WO2024228385A1 - Method for producing carbon material granules - Google Patents

Abstract

A method for producing carbon material granules comprising: a step in which carbon black particles and carbon nanotube particles are pulverized so that the carbon black comes to have a particle diameter, as determined by the method described in JIS K-6219-4, of 500 μm or less and the carbon nanotubes come to have a particle diameter, as determined by the method described in JIS K-6219-4, of 500 μm or less, and are mixed to obtain a mixture; a step in which a solvent-soluble polymer is dissolved in a solvent to prepare a binder solution; a step in which the mixture is mixed with the binder solution to obtain a wet mixture; and a step in which the wet mixture is granulated to obtain carbon material granules.

Description

Method for producing carbon material granules

The present invention relates to a method for producing carbon material granules.

In recent years, various studies have been conducted on imparting electrical conductivity or antistatic properties to resin compositions. For example, trays or carrier tapes molded from thermoplastic resins are known as packaging materials for electronic components that use ICs or LSIs. However, ordinary resin molded products are not electrically conductive and have high surface and volume resistivity. This can cause problems such as insulation breakdown of electronic components due to static electricity, or reduced functionality due to the adhesion of dust. To prevent this, various types of materials have been added to solve the problem. In particular, many studies have been conducted on imparting antistatic properties or static electricity diffusion properties by blending carbon black (hereinafter sometimes referred to as CB) or carbon nanotubes (hereinafter sometimes referred to as CNT).

An example of granulating a mixture of CB and CNT is a method for producing carbon granules (see Patent Document 1), which includes a CNT dispersion process in which CNTs having a particle size of 100 nm or less are dispersed in water, a granulation process in which the CNT dispersion liquid obtained in the CNT dispersion process is mixed with CB powder in a disperser and granulated, and a drying process in which the carbon granules obtained in the granulation process are dried.
Also, there is a method for producing carbon material granules (see Patent Document 2), which includes the steps of dry-pulverizing and mixing carbon black granules and carbon nanotube granules so as to satisfy specified conditions to obtain a mixture, dissolving a specific solvent-soluble polymer in a solvent to prepare a binder solution, and adding a specified amount of the binder solution to the mixture while mixing and granulating to obtain carbon material granules.
There is a method for producing a granulated material of CNTs alone (see Patent Document 3), which includes the steps of: (1) preparing an aqueous solution of a water-soluble polymer having a concentration of 0.005 to 3.0 mass %; (2) preparing a wet agglomerate by impregnating carbon nanotubes with the aqueous solution of the water-soluble polymer in a ratio of 400 to 1000 parts by mass per 100 parts by mass of carbon nanotubes; (3) shearing and crushing the wet agglomerate to obtain a crushed agglomerate; and (4) drying the crushed agglomerate to obtain a carbon nanotube-containing agglomerate containing the water-soluble polymer.

JP 2017-201006 A Patent No. 7126666 Patent No. 6714134

The carbon material granule manufacturing method described in Patent Document 1 or Patent Document 2 can reduce scattering and obtain carbon material granules that can improve electrical conductivity and mechanical properties. The granulation methods described in these patent documents include continuous and batch methods, and a twin-shaft pin mixer that mixes with a twin-shaft screw is cited as a continuous method. This granulator is a method in which CB and CNT are fed into the front stage of a twin-shaft screw rotating at 500 to 3000 rpm, and a binder solution is added from an inlet in the rear stage, mixed, and granulated. However, it has been found that CB and CNT fly in a cloud from the part or area where the CB and CNT are not sufficiently wetted with the binder solution, the base of the shaft rotating at high speed, and the inlet hole for feeding the carbon material, and this is not preferable as a granulation method using this raw material from the perspective of the environment or human safety. Therefore, in these carbon material granule manufacturing methods, the granules are produced in a batch manner in the granulation process, so there is room for improvement in terms of production efficiency.

The present invention aims to provide a method for producing carbon material granules that allows for continuous granulation and improves production efficiency.

That is, according to the present invention, there is provided a method for producing a carbon material granule as follows: [1] A step of obtaining a mixture by pulverizing and mixing carbon black granules and carbon nanotube granules so that the particle size of the carbon black is 500 μm or less according to the method described in JIS K-6219-4 and the particle size of the carbon nanotubes is 500 μm or less according to the method described in JIS K-6219-4, a step of dissolving a solvent-soluble polymer in a solvent to prepare a binder solution, and a step of mixing the binder solution with the mixture to obtain a wet mixture.
and granulating the wet mixture to obtain a carbon material granule.
A method for producing carbon material granules.
[2] The method for producing a carbon material granule according to [1],
The pulverization is carried out by at least one pulverizer selected from the group consisting of a jet mill, a vibrating ball mill, a roll crusher, and a hammer mill.
A method for producing carbon material granules.
[3] In the method for producing a carbon material granule according to [1] or [2],
The solvent-soluble polymer is a water-soluble polymer,
The solvent is water.
A method for producing carbon material granules.
[4] The method for producing a carbon material granule according to any one of [1] to [3],
When granulating the wet mixture, a granulator is used,
The granulator is at least one selected from the group consisting of an extrusion granulator and a shear crushing granulator;
A method for producing carbon material granules.

The present invention provides a method for producing carbon material granules that is free from scattering during the granulation process, enables continuous granulation, and improves production efficiency.

1A to 1C are SEM photographs of the carbon material granules obtained in the present embodiment and their conceptual diagrams. FIG. 2 is a conceptual diagram of an extrusion granulator used in the present embodiment. 4 is a SEM photograph of the carbon material granules obtained in Example 5, Example 6, and Comparative Example 1.

The following describes an embodiment of the present invention, but the present invention is not limited to the following embodiment. Hereinafter, the carbon material granules may also be referred to simply as "granules."

[Method of manufacturing carbon material granules]
The method for producing a granulated material according to this embodiment includes a step of obtaining a mixture by pulverizing and mixing carbon black granules and carbon nanotube granules so that the particle size of the carbon black is 500 μm or less according to the method described in JIS K-6219-4 and the particle size of the carbon nanotubes is 500 μm or less according to the method described in JIS K-6219-4 (pulverizing and mixing step); a step of dissolving a solvent-soluble polymer in a solvent to prepare a binder solution (solution preparation step); a step of adding the binder solution while mixing the pulverized carbon black and carbon nanotubes to obtain a wet mixture (granulation precursor) (wet mixture preparation step); and a step of granulating the wet mixture to obtain a carbon material granulated material (granulation preparation step).

(Crushing and mixing process)
In the grinding and mixing step, the CB granules and the CNT granules are each ground to a specific particle size or less, and then mixed to obtain a mixture. The order of grinding and mixing is not particularly limited. (1) The CB granules and the CNT granules may be dry ground, respectively, and then mixed, or (2) the CB granules and the CNT granules may be mixed and then ground.
As the pulverization method, there are dry pulverization and wet pulverization, and they are used according to the purpose. In this embodiment, it is preferable to use dry pulverization, but in the case of the dry method, the pulverizer to be used varies depending on the target particle size or particle size distribution. For example, when the purpose is (1) medium pulverization (1 mm to several tens of μm), a roll crusher, impeller mill, cutter mill, ring mill, etc. are used. A Henschel mixer or a Redeige mixer, which are generally used as a mixer or granulator, can also be used. On the other hand, when the purpose is (2) fine pulverization (several tens of μm to several μm), a jet mill, roller mill, pin mill, planetary mill, etc. are used.
Among the manufacturers of crushers, manufacturers of jet mill type crushers include Seishin Enterprise Co., Ltd., Aisin Nano Technologies Co., Ltd., and Earth Technica Co., Ltd. Furthermore, manufacturers of pin mills include Makino Sangyo Co., Ltd., Nishimura Machinery Works Co., Ltd., and Hosokawa Micron Co., Ltd. Furthermore, manufacturers of impeller mills include Seishin Enterprise Co., Ltd. and Earth Technica Co., Ltd. Furthermore, manufacturers of sanitary rotary type crushers include Aishin Sangyo Co., Ltd. and Tokuju Kosakusho Co., Ltd. Among them, the sanitary type crusher manufactured by Aishin Sangyo Co., Ltd., and the Randel Mill (RM-1N type) manufactured by Tokuju Kosakusho Co., Ltd. are capable of directly inserting the material from the raw material hopper into a mixer or twin-screw extruder while crushing in a sealed state.
On the other hand, the mixing of CB and CNT may be performed by feeding the pulverized product into a mixing granulator such as a Henschel mixer or a Redeige mixer, and mixing while adding water in which a polymer is dissolved, or by directly feeding the pulverized product into a mixing granulator such as a Henschel mixer without pulverization, stirring at high speed without adding water in which a polymer is dissolved, and then preparing a wet mixture as a granulation precursor by adding water in which a polymer is dissolved. As mentioned above, most brands of CB and CNT are shipped in a granulated form for reasons such as workability, reduction in transportation costs, and prevention of scattering. Generally, CB granules are manufactured with diameters of 0.25 mm to 2 mm, while CNTs come in various shapes and sizes. Currently, CNTs manufactured by LG Chemicals of Korea, which boasts the world's largest production volume of MWCNTs, are button battery-shaped with a diameter of 7 mm and a height of 2 mm, and the weight of one grain is about 0.0198 g. On the other hand, the weight of one 1 mm diameter CB (DC3501 from OCI, Korea) is about 0.0002 g, and the weight ratio of the two is about 100. For example, when the mixture of CB and CNT is 70 g:30 g, the number of CB and CNT granules is (70 g)/(0.0002 g/particle)=350,000 particles for CB and (30 g)/(0.0198 g/particle)=1,515 particles for CNT, and the ratio of the particles of the two is about 231:1, so it can be easily inferred that the two will not be mixed uniformly by a simple mixing operation.
The gist of Patent Document 3 is that water in which a water-soluble polymer is dissolved is added to CNT in a screw conveyor, and then an aggregate is produced in a shear crushing processor, followed by drying. More specifically, the amount of polymer added to CNT is 0.005 to 3 mass%, and the amount of the aqueous solution is 400 to 1000 mass parts per 100 mass parts of CNT. The CNT is supplied to the screw conveyor at a rate of 0.25 to 1.0 kg/min, and the residence time is 1 to 3 minutes. Furthermore, it is stated that a rotary cutter mill or a multi-stage rotary cutter mill is preferable as the shear crushing processor.
Even if CB and CNT are supplied to the screw conveyor described in Patent Document 3 and rotated while adding water, the screw conveyor is a device that transports objects by rotating blades at a low speed, so it has almost no function of mixing two or more types of carbon. In particular, it can be said that it is difficult to uniformly mix granulated CB and CNT using a screw conveyor as described above.
In contrast, according to the method for producing a granulated material according to the present embodiment, CB and CNT can be mixed uniformly (see FIG. 1).

(Particle size measurement of crushed product)
The particle size distribution of CNT and CB is measured according to JIS K-6219-4 "Method of determining the size distribution of granulated particles". The measuring device is a classification method that uses stacked mesh sieves, and there are sonic vibration type, low tap type, electromagnetic type, etc. depending on the way of applying vibration. Manufacturers of sonic vibration type include Hatsuratsu Co., Ltd. and Seishin Enterprise Co., Ltd. In addition to the two companies mentioned above, manufacturers of low taps include CMT Co., Ltd. and AS ONE Co., Ltd. Manufacturers of electromagnetic shaking sieve machines include Tsutsui Rikagakuhin Co., Ltd. As a specific measurement method, for example, a low tap made by CMT Co., Ltd. is set on a four to six-tiered low tap with a 200 mm diameter mesh sieve. As for the type of mesh, a combination of 10 mesh (1000 μm opening), 30 mesh (500 μm), 60 mesh (250 μm), and 100 mesh (150 μm) is generally used, but 86 mesh (2000 μm) and 149 mesh (100 μm) may also be added to this for measurement. In the measurement, a tray is attached to the bottom, 100 g of granulated product is placed in the top mesh sieve, the lid is set, and the sieve is shaken for 1 minute under the conditions of a shaking speed of 290 rpm, an amplitude of 28 mm, and a number of strokes of 156 t.p.m., after which the granulated product stuck in the upper part and the opening of each sieve is scraped off, their weights are measured, and the particle size distribution is calculated. The value of the opening of the mesh with the smallest opening among all the meshes is the particle size of the pulverized product.
The preferred particle size after pulverization is preferably 10 μm to 500 μm for both CB and CNT, and more preferably 25 μm to 250 μm, when viewed in a rotary tap classification method. If it is larger than 500 μm, not only will the number of agglomerates increase and dispersibility deteriorate, but the uniform mixing of CB and CNT will also deteriorate. In addition, processing to make it finer than 10 μm is not easy because it will be an industrial-scale production, and even if it can be processed, it will take a long time and is not realistic. In addition, it is a process that cuts the fibers of CNT, which is not preferable because it will deteriorate the conductivity. Furthermore, the particle size when pulverizing after blending CB and CNT is preferably the same as that of CNT.

Examples of CB include those obtained by thermal decomposition methods such as the thermal method or the acetylene decomposition method, incomplete combustion methods such as the oil furnace method, and those obtained by heavy oil gasification processes such as the Texas process, the Fazer process, and the Shell process. These may be used alone or in combination of two or more.
Specific examples include the #4000 and #5000 series manufactured by Tokai Carbon Co., Ltd., the #3000 series manufactured by Mitsubishi Chemical Corporation, FX, HS, Denka Black and the like manufactured by Denka Co., Ltd., the Conductex series manufactured by Birla Carbon Limited, the Vulcan series and LITX series manufactured by Cabot Corporation, the ENSACO series and Super P-Li series manufactured by Imerys GC Limited, and Printex L manufactured by Orion Engineer Carbons.

For CNT, the fiber diameter is 0.3 nm, which is the diameter that can be produced by current technology, but it may be thinner than 0.3 nm. In addition, as the fiber diameter becomes larger than 50 nm, the electrical properties or mechanical properties tend to decrease, and when the fiber diameter becomes larger than 100 nm, the advantage over CB or carbon nanofibers tends to disappear.
Furthermore, from the viewpoint of allowing the CNTs to efficiently form a three-dimensional network in the granulated product according to this embodiment, the fiber diameter of the CNTs is more preferably 3 nm or more and 50 nm or less, even more preferably 5 nm or more and 40 nm or less, and particularly preferably 10 nm or more and 30 nm or less.
The fiber length of CNT is related to electrical conductivity, mechanical properties, or dispersibility. The fiber length of CNT is preferably 0.1 μm or more and 2000 μm or less, and more preferably 1 μm or more and 1000 μm or less. As the fiber length becomes smaller, there is a tendency that electrical conductivity or mechanical properties are less easily exhibited. On the other hand, as the fiber length becomes larger, the entanglement of the fibers becomes stronger, and not only does it increase the number of poorly dispersed lumps, but it also increases the number of fiber breaks during kneading and dispersion, which is undesirable.
The aspect ratio of the CNT is, for example, 10 or more and 10,000 or less. In addition, as the CNT, a structure in which a hexagonal mesh graphite sheet is cylindrically shaped is preferably used. The CNT may be either a single-layer CNT or a multi-layer CNT, and can be selected according to the final purpose. In addition, there is no limitation on the manufacturing method of the CNT. Examples of the manufacturing method of the CNT include a pyrolysis method in which a carbon-containing gas is brought into contact with a catalyst, an arc discharge method in which an arc discharge is generated between carbon rods, a laser evaporation method in which a carbon target is irradiated with a laser, a CVD method in which a carbon source gas is reacted at high temperature in the presence of metal fine particles, and a HiPco method in which carbon monoxide is decomposed under high pressure. In addition, the CNT may be doped with metal atoms.

In the granulated product according to this embodiment, the amount of CNT is preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 35% by mass or less, relative to 100% by mass of the total amount of CB and CNT.
When the amount of CNTs is equal to or less than the upper limit, the dispersibility of the CNTs can be improved, and when the amount of CNTs is equal to or more than the lower limit, the electrical conductivity can be further improved.
In this embodiment, after mixing CB and CNT, it is essential to pulverize the CB and CNT before a series of processes in which a solvent-soluble polymer is mixed and granulated. Recently, most of the available CNTs are in the form of granules for the purpose of preventing scattering, reducing transportation costs, or improving workability during processing. Therefore, CNTs, which were difficult to disperse even in powder form, are becoming even more difficult to disperse. In addition, among furnace-type CBs, CBs called conductive CBs are almost 100% provided as granules, and are clearly more difficult to disperse than powdered products. As a result of examining various methods for improving this dispersibility, it was discovered that dispersibility can be improved by performing a pulverization process. Furthermore, it was found that the mixability of both materials is improved when both CB and CNT are pulverized. The pulverization method is a method in which energy is applied to a material as a force such as "compression,""impact,""friction," or "shear," generating stress in the material, which is then deformed and destroyed to make it fine. As the pulverization method, there are a dry method and a wet method, but in this embodiment, it is preferable to use the material processed by the dry method.

(Solution preparation process)
In the solution preparation step, a solvent-soluble polymer is dissolved in a solvent to prepare a binder solution.
As the solvent-soluble polymer, any polymer that dissolves in water, organic solvents, and mixtures thereof can be used. Examples of the solvent-soluble polymer include polymer-based surfactants and high molecular weight polymers.
Examples of the surfactant include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants, etc. These may be used alone or in combination of two or more.
Examples of the high molecular weight polymer include ether-based polymers (polyethylene glycol (polyethylene oxide), polypropylene glycol, etc.), vinyl-based polymers (polyvinyl alcohol, polyvinyl acetate, polyvinylpyrrolidone, etc.), acrylamide-based polymers (polyacrylamide, etc.), amine-based polymers (polyethyleneimine, polybutyleneimine, etc.), cellulose-based polymers (methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, etc.), and starch-based polymers (oxidized starch, gelatin, etc.). These may be used alone or in combination of two or more. Among these, from the viewpoint of reducing scattering or improving dispersibility, it is more preferable to use glycol-based polymers, and it is particularly preferable to use polyethylene oxide.

The solvent may be water, an organic solvent, or a mixture thereof, with water being the most preferred. When water is used as the solvent, the solvent-soluble polymer is a water-soluble polymer.
The concentration of the solvent-soluble polymer in the binder solvent is preferably from 1% by mass to 10% by mass, and more preferably from 2% by mass to 5% by mass.
If the concentration of the solvent-soluble polymer is equal to or higher than the lower limit, the solvent-soluble polymer can coat the carbon material more efficiently. On the other hand, if the concentration of the solvent-soluble polymer exceeds the upper limit, the polymer does not sufficiently penetrate into the carbon material, and the effect of expelling air present on the surface or in pores that is detrimental to the conductive performance decreases, which tends to result in a decrease in the conductivity.
By adding the solvent-soluble polymer at the lowest possible concentration, the solvent-soluble polymer can more easily penetrate into the voids in the carbon material, enabling a uniform coating over the entire carbon material. In addition, by adding a surfactant to the binder solution, the binder solution can be more easily penetrated into the carbon material.

(Wet mixture preparation step)
In the mixture preparation step, the mixture obtained in the grinding and mixing step is mixed with the binder solution obtained in the solution preparation step to obtain a wet mixture.
Here, the blending amount of the binder solution is preferably adjusted according to the blending amount of the solvent-soluble polymer, that is, the blending amount of the solvent-soluble polymer is preferably 0.01 parts by mass or more and 15 parts by mass or less, more preferably 0.1 parts by mass or more and 12 parts by mass or less, and particularly preferably 2 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the total blending amount of the carbon black and the carbon nanotubes.

In this embodiment, a shearing process for shearing the CB and CNT may be performed during or after the wet mixture preparation process. Note that in this embodiment, the CB and CNT are sufficiently pulverized in the aforementioned pulverizing and mixing process, so this shearing process is not necessarily required.

(Granulation preparation process)
In the granule preparation step, the wet mixture obtained in the wet mixture preparation step is granulated to obtain carbon material granules. Note that granulation of the wet mixture enables continuous granulation, and the production efficiency of the granules can be improved.
Examples of the granulator used here include an extrusion granulator and a shear crushing granulator. Among these, from the viewpoint of production efficiency, it is particularly preferable to use an extrusion granulator (see FIG. 2, which is a model of the inside of an extrusion granulator). As shown in FIG. 2, the extrusion granulator is equipped with a screw case 1, a screw 2, an extract blade 3, a screen 4, and a screen holder 5. The mainstream of extrusion granulators is a screw type extrusion granulator, and there are single-shaft and double-shaft types. In addition, they are roughly divided into two types, a front extruder and a side extruder, depending on the installation position of the extrusion screen die. In the case of a single-shaft screw, most of them are equipped with a screen die at the front end of the granulation chamber. On the other hand, in the case of a double-shaft, many of them are equipped with a screen die on both sides of the granulation chamber. Comparing the characteristics of a single shaft and a double shaft, the extrusion pressure is stronger in a single shaft, so that the granulated product can have a relatively large particle size and can have a high hardness. Twin-screw extrusion granulators are good for small particle size products and have weak particle strength, but are excellent in production efficiency. Examples of screw-type extrusion granulators and their manufacturers include the Pelleter Double EXD type or Fine Luzer EXR type manufactured by Dalton Co., Ltd., Granumaster manufactured by Okawara Seisakusho Co., Ltd., and Extrude Mix EM manufactured by Hosokawa Micron Co., Ltd.
Examples of the shear crushing granulator include the Speed Mill HM Series manufactured by Fuji Yakuhin Kikai Co., Ltd., and the Chopper Mill manufactured by Nippon Pneumatic Mfg. Co., Ltd.

After the granule preparation step, a step of drying the carbon material granules (drying step) may be carried out as necessary. Vacuum drying and hot air drying are used for drying. As hot air dryers, vibration/fluidized air dryers, fluidized air dryers, box dryers, and dryer-type dryers can be used. On the other hand, as vacuum (reduced pressure) dryers, vacuum tray dryers, reduced pressure outer mixer-type dryers, and box dryers can be used.

The drying temperature is preferably a temperature at which the solvent-soluble polymer does not deteriorate, and there is an optimum or maximum temperature depending on the type of solvent-soluble polymer, but generally, a temperature between 40°C and 200°C is preferable, between 50°C and 150°C is more preferable, and between 60°C and 100°C is particularly preferable. The drying time depends on the drying temperature, but is usually between 1 hour and 20 hours, and preferably between 2 hours and 10 hours.

[Effects of this embodiment]
According to this embodiment, the following advantageous effects can be obtained.
(1) It is possible to produce a carbon material granule that can reduce scattering and has improved electrical conductivity and mechanical properties.
(2) As described above, the present embodiment enables continuous granulation, which improves production efficiency compared to the conventional method for producing granulated materials, in which granulation is performed in a batch manner.

[Modifications of the embodiment]
The present invention is not limited to the above-described embodiment, and includes modifications and improvements within the scope of the present invention that can achieve the object of the present invention.
For example, in the above embodiment, the grinding and mixing process is performed continuously, but this is not limited to this. For example, the CB granules may be purchased from a manufacturer and ground in advance, and used. Also, the CNT granules may be purchased from a manufacturer and ground in advance, and used.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Note that "parts" and "%" in the examples are by weight unless otherwise specified.

The methods for measuring physical properties used in the examples and the like, as well as the samples used in the examples and the like, will be described below.
(1) Ash content (ASH)
The mixability of CB and CNT was judged by the ash content present in both CB and CNT. Ash content was measured by weighing 2.0 g of CB or CNT, placing it in a porcelain crucible, and completely incinerating it in an electric furnace set at 750°C, and then weighing the amount of the incinerated residue. The amount of ash was expressed as a percentage by dividing the remaining amount by the initial sample amount.
(2) Resin Dispersibility Resin dispersibility was measured by mixing 1% of the sample with polycarbonate resin (Teijin Ltd. Panlite 1-1225WP) using a Labo Plastomill at 210°C and 150 rpm for 4 minutes to prepare a resin composition. This was then melt-pressed to prepare thin flakes. The thin flakes were evaluated by observing them under a microscope. The resin dispersibility was rated in the order of "AA", "A", "B", and "C". "AA" indicates the best resin dispersibility. "B" is a practical level.
(3) Scattering property: The scattering property was measured by using SKY-2 manufactured by Shibata Scientific Co., Ltd., and putting the sample from the bottom into an air flow of 10 L/min. The scattering amount was calculated from the weight adsorbed on a filter paper set at the outlet of the device. This method is a measurement method adopted by the Japan Industrial Accident Prevention Association.

(Samples used in the Examples, etc.)
The CB is DC3501, a conductive CB manufactured by OCI Co., Ltd. This CB is a granulated product, and the granulated particles have a diameter of about 0.5 mm to 1.5 mm.
The CNTs were BT1003M manufactured by LG Chemical Co., Ltd. The granulated product was formed into a shape with a diameter of 7 mm and a thickness of 2 mm using a tablet machine.
The binder polymer is polyethylene oxide (PEO), which has a molecular weight of 100,000 to 200,000 and is available under the trade name "Alkox R-150" from Meisei Chemical Industry Co., Ltd.

[Test Example 1]
By changing the pulverizer and pulverization conditions as described below, pulverized products with different particle sizes were produced, and the uniform mixing property of CB and CNT and the resin dispersibility when blended with the resin were evaluated.
(Crushing Condition 1)
The CB and CNT were separately pulverized by stirring for 5 minutes at 1000 rpm using a Henschel mixer (FM-20 manufactured by Nippon Coke & Engineering Co., Ltd.).
(Crushing conditions 2)
The CB and CNT were separately pulverized using a cutter mill (U-210) manufactured by Nishimura Machinery Works, Ltd.
(Crushing condition 3)
The CB and CNT were separately pulverized using a jet mill (single track jet mill FS-4) manufactured by Seishin Enterprise Co., Ltd.
(Crushing condition 4)
Neither the CB nor the CNTs were milled.
The particle sizes of the crushed products crushed under the above crushing conditions are as shown in Table 1.
Next, these crushed products were put into a Henschel mixer in a ratio of 70% CB and 30% CNT, and after stirring at a speed of 500 rpm for 1 minute, about 10 g samples were taken from four locations in the tank and the ash content was measured. Furthermore, the samples collected from the four locations were mixed and the resin dispersibility was examined. The results are shown in Tables 1 and 2.

[Example 1]
CB (DC3501) and CNT (BT1003M) were placed in a Henschel mixer in a ratio of 7:3 and pulverized at 1000 rpm for 5 minutes. Next, a binder solution containing a binder polymer equivalent to 10% of the total amount of CB and CNT was added using a Henschel mixer rotated at 500 rpm for 3 minutes to obtain a wet mixture. The water content of the wet mixture was 80%.
Next, the wet mixture was granulated using a twin-screw horizontal extrusion granulator EXD-100 manufactured by Dalton Co., Ltd. to obtain a carbon material granule. The obtained carbon material granule was dried in a vacuum dryer set at 80°C.

[Example 2]
A carbon material granule was obtained in the same manner as in Example 1, except that the amount of polymer added was 5% based on the total amount of CB and CNT.

[Example 3]
A carbon material granule was obtained in the same manner as in Example 1, except that the amount of polymer added was 2% based on the total amount of CB and CNT.

[Example 4]
A carbon material granule was obtained in the same manner as in Example 1, except that the amount of polymer added was 0.1% based on the total amount of CB and CNT.

[Evaluation of polymer loading amount and scattering property]
The scattering amount of the carbon material granules obtained in Examples 1 to 4 and CB (DC3501) was measured. In addition, the scattering property of K-Nanos 100P, which is a powder-like CNT that is not granulated by Kumho Corporation, was also measured. The obtained results are shown in Table 3.
Here, it was found that the CNT (BT1003M) of LG Chemicals, which has been used in the examples, has large molded particles and must be crushed to measure the scattering properties. Since it is not possible to obtain true data when crushed, it was excluded from the assumption this time.

As is clear from the results shown in Table 3, it was found that in Examples 1 to 4, in which a binder solution was used, a carbon material granule with a small amount of scattering was obtained. Furthermore, even in the case of a polymer amount of 0.1% as in Example 4, the amount of scattering was significantly less than that of K-Nanos 100P or DC3501. As can be seen from the SEM photograph and conceptual diagram shown in Figure 1, it is believed that the granule according to the present invention has CB and CNT conveniently entangled in the micron-order range.

[Example 5, Example 6 and Comparative Example 1]
Example 5
Carbon material granules were produced using a pelletizer double EXD-60 manufactured by Dalton Co., Ltd. Specifically, the ratio of CB to CNT was set to 7:3, and the mixture was pulverized at 1000 rpm for 5 minutes. Then, 325 parts by mass of a binder solution in which a binder polymer was dissolved was added to 100 parts by mass of the total amount of CB and CNT, and this was then granulated using a biaxial horizontal extrusion granulator (screen die opening 1.2 mm). The discharge rate of the carbon material granules was approximately 100 kg/hour in wet equivalent.
(Comparative Example 1)
Patent Document 2 mainly concerns a batch type granulator. As the batch type granulator, a Hensel mixer type and a Loedige mixer type are preferable, and a Loedige mixer is particularly preferable. In order to compare the productivity of Example 5 with that of Patent Document 2, a carbon material granule was produced under the following conditions.
"Productivity of the Redeige Mixer"
The CB and CNT were put into a Redige Mixer M-130 (capacity 130 L) manufactured by Chuo Kiko Co., Ltd. in a ratio of 7:3, and pulverized at 1000 rpm for 5 minutes. A predetermined amount of binder solution was then added over 20 minutes, and granulation and sizing were carried out for another 20 minutes. As a result, 8.6 kg of carbon material granules were obtained in 40 minutes. Converted to 12.9 kg per hour on a dry basis.
Example 6
"Productivity of Extrusion Granulators"
The carbon material granules were granulated in the same manner as in Example 5, except that a pelletizer double EXD-100 manufactured by Dalton Co., Ltd. (the installation area is not significantly different from that of the Loedige Mixer M-130) was used. In the case of this granulator, the discharge amount differs depending on the screen hole diameter, but in the case of a screen die with an opening diameter of 2.0 mm, the discharge amount was 290 kg/hour in a wet state and 113 kg/hour on a dry basis. This was found to be about 8.8 times the production amount of the Loedige Mixer described above.
3 shows SEM photographs of the carbon material granules obtained in Example 5, Example 6, and Comparative Example 1. As shown in FIG. 3, it can be seen that good carbon material granules were obtained in all examples.

1...Screw case, 2...Screw, 3...Extract blade, 4...Screen, 5...Screen holder.

Claims (4)

A method for producing a carbon material granule, comprising the steps of: pulverizing and mixing carbon black granules and carbon nanotube granules to obtain a mixture, such that the particle size of the carbon black is 500 μm or less according to the method described in JIS K-6219-4, and the particle size of the carbon nanotubes is 500 μm or less according to the method described in JIS K-6219-4, and the particle size of the carbon nanotubes is 500 μm or less according to the method described in JIS K-6219-4, respectively; dissolving a solvent-soluble polymer in a solvent to prepare a binder solution; mixing the mixture with the binder solution to obtain a wet mixture; and granulating the wet mixture to obtain a carbon material granule. The method for producing carbon material granules according to claim 1,
The pulverization is carried out by at least one pulverizer selected from the group consisting of a jet mill, a vibrating ball mill, a roll crusher, and a hammer mill.
A method for producing carbon material granules. The method for producing carbon material granules according to claim 1 or 2,
The solvent-soluble polymer is a water-soluble polymer,
The solvent is water.
A method for producing carbon material granules. The method for producing carbon material granules according to claim 1 or 2,
When granulating the wet mixture, a granulator is used,
The granulator is at least one selected from the group consisting of an extrusion granulator and a shear crushing granulator;
A method for producing carbon material granules.

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