JP5131571B2 - Method for producing agglomerated spinning structure and agglomerated spinning structure - Google Patents

Description

  The present invention relates to a method for producing a carbon nanotube aggregated and spun structure containing no resin from a carbon nanotube powder.

  A carbon nanotube is a material in which a graphene sheet made of carbon is formed into a single-layer or multi-layer coaxial tube, and has an ultrafine diameter, lightness, high strength, high flexibility, high current density, high thermal conductivity, and high electrical conductivity. It is a material having properties. It is expected that a fibrous material having unprecedented characteristics can be obtained by spinning such carbon nanotubes into a filament shape.

  Such carbon nanotube spinning methods are roughly classified into a gas phase method and a liquid phase method. The gas phase method is a method in which a step of spinning directly after the step of synthesizing carbon nanotubes is performed, and the synthesis and spinning of carbon nanotubes are performed simultaneously. On the other hand, the liquid phase method is a method of obtaining thread-like and fiber-like carbon nanotubes by dissolving the already synthesized carbon nanotube powder in a liquid and spinning the dispersed carbon nanotubes. This is a method performed in another process.

  As the gas phase method, for example, a catalyst for carbon nanotube synthesis and a hydrocarbon as a carbon nanotube raw material are supplied together with a carrier gas into a cylindrical reactor to grow the carbon nanotube, and the reaction region of the reactor A method for obtaining carbon nanotube fibers by spinning on a spindle outside is disclosed (see Patent Document 1).

  As a liquid phase method, a low-viscosity carbon nanotube dispersion liquid in which carbon nanotubes are uniformly dispersed is injected into a viscous aggregate liquid containing polyvinyl alcohol (PVA) having a constant flow. A method of obtaining a composite fiber of carbon nanotube and PVA is disclosed (see Patent Document 2).

  Furthermore, as another liquid phase method, nanofibers are injected by injecting a carbon nanotube dispersion liquid having a low viscosity in which carbon nanotubes are uniformly dispersed into a strong acid or strong alkali agglomerated liquid (pH is 3 or less or pH 11 or more). Is disclosed (see Patent Document 3).

Special table 2007-535434 gazette US Patent Application Publication No. 2008/0124507 US Patent Application Publication No. 2007/0243124

  However, in the method described in Patent Document 1, since synthesis and spinning of carbon nanotubes are continuously performed, it is difficult to optimize both the synthesis speed and the spinning speed under different optimum conditions. It was. In addition, since the synthesis and spinning of carbon nanotubes are performed continuously, the catalyst is removed from the synthesized carbon nanotubes, the surface treatment of the carbon nanotubes is performed, metallic carbon nanotubes and semiconducting carbon nanotubes. There was a problem that it could not be separated. In particular, since carbon nanotubes are usually synthesized as a mixture of both metallic and semiconducting materials, if they are spun without separation, the electrical conductivity of the resulting fibrous material will not be excellent.

  In the method described in Patent Document 2, since carbon nanotubes are spun using a resin such as PVA, a resin layer is formed on the surface of the carbon nanotubes, and the resin soaks into the carbon nanotubes. The resin layer on the surface increases the contact resistance between the carbon nanotubes and decreases the conductivity of the composite wire. The resin soaked in the inside lowers the electrical conductivity of the carbon nanotube itself. For this reason, the method described in Patent Document 2 has a problem that a composite wire excellent in electrical conductivity cannot be obtained.

  Further, in the method described in Patent Document 3, since a strong acid or strong alkali liquid is used as an aggregating liquid in spinning of carbon nanotubes, defects occur in the carbon nanotubes. When defects occur, the graphite crystals of the carbon nanotubes are damaged, and the electrical conductivity and mechanical properties of the carbon nanotubes alone deteriorate. For this reason, there is a problem that the electrical conductivity and mechanical properties of the obtained secondary nanofibers of carbon nanotubes are also deteriorated.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to obtain an aggregated spinning structure having high electrical conductivity formed by spinning carbon nanotubes.

In order to achieve the above-mentioned object, the following invention is provided.
(1) A step (a) of producing a dispersion in which carbon nanotubes are dispersed in a first solvent that is a water-soluble solvent or a mixed solvent containing an organic solvent and water with a surfactant; the solvent to be different from the second solvent aggregating agent, and injecting the dispersion liquid obtained by dispersing the carbon nanotubes, it viewed including the step (b) to aggregate spinning carbon nanotube, wherein the first solvent is water Or a mixed solvent containing one or more organic solvents selected from the group consisting of methanol, ethanol, propanol, formamide, ethylene glycol, and dimethyl sulfoxide and water, and the aggregate liquid is N-methylpyrrolidone, N, N-dimethylacetamide, propylene carbonate, formamide, N-methylformamide, water, methanol, ethanol Nord, a solution containing any one of propanol, wherein in the said cohesive liquid first solvent, said different affinity with the surfactant agents, pH of the coagulation solution is between 3 and 11 A method for producing an agglomerated spinning structure.
(2) The production of the aggregated spinning structure according to (1), wherein the surfactant is any one or more of surfactants belonging to the following groups (A) to (C): Method.
(A) Nonionic surfactant having an HLB of 8 or more obtained by the Griffin method (B) Anionic surfactant: alkylbenzene sulfonate, alkyl alcohol sulfate, sodium alkyldiphenyl ether disulfonate, polyoxyethylene alkyl Sodium ether sulfate ester, sodium dialkylsulfosuccinate, sodium alkylallylsulfosuccinate, sodium N-lauroyl sarcosine, sodium polyoxyethylene alkylphenyl ether sulfate, sodium (meth) acryloyl polyoxyalkylene sulfate, alkyl alcohol phosphate ( C) Cationic surfactant: Tetraalkylammonium halide (3) Said surfactant is said (A) and said (B) or said (A) and Serial of surfactants belonging to the group of (C), the method of producing aggregate spinning structure described in (2) that is obtained by combining the one or more surfactants.
(4) The method for producing an aggregated spinning structure according to ( 2 ), wherein the surfactant includes a plurality of surfactants having different main chain lengths.
(5) The method for producing an agglomerated spinning structure according to any one of ( 2 ) to ( 4 ), wherein the surfactant contains sodium dodecyl sulfate.
(6) Further, after the step (b), the aggregated spinning structure is removed from the aggregated liquid and immersed in a solvent, the aggregated spinning structure is dried, and the aggregated spinning structure is stretched. The method for producing an agglomerated spinning structure according to any one of (1) to ( 5 ), comprising the step of:
(7) The method for producing an aggregated spinning structure according to ( 6 ), further comprising a step of rolling the aggregated spinning structure.
(8) The method for producing an aggregated spinning structure according to any one of (1) to ( 7 ), wherein the carbon nanotube is subjected to a catalyst removal treatment.
(9) An agglomerated spinning structure produced by the production method described in any one of (1) to ( 8 ).
(10) An aggregated spinning structure comprising carbon nanotubes produced by the production method described in any one of (1) to ( 8 ), wherein the bulk density is 0.5 g / cm ³ or more, and an air atmosphere The temperature after heating from room temperature to 100 ° C. at a temperature rising rate of 10 ° C./min and leaving at 100 ° C. for 10 minutes as the dry weight is 450 ° C. at a temperature rising rate of 10 ° C./min in an air atmosphere. The weight reduction rate obtained by subtracting the heating weight from the dry weight and dividing the dry weight by the weight after the additional heating up to 50% is 50% or less, and is a spectrum obtained by resonance Raman scattering measurement. the maximum peak intensity in the range of 1650 cm ^-1 G, when the maximum peak intensity is D within the 1300~1400cm ^-1, coagulation ratio of G / D is equal to or is 10 or more Spinning structure.

  According to the present invention, it is possible to obtain an agglomerated spun structure having high electrical conductivity formed by spinning carbon nanotubes.

(A) The figure explaining the dispersion manufacturing process in the manufacturing method of the aggregation spinning structure concerning this invention, (b) The figure explaining the aggregation spinning process similarly, The figure which expanded the A section of (c) (b) . The figure which shows the Raman spectrum of the single wall carbon nanotube (FH-P) used in Example 1. FIG. (A) The figure which shows the aggregation spinning structure after inject | pouring a dispersion liquid into an aggregation liquid in Example 1, (b) The figure which shows the aggregation spinning structure when pulled up from water in Example 1, (c) FIG. 3 is a diagram showing an agglomerated spinning structure after drying. (A) Photograph when the surface of the agglomerated spinning structure according to Example 1 is observed with a scanning electron microscope, (b) An enlarged view of the corresponding part in (a), (c) Corresponding in (a) The enlarged view of a location. (A) The photograph which observed the aggregation spinning structure which concerns on Example 1 before FIB processing, (b) The photograph which exposed the longitudinal section by FIB processing of the aggregation spinning structure.

(Aggregated spinning structure of the present invention)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, the aggregated spinning structure according to the present invention is formed by spinning a large number of carbon nanotubes.

The aggregated spinning structure of the present invention has a bulk density of 0.5 g / cm ³ or more. This bulk density can be determined by a known method, but in particular, the weight, diameter and length of the aggregated spinning structure are measured, the volume is obtained assuming that the aggregated spinning structure is cylindrical, and the dry weight. Is preferably obtained by dividing by the volume. In addition, the bulk density of the single wall carbon nanotube before spinning is about 0.2 to 0.3 g / cm ³ . Similarly, the carbon nanotube fiber produced by the vapor phase method is about 0.2 to 0.3 g / cm ³ . That is, the aggregated spinning structure of the present invention is excellent in electrical conductivity and strength because the carbon nanotubes are densely spun as compared with the aggregated spinning structure produced by the gas phase method.

  The agglomerated spinning structure of the present invention is heated from room temperature to 100 ° C. at a rate of temperature increase of 10 ° C./min in an air atmosphere, and then left at 100 ° C. for 10 minutes as a dry weight. The weight reduction rate obtained by dividing the weight obtained by subtracting the heating weight from the dry weight by the dry weight is 65% or less, with the weight after additional heating up to 450 ° C. at a temperature increase rate of 10 ° C./min as the heating weight. In addition, it is preferable that this weight decreasing rate is 50% or less, and it is more preferable that it is 25% or less. The smaller the weight reduction rate, the smaller the amount of organic matter (particularly resin) other than carbon nanotubes contained in the aggregated spinning structure, and the electrical conductivity and heat resistance of the aggregated spinning structure are improved.

  The aggregated spinning structure of the present invention preferably has an electric conductivity of 50 S / cm or more, more preferably 100 S / cm or more, further preferably 200 S / cm or more, and 500 S / cm or more. Even more preferably. The electric conductivity of a general conductive polymer is less than 50 S / cm, and the aggregated spinning structure of the present invention having an electric conductivity of 50 S / cm or more can be used in many applications. Also, higher electrical conductivity is preferable because it can be used for more applications.

  The aggregated spinning structure of the present invention has a plurality of longitudinal grooves having a depth of 1 to 3 μm and a length of 30 μm or more on the surface, and a plurality of cavities of 100 nm to 10 μm in the interior when observed from a cross section. Is. Such longitudinal grooves and cavities are considered to occur when the solution dries out when removed from the agglomerated liquid or immersion liquid.

  The aggregated spinning structure of the present invention preferably has a diameter of 10 μm or more, preferably 30 μm or more and 1 cm or less, and a length / diameter ratio of 100 or more.

The aggregated spinning structure of the present invention is a spectrum obtained by resonance Raman scattering measurement when irradiated with a laser (for example, a 514 nm Ar laser), and has a maximum peak intensity G in the range of 1550 to 1650 cm ⁻¹ , 1300 to 1300. When the maximum peak intensity within the range of 1400 cm ⁻¹ is D, the G / D ratio is preferably 10 or more, and the G / D ratio is more preferably 30 or more. Peak in the range of 1550～1650Cm ^-1 is called G band, a peak derived from a graphite structure of the carbon nanotube, a peak in the range of 1300～1400Cm ^-1 is called D band of amorphous carbon and carbon It is a peak derived from a lattice defect of a nanotube. That the G / D ratio is 10 or more means that it is composed of high-quality carbon nanotubes with few lattice defects. In particular, if it is 30 or more, it is composed of higher quality carbon nanotubes and is excellent in thermal conductivity, electrical conductivity, and heat resistance.

  The aggregated spinning structure of the present invention preferably contains 75% by weight or more of carbon nanotubes.

(carbon nanotube)
The type of carbon nanotubes contained in the aggregated spinning structure of the present invention is not particularly limited, and carbon nanotubes produced by a known process can be used. Specifically, carbon nanotubes synthesized by high pressure carbon monoxide (HiPco) method, laser ablation method, arc discharge method, chemical vapor deposition (CVD) method, and the like. The carbon nanotube may be only a single wall carbon nanotube, only a double wall carbon nanotube, only a multiwall carbon nanotube, or a mixture thereof, but only a metallic single wall carbon nanotube from which a catalyst has been removed. Preferably, it is configured.

  Since carbon nanotubes are usually synthesized using a catalyst of metal particles such as iron, nickel, and cobalt, the carbon nanotube powder often contains a catalyst. When a catalyst is contained, it causes deterioration of conductivity and heat resistance. Therefore, it is preferable to remove the catalyst by treating the carbon nanotubes before spinning with an acid.

  The carbon nanotubes preferably have an average diameter of 0.5 to 100 nm. The average diameter is preferably obtained by averaging measured values of the diameter with an electron microscope. Furthermore, the carbon nanotube may be linear or curved.

The arc discharge method is a method of obtaining multiwall carbon nanotubes deposited on a cathode by performing an arc discharge between electrode materials made of carbon rods in an argon or hydrogen atmosphere at a pressure slightly lower than atmospheric pressure. . The single-walled carbon nanotube is obtained from soot adhering to the inner surface of the processing vessel by performing arc discharge by mixing a catalyst such as nickel / cobalt in the carbon rod.
The laser ablation method melts and evaporates the carbon surface by irradiating a strong YAG laser pulsed laser beam onto a carbon surface mixed with a target catalyst such as nickel / cobalt in a rare gas (eg argon). This is a method for obtaining single-walled carbon nanotubes.
The vapor phase growth method is a method in which hydrocarbons such as benzene and toluene are thermally decomposed in the gas phase to synthesize carbon nanotubes. More specifically, a fluid catalyst method, a zeolite supported catalyst method, and the like can be exemplified.
The high-pressure carbon monoxide (HiPco) method is a kind of vapor phase growth method, which uses an iron compound as a catalyst and thermally decomposes carbon monoxide at high pressure to produce a single wall with high purity and a relatively small diameter (around 1 nm). Obtain carbon nanotubes.

  Moreover, it is preferable that a carbon nanotube contains the carbon nanotube which has ballistic conductivity. Ballistic conductivity is realized when the size of the carbon nanotube is larger than the mean free path of electrons and smaller than the total phase length. Carbon nanotubes having ballistic conductivity are expected to improve electrical conductivity based on non-scattering travel of carriers.

The carbon nanotubes may include doped carbon nanotubes. Doping is to contain a dopant in the internal space of the carbon nanotube or to coat the carbon nanotube with the dopant. The dopant is alkali metal, halogen, conductive polymer (PPyCF ₃ SO ₃ , PPyTFSI), ionic liquid (EMIBF ₄ , EMITFSI), organic molecule (TCNQ (Tetracyanoquinodimethane), DNBN-3,5-Dinitrobenzontrile N, Q4-C Tetrafluorotetracyanoquinodimethane), TDAE (Tetrakis (dimethylamino) ethylene), TTF (Tetrathiafulvalene), TMTSF (Tetramethyltetraleneful), and TTSF (Tetramethyltetraleneful). Masui.

  Moreover, it is preferable that a carbon nanotube contains the carbon nanotube to which metal nanoparticles, such as copper, nickel, titanium, and magnesium, were provided. The provision of nanoparticles means that metal particles are attached to the surface of carbon nanotubes.

  In addition, when single-wall carbon nanotubes are synthesized, metallic ones and semiconducting ones are usually produced at a ratio of about 1: 2. Therefore, it is preferable to separate metallic single-walled carbon nanotubes and semiconducting single-walled carbon nanotubes by ion chromatography or the like and use only metallic ones for spinning.

  As a characteristic of the carbon nanotube used in the present invention, the G / D ratio of the Raman spectrum described above is preferably 10 or more, and the G / D ratio is more preferably 30 or more. A G / D ratio of 10 or more means a high-quality carbon nanotube with few lattice defects. In particular, if it is 30 or more, it is a higher quality carbon nanotube, and is excellent in thermal conductivity, electrical conductivity, and heat resistance.

  Further, the carbon nanotube used in the present invention is preferably not pyrolyzed to about 800 ° C., and the weight loss between 100 ° C. and 800 ° C. is preferably within 50%, more preferably within 25%. It is preferable to become. The weight loss between 100 ° C. and 800 ° C. of the carbon nanotubes originates from the amount of amorphous carbon, and the carbon nanotubes with less amorphous carbon are of higher quality and have better thermal conductivity, electrical conductivity, and heat resistance. Excellent.

(Effect of cohesive spinning structure)
The agglomerated spinning structure of the present invention does not contain a resin and does not pass through a strong acid or strong alkali solution, so that no defects are generated. Therefore, an agglomerated spinning structure with high electrical conductivity can be obtained. Furthermore, if only the metallic single-wall carbon nanotubes from which the catalyst has been removed are used, an agglomerated spun structure having a higher electrical conductivity can be obtained.

  Further, since the aggregated spinning structure of the present invention is free from defects due to the treatment of passing a strong acid or strong alkali solution, it is considered to have higher mechanical strength than the aggregated spinning structure obtained by the conventional method.

  Moreover, since the aggregated spinning structure of the present invention has a wrinkle structure having grooves on the surface, it is excellent in workability and slidability.

  These agglomerated and spun structures can be made into conductors by combining them in a desired size, and if necessary, an outside can be coated with an insulator to form an electric wire. Since such an electric wire has high electric conductivity, high thermal conductivity, and high thermal stability, it becomes a light wire that can flow a large current.

(Method for producing a coagulated spinning structure)
FIG. 1 is a diagram for explaining a method for producing an agglomerated spinning structure according to an embodiment of the present invention. First, as shown in FIG. 1A, carbon nanotubes 3 synthesized by various methods are dispersed in a first solvent 7 together with a surfactant 5 to obtain a dispersion 1.

  Next, as shown in FIG. 1 (b), the dispersion 1 is continuously injected into the aggregating liquid 9 being stirred with a syringe or the like. FIG.1 (c) is the figure which expanded the A section of FIG.1 (b). As shown in FIG. 1C, the surfactant 5 and the first solvent 7 are dispersed in the aggregation liquid 9 from the dispersion injected into the aggregation liquid 9, and the carbon nanotubes 3 are spun. A body 11 is obtained.

  The present invention is characterized in that an agglomerated spinning structure is obtained by “injecting the dispersion continuously into the agglomerated liquid”. For example, an agglomerated spinning structure can be obtained in which an agglomerated liquid is obtained by inserting the agglomerated liquid into a syringe or the like and continuously injecting the agglomerated liquid into a dispersion containing carbon nanotubes. Can't get. Also, even if an agglomerated liquid is put into a beaker and the agglomerated liquid is added to the dispersion at once, an agglomerated spinning structure cannot be obtained although an amorphous aggregate or a film-shaped aggregate can be obtained. .

  Further, after this, the aggregated spinning structure 11 of the carbon nanotubes 3 may be immersed in water and dried, or a process of stretching the aggregated spinning structure. In the stretching process, the orientation of the carbon nanotubes is improved by mechanically stretching the aggregated spinning structure to 50% or more of the breaking strain. Furthermore, a step of winding a plurality of the agglomerated spinning structures 11, that is, a step of twisting and intertwining to form a single thick wire may be included.

  As the carbon nanotube 3, the carbon nanotube that can be included in the aggregated spinning structure as described above is used.

(Surfactant)
Examples of the surfactant 5 include the following (1) to (3), and it is desirable to use at least one of at least one of the surfactants belonging to the groups (1) to (3). . Alternatively, one or more of the surfactants belonging to the groups (1) and (2) or (1) and (3) may be used in combination.
(1) Nonionic surfactant having an HLB of 8 or more (2) Anionic surfactant: alkylbenzene sulfonate (for example, sodium dodecylbenzenesulfonate), alkyl alcohol sulfate (for example, sodium dodecyl sulfate) Etc.), sodium alkyldiphenyl ether disulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium dialkylsulfosuccinate, sodium alkylallylsulfosuccinate, sodium N-lauroyl sarcosine, sodium polyoxyethylene alkylphenyl ether sulfate, (meth) acryloyl poly Sodium oxyalkylene sulfate ester, alkyl alcohol phosphate ester salt, etc. (3) Cationic surfactant: Tetraalkylammonium halo Donado

If the HLB of the nonionic surfactant is 8 or more, water can be used as the first solvent 7 used in the dispersion 1 because it is easily dispersed or dissolved in water. In addition, HLB of a nonionic surfactant is calculated | required by the Griffin method.
The Griffin method is a method defined by HLB value = 20 × (sum of formula weight of hydrophilic part / molecular weight). The Davis method is a method in which the number of bases determined by a functional group is determined and defined by HLB value = 7 + (total number of bases of hydrophilic groups−total number of bases of lipophilic groups).

  The nonionic surfactant (1) is not particularly limited as long as the HLB is 8 or more. For example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester , Glycerin fatty acid ester, polyoxyethylene fatty acid ester, and 8 or more surfactants in HLB, especially poly (oxyethylene) octylphenyl ether (for example, Triton (registered trademark) X-100), polyoxyethylene sorbitan Among monolaurates (for example, Tween (registered trademark) 20) and the like, surfactants having an HLB of 8 or more can be used.

  It is also preferable to use the dispersion 1 by heating it to a temperature higher than room temperature. By heating, the functionality of the surfactant is increased, and the amount of the surfactant to be added can be reduced. If the amount of the surfactant to be added can be reduced, the amount of the surfactant mixed in the aggregated spinning structure can be reduced, and the conductivity of the aggregated spinning structure can be improved. In addition, even a dispersion using a surfactant that does not succeed in spinning at room temperature may be successfully spun by heating.

  It is possible to use a plurality of surfactants (1) to (3) above, but when (2) both an anionic surfactant and (3) a cationic surfactant are included. It is preferable not to mix the anionic surfactant and the cationic surfactant because they associate between the anionic surfactant and the cationic surfactant and do not function as the surfactant. . In other words, when a plurality of surfactants are used, the same type of surfactants such as nonionic surfactants, anionic surfactants, and cationic surfactants are used, or nonionic surfactants are used. And a combination of an anionic surfactant and a combination of a nonionic surfactant and a cationic surfactant.

  Moreover, it may be preferable to include a plurality of surfactants having different main chain lengths. Specifically, it is conceivable to add a plurality of types of surfactants having the same functional group but different alkyl chain lengths. Carbon nanotubes that are actually handled include not only carbon nanotubes that are dispersed one by one, but also carbon nanotubes in which a plurality of carbon nanotubes are aggregated into a lump. At this time, for the carbon nanotubes dispersed one by one, a surfactant with a short main chain is more easily removed than a carbon nanotube at the time of spinning, so that the amount of the surfactant incorporated into the aggregated spinning structure is reduced. In addition, for carbon nanotubes in which a plurality of aggregates are aggregated, a surfactant having a long main chain is not incorporated into the aggregate at the time of dispersion, and the amount of surfactant incorporated into the aggregated spinning structure is less. Reduced and preferred. As described above, when the carbon nanotubes actually handled include both carbon nanotubes dispersed one by one and carbon nanotubes aggregated in a lump, it is preferable to add a plurality of surfactants having different main chain lengths.

(First solvent)
The first solvent 7 is water or a mixed solvent of water and an organic solvent. Examples of the organic solvent include methanol, ethanol, propanol, formamide, ethylene glycol, and dimethyl sulfoxide.

  In dispersion 1, carbon nanotube 3 is contained in an amount of 0.1 wt% to 1.5 wt%, preferably 0.2 wt% to 0.4 wt%, and surfactant 5 is contained in an amount of 0.1 wt% to 2.0 wt%, preferably Contains 0.6 wt% to 1.2 wt%.

  The pH of the dispersion 1 is preferably between 3 and 11. When carbon nanotubes are exposed to a strong acid or strong alkali solution, defects occur in the graphite crystals of the carbon nanotubes, leading to deterioration of the electrical conductivity and mechanical properties of the carbon nanotubes themselves.

(Second solvent)
The second solvent (aggregate) 9 is a solution containing any one of N-methylpyrrolidone, N, N-dimethylacetamide, propylene carbonate, formamide, N-methylformamide, water, methanol, ethanol, and propanol. It is preferable that there is at least N, N-dimethylacetamide. The second solvent 9 is different from the first solvent 7. In addition, the agglomerate 9 and the first solvent 7 have different affinities with the surfactant 5. In other words, the affinity of the carbon nanotube and the surfactant to the aggregate differs between the dispersion and the aggregation liquid, and in the dispersion, the aggregate of the carbon nanotube and the surfactant needs to be well dispersed. Among them, aggregates of carbon nanotubes and surfactants need to aggregate.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

Hereinafter, the present invention will be specifically described using examples and comparative examples.
[Example 1]
(Dispersion preparation)
First, 40 mg of single wall carbon nanotubes (FH-P manufactured by Meijo Nanocarbon Co., Ltd.) and 120 mg of sodium dodecyl sulfate (anionic surfactant, HLB value = 40 (Davis method)) are added to 9840 mg of water, and 700 rpm2 Stir under conditions of time and disperse with an ultrasonic homogenizer (US-50 manufactured by Nippon Seiki Seisakusho Co., Ltd.) for 5 minutes.

The Raman spectrum of FH-P is shown in FIG. When the ratio of the intensity of the G band (1588 cm ⁻¹ ) of FH-P and the D band (1339 cm ⁻¹ ) was taken, the G / D ratio was 38.9.

(Injection and spinning process)
N, N-dimethylacetamide was used as the aggregating liquid as it was, the dispersion was put into a syringe, the tip of the syringe was immersed in the aggregating liquid, and the dispersion was gently injected into the aggregating liquid to agglomerate and spin the carbon nanotubes. The conditions for injecting the dispersion into the agglomerated liquid were as follows: the injection nozzle diameter was 0.51 mm, the distance from the center of the agglomerated liquid to the injection nozzle was about 3 cm, the injection speed was about 1.9 ml / min, and the stirrer for the agglomerated liquid The rotation speed was set to 50 rpm.
FIG. 3A shows the aggregated spinning structure after the dispersion liquid has been poured into the aggregated liquid.
Thereafter, the coagulated spinning structure was immersed in water for 1 day and vacuum-dried for 1 day.
FIG. 3 (b) shows the state when the aggregated spinning structure is pulled up from water, and FIG. 3 (c) shows the aggregated spinning structure after drying.

(Investigation of injection conditions)
The conditions for injecting the dispersion into the agglomerated liquid affected the morphology of the agglomerated spinning structure. In particular, the total amount of the agglomerated liquid compared to the total amount of the dispersion affected the morphology of the agglomerated spinning structure. For example, compared with the total amount of the dispersion liquid contained in the syringe, the total amount of the aggregate liquid is set to 2 times and 4 times less than 5 times, and the other conditions are gradually changed to the aggregate liquid under the conditions of Example 1. When injected, an agglomerated spinning structure was not obtained.
On the other hand, compared with the total amount of the dispersion liquid contained in the syringe, the total amount of the aggregate liquid is 6 times and 10 times exceeding 5 times. When injected into the agglomerated liquid, an agglomerated spinning structure was obtained in both cases. The ratio of the coagulated liquid with respect to the total amount of the dispersion is desirably larger, more preferably 10 times or more, and there is no upper limit to the ratio.

(Evaluation)
The electrical conductivity of the aggregated spinning structure according to Example 1 was measured at 20 ° C. using a four-terminal method. The electrical conductivity of the coagulated spinning structure according to Example 1 was 1275.6 S / cm.

Further, the aggregated spinning structure according to Example 1, the length was measured, the weight was measured using a balance, the diameter was measured using a scanning electron microscope, and the calculation was performed assuming a cylindrical shape. The bulk density of the aggregated spinning structure according to Example 1 was 0.74 g / cm ³ .

  Further, when the agglomerated spinning structure according to Example 1 was subjected to thermogravimetric analysis at a heating rate of 10 ° C./min in an air atmosphere, the weight decreased by 22.7% between 100 ° C. and 450 ° C. did. The G / D ratio of the Raman spectrum of the coagulated spinning structure according to Example 1 was 13.1.

  Moreover, the photograph at the time of observing the surface of the aggregation spinning structure which concerns on Example 1 with a scanning electron microscope is shown to Fig.4 (a)-(c). As shown in FIG. 4 (a), an infinite number of longitudinal grooves are formed on the surface of the cohesive spinning structure, and these grooves have a depth of 1 to 3 μm and a length of 30 μm or more. . 4 (b) and 4 (c), the surface has innumerable white streaks of carbon nanotubes, and the aggregated spinning structure according to Example 1 is formed by spinning a large number of carbon nanotubes. I understand.

  Further, a part of the surface of the aggregated spinning structure according to Example 1 was subjected to focused ion beam (FIB) processing, and the longitudinal section was observed with a scanning electron microscope. FIG. 5A is a photograph of the aggregated spinning structure observed before FIB processing, and FIG. 5B is a photograph of the longitudinal cross-section exposed by FIB processing of the aggregated spinning structure. FIG. 5B shows that the aggregated spinning structure has a plurality of voids of 100 nm to 10 μm inside.

[Examples 2 to 43, Comparative Examples 1 to 6]
From Example 1, water immersion time, ultrasonic conditions, stirring conditions, carbon nanotube ratio, carbon nanotube type, ultrasonic dispersion time, dispersion solvent (first solvent), surfactant type, aggregating liquid The type of (second solvent) was changed, and the aggregated spinning structures according to Examples 2 to 43 and Comparative Examples 1 to 6 were formed, and the electrical conductivity was measured.
In Examples 2 to 6, the time of immersion in water and the ultrasonic time were changed.
Examples 7 to 10 are steps for preparing a dispersion, and in Example 1, what was merely stirring was ultrasonically stirred using an ultrasonic stirrer.
In Examples 11 to 14, the mixing ratio of carbon nanotubes was changed, and the apparatus and conditions for ultrasonic dispersion were changed.
In Examples 15 to 17, the mixing ratio of the carbon nanotube and the surfactant was changed, and the apparatus and conditions for ultrasonic dispersion were changed.
In Examples 18 to 20, the type of the carbon nanotube was changed.
In Examples 21 to 23, the first solvent used in the dispersion was a mixed solvent obtained by adding an organic solvent to water.
In Examples 24-26, the surfactant used in the dispersion was changed to Triton X-100, and the second solvent used in the aggregate was changed.
In Examples 27 to 29, the surfactant used in the dispersion was changed to Tween 20, and the second solvent used in the aggregation liquid was changed.
In Examples 30 to 34, the surfactant used for the dispersion was changed to a hard type or a soft type of sodium dodecylbenzenesulfonate, and the second solvent used for the aggregating liquid was changed.
Example 35 is an example in which the dispersion process of the dispersion liquid of Example 1 was changed.
In Examples 35 to 39, the length of the alkyl chain of the surfactant used in the dispersion was changed from sodium dodecyl sulfate (carbon number 12) alone in Example 35 to sodium octyl sulfate (carbon number 8) and sodium dodecyl sulfate. Changed to mixed. Furthermore, Example 38 is an example in which the amount of sodium dodecyl sulfate was changed from Example 35, and Example 39 was changed to a mixture of sodium octyl sulfate and sodium dodecyl sulfate while reducing the amount of surfactant. This is an example. As shown in Comparative Example 5 described later, when only sodium octyl sulfate was used as the surfactant, spinning could not be performed.
Examples 40 and 41 and Comparative Examples 1 and 2 are examples using sodium hexadecyl sulfate (16 carbon atoms) or sodium octadecyl sulfate (18 carbon atoms). When a surfactant having a long alkyl chain length such as sodium hexadecyl sulfate or sodium octadecyl sulfate was used, spinning was not possible at room temperature, but spinning was successful by heating.
Example 42 is an example in which the period of water immersion in Example 41 was extended from 1 day to 7 days. When sodium octadecyl sulfate was used as the surfactant, the conductivity increased as a result of extending the period of water immersion.
Example 43 and Comparative Examples 3, 4, and 6 are examples in which the amount of the surfactant was reduced to 60 mg. In Example 43, the octadecyl sodium sulfate having 18 carbon atoms could be spun even if the amount of the surfactant was reduced, but in the case of using 16 hexadecyl sodium sulfate in Comparative Example 3 or in Comparative Example 4 When using sodium dodecyl sulfate having 12 carbon atoms, spinning was failed when sodium octyl sulfate having 8 carbon atoms was used in Comparative Example 6. In addition, when using octyl sodium sulfate like the comparative example 5, it was not able to spin even if 120 mg of surfactant was used.
The results are summarized in a table.

The devices and materials used in the examples are as follows.
・ Agitator A: Ultrasonic homogenizer US-50 manufactured by Nippon Seiki Seisakusho Co., Ltd.
・ Agitator B: Ultrasonic stirrer USS-1 manufactured by Nippon Seiki Seisakusho
・ Agitator C: Ultrasonic homogenizer NR-50M manufactured by Microtech Nichion
SN2102: Sun Innovation Inc. SN2102 single wall carbon nanotubes SG-SWNTs: single wall carbon nanotubes manufactured by the Super Growth method manufactured by National Institute of Advanced Industrial Science and Technology Hipco-CNT: single wall carbon nanotubes manufactured by the HiPco method manufactured by unidym (ash content) 5 to 15% by weight of Purifed quality)
Triton X-100: Triton X-100 manufactured by Kishida Chemical Co., poly (oxyethylene) octylphenyl ether (nonionic surfactant, HLB value = 13.4)
Tween 20: Tween 20 manufactured by Kishida Chemical Co., polyoxyethylene sorbitan monolaurate (nonionic surfactant, HLB value = 16.7)
・ Sodium dodecylbenzenesulfonate hard type (anionic surfactant)
・ Sodium dodecylbenzenesulfonate soft type (anionic surfactant)

  As described above, water immersion time, ultrasonic conditions, stirring conditions, carbon nanotube ratio, carbon nanotube type, ultrasonic dispersion time, dispersion solvent (first solvent), surfactant type, and aggregating liquid Even if the type of (second solvent) is changed, the aggregated spinning structure according to each example has a conductivity of 50 S / cm or more.

[Comparative Example 7]
As Comparative Example 7, an agglomerated spinning structure was formed in the same manner as in Example 1 except that a 1% by weight aqueous solution of polyvinyl alcohol (Fluka, MW 49000) was used as the agglomerated liquid of Example 1.

  Further, the aggregated spinning structure according to Comparative Example 7 was subjected to thermogravimetric analysis in the same manner as in Example 1. As a result, the weight reduction rate was 65.7% between 100 ° C. and 450 ° C. Even if the type of carbon nanotube was changed, it did not become 50% or less. The G / D ratio of the Raman spectrum of the aggregated spinning structure according to Comparative Example 7 was 8.37.

  As described above, since the aggregated spinning structure according to Comparative Example 7 contains a resin, the weight loss between 100 ° C. and 450 ° C. is larger than that of the aggregated spinning structure according to Example 1.

DESCRIPTION OF SYMBOLS 1 ......... Dispersion liquid 3 ......... Carbon nanotube 5 ......... Surfactant 7 ......... First solvent 9 ......... Second solvent (aggregate)
11 ... Cohesive spinning structure

Claims (10)

A step (a) of producing a dispersion in which carbon nanotubes are dispersed in a first solvent, which is a mixed solvent containing only water or an organic solvent and water, with a surfactant;
The aggregating agent is a second solvent different from the first solvent, and injecting the dispersion liquid obtained by dispersing the carbon nanotubes, viewed including the step (b) to aggregate spinning carbon nanotube,
The first solvent is either water alone or a mixed solvent containing one or more organic solvents selected from the group consisting of methanol, ethanol, propanol, formamide, ethylene glycol, and dimethyl sulfoxide and water. And
The aggregation liquid is a solution containing any one of N-methylpyrrolidone, N, N-dimethylacetamide, propylene carbonate, formamide, N-methylformamide, water, methanol, ethanol, propanol, In the first solvent, the affinity with the surfactant is different,
The method for producing an aggregated spinning structure, wherein the pH of the aggregated liquid is between 3 and 11 . The method for producing an agglomerated spinning structure according to claim 1, wherein the surfactant is at least one of the surfactants belonging to the following groups (1) to (3).
(1) Nonionic surfactant having an HLB of 8 or more determined by the Griffin method (2) Anionic surfactant: alkylbenzene sulfonate, alkyl alcohol sulfate, sodium alkyldiphenyl ether disulfonate, polyoxyethylene alkyl Sodium ether sulfate ester, sodium dialkylsulfosuccinate, sodium alkylallylsulfosuccinate, sodium N-lauroyl sarcosine, sodium polyoxyethylene alkylphenyl ether sulfate, sodium (meth) acryloyl polyoxyalkylene sulfate, alkyl alcohol phosphate ( 3) Cationic surfactant: tetraalkylammonium halide The surfactant is a combination of one or more surfactants among the surfactants belonging to the groups (1) and (2) or (1) and (3). The method for producing an agglomerated spinning structure according to claim 2 . The method for producing an aggregated spinning structure according to claim 2 , wherein the surfactant includes a plurality of surfactants having different main chain lengths. The method for producing an agglomerated spinning structure according to any one of claims 2 to 4 , wherein the surfactant contains sodium dodecyl sulfate. Furthermore, after the step (b),
Removing the agglomerated spinning structure from the agglomerated liquid and immersing in a solvent;
Drying the agglomerated spinning structure;
Stretching the coagulated spinning structure;
The method for producing an agglomerated spun structure according to any one of claims 1 to 5 , wherein: The method for producing an agglomerated spinning structure according to claim 6 , further comprising a step of rolling the agglomerated spinning structure. The method for producing an agglomerated spinning structure according to any one of claims 1 to 7 , wherein the carbon nanotube is subjected to a catalyst removal treatment. An agglomerated spinning structure produced by the production method according to any one of claims 1 to 8 . An aggregated spinning structure comprising carbon nanotubes produced by the production method according to any one of claims 1 to 8 ,
The bulk density is 0.5 g / cm ³ or more,
The weight after heating from room temperature to 100 ° C. at a temperature increase rate of 10 ° C./min in an air atmosphere and allowing to stand at 100 ° C. for 10 minutes is defined as dry weight, and further at a temperature increase rate of 10 ° C./min in an air atmosphere The weight reduction rate obtained by dividing the weight after additional heating up to 450 ° C. by the weight after heating the weight after subtracting the heating weight from the dry weight is 50% or less,
In yet spectrum obtained by resonance Raman scattering measurement, the maximum peak intensity in the range of 1550~1650cm ^-1 G, when the maximum peak intensity is D within the 1300～1400Cm ^-1, the G / D An agglomerated spinning structure characterized in that the ratio is 10 or more.