Composite material and production method therefor

Abstract

A composite material obtained by conjugating a resin with a modified material obtained by irradiating a carbon nanotube material with ultraviolet rays.

Description

Composite material and its manufacturing method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority based on Japanese Patent Application No. 2024-134309 filed on August 9, 2024, and incorporates by reference all the contents of said Japanese application.

[0002] The present disclosure relates to composite materials and methods for making the same.

[0003] Carbon fiber reinforced resins have excellent physical properties such as strength and rigidity. For this reason, such reinforced resins are widely used in industrial fields such as automobile parts and sporting goods. In recent years, the use of carbon nanotubes instead of carbon fibers in carbon fiber reinforced resins has been investigated (see, for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2023-117181

[0005] The present inventors have investigated composite materials containing a carbon nanotube-based material and a resin. As a result, the present inventors have found that such composite materials or molded articles obtained from the composite materials may have insufficient mechanical properties. An object of the present disclosure is to provide a composite material containing a carbon nanotube-based material and a resin, which has excellent mechanical properties or which can be used to form a molded article having excellent mechanical properties.

[0006] One embodiment of the composite material of the present disclosure is obtained by combining a modified material obtained by irradiating a carbon nanotube-based material with ultraviolet light and a resin.

[0007] One aspect of the composite material disclosed herein is a composite material having excellent mechanical properties or a composite material capable of forming a molded body having excellent mechanical properties, which is obtained by combining a modified material obtained by irradiating a carbon nanotube-based material with ultraviolet light with a resin.

[0008] Fig. 1 is a top view of a carbon nanotube forest and a carbon nanotube web, illustrating a method for manufacturing a carbon nanotube web. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. Fig. 3 is an explanatory diagram of a test piece auxiliary tool for a tensile test.

[0009] An example of an embodiment of the present disclosure will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show characteristic portions enlarged for convenience in order to make the features of the contents of the present disclosure easier to understand. Therefore, the dimensional ratios of each component may differ from the actual ones.

[0010] In this specification, a numerical range A to B means A or more and B or less. In this specification, when the units of the numerical values ​​before and after "to" indicating a numerical range are the same, the unit of the numerical value before "to" may be omitted. The upper and / or lower limit values ​​of the numerical ranges described in this specification can be arbitrarily combined to define a preferred range. For example, the upper and lower limit values ​​of a numerical range can be arbitrarily combined to define a preferred range, the upper limit values ​​of a numerical range can be arbitrarily combined to define a preferred range, and the lower limit values ​​of a numerical range can be arbitrarily combined to define a preferred range. Throughout this specification, singular expressions should be understood to include the concept of the plural, unless otherwise specified. Therefore, singular articles (e.g., "a," "an," "the," etc. in English) should be understood to include the concept of the plural, unless otherwise specified. Furthermore, it should be understood that terms used in this specification are used in the sense commonly used in the relevant field, unless otherwise specified.

[0011] In the following description, the terms "film" and "sheet" are not clearly distinguished from each other, and the term "film" includes "sheet," and the term "sheet" includes "film."

[0012] In this specification, "parallel" includes not only strictly parallel but also approximately parallel. Regarding parallel, the angle formed by them may be, for example, 30° or less, 20° or less, 10° or less, or 5° or less. Regarding "perpendicular" in this specification, "perpendicular" includes not only strictly perpendicular but also approximately perpendicular, and "orthogonal" includes not only strictly perpendicular but also approximately perpendicular. Regarding perpendicular and orthogonal, the angle formed by them may be, for example, 60° or more and 90° or less, 70° or more and 90° or less, 80° or more and 90° or less, or 85° or more and 90° or less.

[0013] Hereinafter, carbon nanotubes will also be referred to as "CNTs," carbon nanotube-based materials will also be referred to as "CNT-based materials," modified materials will also be referred to as "CNT-based modified materials," fibers containing carbon nanotubes will also be referred to as "CNT fibers," yarns made of CNT fibers will also be referred to as "CNT yarns," a web-like body of carbon nanotubes will also be referred to as "CNT web-like body," and a film of carbon nanotubes will also be referred to as "CNT film."

[0014] [Composite Material] The composite material of the present disclosure is obtained by compounding a modified material obtained by irradiating a carbon nanotube-based material with ultraviolet light, and a resin. Here, compounding means impregnating the modified material with the resin or mixing the modified material with the resin.

[0015] <Modified Material> Modified materials (CNT-based modified materials) are obtained by irradiating carbon nanotube-based materials (CNT-based materials) with ultraviolet light. In other words, CNT-based modified materials are materials obtained by irradiating CNT-based materials with ultraviolet light. Note that there are cases where CNT-based materials are exposed to ultraviolet light contained in sunlight or indoor light, to an extent that the following modification or denaturation does not occur. In this case, the CNT-based material does not fall under the category of CNT-based modified materials obtained by irradiating CNT-based materials with ultraviolet light.

[0016] Compared to carbon fibers, CNT-based materials tend to be less compatible with resins, and are therefore less easily impregnated with resins. Therefore, when a composite material is produced by simply impregnating a CNT-based material with resin, the composite material and the molded article obtained therefrom tend to have insufficient mechanical properties, such as tensile strength or modulus of elasticity. In contrast, the composite material of the present disclosure is obtained by combining a modified CNT material, which is a CNT-based material irradiated with ultraviolet light, with a resin. Such a composite material and the molded article obtained therefrom have excellent mechanical properties, such as tensile strength or modulus of elasticity. While the reason for this is unclear, the inventors speculate that this is because the surface of the CNT-based material is modified or denatured by irradiating the CNT-based material with ultraviolet light, making the CNT-based material more compatible with resins.

[0017] Furthermore, the composite material of the present disclosure obtained by compounding a CNT-based modified material with a resin exhibits less resin degradation due to UV irradiation than a material obtained by compounding a CNT-based material with a resin and then irradiating it with UV rays. Therefore, the use of the composite material of the present disclosure allows for the production of high-quality molded articles.

[0018] One type of CNT-based modifier may be used, or two or more types may be used. The content of the CNT-based modifier in the composite material of the present disclosure is preferably 10 to 90 mass%, more preferably 30 to 85 mass%, even more preferably 50 to 80 mass%, and particularly preferably 55 to 75 mass%. Such a composite material has excellent mechanical properties such as tensile strength and elastic modulus, and can form a molded article with excellent mechanical properties.

[0019] From the viewpoint of the above-mentioned modification or denaturation, the wavelength of the ultraviolet light irradiated onto the CNT material is preferably 380 nm or less, more preferably 340 nm or less, even more preferably 300 nm or less, still more preferably 250 nm or less, and particularly preferably 200 nm or less, and is preferably 120 nm or more, more preferably 140 nm or more, and even more preferably 160 nm or more, for example, 120 to 380 nm.

[0020] Examples of sources of ultraviolet light include excimer lamps, low-pressure mercury lamps, high-pressure mercury lamps, extra-high-pressure mercury lamps, xenon lamps, halogen lamps, metal halide lamps, and lasers.

[0021] The excimer lamp may be, for example, a rare gas excimer lamp, a halogen excimer lamp, or a rare gas-halogen excimer lamp such as Ar, Kr, F, ArBr, Xe, ArCl, ArF, KrBr, KrCl, KrF, XeI, Cl, and XeCl.

[0022] Examples of the laser include gas lasers, solid-state lasers, and liquid lasers. Gas lasers include excimer lasers. Excimer lasers include rare gas excimer lasers, halogen excimer lasers, and rare gas-halogen excimer lasers, such as Ar lasers, Kr lasers, F lasers, Xe lasers, ArF lasers, KrCl lasers, KrF lasers, and XeCl lasers. Solid-state lasers include Nd:YAG lasers, Nd:YLF lasers, Nd:glass lasers, Nd:YVO lasers, Yb:YAG lasers, Yb-doped fiber lasers, Er:YAG lasers, and Tm:YAG lasers. Liquid lasers include dye lasers. Laser irradiation may be, for example, continuous wave laser irradiation, pulsed wave laser irradiation, or both continuous wave and pulsed wave laser irradiation.

[0023] Among the above ultraviolet light sources, an excimer lamp or an excimer laser is preferred. The wavelength of ultraviolet light from an excimer lamp or an excimer laser is preferably 120 to 380 nm, more preferably 140 to 300 nm, and even more preferably 160 to 250 nm.

[0024] CNT-based materials will be specifically described below. The CNT-based material is not particularly limited as long as it is a material containing an aggregate of CNTs. Examples of CNT-based materials include CNT powder, CNT fibers, CNT yarns, woven fabrics of CNT fibers or CNT yarns, nonwoven fabrics of CNT fibers or CNT yarns, CNT web-like bodies, and CNT films. Of these, sheet-like bodies such as woven fabrics of CNT fibers or CNT yarns, nonwoven fabrics of CNT fibers or CNT yarns, CNT web-like bodies, and CNT films are preferred as CNT-based materials.

[0025] CNTs can be produced using conventionally known methods, such as thermal chemical vapor deposition (thermal CVD), plasma CVD, laser ablation, arc discharge, or combustion.

[0026] The average length of the CNTs is preferably 10 to 1000 μm, more preferably 30 to 800 μm, and even more preferably 50 to 500 μm. The average length of the CNTs can be adjusted, for example, by adjusting the time for which the CVD method is performed, i.e., the CNT growth time. The average diameter of the CNTs is preferably 1 to 50 nm, more preferably 3 to 30 nm, and even more preferably 5 to 15 nm. The average diameter of the CNTs can be adjusted, for example, by adjusting the thickness of the catalyst layer and the type of catalyst, as described below.

[0027] The average length and average diameter of CNTs are measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Specifically, 10 images of CNTs are obtained using an SEM or TEM. Ten length measurement points are randomly selected and measured for each of the 10 images, resulting in a total of 100 length measurements. The average length of the CNTs is then determined by arithmetically averaging the 100 length measurements. Additionally, ten diameter measurement points are randomly selected and measured for each of the 10 images, resulting in a total of 100 diameter measurements. The average diameter of the CNTs is then determined by arithmetically averaging the 100 diameter measurements.

[0028] The carbon purity of the CNT is, for example, 90.0 to 100% (mass%), preferably 95.0 to 99.999%. The lower limit of the carbon purity of the CNT is preferably 96.0%, more preferably 97.0%, even more preferably 98.0%, still more preferably 99.0%, and particularly preferably 99.8%. The upper limit of the carbon purity of the CNT may be, for example, 99.99% or 99.9%. The carbon purity of the CNT can be determined, for example, by elemental analysis using fluorescent X-rays.

[0029] The crystallinity of CNTs can be evaluated, for example, by Raman spectroscopy. In the evaluation of crystallinity by Raman spectroscopy, the value of the D / G ratio is used as an index. The D / G ratio is the value of the D / G ratio at 1580 cm in the Raman spectrum measured by Raman spectroscopy. -1 The peak intensity of the G band appearing near 1360 cm -1 The D / G ratio is the ratio of the peak intensity of the D band appearing near the center of the carbon nanotube. The smaller the D / G ratio, the higher the crystallinity of the carbon nanotube. The D / G ratio of the CNT before UV irradiation is, for example, 0.4 to 1.1, preferably 0.5 to 1.0, and more preferably 0.6 to 0.8.

[0030] The carbon purity and crystallinity of the CNTs can be adjusted, for example, by adjusting the thickness of the buffer layer in the catalyst substrate described below, the type of material used for the buffer layer, the thickness of the catalyst layer, the type of catalyst, the type and flow rate of the raw material gas in the CVD method, and the temperature and pressure in the reaction chamber.

[0031] The CNT may be a single-walled carbon nanotube or a multi-walled carbon nanotube with two or more walls. The CNT is preferably a multi-walled carbon nanotube. The number of walls of the multi-walled carbon nanotube is not particularly limited, but is preferably 2 to 20.

[0032] CNT powder refers to a powder containing multiple CNTs. CNT fiber refers to a fiber containing multiple CNTs. CNT fiber is a fiber in which multiple CNTs are aligned in one direction. In CNT fiber, the longitudinal direction of multiple CNTs is aligned in one direction.

[0033] CNT fibers can be produced, for example, by extracting multiple CNTs from a CNT forest. CNT yarns can be, for example, linear bodies obtained by bundling CNT webs extracted into a sheet from a CNT forest, or twisted yarns obtained by twisting such linear bodies. CNT yarns can also be obtained, for example, by spinning a CNT dispersion.

[0034] The average diameter of the CNT yarn is preferably 1 nm to 2 mm, more preferably 100 nm to 100 μm, and even more preferably 1 to 30 μm. The average diameter of the CNT yarn is measured by the same method as the average diameter of the CNTs.

[0035] Examples of woven fabrics made of CNT fibers or CNT yarns include plain weave, twill weave, and satin weave fabrics. Examples of nonwoven fabrics made of CNT fibers or CNT yarns include conventionally known nonwoven fabrics made of CNT fibers or CNT yarns.

[0036] A CNT web refers to a web containing a plurality of CNT fibers. When the CNT web is viewed from above, the CNT web may be, for example, an aggregate in which a plurality of CNT fibers extend in one direction and are aligned in a direction perpendicular to that direction. "Viewing a CNT web from above" means viewing the planar CNT web from its normal direction.

[0037] For example, when viewed from above, the CNT web may be an assembly including a first fiber group in which a plurality of CNT fibers extend along a first direction and are aligned in a direction perpendicular to the first direction, and a second fiber group in which a plurality of CNT fibers extend along a second direction and are aligned in a direction perpendicular to the second direction, where the first direction and the second direction intersect. The angle between the first direction and the second direction is not particularly limited. The first direction and the second direction may be, for example, perpendicular to each other. The CNT web may further include an nth fiber group (n is an integer of 3 or greater) in which a plurality of CNT fibers extend along an nth direction and are aligned in a direction perpendicular to the nth direction.

[0038] A CNT web can be produced, for example, by extracting multiple CNTs from a CNT forest, specifically by extracting multiple CNTs into a sheet. The size of the CNT web can be adjusted by adjusting the width of the CNTs extracted from the CNT forest.

[0039] A CNT forest is an aggregate of CNTs arranged on a substrate and aligned perpendicular to the surface of the substrate.

[0040] CNT forests can be obtained, for example, by chemical vapor deposition (CVD) using a catalyst substrate comprising a substrate and a catalyst layer provided on the substrate. CVD involves placing the catalyst substrate in a reaction chamber, supplying raw material gas into the chamber, and growing CNTs on the surface of the catalyst layer. Thermal CVD is preferred as the CVD method.

[0041] Examples of the substrate include a silicon substrate, an alumina substrate, a magnesium oxide substrate, a glass substrate, a sapphire substrate, and a stainless steel substrate.

[0042] The catalyst layer can be formed by depositing catalyst particles on the substrate, for example, by sputtering. Examples of catalysts include metals, specifically iron (Fe), nickel (Ni), cobalt (Co), molybdenum (Mo), gold (Au), and alloys containing at least one metal selected from the group consisting of these. Examples of alloys include iron alloys, nickel alloys, and cobalt alloys. The catalyst may also be a metal precursor, such as a metal oxide or a metal compound. Examples of metal oxides include iron oxide, nickel oxide, and cobalt oxide. Examples of metal compounds include iron chloride. When a precursor is used, it must be converted to a metal by, for example, heating the precursor before performing the CVD method.

[0043] The catalyst substrate may further include a buffer layer between the substrate and the catalyst layer. Materials used for the buffer layer include, for example, silica (SiO), alumina (AlO), silicon nitride (SiN), zinc oxide (ZnO), copper oxide (CuO), and nickel oxide (NiO). The buffer layer can be formed, for example, by sputtering.

[0044] The sputtering for forming the catalyst layer and the sputtering for forming the buffer layer can be performed using known apparatus and conditions depending on the target of sputtering. The pressure condition for sputtering is preferably about 0.01 to 10 Pa, more preferably about 0.1 to 1 Pa.

[0045] The source gas may be a carbon-containing source gas, such as a hydrocarbon, a sulfur-containing organic gas, a phosphorus-containing organic gas, carbon monoxide, or an alcohol. Examples of hydrocarbons include alkane compounds such as methane and ethane, alkene compounds such as ethylene and butadiene, alkyne compounds such as acetylene, aryl hydrocarbon compounds such as benzene, toluene, and styrene, aromatic hydrocarbons with condensed rings such as indene, naphthalene, and phenanthrene, cycloalkane compounds such as cyclopropane and cyclohexane, cycloolefin compounds such as cyclopentene, and alicyclic hydrocarbon compounds with condensed rings such as steroids. Examples of alcohols include methanol and ethanol. From the viewpoint of the carbon purity of the resulting CNTs, the source gas is preferably a hydrocarbon.

[0046] A carrier gas, which is a gas that carries the raw material gas, may be supplied to the reaction chamber together with the raw material gas. Examples of carrier gases include helium, neon, argon, nitrogen, and hydrogen. Hydrogen is also called a reactive carrier gas because it is believed to contribute to the productivity and quality of CNTs.

[0047] The temperature in the reaction chamber in the CVD method is preferably 600 to 850°C, more preferably 650 to 800°C, from the viewpoints of the growth rate of CNTs and the carbon purity of the resulting CNTs. The pressure in the reaction chamber in the CVD method is preferably atmospheric pressure, from the viewpoints of the growth rate of CNTs and the carbon purity. The pressure in the reaction chamber may be reduced or increased from atmospheric pressure depending on other conditions when the CVD method is carried out.

[0048] The average length and average diameter of the CNTs in the CNT forest are, for example, similar to the average length and average diameter of the CNTs described above, respectively.

[0049] The CNT web-like object is preferably a CNT web obtained by extracting multiple CNTs from a CNT forest provided on a substrate, or a laminate of such CNT webs. When the CNT web is viewed in plan, for example, the CNT web is an aggregate in which multiple CNT fibers extend in one direction and are aligned in a direction perpendicular to that direction. Hereinafter, the direction in which the CNT fibers extend in the CNT web is also referred to as the "longitudinal direction of the CNT fibers."

[0050] CNT fibers or CNT webs can be produced, for example, by using a pinching tool such as tweezers to pull out an end-located CNT from a CNT forest in a direction parallel to the surface of the substrate on which the CNT forest is formed. When the end-located CNT is pulled out, the CNTs adjacent to the pulled-out CNT are successively pulled out due to van der Waals forces. The pulled CNTs are oriented so that their longitudinal directions are aligned in the direction of pulling. Therefore, the multiple CNTs that make up a CNT fiber are oriented in one direction. The multiple CNTs that make up a CNT fiber are bonded to each other by van der Waals forces.

[0051] CNT fibers or CNT webs may be produced, for example, by contacting a rectangular tool with the sidewalls or top surfaces of the ends of the CNTs that make up the CNT forest, and then moving the tool away from the CNT forest in a direction parallel to the surface of the substrate on which the CNT forest is provided.

[0052] An example of a method for manufacturing a CNT web will be described with reference to the drawings. Fig. 1 is a top view illustrating the process of manufacturing a CNT web 20 using a CNT forest 12 provided on a substrate 10, and Fig. 2 is a cross-sectional view taken along line AA in Fig. 1.

[0053] 1 and 2 can be produced by pulling out, in a sheet-like form, multiple CNTs located at the end of a CNT forest 12 that is provided on a substrate 10 and aligned perpendicular to the surface of the substrate 10, away from the CNT forest 12 in a direction parallel to the surface of the substrate 10. A CNT web 20 produced by pulling out multiple CNTs in parallel from the CNT forest 12 may be wound around a roller 30 to obtain a laminate of CNT webs 20.

[0054] When the CNT web 20 is viewed from above, the CNT fibers 22 that make up the CNT web 20 extend in the direction in which the CNTs are pulled out, and multiple CNT fibers 22 are aligned in a direction perpendicular to that direction.

[0055] A laminate of CNT webs can be produced, for example, by producing multiple sheet-shaped CNT webs obtained by extracting multiple CNTs from a CNT forest and then stacking these CNT webs, or by producing a roll by wrapping multiple CNT webs obtained by extracting multiple CNTs from a CNT forest around the circumferential surface of a roller, and then slicing the roll open along the direction of the roller's rotation axis. In the latter method, the number of layers of the CNT web is the number of times the CNT web is wrapped around the roller.

[0056] When a plurality of CNT webs are produced in sheet form and then stacked to produce a CNT web laminate, the CNT webs may be stacked so that the longitudinal direction of the CNT fibers constituting one CNT web is parallel to the longitudinal direction of the CNT fibers constituting another CNT web, or the CNT webs may be stacked so that they intersect (for example, orthogonal to) each other.

[0057] The CNT film may be, for example, a laminate of the above-mentioned CNT webs.The CNT film may be, for example, a laminate of CNT webs in which CNT webs are laminated so that the CNT fibers are parallel to each other.

[0058] Examples of CNT films include CNT films obtained by conventionally known methods. CNT films can be obtained, for example, by applying a dispersion of CNTs dispersed in a solvent to a substrate, drying the dispersion to remove the solvent, and peeling the dried product from the substrate; filtering the dispersion using a filter or the like and drying the CNT aggregate deposited on the surface of the filter; uniformly dispersing CNTs in an air current or the like and aggregating the CNTs on the surface of a wire mesh or the like; or by producing multiple CNT fibers, gathering them together, and pressurizing the CNT fiber aggregate to bond the CNT fibers together. CNT films obtained by the above methods are usually films composed of CNTs or CNT fibers.

[0059] The CNT-based materials and CNT-modified materials may be in the form of sheets, such as woven fabrics of CNT fibers or CNT yarns, nonwoven fabrics of CNT fibers or CNT yarns, CNT webs, and CNT films. Examples of the shape of the sheets include rectangular, square, trapezoidal, parallelogram, rhombus, kite, elliptical, and circular.

[0060] The basis weight of the sheet-shaped CNT material and CNT modified material may be set depending on the purpose of the composite material and is not particularly limited. However, from the viewpoint of productivity, for example, it is set to, for example, 0.001 to 170 mg / cm 2 , preferably 0.02 to 170 mg / cm 2 , more preferably 0.03 to 85 mg / cm 2, more preferably 0.05 to 17 mg / cm 2 The basis weight can be determined by measuring the mass of the CNT material or modified CNT material using a scale such as a balance and dividing the mass by the area of ​​the material. When the CNT material is a CNT web laminate, the number of CNT web layers in the laminate is, for example, 2 to 10,000, preferably 20 to 10,000, more preferably 30 to 5,000, and even more preferably 50 to 1,000. In one preferred embodiment, the CNT material is a CNT web or a CNT web laminate.

[0061] <Resin> Examples of resins to be composited with the CNT-based modified material include resins that have traditionally been used as resins to be composited with carbon fibers. Examples of resins to be composited with the CNT-based modified material include thermosetting resins, photocurable resins, and thermoplastic resins. Among these, thermosetting resins are preferred.

[0062] Examples of thermosetting resins include epoxy resins, unsaturated polyester resins, unsaturated group-containing (meth)acrylic resins, vinyl ester resins, urethane resins, (meth)acrylic urethane resins, phenolic resins, melamine resins, urea resins, diallyl phthalate resins, cyanate ester resins, alkyd resins, and thermosetting polyimide resins.

[0063] Examples of photocurable resins include ultraviolet-curable resins such as monofunctional or polyfunctional (meth)acrylic oligomers, including urethane (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, polyether (meth)acrylate oligomers, and polyester (meth)acrylate oligomers.

[0064] Examples of thermoplastic resins include polyolefins, polyvinyl chloride, polyvinylidene chloride, styrene-based resins, (meth)acrylic resins, polyesters, polyamides, thermoplastic polyimides, polycarbonates, polyacetals, polyphenylene ethers, and polyphenylene sulfides.

[0065] When the resin is a thermosetting resin or a photocurable resin, the resin contained in the composite material may be, for example, in an uncured state, a semi-cured state, or a cured state, and is preferably in a semi-cured or cured state.

[0066] The content of the resin in the composite material of the present disclosure is preferably 10 to 90% by mass, more preferably 15 to 70% by mass, even more preferably 20 to 50% by mass, and particularly preferably 25 to 45% by mass.

[0067] <Other Components> The composite material of the present disclosure may further contain components other than the CNT-based modified material and the resin (hereinafter also referred to as "other components"). Examples of other components include fibrous fillers, powdered fillers, and resin additives. Examples of fibrous fillers include carbon fibers, organic fibers, metal fibers, and glass fibers. Examples of resin additives include antioxidants, heat stabilizers, light stabilizers, weather stabilizers, hydrolysis inhibitors, plasticizers, colorants, flame retardants, foaming agents, nucleating agents, pigments, lubricants, and spreading agents. One or more of the other components may be used.

[0068] The composite material of the present disclosure may further contain carbon fiber. In this case, the content of carbon fiber in the composite material is preferably 10 to 20,000 parts by mass, more preferably 100 to 1,000 parts by mass, and even more preferably 500 to 700 parts by mass, relative to 100 parts by mass of the CNT-based modified material. In this case, the total content of the CNT-based modified material and carbon fiber in the composite material of the present disclosure is preferably 10 to 90% by mass, more preferably 30 to 85% by mass, even more preferably 50 to 80% by mass, and particularly preferably 55 to 75% by mass. The carbon fiber may be irradiated with ultraviolet light as described above. One type of carbon fiber may be used, or two or more types may be used.

[0069] Examples of carbon fibers include pitch-based carbon fibers, polyacrylonitrile (PAN)-based carbon fibers, phenolic resin-based carbon fibers, cellulose-based carbon fibers, and polyvinyl alcohol-based carbon fibers.

[0070] The composite material of the present disclosure may contain, for example, a CNT-based modified material, carbon fiber, and the resin, or may contain a CNT-based modified material, carbon fiber, and a thermosetting resin. Such a composite material also has excellent mechanical properties and can be used to form a molded article with excellent mechanical properties.

[0071] <Form of Composite Material> Examples of the form of the composite material include pellets and sheets.

[0072] The pellets can be obtained, for example, by kneading the CNT-based modifier and the resin in a kneading device such as an extruder, extruding the mixture, and pelletizing the mixture. The pellets can also be long fiber pellets obtained, for example, by immersing the CNT-based modifier in a melt of the resin, pultrusion molding the mixture, and then cutting the mixture to a desired pellet length. In long fiber pellets, for example, the CNT fibers contained in the CNT-based modifier are aligned parallel to the longitudinal direction of the pellet.

[0073] In the sheet, the resin is impregnated into the CNT-based modified material (e.g., between the CNT fibers) to form a composite. The sheet is, for example, a prepreg sheet, and more specifically, the resin is impregnated into a sheet-like CNT-based modified material, and if the impregnated resin is a thermosetting resin or a photocurable resin, the prepreg sheet contains the resin in a semi-cured state.

[0074] The thickness of the composite material sheet (for example, prepreg sheet) is preferably 10 nm to 2.0 mm, more preferably 100 nm to 100 μm, and even more preferably 1 μm to 10 μm.

[0075] A laminate may be formed by stacking a plurality of sheets of the composite material. A laminate may be formed by stacking a sheet of the composite material and a semi-cured resin sheet. Examples of semi-cured resin sheets include sheets of semi-cured thermosetting resin or photocurable resin. Examples of these resins are as described above.

[0076] <Method for producing a composite material> The method for producing a composite material of the present disclosure includes, for example, a step of compounding a CNT-based modified material obtained by irradiating a CNT-based material with ultraviolet light with a resin (hereinafter also referred to as a "composite step"). The method for producing a composite material may further include a step of irradiating the CNT-based material with ultraviolet light to produce a CNT-based modified material (hereinafter also referred to as an "irradiation step").

[0077] The wavelength and light source of the ultraviolet light used in the irradiation step are as described above. The irradiation time of the ultraviolet light on the CNT-based material in the irradiation step varies depending on the type of CNT-based material and the intensity of the ultraviolet light (e.g., output, energy density, irradiation speed), but is preferably 10 seconds to 10 minutes, more preferably 30 seconds to 8 minutes, even more preferably 50 seconds to 6 minutes, and particularly preferably 60 seconds to 5 minutes. The irradiation time may be, for example, 4 minutes or less, 3 minutes or less, or 2 minutes or less. When the CNT-based material is in the form of a sheet, the ultraviolet light may be irradiated on one side of the CNT-based material, or both sides may be irradiated with ultraviolet light, taking into account the modification or denaturation of the CNT-based material. In the irradiation step, the ultraviolet light may be irradiated on the CNT-based material in an oxygen-containing atmosphere such as air, or in an inert gas atmosphere such as nitrogen or argon.

[0078] Hereinafter, the D / G ratio of the CNT material before UV irradiation is referred to as R B The D / G ratio of the CNT material after UV irradiation is also expressed as R A The definition of the D / G ratio is as described above. A and R B The difference between A -R B It is preferable to irradiate the CNT material with ultraviolet light so that R is in the range of 0.01 to 1. A and R B The difference is more preferably 0.1 to 0.9, even more preferably 0.2 to 0.8, and may be, for example, 0.7 or less.

[0079] Examples of methods for compounding the CNT-based modified material with the resin in the compounding step include: (1) impregnating the CNT-based modified material with the resin in liquid form, a solution of the resin, or a melt of the resin, and drying or heating as necessary; (2) laminating a sheet of the CNT-based modified material with a sheet of the resin, and heating and pressure-molding as necessary; and (3) mixing the CNT-based modified material with the resin. When the resin is a thermosetting resin or a photocurable resin, compounding may be performed using, for example, uncured materials.

[0080] In the method (1) above, the CNT-based modifier may be in the form of a sheet. In the method (1) above, the impregnation method may involve, for example, immersing the CNT-based modifier in the liquid resin, a solution of the resin, or a melt of the resin, or spraying the liquid resin, a solution of the resin, or a melt of the resin onto the CNT-based modifier. In the method (2) above, sheets of the CNT-based modifier and sheets of the resin may be alternately laminated and, if necessary, heated and pressure-molded. In the method (3) above, the CNT-based modifier and the resin may be kneaded in a kneading device such as an extruder, extruded, and pelletized. After mixing or kneading, the resulting mixture or kneaded product may be molded into a sheet.

[0081] In the compounding step, if the resin is a thermosetting resin or a photocurable resin, a curing treatment appropriate to the type of resin (for example, a heat curing treatment for a thermosetting resin, or a light irradiation treatment for a photocurable resin) may be performed. The curing treatment may be, for example, a semi-curing treatment. The CNT material, CNT modified material, and resin are as described above.

[0082] [Molded body] The molded body of the present disclosure is obtained using the composite material of the present disclosure. The molded body of the present disclosure is formed, for example, from the composite material of the present disclosure. The molded body may be formed entirely from the composite material, or may include a portion formed from the composite material.

[0083] The composite material of the present disclosure can be molded into a molded article by a molding method such as injection molding, blow molding, rotational molding, extrusion molding, press molding, transfer molding, or autoclave molding.

[0084] An example of a method for producing a molded article of the present disclosure includes, for example, cutting a sheet of the composite material (e.g., a prepreg sheet) into the desired shape or dimensions as needed, stacking multiple sheets according to the thickness of the molded article, and molding the resulting article according to a method suitable for the type of resin. When the resin is a thermosetting resin, for example, a method is used in which the composite material sheet is heated to the required temperature while being pressurized with a hot plate or autoclave to harden the sheet. When the resin is a photocurable resin, for example, a method is used in which the composite material sheet is hardened by being irradiated with light. When the resin is a thermoplastic resin, for example, a method is used in which the composite material sheet is heated to the softening point of the resin, and then cooled to a temperature below the softening point while being pressurized to harden the sheet.

[0085] [Applications] The molded article of the present disclosure can be used, for example, as automobile parts, parts for vehicles other than automobiles, marine parts, aviation or space parts, sporting goods, home appliance material parts, communication equipment parts, electrical parts, electronic parts, medical equipment parts, machine mechanism parts, power tool parts, building materials, civil engineering materials, agricultural materials, food containers, or films, and the composite material of the present disclosure can be used as a material for forming these. The composite material of the present disclosure can be applied to applications where carbon fiber reinforced resins have traditionally been used. The composite material of the present disclosure has excellent mechanical properties and is useful as a reinforced resin composition.

[0086] [Method for producing modified material] The method for producing a modified material of the present disclosure includes a step of irradiating a carbon nanotube material (CNT material) with ultraviolet light (irradiation step). The CNT material irradiated with ultraviolet light here is a material that is not compounded with the above-mentioned resin. The above-mentioned production method produces the above-mentioned CNT-based modified material. Details of the irradiation step are as described above.

[0087] [Example Embodiments] The present disclosure relates to, for example, the following [1] to

[10] . [1] A composite material obtained by combining a modified material obtained by irradiating a carbon nanotube-based material with ultraviolet light and a resin. [2] The composite material according to [1] above, wherein the modified material is a material obtained by irradiating the carbon nanotube-based material with ultraviolet light having a wavelength of 120 to 380 nm. [3] The composite material according to [1] or [2] above, wherein the resin is at least one selected from the group consisting of a thermosetting resin, a photocurable resin, and a thermoplastic resin. [4] The composite material according to any one of [1] to [3] above, which is in the form of a pellet or a sheet. [5] The composite material according to [4] above, which is in the form of a prepreg sheet. [6] A method for producing a composite material, which includes a combining step of combining a modified material obtained by irradiating a carbon nanotube-based material with ultraviolet light and a resin. [7] A method for producing a composite material according to [6] above, which further includes an irradiation step of irradiating the carbon nanotube-based material with ultraviolet light to produce the modified material. [8] In the irradiation step, the D / G ratio of the carbon nanotube material before ultraviolet irradiation is R B and the D / G ratio of the carbon nanotube material after ultraviolet irradiation is R A When writing A and R B The difference between A -R B The ultraviolet light is irradiated in a range in which the D / G ratio is 0.01 to 1, and the D / G ratio is 1580 cm in the Raman spectrum measured by Raman spectroscopy. -1 The peak intensity of the G band appearing near 1360 cm -1 [7] A method for producing a composite material according to the above [7], wherein the ratio of the peak intensity of a D band appearing near ...

[0088] The composite material of the present disclosure will be described in more detail below based on examples, but the composite material of the present disclosure is not limited to these examples.

[0089] Example 1: Production of a CNT forest. A wafer (catalyst substrate) coated with a catalyst for carbon nanotube growth was prepared, and vertically aligned carbon nanotubes were grown from the catalyst by chemical vapor deposition to produce a vertically aligned CNT forest aligned perpendicular to the wafer. The carbon nanotubes that made up the CNT forest were multi-walled carbon nanotubes, each with an average length of 250 μm, an average diameter of 6-10 nm, a carbon purity of 99.8% or higher, and a D / G ratio of 0.6-0.8.

[0090] <Production of CNT Film> Of the CNT forests formed on the catalyst substrate, several CNTs located at the ends were picked with a picking tool, and a sheet-like CNT web was pulled out. The CNT web was then wrapped around the circumferential surface of a roller with a diameter of 800 mm 50 times.

[0091] Next, the wound CNT web was cut in the direction of the rotation axis of the roller, unfolded, and then removed from the roller and cut into the desired size. This resulted in a CNT film (1) with 50 layers of CNT web laminated together. The size of the CNT film (1) was 350 mm in length and 50 mm in width. The length of the CNT film (1) refers to the length of the CNT film along the longitudinal direction of the CNT fiber, and the width of the CNT film (1) refers to the length of the CNT film along the transverse direction of the CNT fiber. The basis weight of the CNT film (1) was 0.17 mg / cm 2 It was.

[0092] <Production of Prepreg Sheet> Using an excimer lamp (manufactured by Ushio Inc., model: STA3-317), one entire surface of the CNT film (1) was irradiated with light containing ultraviolet light having a wavelength of 172 nm for 5 minutes in an air atmosphere.

[0093] A thermosetting resin "CBZ" manufactured by Nippon U-Pica Corporation (liquid A, liquid B, and a curing agent were mixed according to the product manual) was placed in a paint airbrush (manufactured by OASSER). An impregnation treatment was performed by spraying the thermosetting resin in an amount such that the amount of the thermosetting resin was 30 mass % relative to the total mass of the thermosetting resin and the CNT film (1) onto the UV-irradiated surface of the CNT film (1) after UV irradiation.

[0094] The CNT film (1) onto which the thermosetting resin was sprayed was placed in a thermostatic chamber "DN-43" (manufactured by Yamato Scientific Co., Ltd.) and subjected to aging treatment for 48 hours in the thermostatic chamber at 50°C. In this way, a prepreg sheet was obtained in which the thermosetting resin in a semi-cured state was impregnated into the UV-irradiated CNT film (1).

[0095] Comparative Example 1 The same procedure as in Example 1 was carried out except that the ultraviolet irradiation was not carried out.

[0096] Comparative Example 2 The same procedure as in Example 1 was carried out, except that the ultraviolet irradiation was carried out not on the CNT film (1) itself but on the entire one surface (the surface onto which the thermosetting resin was sprayed) of the CNT film (1) after the impregnation treatment onto which the thermosetting resin had been sprayed.

[0097] Comparative Example 3 The same procedure as in Example 1 was carried out, except that the ultraviolet irradiation was carried out on the entire one surface of the prepreg sheet (the surface onto which the thermosetting resin was sprayed) rather than on the CNT film (1).

[0098] [Tensile test] The prepreg sheets obtained in the examples and comparative examples, and the CNT film (1) (Comparative Example 4) were autoclaved at 135°C and 0.4 MPa for 5 minutes, and then test pieces measuring 120 mm in length and 12.5 mm in width were cut out. Three test pieces were prepared for each sample, and the average thickness of each test piece was obtained by measuring three arbitrary points using a micrometer.

[0099] A tensile test was conducted under the following conditions, in which the test specimen was pulled in both longitudinal directions, to measure the tensile strength, maximum strain, and modulus of elasticity. The tensile test was conducted three times, and the average values ​​of the three measurements are shown in Table 1. Tensile tester: Shimadzu Corporation, AG-X Plus; Tensile speed: 1 mm / min; Initial chuck distance: 60 mm; Number of tests: 3; Test specimen auxiliary tool: Because the test specimen was an extremely thin film, the test specimen 40 was fixed in the test specimen auxiliary tool 50 as shown in Figure 3, and the upper end portion 52 and the lower end portion 54 of the test specimen auxiliary tool 50 were each gripped with the chucks of the tensile tester so that the initial chuck distance was the above-mentioned value. Just before the tensile test, the center portion of the test specimen auxiliary tool 50 was cut along line 56.

[0100]

[0101] [Reference Test] Using an excimer lamp (manufactured by Ushio Inc., model: STA3-317), one entire surface of the CNT film (1) was irradiated with light containing ultraviolet light at a wavelength of 172 nm for 10 minutes under atmospheric conditions. Before the light irradiation and after each 15-second period of light irradiation, Raman spectroscopy of the CNT film (1) was performed under the following conditions to obtain a Raman spectrum. The D / G ratio and the difference (R A -R B (Measurement conditions for Raman spectroscopy) Measurement device: Raman microscope (XploRA PLUS, manufactured by HORIBA, Ltd.) Wavelength: 532 nm Output: 50 mW Exposure time: 1 second Number of accumulations: 20 Objective lens magnification: 50x Baseline correction was not performed.

[0102]

[0103] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various omissions, substitutions, modifications, and changes are possible within the scope of the gist of the present invention described in the claims. These embodiments and their modifications are included in the scope of the invention and its equivalents, as well as the scope and gist of the invention.

[0104] REFERENCE SIGNS LIST 10...Substrate 12...CNT forest 20...CNT web extracted from the CNT forest 22...CNT fibers constituting the CNT web 30...Roller 40...Test piece 50...Test piece auxiliary tool 52...Upper end portion of the test piece auxiliary tool 54...Lower end portion of the test piece auxiliary tool 56...Cutting line in the center portion of the test piece auxiliary tool

Claims

1. A composite material obtained by combining a modified material obtained by irradiating a carbon nanotube-based material with ultraviolet light with a resin.

2. The composite material according to claim 1, wherein the modified material is a carbon nanotube-based material irradiated with ultraviolet light having a wavelength of 120 to 380 nm.

3. The composite material according to claim 1, wherein the resin is at least one selected from the group consisting of thermosetting resins, photocurable resins, and thermoplastic resins.

4. The composite material of claim 1, which is in the form of a pellet or a sheet.

5. The composite material according to claim 4, which is a prepreg sheet.

6. A method for producing a composite material, comprising a compounding step of compounding a modified material obtained by irradiating a carbon nanotube-based material with ultraviolet light with a resin.

7. The method for producing a composite material according to claim 6, further comprising an irradiation step of irradiating the carbon nanotube-based material with ultraviolet light to produce the modified material.

8. In the irradiation step, the D / G ratio of the carbon nanotube material before ultraviolet irradiation is R B and the D / G ratio of the carbon nanotube material after ultraviolet irradiation is R A When writing A and R B The difference between A -R B The ultraviolet light is irradiated in a range in which the D / G ratio is 0.01 to 1, and the D / G ratio is 1580 cm in a Raman spectrum measured by Raman spectroscopy. -1 The peak intensity of the G band appearing near 1360 cm -1 The method for producing a composite material according to claim 7 , wherein the ratio of the peak intensities of the D bands appearing near the peak intensities of the D bands is 0.015 to 0.

015.

9. A method for producing a modified material, comprising the step of irradiating a carbon nanotube-based material with ultraviolet light.

10. A molded article obtained using the composite material according to claim 1.

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