WO2011077598A1 - Carbon-fiber composite material, process for producing same, insulation article, electronic component, and logging tool - Google Patents

Abstract

Disclosed is a carbon-fiber composite material which comprises 100 parts by mass of an elastomer (30) and 20-100 parts by mass of carbon nanofibers (90) that have a reduced content of branches and have been oxidized. The carbon-fiber composite material (50) has a dynamic modulus (E') at 200ºC and 10 Hz of 10-1,000 MPa and a volume resistivity of 106-1018 O·cm.

Description

Carbon fiber composite material and manufacturing method thereof, insulating article, electronic component, and logging device

The present invention relates to a carbon fiber composite material and a manufacturing method thereof, an insulating article, an electronic component, and a logging apparatus.

Carbon nanofibers are excellent in mechanical properties and are expected to be applied in various fields as composite materials. In particular, since carbon nanofibers are also excellent in electrical conductivity, it has been proposed that a carbon fiber composite material in which carbon nanofibers are uniformly dispersed in an elastomer is applied to, for example, an electron emission device (for example, JP 2008-311083).

Also, composite materials in which carbon nanofibers are blended with elastomers are excellent in mechanical properties, and thus are expected to be used in various applications as substitutes for conventional rubber products. However, many of these conventional rubber products use the insulating properties of rubber, but carbon fiber composites with uniformly dispersed carbon nanofibers can conduct electricity even with a small amount of carbon nanofibers. Because of its excellent performance, it has been difficult to apply it to products that do not require electrical conduction.

An object of the present invention is to provide a carbon fiber composite material having a high volume resistivity, a manufacturing method thereof, an insulating article, an electronic component, and a logging apparatus.

The carbon fiber composite material according to the present invention is
20 parts by mass to 100 parts by mass of carbon nanofibers with reduced branch parts and oxidized with respect to 100 parts by mass of the elastomer,
The dynamic elastic modulus (E ′) at 200 ° C. and 10 Hz is 10 MPa to 1000 MPa,
The volume resistivity is 10 ⁶ Ω · cm to 10 ¹⁸ Ω · cm.

In the carbon fiber composite material according to the present invention,
The carbon nanofibers can reduce branching portions by mechanical action before being blended with the elastomer.

In the carbon fiber composite material according to the present invention,
The mechanical action can be done by a compression process.

In the carbon fiber composite material according to the present invention,
The elastomer is a fluorine-containing elastomer,
The dynamic elastic modulus (E ′) at 200 ° C. and 10 Hz is 15 MPa to 300 MPa,
The volume resistivity value can be 10 ¹¹ Ω · cm to 10 ¹⁸ Ω · cm.

In the carbon fiber composite material according to the present invention,
The elastomer is ethylene-propylene rubber,
The dynamic elastic modulus (E ′) at 200 ° C. and 10 Hz is 10 MPa to 200 MPa,
The volume resistivity value can be 10 ⁷ Ω · cm to 10 ¹⁸ Ω · cm.

In the carbon fiber composite material according to the present invention,
The mechanical action can be performed by a grinding process.

In the carbon fiber composite material according to the present invention,
The elastomer is ethylene-propylene rubber,
The dynamic elastic modulus (E ′) at 200 ° C. and 10 Hz is 10 MPa to 200 MPa,
The volume resistivity value can be 10 ⁸ Ω · cm to 10 ¹⁸ Ω · cm.

In the carbon fiber composite material according to the present invention,
The carbon nanofiber may have a maximum fiber length of less than 20 μm.

The insulating article for oil field according to the present invention may include the carbon fiber composite material.

The electronic component according to the present invention can include the insulating article.

The logging apparatus according to the present invention can include a casing and the electronic component disposed in the casing.

The method for producing a carbon fiber composite material according to the present invention includes:
A step of obtaining a second carbon nanofiber by heat-treating the first carbon nanofiber produced by the vapor deposition method at a temperature higher than the reaction temperature in the vapor deposition method at 1100 ° C. to 1600 ° C. (A) and
Treating the second carbon nanofibers by a mechanical action to reduce the branching portions of the second carbon nanofibers to obtain third carbon nanofibers;
(C) a step of heat-treating the third carbon nanofibers in an atmosphere containing oxygen at 600 ° C. to 800 ° C. to obtain oxidized fourth carbon nanofibers;
A step (d) of mixing the fourth carbon nanofibers with an elastomer and uniformly dispersing in the elastomer with a shearing force to obtain a carbon fiber composite material;
including.

In the method for producing a carbon fiber composite material according to the present invention,
The heat treatment in the step (a) may be performed at 1200 ° C to 1500 ° C.

In the method for producing a carbon fiber composite material according to the present invention,
The third carbon nanofiber obtained in the step (b) may have a maximum fiber length of less than 20 μm.

In the method for producing a carbon fiber composite material according to the present invention,
The mechanical action of the step (b) is performed by a compression process,
The 3rd carbon nanofiber obtained by the said compression process can have no branch part.

In the method for producing a carbon fiber composite material according to the present invention,
The compression treatment can be performed by putting the second carbon nanofibers between at least two rotating rolls and applying a shearing force and a compressive force to the second carbon nanofibers.

In the method for producing a carbon fiber composite material according to the present invention,
The said compression process can use the binder for couple | bonding carbon nanofibers.

In the method for producing a carbon fiber composite material according to the present invention,
The compression treatment can be performed with a dry compression granulator.

In the method for producing a carbon fiber composite material according to the present invention,
The mechanical action of the step (b) is performed by a pulverization process,
The tap density of the third carbon nanofiber may be 1.5 to 10 times the tap density of the second carbon nanofiber.

In the method for producing a carbon fiber composite material according to the present invention,
The pulverization treatment can obtain the third carbon nanofiber having a nitrogen adsorption specific surface area of 1.1 to 5.0 times the nitrogen adsorption specific surface area of the second carbon nanofiber.

In the method for producing a carbon fiber composite material according to the present invention,
The pulverization treatment can be performed by dry pulverization using an impact and / or shear force.

In the method for producing a carbon fiber composite material according to the present invention,
The amount of increase in the oxygen concentration on the surface of the fourth carbon nanofiber relative to the oxygen concentration on the surface of the third carbon nanofiber measured by X-ray photoelectron spectroscopy (XPS) is 0.5 atm% to 2.6 atm. %.

In the method for producing a carbon fiber composite material according to the present invention,
The rate of increase in the oxygen concentration on the surface of the fourth carbon nanofiber relative to the oxygen concentration on the surface of the third carbon nanofiber measured by X-ray photoelectron spectroscopy (XPS) is 20% to 120%. Can do.

In the method for producing a carbon fiber composite material according to the present invention,
In the heat treatment in the step (c), the fourth carbon nanofibers can be obtained by reducing the mass of the third carbon nanofibers by 2% to 20%.

In the method for producing a carbon fiber composite material according to the present invention,
The fourth carbon nanofiber obtained in the step (c) may have a surface oxygen concentration of 2.6 atm% to 4.6 atm% measured by X-ray photoelectron spectroscopy (XPS).

In the method for producing a carbon fiber composite material according to the present invention,
The fourth carbon nanofiber obtained in the step (c) the ratio of the peak intensity D of around 1300 cm ^-1 to the peak intensity G of around 1600 cm ^-1 measured by Raman scattering spectroscopy (D / G) Can be 0.12 to 0.22.

In the method for producing a carbon fiber composite material according to the present invention,
The fourth carbon nanofiber obtained in the step (c) may have a nitrogen adsorption specific surface area of 45 m ² / g to 60 m ² / g.

In the method for producing a carbon fiber composite material according to the present invention,
The fourth carbon nanofiber obtained in the step (c) may have an average diameter of 70 nm to 100 nm.

FIG. 1A is a diagram schematically illustrating a second carbon nanofiber according to an embodiment of the present invention. FIG. 1B is a diagram schematically illustrating a second carbon nanofiber according to an embodiment of the present invention. FIG. 1C is a diagram schematically illustrating a second carbon nanofiber according to an embodiment of the present invention. FIG. 1D is a diagram schematically illustrating a second carbon nanofiber according to an embodiment of the present invention. FIG. 2 is a perspective view schematically showing the compression process in the step (b) according to the embodiment of the present invention. FIG. 3 is a diagram schematically showing a second carbon nanofiber and a third carbon nanofiber according to an embodiment of the present invention. FIG. 4 is a diagram schematically showing the step (d) by the open roll method according to the embodiment of the present invention. FIG. 5 is a diagram schematically showing the step (d) by the open roll method according to the embodiment of the present invention. FIG. 6 is a diagram schematically showing the step (d) by the open roll method according to the embodiment of the present invention. FIG. 7 is a cross-sectional view schematically showing a logging tool for seabed use according to an embodiment of the present invention. FIG. 8 is a cross-sectional view schematically showing a case of the logging apparatus in FIG. 7 according to one embodiment of the present invention. FIG. 9 is a cross-sectional view schematically showing an underground logging tool according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail.

The carbon fiber composite material according to an embodiment of the present invention includes 20 to 100 parts by mass of carbon nanofibers with reduced branching and oxidation with respect to 100 parts by mass of an elastomer, and dynamic elasticity at 200 ° C. and 10 Hz. The rate (E ′) is 10 MPa to 1000 MPa, and the volume resistivity value is 10 ⁶ Ω · cm to 10 ¹⁸ Ω · cm. An insulating article for use in oil fields according to an embodiment of the present invention may include the carbon fiber composite material. An electronic component according to an embodiment of the present invention can include the insulating article. The logging apparatus according to an embodiment of the present invention can include a housing and the electronic component disposed in the housing. In the method for producing a carbon fiber composite material according to an embodiment of the present invention, the first carbon nanofiber produced by the vapor deposition method is higher than the reaction temperature in the vapor deposition method, and 1100 A step (a) of obtaining a second carbon nanofiber by heat treatment at from 1 to 1600 ° C., and treating the second carbon nanofiber by a mechanical action to reduce the number of branches of the second carbon nanofiber. And (b) obtaining third carbon nanofibers, and heat treating the third carbon nanofibers in an atmosphere containing oxygen at 600 ° C. to 800 ° C. to obtain oxidized fourth carbon nanofibers. Step (c) and the fourth carbon nanofibers are mixed with an elastomer and uniformly dispersed in the elastomer by a shearing force so as to be a carbon fiber composite material. A step of obtaining (d), including.

(I) Carbon nanofiber The carbon nanofiber will be described.
The fourth carbon nanofiber used in the present embodiment can be obtained by the steps (a) to (c) described below.
First, as the step (a), the untreated first carbon nanofibers manufactured by the vapor deposition method are heat-treated at a temperature higher than the reaction temperature in the vapor deposition method at 1100 ° C. to 1600 ° C. Thus, the second carbon nanofiber can be obtained. The temperature of this heat treatment is more preferably 1200 ° C. to 1500 ° C. When the temperature of the heat treatment in the step (a) is higher than the reaction temperature of the vapor phase growth method, the surface structure of the first carbon nanofiber can be adjusted and surface defects can be reduced. In addition, when the heat treatment is performed at 1100 ° C. to 1600 ° C., the surface reactivity with the matrix material such as an elastomer is improved, and poor dispersion of the carbon nanofibers in the matrix material can be further improved. The second carbon nanofibers obtained in this manner is heat treatment, for example, the ratio of the peak intensity D of around 1300 cm ^-1 to the peak intensity G of around 1600 cm ^-1 measured by Raman scattering spectroscopy (D / G ) Can be greater than 1.25 and less than 1.6. In the Raman spectrum of the second carbon nanofibers, the absorption peak intensity D of around 1300 cm ^-1 is the absorption based on defects in the crystal that forms the carbon nanofibers, the absorption peak intensity at around 1600 cm ^-1 G is carbon nanofiber Absorption based on crystals that form For this reason, the smaller the ratio (D / G) between the peak intensity D and the peak intensity G, the higher the degree of crystallization of the carbon nanofibers. Therefore, the smaller the ratio of the peak intensity D to the peak intensity G (D / G), the higher the degree of graphitization (graphitization), and the carbon nanofibers with fewer defects on the surface. Therefore, the second carbon nanofiber having the ratio (D / G) of the peak intensity D to the peak intensity G within the above range has a non-crystalline portion on the surface, and thus has good wettability with the elastomer. The strength of the second carbon nanofiber can be sufficient because there are relatively few defects. Here, since the first carbon nanofibers are not subjected to the heat treatment or compression treatment in the steps (a) to (c), the untreated carbon nanofibers produced by the vapor phase growth method are used. It is. In general, the untreated first carbon nanofibers produced by the vapor phase growth method are generally heat-treated at 2000 ° C. to 3200 ° C. in an inert gas atmosphere so-called graphitization (crystallization) treatment. Thus, impurities such as amorphous deposits and remaining catalytic metals deposited on the surface of the first carbon nanofibers during vapor phase growth are removed. In the present embodiment, such an impurity is removed. The second carbon nanofibers can be obtained by subjecting the first carbon nanofibers to the heat treatment of the step (a) at 1100 ° C. to 1600 ° C. sufficiently lower than the graphitization temperature without performing the graphitization treatment. it can. As described above, the carbon fiber composite material using the second carbon nanofiber having a moderately amorphous portion on the surface has a volume compared to the carbon fiber composite material using the general graphitized carbon nanofiber. The specific resistance value can be increased.

The vapor phase growth method is also called a catalytic chemical vapor deposition (CCVD), in which a gas such as a hydrocarbon is pyrolyzed in the presence of a metal catalyst in the presence of a metal-based catalyst to perform untreated first carbon nano-particles. A method of manufacturing a fiber. The vapor phase growth method will be described in more detail. For example, an organic compound such as benzene or toluene is used as a raw material, an organic transition metal compound such as ferrocene or nickelcene is used as a metal catalyst, and these are used together with a carrier gas at a high temperature such as 400 ° C. It is introduced into a reaction furnace set to a reaction temperature of ~ 1000 ° C, and the floating reaction method (floating reaction method) in which a first carbon nanofiber is generated in a floating state or on the reaction furnace wall, or alumina, magnesium oxide, etc. A catalyst-supporting reaction method (Substrate Reaction Method) in which metal-containing particles supported on ceramics are brought into contact with a carbon-containing compound at a high temperature to generate first carbon nanofibers on a substrate can be used. The average diameter of the untreated first carbon nanofibers obtained by such a vapor phase growth method can be 70 nm to 100 nm. The aspect ratio of the first carbon nanofiber can be 50 to 200. In the detailed description of the present invention, the average diameter and the average length of the carbon nanofibers are, for example, 5,000 times as many images as possible with an electron microscope (the magnification can be appropriately changed according to the size of the carbon nanofibers), and the average diameter and average of 200 or more locations. It can be obtained by measuring the length and calculating it as its arithmetic mean.
Examples of the first carbon nanofibers produced by the vapor deposition method include so-called carbon nanotubes. The carbon nanotube has a structure in which one surface of graphite having a carbon hexagonal mesh surface is wound in one layer or multiple layers. A carbon material partially having a carbon nanotube structure can also be used. In addition to the name “carbon nanotube”, it may be called “graphite fibril nanotube” or “vapor-grown carbon fiber”.

1A to 1D are views schematically showing a second carbon nanofiber according to an embodiment of the present invention.
The second carbon nanofiber 60 has substantially the same structure as the untreated first carbon nanofiber manufactured by the vapor deposition method, and is preferably linear in the longitudinal direction as shown in FIG. 1A. Is bent as shown in FIG. 1B, bent at the bent portion 62 as shown in FIG. 1C, and branched into a plurality (four in the figure) at the branch portion 64 as shown in FIG. 1D. Some of them are included. The second carbon nanofiber 60 blended in the composite material is considered to be able to improve the flexibility and durability of the composite material in particular as it is linear as shown in FIG. 1A. The second carbon nanofiber 60 as shown in 1D is considered to cause stress concentration at the bent portion 62 and the branching portion 64, and tends to reduce the original performance of the second carbon nanofiber as a reinforcing material in the composite material. It is thought that there is. The bent portion 62 is a portion that is clearly bent as shown in FIG. 1C and does not include a bent portion as shown in FIG. 1B.

Next, in the step (b), the second carbon nanofibers obtained in the step (a) are processed by a mechanical action to reduce the branch portions of the second carbon nanofibers, and the third carbon nanofibers are reduced. Nanofibers can be obtained.
The process by the mechanical action in the step (b) can be performed by a compression process or a pulverization process.

First, the step (b) using compression processing will be described.
The 3rd carbon nanofiber obtained by the compression process in a process (b) can have no branch part. The compression treatment in the step (b) requires a high pressure for cutting the second carbon nanofiber from at least the branch portion. Here, step (b) will be described in detail with reference to FIG. FIG. 2 is a perspective view schematically showing the step (b) according to the embodiment of the present invention. As shown in FIG. 2, the compression treatment is performed by introducing the second carbon nanofiber 60 as a raw material between a plurality of, for example, at least two rolls 72 and 74 that continuously rotate in the direction of the arrow in the drawing, For example, a dry compression granulator 70 such as a roll press machine or a roller compactor (roll type high pressure compression molding machine) that performs compression force on the first carbon nanofibers can be employed. A plurality of second carbon nanofibers 60 obtained in the step (a) are put into a dry compression granulator 70 and compressed to obtain an aggregate of a plurality of third carbon nanofibers 80. it can. The roll press machine normally uses a smooth roll that does not engrave pockets on the outer peripheral surface of the roll or a roll that engraves pockets. In this embodiment, the roll press machine is smooth to apply a compressive force evenly to the second carbon nanofibers. A roll can be used. The distance between the two rolls is set to 0 mm, that is, the rolls are in contact with each other, and a predetermined compression force F, for example, 980 to 2940 N / cm can be applied between the two rolls, and further 1500 to 2500 N / Cm is preferred. The compressive force F can be set to an appropriate pressure while confirming the presence or absence of a branched portion in the obtained carbon nanofiber aggregate with an electron microscope or the like. If it is 980 N / cm or more, the 2nd carbon nanofiber which has a branch part can be cut | disconnected by a branch part. Such compression treatment can be performed a plurality of times, for example, about twice in order to homogenize the entire carbon nanofiber. In the granulator, a binder such as water is generally blended to bind powder, but the compression treatment in the present embodiment is a dry granulation that does not use a binder for binding third carbon nanofibers. Can be. This is because if a binder is used, it may be difficult to disperse the fourth carbon nanofibers in a later step, and a step of removing the binder may be further required.
Normally, after compression between two rolls by a dry compression granulator 70 to form an aggregate of plate-like (flakes) carbon nanofibers 80, the powder is further crushed by a pulverizer or the like, An aggregate of carbon nanofibers 80 sized to a size can be produced. The pulverizer at this time, for example, rotates the rotary blade at high speed and crushes the aggregate of carbon nanofibers 80 by the shearing force, and uses a screen to adjust the size only through the aggregate of carbon nanofibers 80 having an appropriate size or less. It can be performed. The size of the aggregates of the carbon nanofibers 80 varies greatly only by the compression treatment, but the particle size of the aggregates of the carbon nanofibers 80 is adjusted to an appropriate size by further crushing in this way, so that the matrix material It is possible to prevent the carbon nanofiber aggregates from being biased when kneaded. By this compression treatment, the third carbon nanofibers are cut at the branching portions, become a desired bulk density that does not fluff and become easy to handle, and are granulated into, for example, a plate-like third carbon nanofiber aggregate. be able to.
The 3rd carbon nanofiber obtained by compressing is demonstrated in detail using FIG. FIG. 3 is a diagram schematically showing a third carbon nanofiber according to an embodiment of the present invention.
As shown in FIG. 3, the second carbon nanofiber 60 having the branch part 64 shown on the upper left side of the figure is cut from the branch part 64 by the compression process, and for example 4 as shown on the lower right side of the figure. A third carbon nanofiber 80 of the book is obtained. Therefore, the third carbon nanofibers 80 can reduce the number of branch portions 64 as compared with the second carbon nanofibers 60. In particular, even when observed with an electron microscope, the branch portions 64 can be eliminated. Thus, the third carbon nanofiber having no branch portion becomes the fourth carbon nanofiber through the step (c), and the fourth carbon nanofiber in the composite material is mixed with other materials. Dispersibility can be improved, and flexibility and durability of the composite material can be improved. Furthermore, since the fourth carbon nanofiber does not have a branching portion, when it is compounded in the composite material, there is no stress concentration on the branching portion of the fourth carbon nanofiber, and as a reinforcing material for the fourth carbon nanofiber. The performance degradation can be reduced. Since a part of the second carbon nanofiber having the bent part 62 as shown in FIG. 1C is also cut from the bent part 62, the second carbon nanofiber having the so-called defective part such as the bent part 62 and the branch part 64. 3 carbon nanofibers can be reduced. Of the third carbon nanofibers 80 obtained by the compression treatment, the ratio of the third carbon nanofibers having the bent portions 62 may be less than 10 out of 100. When the ratio including the third carbon nanofibers having the bent portion 62 is 10 or more out of 100, there is a possibility that the defective portion cannot be sufficiently removed by the compression treatment. Thus, the 3rd carbon nanofiber 80 in which the defect parts like the bending part 62 and the branch part 64 reduced can have a maximum fiber length of less than 20 μm. In recent years, as the market demand, it is sometimes preferred that the maximum fiber length of carbon nanofibers is less than 20 μm, and more preferably less than 15 μm. For example, by setting the maximum fiber length of the third carbon nanofiber to less than 20 μm, the flexibility of the composite material containing the fourth carbon nanofiber can be improved. The plurality of third carbon nanofibers 80 may have a bulk density of 0.15 to 0.3 g / cm ³ . If the bulk density is 0.15 to 0.3 g / cm ³ , the third carbon nanofibers 80 are difficult to scatter and can be easily handled during storage, transportation or compounding, and handling properties are also good. Note that the bulk density in this application is JIS-K6219-2 carbon black for rubber-measurement of granulated particles-part 2 according to the measurement of bulk density, carbon nanofibers are poured into a 1000 cm ³ cylindrical container and the mass is calculated. Measured and obtained by calculating the bulk density (g / cm ³ ). In addition, the plurality of third carbon nanofibers 80 obtained by the compression treatment is a set of a plurality of plate-like third carbon nanofibers in which a plurality of third carbon nanofibers gather to form a plate-like lump. Can be granulated in the body. Thus, since it becomes a plate-shaped lump and the 3rd carbon nanofiber 80 can be handled, the handleability at the time of storage, at the time of conveyance, or a mixing | blending can be improved.

Next, the step (b) using the pulverization process will be described.
The tap density of the third carbon nanofibers obtained by the pulverization process in the step (b) is 1.5 to 10 times the tap density of the second carbon nanofibers obtained in the step (a). Can do. In the step (b), the nitrogen adsorption specific surface area of the third carbon nanofiber can be 1.1 to 5.0 times the nitrogen adsorption specific surface area of the second carbon nanofiber before pulverization. According to the step (b), carbon nanofibers having improved surface reactivity with a matrix material such as an elastomer and improved wettability to the matrix material can be produced.
The second carbon nanofiber has defects such as a branched portion where the fiber is branched and a bent portion where the fiber is bent. The surface of the carbon nanofiber is also activated. By reducing the defects, the carbon nanofibers are reduced in branching and bending portions, so that the strength of each fiber is improved and the fiber length is pulverized to such an extent that the fiber length is hardly reduced. Physical properties are improved. In addition, by activating the surface of the carbon nanofibers, the surface reactivity between the carbon nanofibers and the matrix material is improved, and poor dispersion of the carbon nanofibers in the matrix material can be improved. Step (b) can be performed by dry grinding using impact and / or shearing force. The dry pulverization can be performed in the absence of water or / and an organic solvent, for example. Dry pulverization is advantageous because there are no post-treatment steps such as removal of the dispersant after pulverization, drying of the solvent, and defibration of the dried and agglomerated fibers. Such dry pulverization can be performed at a peripheral speed of 50 to 200 m / s for 0.5 to 60 minutes. As the dry pulverization, a high-speed rotary mill, a ball mill, a medium stirring mill, a jet pulverizer, or the like can be used. A vibrating ball mill can be employed.
As described above, in the pulverization process, for example, the second carbon nanofibers having the branch part are cut from the branch part, and the branch parts can be reduced, similarly to the compression process. Therefore, the pulverized third carbon nanofibers can have fewer branch portions than the second carbon nanofibers, and in particular, the branch portions can be eliminated even when observed with an electron microscope.
The tap density of the third carbon nanofibers after the pulverization process can be 1.5 to 10 times the second tap density before the pulverization process. By performing an appropriate pulverization treatment in this manner, wettability with a matrix material such as an elastomer can be improved without substantially impairing the fiber length of the second carbon nanofibers. The third carbon nanofibers after the pulverization treatment can have a tap density of 0.03 to 0.2 g / cm ³ . The tap density is an apparent density measured by the tap method, and represents the degree of bulk of the third carbon nanofiber. Therefore, if the branching locations and defects in the third carbon nanofibers are reduced by the pulverization process, the third carbon nanofibers tend to be densely packed and the tap density tends to increase. The pulverized third carbon nanofibers having a tap density in the above range tend to have good wettability with a matrix material such as an elastomer.
Further, the nitrogen adsorption specific surface area of the third carbon nanofibers after the pulverization treatment can be 1.1 to 5.0 times the nitrogen adsorption specific surface area of the second carbon nanofibers before the pulverization treatment. When the nitrogen adsorption specific surface area increases in this way, the number of contacts between the matrix material and the third carbon nanofibers increases, which facilitates dispersion in the matrix material. The third carbon nanofiber after the pulverization treatment preferably has a nitrogen adsorption specific surface area of 22 to 100 m ² / g. The pulverized third carbon nanofiber having a nitrogen adsorption specific surface area in the above range tends to have good wettability with a matrix material such as an elastomer.

Finally, as the step (c), the third carbon nanofiber obtained in the step (b) is heat-treated at 600 ° C. to 800 ° C. in an oxygen-containing atmosphere to oxidize the fourth carbon nanofiber. Can be obtained.
In step (c), for example, the third carbon nanofiber is placed in a furnace in an air atmosphere, set to a predetermined temperature in the temperature range of 600 ° C. to 800 ° C., and heat-treated, so that the surface has a desired oxygen concentration. A fourth carbon nanofiber oxidized to can be obtained. The heat treatment time in this step (c) is the time for holding the third carbon nanofibers in a heat treatment furnace at a predetermined temperature, and can be, for example, 10 minutes to 180 minutes. The atmosphere containing oxygen may be air, an oxygen atmosphere, or an atmosphere in which an oxygen concentration is appropriately set. However, heat treatment is performed depending on the content of the heat treatment furnace and the amount of the third carbon nanofiber to be treated. The amount of oxygen introduced into the furnace can be adjusted as appropriate. A sufficient oxygen concentration may be present in the atmosphere so that the surface of the fourth carbon nanofiber is oxidized to the desired oxygen concentration in the step (c). The temperature of the heat treatment can be appropriately set in order to obtain a desired oxidation treatment in the range of 600 ° C to 800 ° C. Usually, since the third carbon nanofibers burn and cause great damage to the fibers at around 800 ° C., it is desirable to set the temperature setting and the heat treatment time carefully while repeating the experiment. The heat treatment temperature and heat treatment time can be appropriately adjusted depending on the oxygen concentration in the furnace used in the step (c), the inner volume of the furnace, the amount of the third carbon nanofiber to be treated, and the like. In addition, the heat treatment temperature in the present embodiment indicates the atmospheric temperature in the heat treatment furnace.
In the step (c), the increase in the oxygen concentration on the surface of the fourth carbon nanofiber relative to the oxygen concentration on the surface of the third carbon nanofiber measured by X-ray photoelectron spectroscopy (XPS) is 0.5 atm%. The oxidation treatment can be performed so as to be ~ 2.6 atm%. The amount of increase in the surface oxygen concentration of the fourth carbon nanofiber relative to the surface oxygen concentration of the third carbon nanofiber is 0.9 atm when the mechanical action in the step (b) is performed by the compression treatment. % To 2.6 atm%, and further 1.0 to 2.6 atm%, and 0.9 atm% when the mechanical action in the step (b) is performed by pulverization. It can be ˜1.9 atm%, and further can be 1.0 atm% to 1.6 atm%. In the step (c), the rate of increase in the oxygen concentration on the surface of the fourth carbon nanofiber relative to the oxygen concentration on the surface of the third carbon nanofiber measured by X-ray photoelectron spectroscopy (XPS) is 20%. Oxidation treatment can be performed so as to be ~ 120%. The increase ratio of the surface oxygen concentration of the fourth carbon nanofiber to the surface oxygen concentration of the third carbon nanofiber is 60% when the treatment by the mechanical action in the step (b) is performed by the compression treatment. 120%, and when the mechanical action in the step (b) is performed by pulverization, it can be 43% to 90%, and further can be 48% to 76%. The surface oxygen concentration measured by X-ray photoelectron spectroscopy (XPS) of the fourth carbon nanofiber obtained in the step (c) can be 2.6 atm% to 4.6 atm%, and the step (b ) In the case where the processing by the mechanical action is performed by the compression treatment, it can be 3.0 atm% to 4.6 atm%, and further can be 3.1 atm% to 4.6 atm%, step (b) In the case where the treatment by the mechanical action is performed by pulverization treatment, it can be 3.0 atm% to 4.0 atm%, and further can be 3.1 atm% to 3.7 atm%. As described above, the surface of the third carbon nanofiber is appropriately oxidized to improve the surface reactivity between the fourth carbon nanofiber and the elastomer, thereby improving the dispersion of the carbon nanofiber in the elastomer. can do.
Thus, the mass of the fourth carbon nanofibers oxidized in the step (c) can be reduced by 2% to 20%, for example, from the mass of the third carbon nanofibers. It can be estimated that the fourth carbon nanofibers are appropriately oxidized. If the mass of the fourth carbon nanofiber is less than 2% less than the mass of the third carbon nanofiber, the oxygen concentration on the surface of the fourth carbon nanofiber is low, and it is difficult to improve the wettability. There is. Moreover, although the 4th carbon nanofiber reduced in weight by more than 20% than the mass of the 3rd carbon nanofiber has a wettability almost the same as that of the 4th carbon nanofiber whose weight loss is 20% or less. However, the loss due to the reduction of the carbon nanofibers due to the oxidation treatment is large, and it tends to be economically disadvantageous for the energy consumption of the heat treatment. This is because, when the surface of the third carbon nanofiber is oxidized, a part of the carbon on the surface of the third carbon nanofiber is vaporized as carbon dioxide gas to be reduced. It is preferable because it can be estimated that the length of the fourth carbon nanofiber does not become almost shorter unless the mass of the fourth carbon nanofiber exceeds 20% of the mass of the third carbon nanofiber. The oxygen concentration on the surface of the fourth carbon nanofiber can be analyzed by XPS (X-ray photoelectron spectroscopy). The analysis of the oxygen concentration by XPS is performed by, for example, argon gas for 0.5 minute to 1.0 minute with respect to the fourth carbon nanofiber before measurement in order to remove impurities attached to the surface of the fourth carbon nanofiber. It is preferable to perform analysis after etching to bring out the clean surface of the fourth carbon nanofiber. The argon gas concentration of the argon gas etching can be 5 × 10 ⁻² Pa to 20 × 10 ⁻² Pa. In addition, the analysis of the oxygen concentration by XPS is performed by attaching a carbon tape that is a conductive adhesive on a metal base of the XPS device, and then spraying the fourth carbon nanofiber on the carbon tape to adhere to the carbon tape, It can be performed in a state in which excess fourth carbon nanofibers not attached to the carbon tape are shaken off. As described above, in the analysis of the oxygen concentration by XPS, the analysis can be performed in a state as close to powder as possible without pressing the fourth carbon nanofibers on the carbon tape and solidifying the block. Similarly, the third carbon nanofiber can be measured with an XPS apparatus.

Fourth carbon nanofibers obtained by the step (c), the ratio of the peak intensity D of around 1300 cm ^-1 to the peak intensity G of around 1600 cm ^-1 measured by Raman scattering spectroscopy (D / G) is 0 .12 to 0.22. The Raman peak ratio (D / G) of the fourth carbon nanofiber is larger than the Raman peak ratio (D / G) of the third carbon nanofiber because the crystal on the surface has many defects. The fourth carbon nanofiber is desirably oxidized to such an extent that its Raman peak ratio (D / G) increases by 0.02 or more than the Raman peak ratio (D / G) of the third carbon nanofiber. The fourth carbon nanofiber may have a nitrogen adsorption specific surface area of 34 m ² / g to 58 m ² / g. The nitrogen adsorption specific surface area of the fourth carbon nanofiber is larger than the nitrogen adsorption specific surface area of the third carbon nanofiber because the surface thereof is rough. The fourth carbon nanofiber is desirably oxidized to such an extent that its nitrogen adsorption specific surface area is increased by 9 m ² / g or more from the nitrogen adsorption specific surface area of the third carbon nanofiber. The average diameter of the fourth carbon nanofibers used in the step (c) is almost the same as the average diameter of the first carbon nanofibers. The average diameter of the fourth carbon nanofibers obtained by such a vapor phase growth method can be 70 nm to 100 nm. By using such a fourth carbon nanofiber, the surface reactivity with the elastomer is improved, the wettability to the elastomer can be improved, and the carbon fiber composite having a high volume resistivity and excellent electrical insulation performance. Material can be obtained. The blending amount of the fourth carbon nanofibers into the elastomer can be set according to the use. However, since the fourth carbon nanofibers have improved wettability with the elastomer, for example, carbon fibers having the same rigidity are used. When manufacturing a composite material, a compounding quantity can be reduced conventionally.

(II) Elastomer Next, the elastomer used in the method for producing the carbon fiber composite material will be described.
The elastomer may have a weight average molecular weight of 5,000 to 5,000,000, and further 20,000 to 3,000,000. When the molecular weight of the elastomer is within this range, the elastomer molecules are entangled with each other and are connected to each other. Therefore, the elastomer has good elasticity for dispersing the fourth carbon nanofibers. The elastomer is preferable because it has a viscosity, so that the agglomerated fourth carbon nanofibers can easily enter each other, and the fourth carbon nanofibers can be separated from each other by having elasticity. The elastomer has a spin-spin relaxation time (T2n / 30 ° C.) of the network component in the uncrosslinked body of 100 to 3000 μsec, measured at 30 ° C. by the Hahn echo method using pulsed NMR, and the observation nucleus is ¹ H. Can be 200-1000 μs. By having a spin-spin relaxation time (T2n / 30 ° C.) in the above range, the elastomer can be flexible and have sufficiently high molecular mobility, that is, suitable for dispersing the fourth carbon nanofibers. It can have elasticity. In addition, since the elastomer has viscosity, when the elastomer and the fourth carbon nanofiber are mixed, the elastomer can easily enter the gap between the fourth carbon nanofibers due to high molecular motion. it can. The elastomer has a network component spin-spin relaxation time (T2n) of 100 to 2000 μsec measured at 30 ° C. by the Hahn-echo method using pulsed NMR and the observation nucleus at ¹ H. Can do. The reason is the same as that of the uncrosslinked product described above. That is, when an uncrosslinked body having the above conditions is crosslinked, T2n of the obtained crosslinked body can be approximately included in the above range.

The spin-spin relaxation time obtained by the Hahn-echo method using pulsed NMR is a measure representing the molecular mobility of a substance. Specifically, when the spin-spin relaxation time of the elastomer is measured by the Hahn-echo method using pulsed NMR, a first component having a first spin-spin relaxation time (T2n) having a short relaxation time, and relaxation A second component having a longer spin-spin relaxation time (T2nn) is detected. The first component corresponds to a polymer network component (skeleton molecule), and the second component corresponds to a polymer non-network component (branch and leaf component such as a terminal chain). The shorter the first spin-spin relaxation time, the lower the molecular mobility and the harder the elastomer. Further, it can be said that the longer the first spin-spin relaxation time, the higher the molecular mobility and the softer the elastomer. As a measurement method in the pulse method NMR, the solid echo method, the CPMG method (Car Purcell, Mayboom, Gill method) or the 90 ° pulse method can be applied even if it is not the Hahn echo method. However, since the elastomer according to the present invention has a medium spin-spin relaxation time (T2), the Hahn echo method is most suitable. In general, the solid echo method and the 90 ° pulse method are suitable for short T2 measurement, the Hahn echo method is suitable for medium T2 measurement, and the CPMG method is suitable for long T2 measurement.

The elastomer has an unsaturated bond or group having affinity for the radical at the end of the carbon nanofiber in at least one of the main chain, the side chain and the end chain, or generates such a radical or group. Easy to use. Examples of such unsaturated bonds or groups include double bonds, triple bonds, carbonyl groups, carboxyl groups, hydroxyl groups, amino groups, nitrile groups, ketone groups, amide groups, epoxy groups, ester groups, vinyl groups, halogen groups, It can be at least one selected from functional groups such as urethane groups, burette groups, allophanate groups and urea groups. In this embodiment, at least one of the main chain, side chain, and terminal chain of the elastomer has an unsaturated bond or group having high affinity (reactivity or polarity) with the radical of the carbon nanofiber, so that 4 carbon nanofibers can be bonded. Thereby, it is possible to easily disperse the fourth carbon nanofiber by overcoming the cohesive force. Then, when the elastomer and the fourth carbon nanofiber are kneaded, the free radical generated by breaking the molecular chain of the elastomer attacks the defect of the fourth carbon nanofiber, and the fourth carbon nanofiber is attacked. It can be assumed that radicals are generated on the surface of the fiber.

As the elastomer, natural rubber (NR), epoxidized natural rubber (ENR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), ethylene-propylene rubber (EPR, EPDM), butyl rubber ( IIR), chlorobutyl rubber (CIIR), acrylic rubber (ACM), silicone rubber (Q), fluorine rubber (FKM), perfluoroelastomer (FFKM), butadiene rubber (BR), epoxidized butadiene rubber (EBR), epichlorohydrin rubber Elastomers such as (CO, CEO), urethane rubber (U), polysulfide rubber (T); olefin (TPO), polyvinyl chloride (TPVC), polyester (TPEE), polyurethane (TPU), polyamide (TPEA), Still System (SBS), thermoplastic elastomers, and the like; and may be a mixture thereof. Particularly preferred are highly polar elastomers that easily generate free radicals during elastomer kneading, such as natural rubber (NR) and nitrile rubber (NBR). Even in the case of an elastomer having a low polarity, such as ethylene propylene rubber (EPDM), free radicals are generated by setting the kneading temperature at a relatively high temperature (for example, 50 ° C. to 150 ° C. in the case of EPDM). Can be used for invention. In addition, the carbon fiber composite material which has a comparatively high volume specific resistance value can be obtained by mix | blending a 4th carbon nanofiber by using the fluorine-containing elastomer represented by fluororubber. The elastomer may be either a rubber-based elastomer or a thermoplastic elastomer. In the case of a rubber-based elastomer, the elastomer may be either a crosslinked body or an uncrosslinked body.

(III) Method for Producing Carbon Fiber Composite Material A method for producing a carbon fiber composite material according to an embodiment of the present invention includes the first carbon nanofibers produced by the vapor deposition method in the vapor deposition method. A step (a) of obtaining a second carbon nanofiber by heat treatment at a temperature higher than the reaction temperature and at 1100 ° C. to 1600 ° C., and treating the second carbon nanofiber by mechanical action; The step (b) of obtaining the third carbon nanofiber by reducing the number of branches of the carbon nanofiber 2 and heat-treating the third carbon nanofiber at 600 ° C. to 800 ° C. in an oxygen-containing atmosphere A step (c) of obtaining oxidized fourth carbon nanofibers, and the fourth carbon nanofibers are mixed with an elastomer, and the elastomer is applied with a shearing force. Including the step of obtaining the carbon fiber composite material is uniformly dispersed in the mer (d), the. Steps (a) to (c) have been described in the above (I), and will be omitted. Step (d) will be described in detail with reference to FIGS.
4 to 6 are diagrams schematically showing the step (d) by the open roll method according to the embodiment of the present invention. As shown in FIGS. 4 to 6, the first roll 10 and the second roll 20 in the two-roll open roll 2 are arranged at a predetermined interval d, for example, 0.5 mm to 1.5 mm. 4 to 6, the motor rotates in the direction indicated by the arrow at the rotational speeds V1 and V2 in the normal rotation or reverse rotation.
First, as shown in FIG. 4, the elastomer 30 wound around the first roll 10 is masticated, and the elastomer molecular chain is appropriately cut to generate free radicals. The free radicals of the elastomer generated by mastication are easily combined with the fourth carbon nanofibers obtained in the step (c).
Next, as shown in FIG. 5, the fourth carbon nanofibers 90 are put into the bank 34 of the elastomer 30 wound around the first roll 10 and kneaded. The step of mixing the elastomer 30 and the fourth carbon nanofiber 90 is not limited to the open roll method, and for example, a closed kneading method or a multi-screw extrusion kneading method can also be used.
Further, as shown in FIG. 6, the roll interval d between the first roll 10 and the second roll 20 can be set to 0.5 mm or less, more preferably set to an interval of 0 to 0.5 mm. Then, the mixture 36 is put into the open roll 2 and thinning is performed once to several times. For example, the thinning can be performed about 1 to 10 times. When the surface speed of the first roll 10 is V1 and the surface speed of the second roll 20 is V2, the ratio of the surface speeds (V1 / V2) in thinness is 1.05 to 3.00. Further, it can be 1.05 to 1.2. By using such a surface velocity ratio, a desired shear force can be obtained. The carbon fiber composite material 50 extruded from between the narrow rolls as described above is greatly deformed as shown in FIG. 6 by the restoring force due to the elasticity of the elastomer 30, and the fourth carbon nanofiber 90 moves greatly together with the elastomer 30 at that time. To do. The carbon fiber composite material 50 obtained through thinning is rolled with a roll and dispensed into a sheet having a predetermined thickness. In this thinning process, in order to obtain as high a shearing force as possible, the roll temperature can be set to, for example, 0 to 50 ° C., and more preferably set to a relatively low temperature of 5 to 30 ° C. The actually measured temperature of 30 can also be adjusted to 0 to 50 ° C. Due to the shearing force thus obtained, a high shearing force acts on the elastomer 30, and the aggregated fourth carbon nanofibers 90 are separated from each other so as to be pulled out one by one to the elastomer molecule. Distributed in. In particular, since the elastomer 30 has elasticity, viscosity, and chemical interaction with the fourth carbon nanofibers 90, the fourth carbon nanofibers 90 can be easily dispersed. And the carbon fiber composite material 50 excellent in the dispersibility and dispersion stability of the 4th carbon nanofiber 90 (it is hard to re-aggregate the 4th carbon nanofiber) can be obtained.

More specifically, when the elastomer and the fourth carbon nanofiber are mixed with an open roll, the viscous elastomer penetrates into the fourth carbon nanofiber, and a specific portion of the elastomer is chemically interlinked. By action, it binds to the highly active part of the fourth carbon nanofiber. When the surface of the fourth carbon nanofiber is moderately high by, for example, oxidation treatment, it can be easily bonded to an elastomer molecule. Next, when a strong shearing force acts on the elastomer, the fourth carbon nanofibers move with the movement of the elastomer molecules, and further, the aggregated fourth carbon nanofibers are recovered by the restoring force of the elastomer due to elasticity after shearing. The fibers will be separated and dispersed in the elastomer. According to the present embodiment, when the carbon fiber composite material is extruded from between narrow rolls, the carbon fiber composite material is deformed thicker than the roll interval due to the restoring force due to the elasticity of the elastomer. The deformation can be presumed to cause the carbon fiber composite material with a strong shear force to flow more complicatedly and disperse the fourth carbon nanofibers in the elastomer. The fourth carbon nanofibers once dispersed are prevented from reaggregating due to chemical interaction with the elastomer, and can have good dispersion stability.
The step (d) of dispersing the fourth carbon nanofibers in the elastomer by a shearing force is not limited to the open roll method, and a closed kneading method or a multiaxial extrusion kneading method can also be used. In short, in this step, it is sufficient that a shearing force capable of separating the aggregated fourth carbon nanofibers can be given to the elastomer. In particular, the open roll method can measure and manage the actual temperature of the mixture as well as the roll temperature.
In the step (d), a cross-linking carbon fiber composite material mixed with a cross-linking agent may be mixed and cross-linked to obtain a cross-linked carbon fiber composite material. Further, the carbon fiber composite material may be molded without being crosslinked. The carbon fiber composite material may remain in the form of a sheet obtained by the open roll method, or a rubber molding process generally employed by the carbon fiber composite material obtained in the step (d), for example, injection molding method, transfer molding. A desired shape such as a sheet may be formed by a method, a press molding method, an extrusion molding method, a calendering method, or the like.
In the step (d) according to the present embodiment, a compounding agent usually used for processing an elastomer can be added. A well-known thing can be used as a compounding agent. Examples of the compounding agent include a crosslinking agent, a vulcanizing agent, a vulcanization accelerator, a vulcanization retarder, a softening agent, a plasticizer, a curing agent, a reinforcing agent, a filler, an antiaging agent, and a coloring agent. it can. These compounding agents can be added to the elastomer before the fourth carbon nanofibers in the open roll, for example.

In addition, in the manufacturing method of the carbon fiber composite material according to the present embodiment, the fourth carbon nanofiber is directly mixed with the elastomer having a rubber elasticity, but the present invention is not limited to this, and the following method is adopted. You can also First, before mixing the fourth carbon nanofiber, the elastomer is masticated to lower the molecular weight of the elastomer. Since the viscosity of the elastomer decreases when the molecular weight decreases due to mastication, the elastomer easily penetrates into the voids of the aggregated fourth carbon nanofibers. The elastomer used as a raw material has a ^first spin-spin relaxation time (T2n) of the network component in an uncrosslinked body measured at 30 ° C. by a Hahn-echo method using pulsed NMR with an observation nucleus of ¹ H. It is a rubber-like elastic body of 3000 μsec. The raw material elastomer is masticated to lower the molecular weight of the elastomer, and a liquid elastomer having a first spin-spin relaxation time (T2n) exceeding 3000 μsec is obtained. The first spin-spin relaxation time (T2n) of the liquid elastomer after mastication is 5 to 30 times the first spin-spin relaxation time (T2n) of the raw material elastomer before mastication. Can be. This mastication is not suitable for kneading, unlike the general mastication performed while the elastomer remains in a solid state, by applying a strong shearing force by, for example, the open roll method to cut the molecular weight of the elastomer and significantly reduce the molecular weight. The process is performed until the fluid reaches a certain level, for example, until it reaches a liquid state. For example, when the open roll method is used, this mastication is performed at a roll temperature of 20 ° C. (minimum mastication time 60 minutes) to 150 ° C. (minimum mastication time 10 minutes), and the roll interval d is 0.5 mm to 1 for example. The fourth carbon nanofibers are put into a liquid elastomer that is masticated at 0.0 mm. However, since the elastomer is in a liquid state and its elasticity is remarkably reduced, the aggregated fourth carbon nanofibers are not dispersed so much even when kneaded in a state where the elastomer free radicals and the fourth carbon nanofibers are combined.
Therefore, after increasing the molecular weight of the elastomer in the mixture obtained by mixing the liquid elastomer and the fourth carbon nanofibers, restoring the elasticity of the elastomer to obtain a rubber-like elastic mixture, The fourth carbon nanofibers are uniformly dispersed in the elastomer by performing the thinning of the open roll method described in the above. The mixture having an increased molecular weight of the elastomer has a ^first spin-spin relaxation time (T2n) of 3000 μsec or less as measured by a Hahn-echo method using pulsed NMR at 30 ° C. and an observation nucleus of ¹ H. It is a rubber-like elastic body. The first spin-spin relaxation time (T2n) of the rubber-like elastic mixture having an increased molecular weight of the elastomer is 0. It can be 5 to 10 times. The elasticity of the rubber-like elastic mixture can be represented by the molecular form of the elastomer (observable by molecular weight) and molecular mobility (observable by T2n). The step of increasing the molecular weight of the elastomer can be performed for 10 hours to 100 hours by placing the mixture in a heating furnace set to a heat treatment, for example, 40 ° C. to 100 ° C. By such a heat treatment, the molecular chain is extended by the bond between the free radicals of the elastomer present in the mixture, and the molecular weight is increased. When the molecular weight of the elastomer is increased in a short time, a small amount of a cross-linking agent, for example, ½ or less of an appropriate amount of the cross-linking agent is mixed, and the mixture is subjected to a heat treatment (for example, an annealing treatment) to perform a cross-linking reaction. The molecular weight can be increased in a short time. When the molecular weight of the elastomer is increased by a crosslinking reaction, the amount of crosslinking agent, the heating time, and the heating temperature can be set to such an extent that kneading is not difficult in the subsequent steps.
According to the step (d) described here, the fourth carbon nanofibers can be more uniformly dispersed in the elastomer by reducing the viscosity of the elastomer before introducing the fourth carbon nanofibers. . More specifically, the fourth carbon is agglomerated by using a liquid elastomer having a reduced molecular weight, rather than mixing the fourth carbon nanofiber with an elastomer having a large molecular weight as in the production method described above. The fourth carbon nanofibers can be dispersed more uniformly in the thinning process because it easily penetrates into the voids of the nanofibers. In addition, since the elastomer free radicals produced in large quantities by molecular cleavage of the elastomer can bind more firmly to the moderately oxidized surface of the fourth carbon nanofibers, the fourth carbon nanofibers are further bonded. The fiber can be uniformly dispersed. Therefore, according to the step (d) described here, the same performance can be obtained with a small amount of the fourth carbon nanofiber than in the step (d) described above, and the expensive fourth carbon nanofiber is obtained. Saving money will also improve economic efficiency.

(IV) Carbon fiber composite material Next, the carbon fiber composite material obtained by the step (d) will be described.
The carbon fiber composite material contains 20 to 100 parts by mass of carbon nanofibers that are reduced by mechanical action and oxidized to 100 parts by mass of the elastomer, and has a dynamic elastic modulus (E ′ at 200 ° C. and 10 Hz). ) Is 10 MPa to 1000 MPa, and the volume resistivity is 10 ⁶ Ω · cm to 10 ¹⁸ Ω · cm. The carbon fiber composite material can include an elastomer and fourth carbon nanofibers uniformly dispersed in the elastomer.
In general, many elastomers and plastics have a volume resistivity exceeding 10 ¹² (Ω · cm) at room temperature, and are highly insulating and have a volume resistivity of about 10 ¹⁸ (Ω · cm). Insulation. However, when carbon nanofibers that are commercially available, such as vapor-grown carbon fibers, are uniformly dispersed in the elastomer and blended, even if the vapor-grown carbon fibers are relatively small, 10 ¹ (Ω · cm) It has been found that it exhibits a volume resistivity value of some degree. In other words, it has been a conventional technical common sense that when an attempt is made to reinforce an elastomer with carbon nanofibers, the insulation of the elastomer cannot be maintained, and it is difficult to obtain reinforcement and insulation at the same time. In this embodiment, the volume resistivity value is a value measured by the four-probe method in accordance with JIS-7194 at room temperature.
The carbon fiber composite material in the present embodiment has a high volume resistivity value, even if a relatively large amount of the fourth carbon nanofiber is blended and evenly dispersed to obtain a desired strength, making it difficult to conduct electricity. Can be. The carbon fiber composite material can have high strength and heat resistance due to the reinforcement of the carbon nanofibers, and can also be used for applications that require electrical insulation as a rubber material. The required electrical insulation depends on the use of the rubber material, but for example, a volume resistivity value of 10 ⁶ (Ω · cm) or more may be required, and in particular, a volume resistivity value of 10 ⁷ (Ω · Cm) or more is often required, and can be applied to these applications.
Insulating articles for oil field applications can include carbon fiber composite materials. The electronic component can include the insulating article. The well logging apparatus can include a housing and the electronic component disposed in the housing.
The application requiring a volume resistivity of 10 ⁶ (Ω · cm) or more is effective, for example, in communication using an analog signal in a logging apparatus used in an oil field, and the volume resistivity is 10 ⁷ (Ω As an application requiring cm) or more, for example, it is effective in communication using a digital signal in a logging device, and in order to increase the communication speed, the volume specific resistance value should be 10 ⁸ (Ω · cm) or more. In particular, the volume resistivity value may be required to be 10 ⁹ (Ω · cm) or more. The carbon fiber composite material has a volume resistivity value of 10 ⁶ Ω · cm to 10 ¹⁸ Ω · cm, and can be 10 ⁷ Ω · cm to 10 ¹⁸ Ω · cm, and more preferably 10 ⁸ Ω · cm It can be 10 ¹⁸ Ω · cm, in particular 10 ⁹ Ω · cm to 10 ¹⁸ Ω · cm. For example, a carbon fiber composite material using the fourth carbon nanofiber that has been subjected to compression treatment in the step (b) and a fluorine-containing elastomer as an elastomer has a dynamic elastic modulus (E ′) at 200 ° C. of 15 MPa ~ It can be 300 MPa, and the volume resistivity value can be 10 ¹¹ Ω · cm to 10 ¹⁸ Ω · cm. For example, the carbon fiber composite material using the fourth carbon nanofiber that has been subjected to compression treatment in the step (b) and the ethylene-propylene rubber as the elastomer has a dynamic elastic modulus (E ′) at 200 ° C. of 10 MPa. The volume resistivity value may be 10 ⁷ Ω · cm to 10 ¹⁸ Ω · cm. For example, the carbon fiber composite material using the fourth carbon nanofibers that have been pulverized in the step (b) and the ethylene-propylene rubber as the elastomer has a dynamic elastic modulus (E ′) at 200 ° C. of 10 MPa. The volume resistivity value may be 10 ⁸ Ω · cm to 10 ¹⁸ Ω · cm. In this embodiment, the dynamic elastic modulus (E ′) is measured by performing a dynamic viscoelasticity test based on JIS K6394.

The carbon fiber composite material has a first spin-spin relaxation time (T2n) of 100 to 3000 μsec in a non-crosslinked body, measured at 150 ° C. by the Hahn echo method using pulsed NMR, and the observation nucleus is ¹ H. And the component fraction (fnn) of the component having the second spin-spin relaxation time can be 0 to 0.2. T2n and fnn measured at 150 ° C. of the carbon fiber composite material can represent that the fourth carbon nanofibers are uniformly dispersed in the matrix elastomer. That is, the fact that the fourth carbon nanofibers are uniformly dispersed in the elastomer can be said to be a state where the elastomer is constrained by the fourth carbon nanofibers. In this state, the mobility of the elastomer molecules constrained by the fourth carbon nanofibers is smaller than that when not constrained by the fourth carbon nanofibers. Therefore, the first spin-spin relaxation time (T2n), the second spin-spin relaxation time (T2nn), and the spin-lattice relaxation time (T1) of the carbon fiber composite material do not include the fourth carbon nanofiber. It becomes shorter than the case of the elastomer alone, and particularly becomes shorter when the fourth carbon nanofibers are uniformly dispersed.
In addition, in the state where the elastomer molecules are constrained by the fourth carbon nanofibers, it is considered that the non-network component (non-network chain component) decreases for the following reason. That is, when the molecular mobility of the elastomer is lowered overall by the fourth carbon nanofibers, the non-network component cannot easily move, and the behavior becomes the same as that of the network component. Since the network component (terminal chain) is easy to move, the non-network component is considered to decrease due to the fact that it is easily adsorbed to the active point of the fourth carbon nanofiber. Therefore, since the component fraction (fnn) of the component having the second spin-spin relaxation time (T2nn) is fn + fnn = 1, it is smaller than the case of the elastomer alone not including the fourth carbon nanofiber. Therefore, it can be seen that in the carbon fiber composite material, the fourth carbon nanofibers are uniformly dispersed when the measurement value obtained by the Hahn echo method using the pulse method NMR is in the above range.
In addition, around the fourth carbon nanofiber, an elastomer molecule in which a part of the elastomer is subjected to molecular chain cleavage during kneading, and free radicals generated thereby attack and adsorb the surface of the fourth carbon nanofiber. An interfacial phase that is considered to be an aggregate is formed. The interfacial phase is considered to be similar to bound rubber formed around carbon black when, for example, an elastomer and carbon black are kneaded. Such an interfacial phase is coated and protected by covering the fourth carbon nanofibers, and by blending more than a predetermined amount of carbon nanofibers, the interfacial phases are surrounded by an interfacial phase and divided into nanometer sizes. It is presumed to form small cells of the resulting elastomer. By forming such small cells almost uniformly throughout the carbon fiber composite material, it is possible to expect an effect that exceeds the effect of simply combining the two materials.

(V) Log Logging Device FIG. 7 is a cross-sectional view schematically showing a log logging device for seabed use according to an embodiment of the present invention. FIG. 8 is a cross-sectional view schematically showing a case of the logging apparatus in FIG. 7 according to one embodiment of the present invention. FIG. 9 is a cross-sectional view schematically showing an underground logging tool according to an embodiment of the present invention.
The logging tool is a physical property of the formation, oil layer, etc. in the borehole and around the well and the geometric properties of the well or casing (bore diameter, orientation, inclination, etc.) This is a device for recording the behavior of the oil layer flow for each depth, and can be used in, for example, an oil field. Examples of the logging device for oil field use include a subsea application shown in FIGS. 7 and 8 and an underground application shown in FIG. The logging equipment includes wireline logging (muline logging) and mud logging (mud logging), etc., and logging logging (LWD) with measuring equipment installed in the drilling assembly, While there is a measurement during excavation (MWD: Measurement While Drilling), a logging system used for wireline logging will be described here.
As shown in FIG. 7, the exploration of underground resources using wireline logging in the ocean, for example, in a well 156 composed of vertical holes or horizontal holes provided in the seabed 154 from a platform 150 floating in the sea 152, for example. For example, a downhole apparatus 160 is entered as a logging apparatus, and the underground geological structure and the like are searched for, for example, the presence or absence of petroleum as a target material. The downhole device 160 is fixed to, for example, the end of a long cable or communication link extending from the platform, and has a housing 161 such as a plurality of pressure vessels as shown in FIG. Inside the casing 161, for example, electrical logging (SP logging, normal logging, induction logging, ratello logging, micro resistivity logging, etc.), radioactivity logging (gamma ray logging, neutron logging, Density logging, nuclear magnetic resonance logging, etc.), acoustic logging (acoustic (acoustic) logging, array / sonic logging, cement bond logging, etc.), geological information logging (dip meter, FMI, etc.), earthquake Exploration logging (check shot velocity logging, VSP, etc.), sampling logging (sidewall / coring logging, RFT, MDT, etc.), auxiliary logging (caliper measurement, well geometry logging) Temperature logging, etc.), Special logging (Logs in host environment, logging through drilling pipe, etc.) Which exploration electronics can be selected and enclosed according to the purpose of exploration and can be used for exploring underground geological structures, etc., but they are exposed to high temperatures inside the well 156 deeply drilled deep underground. In addition, since it receives vibration and impact when entering the well 156, the electronic equipment in the housing 161 is also required to have high heat resistance and high strength.
For example, a plurality of electrical connectors 162 are arranged inside the housing 161, or the plurality of housings 161 are connected to each other by electrical connectors 162 formed in the end portions thereof. The electrical connector 162 includes a plurality of pins 162a spaced apart from each other and a support portion 162b that fixes the plurality of pins 162a. The support portion 162b can be formed of a carbon fiber composite material, for example, FIG. It can be fixed while maintaining the insulation between the plurality of pins 162a by the support portion 162b formed of a carbon fiber composite material like the electrical connectors 162 arranged at both ends of the casing 161. The pin 162a of the electrical connector 162 is subjected to the vibration and impact of the downhole device 160, or when connected to the electric wire 163, the electric wire 163 vibrates due to the vibration, and thus the strength for securely fixing the pin 162a is required. By fixing the pin 162a with a carbon fiber composite material, the pin 162a can be used for a relatively long time even in a severe environment at a high temperature in the well 156. It can have an insulation performance of 10 ⁶ (Ω · cm) or more, which is required between them. Further, the support portion 162 b of the electrical connector 162 can function as a feedthrough in the housing 161. Feedthroughs are shown, for example, in US Pat. No. 7,226,312 and are hereby incorporated by reference.
In addition, a plurality of electric wires 163 are arranged inside the housing 161 and connected to, for example, the pins 162 a of the electrical connector 162. The electric wire 163 includes, for example, a conductive metal conductive wire as a core material and a covering portion covering the conductive wire, and the covering portion can be formed of a carbon fiber composite material. Thus, the electric wire 163 covered with the carbon fiber composite material can withstand vibration and impact of the downhole device 160 under a severe environment at high temperature and can have insulation properties. Electrical wires are shown, for example, in US Pat. No. 6,446,723, incorporated herein by reference.
Further, a cable 164 that is connected to the casing 161 and extends to the outside of the casing 161 and in which a plurality of core wires such as electric wires are bundled is disposed. The cable 164 includes a core wire and a covering portion that covers the core wire, and the covering portion can be formed of a carbon fiber composite material. The core wire of the cable 164 can be formed of a plurality of core wires, for example, electric wires. Such a cable 164 has the role of transmitting and receiving data and commands between the case 161 in the underground and the data acquisition system on the ground and sending power to the electronic devices in the case 161 in the wireline logging. Can have. Such a cable 164 can withstand abrasion and breakage due to contact with the inner surface of the rod extending into the well 156, and can have insulating properties. Cables are shown, for example, in US Pat. No. 7,259,331, which is hereby incorporated by reference.
Further, for example, a plurality of coils 165 are arranged inside the housing 161, and a magnet wire is wound around these coils 165. The magnet wire is sometimes called a coil wire. The magnet wire includes a conductive wire and a covering portion that covers the conductive wire, and the covering portion can be formed of a carbon fiber composite material. The covering portion is formed as a thin insulating film by using a carbon fiber composite material, can withstand vibrations and impacts in a severe environment of high temperature of the downhole device 160, and can have insulating properties. By covering the magnet wire with the carbon fiber composite material, it is possible to effectively dissipate heat by the heat transfer effect of the fourth carbon nanofiber while maintaining the insulation. Magnet wires are shown, for example, in US Pat. No. 6,898,997, incorporated herein by reference.
Further, an electric board 166 on which a plurality of electronic components 167 are arranged, for example, is arranged inside the casing 161.
In addition, in the housing 161, for example, a heat dissipation sheet 167a can be disposed in order to prevent overheating due to self-heating of the plurality of electronic components 167, for example. The heat dissipating sheet 167a is also called a heat sink, and is in contact with the surface of the electronic component 167, for example, and is disposed between the electronic component 167 and the electric board 166 in FIG. It can also be arranged so as to contact the surface of the electronic component 167. By forming the heat dissipating sheet 167a from a carbon fiber composite material, it is possible to effectively dissipate heat by the heat transfer effect of the fourth carbon nanofibers while maintaining insulation from the electronic component 167. Further, the heat dissipation sheet 167a can be used as a vibration isolation sheet, and the impact resistance of the electronic component 167 can be improved. The heat dissipation sheet is shown, for example, in US Patent Publication No. 2008/0223579, which is incorporated herein by reference. Isolation sheets are shown, for example, in U.S. Patent No. 6,280,874, U.S. Patent Publication No. 2009/0183941, and U.S. Patent Publication No. 2009/0151589, which are incorporated herein by reference.
Further, the electronic component 167 arranged in the housing 161 and the electronic component (sensor 168) embedded in the wall portion 161a of the housing 161 can be encapsulated so as to cover the whole with a carbon fiber composite material. In this way, the entire electronic component 167 can be waterproofed with the carbon fiber composite material. For example, the sensor 168 is disposed in the opening 168a formed in the wall portion 161a of the housing 161 together with the electric wire 163 including a lead wire (not shown) connected to the sensor 168, and the opening 168a is formed by the carbon fiber composite material 168b. Encapsulated (sometimes called mold). Although not shown, the electronic component 167 may be enclosed in the carbon fiber composite material so as to cover the entire electronic component 167 on the electric substrate 166. As described above, the sensor 168 and the electronic component 167 covered with the carbon fiber composite material 168b can have a waterproof structure against moisture inside the housing 161 and inside the housing 161, and can have insulating performance.
In addition, the blending amount of the fourth carbon nanofibers and other compounding agents such as carbon black can be appropriately blended according to the required performance such as strength and insulation in each component using the carbon fiber composite material. 7 and 8 is an embodiment of the present invention, and in FIG. 8, a casing 161, an electrical connector 162, a cable 164, a coil 165, an electrical board 166, and a heat dissipation sheet 167a. Although the example in which the waterproof structure is incorporated in one logging device has been described, the present invention is not limited to this, and the waterproof structure can be selected and incorporated according to the logging application.
As shown in FIG. 9, the exploration of underground resources using wireline logging on the ground surface 153 is performed, for example, on the ground device 151 composed of a logging track 151a, a winch 151b, and the like, and from the winch 151b to the well 156. For example, it can be performed by a downhole apparatus 160 fixed to the tip of the extending wire line 155. The downhole device 160 is basically the same as the logging device for the seabed application, and the description thereof is omitted here.

As described above, the embodiments of the present invention have been described in detail. However, those skilled in the art can easily understand that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention.

Examples of the present invention will be described below, but the present invention is not limited thereto.
(1) Production of carbon nanofiber (1-1) A spray nozzle is attached to the top of a vertical heating furnace (inner diameter 17.0 cm, length 150 cm). The furnace wall temperature (reaction temperature) is raised to and maintained at 1000 ° C., and 20 g / min of a benzene liquid raw material containing 4% by weight of ferrocene is supplied from the spray nozzle at a flow rate of hydrogen gas of 100 L / min. To be sprayed directly. The shape of the spray at this time is a conical side surface (trumpet shape or umbrella shape), and the apex angle of the nozzle is 60 °. Under such conditions, ferrocene was pyrolyzed to produce iron fine particles, which became seeds, and the first carbon nanofibers were produced and grown from carbon obtained by pyrolysis of benzene. The first carbon nanofibers grown by this method were continuously produced for 1 hour while scraping off at intervals of 5 minutes.

(1-2) As carbon nanofibers for producing a comparative sample, graphitized carbon nanofibers (shown as “S” in the table), pulverized carbon nanofibers (shown as “SH” in the table), Oxidized carbon nanofibers (shown as “SO” in the table) were obtained.
The graphitized carbon nanofiber (S) was graphitized by further heat-treating the first carbon nanofiber obtained in (1-1) above at 2800 ° C. in an inert gas atmosphere. The graphitized carbon nanofiber (S) had an average diameter of 87 nm, an average length of 9.1 μm, and a surface oxygen concentration of 2.1 atm%. The graphitized carbon nanofiber (S) is a commercially available carbon nanofiber, and is a trade name VGCF-S manufactured by Showa Denko K.K.
For the pulverized carbon nanofiber (SH), the graphitized carbon nanofiber (S) was put into a rotary pulverizer Wonder Blender WB-1 (stainless steel pulverization blade, peripheral speed 180 m / s) manufactured by Osaka Chemical Co., Ltd. Obtained by grinding for 5 minutes.
Oxidation treated carbon nanofiber (SO) is a heating furnace (size is 700 mm) in which 120 g of graphitized carbon nanofiber (S) is put in a container (size is 300 mm × 300 mm × 150 mm) and air atmosphere is continuously introduced at 50 ml / min. × 350 mm × 900 mm), and obtained by performing an oxidation treatment by holding in a heating furnace at a heat treatment temperature and a heat treatment time in the step (c) shown in Table 1 and performing a heat treatment. The actual temperature in the heating furnace was in the range of ± 30 ° C. with respect to the set temperature.

(1-3) The fourth carbon nanofiber (shown as “SAPO” in the table) using the compression treatment in step (b) is the first carbon nanofiber obtained in (1-1), A second carbon nanofiber (SA) is obtained by heat treatment at a heat treatment temperature (1200 ° C.) of step (a) shown in Table 1 which is lower than the reaction temperature in the vapor phase growth method in an inert gas atmosphere, The second carbon nanofiber (SA) is put into a dry compression granulator having two rolls and the roll treatment in the step (b) shown in Table 1 is performed to obtain a third carbon nanofiber (SAP). Then, the third carbon nanofiber (SAP) is put in a heating furnace in an air atmosphere, and is held in the heating furnace at a heat treatment temperature (650 ° C.) and a heat treatment time (2 hours) in step (c) shown in Table 1. Oxidation treatment by heat treatment Give me. In addition, the roll process of the process (b) in manufacture of a 4th carbon nanofiber was obtained by throwing the 2nd carbon nanofiber (SA) into the dry compression granulator which has two rolls. The dry compression granulator is a roll press (roll diameter is 150 mm, roll is smooth roll, roll interval is 0 mm, set compression force between rolls (linear pressure) is 1960 N / cm, gear ratio is 1: 1.3, roll rotation Several rpm). The roll-treated carbon nanofiber was granulated into a plate-like lump (carbon nanofiber aggregate) having a diameter of about 2 to 3 cm. The granulated plate-like lump was further crushed through a crushing and granulating machine (rotation speed: 15 rpm, screen: 5 mm) having eight rotary blades to adjust the particle size. In addition, since the oxidation treatment in the step (c) in the production of the fourth carbon nanofiber was the same as the production conditions of the oxidation treatment carbon nanofiber (SO), description thereof is omitted here.
The fourth carbon nanofiber (shown as “SAHO” in the table) using the pulverization treatment in step (b) is the same as the first carbon nanofiber obtained in (1-1) above in an inert gas atmosphere. The second carbon nanofiber (SA) is obtained by heat treatment at the heat treatment temperature (1200 ° C.) of step (a) shown in Table 1 which is lower than the reaction temperature in the vapor phase growth method. The fiber (SA) was put into a rotary pulverizer wonder blender WB-1 (stainless steel pulverizing blade, peripheral speed 180 m / s) manufactured by Osaka Chemical Co. A third carbon nanofiber (SAH) is obtained, and the third carbon nanofiber (SAH) is placed in a heating furnace in an air atmosphere, and the heat treatment temperature (650 ° C.) and heat treatment time in step (c) shown in Table 1 Held in a heating furnace obtained by performing an oxidation process by heat treatment for 2 hours). In addition, the grinding process of the process (b) in manufacture of a 4th carbon nanofiber is the same as the manufacturing conditions of the said grinding | pulverization process carbon nanofiber (SH), and the process (c) in manufacture of a 4th carbon nanofiber. Since the oxidation treatment was the same as the production conditions for the oxidation-treated carbon nanofiber (SO), description thereof is omitted here.
(1-4) For each carbon nanofiber (S, SH, SO, SAPO, SAHO) thus obtained, the bulk density, fiber length, defect ratio, mass residual ratio, Raman peak ratio, tap density The nitrogen adsorption specific surface area, the oxygen concentration, the amount of increase in oxygen concentration and the rate of increase in oxygen concentration were measured, and the results are shown in Table 1. In Table 1, unmeasured columns are indicated by “−”.
The measurement of the bulk density is sometimes called a zero tap density, and was measured according to JIS-K6219-2.
The measurement of the fiber length and the ratio of having defects are performed by taking 40 field images of carbon nanofibers at a magnification of 5000 with a scanning electron microscope (SEM), and 50 fiber lengths for a total of 200 fibers for each field of view. And the number of fibers having defects was determined by measurement. Defects count the number of fibers having branched portions and bent portions, respectively, and the ratio of defects (branched portions and bent portions) is the ratio (%) that the number of fibers having each defect is included in 200. Calculated. The ratio of carbon nanofibers having a maximum fiber length of 20 μm or more (shown as “a ratio of 20 μm or more” in Table 1) was calculated.
The measurement of the remaining mass ratio of the fourth carbon nanofiber (SAPO) is the ratio of the mass of the fourth carbon nanofiber (SAPO) when the mass of the third carbon nanofiber (SAP) is 100 mass%. Was defined as the remaining mass rate. The measurement of the remaining mass ratio of the fourth carbon nanofiber (SAHO) is the ratio of the mass of the fourth carbon nanofiber (SAHO) when the mass of the third carbon nanofiber (SAH) is 100 mass%. Was defined as the remaining mass rate. Moreover, the measurement of the residual mass ratio of oxidized carbon nanofibers (SO) is based on the ratio of the mass of oxidized carbon nanofibers (SO) when the mass of graphitized carbon nanofibers (S) is 100% by mass. The residual mass rate was assumed.
Measurement of the Raman peak ratio, KAISER OPTICAL SYSTEM Co. HOLOLAB-5000 Type: peak intensity at around 1300 cm ^-1 by Raman scattering spectroscopy using a (532nmND YAG) to the peak intensity G in the vicinity of 1600 cm ^-1 in each carbon nanofiber The ratio of D (D / G) was measured.
The nitrogen adsorption specific surface area was measured by measuring the nitrogen adsorption specific surface area (m ² / g) of each carbon nanofiber using NOVA3000 type (nitrogen gas) manufactured by Yuasa Ionics. Although not shown in the table, the nitrogen adsorption specific surface area of the third carbon nanofiber (SAH) was 38 (m ² / g).
The measurement of the oxygen concentration was performed using XPS (third carbon nanofiber (SAP or SAH), graphitized carbon nanofiber (S), oxidized carbon nanofiber (SO) and fourth carbon nanofiber (SAPO or SAHO). It measured using the X-ray photoelectron spectroscopy (X-ray Photoelectron Spectroscopy). Specifically, for example, the fourth carbon nanofiber will be described. First, the fourth carbon nanofiber is sprinkled on the carbon tape on the metal base to adhere to the carbon tape, and the extra carbon nanofiber that has not adhered to the carbon tape is first attached. The fourth carbon nanofiber was shaken off and a metal base was mounted in the XPS apparatus. As the XPS apparatus, “X-ray photoelectron spectrometer JPS-9200 for micro analysis (hereinafter referred to as XPS apparatus) manufactured by JEOL Ltd. was used. Next, a fourth carbon nanofiber as a powder sample was used. Argon gas etching was performed at an argon gas concentration of 8 × 10 ⁻² Pa for 0.5 minutes to bring out a clean surface of the fourth carbon nanofiber, and the X-ray source of the XPS apparatus had an analysis diameter of 1 mm and a counter cathode. The oxygen concentration on the surface of the fourth carbon nanofiber was measured by setting an Al / Mg twin target, an acceleration voltage of 10 kV, and an emission current of 30 mA.The elements on the surface of the fourth carbon nanofiber detected by XPS were oxygen and The same measurement was performed on other carbon nanofibers.
Based on the measurement result of the oxygen concentration on the surface of each carbon nanofiber, the fourth carbon nanofiber (SAPO) of the fourth carbon nanofiber (SAPO) with respect to the surface oxygen concentration ( _ap ) of the third carbon nanofiber (SAP) before the oxidation treatment is performed. The amount of increase in surface oxygen concentration (b _p ) (c _p = b _p −a _p ) and the rate of increase in surface oxygen concentration (d _p = 100 · c _p / a _p ) were calculated and are shown in Table 1. Further, the amount of increase in the surface oxygen concentration (b _h ) of the fourth carbon nanofiber (SAHO) relative to the surface oxygen concentration (a _h ) of the third carbon nanofiber (SAH) before the oxidation treatment (c _h = b _h −a _h ) and the rate of increase of the surface oxygen concentration (d _h = 100 · c _h / a _h ) were calculated and shown in Table 1. Further, the amount of increase in the surface oxygen concentration (b _S ) of the oxidized carbon nanofiber (SO) relative to the surface oxygen concentration (a _S ) of the graphitized carbon nanofiber (S) before the oxidation treatment (c _S = b _S- a _S ) and the rate of increase in surface oxygen concentration (d _S = 100 · c _S / a _S ) were calculated and are shown in Table 1.

(2) Production of carbon fiber composite material samples of Examples 1 to 8 and Comparative Examples 1 to 9 (2-1) Examples of Examples 1 to 2 and Comparative Examples 1 to 5 are open rolls having a roll diameter of 6 inches ( 100 parts by mass (phr) of a fluorine-containing elastomer (“FKM”) shown in Tables 2 and 3 was added to a roll temperature of 10 to 20 ° C. and wound around a roll. Next, each carbon nanofiber obtained in (1) in parts by mass (phr) shown in Tables 2 and 3 was added to the elastomer together with compounding agents such as triallyl isocyanate and peroxide. At this time, the roll gap was set to 1.5 mm. When the compounding agent was charged, the mixture containing the compounding agent was taken out from the roll. The roll gap was narrowed from 1.5 mm to 0.3 mm, and the mixture was further introduced into the roll for thinning. At this time, the surface speed ratio of the two rolls was set to 1.1. Thinning was repeated 10 times. A roll was set in a predetermined gap (1.1 mm), a thin composite material was charged, and dispensed to obtain a non-crosslinked carbon fiber composite material. The carbon fiber composite material thus obtained was rolled with a roll, press-molded (cured) at 170 ° C. for 10 minutes, and further post-cured at 200 ° C. for 24 hours. Examples 1-2 and Comparative Example 1 A crosslinked carbon fiber composite material (sheet shape having a thickness of 1 mm) was obtained. “FKM” in Tables 2 and 4 is Viton GF-600S (a weight average molecular weight of 50,000, T2n / 30 ° C. is 50 μsec), a ternary fluorine-containing elastomer manufactured by DuPont Dow Elastomer Japan. there were.

(2-2) As examples 3 to 8 and comparative examples 6 to 9, a predetermined amount of EPDM (ethylene-propylene rubber) shown in Tables 2, 3 and 5 was put into an open roll (roll set temperature 20 ° C.). After kneading, each carbon nanofiber obtained in (1) was put into an elastomer and kneaded, and then the first kneading step was performed and taken out from the roll. Further, the mixture was again put into an open roll set at a roll temperature of 100 ° C., and taken out by performing a second kneading step. Next, this mixture was wound around an open roll (roll temperature: 10 to 20 ° C., roll interval: 0.3 mm), and thinning was repeated 5 times. At this time, the surface speed ratio of the two rolls was set to 1.1. Furthermore, the carbon fiber composite material obtained by setting the roll gap to 1.1 mm and passing through was put and dispensed. The separated sheets were compression molded at 90 ° C. for 5 minutes to obtain uncrosslinked carbon fiber composite material samples of Examples 3 to 8 and Comparative Examples 6 to 9 having a thickness of 1 mm. Further, 2 parts by mass of peroxide (phr) was mixed with the non-crosslinked carbon fiber composite material obtained through thinning, and the mixture was put into an open roll having a roll gap set to 1.1 mm and dispensed. Carbon fiber composite material containing peroxide that was dispensed and cut into a mold size was set in a mold, compression molded at 175 ° C., 100 kgf / cm ² for 20 minutes, and Examples 3 to 5 having a thickness of 1 mm and comparison The crosslinked carbon fiber composite material samples of Examples 6 to 8 were obtained. In Tables 2, 3, and 5, “EPDM” was the trade name EP103AF of ethylene-propylene rubber manufactured by JSR. In Comparative Examples 1 and 6, carbon nanofibers were not blended, but the same kneading process was performed.

(3) Measurement using pulsed NMR The uncrosslinked carbon fiber composite material samples of Examples 1 to 8 and Comparative Examples 1 to 9 were measured by the Hahn echo method using pulsed NMR. This measurement was performed using “JMN-MU25” manufactured by JEOL Ltd. The measurement is performed under the condition that the observation nucleus is ¹ H, the resonance frequency is 25 MHz, the 90 ° pulse width is 2 μsec, and Pi is changed in various ways by the pulse sequence of the Hahn echo method (90 ° x-Pi-180 ° x). The decay curve was measured. Further, the sample was measured by inserting it into a sample tube up to an appropriate range of the magnetic field. The measurement temperature was 150 ° C. By this measurement, the first spin-spin relaxation time (T2n / 150 ° C.) and the component fraction (fnn) of the component having the second spin-spin relaxation time were determined for each sample. The measurement results are shown in Tables 2-4. The first spin-spin relaxation times (T2n / 30 ° C.) of the raw rubber measured in the same manner are also shown in Tables 2 to 5. Note that the carbon fiber composite material samples of Examples 1 to 5, 7, and 8 were affected by the magnetic field generated by the carbon nanofibers and could not be measured.

(4) Measurement of Hardness (Hs), 100% Modulus (M100), Tensile Strength (TB), Elongation at Break (EB), Dynamic Elastic Modulus (E ′) and Volume Specific Resistance Examples 1 to 8 and Comparison For the crosslinked carbon fiber composite material samples of Examples 1 to 9, rubber hardness (Hs (JIS-A)) was measured based on JIS K 6253.
About the test piece which cut the carbon fiber composite material sample of the bridge | crosslinking body of Examples 1-8 and Comparative Examples 1-9 into the dumbbell shape of JIS6 type, it was 23 +/- 2 degreeC using the tensile tester by Toyo Seiki Co., Ltd. Then, a tensile test was performed based on JIS K6251 at a tensile speed of 500 mm / min, and tensile strength (TB (MPa)), elongation at break (EB (%)) and 100% stress (M100) were measured.
A dynamic viscoelasticity test made by SII Co., Ltd. was performed on test pieces obtained by cutting the carbon fiber composite material samples of the crosslinked bodies of Examples 1 to 8 and Comparative Examples 1 to 9 into strips (40 × 1 × 5 (width) mm). Using a machine DMS6100, a distance between chucks of 20 mm, a measurement temperature of −100 to 300 ° C., a dynamic strain of ± 0.05%, and a frequency of 10 Hz were subjected to a dynamic viscoelasticity test based on JIS K6394, and the measurement temperatures were 30 ° C. and 200 ° C. The dynamic elastic modulus at E ° C. (E ′, unit is MPa) was measured.
Samples of carbon fiber composite materials (width 50 mm × length 50 mm × thickness 1 mm) of the crosslinked bodies of Examples 1 to 8 and Comparative Examples 1 to 9 were measured based on JIS K 6271 at a volume specific resistance value (Ω · cm). Based on the measurement results, the electrical insulation of the carbon fiber composite material sample is evaluated. If the volume resistivity is 1 × 10 ⁶ or more, the insulation is good (shown as “◯” in the table), and the volume is specific. If the resistance value is less than 1 × 10 ⁶ , the insulation is low (shown as “x” in the table).

As is apparent from the results in Tables 2 to 5, the crosslinked carbon fiber composite material containing the fourth carbon nanofibers of Examples 1 and 2 is more in comparison with the carbon fiber composite materials of Comparative Examples 1 to 5. Even when a large amount of the fourth carbon nanofiber was blended, the volume resistivity was high and the electrical insulation was good. In addition, the crosslinked carbon fiber composite material containing the fourth carbon nanofibers of Examples 3 to 8 contains a larger amount of the fourth carbon nanofiber than the carbon fiber composite materials of Comparative Examples 6 to 9. Even so, the volume resistivity was high and the electrical insulation was good.

2 Open roll 10 1st roll 20 2nd roll 30 Elastomer 60 2nd carbon nanofiber 62 Bending part 64 Branching part 70 Dry compression granulator 72 1st roll 74 2nd roll 80 3rd carbon Nanofiber 90 Fourth carbon nanofiber 150 Platform 160 Downhole device 161 Housing 162 Electric connector 163 Electric wire 164 Cable 165 Coil 166 Electric substrate 167 Electronic component 168 Sensor

Claims (28)

20 parts by mass to 100 parts by mass of carbon nanofibers with reduced branch parts and oxidized with respect to 100 parts by mass of the elastomer,
The dynamic elastic modulus (E ′) at 200 ° C. and 10 Hz is 10 MPa to 1000 MPa,
A carbon fiber composite material having a volume resistivity of 10 ⁶ Ω · cm to 10 ¹⁸ Ω · cm. In claim 1,
The carbon nanofiber is a carbon fiber composite material in which branch portions are reduced by a mechanical action before being blended with the elastomer. In claim 2,
The mechanical action is a carbon fiber composite material made by a compression process. In claim 3,
The elastomer is a fluorine-containing elastomer,
The dynamic elastic modulus (E ′) at 200 ° C. and 10 Hz is 15 MPa to 300 MPa,
A carbon fiber composite material having a volume resistivity of 10 ¹¹ Ω · cm to 10 ¹⁸ Ω · cm. In claim 3,
The elastomer is ethylene-propylene rubber,
The dynamic elastic modulus (E ′) at 200 ° C. and 10 Hz is 10 MPa to 200 MPa,
A carbon fiber composite material having a volume resistivity of 10 ⁷ Ω · cm to 10 ¹⁸ Ω · cm. In claim 2,
The mechanical action is a carbon fiber composite material made by a pulverization process. In claim 6,
The elastomer is ethylene-propylene rubber,
The dynamic elastic modulus (E ′) at 200 ° C. and 10 Hz is 10 MPa to 200 MPa,
A carbon fiber composite material having a volume resistivity of 10 ⁸ Ω · cm to 10 ¹⁸ Ω · cm. In any one of Claims 1-7,
The carbon nanofiber is a carbon fiber composite material having a maximum fiber length of less than 20 μm. An insulating article for use in oil fields, comprising the carbon fiber composite material according to any one of claims 1 to 8. Electronic parts including the insulating article according to claim 9. A logging apparatus comprising a housing and the electronic component according to claim 10 disposed in the housing. A step of obtaining a second carbon nanofiber by heat-treating the first carbon nanofiber produced by the vapor deposition method at a temperature higher than the reaction temperature in the vapor deposition method at 1100 ° C. to 1600 ° C. (A) and
Treating the second carbon nanofibers by a mechanical action to reduce the branching portions of the second carbon nanofibers to obtain third carbon nanofibers;
(C) a step of heat-treating the third carbon nanofibers in an atmosphere containing oxygen at 600 ° C. to 800 ° C. to obtain oxidized fourth carbon nanofibers;
A step (d) of mixing the fourth carbon nanofibers with an elastomer and uniformly dispersing in the elastomer with a shearing force to obtain a carbon fiber composite material;
A method for producing a carbon fiber composite material, comprising: In claim 12,
The method for producing a carbon fiber composite material, wherein the heat treatment in the step (a) is 1200 ° C to 1500 ° C. In claim 12 or 13,
The third carbon nanofiber obtained in the step (b) has a maximum fiber length of less than 20 μm, and is a method for producing a carbon fiber composite material. In any one of claims 12 to 14,
The mechanical action of the step (b) is performed by a compression process,
The 3rd carbon nanofiber obtained by the said compression process is a manufacturing method of a carbon fiber composite material which does not have a branch part. In claim 15,
The compression treatment is performed by putting the second carbon nanofiber between at least two rotating rolls and applying a shearing force and a compression force to the second carbon nanofiber. Material manufacturing method. In claim 15 or 16,
The said compression process is a manufacturing method of a carbon fiber composite material which does not use the binder for couple | bonding carbon nanofibers. In any one of claims 15 to 17,
The said compression process is a manufacturing method of a carbon fiber composite material performed with a dry compression granulator. In any one of claims 12 to 14,
The mechanical action of the step (b) is performed by a pulverization process,
The method for producing a carbon fiber composite material, wherein the tap density of the third carbon nanofiber is 1.5 to 10 times the tap density of the second carbon nanofiber. In claim 19,
The pulverization treatment produces the third carbon nanofiber having a nitrogen adsorption specific surface area that is 1.1 to 5.0 times the nitrogen adsorption specific surface area of the second carbon nanofiber. Method. In claim 19 or 20,
The method for producing a carbon fiber composite material, wherein the pulverization is performed by dry pulverization using impact and / or shear force. In any one of claims 12 to 21
The amount of increase in the oxygen concentration on the surface of the fourth carbon nanofiber relative to the oxygen concentration on the surface of the third carbon nanofiber measured by X-ray photoelectron spectroscopy (XPS) is 0.5 atm% to 2.6 atm. %, The method for producing a carbon fiber composite material. In any one of claims 12 to 22,
The increase rate of the oxygen concentration on the surface of the fourth carbon nanofiber relative to the oxygen concentration on the surface of the third carbon nanofiber measured by X-ray photoelectron spectroscopy (XPS) is 20% to 120%. A method for producing a carbon fiber composite material. In any one of claims 12 to 23
The heat treatment in the step (c) is a method for producing a carbon fiber composite material, wherein the fourth carbon nanofibers are obtained by reducing the mass of the third carbon nanofibers by 2% to 20%. In any one of claims 12 to 24,
The fourth carbon nanofiber obtained in the step (c) has a surface oxygen concentration of 2.6 atm% to 4.6 atm% measured by X-ray photoelectron spectroscopy (XPS). Manufacturing method. In any one of claims 12 to 25
The fourth carbon nanofiber obtained in the step (c) the ratio of the peak intensity D of around 1300 cm ^-1 to the peak intensity G of around 1600 cm ^-1 measured by Raman scattering spectroscopy (D / G) A method for producing a carbon fiber composite material having a thickness of 0.12 to 0.22. In any one of claims 12 to 26,
The method for producing a carbon fiber composite material, wherein the fourth carbon nanofiber obtained in the step (c) has a nitrogen adsorption specific surface area of 45 m ² / g to 60 m ² / g. In any one of claims 12 to 26,
The method for producing a carbon fiber composite material, wherein the fourth carbon nanofiber obtained in the step (c) has an average diameter of 70 nm to 100 nm.

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