JP4456965B2 - Composite fiber composed of wholly aromatic polyamide and single-walled carbon nanotubes - Google Patents

Description

  The present invention is a composite fiber composed of wholly aromatic polyamide and single-walled carbon nanotubes, and is excellent in mechanical properties characterized by being highly dispersed and having single-walled carbon nanotubes oriented in the fiber axis direction. It relates to composite fibers.

  Fully aromatic polyamides have a structure in which rigid aromatic rings are connected, and as materials with excellent heat resistance, mechanical properties, chemical resistance, etc., in the form of fibers or films, electrical insulating materials, various reinforcing agents, bulletproof Although it is one of the materials that are widely used and industrially extremely valuable, such as fibers, higher properties have been required for resins depending on the intended use.

  As a technique for satisfying such required characteristics, a composition in which carbon nanotubes are dispersed in a thermoplastic resin on a nanoscale, so-called nanocomposites, has recently attracted attention. There is a description that alignment is performed in a matrix by combing (Patent Document 1).

  There is also a description of a method for producing a composition comprising single-walled carbon nanotubes and an aromatic polyamide and fibers (Patent Document 2), and a method of adding carbon nanotubes to an anhydrous sulfuric acid solution of an aromatic polyamide is preferred. There is no description of the dispersion and orientation state of carbon nanotubes in the composite fiber, and the effect on the physical properties, and the effect of improving the mechanical properties of the fiber is unknown.

Japanese Patent Publication No. 8-26164 WO03 / 085049

  An object of the present invention is to provide a composite fiber composed of wholly aromatic polyamide and single-walled carbon nanotubes having improved mechanical properties, particularly elastic modulus and strength, and a method for producing the same.

  As a result of intensive studies to solve the above problems, the present inventors have added a small amount of aromatic polyamide to the solvent dispersion of single-walled carbon nanotubes, so that the single-walled carbon nanotubes are highly dispersed, and The inventors have found that a composite fiber made of wholly aromatic polyamide and single-walled carbon nanotubes dispersed in the fiber axis direction can be obtained, and the present invention has been achieved.

That is, the present invention is as follows.
1. The following formulas (A) and (B)
-NH-Ar ¹ -NH- (A)
—OC—Ar ² —CO— (B)
(Ar ¹ and Ar ² each independently represents a divalent aromatic group having 6 to 20 carbon atoms.)
Is a composite fiber composed of 100 parts by weight of wholly aromatic polyamide mainly composed of the following structural units and 0.01 to 20 parts by weight of single-walled carbon nanotubes, and 90% or more of single-walled carbon nanotubes have an aggregate diameter of 10 nm or less. Composite fiber characterized by dispersion.

2. In the Raman spectrum derived from carbon nanotubes when the incident laser is irradiated on the side of the fiber from the direction orthogonal to the fiber axis in polarized Raman spectroscopy measurement, the following formula (1)
P = I _YY / I _XX (1)
(The G band intensity when the laser polarization plane is arranged parallel to the fiber axis is I _XX , and the G band intensity when the laser polarization plane is arranged perpendicular to the fiber axis is I _YY .)
The composite fiber according to the above, wherein the orientation degree P represented by the formula is greater than 0 and satisfies 0.2 or less.

及び／または

であり、Ａｒ^２が

である上記に記載のコンポジットファイバー。 3. Wholly aromatic polyamide, Ar ¹ is

And / or

And Ar ² is

The composite fiber as described above.

及び

であり、Ａｒ^２が

である共重合体であって、その共重合比が１：０．８〜１：１．２である上記に記載のコンポジットファイバー。 4). Wholly aromatic polyamide, Ar ¹ is

as well as

And Ar ² is

The composite fiber according to the above, wherein the copolymer ratio is 1: 0.8 to 1: 1.2.

5. A step of mixing a single-walled carbon nanotube having a D / G value (D-band intensity / G-band intensity) calculated from Raman spectroscopy of the single-walled carbon nanotube of 0.1 or less and a dispersion solvent to obtain a mixed solution; A step of preparing a single-walled carbon nanotube dispersion by adding a small amount of wholly aromatic polyamide to the mixed liquid, and then adding the wholly aromatic polyamide to the dispersion and spinning comprising the wholly aromatic polyamide and the single-walled carbon nanotube. The method for producing a composite fiber according to the above, wherein a process for obtaining a working solution is performed, and spinning is performed from the solution.

  The composite fiber composed of wholly aromatic polyamide and single-walled carbon nanotubes obtained in the present invention has single-walled carbon nanotubes finely dispersed in the composite fiber, and the single-walled carbon nanotubes are highly oriented in the fiber axis direction. It excels in mechanical properties, especially elastic modulus and tensile strength.

Hereinafter, the present invention will be described in detail.
(About single-walled carbon nanotubes)
In the present invention, the single-walled carbon nanotube is a tube-like material made of carbon having a diameter of about 0.4 to 2 nm and a length of about several nm to several μm, and an ideal structure is a hexagonal network of carbon. The surface (graphene sheet) forms a tube parallel to the tube axis, forming a single tube. Single-walled carbon nanotubes are extremely cohesive due to van der Waals forces acting between single-walled carbon nanotubes and cannot be easily and completely dispersed in solvents and polymers.

  Conventionally known methods for producing the above single-walled carbon nanotubes are currently chemical vapor deposition methods (hereinafter referred to as CVD methods) in which carbon compounds are thermally decomposed by contacting them with catalytic metal fine particles at high temperatures, and arc discharge methods. And laser evaporation methods are used. In addition to the above, a plasma synthesis method and a solid phase reaction method are known, but the production method of the single-walled carbon nanotube used in the present invention is not limited to these. Shinohara et al. Reported a method for producing single-walled carbon nanotubes by a CVD method in which a carbon compound gas serving as a raw material carbon source is brought into contact with a substrate carrying a metal catalyst on a porous carrier, without any purification. This is a preferable production method because it provides high-purity and highly graphitized single-walled carbon nanotubes. (Chemical Physics Letter 303 (1999) 117-124)

  Fullerene, activated carbon, carbon black, amorphous carbon, catalytic metal, and the like are known as impurities of single-walled carbon nanotubes, but single-walled carbon nanotubes in the present invention are 80% or more, and more than 90% are single-walled carbon nanotubes. It is more preferable that

  In the present invention, as the single-walled carbon nanotube, for example, a single-walled carbon nanotube synthesized by a conventionally known method as described above can be used. Conventionally known strong acid treatment or chemically modified single-walled carbon nanotubes can also be used, but it is preferable to use single-walled carbon nanotubes that are not chemically modified in terms of few defect structures.

  Normally, single-walled carbon nanotubes that have not been chemically modified have a remarkably strong cohesive force due to the van der Waals force acting between the single-walled carbon nanotubes, and it is difficult to disperse only by placing them in a liquid. Even if it was possible, the concentration was extremely low.

(All aromatic polyamides)
The wholly aromatic polyamide in the composite fiber of the present invention has substantially the following formulas (A) and (B):
-NH-Ar ¹ -NH- (A)
—OC—Ar ² —CO— (B)
In the general formulas (A) and (B), Ar ¹ and Ar ² each independently represents a divalent aromatic group having 6 to 20 carbon atoms.
Is a wholly aromatic polyamide having a structure in which these two structural units are alternately repeated.

Ar ¹ and Ar ² are each independently a divalent aromatic group having 6 to 20 carbon atoms. Specific examples thereof include a metaphenylene group, a paraphenylene group, an orthophenylene group, and 2,6-naphthylene. Group, 2,7-naphthylene group, 4,4′-isopropylidene diphenylene group, 4,4′-biphenylene group, 4,4′-diphenylene sulfide group, 4,4′-diphenylene sulfone group, 4, Examples thereof include 4′-diphenylene ketone group, 4,4′-diphenylene ether group, 3,4′-diphenylene ether group, metaxylylene group, paraxylylene group, and orthoxylylene group.

  1 or more of hydrogen atoms of these aromatic groups are each independently halogen groups such as fluorine, chlorine, bromine; alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, hexyl group; A cycloalkyl group having 5 to 10 carbon atoms such as a cyclopentyl group and a cyclohexyl group; an aromatic group having 6 to 10 carbon atoms such as a phenyl group may be substituted. In addition, the structural unit of the above formula (A) and / or (B) may be a copolymer composed of two or more aromatic groups.

Of these, Ar ¹ is preferably a metaphenylene group, a paraphenylene group, or a 3,4′-diphenylene ether group, and a paraphenylene group or a combination of a paraphenylene group and a 3,4′-diphenylene ether group. Is more preferable, and when a paraphenylene group and a 3,4′-diphenylene ether group are used in combination, the molar ratio is more preferably in the range of 1: 0.8 to 1: 1.2.
Ar ² is preferably a metaphenylene group or a paraphenylene group, and more preferably a paraphenylene group.

That is, specifically, a copolymer suitably used in the present invention is a copolymer in which Ar ¹ is a paraphenylene group and a 3,4′-diphenylene ether group, and Ar ² is a paraphenylene group, Wholly aromatic polyamides having a copolymerization ratio (molar ratio of paraphenylene group to 3,4'-diphenylene ether group of Ar ¹ ) in the range of 1: 0.8 to 1: 1.2, and Ar ¹ and Ar Mention may be made of wholly aromatic polyamides in which ² is a paraphenylene group.

  These wholly aromatic polyamides can be produced by a conventionally known method such as a solution polymerization method, an interfacial polymerization method, or a melt polymerization method. The degree of polymerization can be controlled by the ratio of the aromatic diamine component and the aromatic dicarboxylic acid component, and the molecular weight of the polymer obtained is a solution of 98% by weight concentrated sulfuric acid at a concentration of 0.5 g / 100 mL at 30 ° C. The inherent viscosity ηinh measured in the above is preferably 0.05 to 20 dL / g, more preferably 1.0 to 10 dL / g.

(composition)
The composition of the composite fiber of the present invention is 0.01 to 20 parts by weight, preferably 0.05 to 15 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of wholly aromatic polyamide. Part. If the carbon nanotube is less than 0.01 part by weight, the effect of improving the mechanical properties is difficult to observe, and if the carbon nanotube is above 20 part by weight, the dispersibility of the single-walled carbon nanotube decreases.

(About dispersibility)
The present invention is characterized in that 90% or more of the single-walled carbon nanotubes in the composite fiber are dispersed with an aggregate diameter of 10 nm or less. In the present invention, the dispersibility of the single-walled carbon nanotube can be observed directly with an electron microscope such as TEM, the fiber cross section cut parallel to the fiber axis. It can also be evaluated by X-ray scattering measurement.

  In the X-ray scattering measurement, the dispersibility of the single-walled carbon nanotube can be determined by the scattering angle intensity distribution of the scattered X-ray derived from the single-walled carbon nanotube in the composite fiber. That is, when the single-walled carbon nanotubes are uniformly dispersed in the composite fiber, the diameter of the scatterer is several nanometers, and the scattered X-ray pattern spreads to the wide-angle side due to the inverse correlation between the size of the scatterer and the scattering angle. Become. On the other hand, when the single-walled carbon nanotubes are aggregated in the composite fiber, the size of the scatterer is larger than that of the uniform dispersion, and the scattered X-ray pattern is relatively concentrated on the low angle side. . Thus, the dispersion evaluation of the single-walled carbon nanotubes in the composite fiber can be performed by comparing the scattered X-ray patterns.

(About orientation and orientation method)
The present invention is characterized in that the single-walled carbon nanotubes in the composite fiber are oriented in the fiber axis direction. The orientation of the single-walled carbon nanotube is evaluated by X-ray scattering measurement and deflection Raman spectroscopic measurement in the present invention, in addition to directly observing the cross section of the fiber cut parallel to the fiber axis with an electron microscope such as TEM.

  The orientation evaluation by the X-ray scattering measurement can be determined by the anisotropy of the scattering azimuth distribution of the scattered X-rays derived from the single-walled carbon nanotubes in the composite fiber. When single-walled carbon nanotubes are highly oriented in the fiber axis direction, scattered X-rays derived from the nanotubes form a streak-like scattering pattern concentrated in the fiber equator direction. On the other hand, when the orientation of the single-walled carbon nanotube is low, the equator direction anisotropy of the scattering pattern of the nanotube becomes small, and when it is not oriented, a completely isotropic scattering pattern is drawn. Thus, the orientation of the single-walled carbon nanotube in the composite fiber can be evaluated from the azimuthal anisotropy of the X-ray scattering pattern.

Polarization Raman spectroscopy is a Raman spectrum derived from a single-walled carbon nanotube when an incident laser is irradiated on the side of the fiber from the direction orthogonal to the fiber axis.
P = I _YY / I _XX (1)
(In the formula, the G band intensity when the laser polarization plane is arranged parallel to the fiber axis is I _XX , and the G band intensity when the laser polarization plane is arranged perpendicular to the fiber axis is I _YY .)
The orientation is evaluated by the orientation degree P represented by In the present invention, the orientation degree P preferably satisfies 0 or more and 0.2 or less.

  The orientation degree P is asymptotic to P = 0 when the nanotubes are oriented in parallel to the fiber axis direction, and P = 1 in the random orientation. The upper limit of the value of P is more preferably 0.2, still more preferably 0.1, and the closer to 0, the better. If the value of P exceeds 0.2, the orientation of the single-walled carbon nanotube is insufficient, which is not preferable.

  As a method of aligning single-walled carbon nanotubes and wholly aromatic polyamides in the fiber axis direction, when spinning from a mixed solution composed of wholly aromatic polyamides and single-walled carbon nanotubes, fluid orientation, liquid crystal orientation, shear orientation, or stretch orientation is used. Things are mentioned. It is further preferable to increase the orientation coefficient of the single-walled carbon nanotubes by further stretching and orientation of the obtained fiber composition in order to obtain the composite fiber of the present invention. The degree of decrease in the orientation degree P is 0.01 or more, preferably 0.05 or more preferably 0.1 or more.

(Composite fiber)
The composite fiber of the present invention has a single fiber diameter of 0.01 to 1000 dtex. Preferably, it is 0.1 to 500 dtex.

(Production method of composite fiber)
As a method for producing the composite fiber of the present invention, a method of preparing a mixed solution of wholly aromatic polyamide and single-walled carbon nanotubes and spinning from the mixed solution is preferable.

  As a method for preparing the mixed solution, for example, 1) Solid carbon nanotubes are added to a wholly aromatic polyamide solution. 2) A wholly aromatic polyamide solution and a carbon nanotube solvent dispersion are mixed. 3) A solid wholly aromatic polyamide is added to the solvent dispersion of carbon nanotubes. 4) A method of performing in-situ polymerization of wholly aromatic polyamide in a solvent dispersion of carbon nanotubes is known. However, the uniform dispersion of single-walled carbon nanotubes in the mixed solution is important for improving the orientation of the single-walled carbon nanotubes, that is, the mechanical properties of the composite fiber. From this point of view, the method of preparing the carbon nanotube solvent dispersion described in 2) above and mixing with the wholly aromatic polyamide solution is preferable as a method for preparing the mixed solution for spinning.

  However, single-walled carbon nanotubes tend to form bundles due to van der Waals interactions, and the entanglement is significant. Therefore, simply mixing a solvent dispersion of carbon nanotubes with a pre-aromatic polyamide solution provides excellent dispersibility. It is difficult to obtain a mixed solution for spinning.

  Therefore, as a method for improving the dispersibility of the single-walled carbon nanotube dispersion liquid, the present inventors have dramatically added a small amount of wholly aromatic polyamide as a dispersant to the single-walled carbon nanotube solvent dispersion liquid and dispersed it. It has been found that the dispersibility of single-walled carbon nanotubes is improved.

  That is, a step of mixing a single-walled carbon nanotube and a dispersion solvent to obtain a mixed solution, a step of preparing a single-walled carbon nanotube dispersion by adding a small amount of wholly aromatic polyamide to the mixed solution, and then in the dispersion The composite fiber of the present invention can be preferably produced by adding a wholly aromatic polyamide to obtain a spinning solution composed of wholly aromatic polyamide and single-walled carbon nanotubes, and spinning from the solution.

Hereinafter, the method for producing the composite fiber of the present invention will be described in detail.
The single-walled carbon nanotube used has an intensity ratio (D / G) of D band and G band calculated from Raman scattering measurement of 0.1 or less, preferably 0.05 or less. When the value of D / G is larger than 0.1, it is not preferable because many impurities such as amorphous carbon are contained, or the single-walled carbon nanotube has many defect structures.

  The type of the dispersion solvent is not particularly limited. Specifically, N, N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfoxide, N- Acid solvents such as acetyl-2-pyrrolidone, N, N-dimethylacetamide and the like, 100% sulfuric acid, phosphoric acid, polyphosphoric acid, methanesulfonic acid and the like can be mentioned. These liquids can be used alone or in combination of two or more. These dispersion media are preferable liquids for dispersing the single-walled carbon nanotubes. In addition, water, methanol, ethanol, propanol, isopropanol, butanol, monohydric alcohols such as ethylene glycol and propylene glycol, trihydric alcohols such as glycerin, ketones such as acetone, and cyclic ethers such as tetrahydrofuran, as long as the dispersibility is not impaired. In addition, halogenated aromatic hydrocarbons such as 1,2-dichlorobenzene, haloalkanes such as chloroform, and substituted heterocyclic compounds such as 1-methylnaphthalene may be included.

  When mixing single-walled carbon nanotubes with a dispersion medium, although not particularly limited, ultrasonic waves and various stirring methods can be used. As the stirring method, high-speed stirring such as a homogenizer, stirring methods such as an attritor and a ball mill can be used. Of these, an ultrasonic treatment apparatus is preferable.

  The concentration of the single-walled carbon nanotubes with respect to the dispersion medium is not particularly limited. However, if the concentration is too low, the utility value is low, and if the concentration is too high, the dispersibility of the single-walled carbon nanotubes may decrease. 0.0001 to 1% by weight is preferable, and 0.005 to 0.5% by weight is more preferable.

  In the present invention, the dispersibility of the single-walled carbon nanotube dispersion is greatly improved by adding a small amount of wholly aromatic polyamide as a dispersant.

The wholly aromatic polyamide used as a dispersant in the present invention is substantially represented by the following formulas (A) and (B):
-NH-Ar ¹ -NH- (A)
—OC—Ar ² —CO— (B)
(Ar ¹ and Ar ² each independently represents a divalent aromatic group having 6 to 20 carbon atoms.)
Is a wholly aromatic polyamide having a structure in which these two structural units are alternately repeated.

Ar ¹ and Ar ² are each independently a divalent aromatic group having 6 to 20 carbon atoms. Specific examples thereof include a metaphenylene group, a paraphenylene group, an orthophenylene group, and 2,6-naphthylene. Group, 2,7-naphthylene group, 4,4′-isopropylidene diphenylene group, 4,4′-biphenylene group, 4,4′-diphenylene sulfide group, 4,4′-diphenylene sulfone group, 4, Examples thereof include 4′-diphenylene ketone group, 4,4′-diphenylene ether group, 3,4′-diphenylene ether group, metaxylylene group, paraxylylene group, and orthoxylylene group.

  1 or more of hydrogen atoms of these aromatic groups are each independently halogen groups such as fluorine, chlorine, bromine; alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, hexyl group; A cycloalkyl group having 5 to 10 carbon atoms such as a cyclopentyl group and a cyclohexyl group; an aromatic group having 6 to 10 carbon atoms such as a phenyl group may be substituted. In addition, the structural unit of the above formula (A) and / or (B) may be a copolymer composed of two or more aromatic groups.

Of these, Ar ¹ is preferably a metaphenylene group, a paraphenylene group, or a 3,4′-diphenylene ether group, and a paraphenylene group or a combination of a paraphenylene group and a 3,4′-diphenylene ether group. Is more preferable, and when a paraphenylene group and a 3,4′-diphenylene ether group are used in combination, the molar ratio is more preferably in the range of 1: 0.8 to 1: 1.2.
Ar ² is preferably a metaphenylene group or a paraphenylene group, and more preferably a paraphenylene group.

That is, specifically, a copolymer suitably used in the present invention is a copolymer in which Ar ¹ is a paraphenylene group and a 3,4′-diphenylene ether group, and Ar ² is a paraphenylene group, Wholly aromatic polyamides having a copolymerization ratio (molar ratio of paraphenylene group to 3,4'-diphenylene ether group of Ar ¹ ) in the range of 1: 0.8 to 1: 1.2, and Ar ¹ and Ar Mention may be made of wholly aromatic polyamides in which ² is a paraphenylene group.

  These wholly aromatic polyamides can be produced by a conventionally known method such as a solution polymerization method, an interfacial polymerization method, or a melt polymerization method. The degree of polymerization can be controlled by the ratio of the aromatic diamine component and the aromatic dicarboxylic acid component, and the molecular weight of the polymer obtained is a solution of 98% by weight concentrated sulfuric acid at a concentration of 0.5 g / 100 mL at 30 ° C. The inherent viscosity ηinh measured in the above is preferably 0.05 to 20 dL / g, more preferably 1.0 to 10 dL / g.

In the present invention, the wholly aromatic polyamide used as the dispersant is preferably the same as the wholly aromatic polyamide that is a component of the composite fiber.
The amount of wholly aromatic polyamide used as the dispersant is preferably 0.1 to 50% by weight, more preferably 0.2 to 20% by weight, based on the single-walled carbon nanotube.

  In the present invention, as a method of adding a wholly aromatic polyamide to the mixed solution of single-walled carbon nanotubes, a method of adding it in a solid state or a method of adding it in the state of a solution dissolved in a solvent that dissolves a dispersant can be mentioned. It is done. When added as a dispersant solution, the solvent used is not particularly limited, but is preferably the same type as the dispersion medium used to disperse the single-walled carbon nanotubes.

  The method for adjusting the single-walled carbon nanotube dispersion by adding wholly aromatic polyamide to the mixed solution is not particularly limited, but ultrasonic waves and various stirring methods can be used. As the stirring method, high-speed stirring such as a homogenizer, stirring methods such as an attritor and a ball mill can be used. Among these, it is preferable to perform ultrasonic treatment.

Thus, by adding a wholly aromatic polyamide as a dispersant in the present invention, it is possible to improve the dispersibility, to maintain and stabilize the dispersed state, and to obtain a single-walled carbon nanotube dispersion excellent in dispersibility. it can. Although it is not clear about the mechanism of these actions, the dispersing agent is uniformly inserted between the dispersed single-walled carbon nanotubes, suppressing the van der Waals force between the single-walled carbon nanotubes and agglomerating. It is presumed to be suppressed.
By concentrating the obtained single-walled carbon nanotube dispersion, it is also possible to obtain a single-walled carbon nanotube dispersion having a high concentration while maintaining dispersibility.

Next, a mixed solution for spinning can be prepared by mixing the single-walled carbon nanotube dispersion and the wholly aromatic polyamide solution.
The method for mixing the single-walled carbon nanotube dispersion and the wholly aromatic polyamide solution is not particularly limited, and ultrasonic waves and various stirring methods can be used.

  As a spinning method from the mixed solution for spinning, any of wet, dry, and dry wet combination may be used. As described above, in the spinning process, the orientation of the wholly aromatic polyamide and the carbon nanotube can be increased and the mechanical properties can be improved by performing the flow orientation, liquid crystal orientation, shear orientation, or stretch orientation.

The wholly aromatic polyamide is, for example, Ar ¹ is a paraphenylene group and 3,4′-diphenylene ether group, Ar ² is a paraphenylene group, and its copolymerization ratio (the paraphenylene group of Ar ¹ and 3,4 In the case of a copolymerized wholly aromatic polyamide having a molar ratio of '-diphenylene ether groups) in the range of 1: 0.8 to 1: 1.2, an amide system such as dimethylacetamide or N-methyl-2-pyrrolidone After performing dry and wet spinning using a solvent as a mixed solvent, a composite fiber can be obtained by stretching and orientation at a high magnification at a high temperature. In this case, the preferred draw ratio is 2 to 40 times, more preferably 5 to 30 times, but it is desirable from the viewpoint of mechanical properties that the draw ratio is as close as possible to the maximum draw ratio (MDR). The temperature during preferred stretching orientation is 100 ° C to 800 ° C, more preferably 200 ° C to 600 ° C. When the wholly aromatic polyamide is, for example, poly (paraphenylene terephthalamide) in which both Ar ¹ and Ar ² are paraphenylene groups, an acid solvent such as 100% sulfuric acid, phosphoric acid, polyphosphoric acid, methanesulfonic acid or the like is used. As a mixed solvent, a composite fiber can be obtained by liquid crystal spinning. In liquid crystal spinning, it is usually possible to align by spinning a solution from a cap with a high draft ratio.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples.
(1) Agglomerated diameter of single-walled carbon nanotubes in composite fiber: Aggregation in the range of 4 μm ² using a fiber cross section (magnification: 100,000 times) cut parallel to the fiber axis using TECNAI12 BIO TWIN manufactured by EFI The diameter was evaluated by directly observing.
(2) X-ray scattering measurement: The X-ray generator (manufactured by Rigaku Corporation) was measured under the conditions of target CuKα ray, voltage 45 kV, and current 70 mA. Incident X-rays were collected and monochromated by a multilayer mirror manufactured by Osmic Co., Ltd., and the incident X-rays were measured by a transmission method in which a fiber sample was bundled to a diameter of 1 mm and the incident X-rays were arranged perpendicular to the fiber axis. The scattered X-ray was detected using an imaging plate (made by Fuji Photo Film) having a size of 200 mm × 250 mm under the conditions of a camera length of 200 mm and an exposure time of 10 minutes.
(3) Deflection Raman spectroscopic measurement: As the Raman spectroscopic apparatus, a microscopic laser Raman spectroscopic measurement apparatus (LabRamHR manufactured by Horiba Joban Yvon) was used. A semiconductor laser having a wavelength of 785 nm was used as an excitation laser light source, and the laser beam diameter was focused to about 1 μm. Using such an apparatus, polarized Raman spectroscopic measurement was performed as follows. When measuring the Raman spectrum of a carbon nanotube by irradiating the side surface of the fiber composition with an incident laser from the direction orthogonal to the fiber axis, graphite having a Raman shift wavenumber of about 1580 cm ⁻¹ when the laser polarization plane is arranged parallel to the fiber axis G band intensity from the structure (I _XX), the laser polarization plane was measured G band intensity when placed perpendicular to the fiber axis (I _YY).
(4) Raman spectroscopic measurement: As the Raman spectroscopic apparatus, a microscopic laser Raman spectroscopic measuring apparatus (T64000 manufactured by Horiba Joban Yvon) was used. An Ar ion laser with a wavelength of 514.5 nm was used as an excitation laser light source, and the laser beam diameter was focused to about 1 μm. The value of D / G was calculated from the D band intensity derived from the disordered structure near the Raman shift wave number of 1360 cm ⁻¹ and the G band intensity derived from the graphite structure near the Raman shift wave number of 1580 cm ⁻¹ .
(5) Mechanical properties of the fiber: Tensylon universal testing machine 1225A manufactured by Orientec Co., Ltd. was used to conduct a tensile test on the obtained fiber with a single yarn to determine the elastic modulus and strength.

[Reference Example 1] Preparation of aramid resin solution To a sufficiently dry three-necked flask equipped with a stirrer, 2152 g of dehydrated and purified NMP, 27.04 g of p-phenylenediamine and 50.06 g of 3,4′-diaminodiphenyl ether were added at room temperature. After dissolution in nitrogen, 101.51 g of terephthalic acid dichloride was added while stirring on ice and stirring. Thereafter, the temperature was gradually raised and finally reacted at 80 ° C. for 60 minutes. Then, 37.04 g of calcium hydroxide was added to carry out a neutralization reaction to obtain an aramid resin solution of NMP. The specific viscosity measured at 30 ° C. of a concentrated sulfuric acid solution having an aramid resin concentration of 0.5 g / 100 mL obtained by reprecipitation of the obtained dope with water was 3.5 dL / g.

[Reference Example 2] Synthesis of single-walled carbon nanotubes A Y / zeolite powder (manufactured by Tosoh; HSZ-320NAA) is used as a porous carrier, ferric acetate and cobalt acetate are used as catalytic metal compounds, and an Fe / Co catalyst is prepared. Supported on zeolite. The catalyst loading was adjusted to 2.5% by weight, respectively. Thereafter, the catalyst powder was placed on a quartz boat, placed in a quartz tube of a CVD apparatus, evacuated, and heated from room temperature to 800 ° C. while introducing Ar gas at a flow rate of 10 mL / min. After reaching a predetermined 800 ° C., ethanol vapor was introduced at a flow rate of 3000 mL / min, and held for 30 minutes in an Ar / ethanol atmosphere. As a result of analyzing the obtained black product by laser Raman spectroscopy and a transmission electron microscope, it was confirmed that single-walled carbon nanotubes were produced. Subsequently, the obtained product (single-walled carbon nanotube / zeolite / metal catalyst) is immersed in 10% hydrofluoric acid for 3 hours, and then washed with ion-exchanged water until neutral, so that the zeolite and the metal catalyst are obtained. The carbon nanotube was purified by removal. The D / G value calculated from the Raman spectroscopic measurement was 0.11.

[Reference Example 3] Purification of Single-Walled Carbon Nanotubes The single-walled carbon nanotubes synthesized in Reference Example 2 were heat-treated at 450 ° C. for 10 minutes and then washed with hydrochloric acid to purify the single-walled carbon nanotubes. The D / G value calculated from the Raman spectroscopic measurement was 0.035.

[Example 1]
0.1 g of single-walled carbon nanotubes purified in Reference Example 3 was added to 30 g of NMP, and sonication was performed for 8 hours with ultrasonic waves having an oscillation frequency of 38 kHz. A single layer containing a small amount of an aramid resin by adding 1.67 g of an aramid resin solution of NMP prepared in Reference Example 1 to this single-walled carbon nanotube NMP mixed solution as a dispersant and sonicating at a temperature of 0 ° C. for 4 hours. A carbon nanotube dispersion was prepared. By adding the aramid resin solution, the dispersibility of the single-walled carbon nanotubes was dramatically improved. Further, the aramid resin solution was added to the single-walled carbon nanotube dispersion while stirring little by little to obtain a mixed solution for spinning having a polymer concentration of 5% by weight consisting of 100 parts by weight of uniform wholly aromatic polyamide / 1 part by weight of single-walled carbon nanotubes. Prepared. The polymer dope thus obtained was fed into a coagulation bath at a temperature of 50 ° C., which is an aqueous solution of 30% by weight of NMP at a cylinder temperature of 50 ° C., using a cap having a pore diameter of 0.3 mm, L / D = 1, and 5 holes. Extrusion was performed at 3 m / min. The distance between the cap surface and the coagulation bath surface was 10 mm. The fiber taken out from the coagulation bath was washed with water in a 50 ° C. water bath, dried with a drying roller at 120 ° C., and then stretched on a hot plate at 500 ° C. First, the maximum draw ratio (MDR) in this drawing step was determined, and drawing was performed at a 0.9 times ratio (15.3 times) to obtain a composite fiber. From the TEM observation results, it was found that the aggregate diameter of all the single-walled carbon nanotubes present in the composite fiber was 10 nm or less. In addition, from the X-ray scattering measurement results, the size of the single-walled carbon nanotube is 1 to 10 nm, and the streak based on the single-walled carbon nanotube is developed in the equator direction. It was found to be oriented. From the deflection Raman spectroscopic measurement, the orientation coefficient P was 0.069. The single fiber diameter of the fiber was 1.9 de, the elastic modulus was 87.5 GPa, and the strength was 29.6 de.

[Example 2]
0.1 g of single-walled carbon nanotubes purified in Reference Example 3 was added to 1000 g of NMP, and sonication was performed for 8 hours with ultrasonic waves having an oscillation frequency of 38 kHz. A single layer containing a small amount of an aramid resin by adding 1.67 g of an aramid resin solution of NMP prepared in Reference Example 1 to this single-walled carbon nanotube NMP mixed solution as a dispersant and sonicating at a temperature of 0 ° C. for 4 hours. A carbon nanotube dispersion was prepared. The obtained single-walled carbon nanotube dispersion was concentrated with an evaporator until NMP became 30 g, thereby preparing a single-walled carbon nanotube dispersion having excellent dispersibility. Further, the aramid resin solution was added to the single-walled carbon nanotube dispersion while stirring little by little to obtain a mixed solution for spinning having a polymer concentration of 5% by weight consisting of 100 parts by weight of uniform wholly aromatic polyamide / 1 part by weight of single-walled carbon nanotubes. Prepared. The polymer dope thus obtained was fed into a coagulation bath at a temperature of 50 ° C., which is an aqueous solution of 30% by weight of NMP at a cylinder temperature of 50 ° C., using a cap having a pore diameter of 0.3 mm, L / D = 1, and 5 holes. Extrusion was performed at 3 m / min. The distance between the cap surface and the coagulation bath surface was 10 mm. The fiber taken out from the coagulation bath was washed with water in a 50 ° C. water bath, dried with a drying roller at 120 ° C., and then stretched on a hot plate at 500 ° C. First, the maximum draw ratio (MDR) in this drawing step was determined, and drawing was performed at a ratio of 0.9 times (15.4 times) to obtain a composite fiber. From the TEM observation results, it was found that all the aggregate diameters of the single-walled carbon nanotubes present in the composite fiber were 5 nm or less. The X-ray scattering measurement results indicate that the size of the single-walled carbon nanotube is 1 to 3 nm, and the streak based on the single-walled carbon nanotube is developed in the equator direction. It was found to be oriented. (FIG. 1) The orientation coefficient P was 0.032 from the deflection Raman spectroscopic measurement. The single fiber diameter of the fiber was 1.8 de, the elastic modulus was 89.1 GPa, and the strength was 31.3 de.

[Comparative Example 1]
0.1 g of single-walled carbon nanotubes purified in Reference Example 3 was added to 30 g of NMP, and sonication was performed for 8 hours with ultrasonic waves having an oscillation frequency of 38 kHz. An aramid resin solution is added to the single-walled carbon nanotube NMP dispersion while stirring little by little to prepare a mixed solution for spinning having a polymer concentration of 5% by weight consisting of 100 parts by weight of wholly aromatic polyamide / 1 part by weight of single-walled carbon nanotubes. did. In the obtained solution, aggregates of single-walled carbon nanotubes were partially observed. The polymer dope thus obtained was fed into a coagulation bath at a temperature of 50 ° C., which is an aqueous solution of 30% by weight of NMP at a cylinder temperature of 50 ° C., using a cap having a pore diameter of 0.3 mm, L / D = 1 and 5 holes Extrusion was performed at 3 m / min. The distance between the cap surface and the coagulation bath surface was 10 mm. The fiber taken out from the coagulation bath was washed with water in a 50 ° C. water bath, dried with a drying roller at 120 ° C., and then stretched on a hot plate at 500 ° C. First, the maximum draw ratio (MDR) in this drawing step was determined, and drawing was performed at a 0.9 times ratio (15.3 times) to obtain a composite fiber. From the TEM observation results, it was found that the 80% aggregation diameter of the single-walled carbon nanotubes present in the composite fiber was 50 nm or more. In addition, in the X-ray scattering measurement results, since a halo pattern in the low-angle region without an equatorial streak has developed, there are single-walled carbon nanotubes that have a large scatterer size and are not oriented in the fiber axis direction. I found out. From the deflection Raman spectroscopic measurement, the orientation coefficient P was 0.22. The single fiber diameter of the fiber was 1.9 de, the elastic modulus was 79.7 GPa, and the strength was 27.6 de.

[Comparative Example 2]
0.1 g of unpurified single-walled carbon nanotubes synthesized in Reference Example 2 was added to 30 g of NMP, and sonication was performed for 8 hours with ultrasonic waves having an oscillation frequency of 38 kHz. A single layer containing a small amount of an aramid resin by adding 1.67 g of an aramid resin solution of NMP prepared in Reference Example 1 to this single-walled carbon nanotube NMP mixed solution as a dispersant and sonicating at a temperature of 0 ° C. for 4 hours. A carbon nanotube dispersion was prepared. Although the dispersibility of the single-walled carbon nanotubes was improved by adding the aramid resin solution, the aggregates of the single-walled carbon nanotubes were partially observed. Further, the aramid resin solution was added to the single-walled carbon nanotube dispersion while stirring little by little, and a spinning metal-rigid solution consisting of 100 parts by weight of uniform wholly aromatic polyamide / 1 part by weight of single-walled carbon nanotubes and having a polymer concentration of 5% by weight. Prepared. The polymer dope thus obtained was fed into a coagulation bath at a temperature of 50 ° C., which is an aqueous solution of 30% by weight of NMP at a cylinder temperature of 50 ° C., using a cap having a pore diameter of 0.3 mm, L / D = 1 and 5 holes Extrusion was performed at 3 m / min. The distance between the cap surface and the coagulation bath surface was 10 mm. The fiber taken out from the coagulation bath was washed with water in a 50 ° C. water bath, dried with a drying roller at 120 ° C., and then stretched on a hot plate at 500 ° C. First, the maximum draw ratio (MDR) in this drawing step was determined, and drawing was performed at a 0.9 times magnification (15.9 times) to obtain a composite fiber. From the TEM observation results, it was found that the aggregate diameter of 85% or more of the single-walled carbon nanotubes present in the composite fiber was 50 nm or more. In addition, in the X-ray scattering measurement results, a halo pattern in a low-angle region without an equatorial streak has developed, so there are single-walled carbon nanotubes that have a large scatterer size and are not oriented in the fiber axis direction. I understood it. (FIG. 2) The orientation coefficient P was 0.2 from the deflection Raman spectroscopic measurement. The single fiber diameter of the fiber was 2.0 de, the elastic modulus was 83.2 GPa, and the strength was 27.6 de.

[Comparative Example 3]
NMP 55 g was further added to 245 g of NMP aramid resin solution prepared in Reference Example 1, and the mixture was stirred at a temperature of 80 ° C. for 4 hours to obtain an aramid resin solution containing substantially the same polymer concentration as that of Example but not including carbon nanotubes. . The polymer dope thus obtained was fed into a coagulation bath at a temperature of 50 ° C., which is an aqueous solution of 30% by weight of NMP at a cylinder temperature of 50 ° C., using a cap having a pore diameter of 0.3 mm, L / D = 1 and 5 holes Extrusion was performed at 3 m / min. The distance between the cap surface and the coagulation bath surface was 10 mm. The fiber taken out from the coagulation bath was washed with water in a 50 ° C. water bath, dried with a drying roller at 120 ° C., and then stretched on a hot plate at 500 ° C. First, the maximum draw ratio (MDR) in this drawing process was determined, and the fiber was obtained by drawing at a 0.9-fold ratio (15.3 times). The single fiber diameter of the fiber was 2.0 de, the elastic modulus was 79.5 GPa, and the strength was 27.3 de. FIG. 3 shows the X-ray scattering measurement results.

The X-ray-scattering measurement result of the single-walled carbon nanotube obtained in Example 2. The X-ray-scattering measurement result of the single-walled carbon nanotube obtained by the comparative example 2. The X-ray scattering measurement result of the single-walled carbon nanotube obtained in Comparative Example 3.

Claims (5)

The following formulas (A) and (B)
-NH-Ar ¹ -NH- (A)
—OC—Ar ² —CO— (B)
(Ar ¹ and Ar ² each independently represents a divalent aromatic group having 6 to 20 carbon atoms.)
Is a composite fiber composed of 100 parts by weight of wholly aromatic polyamide mainly composed of the following structural units and 0.01 to 20 parts by weight of single-walled carbon nanotubes, and 90% or more of single-walled carbon nanotubes have an aggregate diameter of 10 nm or less. Composite fiber characterized by dispersion. In the Raman spectrum derived from carbon nanotubes when the incident laser is irradiated on the side of the fiber from the direction orthogonal to the fiber axis in polarized Raman spectroscopy measurement, the following formula (1)
P = I _YY / I _XX (1)
(The G band intensity when the laser polarization plane is arranged parallel to the fiber axis is I _XX , and the G band intensity when the laser polarization plane is arranged perpendicular to the fiber axis is I _YY .)
2. The composite fiber according to claim 1, wherein an orientation degree P represented by the formula is greater than 0 and satisfies 0.2 or less. Wholly aromatic polyamide, Ar ¹ is

And / or

And Ar ² is

The composite fiber according to claim 1 or 2. Wholly aromatic polyamide, Ar ¹ is

as well as

And Ar ² is

The composite fiber according to claim 3, wherein the copolymer ratio is 1: 0.8 to 1: 1.2. A step of mixing a single-walled carbon nanotube having a D / G value (D-band intensity / G-band intensity) calculated from Raman spectroscopy of the single-walled carbon nanotube of 0.1 or less and a dispersion solvent to obtain a mixed solution; A step of preparing a single-walled carbon nanotube dispersion by adding 0.1 to 50% by weight of a wholly aromatic polyamide to the single-walled carbon nanotube in the mixed solution, and then adding a wholly aromatic polyamide to the dispersion The method for producing a composite fiber according to any one of claims 1 to 4, wherein a spinning solution comprising a wholly aromatic polyamide and single-walled carbon nanotubes is obtained, and spinning is performed from the solution.

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