Method for manufacturing carbon material granules

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

Technical Field

[0001] The present invention relates to a method for producing a carbon material granulate.

Background Art

[0002] In recent years, various studies have been conducted on imparting conductivity or antistatic properties to resin compositions. For example, as packaging materials for electronic device components using ICs or LSIs, trays or carrier tapes formed of thermoplastic resins are known. However, ordinary resin molded products have no conductivity and have high surface resistance values and volume resistance values. Therefore, problems such as dielectric breakdown of electronic components due to charging or functional degradation due to dust adhesion may occur. To prevent this, it has been attempted to solve the problem by adding various types of materials. Among them, many studies have been conducted on imparting antistatic properties or static electricity dissipation properties by blending carbon black (hereinafter sometimes referred to as CB) or carbon nanotubes (hereinafter sometimes referred to as CNT).

[0003] As an example of granulating a mixture of CB and CNT, there is a method for producing a carbon granulate comprising a CNT dispersion step of dispersing CNTs having a particle size of 100 nm or less in water, a granulation step of mixing the CNT dispersion liquid obtained in the CNT dispersion step with CB powder in a disperser and granulating, and a drying step of drying the carbon granulate obtained in the granulation step (see Patent Document 1). Further, there is a method for producing a carbon material granulate comprising a step of dry-grinding and mixing carbon black granules and carbon nanotube granules to obtain a mixture under conditions satisfying predetermined conditions, a step of dissolving a specific solvent-soluble polymer in a solvent to prepare a binder solution, and a step of mixing and granulating the mixture while adding a predetermined amount of the binder solution to obtain a carbon material granulate (see Patent Document 2). Furthermore, there is a method for producing granules of carbon nanotubes alone, which includes the steps of: (1) preparing an aqueous solution of a water-soluble polymer having a concentration of 0.005 to 3.0% by mass; (2) impregnating the carbon nanotubes with the aqueous solution of the water-soluble polymer at a ratio of 400 to 1000 parts by mass per 100 parts by mass of carbon nanotubes to prepare a wet aggregate; (3) shearing and crushing the wet aggregate to obtain an aggregate of crushed material; and (4) drying the aggregate of crushed material to obtain a carbon nanotube-containing aggregate containing the water-soluble polymer (see Patent Document 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-201006 [Patent Document 2] Patent No. 7126666 [Patent Document 3] Patent No. 6714134 [Overview of the project] [Problems that the invention aims to solve]

[0005] According to the method for manufacturing carbon material granules described in Patent Document 1 or Patent Document 2, carbon material granules can be obtained that can reduce scattering and improve conductivity and mechanical properties. The granulation methods described in these patent documents include continuous and batch methods, and a twin-screw pin mixer is cited as an example of the continuous method. In this granulator, CB and CNT are introduced in front of a twin-screw rotating at 500 to 3000 rpm, and a binder solution is added from an inlet located downstream to mix and granulate. However, it has been found that CB and CNT scatter profusely from parts or locations until the CB and CNT are sufficiently wetted with the binder solution, as well as from the base of the rapidly rotating shaft and the input hole into which the carbon material is introduced, making this granulation method using these raw materials undesirable from an environmental or human safety standpoint. Therefore, in these methods for manufacturing carbon material granules, since the granules are produced in a batch method during the granulation process, there was room for improvement in terms of production efficiency.

[0006] The present invention aims to provide a method for producing carbon material granules that enables continuous granulation and improves production efficiency. [Means for solving the problem]

[0007] In other words, the present invention provides a method for producing carbon material granules as follows: [1] A step of grinding carbon black granules and carbon nanotube granules and mixing them to obtain a mixture such that the particle size of the carbon black according to the method of JIS K-6219-4 is 500 μm or less and the particle size of the carbon nanotubes according to the method of JIS K-6219-4 is 500 μm or less; 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. The process includes granulating the aforementioned wet mixture to obtain carbon material granules. A method for manufacturing carbon material granules. [2] In the method for producing carbon material granules described in [1], The aforementioned grinding is carried out by at least one grinder selected from the group consisting of a jet mill, a vibrating ball mill, a roll crusher, and a hammer mill. A method for manufacturing carbon material granules. [3] In the method for producing carbon material granules described in [1] or [2], The solvent-soluble polymer is a water-soluble polymer. The solvent is water. A method for manufacturing carbon material granules. [4] In the method for producing carbon material granules described in any of [1] to [3], When granulating the aforementioned 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 manufacturing carbon material granules.

[0008] According to the present invention, it is possible to provide a method for manufacturing carbon material granules that does not scatter during the granulation process, enables continuous granulation, and improves production efficiency. [Brief explanation of the drawing]

[0009] [Figure 1] This shows an SEM image of the carbon material granules obtained in this embodiment, and a conceptual diagram thereof. [Figure 2] This is a conceptual diagram of the extrusion granulator used in this embodiment. [Figure 3] These are SEM images of the carbon material granules obtained in Example 5, Example 6, and Comparative Example 1. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described below, but the present invention is not limited to the embodiments described below. Hereinafter, carbon material granules may also be simply referred to as "granules".

[0011] [Method for manufacturing carbon material granules] The method for producing granules according to this embodiment comprises the steps of: grinding carbon black granules and carbon nanotube granules so that the particle size of the carbon black according to the method of JIS K-6219-4 is 500 μm or less, and mixing them to obtain a mixture (grinding and mixing step); dissolving a solvent-soluble polymer in a solvent to prepare a binder solution (solution preparation step); adding the binder solution while mixing the ground carbon black and carbon nanotubes to obtain a wet mixture (granulation precursor) (wet mixture preparation step); and granulating the wet mixture to obtain carbon material granules (granule preparation step).

[0012] (Grinding and mixing process) In the grinding and mixing process, the CB granules and CNT granules are each ground to a specific particle size or smaller, and then mixed to obtain a mixture. The order of grinding and mixing is not particularly limited. (1) The CB granules and CNT granules may be dry-ground separately and then mixed, or (2) the CB granules and CNT granules may be mixed and then ground. There are two types of grinding methods: dry grinding and wet grinding, and they are used depending on the purpose. In this embodiment, dry grinding is preferred, but in the case of dry grinding, the type of grinder used will differ depending on the desired particle size or particle size distribution. For example, (1) for medium grinding (1 mm to several tens of μm), a roll crusher, impeller mill, cutter mill, or ring mill can be used. A Henschel mixer or Lödige mixer, which are generally used as mixers or granulators, can also be used. On the other hand, (2) for fine grinding (several tens of μm to several μm), a jet mill, roller mill, pin mill, or planetary mill can be used. Among the manufacturers of crushing machines, jet mill type crushers include Seishin Corporation, Aisin Nanotechnologies Corporation, and Earth Technica Corporation. Pin mill manufacturers include Makino Sangyo Co., Ltd., Nishimura Machinery Works Co., Ltd., and Hosokawa Micron Corporation. Impeller mill manufacturers include Seishin Corporation and Earth Technica Corporation. Furthermore, sanitary rotary crushers are manufactured by Aisin Sangyo Co., Ltd. and Tokuju Kogyo Co., Ltd. In particular, sanitary type crushers manufactured by Aisin Sangyo Co., Ltd., or the Randell Mill (RM-1N type) manufactured by Tokuju Kogyo Co., Ltd., can be directly inserted 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 can be done by feeding the crushed material into a mixing granulator such as a Henschel mixer or a Lödige mixer, and then mixing while adding water in which the polymer has been dissolved. Alternatively, the material can be directly fed into a mixing granulator such as a Henschel mixer without crushing, and then pulverized within the granulator by high-speed agitation without adding water in which the polymer has been dissolved, and then water in which the polymer has been dissolved is added to create a wet mixture that serves as a precursor to granulation. As mentioned above, for reasons such as workability, reduced transportation costs, and prevention of scattering, most brands of CB and CNT are shipped in granulated form. Generally, granulated CB is manufactured in diameters ranging from 0.25 mm to 2 mm, while CNT comes in various shapes and sizes. Currently, LG Chemical of South Korea, which boasts the world's largest production volume of MWCNT, produces CNTs in the shape of a button battery with a diameter of 7 mm and a height of 2 mm, and the weight of one granule is approximately 0.0198 g. On the other hand, the weight of one 1mm diameter CB (DC3501 from OCI, Korea) is approximately 0.0002g, and the weight ratio of the two is approximately 100 times. For example, if the mixture of CB and CNT is 70g to 30g, the number of granulated CB and CNT products will be (70g) / (0.0002g / granule) = 350,000 granules for CB and (30g) / (0.0198g / granule) = 1,515 granules for CNT. The ratio of the two granules is approximately 231 times, so it can be easily inferred that the two will not mix uniformly in a simple mixing operation. Patent Document 3 is essentially about adding water in which a water-soluble polymer is dissolved in a screw conveyor to CNT, then producing aggregates with a shear crushing processor, and then drying. More specifically, the addition amount of the polymer to CNT is 0.005 to 3% by mass, and the aqueous solution is 400 to 1000 parts by mass with respect to 100 parts by mass of CNT. Also, the supply rate of CNT to the screw conveyor is 0.25 to 1.0 kg / min, and the residence time is 1 to 3 minutes. Furthermore, a rotary cutter mill or a multi-stage rotary cutter mill is said to be preferable as the shear crushing processor. Even if CB and CNT are supplied to the screw conveyor described in Patent Document 3 and it is rotated while adding water, the screw conveyor is a device that conveys an object by rotating the blades at a low speed, so it has almost no function of mixing two or more kinds of carbon. In particular, as described above, it can be said that it is difficult to uniformly mix the granulated CB and CNT with a screw conveyor. On the other hand, according to the method for producing the granulated product according to this embodiment, CB and CNT can be uniformly mixed (see FIG. 1).

[0013] (Measurement of the particle size of the pulverized product) The particle size distribution of CNTs and CBs is measured according to JIS K-6219-4, "Method for determining the size distribution of granulated particles." The measuring instrument is a classification method that uses stacked mesh sieves, and there are different types depending on how vibration is applied, such as sonic vibration type, rotap type, or electromagnetic type. Manufacturers of sonic vibration type sieves include Hatsuratsu Co., Ltd. and Seishin Corporation. In addition to the two companies mentioned above, manufacturers of rotap sieves include CMT Co., Ltd. and AS ONE Corporation. Manufacturers of electromagnetic shaking sieves include Tsutsui Chemicals Co., Ltd. As a specific example of the measurement method, using the rotap type manufactured by CMT Co., Ltd., four to six layers of 200 mm diameter mesh sieves are stacked and set in the rotap. The most common types of mesh sizes used are typically 10 mesh (1000 μm opening), 30 mesh (500 μm), 60 mesh (250 μm), and 100 mesh (150 μm). However, 86 mesh (2000 μm) and 149 mesh (100 μm) may also be added for measurement. For measurement, a receiving tray is attached to the bottom, 100 g of granulated material is placed in the top sieve, the lid is set, and the sieve is shaken for 1 minute at a shaking speed of 290 rpm, an amplitude of 28 mm, and a beat rate of 156 t.pm. After shaking, the granulated material packed in the top and openings of each sieve is scraped off, and their weights are measured to calculate the particle size distribution. The value of the opening of the smallest mesh among the meshes that passed through is the particle size of the crushed material. The preferred particle size after grinding, as measured by the Rotap classification method, is preferably 10 μm to 500 μm for both CB and CNT, and more preferably 25 μm to 250 μm. If the particle size exceeds 500 μm, not only will the amount of aggregate increase and dispersibility worsen, but the uniform mixing of CB and CNT will also deteriorate. Furthermore, processing to a particle size finer than 10 μm is not easy as it would require industrial-scale production, and even if it were possible, it would take a long time to process, making it impractical. Moreover, this process also involves cutting the CNT fibers, which is undesirable as it worsens conductivity. In addition, when grinding after blending CB and CNT, it is preferable to make the particle size the same as that of the CNT.

[0014] Examples of the CB include those obtained by thermal decomposition methods such as the thermal method or the acetylene decomposition method, those obtained by incomplete combustion methods such as the oil furnace method, and those obtained by gasification processes of heavy oils such as the Texas method, the Fischer method, or the Shell method. These may be used alone or in combination of two or more. Specifically, for example, #4000 and #5000 series manufactured by Tokai Carbon Co., Ltd., #3000 series manufactured by Mitsubishi Chemical Corporation, FX, HS, Denka Black, etc. manufactured by Denka Co., Ltd., Conductex series manufactured by Birla Carbon Co., Ltd., Vulcan series or LITX series manufactured by Cabot Corporation, ENSACO series manufactured by Imerys Graphene, and SuperP-Li series, Printex L manufactured by Orion Engineered Carbons Co., Ltd., etc.

[0015] Regarding the CNT, the fiber diameter is 0.3 nm which can be manufactured by modern technology, but it may be thinner than 0.3 nm. Also, as the fiber diameter of the CNT becomes larger than 50 nm, the electrical or mechanical physical properties tend to deteriorate, and when it becomes larger than 100 nm, the superiority over CB or carbon nanofibers tends to disappear. Further, in the granulated product according to the present embodiment, from the viewpoint of the CNT efficiently forming a three-dimensional network structure, the fiber diameter of the CNT is more preferably 3 nm or more and 50 nm or less, still 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 the CNT is related to conductivity, mechanical physical properties, or dispersibility. The fiber length of the 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, the conductivity or mechanical physical properties tend to be difficult to exhibit. On the other hand, as the fiber length becomes larger, the entanglement of the fibers becomes stronger, so not only do the number of dispersion-defective lumps increase, but also the fibers are frequently cut during kneading and dispersion, which is not preferable. The aspect ratio of the CNTs is, for example, between 10 and 10000. Furthermore, a structure in which hexagonal mesh-like graphite sheets form a cylindrical shape is preferably used as the CNT. The CNTs can be single-layer or multi-layer, and can be selected according to the final purpose. There are also no restrictions on the manufacturing method of the CNTs. Examples of CNT manufacturing methods include thermal decomposition by contacting a carbon-containing gas with a catalyst, arc discharge by generating an arc discharge between carbon rods, laser evaporation by irradiating a carbon target with a laser, CVD by reacting a carbon source gas at high temperature in the presence of metal nanoparticles, and HiPco by decomposing carbon monoxide under high pressure. Additionally, metal atoms may be doped into the CNTs.

[0016] In the granulated material according to this embodiment, the amount of CNTs 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, based on the total amount of CB and CNTs (100% by mass). If the amount of CNTs is below the upper limit, the dispersibility of the CNTs can be improved. If the amount of CNTs is above the lower limit, the conductivity can be further improved. In this embodiment, grinding the CB and CNTs is an essential step before the series of steps that involve mixing the CB and CNTs, then mixing them with a solvent-soluble polymer, and finally granulating them. Recently, most commercially available CNTs are in granular form for purposes such as preventing scattering, reducing transportation costs, or improving workability during processing. As a result, CNTs, which were already difficult to disperse in powder form, have become even more difficult to disperse. In addition, among furnace-type CBs, almost 100% of those called conductive CBs are supplied as granules, making them significantly more difficult to disperse than powdered products. After investigating various methods to improve this dispersibility, it was discovered that grinding improves dispersibility. Furthermore, it was found that grinding both the CB and CNTs also improves the mixability of the two materials. Grinding is a method of fine-tuning a material by applying energy as a force such as "compression," "impact," "friction," or "shear," which generates stress within the material, causing it to deform and break. There are two grinding methods: dry and wet. In this embodiment, it is preferable to use a material processed by the dry method.

[0017] (Solution preparation process) In the solution preparation step, a solvent-soluble polymer is dissolved in a solvent to prepare a binder solution. Any solvent-soluble polymer that dissolves in water, organic solvents, or mixtures thereof can be used. Examples of solvent-soluble polymers include polymer-based surfactants and high-molecular-weight polymers. Examples of surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. These may be used individually or in combination of two or more types. Examples of polymeric polymers include ether polymers (polyethylene glycol (polyethylene oxide), and polypropylene glycol, etc.), vinyl polymers (polyvinyl alcohol, polyvinyl acetate, and polyvinylpyrrolidone, etc.), acrylamide polymers (polyacrylamide, etc.), amine polymers (polyethyleneimine, and polybutyleneimine, etc.), cellulose polymers (methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose, etc.), and starch polymers (oxidized starch, and gelatin, etc.). These may be used individually or in combination of two or more. Among these, glycol polymers are even more preferable from the viewpoint of reducing scattering or improving dispersibility, and polyethylene oxide is particularly preferable.

[0018] The solvents used are water, organic solvents, and mixtures thereof, but water is the most preferred. Furthermore, when water is used as the solvent, the solvent-soluble polymer is a water-soluble polymer. binder solution The concentration of the solvent-soluble polymer in the mixture is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 5% by mass or less. If the concentration of the solvent-soluble polymer is above 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, it does not penetrate the carbon material sufficiently, reducing its effectiveness in expelling air present on the surface or in pores that would negatively affect conductivity, and consequently tending to lead to a decrease in conductivity. By adding solvent-soluble polymers at the lowest possible concentration, the polymers can penetrate more easily into the voids of the carbon material, enabling uniform coating of the entire carbon material. Furthermore, adding surfactants to the binder solution can facilitate the penetration of the binder solution into the carbon material.

[0019] (Preparation process of wet mixture) 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 amount of binder solution is preferably adjusted according to the amount of solvent-soluble polymer. Specifically, the amount of 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, based on 100 parts by mass of the total amount of carbon black and carbon nanotubes.

[0020] In this embodiment, a shearing treatment may be performed on the CB and CNT during or after the wet mixture preparation step. However, in this embodiment, since the CB and CNT are sufficiently pulverized in the aforementioned pulverization and mixing step, this shearing treatment is not necessarily required.

[0021] (Granule preparation process) In the granulation preparation process, the wet mixture obtained in the wet mixture preparation process is granulated to obtain carbon material granules. By granulating the wet mixture, continuous granulation becomes possible, improving the production efficiency of the granules. The granulators used here include extruder granulators and shear crushing granulators. Among these, from the viewpoint of production efficiency, it is particularly preferable to use an extruder granulator (see Figure 2, which is a model of the inside of an extruder granulator). As shown in Figure 2, an extruder 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 type of extruder granulator is the screw-type extruder granulator, which comes in single-screw and double-screw versions. Furthermore, they are broadly classified into two types, front extruders and side extruders, depending on the installation position of the screen die used for extrusion. In the case of a single-screw screw, the screen die is almost always mounted at the front of the granulation chamber. On the other hand, in the case of a double-screw screw, screen dies are often mounted on both sides of the granulation chamber. Comparing the characteristics of single-screw and double-screw machines, the extrusion pressure is stronger with a single-screw machine, so it is possible to produce granulated products with relatively large particle sizes and higher hardness. Twin-screw extruders excel at producing small particle sizes, and while the particle strength is weaker, they offer superior production efficiency. Examples of screw-type extruder granulators and their manufacturers include the Pelletter Double EXD or Fine Luzer EXR models from Dalton Co., Ltd., the Granumaster from Okawara Seisakusho Co., Ltd., and the Extrude Mix EM from Hosokawa Micron Corporation. Examples of shear crushing and granulating machines include the Speedmill HM series manufactured by Fuji Pharmaceutical Machinery Co., Ltd., and the Choppermill manufactured by Nippon Pneumatic Mfg. Co., Ltd.

[0022] After the granulation preparation process, a drying process (drying step) for the carbon material granules may be performed as needed. Vacuum drying and hot air drying are used for drying. Suitable hot air dryers include vibrating / fluidized bed dryers, fluidized bed dryers, box dryers, and dryer-type dryers. Suitable vacuum (reduced pressure) dryers include vacuum shelf dryers, reduced pressure outer mixer dryers, and box dryers.

[0023] The drying temperature should be such that the solvent-soluble polymer does not degrade. While there is an optimal or maximum temperature depending on the type of solvent-soluble polymer, generally, a temperature of 40°C to 200°C is preferred, 50°C to 150°C is more preferred, and 60°C to 100°C is particularly preferred. The drying time also depends on the drying temperature, but is usually between 1 hour and 20 hours, and preferably between 2 hours and 10 hours.

[0024] [Effects of this embodiment] According to this embodiment, the following effects can be achieved. (1) It is possible to manufacture carbon material granules that can reduce scattering and improve conductivity and mechanical properties. (2) In this embodiment, as described above, continuous granulation is possible. Therefore, compared to conventional methods of manufacturing granulated products that were performed in batches, production efficiency can be improved.

[0025] [Variations of the Embodiment] The present invention is not limited to the embodiments described above, and any modifications, improvements, etc., that can achieve the objectives of the present invention are included in the present invention. For example, in the embodiment described above, the crushing and mixing process was carried out continuously, but this is not limited to this. For example, as CB granules, pre-crushed material may be purchased from a supplier and used. Similarly, as CNT granules, pre-crushed material may be purchased from a supplier and used. [Examples]

[0026] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples refer to mass.

[0027] The methods for measuring physical properties used in the examples, as well as the samples used in the examples, are described below. (1) Ash content (ASH) The miscibility of CB and CNT was determined by the ash content present in both CB and CNT. Ash content was measured by weighing 2.0 g of either CB or CNT, placing it in a porcelain crucible, and completely ashing it in an electric furnace set to 750°C. The remaining ash was then weighed. The ash content was calculated by dividing the remaining amount by the initial sample amount and expressed as a percentage. (2) Resin dispersibility Resin dispersibility was evaluated by mixing 1% of the sample with polycarbonate resin (Teijin Corporation, Panlite l-1225WP) using a Laboplastmill and kneading it at 210°C and 150 rpm for 4 minutes to prepare a resin composition. Next, thin sections were prepared by melt pressing this composition. These sections were evaluated by observing them under a microscope. Resin dispersibility was judged on a scale of "AA," "A," "B," and "C," in that order. "AA" indicates the best resin dispersibility, while "B" indicates a practically usable level. (3) Shatterability The dispersion test was conducted using a SKY-2 device manufactured by Shibata Scientific Co., Ltd., with the sample introduced from below into an airflow of 10 L / min. The amount of dispersion was calculated from the weight adsorbed onto the filter paper set at the device outlet. This method is the measurement method adopted by the Japan Industrial Safety and Health Association.

[0028] (Samples used in the examples, etc.) The CB is DC3501 conductive CB manufactured by OCI. This CB is a granulated product with a particle size of approximately 0.5 mm to 1.5 mm in diameter. The CNT is BT1003M manufactured by LG Chemical. This granulated product was formed using a tablet machine into a shape with a diameter of 7 mm and a thickness of 2 mm. The binder polymer is PEO (polyethylene oxide). The PEO has a molecular weight of 100,000 to 200,000, is sold under the trade name "Alcox R-150," and is manufactured by Meisei Chemical Co., Ltd.

[0029] [Test Example 1] By changing the pulverizer and pulverization conditions as described below, pulverized products with different particle sizes were prepared, and the uniformity of mixing CB and CNT, as well as the resin dispersibility when compounded with resin, were evaluated. (Crushing condition 1) Using a Henschel mixer (FM-20, manufactured by Nippon Coke Industries Co., Ltd.), the mixture was stirred at 1000 rpm for 5 minutes to grind the CB and CNT separately. (Crushing condition 2) Using a cutter mill (U-210) manufactured by Nishimura Machinery Works Co., Ltd., CB and CNT were crushed separately. (Crushing condition 3) Using a jet mill (Single Track Jet Mill FS-4) manufactured by Seishin Corporation, CB and CNT were crushed separately. (Crushing condition 4) Neither the CB nor the CNT were crushed. The particle size of the pulverized product obtained under the above pulverization conditions is shown in Table 1. Next, these pulverized materials were placed in a Henschel mixer in a ratio of 70% CB and 30% CNT, and stirred at a speed of 500 rpm for 1 minute. Approximately 10 g samples were then taken from four locations within the mixer, and the ash content was measured. Furthermore, the samples from the four locations were mixed, and the resin dispersibility was examined. These results are shown in Tables 1 and 2.

[0030] [Table 1]

[0031] [Table 2]

[0032] [Example 1] CB (DC3501) and CNT (BT1003M) were placed in a Henschel mixer in a 7:3 ratio and ground at 1000 rpm for 5 minutes. Next, a binder solution containing 10% of the total amount of binder polymer relative to the total amount of CB and CNT was added to the Henschel mixer at 500 rpm over 3 minutes to obtain a wet mixture. The water content of the wet mixture was 80%. Next, the wet mixture was granulated using a Dalton EXD-100 twin-screw transverse extrusion granulator to obtain carbon material granules. The obtained carbon material granules were dried in a vacuum dryer set to 80°C.

[0033] [Example 2] Carbon material granules were obtained in the same manner as in Example 1, except that the amount of polymer impregnation relative to the total amount of CB and CNT was set to 5%.

[0034] [Example 3] Carbon material granules were obtained in the same manner as in Example 1, except that the amount of polymer impregnation relative to the total amount of CB and CNT was set to 2%.

[0035] [Example 4] Carbon material granules were obtained in the same manner as in Example 1, except that the amount of polymer impregnation relative to the total amount of CB and CNT was set to 0.1%.

[0036] [Evaluation of polymer impregnation amount and dispersion] The amount of carbon material granules obtained in Examples 1-4 and the amount of CB(DC3501) dispersed were measured. The dispersion of Kumho's ungranulated powdered CNT, K-Nanos 100P, was also measured. The results are shown in Table 3. Here, it was found that the CNT (BT1003M) from LG Chemical, which has been used in the examples, has large molded particles, and grinding is necessary to measure its dispersibility. Since grinding would prevent obtaining true data, it was excluded from this consideration.

[0037] [Table 3]

[0038] As is clear from the results shown in Table 3, in Examples 1 to 4, which used a binder solution, it was found that carbon material granules with low dispersion were obtained. Furthermore, even in the case of 0.1% polymer content as in Example 4, the amount of dispersion was significantly lower compared to K-Nanos 100P or DC3501. As can be seen from the SEM image or conceptual diagram shown in Figure 1, we believe that this is because the granules according to the present invention have CB and CNTs conveniently intertwined in the micron-order range.

[0039] [Examples 5, 6, and Comparative Example 1] (Example 5) Carbon material granules were prepared using a Dalton Co., Ltd. Double EXD-60 pelletizer. Specifically, the ratio of carbon dioxide (CB) to carbon nanotubes (CNT) was set to 7:3, and the mixture was ground at 1000 rpm for 5 minutes. Then, 325 parts by mass of a binder solution containing a dissolved binder polymer was added to 100 parts by mass of the total amount of CB and CNT, and this mixture was then granulated using a twin-screw transverse extruder (screen die opening of 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 describes batch-type granulators. Among batch-type granulators, the Hensel mixer type and the Lödige mixer type are preferred, with the Lödige mixer being particularly preferred. To compare the productivity of Example 5 with that of Patent Document 2, carbon material granules were produced under the following conditions. "Productivity of a Redigeg mixer" A 7:3 ratio of carbon dioxide (CB) to carbon nanotubes (CNT) was placed in a 130L capacity Redigge mixer (M-130) manufactured by Chuo Kiko Co., Ltd., and ground at 1000 rpm for 5 minutes. Then, a predetermined amount of binder solution was added over 20 minutes, followed by granulation and sizing over another 20 minutes. As a result, 8.6 kg of carbon material granules were obtained in 40 minutes. Converted to an hourly rate, this is 12.9 kg on a dry basis. (Example 6) "Productivity of extrusion granulators" Except for using a Dalton EXD-100 pelletizer (whose installation area is not significantly different from that of the M-130 Redigge mixer), carbon material granules were produced in the same manner as in Example 5. In this granulator, the discharge rate differs depending on the screen pore size, but with a screen die opening of 2.0 mm, the discharge rate was 290 kg / hour in the wet state and 113 kg / hour on a dry basis. This was found to be approximately 8.8 times the production rate of the aforementioned Redigge mixer. Furthermore, SEM images of the carbon material granules obtained in Example 5, Example 6, and Comparative Example 1 are shown in Figure 3. As can be seen in Figure 3, good carbon material granules were obtained in all examples. [Explanation of symbols]

[0040] 1...Screw case, 2...Screw, 3...Extract vanes, 4...Screen, 5...Screen holder.

Claims

1. The process comprises the steps of: grinding carbon black granules and carbon nanotube granules so that the particle size of the carbon black and the particle size of the carbon nanotubes are 500 μm or less according to the method of JIS K-6219-4, and mixing them to obtain a mixture; dissolving a solvent-soluble polymer in a solvent to prepare a binder solution; mixing the binder solution with the mixture to obtain a wet mixture; and granulating the wet mixture to obtain carbon material granules. When granulating the aforementioned wet mixture, a granulator is used. The granulator is an extrusion granulator. A method for manufacturing carbon material granules.

2. In the method for producing carbon material granules according to claim 1, The aforementioned grinding is carried out by at least one grinder selected from the group consisting of a jet mill, a vibrating ball mill, a roll crusher, and a hammer mill. A method for manufacturing carbon material granules.

3. In the method for producing carbon material granules according to claim 1 or claim 2, The solvent-soluble polymer is a water-soluble polymer. The solvent is water. A method for manufacturing carbon material granules.

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