Carbon fiber composite material and method for manufacturing carbon fiber composite material

Abstract

To provide a carbon fiber composite material having excellent tear strength, while having low harness, and a manufacturing method of a carbon fiber composite material.SOLUTION: A carbon fiber composite material 50 includes a carbon nano-tube in cross-linked silicone rubber 30. The carbon fiber composite material includes a cell structure formed by enclosing a first silicone rubber region with the carbon nano-tube and an interfacial phase thereof and a continuous structure 70 where a second silicone rubber region 72 is continuously enclosed and cyclically formed by a plurality of cell structures. The continuous structure 70 in the cross section of the carbon fiber composite material is a region where the carbon nano-tube is 2 or more per 1 μm2. The second silicone rubber region 72 in the cross section has an area of 0.1 μm2 or more and the carbon nano-tube of 2 or less per 1 μm2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a carbon fiber composite material containing carbon nanotubes and a method for manufacturing the carbon fiber composite material.

Background Art

[0002] Silicone rubber is characterized by a very wide service temperature range compared to other rubbers because its properties change little over a wide temperature range from low to high temperatures. However, there is a problem in that its mechanical strength is low. Therefore, carbon nanotubes are compounded into silicone rubber instead of silica particles as a reinforcing material, and furthermore, by using a silane coupling agent or the like to increase the adhesion strength between the carbon nanotubes and the silicone rubber molecules, the tensile strength and tensile fatigue durability that could not be achieved with the normal compounding of silica particles have been successfully developed in a carbon fiber composite material (Patent Document 1).

[0003] In addition, by compounding a small amount of carbon nanotubes into silicone rubber, a carbon fiber composite material having flexibility as a rubber and a large loss tangent (tan δ) value has been proposed (Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the carbon fiber composite material of Patent Document 1 has low flexibility and high hardness, so there are limitations in its applications. The carbon fiber composite material of Patent Document 2 has excellent flexibility, but tends to tear easily when it has low hardness.

[0006] Therefore, an object of the present invention is to provide a carbon fiber composite material having low hardness and excellent tearing strength, and a method for manufacturing the carbon fiber composite material.

Means for Solving the Problems

[0007] The present invention has been made to solve at least a part of the above-described problems, and can be realized as the following aspects or application examples.

[0008] [1] One aspect of the carbon fiber composite material according to the present invention is a carbon fiber composite material containing carbon nanotubes in crosslinked silicone rubber, a cell structure formed by surrounding the carbon nanotubes and their interfacial phase with a first silicone rubber region, and a continuous structure formed annularly so that a plurality of the cell structures continuously surround a second silicone rubber region, in a cross section of the carbon fiber composite material, the continuous structure is a region where the number of the carbon nanotubes per 1 μm 2 exceeds 2, in the cross section, the second silicone rubber region has an area of 0.1 μm 2 or more 10 μm 2 or less and is a region where the number of the carbon nanotubes per 1 μm 2 is 2 or less. and the total area occupied by the second silicone rubber region is 45% or more and 80% or less, the maximum width of the second silicone rubber region is 0.1 μm or more and 6 μm or less It is characterized by this.

[0010] 2 In one aspect of the above carbon fiber composite material, the width of the continuous structure can be 0.01 μm to 5 μm.

[0011] 3 In one aspect of the above carbon fiber composite material, the average diameter of the carbon nanotubes can be 2 nm to 30 nm. ​​

[0012] 4 In one embodiment of the above carbon fiber composite material, the carbon nanotubes can be included in an amount of 0.5 parts by mass to 7.0 parts by mass with respect to 100 parts by mass of the silicone rubber.

[0013] 5 In one embodiment of the above carbon fiber composite material, the hardness based on JIS K6253 can be 65 degrees to 78 degrees.

[0014] 6 In one embodiment of the above carbon fiber composite material, the stress at 50% elongation in the tensile test based on JIS K6251 at room temperature can be 2.0 MPa to 5.0 MPa.

[0015] 7 In one embodiment of the above carbon fiber composite material, the tear strength (Tr) in the tear test based on JIS K6252 at room temperature can be 45 N / mm to 65 N / mm.

[0016] 8 One embodiment of the method for manufacturing the carbon fiber composite material according to the present invention is a first mixing step of mixing carbon nanotubes with silicone rubber to obtain a mixture, a first kneading step of charging the mixture into an open roll having a roll interval set to more than 0 mm and 0.5 mm or less and a roll temperature set to 0°C to 50°C and passing it thinly to obtain a first composite rubber, a second mixing step of further mixing silicone rubber with the first composite rubber to obtain a second composite rubber, a second kneading step of charging the second composite rubber into an open roll having a roll interval set to more than 0 mm and 0.5 mm or less and a roll temperature set to 0°C to 50°C and passing it thinly to obtain a carbon fiber composite material, and including see the average diameter of the carbon nanotubes is 2 nm to 30 nm, in the first mixing step, 3 parts by mass to 15 parts by mass of the carbon nanotubes are mixed with 100 parts by mass of the silicone rubber, ​​​​​ in the second mixing step, the silicone rubber is mixed so that the second composite rubber contains 0.5 parts by mass to 7 parts by mass of the carbon nanotubes with respect to 100 parts by mass of the silicone rubber It is characterized by the following.

Brief Description of the Drawings

[0018]

Figure 1

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Figure 10

Modes for Carrying Out the Invention

[0019] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the embodiments described below do not unduly limit the content of the present invention described in the claims. Also, not all of the configurations described below are essential constituent elements of the present invention.

[0020] 1. Carbon Fiber Composite Material The carbon fiber composite material according to an embodiment of the present invention is a carbon fiber composite material containing carbon nanotubes in crosslinked silicone rubber, wherein a cell structure is formed by the carbon nanotubes and their interfacial phase surrounding a first silicone rubber region, and a continuous structure is formed in an annular shape such that a plurality of the cell structures continuously surround a second silicone rubber region.

[0021] In the carbon fiber composite material, the carbon nanotubes are dispersed throughout in a defibrated state. There are no agglomerates of carbon nanotubes in the carbon fiber composite material. This is because the presence of agglomerates would serve as a starting point for fracture and cause a decrease in mechanical strength.

[0022] The hardness of the carbon fiber composite material based on JIS K6253 can be 65 to 78 degrees. By achieving a relatively low hardness of 78 degrees or less while having the reinforcing effect of carbon nanotubes, the application range, uses, and market of the carbon fiber composite material in silicone rubber products can be expanded.

[0023] The stress at 50% elongation in the tensile test based on JIS K6251 at room temperature of the carbon fiber composite material can be 2.0 MPa to 5.0 MPa. Since the stress at 50% elongation of the carbon fiber composite material is 2.0 MPa or more, it is excellent in resistance to instantaneous elongation deformation, and thus material fracture can be suppressed. Further, it is more preferable that the stress at 50% elongation in the tensile test based on JIS K6251 at room temperature of the carbon fiber composite material is 2.2 MPa to 4.5 MPa.

[0024] The tear strength (Tr) in the tear test based on JIS K6252 at room temperature of the carbon fiber composite material can be 45 N / mm to 65 N / mm. Since the tear strength of the carbon fiber composite material at room temperature is 45 N / mm or more, it has excellent mechanical strength. Therefore, the carbon fiber composite material can suppress damage during demolding in molding. Further, it is more preferable that the tear strength in the tear test conforming to JIS K6252 at room temperature of the carbon fiber composite material is 48 N / mm to 61 N / mm.

[0025] Next, the materials constituting the carbon fiber composite material will be described.

[0026] 1.1. Silicone Rubber The silicone rubber is not particularly limited, but it can be a raw rubber of organopolysiloxane. The main chain is composed of siloxane bonds, and the side chains have alkyl groups such as methyl group, ethyl group, propyl group, butyl group, cycloalkyl groups such as cyclohexyl group, alkenyl groups such as vinyl group, allyl group, butenyl group, hexenyl group, aryl groups such as phenyl group, tolyl group, aralkyl groups such as benzyl group, γ-phenylpropyl group, or groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with halogen atoms, cyano groups, etc., for example, chloromethyl group, trifluoropropyl group, cyanoethyl group, etc. The molecular structure of the silicone rubber can be linear or linearly branched in part.

[0027] Known crosslinking agents can be used for the silicone rubber. For example, condensation type reactions, addition type reactions, and peroxide reactions can be used as crosslinking forms, and peroxide crosslinking is preferred. By crosslinking the silicone rubber with a crosslinking agent, a carbon fiber composite material excellent in heat resistance and chemical resistance can be produced.

[0028] In addition, the silicone rubber includes a silicone rubber compound in which silica is previously compounded. Commercially available silicone rubbers usually contain silica. Although the silicone rubber is characterized by having excellent properties over a wide temperature range from low temperature to high temperature, since its physical strength is low, compounds in which silica particles are previously compounded are common.

[0029] 1.2. Carbon Nanotube The carbon nanotubes can have an average diameter (fiber diameter) of 2 nm to 30 nm, and can further be 9 nm to 20 nm. Since such carbon nanotubes have a relatively small average diameter, they have a large specific surface area, improved surface reactivity with the elastomer as the matrix, and tend to easily improve the poor dispersion of the carbon nanotubes in the elastomer. Carbon nanotubes are commercially available if their diameter is 2 nm or more, and have the effect of being excellent in tear strength and maintaining tensile fiber after heating if they are 30 nm or less. Carbon nanotubes can be subjected to a known activation treatment to improve their reactivity with the elastomer on their surface. The average diameter of the carbon nanotubes can be measured by observation with an electron microscope. In the detailed description of the present invention, the average diameter and average length of the carbon nanotubes can be obtained by measuring the diameters and lengths of 200 or more locations from an image taken by an electron microscope at, for example, a magnification of 5,000 times (the magnification can be appropriately changed depending on the size of the carbon nanotubes) and calculating the arithmetic mean value thereof.

[0030] The carbon nanotubes are at least one of so-called multi-walled carbon nanotubes (MWCNT: multi-wall carbon nanotubes) and single-walled carbon nanotubes (SWCNT: single-wall carbon nanotubes) having a shape formed by rolling up one sheet (graphene sheet) of graphite with a carbon hexagonal network plane into a cylindrical shape, and a carbon material having a carbon nanotube structure partially can also be used. The carbon nanotubes may include multi-walled carbon nanotubes and single-walled carbon nanotubes. In addition to the name carbon nanotubes, they may also be referred to by names such as graphite fibril nanotubes and vapor-grown carbon fibers.

[0031] Carbon nanotubes can be obtained by the vapor growth method. The vapor growth method, also called the Catalytic Chemical Vapor Deposition (CCVD), is a method of producing untreated carbon nanotubes by thermally decomposing a gas such as a hydrocarbon in the presence of a metal-based catalyst in the gas phase. To explain the vapor growth method in more detail, for example, organic compounds such as benzene and toluene are used as raw materials, and organic transition metal compounds such as ferrocene and nickelocene are used as the metal-based catalyst. These are introduced together with a carrier gas into a reaction furnace set at a high temperature, for example, a reaction temperature of 400 °C to 1000 °C, to generate carbon nanotubes in a floating state or on the reaction furnace wall by the Floating Reaction Method, or to bring metal-containing particles supported in advance on ceramics such as alumina and magnesium oxide into contact with a carbon-containing compound at a high temperature to generate carbon nanotubes on a substrate by the Substrate Reaction Method, etc. can be used. For example, carbon nanotubes with an average diameter of 9 nm to 20 nm can be obtained by the substrate reaction method, and thicker carbon nanotubes can be obtained by the floating reaction method. The diameter of the carbon nanotubes can be adjusted, for example, by the size of the metal-containing particles and the reaction time. ーves on the substrate.

[0032] The compounding amount of the carbon nanotubes can be adjusted, for example, according to the required hardness, and can be included in an amount of 0.5 to 7.0 parts by mass based on 100 parts by mass of the silicone rubber. Further, it is more preferable to compound 2 to 5 parts by mass of the carbon nanotubes with respect to 100 parts by mass of the silicone rubber, and it is even more preferable to compound 3 to 5 parts by mass. If the carbon nanotubes are 7.0 parts by mass or less, the carbon fiber composite material can be excellent in cost competitiveness, and it is easy to adjust the rubber hardness to 78 degrees or less while maintaining elongation and flexibility, and moreover, it can be excellent in tear strength due to the reinforcement by the carbon nanotubes. Further, when 0.5 parts by mass or more of the carbon nanotubes are compounded with 100 parts by mass of the silicone rubber and compounded in a defibrated state, a minute cell structure and a continuous structure described later are formed in the carbon fiber composite material, and a reinforcing effect is exhibited.

[0033] 1.3. Other compounding agents For the silicone rubber, for example, metal oxides such as silica, alumina, magnesium oxide, and zinc oxide, reinforcing agents such as carbon black, fillers such as talc, clay, graphite, and calcium silicate, processing aids such as stearic acid, palmitic acid, and paraffin wax, antioxidants, plasticizers, coupling agents, etc., which are generally used as compounding agents for rubber, can be appropriately added and used as necessary. Carbon black and graphite have almost no effect as mechanical reinforcement of the carbon fiber composite material, but an improvement in kneading processability can be expected.

[0034] The coupling agent used in this embodiment can be one or more selected from the group consisting of titanate coupling agents, silane coupling agents, aluminate coupling agents, and zirconate coupling agents.

[0035] As the silane coupling agent, those of Shin-Etsu Chemical Co., Ltd., Toray Industries, Inc., Momentive Performance Materials Inc., etc. can be used. For example, silane-based -1: 3-methacryloxypropyltrimethoxysilane, silane-based -2: 3-glycidoxypropyltrimethoxysilane, silane-based -3: 3-mercaptopropyltrimethoxysilane, etc. can be used.

[0036] As the titanate coupling agent, aluminate coupling agent and zirconate coupling agent, those of Ajinomoto Co., Inc., KENRICH Co., etc. can be used. As the titanate-based, for example, tetra(2,2 diallyloxymethyl)butyl, di(ditridecyl)phosphite titanate, etc. can be used. As the aluminate-based, for example, alkyl acetoacetate aluminum diisopropylate, etc. can be used. As the zirconate-based, tetra(2,2 diallyloxymethyl)butyl, di(ditridecyl)phosphite zirconate, etc. can be used.

[0037] 1.4. Structural characteristics As a result of the measurement using a scanning electron microscope by the inventors of the carbon fiber composite material, it was found that there are common structural characteristics in the carbon fiber composite material having a hardness of 78 degrees or less and excellent mechanical strength.

[0038] Therefore, with reference to FIGS. 1 and 2, the structural characteristics of the carbon fiber composite material 50 will be described in detail. FIG. 1 is a schematic diagram for explaining the structure in the cross-sectional image 90 of the carbon fiber composite material 50, and FIG. 2 is an enlarged view showing the frame of the broken line in FIG. 1. The image 90 is a photograph obtained by photographing the cross-section of the carbon fiber composite material 50, and the cross-section may be a freeze-fractured cross-section or a tensile fracture cross-section. Further, the image 90 is obtained by observing and photographing with a scanning electron microscope (SEM: Scanning Electron Microscope).

[0039] The carbon fiber composite material 50 shown in FIGS. 1 and 2 contains a plurality of carbon nanotubes 20 in a crosslinked silicone rubber 30. The carbon nanotubes 20 are present in the silicone rubber 30 in a defibrated state.

[0040] The carbon fiber composite material 50 includes a cell structure 60 formed by the carbon nanotubes 20 and their interface phase 62 surrounding a first silicone rubber region 64, and a continuous structure 70 formed annularly so that a plurality of cell structures 60 continuously surround a second silicone rubber region 72. The interface phase 62 is something like a so-called bound rubber formed around the carbon nanofibers including the interface between the elastomer and the carbon nanofibers.

[0041] In the cross-section of the carbon fiber composite material 50, the continuous structure 70 is a region where the number of carbon nanotubes 20 per 1 μm 2 exceeds 2. Since the continuous structure 70 is in a dense state where the number of carbon nanotubes 20 per 1 μm 2 exceeds 2, it is considered that the interface phases 62 around the carbon nanotubes are in a continuous state. And the silicone rubber 30 having a small volume surrounded by the adjacent carbon nanotubes 20 and the interface phase 62 becomes the first silicone rubber region 64. The first silicone rubber region 64 is suppressed from deforming by becoming a part of the cell structure 60. And the continuous structure 70 forms a three-dimensional network structure throughout the carbon fiber composite material 50 to restrain the deformation of the carbon fiber composite material 50. However, since the blending amount of the carbon nanotubes 20 is small, the influence on the flexibility of the carbon fiber composite material 50 is relatively small. And since the continuous structure 70 is formed throughout the carbon fiber composite material 50, it can be excellent in mechanical strength, particularly tear strength.

[0042] The width of the continuous structure 70 can be 0.01 μm to 5 μm, and further can be 0.05 μm to 3 μm. The said width is the interval between the second silicone rubber regions 72 adjacent to each other with the continuous structure 70 interposed therebetween, and is the shortest interval at each of a plurality of measurement locations at the boundary between the continuous structure 70 and the second silicone rubber region 72.

[0043] In the cross-section of the carbon fiber composite material 50, the second silicone rubber region 72 has an area of 0.1 μm 2 or more, and the number of the carbon nanotubes per 1 μm 2 is 2 or less. The second silicone rubber region 72 has a larger area than the first silicone rubber region 64. And since the number of the carbon nanotubes 20 in the second silicone rubber region 72 with a large area is 2 or less, the second silicone rubber region 72 is considered to be excellent in flexibility. The second silicone rubber region 72 and the first silicone rubber region 64 constituting the continuous structure 70 do not have a clear boundary and are compatible because they are composed of the same silicone rubber 30.

[0044] The area of the second silicone rubber region 72 can be 0.1 μm 2 or more and 10 μm 2 or less. Since the second silicone rubber region 72 is an area surrounded by the continuous structure 70, the area will not be less than 0.1 μm 2 . Further, since the area is 10 μm 2 or less, the carbon fiber composite material 50 can be excellent in mechanical strength, particularly tear strength. The area of the second silicone rubber region 72 can be 0.2 μm 2 or more and 8 μm or less 2 and can be 0.2 μm 2 or more and 6 μm 2 or less.

[0045] The total area occupied by the second silicone rubber region 72 in the cross-section of the carbon fiber composite material 50 can be 45% or more and 80% or less, and further, the total area can be 50% or more and 75% or less. Also, the maximum width of the second silicone rubber region 72 can be 0.1 μm or more and 6 μm or less. When the total area is less than 45%, the continuous structure 70 tends to develop, resulting in an increase in hardness and a decrease in flexibility. Also, when the ratio of the total area to the whole exceeds 80%, there are more places where the continuous structure 70 is interrupted, and the reinforcing effect by the carbon nanotubes 20 tends to decrease. The measurement of the total area can be determined as the total area of the second silicone rubber region 72 in the image 90, and the total area is the area of the image 90.

[0046] The second silicone rubber region 72 is specified by using image editing software to draw points at locations where the carbon nanotubes 20 in the image 90 are present and then drawing a line to enclose the region where the number of carbon nanotubes 20 per 1 μm 2 is 2 or less. And in the image 90, the region other than the second silicone rubber region 72 can be specified as the continuous structure 70. For the image 90 used to measure the area etc. of the second silicone rubber region 72, it is preferable to use a plurality of images 90 taken at a plurality of locations (for example, 3 locations) of the cross-section in the sample of the carbon fiber composite material 50. The image 90 is taken at a magnification at which the carbon nanotubes 20 can be confirmed, for example, 10,000 times.

[0047] 2. Manufacturing method of carbon fiber composite material The manufacturing method of the carbon fiber composite material will be described in detail with reference to FIGS. 3 to 8.

[0048] FIG. 3 is a flowchart of the manufacturing method of the carbon fiber composite material according to the present embodiment, and FIGS. 4 to 8 are diagrams schematically showing the manufacturing method of the carbon fiber composite material according to the present embodiment.

[0049] As shown in FIG. 3, the method for manufacturing a carbon fiber composite material includes a first mixing step (S10), a first kneading step (S20), a second mixing step (S30), and a second kneading step (S40). The method for manufacturing a carbon fiber composite material may further include a preliminary kneading step and / or a molding step.

[0050] As shown in FIGS. 4 to 8, the method for manufacturing a carbon fiber composite material according to the present embodiment will be described by taking an example using an open roll 100. In the open roll 100 having two rolls, a first roll 110 and a second roll 120 are arranged at a predetermined roll interval d, for example, an interval of 0.5 mm to 1.5 mm, and rotate forward or reverse at rotational speeds V1 and V2 in the directions indicated by arrows in FIGS. 4 to 6.

[0051] First, as shown in FIG. 4, the silicone rubber 30 wound around the first roll 110 is kneaded to appropriately cut the silicone rubber molecular chains to generate free radicals. The free radicals of the silicone rubber generated by kneading are in a state where they are likely to bind to the carbon nanotubes.

[0052] 2.1. First mixing step Next, as shown in FIG. 5, in the first mixing step (S10), carbon nanotubes 20 are mixed into the bank 34 of the silicone rubber 30 wound around the first roll 110 to obtain a mixture 36 (FIG. 6). In the first mixing step (S10), 3 to 15 parts by mass of carbon nanotubes 20 can be mixed with 100 parts by mass of the silicone rubber 30. The defibrillation of the carbon nanotubes 20 can be achieved by appropriate elasticity and viscosity as described later. The silicone rubber 30 is originally a material with low elasticity, but by containing 3 parts by mass or more of the carbon nanotubes 20, the elasticity of the entire material can be improved, and the defibrillation of the carbon nanotubes 20 can be promoted. Also, if there are too many carbon nanotubes 20, the viscosity of the entire material becomes too high and processing becomes difficult, but if the carbon nanotubes 20 are 15 parts by mass or less, the carbon nanotubes 20 can be defibrillated with an appropriate viscosity.

[0053] 2.2. First Kneading Step Next, as shown in FIG. 6, in the first kneading step (S20), the mixture 36 is put into an open roll 100 with a roll gap d set to be more than 0 mm and not more than 0.5 mm and a roll temperature set to be from 0°C to 50°C, and is passed through thinly to obtain a first composite rubber 37.

[0054] The number of times of passing through thinly can be, for example, about 1 to 10 times.

[0055] When the surface speed of the first roll 110 is V1 and the surface speed of the second roll 120 is V2, the surface speed ratio (V1 / V2) in passing through thinly can be from 1.05 to 3.00, and more preferably from 1.05 to 1.2. By using such a surface speed ratio, a desired shearing force can be obtained.

[0056] The first composite rubber 37 extruded from between such narrow rolls is greatly deformed as shown in FIG. 6 by the restoring force due to the elasticity of the silicone rubber, and at this time, the carbon nanotubes move greatly together with the silicone rubber.

[0057] The first composite rubber 37 obtained by passing through thinly may be rolled by a roll and separated into a sheet having a predetermined thickness.

[0058] In this step of passing through thinly, in order to obtain as high a shearing force as possible, it is carried out with the roll temperature set to a relatively low temperature of, for example, 0 to 50°C, more preferably 5 to 30°C, and the actually measured temperature of the silicone rubber can also be adjusted to 0 to 50°C.

[0059] Due to the shear force obtained in this way, a high shear force acts on the silicone rubber, causing the aggregated carbon nanotubes to be separated from each other and defibrillated one by one from the silicone rubber molecules and dispersed in the silicone rubber. In particular, since the silicone rubber has elasticity, viscosity, and chemical interaction with the carbon nanotubes, the carbon nanotubes can be easily dispersed. And a first composite rubber 37 excellent in the dispersibility and dispersion stability of the carbon nanotubes (the carbon nanotubes are not easily re-aggregated) can be obtained.

[0060] More specifically, when the silicone rubber and the carbon nanotubes are mixed with the open roll 100, the viscous silicone rubber penetrates into the carbon nanotubes, and a specific part of the silicone rubber binds to the highly active part of the carbon nanotubes by chemical interaction. When the surface activity of the carbon nanotubes is moderately high, it can be particularly easily bonded to the silicone rubber molecules. Next, when a strong shear force acts on the silicone rubber, the carbon nanotubes also move along with the movement of the silicone rubber molecules, and further, due to the restoring force of the silicone rubber due to the elasticity after shearing, the aggregated carbon nanotubes are separated and dispersed in the silicone rubber.

[0061] According to the present embodiment, when the first composite rubber 37 is extruded from between the narrow rolls, the first composite rubber 37 deforms thicker than the roll interval d due to the restoring force of the silicone rubber's elasticity. It can be speculated that the deformation further complicates the flow of the first composite rubber 37 under the action of a strong shear force, dispersing the carbon nanotubes in the silicone rubber. And once the carbon nanotubes are dispersed, they are prevented from re-aggregating by the chemical interaction with the silicone rubber and can have good dispersion stability.

[0062] The first kneading step (S20) is not limited to the open roll method as long as the carbon nanotubes can be defibrated in the silicone rubber by shear force, and a closed kneading method or a multi-axis extrusion kneading method can also be used. In short, in this step, it is sufficient to apply a shear force to the silicone rubber that can separate and defibrate the aggregated carbon nanotubes. In particular, the open roll method is preferable because not only the roll temperature can be controlled, but also the actual temperature of the mixture can be measured and controlled.

[0063] 2.3. Second mixing step Next, as shown in FIG. 7, in the second mixing step (S30), silicone rubber 30 is further mixed with the bank 34 of the first composite rubber 37 wound around the first roll 110 to obtain a second composite rubber 38 (FIG. 8). In the second mixing step (S30), silicone rubber 30 can be mixed so that the second composite rubber 38 contains 0.5 to 7 parts by mass of carbon nanotubes with respect to 100 parts by mass of silicone rubber.

[0064] 2.4. Second kneading step Next, as shown in FIG. 8, in the second kneading step (S40), the second composite rubber 38 is put into an open roll 100 with a roll gap d set to be more than 0 mm and not more than 0.5 mm and a roll temperature set to 0°C to 50°C, and passed through the rolls thinly to obtain a carbon fiber composite material 50. The second kneading step (S40) can be performed in the same manner as the first kneading step (S20).

[0065] Since the carbon nanotubes have already been defibrated in the first composite rubber 37 and a uniform structure has developed throughout, in the second mixing step (S30) alone, the additional silicone rubber 30 and the first composite rubber 37 do not mix completely, and do not form the special structure of the continuous structure as described above and the second silicone rubber region surrounded by the continuous structure. However, by passing through the second kneading step (S40), the carbon fiber composite material 50 will have the special structure of the continuous structure as described above and the second silicone rubber region surrounded by the continuous structure.

[0066] The carbon fiber composite material 50 obtained by calendering may be rolled with a roll and separated into a sheet having a predetermined thickness.

[0067] Since the carbon fiber composite material 50 obtained from the second kneading step (S40) is in an uncrosslinked state, it can be crosslinked and molded at a predetermined temperature after mixing a crosslinking agent. The crosslinking agent can be appropriately mixed before, during, or after the separation after calendering, etc., before the mixing of the silicone rubber and the carbon nanotube.

[0068] As described above, although the embodiments of the present invention have been described in detail, those skilled in the art will easily understand that many modifications can be made without substantially departing from the novel matters and effects of the present invention. Therefore, all such modified examples are intended to be included in the scope of the present invention.

Examples

[0069] (1) Preparation of Samples The samples of Examples 1 to 6 and Comparative Examples 4 and 5 were prepared by the following steps.

[0070] Masterbatch kneading step: 100 parts by mass (phr) of the silicone rubber shown in Tables 1 and 2 was put into an open roll with a roll diameter of 6 inches (roll temperature 10 to 20°C) and wound around the roll (see Fig. 4).

[0071] First mixing step: Next, 8 parts by mass of carbon nanotubes (described as "CNT-1", "CNT-2", "CNT-3" in Tables 1 and 2) and compounding agents such as silane coupling agents were added to 100 parts by mass of the silicone rubber and put into the silicone rubber (see Fig. 5). At this time, the roll gap d was set to 1.5 mm. The mixture of the silicone rubber mixed with the carbon nanotubes was taken out from the roll. At this time, the roll gap d was set to 1.5 mm. The mixture of the silicone rubber mixed with the carbon nanotubes was taken out from the roll.

[0072] First kneading step: The roll gap d was narrowed from 1.5 mm to 0.3 mm, and the mixture was put into rolls set at a roll temperature of 10°C to 20°C for thin pass rolling to obtain the first composite rubber (see Fig. 6). At this time, the surface speed ratio of the two rolls was set to 1.1. The thin pass rolling was repeated 5 times.

[0073] Second mixing step: The roll gap d was changed from 0.3 mm to 1.5 mm, the first composite rubber was put into an open roll, and silicone rubber was further mixed to obtain the second composite rubber according to the formulation in Table 1 (see Fig. 7).

[0074] Second kneading step: The roll gap d was narrowed from 1.5 mm to 0.3 mm, the second composite rubber was put into an open roll for thin pass rolling to obtain a carbon fiber composite material (see Fig. 8). At this time, the surface speed ratio of the two rolls was set to 1.1. The thin pass rolling was repeated 5 times.

[0075] Furthermore, as a crosslinking agent, DS-8 (2,5-dimethyl-2,5-di(t-butylperoxy)hexane) manufactured by Asahi Kasei Wakker Silicone, with a content of 50%, was added to the carbon fiber composite material at 0.5 parts by mass per 100 parts by mass of silicone rubber. The rolls were set at a predetermined interval (from 2.1 mm to 2.2 mm) to separate the uncrosslinked carbon fiber composite material.

[0076] In Comparative Examples 1 and 2, since carbon nanotubes were not compounded, after the above-mentioned kneading step, a crosslinking agent was added to obtain an uncrosslinked sample. In addition, in Comparative Example 3, 3 parts by mass of carbon nanotubes were added to 100 parts by mass of silicone rubber in the first mixing step and mixed, and a crosslinking agent was added to the mixture obtained by performing the first kneading step to obtain an uncrosslinked sample.

[0077] Molding step: For Examples 1 to 6 and Comparative Examples 1 to 5, the uncrosslinked carbon fiber composite material (Comparative Examples 1 and 2 are uncrosslinked rubber compositions) was put into a vacuum press and press-molded (primary crosslinking) at 170°C to 180°C for 5 to 10 minutes.

[0078] Furthermore, the carbon fiber composite material was transferred to an oven and subjected to secondary crosslinking at 200 °C for 2 hours to obtain crosslinked sheet-like carbon fiber composite material samples of Examples 1 to 6 and Comparative Examples 1 to 5 (Comparative Examples 1 and 2 are crosslinked rubber composition samples).

[0079] For each sample of Examples 1 to 6, the compounding amount of carbon nanotubes was adjusted so that the rubber hardness (Hs) would be about 70 ± 5 degrees. As the sample of Comparative Example 2, a rubber hardness of 70 degrees without compounding carbon nanotubes was used.

[0080] The details of the silicone rubber and various compounding agents in the compounding column of the table were as follows.

[0081] CNT-1: Multi-walled carbon nanotubes (average diameter 15.3 nm), CNT-2: Multi-walled carbon nanotubes (fiber diameter 18.5 nm), CNT-3: Multi-walled carbon nanotubes (fiber diameter 17.0 nm), Silane coupling agent: Manufactured by Shin-Etsu Chemical Co., Ltd., silane coupling agent KMB-503 (3-methacryloxypropyltrimethoxysilane), It was as follows.

[0082] For the test samples of Examples 1 to 6 and Comparative Examples 1 to 5, various tests described below were performed, and the test results are shown in Tables 1 and 2.

[0083] (2) Basic property test For each sample of the examples and comparative examples, the rubber hardness (Hs (JIS-A)) was measured based on JIS K 6253.

[0084] Also, for the test pieces punched out in the shape of a JIS No. 3 dumbbell from each sample of the examples and comparative examples, a tensile test was carried out based on JIS K6251 at 23 ± 2 °C and a tensile speed of 500 mm / min using an autograph AG-X tensile tester manufactured by Shimadzu Corporation, and the tensile strength (TS (MPa)), elongation at break (Eb (%)), stress at 50% elongation (M50 (MPa)), and stress at 100% elongation (M100 (MPa)) were measured. The measurement results are shown in each column of the table.

[0085] (3) Tear test Each sample of the examples and comparative examples was punched out into an angled test piece without a cut according to JIS K6252, and a tear test was carried out in accordance with JIS K6252 at room temperature and a tensile speed of 500 mm / min using an autograph AG-X manufactured by Shimadzu Corporation. For the samples in the longitudinal and transverse directions, the tear strength (Tr (N / mm)) was calculated. The measurement results are shown in each column of the table.

[0086] (4) SEM measurement The fracture surfaces of each sample after the tensile test in the examples and comparative examples were photographed with a 10,000-fold magnification by SEM. Image 90 (photo) obtained by SEM of the tensile fracture surface of the sample of Example 2 is shown in FIG. 9. The white, thin filamentous parts and white dots in each image are carbon nanotubes. Next, as shown in FIG. 10, using image editing software, points were drawn at the locations of the carbon nanotubes 20 in each image 90, and further, the second silicone rubber region 72 was specified by drawing a line to enclose the region where the number of carbon nanotubes 20 per 1 μm 2 was 2 or less. As a result, the region other than the second silicone rubber region 72 in each image 90 could be specified as the continuous structure 70. Also, three different locations were photographed for each sample to obtain three images 90, and the second silicone rubber region 72 and the continuous structure 70 were similarly specified in each image 90. Note that no agglomerates of carbon nanotubes 20 were confirmed in the samples of the examples.

[0087] Next, in each image 90, the maximum width of the second silicone rubber region 72 (referred to as "maximum width" in the table, μm), the area of the second silicone rubber region 72 (referred to as "area" in the table, μm 2 ), the ratio of the sum of the areas to the entire image 90 (referred to as "ratio" in the table, %), and the width of the continuous structure 70 (referred to as "width" in the table, μm) were measured. The maximum width was measured by drawing the longest straight line connecting the outer edges facing each other through the centroid of each second silicone rubber region 72 using image editing software, and the maximum and minimum values of the maximum widths of all the second silicone rubber regions 72 were extracted. The area was measured by measuring the area of the second silicone rubber region 72 in the image 90 using image editing software, and the maximum and minimum values were extracted. The ratio was obtained by dividing the sum of the measured areas by the area of the image 90. The width was obtained by drawing a plurality of straight lines between the outer edges of adjacent second silicone rubber regions 72 in each image 90 using image editing software, and the maximum and minimum values of the lengths of the straight lines were determined. The straight line is the shortest straight line among the straight lines drawn from an arbitrary point on the outer edge of the second silicone rubber region 72 towards the outer edge of the adjacent second silicone rubber region 72. The results are shown in Tables 1 and 2.

[0088]

Table 1

[0089]

Table 2

[0090] According to Tables 1 and 2, the samples of Examples 1 to 6 and Comparative Examples 1 to 4 had a hardness of 74 degrees or less. Comparative Example 5 had a hardness of 91 degrees.

[0091] According to Table 1 and Table 2, the samples of Examples 1 to 6 showed values of stress at 50% elongation (M50) of 2.2 MPa or more and values of stress at 100% elongation (M100) of 2.7 MPa or more. The samples of Comparative Examples 1 to 4 showed values of stress at 50% elongation (M50) of 1.9 MPa or less and values of stress at 100% elongation (M100) of 2.1 MPa or less. The sample of Comparative Example 5 showed values of stress at 50% elongation (M50) and stress at 100% elongation (M100) that were larger than those of the Examples.

[0092] According to Table 1 and Table 2, the samples of Examples 1 to 6 had a tear strength (Tr) at room temperature of 48.6 N / mm or more. The samples of Comparative Examples 1 to 5 showed values of tear strength at room temperature that were smaller than those of the Examples.

[0093] According to Table 1 and Table 2, for the samples of Examples 1 to 6, the ratio of the area of the second silicone rubber region 72 in the image 90 was 52.3% to 74.8%. In the samples of Comparative Examples 1 and 2, the second silicone rubber region 72 did not exist. For the samples of Comparative Examples 3 to 5, the ratio of the area of the second silicone rubber region 72 in the image 90 was 33.6% to 89.3%.

[0094] According to Table 1 and Table 2, for the samples of Examples 1 to 6, the area of the second silicone rubber region 72 was 0.24 μm 2 to 5.54 μm 2 The samples of Comparative Examples 3 and 4 were 0.92 μm 2 to 13.8 μm 2 The sample of Comparative Example 5 had an area of the second silicone rubber region 72 of 0.23 μm 2 to 1.85 μm 2 The sample of Comparative Example 5 had an area of the second silicone rubber region 72 of 0.23 μm to 1.85 μm.

[0095] According to Table 1 and Table 2, for the samples of Examples 1 to 6, the maximum width of the second silicone rubber region 72 was 0.50 μm to 4.42 μm. For the samples of Comparative Examples 3 and 4, the maximum width of the second silicone rubber region 72 was 1.21 μm to 9.43 μm, and for the sample of Comparative Example 5, the maximum width of the second silicone rubber region 72 was 0.37 μm to 2.55 μm.

[0096] According to Table 1 and Table 2, for the samples of Examples 1 to 6, the width of the continuous structure 70 was 0.05 μm to 2.70 μm. For the samples of Comparative Examples 3 and 4, the continuous structure 70 did not exist, and for the sample of Comparative Example 5, the width of the continuous structure 70 was 1.13 μm to 6.70 μm.

Explanation of Reference Signs

[0097] 20…Carbon Nanotube, 30…Silicone Rubber, 34…Bank, 36…Mixture, 37…First Composite Rubber, 38…Second Composite Rubber, 50…Carbon Fiber Composite Material, 60…Cell Structure, 62…Interface Phase, 64…First Silicone Rubber Region, 70…Continuous Structure, 72…Second Silicone Rubber Region, 90…Image, 100…Open Roll, 110…First Roll, 120…Second Roll, d…Roll Interval, V1, V2…Rotation Speed

Claims

1. A carbon fiber composite material containing carbon nanotubes in a crosslinked silicone rubber, comprising a cell structure formed by surrounding the carbon nanotubes and their interfacial phase with a first silicone rubber region, and a continuous structure formed annularly so that a plurality of the cell structures continuously surround a second silicone rubber region, In the cross-section of the carbon fiber composite material, the continuous structure is a region where the number of carbon nanotubes per 1 μm ２ exceeds 2, In the cross-section, the second silicone rubber region has an area of 0.1 μm ２ or more and 10 μm 2 or less, and is a region where the number of carbon nanotubes per 1 μm ２ is 2 or less. wherein the total area occupied by the second silicone rubber region is 45% or more and 80% or less, and the maximum width of the second silicone rubber region is 0.1 μm or more and 6 μm or less. The carbon fiber composite material.

2. In Claim 1, the width of the continuous structure is 0.01 μm to 5 μm. The carbon fiber composite material.

3. In Claim 1 or Claim 2, the average diameter of the carbon nanotubes is 2 nm to 30 nm. The carbon fiber composite material.

4. In any one of Claims 1 to 3, the carbon nanotubes are contained in an amount of 0.5 parts by mass to 7.0 parts by mass with respect to 100 parts by mass of the silicone rubber. The carbon fiber composite material.

5. In any one of Claims 1 to 4, the hardness based on JIS K6253 is 65 degrees to 78 degrees. The carbon fiber composite material.

6. In any one of Claims 1 to 5, the stress at 50% elongation in a tensile test based on JIS K6251 at room temperature is 2.0 MPa to 5.0 MPa. The carbon fiber composite material.

7. In any one of Claims 1 to 6, the tear strength (Tr) in a tear test based on JIS K6252 at room temperature is 45 N / mm to 65 N / mm. The carbon fiber composite material.

8. a first mixing step of mixing carbon nanotubes with silicone rubber to obtain a mixture, a first kneading step of charging the mixture into an open roll having a roll gap set to more than 0 mm and 0.5 mm or less and a roll temperature set to 0°C to 50°C and passing it thinly to obtain a first composite rubber, a second mixing step of further mixing silicone rubber with the first composite rubber to obtain a second composite rubber, and a second kneading step of charging the second composite rubber into an open roll having a roll gap set to more than 0 mm and 0.5 mm or less and a roll temperature set to 0°C to 50°C and passing it thinly to obtain a carbon fiber composite material, wherein the average diameter of the carbon nanotubes is 2 nm to 30 nm, ​ The first mixing step mixes 3 to 15 parts by mass of the carbon nanotubes with 100 parts by mass of the silicone rubber. The second mixing step is a method for producing a carbon fiber composite material, which mixes the silicone rubber so that the second composite rubber contains 0.5 to 7 parts by mass of the carbon nanotubes with respect to 100 parts by mass of the silicone rubber.

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