JPH03187908A - Production of spherical carbon material - Google Patents

Abstract

PURPOSE:To improve electrical conductivity and dispersion stability by coating the surface of spherical particles comprising phenol resin, naphthalene resin, etc., with bulk mesophase pitch by mechanochemical method, heat-treating and burning under given conditions. CONSTITUTION:Spherical particles comprising phenol resin, naphthalene resin, xylene resin, divinylbenzene polymer, etc., having 3-50mum particle diameter are prepared. Fine particles of bulk mesophase pitch having particle diameter of <=2/5 the particle diameter of the spherical particle and <=10mum are prepared. Both the particles are blended in a dry state by mechanochemical method to give particles wherein the surface of the spherical particles is coated with the fine particles of bulk mesophase pitch. Then the particles are burnt in an inert atmosphere or in vacuum and carbonized and/or graphitized.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a spherical carbon material, and more specifically to a method for producing a spherical carbon material, and more specifically, a graphite or carbon material useful as a filler for conductive rubber, conductive plastic, conductive paint, etc. The present invention relates to a method for producing a high quality spherical carbon material.

[Prior art and problems to be solved by the invention] Conventionally, spherical carbon materials with excellent heat resistance and chemical resistance have been used as fillers for rubber, plastics, paints, etc. As such, resin-based spherical particles such as phenol resin or mesocarbon microbeads are fired to carbonize and/or graphitize them.

Among these, phenolic resin, divinylbenzene polymer,
Carbonaceous spherical carbon materials obtained by carbonizing resin-based spherical particles such as styrene-divinylbenzene copolymer and polyacrylonitrile have no particular problems with respect to sphericity and dispersion stability, but are glassy and crystalline. It has poor properties, has many micropores, and has low electrical conductivity. In addition, graphite spherical carbon materials obtained by graphitizing resin-based spherical particles have a limit in reducing electrical conductivity, and a material with sufficiently low electrical conductivity has not yet been obtained, and furthermore, when graphitizing The pyrolysis gas generated from the spherical particles precipitates and becomes rod-shaped products that adhere in large numbers to the surface of the spherical carbon material. Therefore, carbonaceous and/or graphite spherical carbon materials obtained from resin-based spherical particles are unsuitable as fillers for conductive rubber, conductive plastics, conductive paints, etc., which have been in increasing demand in recent years. .

On the other hand, the spherical carbon material is obtained by firing mesocarbon microbeads, which are usually produced by washing the spherical crystals generated during the heating and firing process with a large amount of tar oil, quinoline, or other solvents. , has sufficient electrical conductivity to be used as a filler in conductive paints, etc. However, since such mesocarbon microbeads shrink irregularly during firing, the sphericity of the obtained spherical carbon material is significantly reduced, and furthermore, the particle size distribution thereof is also extremely wide. Therefore, for example, if a thin film is formed with a conductive paint containing these as fillers, the conductivity will vary, making it impossible to use it particularly in applications that require uniform conductivity, such as contact materials. In addition, the spherical carbon material obtained by firing mesocarbon microbeads has a large true specific gravity, for example, about 2.1 to 2.2 when graphitized, and has poor dispersion stability in liquids, resulting in filling of paints. It was unsuitable for materials such as wood.

In view of the problems of the prior art described above, the present invention has excellent electrical conductivity, dispersion stability, and sphericity, and is useful as a filler for conductive rubber, conductive plastic, conductive paint, etc. It is an object of the present invention to provide a method that can efficiently produce a spherical carbon material with a narrow particle size distribution.

[Means for Solving the Problems] As a result of intensive research, the present inventors found that the surface of spherical particles made of a specific material was coated with mesophase pitch using a mechanochemical method, and then it was heat-treated under certain conditions and then fired. We have found that the above purpose can be achieved by
We have arrived at the present invention.

That is, the present invention provides phenolic resin, naphthalene resin,
Furan resin, xylene resin, divinylbenzene polymer,
Particle size 3-50 consisting of at least one of styrene-divinylbenzene copolymer and polyacrylonitrile
Spherical particles of μm and bulk mesophase pitch fine particles having a particle size of 10 μm or less and 275 or less of the above spherical particle size are dry mixed by a mechanochemical method, and the surfaces of the spherical particles are coated with the bulk mesophase pitch. The resulting pitch-coated spherical particles are thermally stabilized by heat treatment in an oxidizing atmosphere, and then fired in an inert atmosphere or under vacuum to carbonize and/or graphitize the spherical carbon material. It's in the manufacturing method.

The spherical particles used as a starting material in the production method of the present invention are made of at least one of phenolic resin, naphthalene resin, furan resin, xylene resin, divinylbenzene polymer, styrene-divinylbenzene copolymer, and polyacrylonitrile. It is. These resin-based spherical particles are prepared from each raw material by a known emulsion polymerization method or the like. The above-mentioned spherical particles having a particle diameter of 3 to 50 μl, preferably 3 to 30 μl, are effectively used.

In addition, the bulk mesophase pitch fine particles used as a starting material together with the spherical particles in the production method of the present invention are petroleum-based or coal-based bulk mesophase pitch (pitch containing optically anisotropic liquid crystal called mesophase). It is obtained by coarsely pulverizing it with a pulverizer such as a show crusher, and then finely pulverizing it with a dry or wet ball mill to the following particle size. In the present invention, the particle size is 10 μm or less, preferably 3 μm or less, and 2 μm or less of the above spherical particle size.
Bulk mesophase pitch particles of 15 or less are effectively used. In addition, the composition of the quinoline soluble content (Ql), ) luene insoluble content (TI), etc. of the bulk mesophase pitch is not particularly limited, but the softening point is preferably 200 to 38
When a temperature of 0° C., particularly preferably 280 to 340° C., is used, heat treatment in an oxidizing atmosphere for heat stabilization can be completed in a short time, and efficiency tends to be improved.

In the production method of the present invention, first, the spherical particles and bulk mesophase pitch fine particles are dry mixed by a mechanochemical method to coat (encapsulate) the surface of the spherical particles with bulk mesophase pitch, thereby producing pitch-coated spherical particles. (hereinafter referred to as pitch-coated spherical particles). By using the mechanochemical method, coating can be performed efficiently and a spherical carbon material having excellent properties such as sphericity can be obtained without having a wide particle size distribution.

The mechanochemical method carried out in the production method of the present invention is generally also called a powder/powder mixing method. That is, by dry mixing different types of powders with different particle sizes, for example, the spherical particles and fine particles in the present invention, the fine particles are first attached to the surface of the spherical particles, and when the mixing is continued, shearing force, mechanical impact, Fine particles attached to spherical particles change into a continuous wall film due to frictional force, etc.
They become so-called microcapsules.

In the present invention, it is preferable to carry out the dry mixing at a mixing ratio of 12.5 to 25 parts by weight of fine particles to 100 parts by weight of spherical particles. In addition, dry mixing in the mechanochemical method is possible at room temperature or in air, and the conditions at that time are appropriately selected depending on the starting materials used, the amount of processing, etc., and the spherical particles are not crushed during mixing and their surface It is sufficient that the bulk mesophase pitch is uniformly coated on the surface of the carbon material, resulting in a good spherical carbon material. In general, the desired pitch-coated spherical particles can be obtained by mixing for 1 to 10 hours, and
．． Pitch-coated spherical particles can be obtained more efficiently by suppressing mixing under a pressurized condition of 2 to 2.0 kg/c 2.

In addition, as a device used for dry mixing in the above mechanochemical method, a general mixing device such as a V-type mixer can be used as long as the bulk mesophase pitch fine particles are simply attached to the surface of the spherical particles. In order to form a continuous wall film, a device that can continuously apply pressure, shearing force, mechanical impact, frictional force, etc. is required, and a laikai machine (automatic mortar), centrifugal rotating mixer, etc. are preferable. In terms of industrial applicability, the Laikai machine is particularly preferred.

An example of dry mixing using a Raikai machine is shown in Figure 1. In the figure] is a pestle, 2 is a mortar, 3 is a mixture of spherical particles and fine particles, a is the rotation direction of pestle 1, b
indicates the rotation direction of the mortar 2.

In this case, the pressure with which pestle 1 is pressed against mortar 2 is 0.2~
2.0 kg/cIl12, number of rotations of pestle 1/mortar 2
The rotation speed is 1b to 20c, and the thickness of the layer of mixture 3 is 0.2
It is preferable to set the range to 3.0 m+n because dry mixing can be carried out efficiently. Note that the structure of the Raikai machine, such as the size and number of pestles 1 and the size of the mortar 2, is not particularly limited, and a commercially available Raikai machine may be used depending on the throughput and the like.

In the present invention, it is preferable that both the steps of adhesion and continuous wall film formation are carried out successively using the same mixing device, but it is also possible to carry out each step using separate devices.

Next, the pitch-coated spherical particles obtained by the above method are thermally stabilized (infusible) by heat treatment in an oxidizing atmosphere such as air or oxygen in a heat treatment furnace such as a batch type, continuous type, or rotary kiln type. do. The heat treatment conditions at this time are such that the temperature is raised to 250 to 350°C at a heating rate of 10 to 80°C/hr. Although it is not necessarily necessary to maintain the temperature within the above temperature range, it is more preferable to maintain it for 10 minutes to 1 hour.

Furthermore, in the production method of the present invention, the pitch-coated spherical particles heat-treated in this way are carbonized and/or graphitized by firing in an inert atmosphere such as nitrogen gas or argon gas or under vacuum, and the pitch-coated spherical particles are carbonized and/or graphitized to form spherical particles. Obtain carbon material. The firing conditions at that time include a heating rate of 30 to 30
The temperature is raised to 800 to 1000°C at 0'C/hr to carbonize. Although it is not necessarily necessary to maintain the temperature once it reaches this temperature range, l.

It is more preferable to hold it for minutes to 2 hours. Furthermore, after the above carbonization, the temperature is increased to 2000 to 300°C at a heating rate of 50 to 1000°C/hr in an inert atmosphere or under vacuum.
Graphitize by raising the temperature to 0°C. It is not necessary to hold the temperature once it reaches this temperature range, but it is more preferable to hold it for 10 minutes to 1 hour. Graphitization is preferable because the resulting coated portion of the spherical carbon material becomes more crystallized, which further improves electrical conductivity.

By the above-described manufacturing method of the present invention, the powder electrical resistivity is generally 5.0X10-1 to 5.0X1G-2ΩCl11
1 true specific gravity is 1.4 to 1.6, bulk specific gravity is O,S to 0.9,
It is possible to obtain a spherical carbon material having a specific surface area of less than about ITIt,/g and having high sphericity.

[Examples] Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples.

Example 1 600 g of a commercially available spherical phenol resin sized to 10 to 15 μ■ by wet classification and coal-based bulk mesophase pitch powder (softening point 82
0° C.) was used as starting material. After uniformly mixing these, dry mixing treatment (mechanochemical treatment) is performed in a Raikai machine (automatic mortar, manufactured by Ishikawa factory, model number 71) under the following conditions, and the surface of the spherical phenolic resin particles is uniformly coated with bulk mesophase pitch. Pitch-coated spherical particles were obtained by coating.

(Mechanochemical conditions) ・Processing time...8.5hr ・Pressure for pressing pestle against mortar...1.2 kg/C
n2・Rotation speed of pestle/Rotation speed of mortar...BOrpm/
80 rpm・Mixture layer thickness: approx. 1 ma+ The pitch-coated spherical particles were heated to 280°C at a heating rate of 30°C/hr in air, and maintained for 1 hour for thermal stabilization treatment. .

Next, the heat-stabilized pitch-coated spherical particles were heated to 1000°C at a heating rate of 200°C/hr in a nitrogen atmosphere, and held for 1 hour to carbonize the carbonaceous spherical carbon material. Obtained.

Table 1 shows the particle diameter and various properties of the obtained spherical carbon material.

1 2 As is clear from Table 1, in this example, a spherical carbon material with low powder electrical resistivity and excellent other properties could be obtained.

Comparative Example 1 A spherical carbon material was obtained in the same manner as in Example 1, except that the spherical particles were thermally stabilized and carbonized as they were without being coated with bulk mesophase pitch.

Table 1 shows the particle diameter and various properties of the obtained spherical carbon material.

As is clear from Table 1, the spherical carbon material obtained in this comparative example had a large number of micropores and had a significantly poor powder electrical resistivity.

Example 2 After carbonizing the heat-stabilized pitch-coated spherical particles, the temperature was subsequently raised to 2800°C at a rate of 600°C/hr in a graphitization furnace and held for 30 minutes. A graphite spherical carbon material was obtained in the same manner as in Example 1 except that it was graphitized.

4 Photograph showing the particle structure of the obtained spherical carbon material (SEM
(photo) is shown in FIG. 2, and its particle size and various properties are shown in Table 1.

As is clear from Table 1, in this example, a spherical carbon material with a very low powder electrical resistivity and excellent other properties could be obtained.

Comparative Example 2 A spherical carbon material was obtained in the same manner as in Example 2, except that the spherical particles were thermally stabilized, carbonized, and graphitized without being coated with bulk mesophase pitch.

Table 1 shows the particle diameter and various properties of the obtained spherical carbon material.

As is clear from Table 1, the spherical carbon material obtained in this comparative example has an inferior powder electrical resistivity, and furthermore, the pyrolysis gas generated from the spherical particles precipitates and becomes a rod-shaped product. A large number of particles were attached to the surface of the carbon material.

Example 3 The spherical phenol resin used had a particle size of 45 to 50 μm, and the coal-based bulk mesophase pitch powder had a particle size of 1.
A graphite spherical carbon material was obtained in the same manner as in Example 2 except that the particle size was 0 μm or less and the dry mixing conditions in the Laikai machine were as follows.

(Mechanochemical conditions) ・Processing time...3hr ・Pressure for pressing pestle against mortar...0.5 kg/c
+n2・Rotation speed of pestle/Rotation speed of mortar...80rpm
/80 rpm・Thickness of layer of mixture...approximately 2 mm The particle diameter and various properties of the obtained spherical carbon material are shown in Table 1.

As is clear from Table 1, in this example, a spherical carbon material with sufficiently low powder electrical resistivity and excellent other properties could be obtained.

Example 4 First, polyvinyl alcohol 2 with an average molecular weight of 2000
0 g and 400 g of water are stirred in a flask to completely dissolve. Here, 50g of divinylbenzene and 50g of styrene.
100 g of a mixed solution, 1.0 g of ben 5 6 sember oxide as a polymerization catalyst, and nonionic (nonionic surfactant; polycarboxylic acid type polymeric surfactant) as an emulsifier. Og was added and suspended, and the mixture was heated to 75 to 85° C. while stirring to initiate a polymerization reaction, and the polymerization reaction was carried out for 1 hour. During this time, the temperature of the reaction solution was raised to 95 to 98°C due to heat generated by the polymerization reaction. after that,
The resulting reaction solution was cooled to 50° C. or below while stirring, and then allowed to cool to room temperature to obtain a dispersion. A spherical product was filtered from the resulting dispersion, washed twice with water and three times with methanol, and dried at around 100°C while being careful not to catch fire from volatile components to obtain a spherical divinylbenzene polymer. I got it.

As starting materials, 750 g of the obtained spherical divinylbenzene polymer was sized to 15 to 20 μm by wet classification, and 100 g of petroleum-based bulk mesophase pitch powder (softening point 334 ° C.) finely pulverized to a particle size of 5 μm or less. The dry mixing conditions in the Laikai machine were as follows, and the temperature increase rate during graphitization was set to 60°C.
A graphite spherical carbon material was obtained in the same manner as in Example 2 except that the final temperature was 2300°C.

(Mechanochemical conditions) ・Processing time: 2.5 hr ・Pressure to press the pestle against the mortar: 1.5 kg/c
m2・Rotation speed of pestle/Rotation speed of mortar...Hrpm/3
0 rpm・Thickness of layer of mixture: approx. 11 Table 1 shows the particle size and various properties of the obtained spherical carbon material.

As is clear from Table 1, in this example as well, a spherical carbon material with sufficiently low powder electrical resistivity and excellent other properties could be obtained.

Comparative Example 3 A spherical carbon material was obtained in the same manner as in Example 4, except that the spherical particles were thermally stabilized, carbonized, and graphitized without being coated with bulk mesophase pitch.

Table 1 shows the particle diameter and various properties of the obtained spherical carbon material.

As is clear from Table 1, the spherical carbon material obtained in this comparative example had poor powder electrical resistivity, and furthermore, the pyrolysis gas generated from the spherical particles precipitated and became rod-shaped products. A large number of particles were attached to the surface of the spherical carbon material.

Comparative Example 4 After finely pulverizing a coal-based bulk mesophase having a softening point of 311°C, it was classified to obtain pitch powder particles having a diameter of 25 to 50 μm.

80 g of the obtained pitch powder was mixed with 14 g of diisobutyl phthalate.
The mixture was dispersed in J and the entire amount was put into a 20J autoclave.

After charging, the inside of the autoclave system was evacuated and purged with nitrogen gas. Then, in order to prevent the pitch powder from settling, immediately rotate the stirrer at 500 rpm, and while stirring,
The temperature was started to increase at 20°C/hr. Thereafter, as soon as the temperature inside the system reached 330° C., the system was allowed to cool to obtain a dispersion liquid. Note that stirring was continued until the temperature dropped to 150°C.

At this time, the maximum autogenous pressure was 6 kg/cm.

Next, the obtained dispersion was taken out from the autoclave and filtered by suction, and the filtered spherical product was washed with acetone and dried to prepare spherical mesocarbon microbeads.

The obtained spherical mesocarbon microbeads were sized to 25 to 35 μm by wet classification and used as spherical particles, which were then thermally stabilized under the same conditions as in Example 2 without being coated with bulk mesophase pitch. A graphitic spherical carbon material was obtained by carbonization and graphitization.

Table 1 shows the particle size and mechanical properties of the obtained spherical carbon material.

As is clear from Table 1, the spherical carbon material obtained in this comparative example had a large true specific gravity and extremely poor sphericity, and the particle size distribution of the obtained spherical carbon material was wide.

[Effects of the Invention] As explained above, the production method of the present invention can efficiently produce carbonaceous and/or graphitic spherical carbon materials that are excellent in electrical conductivity, dispersion stability, and sphericity. Moreover, it becomes possible to manufacture with a narrow particle size distribution.

Therefore, the spherical carbon material obtained by the production method of the present invention is suitably used as a filler for conductive rubber, conductive plastic, conductive paint, and the like.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of dry mixing using a Raikai machine in the present invention, and FIG. 2 is a spherical carbon material particle obtained in an example (Example 2) of the present invention. This is a photo showing the structure.

Claims (1)

[Scope of Claims] 1. Spherical particles with a particle size of 3 to 50 μm made of at least one of phenol resin, naphthalene resin, furan resin, xylene resin, divinylbenzene polymer, styrene-divinylbenzene copolymer, and polyacrylonitrile. and the particle size is 10 μm or less and 2/2 of the above spherical particle size.
Pitch-coated spherical particles obtained by dry mixing bulk mesophase pitch fine particles having a particle diameter of 5 or less using a mechanochemical method and coating the surface of the spherical particles with the bulk mesophase pitch are heat-treated in an oxidizing atmosphere. A method for producing a spherical carbon material, which comprises stabilizing it and then carbonizing and/or graphitizing it by firing in an inert atmosphere or under vacuum. 2. The spherical particles and the bulk mesophase pitch fine particles are dry mixed using a Raikai machine at a concentration of 0.2 to 2.0
2. The method for producing a spherical carbon material according to claim 1, wherein the method is carried out under a pressure of kg/cm^2.