JP2013163630A - Carbon nanotube aggregate and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of producing a carbon nanotube aggregate having superior orientation in a specific direction with high productivity.SOLUTION: A method for producing a carbon nanotube aggregate is characterized by comprizing: a step to obtain a carbon nanotube (A) where a stage to synthesize the carbon nanotube by a substrate growing method in chemical vapor deposition methods is included; a step to obtain a carbon nanotube (B) having a ratio of an aggregate gathering two or more carbon nanotubes in bundle form of 10% or less where a stage to immerse the carbon nanotube (A) in an acid is included; a step to obtain a yarn spinning raw solution (C) where a stage to mix the carbon nanotube (B), a polyvinyl alcohol-based polymer and water is included; a step to obtain a vinylon fiber (D) containing the carbon nanotube (B) where a stage to make the yarn spinning raw solution (C) fibrous by wet yarn spinning; and a step to obtain the carbon nanotube aggregate by burning the vinylon fiber (D).

Description

  The present invention relates to an aggregate of carbon nanotubes and a method for producing the same. More specifically, the present invention relates to an aggregate of carbon nanotubes having excellent orientation in a specific direction. Furthermore, the present invention relates to a production method capable of producing the aggregate of carbon nanotubes with high productivity.

  Carbon nanotubes (CNTs), a material with a hollow tubular structure (single-layer or multi-layer structure) with a graphene sheet rounded into a cylindrical shape with a diameter of nanometer order, are excellent in electrical properties, mechanical properties, and heat conduction properties In particular, it has characteristics such as high elasticity, thermal conductivity, and conductivity in the direction of the cylindrical axis (tube axis). Based on these characteristics, a material containing a plurality of carbon nanotubes oriented in a specific direction, that is, a carbon nanotube orientation material is expected to be used as various industrial materials.

  Examples of the carbon nanotube-containing material having orientation include an LB film made of solubilized carbon nanotubes (Patent Document 1); a carbon nanotube dispersion film in which a plurality of carbon nanotubes are dispersed independently from each other in an oriented state in a transparent binder ( Patent Document 2); In a solution in which a carbon nanotube of a specific length is dissolved in a mixed solvent of water and a low molecular alcohol, the substrate is immersed and pulled up between electrodes to which a specific AC voltage is applied, thereby A method for producing a carbon nanotube alignment film (Patent Document 3) that forms an aligned carbon nanotube is known.

JP 2002-226209 A JP 2006-27961 A JP 2010-91844 A

  However, none of the above-mentioned carbon nanotube-containing materials has a sufficient orientation of carbon nanotubes, and a carbon nanotube-containing material having better orientation is required. Furthermore, there is a demand for an excellent productivity manufacturing method that can easily manufacture the carbon nanotube-containing material.

  That is, an object of the present invention is to provide an aggregate of carbon nanotubes having excellent orientation in a specific direction. Another object of the present invention is to provide a production method capable of producing the aggregate of carbon nanotubes with high productivity.

  As a result of intensive investigations to achieve the above object, the present inventors obtained carbon nanotubes with a small amount of bundle aggregates by a specific synthesis method and processing method, and then wet using the obtained carbon nanotubes. Spinning, producing a vinylon fiber containing carbon nanotubes, and further firing the obtained vinylon fiber, it was found that an aggregate of carbon nanotubes having excellent orientation in a specific direction can be obtained. Completed the invention.

  That is, the present invention includes a step of obtaining a carbon nanotube (A) including a step of synthesizing a carbon nanotube by a substrate growth method in a chemical vapor deposition method, and a step of immersing the carbon nanotube (A) in an acid. A step of obtaining a carbon nanotube (B) in which the ratio of aggregates of two or more carbon nanotubes gathered in a bundle is 10% or less, and the carbon nanotube (B), the polyvinyl alcohol polymer, and water are mixed. A step of obtaining a spinning dope (C) including steps, and a step of obtaining vinylon fibers (D) containing the carbon nanotubes (B), including the step of fiberizing the spinning dope (C) by wet spinning; And a step of obtaining a carbon nanotube aggregate by firing the vinylon fiber (D). To provide a process for the preparation of the body.

  Furthermore, the present invention provides the aggregate of carbon nanotubes in which the ratio of the multi-walled carbon nanotubes having a diameter of 5 to 40 nm and two or more layers is 80 to 100% in 100% of the carbon nanotubes (B). A manufacturing method is provided.

  Furthermore, this invention provides the manufacturing method of the said carbon nanotube aggregate whose ratio of the carbon nanotube of 1-10 micrometers in length is 100% of 100% of the said carbon nanotube (B).

  Furthermore, this invention provides the manufacturing method of the said carbon nanotube aggregate in which the process of obtaining the said carbon nanotube (B) further includes the step isolate | separated by chromatography.

  Furthermore, the present invention provides the method for producing an aggregate of carbon nanotubes, wherein the chromatography is column chromatography using glass beads having a particle size of 0.05 to 5 mm as a stationary phase.

  Furthermore, in the present invention, the step of mixing the carbon nanotube (B), the polyvinyl alcohol polymer and water contains the carbon nanotube (B) and the polyvinyl alcohol polymer (PVA1), and the polyvinyl alcohol An aqueous dispersion (c1) having a concentration of the polymer (PVA1) of 0.1 to 10% by weight and a polyvinyl alcohol polymer (PVA2) are contained, and the concentration of the polyvinyl alcohol polymer (PVA2) is 0. Provided is a method for producing the aggregate of carbon nanotubes, which is a step of mixing an aqueous solution (c2) of 1 to 20% by weight.

  Further, in the present invention, the step of obtaining the spinning dope (C) further comprises mixing the aqueous dispersion (c1) and the aqueous solution (c2) to obtain a mixed solution (c3), and the mixed solution. And (c3) a method for producing the aggregate of carbon nanotubes including a step of distilling off a part of the water contained therein.

  Furthermore, this invention provides the manufacturing method of the said carbon nanotube aggregate in which the process of obtaining the said vinylon fiber (D) further includes the process of extending | stretching fiber.

  Furthermore, this invention provides the manufacturing method of the said carbon nanotube aggregate whose content of the said carbon nanotube (B) in 100 weight% of said vinylon fibers (D) is 0.1 to 10 weight%.

  The present invention also provides a carbon nanotube aggregate produced by the carbon nanotube aggregate production method described above.

  In addition, the present invention includes a step of obtaining a carbon nanotube (A) including a step of synthesizing a carbon nanotube by a substrate growth method in a chemical vapor deposition method, and a step of immersing the carbon nanotube (A) in an acid. A step of obtaining a carbon nanotube (B) in which the ratio of aggregates of two or more carbon nanotubes gathered in a bundle is 10% or less, and the carbon nanotube (B), the polyvinyl alcohol polymer, and water are mixed. A step of obtaining a spinning dope (C) including steps, and a step of obtaining vinylon fibers (D) containing the carbon nanotubes (B), including the step of fiberizing the spinning dope (C) by wet spinning. A method for producing a vinylon fiber containing carbon nanotubes is provided.

  The present invention also provides a vinylon fiber containing carbon nanotubes, which is produced by the above-described method for producing a vinylon fiber containing carbon nanotubes.

  Since the method for producing an aggregate of carbon nanotubes of the present invention includes the above steps, an aggregate of carbon nanotubes having excellent orientation in a specific direction can be produced with high productivity.

FIG. 1 is an SEM photograph of the aggregate of linear carbon nanotubes obtained in Example 1. FIG. 2 is an SEM photograph of the aggregate of linear carbon nanotubes obtained in Example 1. FIG. 3 is a SEM photograph of the film-like carbon nanotube aggregate obtained in Example 1. FIG. 4 is an SEM photograph of the film-like carbon nanotube aggregate obtained in Example 1. FIG. 5 is a SEM photograph of the aggregate of linear carbon nanotubes obtained in Example 2. FIG. 6 is an SEM photograph of the aggregate of linear carbon nanotubes obtained in Example 2. FIG. 7 is a SEM photograph of the film-like carbon nanotube aggregate obtained in Example 2. FIG. 8 is a SEM photograph of the film-like carbon nanotube aggregate obtained in Example 2. FIG. 9 is an SEM photograph of a cross section of the linear carbon nanotube aggregate obtained in Example 1. 10 is a cross-sectional photograph of a vinylon fiber containing carbon nanotubes obtained in Example 1. FIG. FIG. 11 is a cross-sectional photograph of a vinylon fiber containing carbon nanotubes obtained in Example 1. FIG. 12 is a photograph of the surface of a vinylon fiber containing carbon nanotubes obtained in Example 1. FIG. 13 is a cross-sectional photograph of a vinylon fiber containing carbon nanotubes obtained in Example 2. 14 is a cross-sectional photograph of a vinylon fiber containing carbon nanotubes obtained in Example 2. FIG. FIG. 15 is a surface photograph of a vinylon fiber containing carbon nanotubes obtained in Example 2. FIG. 16 is an example of an SEM photograph of an evaluation sample prepared from the CNT aqueous dispersion (2) of Example 1 in evaluating the ratio of bundled aggregates in carbon nanotubes. FIG. 17 is an explanatory diagram showing a measurement method of temperature rise measurement by resistance heating.

  The method for producing a carbon nanotube aggregate of the present invention includes a step of obtaining a carbon nanotube (A) including a step of synthesizing a carbon nanotube by a substrate growth method among chemical vapor deposition methods, and a step of obtaining the carbon nanotube (A) from an acid. A step of obtaining a carbon nanotube (B) in which the ratio of aggregates of two or more carbon nanotubes assembled in a bundle is 10% or less, including the step of immersing in carbon nanotubes, and the carbon nanotube (B) and the polyvinyl alcohol polymer A vinylon fiber (D) containing the carbon nanotube (B), which comprises a step of obtaining a spinning dope (C) including a step of mixing water and water, and a step of fiberizing the spinning dope (C) by wet spinning. And a step of firing the vinylon fiber (D) to obtain a carbon nanotube aggregate.The method for producing an aggregate of carbon nanotubes of the present invention may further include steps other than the above steps.

  In the present specification, the “process for obtaining the carbon nanotube (A) including the step of synthesizing the carbon nanotube by the substrate growth method in the chemical vapor deposition method” may be referred to as a “CNT manufacturing step”. In addition, “the step of obtaining a carbon nanotube (B) in which the ratio of an aggregate of two or more carbon nanotubes aggregated in a bundle including the step of immersing the carbon nanotubes (A) in an acid” is 10% or less. It may be referred to as “CNT purification step”. In addition, the “process for obtaining the spinning dope (C) including the step of mixing the carbon nanotube (B), the polyvinyl alcohol polymer and water” may be referred to as a “spinning dope preparation process”. In addition, the “process for obtaining vinylon fibers (D) containing carbon nanotubes (B) including the step of fiberizing the spinning dope (C) by wet spinning” may be referred to as “fiber manufacturing process”. Further, the “step of firing the vinylon fiber (D) to obtain a carbon nanotube aggregate” may be referred to as a “firing step”.

  Further, in the present specification, the “manufacturing method of the carbon nanotube aggregate of the present invention” may be referred to as “the manufacturing method of the present invention”, and “the carbon nanotube manufactured by the manufacturing method of the carbon nanotube aggregate of the present invention” may be referred to. The “aggregate” may be referred to as “the carbon nanotube aggregate of the present invention”. In addition, “carbon nanotube” may be referred to as “CNT”, and “carbon nanotube aggregate” may be referred to as “CNT aggregate”. Furthermore, “chemical vapor deposition” may be referred to as “CVD”, and “substrate growth among chemical vapor deposition” may be referred to as “substrate growth CVD”. In addition, the carbon nanotube in this specification shall include the meaning of the carbon nanotube by which the surface was modified by the functional group.

[CNT production process]
The step of obtaining the carbon nanotube (A) (CNT manufacturing step) includes at least a step of synthesizing the carbon nanotube by the substrate growth method (substrate growth CVD method) in the chemical vapor deposition method. The CNT manufacturing process may further include a step other than the step of synthesizing the carbon nanotubes by the substrate growth CVD method.

  As a method for synthesizing carbon nanotubes by the above-mentioned substrate growth CVD method, a known substrate growth CVD method can be used. For example, edited by Yahachi Saito, “Introduction to Material Science of Carbon Nanotubes”, First Edition, Corona Corporation, 2006 September, p. 16-19. More specifically, the substrate growth CVD method includes Takuji Komukai and five others, “Density Control of Carbon Nanotubes through the Thickness of Fe / Al Multilayer Catalyst”, Japanese Journal of Applied 200, Year, Vol. 45, No. 7, p. It is preferable to use the method described in 6043-6045 (Japanese Journal of Applied Physics, Vol. 45, No. 7, 2006, p. 6043-6045). The substrate growth CVD method is preferably a thermal CVD method.

  Although the said substrate growth CVD method is not specifically limited, For example, the following method is mentioned. First, a catalyst is fixed on a substrate. Preferably, a catalyst film is formed on the substrate, and the catalyst (particularly a metal catalyst) is further finely divided. Next, carbon nanotubes are synthesized by bringing a carbon-containing gas into contact with the catalyst in a heated atmosphere. Although the atmospheric temperature at the time of making the said carbon containing gas contact the said catalyst is not specifically limited, 350-900 degreeC is preferable, More preferably, it is 600-800 degreeC.

  Examples of the substrate include a silicon substrate, a quartz glass substrate, a metal substrate (for example, a stainless steel substrate), a ceramic substrate, and the like. Among these, a silicon substrate is preferable. The catalyst is generally a substance that promotes the growth of carbon nanotubes and is not particularly limited. For example, a metal such as iron (Fe), cobalt (Co), nickel (Ni) or an oxide thereof is used. Can be mentioned. Among these, metals and / or metal oxides are preferable, and iron (Fe) and oxides thereof are particularly preferable. In the present specification, a catalyst that is a metal and / or a metal oxide may be referred to as a “metal catalyst”. As what fixed the catalyst on said board | substrate, what formed the thin film of aluminum and the thin film of iron on the board | substrate in order of a board | substrate / aluminum thin film / iron thin film, respectively is preferable. A method for forming a catalyst film on a substrate, for example, a method for forming the above-described aluminum thin film or iron thin film is not particularly limited. For example, an electron beam physical vapor deposition method (EB-PVD method), a sputtering method, Examples thereof include a method of applying a liquid containing a catalyst to a substrate.

  The carbon-containing gas is a so-called carbon source. The carbon-containing gas is preferably a hydrocarbon gas. Examples of the carbon-containing gas include acetylene, methane, ethylene, benzene, toluene, methanol, ethanol, acetone, carbon monoxide, and the like. Among them, acetylene (that is, acetylene gas) is preferable.

  The CNT manufacturing process may include a step other than the step of synthesizing the carbon nanotubes by the substrate growth CVD method. For example, the step of peeling the synthesized carbon nanotube from the substrate, the step of heat treatment in an inert gas, and the like can be mentioned. The method for peeling the synthesized carbon nanotubes from the substrate is not particularly limited, and examples thereof include a method for peeling carbon nanotubes grown on the substrate from the substrate with a scraper, and a method for peeling the carbon nanotubes from the substrate by gas pressure. Furthermore, for example, methods described in JP 2011-6822 A, JP 2011-6306 A, and JP 2011-79711 A can be cited.

  In the CNT production step, carbon nanotubes (ie, coarse carbon nanotubes) that are the raw materials for carbon nanotubes that constitute the aggregate of carbon nanotubes of the present invention are produced. In the CNT manufacturing process, by using the substrate growth CVD method, it is possible to synthesize carbon nanotubes (particularly multi-walled carbon nanotubes) having high linearity and little entanglement. Further, the synthesized carbon nanotubes have small variations in diameter, and carbon nanotubes having relatively uniform diameters can be obtained. Furthermore, amorphous carbon produced as a by-product (by-product) is relatively small and can be easily removed by a purification process or the like. In the production method of the present invention, a carbon nanotube aggregate having excellent orientation can be obtained by producing and using crude carbon nanotubes having the above-described characteristics by a substrate growth CVD method. On the other hand, for example, when a gas phase fluidized bed method (also referred to as a gas phase fluidization method) is used as a synthesis method, the variation in the diameter of the synthesized carbon nanotubes increases, and the orientation of the carbon nanotube aggregates is increased. descend.

[CNT purification process]
The step of obtaining the carbon nanotube (B) (CNT purification step) includes at least a step of immersing the carbon nanotube (A) obtained in the CNT production step in an acid. The CNT purification step may further include a step other than the step of immersing the carbon nanotube (A) in an acid.

(Step of immersing carbon nanotube (A) in acid)
The acid in the step of immersing the carbon nanotube (A) in the acid is not particularly limited. For example, sulfuric acid, nitric acid, chlorosulfuric acid, hydrochloric acid, caroic acid, dilute sulfuric acid solution of potassium permanganate, sulfuric acid, and hydrogen peroxide solution Of the mixture. Among these, sulfuric acid, nitric acid, a mixture of sulfuric acid and nitric acid (particularly, a mixture of concentrated sulfuric acid and concentrated nitric acid), a mixture of sulfuric acid and hydrogen peroxide (for example, sulfuric acid / hydrogen peroxide) are preferable. The ratio of sulfuric acid to nitric acid (sulfuric acid / nitric acid) (volume ratio) in the mixture of sulfuric acid and nitric acid is preferably 0.25 to 9, and more preferably 1 to 4. Particularly preferred is a so-called mixed acid in which the ratio of sulfuric acid to nitric acid is about 3 (sulfuric acid: nitric acid = 3: 1). In addition, the said acid may use only 1 type and may use 2 or more types.

  Although the immersion time in the stage which immerses the said carbon nanotube (A) in an acid is not specifically limited, 1-48 hours are preferable, More preferably, it is 1-24 hours, More preferably, it is 2-12 hours. By setting the immersion time to 1 hour or longer, the removal effect of the metal catalyst and the modification effect of the carbon nanotube surface can be obtained more easily. Moreover, it is preferable to set it to 48 hours or less because structural destruction of the carbon nanotube is suppressed. In addition, although immersion temperature is not specifically limited, 20-80 degreeC is preferable.

  The CNT purification step may include a step other than the step of immersing the carbon nanotube (A) in an acid. Examples thereof include a filtration step, a neutralization step, a washing step, a drying step, a step of separating by chromatography, and a step of irradiating with ultrasonic waves.

The filtration step is, for example, a step of filtering the carbon nanotube composition obtained through the step of immersing the carbon nanotube (A) in an acid. As the filtration method, a known filtration method can be used, and examples thereof include pressure filtration, vacuum filtration, centrifugal filtration, and crossflow filtration.
The neutralization step is a step of neutralizing the acid adhering to the surface of the carbon nanotube, for example, a step of neutralizing the carbon nanotube filtered in the filtration step. As the neutralizing agent used in the neutralization step, a known neutralizing agent can be used, and examples thereof include sodium hydroxide, calcium hydroxide, ammonium hydroxide, and sodium bicarbonate.
The washing step is a step of washing the carbon nanotubes, for example, a step of washing the carbon nanotubes neutralized in the neutralization step or the carbon nanotubes filtered in the filtration step. As the cleaning method, a known cleaning method can be used, and examples thereof include cleaning with pure water.
The drying step is a step of drying the carbon nanotubes, for example, a step of drying the carbon nanotubes washed in the washing step. As a drying method, a known drying method can be used. Examples thereof include drying with a hot air dryer, natural drying, and drying under reduced pressure. Although a drying temperature is not specifically limited, 20-100 degreeC is preferable. The drying time is not particularly limited, but is preferably 1 to 48 hours.

(Stage separated by chromatography)
The step of separating by chromatography is a step of separating a carbon nanotube by chromatography and collecting a specific component. In particular, it is preferable to remove an aggregate (aggregate) in which two or more carbon nanotubes aggregate (aggregate) from the carbon nanotubes before the chromatography treatment by chromatography. Furthermore, it is preferable to collect carbon nanotubes having a length in a specific range. In addition, as the aggregate in which the two or more carbon nanotubes are aggregated, for example, an aggregate in which two or more carbon nanotubes are aggregated in a bundle (bundle shape) or an aggregate in which two or more carbon nanotubes are aggregated in a lump shape. Can be mentioned. In the present specification, the “aggregate in which two or more carbon nanotubes are aggregated in a bundle” may be referred to as “bundle aggregate”, and “the aggregate in which two or more carbon nanotubes are aggregated in a lump” May be referred to as a “bulk aggregate”. As a method for separating carbon nanotubes by the above chromatography, it is preferable to use a method for producing an isolated dispersion of long CNT described in JP-A-2011-230952.

  The chromatography is preferably column chromatography. The method for separating by column chromatography is not particularly limited, and examples thereof include the following methods. First, carbon nanotubes and water are mixed, and the carbon nanotubes are dispersed to prepare a carbon nanotube dispersion. Next, the carbon nanotube dispersion liquid is developed as a mobile phase in a column packed with glass beads having a predetermined particle size range as a stationary phase. Furthermore, a permeated liquid (effluent) that has permeated through the column is collected in a certain amount. From the collected permeate, a permeate corresponding to an independent carbon nanotube having a specific length is collected. In the present specification, a carbon nanotube that does not aggregate (aggregate) with other carbon nanotubes to form an aggregate and exists independently as a single carbon nanotube is referred to as “independent carbon nanotube. May be called.

  The carbon nanotube dispersion may contain a dispersant such as a surfactant. In addition, when preparing a carbon nanotube dispersion by dispersing carbon nanotubes, for example, a bath ultrasonic disperser, a bath ultrasonic cleaner, an ultrasonic homogenizer, a pressure homogenizer, a rotary homogenizer, a ball mill, a bead mill It is preferable to use a dispersing device such as

  The particle size of the glass beads is not particularly limited, but is preferably 0.05 to 5 mm, more preferably from the viewpoint of separation of long carbon nanotubes and short carbon nanotubes and separation of massive aggregates and bundle aggregates. Is 0.05 to 2 mm, more preferably 0.10 to 0.13 mm. That is, the chromatography is preferably column chromatography using glass beads having a particle size of 0.05 to 5 mm as a stationary phase.

  The step of separating by the chromatography is preferably provided after the step of immersing the carbon nanotube (A) in an acid and the filtration step, neutralization step, washing step, and drying step provided as necessary. Further, after the step of separation by chromatography, a filtration step and a drying step may be further provided.

  The carbon nanotube (B) is obtained by the CNT purification step. The carbon nanotube (B) may be obtained, for example, in a dry state (for example, in a powder state) or may be obtained in an aqueous dispersion state.

  In 100% of the carbon nanotubes (B), the ratio (number ratio) of aggregates in which two or more carbon nanotubes aggregate in a bundle (bundle shape) is 10% or less (0 to 10%), preferably Is 5% or less, more preferably 1% or less. From the viewpoint of productivity and technical difficulty, the ratio is often 0.01% or more, and more preferably 0.1% or more. When the ratio is 10% or less, a carbon nanotube aggregate having excellent orientation can be obtained. When carbon nanotubes containing more than 10% of aggregates (bundle aggregates) in which two or more carbon nanotubes are aggregated in a bundle are used, the orientation of the carbon nanotubes is disturbed in the fiber production process, and the carbon nanotube aggregates The orientation of is reduced. In addition, the said ratio is a ratio on the basis of the number (number) of carbon nanotubes, for example, can be measured with a scanning electron microscope (SEM). More specifically, it can be measured by the method described in “(1) Ratio of bundle aggregate (bundle aggregate) in carbon nanotube” of “(Evaluation)” described later.

  Further, the ratio (number ratio) of aggregates of two or more carbon nanotubes in 100% of the carbon nanotubes (B) is not particularly limited, but the orientation and productivity of the carbon nanotube aggregates of the present invention are not limited. From the viewpoint of further improving the content, it is preferably 10% or less (0 to 10%), more preferably 5% or less, and still more preferably 1% or less. From the viewpoint of productivity and technical difficulty, the ratio is often 0.01% or more, and more preferably 0.1% or more. Compared to the bundle aggregate, the bulk aggregate is often removed by a die or a filter in the fiber production process, and the influence of the decrease in the orientation of the carbon nanotube aggregate is small. However, it may have adverse effects such as filter clogging.

  The ratio (number ratio) of multi-walled carbon nanotubes having a diameter of 5 to 40 nm and two or more layers in 100% of the carbon nanotubes (B) is not particularly limited, but is preferably 80 to 100%. More preferably, it is 90 to 100%, and more preferably 95 to 100%. The diameter is more preferably 10 to 30 nm. The number of layers is more preferably 2 to 35 layers, and further preferably 5 to 20 layers. Multi-walled carbon nanotubes having two or more layers are more rigid than single-walled carbon nanotubes, and are therefore easily oriented in the fiber production process. Moreover, it is excellent also in heat conductivity. Since single-walled carbon nanotubes have low rigidity, they may be damaged in the fiber production process, and the orientation of the carbon nanotube aggregate may be lowered. In addition, when the above conditions are satisfied and the diameter of the carbon nanotubes in the carbon nanotube (B) is in a specific range and the variation in diameter is small, it is preferable because a carbon nanotube aggregate with particularly excellent orientation can be obtained. In addition, the said ratio is a ratio on the basis of the number (number) of carbon nanotubes, for example, can be measured with a transmission electron microscope (TEM). More specifically, by the method described in “(3) Ratio of multi-walled carbon nanotubes having a diameter of 5 to 40 nm and two or more layers in carbon nanotubes” in “(Evaluation)” described later. Can be measured.

  The ratio (number ratio) of carbon nanotubes having a length of 1 to 10 μm in 100% of the carbon nanotubes (B) is not particularly limited, but is preferably 80 to 100%, more preferably 90 to 100%, Preferably it is 95 to 100%. The length is more preferably 3 to 10 μm, and further preferably 5 to 10 μm. When the above conditions are satisfied and the length of the carbon nanotubes in the carbon nanotube (B) is in a specific range and the variation in length is small, the carbon nanotubes are preferable because they are particularly easily oriented in the fiber production process. In addition, the said ratio is a ratio on the basis of the number (number) of carbon nanotubes, for example, can be measured with a scanning electron microscope (SEM). More specifically, it can be measured by the method described in “(2) Ratio of carbon nanotubes having a length of 1 to 10 μm in carbon nanotubes” in “(Evaluation)” described later.

The G / D ratio calculated from the Raman spectroscopic analysis of the carbon nanotube (B) is not particularly limited. However, from the viewpoint of the electrical conductivity and strength of the carbon nanotube aggregate of the present invention, it is 1.0 or more (for example, 1.0 to 20.0) is preferable, more preferably 1.5 or more, and still more preferably 2.0 or more. The G / D ratio is the ratio of the G peak derived from the graphite crystal near 1580 cm ⁻¹ and the D peak indicating the disorder component of carbon near 1350 cm ⁻¹ in the Raman spectrum (the peak of the G band relative to the peak intensity of the D band). Strength ratio). The G / D ratio can be calculated by Raman spectroscopic analysis. For example, the G / D ratio can be measured and calculated using a laser Raman microscope manufactured by Renishaw.

  In the CNT refining step, carbon nanotubes (B) constituting the carbon nanotube aggregate of the present invention are produced, which are used for producing a spinning dope (also referred to as “spinning solution”) used in the fiber producing step. In the CNT purification step, a catalyst (metal) attached to the carbon nanotube (A) by immersing the carbon nanotube (A) obtained in the CNT production step in an acid (sometimes referred to as “acid treatment”). (Catalyst) is dissolved. Moreover, by the acid treatment, aggregates such as bundle aggregates in the carbon nanotubes (A) are separated and become independent carbon nanotubes. Furthermore, the acid treatment modifies the surface of the carbon nanotubes to be hydrophilic, increases the affinity for water and polyvinyl alcohol polymers, and improves the dispersibility in water and polyvinyl alcohol polymers. Due to the above effects, the carbon nanotubes (B) obtained in the CNT purification step have a small content of aggregates (particularly bundles) in which two or more carbon nanotubes are aggregated, and are oriented in the subsequent fiber production process. It becomes easy. For this reason, the carbon nanotube aggregate which has the outstanding orientation property can be obtained.

  In addition to the acid treatment, in the CNT purification step, it is preferable to remove impurities from the carbon nanotubes by a filtration step, a neutralization step, a washing step, a drying step, and the like. Furthermore, by providing at least one step selected from the group consisting of a step of separating by chromatography and a step of irradiating ultrasonic waves, the aggregate in the carbon nanotubes can be further reduced, and the number of independent carbon nanotubes can be increased. Thus, it is possible to obtain an aggregate of carbon nanotubes having even more excellent orientation.

[Spinning solution preparation process]
The step of obtaining the spinning dope (C) (spinning stock preparation step) includes at least a step of mixing the carbon nanotube (B) obtained in the CNT purification step, the polyvinyl alcohol polymer, and water. The spinning solution preparation process may further include a stage other than the stage of mixing the carbon nanotube (B), the polyvinyl alcohol polymer, and water.

As the polyvinyl alcohol-based polymer, known polyvinyl alcohol can be used. The polyvinyl alcohol polymer is, for example, a polymer containing a structural unit (structural unit) represented by [—CH ₂ CH (OH) —], and a polymer produced by saponifying polyvinyl acetate. Can be mentioned. The saponification degree of the polyvinyl alcohol polymer is not particularly limited, but is preferably 85 to 99.5 mol%, more preferably 95 to 99.5 mol% from the viewpoint of spinnability and yarn strength. Moreover, although the average degree of polymerization of the said polyvinyl alcohol-type polymer is not specifically limited, 1000-2500 are preferable from a viewpoint of thread | yarn strength, More preferably, it is 1500-2400. The degree of saponification and the average degree of polymerization can be determined according to JIS K6726.

  A commercially available product may be used as the polyvinyl alcohol polymer. Examples of commercially available products include Kuraray Co., Ltd., trade names “Kuraray Poval PVA-117”, “Kuraray Poval PVA-217”, “Kuraray Poval PVA-205”, “Kuraray Poval PVA-105”, and the like.

  In addition, the description about the above-mentioned polyvinyl alcohol-type polymer is applied also to the below-mentioned polyvinyl alcohol-type polymer (PVA1) and polyvinyl alcohol-type polymer (PVA2).

(Step of mixing carbon nanotube (B), polyvinyl alcohol polymer and water)
In the step of mixing the carbon nanotube (B), the polyvinyl alcohol-based polymer, and water, it is sufficient that a mixed solution containing at least the carbon nanotube (B), the polyvinyl alcohol-based polymer, and water is obtained. The mixed solution may contain a dispersant such as a surfactant. Examples of the surfactant include an anionic surfactant, a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant.

  For the above mixing, it is preferable to use a rotary homogenizer, a planetary stirrer (spinning / revolving mixer) or the like.

  As a method of mixing the carbon nanotube (B), the polyvinyl alcohol-based polymer, and water, for example, a method of mixing the carbon nanotube (B), the polyvinyl alcohol-based polymer, and water at once; Examples thereof include a method of mixing in an aqueous solution of a polyvinyl alcohol polymer; a method of mixing an aqueous dispersion of carbon nanotubes (B) and an aqueous solution of a polyvinyl alcohol polymer. When the carbon nanotube (B) is obtained in the state of an aqueous dispersion by the CNT purification step, the aqueous dispersion may be used as the aqueous dispersion of the carbon nanotube (B).

  Among these, from the viewpoint of improving the dispersibility of the carbon nanotube (B), a method of mixing an aqueous dispersion of the carbon nanotube (B) and an aqueous solution of a polyvinyl alcohol polymer is preferable. Since the aqueous solution of the polyvinyl alcohol polymer has a relatively high viscosity, if the carbon nanotube (B) is added directly to the aqueous solution of the polyvinyl alcohol polymer and mixed, the dispersibility of the carbon nanotube (B) in the mixed solution decreases. There is a case. For this reason, once the aqueous dispersion of the carbon nanotube (B) is prepared, the aqueous dispersion of the aqueous solution of the polyvinyl alcohol polymer is mixed with the aqueous dispersion so that the dispersibility of the carbon nanotube (B) in the mixed liquid is increased. It is preferable because it improves. The aqueous dispersion of the carbon nanotube (B) may contain a small amount of a polyvinyl alcohol polymer. A small amount of the polyvinyl alcohol-based polymer has an effect of improving the dispersibility of the carbon nanotube (B) in the aqueous dispersion as a surfactant.

  More specifically, the step of mixing the carbon nanotube (B), the polyvinyl alcohol-based polymer, and water contains the carbon nanotube (B) and the polyvinyl alcohol-based polymer (PVA1), and the polyvinyl alcohol-based polymer ( An aqueous dispersion (c1) having a concentration of PVA1) of 0.1 to 10% by weight and a polyvinyl alcohol polymer (PVA2) are contained, and the concentration of the polyvinyl alcohol polymer (PVA2) is 0.1 to 10% by weight. It is preferable that it is a stage which mixes 20 wt% aqueous solution (c2). The polyvinyl alcohol polymer (PVA1) and the polyvinyl alcohol polymer (PVA2) may be the same or different from each other.

  The concentration of the polyvinyl alcohol polymer (PVA1) in 100% by weight of the aqueous dispersion (c1) is preferably 0.1 to 10% by weight, more preferably 0.1 to 5% by weight, and still more preferably 0.8. 1-1% by weight. It is preferable that the concentration is 0.1% by weight or more because the effect of the polyvinyl alcohol polymer (PVA1) as a surfactant is effectively exhibited and the dispersibility of the carbon nanotube (B) is improved. Moreover, it is preferable to adjust the concentration to 10% by weight or less because the viscosity of the aqueous dispersion (c1) can be maintained low and a decrease in dispersibility of the carbon nanotubes (B) due to an increase in viscosity can be suppressed. In the aqueous dispersion (c1), by using the polyvinyl alcohol polymer (PVA1) as a surfactant, it is not necessary to use a surfactant other than the polyvinyl alcohol polymer. For this reason, since an additional component other than a carbon nanotube (B) and a polyvinyl alcohol-type polymer in a vinylon fiber (D) can be reduced, and the bad influence by an additional component can be suppressed, it is preferable.

  The concentration of the carbon nanotube (B) in 100% by weight of the aqueous dispersion (c1) is not particularly limited, but the viewpoint of the dispersibility of the carbon nanotube (B) and the carbon nanotube (B in the spinning dope (C) ) Is preferably within a range of 0.001 to 10% by weight, more preferably 0.01 to 5% by weight, and still more preferably 0.1 to 1% by weight.

  The concentration of the polyvinyl alcohol polymer (PVA2) in 100% by weight of the aqueous solution (c2) is from the viewpoint of controlling the concentration of the polyvinyl alcohol polymer in the spinning dope (C) to a preferable range, etc. 1 to 20 weight% is preferable, More preferably, it is 3 to 15 weight%, More preferably, it is 4 to 12 weight%.

(Stage to adjust density)
The spinning dope preparation step may further include a step of adjusting the concentration of a mixed solution containing at least the carbon nanotube (B), the polyvinyl alcohol polymer, and water. As a method for adjusting the concentration, for example, a method in which a part of water contained in the mixed solution is distilled off under reduced pressure (a reduced pressure distillation method), and a part of the water contained in the mixed solution is removed by heating. And the like. Among these, the vacuum distillation method is preferable from the viewpoint of suppressing solidification of the polyvinyl alcohol polymer. That is, the spinning solution preparation step includes, for example, a step of mixing the aqueous dispersion (c1) and the aqueous solution (c2) to obtain a mixed solution (c3), and water contained in the mixed solution (c3). A part of which may be distilled off under reduced pressure. A known method can be used as the vacuum distillation method. Examples thereof include a vacuum distillation method using a rotary evaporator and a distillation apparatus.

  The spinning dope (C) is obtained by the spinning dope preparation step. The spinning dope (C) contains at least the carbon nanotube (B), the polyvinyl alcohol polymer, and water. The spinning dope (C) may further contain a dispersant such as a surfactant (a surfactant other than the polyvinyl alcohol polymer), boric acid, borate, and the like.

  The concentration of the polyvinyl alcohol polymer in 100% by weight of the spinning dope (C) is not particularly limited, but is preferably 1 to 20% by weight, more preferably 5 to 15% by weight, and still more preferably 10 to 15% by weight. %. It is preferable that the concentration is 1% by weight or more because spinnability (spinnability) is improved. Moreover, it is preferable to make it 20% by weight or less because the density of the carbon nanotubes in the aggregate of carbon nanotubes can be easily improved, and the stretchability of the unstretched fibers obtained from the spinning dope (C) is improved. .

  The concentration of the carbon nanotube (B) in 100% by weight of the spinning dope (C) is not particularly limited, but is preferably 0.001 to 10% by weight, more preferably 0.01 to 5% by weight, and still more preferably. 0.1 to 1% by weight. The concentration of 0.001% by weight or more is preferable because the density of carbon nanotubes in the aggregate of carbon nanotubes can be easily improved. Further, the content is preferably 10% by weight or less because the dispersibility of the carbon nanotubes is further improved.

  The viscosity of the spinning dope (C) is not particularly limited, but is preferably from 1,000 to 100,000 mPa · s, more preferably from the viewpoint of improving the orientation of the carbon nanotubes in the fiber production process and improving the spinning property. 3,000 to 50,000 mPa · s, more preferably 5,000 to 20,000 mPa · s. The viscosity can be measured under conditions of a temperature of 25 ° C. and a shear rate of 10 (1 / second) in accordance with JIS Z8803.

  In the spinning dope preparation process, a spinning dope (C) used in the subsequent fiber preparation process is prepared. By using the carbon nanotubes (B) obtained through the CNT production step and the CNT purification step, the spinning dope (C) has a small content ratio of an aggregate of two or more carbon nanotubes, and the spinning. Most of the carbon nanotubes in the stock solution (C) are dispersed in the form of independent carbon nanotubes. Furthermore, after preparing an aqueous dispersion of carbon nanotubes (B), when using a specific mixing method of mixing the aqueous dispersion and an aqueous solution of a polyvinyl alcohol polymer, the carbon nanotubes in the spinning dope (C) Can be further improved.

[Fiber manufacturing process]
The step of obtaining the vinylon fiber (D) (fiber production step) includes at least a step of fiberizing the spinning dope (C) by wet spinning. The fiber production process may further include a stage other than the stage of fiberizing the spinning dope (C) by wet spinning.

(Step of spinning the spinning dope (C) by wet spinning)
In the step of fiberizing the spinning dope (C) by wet spinning, the spinning dope (C) is used as a spinning dope (spinning solution), fiberized by wet spinning (wet spinning method), and spun yarn (fiber). Get. As the wet spinning method, a wet spinning method in a known method for producing vinylon fibers (polyvinyl alcohol fibers) can be used. Specifically, for example, the spinning dope (C) is discharged (spun) from a die (spinning die) into a coagulating liquid to be fiberized to obtain a spun yarn.

  The discharge amount (discharge amount per unit time) at the time of discharge is not particularly limited, but is preferably 1 to 50 g / min, more preferably 10 to 15 g / min from the viewpoint of improving the orientation of the carbon nanotubes by shearing. It is. When discharging, it is preferable to filter the spinning dope using a filter from the viewpoint of removing foreign substances and coarse aggregates of carbon nanotubes.

  The spinning draft (ratio of the roller speed for lifting the spun yarn with respect to the discharge speed) during the fiberization is preferably 2 or less, more preferably 1 or less.

As the coagulating solution is not particularly limited, sodium sulfate (Na ₂ SO ₄₎ aqueous solution, ammonium sulfate _{((NH 4) 2 SO 4} ) aqueous solution of zinc sulfate (ZnSO ₄₎ aqueous solution, magnesium sulfate (MgSO ₄₎ solution, sulfuric acid An aluminum (Al ₂ (SO ₄ ) ₃ ) aqueous solution or the like can be given. Of these, sodium sulfate aqueous solution and ammonium sulfate aqueous solution are preferable.

  The fiber preparation step may include a stage other than the stage of fiberizing the spinning dope (C) by wet spinning. For example, it is preferable to include a washing step, an oil agent dipping step, a drying step, and a fiber drawing step.

  The washing step is a step of washing the spun yarn obtained in the step of fiberizing the spinning dope (C) by wet spinning. The oil agent immersion step is a step in which the spun yarn or the spun yarn after washing is immersed in an oil agent such as a fatty acid ester. Furthermore, the drying step is a step of drying the spun yarn, the spun yarn after washing, or the spun yarn after oil agent immersion.

  The stretching in the stage of stretching the fiber is preferably thermal stretching. Although a draw ratio is not specifically limited, 2-20 times are preferable from a viewpoint of improving the orientation of the carbon nanotube in a carbon nanotube aggregate more, More preferably, it is 7-10 times. Moreover, although extending | stretching temperature is not specifically limited, From a viewpoint of improving a drawability, 200-250 degreeC is preferable, More preferably, it is 210-230 degreeC.

  The vinylon fiber (D) containing the said carbon nanotube (B) is obtained by the said fiber preparation process. The vinylon fiber (D) is a polyvinyl alcohol fiber formed from a polyvinyl alcohol polymer. The vinylon fiber (D) may be an undrawn yarn or a drawn yarn.

  The content of the carbon nanotube (B) in 100% by weight of the vinylon fiber (D) is not particularly limited, but is preferably 0.1 to 10% by weight, more preferably 0.5 to 8% by weight, Preferably it is 1 to 6% by weight. The content of 0.1% by weight or more is preferable because the density of the carbon nanotubes in the carbon nanotube aggregate can be easily improved. On the other hand, if it is larger than 10% by weight, the dispersibility of the carbon nanotubes may be lowered, or spinning may be difficult and the productivity may be lowered.

  Although the fineness of the said vinylon fiber (D) is not specifically limited, 0.5-10 dtex is preferable, More preferably, it is 1-5 dtex.

  In the fiber production step, a vinylon fiber containing carbon nanotubes is produced. In the fiber production step, a shear force is applied to the spinning dope (C) during spinning, so that the carbon nanotubes in the spinning dope (C) are oriented in the spinning direction, that is, the fiber axis direction. Thereby, in the vinylon fiber (D) obtained by the said fiber preparation process, the length direction (namely, cylindrical axial direction) of each carbon nanotube corresponds with the fiber axis direction of a vinylon fiber (D). As such, it is oriented with excellent orientation. Furthermore, the orientation of carbon nanotubes is further improved by performing stretching (particularly, thermal stretching).

  When the spinning stock solution contains a large number of aggregates of two or more carbon nanotubes such as bundles and aggregates, or when the diameter of the carbon nanotubes contained in the spinning stock solution is large. The orientation of the carbon nanotubes in the vinylon fiber is insufficient. In the production method of the present invention, the carbon nanotubes in the fibers are aligned with excellent orientation by using a spinning stock solution in which carbon nanotubes with small variations in diameter are mostly dispersed in the form of independent carbon nanotubes. Vinylon fibers are obtained. Furthermore, due to the above characteristics, excellent orientation can be maintained even if the content of carbon nanotubes in the fiber is relatively high.

[Baking process]
In the step (firing step) of firing the vinylon fiber (D) to obtain a carbon nanotube aggregate, the carbon nanotube aggregate is produced by firing at least one of the vinylon fibers (D).

  In the firing step, only one vinylon fiber (D) may be fired according to the desired form of the carbon nanotube aggregate to produce a carbon nanotube aggregate, or two or more vinylon fibers ( D) may be fired to produce a carbon nanotube aggregate. Further, the vinylon fiber (D) may be fired after being fixed linearly or in a predetermined shape. Further, for example, a plurality of vinylon fibers (D) are arranged and fixed in a form in which the fiber axes are oriented in a certain direction on a substrate, and then fired, and then a film-like (thin-film-like) carbon nanotube assembly The body can also be made.

  Although the calcination temperature in the said calcination process is not specifically limited, 200-600 degreeC is preferable, More preferably, it is 300-500 degreeC, More preferably, it is 350-450 degreeC. When the firing temperature is less than 200 ° C., many polyvinyl alcohol polymers remain after firing, and the characteristics (rigidity, electrical conductivity, thermal conductivity, etc.) of the carbon nanotube aggregate may be deteriorated. On the other hand, if the firing temperature exceeds 600 ° C., the carbon nanotubes are damaged by heat, and the characteristics (rigidity, electrical conductivity, thermal conductivity, etc.) of the carbon nanotube aggregate may be deteriorated, or the carbon nanotubes may be burned out. is there.

  Although the baking time in the said baking process is not specifically limited, 10 minutes-24 hours are preferable, More preferably, they are 30 minutes-12 hours, More preferably, they are 1-8 hours. When the firing time is less than 10 minutes, many polyvinyl alcohol-based polymers remain after firing, and the characteristics (rigidity, electrical conductivity, thermal conductivity, etc.) of the carbon nanotube aggregate may deteriorate. On the other hand, if the firing time exceeds 24 hours, the carbon nanotubes may be damaged by heat, and the characteristics (rigidity, electrical conductivity, thermal conductivity, etc.) of the carbon nanotube aggregate may deteriorate.

  Although it does not specifically limit in the baking in the said baking process, For example, an electric furnace, a muffle furnace, an infrared gold image furnace etc. can be used.

  In the firing step, the carbon nanotube aggregates are produced by firing the vinylon fibers (D) to burn away and remove the polyvinyl alcohol polymer in the fibers. Since the carbon nanotubes in the vinylon fibers (D) are oriented with excellent orientation in the fiber axis direction, the carbon nanotube aggregates obtained from the vinylon fibers (D) each constitute the carbon nanotube aggregates. The carbon nanotubes are oriented with an excellent orientation in a specific direction (that is, the direction of the fiber axis of the vinylon fiber (D)).

  In the production method of the present invention, linear carbon in which each carbon nanotube constituting the aggregate of carbon nanotubes is oriented with excellent orientation in one direction by firing one vinylon fiber (D). Nanotube aggregates can be obtained. In addition, by arranging a plurality of vinylon fibers (D) so that the fiber axes of the respective vinylon fibers (D) are in the same direction and firing, each carbon nanotube constituting the carbon nanotube aggregate is 1 A carbon nanotube aggregate (for example, a film-like carbon nanotube aggregate) that is oriented with an excellent orientation in the direction can be obtained.

  In the production method of the present invention, the orientation direction of each carbon nanotube constituting the aggregate of carbon nanotubes is not limited to one direction, and the aggregate of carbon nanotubes having a plurality of orientations in which the carbon nanotubes are oriented in a plurality of directions. (For example, a film-like carbon nanotube aggregate) can also be obtained. For example, the plurality of vinylon fibers (D) are arranged so that their fiber axes are in one direction (referred to as “X direction”), and further, the other vinylon fibers (D) are arranged with the above-mentioned X Film-like carbon nanotubes having excellent orientation in the two directions of the X direction and the Y direction by firing after being combined and arranged so as to be in one direction orthogonal to the direction (referred to as “Y direction”) Aggregates can be obtained.

  Moreover, in the manufacturing method of this invention, since it manufactures by the method of removing a polyvinyl alcohol-type polymer from a vinylon fiber (D) by a baking process, the carbon nanotube aggregate containing a carbon nanotube at high density can be obtained. .

  Furthermore, the production method of the present invention can obtain an aggregate of carbon nanotubes by a simple method by utilizing spinning, and is excellent in productivity. In addition, a long linear carbon nanotube aggregate or a large-area film-like carbon nanotube aggregate can be obtained.

[Aggregate of carbon nanotubes]
The carbon nanotube aggregate produced by the production method of the present invention (carbon nanotube aggregate of the present invention) is an aggregate constituted by aggregating a plurality of carbon nanotubes. The aggregate of carbon nanotubes of the present invention is composed of a plurality of carbon nanotubes as essential constituent components. The aggregate of carbon nanotubes of the present invention may contain components other than carbon nanotubes. The constituent components other than the carbon nanotubes are not particularly limited, and examples include polyvinyl alcohol polymers (such as those remaining in the firing step), additives such as dispersants (such as those remaining in the firing step), and the like. It is done.

  The carbon nanotube content in 100% by weight of the carbon nanotube aggregate of the present invention is not particularly limited, but is preferably 80% by weight or more (80 to 100% by weight), more preferably 85% by weight or more, and still more preferably. 90% by weight or more. It is preferable that the content is 80% by weight or more because excellent rigidity, electrical conductivity, and thermal conductivity can be obtained. The content is preferably 99% by weight or less, more preferably 98% by weight or less from the viewpoint of difficulty in production technology and suppression of embrittlement of the carbon nanotube aggregate.

  The shape of the carbon nanotube aggregate of the present invention is not particularly limited, and examples thereof include a linear shape (a wiring shape) such as a curved shape or a broken line shape, and a film shape (a thin film shape).

  The size (length, width, thickness) of the carbon nanotube aggregate of the present invention varies depending on the shape, application, and the like and is not particularly limited, but the following ranges are preferable from the viewpoint of productivity and the like. The length of the aggregate of carbon nanotubes of the present invention is preferably 1 mm to 1 m, more preferably 1 cm to 50 cm. The width of the carbon nanotube aggregate of the present invention is preferably 1 μm to 1 m, more preferably 5 μm to 50 cm. The thickness of the aggregate of carbon nanotubes of the present invention is preferably 3 nm to 3 μm, more preferably 10 nm to 2 μm.

  In the carbon nanotube aggregate of the present invention, each carbon nanotube constituting the carbon nanotube aggregate has an excellent orientation in a specific direction (that is, the direction of the fiber axis of the vinylon fiber (D)). Oriented. In the present specification, the direction in which the carbon nanotubes constituting the carbon nanotube aggregate of the present invention are oriented (that is, the specific direction) may be referred to as “CNT orientation direction”. Specifically, for example, when the carbon nanotube aggregate of the present invention is a carbon nanotube aggregate having a linear shape (linear carbon nanotube aggregate), the alignment direction of the CNTs is the linear carbon nanotube aggregate. It is the length direction of the body. In addition, when the carbon nanotube aggregate of the present invention is a carbon nanotube aggregate having a film shape (film carbon nanotube aggregate), the CNT orientation direction is the plane direction of the film carbon nanotube aggregate ( The direction perpendicular to the thickness direction). Although the CNT orientation direction of the film-like carbon nanotube aggregate is not particularly limited, one direction or two directions (particularly, two directions orthogonal to each other) are preferable.

  The aggregate of carbon nanotubes of the present invention has high rigidity in the CNT alignment direction. On the other hand, it has flexibility in the direction orthogonal to the CNT alignment direction. Moreover, it has high electrical conductivity and thermal conductivity in the CNT alignment direction. In the case of a film-like carbon nanotube aggregate, it has optical anisotropy in the plane of the film. For example, it has optical anisotropy in the direction perpendicular to the CNT alignment direction.

  The aggregate of carbon nanotubes of the present invention can be used for, for example, an electrode, wiring, etc., utilizing high conductivity. Moreover, it can use for a heater wire, a heat sink (heat sink), especially an anisotropic heat conductive heat sink using thermal conductivity. Furthermore, in particular, a film-like carbon nanotube aggregate can be used as a polarizing material by utilizing optical anisotropy. That is, from the carbon nanotube aggregate of the present invention, an electrode, a wiring, a heater wire, a heat sink (such as an anisotropic heat conductive heat sink), a polarizing material and the like including the carbon nanotube aggregate of the present invention can be obtained.

[Vinylon fiber containing carbon nanotube and method for producing the same]
The vinylon fiber (D) is a vinylon fiber containing carbon nanotubes, and can be used industrially by itself. That is, this application includes invention of the vinylon fiber (vinylon fiber (D)) containing a carbon nanotube, and its manufacturing method. In the vinylon fiber (D), the carbon nanotubes are aligned with excellent orientation so that the length direction of each carbon nanotube (that is, the cylindrical axis direction) coincides with the fiber axis direction of the vinylon fibers (D). doing. Thereby, the said vinylon fiber (D) has effects, such as being excellent in bending strength. For this reason, the said vinylon fiber (D) can be used for the fiber for cement reinforcement, etc. using high bending strength, for example.

  The method for producing the vinylon fiber (D) is as described above, and includes the step of obtaining the carbon nanotube (A) including the step of synthesizing the carbon nanotube by the substrate growth method in the chemical vapor deposition method, and the carbon nanotube. Including a step of immersing (A) in an acid, obtaining a carbon nanotube (B) in which the ratio of aggregates of two or more carbon nanotubes assembled in a bundle is 10% or less, and the carbon nanotube (B) Containing the carbon nanotube (B), including a step of obtaining a spinning dope (C) including a step of mixing a polyvinyl alcohol polymer and water, and a step of fiberizing the spinning dope (C) by wet spinning To obtain vinylon fibers (D).

  EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
(CNT production process)
Using an electron beam physical vapor deposition (EB-PVD) method, an aluminum (Al) thin film having a thickness of 3 nm is deposited on a silicon substrate having a surface area of about 50 mm ² , and further, iron (Fe) having a thickness of 2 nm is further formed thereon. A multilayer substrate having a structure of silicon substrate / aluminum thin film / iron thin film was produced.
The multilayer substrate was placed in a quartz tube having a diameter of 160 mm and heated to 700 ° C. under vacuum. Next, acetylene gas was flowed into the quartz tube under the condition of 200 Pa, and carbon nanotubes were synthesized on the multilayer substrate.
Carbon nanotubes [corresponding to carbon nanotubes (A)] grown on the multilayer substrate were peeled from the multilayer substrate and collected.

(CNT purification process)
The carbon nanotubes obtained above were immersed in mixed acid [concentrated sulfuric acid (concentration 98%): concentrated nitric acid (concentration 60%, density 1.38 g / cm ³ ) = 3: 1 (volume ratio)] for 2 hours. Thereafter, the solution was filtered through a polytetrafluoroethylene (PTFE) membrane filter (pore size: 0.2 μm), and the carbon nanotubes collected on the filter were neutralized with 0.1 mol / L ammonia water and washed with pure water. And dried at 60 ° C. for 24 hours.
100 mg of the carbon nanotubes after drying and 100 g of water are mixed, and dispersed using a rotary homogenizer (manufactured by ASONE Co., Ltd., trade name “CM-100”) for 1 hour as a dispersion device, and a CNT aqueous dispersion (1 )
A column tube for chromatography (made of borosilicate glass, column length 300 mm, inner diameter 20 mm) is filled with glass beads (made of soda glass, diameter 0.105 to 0.125 mm) and water to a height of 100 mm, A column was prepared. Next, 10 ml of the CNT aqueous dispersion (1) was developed on a column. Further, among the permeated liquid that permeated through the column, a permeated liquid of 3 ml to 5 ml was fractionated after the outflow from the column was started. Next, 20 mg of a polyvinyl alcohol polymer was mixed and dissolved in 2 ml of the permeated liquid between 3 ml and 5 ml after the start of the outflow from the column to obtain a CNT aqueous dispersion (2).
The ratio of bundled aggregates in 100% of the carbon nanotubes [corresponding to carbon nanotubes (B)] contained in the CNT aqueous dispersion (2) was 0.1%. The concentration of carbon nanotubes in the CNT aqueous dispersion (2) was 0.1% by weight.

(Spinning solution preparation process)
216 g of the above CNT aqueous dispersion (2) and 30 g of an aqueous polyvinyl alcohol polymer solution (polyvinyl alcohol polymer concentration: 4.8% by weight) were mixed, and a planetary stirrer (trade name, manufactured by Shinky Co., Ltd.) "AR-100") and stirred and mixed.
Further, the concentration of the mixed solution obtained above was adjusted by a reduced pressure distillation method using a rotary evaporator to obtain a spinning dope [corresponding to the spinning dope (C)]. The concentration of carbon nanotubes in the spinning dope was 0.72% by weight, and the concentration of polyvinyl alcohol polymer was 12.0% by weight.

  About 100 g of the spinning dope was obtained by performing the above-described CNT production process, CNT purification process, and spinning dope preparation process a plurality of times. In addition, as said polyvinyl alcohol-type polymer, the product name "Kuraraypoval PVA-117" (average polymerization degree 1700, saponification degree 98-99 mol%) by Kuraray Co., Ltd. was used.

(Fiber production process)
Using a gear pump, the above spinning stock solution at 95 ° C. is discharged from a die (platinum die, hole diameter 0.1 mm, number of holes 250) at a discharge rate of 13.1 g / min and a saturated sodium sulfate aqueous solution at 42 ° C. It was spun in and made into fibers (process speed 4.5 m / min).
Next, the obtained fiber was washed with water, dried at 80 ° C., and further heat-drawn under the conditions of a drawing temperature of 200 ° C. and a draw ratio of 7 times to obtain a vinylon fiber containing carbon nanotubes [Vinylon fiber (D)]. Corresponding] was obtained.
The average fineness of the vinylon fiber was 1.6 dtex. The content of carbon nanotubes in 100% by weight of the vinylon fiber was 6% by weight.

(Firing process: Production of aggregate of linear carbon nanotubes)
One vinylon fiber cut to a length of 5 cm was placed on a silicon substrate, and both ends of the fiber were fixed with an adhesive.
Subsequently, the substrate on which the vinylon fibers obtained above were fixed was baked at 400 ° C. for 2 hours using a muffle furnace (manufactured by Yamato Kagaku Co., Ltd., model “FO100”) to obtain a carbon nanotube aggregate (carbon of the present invention). Nanotube aggregate).
The carbon nanotube aggregate was linear with a length of 5 cm, a width of 10 μm, and a thickness of 0.7 μm.

(Baking process: Production of membrane-like carbon nanotube aggregate)
250 vinylon fibers cut to a length of 5 cm are arranged on a silicon substrate in a direction orthogonal to the fiber axis direction so that the fiber axis directions are the same, and both ends of each fiber are bonded with an adhesive. Fixed.
Subsequently, the substrate on which the vinylon fibers obtained above were fixed was baked at 400 ° C. for 2 hours using a muffle furnace (manufactured by Yamato Kagaku Co., Ltd., model “FO100”) to obtain a carbon nanotube aggregate (carbon of the present invention). Nanotube aggregate).
The carbon nanotube aggregate was a film having a length of 5 cm, a width of 3 mm, and a thickness of 0.7 μm.

Example 2
In the spinning dope preparation process, “216 g of CNT aqueous dispersion (2) and 30 g of polyvinyl alcohol polymer aqueous solution (polyvinyl alcohol polymer concentration: 4.8 wt%)” were mixed with “CNT water dispersion”. 36 g of the liquid (2) and 30 g of an aqueous polyvinyl alcohol polymer solution (polyvinyl alcohol polymer concentration: 10.8% by weight) were changed to “mixing”, Obtained. The concentration of carbon nanotubes in the spinning dope was 0.12% by weight, and the concentration of polyvinyl alcohol polymer was 12.0% by weight.
Next, using the above spinning solution, in the same manner as in Example 1, vinylon fibers containing carbon nanotubes, linear carbon nanotube aggregates, and film-like carbon nanotube aggregates were obtained. The linear carbon nanotube aggregate had a length of 5 cm, a width of 10 μm, and a thickness of 0.1 μm. The film-like carbon nanotube aggregate had a length of 5 cm, a width of 3 mm, and a thickness of 0.1 μm.

(Evaluation)
The following evaluation was performed on the carbon nanotube, the CNT aqueous dispersion (2), the vinylon fiber, and the carbon nanotube aggregate obtained in the above examples.

(1) Ratio of bundled aggregates (bundle aggregates) in carbon nanotubes The ratio of bundled aggregates in carbon nanotubes contained in the CNT aqueous dispersion (2) obtained in the CNT purification step is as follows. Measured by the method.
The CNT aqueous dispersion (2) obtained in the CNT purification step was applied on a silicon substrate with a coating thickness of 4 μm and dried to obtain an evaluation sample. A field emission scanning electron microscope (FE-SEM) (manufactured by Hitachi High-Technologies Corporation, “S-4300”) was used, and a visual field area of 4.4 μm ² was observed at a magnification of 50,000 times. Note that one evaluation sample was observed at 20 points. FIG. 16 shows one example (SEM photograph) obtained by observing an evaluation sample prepared from the CNT aqueous dispersion (2) of Example 1 by the above method. The fibrous substance in FIG. 16 is a carbon nanotube.
The total number of carbon nanotubes within the viewing area was counted. Note that an aggregate (aggregate) in which two or more carbon nanotubes aggregate was counted as one aggregate. Furthermore, the number of aggregates (bundle aggregates) in which two or more carbon nanotubes within the visual field area were aggregated was counted.
The ratio (%) of the number of bundled aggregates to the total number of carbon nanotubes [= (number of bundled aggregates) / (total number of carbon nanotubes) × 100] was calculated, and the bundles in the carbon nanotubes were calculated. The percentage (%) of the aggregate was used.

(2) The proportion of carbon nanotubes having a length of 1 to 10 μm in the carbon nanotubes The proportion of carbon nanotubes having a length of 1 to 10 μm in the carbon nanotubes contained in the CNT aqueous dispersion (2) obtained in the CNT purification step, It measured by the following method.
The CNT aqueous dispersion (2) obtained in the CNT purification step was applied on a silicon substrate with a coating thickness of 4 μm and dried to obtain an evaluation sample. A field emission scanning electron microscope (FE-SEM) (manufactured by Hitachi High-Technologies Corporation, “S-4300”) was used, and a visual field area of 4.4 μm ² was observed at a magnification of 50,000 times. One evaluation sample was observed at four points.
The total number of carbon nanotubes within the viewing area was counted. Further, the number of carbon nanotubes having a length of 1 to 10 μm within the visual field area was counted. Note that an aggregate (aggregate) in which two or more carbon nanotubes aggregate was excluded from the calculation of the number.
The ratio (%) of the number of carbon nanotubes with a length of 1 to 10 μm to the total number of carbon nanotubes [= (number of carbon nanotubes with a length of 1 to 10 μm) / (total number of carbon nanotubes) × 100] And the ratio (%) of carbon nanotubes having a length of 1 to 10 μm in the carbon nanotubes.

(3) Ratio of multi-walled carbon nanotubes having a diameter of 5 to 40 nm and having two or more layers in carbon nanotubes Diameter in carbon nanotubes contained in CNT aqueous dispersion (2) obtained in CNT purification step Was 5 to 40 nm and the ratio of multi-walled carbon nanotubes having two or more layers was measured by the following method.
The carbon mesh was dipped in the CNT aqueous dispersion (2) obtained in the CNT purification step and pulled up, and then dried to obtain an evaluation sample. Using a transmission electron microscope (TEM) (manufactured by FEI, “Tecnai 20 ST”), observation was performed at a magnification of 285000 times. Observation was made on 50 (50) carbon nanotubes.
Of the 50 carbon nanotubes, the number of multi-walled carbon nanotubes having a diameter of 5 to 40 nm and two or more layers was counted.
Ratio (%) of the number of multi-walled carbon nanotubes in which the diameter is 5 to 40 nm and the number of layers is two or more with respect to the total number (50) of carbon nanotubes to be observed [= (diameter is 5 to 40 nm and layer Number of multi-walled carbon nanotubes having two or more layers) / 50 × 100], and the ratio (%) of multi-walled carbon nanotubes having a diameter of 5 to 40 nm and two or more layers in the carbon nanotubes It was.

(4) Scanning Electron Microscope (SEM) Photo “S-4300” manufactured by Hitachi High-Technologies Corporation was used.

(5) G / D ratio The G / D ratio of the carbon nanotubes obtained in the CNT purification step was measured by the following method.
After the outflow from the column obtained in the CNT purification step, 3 to 5 ml of the permeate (permeate used for preparing the CNT aqueous dispersion (2)) was dried, and the obtained powdered carbon nanotubes were evaluated. A sample was used.
The evaluation sample was measured under the following conditions using a laser Raman microscope manufactured by Renishaw. The intensity ratio between the G peak (1580 cm ⁻¹ ) and D peak (1350 cm ⁻¹ ) of the obtained spectrum was determined and used as the G / D ratio.
<Measurement conditions>
Excitation light source: Argon laser (wavelength: 514.5 nm)
Magnification: 1200 times Measurement spot diameter: 4μmφ
Integration count: 5 times The G / D ratio of the carbon nanotubes obtained in the CNT purification steps of Examples 1 and 2 was 4.1.

(6) Electrical resistance measurement The electrical resistance of the linear carbon nanotube aggregate obtained in Example 1 was measured by the following method.
Two silver electrodes were attached on the carbon nanotube aggregate so that the distance between the electrodes was 10 mm. A DC power supply was attached to the electrode, a voltage was applied, and the current value was read with a multimeter. The applied voltage was measured at 10V intervals from 0V to 150V. The electrical resistance value was calculated from the relationship between the obtained voltage and current.
The linear carbon nanotube aggregate obtained in Example 1 had an electrical resistance value of 44.4 kΩ / cm and a volume resistivity of 3.11 × 10 ⁻³ Ω · cm.

(7) Temperature rise measurement by resistance heating The temperature rise by the resistance heating of the linear carbon nanotube aggregate obtained in Example 1 was measured by the following method. In the firing step, a borosilicate glass substrate was used instead of the silicon substrate, and a linear carbon nanotube aggregate was produced on the borosilicate glass substrate and used for measurement. The size of the borosilicate glass substrate used for the measurement is 75 mm in length, 75 mm in width, and 0.7 mm in thickness.
As shown in FIG. 17, two silver electrodes 12 were attached to the carbon nanotube aggregate 11 produced on the borosilicate glass substrate 13 so that the distance between the electrodes was 10 mm. A K thermocouple 15 and a temperature monitor 16 were mounted on a substrate 13 that was an intermediate portion between the electrodes (position of about 5 mm from the silver electrode on one side) and was separated from the carbon nanotube aggregate 11 by 0.5 mm. . A DC power supply 14 was attached to the electrode 12, a voltage of 150 V was applied, and the temperature was measured by the K thermocouple 15. The substrate temperature and ambient temperature before applying the voltage were 23 ° C.
The current value when a voltage of 150 V was applied was 3.38 mA. The temperature measured by a K thermocouple 10 seconds after applying a voltage of 150 V was 83.3 ° C. Moreover, the temperature measured by the K thermocouple 20 seconds after applying the voltage of 150V was 105.6 degreeC. Furthermore, the temperature measured by a K thermocouple 100 seconds after applying a voltage of 150 V was 133.2 ° C. Note that the temperature had already reached equilibrium after 100 seconds.

  In Examples 1 and 2, the proportion of bundled aggregates in the carbon nanotubes contained in the CNT aqueous dispersion (2) obtained in the CNT purification step, the proportion of carbon nanotubes having a length of 1 to 10 μm, and a diameter of 5 Table 1 shows the ratio of multi-walled carbon nanotubes having a thickness of ˜40 nm and two or more layers.

An SEM photograph of the linear carbon nanotube aggregate obtained in Example 1 (the diagonal direction from the lower right to the upper left of the photograph is the fiber axis direction of the vinylon fiber) is shown in FIGS. A photograph (the lateral direction of the photograph is the fiber axis direction of vinylon fiber) is shown in FIGS. 5 and 6 show SEM photographs of the linear carbon nanotube aggregates obtained in Example 2 (the diagonal direction from the lower left to the upper right of the photograph is the fiber axis direction of the vinylon fibers). SEM photographs (the horizontal direction of the photograph is the fiber axis direction of vinylon fiber) are shown in FIGS. The aggregate of carbon nanotubes produced by the production method of the present invention had excellent orientation in the fiber axis direction of the vinylon fibers. Furthermore, the SEM photograph of the cross section of the linear carbon nanotube aggregate obtained in Example 1 is shown in FIG.
Further, cross-sectional photographs of the vinylon fibers containing carbon nanotubes obtained in Example 1 are shown in FIGS. 10 and 11, and surface photographs are shown in FIG. Moreover, the cross-sectional photograph of the vinylon fiber containing the carbon nanotube obtained in Example 2 was shown in FIGS. 13 and 14, and the surface photograph was shown in FIG.

  The aggregate of carbon nanotubes of the present invention is useful as an electrode, wiring, heater wire, heat sink (such as an anisotropic heat conductive heat sink), and a polarizing material.

11 Aggregate of carbon nanotubes 12 Silver electrode 13 Borosilicate glass substrate 14 Direct current (DC) power supply 15 K thermocouple 16 Temperature monitor

Claims (12)

A step of obtaining a carbon nanotube (A) including a step of synthesizing a carbon nanotube by a substrate growth method in chemical vapor deposition;
Including the step of immersing the carbon nanotube (A) in an acid, obtaining a carbon nanotube (B) having a ratio of an aggregate of two or more carbon nanotubes aggregated in a bundle of 10% or less;
A step of obtaining a spinning dope (C) comprising the step of mixing the carbon nanotube (B), the polyvinyl alcohol polymer and water;
Obtaining the vinylon fiber (D) containing the carbon nanotubes (B), comprising the step of fiberizing the spinning dope (C) by wet spinning;
And a step of obtaining a carbon nanotube aggregate by firing the vinylon fiber (D).   2. The production of a carbon nanotube aggregate according to claim 1, wherein the ratio of multi-walled carbon nanotubes having a diameter of 5 to 40 nm and two or more layers in the carbon nanotube (B) of 100% is 80 to 100%. Method.   3. The method for producing a carbon nanotube aggregate according to claim 1, wherein a ratio of carbon nanotubes having a length of 1 to 10 μm in 100% of the carbon nanotubes (B) is 80 to 100%.   The method for producing a carbon nanotube aggregate according to any one of claims 1 to 3, wherein the step of obtaining the carbon nanotube (B) further includes a step of separation by chromatography.   The method for producing a carbon nanotube aggregate according to claim 4, wherein the chromatography is column chromatography using glass beads having a particle diameter of 0.05 to 5 mm as a stationary phase.   The step of mixing the carbon nanotube (B), the polyvinyl alcohol polymer and water contains the carbon nanotube (B) and the polyvinyl alcohol polymer (PVA1), and the polyvinyl alcohol polymer (PVA1) An aqueous dispersion (c1) having a concentration of 0.1 to 10% by weight and a polyvinyl alcohol polymer (PVA2) are contained, and the concentration of the polyvinyl alcohol polymer (PVA2) is 0.1 to 20% by weight. The method for producing a carbon nanotube aggregate according to any one of claims 1 to 5, which is a step of mixing the aqueous solution (c2).   The step of obtaining the spinning dope (C) further includes mixing the aqueous dispersion (c1) and the aqueous solution (c2) to obtain a mixed solution (c3), and the mixed solution (c3). The method for producing a carbon nanotube aggregate according to claim 6, comprising a step of distilling off a part of the water to be distilled under reduced pressure.   The method for producing a carbon nanotube aggregate according to any one of claims 1 to 7, wherein the step of obtaining the vinylon fiber (D) further includes a step of drawing the fiber.   The content of the carbon nanotube (B) in 100% by weight of the vinylon fiber (D) is 0.1 to 10% by weight. The production of the carbon nanotube aggregate according to any one of claims 1 to 8. Method.   A carbon nanotube aggregate produced by the method for producing a carbon nanotube aggregate according to any one of claims 1 to 9. A step of obtaining a carbon nanotube (A) including a step of synthesizing a carbon nanotube by a substrate growth method in chemical vapor deposition;
Including the step of immersing the carbon nanotube (A) in an acid, obtaining a carbon nanotube (B) having a ratio of an aggregate of two or more carbon nanotubes aggregated in a bundle of 10% or less;
A step of obtaining a spinning dope (C) comprising the step of mixing the carbon nanotube (B), the polyvinyl alcohol polymer and water;
A step of obtaining a vinylon fiber (D) containing the carbon nanotube (B), comprising the step of fiberizing the spinning dope (C) by wet spinning. Production method.   A vinylon fiber containing carbon nanotubes produced by the method for producing a vinylon fiber containing carbon nanotubes according to claim 11.