JP2004307334A - Carbon composition, composite material containing the same, and dispersing body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a carbon composition which effectively induces various functions by using a nano-graphite fiber as a dispersing material. <P>SOLUTION: The carbon composition comprises the nano-graphite fiber of 30-95% and nano-graphite particles of 0.5-50%, where the total of both shares ≥40% of the total of the composition and the ratio of the nano-graphite particles vs. the nano-graphite fiber is 1-60%. These ratios are determined as area ratios observed on micrographs taken by a transmission electron microscope of ≥50,000 magnifications. The nano-graphite fiber having the shape of a carbon nanotube, a diameter of 1-100 nm, and an aspect ratio of ≥3 and the nano-graphite particles having a short diameter of 5-100 nm and an aspect ratio of 1 to <3 are preferable. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a carbon composition, and more particularly, to a carbon composition containing nanographite fibers and nanographite particles. The present invention also relates to a composite material and a dispersion containing the above composition.

  In recent years, carbon fibers having a nano-sized graphite structure (nano-graphite fibers) have attracted attention for various uses. In particular, while the conventional carbon fiber has a graphite structure developed in the longitudinal direction, the nanographite fiber has a graphite structure that is continuous but short in the longitudinal direction, and is controlled in the interlayer structure, that is, in the Lc direction. I have. Therefore, with regard to nano-graphite fibers, attempts have been made in various fields as fillers for different materials in order to efficiently reflect the physical properties (eg, electrical conductivity) derived from the controlled graphite structure throughout the individual. ing.

  In particular, carbon nanotubes having a shape in which a two-dimensionally developed graphitic carbon structure is wound into a cylindrical shape have attracted attention for their unique physical properties, and various production methods have been tried as industrial supply methods. For example, using a carbon source gas as a raw material, a vapor phase growth method (CVD method) in which carbon nanotubes are grown from the surface of a finely prepared transition metal catalyst as a starting point, or arc discharge using carbon graphite as a discharge electrode There is an arc discharge method in which carbon nanotubes are produced by using the method. From the viewpoint of production efficiency, a vapor phase growth method is suitable for a mass production method.

  In the case of the vapor phase growth method, it is difficult to control the shape because the diameter and shape of the nanotube are affected by the size and shape of the catalyst particles in the process of forming carbon nanotubes. Further, it is known that the growth rate of the graphite structure is affected by the supply rate of the carbon source gas as a raw material and the reaction temperature, and these cause carbon amorphous or coke which does not have a graphite structure. Further, particles containing a catalyst-derived transition metal may be included. That is, the control of the shape of the carbon nanotube, the graphite structure, and the contamination of the metal is a problem based on the generation principle of the vapor phase growth method. Desired performance cannot be obtained such as deterioration of conductivity.

  On the other hand, as a general applied technology of the above-mentioned nano-graphite fiber, a technology of preparing a composite material having static elimination by dispersing in resin, rubber, etc. utilizing the high conductivity, and dispersing in a coating material to form an electrostatic coating material. Techniques for preparation are expected. As described above, in order to exhibit characteristics as a composite material by dispersing it in another material, it is necessary to enhance the dispersibility of the nanographite fibers.

  However, in general, carbon nanotubes and the like having an aspect ratio of 3 or more have a surface of a graphite carbon structure, and therefore have a low surface tension and are extremely difficult to disperse well in the above-described dispersion matrix. As a result, desired material properties have not been obtained at present.

  On the other hand, there has been proposed a method for preparing carbon nanotubes whose surfaces are chemically modified with functional groups, or carbon nanotubes called BN or BCN tubes containing nitrogen or boron (for example, see Non-Patent Documents 1 to 3). By applying these substances, there is an expectation to obtain carbon nanotubes having high chemical affinity with resin or rubber as a dispersion matrix.

  However, in order to increase the dispersibility of carbon nanotubes, besides increasing the chemical affinity of their surface, as a morphological effect, the dispersibility of carbon nanotubes is good, that is, a material that is easily loosened. Although it is necessary, no effective means has been found for them at present.

  As a method for producing carbon nanotubes, a method is known in which composite particles comprising an organic polymer of a carbon precursor and a thermally decomposable organic polymer are melt-spun and then subjected to thermal carbonization (for example, see Non-Patent Document 4 and Patent Document 1). ). However, there is no known effect of the appearance and shape of the carbon nanotube on the ease of loosening and dispersion characteristics.

  On the other hand, an example of the generation of carbon nanotubes by arc discharge has been reported, and the photograph also shows that nanoparticles exist in the carbon nanotubes, but there is no report on the ease of loosening of the carbon nanotubes (Non-Patent Document 5). This production process is considered to be a morphological change due to the electrostatic tension of the carbon fine particles quasi-liquefied under a strong electric field and high vacuum (Non-Patent Document 5). Therefore, it is extremely difficult to control the amount of carbon nanotubes and nanoparticles generated in a desired range.

J. Mater. Chem. , 7 (12), 2335-2337,1997 Appl. Phys. Lett. , 75,3932,1999 Chem. Phys. Lett. , 316,365-372,2000 Advanced Materials 14,452-455,2002 Chem. Phys. Lett. 204,277,1993 JP-A-2002-29719

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a carbon composition that is effective for inducing various functions by using nanographite fibers as a dispersant.

  The present inventors have made intensive studies and as a result, for example, the above object can be easily achieved by a specific carbon composition obtained by a predetermined production method using polyacrylonitrile resin as a raw material and containing nanographite fibers. Thus, the present invention was completed.

  That is, the first gist of the present invention is a carbon composition, in which the content of nanographite fibers is 30 to 95% and the ratio of nanographite particles is as an area ratio based on a transmission electron micrograph at a magnification of 50,000 or more. The carbon composition, wherein the content is 0.5 to 50%, the total amount of both is 40% or more of the whole composition, and the ratio of nanographite particles to nanographite fibers is 1 to 60%. Exists.

  The second aspect of the present invention resides in a composite material characterized in that the above composition is contained in a matrix. Further, the third aspect of the present invention resides in that Wherein the composition is a dispersion of the carbon composition.

  According to the present invention, there is provided a carbon composition that is effective for inducing various functions by using nanographite fibers as a dispersant.

  Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist. The carbon composition of the present invention contains, as essential components, two components, that is, nanographite fibers and nanographite particles in a specific ratio.

  The central axis region of the nano-graphite fiber in the present invention has a structure in which continuous carbon hexagonal mesh layers are stacked in a concentric scroll shape around the fiber axis, and the mesh surface is oriented parallel to the fiber longitudinal direction. I have. Further, the nano-graphite fiber in the present invention preferably has a shape having a diameter of 1 to 100 nm and an aspect ratio of 3 or more. As a specific example of such a nano-graphite fiber, there is a graphene structure of a nano-graphite fiber in which a graphite layer is oriented in a major axis direction and a carbon netting layer in which an outer peripheral portion is almost parallel, and a hollow portion is formed around a fiber central axis. Carbon nanotubes and the like.

  In a carbon nanotube in which graphene is stacked in two or more layers, it is necessary that the crystal in graphene has a continuous structure oriented in the long axis direction from the viewpoint of performance development such as electric conductivity, and the crystal is constant with respect to the longitudinal direction. They are stacked at an angle, and are different from those of the so-called Herringbone type or cup-stack structure in which the edge portion of the crystallite exists at the outer periphery of the fiber. The diameter is preferably from 1 to 50 nm, more preferably from 1 to 30 nm, from the viewpoint of performance.

  In the nano-graphite fiber of the present invention, most of the surface region of the fiber has an amorphous structure, and the central axis region of the fiber has a graphite structure. Such a two-layer structure is effective for further increasing the dispersibility of the fiber itself when used as a dispersant in a resin or a solvent, for example.

  In the present invention, graphite may have a structure in which a carbon crystal structure in a hexagonal mesh plane direction is laminated in two or more layers in substantially the same direction from the viewpoint of performance development such as electric conductivity. It is not limited to what is defined as "graphite". That is, it is not limited to graphite having a single crystal structure generally obtained by being treated at a high temperature of 2800 ° C. or higher, and graphite having an interlayer distance d in the crystal C-axis direction of 3.354 ° or the like as a representative characteristic. For example, as shown in Koyama et al. (“Industrial Materials”, Vol. 30, No. 7, p. 109-115), it is constructed based on a turbostratic graphite structure in which no crystal regularity is observed in three-dimensional directions. Fiber may be used. In an image at a magnification of 1,000,000 or more by a transmission electron microscope (TEM), the crystal length in the fiber axis direction is at least 2 nm or more, and two or more continuous carbon crystal layers are substantially linear and substantially linear. Any structure may be used as long as it has a structure that is laminated in parallel with the fiber axis direction (the crystal C axis is substantially perpendicular to the fiber axis). In the present invention, a region mainly containing them is defined as a graphite structure. Here, the angle formed by the normal to the C axis of the crystallite and the fiber central axis is preferably 25 ° or less.

  On the other hand, an amorphous structure is a structure that does not correspond to the above-described graphite structure. For example, in a TEM photograph at a magnification of 1,000,000 or more, a crystal length is shorter than 2 nm, or a crystal layer is arranged in a substantially parallel arrangement. Means those which do not have a laminated structure. Further, a certain crystal layer observed in the TEM photograph has a non-uniform orientation angle with respect to the fiber axis, that is, a crystal layer having a round dispersion structure.

  In the present invention, the surface area of the fiber is the thickness of the carbon layer from the surface layer to the central axis in the direction of the central axis, or the distance to the innermost end of the carbon layer when the carbon layer does not exist up to the central axis. On the other hand, the range from the surface layer generally indicates a range of up to 49%, preferably a range of up to 30%, and more preferably a range of up to 20%. In addition, the central axis region of the fiber is the thickness of the carbon layer from the surface layer to the central axis in the central axis direction, or the distance to the innermost end of the carbon layer if the carbon layer does not exist to the central axis. The range from the surface layer is usually in the range of 50 to 100%, preferably in the range of 70 to 100%, and more preferably in the range of 80 to 100%. Here, when the nano graphite fiber is a hollow core near the fiber central axis like a carbon nanotube, the distance from the surface layer to the central axis is the distance from the end of the innermost layer of the tube wall not including the hollow core. , Ie the thickness of the tube wall.

  As an example corresponding to the above structure of the nano-graphite fiber in the present invention, a carbon nanotube is taken as an example. The above structure is obtained by image analysis according to the following procedure using a transmission electron microscope image of a carbon nanotube having a magnification of 1,000,000 or more and a distance between adjacent pixels of 0.06 nm or less, and The ratio of B to A (B / A) or D to C (D / C) defined below is 1.20 or more (preferably 1.40 or more, more preferably 2.00 or more) Can be characterized.

(1) Two parallel lines (referred to as line 1 and line 2 respectively) at 3 nm intervals are drawn in the thickness direction of the wall on the fiber surface of the carbon nanotube in the transmission electron microscope image (see FIG. 1 described later). ).

(2) The distance (L) from the point where the line 1 intersects the outside of the fiber wall in the thickness direction of the wall is plotted on the horizontal axis, and the point on the line 1 corresponding to the distance on the horizontal axis is perpendicular to the line 1 On the vertical axis, the value (P) obtained by integrating the pixel densities of the pixels until the line 2 comes into contact with the line 2 is plotted on the vertical axis to obtain a graph of the relationship between the distance (L) and the pixel density integrated value (P) (see FIG. ).

(3) In the above graph, the average value of the difference between the adjacent maximum value and minimum value of the pixel density integrated value (P) in a region at a distance of 20% from the outside of the tube wall is A, and 50 to 50 to The average value of the difference between the adjacent maximum value and minimum value of the pixel density integrated value (P) in an area at a distance of 100% is B. Here, the average value of the difference between the adjacent maximum value and the minimum value is the difference (Δ1) between the first maximum value and the minimum value adjacent thereto, the minimum value and the next maximum value adjacent thereto. (Δ2)... (Δn), the difference between all the maximum values and the minimum values is sequentially obtained, and these differences are averaged.

(4) Alternatively, in the above graph, the average value of the difference between the adjacent maximum value and minimum value of the pixel density integrated value (P) in a region at a distance of 1.5 nm from the outside of the wall is C, and the fiber center of the wall is The average value of the difference between the adjacent maximum value and minimum value of the pixel density integrated value (P) in a region within a range of 1.5 nm from the innermost layer on the axial side toward the outer peripheral portion is defined as D.

  The magnification of the transmission electron microscope image used for the image analysis of FIG. 1 is 1.6 million times. When using this image analysis method, the magnification of the transmission electron microscope image needs to be a magnification that allows the graphene sheet to be clearly confirmed, and is usually preferably 1,000,000 times or more. Note that even if the graphene sheet is unclear even if the graphene sheet is less than 1,000,000 times or 1,000,000 times or more, the crystallinity of the carbon nanotube cannot be accurately expressed.

  The number of pixels between the lines 1 and 2 of the transmission electron microscope image used for the image analysis of FIG. 1 is 75 pixels, and the distance between the pixels is 0.04 nm. The distance between pixels of a transmission electron microscope image when using this image analysis method is preferably 0.06 nm or less. In a low-resolution image in which the distance between pixels is larger than 0.06 nm, the crystallinity of the carbon nanotube cannot be accurately represented.

  As the nano-graphite particles in the present invention, those having a graphite surface are preferred from the viewpoint of performance development such as electric conductivity, and those having a minor axis of 5 to 100 nm and an aspect ratio of 1 or more and less than 3. Is preferred. Examples of such nano-graphite particles include those in which the peripheral portion of the particle has at least two graphite layers, and is formed of a crystal having a closed structure without a clear edge portion. In this case, two or more layers of graphene are typically arranged at substantially constant and parallel plane intervals around a concentric sphere, concentric circle, or the same point, and have a three-dimensional structure. The shape of the nanographite particles may be spherical, elliptical, or angular. Here, the nano-graphite particles are a carbon component having a graphene structure on the surface of the catalytic metal particles, which is often found in a product obtained by a so-called CVD method using a catalytic vapor phase production method using nano-sized transition metal fine particles as a catalyst. Unlike those covered with, the particles are mainly composed of a carbon component, and are observed in a TEM as an image in which the central portion of the particles transmits electrons well.

  The carbon composition of the present invention is obtained as a carbonization product of a carbonizable organic substance such as a polyacrylonitrile resin, and contains the above two components as essential components. In terms of practical use, such as exhibiting properties as a filler of a composite material, the ratio of the total amount of the above two components to the entire composition may be any value because the nano-graphite fiber and the nano-graphite particles are mixed. The content is 40% or more, preferably 45% or more, and more preferably 50% or more, including those that are difficult to determine. The carbon composition of the present invention may contain a component other than the above two components, such as amorphous carbon, as long as the carbon composition does not hinder the development of properties as a filler.

  For the same reason as above, the proportion of nanographite fibers in the carbon composition is 30 to 95%, preferably 40 to 90%, and the proportion of nanographite particles is 0.5 to 50%, preferably 1 to 50%. ~ 45%.

  The ratio of the nanographite particles to the nanographite fibers is 1 to 60%, preferably 2.5 to 55%, except for components which are hardly determined due to the mixture of the nanographite fibers and the nanographite particles. %. If the proportion of the nanographite particles is too small, the dispersibility of the nanographite fibers will be impaired.On the other hand, if the proportion of the nanographite particles is too large, when the nanographite is used as a filler in the composite, The performance characteristics of the fiber filler are impaired. When the aspect ratio of the nano graphite particles is 3 or more, the dispersibility of the nano graphite fibers is not sufficiently improved.

  Here, the shape and ratio of each component described above means a ratio calculated as a shape and area ratio based on a transmission electron micrograph at a magnification of 50,000 or more. A preferred calculation method is a method of calculating based on the respective areas obtained by observing any three or more portions of the carbon composition with a TEM at a magnification of 50,000 times or more (preferably 100,000 times or more) using a TEM. is there. The ratio of each component to the area of the entire carbon composition in the visual field can be easily determined by image processing using a computer. The pixel density particularly required for image processing is usually 50,000 or more per square micrometer, but from the viewpoint of numerical accuracy, it is preferably 200,000 or more, and the distance between one pixel is It is most preferable that the pixel density be 0.25 nm or less in order to determine the structure.

  The constituent elements of the carbon composition of the present invention contain carbon as a main component, hydrogen and nitrogen, and the content of elements other than these three components is preferably 0.5% by weight or less. The content of nitrogen may be any amount that is effective to impart a chemical affinity to the above-described dispersion matrix without impairing the electrical conductivity of the nanographite fiber. It is usually 1 to 15% by weight, preferably 1 to 12% by weight, based on the total amount. Further, it is also possible to impart various functional groups to the nano graphite fiber by a separate chemical reaction from the nitrogen element as a base point.

  By the way, among the elements other than the above three elements, especially when the following transition metals are contained beyond the above range, the conductive properties, magnetic properties and heat conductive properties are greatly different. For example, an organic polymer or the like is used as a matrix. When the composition of the present invention is used as a filler of a composite material, desired properties may not be obtained from the composite material in some cases. Further, since the transition metal is easily oxidized, the filler itself is easily oxidized, and properties such as mechanical strength of the entire composite material including the filler are easily deteriorated. Therefore, the total content of the transition metals is preferably 0.5% by weight or less of the whole. Here, the transition metal includes Mn, Fe, Co, Ni, Zr, Mo and the like.

  On the other hand, the carbon composition obtained by the below-described production method that does not require a carbon growth catalyst is a catalyst-derived metal component found in the case of a vapor phase production method, for example, a transition metal component such as Fe, Ni, or Co and an Al component. Group 13 to 16 elements represented by the formula (1), and even if contained, the amount is 0.5% by weight or less as an impurity in the process.

  Although the carbon composition of the present invention contains both nanographite fibers and nanographite particles as essential components, the action of each component is presumed as follows. That is, the nanographite fibers exhibit the original function required as a filler of the composite material, and the nanographite particles play a role of improving the dispersibility of the nanographite fibers. Specifically, the nano-graphite particles, when kneaded with the dispersion medium, act on the gaps between the nano-graphite fiber bundles to aid in loosening and diffusion of the bundles, and the resin or rubber serving as a matrix between the nano-graphite fiber individuals And has a function of holding as an anchor effect on the surface. At this time, if the surface layer of the nano-graphite fiber has an amorphous structure, the anchor effect can be further enhanced by the graphite fiber itself due to fine irregularities on the surface, thereby exhibiting a higher degree of dispersibility. As a result, a composite material having a high interfacial strength is provided by improving the adhesiveness and the adhesiveness between the filler and the matrix with respect to the brittleness of the material, which is a problem of the filler-filled composite material. That is, the dispersion behavior of the filler having an aspect ratio of 3 or more is such that the leading end portion becomes the starting point of dispersion and is dispersed by the shear stress with the matrix material. In addition, the nano-graphite fiber of the present invention has a higher flexibility than a fiber consisting of only a graphite layer because only the periphery of the fiber is a graphite layer around the central axis of the fiber. is expected. Conversely, it is not preferable that the filler has a large amount of solid interaction and morphological entanglement on the side surface of the filler, such as a carbon nanotube obtained by a general vapor deposition method. However, fibers consisting only of an amorphous structure are inferior in fiber strength. On the other hand, the nanographite fiber of the present invention is excellent because it has both of the above characteristics.

  Nano-graphite particles in the present invention, for example, during the dispersion process such as kneading, to ensure the spacing between the solids on the side of the filler, is a component that acts to weaken the interaction, a component necessary to exhibit good dispersibility is there. In addition to the above-mentioned effects, the fact that the filler is easily dispersed can exhibit the effects of the original filler such as conductivity and rigidity in the composite material with a small filler loading. It is possible to provide a composite material that does not impair the performance, and for example, effects such as surface colorability, surface smoothness, and viscosity control during resin molding are exhibited.

  The carbon composition of the present invention is obtained by, for example, orienting a carbon composition containing a carbonizable organic substance such as acrylonitrile phase-separated as a micron and submicron size domain in a matrix of a heterogeneous polymer in any one direction. And carbonization in an atmosphere of an inert gas such as nitrogen or argon under atmospheric pressure, usually at a temperature of 500 to 1500 ° C, preferably 550 to 1200 ° C. The carbonizable organic substance may be any substance that can be deformed in the next stretching process. Since it can be deformed while heating during stretching, it may be softened by heat. Specific examples thereof include materials that undergo liquid phase carbonization such as pitch, coal tar, aromatic hydrocarbons, and thermoplastic resins, and materials that undergo solid phase carbonization such as wood raw materials, phenolic resins, and polyacrylonitrile. Hereinafter, a preferred example using polyacrylonitrile will be described.

  In order to obtain the carbon composition of the present invention, it is important to give a polymer containing acrylonitrile units a sufficient orientation and to carry out carbonization while maintaining the orientation. That is, the nano-graphite fiber and the nano-graphite particle in the present invention are surely derived from the presence of the drawn polymer domain, and the ratio of the nano-graphite particle to the nano-graphite fiber is controlled by the draw ratio. In particular, it is important to control the width of the stretched polymer domain within a certain range. By forming such a domain morphology, the acrylonitrile constituting the domain becomes a component in the subsequent carbonization process by heating. According to the quasi-crystal morphology with respect to the chemical structure (acrylonitrile chain length) of the polymer to be used, nanographite fibers and nanographite particles can be obtained in a desired ratio.

  If the stretching of the polymer is insufficient, or if the stretched form of the polymer is relaxed during the high-temperature treatment process for carbonization, the crystallinity with the longitudinal direction of La will not be obtained in the nanographite fiber after carbonization. Furthermore, nanographite particles having a nanosized shape and a controlled crystal structure cannot be obtained. Therefore, the composition of the present invention cannot be obtained by simply melting a polymer containing acrylonitrile, for example, polymer particles, by heat melting and deforming the appearance in one direction to carbonize. The preferred shape of the acrylonitrile-containing polymer domain obtained after stretching is such that the width defined in the direction perpendicular to the stretching direction is 5 to 150 nm and the ratio of the length parallel to the stretching direction to the width (aspect ratio) is 3 or more and 250 or less. It is. From the viewpoint of control accuracy of the production ratio of the nanographite fibers and the nanographite particles, the width is more preferably 10 to 70 nm, and the aspect ratio to the width is 3 to 150. The preferred draw ratio for obtaining such a polymer domain depends on the type, molecular weight and material form of the polymer, but is generally in the range of 3 to 30 times. The stretching ratio here refers to the ratio of the length in the major axis direction to the diameter of the polymer particles before stretching.

  In the above production method, if the carbonization temperature is too low, the graphitization formation yield tends to be low. Conversely, if the carbonization temperature is too high, there is no effect on the carbonization yield, but the process efficiency is greatly lost. When carbonization is performed in the above temperature range in an actual process, it is preferable to include a temperature history of raising the temperature from room temperature to the temperature in order to allow the carbonization reaction of the polymer to proceed uniformly. Specifically, for example, conditions such as a temperature rising process at 5 ° C. per minute and a temperature lowering process at 5 ° C. per minute to 400 ° C. may be mentioned.

  Further, as a generally known technique, before carbonization at the above-mentioned temperature, a step of oxidizing and cross-linking polyacrylonitrile in advance for the purpose of infusibility and flame resistance may be included. For example, in an oxygen atmosphere, the temperature is generally maintained at 120 to 300 ° C., preferably 160 to 250 ° C. for 1 hour or more, and the oxidation treatment is performed until a weight increase by oxidation of 1 to 7% by weight in terms of polyacrylonitrile is detected. The oxidation treatment conditions are not particularly limited, and for example, a method of holding at a temperature of 60 to 150 ° C. for a predetermined time in an ozone gas atmosphere may be used.

  Here, the domain of a polymer containing acrylonitrile units phase-separated in a matrix polymer refers to a polymer containing acrylonitrile as a monomer, including polyacrylonitrile. A preferred size of the domain is 50 to 1000 nm, preferably 50 to 600 nm, as a range in which the subsequent stretching orientation can be controlled. The nano-graphite fiber and the nano-graphite particle in the present invention are formed by reliably stretching these polymer domains, and the stretching ratio controls the amount ratio of the nano-graphite particle to the nano-graphite fiber. It has the property of being easily stretched mechanically, but it is necessary to bring about carbonization under the conditions that maintain the shape in subsequent steps.

  The polymer component constituting the domain may be either a homopolymer of polyacrylonitrile or a copolymer containing acrylonitrile as a main component in terms of carbon yield.However, the content of the acrylonitrile constituent ratio is as follows. From the viewpoint of inducing, the content is usually 40% by weight or more, preferably 50% by weight or more. Examples of the copolymerizable monomer include esters such as methyl acrylate and isobutyl acrylate, and acids such as acrylic acid and itaconic acid from the viewpoint of synthesis described later. It is necessary for the mechanical orientation of the polymer material that the domains of these components be physically solid with respect to the matrix, that is, form an integral solid without separation. It is.

  In order to prepare a polymer material containing the above domains, a method of dispersing polymer particles prepared in advance in a particle size controlled in the range described below by a polymerization recipe and conditions in a matrix polymer, specifically, both In addition to a method of physically dispersing the polymer in a particle state by mixing and kneading, a method of dispersing the particles in a gel matrix using a solvent and then removing the solvent is used.

  As the type of the matrix polymer to be used, those having low compatibility with polyacrylonitrile are preferable in order to maintain the dispersed form. In the case where the polymer is used by heat melting, a polymer whose molecular weight can be easily controlled by using a reaction temperature or a chain transfer agent such as alkyl thiols during polymerization is selected. Specific examples of such a polymer include polystyrene, polypropylene, polyethylene, poly 4-methyl-1-pentene, and the like. Further, the solvent is preferably a poor solvent for polyacrylonitrile in order to maintain the domain size.

  Further, as another method for producing a domain, a method utilizing the difference in interface characteristics between two kinds of polymers, specifically, a copolymer containing acrylonitrile units synthesized by an arbitrary method and a matrix polymer are used together. A solution or swollen gel is prepared by dissolving the mixture in a good solvent, and then immersed in any poor solvent to separate the acrylonitrile-containing polymer by phase difference due to the difference in surface tension and then removing the solvent. For example, a method in which the polymer of the acrylonitrile unit is phase-separated by intermolecular affinity after the polymerized polymer and the matrix polymer are both melted by heat.

  The domain polymer obtained by the above method is stretched and oriented in any one direction, but may be stretched and oriented in at least one direction, such as stretching in two or more directions. The morphology of a domain composed of an acrylonitrile polymer, which is usually a unit of phase-separated domains and having an aspect ratio of 3 or more (preferably 5 or more). The stretching method is not particularly limited, and is a method of mechanically stretching the domain-containing multiphase polymer film in a uniaxial direction and stretching, or by drawing a polymer solution or a hot-melted polymer in a thread form from a nozzle of a limited size. And the like.

  For example, the relative state of the electron beam transmittance between the polyacrylonitrile phase and the matrix polymer phase, which is observed when observed with a TEM, may appear as a contrast in the dispersed state and stretched form of the domains in the matrix polymer. And can be confirmed.

  Particles mainly composed of polyacrylonitrile, which is a precursor of the domain, can be synthesized by a method of polymerizing an acrylonitrile monomer using a water-soluble persulfuric acid or azo-based initiator in an aqueous solvent. Alternatively, it may be synthesized by emulsion polymerization using a surfactant in this system.

  The particles containing polyacrylonitrile as a main component preferably have a particle size of 30 to 1000 nm and a weight average molecular weight of 1,000 to 1,000,000 from the viewpoint of orientation. If the particle size is too large, poorly oriented portions are likely to occur in the domains. If the particle size is too small, the domains are likely to be discontinuous during orientation, and it is difficult to control the domain form after stretching. In addition, polyacrylonitrile has strong cohesion due to the interaction between molecules and within the molecule, and it is often difficult to orient the molecules by mechanical stretching or the like. Further, during stretching, a slip phenomenon may occur at the interface due to a difference in surface tension with the matrix polymer, and the orientation may be insufficient. Therefore, in the present invention, the particles containing polyacrylonitrile as the main component can be polymer particles using acrylonitrile and a copolymerized monomer.

  From the viewpoint of obtaining a graphite structure after carbonization, the content of acrylonitrile in the copolymer is usually at least 40 mol%, more preferably at least 60 mol%, as a proportion in the copolymer. From the viewpoint of obtaining the polymerization regularity and quantitativeness, a copolymer monomer specifically used is preferably a monomer having a similar polymerization reaction rate ratio between the polymer used for the matrix and a common monomer or acrylonitrile such as methyl acrylate.

  Further, in addition to the above polymerization method, it is also possible to adopt a seed polymerization method in which fine particles of the same component as the matrix polymer are dispersed in an aqueous solution, a monomer containing acrylonitrile as a main component is added, and polymerization is performed on the surface of the fine particles. I can do it.

  The carbon composition of the present invention may be a composition obtained by carbonizing bundled fine organic fibers made of a polymer containing acrylonitrile oriented in one direction. The polymer bundles containing oriented acrylonitrile units herein may include partially or fully crystallized ones.

  As an example of the method for producing the oriented fine bundle-shaped polymer fibers, as described above, after the domains dispersed in the matrix polymer are stretched, the matrix polymer is eluted with a solvent, so that the stretch remaining as a solid content is performed. A method of taking out a polymer containing an acrylonitrile unit may be mentioned. As the polymer in this method, the same polymer as described above can be used for both the domain and the matrix. The solvent that elutes the bundle of acrylonitrile-containing organic fibers in the domain from the matrix polymer is selected according to the type of the polymer combination, but a poor solvent for polyacrylonitrile is preferable. For example, when the matrix polymer is polyvinyl alcohol, if water, ethanol, isopropyl alcohol, or the like is used as a solvent, a bundle of oriented fibers of the polymer having acrylonitrile as a unit oriented and dispersed in the film is effectively taken out. I can do it.

  As still another method, an acrylonitrile-containing copolymer is used alone without using another type of matrix polymer, and is then stretched into a fiber or a film by a method of drying a solvent from a melt-spun or gel film and then pulling. It is also possible to adopt a method of stretching and carbonizing it under the same conditions as described above. In the case of this method, the isolated polymer of oriented fine polymer fiber is not used as the carbon precursor, but the fiber and the film-shaped stretched product contain partially oriented units, so that the carbon composition of the present invention can be obtained. Becomes possible. As a method for producing the acrylonitrile copolymer, the above-described method for preparing particles of the domain component can be used, and a method based on solution polymerization can also be used.

  Next, the composite material of the present invention will be described. The composite material of the present invention is characterized in that the above-mentioned carbon composition is contained in a matrix. That is, the carbon composition of the present invention can be used as a suitable filler because of its good dispersibility when used as a functional imparting material for resins, rubbers and the like. In addition, the composite material of the present invention makes use of the conductivity and rigidity imparted by the filler, and is used as a functional composition in various fields such as an antistatic material, a static elimination material, an electrostatic paint, and an electromagnetic wave absorbing material. Can be done. Confirmation that the carbon composition of the present invention is contained can be carried out by dissolving the matrix component in the sample with a solvent, an acid, or the like, and observing the solid component obtained by filtration with a TEM.

  Examples of the resin include, but are not limited to, polyethylene, polypropylene, polyolefins such as polystyrene, polymethyl methacrylate, polyisobutyl methacrylate, acrylic resins such as polymethyl acrylate, polycarbonate, polyethylene terephthalate, polyester resins such as polybutylene terephthalate, Polyamide resin, polyacetal resin, polyetherimide resin, polyphenylene oxide resin, polyphenylene sulfide resin, polyethersulfone resin, polyetheretherketone resin, AS or ABS (copolymerization of acrylonitrile / styrene or ternary copolymer of acrylonitrile / styrene / butadiene) Polymerization) Resin, thermoplastic resin such as fluorine resin, unsaturated polyester, epoxy resin, phenol resin Urea resin include thermosetting resins such as silicone resin.

  The above-mentioned rubber widely refers to an elastomer, and a general synthetic rubber can be used in addition to a natural rubber. Specific examples include natural rubber, synthetic natural rubber containing polyisoprene as a main component, butadiene rubber containing 1,2-polybutadiene and 1,4-polybutadiene as components, and butadiene-styrene containing a butadiene-styrene copolymer as a component. Rubber (commonly known as SBR), butadiene-acrylonitrile rubber as a component (commonly known as NBR), ethylene-propylene rubber (commonly referred to as EPM and EPDM) including an ethylene-propylene copolymer as a component, and polydimethylsiloxane. In addition to silicone rubber as a main component, chloroprene rubber and the like containing polychloroprene as a main component are exemplified.

  The carbon composition of the present invention can be dispersed by mixing with the above resin or rubber and optional additives such as pigments with a mixer or kneader and kneading with an extrusion screw or the like. The obtained composition is formed into a sheet, film, or other desired shape by an injection molding machine, pressure molding, or the like, and is used in various applications as a composite material having good filler dispersibility. The mixing ratio of the carbon composition of the present invention in the matrix is appropriately selected depending on the application. For example, the concentration for use as a masterbatch is usually 1 to 30% by weight. The concentration of the final product is usually 1 to 15% by weight.

  Next, the dispersion of the carbon composition of the present invention will be described. The dispersion of the present invention is characterized in that the carbon composition is dispersed in a dispersion solvent. As the dispersing solvent, any solvent can be used arbitrarily as long as the carbon composition is not dissolved. Examples of suitable dispersion solvents include water and alcohols such as ethanol. The concentration of the carbon composition in the dispersion solvent is usually from 0.1 to 10% by weight. Dispersion of the carbon composition in the dispersion solvent can be performed using a usual stirrer.

  The dispersion of the carbon composition of the present invention is, for example, applied to the surface of a molded article, and used in the same manner as the method of using the functional composition of the composite material of the present invention, such as an antistatic material, a neutralizing material, an electrostatic paint, Can be used as an absorbent. A binder resin can be blended with the dispersion of the carbon composition of the present invention from the viewpoint of coatability of the carbon composition after coating and drying. The binder resin is appropriately selected depending on the type of the dispersion solvent. When the dispersion solvent is water, a water-soluble resin such as an acrylic resin is preferable. The concentration of the binder resin is usually 1 to 15% by weight. The coatability of the carbon composition after application and drying can also be enhanced by a resin top coat. In addition, various surfactants may be added to the dispersion solvent as needed in order to further enhance the dispersibility of the carbon composition.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1
0.32 g of sodium dodecyl sulfate is dissolved in 145 g of water, and a mixture of 12.71 g of acrylonitrile, 2.29 g of methyl acrylate, and 0.30 g of n-butylmercaptan is added thereto, and the mixture is stirred at 250 to 300 rpm under a flow of nitrogen gas. While increasing the temperature from room temperature, an aqueous solution of potassium persulfate (0.1 g dissolved in 5 g of water) was added at 60 ° C. to start polymerization, and polymerization was performed at 70 ° C. for 3 hours. After the reaction was stopped, water was removed to obtain 12.0 g of polyacrylonitrile resin particles having an average particle size of 105 nm.

  10 g of polyvinyl alcohol (manufactured by Kuraray: trade name "Kuraray Poval PVA217") is dissolved in 200 g of water, and 2.0 g of the above-mentioned polyacrylonitrile resin particles are mixed, stirred, dispersed, cast and dried. As a result, a polyvinyl alcohol film having resin particles dispersed as domains was obtained. The domain shape of the film sample was confirmed by a TEM photograph. As a result, an image of the acrylonitrile-containing polymer in the form of particles having a particle size of 100 to 150 nm was confirmed by the contrast of the TEM photograph. This was uniaxially stretched at 160 ° C. (stretching ratio: 6 times). The film sample after the 6-fold stretching was also observed by TEM. As a result, an image of the domain stretched in the range of the width (perpendicular to the stretching direction) of 30 to 50 nm and the aspect ratio to the width of the length in the range of 10 to 15 was confirmed.

  The stretched film was heated in an oxygen atmosphere at 220 ° C. for 2 hours to crosslink and polymerize acrylonitrile, and then heated in a nitrogen atmosphere at 1000 ° C. for 1 hour to obtain a carbon composition. By TEM observation in three visual fields (magnification: 193,000 times), it was confirmed that the carbon composition contained 34% of carbon nanotubes and 12% of nanographite particles. The remaining components were a graphite component (5%) and amorphous carbon, which were difficult to determine due to the mixture of carbon nanotubes and nanographite particles. The ratio of each of the above components is an area ratio of the product in the visual field (the same applies hereinafter). The diameter of the carbon nanotube was 10 to 20 nm, the aspect ratio was 20 to 50, and the minor axis of the nanographite particles was 15 to 40 nm, and the aspect ratio was 1 to 1.8.

Example 2:
After 31.8 g of styrene was dispersed in 350 g of water at room temperature, 300 g of potassium persulfate was added and dissolved. With stirring, the temperature was raised to 70 ° C. in 40 minutes, and a polymerization reaction was carried out at this temperature for 8 hours. A polystyrene having an styrene conversion rate (ratio of polystyrene weight to styrene monomer weight used) of 88% and an average particle size of 565 nm was used. A suspension in which the particles were dispersed was obtained. 90 g of this suspension (containing 7.83 g of polystyrene and styrene monomer remaining after the reaction) and 2.4 g of acrylonitrile were dispersed and dissolved in 250 g of water, and 25 mg of potassium persulfate was further dissolved. The temperature was raised to 65 ° C., and the mixture was stirred at this temperature for 8 hours to carry out a polymerization reaction. After completion of the reaction, the suspension as a reaction solution was centrifuged to take out particles, and water was removed by drying to obtain 8.28 g of polystyrene-polyacrylonitrile seed copolymer particles having an average particle diameter of 610 nm.

  While the above polymer particles are heated and melted at 270 ° C., the molten resin is dripped from a nozzle hole having a diameter of 1 mm by its own weight. Stretched in form. Before being pulled out from the nozzle hole, a part of the polymer in which the polymer particles were melted was taken out, and a thin section thereof was observed with a TEM. As a result, the TEM electron beam contrast confirmed that a polymer domain containing acrylonitrile was present in the polystyrene matrix, and the domain size distribution was 200 to 500 nm.

  Further, a drawn cross section was taken out from the resin yarn obtained by drawing, and the domain shape of polyacrylonitrile was similarly examined by TEM. As a result, the width (vertical direction of the drawing direction) was 10 to 50 nm and the aspect ratio was 5 or more. In the winding and drawing direction of the yarn. After heating this filamentous polymer in an oxygen atmosphere at 220 ° C. for 3 hours to carry out cross-linking polymerization of acrylonitrile, it was heated in a nitrogen atmosphere at 1000 ° C. for 1 hour to obtain a carbon composition. According to TEM observation in three visual fields (magnification: 80,000 times), the above carbon composition contained 58% of carbon nanotubes having a diameter of 10 to 20 nm and an aspect ratio of 20 to 50, a minor axis of 20 to 40 nm, and an aspect ratio of 1 to 1. It was confirmed that the sample contained 31% of polygonal nano-graphite particles of 0.8. Note that the remaining components were a graphite component (6%) and amorphous carbon, which are difficult to determine due to the mixture of carbon nanotubes and nanographite particles.

  FIG. 3 shows a photograph of the carbon nanotubes observed with a TEM (magnification: 4,000,000 times). Most of the outer region of the carbon nanotube wall had an amorphous structure, and the inner region had a graphite structure. Image analysis was performed on three sections of 3 nm in the fiber axis direction shown here, and 1 nm in the tube wall thickness direction and the fiber axis direction of the tube wall was analyzed with 25 pixels (0.04 nm per pixel). FIGS. 4 and 5 show plots of pixel luminance with respect to the crystal layer existing from the surface layer of the wall toward the central axis direction.

  As is clear from FIGS. 4 and 5, the inner region of the carbon nanotube wall has a large amplitude of the periodic function, and the outer region has a small amplitude of the periodic function. This indicates that the crystallinity inside the carbon nanotube wall is high and the crystallinity outside the carbon nanotube wall is low.

  B / A was calculated from FIG. 4 to be 1.77, 3.16, 4.01. Both values are greater than 1.20. This indicates that the crystallinity of the inner region of the carbon nanotube wall is higher than that of the outer region. Also, when D / C was calculated from FIG. 5, it was 1.45, 2.22, and 4.97. Both values are greater than 1.20. This indicates that the crystallinity of the inner region of the carbon nanotube wall is higher than that of the outer region.

Example 3
32.7 g of methyl methacrylate was dispersed in 350 ml of water, heated to 70 ° C., 100 mg of potassium persulfate was added thereto with stirring, polymerization was carried out at the same temperature (70 ° C.) for 4 hours, and polymethyl methacrylate was used as a reaction solution. Was obtained by dispersing particles (average particle size: 320 nm) in water. 90 g of this liquid (containing 8.4 g of polymethyl methacrylate), 8.0 g of acrylonitrile and 12.0 g of methyl methacrylate were mixed and dispersed in 260 g of water, the temperature was raised to 65 ° C, 100 mg of potassium persulfate was added, and the same temperature was added. (65 ° C.) for 4 hours. The suspension after the reaction was centrifuged to remove the particles, and water was removed to obtain 24.8 g of particles having an average particle size of 480 nm.

  Using an air-flow type molten resin co-extrusion device (manufactured by Nippon Nozzle Co., Ltd., trade name: "Melt Blown"), 3 g of the above particles were heated at a rate of 2.5 ° C./min. Stretching was performed in the form of a thread while blowing argon gas at a blow pressure of 0.1 MPa from a nozzle hole of 5 mm to obtain a short thread having an average diameter of 50 nm (diameter distribution of 1 to 70 nm). The cross section was observed with a TEM, and the domain shape of the polyacrylonitrile was examined. As a result, the width (direction perpendicular to the stretching direction) was in the range of 10 to 50 nm and the aspect ratio was 5 or more. It had been. The drawn polymer in the form of a thread was heated in an oxygen atmosphere for 3 hours to cross-link and polymerize acrylonitrile, and then heated in a nitrogen atmosphere for 1 hour to obtain a carbon composition.

  Observation of three visual fields with a TEM (magnification: 128,000 times) confirmed that the carbon composition contained 54% of carbon nanotubes and 6% of nanographite particles. The remaining components were a graphite component (12%) and amorphous carbon, which are difficult to determine due to the mixture of carbon nanotubes and nanographite particles. The carbon nanotube has a continuous graphene layer on the wall and is laminated with two or more layers of graphene oriented so as to have a C axis substantially perpendicular to the fiber axis, and the tip is formed by layered graphene. Closed, diameter was 10-20 nm, aspect ratio was 20-50. The nano-graphite particles are three-dimensional polygons having a minor axis of 10 to 30 nm and an aspect ratio of 1 to 2. The outer peripheral portion except the central portion has two or more layers of graphite structure in layers, and the graphite layer has an edge. It was a closed polygonal particle without any parts. As a result of elemental analysis, this carbon composition was composed of nitrogen, carbon, and hydrogen, and contained 9.48% by weight of nitrogen, 89.32% by weight of carbon, and 1.20% by weight of hydrogen. Transition metals such as Fe, Co, Ni, Zr, and Mo were below the detection limit.

Comparative Example 1:
The polymer particles described in Example 2 were heated and melted at 270 ° C., then pulled out into a thread form, stretched, and wound without being heated under the same conditions as in Example 2, that is, at 220 ° C. for 3 hours in an oxygen atmosphere. After the acrylonitrile was crosslinked and infusibilized by heating, it was heated at 1000 ° C. for 1 hour in a nitrogen atmosphere to obtain a carbon composition. As a result of observing 10 visual fields with a TEM, in this carbon composition, products having a graphite structure including carbon nanotubes and nano-graphite particles could not be confirmed, and amorphous carbides having extremely low electron beam permeability were found. Was only confirmed.

Comparative Example 2:
In a round bottom flask, 4.7 g of cobalt nitrate, 1.4 g of ammonium molybdate, and 14.5 g of magnesium nitrate were added to 40 ml of water, and mechanically stirred for 1 hour. The water was removed at 40 ° C. under reduced pressure for 18 hours, further dried at 150 ° C., 10 mmHg for 30 minutes, and further heated at 550 ° C. (temperature rising from room temperature at a rate of 5 ° C./min) for 6 hours. 5.2 g of a solid were obtained. As a result of analysis, this solid contained Co, Mo, and MgO at a molar ratio of 0.2, 0.1, and 0.7. This was pulverized by a jet mill, and a product passed through an 80-mesh sieve was used as a catalyst for the next reaction.

  In a quartz glass reaction tube (10.2 L), 0.64 g of the above catalyst was placed in a quartz glass boat and allowed to stand. After purging the reaction tube with nitrogen gas, the reactor was heated to 600 ° C. and hydrogen gas was supplied for 1 hour. Introduced to reduce the catalyst surface. Thereafter, the introduced gas was changed to a mixed gas of carbon monoxide (0.9 L / min) and hydrogen (0.1 L / min), and the mixture was allowed to flow for 6 hours to deposit carbonaceous materials on the catalyst surface.

  After completion of the reaction, 19.4 g of a product from which carbon was precipitated was recovered (the yield includes the weight of the recovered catalyst). As a result of observation with a TEM, this carbon product has a diameter of 20 to 40 nm and a length of 100 nm or more, and is mainly composed of a nanographite fiber having a graphene structure in which a central portion is hollow and an outer peripheral portion is continuous in a longitudinal direction. The main component was a carbon fiber product. Other components are (a) an amorphous carbon fiber having a diameter of 50 to 500 nm and a length of 100 nm or more, and (b) a crystalline metal which has catalytic metal particles at the center thereof and which is considered to have grown radially in two or more directions. An aggregate of carbon fibers, and (c) an aggregate of carbon fibers in which these components were entangled. As a result of observation with a TEM, no particulate product composed of crystalline carbon having an aspect ratio of less than 3 was found in the carbon product.

  For each of the carbon products obtained in Example 1 and Comparative Example 2, 10 mg of each of the carbon products was ultrasonically dispersed in 10 ml of a predetermined solvent for 3 minutes, and then left standing for 5 minutes. The dispersion size was measured by the laser diffraction method. The laser diffraction method used was a HORIBA LA-500 laser diffraction particle size distribution analyzer manufactured by Horiba, Ltd. From the distribution of the dispersed particle diameter measured in each solvent, the median diameter is shown in Table 1 below as a representative value. As is clear from Table 1, the composition of the present invention shows a good dispersion state in each solvent.

Comparative Example 3:
In Example 2, while the polymer particles were heated and melted at 320 ° C., they were dropped from the nozzle hole having a diameter of 1 mm by the weight of the molten resin. When the polymer, which had been formed into a thread during the hanging, was wound by a drum having a diameter of 12 cm, the thread was wound by rotating the polymer at 220 rpm. A stretched cross section was obtained from the obtained resin yarn, and the domain shape of polyacrylonitrile was examined by TEM in the same manner as in Example 2. As a result, the polyacrylonitrile component was aggregated after hot melting, and was formed in a width (perpendicular to the stretching direction). Was in the range of 200 to 1000 nm, and there were domains containing many of those having an aspect ratio with respect to the length direction of the yarn of 2 or less.

  The above resin yarn was heated at 220 ° C. for 3 hours in an oxygen atmosphere under the same conditions as in Example 2 to crosslink and polymerize acrylonitrile, and then heated at 1000 ° C. for 1 hour in a nitrogen atmosphere to obtain a carbon composition. . As a result of observing three visual fields with a TEM (magnification 100,000 times), almost all of the visual fields were particles of irregular shape and irregular size. That is, a fiber structure having a diameter of 1 to 100 nm and an aspect ratio of 3 or more and a particle structure having a short diameter of 5 to 100 nm and an aspect ratio of 1 or more and less than 3 are not observed. A slight が 20 nm fiber structure was observed.

Reference Example 1:
FIG. 6 shows a TEM photograph (magnification: 1.25 million times) of a CC type of a commercially available carbon nanotube "Graphite Fibrils" (registered trademark, manufactured by Hyperion Catalysis International, Inc.) by a vapor phase growth method. In FIG. 6, it can be seen that many shadows derived from the inclusion of the metal are observed.

  FIG. 7 is an enlarged view of a main part of FIG. 6 prepared for image analysis. FIGS. 8 and 9 show graphs obtained by performing image analysis on the entire region (three places) between two lines drawn at 3 nm intervals on the carbon nanotube wall in FIG. 7 by the above method. Show.

  When B / A was calculated from FIG. 8, they were 0.67, 0.68, and 0.80. Both values are smaller than 1.20. This indicates that the crystallinity of the inner region of the carbon nanotube wall is not higher than that of the outer region. Also, assume that D / C is calculated from FIG. 0.99, 0.71, and 0.89. Both values are smaller than 1.20. This indicates that the crystallinity of the inner region of the carbon nanotube wall is not higher than that of the outer region.

  FIGS. 10 and 11 show data of one image analysis area from the image analysis data of Example 2 (data shown in FIGS. 4 and 5) and the image analysis data of Comparative Example 3 (data shown in FIGS. 8 and 9). FIG. 4 is a diagram comparing extracted graphs according to the above method. According to the data of Example 2, the amplitude of the periodic function in the inner region of the wall constituting the carbon nanotube is clearly larger than that in the outer region. On the other hand, the data of Comparative Example 3 shows that the amplitude of the periodic function in the inner region of the carbon nanotube wall is not larger than that in the outer region.

In addition, 10 mg of the above-mentioned commercially available carbon nanotubes were ultrasonically dispersed in 10 cc of water for 3 minutes by the above-described method, and then the dispersion size of the carbon composition in the dispersion which was allowed to stand for 5 minutes was measured by the same laser diffraction method as described above. As a result, it was 4.25 μm. As shown in FIGS. 6 and 7, the above-mentioned commercially available carbon nanotube has a structure having no clear amorphous structure in the outer region of the wall. This fact also indicates that the carbon nanotube having a clear amorphous structure in the outer region of the wall, which is used as a preferred embodiment in the present invention, exhibits more excellent dispersibility due to its own surface structure.

Explanatory diagram showing areas used for image analysis in transmission electron microscope images of carbon nanotubes Schematic explanatory view showing an image analysis method for evaluating the crystallinity of the carbon nanotube wall Drawing substitute TEM photograph of carbon nanotube in the composition obtained in Example 2. Graph obtained from image analysis using FIG. Graph obtained from image analysis using FIG. Drawing substitute TEM picture of commercial carbon nanotube by vapor phase growth method Main part enlarged view of FIG. 6 prepared for image analysis Graph obtained from image analysis of the region in FIG. Graph obtained from image analysis of the region in FIG. Explanatory diagram comparing graphs obtained from image analysis of Example 2 and Comparative Example 3 Explanatory diagram comparing graphs obtained from image analysis of Example 2 and Comparative Example 3

Claims (6)

  A carbon composition, wherein the content of nanographite fibers is 30 to 95%, and the content of nanographite particles is 0.5 to 50%, as an area ratio based on a transmission electron micrograph at a magnification of 50,000 or more, A carbon composition, wherein the total amount of both is 40% or more of the entire composition, and the ratio of nanographite particles to nanographite fibers is 1 to 60%.   2. The carbon composition according to claim 1, wherein C is a main component and H and N are further included as an elemental composition, and N is 1 to 15% by weight in an elemental composition ratio. 3.   The carbon composition according to claim 1, wherein the shape of the nano-graphite fiber is a carbon nanotube, the diameter is 1 to 100 nm, and the aspect ratio is 3 or more.   The carbon composition according to any one of claims 1 to 3, wherein the minor diameter of the nanographite particles is 5 to 100 nm and the aspect ratio is 1 or more and less than 3.   A composite material comprising the composition according to any one of claims 1 to 4 in a matrix.   A dispersion of a carbon composition, wherein the composition according to any one of claims 1 to 4 is dispersed in a dispersion solvent.