CN104746181A - Method for producing carbon nanofibers, carbon composite and method for producing same - Google Patents

Abstract

The present invention provides: a production method for efficiently producing highly conductive carbon nanofibers that reduces variation in quality; and a carbon composite having excellent dispersibility and ability to impart conductivity, and a method for producing the same. The present invention pertains to: a method for producing carbon nanofibers by causing a catalyst to contact carbide furnace gas used as a starting material; a carbon black/carbon nanofiber carbon composite that is characterized by having a carbon black particle or particle aggregate as a nucleus, and having carbon black and carbon nanofibers joined to one another; and a method for producing a carbon composite by holding a carbon nanofiber-forming catalyst to carbon black, and causing carbide furnace gas to contact the same.

Description

Method for producing carbon nanofiber, carbon composite and method for producing the same

This application is a divisional application of the Chinese invention patent application with the application number 201180050711.4 and the title of the invention "manufacturing method of carbon nanofiber, carbon composite and its manufacturing method" which entered the Chinese national phase on April 19, 2013.

technical field

The present invention relates to a method for producing carbon nanofibers. In addition, the present invention also relates to a carbon composite using carbon nanofibers and a method for producing the same.

Background technique

Conventionally, resins, rubbers, etc. are made to contain carbon black to impart conductivity thereto. In particular, acetylene black has a chain structure of carbon particles, so it is superior in conductivity-imparting ability compared with conventional carbon black. In addition, carbon black can exhibit its excellent conductivity-imparting ability, and can be used as a conductive material for secondary battery electrodes. However, in recent years, there has been a demand for a conductive material capable of imparting higher conductivity without deteriorating the original properties of resins, battery materials, and the like.

To address these issues, a proposal to use carbon nanofibers (CNFs) as a conductive material has been proposed. CNF is fibrous carbon with a wire diameter of tens of nanometers to one hundred and tens of nanometers. It has excellent properties such as high electrical conductivity and high thermal conductivity, so it can be used as a conductive filler or high Thermally conductive fillers are used in industrial fields. The shape of CNF obtained by bringing a raw material into contact with a catalyst is often a hollow fiber shape. They are sometimes referred to specifically as carbon nanotubes (CNTs).

Compared with carbon black, CNF has high crystallinity and low powder resistance, but it exists in the form of aggregates formed by entangled fibers, so it has poor dispersibility when mixed with resins, etc. The ability to impart conductivity cannot be fully exhibited. Therefore, studies have been made on dispersing aggregates by acid treatment or mechanical stirring treatment, but CNFs tend to be cut short and lose their original characteristics. Therefore, people have studied the composite of carbon black and CNF. For example, it has been proposed to generate CNF at the reaction site of acetylene black (Patent Document 1). However, since the production conditions of acetylene black and CNF are different, simultaneous production at the same production site has a problem of unstable quality. There is also a proposal to introduce CNF into the carbon black generation site to obtain a composite (patent document 2), but because the raw material CNF aggregates, it is impossible to increase the content of CNF in the composite, and it is difficult to keep it in contact with other materials such as resins. The fluidity of the conductive composition obtained by mixing while reducing the resistance value has not yet found a satisfactory solution.

In addition, CNF is also obtained by a method of contacting hydrocarbons such as benzene with a catalyst (Patent Document 3), a method of reacting hydrocarbons such as benzene with a metal complex of a catalyst (Patent Document 4), and making carbon monoxide (CO) and hydrogen (H ₂ ) in contact with catalyst particles containing metal or metal oxide (Patent Document 5) and the like. When hydrocarbons are used as raw materials, hydrocarbons are cheap and easy to obtain, but on the other hand, soot (soot) is by-generated and easily mixed into the product (CNF). Since the electrical conductivity and thermal conductivity of soot are inferior to those of CNF, there is a problem that the performance of CNF decreases due to the incorporation.

On the other hand, in the case of using a mixed gas of CO and _H2 as a raw material, there is an advantage that it is easy to suppress the by-generation of soot, but on the other hand, the yield and physical properties of CNF tend to vary, so in terms of productivity There is a problem. In addition, CO as an industrial raw material is not easy to obtain and is expensive compared with hydrocarbons, so there is a problem that the price of the produced CNF is also high.

[Prior Art Document]

[Patent Document]

Patent Document 1: WO/2007/013678

Patent Document 2: Japanese Patent Laid-Open No. 2010-248397

Patent Document 3: Japanese Patent Application Publication No. 62-500943

Patent Document 4: Japanese Patent Laid-Open No. 2003-146633

Patent Document 5: Japanese Patent Laid-Open No. 2004-300631

Contents of the invention

(problem to be solved by the invention)

The present invention is made to solve the above-mentioned problems in the conventional CNF production method, and provides a method capable of reducing quality variation and efficiently producing highly conductive CNF. In addition, the present invention provides a carbon composite having excellent dispersibility and conductivity-imparting ability, and a method for producing the same.

(means to solve the problem)

That is, the present invention adopts the following means in order to solve the above-mentioned problems.

(1) A method for producing carbon nanofibers, characterized in that calcium carbide furnace gas is used as a raw material, and a catalyst is brought into contact with the raw material.

(2) The method for producing carbon nanofibers described in (1) above, wherein calcium carbide furnace gas from which moisture has been removed is used as a raw material.

(3) The method for producing carbon nanofibers described in (1) or (2) above, wherein the catalyst is a simple substance of an iron group element (iron, cobalt or nickel) or a compound containing an iron group element.

(4) The method for producing carbon nanofibers described in (3) above, wherein the compound containing an iron group element is an oxide or hydroxide of an iron group element.

(5) The method for producing carbon nanofibers described in (1) or (2) above, wherein the catalyst is an alloy containing an iron group element or a compound containing an alloy containing an iron group element.

(6) The method for producing carbon nanofibers according to (5) above, wherein the compound containing an alloy containing an iron group element is an oxide or hydroxide of an alloy containing an iron group element.

(7) The method for producing carbon nanofibers described in any one of the above (1) to (6), wherein the catalyst includes a powdery substance, and under the temperature/pressure conditions for generating carbon nanofibers, the carbon nanofibers are not The substance that reacts with the calcium carbide furnace gas is used as a carrier of the catalyst together with the catalyst powder, and is brought into contact with the calcium carbide furnace gas.

(8) The method for producing carbon nanofibers described in (7) above, wherein the catalyst carrier is magnesia and/or alumina.

(9) The method for producing carbon nanofibers according to any one of the above (1) to (8), characterized in that: after disposing a catalyst in the carbon nanofiber synthesis device, first introducing a reducing gas into the device, Then import the calcium carbide furnace gas. (10) The method for producing carbon nanofibers described in (9) above, wherein the reducing gas is hydrogen.

(11) A carbon black/carbon nanofiber-carbon composite, characterized in that it has carbon black particles or aggregated particles as nuclei, and is formed by linking carbon black and carbon nanofibers.

(12) The carbon composite described in (11) above, characterized in that: the top end of the carbon nanofiber is selectively connected to the surface of the particles of carbon black or aggregated particles, and the fiber length of the carbon nanofiber is longer than that of the particles of carbon black. Or the length of the aggregated particles is long.

(13) The carbon composite described in (11) above, wherein the carbon black is acetylene black.

(14) The method for producing a carbon composite described in (11) above, characterized in that the catalyst for forming carbon nanofibers is supported on carbon black and brought into contact with calcium carbide furnace gas.

(15) The method for producing a carbon composite described in (14) above, wherein calcium carbide furnace gas from which moisture has been removed is used as a raw material.

(16) The method for producing a carbon composite described in (14) above, wherein the catalyst for forming carbon nanofibers is a simple substance of an iron group element (iron, cobalt, or nickel) or a compound containing an iron group element.

(17) The method for producing a carbon composite described in (16) above, wherein the compound containing an iron group element is an oxide or hydroxide of an iron group element.

(18) The method for producing a carbon composite described in (14) above, wherein the catalyst for forming carbon nanofibers is an alloy containing an iron group element or a compound containing an alloy containing an iron group element.

(19) The method for producing a carbon composite described in (18) above, wherein the compound containing an alloy containing an iron group element is an oxide or hydroxide of an alloy containing an iron group element.

(20) The method for producing a carbon composite as described in (14) above, characterized in that: after arranging carbon black loaded with a catalyst for generating carbon nanofibers in the carbon nanofiber generating device, firstly, the reducing gas is introduced into the device Inside, and then introduce calcium carbide furnace gas.

(21) The method for producing a carbon composite described in (20) above, wherein the reducing gas is hydrogen.

(22) A conductive composition characterized by filling resin and/or rubber with the carbon composite described in (11) above.

(invention effect)

By adopting the manufacturing method of carbon nanofiber (CNF) of the present invention, the deviation of quality can be reduced and highly conductive CNF can be produced efficiently, and the application of CNF as conductive filler or high thermal conductivity filler can be promoted, so it is very important to the industry. great contribution to development. Also, in the case of using calcium carbide furnace gas as fuel, most of the CO contained in the calcium carbide furnace gas is burned and released into the atmosphere as carbon dioxide (CO ₂ ), but the method of the present invention utilizes calcium carbide furnace gas CNF is produced from the CO contained in the carbon dioxide, so the CO ₂ released into the atmosphere is reduced, which also contributes to the reduction of the environmental load.

In addition, according to the present invention, a carbon composite having excellent dispersibility and conductivity-imparting ability and stable quality can be obtained.

Description of drawings

Fig. 1 is an example of the structure of the carbon composite of the present invention.

Fig. 2 is an example of the structure of a carbon composite obtained by introducing carbon nanofibers at the carbon black production site.

Detailed ways

(Embodiment 1)

In the present invention, calcium carbide refers to calcium carbide (CaC ₂ ). Calcium carbide is a raw material such as acetylene (C ₂ H ₂ ) used as an industrial raw material or fuel, or calcium cyanamide (CaCN ₂ ) used as a nitrogen fertilizer component, and thus is widely synthesized industrially. General calcium carbide synthesis is carried out in a high-temperature furnace called a calcium carbide furnace using quicklime (CaO) and carbon (C) such as coke as raw materials, through a synthesis process using the reaction of Formula 1.

CaO+3C→CaC ₂ +CO (Formula 1)

In the calcium carbide synthesis process, as shown in Formula 1, carbon monoxide (CO) gas is by-generated. CO is harmful and cannot be released directly. Therefore, the calcium carbide furnace is usually made into a closed structure to collect the by-product gas (calcium carbide furnace gas), and then use it as fuel (Formula 2) for harmless treatment.

CO+(1/2)O ₂ →CO ₂ (Formula 2)

Industrial furnaces that by-generate gas containing CO are not limited to calcium carbide furnaces. For example, by-product gases (coke oven gas, blast furnace gas) of coke ovens and blast furnaces used in the iron industry also contain CO. However, coke oven gas and blast furnace gas contain many components other than CO such as hydrocarbons and carbon dioxide (CO ₂ ), and the CO content is only about 30% by volume or less, so they are not suitable as raw materials for CNF. Calcium carbide furnace gas contains CO at a high concentration of 50 to 90%, and hydrogen (H ₂ ) is generated by the reaction of moisture and carbon contained in quicklime or coke (water gas reaction). Therefore, CO:H ₂ = H ₂ is contained in a ratio of 60:40 to 90:10 (volume ratio). In the present invention, the by-product gas mainly containing CO and hydrogen that is by-produced in the calcium carbide synthesis step is defined as calcium carbide furnace gas.

It is considered that the formation of CNF from the CO raw material is realized by advancing the reaction shown in Formula 3 in the presence of a catalyst. It can be seen from Equation 3 that it seems that CNF can be produced only by the presence of CO as a raw material, but in fact, if _H2 is not coexisted, the reaction rate is significantly reduced. The reason for this may be due to the oxidative deactivation of the catalyst by the by-produced _CO2 at the time of CNF generation, and it is considered that the reason for the improvement of the reaction rate due to the coexistence of _H2 is that the deactivation of the catalyst is suppressed by the reduction of _H2 .

2CO→C(CNF)+CO ₂ (Formula 3)

A method of using a mixed gas of CO and H ₂ as a raw material of CNF is disclosed in Patent Document 5 and is known. Conventional mixed gas is obtained by mixing industrial raw material CO gas and H ₂ gas at a predetermined ratio such as CO:H ₂ =40:60 to 90:10. At this time, mixing is usually performed at normal temperature.

On the other hand, synthesis of calcium carbide is usually carried out at a high temperature of 1600 to 2000°C. CO and _H2 contained in calcium carbide furnace gas are also mixed at high temperature, so it is considered that the mixed state is different from the conventional mixed gas that is mixed near normal temperature. The inventors have newly found out that when the mixed gas of CO and _H mixed at high temperature is used as a raw material in this way, the yield of CNF produced can be significantly improved and stabilized compared with the conventional CNF synthesis method, so that it can be The present invention has been accomplished by efficiently producing CNFs with little variation in quality and improving/stabilizing the electrical conductivity characteristics.

The main components of calcium carbide furnace gas are carbon monoxide (CO) and hydrogen (H ₂ ), and usually contain nitrogen (N ₂ ) as a safety gas. The concentration of each component is 50-80 volume % of CO, 10-30 volume % of H ₂ , and several to 30 volume % of N ₂ . In addition, in addition to CO, H ₂ and N ₂ , calcium carbide furnace gas also contains impurities such as CO ₂ , hydrocarbons, hydrogen sulfide, nitrogen oxides and/or sulfur oxides, all of which are in trace amounts and have almost no effect on the formation of CNF . In addition, it also contains solid impurities (dust) generated in the calcium carbide production process, which can be removed by filtration (dry method) or water washing (wet method). Calcium carbide furnace gas from which dust has been removed by a wet method contains several percent by volume of water vapor, which may deactivate the catalyst. Therefore, it is preferable to remove it to 0.1% or less with a dryer or a dehydration column.

The calcium carbide furnace gas thus obtained is introduced into a CNF synthesis furnace, and CNF is synthesized by contacting with a catalyst. The calcium carbide furnace gas can be further diluted with inert gases such as nitrogen and argon. Preferably, the temperature of the synthesis furnace is 300-700° C., and the pressure is 0.01 MPa-1 MPa. When the temperature is lower than 300° C. or higher than 700° C., or the pressure is lower than 0.01 MPa, the reaction hardly occurs, which is not preferable. In addition, when the pressure exceeds 1 MPa, the design of the pressure resistance of the device is complicated, and the improvement effect of the yield or physical properties is not obvious, so it is not preferable. The reaction time is preferably 1 to 24 hours. If it is less than 1 hour, the amount of CNF produced is very small, and even if it exceeds 24 hours, the amount of produced CNF will not increase significantly, so neither is preferable.

The catalyst can use iron group elements (iron, cobalt or nickel) or compounds containing iron group elements, such as oxides or hydroxides of iron group elements, or alloys containing iron group elements or alloys containing iron group elements Compounds, such as oxides or hydroxides of alloys containing iron group elements. These substances may be used alone, or two or more substances may be used in combination.

In addition, the powder of the above-mentioned substance is used as a catalyst, and further, materials that do not react with calcium carbide furnace gas under the above-mentioned temperature/pressure conditions for generating CNF, such as magnesium oxide and/or aluminum oxide, can be used as a catalyst together with the above-mentioned catalyst powder. carrier.

Preferably, after disposing the catalyst in the furnace, the catalyst is activated (activation treatment) before introducing calcium carbide furnace gas. Specifically, a catalyst is first arranged in a synthesis furnace, and after adjusting the temperature/pressure in the furnace to generate CNF, a reducing gas such as _H2 is introduced into the furnace for tens of minutes to an hour before introducing calcium carbide furnace gas. Oxygen or moisture is removed from the surface of the catalyst, whereby the catalyst can be activated.

The generated CNF can be directly dried or treated with an aqueous acid solution to remove residual catalyst and then dried and made into a powder, or supplied as a slurry dispersed in water or an organic solvent for practical applications.

(Embodiment 2)

The carbon composite according to the present embodiment of the present invention is formed by linking carbon black and CNF. Here, connection is not a simple contact, but refers to the physical fusion of carbon, which is not easily separated by ordinary mechanical operations, and electrons can move freely between the connected carbon black and CNF without contact resistance. Therefore, when mixed with other materials such as resins and battery materials, carbon black and CNF also exist in a linked state, and good dispersibility can be obtained, and at the same time, high conductivity can be imparted. When carbon black is contained alone, it is necessary to increase the amount of resin added to impart conductivity, and the fluidity of the resulting conductive composition is impaired. When CNF is contained alone, orientation occurs when mixed with resin, etc. Entanglement, so it is difficult to obtain good dispersion, and there will be deviations in conductivity. In addition, when simply mixing carbon black and CNF, the contact state between the two tends to change, so the variation further increases.

The carbon composite of the present invention is a carbon composite characterized in that it has particles or aggregated particles of carbon black as a core, and that carbon black and CNF are linked. The inventors of the present invention conducted intensive studies to improve the dispersibility and conductivity-imparting ability of the carbon composite, and as a result, found that the structure of the carbon composite greatly affects these characteristics. That is, by adopting a structure in which carbon black particles or aggregated particles are centered, CNFs are present on the outer periphery thereof, and both are connected, when mixed with a resin or the like, the contact area of the CNF with excellent conductivity and the resin or the like increases. In addition, in the above-mentioned structure, the aggregation of CNFs is reduced, so orientation and entanglement are less likely to occur, and the amount of CNFs to be mixed in the resin or the like can be increased to significantly improve the conductivity-imparting ability. On the other hand, conventional carbon composites have a structure in which carbon black surrounds the outer periphery of aggregated CNFs, so the contact area with resins and the like is reduced, and most of the contact with resins and the like is carbon black, so carbon composites cannot be fully utilized. Conductivity-Enabling Capabilities of CNFs in Materials. FIG. 1 shows an example of the structure of the carbon composite of the present invention, and FIG. 2 shows an example of the structure of a conventional carbon composite obtained by introducing CNF at the carbon black production site.

In the present invention, preferably, the tip of the CNF is selectively bonded to the surface of the carbon black particles or the aggregated particles, and the fiber length of the CNF is larger than the particle diameter of the carbon black particles or the aggregated particles. Here, the tip of CNF refers to the end in the direction in which CNF is generated and elongated. When the fiber length of CNF is larger than the particle size of carbon black particles or aggregated particles, even if the amount of carbon composite added to the resin or the like is the same as in the past, it is easy to diffuse in the resin or the like in a wide range, so it can be Effectively function as a conductive path. The fiber length of CNF can be adjusted by the formation reaction temperature and formation reaction time, and is more preferably 1 μm or more.

The type of carbon black constituting the carbon composite of the present invention is not particularly limited. For example, thermal black, furnace black, lamp black, channel black, acetylene black, etc. can be used, among which acetylene black is more preferred. This is because acetylene black has a structure in which high-purity and highly crystalline primary particles are connected in a chain, and thus is excellent in electrical conductivity.

The CNF content in the carbon composite of the present invention is preferably 10 to 80% by mass. If the content of CNF is less than 10% by mass, sufficient electrical conductivity cannot be obtained, and if it exceeds 80% by mass, the dispersibility will decrease due to aggregation of CNF or the like. The CNF content can be adjusted by the catalyst for CNF production, the amount of carbon black, the production reaction temperature, and the production reaction time charged into the CNF production device.

The method for producing the carbon composite of the present invention is not particularly limited. For example, carbon black can be supported by a catalyst for generating CNF and brought into contact with carbide furnace gas to generate and connect CNF on the surface of carbon black particles. Since the calcium carbide furnace gas was described in Embodiment 1, its detailed description is omitted here.

CNF can be produced by introducing the calcium carbide furnace gas obtained in this way into a CNF producing device and bringing it into contact with a catalyst. The calcium carbide furnace gas can be further diluted with inert gases such as nitrogen and argon. Preferably, the temperature of the synthesis furnace is 300-700° C., and the pressure is 0.01 MPa-1 MPa. When the temperature is lower than 300° C. or higher than 700° C., or the pressure is lower than 0.01 MPa, the reaction hardly occurs, which is not preferable. In addition, if the pressure exceeds 1 MPa, the design of the pressure resistance of the device will be complicated, and the improvement effect of yield and physical properties will not be evident, so it is not preferable. The reaction time is preferably 1 to 24 hours. If it is less than 1 hour, the amount of production of CNF is very small, and even if it exceeds 24 hours, the amount of production does not increase significantly, so neither is preferable.

The catalyst for CNF generation can use iron group elements (iron, cobalt, or nickel) or compounds containing iron group elements, such as oxides or hydroxides of iron group elements, or alloys containing iron group elements or iron group elements. Compounds of alloys of iron group elements, such as oxides or hydroxides of alloys containing iron group elements. These substances may be used alone, or two or more substances may be used in combination.

Preferably, the catalyst for CNF production is supported on carbon black. The loading method is not particularly limited. For example, a catalyst for CNF production such as a simple substance of an iron group element or a compound containing an iron group element can be suspended or dissolved in a liquid such as ethanol, and carbon black can be added to the liquid, stirred, mixed, dehydrated, Drying is carried out by carrying out loading. The raw material powder thus obtained is brought into contact with calcium carbide furnace gas in a CNF generating apparatus, thereby obtaining a carbon composite characterized in that it has carbon black particles or aggregated particles as nuclei, and carbon black and CNF are bonded together. made. Furthermore, since carbon black particles or aggregated particles exist in the form of nuclei, the tips of CNFs can be selectively connected, allowing CNFs to grow in multiple directions, and aggregation can be suppressed. In addition, it is difficult to obtain a carbon composite having the structure of the present invention in conventional methods, such as a method of simultaneously generating carbon black and CNF at the same production site, or a method of adding CNF at a carbon black production site.

When producing CNF, it is preferable to previously activate the catalyst (activation treatment) before introducing calcium carbide furnace gas. Specifically, carbon black carrying a catalyst for CNF production is arranged in a CNF production device, and after adjusting the temperature and pressure in the furnace to generate CNF, _H2 is introduced into the device for several tens of minutes to one hour to reduce the carbon black. The active gas removes oxygen or moisture from the surface of the catalyst, thereby activating the catalyst. After that, the generation of CNF was promoted by introducing calcium carbide furnace gas.

The resulting carbon composite can be directly dried or treated with an aqueous acid solution to remove residual catalyst and then dried and made into a powder, or supplied to practical use as a slurry dispersed in water or an organic solvent. By filling resin, rubber, etc. with the carbon composite of the present invention, a conductive composition having better conductivity than conventional ones can be obtained.

Example

The manufacturing method of the carbon nanofiber, the carbon composite and the manufacturing method thereof of the present invention will be described in detail below by way of examples and comparative examples. However, the present invention is not limited to the following examples within the range not exceeding the gist.

[Example 1]

Using a closed calcium carbide furnace, add quicklime (CaO) and petroleum coke (C) into the furnace, and then apply 25,000kW of electricity to the graphite electrode inserted into the furnace from the upper center of the furnace to heat the furnace to 2000°C. Calcium carbide (CaC ₂ ) is synthesized by reacting CaO with C. The calcium carbide furnace gas by-generated at this time is collected, washed with water to remove dust, and stored in a water-sealed gas storage tank. A part of the stored calcium carbide furnace gas was extracted, and the main components were analyzed with a gas chromatograph (manufactured by Shimadzu Corporation, GC-14B), and the trace components were analyzed with a gas detection tube (manufactured by GASTEC). The results are shown in Table 1.

[Table 1]

A reaction vessel made of quartz glass was filled with cobalt oxide (Co ₃ O ₄ ) (manufactured by Sigma-Aldrich, "637025", purity 99.8%, average particle diameter 20-30 nm) and magnesium oxide (MgO) (Sigma Aldrich Co., Ltd. "549649" manufactured by Derich Co., a mixed powder catalyst having an average particle diameter of 12.8 nm and a specific surface area of 130 m ² /g), and the container was filled in a CNF synthesis apparatus. Fill the device with inert gas (N ₂ ), raise the temperature to 600°C after the pressure is 0.1MPa, replace it with reducing gas (H ₂ ) and keep it for 30 minutes, and then the above calcium carbide furnace gas stored in the gas storage tank Introduce into the furnace and hold for 8 hours. Then, replace the calcium carbide furnace gas with N ₂ and stop heating. After cooling to room temperature, open the device and recover the product from the reaction vessel. These conditions are summarized in Table 2.

[Table 2]

The product is a black powder. The yield (parts by weight) of the product per 1 part by weight of the catalyst used was calculated as the yield. The microstructure was observed with a transmission electron microscope (TEM: manufactured by JEOL, transmission electron microscope 2000FX, acceleration voltage 200 kV, observation magnification 200,000 times), and it was found to be a hollow fiber-shaped carbon nanofiber (CNF). The outer diameters of 10 CNFs were measured by TEM images, and the average value was taken as the CNF diameter. Regarding conductivity, the powder resistance value was measured with a load of 4.9 kN and a four-probe method using a powder resistance meter (manufactured by Mitsubishi Chemical Analytech Corporation, LORESTAGP). The synthesis test was carried out 10 times under the same conditions, and the average value and standard deviation of yield, CNF diameter and powder resistance value were calculated. These results are summarized in Table 3.

[table 3]

[Embodiments 2-4]

Using the calcium carbide furnace gas of Example 1, the synthesis was carried out according to the conditions shown in Table 2 respectively. Table 3 summarizes the morphological observation of the microstructure of the obtained product and the calculation results of the yield, CNF diameter and powder resistance value.

[Examples 5-7]

Using calcium carbide furnace gas having the composition shown in Table 1, the synthesis was carried out under the conditions shown in Table 2, respectively. Table 3 summarizes the morphological observation of the microstructure of the obtained product and the calculation results of the yield, CNF diameter and powder resistance value.

[Embodiments 8-14]

Similar to Examples 1-7, the calcium carbide furnace gas stored in the water-sealed gas storage tank was passed through a dehydration column (manufactured by Nichika Seiko, dry column, DC-L4) to reduce the water content to 0.01% by volume. The main components of the gas were analyzed with a gas chromatograph, and the trace components were analyzed with a gas detection tube. The results are shown in Table 1. Then, the synthesis was carried out under the same conditions as in Examples 1-7, and the results of morphological observation of the microstructure of the obtained product and calculation results of yield, CNF diameter and powder resistance value were summarized in Table 3.

[Comparative examples 1 to 7]

As the raw material gas, a gas obtained by mixing commercially available carbon monoxide gas (purity 99.95%) and hydrogen gas (purity 99.99%) at room temperature in the ratio shown in Table 4 was used instead of calcium carbide furnace gas. The synthesis was carried out under the same conditions as in Examples 1 to 7, and the results of morphological observation of the microstructure of the obtained products and calculation results of yield, CNF diameter and powder resistance value are summarized in Table 3.

As can be seen from Table 3, Comparative Examples 1 to 7 are all the same embodiments (for example, Comparative Example 1 and Example 1 and Example 8, Comparative Example 2 and Example 2 and Example 9, the following Similarly) for comparison, the yield is low, the fiber diameter is fine, and the powder resistance value is high. And they have large standard deviation values and large deviations.

[Comparative Examples 8-9]

The synthesis was carried out under the same conditions as in Example 1 except that coke oven gas generated during carbonization of coal in a coke oven was used instead of calcium carbide oven gas as the raw material gas, and CNF formation was not observed. CNF formation was not observed even when blast furnace gas generated when iron ore was reduced with blast furnace coke was used as the raw material gas. The results of component analysis of the used coke oven gas and blast furnace gas are shown in Table 1.

As can be seen from Examples and Comparative Examples, according to the method for producing carbon nanofibers (CNFs) using calcium carbide furnace gas as a raw material of the present invention, CNFs having high conductivity can be efficiently produced with reduced quality variation. In addition, since calcium carbide furnace gas by-produced in the calcium carbide synthesis process can be used as a raw material, compared with the case of using commercially available carbon monoxide gas and hydrogen gas, the emission of carbon dioxide (CO ₂ ) can be reduced, and CNF can be produced at low cost.

Example 15 Use the calcium carbide furnace gas synthesized in Example 1 to produce carbon composites. 50 g of furnace black (manufactured by Tokai Carbon Co., Ltd., "SEAST SO") and 0.5 g of cobalt oxide (Co ₃ O ₄ ) powder (manufactured by Sigma Aldrich, "637025", purity 99.8%, average particle size 20-30 nm) Add it to 500 g of ethanol, and mix it with a ball mill for 1 hour. Filtration/drying was then performed to obtain a raw material powder. Next, the obtained raw material powder was filled in a reaction container made of quartz glass, and the container was loaded in a carbon nanofiber production apparatus. The inside of the apparatus was made into a vacuum atmosphere, and then filled with an inert gas (N ₂ ), the temperature was raised to 600° C. at a pressure of 0.1 MPa. Next, the calcium carbide furnace gas stored in the water-sealed gas tank was introduced into the furnace and kept for 6 hours. Then, replace the calcium carbide furnace gas with _N2 and stop heating, cool to room temperature, and then open the device to recover the product from the reaction vessel. Their generation conditions are shown in Table 4.

[Table 4]

The evaluation items of the product and their evaluation methods are as follows.

(1) Whether or not the carbon nanofibers are connected and the connected parts were observed and confirmed by observing the fine structure with a transmission electron microscope ("Transmission Electron Microscope JEM-2000FX", manufactured by JEOL Ltd., observation magnification: 100,000 times).

(2) Regarding the fiber length of carbon nanofibers, 10 carbon nanofibers were measured with a transmission electron microscope (observation magnification: 5000 times), and the average value was calculated. Moreover, the aggregation particle|grains of carbon black were evaluated similarly, and it was 500 nm.

(3) The content of the carbon nanofibers was calculated by subtracting the weight of the raw material powder from the weight of the recovered product to obtain the weight of the produced carbon nanofibers.

(4) The conductivity-imparting ability of the carbon composite was evaluated by the volume resistivity of the resin composite obtained as follows. 10 parts by mass of the carbon composite was mixed with 90 parts by mass of PS resin (manufactured by Toyo Styrene Co., Ltd. "H700"), using a kneader (manufactured by Toyo Seiki Seisakusho, "LABO PLASTOMILL"), at a blade speed of 30rpm, temperature Kneading was carried out at 220° C. for 10 minutes. The kneaded product was heated to 200° C., pressurized and molded at a pressure of 9.8×106 Pa, and a test piece of 2×2×70 mm was produced, and a digital multimeter (Yokogawa Electric Co., Ltd., "Digital Multimeter 7562") was used to measure the temperature according to SRI2301. Test Method Measures Volume Resistivity.

(5) The dispersibility in the resin and the fluidity of the resin composition were evaluated by MFI (melt flow index) obtained below. The test piece used in the measurement of the volume resistivity was cut into a size of 2×2×5mm, and a fluidity measuring instrument (manufactured by Toyo Seiki Seisakusho, Melt Indexer A-111) was used to heat at 200° C. The mass of the resin composition per 10 minutes flowing out from a nozzle with an inner diameter of 2 mm was measured under a load of 5 kg.

These results are shown in Table 5.

[table 5]

[Example 16]

A carbon composite was obtained in the same manner as in Example 15 except that the raw material carbon black was changed to acetylene black (manufactured by Denki Kagaku Kogyo, "HS-100"). The evaluation results are shown in Table 5.

[Example 17]

Fill inert gas (N ₂ ) and make the pressure 0.1MPa, raise the temperature to 600°C, replace with reducing gas (NH ₃ ) and keep it for 30 minutes, and introduce the calcium carbide furnace gas stored in the water-sealed gas storage tank into the furnace , except that it was the same as in Example 16 to obtain a carbon composite. The evaluation results are shown in Table 5.

[Example 18]

A carbon composite was obtained in the same manner as in Example 17 except that the reducing gas was changed to H ₂ . The evaluation results are shown in Table 5.

[Example 19, 20]

The catalyst for carbon nanofiber formation was changed to cobalt metal (manufactured by Sigma-Aldrich, "266639", purity 99.8%, average particle size 2 μm), iron-manganese-cobalt alloy (composition 5:2.5:2.5, average particle size 30 nm), except that it was the same as in Example 18 to obtain a carbon composite. The evaluation results are shown in Table 5.

[Example 21-26]

A carbon composite was obtained in the same manner as in Examples 15 to 20 except that the calcium carbide furnace gas stored in the water-sealed gas receiver was passed through a dehydration column (manufactured by Nichika Seiko, "dry column DC-L4"). The evaluation results are shown in Table 5.

[Example 27-29]

A carbon composite was obtained in the same manner as in Example 24 except that the formation reaction temperature and formation reaction time were changed as shown in Table 4. The evaluation results are shown in Table 5.

[Example 30]

A carbon composite was obtained in the same manner as in Example 29 except that the amount of cobalt oxide (Co ₃ O ₄ ) powder mixed with 50 g of acetylene black was changed to 0.7 g. The evaluation results are shown in Table 5.

[Comparative Example 10]

0.5 g of cobalt oxide (Co ₃ O ₄ ) powder was filled in a reaction container made of quartz glass, and the container was loaded in a carbon nanofiber production device. The inside of the apparatus was made into a vacuum atmosphere, and then an inert gas (N ₂ ) was filled, and the pressure was set to 0.1 MPa, and the temperature was raised to 600°C. Then, it was replaced with reducing gas (H ₂ ) and kept for 30 minutes, and then, calcium carbide furnace gas passed through the dehydration column was introduced into the furnace and kept for 6 hours. Then replace the calcium carbide furnace gas with N ₂ and stop heating. After cooling to room temperature, open the device and recover the generated carbon nanofiber simple substance from the reaction vessel. The evaluation results are shown in Table 5.

[Comparative Example 11]

The carbon nanofibers obtained in Comparative Example 10 and acetylene black were mixed with a ball mill to obtain a mixed powder. The evaluation results are shown in Table 5.

[Comparative Example 12]

As the source gas, a gas mixed in a ratio of 70% by volume of commercially available carbon monoxide gas (99.95% purity), 15% by volume of hydrogen (99.99% purity) and 15% by volume of nitrogen (99.99% purity) was used, Other than that, a carbon composite was obtained in the same manner as in Example 24. The evaluation results are shown in Table 5.

(industrial applicability)

The CNF obtained by the production method of the present invention is filled in a matrix such as a resin as a highly conductive filler, and can be used as a composite material in various industrial fields. In addition, the carbon composite of the present invention can be used as a conductivity-imparting agent for rubber and the like, and as a conductive material for batteries such as primary batteries, secondary batteries, fuel cells, and capacitors.

(Explanation of Reference Signs)

1: carbon black; 2: carbon nanofibers.

Claims (12)

1. carbon black/carbon nano-fiber carbon complex; it is characterized in that: there is the particle of carbon black or aggregated particle as core; the surface of the top ends of carbon nano-fiber and the particle of carbon black or aggregated particle optionally links, the fibre length of carbon nano-fiber than the particle of carbon black or the length of aggregated particle long.

2. carbon complex according to claim 1, is characterized in that: carbon black is acetylene black.

3. the manufacture method of carbon complex according to claim 1, is characterized in that: by carbon nano-fiber generation catalyst loading on carbon black, and make it contact with calcium carbide furnace gas.

4. the manufacture method of carbon complex according to claim 3, is characterized in that: use the calcium carbide furnace gas eliminating moisture as raw material.

5. the manufacture method of carbon complex according to claim 3, is characterized in that: carbon nano-fiber generation catalyst is the simple substance of iron family element or the compound containing iron family element.

6. the manufacture method of carbon nano-fiber according to claim 5, is characterized in that: described iron family element is iron, cobalt or nickel.

7. the manufacture method of carbon complex according to claim 5, is characterized in that: the compound containing iron family element is oxide or the hydroxide of iron family element.

8. the manufacture method of carbon complex according to claim 3, is characterized in that: carbon nano-fiber generation catalyst is containing iron group mischmetal or containing the compound containing iron group mischmetal.

9. the manufacture method of carbon complex according to claim 8, is characterized in that: be oxide or the hydroxide containing iron group mischmetal containing the compound containing iron group mischmetal.

10. the manufacture method of carbon complex according to claim 3, it is characterized in that: after in carbon nano-fiber generating apparatus, configuration has supported the carbon black of carbon nano-fiber generation catalyst, first by reducibility gas gatherer, then calcium carbide furnace gas is imported.

The manufacture method of 11. carbon complexes according to claim 10, is characterized in that: reducibility gas is hydrogen.

12. 1 kinds of conductive compositions, is characterized in that: be filled in resin and/or rubber by carbon complex according to claim 1 and form.