JP2007302520A - Carbon microsphere and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon microsphere having large particle size in which the size of particle agglomerates is made small and the width of a particle size distribution of the particle agglomerates is made narrow and which can be used suitably as, for example, a black fine particle to be used in electronic paper or a black matrix, a PTC element, a semiconductor sealant, an anode material of a lithium secondary battery or the like. <P>SOLUTION: The carbon microsphere has 150-450 nm arithmetical mean primary particle diameter measured by an electron microscope and such an agglomerated particle characteristic that the ratio ΔDst/Dst of the half-value width ΔDst indicating the distribution characteristics of particle agglomerates to the Stokes mode diameter Dst of particle agglomerates, which are measured by a disc centrifuge (DCF), is 0.40-0.85, and satisfies an expression: N<SB>2</SB>SA<6,000/(Dst×1.85)+5 (wherein N<SB>2</SB>SA is the specific surface area measured by adsorbing nitrogen; and Dst is the Stokes mode diameter of particle agglomerates). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a black pigment consisting of black fine particles used for electronic paper and black matrix, or a single agglomeration of spherical particles which is suitably used for PTC elements, semiconductor encapsulants, negative electrode materials for lithium secondary batteries, etc. The present invention relates to a carbon microsphere having a particle shape close to a sphere, and having a narrow distribution width of aggregated particles and a sharp distribution property.

  Carbon black is known as a fine carbon microsphere. Carbon black is consumed in large quantities as a reinforcing material for rubber, including tires, and is widely used for other applications such as colorants, pigments, and paints. The types of carbon black are generally classified according to the production method, and are roughly classified into an incomplete combustion method of raw material hydrocarbons and a thermal decomposition method.

  Of these, the oil furnace method, one of the incomplete combustion methods, uses coal-based or petroleum-based hydrocarbon feedstock as the raw material, introduces liquid or gaseous fuel and a large amount of air into a special reactor, The hydrocarbon feedstock is injected into the high-temperature combustion gas formed by complete combustion and continuously supplied in the form of a mist to burn a portion of the feedstock, and the remaining most of the hydrocarbon feedstock is carbon black. It is pyrolyzed to hydrogen.

  The oil furnace black produced by this oil furnace method is capable of producing a carbon black having a particle property over a wide range and is easily mass-produced.

  And, the furnace black for rubber is classified according to the particle diameter, and the particle diameter ranges widely from 11 to 19 nm of SAF grade carbon black to 61 to 100 nm of SRF grade carbon.

  Oil furnace black has a complex agglomeration structure in which fine spherical basic particles are branched in an irregular chain from the formation process, and usually several to several tens of basic particles are fusion-bonded. It consists of a three-dimensional structure. This three-dimensional structure is called a structure, and its size is evaluated by the DBP absorption amount.

  It is impossible to unravel this agglomerated structure and separate it into the individual basic particles that make up the structure because the basic particles are firmly fused and bonded. A particle-shaped carbon sphere cannot be obtained.

  In addition, thermal black obtained by pyrolyzing hydrocarbon raw materials is a thermal storage chamber type cracking furnace in which refractory bricks are stacked in a checkered form, and pyrolyzes carbon and hydrogen using natural gas as raw materials. Is characterized in that carbon black having a large particle diameter can be obtained, the development of the structure is small, the DBP absorption is small, that is, the aggregate structure of the carbon black particles is small. For example, the arithmetic average primary particle diameter of FT class carbon black is 101 to 200 nm, the DBP absorption is 30 to 50 ml / 100 g, the arithmetic average primary particle diameter of MT class carbon black is 180 to 500 nm, and the DBP absorption is 30 to It is about 50 ml / 100 g. Therefore, it can be said that the aggregated structure in which the particles are bonded is relatively small, and the carbon sphere has a large particle diameter exceeding 101 nm.

  On the other hand, channel blacks that are useful as pigments for inks, paints, etc. are fine particles with an arithmetic average primary particle size of about 10 to 20 nm, a high structure, and a large aggregate structure in which many carbon black fine particles are bonded. It is very different from a single particle shape.

  It is extremely difficult to produce thermal black having such particle characteristics by directly applying the oil furnace manufacturing technique. Therefore, the present applicant, as a production technique of carbon black having particle properties equivalent to thermal black, uses gaseous hydrocarbons that are thermally decomposed by an endothermic reaction as raw materials, and the raw material gas is supplied in a reducing atmosphere at a supply concentration of 5 to 50 vol%. A manufacturing method (Patent Document 1) was developed in which a gas stream was fed into an externally heated reactor held in a reactor and pyrolyzed at a temperature of 1400 ° C. or higher in a laminar flow with a Reynolds number of 2300 or less.

However, the carbon black obtained by this production technique has a property that the aggregated particles are easily developed although the produced particles collide and the specific surface area is low due to the high linear flow velocity.
In addition, this production method has a high thermal decomposition temperature and a low carbon black production yield at low temperatures. As an improvement technique, a liquid or solid hydrocarbon raw material is heated and vaporized at room temperature, and the vaporized hydrocarbon raw material gas is kept in an oxygen-free atmosphere at a gas concentration of 0.01 to 2.0 vol% together with a carrier gas. A method for producing carbon black (Patent Document 2) was proposed, which was introduced into a thermal pyrolysis furnace and thermally decomposed by heating to a temperature of 1000 to 1400 ° C. By this method, carbon black having particle properties equivalent to thermal black having an arithmetic average primary particle size of 160 to 500 nm and a DBP absorption of 40/100 g or less can be produced. However, since the gas concentration is low, the productivity is low, and the particle size distribution of the particle aggregate is broadened.

Therefore, the present applicant has further researched and proposed a carbon microsphere which is designed to suppress the broadening of the particle size distribution of the particle aggregates and to develop a carbon microsphere with a narrow particle size distribution width and small variation. did. That is, in Patent Document 3, the arithmetic average particle diameter dn measured by an electron microscope is 20 to 150 nm, and s / dn indicating the degree of variation is 0.1 to 0.3 (where s is a standard deviation of dn). There are disclosed carbon microspheres having particle properties in which the ratio Dst / dn of Stokes mode diameter Dst indicating the size of particle aggregates to arithmetic average particle diameter dn is 1.2 or less, and a method for producing the same.
JP 07-034001 A Japanese Patent Laid-Open No. 10-168337 JP 2004-211012 A

  In the production method of Patent Document 3, hydrogen gas is used as a carrier gas, and raw material hydrocarbon gas is supplied to a pyrolysis furnace together with hydrogen gas. This mixed gas is slowly pyrolyzed at a relatively low temperature, and the particle size distribution is sharp. A carbon microsphere having a small particle aggregation structure and a substantially single spherical shape is produced.

  However, this method has a difficulty that it is difficult to obtain a larger particle having an arithmetic average particle diameter of 20 to 150 nm, which is smaller than that of MT grade thermal black. In addition, the thermal decomposition reaction of the raw material hydrocarbon gas is suppressed by hydrogen gas, and the formation of particle aggregates is prevented by reducing the chance of fusion bonding of carbon particles. In addition, there is a problem that it is difficult to proceed completely, and there is a problem that tar-like undecomposed carbonaceous matter remains on the surface of the obtained carbon microspheres. Residue of the undecomposed carbonaceous matter may be fatal depending on the use, and there is a problem that the yield of carbon microspheres is low. In addition, since the hydrogen atmosphere is on the surface of the carbon microsphere, the progress of the dehydrogenation reaction in the carbonization process is also hindered, so the carbon microsphere has a large specific surface area. If not, it can be considered.

  An object of the present invention is to solve the above-mentioned problems and to provide carbon microspheres having a primary particle having a large particle diameter, a narrow particle aggregate distribution width, and a small specific surface area.

  The carbon microspheres can be suitably used, for example, as a black pigment made of black fine particles used for electronic paper or black matrix, a PTC element, a semiconductor encapsulant, a negative electrode material for a lithium secondary battery, or the like.

In order to achieve this object, the carbon microsphere according to claim 1 of the present invention has an arithmetic average primary particle diameter dn of 150 to 450 nm by an electron microscope, and a Stokes mode diameter of a particle aggregate measured by a disk centrifuging apparatus (DCF). The ratio ΔDst / Dst between Dst and the half-value width ΔDst indicating the distribution property of the particle aggregate has an aggregate particle property of 0.40 to 0.85, the nitrogen adsorption specific surface area (N ₂ SA) and the Stokes of the particle aggregate A structural feature is that the mode diameter Dst satisfies the relationship of N ₂ SA <6000 / (Dst × 1.85) +5.

In addition, the carbon microsphere according to claim 2 of the present invention has an arithmetic average primary particle size dn measured by an electron microscope of more than 450 nm and 1000 nm or less, and a Stokes mode diameter Dst of the particle aggregate measured by a disk centrifuging device (DCF) and particles. The ratio ΔDst / Dst to the half-value width ΔDst indicating the distribution property of the aggregate has an aggregate particle property exceeding 0.80, and the nitrogen adsorption specific surface area (N ₂ SA) and the Stokes mode diameter Dst of the particle aggregate are A structural feature is that the relationship of N ₂ SA <6000 / (Dst × 1.85) +5 is satisfied.

  In the method for producing carbon microspheres according to claim 1, the hydrocarbon gas is introduced into the externally heated reactor together with the inert carrier gas, the furnace temperature is 1000 ° C. to 1400 ° C., and the hydrocarbon gas concentration is 10 to 10. It is a structural feature that pyrolysis is performed under the conditions of 50 vol% and a linear flow rate of hydrocarbon gas of 0.02 to 4.0 m / sec.

  The method for producing carbon microspheres according to claim 2 is characterized in that, in addition to the production method according to claim 3, the hydrocarbon gas source gas is introduced again from the rear stage portion of the external heating reactor. And

  The carbon microspheres of the present invention are composed of black fine particles used for, for example, electronic paper and black matrix, because they have little aggregation of spherical particles, and also have a narrow distribution width, sharp distribution, and small specific surface area. It can be suitably used as a black pigment, or directly used as a PTC element, a semiconductor encapsulant, a negative electrode material of a lithium secondary battery, or after being treated by an appropriate method such as surface treatment or heat treatment. .

  The first carbon microsphere according to the present invention has a basic particle size larger than that of a conventional carbon microsphere, and an arithmetic average primary particle size dn measured by an electron microscope is 150 to 450 nm. And the arithmetic average primary particle size comparable to that of thermal black obtained in the past. In addition, the arithmetic average primary particle diameter dn (nm) by an electron microscope is measured by the following method.

  After the sample is dispersed in chloroform for 30 seconds at a frequency of 28 kHz by an ultrasonic disperser, the dispersed sample is fixed to a carbon support membrane (for example, “Powder Physical Properties”, edited by the Powder Engineering Society p68 (c) “Water surface membrane method” "by). This was directly photographed with an electron microscope at a magnification of 10,000 times and a total magnification of 100,000 times, and the diameter of 1000 carbon particles was randomly measured from the obtained photo, and the arithmetic average primary particles were divided from each 14 nm and created. Find the diameter.

  Further, the carbon microspheres of the present invention have a narrow particle aggregate distribution width and a sharp particle size distribution, and the ratio ΔDst / Dst between the half-value width ΔDst and Dst indicating the distribution property of the particle aggregate is 0.00. It has an aggregate particle property of 40 to 0.85. The Stokes mode diameter Dst (nm) and its half-value width ΔDst (nm) are measured by the following method.

The dried carbon microspheres are mixed with a 20 vol% aqueous ethanol solution containing a small amount of a surfactant to prepare a dispersion having a carbon content of 0.1 kg / m ³ , and this is sufficiently dispersed with ultrasound to prepare a sample. . Set disk centrifuge apparatus (manufactured by UK Joyes Lobel Ltd.) to the speed of 100 s ^-1, spin solution (2 wt% glycerine aqueous solution, 25 ° C.) a After addition 0.015dm ^3, 0.001dm ³ of buffer solution ( 20 vol% ethanol aqueous solution, 25 ° C.). Next, after adding 0.0005 dm ³ of carbon dispersion liquid at a temperature of 25 ° C. with a syringe, centrifugal sedimentation was started, and simultaneously the recorder was operated, and the distribution curve (horizontal axis; carbon dispersion liquid was added with a syringe). Elapsed time, vertical axis; absorbance at a specific point changed with centrifugal sedimentation of the carbon sample). Each time T is read from this distribution curve and substituted into the following equation (Equation 1) to calculate the Stokes equivalent diameter corresponding to each time.

In Equation 1, η is the viscosity of the spin liquid (0.935 × 10 ⁻³ Pa · s), N is the disk rotation speed (100 s ⁻¹ ), r ₁ is the radius of the carbon dispersion injection point (0.0456 m), r ₂ is the absorbance radius to the measurement point (0.0482m), ρ _CB is the density of carbon ^{(kg / m 3), ρ} 1 is the density of the spin fluid (1.00178kg / ^{m 3).}

  The maximum Stokes equivalent diameter in the Stokes equivalent diameter and absorbance distribution curve (FIG. 2) thus obtained is the Stokes mode diameter Dst (nm). The difference (half-value width) of the Stokes equivalent diameter is taken as ΔDst (nm).

  Conventionally obtained thermal black grade carbon black has a ratio ΔDst / Dst of the Stokes mode diameter Dst of the particle aggregate to the half width ΔDst indicating the distribution property of the particle aggregate exceeding 0.90. The carbon microspheres of the present invention have an aggregated particle property in which the ratio ΔDst / Dst of the half-value width ΔDst to Dst indicating the distribution property of the particle aggregate is 0.40 to 0.85, and the particle size distribution is sharp. Is shown. In addition, what the ratio (DELTA) Dst / Dst is less than 0.40 is not confirmed by the manufacturing method which concerns on this invention. The ratio between the Stokes mode diameter Dst of the particle aggregate, which is an index indicating the independence of the particles, and the arithmetic average primary particle diameter dn is particularly preferably 1.20 to 1.3, which is about the same as that of thermal black. A value of 20 to 2.0 may be used.

In general, assuming that the particle has no irregularities on the surface and is a true sphere, the nitrogen adsorption specific surface area (N ₂ SA) and the particle size can be expressed by the following relational expression.
N ₂ SA (m ² / g) = 6000 / {arithmetic average primary particle size (nm) × specific gravity (g / cm ³ )}
On the other hand, the carbon microspheres of the present invention have the following relationship in the nitrogen adsorption specific surface area (N ₂ SA) and the Stokes mode diameter Dst (nm):
N ₂ SA <6000 / (Dst × 1.85) +5
It has a property close to an ideal spherical property with small surface irregularities.

Therefore, the carbon microspheres of the present invention have an agglomerated particle diameter (Dst mode diameter) with a sharp particle size distribution as described above, and have properties that are relatively monospherical and approximate to a true sphere, and small surface irregularities. It has a small property, that is, a specific surface area. When the value of ΔDst / Dst is large and the distribution width is broad, particles smaller than the aggregated particle diameter Dst mode diameter increase and the specific surface area may take a large value. In addition, when carbon microspheres are produced by a method using hydrogen gas as a carrier gas, the progress of the dehydrogenation reaction in the carbonization process is hindered. In order to become, it becomes the relationship of the following formula.
N ₂ SA <6000 / (Dst × 1.85) +5

The specific surface area and true specific gravity are measured as follows.
Specific surface area (N ₂ SA); m ² / g
According to ASTM D3037-78 “Standard Methods of Testing Carbon Black Surface Area by Nitrogen Adsorption” Method B with nitrogen as the adsorption gas. The measured value of IRB # 5 by this method was 80.3 m ² / g.

-True specific gravity or carbon density ((kg / m ³ ))
In accordance with the Japanese Industrial Standard “Method for Measuring Particle Density of Fine Ceramics Powder (JIS R1620-1995)”, it is obtained by measuring by a pycnometer method. That is, after first drying in an air bath at 200 ° C. for 1 hour, a sample cooled to room temperature in a desiccator is prepared. Subsequently, a sample of about 4 g is collected in a specific gravity bottle, completely immersed in a small amount of 1-butanol, and then no bubbles are observed under a vacuum of 5 Torr (6.65 × 10 ² Pa) or less. Degas under vacuum. Next, 1-butanol is filled in the specific gravity bottle to a predetermined liquid amount, and the mass at that time is measured. The true specific gravity value is calculated by the following equation.
(True specific gravity value) = ρ ₁ × (m _P2 −m _P1 ) / [(m _P4 −m _P1 ) − (m _P3 −m _P2 )]
However, in the above formula,
ρ ₁ : Specific gravity of immersion liquid (1-butanol) at measurement temperature
m _P1 : Mass of the measurement container (specific gravity bottle) m _P2 : Mass when the sample is put in the measurement container m _P3 : Mass when the sample and the immersion liquid are put in the specified amount of the measurement container m _P4 : The immersion liquid is the measurement container This is the mass when a specified amount of is added.
The measurement was performed at room temperature (20 to 30 ° C.), and the specific gravity of the immersion liquid was obtained by linearly interpolating the literature values shown below, and this was used for the calculation of the true specific gravity value.
(Specific gravity of 1-butanol at 20 ° C.) = 0.8096 (Specific gravity of 1-butanol at 30 ° C.) = 0.8021

  The second carbon microsphere according to the present invention is intended for a carbon microsphere having a larger particle diameter than the first carbon microsphere, that is, a carbon sphere having an arithmetic average primary particle diameter dn of more than 450 nm by an electron microscope. The ratio ΔDst / Dst of the Stokes mode diameter Dst of the particle aggregate measured by a disc centrifuging apparatus (DCF) to the half-value width ΔDst indicating the distribution property of the particle aggregate has an aggregated particle property exceeding 0.80. And

  When the arithmetic average primary particle diameter dn is increased, the distribution of particle aggregates is likely to be widened, and in a large particle diameter where dn exceeds 450 nm, the aggregated particles having a value of ΔDst / Dst exceeding 0.80 indicating the distribution properties of the particle aggregates. It has properties. However, it is desirable that the arithmetic average primary particle diameter dn is 1000 nm or less and ΔDst / Dst is 1.10 or less. The arithmetic average primary particle diameter dn was excluded because it was not confirmed by the production method according to the present invention that the average particle diameter dn exceeded 1000 nm. Further, the ratio between the Stokes mode diameter Dst of the particle aggregate, which is an index indicating the independence of the particles, and the arithmetic average primary particle diameter dn is particularly preferably 1.20 to 1.3 which is the same as that of the thermal black. A value of 20 to 2.0 may be used.

Further, the second carbon microsphere according to the present invention has the following relationship in the nitrogen adsorption specific surface area (N ₂ SA) and the Stokes mode diameter Dst (nm):
N ₂ SA <6000 / (Dst × 1.85) +5
However, N ₂ SA ≧ 6000 / (Dst × 1.85}
1.85 is the true specific gravity of the carbon microsphere.
It has a property close to an ideal spherical property with small surface irregularities.

Therefore, the carbon microspheres of the present invention have an agglomerated particle diameter (Dst mode diameter) with a sharp particle size distribution as described above, and have properties that are relatively monospherical and approximate to a true sphere, and small surface irregularities. It has a small property, that is, a specific surface area. When the value of ΔDst / Dst is large and the distribution width is broad, particles smaller than the aggregated particle diameter Dst mode diameter increase and the specific surface area may take a large value. In addition, when carbon microspheres are produced by a method using hydrogen gas as a carrier gas, the progress of the dehydrogenation reaction in the carbonization process is hindered. In order to become, it becomes the relationship of the following formula.
N ₂ SA ≧ 6000 / {(Dst-80) × 1.85} +5

  When the carbon microspheres of the present invention having such particle properties are used as, for example, black pigment fine particles for electrophoretic electronic paper, the aggregated particles have a sharp particle size distribution. Since non-uniformity of the electrophoresis speed is less likely to occur, display blurring is prevented and the sharpness is improved.

  In addition, for example, when used as a black pigment for a black matrix, if the particle size distribution of the aggregated particles is broad, the gaps between the particles are increased, so that the light shielding property is deteriorated. According to this, since the particle size distribution is sharp, it is possible to effectively prevent the deterioration of the light shielding property.

  In addition, according to the carbon microspheres of the present invention, for example, it can be suitably used as a filler for black pigments, rubbers and resins such as PTC elements, semiconductor encapsulants, and negative electrode materials for lithium secondary batteries, and the like. It is extremely useful in the industrial field.

  These carbon microspheres are produced by gasifying hydrocarbons as raw materials, feeding them into an externally heated furnace together with an inert carrier gas excluding hydrogen gas, and pyrolyzing the hydrocarbon gas.

  Hydrocarbon gases include aliphatic hydrocarbons such as methane, ethane, propane, butane, ethylene, propylene, and butadiene, monocyclic aromatic hydrocarbons such as benzene, toluene, and xylene, and polycyclic aromatics such as naphthalene and anthracene. Group hydrocarbons, natural gas, city gas, liquefied natural gas, liquefied petroleum gas, etc. can be used. When the raw material hydrocarbon is liquid or solid at room temperature, it is vaporized by heating and used in a gaseous state .

  As the inert carrier gas, an inert gas that is stable and does not react at the time of thermal decomposition of hydrocarbon gas is used except hydrogen gas, and examples thereof include gases such as nitrogen, argon, helium, neon, xenon, krypton, etc. The Nitrogen gas, argon gas, and helium gas are preferable.

  In this case, since the inert carrier gas promotes the thermal decomposition reaction of the hydrocarbon gas, thermal decomposition at a lower temperature, that is, 1000 to 1400 is possible. Moreover, it becomes a carbon microsphere with few surface irregularities and a small specific surface area. In addition, the production yield is improved and the production efficiency is improved. Furthermore, since the carbon microspheres of the present invention have a large particle diameter, the linear flow velocity is slowed to grow the particles, and the thermal decomposition reaction is performed under relatively mild conditions. On the other hand, when hydrogen gas is used as the carrier gas, the thermal decomposition reaction of hydrocarbon gas is suppressed, so that the progress of the dehydrogenation reaction in the carbonization process is hindered on the surface of the carbon microsphere, and the surface unevenness is large. It becomes a carbon microsphere with a large surface area. In addition, the production yield is lowered and the production efficiency is deteriorated. In addition, tar-like carbon components in an undecomposed decomposition process in which hydrocarbons are polymerized are likely to remain, and depending on the application, it is necessary to perform heat treatment, which also deteriorates production efficiency. In addition, however, when the linear flow rate is slowed, tar-like carbon content tends to remain.

  The carbon microspheres of the present invention are manufactured by supplying raw material hydrocarbon gas together with an inert carrier gas to an external heating furnace and pyrolyzing. In this case, the temperature during the pyrolysis, the furnace By adjusting the linear velocity of hydrocarbon gas passing through the inside, the ratio (raw material concentration) of hydrocarbon gas and inert carrier gas, the arithmetic average primary particle diameter dn of carbon microspheres, the Stokes mode of particle aggregates A ratio ΔDst / Dst between the diameter Dst and the half-value width ΔDst and Dst can be controlled.

  For example, the carbon microspheres according to claim 1 maintain the temperature during pyrolysis at 1000 to 1400 ° C., preferably 1050 ° C. to 1350 ° C., the raw material concentration of hydrocarbon gas passing through the furnace is 10 to 50 vol%, and the linear velocity Can be produced by setting 0.02 to 4.0 m / sec, preferably 0.04 to 2.0 m / sec.

  The arithmetic average primary particle diameter dn can be reduced by increasing the temperature. Further, the Stokes mode diameter Dst of the particle aggregate can be increased by increasing the raw material concentration. Furthermore, the ratio ΔDst / Dst between the Stokes mode diameter Dst and the half-value width ΔDst and Dst of the particle aggregate decreases as the linear velocity decreases, and a sharp particle distribution state can be obtained. These conditions are set as appropriate.

  When the thermal decomposition temperature is lower than 1000 ° C., the hydrocarbon gas raw material gas is not carbonized and goes out of the furnace as droplets, and carbon microsphere powder cannot be obtained. When the temperature exceeds 1400 ° C., it is difficult to obtain a sharp particle distribution because the carbonization reaction of the raw material hydrocarbon gas is fast. Moreover, when the linear flow rate exceeds 4.0 m / sec, the flow of the raw material gas becomes less uniform and the particle size distribution becomes wide, and a sufficient residence time of the raw material gas cannot be obtained and the thermal decomposition reaction is not performed. Since the progress is not sufficient, unburned content (reaction intermediate with insufficient carbonization) increases. If it falls below 0.02 m / sec, the adhesion of the powder to the reaction tube wall becomes remarkable, and it becomes easy to cause clogging of the path, making it difficult to manufacture. 10-50 vol% is suitable for the density | concentration to the total gas amount of the raw material gas of hydrocarbon. When it is less than 10 vol%, the powder adheres to the reaction tube wall, although it is necessary to reduce the linear flow velocity. On the other hand, if it exceeds 50 vol%, it is difficult for a uniform reaction to proceed, and it is difficult to obtain a sharp particle distribution, and the reaction tube is blocked.

  Furthermore, in order to achieve a particle size exceeding 450 nm with the carbon microspheres according to claim 2, a furnace in which the temperature at the time of pyrolysis of the raw material gas of hydrocarbon gas is maintained at 1000 to 1400 ° C, preferably 1050 ° C to 1350 ° C. The raw material concentration of the hydrocarbon gas passing through the inside is set to 10 to 50 vol%, the linear velocity is set to 0.02 to 4.0 m / sec, preferably 0.04 to 2.0 m / sec. After the raw material gas has passed through the heating zone in the external heating reactor, it is manufactured by a method of introducing the raw material gas of hydrocarbon gas again. The hydrocarbon gas source gas introduced first is thermally decomposed to produce carbon microspheres with an arithmetic average primary particle size of 150 to 450 nm. However, the concentration of hydrocarbon gas feedstock is dilute with the formation of carbon microspheres. Thus, it is difficult to supply carbon necessary for grain growth. Thus, by introducing the hydrocarbon gas source gas again after the heater exit, the particle size growth will continue. The amount of the hydrocarbon gas source gas to be reintroduced is adjusted from 50% to 100% with respect to the amount of the hydrocarbon gas source gas initially introduced. The ratio is changed as needed according to the primary particle size.

  FIG. 3 is an explanatory view illustrating the overall configuration of an apparatus for producing the carbon microspheres of the present invention. In FIG. 3, 11 is a gas cylinder filled with a hydrocarbon source gas (for example, methane gas), 12 is a gas cylinder filled with an inert carrier gas (for example, nitrogen gas), and 13 is a flow meter. Reference numeral 14 denotes a raw material tank that stores a liquid hydrocarbon raw material, and stores, for example, toluene in a liquid state. 15 is an apparatus for preheating the liquid hydrocarbon raw material, and the liquid raw material gas is vaporized by preheating. The heating furnace 17 is a heating furnace for thermally decomposing hydrocarbon gas as a raw material and converting it into carbon microspheres. For example, the heating furnace 17 is an opaque quartz tube having an inner diameter of 145 mm and a length of 1500 mm. A heat generation source 18 is installed. As the external heating method, a high frequency induction heating method, an electrothermal heating method, or a method of flowing a combustion gas is applied. The inside of the heating furnace 17 is previously deoxygenated by a vacuum pump 22 or is replaced with an inert gas.

  In the heating furnace 17, in order to control the flow rate of the mixed gas, heat-resistant tubes made of, for example, mullite or silicon carbide having different reaction tube diameters can be inserted. The same can be done by arbitrarily changing the flow rates of the source gas 11 and the carrier gas 12. In the case of producing carbon microspheres having an arithmetic primary average particle diameter exceeding 450 nm, a raw material gas is inserted after the heater exit. The temperature in the furnace is detected by a thermocouple or a radiation thermometer and controlled to a predetermined temperature by a temperature controller 19. The cracked gas containing the carbon microspheres after pyrolysis is cooled by the cooling pipe 20, and after separating and collecting the carbon microspheres in the collection chamber 23, the cracked gas is completely burned by the combustion device 25 via the water tank 24. Are discharged outside the system.

  Hereinafter, the present invention will be specifically exemplified.

Example 1
With the apparatus shown in FIG. 3, methane gas is used as the source hydrocarbon gas, nitrogen gas is used as the carrier gas, the pyrolysis temperature is 1350 ° C., the source gas concentration is 20 vol%, and the linear velocity of methane passing through the furnace. Was set to 0.75 m / sec and pyrolyzed for 2 hours to produce carbon microspheres.

Examples 2-7, Comparative Examples 1-5
Using methane gas, propane gas, butane gas, and toluene gas vaporized as the raw material hydrocarbon gas, the pyrolysis temperature, the raw material gas concentration, and the linear velocity of the raw material hydrocarbon gas passing through the furnace are changed to 2 respectively. Carbon microspheres were produced by pyrolysis for a period of time.

For these carbon microspheres, the arithmetic average primary particle diameter dn was measured with an electron microscope, the Stokes mode diameter Dst and the half-value width ΔDst of the aggregate were measured with a disc centrifuging device, and the toluene coloring permeability LT, nitrogen adsorption specific surface area (N ₂ SA) was also measured. Furthermore, the weight of the carbon microspheres discharged outside the furnace was measured to calculate the yield. The obtained results are shown in Table 1. In addition, toluene coloring transmittance | permeability LT was measured as follows. It is measured by the method described in Item 8B of JIS K6218: 1997, and is expressed as the transmittance of the sample when the transmittance of pure toluene is 100%. A larger number means a lower degree of toluene contamination, that is, a smaller amount of undecomposed aromatic hydrocarbon components.

(Table note)
a value = 6000 / (Dst × 1.85) +5
Reference Example 1: Properties of carbon black particles obtained in Example 11 of JP-A-7-34001 Reference Example 2: * 1 Commercial product of FT class thermal black Reference Example 3: * 2 Commercial product of MT class thermal black
* 3 Powder cannot be obtained due to blockage in the furnace path.
* 4 No powder is obtained

Examples 8 to 10, Comparative Examples 6 and 7
Using methane gas and propane gas as the raw material hydrocarbon gas, changing the thermal decomposition temperature, the raw material gas concentration, the linear velocity of the raw material hydrocarbon gas passing through the furnace, and further inserting the raw material gas after the heater exit, Carbon microspheres were produced by pyrolysis for 2 hours each.

  From the results of Table 1, the carbon microspheres of Examples 1 to 7 have an arithmetic average primary particle diameter dn of 150 to 450 nm, ΔDst / Dst in the range of 0.40 to 0.85, and are commercially available thermal blacks. It can be seen that the particle diameter is sharper than FT and MT. Moreover, the carbon microsphere which exhibits the property of Claim 1 of this invention is obtained by the manufacturing method which satisfies Claim 3 of this invention. On the other hand, Comparative Examples 1 to 5 are production methods that do not satisfy the conditions of the present invention, and carbon microspheres exhibiting the properties of claims 1 and 2 of the present invention cannot be obtained.

  In Comparative Example 3, since the linear flow rate was as slow as 0.01 m / sec, the generated carbon powder adhered to the reaction tube and was not discharged out of the furnace. With the passage of time, the furnace path was blocked, and as a result, carbon powder could not be obtained. In Comparative Example 4, the pyrolysis temperature was as low as 900 ° C., and the pyrolysis reaction did not proceed smoothly, and the product was mainly tar-like undecomposed hydrocarbons (unburned content). Furthermore, in Comparative Example 5 in which hydrogen was used as the carrier gas, thermal decomposition was suppressed, a large amount of undecomposed carbonaceous matter remained on the surface of the obtained powder, and the toluene coloring transmittance LT was 0%. In addition, the yield is 10%, and the production efficiency is extremely low. In addition, the specific surface area relative to the particle size is large, indicating that there are many irregularities.

  Furthermore, from the results of Table 2, the carbon microspheres of Examples 8 to 11 have an arithmetic average primary particle diameter dn of 450 to 1000 nm and ΔDst / Dst of 0.80 to 1.05. It can be seen that the following properties are exhibited. By introducing the raw material gas from the heater outlet in the reaction furnace by the manufacturing method according to claim 4 of the present invention, carbon microspheres exhibiting the properties of claim 2 of the present invention are obtained.

  In Comparative Example 6, the yield was low and a large amount of undecomposed carbonaceous matter remained in the carbon powder, and the LT was 10. Further, since the yield is as low as 10%, the production efficiency is poor. In addition, the particles were agglomerated. On the other hand, in Comparative Example 7, since hydrogen was used as the carrier gas, thermal decomposition was suppressed, and a large amount of undecomposed carbonaceous matter remained in the resulting carbon powder, and LT was 0. Further, since the yield is as low as 10%, the production efficiency is poor. Furthermore, the specific surface area with respect to the particle size was large, indicating that there were many irregularities.

It is the distribution curve which showed the elapsed time after adding the dispersion liquid of the carbon microsphere at the time of Dst measurement, and the change of the light absorbency by centrifugal sedimentation of the carbon microsphere. It is a distribution curve which shows the relationship between the Stokes equivalent diameter obtained at the time of Dst measurement, and a light absorbency. It is explanatory drawing which illustrated the whole structure of the apparatus for manufacturing the carbon microsphere of this invention.

Explanation of symbols

11 Raw material gas cylinder 12 Carrier gas cylinder 13 Flow meter 14 Raw material tank 15 Preheating heater 16 Pressure gauge 17 Heating furnace (external heating type reactor)
18 Heater 19 Source Gas Inlet 20 Temperature Controller 21 Cooling Pipe 22 Valve 23 Vacuum Pump 24 Collection Chamber 25 Water Tank 26 Combustion Device 27 Stainless Steel Piping

Claims (4)

Arithmetic average primary particle diameter dn by electron microscope is 150 to 450 nm, and ratio ΔDst / Dst between Stokes mode diameter Dst of particle aggregate measured by disk centrifuging apparatus (DCF) and half width ΔDst indicating distribution property of particle aggregate is It has an aggregate particle property of 0.40 to 0.85, and the nitrogen adsorption specific surface area (N ₂ SA) and the Stokes mode diameter Dst of the particle aggregate are N ₂ SA <6000 / (Dst × 1.85) +5 A carbon microsphere characterized by satisfying the above relationship. Arithmetic average primary particle diameter dn by electron microscope is more than 450 nm and not more than 1000 nm, and ratio ΔDst / of Stokes mode diameter Dst of particle aggregate measured by disk centrifuging device (DCF) and half width ΔDst indicating distribution property of particle aggregate Dst has an aggregate particle property exceeding 0.80, and the nitrogen adsorption specific surface area (N ₂ SA) and the Stokes mode diameter Dst of the particle aggregate are N ₂ SA <6000 / (Dst × 1.85) +5 Carbon microspheres characterized by satisfying the relationship.   A hydrocarbon gas is introduced into an externally heated reactor together with an inert carrier gas, the furnace temperature is 1000 ° C. to 1400 ° C., the hydrocarbon gas concentration is 10 to 50 vol%, and the linear flow rate of the hydrocarbon gas is 0.02 to 0.02%. 2. The method for producing carbon microspheres according to claim 1, wherein pyrolysis is performed under a condition of 4.0 m / sec. 4. The method for producing carbon microspheres according to claim 2, wherein, in addition to the production method of claim 3, a hydrocarbon gas source gas is introduced again from the latter part of the external heating type reactor.