JP2007119647A - Composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite material containing a newly structured carbon fiber structure that has preferred physical properties as a filler for use in a composite material and be capable of improving physical properties such as electrical properties, mechanical properties and thermal properties without lowering properties of a matrix by addition of a small amount of the structure. <P>SOLUTION: The carbon fiber structure has a three-dimensional network form composed of carbon fibers having an outer diameter of 15-100 nm. The carbon fiber structure has granular parts to bond the carbon fibers with each other in a state extending a plurality of carbon fibers and the granular parts are formed during the growing process of the carbon fiber. The composite material contains the carbon fiber structure, which contains boron, in the matrix at a ratio of 0.001-30 mass% based on the total composite material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel composite material. More specifically, the present invention relates to a composite material obtained by blending a fine carbon fiber structure containing boron with a soft, high strength, tough special structure and further containing boron.

  In order to obtain characteristics that cannot be obtained with a single material, the materials are combined. Conventionally, glass fiber reinforced plastic has been widely used as a composite material. However, since carbon fiber was developed and carbon fiber reinforced fiber reinforced plastic (CFRP) was developed, composite materials became particularly popular. .

  These materials are widely used in sports equipment and the like, and have attracted attention as lightweight, high-strength and high-elasticity structural materials for aircraft. Thereafter, composite materials include not only fiber reinforced materials but also fine particle reinforced materials. Furthermore, in addition to structural materials where strength and heat resistance are important, functional materials that focus on electrical / electronic properties, optical properties, and chemical properties are also treated as composite materials.

  On the other hand, with the widespread use of electronic devices, problems such as radio wave interference in which peripheral components are affected by noise generated from electronic components and malfunctions due to static electricity have become serious problems. In order to solve these problems, a material excellent in conductivity and braking performance is required in this field.

  Conventionally, in a polymer material having poor conductivity, a conductive polymer material imparted with a conductivity function by blending a highly conductive filler or the like has been widely used. As the conductive filler, metal fiber and metal powder, carbon black, carbon fiber, etc. are generally used. However, when the metal fiber and metal powder are used as the conductive filler, the corrosion resistance is poor and the mechanical strength is obtained. There is a drawback that it is difficult. On the other hand, when carbon fiber is used as a conductive filler, desired strength and elastic modulus can be achieved by blending a certain amount of general reinforcing carbon fiber, but it is sufficient in terms of conductivity. However, since high filling is required to obtain the desired conductivity, the original physical properties of the original resin are lowered. In addition, in the carbon fiber, when the fiber diameter is smaller, when the same amount of fiber is added, the contact area between the matrix resin and the fiber is increased, so that it is expected to be excellent in conductivity imparting effect.

  Carbon fibers currently contain continuous filaments of organic polymers, especially cellulose or polyacrylonitrile, as precursors under carefully maintained tensile forces to ensure good orientation of the anisotropic sheet of carbon atoms in the final filament. It is manufactured by thermal decomposition under control, and becomes expensive due to a weight loss in carbonization and a slow carbonization rate.

  Furthermore, in recent years, fine carbon fibers such as carbon nanostructures represented by carbon nanotubes (hereinafter also referred to as “CNT”) have attracted attention as another example of carbon fibers.

  The graphite layer constituting the carbon nanostructure is a substance having a regular, six-membered ring arrangement structure, and chemically, mechanically and thermally stable properties as well as its unique electrical properties. Therefore, for example, by dispersing and blending such fine carbon fibers in solid materials such as various resins, ceramics, metals, or liquid materials such as fuel oil and lubricant, the above-described physical properties can be utilized. If possible, use as an additive is expected.

  However, on the other hand, such fine carbon fibers are already agglomerated at the time of production, and if they are used as they are, there is a risk that dispersion will not proceed in the matrix and performance will be deteriorated. Accordingly, when trying to exhibit predetermined characteristics such as conductivity in a matrix such as a resin, a considerable amount of addition is required.

  Patent Document 1 discloses a resin containing an aggregate in which carbon fibrils having a diameter of 3.5 to 70 nm are entangled with each other, the longest diameter is 0.25 mm or less, and the diameter is 0.10 to 0.25 mm. A composition is disclosed. As is clear from the description of Examples and the like in Patent Document 1, numerical values such as the longest diameter and diameter of the carbon fibril aggregate are characteristic values of the aggregate before blending into the resin. Patent Document 2 discloses an aggregate of carbon fibers having a diameter of 50 to 5000 nm, in which carbon fiber mainly includes a structure having a size of 5 μm to 500 μm in which a contact point between the fibers is fixed by a carbonaceous carbide. A composite comprising a fiber material blended in a matrix is disclosed. Also in this patent document 2, numerical values such as the size of the structure are characteristic values before blending into the resin.

  By using such a carbon fiber aggregate, an improvement in dispersibility in the resin matrix is expected to some extent as compared with the case of mixing in a larger lump. However, the agglomerates described in Patent Document 1 are obtained, for example, by dispersing carbon fibrils by applying a shearing force with a vibrating ball mill or the like. It has not yet been satisfactory as an additive that efficiently improves properties such as conductivity. Further, in the carbon fiber structure shown in Patent Document 2, the contact point between the fibers is fixed in a state where the carbon fiber aggregate is compression-molded and formed as a contact point between the fibers after the carbon fiber is manufactured. Since it is formed by carbonizing the residual organic matter such as pitch remaining on the carbon fiber surface or the organic matter added as a binder after heat treatment, the adhesive strength of the contact point is weak, and the structure itself The electrical characteristics were not very good. Therefore, when blended in a matrix such as a resin, the contact point easily dissociates, so that the shape of the structure cannot be maintained. For example, good electrical characteristics are exhibited even when added in a small amount. Above, it was difficult to form a good conductive path in the matrix. Furthermore, when carbonization is performed by adding a binder or the like for fixing the contact point, it is difficult to attach the binder or the like only to the site of the contact point, and also adheres to the entire fiber. There is a high possibility that only fibers having a large fiber diameter and inferior surface characteristics will be obtained.

  By the way, when imparting conductivity by blending carbon fibers in a matrix such as a resin, a technique is known that contains boron in the carbon fiber crystals (for example, Patent Document 3). The technology aims to improve the crystallinity of the carbon fiber by incorporating boron into the crystal of the carbon fiber, and to control the electronic state by appropriately generating defects, thereby improving the conductive properties. .

However, for the same reason as described above, with the carbon fiber disclosed in Patent Document 3, it has been difficult to form a good conductive path in the matrix.
Japanese Patent No. 2862578 JP 2004-119386 A JP 2004-3097 A

  The present invention provides a carbon fiber having a novel structure that has favorable physical properties as a filler for composite materials and can improve physical properties such as electrical properties, mechanical properties, thermal properties, etc. without impairing the properties of the matrix with a small amount of addition. A composite material including a structure is provided.

  In order to solve the above-mentioned problems, the present inventors have intensively studied, and in order to exhibit sufficient characteristics improvement even if the addition amount is small, the finest possible carbon fibers are used. Are firmly bonded to each other without being separated and held in a matrix with a sparse structure, and each carbon fiber itself has as few defects as possible. In addition to being effective, it has been found that changing the electronic state by incorporating boron is effective, and the present invention has been achieved.

  That is, the present invention that solves the above problems presents a three-dimensional network formed of carbon fibers having an outer diameter of 15 to 100 nm, and the carbon fiber structure is a mode in which a plurality of the carbon fibers extend, A carbon fiber structure having a granular part for bonding the carbon fibers to each other, the granular part being formed in the growth process of the carbon fiber, and further containing boron Is contained in the matrix in a proportion of 0.001 to 30% by mass of the whole.

  The present invention also shows the composite material, wherein the boron content is 0.001 to 2.1% by mass with respect to the carbon fiber structure.

  The present invention also provides the composite material, wherein the carbon fiber structure has an area-based circle-equivalent mean diameter of 50 to 100 μm.

The present invention further shows the composite material, wherein the carbon fiber structure has a bulk density of 0.0001 to 0.05 g / cm ³ .

In the carbon fiber structure according to the present invention, I _D / I _G measured by Raman spectroscopy is 0.2 to 1.4, and I _{G ′} / I _G is 0.25 to 0. The composite material is characterized by being .75.

  The present invention also provides the composite material, wherein the carbon fiber structure has a combustion start temperature in air of 700 ° C. or higher.

  The present invention also shows the above-mentioned composite material, wherein the particle diameter of the granular part is larger than the outer diameter of the carbon fiber at the bonded portion of the carbon fiber.

  The present invention also shows the composite material, wherein the carbon fiber structure is produced using at least two or more carbon compounds having different decomposition temperatures as a carbon source.

  The present invention also shows the above composite material in which the matrix comprises an organic polymer.

  The present invention also shows the above composite material in which the matrix includes an inorganic material.

  The present invention also shows the above composite material in which the matrix contains a metal.

  The present invention is also characterized in that the matrix further contains at least one filler selected from the group consisting of metal fine particles, silica, calcium carbonate, magnesium carbonate, carbon black, glass fiber and carbon fiber in the matrix. Indicates the material.

  In the present invention, the carbon fiber structure is finely bonded to each other by the granular portions formed in the growth process of the carbon fibers, and the fine carbon fibers arranged in a three-dimensional network as described above, In order to have a shape in which a plurality of the carbon fibers extend from the granular portion, when blended in a matrix such as a resin, the carbon fiber structure is easily dispersed while leaving a sparse structure, Even with a small amount of addition, fine carbon fibers can be arranged in the matrix with a uniform spread.

  Furthermore, in the present invention, since the carbon fiber structure contains boron, each of the carbon fibers and the granular portion can be made into a highly crystalline carbon fiber and the electronic state is changed. be able to.

  In addition, by incorporating boron, removal of the catalyst metal is promoted, and a carbon fiber structure having a low metal content and a low impurity content can be obtained.

  As described above, in the composite material according to the present invention, the fine and highly crystalline carbon fiber structure is uniformly dispersed and distributed throughout the matrix even by arranging a relatively small amount of the above-described carbon fiber structure. Therefore, for example, with respect to electrical characteristics, a good conductive path can be formed throughout the matrix, and the conductivity can be improved. Also, with respect to mechanical characteristics, thermal characteristics, etc., the filler made of fine carbon fibers throughout the matrix. As a result, the characteristics can be improved. Therefore, according to the present invention, a composite material useful as a functional material excellent in electrical conductivity, radio wave shielding property, thermal conductivity, etc., a structural material having high strength, and the like can be obtained.

  Hereinafter, the present invention will be described in detail based on preferred embodiments.

  The composite material of the present invention is characterized in that a three-dimensional network-like carbon fiber structure having a predetermined structure as described later is contained in the matrix in a proportion of 0.001 to 30% by mass. .

  The carbon fiber structure used in the present invention is, for example, a three-dimensional network-like carbon composed of carbon fibers having an outer diameter of 15 to 100 nm, as seen in the TEM photographs shown in FIGS. 3 (a) and 3 (b). It is a fiber structure, Comprising: The said carbon fiber structure has the granule part which couple | bonds the said carbon fiber mutually in the aspect with which the said carbon fiber extends in multiple numbers. The carbon fiber structure used in the present invention is a carbon fiber structure characterized by further containing boron in the carbon fiber structure shown in FIGS. 3 (a) and 3 (b).

  The outer diameter of the carbon fiber constituting the carbon fiber structure is in the range of 15 to 100 nm, when the outer diameter is less than 15 nm, the cross section of the carbon fiber is not polygonal as described later, On the other hand, as the diameter of the carbon fiber is smaller, the number per unit amount increases, the length of the carbon fiber in the axial direction also becomes longer, and high conductivity is obtained, so having an outer diameter exceeding 100 nm This is because it is not suitable as a carbon fiber structure to be disposed as a modifier or additive in a matrix such as a resin. The outer diameter of the carbon fiber is particularly preferably in the range of 20 to 70 nm. In this outer diameter range, a cylindrical graphene sheet laminated in a direction perpendicular to the axis, that is, a multilayer, is not easily bent, and is elastic, that is, has the property of returning to its original shape even after deformation. Therefore, even after the carbon fiber structure is once compressed, it is easy to adopt a sparse structure after being arranged in a matrix such as a resin.

Incidentally, when annealing at 2400 ° C. or higher, with a true density narrowed spacing of graphene sheets stacked is increased from 1.89 g / cm ³ to 2.1 g / cm ^3, perpendicular to the axis the cross-section of the carbon fiber becomes a polygonal shape The carbon fiber having this structure is dense and has few defects both in the laminating direction and in the plane direction of the cylindrical graphene sheet constituting the carbon fiber, so that the bending rigidity (EI) is improved.

  In addition, it is desirable that the fine carbon fiber has an outer diameter that changes along the axial direction. If the outer diameter of the carbon fiber is not constant along the axial direction and varies, it is considered that a kind of anchoring effect occurs in the carbon fiber in the matrix such as resin, and the movement in the matrix Is less likely to occur and the dispersion stability is increased.

  In the carbon fiber structure according to the present invention, fine carbon fibers having such a predetermined outer diameter are present in a three-dimensional network, and these carbon fibers are formed in a granular portion formed during the growth process of the carbon fibers. Are bonded to each other, and a plurality of the carbon fibers extend from the granular portion. In this way, the fine carbon fibers are not simply entangled with each other, but are firmly bonded to each other in the granular portion, so that when the structure is disposed in a matrix such as a resin, the structure is Without being disperse | distributed as a carbon fiber single-piece | unit, it can be disperse-blended in a matrix with a bulky structure. Further, in the carbon fiber structure according to the present invention, since the carbon fibers are bonded to each other by the granular part formed in the growth process of the carbon fiber, the electrical characteristics of the structure itself are also very high. For example, the electrical resistance value measured at a constant compression density is such that a simple entangled body of fine carbon fibers or a joint point between fine carbon fibers is adhered by a carbonaceous material or a carbide thereof after the carbon fiber is synthesized. Compared with the value of the structure or the like, it shows a very low value, and when it is dispersed and blended in the matrix, a good conductive path can be formed.

Since the granular part is formed in the growth process of the carbon fiber as described above, the carbon-carbon bond in the granular part is sufficiently developed, and although it is not exactly clear, sp ² bond and It seems to include a mixed state of sp ³ bonds. And after the generation (intermediate and first intermediate described later), the granular part and the fiber part are continuous with a structure in which patch-like sheet pieces made of carbon atoms are bonded together, and thereafter After the high-temperature heat treatment, as shown in FIGS. 3A and 3B, at least a part of the graphene layer constituting the granular part is formed on the graphene layer constituting the fine carbon fiber extending from the granular part. It will be continuous. In the carbon fiber structure according to the present invention, between the granular portion and the fine carbon fiber, it is symbolized that the graphene layer constituting the granular portion as described above is continuous with the graphene layer constituting the fine carbon fiber. As described above, they are connected by carbon crystal structural bonds (at least a part thereof), whereby a strong bond between the granular portion and the fine carbon fiber is formed.

  In the present specification, the term “extending” the carbon fiber from the granular part simply means that the granular part and the carbon fiber are apparently connected by other binder (including carbonaceous material). It does not indicate such a state, but mainly means a state in which they are connected by carbon crystal structural bonds as described above.

  Further, as described above, the granular part is formed in the carbon fiber growth process. As a trace, at least one catalyst particle or the catalyst particle is volatilized and removed in the subsequent heat treatment process. And the resulting voids. These pores (or catalyst particles) are essentially independent from the hollow portions formed inside the fine carbon fibers extending from the granular portions (note that only a small part is accidental) In addition, it is also observed that it is continuous with the hollow part.)

  The number of catalyst particles or holes is not particularly limited, but is about 1 to 1000, more preferably about 3 to 500, per granular part. By forming the granular portion in the presence of such a number of catalyst particles, it is possible to obtain a granular portion having a desired size as described later.

  The size of each catalyst particle or hole present in the granular part is, for example, 1 to 100 nm, more preferably 2 to 40 nm, and further preferably 3 to 15 nm.

  Further, although not particularly limited, it is desirable that the particle size of the granular portion is larger than the outer diameter of the fine carbon fiber as shown in FIG. Specifically, for example, the outer diameter of the fine carbon fiber is 1.3 to 250 times, more preferably 1.5 to 100 times, and still more preferably 2.0 to 25 times. In addition, the said value is an average value. Thus, when the particle diameter of the granular part which is a bonding point between carbon fibers is sufficiently large as 1.3 times or more of the outer diameter of the fine carbon fiber, it is higher than the carbon fiber extending from the granular part. When a carbon fiber structure is arranged in a matrix such as a resin due to a bonding force, even if a certain amount of elasticity is applied, the three-dimensional network structure is maintained and dispersed in the matrix. be able to. On the other hand, if the size of the granular part is extremely large exceeding 250 times the outer diameter of the fine carbon fiber, the fibrous properties of the carbon fiber structure may be impaired, for example, into various matrices. This is not desirable because it may not be suitable as an additive or compounding agent. The “particle size of the granular part” in the present specification is a value measured by regarding the granular part, which is a bonding point between carbon fibers, as one particle.

  The specific particle size of the granular part depends on the size of the carbon fiber structure and the outer diameter of the fine carbon fiber in the carbon fiber structure, but for example, an average value of 20 to 5000 nm, more preferably It is about 25 to 2000 nm, more preferably about 30 to 500 nm.

  Furthermore, since this granular part is formed in the growth process of the carbon fiber as described above, it has a relatively spherical shape, and the circularity is 0.2 to <1 on average. , Preferably 0.5 to 0.99, more preferably about 0.7 to 0.98.

  In addition, the granular portion is formed in the carbon fiber growth process as described above, and, for example, the joining point between the fine carbon fibers is adhered by the carbonaceous material or the carbide after the carbon fiber synthesis. Compared with the structure, etc., the bonds between the carbon fibers in the granular part are very strong, and even under conditions where the carbon fiber breaks in the carbon fiber structure, the granular part (Coupling part) is held stably. Specifically, for example, as shown in the examples described later, the carbon fiber structure is dispersed in a liquid medium, and ultrasonic waves with a predetermined output and a predetermined frequency are applied to the carbon fiber structure so that the average length of the carbon fibers is almost halved. Even when the load condition is such that the change rate of the average particle diameter of the granular part is less than 10%, more preferably less than 5%, the granular part, that is, the bonded part of the fibers is stably held. It is what.

  Furthermore, since the carbon fiber structure used in the present invention contains boron, each carbon fiber can be made into a carbon fiber with high crystallinity. In the present invention, "boron is contained in the carbon fiber structure" is not only a state in which a part of carbon atoms in the carbon fiber and the granular part constituting the carbon fiber structure is substituted with boron, It also includes a state in which boron is attached to the surface.

  The method for containing (doping) boron in the carbon fiber structure is not particularly limited. For example, the carbon fiber structure is not heat-treated at a low temperature (eg, 1500 ° C. or less) and has not yet developed crystals. Carbon fiber, and carbon fiber in an unheated (as-grown) state and boron (including a boron compound) are mixed, and then graphitized (annealed) at a high temperature to obtain a carbon fiber structure. Boron can be included. It is not impossible to incorporate boron into the carbon fiber that has been annealed at a temperature of 1600 ° C. or higher, or even 1800 ° C. or higher, but it is not preferable from the viewpoint of energy for doping boron. It also acts as a catalyst for promoting the crystallization of carbon fibers, and is effective in removing the catalytic metal during annealing. Therefore, it is preferable to contain boron before the annealing treatment.

Even if boron is contained in the carbon fiber structure, the present invention is not particularly limited. Here, “boron” in the present invention is a concept including not only elemental boron but also boron compounds. As described above, when boron is included in the carbon fiber structure, boron that is not evaporated by decomposition or the like before reaching at least 1600 ° C. is used because of annealing treatment at a high temperature (eg, 1600 ° C. or higher). It is necessary. Examples of boron that satisfies this condition include elemental boron, B ₂ O ₃ , H ₃ BO ₄ , B ₄ C, and BN.

  As content of boron, it is preferable that it is 0.001-2.1 mass% with respect to a carbon fiber structure, and it is especially preferable that it is 0.01-1.8 mass%. When the boron content is less than 0.001% by mass, it is difficult to improve the effect of boron content, that is, the crystallinity of the carbon fiber. On the other hand, if the content exceeds 2.1% by mass, it is less effective even if added because it exceeds the solid solution limit, and not only the processing cost increases, but also at the stage of heat treatment, it is easy to melt and set, In some cases, the surface of the fiber is covered with a boron compound, and the conductivity may be deteriorated.

  The carbon fiber structure used in the present invention desirably has an area-based circle-equivalent mean diameter of about 50 to 100 μm, more preferably about 60 to 90 μm. Here, the area-based circle-equivalent mean diameter is obtained by photographing the outer shape of the carbon fiber structure using an electron microscope or the like, and in this photographed image, the contour of each carbon fiber structure is represented by an appropriate image analysis software such as WinRoof. (Trade name, manufactured by Mitani Shoji Co., Ltd.) is used to determine the area within the contour, calculate the equivalent circle diameter of each fiber structure, and average it.

  Since it depends on the type of matrix material such as a resin to be compounded, it may not be applied in all cases, but this circle-equivalent average diameter is the carbon when mixed in a matrix such as a resin. This is a factor that determines the longest length of the fiber structure. Generally, when the average equivalent circle diameter is less than 50 μm, there is a possibility that the electrical conductivity may not be sufficiently exhibited, whereas it exceeds 100 μm. This is because, for example, when blending into a matrix by kneading or the like, a large increase in viscosity occurs, making it difficult to mix and disperse or to deteriorate moldability.

  Further, as described above, the carbon fiber structure used in the present invention has a shape in which carbon fibers existing in a three-dimensional network are bonded to each other in the granular portion, and a plurality of the carbon fibers extend from the granular portion. However, in a single carbon fiber structure, when a plurality of granular portions that combine carbon fibers are present to form a three-dimensional network, the average distance between adjacent granular portions is, for example, 0.5 μm. ˜300 μm, more preferably 0.5 to 100 μm, and even more preferably about 1 to 50 μm. In addition, the distance between this adjacent granule part measures the distance from the center part of one granular material to the center part of the granule part adjacent to this. When the average distance between the granular materials is less than 0.5 μm, the carbon fiber does not sufficiently develop into a three-dimensional network. For example, when dispersed in a matrix, a good conductive path is obtained. On the other hand, if the average distance exceeds 300 μm, it becomes a factor of increasing the viscosity when dispersed in the matrix, and the dispersibility of the carbon fiber structure in the matrix This is because there is a risk of lowering.

Furthermore, as described above, the carbon fiber structure used in the present invention has a shape in which carbon fibers existing in a three-dimensional network are bonded to each other in the granular portion, and a plurality of the carbon fibers extend from the granular portion. For this reason, the structure has a bulky structure in which carbon fibers are sparsely present. Specifically, for example, the bulk density is 0.0001 to 0.05 g / cm ³ , more preferably 0.00. It is desirable that it is 001-0.02 g / cm < ³ >. This is because if the bulk density exceeds 0.05 g / cm ³ , it becomes difficult to improve the physical properties of the matrix such as a resin by adding a small amount.

In addition, since the carbon fiber structure used in the present invention is bonded to each other in the granular portion formed in the growth process, the carbon fibers existing in a three-dimensional network form are electrically connected as described above. For example, the powder resistance value measured at a constant compression density of 0.8 g / cm ³ is 0.02 Ω · cm or less, more preferably 0.001 to 0.00. It is preferably 010 Ω · cm. This is because when the powder resistance value exceeds 0.02 Ω · cm, it is difficult to form a good conductive path when blended in a matrix such as a resin.

In addition, the carbon fiber structure used in the present invention desirably has boron contained in the graphene sheet constituting the carbon fiber from the viewpoint of having high strength and conductivity. Specifically, for example, Raman _I D / _{I G} ratio of _the measured by spectroscopy is 0.2 to 1.4, and it is desirable _{I G '/} I _G is 0.25 to 0.75. Here, in the Raman spectroscopic analysis, only a peak (G band) near 1580 cm ⁻¹ appears in large single crystal graphite. A peak (D band) appears in the vicinity of 1360 cm ⁻¹ due to the crystal having a finite minute size or lattice defects. Further, when the measurement range is expanded, a G ′ band appears in the vicinity of 2700 cm ⁻¹ . Therefore, the intensity ratio between the D band and the G band (R = I ₁₃₆₀ / I ₁₅₈₀ = I _D / I _G ) and the intensity ratio between the G ′ band and the G band (I ₂₇₀₀ / I ₁₅₈₀ = I _{G ′} / I _G ) This is because it is considered that boron is contained in the graphene sheet when it is within the predetermined range as described above. When boron is contained in the graphene sheet, the G band waveform in Raman spectroscopy becomes asymmetric, and a shoulder is recognized on the high wave number side.

  Moreover, it is desirable that the carbon fiber structure used in the present invention has a combustion start temperature in air of 700 ° C. or higher, more preferably 750 to 900 ° C. As described above, since the graphene sheet of the carbon fiber structure contains boron and the carbon fiber has an intended outer diameter, it has such a high thermal stability.

  The carbon fiber structure having the desired shape as described above is not particularly limited, but can be prepared, for example, as follows.

  Basically, an organic compound such as a hydrocarbon is chemically pyrolyzed by CVD using transition metal ultrafine particles as a catalyst to obtain a fiber structure (hereinafter referred to as an intermediate), which is mixed with boron or a boron compound. Further heat treatment at Note that boron or a boron compound may be mixed in advance with an organic compound such as hydrocarbon (that is, boron is added before obtaining an intermediate), and further boron is mixed after high-temperature heat treatment. It is also possible.

  As the raw material organic compound, hydrocarbons such as benzene, toluene and xylene, alcohols such as carbon monoxide (CO) and ethanol can be used. Although not particularly limited, in obtaining the fiber structure used in the present invention, it is preferable to use at least two or more carbon compounds having different decomposition temperatures as the carbon source. The “at least two or more carbon compounds” described in the present specification does not necessarily mean that two or more kinds of raw material organic compounds are used, and one kind of raw material organic compound is used. However, in the process of synthesizing the fiber structure, for example, a reaction such as hydrodealkylation of toluene or xylene occurs, and in the subsequent thermal decomposition reaction system, two decomposition temperatures are different. The aspect which becomes the above carbon compound is also included.

  In addition, when two or more types of carbon compounds are present as carbon sources in the thermal decomposition reaction system, the decomposition temperature of each carbon compound is not limited to the type of the carbon compound, but the carbon compound in the raw material gas. Since it varies depending on the gas partial pressure or molar ratio, a relatively large number of combinations can be used as carbon compounds by adjusting the composition ratio of two or more carbon compounds in the raw material gas.

  For example, alkanes or cycloalkanes such as methane, ethane, propanes, butanes, pentanes, hexanes, heptanes, cyclopropane, cyclohexane, etc., particularly alkanes having about 1 to 7 carbon atoms; ethylene, propylene, butylenes, Alkenes or cycloolefins such as pentenes, heptenes and cyclopentenes, especially alkenes having about 1 to 7 carbon atoms; alkynes such as acetylene and propyne, especially alkynes having about 1 to 7 carbon atoms; benzene, toluene, styrene, xylene, naphthalene , Aromatic or heteroaromatic hydrocarbons such as methylnaphthalene, indene and phenanthrene, especially aromatic or heteroaromatic hydrocarbons having about 6 to 18 carbon atoms, alcohols such as methanol and ethanol, especially about 1 to 7 carbon atoms Of alcohol; its Combine two or more carbon compounds selected from carbon monoxide, ketones, ethers, etc., by adjusting the gas partial pressure so that different decomposition temperatures can be exhibited in the desired thermal decomposition reaction temperature range. The carbon fiber structure according to the present invention can be efficiently produced by using the material and / or adjusting the residence time in a predetermined temperature range and optimizing the mixing ratio.

  Among such combinations of two or more carbon compounds, for example, in the combination of methane and benzene, the molar ratio of methane / benzene is> 1 to 600, more preferably 1.1 to 200, still more preferably. It is desirable to set it as 3-100. This value is the gas composition ratio at the entrance of the reactor. For example, when toluene is used as one of the carbon sources, toluene is decomposed 100% in the reactor, and methane and benzene are 1 In consideration of the occurrence of: 1, a shortage of methane may be supplied separately. For example, when the methane / benzene molar ratio is 3, 2 moles of methane may be added to 1 mole of toluene. In addition, as methane added to such toluene, not only a method of preparing fresh methane separately, but also the unreacted methane contained in the exhaust gas discharged from the reactor is circulated and used. It is also possible to use it.

  By setting the composition ratio within such a range, it becomes possible to obtain a carbon fiber structure having a structure in which both the carbon fiber part and the granular part are sufficiently developed.

  Note that an inert gas such as argon, helium, or xenon, or hydrogen can be used as the atmospheric gas.

  As the catalyst, a transition metal such as iron, cobalt or molybdenum, or a mixture of a transition metal compound such as ferrocene or metal acetate and sulfur or a sulfur compound such as thiophene or iron sulfide is used.

  The synthesis of the intermediate is carried out by using a CVD method such as hydrocarbon which is usually performed, evaporating a mixed liquid of hydrocarbon and catalyst as raw materials, introducing hydrogen gas or the like into the reaction furnace as a carrier gas, Pyrolysis at a temperature of 1300 ° C. Thereby, from several centimeters in which a plurality of carbon fiber structures (intermediates) having a sparse three-dimensional structure in which fibers having an outer diameter of 15 to 100 nm are bonded together by granular materials grown using the catalyst particles as nuclei are collected. Synthesize an aggregate of several tens of centimeters.

  The thermal cracking reaction of the hydrocarbon as a raw material mainly occurs on the surface of the granular particles grown using the catalyst particles or the core, and the recrystallization of carbon generated by the decomposition proceeds in a certain direction from the catalytic particles or granular materials. Grows in a fibrous form. However, in obtaining the carbon fiber structure according to the present invention, the balance between the thermal decomposition rate and the growth rate is intentionally changed. For example, as described above, at least two carbon sources having different decomposition temperatures are used. By using the above carbon compound, the carbon material is grown three-dimensionally around the granular material without growing the carbon material only in a one-dimensional direction. Of course, the growth of such three-dimensional carbon fibers does not depend only on the balance between the thermal decomposition rate and the growth rate, but the crystal surface selectivity of the catalyst particles, the residence time in the reactor, and the furnace temperature. The balance between the pyrolysis reaction and the growth rate is influenced not only by the type of carbon source as described above but also by the reaction temperature and gas temperature, etc. When the growth rate is faster than the thermal decomposition rate, the carbon material grows in a fibrous form. On the other hand, when the thermal decomposition rate is faster than the growth rate, the carbon material grows in the circumferential direction of the catalyst particles. To do. Therefore, by intentionally changing the balance between the pyrolysis rate and the growth rate, the carbon material growth direction as described above is made to be a multi-direction under control without changing the growth direction to a constant direction, as in the present invention. A three-dimensional structure can be formed. In order to easily form the three-dimensional structure in which the fibers are bonded to each other by the granular material in the produced intermediate, the composition of the catalyst, the residence time in the reaction furnace, the reaction temperature, and the gas temperature Etc. are desirable.

  In addition, as a method for efficiently producing the carbon fiber structure according to the present invention, the carbon fiber structure is supplied to the reaction furnace in addition to the above approach using two or more carbon compounds having different decomposition temperatures at an optimum mixing ratio. An approach for generating turbulent flow in the vicinity of the supply port of the raw material gas can be mentioned. The turbulent flow here is a flow that is turbulent and turbulent and flows in a spiral.

  In the reaction furnace, immediately after the raw material gas is introduced into the reaction furnace from the supply port, metal catalyst fine particles are formed by the decomposition of the transition metal compound as the catalyst in the raw material mixed gas. It is brought about through such a stage. That is, first, the transition metal compound is decomposed to become metal atoms, and then cluster generation occurs by collision of a plurality of, for example, about 100 atoms. At the stage of this generated cluster, it does not act as a catalyst for fine carbon fibers, and the generated clusters are further aggregated by collision and grow into crystalline particles of metal of about 3 nm to 10 nm to produce fine carbon fibers. It will be used as metal catalyst fine particles.

  In this catalyst formation process, if there is a vortex due to intense turbulence as described above, more intense collision is possible compared to collisions between metal atoms or clusters with only Brownian motion, and by increasing the number of collisions per unit time Metal catalyst fine particles can be obtained in a high yield in a short time, and metal catalyst fine particles having a uniform particle size can be obtained by equalizing the concentration, temperature, etc. by vortex. Furthermore, in the process of forming the metal catalyst fine particles, an aggregate of metal catalyst fine particles in which a large number of metal crystalline particles are gathered is formed by vigorous collision due to the vortex. In this way, the metal catalyst fine particles are rapidly generated, so that the decomposition of the carbon compound is promoted and sufficient carbon material is supplied, and the metal catalyst fine particles of the aggregate are radially formed as nuclei. On the other hand, when the fine carbon fibers grow, and as described above, when the thermal decomposition rate of some of the carbon compounds is faster than the growth rate of the carbon material, the carbon material also grows in the circumferential direction of the catalyst particles, A granular part is formed around the body, and a carbon fiber structure having an intended three-dimensional structure is efficiently formed. The metal catalyst fine particle aggregate may include a part of catalyst fine particles that are less active than other catalyst fine particles or have been deactivated during the reaction. A non-fibrous or very short fibrous carbon material layer that has grown on the surface of such a catalyst fine particle before agglomeration or has grown into an aggregate after such a fine particle has become an aggregate. It seems that the granular part of the carbon fiber structure according to the present invention is formed by being present at the peripheral position of the body.

  The specific means for generating a turbulent flow in the raw material gas flow in the vicinity of the raw material gas supply port of the reaction furnace is not particularly limited. For example, the raw material gas introduced into the reaction furnace from the raw material gas supply port It is possible to adopt means such as providing some type of collision part at a position where it can interfere with the current flow. The shape of the collision part is not limited in any way, as long as a sufficient turbulent flow is formed in the reactor by the vortex generated from the collision part. It is possible to adopt a form in which one or a plurality of plates, paddles, taper tubes, umbrellas, etc. are arranged alone or in combination.

  Thus, the intermediate obtained by heating and producing the mixed gas of catalyst and hydrocarbon at a constant temperature in the range of 800 to 1300 ° C. is like a patch-like sheet piece made of carbon atoms ( When it is analyzed by Raman spectroscopy, the D band is very large, the G ′ band is small, and there are many defects. The produced intermediate contains unreacted raw material, non-fibrous carbide, tar content and catalytic metal.

  In order to remove these residues from such an intermediate and obtain the desired carbon fiber structure with few defects, high-temperature heat treatment at 1600 to 3000 ° C. is performed by an appropriate method.

  That is, for example, the intermediate is heated at 800 to 1200 ° C. to remove volatile components such as unreacted raw materials and tars, and then annealed at a high temperature of 1600 to 3000 ° C. to prepare the desired structure. At the same time, the catalyst metal contained in the fiber is removed by evaporation. At this time, a reducing gas or a small amount of carbon monoxide gas may be added to the inert gas atmosphere in order to protect the material structure.

  When the intermediate is annealed at a temperature in the range of 1600 to 3000 ° C., the patch-like sheet pieces made of carbon atoms are bonded to each other to form a plurality of graphene sheet-like layers.

  In the stage of performing the high temperature heat treatment, boron can be contained in the carbon fiber structure (doping) by mixing the intermediate and boron. Here, in order to efficiently contain boron in the carbon fiber structure, it is necessary to mix the intermediate and boron well so that they are in uniform contact. For this purpose, it is preferable to use boron (or boron compound) particles having a particle size as small as possible. If the particles are large, a high concentration region is partially generated, which may cause solidification. Specifically, the average particle size of boron is 100 μm or less, preferably 50 μm or less, and more preferably 20 μm or less. When boric acid or the like is used as the boron source, a method of adding a solution and evaporating the solvent in advance or a method of evaporating the solvent during the heating process can be used. If the solution is mixed uniformly, the boron compound can be uniformly attached to the fiber surface after the solvent is evaporated.

  Moreover, before or after such high-temperature heat treatment, a step of crushing the equivalent circle average diameter of the carbon fiber structure to several centimeters, and a circle equivalent average diameter of the crushed carbon fiber structure of 50 to A carbon fiber structure having a desired circle-equivalent mean diameter is obtained through a step of pulverizing to 100 μm. In addition, you may perform a grinding | pulverization process, without passing through a crushing process. Moreover, you may perform the process which granulates the aggregate | assembly which has two or more carbon fiber structures which concern on this invention in the shape, size, and bulk density which are easy to use. More preferably, in order to effectively utilize the structure formed at the time of the reaction, if annealing is performed in a state where the bulk density is low (a state where the fiber is fully stretched and the porosity is large), further conductivity to the resin is achieved. It is effective for imparting sex.

Fine carbon fiber structure used in the present invention,
A) low bulk density,
B) Good dispersibility in the matrix of resin, etc.
C) High conductivity
D) High thermal conductivity,
E) Good slidability,
F) Good chemical stability
G) High thermal stability,
These can be used in a wide range as fillers for composite materials for solid materials such as resins, ceramics, and metals as will be described later, and can be used as composite materials according to the present invention.

  Next, in the composite material of the present invention, as the matrix for dispersing the carbon fiber structure as described above, an organic polymer, an inorganic material, a metal or the like can be preferably used, and an organic polymer is most preferable.

  Examples of organic polymers include polypropylene, polyethylene, polystyrene, polyvinyl chloride, polyacetal, polyethylene terephthalate, polycarbonate, polyvinyl acetate, polyamide, polyamideimide, polyetherimide, polyetheretherketone, polyvinyl alcohol, polyphenylene ether, and poly (meth) acrylate. And various thermoplastic resins such as liquid crystal polymers, epoxy resins, vinyl ester resins, phenol resins, unsaturated polyester resins, furan resins, imide resins, urethane resins, melamine resins, silicone resins and urea resins, Natural rubber, styrene / butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), ethylene / propylene rubber (EPDM), Various elastomers such as tolyl rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), urethane rubber, silicone rubber, fluorine rubber, acrylic rubber (ACM), epichlorohydrin rubber, ethylene acrylic rubber, norbornene rubber and thermoplastic elastomer Is mentioned.

  The organic polymer may be in the form of various compositions such as adhesives, fibers, paints, and inks.

  That is, the matrix is, for example, epoxy adhesive, acrylic adhesive, urethane adhesive, phenol adhesive, polyester adhesive, vinyl chloride adhesive, urea adhesive, melamine adhesive, olefin adhesive Adhesives, vinyl acetate adhesives, hot melt adhesives, cyanoacrylate adhesives, rubber adhesives and cellulose adhesives, acrylic fibers, acetate fibers, aramid fibers, nylon fibers, novoloid fibers, Cellulose fiber, viscose rayon fiber, vinylidene fiber, vinylon fiber, fluorine fiber, polyacetal fiber, polyurethane fiber, polyester fiber, polyethylene fiber, polyvinyl chloride fiber, polypropylene fiber, etc., phenol resin paint, alkyd resin paint Epoxy resin paint, Acrylic resin paint, unsaturated polyester paint, polyurethane paint, silicone paint, fluorine resin paint may be a paint such as a synthetic resin emulsion based paint.

  As an inorganic material, it consists of a ceramic material or an inorganic oxide polymer, for example. Preferred examples include carbon materials such as carbon carbon composites, glass, glass fibers, sheet glass and other molded glasses, silicate ceramics and other refractory ceramics such as aluminum oxide, silicon carbide, magnesium oxide, silicon nitride, Examples include boron nitride and zirconium oxide.

  Also, when the matrix is a metal, suitable metals include aluminum, magnesium, lead, copper, tungsten, titanium, niobium, hafnium, vanadium, and alloys and mixtures thereof.

  Furthermore, the composite material of the present invention may contain other fillers in addition to the carbon fiber structure described above. Examples of such fillers include metal fine particles, silica, calcium carbonate, magnesium carbonate, Carbon black, glass fiber, carbon fiber, etc. are mentioned, These can be used individually or in combination of two or more.

The composite material of the present invention contains an effective amount of the above-described carbon fiber structure in the matrix as described above.
The amount varies depending on the use of the composite material and the matrix, but is approximately 0.001% to 30%. If it is less than 0.001%, the reinforcing effect of strength as a structural material is small, and the electrical conductivity is not sufficient. On the other hand, if it exceeds 30%, the strength is lowered, and the adhesion of paints, adhesives, etc. is also deteriorated. In the composite material of the present invention, even if the amount of the carbon fiber structure as the filler is relatively low, fine carbon fibers can be arranged in the matrix with a uniform spread, As described above, it is a composite material useful as a functional material excellent in electrical conductivity, radio wave shielding property, thermal conductivity, etc., a structural material having high strength, and the like.

  Furthermore, regarding the composite material according to the present invention, specific examples according to the function of the carbon fiber structure to be blended are exemplified as follows, but of course not limited thereto. Absent.

1) Utilizing conductivity As a conductive resin and a conductive resin molding by mixing with a resin, for example, a packaging material, gasket, container, resistor, conductive fiber, electric wire, adhesive, ink, paint, etc. Is preferably used. In addition to composite materials with resins, similar effects can be expected with composite materials added to inorganic materials, particularly ceramics and metals.

2) Using thermal conductivity The same usage as in the case of using the above-mentioned conductivity can be performed.

3) Utilizing electromagnetic wave shielding properties By mixing with a resin, it is suitable as an electromagnetic wave shielding material or the like by forming an electromagnetic wave shielding paint or molding.

4) Items that use physical properties In order to improve slidability, they are mixed with resin and metal and used for rolls, brake parts, tires, bearings, lubricants, gears, pantographs, etc.

  In addition, it can be used for the body of electric wires, home appliances / vehicles / airplanes, and machine housings by utilizing its light weight and tough characteristics.

  In addition, it can be used as an alternative to conventional carbon fibers and beads, and is applied to, for example, battery pole materials, switches, and vibration-proof materials.

5) Utilization of filler characteristics The fine fibers of the carbon fiber structure have excellent strength, flexibility, and excellent filler characteristics that constitute a network structure. By utilizing this characteristic, it can contribute to the enhancement of the electrodes of energy devices such as lithium ion secondary batteries, lead storage batteries, capacitors, fuel cells, and improvement of cycle characteristics.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to the following Example at all.

  In addition, below, each physical-property value of the carbon fiber structure used for this invention was measured as follows.

<Area-based circle equivalent average diameter>
First, a photograph of the pulverized product is taken with an SEM. In the obtained SEM photograph, only the carbon fiber structure with a clear outline was targeted, and the carbon fiber structure with a broken outline was not targeted because the outline was unclear. All carbon fiber structures (about 60 to 80) that can be targeted in one field of view were used, and about 200 carbon fiber structures were targeted in three fields of view. Trace the contour of each carbon fiber structure targeted using image analysis software WinRoof (trade name, manufactured by Mitani Corp.), obtain the area within the contour, and calculate the equivalent circle diameter of each fiber structure This was averaged.

<Measurement of bulk density>
A transparent cylinder with an inner diameter of 70 mm is filled with 1 g of powder, and air with a pressure of 0.1 Mpa and a capacity of 1.3 liters is sent from the lower part of the dispersion plate to blow out the powder and let it settle naturally. At the time of blowing out 5 times, the height of the powder layer after settling is measured. At this time, the number of measurement points was six, and after calculating the average of the six points, the bulk density was calculated.

<Raman spectroscopy>
Using a LabRam800 manufactured by Horiba Jobin Yvon, measurement was performed using a wavelength of 514 nm of an argon laser.

<TG combustion temperature>
Using TG-DTA manufactured by Mac Science, the temperature was increased at a rate of 10 ° C./min while circulating air at a flow rate of 0.1 L / min, and the combustion behavior was measured. During combustion, TG indicates a decrease in weight and DTA indicates an exothermic peak. Therefore, the top position of the exothermic peak was defined as the combustion start temperature.

<Powder resistance and resilience>
1 g of CNT powder is weighed, filled and compressed in a resin die (inner dimensions 40 L, 10 W, 80 Hmm), and the displacement and load are read. When a constant current was passed by the 4-terminal method, the voltage at that time was measured, and when the density was measured to a density of 0.9 g / cm ³ , the pressure was released and the density after restoration was measured. As for powder resistance, resistance when compressed to 0.5, 0.8 and 0.9 g / cm ³ is measured.

<Average particle size of granular part, circularity, ratio with fine carbon fiber>
Similar to the measurement of the area-based circle-equivalent mean diameter, first, a photograph of the carbon fiber structure is taken with an SEM. In the obtained SEM photograph, only the carbon fiber structure with a clear outline was targeted, and the carbon fiber structure with a broken outline was not targeted because the outline was unclear. All carbon fiber structures (about 60 to 80) that can be targeted in one field of view were used, and about 200 carbon fiber structures were targeted in three fields of view.

  In each of the targeted carbon fiber structures, a granular portion that is a bonding point between carbon fibers is regarded as one particle, and its outline is defined by using image analysis software WinRoof (trade name, manufactured by Mitani Corporation). By tracing, the area in the contour was obtained, the equivalent circle diameter of each granular part was calculated, and this was averaged to obtain the average particle diameter of the granular part. Further, the circularity (R) is calculated based on the following equation from the area (A) in the contour measured using the image analysis software and the measured contour length (L) of each granular portion. Was averaged.

R = A × 4π / L ²
Furthermore, the outer diameter of fine carbon fibers in each targeted carbon fiber structure is obtained, and the size of the granular portion in each carbon fiber structure is determined from this and the equivalent circle diameter of the granular portion in each carbon fiber structure. It calculated | required as a ratio with a fine carbon fiber, and averaged this.

<Average distance between granular parts>
Similar to the measurement of the area-based circle-equivalent mean diameter, first, a photograph of the carbon fiber structure is taken with an SEM. In the obtained SEM photograph, only the carbon fiber structure with a clear outline was targeted, and the carbon fiber structure with a broken outline was not targeted because the outline was unclear. All carbon fiber structures (about 60 to 80) that can be targeted in one field of view were used, and about 200 carbon fiber structures were targeted in three fields of view.

  In each target carbon fiber structure, find all the places where the granular parts are connected by the fine carbon fibers, and the distance between adjacent granular parts connected by the fine carbon fibers in this way (the center of the granular material at one end) The length of the fine carbon fiber including the part to the central part of the granular material at the other end) was measured and averaged.

<Destructive test of carbon fiber structure>
A carbon fiber structure was added to 100 ml of toluene in a vial with a lid at a rate of 30 μg / ml to prepare a dispersion sample of the carbon fiber structure.

  The dispersion sample of the carbon fiber structure thus obtained was subjected to ultrasonic waves using an ultrasonic cleaner having a transmission frequency of 38 kHz and an output of 150 w (trade name: USK-3, manufactured by SND Co., Ltd.). Irradiation was performed, and changes in the carbon fiber structure in the dispersion liquid sample were observed over time.

First, ultrasonic waves are irradiated, and after 30 minutes, a predetermined amount of 2 ml of the dispersion liquid sample is extracted from the bottle, and a photograph of the carbon fiber structure in the dispersion liquid is taken with an SEM. 200 fine carbon fibers (fine carbon fibers having at least one end bonded to the granular part) in the carbon fiber structure of the obtained SEM photograph were randomly selected, and the length of each selected fine carbon fiber It was measured to obtain the D ₅₀ average, which was used as the initial average fiber length.

On the other hand, 200 granular parts which are the bonding points between carbon fibers in the carbon fiber structure of the obtained SEM photograph are selected at random, and each selected granular part is regarded as one particle, and its outline is defined. Then, the image analysis software WinRoof (trade name, manufactured by Mitani Corporation) was traced to determine the area within the contour, calculate the equivalent circle diameter of each granular portion, and determine the D ₅₀ average value. And the resulting D ₅₀ average value as the initial average diameter of the granular part.

Thereafter, a fixed amount of 2 ml of the dispersion liquid sample was taken out from the bottle at regular intervals in the same manner as described above, a photograph of the carbon fiber structure in the dispersion liquid was taken with an SEM, and the carbon fiber of the obtained SEM photograph the D ₅₀ average diameter of D ₅₀ average length and granular part of the carbon fibers in the structure in was determined in the same manner as above.

And the D ₅₀ average length of the calculated fine carbon fiber is about half of the initial average fiber length (in this example, after irradiating ultrasonic waves and 500 minutes have elapsed), the D of the granular portion _{The 50} average diameter was compared with the initial average diameter, and the variation ratio (%) was examined.

<Conductivity>
Using a four-probe type low resistivity meter (Loresta GP, manufactured by Mitsubishi Chemical), measure the resistance (Ω) of the coating surface of the composite material test piece at 9 locations. cm), and the average value was calculated.

<Thermal conductivity>
A test piece was cut into a predetermined shape, and the thermal conductivity (W / mK) was measured by a laser flash method.

Example 1
i) Synthesis of carbon fiber structure A carbon fiber structure was synthesized by a CVD method using toluene as a raw material.

  A mixture of ferrocene and thiophene was used as a catalyst, and the reaction was performed in a hydrogen gas reducing atmosphere. Toluene and the catalyst were heated to 380 ° C. together with hydrogen gas, supplied to the production furnace, and pyrolyzed at 1250 ° C. to obtain a carbon fiber structure (first intermediate).

  In addition, the schematic structure of the production | generation furnace used when manufacturing this carbon fiber structure (1st intermediate body) is shown in FIG. As shown in FIG. 6, the production furnace 1 has an introduction nozzle 2 for introducing a raw material mixed gas composed of toluene, a catalyst and hydrogen gas as described above into the production furnace 1 at the upper end thereof. Further, a cylindrical collision portion 3 is provided outside the introduction nozzle 2. The collision unit 3 is capable of interfering with the flow of the raw material gas introduced into the reaction furnace from the raw material gas supply port 4 located at the lower end of the introduction nozzle 2. In the production furnace 1 used in this embodiment, the inner diameter a of the introduction nozzle 2, the inner diameter b of the production furnace 1, the inner diameter c of the cylindrical collision portion 3, and the raw material mixed gas inlet 4 from the upper end of the production furnace 1 are used. Distance d, the distance e from the raw material mixed gas inlet 4 to the lower end of the collision part 3, and the distance from the raw material mixed gas inlet 4 to the lower end of the production furnace 1 are f, : B: c: d: e: f = 1.0: 3.6: 1.8: 3.2: 2.0: 21.0. The raw material gas introduction rate into the reactor was 1850 NL / min, and the pressure was 1.03 atm.

  The intermediate synthesized as described above was calcined at 900 ° C. in nitrogen to separate hydrocarbons such as tar to obtain a second intermediate. The R value of this second intermediate measured by Raman spectroscopy was 0.98. 1 and 2 show SEM and TEM photographs observed after the first intermediate is dispersed in toluene and a sample for an electron microscope is prepared.

Next, the second intermediate and 0.1% by mass of B ₂ O ₃ (manufactured by Wako Chemical Company) were uniformly dispersed in ethanol for 20 minutes using ultrasonic waves (KUBOTA UP50H). . Then, it dried under reduced pressure for 24 hours.

  The boron-added second intermediate is heat treated at 2300 ° C. in argon at high temperature, and the resulting carbon fiber structure aggregate is pulverized by an airflow pulverizer to obtain a carbon fiber structure used in the present invention. It was.

  FIG. 4 shows an SEM photograph obtained by dispersing the obtained carbon fiber structure in toluene with ultrasonic waves and observing it after preparing a sample for an electron microscope.

  Further, FIG. 5 shows an SEM photograph of the obtained carbon fiber structure as it is placed on an electron microscope sample holder, and Table 1 shows the particle size distribution.

Furthermore, the circle-equivalent mean diameter of the obtained carbon fibrous structures, 75.8Myuemu, bulk density 0.0035 g / cm ^3, Raman _I D / _{I G} ratio is 0.68, _{I G '/} I _G ratio The value was 0.44, the TG combustion temperature was 818 ° C., the powder resistance value was 0.0048 Ω · cm, and the density after restoration was 0.33 g / cm ³ .

  Further, the average particle size of the granular portion in the carbon fiber structure was 452 nm (SD 208 nm), which was 7.38 times the outer diameter of the fine carbon fiber in the carbon fiber structure. Further, the circularity of the granular portion was 0.68 (SD 0.14) on average.

Moreover, when the destructive test of the carbon fiber structure was performed according to the above-described procedure, the initial average fiber length (D ₅₀ ) after 30 minutes of application of ultrasonic waves was 13.0 μm, but after 500 minutes of application of ultrasonic waves, The average fiber length (D ₅₀ ) was approximately half of 6.8 μm, indicating that many cuts were generated in the fine carbon fibers in the carbon fiber structure. However, when the average diameter (D ₅₀ ) of the granular part 500 minutes after application of ultrasonic waves is compared with the initial initial average diameter (D ₅₀ ) 30 minutes after application of ultrasonic waves, the variation (decrease) rate is only 4 .7%, and taking into account measurement errors, etc., even under load conditions where many cuts occurred in the fine carbon fiber, the cut granular part itself hardly functions and functions as a bonding point between the fibers. It became clear.

  The various physical property values of the carbon fiber structure synthesized in Example 1 are summarized in Table 2.

ii) Production of Composite Material A composite material of the present invention was produced, which contains the carbon fiber structure of Example 1 synthesized in i) above in a matrix.

  Specifically, the carbon fiber structure synthesized in the above i) with the formulation shown in Table 3 below was prepared by using an epoxy resin (Adeka Resin, manufactured by Asahi Denka Kogyo Co., Ltd.), a curing agent (Adeka Hardener, Asahi Denka Kogyo Co., Ltd.). And an epoxy adhesive composition was produced by kneading for 10 minutes with a rotation-revolution centrifugal stirrer (Awatori Netaro AR-250, manufactured by Sinky Corporation).

  The epoxy adhesive composition obtained here was applied onto a glass plate with an applicator having a coating width of 100 mm and a gap of 200 μm, and kept at 170 ° C. for 30 minutes to prepare a cured coating film.

  The prepared coating film was cut into a 50 mm square to obtain a test piece. Volume resistivity and thermal conductivity were measured using this test piece. The results are shown in Table 3.

  Further, an epoxy resin film was formed in the same manner so that the content of the carbon fiber structure was 0.5% by mass.

(Comparative Example 1)
ii) Production of Composite Material A composite material of Comparative Example 1 was produced that contained commercially available carbon black in the matrix instead of the carbon fiber structure.

  The specific method is the same as that of the composite material in Example 1 except that carbon black is used instead of the carbon fiber structure.

  The volume resistivity and thermal conductivity were measured using the composite specimen of Comparative Example 1. The results are shown in Table 3 together with those of Example 1.

P-4100E: manufactured by Asahi Denka Kogyo Co., Ltd., Adeka Resin EP-4100E; bisphenol A type epoxy resin, epoxy equivalent 190
As apparent from Table 1 above, the volume resistivity and the thermal conductivity can be improved by incorporating boron into the carbon fiber structure constituting the composite material.

It is a SEM photograph of the intermediate body of the carbon fiber structure used for the composite material of this invention. It is a TEM photograph of the intermediate body of the carbon fiber structure used for the composite material of this invention. (A) (b) is a TEM photograph of the intermediate body of the carbon fiber structure used for the composite material of the present invention, respectively. It is a SEM photograph of the carbon fiber structure used for the composite material of the present invention. It is a SEM photograph of the carbon fiber structure used for the composite material of the present invention. It is drawing which shows schematic structure of the production | generation furnace used for manufacture of the carbon fiber structure in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Generation furnace 2 Introduction nozzle 3 Collision part 4 Raw material gas supply port a Inner diameter of introduction nozzle b Inner diameter of production furnace c Inner diameter of collision part d Distance from upper end of production furnace to raw material mixed gas introduction port e From raw material mixed gas introduction port Distance to the lower end of the collision part f Distance from the raw material mixed gas inlet to the lower end of the generating furnace

Claims (12)

  It has a three-dimensional network configuration composed of carbon fibers having an outer diameter of 15 to 100 nm, has a granular portion that binds the carbon fibers to each other in a form in which a plurality of the carbon fibers extend, and the A granular part is formed in the growth process of the said carbon fiber, Furthermore, the carbon fiber structure which is what contains the boron is contained in the matrix in the ratio of 0.001-30 mass% of the whole. A composite material characterized by containing.   2. The composite material according to claim 1, wherein a content of the boron is 0.001 to 2.1% by mass with respect to the carbon fiber structure.   The composite material according to claim 1, wherein the carbon fiber structure has an area-based circle-equivalent mean diameter of 50 to 100 μm. The composite material according to claim 1, wherein the carbon fiber structure has a bulk density of 0.0001 to 0.05 g / cm ³ . The carbon fiber structure has an I _D / I _G measured by Raman spectroscopy of 0.2 to 1.4 and an I _{G ′} / I _G of 0.25 to 0.75. The composite material according to any one of claims 1 to 4.   The composite material according to any one of claims 1 to 5, wherein the carbon fiber structure has a combustion start temperature in air of 700 ° C or higher.   The composite material according to any one of claims 1 to 6, wherein a particle diameter of the granular portion is larger than an outer diameter of the carbon fiber at a bonding portion of the carbon fibers.   The composite material according to any one of claims 1 to 7, wherein the carbon fiber structure is formed using at least two or more carbon compounds having different decomposition temperatures as a carbon source.   The composite material according to claim 1, wherein the matrix contains an organic polymer.   The composite material according to any one of claims 1 to 8, wherein the matrix contains an inorganic material.   The composite material according to any one of claims 1 to 8, wherein the matrix contains a metal.   The matrix according to any one of claims 1 to 11, further comprising at least one filler selected from the group consisting of metal fine particles, silica, calcium carbonate, magnesium carbonate, carbon black, glass fibers, and carbon fibers. A composite material according to any one of the above.