JP2005225751A - Carbon material and method of producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel carbon material having a characteristic property of high volume electric resistance. <P>SOLUTION: The carbon material is insoluble in organic solvents and has peak height ratio H(B)/H(A) of 0.2 to 0.9, wherein H(A) represents height of the most intensive peak at the diffraction angle 2θ of 12°-16° and H(B) represents height of peak at the diffraction angle 2θ of 22°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a carbon material, and more particularly to a novel carbon material having a characteristic property of high volume electric resistance and different from conventional carbon materials such as carbon black.

  Carbon black, which is a typical carbon material, has functions such as light weight, heat resistance, conductivity, and chemical resistance. Conventionally, as a pigment, light stabilizer, conductivity enhancer, filler, etc. , Plastics, rubber, solvent, etc., general-purpose products such as various inks, toners, resins, tires, brakes for racing, special applications such as aircraft, ink jet, e-paper (carbon black in microcapsules) And a novel display that forms an image by using both positive and negative charging characteristics), electrodes, and conductive resins.

However, since carbon black is conductive, in order to use it in a member that requires insulation or in a field that uses chargeability, it is necessary to remove the conductivity to provide insulation. Therefore, a post-treatment process such as resin attachment for coating the surface with a resin is essential, which increases costs. Moreover, since complete coating is difficult, there is a problem that insulation is insufficient.
Japanese Patent Laid-Open No. 11-60988

  An object of the present invention is to provide a novel carbon material having a characteristic property of high volume electric resistance and different from conventional carbon black.

That is, the first gist of the present invention is that the height of the strongest peak in which the diffraction angle 2θ is in the range of 12 to 16 ° in the X-ray diffraction measurement result using the CuKα ray is H. (A), the peak height at a diffraction angle 2θ of 22 degrees is H (B), and in the Raman spectrum measurement result at an excitation wavelength of 5145 ピ ー ク, the peak intensity of band G1590 ± 20 cm ⁻¹ is I (G), and band D1340 When the peak intensity at ± 40 cm ⁻¹ is I (D), the former peak height ratio H (B) / H (A) is taken as the X axis, and the latter peak intensity ratio I (D) / I (G) When the Y axis is the Y axis, both values are (X, Y) = (0.86, 0.71), (0.65, 0.86), (0.28, 0.59) and (0.23, 0.63) It consists in the carbon material characterized.

  The second gist of the present invention is that after the raw material hydrocarbon-containing compound and the oxygen-containing gas are discharged from the discharge portion provided in the reaction furnace into the reaction furnace and burned, and then the generated soot is recovered In the method for producing a carbon material, which is brought into contact with an organic solvent, when generating the soot, an average discharge rate from the discharge portion of the raw material hydrocarbon-containing gas and the oxygen-containing gas exceeds 75 cm / sec and 1000 cm / sec or less, the pressure in the reactor is 20 to 100 Torr, and the elemental composition ratio of carbon in the raw material hydrocarbon-containing gas to oxygen in the oxygen-containing gas when the raw material hydrocarbon-containing gas burns is 0 The present invention resides in the above carbon material manufacturing method, characterized by being set in the range of 89 to 1.56.

  According to the present invention, there is provided a novel carbon material having a characteristic property of high volume electric resistance and different from conventional carbon black. Such a carbon material of the present invention is extremely promising for application to uses where a high resistance carbon material such as a color filter-on-array, which is a new technology for liquid crystal displays, is required. In addition, since it is expected to be excellent in chargeability, it is considered to be a promising material for applications utilizing the chargeability of carbon black, such as copying toner and e-paper in which carbon black is dispersed in a resin. It is done. Furthermore, it can be expected to be used as a filler in a coating composition for a member that is expected to have low thermal conductivity and requires thermal insulation.

  Hereinafter, the present invention will be described in detail. However, the description of the constituent elements described below is a representative example of embodiments of the present invention, and the present invention is not limited to these contents.

(Carbon material)
The carbon material of the present invention has a carbon content by elemental analysis of usually 90% by weight or more, preferably 95% by weight or more. The carbon material of the present invention may contain a small amount of functional groups such as, for example, a hydroxyl group and a carboxyl as in the case of carbon black. The carbon material of the present invention is usually a powder composed of aggregates of primary particles of 1 to 100 nm.

  The carbon material of the present invention is insoluble in an organic solvent. Examples of the organic solvent include aromatic hydrocarbons, aliphatic hydrocarbons, chlorinated hydrocarbons, and the like. From an industrial point of view, suitable organic solvents include those which are liquid at normal temperature and have a boiling point of 100 to 300 ° C., particularly 120 to 250 ° C. Specific examples include aromatic hydrocarbons such as benzene, toluene, xylene, methicylene, 1-methylnaphthalene, 1,2,3,5-tetramethylbenzene, 1,2,4-trimethylbenzene, and tetralin. Of these, 1,2,4-trimethylbenzene and tetralin are preferred. Further, as a property insoluble in an organic solvent, 90 weight times 1,2,4-trimethylbenzene was added to a carbon material at room temperature, sufficiently stirred and filtered, and then vacuum-dried at 150 ° C. for 10 hours. The characteristic is that the weight difference of the subsequent carbon material is usually 5% or less, preferably 3% or less, more preferably 1% or less.

  The carbon material of the present invention has a completely new internal structure that is not known in conventional carbon materials. This structure can be defined by an X-ray diffraction measurement result using CuKα rays (wavelength = 1.54Å) and a Raman spectrum measurement result at an excitation wavelength of 5145Å.

  The X-ray diffraction measurement result of the carbon material of the present invention has a peak A (a maximum point in the range of diffraction angle 2θ = 12 ° to 16 °) and a peak B (diffraction angle 2θ = 22 °). In the case of general carbon black, a diffraction peak due to 002 reflection (lattice spacing: 3.3 to 3.9 mm) is observed at a diffraction angle of 23 to 27 ° with the development of a micrographite structure. There is no peak corresponding to this in the material, or even if it exists, its intensity is weaker than the peak existing in the diffraction angle range of 12 to 16 °. The diffraction angle 2θ = 12 to 16 ° corresponds to 5.5 to 7.4 mm when converted to the lattice spacing d value. The carbon material of the present invention has a gentle periodic structure with a constant interval of about 6 to 7 mm, but is different from carbon black in that there is no micrographite structure. Therefore, the carbon material of the present invention is expected to have a characteristic property of high volume electric resistance and low thermal conductivity.

  FIGS. 2 and 3 show transmission-type electron microscope (TEM) photographs of the carbon material of the present invention in place of drawings. The carbon material of the present invention is observed as a mixed phase mainly composed of an amorphous structure having a moderate periodicity with a regular interval of about 6 to 7 mm and containing a small amount of onion structure (also referred to as bucky onion or carbon onion). . The micrographite structure confirmed with ordinary carbon black is not substantially observed. The onion structure is observed as a wide diffraction line near the diffraction angle of 22 ° in the X-ray diffraction measurement result, and is not as remarkable as the micrographite structure, but it reduces the volume electrical resistance and has an effect as a disturbing component. As an index indicating the mixing ratio of the onion structure to the amorphous structure, the peak height ratio H (B) / H (A) in the X-ray diffraction measurement result is preferably 0.9 or less, more preferably 0.5 or less. good. The lower limit is preferably 0.2 or more.

The carbon material of the present invention has peaks in band G1590 ± 20 cm ⁻¹ and band D1340 ± 40 cm ⁻¹ in the Raman spectrum measurement result at an excitation wavelength of 5145 Å. When the peak intensity of each band is I (G) and I (D), the upper limit of the peak intensity ratio I (D) / I (G) is usually 0.9, preferably 0.7, and the lower limit is usually 0. .6.

By the way, there is a peak in the band G1590 ± 20 cm ⁻¹ and the band D1340 ± 40 cm ⁻¹ , and this peak intensity ratio I (D) / I (G) is smaller than 1. It is understood that the micrographite structure (G) having a high particle size is relatively large and the edge carbon (D) is small. In the case of the carbon material of the present invention, as described above, there is no diffraction peak due to the 002 reflection at the diffraction angle of 23 to 27 ° in the X-ray diffraction measurement result, or even if it exists, the Raman spectrum of The structures observed in both the G and D bands are considered to be the aromatic plane (G) and edge carbon (D) derived from each structure derived from the amorphous structure having periodicity and the onion structure. When heterogeneous structures such as an onion structure or edge carbon are mixed, electrical conduction is likely to be caused based on these structures, so that the electrical resistance decreases. Therefore, if the conductive electrons derived from these are observed by electron spin resonance spectroscopy (EPR: Electronic Paramagnetic Resonance), the difference between the present carbon material and a conventionally known carbon material can be easily discriminated.

  Furthermore, in the carbon material of the present invention, the balance between the X-ray diffraction measurement result and the Raman measurement result described above affects the volume electric resistance. That is, the two peak intensity ratios H (B) / H (A) of the X-ray diffraction measurement result are taken as the X axis, and the two peak intensity ratios I (D) / I (G) of the Raman measurement result are taken as the Y axis. In some cases, the coordinates (X, Y) are within a range surrounded by the following four points. These four points are usually (0.86, 0.71), (0.65, 0.86), (0.28, 0.59) and (0.23, 0.63), preferably Are (0.66, 0.67), (0.52, 0.79), (0.28, 0.59) and (0.23, 0.63), more preferably (0.47, 0.63), (0.37, 0.71), (0.28, 0.59) and (0.23, 0.63). For other regions, it is presumed that the volume resistivity (volume electrical resistance) is low or the industrial value is low because it is not easy to obtain a carbon material in production. The peak height ratio H (B) / H (A) based on the X-ray diffraction measurement result and the peak intensity ratio I (D) / I (G) based on the Raman spectrum measurement result are each a physical period depending on the arrangement of carbon atoms. It shows the index of different viewpoints of the structure and the chemical defect ratio contained in a certain carbon array, and since the defect amount ratio contained in the same kind of carbon array is not necessarily constant, X and Y are It is not necessarily a linear relationship.

(Method for producing carbon material)
The carbon material of the present invention is produced by discharging a raw material hydrocarbon-containing compound and an oxygen-containing gas into a reaction furnace from a discharge portion provided in the reaction furnace, and then recovering the generated soot, and then using it as an organic solvent. It can be easily produced by a method in which impurities such as polycyclic aromatic compounds are removed from the soot by contact. Specifically, the carbon material of the present invention burns hydrocarbon-containing gas under reduced pressure in a burner flame, cools the generated soot to the vacuum pump, collects it with a dust collector such as a high-temperature heat-resistant filter, etc. The organic solvent-soluble component contained in the carbon material can be extracted and removed, filtered and dried.

  The process for producing soot is generally called a combustion method, and as an apparatus, for example, a (water-cooled) burner is installed in a decompression chamber, and the system is evacuated with a vacuum pump and continues to burn stably. A device capable of being used is used. And as said burner, the thing etc. of the structure which can implement | achieve the premixed laminar flame and diffusion flame of raw material hydrocarbon containing gas, such as benzene, and oxygen containing gas are used.

  In the present invention, when generating soot in the above combustion method, the average discharge rate from the discharge part of the raw material hydrocarbon-containing gas and the oxygen-containing gas is more than 75 cm / sec and 1000 cm / sec or less. The pressure is 20 to 100 Torr, and the elemental composition ratio of carbon in the raw material hydrocarbon-containing gas to oxygen in the oxygen-containing gas when the raw material hydrocarbon-containing gas burns is in the range of 0.89 to 1.56. It is important to set

  The upper limit of the average discharge speed (gas speed) from the discharge section when the hydrocarbon-containing gas and the oxygen-containing gas are discharged into the reaction furnace is preferably 300 cm / sec. The upper limit of the elemental composition ratio (C / O ratio) of carbon in the raw material hydrocarbon-containing gas to oxygen in the oxygen-containing gas when the raw material hydrocarbon-containing gas burns is preferably 1.05. In the carbon material manufacturing technology, controlling the C / O ratio means controlling the flame temperature. Under incomplete combustion conditions, generally, the lower the C / O ratio, the higher the maximum temperature in the flame. If the temperature is too high, the amorphous structure is converted to an onion structure, and therefore there is an optimum temperature range (that is, an optimum C / O ratio). In general, the flame has a temperature distribution in the cross-sectional direction, but the average discharge rate (gas velocity) is more than a certain level, and as a result, the temperature distribution in the cross-sectional direction in the flame becomes gentler, resulting in a uniform carbon material structure. It is estimated that there is an effect. Therefore, by satisfying the above-described flame conditions at the same time, the novel carbon material according to the present invention can be manufactured.

  In the production method of the present invention, the use of a diluent is not essential, but usually a general inert gas, particularly argon, is preferably used. The upper limit of the diluent concentration is usually 40 mol%.

  The soot produced by combustion contains impurities such as a polycyclic aromatic compound together with the novel carbon material of the present invention. Therefore, the impurities are usually removed by extraction or washing with an organic solvent. Although the organic solvent used for impurity removal is not particularly limited, the above-mentioned organic solvent insoluble in the carbon material of the present invention is preferable.

  The extraction is performed by mixing soot and an organic solvent, and then separating and recovering the carbon material from the organic solvent. As the extraction device, a stirring and mixing tank is preferably used industrially. During the extraction, the pressure in the container is not particularly limited, but is usually a normal pressure. The extraction temperature is usually in the range of 10 to 90 ° C, preferably 15 to 40 ° C, more preferably 25 to 35 ° C. The extraction time is usually in the range of 1 to 60 minutes, preferably 20 to 40 minutes. In order to shorten the extraction time, extraction may be performed while irradiating the extraction liquid with ultrasonic waves or the like as necessary. The amount of the organic solvent can be appropriately selected, but the ratio of the weight of the raw material to the organic solvent is usually 4 to 200. If there are too many organic solvents, cost will increase, and conversely, if there are too few organic solvents, the contact between the raw material and the organic solvent may not be sufficient, and extraction may not be performed sufficiently. Separation of the carbon material from the organic solvent is usually performed by one or two or more methods of vacuum filtration, pressure filtration, centrifugal separation, and sedimentation separation. In order to obtain a stable carbon material, it is preferable that the carbon material is exposed to the atmosphere after drying at 100 ° C. or lower. Specifically, it is more preferable that the separated and recovered carbon material is further dried in an inert gas and exposed to the atmosphere after the temperature becomes 100 ° C. or lower. This is because, for example, when the carbon material is heated to 110 ° C. or higher in the atmosphere (air), it is oxidized by air. Industrially preferable drying includes a material stirring type drying apparatus. Note that the above extraction operation may be repeated.

(Function of carbon material)
The carbon material of the present invention exhibits a high volume electric resistance value. For example, the volume electrical resistance in a state where 1 g of a sample is filled in a cylindrical cell having a diameter of 2 cm having four probe electrodes and a pressure of 120 kgf / cm ² is applied is usually 1 Ω · cm or more, preferably 10 Ω · cm or more. More preferably, it is 10 ⁵ Ω · cm or more.

  The carbon material of the present invention is suitable for applications requiring a high-resistance carbon material such as a color filter on array, which is a new technology for liquid crystal displays. In addition, since the carbon material of the present invention is excellent in chargeability, it can be used as an alternative to carbon black used in, for example, copying toner and e-paper. Furthermore, since the carbon material of the present invention usually has low thermal conductivity, it can be used as a filler in a coating composition for a member that requires thermal insulation.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail in an Example, this invention is not limited to a following example, unless the summary is exceeded. Evaluation of the obtained carbon material and measurement of physical properties were performed as follows.

(1) X-ray diffraction measurement:
Using “PW1700” manufactured by Philips as a device, radiation source: CuKα, output: 40 kV, 30 mA, scanning axis: θ / 2θ, measurement mode: Continuous, measurement range: 2θ = 3 to 90 °, spec width: 0.05 ° The measurement was performed under the condition of scanning speed: 3.0 ° / min.

(2) Raman spectrum measurement:
“NR1800” manufactured by JASCO Corporation was used as an apparatus, and the conditions of excitation wavelength: 5145 mm, excitation output: 5 mW or less, exposure time: 50 seconds, number of integrations: 2 times were measured as a backscattering arrangement. Then, a straight baseline was drawn in the range of 1740 to 1165 cm ⁻¹ , and the height to the peak top was determined to obtain the peak intensity.

(3) Volumetric electrical resistance measurement:
Measurement was performed using a powder resistance measurement system “MCP-PD51” manufactured by Dia Instruments. The sample was crushed with a ball mill and subjected to measurement. 1 g of the above ground sample is set in a cylindrical cell having a diameter of 2 cm having four probe electrodes, and the thickness and resistance value of the sample are measured with a pressure of 120 kgf / cm ² applied to the sample. The electric resistance (Ω · cm) was calculated.

(Example 1)
A device in which a premixed water-cooled burner was installed in a vacuum chamber was used. While the system was evacuated with a vacuum pump, the raw material (toluene) and oxygen were premixed and supplied to the burner to generate a stable laminar flame. Combustion was performed under the conditions of C / O ratio: 1.01, combustion chamber pressure: 40 torr, gas flow rate: 76 cm / sec, and no argon dilution. The generated soot was cooled to 400 to 500 ° C. by piping led to a vacuum pump. The generated soot was collected by a bag filter installed in front of the vacuum pump.

  Weigh 10.30 g of sputum collected in a 1 L volumetric flask, add 286.2 g of tetralin to this, stir while applying ultrasonic waves at room temperature for 30 minutes, and then vacuum filter with a 0.45 μm pore size filter. Solute was removed. After removing the soluble content by tetralin three more times, it was dried under reduced pressure at 150 ° C. for one day, and after cooling to 100 ° C. or lower, it was exposed to the atmosphere to obtain 9.27 g of black powder (by this method) The obtained carbon material is referred to as “the present carbon material”). The carbon yield after solvent extraction was 90%.

  Since 889 g of 1,2,4-trimethylbenzene was added to 9.60 g of the present carbon material at room temperature, and after sufficiently stirring and filtering, the weight after vacuum drying at 150 ° C. for 10 hours was 9.60 g. The carbon material was confirmed to be substantially insoluble in organic solvents. The elemental analysis values of the carbon material were a carbon content of 97% by weight and an oxygen content of 2.4% by weight. This carbon material was an aggregate of primary particles of several nm to 100 nm.

This carbon material has a strong peak (A) in the vicinity of a diffraction angle of 14 ° in X-ray diffraction, and the height ratio H (B) / H (A) between this peak and a peak (B) at a diffraction angle of 22 ° is calculated. It was 0.38. The graphite peak around 23-27 ° was found to be very weak and substantially amorphous (see FIG. 4). In the Raman spectrum (see FIG. 5), there are peaks at 1580 cm ⁻¹ and 1330 cm ⁻¹ , and when the peak intensity ratio I (D) / I (G) is calculated, it is 0.63 and coordinates (X, Y) = (0.38, 0.63). Moreover, the volume electrical resistance of this carbon material was 8.9 × 10 ⁵ Ω · cm (value at a pressure of 120 kgf / cm ² ).

(Examples 2 to 5)
A carbon material was obtained in the same manner as in Example 1 using the conditions shown in Table 1. Table 1 shows the physical property values of the obtained carbon material. Further, the volume electric resistance (value at a pressure of 120 kgf / cm ² ) of the obtained carbon material was as shown in Table 1. However, in Example 3, the operating conditions were significantly changed from those in Example 5 which was the previous experiment. That is, the flow rate was decreased from 305 to 76 cm / sec, and the C / O ratio was decreased from 1.15 to 1.01. In Examples 1 to 5, samples were taken 6 hours after the start of each experiment.

(Reference Example 1)
X-ray diffraction, Raman spectrum, and volume electric resistance were measured for commercially available carbon black (trade name: CF9, manufactured by Mitsubishi Chemical Corporation). In X-ray diffraction, there was a strong peak near a diffraction angle of 23 to 27 ° (see FIG. 6). The Raman spectra peak exists in 1590 cm ^-1 and 1360 cm ^-1 (see FIG. 7), I (D) / I (G) was 0.78. The volume electrical resistance was 1 Ω · cm (value at a pressure of 120 kgf / cm ² ).

The figure which shows the structure range of the novel carbon material of this invention prescribed | regulated from X-ray-diffraction measurement result: H (B) / H (A) and Raman spectrum measurement result: I (D) / I (G) Transmission-type electron micrograph of the amorphous structure of the novel carbon-based material of the present invention instead of a drawing (5.0 nm scale is shown in the photograph) Transmission-type electron micrograph of the amorphous structure of the novel carbon-based material of the present invention in place of a drawing (2.0 nm scale is shown in the photograph) X-ray diffraction chart of the novel carbon-based material of the present invention Raman spectrum of the novel carbon-based material of the present invention X-ray diffraction chart of commercially available carbon black Raman spectrum of commercial carbon black

Claims (8)

  The height of the strongest peak between the diffraction angle 2θ of 12 to 16 ° in the X-ray diffraction measurement result using CuKα ray is H (A) and the diffraction angle 2θ is 22 °. A carbon material, wherein the peak height ratio H (B) / H (A) is 0.2 or more and 0.9 or less when the peak height is H (B). The height of the strongest peak between the diffraction angle 2θ of 12 to 16 ° in the X-ray diffraction measurement result using CuKα ray is H (A) and the diffraction angle 2θ is 22 °. In the Raman spectrum measurement result at an excitation wavelength of 5145 Å with the peak height being H (B), the peak intensity of the band G1590 ± 20 cm ⁻¹ is I (G), and the peak intensity of the band D1340 ± 40 cm ⁻¹ is I (D ), The peak height ratio H (B) / H (A) is on the X axis and the peak intensity ratio I (D) / I (G) is on the Y axis. In the coordinates shown, (X, Y) = (0.86, 0.71), (0.65, 0.86), (0.28, 0.59) and (0.23, 0.63) A carbon material characterized by being in a range surrounded by four points.   In the coordinates shown in FIG. 1, (X, Y) = (0.47, 0.63), (0.37, 0.71), (0.28, 0.59) and (0.23, 0. 63) The carbon material according to claim 2, which is within a range surrounded by four points. The volumetric electric resistance in a state where 1 g of carbon material is filled in a cylindrical cell having a diameter of 2 cm having four probe electrodes and a pressure of 120 kgf / cm ² is applied is 1 Ω · cm or more. The carbon material as described in 1.   As a property insoluble in an organic solvent, after adding 90 weight times 1,2,4-trimethylbenzene to a carbon material at room temperature, stirring, filtering, and then vacuum drying at 150 ° C. for 10 hours, The carbon material according to any one of claims 1 to 4, which has a characteristic that a weight difference is 5% or less.   A method for producing a carbon material in which a raw material hydrocarbon-containing compound and an oxygen-containing gas are discharged into a reaction furnace from a discharge portion provided in the reaction furnace and burned, and then the generated soot is recovered and then contacted with an organic solvent. In producing the soot, the average discharge rate from the discharge part of the raw material hydrocarbon-containing gas and the oxygen-containing gas is more than 75 cm / sec and 1000 cm / sec or less, and the pressure in the reactor is 20 to 100 Torr, the elemental composition ratio of carbon in the raw material hydrocarbon-containing gas to oxygen in the oxygen-containing gas when the raw material hydrocarbon-containing gas burns is set in the range of 0.89 to 1.56. The manufacturing method of the carbon material in any one of Claims 1-5.   The average discharge speed exceeds 75 cm / sec and is 300 cm / sec or less, and the elemental composition ratio of carbon in the raw material hydrocarbon-containing gas to oxygen in the oxygen-containing gas when the raw material hydrocarbon-containing gas burns is 0. The manufacturing method of the carbon material of Claim 6 which is the range of 89-1.05.   The method for producing a carbon material according to claim 5, wherein the carbon material is exposed to the atmosphere after being brought to 100 ° C. or less after being contacted with an organic solvent.

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