Fine carbon fiber mixture and composition thereof

Fine carbon fiber mixture and composition thereof

Technical field of invention

The present invention relates to a fine carbon fiber mixture containing non-fibrous carbon such as a sheet, a granule or a flake, and particularly to a fine carbon fiber mixture excellent in electrical conductivity, thermal conductivity, and detachability, and a resin or rubber composition thereof. Things.

Background technique

Carbon fiber is used in various composite materials because of its excellent properties such as high strength, high modulus of elasticity, and high electrical conductivity. Not only the excellent mechanical properties previously applied, but also the flexibility of the carbon fiber or carbon material. With the development of electronic technology in recent years, it can be expected as an electromagnetic wave shielding material, a conductive resin filler for antistatic, or It is used as a filler for electrostatic spraying of resin. In addition, it is used as a chemical stability, thermal stability, and fine structure of a carbon material, and can be expected to be used as an electric field electron emission material such as a flat panel display. Further, it is also expected to be used as a brush or a variable resistor which is a highly abrasive conductive material.

The conventional carbon fiber is produced by a so-called organic carbon fiber type produced by heat-treating a fiber such as PAN, pitch, or cellulose. When it is used as a filler of a fiber-reinforced composite material, in order to increase the contact area with the base material, it is desirable to increase the diameter and to lengthen the length to enhance the reinforcing effect. Further, in order to improve the adhesion to the base material, it is preferable that the surface of the carbon fiber is not smooth and has a certain degree of roughness. Therefore, it is exposed to a high temperature in the air to oxidize it, and a surface such as a coating is applied to the surface. deal with.

However, in these carbon fibers, the organic fiber diameter of the raw material is It is impossible to manufacture carbon fibers having a small diameter of about 5 to 10 μm. Further, the ratio of the length to the diameter (aspect ratio) is limited, and a carbon fiber having a large aspect ratio is desired.

In addition, the use of a resin for an automobile body, or the use of a resin or the like for an electronic device, requires electrical conductivity of a metal, and is accompanied by carbon fiber as a filling material to satisfy the conductivity of the various conductive coatings. Resin or the like is required, and conductivity must be improved.

The means must be improved by black lead to improve these characteristics, so that the black lead treatment at high temperatures is usually performed. However, even if the conductivity of the metal is not obtained by the black lead treatment, if the amount of the compound is increased in order to remedy the problem, the workability and the mechanical properties are lowered, and the conductivity of the fiber itself must be further improved. The strength of the fiber is increased to increase the strength and the like.

Thereafter, in the latter half of the 1980s, a Vapor Grown Carbon Fiber (hereinafter abbreviated as VGCF) which is completely different from the organic fiber production method was studied.

This VGCF is known to be a carbon fiber having a diameter of 1 μm or less and a number of 100 nm by gas phase thermal decomposition in the presence of a gas such as a hydrocarbon in the presence of an organic transition metal catalyst.

For example, a method of introducing an organic compound such as benzene as a raw material and introducing an organic transition metal compound such as ferrocene as a catalyst into a high-temperature reaction furnace together with a carrier gas is disclosed. Japanese Patent Publication No. 27700), a method of generating VGCF in a floating state (Japanese Patent Publication No. Sho 60-54998), or a method of growing on a reactor wall (Patent No. 2778434).

According to such a production method, it is possible to obtain a carbon fiber which is fine and has excellent conductivity and is suitable for a filling material having a large aspect ratio, and mass-produces a material having a diameter of about 100 to 200 μm and an aspect ratio of about 10 to 500, and A filler for a resin used as a conductive filler, an additive for a lead storage battery, and the like are used.

These VGCFs are characterized by a shape and a crystal structure, and the crystals of the carbon hexagonal mesh surface have a structure in which an annual ring shape is formed and wound in a cylindrical shape, and the center portion thereof is a fiber having a very fine cavity portion.

Further, carbon fibers which are finer than the VGCF are multi-layer carbon nanotubes which are found in a coal in which a carbon electrode is evaporated by an electric arc in a helium gas by Iijima et al. The multilayer carbon nanotube has a diameter of 1 mm to 30 nm. Like the VGCF, the carbon hexagonal mesh has a crystal centered on the fiber and is tightly closed in a ring shape in an annual ring shape, and has a central portion at the center thereof. Fine carbon fiber with hollow diameter.

Regarding this method of using arc discharge, it has not been put to practical use due to its production method.

On the other hand, according to the possibility that the oxygen phase method has a large aspect ratio and high conductivity, attempts have been made to improve the method to produce finer carbon fibers. In the U.S. Patent No. 4,663,230, Japanese Patent Publication No. Hei 3-64606 discloses a cylindrical carbon fiber yarn composed of lead having a diameter of about 3.5 to 70 nm and an aspect ratio of 100 or more. The continuous layer of carbon atoms configured in a regular arrangement is arranged in a concentric arrangement with respect to the cylindrical axis by a plurality of layers, and the C axis of each layer of the carbon atoms is substantially perpendicular to the cylindrical axis of the fiber filament, and does not contain the hot carbon film deposited by the entire thermal decomposition. Has a smooth surface.

Similarly, in Japanese Patent Laid-Open Publication No. 61-70014, 10~500nm is introduced. Further, the carbon fiber having an aspect ratio of 2 to 30,000 in the oxygen phase method describes that the thickness of the thermally decomposed carbon layer is 20% or less of the diameter.

In the above-mentioned fine carbon fiber according to the vapor phase method, when a conductive material such as friction, heat release or the like is used as a folding electric contact (brush, variable resistor, etc.), it is desired to have a higher folding. Sex, conductivity, thermal conductivity.

In the present invention, it is an object of obtaining a fine carbon fiber having a diameter of 500 nm or less and an aspect ratio of 10 to 15,000, and excellent in characteristics such as crease, conductivity, and thermal conductivity, on a mass production scale.

Invention disclosure

The present invention provides the following in order to achieve the above object.

(1) A fine carbon fiber mixture characterized by a fine carbon fiber mixture produced by a vapor phase method, wherein a cylindrical carbon layer is an overlapping multilayer structure, the central axis of which is a void groove, and has an outer diameter of 1 to 500 nm, and an aspect ratio. A mixture of 10 to 15,000 fine carbon fibers and non-fibrous carbon such as flakes, granules, and flakes.

(2) The fine carbon fiber mixture according to (1), which is a non-fibrous carbon which must contain a sheet or a sheet.

(3) The fine carbon fiber mixture according to (1) or (2), wherein the granular carbon has a hollow structure or contains a metal or a metal compound therein.

(4) The fine carbon fiber mixture according to (1) to (3), wherein the mass ratio of the fine carbon fibers to the non-fibrous carbon is in the range of 10:90 to 95:5.

(5) The fine carbon fiber mixture according to (1) to (4), wherein the non-fibrous carbon is 0.1 to 500 times the outer diameter of the fine carbon fiber.

(6) The fine carbon fiber mixture according to any one of (1) to (5), wherein the non-fibrous carbon in the form of flakes or flakes is 0.01 to 0.5 times the outer diameter of the fine carbon fibers.

(7) The fine carbon fiber mixture according to (1) to (6), wherein the fine fiber carbon is a branched carbon fiber.

(8) The fine carbon fiber mixture according to (1) to (7), wherein at least a part of the non-fibrous carbon is attached to the fine carbon fiber.

(9) A composition of a fine carbon fiber mixture, characterized in that the resin or rubber contains the fine carbon fiber mixture described in (1) to (8).

(10) A conductive article comprising the composition according to (9).

(11) A detachable article comprising the composition according to (9).

<p>1. . . Vertical heating furnace</p><p>4. . . Raw material supply pipe</p><p>5. . . Raw material vaporizer</p><p>6. . . Carrier gas supply piping</p>

Fig. 1 is a schematic view showing a manufacturing apparatus shown in an embodiment of the present invention.

Fig. 2 is a transmission electron micrograph of the fine carbon fiber of the example.

Fig. 3 is a transmission electron micrograph of the fine carbon fiber of the example.

Figure 4 is a transmission electron micrograph of the fine carbon fiber of the example .

Fig. 5 is a transmission electron micrograph of the fine carbon fiber of the example.

Embodiment of the invention

Hereinafter, the present invention will be described in detail.

In order to obtain a fine carbon fiber having an outer diameter of 500 nm or less, in order to obtain a variety of changes in the production conditions for producing fine carbon fibers (VGCF) by a vapor phase method, the present invention obtains the previous conditions under the production conditions. It is not known that a fine carbon fiber mixture containing fine carbon fibers and non-fibrous carbon is a carbon fiber material which is excellent in electrical conductivity and excellent in resilience, and therefore excellent in thermal conductivity and the like. The fine carbon fiber mixture of the present invention is understood to be a carbon fiber mixture containing non-fibrous carbon obtained in the course of producing a fine carbon fiber (VGCF) by a basic gas phase method.

A fine carbon fiber mixture relating to the present invention will be described.

The fine carbon fiber contained in the fine carbon fiber mixture of the present invention contains a fiber diameter of about 1 to 500 nm which is the same as that of the conventional fine carbon fiber. It is preferably a fine carbon fiber having an aspect ratio of 10 to 15,000, an aspect ratio of 10 to 15,000, preferably 10 to 10,000, and the fine carbon fiber is a multi-layered structure (annual ring structure) in which a cylindrical carbon layer is superposed, and a central axis thereof is a hollow structure. Further, the fine carbon fibers contained in the fine carbon fiber mixture of the present invention have a tumor-like portion at the middle or the end of the fiber, and a branch of the fiber.

The fine carbon fiber mixture of the present invention is characterized by containing fine carbon fibers produced by a vapor phase method and non-fibrous carbon which is still simultaneously formed by a vapor phase method.

The non-fibrous carbon is in the process of producing a fine carbon fiber by a gas phase method, and the fine carbon fiber cannot be sufficiently grown by changing the manufacturing conditions, for example, in the case where the sulfonic compound is used as a catalyst. Non-fibrous carbon such as granules and flakes is obtained for growth. Here, the shape of the sheet, the granules, the flakes, and the like means carbons which are all non-fibrous shapes, and these have a size which is about 0.1 to 500 times the diameter of the fine carbon fibers which are simultaneously formed, in other words, In the case of granular form, it is about 0.1 to 50 times the fiber diameter in all directions of isotropic three-dimensional. In the case of flaky, the size of the secondary element is about 20 to 500 times. The thin object, in the case of a sheet, has a size of about 1 to 50 times in the direction of the secondary element. In the case of a sheet or a sheet, although the thickness is not clear under a transmission electron microscope, it is found to be a thin material having a fiber diameter of about 0.01 to 0.5 times.

These non-fibrous carbons such as flakes, granules, and flakes are all formed by a vapor phase method, so that a relatively uniform carbon layer covering the entire surface is observed, for example, in the broken carbon fiber, There is a broken surface, but it has It is clearly different from the crystal structure. Further, the non-fibrous carbon such as flakes, granules, and flakes of the present invention is different from the so-called carbon black in size and carbon crystal. In addition, it is of course different from pure amorphous carbon.

Further, in the case of granular carbon, a structure in which the inside is hollow can be employed. It was confirmed to be deformable non-fibrous carbon during the growth of fine carbon fibers. Further, the void may contain amorphous carbon, a metal compound (such as a catalyst metal compound such as carbide), or the like. In the growth process of the fine carbon fibers, the presence of the catalyst substance or the like is a cause of formation of non-fibrous carbon, or conversely, non-fibrous carbon is generated due to abnormal carbon growth, and the result is incorporated in the non-fibrous carbon. Catalyst substances, etc. When a catalyst substance is contained in the interior of the non-fibrous carbon, the catalyst substance may vaporize and disappear in the calcination stage, but since it is completely enclosed in the non-fibrous carbon, it cannot be eliminated and remains easily.

Further, the flaky carbon is a substance which is not involved in the catalyst substance and is formed by depositing a nucleus type carbon from the gas phase starting from the surface of the fine fiber.

Further, the non-fibrous carbon such as the sheet, the granule, and the flaky material described above is formed in parallel with the fine carbon fibers in the process of forming the fine carbon fibers by the vapor phase method, and the fine carbon fibers and the non-fibrous carbon are independently present, but A part of the non-fibrous carbon is also attached to the fine carbon fibers depending on the formation process or the conditions after the formation.

The fine carbon fiber mixture of the present invention is a novel material which has not been reported in the production of fine carbon fibers by the prior gas phase method. It is novel, especially in the case of a predetermined amount or more, and in particular, a flake-form fine carbon fiber mixture in which flake or flake-shaped carbon is simultaneously formed.

Since the fine carbon fiber mixture of the present invention has non-fibrous carbon in comparison with the conventional fine carbon fibers, it is more improved in electrical conductivity than in the case of the fine carbon fiber produced only by the vapor phase method in the case of the entire mixture type. The effects of characteristics such as thermal conductivity and detachment.

The fine carbon fiber mixture of the present invention is characterized in that it contains 5% by mass of non-fibrous carbon, and 5 to 95% by mass, preferably 10 to 70% by mass, particularly 10 to 50% by mass, so that the above effects can be obtained. More effective.

The fine carbon fiber of the fine carbon fiber mixture of the present invention is a fine and long fiber having an outer diameter of 1 to 500 nm and an aspect ratio of 10 to 15,000. Therefore, the type of the filler material can be added in a large amount and the reinforcing effect is excellent.

A suitable method for producing the fine carbon fiber mixture of the present invention is explained below.

The fine carbon fiber of the present invention generally uses a transition metal catalyst, and an organic compound, particularly a hydrocarbon, can be thermally decomposed to obtain a fine carbon fiber. In order to remove the tar or the like adhering to the surface of the fine carbon fibers, it is preferably subjected to heat treatment at 900 to 1,300 ° C, and then usually subjected to heat treatment at 2,000 to 3,500 ° C, preferably 2,500 to 3,500 ° C for graphitization.

That is, the fine carbon fibers are obtained by using a transition metal catalyst and thermally decomposing the organic compounds, particularly hydrocarbons.

The organic compounds used as carbon fiber raw materials are organic compounds such as benzene, toluene, xylene, methanol, ethanol, naphthalene, phenanthrene, cyclopropane, cyclopentane, cyclohexane, and volatile oils, lamp oils, etc. or CO, natural gas, methane, ethane. And gases such as ethylene, acetylene, butadiene and the like and mixtures thereof may also be used. Among them, aromatic compounds such as benzene, toluene and xylene are particularly preferred.

The organic transition metal compound contains a transition metal as a catalyst. The transition metal is an organic compound comprising a metal of Group IVa, Va, VIa, VIIa, VIII of the Periodic Table. Among them, compounds such as ferrocene and ferrocene are preferred. The content of the organic transition metal compound as a catalyst is 0.01 to 15% by mass, preferably 0.03 to 10% by mass, and more preferably 0.1 to 5% by mass based on the amount of the carbon of the organic compound.

It is found that, according to the present invention, in addition to the form of the reaction apparatus, the reaction system, and the reaction conditions, the type and amount of the organic compound and the organic transition metal compound used as the catalyst, and the type and amount of the auxiliary catalyst are controlled, in particular, by selection. Under various conditions, fine carbon fibers having the nodular portion of the present invention can be obtained.

In particular, in order to make an organic compound and an organic transition metal compound as a catalyst, an organic compound is generally selected from a mixture of benzene, toluene, acetylene, ethylene, butadiene or the like, and a combination of nickel or ferrocene is used. Iron is preferred as the organic transition metal compound, and a combination of benzene and ferrocene is suitable for the purpose of the present invention.

In the present invention, although it is not limited, it is particularly advantageous to obtain the fine carbon fiber mixture of the present invention if a sulfur compound is used as a catalyst, particularly in the case where the amount thereof is used less than before. The form of the sulfur compound is not particularly limited, and if it is dissolved in an organic compound of a carbon source, thiophene, various mercaptans, inorganic sulfur or the like can be used as the sulfur compound. The amount of the sulfur compound used is 3 to 10% by mass, preferably 4 to 10% by mass, and more preferably 4 to 8% by mass based on the total of the organic compound (carbonaceous material such as a hydrocarbon). If the sulfur is less than 3% by mass, the growth of the fine carbon fiber is fast, almost Unable to obtain non-fibrous carbon. When the sulfur content is more than 10% by mass, the growth of the fine carbon fibers is slow, and the carbon fibers cannot be efficiently obtained.

Thus, by selecting, controlling the reaction system, particularly the type and amount of the organic compound and the organic transition metal compound as a catalyst, and the kind and amount of the catalyst, it is possible to produce a fine carbon fiber mixture having a specific composition. As previously unknown, and the usefulness of this novel fine carbon fiber mixture is also unknown, it is an industrially useful invention to provide a fine carbon fiber mixture of the novel construction according to the present invention.

As the carrier gas, a reducing gas such as a usual hydrogen gas can be used. The carrier gas is preferably heated in advance at 500 to 1,300 °C. The reason for the heating is to make the formation of the catalytic metal in the reaction coincide with the carbon source supplied by the thermal decomposition of the carbon compound, and to cause a reaction instantaneously, and to obtain finer carbon fibers. When the carrier gas is mixed with the raw material, the heating temperature of the carrier gas is less than 500 ° C, and it is difficult to cause thermal decomposition of the raw material carbon compound. When the temperature exceeds 1,300 ° C, the carbon fiber grows in the radial direction, and the diameter tends to be coarse.

The carrier gas is used in an amount of 1.0 part by mole based on the organic compound of the carbon source, and is preferably 1 to 70 moles. The diameter of the carbon fiber can be controlled by varying the ratio of the carbon source to the carrier gas.

The raw material is a solution in which a transition metal compound and a sulfur compound of a promoter are dissolved and dissolved in an organic compound of a carbon source. Thereafter, the raw material is sprayed to the reaction furnace as a liquid as a carrier gas, or a part of the carrier gas may be vaporized and supplied to the reaction furnace in a purge gas type to be reacted. When a carbon fiber having a fine fiber diameter is obtained, it is preferred to vaporize the raw material and supply it to the reaction furnace.

The reactor is an electric furnace of a normal vertical type. The temperature of the reactor is 800 to 1,300 ° C, preferably 1,000 to 1,300 ° C. The reaction furnace which is heated to a predetermined temperature is supplied with a raw material liquid and a carrier gas, or a raw material gas which is vaporized by the raw material, and a carrier gas, and reacts to obtain carbon fibers.

In this way, the gas which is blown into the reaction furnace is thermally decomposed, and the organic compound is used as a carbon source, and the organic transition metal compound is used as a transition metal particle of the catalyst, and the formation of the fine carbon fiber using the transition metal particle as a core is performed. In the process of producing the fine carbon fibers, the present invention partially inhibits the growth of the fine carbon fibers under the conditions of the reaction system, particularly in the case where the amount of the sulfur compound is small, and causes the particles containing the carbon particles or the catalytic metal to grow. A fine carbon fiber mixture is obtained.

The obtained fine carbon fiber mixture is vaporized by an inert gas atmosphere such as helium, argon or the like, and heat-treated at 900 to 1,500 °C. Alternatively, heat treatment at 2,000 to 3,500 ° C is carried out, or the fine carbon fiber mixture obtained in the reaction state is vaporized in an inert gas atmosphere, and heat treatment at 2,000 to 3,500 ° C is preferably carried out.

The fine carbon mixture obtained in the reaction state, or a fine carbon fiber mixture thereof is subjected to heat treatment at 900 to 1,500 ° C in an inert gas atmosphere, and boron carbide (B)₄C), boron oxide (B₂O₃), elemental boron, boric acid (H₃BO₃The boron compound such as borate may be mixed and further heat-treated at 2,000 to 3,500 ° C in an inert gas atmosphere. The amount of the boron compound added is not limited as long as it depends on the chemical characteristics and physical properties of the boron compound used, for example, in the use of boron carbide (B).₄In the case of C), it is 0.05 to 10% by mass, preferably 0.1 to 8% by mass, and more preferably 0.5 to 5% by mass based on the fine carbon fiber mixture.

Example

Hereinafter, an embodiment of the present invention will be described.

(Example)

As shown in FIG. 1 of the schematic view, a raw material supply pipe 4 for supplying a raw material vaporized by the raw material vaporizer 5, and a carrier gas supply pipe 6 are attached to the top of the vertical heating furnace 1 (inner diameter: 170 mm, length: 1,500 mm). .

From the raw material supply pipe 4, benzene which dissolves 4 mass% of ferrocene and 5 mass% of thiophene (1.9 mass% of sulfur atoms) is vaporized and kept at 200 ° C and supplied at 15 g/min, and hydrogen is used as a carrier. The gas was supplied and reacted at 180 liters/min.

The fine carbon fiber obtained by the reaction is heat-treated at 1,300 ° C in an Ar (argon) atmosphere, and the treated product at 1,300 ° C is heat-treated at 2,800 ° C under an Ar atmosphere, and a fine carbon fiber mixture is obtained at a mass recovery rate of 90% in the heat treatment step. .

A transmission electron micrograph of the obtained fine carbon fiber mixture is shown in Figs. 2 to 5 . In Fig. 2 to Fig. 5, the fine carbon fibers in the fine carbon fiber mixture have a multi-layered structure in which the tubular carbon layers composed of carbon atoms are superposed, and the central axis thereof has a hollow structure. The fiber has an outer diameter of 5 to 200 nm and an aspect ratio of 2000 or more.

In Fig. 2, fine carbon fibers and carbon particles close to a spherical shape were observed, and the diameter of the fine carbon fibers was about 5 to 20 μm, and the relative carbon particle size was about 5 to 50 nm. The inside of this granular carbon is hollow. Again, this carbon particle is Adhesive to each other, and adhesion to the surface of the fine carbon fibers was observed.

In Fig. 3, the same granular carbon as in Fig. 2 was observed, but a metal or a metal compound was observed inside the particles.

In Fig. 4, a carbon flake or a film was observed between the fine carbon fibers. The size is from about 100 nm x 100 nm to about 10,000 nm x 10,000 nm. It is buried in a wide range of fine carbon fibers in a wide range, and the thickness is unknown. However, although it is considered that the thinner is smaller than the diameter of the fine fiber, there is a possibility that the sheet is thicker than the fiber diameter. Further, the sheet-like carbon is developed in carbon crystals, and this laminated structure is observed. However, the flakes are amorphous and the carbon crystals are less developed.

Fig. 5 is a transmission electron micrograph of fine carbon fibers after treatment at 1,300 ° C, and it is observed that many carbon particles are mutually sticky and agglomerated.

(Comparative example)

As shown in FIG. 1 of the schematic view, a raw material supply pipe 4 for supplying a raw material vaporized by the raw material vaporizer 5, and a carrier gas supply pipe 6 are attached to the top of the vertical heating furnace 1 (inner diameter: 170 mm, length: 1,500 mm).

From the raw material supply pipe 4, toluene in which 4% by mass of ferrocene and 0.5% by mass of thiophene (in terms of sulfur atom 0.4% by mass) were vaporized and kept at 200 ° C and supplied at 15 g/min, and hydrogen was used as a carrier. The gas was supplied and reacted at 180 liters/min.

The fine carbon fibers obtained by the reaction were heat-treated at 1300 ° C in an Ar (argon) atmosphere, and the treated product at 1300 ° C was heat-treated at 2800 ° C in an Ar atmosphere, and fine carbon fibers were obtained at a mass recovery rate of 90% in the heat treatment step.

The fine carbon fiber similar to the fine carbon fiber in the fine carbon fiber mixture of the example was observed except for having a uniform fiber diameter and having no non-fibrous carbon as observed by a transmission electron microscope.

(modulation of composite materials)

Using the fine carbon fibers obtained in the examples and the comparative examples, a composite material with polyacetal was prepared, and the friction coefficient of the composite material was measured in accordance with JIS-K-7125, and the volume specific resistance was measured in accordance with JIS-K-7194. The results are shown in Table 1 below.<tables><img file="TW593136B_D0001.tif" /></tables>

From Table 1, it was confirmed that fine carbon fibers and non-fibrous carbons can be formed by selecting reaction conditions, and the effect is that a fine carbon fiber mixture excellent in folding characteristics and the like can be obtained when a composite material is formed with a resin.

Industrial availability

According to the present invention, it is possible to provide a fine carbon fiber mixture having an outer diameter of 1 to 500 nm, an aspect ratio of 10 to 15,000, and a fine carbon fiber and a non-fibrous carbon, which are different from the conventional carbon fiber and vapor phase carbon fiber. The compound can be used as a filling material for a conductive material, a heat conductive material, an electrical folding material, an electrical friction material, etc., and can be used for an electrical machine component, an automobile component, and a mechanical component.