Carbon material granulates, method for producing the same, and conductive resin composition

Abstract

A carbon material granulate containing carbon black having a particle diameter D determined by the laser diffraction / scattering method specified in ISO 13320 of 250 μm or less, carbon nanotubes having a particle diameter D determined by the laser diffraction / scattering method specified in ISO 13320 of 50 μm or less, and a solvent-soluble polymer added to the carbon black and the carbon nanotubes, the solvent-soluble polymer being at least one selected from the group consisting of ether-based polymers, vinyl-based polymers, amine-based polymers, cellulose-based polymers, and starch-based polymers, and the compounding amount of the solvent-soluble polymer being 1 part by mass or more and 15 parts by mass or less relative to 100 parts by mass of the total compounding amount of the carbon black and the carbon nanotubes. 50 Carbon black having a particle diameter D determined by the laser diffraction / scattering method specified in ISO 13320 of 50 μm or less, carbon nanotubes having a particle diameter D determined by the laser diffraction / scattering method specified in ISO 13320 of 50 μm or less, and a solvent-soluble polymer added to the carbon black and the carbon nanotubes, the solvent-soluble polymer being at least one selected from the group consisting of ether-based polymers, vinyl-based polymers, amine-based polymers, cellulose-based polymers, and starch-based polymers, and the compounding amount of the solvent-soluble polymer being 1 part by mass or more and 15 parts by mass or less relative to 100 parts by mass of the total compounding amount of the carbon black and the carbon nanotubes. 50 Carbon black having a particle diameter D determined by the laser diffraction / scattering method specified in ISO 13320 of 50 μm or less, carbon nanotubes having a particle diameter D determined by the laser diffraction / scattering method specified in ISO 13320 of 50 μm or less, and a solvent-soluble polymer added to the carbon black and the carbon nanotubes, the solvent-soluble polymer being at least one selected from the group consisting of ether-based polymers, vinyl-based polymers, amine-based polymers, cellulose-based polymers, and starch-based polymers, and the compounding amount of the solvent-soluble polymer being 1 part by mass or more and 15 parts by mass or less relative to 100 parts by mass of the total compounding amount of the carbon black and the carbon nanotubes.

Description

Technical Field

[0001] The present invention relates to a carbon material granulate, a method for manufacturing the carbon material granulate, and a conductive resin composition. Background Art

[0002] Regarding imparting conductivity or antistatic properties to resin compositions, various studies have been conducted in recent years. For example, as packaging materials for component products of electronic devices obtained using ICs or LSIs, trays or carrier tapes obtained by molding thermoplastic resins are known. However, ordinary resin molded products do not have conductivity, and the surface resistance value and volume resistance value are high. Therefore, problems such as insulation breakdown of electronic components caused by charging or reduction in function caused by dirt adhesion sometimes occur. To prevent this, it is solved by adding various materials. Among them, a great deal of research has been done on imparting antistatic properties or static dissipation properties by compounding carbon black (hereinafter sometimes referred to as CB) or carbon nanotubes (hereinafter sometimes referred to as CNT), etc. As the carbon black used for imparting conductivity, generally, carbon blacks such as Ketjen black, acetylene black, or furnace black, which are called conductive carbon blacks, are mostly compounded. Among these, Ketjen black can achieve high conductivity with the smallest addition amount, so it is widely used.

[0003] However, when the compounding amount of Ketjen black is increased as with other carbon blacks, the melt viscosity becomes high, and molding processing such as injection molding becomes difficult. In addition, not only that, but there is also a problem that molded products with poor mechanical properties such as impact strength are formed. In addition, even if higher conductivity is desired, there is a physical limit in the compounding amount of carbon black, and sometimes there are difficulties in that the obtained volume resistivity (hereinafter sometimes referred to as VR) is limited. Carbon black is manufactured by incomplete combustion or pyrolysis of hydrocarbons. In addition, the manufacturing method of carbon black is subdivided into a thermal method, an acetylene decomposition method, a contact method, or a furnace method according to the type of hydrocarbon used as the raw material. The basic properties of carbon black are particle size, structure as the state of particle connection, and physicochemical properties of the particle surface, which are called the three major characteristics. Generally speaking, the quality desired for conductive carbon black can be said to be small particle size (i.e., large specific surface area), large structure, and furthermore, few physicochemical properties on the surface.

[0004] On the other hand, carbon nanotubes have a structure obtained by forming a cylindrical shape with hexagonal network-like graphite sheets having a diameter of about 1 nm to 200 nm and a length of about 0.1 μm to 2000 μm. When the cylindrical graphite sheet is a single layer, it is called a single-walled carbon nanotube (SWCNT), and when it is a multi-layer, it is called a multi-walled carbon nanotube (MWCNT). Regarding carbon nanotubes, sometimes carbon nanotube fibers also aggregate once with each other and wind around each other or form a primary aggregate in a bundle shape, and the primary aggregates mostly aggregate to form a secondary aggregate.

[0005] If the specific surface area of about 150 m is compounded into resin or the like2 When the amount of carbon nanotubes is more than / g, it is possible to obtain the desired conductivity with a smaller compounding amount than Ketjenblack, and a composite with mechanical properties such as impact strength superior to those of the carbon black compounded product can be formed, but there are the following difficulties (1) to (3).

[0006] (1) The dispersibility is worse than that of carbon black.

[0007] (2) The scattering property during kneading is large, and there are unstable factors in terms of safety.

[0008] (3) The price is usually 5 to 10 times higher than that of conductive carbon black.

[0009] As an example of dispersing CB or other carbon materials into a thermoplastic resin, there is a conductive resin composition obtained by adding a conductive carbon material such as CB or CNT to polycarbonate and polyethylene terephthalate resins (Patent Document 1). There is the following conductive sheet: using an aqueous xylan solution as a dispersant and acetone as a solvent respectively, preparing a dispersion of carbon black and carbon nanotubes, mixing the resulting substances, and then separating, drying, weakly pulverizing and adding them by filtration to obtain a conductive sheet (Patent Document 2). There is a method of obtaining an aggregate by adding a poly(diallyldimethylammonium chloride) polymer, which is a water-soluble polymer, to CNT (Patent Document 3). There is the following technique: adding various carbon materials to an HDPE resin, measuring the volume resistivity, and evaluating various carbon materials (Non-Patent Document 1). In addition, in Non-Patent Document 2, Fig. 17 shows the volume resistivity of six types of CB with a specific surface area between 50 m 2 / g to 1500 m 2 / g, but it shows that CB with a larger specific surface area gives higher conductivity.

[0010] Furthermore, as an example of granulating a mixture of CB and CNT, there is a method for manufacturing the following granulated product of carbon, which includes: a CNT dispersion step of dispersing CNT with a particle size of 100 nm or less in water; a granulation step of mixing the CNT dispersion obtained through the CNT dispersion step with CB powder in a disperser and granulating; and a drying step of drying the granulated product of carbon obtained through the granulation step (Patent Document 4).

[0011] Prior Art Documents

[0012] Patent Documents

[0013] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-202751

[0014] Patent Document 2: International Publication No. 2015 / 064708

[0015] Patent Document 3: Japanese Patent No. 6714134 Gazette

[0016] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2017-201006

[0017] Non-Patent Literature

[0018] Non-Patent Literature 1: Structure and Characteristics of Conductive Carbon Black "Ketjenblack EC", Carbon, 2006, Vol. 222, No. 222, pp. 140-146

[0019] Non-Patent Literature 2: Carbon Black and Functional Carbon Black, Journal of the Rubber Society of Japan, No. 73, No. 7 (July 2000, pp. 362-370) Summary of the Invention

[0020] Problems to be Solved by the Invention

[0021] In Patent Document 1, CB and CNT are used as the conductive carbon materials. However, in Patent Document 1, adding a glass component or glass fiber to improve the strength of the resin composition is completely different from the effects or problems as the purpose in the present invention. Regarding the mixing method of CB and CNT in Patent Document 1, there is also a description in Paragraph

[0055] of Patent Document 1 that "after dry mixing, granulation is carried out using an extrusion granulator, a briquetting machine, etc. as needed, and then melt mixing and pelletizing are carried out using a twin-screw extruder, etc.", but in both the examples and comparative examples, after dry mixing, melt mixing is carried out using a twin-screw mixer to obtain pellets. In addition, in Patent Document 1, there is no process of pulverizing in the dry mixing process, and also no treatment of adding a water-soluble polymer to the mixture of CB and CNT.

[0022] Patent Document 2 discloses that a composite paste of CNT dispersed in an aqueous xylan solution and CB dispersed in acetone is dried to prepare a composite filler, which is compounded into a resin or rubber to obtain a conductive material with excellent dispersibility. However, Patent Document 2 does not disclose pulverizing and mixing CB and CNT and then granulating with a water binder and then drying. In addition, it does not disclose adding a water-soluble polymer during granulation.

[0023] Patent Document 3 relates to manufacturing aggregates by adding a water-soluble polymer to CNT, and Patent Document 3 does not disclose content related to adding CB. Among them, the feature of the present invention is that it is found that it is not easy to think of specifically combining CB.

[0024] In Non-Patent Literature 1 Figure 3The relationship between the addition amount and the volume resistivity when various carbon blacks are added to the HDPE resin is shown. And it is known that: Ketjenblack exhibits conductivity with a smaller compounding amount than acetylene black or furnace black conductive carbon black. Furthermore, it is confirmed that: regarding the conductivity when the addition amounts are the same, the following relationship exists: Ketjenblack is greater than furnace black, and furnace black is greater than acetylene black. However, an increase in the compounding amount of carbon black leads to an increase in the melt viscosity of the resin, making it difficult not only to perform molding processes such as injection molding but also causing a decrease in mechanical properties such as impact strength. In addition, even if one wants to obtain higher conductivity, there is a physical upper limit in terms of the compounding amount of carbon black and a limit in terms of the resulting volume resistivity. At the same time, there is no relevant insight into the combination of CB and CNT in Non-Patent Document 1.

[0025] In addition, there is no relevant insight into the combination of CB and CNT in Non-Patent Document 2 either.

[0026] Patent Document 4 is characterized in that, instead of directly mixing and granulating easily scattered and difficult-to-handle CB powder and CNT powder, CNT powder, which is hydrophobic compared to CB powder, has a small bulk density and is easily scattered, is pre-dispersed in water to prepare a CNT dispersion liquid, and then added to the CB powder as a granulation binder, whereby a dense granulated product in which CB and CNT are uniformly mixed is obtained. In addition, Patent Document 4 also discloses that: 30% or less of a water-soluble organic solvent is added to the water in which the CNT is dispersed, and furthermore, a surfactant and a water-soluble polymer are used as dispersants. However, for the aqueous dispersion of CNT powder described in Patent Document 4, a medium-type disperser and an ultrasonic disperser are used, and an object refined to below the micron order is used. Regarding the dispersion described in the examples, two pre-mixings, the first and the second, are performed, and thereafter, a bead mill is used to obtain the final dispersion liquid. That is, the dispersion of CNT powder requires several hours to several tens of hours, and the manufacturing is carried out by a method with extremely poor productivity. In contrast, in the present invention, in order to make the mixing state of CB powder and CNT powder uniform, the CB powder and the CNT powder are directly and simultaneously subjected to a dry pulverization process, or, after CB and CNT are mixed in advance using a powder mixer, the dry pulverization process is performed. The dry pulverization process refers to a process in which a mixture of CB and CNT is passed through an ultrafine pulverizer such as a jet mill or a JET NANOMIZER, whereby a uniform mixture pulverized to the micron order to the nano order is obtained. Furthermore, another purpose of the ultrafine pulverization treatment before granulation is also to make the commercially available CB and CNT in their usual granular form (granulated product) into powder form. Recently, especially for CB and CNT, in order to reduce the transportation cost, improve the ease of handling by end users, and safety, the vast majority of trademarks are in a granulated form. From the viewpoint of dispersibility, it is worse than the powder form. Furthermore, as a commercially available product, even if there is a slightly remaining powder product, several percent of the granular products formed in the production line are mixed, and therefore, from the viewpoint of dispersibility, it is preferable that the granular product is also pre-pulverized, and the above dry pulverization process is also suitable for this treatment.

[0027] An object of the present invention is to provide a carbon material granulated product, a method for manufacturing a carbon material granulated product, and a conductive resin composition that can reduce the dispersibility and improve the conductivity and mechanical properties.

[0028] Means for solving the problem

[0029] That is, according to the present invention, a carbon material granulated product, a method for manufacturing a carbon material granulated product, and a conductive resin composition shown below can be provided.

[0030] [1] A carbon material granulated product containing a particle size D obtained by the laser diffraction / scattering method specified in ISO13320 50Carbon black with a particle size D of 250 μm or less, determined by the laser diffraction / scattering method specified in ISO 13320 50 Carbon nanotubes with a particle size of 50 μm or less, and a solvent-soluble polymer added to the carbon black and the carbon nanotubes. The solvent-soluble polymer is at least one selected from the group consisting of ether-based polymers, vinyl-based polymers, amine-based polymers, cellulose-based polymers, and starch-based polymers. The compounding amount of the solvent-soluble polymer is 1 part by mass or more and 15 parts by mass or less relative to 100 parts by mass of the total compounding amount of the carbon black and the carbon nanotubes.

[0031] [2] The carbon material granulate according to the above [1], wherein, after reducing the pressure to the range of 10 2 mmHg to 10 -2 mmHg, heating at 1500 °C for 30 minutes, and the desorbed hydrogen amount of the carbon black quantified by gas chromatography is 2 mg / g or less.

[0032] [3] A method for manufacturing a carbon material granulate, comprising the following steps: dry-crushing carbon black granulates and carbon nanotube granulates so that the particle size D of the carbon black determined by the laser diffraction / scattering method specified in ISO 13320 50 becomes 250 μm or less, and the particle size D of the carbon nanotubes determined by the laser diffraction / scattering method specified in ISO 13320 50 becomes 50 μm or less, and mixing to obtain a mixture; a step of dissolving a solvent-soluble polymer in a solvent to prepare a binder solution; and a step of granulating by mixing while adding the binder solution to the mixture to obtain a carbon material granulate. The solvent-soluble polymer is at least one selected from the group consisting of ether-based polymers, vinyl-based polymers, amine-based polymers, cellulose-based polymers, and starch-based polymers. The compounding amount of the solvent-soluble polymer added to the carbon black and the carbon nanotubes is 1 part by mass or more and 15 parts by mass or less relative to 100 parts by mass of the total compounding amount of the carbon black and the carbon nanotubes.

[0033] [4] A conductive resin composition containing the carbon material granulate according to the above [1] or [2] and a resin. The resin is at least one selected from the group consisting of polyolefin resins, polyhaloolefin resins, polyester resins, polyamide resins, polyimide resins, polyether resins, polyvinyl resins, polystyrene resins, polyvinyl alcohol resins, polymethacrylate resins, polyurethane resins, polyepoxy resins, polyphenol resins, polyurea resins, and polyethersulfone resins.

[0034] According to the present invention, there can be provided a granulated carbon material capable of reducing scattering, a method for manufacturing the granulated carbon material, and a conductive resin composition, which can improve conductivity and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a photograph or the like showing the dispersibility of the resin composition before and after pulverization of CB and CNT obtained in Test Example 1.

[0036] Figure 2 It is a photograph showing the dispersibility in the resin composition when the mixing ratio of CB and CNT obtained in Test Example 3 is changed.

[0037] Figure 3 It is a photograph of the dispersibility of the resin composition when the solvent-soluble polymer obtained in Test Example 4 is changed.

[0038] Figure 4 It is a graph showing the relationship between the compounding amount and the resistance of the resin composition obtained by changing the compounded CB of the granulated carbon material obtained in Test Example 6.

[0039] Figure 5 It is a graph showing the relationship between the volume resistivity value at 1.5% compounding in the granulated carbon material obtained in Test Example 7 and the amount of hydrogen when CB is heated at 1500 °C.

[0040] Figure 6 It is based on Non-Patent Document 1 Figure 3 to calculate the required CB compounding amount for obtaining a resin composition of 100 Ω·cm, and its relationship with the amount of hydrogen when CB is heated at 1500 °C.

[0041] Figure 7 It is a transmission electron microscope photograph showing the mixing state of carbon black and carbon nanotubes. DETAILED DESCRIPTION OF THE INVENTION

[0042] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. Hereinafter, the granulated carbon material may sometimes be abbreviated as "granulate".

[0043] <Granulated Carbon Material>

[0044] First, the granulated carbon material according to the present embodiment will be described.

[0045] The granulate according to the present embodiment contains: CB having a particle size below a specific value, CNT having a particle size below a specific value, and a solvent-soluble polymer added to the CB and the CNT.

[0046] The reason for obtaining a carbon material granulate that can reduce scatterability and improve conductivity and mechanical properties through this embodiment is not yet certain, and the inventors of the present invention speculate as follows.

[0047] First, the reason for the ability to reduce scatterability is speculated as follows. That is, if both CB and CNT are powders or dry granulated products, they are prone to scattering. However, in this embodiment, a solvent-soluble polymer is added to CB and CNT to cover the surface of the carbon material granulate, etc. Moreover, CB and CNT do not separate in the form of powders. Therefore, when the carbon material granulate is mixed into a resin or the like, scatterability can also be reduced, and problems such as a decrease in safety or workability can be prevented.

[0048] In addition, among CB and CNT, especially CNT has a problem of poor dispersibility when mixed into a resin or the like. Therefore, there may be a problem that the conductivity and mechanical properties cannot be sufficiently improved using the carbon material granulate. In contrast, in this embodiment, the respective particle sizes of CB and CNT are adjusted to be below a specific size, and thus a uniform mixture is formed. If a solvent-soluble polymer is added to such CB and CNT, the dispersibility becomes good when mixed into a resin or the like. Therefore, the conductivity and mechanical properties can be sufficiently improved using the carbon material granulate.

[0049] In addition, when compounded into a resin or the like as conductive carbon black, the CB with the largest reduction in resistance per unit compounding amount, that is, the CB with the most excellent conductivity, is Ketjenblack. However, if Ketjenblack is compounded at a high concentration until a low VR is reached, the mechanical properties, especially the impact strength, are significantly reduced. CNT is considered to be one of the most suitable materials for ensuring conductivity and further improving mechanical properties. However, there is a problem of difficulty in dispersing CNT when compounded into a resin or the like. In addition, since the bulk specific gravity is lower than that of CB, there is more scattering during processing. Therefore, it is said that there are also problems in terms of safety. Furthermore, there is also a disadvantage in terms of cost.

[0050] The inventors of the present invention have tried mixing CB and CNT as a means to improve these situations. Thereby, first, the mechanical properties can be improved. In addition, in this embodiment, a solvent-soluble polymer is added to CB and CNT. Moreover, CB and CNT do not separate in the form of powders. Therefore, when the carbon material granulate is mixed into a resin or the like, scatterability can also be reduced, and problems such as a decrease in safety or workability can be prevented.

[0051] The reason for the ability to improve conductivity is speculated as follows. That is, the mechanism of exhibiting conductivity when compounding CB is generally explained by the percolation phenomenon and the tunneling phenomenon (the "tunneling" effect caused by π electron transition). Based on these statements, the key to effectively forming a conductive circuit is the following (1) to (5).

[0052] (1) Small particle size.

[0053] (2) Large surface area.

[0054] (3) Highly developed structure.

[0055] (4) Well-developed crystal structure.

[0056] (5) Few impurities that capture π electrons.

[0057] It can be considered that the mixture described in this embodiment is particularly related to (3), (4), and (5). However, before discussing the mechanism of conductivity performance, it is important to consider how to make CB itself into a conductor. CB is a raw material for forming an electrical conductor by the movement of π electrons on the microcrystalline plane of the particle surface. Therefore, the development of microcrystals leads to the easy movement of π electrons, which is a preferred direction as a conductor. In addition, in the process of developing microcrystals, impurities inside and on the surface of the particles can be reduced. Therefore, this aspect is also preferred. What are called impurities in the category of conductive CB are hydrogen, oxygen, or sulfur that form functional groups on the particle surface, un-decomposed raw material hydrocarbons (PAH), etc. However, the ones that have the greatest impact on conductivity are hydrogen and oxygen. They exist in the form of hydrogen in carboxyl groups, hydroxyl groups, carbonyl groups, phenolic hydroxyl groups, the hydrogen at the end of their benzene rings, etc. Among them, the carboxyl group and hydrogen have an obvious impact on conductivity.

[0058] In addition, in this embodiment, the carbon nanotubes mixed with carbon black form a preferred surface as a conductor with a fiber diameter in the order of 3 nm to 50 nm, a fiber length in the order of 0.1 μm to 2000 μm, a well-developed crystal structure, and few functional groups on the fiber surface. In addition, compared with the length of the structure of carbon black, carbon nanotubes have fibers that are several times to hundreds of times longer. The inventors of the present invention speculate that the unexpectedly high conductivity shown in the mixture obtained by blending with CB may be because: compared with when they exist alone, the three-dimensional structure network expands, and the π electron transition (tunneling effect) from the fibers formed at the ends of the network increases.

[0059] (Carbon material)

[0060] The carbon material used in this embodiment is CB with a particle size D 50 of 500 μm or less and CNT with a particle size D 50 of 100 μm or less.

[0061] Here, the particle size D of CB and CNT 50 can be measured by the laser diffraction / scattering method described in detail later.

[0062] As CB, known substances can be appropriately used. It is known that the less the amount of hydrogen on the surface of CB particles, the more excellent the conductivity.

[0063] The measurement of the hydrogen content uses a method called vacuum pyrolysis method, based on the research of Barton et al. Specifically, the following method is used: After precisely weighing about 0.5 g of dry CB, it is put into a heat-resistant test tube, and the pressure is reduced to medium vacuum (10 2 Pa to 10 -2 Pa) or less, then it is loaded into an electric furnace and heated at 1500 °C for 30 minutes, and the hydrogen on the surface of the desorbed CB is quantified by gas chromatography.

[0064] The hydrogen content obtained in this way is preferably 2 mg / g or less, more preferably 1.5 mg / g or less, and further preferably 1 mg / g or less.

[0065] Regarding the reason why the conductivity of the carbon material granulate can be further improved if the hydrogen content at 1500 °C is below the aforementioned upper limit, the present inventors speculated as follows.

[0066] That is, when explaining the conductivity performance mechanism of carbon materials including CB alone using percolation theory, there are functional groups such as carboxyl, hydroxyl, carbonyl or hydrogen on the surface of carbon black. It can be considered that: the functional group of carbon nanotubes is mainly hydrogen, but the amount is very small. Therefore, the functional groups of the mixture of CB and CNT are mostly the functional groups derived from carbon black. Hydrogen becomes a barrier when π electrons move. Therefore, as conductive CB, it is said that hydrogen is preferably as little as possible. However, when CB is added to the resin alone, no correlation is observed between the conductivity and the hydrogen content. In addition, in the mixed system of CB and CNT, there is no research related to whether hydrogen in the functional group has an impact.

[0067] When CB is compounded into the resin alone, according to Figure 3 of Non-Patent Document 1, although the effectiveness of the volume resistivity achieved by the type of CB is clearly ranked, no correlation with the inherent hydrogen content of CB is observed. In contrast, the present inventors found that in the system of mixing CNT and CB, the same tendency as the volume resistivity when CB is compounded into the resin alone is not observed, that is, the conductivity of the mixture cannot be assumed based on the conductivity of CB alone. Therefore, it can be known that compared with the aforementioned generally mentioned characteristics (small particle size, long structure, etc.) preferred for conductive CB, the hydrogen content on the surface of CB obtained by heating at 1500 °C significantly contributes, and it can be known that by slightly varying the hydrogen content at 1500 °C, the volume resistivity when compounded into the resin is about six orders of magnitude different. Not only the specific surface area or the formation of the structure, but the lower the inherent hydrogen content of the selected CB, the smaller the volume resistance value after mixing with CNT. Based on this insight, the present inventors speculated that by selecting CB for obtaining the expected conductivity, conductive performance more excellent than required can be obtained.

[0068] Next, CNT, which is preferably used as a conductive raw material, will be described. The key to the preferred CNT is as follows (1) to (5).

[0069] (1) The fiber diameter is fine.

[0070] (2) The specific surface area is large.

[0071] (3) The fiber length is an appropriate length (in one description, several μm to several tens of μm).

[0072] (4) The crystallite is well-developed and the number of functional groups is small.

[0073] (5) The amount of impurities such as catalysts is small.

[0074] The key to the preferred CNT is a substance having the above-described characteristics and properties. Usually, the available CNT is limited. Therefore, how to make flexible use of it is a technology today. As described in (4), in CNT, the amount of functional groups, especially the amount of hydrogen, also affects the conductivity. However, since the crystal structure of CNT is well-developed, the amount of hydrogen is very small. Therefore, it can be considered that the vast majority of the functional groups in the mixture of CB and CNT are hydrogen functional groups derived from CB. Hydrogen becomes a barrier when π electrons move. Therefore, as conductive carbon black, it is said that the amount should be as small as possible.

[0075] However, as will be described later, when CB is added to the resin alone, no correlation is observed between the conductivity and the amount of hydrogen. In addition, in the mixed system of CB and CNT, there is no research on whether the hydrogen in the functional groups has an impact.

[0076] Examples of CB include CB obtained by pyrolysis methods such as thermal method or acetylene decomposition method, and incomplete combustion methods such as oil furnace method; and CB obtained by gasification processes of heavy oils such as Texas method, Fauser method or Shell method. They can be used alone or in combination of two or more.

[0077] Specifically, for example, #4000 and #5000 series manufactured by Tokai Carbon Co., Ltd.; #3000 series manufactured by Mitsubishi Chemical Corporation; FX, HS, DENKABLACK, etc. manufactured by DENKA Co., Ltd.; Conductex series manufactured by Birla Carbon; Vulcan series and LITX series manufactured by Cabot Corporation; ENSACO series and SuperP-Li series manufactured by Imerys GC; Printex L manufactured by Orion Engineered Carbons, etc.

[0078] As for the CNT, the fiber diameter can be 0.3 nm which can be manufactured using modern technology, and it can be finer than 0.3 nm. In addition, as the fiber diameter is greater than 50 nm, there is a tendency for the electrical and mechanical properties to decrease. If it is greater than 100 nm, there is a tendency for the advantages to disappear compared with CB, carbon nanofibers, etc.

[0079] In addition, in the granulated product described in the present embodiment, from the viewpoint of effectively forming a three-dimensional network structure by CNT, the fiber diameter of the CNT is more preferably 3 nm or more and 50 nm or less, further preferably 5 nm or more and 40 nm or less, and particularly preferably 10 nm or more and 30 nm or less.

[0080] The fiber length of the CNT is related to the conductivity, mechanical 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, there is a tendency that the conductivity or mechanical properties are not easily exhibited. As the fiber length becomes larger, the entanglement of the fibers becomes stronger. Therefore, not only are there more poor dispersion blocks, but also more fiber cuttings occur during kneading and dispersion, showing an unfavorable tendency.

[0081] As for the aspect ratio of the CNT, it is about 10 to 10000. In addition, as the CNT, a structure in which hexagonal network-shaped graphite sheets are cylindrical is suitable. The CNT can 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 occurs between carbon rods; a laser evaporation method in which a carbon target is irradiated with a laser; a CVD method in which a gas of a carbon source reacts at a high temperature in the presence of metal fine particles; and a HiPco method in which carbon monoxide is decomposed under high pressure, etc. In addition, metal atoms can be doped into the CNT.

[0082] In the granulated product described in the present embodiment, the compounding amount of the CNT is preferably 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 35% by mass or less, based on 100% by mass of the total compounding amount of CB and CNT.

[0083] If the compounding amount of the CNT is below the aforementioned upper limit, the dispersibility of the CNT can be improved. If the compounding amount of the CNT is above the aforementioned lower limit, the conductivity can be further improved.

[0084] In the present invention, before a series of steps of mixing CB and CNT, adding a solvent-soluble polymer, and granulating, crushing CB and CNT is an essential step. Most of the commercially available CNTs currently available are in the form of granules for the purposes of preventing scattering, reducing transportation costs, and improving workability during processing. Therefore, CNTs, which are difficult to disperse even in powder form, are becoming increasingly difficult to disperse. In addition, almost 100% of the CBs known as conductive CBs in furnace black are provided in the form of granulated products, making them significantly more difficult to disperse compared to powdered products. Various studies have been conducted on methods to improve this dispersibility, and it has been found that the dispersibility can be improved by performing a crushing treatment. The crushing method refers to a method in which energy is applied to a material in the form of forces such as "compression", "impact", "friction", and "shearing", causing stress to be generated in the material, deforming and breaking it, thereby achieving micronization. As the crushing method, there are dry methods and wet methods, but in the present invention, a substance treated by a dry method is preferably used.

[0085] (solvent-soluble polymer)

[0086] The solvent-soluble polymer used in this embodiment is added to CB and CNT.

[0087] Carbon nanotubes have poor workability due to their low bulk density and cause environmental pollution due to their scattering properties. Therefore, it is said that there are also problems in terms of safety. To solve this problem, in this embodiment, a solvent-soluble polymer is added to CNT and CB.

[0088] As the solvent-soluble polymer, any polymer that can be dissolved in water, organic solvents, and solvents that are mixtures of them can be used. Examples of the solvent-soluble polymer include polymeric surfactants and high molecular polymers.

[0089] Examples of the surfactant include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. They can be used alone or in combination of two or more.

[0090] Examples of the high molecular polymer include ether polymers (such as polyethylene glycol (polyethylene oxide) and polypropylene glycol), vinyl polymers (such as polyvinyl alcohol, polyvinyl acetate, and polyvinylpyrrolidone), acrylamide polymers (such as polyacrylamide), amine polymers (such as polyethyleneimine and polybutyleneimine), cellulose polymers (such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropylmethyl cellulose), and starch polymers (such as oxidized starch and gelatin). They may be used alone or in combination of two or more. Among these, from the viewpoint of reducing scattering or improving dispersibility, glycol polymers are more preferably used, and polyethylene oxide is particularly preferably used.

[0091] In the granulated product according to this embodiment, the compounding amount of the solvent-soluble polymer is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 3 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the total compounding amount of carbon black and carbon nanotubes.

[0092] (Carbon material granulated product)

[0093] The granulated product according to this embodiment is a granulated product formed from a mixture of CB, CNT, and a solvent-soluble polymer. The shape of the granulated product is preferably spherical.

[0094] The particle size of the granulated product is preferably 0.1 mm or more and 5 mm or less, more preferably 0.3 mm or more and 3 mm or less. As the particle size of the granulated product is less than 0.3 mm, there is a tendency that the fluidity of the flow from a hopper or the like decreases and the amount of scattering of CNTs or the like in the use environment increases. On the other hand, as the particle size of the granulated product is greater than 3 mm, there is a tendency that it is difficult to micronize or break the granulated product during kneading or dispersion with a synthetic resin or the like, and it is easy to cause poor dispersion, so it is not preferred. In particular, if the particle size of the granulated product is less than 0.1 mm or greater than 5 mm, this tendency is significant, so it is not preferred. The particle size of the granulated product is measured by placing the granulated product together with a measuring tool and observing it with an optical microscope.

[0095] The hardness of the granulated product is preferably 5 g / granule or more and 20 g / granule or less, more preferably 10 g / granule or more and 15 g / granule or less. As the hardness exceeds 15 g / granule, there is a tendency that not only the initial dispersibility but also the final dispersibility deteriorates when compounded into a synthetic resin, rubber, water, solvent, or color carrier and dispersed. On the other hand, as the hardness is less than 10 g / granule, there is a tendency that powdering occurs during packaging, transportation, storage, kneading compounding, etc., and environmental pollution is likely to occur, so it is not preferred. In particular, if the hardness is less than 5 g / granule or greater than 20 g / granule, this tendency is significant, so it is not preferred. The hardness of the granulated product can be measured in accordance with JIS K6219-3.

[0096] The hardness of the granulated product can be adjusted by changing, for example, the type of the solvent-soluble polymer. From the viewpoint of adjusting the hardness of the granulated product within the above range, as the solvent-soluble polymer, a glycol-based polymer is preferably used, and polyethylene oxide is particularly preferably used.

[0097] <Method for manufacturing carbon material granulated product>

[0098] Next, the method for manufacturing the granulated product according to the present embodiment will be described.

[0099] In the method for manufacturing the granulated product according to the present embodiment, as a specific implementation method, although there are slightly different matters, it is basically a method having the following steps: a step of finely pulverizing and mixing CNT granulated matter and CB granulated matter in an inert atmosphere by a dry method (pulverization and mixing step); a step of dissolving a solvent-soluble polymer in a solvent to prepare a binder solution (solution preparation step); and a step of obtaining a carbon material granulated product by mixing while adding the aforementioned binder solution to the mixture of CB and CNT little by little (granulated product preparation step).

[0100] By the method for manufacturing the granulated product according to the present embodiment, the granulated product according to the aforementioned present embodiment can be produced. Among them, the method for manufacturing the granulated product according to the aforementioned present embodiment is not limited to the method for manufacturing the granulated product according to the present embodiment. For example, in the pulverization and mixing step, CNT granulated matter and CB granulated matter are used and pulverized, but equivalent CNT or CB after the pulverization treatment can be used, and the pulverization treatment can be omitted.

[0101] (Pulverization and mixing step)

[0102] In the pulverization and mixing step, the CB granulated matter and the CNT granulated matter are each dry-pulverized to a specific particle size or less, and they are mixed to obtain a mixture. Here, the order of dry pulverization and mixing is not particularly limited. (1) The CB granulated matter and the CNT granulated matter can be dry-pulverized separately, and then mixed; (2) The CB granulated matter and the CNT granulated matter can be mixed, and then dry-pulverized.

[0103] As the pulverization method, there are dry pulverization and wet pulverization, which are distinguished and used according to their purposes. In the present invention, dry pulverization is used, but in the case of dry, the pulverizer used varies depending on the target particle size, particle size distribution, etc. For example, (1) in the case of medium pulverization (10 mm or less) as the purpose, a turbo mill, a pin mill, a roll mill, etc. are used, and (2) in the case of fine pulverization (tens of μm or less) as the purpose, a jet mill, a ball mill, a vibration ball mill, a planetary mill, etc. are used.

[0104] Generally, dry pulverization treatment is carried out in the atmosphere. Therefore, most of the treated products are oxidized. For example, regarding the physical properties after charging about 60% of the volume of CNT into a steel ball mill with an internal volume of about 2 liters and treating for 48 hours, the powder resistance (the resistance of CNT itself) increased from 8.2×10 -2 Ω·cm to 5.1×10 -1 Ω·cm. In addition, the pH decreased from 8.5 to 6.9. It can be considered that this is because the fibers of CNT are cut off, reactive sites are generated here, and so-called air oxidation has occurred. Therefore, in the present invention, in order to avoid oxidation of the raw materials, in the fine pulverization and ultrafine pulverization treatments using a jet mill, a vibration ball mill, etc., it is carried out in an inert atmosphere. As the inert gas, nitrogen, argon, carbon dioxide, etc. are used, but in this embodiment, argon is used.

[0105] Among the manufacturers of pulverizers, as manufacturers of jet mill type pulverizers, there are SEISHIN ENTERPRISE Co., Ltd., Aishin Nano Technologies Co., Ltd., EARTH TECHNICA Co., Ltd., etc. In addition, as manufacturers of pin mills, there are Makino Sangyo Co., Ltd., Nishimura Machinery Works, Hosokawa Micron Corporation, etc. In addition, as manufacturers of turbo mills, there are SEISHIN ENTERPRISE Co., Ltd. or EARTH TECHNICA Co., Ltd., etc.

[0106] (Measurement of the particle size of the pulverized product)

[0107] In the measurement of the particle size distribution of CNT and CB, the laser diffraction / scattering method specified in ISO13320 is used to obtain it. As the measuring instrument, Laser Micronsizer LMS-3000 (manufactured by SEISHIN ENTERPRISE Co., Ltd.) is used for the measurement. The measurable range of this device is 0.01 to 3500 μm. The aqueous dispersion medium is prepared by adding 0.05 g of polyoxyethylene alkyl ether (trade name EMULGEN 705 manufactured by Kao Corporation) as a surfactant to 50 mL of pure water. In the measurement, 10 mg of CB and CNT are weighed into a vial with an internal volume of 20 mL, 10 mL of the aqueous dispersion medium is added, and then it is dispersed for about 10 minutes using an ultrasonic disperser. Regarding the optical model of the measuring instrument, the refractive indices of CB and CNT are set to 1.520 respectively, and the refractive index of water is set to 1.333 for the measurement.

[0108] Regarding the suitable particle size after pulverization, the median particle size D 50When observed, in the case of CB, it is 1 μm or more and 500 μm or less, preferably 10 μm or more and 250 μm or less. If it is greater than 500 μm, there are more agglomerates and the dispersibility becomes poor. In addition, in the case of industrial-scale production, it is not easy to process those finer than 1 μm. Even if it can be processed, the processing takes a long time and is not practical. On the other hand, the suitable particle size D of CNT 50 is 10 μm or more and 100 μm or less, preferably 10 μm or more and 50 μm or less. If it is greater than 50 μm, similar to the case of CB, there are multiple agglomerates and the dispersibility becomes poor. In addition, the processing finer than 10 μm causes the CNT fibers to break and the conductivity becomes poor, so it is not preferred. Furthermore, when CB and CNT are blended and then pulverized, the particle size is preferably the same as that of CNT.

[0109] (Solution preparation process)

[0110] In the solution preparation process, a solvent-soluble polymer is dissolved in a solvent to prepare a binder solution.

[0111] The solvent-soluble polymer is as described above.

[0112] As the solvent, it is water, an organic solvent, and a mixture thereof, and among them, water is most preferred.

[0113] The concentration of the solvent-soluble polymer in the binder solution is preferably 1% by mass or more and 10% by mass or less, more preferably 2% by mass or more and 5% by mass or less.

[0114] If the concentration of the solvent-soluble polymer is at least the aforementioned lower limit, the solvent-soluble polymer can be added to the carbon material more efficiently. On the other hand, when the concentration of the solvent-soluble polymer exceeds the aforementioned upper limit, there is a tendency that it will not sufficiently penetrate into the carbon material, the effect of expelling the air present on the surface or in the pores that will damage the electrical conductivity is reduced, and as a result, the electrical conductivity is reduced.

[0115] The solvent-soluble polymer is added at as low a concentration as possible, so that the solvent-soluble polymer can more easily penetrate into the voids of the carbon material and can be uniformly coated on the entire carbon material. In addition, by adding a surfactant to the binder solution, the binder solution can be easily penetrated into the carbon material.

[0116] (Granule preparation process)

[0117] In the granule preparation process, the binder solution is added to the mixture of CB and CNT in small amounts while mixing to obtain a carbon material granule.

[0118] As the mixing devices used herein, they can be roughly divided into batch type and continuous type. As representatives of the batch type, Henschel type stirring mixers, batch type Loedige mixers, etc. can be cited. In addition, as the continuous type, a twin-shaft pin type mixer that mixes by the rotation of a twin-shaft screw can be cited.

[0119] As for the Henschel type, the "High Speed Mixer" series manufactured by EARTHTECHNICA, the "SPG" series manufactured by TECHNOPAUDAL, the "FM mixers" manufactured by NIPPON COKE&ENGINEERING, the "SMB" or "SM" series manufactured by KAWATAMFG, and the "VG" series manufactured by POWLEX, etc. can be cited. The Loedige mixer has various models of M20 to M8000D sold by MATSUBO.

[0120] As for the twin-shaft pin type, the "Dough Pelletizer" manufactured by Shin Nippon can be cited.

[0121] When continuous mixing is carried out in the granule preparation process, taking the pin type mixer as an example, the process is as follows. That is, a mixture of carbon nanotubes pulverized to less than 100 μm and carbon black pulverized to less than 500 μm is quantitatively charged into the device where the rotating body works from the charging port, a binder solution is added and mixed from the injection port located at the rear stage of the charging port, the granule is taken out from the discharge port, and it is dried in the drying process described later. The mixing performance is adjusted according to the residence time in the device. The longer the residence time, the more spherical the mixture can be obtained. When the desired granule cannot be obtained, sometimes the pin type mixer is increased to two stages in series for granulation. The rotation speed of the rotating body is preferably 500 rpm or more and 3000 rpm or less, more preferably 1000 rpm or more and 2000 rpm or less.

[0122] On the other hand, when batch mixing is carried out in the granule preparation process, taking the Henschel type mixer as an example, the process is as follows. That is, in the same way as in the continuous type case, after charging a specified amount of pulverized carbon nanotubes and carbon black powder into the mixer, it is stirred by the rotating blades, a small amount of binder solution is added thereto, and while confirming the mixing state, the solvent is gradually added. When it is estimated that the desired granule size is reached, the granule is taken out and dried in the drying process described later. The rotation speed of the rotating blades is preferably 300 rpm or more and 2500 rpm or less, more preferably 500 rpm or more and 2000 rpm or less.

[0123] After the granule preparation step, a step of drying the carbon material granules (drying step) is performed. Drying is performed using vacuum drying, hot air drying, etc. As the hot air dryer, a vibration / fluidized dryer, a fluidized dryer, a box dryer, a dryer type dryer, etc. can be used. On the other hand, as the vacuum (reduced pressure) dryer, a vacuum tray dryer, a reduced-pressure outer mixer type dryer, a box dryer, etc. can be used.

[0124] As the drying temperature, a temperature at which the solvent-soluble polymer does not deteriorate is preferred. Therefore, there is an optimum temperature or a maximum temperature depending on the type of the solvent-soluble polymer. Generally, it is preferably 40°C or higher and 200°C or lower, more preferably 50°C or higher and 150°C or lower, and particularly preferably 60°C or higher and 100°C or lower. In addition, the drying time also varies depending on the drying temperature and is usually 1 hour or longer and 20 hours or shorter, preferably 2 hours or longer and 10 hours or shorter.

[0125] <Conductive resin composition>

[0126] Next, the conductive resin composition according to the present embodiment will be described.

[0127] The conductive resin composition according to the present embodiment contains the aforementioned carbon material granules and a resin.

[0128] According to the granules of the present embodiment, conductivity and mechanical properties can be improved. Therefore, the granules of the present embodiment can be used to produce an extremely wide range of conductive resin compositions.

[0129] Examples of the resin include polyolefin resins, polyhaloolefin resins, polyester resins, polyamide resins, polyimide resins, polyether resins, polyvinyl resins, polystyrene resins, polyvinyl alcohol resins, polymethacrylate resins, polyurethane resins, polyepoxy resins, polyphenol resins, polyurea resins, and polyethersulfone resins.

[0130] <Article>

[0131] In the carbon material granules according to the present embodiment described above, the carbon material containing carbon black and carbon nanotubes is well dispersed and substantially no large aggregates are generated, and antistatic and strength are excellent. Therefore, by utilizing this property, the following articles can be provided. That is, the following articles can be provided: a coating, an ink, a coating agent, a resin molding material, a conductive material, a heat conductive material, and an antistatic material containing the aforementioned carbon material granules. In addition, the following articles can be provided: a battery material and a mechanical component that use the aforementioned carbon material granules as a dispersion liquid and have a coating film formed therefrom.

[0132] As a method for preparing a coating or an ink, there are, for example, the following methods: a method of adding the carbon material granulated product to a solvent, a resin, various additives, etc. in such a manner as to form a coating composition or an ink composition; or a method of adding the carbon material granulated product to a commercially available coating or ink, etc. As a method for manufacturing a resin molded article in which a carbon material containing carbon black and carbon nanotubes is dispersed, there is, for example, a method of mixing the carbon material granulated product into a molten resin material, etc. Regarding the amount of the carbon material granulated product used, it is desirable to be 30% by mass or less. If it exceeds 30% by mass, various mechanical properties such as tensile strength or impact strength may decrease.

[0133] Examples

[0134] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. It should be noted that "parts" and "%" in the examples and the like are based on mass unless otherwise specified.

[0135] <Preparation of Materials>

[0136] Prepare the carbon materials and solvent-soluble polymers shown below.

[0137] (Carbon Materials)

[0138] [Carbon Nanotubes (CNT)]

[0139] As CNTs, three types named "NC7000", "BT-1001M", and "CP-1001M" are used. They are all multi-walled CNTs, and the manufacturer names and physical properties are shown in Table 1.

[0140] [Table 1]

[0141]

[0142] [Carbon Black (CB)]

[0143] As CB, eight types named "Ketjenblack EC600JD", "Li400", "Li435", "Vulcan XC72", "DC-3501", "#3030B", "#3050B", and "#3230B jet mill ground product" are used. The manufacturer names and physical properties are shown in Table 2.

[0144] [Table 2]

[0145]

[0146] (Solvent-Soluble Polymer)

[0147] · PVP (Polyvinylpyrrolidone): Molecular weight is 10,000, trade name "PITZCOL K-30", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., solid content is 95% or more

[0148] · PEO (Polyethylene oxide): Molecular weight is 100,000 - 200,000, trade name "ALKOX R-150", manufactured by Myojo Chemical Co., Ltd.

[0149] · PVA (Polyvinyl alcohol): Trade name "Gohsenol GL-05", manufactured by Mitsubishi Chemical Corporation, saponification degree (mol%) is 86.5 - 89.0

[0150] (Solvent)

[0151] · Water: Ion-exchanged water

[0152] [Test Example 1] (Study on pulverization treatment and dispersibility)

[0153] Regarding CNT (BT1001M manufactured by LG Chem, granulated product with a diameter of about 5 mm based on a tablet press), using a jet mill FS-4 manufactured by SEISHIN ENTERPRISE Co., Ltd., pulverization treatment was carried out at a speed of 0.8 kg / h in an argon atmosphere. The average particle size of the obtained CNT was 21 μm.

[0154] On the other hand, regarding CB (DC-3501 of OCI, granulated product with a diameter of about 1 mm), using a pin mill DD-2-3.7 manufactured by SEISHIN ENTERPRISE Co., Ltd., pulverization treatment was carried out at a speed of 1 kg / h in an argon atmosphere. The average particle size of the obtained CB was 35 μm.

[0155] 2% of CB and CNT before and after pulverization were each compounded into a polypropylene resin (J229E manufactured by Prime Polymer Co., Ltd.), and using a Plastomill, they were kneaded at 210 °C for 4 minutes to produce a resin composition.

[0156] Regarding the evaluation of dispersibility, the resin composition was melt-pressed to produce a thin sheet, and the thin sheet was observed using transmitted light of a microscope (magnification 50 times and 200 times) for evaluation. The obtained results are shown in Figure 1 .

[0157] According to Figure 1 the results shown, it can be seen that by pulverizing CB and CNT together, the dispersibility becomes better. In particular, the improvement of the dispersibility of CNT was confirmed.

[0158] [Test Example 2] (Study on the presence or absence of oxidation during pulverization)

[0159] Regarding #3030B and #3050B of Mitsubishi Chemical Corporation as CBs, using the SK Jet-O-Mill JOM-0101 manufactured by SEISHIN ENTERPRISE Co., Ltd., CBs were fed at a rate of 1 kg / h and subjected to a pulverization process. As the compressed fluid, air and argon were used and circulated at 1 m 3 / min. The average pulverized particle size after the treatment was 15 to 30 μm. In addition, it was confirmed that the pH values before and after pulverization were as shown in Table 3. In an air atmosphere, the pH decreased and weak oxidation occurred. On the other hand, in argon, the pH did not change.

[0160] [Table 3]

[0161]

[0162] [Test Example 3] (Study on the mixing ratio of CB and CNT)

[0163] The mixing ratio of CB and CNT was evaluated. Using a Plastomill, the ratios of CB (pulverized product of #3230B by jet mill) to CNT (NC-7000) were set to 100 / 0, 80 / 20, 70 / 30, 60 / 40, and 0 / 100 and mixed into a polypropylene resin (J229E manufactured by Prime Polymer Co., Ltd.) to obtain five points, and kneaded at 210 °C and 100 rpm for 4 minutes to produce a resin composition. It should be noted that the total compounding amount of CB and CNT in the resin composition was 2%, and only the 100% CNT product was compounded at 1%.

[0164] The resin composition was melt-pressed to produce a thin sheet. And, the dispersibility was evaluated by observing the thin sheet through transmitted light using a microscope (magnification: 50 times and 200 times). In addition, the volume resistivity of the resin composition was measured. The obtained results are shown in Figure 2 .

[0165] According to Figure 2 the results shown, it was confirmed that the greater the ratio of carbon nanotubes in the carbon material, the lower the dispersibility. In addition, it was confirmed that by mixing carbon black and carbon nanotubes, the volume resistivity could be significantly reduced (good conductivity).

[0166] [Test Example 4] (Study on solvent-soluble polymers)

[0167] In this test example, NC7000 was used for CNT and DC-3501 was used for CB. Test example 4-1 was the following substance: CB and CNT were put into a Loedige mixer of model N20L at a ratio of 6:4 (total quantity being 1.2 kg), and while stirring and mixing at a blade speed of 260 rpm and a chopper speed of 6000 rpm, water was added. After granulation for 15 - 20 minutes, drying was carried out using a vacuum dryer set at 70°C to obtain the substance. Test examples 4-2 to 4-5 were the following substances: After putting CB and CNT into the Loedige mixer at a ratio of 6:4, a binder solution was added while stirring and mixing, followed by granulation and drying. The compounding ratios of solvent-soluble polymers and the like are shown in Table 4 as follows.

[0168] [Table 4]

[0169]

[0170] Next, using a Labo Plastomill, 1% of the granulated products shown in Table 4 and the like were compounded and mixed into a polycarbonate resin (manufactured by Teijin Limited, Panlite L-1225WP). The resulting substance was kneaded at 210°C and 150 rpm for 4 minutes to prepare a resin composition. Then, the resin composition was melt-pressed to make a thin sheet. The dispersibility was evaluated by observing the thin sheet through transmitted light using a microscope (magnification 50 times and 200 times). The obtained results are shown in Figure 3 .

[0171] According to Figure 3 the results shown, it can be seen that the dispersibility varies depending on the type of solvent-soluble polymer. It can be known that as the solvent-soluble polymer, it is preferable to use glycol-based polymers such as polyethylene oxide.

[0172] [Test example 5] (Study on scattering property)

[0173] First, the materials of the carbon materials and binder solutions shown in Table 5 below were prepared. It should be noted that in test examples 5-2 to 5-5, a Loedige mixer (manufactured by Loedige Company) was used. After adding CNT (NC7000), the binder solution was added while stirring and mixing. Drying was carried out using a vacuum dryer set at 70°C. In addition, in test example 5-6, a Loedige mixer (manufactured by Loedige Company) was used. After adding CNT, water was added while stirring and mixing, and it was dried to make a granulated product of CNT alone.

[0174] [Table 5]

[0175]

[0176] Next, regarding the evaluation of the dispersibility, 95 g of an ABS resin was wound around a two-roll mill (hereinafter referred to as 2RM) heated to 175°C, and 5 g of carbon material granules or carbon nanotubes were dropped onto it in small amounts from above each time. The dropping was stopped when the carbon nanotubes alone or the granules of the carbon nanotubes and the solvent-soluble polymer were completely blended into the resin. The scattering rate was calculated by recovering all of the carbon nanotubes alone or the mixture of the carbon nanotubes and the solvent-soluble polymer scattered around, and based on the value of the scattered amount / input amount. The hardness of the granules was determined according to JIS K6219-3. Specifically, 20 particles with a particle size of 1 mm were measured, and the average value was used to represent it. The obtained results are shown in Table 6.

[0177] [Table 6]

[0178]

[0179] From the results shown in Table 6, it was confirmed that by adding a solvent-soluble polymer to the carbon nanotubes, the dispersibility could be significantly reduced. In addition, it was found that the dispersibility and the hardness of the granules varied depending on the type of the solvent-soluble polymer. It was found that as the solvent-soluble polymer, a glycol-based polymer such as polyethylene oxide was preferably used.

[0180] [Test Example 6] (Study on the volume specific resistance of carbon material granules)

[0181] Granules were prepared by adding a solvent-soluble polymer (here, polyethylene oxide (PEO)) to CB and CNT, and the volume specific resistance (VR) was studied.

[0182] As the CNT, a substance obtained by pulverizing BT1001M to 15 μm using a jet mill was used. In addition, for CB, a pin mill DD-2-3.7 manufactured by SEISHIN ENTERPRISE Co., Ltd. was used, and it was charged at a rate of 1 kg / h in an argon atmosphere and pulverized. The average pulverized particle size after the treatment was 40 μm. As the CB trademarks, there were five points: #3030B, DC-3501, VulcanXC-72 (the above are furnace-type CB) and Li400 and Li435 as acetylene black (for the basic physical properties, refer to Table 2). Regarding the ratio, CB and CNT were set to 7:3, and the solvent-soluble polymer was 3% relative to the total amount of CB and CNT (an amount such that the mixed granulated product did not scatter).

[0183] Granulation was carried out using a Loedige mixer. CNT was added when CB was charged and stirred, and PEO dissolved in water was added little by little while mixing to carry out granulation. Drying was carried out using a vacuum dryer set to 70°C.

[0184] Next, using a Labo Plastomill, the compounding amounts of the carbon materials were set to 1.0%, 1.5%, 1.7%, and 2% and mixed with a polycarbonate (hereinafter sometimes referred to as PC) resin (manufactured by Teijin Limited, Panlite L-1225WP) to obtain four points, kneaded at 280 °C and 100 rpm for 4 minutes to produce a resin composition. Then, the volume resistivity of the resin composition was measured. The obtained results are shown in Table 7 and Figure 4 .

[0185] [Table 7]

[0186]

[0187] According to Non-Patent Document 1 Figure 3 , as described above, regarding the compounding amount required to obtain the desired resistance, Ketjenblack EC600JD was overwhelmingly less, showing excellent conductivity results, and acetylene blacks such as Li435 were in the worst category.

[0188] In contrast, according to Figure 4 the results, in the form of carbon granulates obtained by adding a solvent-soluble polymer to CB and CNT, acetylene blacks of Li435 and Li400 were the most excellent, and Ketjenblack EC600JD compounded alone showed much worse results than Li435.

[0189] It was found that the reason for the different conductive positions of the CB and CNT mixed granulated products compared to the case of CB alone could not be accurately explained in the above-mentioned "quality affecting conductivity".

[0190] [Test Example 7] (Relationship between the amount of hydrogen and the volume resistance value when CB is heated at 1500 °C)

[0191] The measurement of the amount of hydrogen in CB was carried out with reference to Surface studies of carbon: Acidic oxides on spheron 6 (Carbon Volume 11, Issue 6, December 1973, Pages 649-654). Specifically, after accurately weighing about 0.5 g of dried CB, it was put into a heat-resistant test tube (aluminum oxide tube), and the pressure was reduced to medium vacuum (10 2 Pa to 10 -2After (Pa), the reduced-pressure system was sealed, and heating was maintained at 1500 °C for 30 minutes using an electric furnace to decompose and volatilize the oxygen compounds or hydrogen compounds present in the CB. The volatile components were collected into a gas trap tube of a specified volume by a quantitative suction pump. The gas volume was determined based on the pressure and temperature, and the hydrogen on the surface of the desorbed CB was quantified using gas chromatography. In this experiment, the value obtained by converting to the amount of hydrogen per 1 g of CB was used. The obtained results are listed in Table 7 together. In addition, the relationship between the hydrogen amount at 1500 °C of the carbon black and the volume resistivity at 1.5% compounding shown in Table 7 is shown in Figure 5 .

[0192] According to Figure 5 the results shown, it can be confirmed that the lower the hydrogen amount at 1500 °C of the carbon black, the more the volume resistivity can be reduced. Based on this result, the following conclusion can be drawn. That is, it was found that when conductive CB was compounded alone into the resin, the conductivity of Ketjen black was excellent, followed by furnace black and acetylene black. However, when conductive carbon black was mixed with carbon nanotubes and granulated, in the case of the mixed granulated product containing a polymer, the conductivity of furnace black and acetylene black was excellent compared to the resin using Ketjen black alone.

[0193] To further clarify the above conclusion, as a representative example when carbon black was compounded alone into the resin, in Figure 3 of Non-Patent Document 1, the amount of CB compounding required to obtain 100 Ω·cm was calculated, and Figure 6 showing the relationship between this and the hydrogen amount at 1500 °C of each CB is Figure 6 . According to this Figure 3 presented the following results: The more the hydrogen amount present in the CB described in Non-Patent Document 1, the more excellent the conductivity.

[0194] In contrast, the present inventors found that in the system of the present invention in which CNT and CB were mixed and a solvent-soluble polymer was added, a tendency similar to the volume resistivity when CB was compounded alone into the resin was observed. In addition, a result close to the opposite was also obtained for the relationship with the hydrogen amount, that is, the conductivity when CNT and CB were mixed could not be imagined based on the conductivity of CB alone.

[0195] In addition, it was also found that in the granulated product in which a polymer was added to the mixed system of CNT and CB, compared with the aforementioned characteristics generally said to be preferable as conductive carbon black (small particle size, long structure, etc.), the hydrogen amount on the surface of CB obtained by heating at 1500 °C made a greater contribution. It was also found that by slightly varying the hydrogen amount at 1500 °C, there was sometimes a difference of about six orders of magnitude in the volume resistivity when compounded into the resin. Conversely, it can be known that for the conductivity of the granulated product in which a polymer was added to the mixed system of CNT and CB, compared with characteristics such as specific surface area, structure, fiber diameter, and length, the magnitude of the hydrogen amount made a greater contribution.

[0196] [Examples 1 to 4 and Comparative Examples 1 to 5] (Manufacture of Carbon Material Granules)

[0197] In Examples 1 to 4 and Comparative Examples 1 to 5, first, materials of carbon materials and binder solutions shown in Table 8 below and Table 9 below were prepared. Regarding the manufacture of the binder solution, specifically, 120 g of a solvent-soluble polymer was added to 3480 g of water, and using a high-speed homogenizing stirrer (manufactured by Central Science Co., Ltd., LZB14-HM-1), it was mixed at 3000 rpm for 5 minutes to obtain a binder solution.

[0198] In Examples 1 to 4, next, carbon material granules were manufactured according to the compositions shown in Table 8 below and Table 9 below. Specifically, 840 g of carbon black pulverized (particle size after pulverization: 40 μm) using a pin mill (DD-2-3.7) manufactured by SEISHIN ENTERPRISE Co., Ltd. and 360 g of carbon nanotubes micro-pulverized (particle size after pulverization: 15 μm) using a jet mill (FS-4) manufactured by SEISHIN ENTERPRISE Co., Ltd. were put into a Loedige mixer (manufactured by Loedige Co., Ltd., model: M20, volume: 20 L), and while stirring at 250 rpm, 3600 g of an aqueous polymer solution was sprayed from the upper inlet hole and mixed for 15 minutes. Then, the spraying of the aqueous solution was stopped, and it was stirred for 15 minutes for granulation to obtain carbon material granules in a wet state. Thereafter, it was dried using a hot air dryer to obtain carbon material granules.

[0199] In Comparative Examples 1 to 5, according to the compositions shown in Table 8 below and Table 9 below, the same operations as in Examples 1 to 4 above were carried out to manufacture carbon material granules.

[0200] [Table 8]

[0201]

[0202] [Table 9]

[0203]

[0204] (Manufacture and Evaluation of Conductive Resin Composition Obtained Using Carbon Material Granules)

[0205] Using the carbon material granules having the compositions shown in Tables 8 and 9, a conductive resin composition was produced. Specifically, a polycarbonate resin (manufactured by Teijin Limited, Panlite L-1225WP) and the carbon material granules were put into a stirrer (manufactured by KAWATA Corporation, Super Stirrer), and mixed at 25°C for 3 minutes, whereby a resin composition containing a resin and a carbon material was obtained. This resin composition was put into a twin-screw extruder (manufactured by Japan Steel Works, Ltd., TEX series) set at 280°C, and after melt-kneading, a pelletized conductive resin composition was obtained using a granulator (manufactured by Isuzu Kakoki Co., Ltd., SCF-100). It should be noted that in Examples 1 to 4 and Comparative Examples 1, 3 to 5, 5% of the carbon material granules or carbon material was compounded with respect to 95% of the polycarbonate resin. In addition, in Comparative Example 2, 3% of carbon nanotubes was compounded with respect to 97% of the polycarbonate resin.

[0206] In addition, in order to evaluate the mechanical properties, an injection molding machine (manufactured by Japan Steel Works, Ltd., J100E-D) was used to perform injection under the conditions of a barrel temperature of 320°C and a mold temperature of 120°C to obtain evaluation samples.

[0207] Then, the surface resistivity, volume resistivity, fluidity (hereinafter sometimes referred to as MFR), tensile strength, tensile elongation, flexural strength, flexural modulus, and impact strength of the conductive resin composition were evaluated. The obtained results are shown in Tables 10 and 11.

[0208] [Table 10]

[0209]

[0210] [Table 11]

[0211]

[0212] From the above evaluation results, it was found that: compared with the case where a resin composition was made using only Ketjenblack, the MFR, impact strength, and tensile elongation of the mixture of acetylene black and CNT increased. In addition, the impact strength and tensile elongation of the mixture of furnace black and CNT increased. When the physical properties of the resin compositions of Ketjenblack alone and CNT alone were compared, in terms of the impact strength, CNT showed a value of about 2 times, presenting a result characteristic of CNT as fibrous carbon. On the other hand, it was found that: the impact strength of the sample of the present specification in which 30% of CNT was mixed with acetylene black or furnace black was approximately equal to that of CNT, and in addition, the tensile elongation exceeded that of CNT. That is, it was found that by forming granules by mixing 30% of CNT and about 10% of a polymer with a specific CB, the disadvantages of the resin composition made using only Ketjenblack, namely the impact strength and tensile elongation, were significantly improved, presenting a level superior to that of CNT.

[0213] Furthermore, from Examples 3 and 4, it can be seen that by adding a solvent-soluble polymer, VR and MFR are improved. In particular, regarding VR, the above evaluation results are those when 5% of the carbon material granulate is compounded into 95% of the resin. This means that the carbon material compounding amount after removing the polymer of the carbon material granulate is 4.5%, which is 0.5% less in carbon amount than in the case where no solvent-soluble polymer is added. It can be seen that even so, an equal or higher VR is exhibited. Therefore, the addition of the solvent-soluble polymer significantly contributes to improving the conductivity of the mixture of CB and CNT. As the reason for the improvement of VR and MFR, it can also be seen that the CB structure is covered with CNT fibers as if covered with a net (refer to Figure 7 ), and there are a large number of voids in the CB and CNT structures. The crystallinity on the surface of CB and CNT, especially CNT, progresses. The contact angle of CNT obtained using pure water is 98°, which is higher than the 50° - 65° of general graphite materials, and it can be said to be a hydrophobic material. Therefore, it generally has poor compatibility with the matrix resin. On the other hand, it can be considered that the solvent-soluble polymer dissolved in the solvent is first added to the surface of CB, and is also added to the surface of CNT that is basically integrated with CB. Furthermore, it can be considered that the polymer not only penetrates into the interface, but also penetrates into the multiple voids (holes) formed by the weaving of the skeletons of CB and CNT, and plays a role of expelling the air present here. If the air, which is an insulator, from the dispersion system of CB and CNT decreases, the conductivity will be improved, needless to say. In addition, as the reason for the increase in MFR, an improvement in the affinity with the matrix resin achieved by adding the polymer can also be considered. The main reason is that the same VR can be achieved with a smaller compounding amount. That is, the inventors believe that it is a composition with a 10% less carbon compounding amount.

[0214] Industrial Applicability

[0215] The carbon material granulate of the present invention is useful as a constituent material for coatings, inks, resin moldings, etc. that exhibit characteristics such as high conductivity and high heat conductivity, and is suitable for various applications such as battery materials, electronic component trays, covers for IC chips, electromagnetic wave shields, automotive components, and robot components.

Claims

1. A carbon material granulate containing carbon black having a particle size D determined by the laser diffraction / scattering method specified in ISO 13320 of 250 μm or less, carbon nanotubes having a particle size D determined by the laser diffraction / scattering method specified in ISO 13320 of 50 μm or less, and a solvent-soluble polymer added to the carbon black and the carbon nanotubes 50 A carbon material granulate containing carbon black having a particle size D determined by the laser diffraction / scattering method specified in ISO 13320 of 250 μm or less, carbon nanotubes having a particle size D determined by the laser diffraction / scattering method specified in ISO 13320 of 50 μm or less, and a solvent-soluble polymer added to the carbon black and the carbon nanotubes 50 A carbon material granulate containing carbon black having a particle size D determined by the laser diffraction / scattering method specified in ISO 13320 of 250 μm or less, carbon nanotubes having a particle size D determined by the laser diffraction / scattering method specified in ISO 13320 of 50 μm or less, and a solvent-soluble polymer added to the carbon black and the carbon nanotubes The compounding amount of the carbon nanotubes is 5% by mass or more and 40% by mass or less relative to the total compounding amount of 100% by mass of the carbon black and the carbon nanotubes. After reducing the pressure to the range of 10 2 mmHg to 10 -2 mmHg, the amount of desorbed hydrogen of the carbon black heated at 1500 °C for 30 minutes and quantified by gas chromatography is 2 mg / g or less, The solvent-soluble polymer is at least one selected from the group consisting of polyethylene oxide, polyvinylpyrrolidone, and polyvinyl alcohol. The compounding amount of the solvent-soluble polymer is 1 part by mass or more and 15 parts by mass or less relative to 100 parts by mass of the total compounding amount of the carbon black and the carbon nanotubes.

2. A method for manufacturing a carbon material granulate, comprising the following steps: Dry-crush carbon black granules and carbon nanotube granules so that the particle size D of the carbon black determined by the laser diffraction / scattering method specified in ISO 13320 50 becomes 250 μm or less, and the particle size D of the carbon nanotubes determined by the laser diffraction / scattering method specified in ISO 13320 50 becomes 50 μm or less, and mix them to obtain a mixture; A step of dissolving a solvent-soluble polymer in a solvent to prepare a binder solution; and A step of mixing while adding the binder solution to the mixture and granulating to obtain a carbon material granulate. The compounding amount of the carbon nanotubes is 5% by mass or more and 40% by mass or less relative to the total compounding amount of 100% by mass of the carbon black and the carbon nanotubes. After reducing the pressure to the range of 10 2 mmHg to 10 -2 mmHg, the desorbed hydrogen amount of the carbon black heated at 1500 °C for 30 minutes and quantified by gas chromatography is 2 mg / g or less, The solvent-soluble polymer is at least one selected from the group consisting of polyethylene oxide, polyvinylpyrrolidone, and polyvinyl alcohol. The compounding amount of the solvent-soluble polymer added to the carbon black and the carbon nanotubes is 1 part by mass or more and 15 parts by mass or less relative to 100 parts by mass of the total compounding amount of the carbon black and the carbon nanotubes.

3. A conductive resin composition containing the carbon material granulate according to claim 1 and a resin. The resin is at least one selected from the group consisting of polyolefin resins, polyester resins, polyamide resins, polyimide resins, polyether resins, polyvinyl alcohol resins, polymethacrylate resins, polyurethane resins, polyepoxy resins, polyphenol resins, polyurea resins, and polyethersulfone resins.

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