicly known cellulose nanofibers can be widely used. In addition, as the cellulose constituting the cellulose nanofibers, any one of plant-derived cellulose, animal-derived cellulose, and bacteria-derived cellulose can be used. It should be noted that these kinds of materials can be used alone or in combination of two or more.

[0038] As the plant-derived cellulose, for example, cellulose derived from broad-leaved trees (such as eucalyptus and poplar), cellulose derived from coniferous trees (such as pine, fir, cedar, and hinoki), cellulose derived from herbs (such as rice straw, bagasse, reed, kenaf, abaca, and sisal), and seed hair fibers (such as cotton) can be used. In addition, the pulp as the raw material can be mechanical pulp obtained by mechanically treating wood chips, chemical pulp obtained by chemically removing non-cellulose components from wood chips, or dissolving pulp obtained by further removing non-cellulose components and purifying.

[0039] In addition, it is also possible to use cellulose derived from animals such as ascidians, cellulose derived from bacteria such as nata de coco, and the like. In addition, such cellulose does not necessarily have to be composed only of pure cellulose components, and non-cellulose components may be attached to the cellulose as the main component.

[0040] There is no particular limitation on the main non-cellulose components attached to the cellulose nanofibers, and they can be appropriately selected according to the use. For example, hemicellulose and lignin can be cited.

[0041] In addition, the proportion of the pure cellulose component in the cellulose nanofibers can also be appropriately set according to the use. For example, in 100% by mass of the cellulose nanofibers, the proportion of the pure cellulose component is preferably 70% by mass or more, more preferably 80% by mass or more. In addition, as the upper limit of the proportion of the pure cellulose component, it can be set to 100% by mass.

[0042] It should be noted that the "cellulose ratio" mentioned here refers to the ratio of the pure cellulose component polymerized linearly by glycosidic bonds from β-glucose molecules to the total mass (100% by mass) of the cellulose nanofibers.

[0043] In addition, the degree of polymerization of the pure cellulose component contained in the cellulose nanofibers can also be appropriately set according to the use. For example, a cellulose component with a degree of polymerization of 500 or more, particularly 600 or more, can be used. It should be noted that there is no particular limitation on the upper limit value of the degree of polymerization of the cellulose component, and it can be set to 100,000, for example.

[0044] There is no particular limitation on the crystallinity of the pure cellulose component contained in the cellulose nanofibers, and it is preferably 60% or more, more preferably 70% or more. In addition, there is no particular limitation on the upper limit of the crystallinity of the cellulose, and it can be set to 99%, for example. It should be noted that the crystal structures of the cellulose component can include type I, type II, type III, and type IV.

[0045] The size of the cellulose nanofibers is not particularly limited, but from the viewpoints of forming a certain network or structure in rubber or resin and its effectiveness in terms of elasticity, it is preferably in a filamentous shape with a high length-to-diameter ratio, the diameter is preferably 3 to 100 nm, the length is preferably 100 nm or more, and more preferably 5 μm or more.

[0046] It should be noted that the "diameter of the cellulose nanofibers" mentioned here refers to the median diameter obtained by observing 50 or more randomly selected cellulose nanofibers through a scanning electron microscope (SEM).

[0047] In addition, from the perspective of being easily dispersed in the above-mentioned thermosetting resin, as the cellulose nanofibers, those having polar groups such as carboxyl groups or hydrophobic functional groups introduced by oxidation treatment (TEMPO oxidation treatment) in the presence of a TEMPO (2,2,6,6-tetramethyl-1-piperidine-N-oxide) catalyst can be used.

[0048] For example, by adding pulp as the fiber raw material, TEMPO as the catalyst, and sodium hypochlorite or sodium hypobromite, etc. to a sodium phosphate buffer solution and performing the above-mentioned oxidation treatment, cellulose nanofibers that have been chemically fibrillated and have carboxyl groups introduced can be obtained.

[0049] It should be noted that as the cellulose nanofibers after fibrillation using a TEMPO oxidation catalyst, commercially available products can also be used. For example, "cellenpia" manufactured by Nippon Paper Industries Co., Ltd. or "RHEOCRYSTA" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. etc. (both are in slurry form) can be used.

[0050] In addition, although different from TEMPO oxidation, as a similar chemical fibrillation method, a phosphorylation method, a phosphite esterification method, etc. can be used. In addition, in the present invention, the aim is to provide a composite powder that is easily dispersed in the above-mentioned thermosetting resin. In the production of the composite powder, the starting material is an aqueous solution of cellulose nanofibers. Therefore, commercially available products of aqueous dispersions / aqueous solutions of cellulose nanofibers obtained by using a fibrillation method different from the above-mentioned chemical fibrillation method (for example, a water collision method, a water jet method, a mechanical fibrillation method using a pulverizer, etc.) can be used.

[0051] <Silicon-based porous material>

[0052] The silicon-based porous material is a material (porous body) having a lot of micropores. In the present invention, diatomaceous earth or zeolite can be used. It should be noted that one of these materials can be used alone, or two or more of them can be used in combination.

[0053] The pore diameter of the micropores of the silicon-based porous material is not particularly limited, but from the perspective of making it easy for cellulose nanofibers to enter the micropores, it is preferably 0.2 nm to 2000 nm. In addition, the shape of the micropores of the silicon-based porous material is not particularly limited.

[0054] For example, by using diatomaceous earth as the silicon-based porous material, the cellulose nanofibers are carried in a state of entering the micropores of the diatomaceous earth, so that the aggregation of cellulose nanofibers can be prevented. In addition, the cellulose nanofibers entering the micropores of the diatomaceous earth can be uniformly dispersed in the thermosetting resin.

[0055] In addition, for example, when using zeolite with a micropore diameter smaller than that of cellulose nanofibers as the silicon-based porous material, although the cellulose nanofibers do not enter the micropores of the zeolite, since the specific surface area of the zeolite is larger than that of diatomaceous earth, the cellulose nanofibers are likely to adhere to the surface of the zeolite. As a result, similar to the case where the cellulose nanofibers enter the micropores of diatomaceous earth, the cellulose nanofibers adhering to the surface of the zeolite can be uniformly dispersed in the thermosetting resin.

[0056] That is to say, in the composite powder of the present invention, the cellulose nanofibers at least adhere to the surface of the silicon-based porous material or at least enter the pores of the silicon-based porous material, whereby the cellulose nanofibers can be uniformly dispersed in the thermosetting resin. As a result, the strength of the resin composition for curing and CFRP of the present invention can be reliably improved.

[0057] In addition, in the resin composition for curing of the present invention, based on mass, the content ratio of the cellulose nanofibers to the silicon-based porous material in the composite powder (i.e., in the resin composition for curing) is: cellulose nanofibers: silicon-based porous material = 1:5 to 1:20 (that is, relative to 1 part by mass of cellulose nanofibers, the silicon-based porous material is 5 to 20 parts by mass).

[0058] And by setting the content ratio to 1:5 to 1:20, it is possible to suppress the decrease in the amount of cellulose nanofibers entering the micropores (or the amount of cellulose nanofibers adhering to the surface of the silicon-based porous material) due to insufficient silicon-based porous material. Therefore, the cellulose nanofibers can be reliably introduced (adhered), and when the composite material is mixed in the above thermosetting resin, it is possible to prevent the decrease in the dispersibility of the silicon-based porous material into which the cellulose nanofibers have entered.

[0059] In other words, when the content ratio of the cellulose nanofibers is large (that is, when the silicon-based porous material is less than 5 parts by mass relative to 1 part by mass of cellulose nanofibers), since the ratio of the silicon-based porous material to the cellulose nanofibers becomes smaller, the cellulose nanofibers cover the entire surface of the silicon-based porous material, resulting in the formation of aggregates of cellulose nanofibers. As a result, when the composite powder is mixed in the thermosetting resin, the dispersibility of the silicon-based porous material into which the cellulose nanofibers have entered will decrease.

[0060] In addition, when the content ratio of the silicon-based porous material is large (that is, when the silicon-based porous material is more than 20 parts by mass relative to 1 part by mass of cellulose nanofibers), since the ratio of the silicon-based porous material to the cellulose nanofibers becomes larger, the dispersibility of the silicon-based porous material into which the cellulose nanofibers have entered will decrease.

[0061] As described above, in the present invention, in order to improve the dispersibility of the composite powder in the thermosetting resin (i.e., the silicon-based porous material into which the cellulose nanofibers have entered), based on mass, the content ratio of the cellulose nanofibers to the silicon-based porous material in the composite powder (i.e., in the resin composition for curing) is set to cellulose nanofibers:silicon-based porous material = 1:5 to 1:20.

[0062] In addition, in the resin composition for curing of the present invention, the content of the composite powder relative to 100 parts by mass of the thermosetting resin is 0.1 to 10 parts by mass.

[0063] This is because, when the content of the composite powder is less than 0.1 part by mass, since the amount of the composite powder is small, it is difficult to sufficiently improve the strength of the resin composition for curing. In addition, this is because, when the content of the composite powder is more than 10 parts by mass, since the amount of the composite powder is large, the viscosity of the resin composition for curing becomes too high (that is, the fluidity of the resin composition for curing decreases), making it difficult for reinforcing fibers such as carbon fibers to infiltrate into the resin composition for curing. As a result, it is difficult to improve the strength of the resin composition for curing in the CFRP.

[0064] As described above, in the present invention, by setting the content of the composite powder relative to 100 parts by mass of the thermosetting resin to 0.1 to 10 parts by mass, it is possible to improve the strength of the resin composition for curing in the CFRP and maintain the impregnability of the resin composition for curing with respect to reinforcing fibers such as carbon fibers.

[0065] It should be noted that, from the viewpoint of improving strength and reducing costs while maintaining the above-mentioned impregnability, the content of the composite powder relative to 100 parts by mass of the thermosetting resin is preferably 0.1 to 5.0 parts by mass, more preferably 0.1 to 2.5 parts by mass.

[0066] (Other components)

[0067] In the resin composition for curing of the present invention, other components can be added within the range that does not impair the effects of the present invention.

[0068] For example, it can be cited: thermoplastic resins for controlling fluidity, curing accelerators for improving reactivity, rubber particles for imparting toughness to epoxy resins, surfactants for improving the wettability with reinforcing fibers, etc.

[0069] Examples of the thermoplastic resin include: polyester, polycarbonate, polyphenylene sulfide, polyacrylate, polyamide, polyimide, polyaramide, polybenzimidazole, polyetherimide, polysulfone, polyethersulfone, and the like. It should be noted that these thermoplastic resins can be added in a state dissolved in the epoxy resin, or arranged in the form of non-woven fabric, net, slurry, fine particles, long fibers, short fibers, fabric, etc. on the surface layer of the prepreg or preform. It should be noted that these materials can be used alone or in combination of two or more.

[0070] Examples of the curing accelerator include: monofluoroethylamine, urea compounds such as phenyl dimethyl urea (PDMU), imidazole compounds, and amine complexes such as boron trichloride amine complex.

[0071] Examples of the rubber particles include core-shell rubber particles or crosslinked rubber particles obtained by graft-polymerizing a different polymer on the surface of crosslinked rubber particles, etc. from the viewpoint of processability. Examples of the rubber type include silicone rubber, butyl rubber, NBR, SBR, butadiene rubber, acrylic rubber, etc. It should be noted that these materials can be used alone or in combination of two or more.

[0072] As the surfactant, for example, "BYK-A530" manufactured by BYK Chemie Co., Ltd. can be used.

[0073] Next, the manufacturing method of the curable resin composition of the present invention will be described. The manufacturing method of the curable resin composition of the present invention includes: a step of preparing a dispersion of composite powder, a step of drying the dispersion of composite powder to produce a dried body, a step of pulverizing the dried body to produce composite powder, and a step of mixing the produced composite powder in a thermosetting resin to produce a curable resin composition.

[0074] (Dispersion preparation step)

[0075] First, a silicon-based porous material is mixed in an aqueous solvent in which cellulose nanofibers are dispersed to prepare a dispersion.

[0076] Here, the aqueous solvent (dispersion medium) is not particularly limited. Although water (purified water, etc.) is used, alcohols such as ethanol and isopropanol can also be contained in the water as needed.

[0077] In addition, the content of the cellulose nanofibers contained in the aqueous solvent is set such that when the content of the silicon-based porous material relative to 1 mass part of the cellulose nanofibers contained in the dispersion is X (unit: mass part) and the concentration of the cellulose nanofibers is Y (unit: mass %), the relationship of the following formula (1) holds.

[0078] [Formula 1]

[0079] Y ≤ -0.048X + 1.96 (1)

[0080] This is because when the concentration Y of the cellulose nanofibers is greater than the right side of formula (1) (i.e., -0.048X + 1.96), due to the thickening effect of the cellulose nanofibers, the viscosity of the aqueous solvent in which the cellulose nanofibers are dispersed increases sharply. When the silicon-based porous material is mixed in the aqueous solvent in which the cellulose nanofibers are dispersed, it is difficult to stir and mix sufficiently.

[0081] Here, formula (1) above will be further described in detail. The inventors et al. used two types of cellulose nanofibers fibrillated by TEMPO oxidation (denoted as "TEMPO-oxidized fibrillated CNF" in Table 1) and fibrillated by mechanical fibrillation (denoted as "mechanically fibrillated CNF A" and "mechanically fibrillated CNF B" in Table 1). The content (in parts by mass) of the silicon-based porous material (diatomaceous earth) relative to 1 part by mass of the cellulose nanofibers (unit: mass%) contained in the mixed aqueous solution (dispersion) was varied between 0 and 20 parts by mass, and the viscosity of the mixed aqueous solution was measured. It should be noted that the viscosity measurement of the mixed aqueous solution (temperature of the mixed aqueous solution: 25 °C) was measured using an RE80 viscometer manufactured by Toki Sangyo Co., Ltd. Also, the case where the mixed aqueous solution could be stirred was denoted as 〇, and the case where the mixed aqueous solution could not be stirred was denoted as × to evaluate the stirrability. The above results are shown in Table 1.

[0082]

Table 1

[0083]

[0084] As shown in Table 1, when the concentration of the cellulose nanofibers in the aqueous solution in which the cellulose nanofibers are dispersed is 2 mass%, even without adding diatomaceous earth, the viscosity of the aqueous solution in which the cellulose nanofibers are dispersed is very high, indicating that stirring is difficult.

[0085] In addition, it is clearly known from Table 1 that the viscosity of the mixed aqueous solution that can be stirred is 1495 mPa·s or less (in Table 1, the concentration of the cellulose nanofibers in this case is 1.34 mass%). In addition, if the concentration of the cellulose nanofibers is 1.68 mass% or less, it can be stirred.

[0086] Therefore, it can be said that the concentration of the cellulose nanofibers in the aqueous solution in which the cellulose nanofibers are dispersed needs to be 1.68% or less.

[0087] In addition, using the results of Table 1, the relationship between the content X (parts by mass) of the diatomaceous earth and the concentration Y (mass%) of the cellulose nanofibers was plotted as a graph and shown inFigure 1 in

[0088] As Figure 1 shown, it can be found that if the content X of diatomaceous earth increases, the concentration Y of CNF decreases, and at each content X of diatomaceous earth, the highest concentration Y of CNF that can be stirred has a negative linear correlation with the addition ratio of diatomaceous earth.

[0089] From the above, it can be known that as Figure 1 shown, between the content X (in parts by mass) of the silicon-based porous material and the concentration Y (in mass%) of cellulose nanofibers relative to 1 part by mass of cellulose nanofibers contained in the dispersion liquid, it is sufficient that the relationship of the above formula (1) holds.

[0090] It should be noted that between the content X (in parts by mass) of the silicon-based porous material and the concentration Y (in mass%) of cellulose nanofibers relative to 1 part by mass of cellulose nanofibers contained in the dispersion liquid, it is preferable that the following formula (2) holds. This formula (2) is obtained based on the relationship between the content X (in parts by mass) of diatomaceous earth and the concentration Y (in mass%) in Figure 1 Table 1 (i.e., the two points of X = 5, Y = 1.68 and X = 20, Y = 0.95).

[0091] [Formula 2]

[0092] Y ≤ -0.0487X + 1.9233 (2)

[0093] In addition, the hydroxyl groups originally attached to cellulose nanofibers will become -O- in water, and the carboxyl groups replaced by hydroxyl groups through Tempo oxidation treatment will become -COO-, which means that cellulose nanofibers are negatively charged. Therefore, from the viewpoint of making them stable in terms of chemical properties and improving dispersibility, it is preferable that the pH of the aqueous solvent in which cellulose nanofibers are dispersed is alkaline.

[0094] In addition, in the present invention, as described above, based on mass, the content ratio of cellulose nanofibers to the silicon-based porous material in the composite material (i.e., in the curing resin composition) is set to cellulose nanofibers:silicon-based porous material = 1:5 to 1:20. Therefore, based on mass, the content ratio of cellulose nanofibers to the silicon-based porous material in the dispersion liquid is also cellulose nanofibers:silicon-based porous material = 1:5 to 1:20 (that is, relative to 1 part by mass of cellulose nanofibers, the silicon-based porous material is 5 to 20 parts by mass).

[0095] It should be noted that, compared with the cellulose nanofibers obtained by mechanical fibrillation treatment, the cellulose nanofibers obtained by chemical fibrillation treatment have uniform thickness, and thus are more likely to enter the micropores of the silicon-based porous material. Therefore, in the present invention, it is preferable to use the cellulose nanofibers obtained by chemical fibrillation treatment.

[0096] In addition, as a device for mixing the silicon-based porous material in the aqueous solvent in which the cellulose nanofibers are dispersed, for example, a beaker or a flask and various mixers such as a stirring rod, a propeller mixer, a planetary centrifugal mixer, a homogenizer, an ultrasonic mixer, a bead mill, a ball mill, a planetary mixer, etc. can be used.

[0097] (Drying step)

[0098] Next, the prepared dispersion is dried to remove the aqueous solvent as the dispersion medium, and a dried body containing cellulose nanofibers and a silicon-based porous material is produced.

[0099] The device used in this step is not particularly limited. For example, a hot air dryer or a vacuum dryer can be used. Specifically, for example, a hot air dryer (Labostar CONVECTION OVEN LC-122) manufactured by ESPEC Corporation can be used.

[0100] In addition, from the viewpoints of removing moisture from the mixed aqueous solution of cellulose nanofibers and a silicon-based porous material and shortening the drying time, the drying temperature is preferably 80 to 100 °C. It should be noted that natural drying can also be carried out at room temperature regardless of the drying time.

[0101] In addition, from the viewpoint of not leaving moisture in the dried body, for example, when drying in an environment of 80 °C to 100 °C, the drying time is preferably at least half a day to about two days.

[0102] (Dried body pulverization step)

[0103] Next, the prepared dried body is pulverized to produce the composite powder of the present invention in which cellulose nanofibers are attached to the surface of the silicon-based porous material or the cellulose nanofibers enter the pores of the silicon-based porous material.

[0104] The device used in this step is not particularly limited. For example, if it is on a small scale, a household grinder or a mixer or a juicer for crushing food can be flexibly used. When producing on a larger scale (in large quantities), a large device, a powder mill, a grinder, etc. can be used.

[0105] In addition, when adding the obtained composite powder to a resin or the like, a wet atomization device accompanied by high pressure can be used. In this case, the size of the powder for which this treatment can be performed depends on the diameter of the nozzle that generates high pressure. Therefore, after this dry body pulverization step, in order to obtain only a composite powder having a size equal to or smaller than the diameter of the nozzle used, the size of the composite powder can be sieved (classified) using a sieve or the like.

[0106] It should be noted that as a method for obtaining a composite powder from a dispersion liquid, a spray drying method can also be used, and this spray drying method can shorten the above-mentioned drying step, pulverization step, and classification step. In addition, in this spray drying, the drying step and the pulverization step can be performed separately, or the drying step and the pulverization step can be performed simultaneously.

[0107] Moreover, according to the manufacturing method of the composite powder of the present invention described above, the cellulose nanofibers are carried in a state of entering the micropores of the silicon-based porous material (or in a state where the cellulose nanofibers are attached to the surface of the silicon-based porous material), so that a composite powder that can be uniformly dispersed in a thermosetting resin can be obtained. As a result, the strength of the curable resin composition of the present invention and the CFRP containing the curable resin composition of the present invention can be reliably improved.

[0108] (Manufacturing process of curable resin composition)

[0109] Next, a curable resin composition in which the composite powder is dispersed in the above-mentioned thermosetting resin is produced. More specifically, first, the obtained composite powder is added to the thermosetting resin and stirred and mixed using a device, thereby producing a curable resin composition in which the composite powder is dispersed in the thermosetting resin.

[0110] It should be noted that as a device for mixing the composite powder into the thermosetting resin, for example, a propeller type stirrer, a planetary centrifugal mixer, a homogenizer, an ultrasonic stirrer, a bead mill, a ball mill, a kneader, a three-roll mill, a planetary mixer, a wet atomization device, etc. can be used.

[0111] At this time, in the curable resin composition of the present invention, since, as described above, the content of the composite powder relative to 100 parts by mass of the thermosetting resin is 0.1 to 10 parts by mass, the strength of the curable resin composition can be improved, and the impregnation property of the curable resin composition with respect to reinforcing fibers such as carbon fibers can be maintained.

[0112] In addition, in the composite powder, since the cellulose nanofibers are at least attached to the surface of the silicon-based porous material or at least enter the pores of the silicon-based porous material, unlike the above prior art, the composite powder (i.e., cellulose nanofibers) can be directly added to a matrix resin such as a liquid epoxy resin before curing by a simple device such as the above-mentioned blender, without the need for water or a solvent that needs to be removed in subsequent processes. Therefore, the dispersibility of cellulose nanofibers in the thermosetting resin can be improved by a simple method.

[0113] It should be noted that the addition amount of the composite powder in the curable resin composition of the present invention is expressed in mass% relative to the entire matrix resin (thermosetting resin) impregnated in the CFRP (i.e., the content (mass parts) of the composite powder relative to 100 mass parts of the thermosetting resin). However, in a two-component resin using a main agent and a curing agent, the amount of the composite powder added can be, for example, the amount of mass increase expected when the curing agent is added to the main agent.

[0114] In addition, when multiple epoxy resins are used in combination, although the composite powder can be evenly dispersed in all the epoxy resins, correspondingly, it is time-consuming and laborious to disperse the composite powder in various epoxy resins. Therefore, the following method can also be adopted: First, the composite powder is dispersed into one of the epoxy resins to be mixed to an extent that no kneading defect occurs, and then it is mixed with other epoxy resins. Here, the amount of the composite powder is the amount expected to be diluted by other epoxy resins.

[0115] <Cured product>

[0116] The cured product of the present invention is manufactured by curing the curable resin composition of the present invention. The method for curing the curable resin composition of the present invention is not particularly limited. Since the curable resin composition of the present invention contains a thermosetting resin, it can be cured by a known heating method.

[0117] <Fiber-reinforced plastic>

[0118] The fiber-reinforced plastic of the present invention contains the curable resin composition of the present invention and reinforcing fibers (except for the above-mentioned cellulose nanofibers), and is formed by curing a composition (matrix resin) containing the curable resin composition of the present invention and the above-mentioned reinforcing fibers.

[0119] Here, as the reinforcing fiber (except for the above-mentioned cellulose nanofiber), for example, carbon fiber (e.g., pitch-based, PAN-based), aramid fiber, polyarylate fiber, glass fiber, polyethylene fiber, ceramic fiber, PBO fiber (poly(p-phenylene benzobisoxazole)), plant fiber (hemp fiber, linen fiber, bamboo fiber) or animal fiber (wool, silk) and other fibers from natural sources can be used. It should be noted that these materials can be used alone or in combination of two or more.

[0120] In addition, as the manufacturing method of the fiber-reinforced plastic of the present invention, for example, SMC (Sheet Molding Compound) manufacturing method, pultrusion, filament-winding molding, RTM (Resin Transfer Molding), VaRTM (Vacuum-assisted RTM), autoclave molding, oven molding, sheet-wrap molding, internal pressure molding, stamping molding, etc. can be used.

[0121] In addition, the resin content (R.C.) of the fiber-reinforced plastic represented by the following formula (3) is preferably 20% by mass to 60% by mass, and more preferably 20% by mass to 40% by mass from the viewpoint of further exerting the strength of the fiber. However, in order to reduce the resin content, it is necessary to impregnate the resin into the space between the reinforcing fibers in a sufficient amount with a small amount of resin. Therefore, it goes without saying that the impregnability of the resin needs to be fully considered.

[0122] [Formula 3]

[0123] Resin content = [(weight of the resin composition for curing) / (weight of the reinforcing fiber + weight of the resin composition for curing)]×100 (3)

[0124]

Examples

[0125] Hereinafter, the present invention will be described based on examples. It should be noted that the present invention is not limited to these examples, and these examples can be modified and changed based on the gist of the present invention, and such modifications and changes should not be excluded from the scope of the present invention.

[0126] The materials used to prepare the resin composition for curing are as follows.

[0127] (1) Thermosetting resin 1: Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name: JER828)

[0128] (2) Thermosetting resin 2: Polyfunctional epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name: JER604)

[0129] (3) Thermosetting resin 3: Bisphenol A / F type mixed epoxy resin (manufactured by Nagase ChemteX Corporation, trade name: DENATOOL XNR6809)

[0130] (4) Curing agent 1: Modified aromatic amine grade (manufactured by Mitsubishi Chemical Corporation, trade name: WA)

[0131] (5) Curing agent 2: Modified alicyclic anhydride (manufactured by Nagase ChemteX Corporation, trade name: DENATOOLXNH6809)

[0132] (Example 1)

[0133] <Production of composite powder>

[0134] First, a composite powder containing cellulose nanofibers and a silicon-based porous material was produced. More specifically, first, an aqueous solution of cellulose nanofibers (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: RHEOCRYSTA I-2SX, cellulose nanofiber solid content: 2.0 mass%) in which cellulose nanofibers opened by TEMPO oxidation catalyst were dispersed was diluted with ion-exchanged water so that the content of cellulose nanofibers was 1.0 mass%.

[0135] It should be noted that if the aqueous solution of cellulose nanofibers becomes acidic, the double-layer repulsive force of the cellulose fibers becomes weak, and then due to the formation of hydrogen bond binding points between the fibrils, it aggregates and gels. In the case of adding an aqueous solution of polyvalent metal salt, for example, through the TEMPO oxidation reaction, the COONa groups introduced into the cellulose nanofibers are replaced with COOM groups (M is a polyvalent metal), resulting in gelation. Therefore, in order to prevent this, ammonia water can be appropriately added to the aqueous solution of cellulose nanofibers in this example to keep it alkaline at all times.

[0136] Next, 9.09 g of diatomaceous earth (manufactured by Shinsei Filter Kogyo Co., Ltd., trade name: Celpure S-300, micropore aperture: 50 to 600 nm) was added to 91 g of the diluted aqueous solution of cellulose nanofibers, and then continuously stirred for 5 hours to prepare a dispersion (slurry).

[0137] Note that, based on mass, when the content ratio of cellulose nanofibers to diatomaceous earth in an aqueous solution in which cellulose nanofibers are dispersed is cellulose nanofibers:diatomaceous earth = 1:10 (that is, in the above formula (1), X = 10), the concentration of cellulose nanofibers in the cellulose nanofiber aqueous solution, which is 1.0 mass% (that is, in the above formula (1), Y = 1.0), satisfies the relationship of the above formula (1).

[0138] Next, the prepared dispersion is dried to remove water as the dispersion medium, thereby producing a dried body containing cellulose nanofibers and a silicon-based porous material. More specifically, by transferring the prepared dispersion to a thin stainless-steel tray (pallet) and leaving it standing in a hot-air drying oven at 80°C for more than one night, water as the dispersion medium is removed, thereby producing a plate-shaped dried body.

[0139] Next, after the obtained plate-shaped dried body is pulverized using a food processor (manufactured by Cuisinart Co., Ltd., product name: Powder Grinder SG-10BJK), it is classified using a classifier (specifically, using a sieve (manufactured by SANPO Co., Ltd., stainless-steel sieve)), and the composite powder of Example 1 with a particle diameter of 150 μm or less and having the composition (parts by mass) shown in Table 1 (that is, based on mass, cellulose nanofibers:diatomaceous earth = 1:10) is recovered.

[0140] Note that a scanning electron microscope (SEM) photograph showing the state of the composite powder of this example is shown in Figure 2 as follows. As Figure 2 shown, it can be seen that in the composite powder of this example, the cellulose nanofibers are carried in a state of entering the micropores (hollow micropores) of the diatomaceous earth located in the central part of the photograph.

[0141] <Elemental Analysis of Composite Powder>

[0142] In addition, the results of analyzing the composite powder of this example (carbon atom analysis) by energy dispersive X-ray spectroscopy (EDS) using a scanning electron microscope (SEM) are shown together with the scanning electron microscope (SEM) photograph in Figure 3 as follows.

[0143] As Figure 3 shown, there are carbon atoms derived from cellulose nanofibers (the white parts in Figure 3 ), and the cellulose nanofibers are dispersed throughout the composite powder.

[0144] It should be noted that the above SEM observation and EDS analysis were performed using a scanning electron microscope (manufactured by JEOL Ltd., trade name: JSM-IT100).

[0145] <Production of Resin Composition for Curing and Evaluation of Dispersibility of Composite Powder in Thermosetting Resin>

[0146] At room temperature (25 °C), the prepared composite powder was mixed into the thermosetting resin 1 (epoxy resin) shown in Table 2 to produce a resin composition for curing, and the dispersibility of the composite powder in the prepared resin composition for curing relative to the epoxy resin was evaluated.

[0147] More specifically, first, 25 parts by mass of a curing agent was added to 100 parts by mass of the thermosetting resin, and the prepared composite powder was added so that the composite powder was 0.1 part by mass. Then, using a stirring and defoaming machine (manufactured by Kyoritsu Seiki Co., Ltd., trade name: Hi-Merger HM-200WD), under setting 7 of this device, stirring and mixing were carried out at room temperature, with a stirring time of 5 minutes and a defoaming time of 3 minutes, thereby producing a resin composition for curing in which the composite powder was dispersed in the thermosetting resin.

[0148] Next, the dispersibility of the composite powder in the prepared resin composition for curing relative to the epoxy resin was evaluated. More specifically, those in which no precipitation of the composite powder was observed during the 1 minute after adding the composite powder and mixing were marked as 〇, and those in which aggregation of the composite powder was observed during the operation of adding the composite powder and mixing, or precipitation of the composite powder was observed during the 1 minute after adding the composite powder and mixing were marked as ×. The above results are shown in Table 2.

[0149] <Evaluation of Impregnability>

[0150] Next, the viscosity of the prepared resin composition for curing was measured using an E-type viscometer (cone-plate type rotational viscometer, manufactured by Toki Sangyo Co., Ltd., trade name: TPE-100). It should be noted that the measurement was carried out under the conditions of a cone rotor (3°×R12), a rotation speed of 1.9 rpm, and a shear rate of 3.8 (1 / s). In addition, starting from room temperature (25 °C), the temperature was raised at a rate of 5 °C / min, and the viscosity was measured at room temperature (25 °C), 30 °C, 40 °C, 50 °C, 60 °C, and 70 °C while maintaining each temperature for 1 minute.

[0151] In addition, as a reference sample, a curable resin composition without the added composite powder shown in Table 2 (a curable resin composition formed only of thermosetting resin 1 and curing agent 1) was prepared. Using the same method, the viscosity of the reference sample was measured, and the viscosity of the reference sample at each measurement temperature (i.e., normal temperature (25 °C), 30 °C, 40 °C, 50 °C, 60 °C, and 70 °C) was compared with the viscosity of the curable resin composition of the present example. When the viscosity of the curable resin composition of the present example was 3.5 times or less the viscosity of the reference sample (that is, when the viscosity of the curable resin composition added with the composite powder did not become too high and the curable resin composition could easily penetrate into reinforcing fibers such as carbon fibers), it was marked as 〇. When the viscosity of the curable resin composition of the present example was more than 3.5 times the viscosity of the reference sample (that is, when the viscosity of the curable resin composition added with the composite powder became too high and it was difficult for the curable resin composition to penetrate into reinforcing fibers such as carbon fibers), it was marked as ×. The above results are shown in Table 2.

[0152] <Strength evaluation>

[0153] Next, the above-prepared curable resin composition was impregnated into carbon fibers (manufactured by Toray Industries, Inc., product name: TORAYCA T700S) to produce a unidirectional long fiber prepreg (a sheet-like intermediate material in which the prepared curable resin composition was impregnated into carbon fibers). As Figure 4 shown, 16 pieces of the above-prepared prepregs (210 mm × 210 mm) were prepared, stacked in such a way that the alignment direction of the carbon fibers 2 in each prepreg 1 was the same direction (i.e., the direction of arrow X in the figure), and pressed under the conditions of a pressing pressure of 7.85 MPa, a pressing temperature of 175 °C, and a pressing time of 4 hours to produce a prepreg laminate (CFRP) 10 with a thickness of 2 mm.

[0154] Furthermore, the prepared prepreg laminate 10 was cut to produce a specimen of 25 mm × 110 mm. An Al electrode tab of 25 mm × 50 mm (the top 15 mm was tapered) was attached to the upper and lower end faces of the prepared specimen to obtain a test piece. Then, using a tensile testing machine (manufactured by Shimadzu Corporation, product name: “Autograph” AG-X plus), a tensile test was conducted at a tensile speed of 1 mm / min in a direction perpendicular to the alignment direction of the carbon fibers 2 (i.e., the direction of arrow Y in the figure), and the strength at the time of its fracture was taken as the tensile strength of the curable resin composition 3.

[0155] It should be noted that “the direction perpendicular to the alignment direction of the carbon fibers” means: as Figure 4As shown, when the arrangement direction of the carbon fibers 2 in the prepreg laminate 10 (axial direction, direction of arrow X) is defined as 0°, the direction (direction of arrow Y) orthogonal to the arrangement direction of the carbon fibers 2 (0° axis).

[0156] In addition, the strength in the direction 90° relative to the arrangement direction of the carbon fibers represents the strength brought by the curing resin composition without being affected by the strength of the carbon fibers (the strength of the curing resin composition alone, or the strength of the tightness at the interface between the carbon fibers and the curing resin composition, or both).

[0157] In addition, as a reference sample, a curing resin composition (a curing resin composition composed only of thermosetting resin 1 and curing agent 1) without adding composite powder as shown in Table 2 was prepared, and the tensile strength of the reference sample was calculated by the same method and compared with the tensile strength of the curing resin composition of this embodiment, and the tensile strength of the curing resin composition of this embodiment was greater than the tensile strength of the reference sample. The tensile strength of the curing resin composition of this embodiment was recorded as 0, and the tensile strength of the curing resin composition of this embodiment was recorded as ×. The above results are shown in Table 2.

[0158] Here, since the strength of carbon fiber is greater than that of the curing resin composition used, the starting point of damage in the structure of the curing resin composition (CFRP) is located in the resin, at the interface between the resin and the fiber, or when the structure is formed by overlapping sheet-shaped prepregs, the starting point of damage is located at the interface between the sheets (layers). It should be noted that damage at the interface between layers is also called "interlayer delamination".

[0159] Furthermore, in the various methods for manufacturing the above-mentioned fiber-reinforced plastics, common features include: the presence of gaps between fibers at a microscopic level, the presence of portions consisting only of resin, and the presence of interfaces between the resin and the fibers. Therefore, it goes without saying that the improvement in the above-mentioned "tensile strength in a direction 90° to the arrangement direction of the carbon fibers 2" is very effective for strengthening portions consisting only of resin or strengthening the interfaces between the resin and the fibers.

[0160] Furthermore, in the above-mentioned various methods for producing fiber-reinforced plastics, when a laminate is produced, the curing resin composition to which the composite powder of the present application is added can be partially used, particularly in a layer that receives stress.

[0161] (Examples 2 to 44, Comparative Examples 1 to 3, 6 to 8, 10 to 13)

[0162] In these Examples and Comparative Examples, the types and contents of the thermosetting resin and the curing agent, the type of the silicon-based porous material, the addition amount of the composite powder relative to 100 parts by mass of the thermosetting resin, and the content ratio of cellulose nanofibers to the silicon-based porous material in the composite powder were changed to the values shown in Tables 2 to 8, and other than that, it was the same as Example 1 above. In this way, the resin composition for curing was prepared.

[0163] Moreover, the same as in Example 1 above, the dispersibility evaluation, impregnation evaluation, and strength evaluation of the composite powder relative to the thermosetting resin were carried out. The above results are shown in Tables 2 to 8.

[0164] It should be noted that in Comparative Examples 10 to 12, the proportion of diatomaceous earth relative to cellulose nanofibers was small, and in the dispersibility evaluation, the cellulose nanofibers aggregated and precipitated, so the above impregnation evaluation and strength evaluation could not be carried out.

[0165] In addition, in Comparative Example 13, the proportion of diatomaceous earth relative to cellulose nanofibers was large, and the content of the composite powder relative to 100 parts by mass of the thermosetting resin was more than 10 parts by mass. Therefore, in the dispersibility evaluation, the dispersibility of the composite powder decreased. As a result, the above impregnation evaluation and strength evaluation could not be carried out.

[0166] (Comparative Example 4)

[0167] In Comparative Example 4, the composite powder was not prepared, and only diatomaceous earth (9.1 parts by mass) was used to replace the composite powder in Example 1 above (that is, diatomaceous earth was used as a monomer), and other than that, it was the same as Example 1 above. In this way, the resin composition for curing was prepared.

[0168] Moreover, the same as in Example 1 above, the dispersibility evaluation, impregnation evaluation, and strength evaluation of the composite powder relative to the thermosetting resin were carried out. It should be noted that in the impregnation evaluation and strength evaluation, as a reference sample, the resin composition for curing without adding diatomaceous earth shown in Table 6 (the resin composition for curing formed only by thermosetting resin 1 and curing agent 1) was used. The above results are shown in Table 6.

[0169] (Comparative Example 5)

[0170] In Comparative Example 5, the composite powder was not prepared, and only cellulose nanofibers (0.9 parts by mass) were used to replace the composite powder in Example 1 above (that is, cellulose nanofibers were used as a monomer), and other than that, it was the same as Example 1 above. In this way, the resin composition for curing was prepared.

[0171] Moreover, the same as in Example 1 above, the dispersibility evaluation of the composite powder relative to the thermosetting resin was carried out. The above results are shown in Table 6.

[0172] It should be noted that in the dispersion evaluation, the cellulose nanofibers aggregated and precipitated, so the above impregnation evaluation and strength evaluation could not be carried out.

[0173] In addition, in this comparative example, as the cellulose nanofibers, an aqueous solution of cellulose nanofibers (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name: RHEOCRYSTA I-2SX, content of solid component of cellulose nanofibers: 2.0% by mass) in which cellulose nanofibers fibrillated by a TEMPO oxidation catalyst were dispersed was used, and the dried and pulverized cellulose nanofibers (dried by standing for three days in an environment of 80 °C and then pulverized with a food processor) were obtained.

[0174] (Comparative Example 9)

[0175] In Comparative Example 9, the composite powder was not prepared, and only zeolite (9.1 parts by mass) was used instead of the composite powder in Example 1 above (that is, zeolite was used as a monomer), and the other conditions were the same as those in Example 1 above. In this way, the curable resin composition was prepared.

[0176] And, the same as in Example 1 above, the dispersion evaluation, impregnation evaluation, and strength evaluation of the composite powder with respect to the thermosetting resin were carried out. It should be noted that in the impregnation evaluation and strength evaluation, as a reference sample, the curable resin composition without zeolite shown in Table 7 (the curable resin composition formed only of thermosetting resin 1 and curing agent 1) was used. The above results are shown in Table 7.

[0177]

Table 2

[0178]

[0179]

Table 3

[0180]

[0181]

Table 4

[0182]

[0183]

Table 5

[0184]

[0185]

Table 6

[0186]

[0187]

Table 7

[0188]

[0189]

Table 8

[0190]

[0191] As shown in Tables 2 to 5, in the curable resin compositions of Examples 1 to 44, on a mass basis, the content ratio of cellulose nanofibers to the silicon-based porous material is cellulose nanofibers:silicon-based porous material = 1:5 to 1:20 (that is, relative to 1 part by mass of cellulose nanofibers, the silicon-based porous material is 5 to 20 parts by mass). Therefore, it can be known that in the composite powder, the cellulose nanofibers enter the pores of the silicon-based porous material (or adhere to the surface of the silicon-based porous material), and suppress the decrease in the amount of cellulose nanofibers entering the micropores (or the amount of cellulose nanofibers adhering to the surface of the silicon-based porous material) due to the shortage of the silicon-based porous material. As a result, the formation of aggregates of cellulose nanofibers on the surface of the silicon-based porous material can be prevented. As a result, in the curable resin composition, the cellulose nanofibers can be uniformly dispersed in the thermosetting resin (epoxy resin).

[0192] In addition, in the curable resin compositions of Examples 1 to 44, the content of the composite powder relative to 100 parts by mass of the thermosetting resin is 0.1 to 10 parts by mass. Therefore, it can be known that even when the composite powder is contained, the viscosity of the curable resin composition does not become too high, and the curable resin composition can easily penetrate into the carbon fiber (that is, the impregnation property of the curable resin composition with respect to the carbon fiber can be maintained), and the strength of the curable resin composition in the CFRP can be improved.

[0193] -Industrial Applicability-

[0194] In summary, the present invention is very suitable for curable resin compositions for rubber, resin, and carbon fiber reinforced plastics.

Claims

1. A resin composition for curing, the resin composition for curing contains at least a thermosetting resin and a composite powder, the composite powder contains cellulose nanofibers and a silicon-based porous material, and is characterized in that: Based on mass, the content ratio of the cellulose nanofibers to the silicon-based porous material is cellulose nanofibers:silicon-based porous material = 1:5 to 1:20, In the composite powder, the cellulose nanofibers are at least attached to the surface of the silicon-based porous material or at least enter the pores of the silicon-based porous material, The content of the composite powder relative to 100 parts by mass of the thermosetting resin is 0.1 to 10 parts by mass.

2. The resin composition for curing according to claim 1, characterized in that: The cellulose nanofibers are cellulose nanofibers obtained by chemical fibrillation treatment.

3. The resin composition for curing according to claim 1 or 2, characterized in that: The silicon-based porous material includes at least one of diatomaceous earth and zeolite.

4. The resin composition for curing according to claim 1 or 2, characterized in that: The thermosetting resin is an epoxy resin.

5. The resin composition for curing according to claim 3, characterized in that: The thermosetting resin is an epoxy resin.

6. A cured product, characterized in that: The cured product is obtained by curing the resin composition for curing according to claim 1 or 2.

7. A fiber-reinforced plastic, characterized in that: The fiber-reinforced plastic contains the resin composition for curing according to claim 1 or 2 and reinforcing fibers other than the cellulose nanofibers.

Images