Title of the invention: Method for producing agglomerates containing carbon nanotubes
Technical field
[0001]
　The present invention relates to a method for producing a carbon nanotube-blended aggregate.
Background technology
[0002]
　In recent years, carbon nanotubes (hereinafter, also referred to as CNTs) have attracted attention as a dream next-generation material, and are used not only as antistatic agents and conductivity-imparting materials, but also as conductive aids for tires, capacitors, Li batteries, and fiber reinforced plastics. Application development is underway for utilization in plastics and the like.
[0003]
　CNTs are carbon crystals having a diameter of several nm to about 500 nm, a length of about 10 μm to 1000 μm, a large aspect ratio, and a tubular structure. There are various types, such as single-walled CNTs having a single-walled structure and double-walled double-walled CNTs having two layers, which fall into the category of multi-walled CNTs having a multi-walled structure. In addition, there are those in which both ends are closed, those in which only one end is closed, and those in which both ends are open, and there are several types of rounding structures such as an armchair type.
[0004]
　There are also arc discharge type, catalytic vapor phase production method, laser ablation method and other methods for producing CNT, each of which has advantages and disadvantages.
[0005]
　In general, it is known that CNTs are blended with various synthetic resins, rubbers and other base materials to impart electrical conductivity, high elasticity, high strength, thermal conductivity and the like to the base materials.
[0006]
　However, when using CNTs, there are concerns about safety, and because the CNTs are tubular and entangled one by one, they are difficult to disperse, lack dispersibility, are easily scattered, and are not easy to handle. There are challenges. Therefore, it has not been put into practical use even though it was expected to be a "dream material".
[0007]
　Regarding the safety of CNTs, according to the opinion released by the IARC (International Agency for Research on Cancer) in 2014, most CNTs are classified as "Group 3" (cannot be classified as carcinogenic), but today. However, there is a strong recognition among general users that "but CNT is a dangerous material." One of the reasons is that CNTs form a fibrous structure similar to asbestos, the bulk density is very low at 1 to 5 g / 100 cc, and a large amount of air is entrained, so it is highly scattered. It is said that the cause is that the risk of suction to asbestos is high.
[0008]
　In general, environmental risk is the possibility that chemical substances and the like may adversely affect human health and the growth and growth of animals and plants via the environment. Conceptually, "risk = harmful (toxicity) x" Expressed as "exposure (intake)", even if the material is clearly toxic, if there is no exposure, it can be said that the material is almost safe.
[0009]
　As a product with reduced exposure, it does not pulverize and scatter during packaging, transportation, inventory, actual use, etc., and shows easy dispersion in the dispersion process during master batches of synthetic resins, kneading of compounds, molding, etc. Granules and agglomerates are preferred. In addition, if it is an agglomerate that does not pulverize, the bulk density will naturally increase, and for example, in the kneading process with synthetic resin, it will be possible to prevent the occurrence of bridges in the storage tank and to automatically measure at the time of supply, and it will be possible to transport and transport. There are also merits such as reduction of inventory cost.
[0010]
　As a carbon-based powder whose final form of the product is spherical particles, there is carbon black (hereinafter also referred to as CB) manufactured and sold worldwide at 12 million tons / year. Since the bulk density of CB is not as high as that of CNT, it is generally low, so generally, bread type granulation method, drum type granulation method, screw extrusion type granulation method, stirring type granulation method, compression using water as a binder. A granulation method such as a molding granulation method is adopted. In CB, the primary particles are spherical and form a structure in which the particles are fused, and functional groups such as oxygen and hydrogen are present on the surface of the particles, and they have an affinity with water that functions as a binder, so that granulation is relatively easy. It is possible to do.
[0011]
　Considering the influence on the environment, it is preferable to use water as a solvent for producing CNT aggregates and granules. However, CNT has a poor crystal structure, few surface functional groups, and more air is entrained in the powder agglomerate than CB. Therefore, CNT has poor affinity with water and is not easy to granulate. There wasn't. Therefore, various methods for uniformly dispersing CNTs while using water as a solvent have been previously studied. Patent Document 1 discloses a method of adding CNTs to an organic solvent such as acetone and performing ultrasonic dispersion to disperse the CNTs.
[0012]
　Further, Patent Document 2 discloses a method of dispersing CNTs in water using a dispersant composed of a diallylamine-based cationic polymer, an anionic surfactant, and a nonionic surfactant.
[0013]
　However, Patent Document 1 and Patent Document 2 do not report any bulk density or scattering property of the CNT-blended aggregate obtained when water is used as a solvent.
Prior art literature
Patent documents
[0014]
Patent Document 1: Japanese Patent Application Laid-Open No. 2000-08621
Patent Document 2: Japanese Patent Application Laid-Open No. 2010-241668
Outline of the invention
Problems to be solved by the invention
[0015]
　One object of the present invention is to provide a method for efficiently obtaining CNT-blended aggregates having a high bulk density and low scattering property by using water as a dispersion medium.
[0016]
　The present inventors have recently impregnated CNT with an aqueous solution containing a water-soluble polymer at a predetermined concentration to form a wet agglomerate, which is subjected to shearing and crushing treatment and then dried to easily and easily scatter with high bulk density. It has been found that a low-quality CNT-blended aggregate can be efficiently obtained. The present invention is based on such findings.
Means to solve problems
[0017]
　The method for producing a carbon nanotube-blended aggregate according to the present invention is as follows:
(1) a step of preparing an aqueous solution of a water-soluble polymer having a concentration of 0.005 to 3.0% by mass, and
(2) 100 parts by mass of carbon nanotubes. , A step of impregnating the carbon nanotubes with an aqueous solution of the water-soluble polymer at a ratio of 400 to 1000 parts by mass to prepare wet aggregates,
(3) shearing and crushing the wet aggregates to obtain aggregates of crushed products. The steps include
(4) drying the agglomerates of the crushed material to obtain a carbon nanotube-blended agglomerates containing the water-soluble polymer
.
The invention's effect
[0018]
　According to the present invention, it is possible to efficiently produce a CNT-blended agglomerate having a high bulk density and low scattering property while using water as a dispersion medium. Further, since the CNT-blended aggregate can be produced substantially without using an organic solvent, it is advantageous in reducing the environmental load.
A brief description of the drawing
[0019]
FIG. 1 is a schematic diagram of an apparatus for producing a carbon nanotube-blended agglomerate used in Example 1.
2C are scanning electron microscope (SEM) images of CNT-blended aggregates of Example 1. FIG. A, B and C are 300x, 5000x and 12000x SEM images, respectively.
3C are SEM images of CNT-blended aggregates of Reference Example 1. FIG. A, B and C are 300x, 5000x and 12000x SEM images, respectively.
Embodiment for carrying out the invention
[0020]
　According to one embodiment of the present invention, in the method for producing CNT-blended aggregates, an aqueous solution of a water-soluble polymer having a concentration of 0.01 to 3.0% by mass is prepared (step 1), and 100 mass of carbon nanotubes is prepared. The carbon nanotubes are impregnated with an aqueous solution of the water-soluble polymer at a ratio of 0.1 to 0.25 parts by mass to prepare wet aggregates (step 2), and then the wet aggregates are sheared. After crushing to obtain agglomerates of crushed products (step 3), the agglomerates of the crushed products are dried (step 4) to obtain CNT-blended agglomerates. Hereinafter, the method for producing the CNT-blended aggregate according to the present invention will be described in detail for each step.
[0021]
[Step (1): Preparation Step of Water-Soluble Polymer Aqueous Solution]
　In one embodiment of the present invention, in the above step (1), an aqueous solution of a water-soluble polymer is prepared. The water-soluble polymer is not particularly limited as long as CNT can be dispersed and stabilized in water, but a polymer having a cationic group such as a quaternary ammonium group in the main chain or side chain can be preferably used.
[0022]
　According to one embodiment of the present invention, a diallylamine-based cationic polymer can be preferably used as the water-soluble polymer. Examples of the diallylamine-based cationic polymer include polymers of secondary amine salts such as diallylamine hydrochlorides and sulfates, and polymers of quaternary ammonium salts such as polydiallyldialkylammonium chloride and polydiallyldialkylammonium bromide. A polymer of a quaternary ammonium salt is preferable, and a polymer of diallyldimethylammonium chloride is particularly preferable.
[0023]
　Further, according to another embodiment of the present invention, the water-soluble polymer is obtained by polymerizing a monomer having at least one quaternary ammonium group and a polyfunctional monomer having at least one quaternary ammonium group. It may be a copolymer to be used. The mass ratio of the monomer having a quaternary ammonium group to the polyfunctional monomer is preferably 90/10 to 10/90, more preferably 75/25 to 40/60, and further preferably 60/40 to 50. / 50.
[0024]
　Among the constituents of the copolymer constituting the water-soluble polymer, the monomer having a quaternary ammonium group is preferably the following formula (I):
[Chemical formula 1]

　(in the formula (I), R 1 is H or C 1 ~ C 4 -alkyl, R 2 is H or methyl, R 3 is C 1 ~ C 4 -alkylene, R 4 , R 5 and R 6 are H or C 1 ~ independently, respectively . C 30 -alkyl, X is -O- or -NH-, and Y may be selected from Cl, Br, I, hydrogen sulphate or methsulfate) monomers. Preferred monomers of formula (I) are R 1 and R 2 , respectively H, or R 1 is H and R 2Is CH 3 or preferably H as well.
[0025]
　A particularly preferable monomer of the formula (I) is also referred to as dimethylaminoethyl acrylate methchloride (DMA3 * MeCl) [2- (acryloyloxy) ethyl] trimethylammonium chloride or dimethylaminoethyl methacrylate methchloride (DMAEMA * MeCl). It is called trimethyl- [2- (2-methylprop-2-enoyloxy) ethyl] azanium chloride.
[0026]
　Among the constituent elements of the copolymer constituting the water-soluble polymer, at least one polyfunctional monomer having no quaternary ammonium group includes acrylic acid, methacrylic acid, N-vinylpyrrolidone, N-vinylimidazole, and itaconic acid. Alternatively, a methyl ester or ethyl ester of maleic acid, ethyl acrylate or methyl acrylate and the like can be mentioned.
[0027]
　Further, according to one embodiment, the polyfunctional monomer having no quaternary ammonium group is preferably the following formula (II):
[Chemical formula 2]

(in the formula, R 7 is H or C 1 to C 1 to It is C 4 -alkyl, R 8 is H or methyl, and R 9 and R 10 are independently selected from the monomers represented by H or C 1 to C 30 -alkyl).
[0028]
　The monomer of the above formula (II) is preferably acrylamide, methacrylamide or dialkylaminoacrylamide.
[0029]
　Further, in the above-mentioned polyfunctional monomer, as the polyfunctional monomer having no quaternary ammonium group, the following formula (III):
[Chemical formula 3]

(in the formula, R is H or C 6 to C 50- It may be an alkyl, R'is H or C1-C4-alkyl, R'is H or methyl, and
　n is an integer from 0 to 100).
[0030]
　In the non-amine-based monomer of the above formula (III), R is preferably C8 to C30 - alkyl, more preferably C16 to C22 - alkyl, and R'is preferably H. n is preferably 3 to 50.
[0031]
　The non-amine-based monomer of formula (III) is preferably an aliphatic alcohol ethoxylate or a methacrylate thereof.
[0032]
　A plurality of types of the monomers of the above formula (I), the above formula (II), and the above formula (III) may be used in the copolymer constituting the water-soluble polymer. Therefore, for example, the R group of the monomer of the above formula (III) may have monomers having different chain lengths such as C 16 and C 18 in the copolymer.
[0033]
　According to one embodiment, the copolymer constituting the water-soluble polymer is preferably selected from dialkylaminoalkyl (meth) acrylate, alkyl (meth) acrylate, hydroxyalkyl (meth) acrylate and combinations thereof. It is a copolymer composed of monomer units. More specifically, the copolymers are preferably di-C 1 to C 2 alkyl (meth) acrylate amino C 1 to C 2 alkyl , C 1 to C 4 alkyl (meth) acrylate, and (meth) acrylic. It is a copolymer containing monohydroxy C2 to C4 alkyl acids and monomer units selected from these combinations, and more preferably methyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic acid. It is a dimethylaminoethyl copolymer, more preferably a methyl methacrylate / butyl methacrylate / dimethylaminoethyl methacrylate copolymer. As such a methyl methacrylic acid / butyl methacrylic acid / dimethylaminoethyl methacrylic acid copolymer, a commercially available one may be used, and examples thereof include Eudragit (registered trademark) E100 (Degussa).
[0034]
　Examples of water-soluble polymers other than those described above include polystyrene derivatives, cationized starch, cationized guar gum, modified polyvinyl alcohol, cationized polyacrylamide, polyamide epichlorohydrin (PAE), melamine resin derivatives, polyvinylamine or derivatives thereof. , Polyvinylpyridine or its derivatives, polyamines, polymethacrylic acid ester derivatives, polyacrylic acid ester derivatives, sodium polyacrylate derivatives, polyethyleneimine or its derivatives, polydadomac, polyalkylene polyamines or its derivatives, polyallylamine or its derivatives and other cations. Examples thereof include a polymer in which a group (1st to 4th grade ammonium salt, etc.) is introduced into the main chain or the side chain.
[0035]
　The molecular weight of the water-soluble polymer depends on the type of CNT impregnated with the water-soluble polymer, but from the viewpoint of dispersing and stabilizing the CNT in water, the weight average molecular weight may be about 5,000 to 100,000. Further, from the viewpoint of adhesion (cohesiveness) between the granules when they are formed into wet agglomerates and then sheared and crushed into granules, the weight average molecular weight is preferably 8000 to 50,000. The weight average molecular weight can be measured by a gel permeation chromatography (GPC) method (polystyrene standard) according to a conventional method.
[0036]
　The aqueous solution of the water-soluble polymer as described above can be prepared by adding the water-soluble polymer to water and dissolving it. In the production method of the present invention, the concentration of the water-soluble polymer in the aqueous solution of the water-soluble polymer is 0.005 to 3.0% by mass. When the concentration of the water-soluble polymer is lower than 0.005% by mass, it is difficult for water to impregnate the CNTs when preparing the wet aggregates containing CNTs, and the wet aggregates containing CNTs cannot be obtained. On the other hand, when the concentration of the water-soluble polymer is higher than 3.0% by mass, the obtained CNT-blended wet agglomerates become hard and it becomes difficult for the CNTs to be uniformly dispersed. The preferred water-soluble polymer concentration is 0.01 to 3.0% by mass, more preferably 0.1 to 2.5% by mass.
[0037]
　As the water to be used, it is preferable to use purified water such as distilled water with few impurities, ion-exchanged water, or pure water from the viewpoint of maintaining the quality of the CNT-blended agglomerates.
[0038]
[Step (2): Preparation Step of Wet Aggregate]
　Next, the carbon nanotube is impregnated with an aqueous solution of the water-soluble polymer at a ratio of 700 to 950 parts by mass with respect to 100 parts by mass of the carbon nanotube to obtain the wet aggregate. Prepare.
[0039]
　The CNT used in the present invention is not particularly limited, and may be in any form such as a single wall CNT having a single layer structure and a two-layer double wall CNT falling into the category of a multi-wall CNT having a multi-layer structure. Further, it is known that the form of CNTs obtained differs depending on the manufacturing method, but in the present invention, any of the manufacturing methods including the arc discharge type, the catalytic vapor phase manufacturing method, the laser ablation method, and other methods can be used. It may be obtained.
[0040]
　The CNT as a raw material used in the method for producing a CNT-blended agglomerate of the present invention preferably has a fiber diameter of 1 nm or more from the viewpoint of ensuring superiority in physical properties such as electrical and mechanical properties and dispersibility. It is 200 nm, more preferably 1 nm to 150 nm, and even more preferably 1 nm to 100 nm.
[0041]
　The fiber length of CNTs is preferably 0.1 μm to 2000 μm, more preferably 0.1 μm to 1000 μm, from the viewpoint of ensuring conductivity, mechanical properties, dispersibility and avoiding cutting of fibers. More preferably, it is 0.1 μm to 500 μm.
[0042]
　The aspect ratio of CNTs is usually about 10 to 10000, and a structure in which a hexagonal mesh graphite sheet has a cylindrical shape is preferably used. It may be either a single-walled CNT or a multi-walled CNT, and can be selected according to the final purpose. In addition, the method for producing CNTs is not limited, such as a pyrolysis method in which a carbon-containing gas is brought into contact with a catalyst, an arc discharge method in which an arc discharge is generated between carbon rods, and laser evaporation in which a carbon target is irradiated with a laser. Either the method, the CVD method in which the gas of the carbon source is reacted at a high temperature in the presence of metal fine particles, the HiPco method in which carbon monoxide is decomposed under high pressure, or the like may be used. Further, CNTs doped with metal atoms may be used. In addition, these CNTs may be used alone or in combination of two or more.
[0043]
　The method of impregnating the CNT with the aqueous solution of the water-soluble polymer obtained as described above is performed by adding the aqueous solution of the water-soluble polymer to the CNT aggregate. The addition of the aqueous solution of the water-soluble polymer may be carried out in one step by a batch method or may be carried out in a plurality of steps. It is preferable to use and carry out continuously.
[0044]
　According to one embodiment of the present invention, while transporting CNT by a screw conveyor, an aqueous solution of a water-soluble polymer is sent from the middle of the screw conveyor, and the CNT and the aqueous solution of the water-soluble polymer are mixed in the screw conveyor. May be good. This mixing method is preferable for continuously and efficiently impregnating CNTs with an aqueous solution of a water-soluble polymer, and wet aggregates in which CNTs are uniformly dispersed can be obtained. The speed at which the CNTs are transported in the screw conveyor is not particularly limited, but is, for example, 0.25 to 1.0 kg / min. The blending amount of the aqueous solution of the water-soluble polymer will be described later.
[0045]
　In the step of preparing the wet agglomerates, the aqueous solution of the water-soluble polymer is added to the CNTs at a ratio of 400 to 1000 parts by mass with respect to 100 parts by mass of the CNTs. When the amount of the aqueous solution of the water-soluble polymer added is less than 400 parts by mass, there are some portions of the obtained wet agglomerates in which the CNT is not impregnated with the aqueous solution of the water-soluble polymer. , Appropriate granularity cannot be obtained. On the other hand, if the amount of the aqueous solution of the water-soluble polymer added exceeds 1000 parts by mass, the CNTs cannot completely absorb the aqueous solution and become a slurry state, and cannot be crushed in the subsequent shear crushing step. The amount of the water-soluble polymer aqueous solution added is preferably 500 to 950 parts by mass, more preferably 700 to 900 parts by mass.
[0046]
　The wet agglomerates obtained by impregnating the CNT with an aqueous solution of a water-soluble polymer preferably have a water content of 600 to 980 parts by mass, more preferably 700 to 900 parts by mass, based on 100 parts by mass of the CNT. be. By setting the water content of the wet agglomerate within the above range, it becomes easy to obtain a desired agglomerate in the shear crushing step.
[0047]
　When an aqueous solution of a water-soluble polymer is added (impregnated) to CNTs using a screw conveyor, the time required for the impregnation is usually about 1 to 3 minutes, and can be appropriately adjusted by the rotation speed of the screw.
[0048]
　As described above, in the present invention, since the CNT is impregnated with an aqueous solution of a water-soluble polymer to prepare a wet agglomerate, it is not necessary to use an organic solvent as a dispersion medium as in the conventional case. Therefore, a recovery device for the organic solvent used is not required, and the CNT-blended aggregate can be easily and easily produced. It is preferable not to use an organic solvent, but it is not prohibited to use it, and it may be contained in a solution of a water-soluble polymer as long as it is in a small amount.
[0049]
[Step (3): Shearing and crushing of wet agglomerates]
　Next, the CNT-containing wet agglomerates obtained in the above step (2) are sheared and crushed to obtain agglomerates of crushed products. The agglomerates of the crushed material are formed by the crushed materials of the wet agglomerates coming into contact with each other and adhering to each other during the shear crushing treatment, and have low scattering property, which is advantageous for safely aligning the CNT-blended agglomerates. It can be used.
[0050]
　Here, the shear crushing process refers to a process of applying a shearing force to a sample to make the sample finer. Devices used for shear crushing include those in which CNT-blended wet agglomerates introduced by a blade that rotates at high speed and a blade of a fixed cutting head are subdivided, and between two discs that have a large relative velocity. Examples thereof include a device that simultaneously performs shearing and high-speed stirring of a CNT-blended wet agglomerate by utilizing the shearing force and impact generated in the gap between the two. Specific devices used for shear crushing include a comitroll, a colloidal mill, an electric mill, a mass colloider, a food processor, a pulper finisher, a rotary cutter mill, a micromeister, a nanochopper, and the like, and a rotary cutter is preferable. It is a mill, more preferably a multi-stage rotary cutter mill. The multi-stage rotary cutter mill is advantageous for adjusting the cutting efficiency by appropriately changing the number of blades in consideration of the particle size of the crushed material of the CNT-blended wet agglomerate and the generation rate of the agglomerate. be able to.
[0051]
　The operating conditions of the apparatus in the shear crushing treatment are not particularly limited, but are preferably set from the viewpoint of efficient production of CNT-blended agglomerates. Specifically, the temperature in the apparatus during the shear crushing treatment is, for example, about 20 ° C to 90 ° C. The rotation speed of the blade is about 350 to 600 rpm, preferably about 500 to 600 rpm.
[0052]
　The shearing and crushing treatment step may be performed once or repeated twice or more.
[0053]
[Step (4): Drying Step]
　According to one embodiment of the present invention, the agglomerates of the crushed material obtained in the step (3) are dried to obtain carbon nanotube-blended agglomerates.
[0054]
　The drying method is not particularly limited, and can be carried out by methods such as steam drying, vacuum drying, and hot air drying. The temperature at this time is 200 ° C or lower for a steam dryer, 150 ° C or lower for a vacuum dryer, and 100 for hot air drying from the viewpoint of preventing decomposition and denaturation of the water-soluble polymer that coats the CNT. ℃ or less is preferable. Further, before drying with a dryer, if the granulated product is spread on a vat or the like and naturally dried at room temperature in a draft or the like, the subsequent process becomes easy.
[0055]
　Further, according to one embodiment of the present invention, granulation of carbon nanotube-blended aggregates may be further carried out. The granulators used are roughly divided into horizontal type and vertical type. Most of the horizontal types are continuous type, which are composed of one-stage or multiple-stage drums, granulated with a stirring pin, and continuously dried in a kiln-type drum, or compressed while kneading with two shafts. There are various things such as those that dry and those that dry. These are useful because they have a large cost merit due to their continuous workability and are widely used for general purposes. Further, in the case of the vertical type, it is divided into a continuous type and a batch type. Some of the continuous type are suitable for mass production because the granulation process and the drying process are performed at the same time. In addition, some batch-type products perform the granulation process and the drying process separately, and some require filtration or the like to collect the granulated products in the middle of the process.
[0056]
　In the wet method, granulation and drying are generally performed. Typical examples include a fluidized bed granulation device, a stirring granulation device, a rolling granulation device, a spray-drying granulation device, and the like, but there are also composite types of these devices. In addition, methods such as a granulation method using an air flow drying device, a vacuum compression granulation method, and a flushing method can also be mentioned.
[0057]
　Since the method of the present invention does not require a step of removing the organic solvent and can be continuously carried out in a small number of steps, it can be advantageously used for efficiently and quickly producing the CNT-blended aggregate.
[0058]
[CNT-blended agglomerates]
　According to one embodiment of the present invention, the CNT-blended agglomerates obtained by the above method are provided. According to one embodiment, the bulk density of the CNT-blended aggregate is preferably 0.1 to 0.4 g / cm 3 , more preferably 0.15 to 0.3 g / cm 3 , and even more preferably 0.15 to 0.3 g / cm 3. It is 0.2 to 0.25 g / cm 3 .
[0059]
　The average particle size of the CNT-blended agglomerates is preferably 0.3 to 2.5 mm, more preferably 0.5 to 2.0 mm, and even more preferably 1.0 to 1.5 mm. The average particle size means the average value obtained by calculating the particle size of each of the 100 randomly extracted aggregates by microscopic observation of the CNT-blended aggregate.
[0060]
　The porosity of the CNT-blended agglomerates is preferably 10 to 35%, more preferably 15 to 30%, and even more preferably 20 to 25%.
[0061]
　The CNT-blended agglomerates obtained by the production method of the present invention have a very high bulk density as described above. There are also merits such as the possibility of automatic weighing, which leads to the reduction of transportation and inventory costs.
[0062]
　The gist of the present invention is as follows.
[1] A method for producing a carbon nanotube-blended aggregate,
(1) a step of preparing an aqueous solution of a water-soluble polymer having a concentration of 0.01 to 3.0% by mass, and
(2) 100 parts by mass of carbon nanotubes. On the other hand, a step of impregnating the carbon nanotubes with an aqueous solution of the water-soluble polymer at a ratio of 400 to 1000 parts by mass to prepare wet aggregates,
(3) shearing and crushing the wet aggregates to crush the aggregates. A method for producing a carbon nanotube-blended agglomerate, which comprises a step of obtaining the above-mentioned step and
(4) a step of drying the agglomerate of the crushed product . [2] The method according to [1], wherein the wet agglomerate preparation step of the step (1) is continuously carried out using a screw conveyor. [3] The method according to [1] or [2], wherein the wet agglomerate has a water content of 680 to 980 parts by mass with respect to 100 parts by mass of carbon nanotubes at room temperature. [4] The method according to any one of [1] to [3], wherein the water-soluble polymer is polydiallyldimethylammonium chloride. [5] The method according to any one of [1] to [4], wherein the shearing and crushing treatment in the step (2) is continuously performed using a cutter mill. [6] The method according to [5], wherein the cutter mill is a multi-stage cutter mill.

[7] The method according to any one of [1] to [6], wherein the wet aggregate is sheared and crushed until the average particle size of the crushed product is in the range of 0.5 to 2 mm.
[8] The method according to any one of [1] to [7], wherein the drying step of the step (4) is carried out by hot air drying. [9] The method according to any one of [1] to [8],
wherein the bulk density of the carbon nanotube-blended aggregate is 0.15 to 0.30 g / cm 3 .
[10] The method according to any one of [1] to [9], wherein the carbon nanotube-blended aggregate has an average particle size of 0.5 to 2.0 mm.
[11] The method according to any one of [1] to [10], wherein the carbon nanotube-blended aggregate has a porosity of 15 to 30%.
Example
[0063]
　Hereinafter, the present invention will be specifically described with reference to Examples. The present invention is not limited to these examples.
[0064]
　The physical characteristics of the CNTs (trade names: Knanos-100P, 100T, 210T, 300T, manufactured by Kumoho Co., Ltd.) used in the following experiments were as shown in Table 1.
[0065]
[table 1]

[0066]
[Example 1]
　A CNT-blended agglomerate was produced using the CNT-blended agglomerate manufacturing apparatus 1 shown in FIG. First, 500 g of CNT was put into the feeder 2 for the main raw material, and an aqueous solution of a water-soluble polymer in which 4.37 g of a polydiallyldimethylammonium chloride polymer (trade name: FPA1000L, manufactured by Senka Co., Ltd.), which is a water-soluble polymer, was dissolved in 3500 g of water. Was put into the feeder 3 for a dispersion medium.
　Next, the screw mixer 4 was operated to transfer the CNTs charged into the feeder 2, and the water-soluble polymer aqueous solution was sent from the dispersion medium feeder 3 into the screw mixer 4 through the piping by the liquid feed pump 5. .. In this way, the CNTs are impregnated with the aqueous solution of the water-soluble polymer in the screw mixer 4 to obtain wet aggregates (CNTs impregnated with the aqueous solution of the water-soluble polymer), which are continuously supplied into the cutter mill 6. did.
　Subsequently, the wet agglomerates were continuously sheared and crushed by the cutter mill 6. At this time, the crushed material self-aggregated, and an aggregate of granular crushed material was generated. The agglomerates of the obtained granular crushed products were dried with hot air using a drying device 7 to obtain CNT-blended agglomerates.
[0067]
　The physical characteristics (bulk density, porosity, carbon content, particle size) of the obtained CNT-blended agglomerates were measured by the following methods, and the results were as shown in Table 2. Further, when the CNT-blended aggregate was observed with an electron microscope, it was as shown in FIGS. 2A to 2C. In the CNT-blended agglomerates, the formation of bundle agglomeration sites between CNTs was not confirmed.
[0068]
(Bulk Density)
　The bulk density was determined according to the method for measuring the bulk density of carbon black specified in JIS K 6219.
[0069]
(Carbon content)
　The carbon content was determined by subtracting the ash content (%) measured according to JIS K 6218-2 from 100%.
[0070]
(Grain size)
　The morphology of the CNT-blended aggregate was observed with a scanning electron microscope (SEM). For observation, the outer diameter of 100 CNT-blended aggregates was arbitrarily measured using a 300-fold SEM image, and the average value thereof was taken as the average particle size (mm) of the CNT-blended agglomerates.
[0071]
[Table 2]

[0072]
[Comparative Example 1]
　First, polyethylene (High Wax 320P, manufactured by Mitsui Kagaku Co., Ltd.), which is a water-insoluble polymer, is dissolved in an organic solvent xylene heated to 80 to 90 ° C., and a resin binder solution containing 3% by weight of polyethylene. It was created.
[0073]
　Next, 50 g of CNT and 4950 g of pure water were placed in a 10 L stainless steel round container and treated with a homogenizer type stirrer at 6000 rpm for 30 minutes to obtain a dispersion liquid.
[0074]
　Next, the blade of the stirrer was changed to a paddle blade, and 300 g of the resin binder solution was added dropwise at a uniform rate for 5 minutes while stirring the dispersion at 1000 rpm. After all the droppings, the obtained mixed solution was stirred at 600 rpm for about 5 minutes to form granules in the mixed solution.
[0075]
　Next, granules were separated from the mixture using a 60 mesh sieve. The obtained granules are naturally dried in a draft at room temperature for about 20 hours, and further heated at 90 to 110 ° C. using a vacuum dryer, and the remaining xylene and water are reduced by heating at 150 ° C. for 1 hour. Drying to 5% or less gave CNT-blended aggregates.
　Since it is prohibited to dissipate xylene to the atmosphere, the entire amount of xylene was recovered by a vacuum-based cooling trap.
[0076]
　The physical characteristics (bulk density, porosity, CNT content, particle size) and production rate of the obtained CNT-blended agglomerates were as shown in Table 3. Further, when the CNT-blended aggregate was observed by SEM, it was as shown in FIGS. 3A to 3C. The formation of bundle aggregation sites between CNTs was confirmed.
[0077]
[Table 3]

[0078]
　From the results of Tables 2 and 3, in Example 1 in which the water-soluble polymer was added to the dispersion medium (water) and sheared and crushed, CNTs having a higher CNT content and higher bulk density than Comparative Example 1 were used. It can be seen that the compounded aggregates are efficiently and continuously produced in a short time. In the method of Example 1, since the CNT-blended aggregate is produced without using an organic solvent, it is considered that it can be used to reduce the environmental load. Further, in the method of Example 1, CNTs produce wet agglomerates having low scattering properties in a closed system, and continuously shear and crush to rapidly generate bulky agglomerates. Scattering can be prevented and the risk to safety can be significantly reduced.
Industrial applicability
[0079]
　According to the present invention, it is possible to efficiently produce a CNT-blended agglomerate having a high bulk density and low scattering property while using water as a dispersion medium. According to the present invention, since the CNT-blended aggregate can be produced without substantially using an organic solvent, it is advantageous in reducing the environmental load.
　Further, according to the present invention, workability such as workability and handleability when acquiring CNT-blended agglomerates can be remarkably improved, and the manufacturing process can be shortened without the need for large-scale equipment. Further, since CNT-blended agglomerates having a good particle size distribution can be mass-produced at low cost, it is particularly advantageous in industrial production.
Code description
[0080] [0080]
1 CNT-blended agglomerate production equipment
2 Feeder for main raw material
3 Feeder for dispersion medium
4 Screw mixer
5 Liquid feed pump
6 Cutter mill
7 Drying equipment
The scope of the claims
[Claim 1]
(1) A step of preparing an aqueous solution of a water-soluble polymer having a concentration of 0.005 to 3.0% by mass,
(2) 400 to 1000 parts by mass of the aqueous solution of the water-soluble polymer with respect to 100 parts by mass of carbon nanotubes. The step of impregnating the carbon nanotubes with the above-mentioned ratio to prepare a wet agglomerate,
(3) a step of shearing and crushing the wet agglomerate to obtain an agglomerate of a crushed product, and
(4) a step of obtaining an agglomerate of the crushed product.
A method for producing a carbon nanotube-blended agglomerate, which comprises a step of drying to obtain a carbon nanotube-blended agglomerate containing the water-soluble polymer .
[Claim 2]
　The method according to claim 1, wherein the wet agglomerate preparation step of the step (1) is continuously carried out using a screw conveyor.
[Claim 3]
　The method according to claim 1 or 2, wherein the wet agglomerate has a water content of 600 to 980 parts by mass with respect to 100 parts by mass of carbon nanotubes at room temperature.
[Claim 4]
　The method according to any one of claims 1 to 3, wherein the water-soluble polymer is polydiallyldimethylammonium chloride.
[Claim 5]
　The method according to any one of claims 1 to 4, wherein the shearing and crushing treatment in the step (2) is continuously performed using a cutter mill.
[Claim 6]
　The method according to claim 5, wherein the cutter mill is a multi-stage cutter mill.
[Claim 7]
　The method according to any one of claims 1 to 6, wherein the drying step of the step (4) is carried out by hot air drying.
[Claim 8]
The method according to any one of claims 1 to 7, 　wherein the bulk density of the carbon nanotube-blended aggregate is 0.15 to 0.30 g / cm 3 .
[Claim 9]
　The method according to any one of claims 1 to 8, wherein the carbon nanotube-blended aggregate has an average particle size of 0.5 to 2.0 mm.
[Claim 10]
　The method according to any one of claims 1 to 9, wherein the carbon nanotube-blended aggregate has a porosity of 15 to 30%.