WO2023054716A1

WO2023054716A1 - Fluororubber composition and shaped object

Info

Publication number: WO2023054716A1
Application number: PCT/JP2022/036854
Authority: WO
Inventors: 真寛上野
Original assignee: 日本ゼオン株式会社
Priority date: 2021-09-30
Filing date: 2022-09-30
Publication date: 2023-04-06
Also published as: JPWO2023054716A1

Abstract

The purpose of the present invention is to provide a new technique whereby a shaped object capable of exhibiting excellent stretchability at high temperatures can be formed using a fluororubber and single-layer carbon nanotubes (CNTs). The fluororubber composition according to the present invention comprises a fluororubber and carbon nanotubes. The carbon nanotubes include single-layer CNTs. This fluororubber composition, in a dynamic viscoelasticity test conducted under the measurement conditions of a frequency of 1 Hz and a temperature of 40°C, has a γG^* as calculated with the following equation (I) of 20 or greater. Equation (I): γG^*=G^* _L/G^* _H (wherein G^* _L (kPa) is the complex modulus at a dynamic strain of 0.1% and G^* _H (kPa) is the complex modulus at a dynamic strain of 630%).

Description

Fluororubber composition and molded article

The present invention relates to a composition containing fluororubber and a molded article obtained by molding the composition.

　Fluororubber is known to have excellent performance such as chemical resistance, oil resistance, heat resistance, and cold resistance, and is used for various purposes. Conventionally, attempts have been made to add a carbon material to the fluororubber in order to improve the performance of the fluororubber.

For example, Patent Document 1 describes a fluororubber composition obtained by adding carbon black as a carbon material to a fluororubber having predetermined properties. According to Patent Document 1, the fluororubber composition containing the fluororubber and the carbon black is subjected to a dynamic viscoelasticity test conducted under predetermined conditions. By setting the difference in shear modulus at 100% strain within a predetermined range, it is possible to improve the tensile physical properties and tensile fatigue properties of the crosslinked product obtained using the fluororubber composition at high temperatures.

Japanese Patent Publication No. 2015-512954

Here, in recent years, carbon nanotubes such as single-walled carbon nanotubes (hereinafter sometimes abbreviated as "CNT") have been attracting attention as carbon materials that are excellent in various properties such as electrical conductivity and thermal conductivity.

However, in a fluororubber composition obtained by adding single-walled CNTs to a fluororubber, a molded article formed from the fluororubber composition exhibits excellent extensibility in a high-temperature environment (e.g., 200°C or higher). In this respect, there is room for improvement.

Therefore, an object of the present invention is to provide a new technology that can form a molded body that can exhibit excellent extensibility at high temperatures using fluororubber and single-walled CNTs.

The inventor of the present invention has diligently studied in order to achieve the above purpose. The present inventor focused on dynamic viscoelasticity of a fluororubber composition obtained by using fluororubber and single-walled CNTs. In addition, in a dynamic viscoelasticity test conducted under predetermined conditions for the fluororubber composition, the ratio of the complex elastic modulus when the dynamic strain is 0.1% to the complex elastic modulus when the dynamic strain is 630% is a predetermined value or more, the fluororubber composition can be used to obtain a molded article having excellent extensibility at high temperatures, and the present invention has been completed.

That is, an object of the present invention is to advantageously solve the above problems, and according to the present invention, the following fluororubber compositions [1] to [7] and the following [8] molded article is provided.
[1] A fluororubber composition containing fluororubber and carbon nanotubes, wherein the carbon nanotubes include single-walled carbon nanotubes, and the measurement frequency is 1 Hz and the measurement temperature is 40°C. In a dynamic viscoelasticity test, when the complex elastic modulus at a dynamic strain of 0.1% is G ^* _L (kPa) and the complex elastic modulus at a dynamic strain of 630% is G ^* _H (kPa), Formula (I) below:
γG ^* =G ^* _L /G ^* _H (I)
A fluororubber composition having a γG ^* of 20 or more, as calculated by
Thus, by using a fluororubber composition containing fluororubber and single-walled CNTs and having γG ^* equal to or higher than the above-mentioned value, it is possible to form a molded article that can exhibit excellent extensibility at high temperatures. .
In the present invention, the complex elastic modulus G ^* _L , the complex elastic modulus G ^* _H , and γG ^* can be specified in more detail using the methods described in the examples.

[2] The fluororubber composition according to [1] above, wherein the carbon nanotubes further include multi-walled carbon nanotubes.
A fluororubber composition containing both single-walled CNTs and multi-walled CNTs ensures sufficient processability, and according to the fluororubber composition, it is possible to form a molded article that can exhibit even better extensibility at high temperatures. can be done.

[3] The fluororubber composition according to [1] or [2] above, which further contains a reinforcing filler other than the carbon nanotubes.
By using a fluororubber composition containing a reinforcing filler in addition to single-walled CNTs, it is possible to form a molded article that can exhibit even better extensibility at high temperatures.
In the present invention, the term "reinforcing filler" does not include carbon nanotubes.

[4] The fluororubber composition according to [3] above, wherein the reinforcing filler contains at least one of carbon black and silica.
By using a fluororubber composition containing carbon black and/or silica as the above-mentioned reinforcing filler, it is possible to form a molded article that can exhibit even better extensibility at high temperatures.

[5] The fluororubber composition according to any one of [1] to [4] above, wherein the content of the single-walled carbon nanotubes is 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the fluororubber. thing.
A fluororubber composition in which the content of single-walled CNTs per 100 parts by mass of fluororubber is within the above range is excellent in workability, and when the fluororubber composition is used, it exhibits even better extensibility at high temperatures. A molded body can be formed.

[6] The fluororubber composition according to any one of [1] to [5] above, further comprising a cross-linking agent.

[7] The fluororubber composition according to [3] or [4] above, wherein the fluororubber composition further contains a cross-linking agent, and a crosslinked rubber sheet formed from the fluororubber composition containing the cross-linking agent Regarding X, according to JIS K6251: 2010, the tensile strength measured under the conditions of test temperature: 200 ° C., test humidity: 50%, tensile speed: 500 ± 50 mm / min is defined as T _X (MPa), Regarding the crosslinked rubber sheet Y formed from the test rubber composition obtained by removing the carbon nanotubes and the reinforcing filler from the fluororubber composition containing the crosslinking agent, the test temperature was 200°C in accordance with JIS K6251:2010. When the tensile strength measured under the conditions of test humidity: 50%, tensile speed: 500 ± 50 mm / min is T _Y (MPa), the following formula (II):
Tensile strength ratio = T _X /T _Y (II)
A fluororubber composition having a tensile strength ratio of 3.0 or more.
By using a fluororubber composition having a tensile strength ratio equal to or higher than the above value, the durability of the molded article can be enhanced. In addition, since the durability is improved, it becomes possible to reduce the size of various members composed of the molded body.
In addition, in the present invention, the tensile strength T _X , the tensile strength T _Y , and the tensile strength ratio can be specified in more detail using the methods described in Examples.

[8] A molded article formed using the fluororubber composition described in [6] or [7] above.
A molded article formed using any one of the above-described fluororubber compositions containing a cross-linking agent can exhibit excellent extensibility at high temperatures.

According to the present invention, it is possible to provide a molded article that contains fluororubber and single-walled carbon nanotubes and that can exhibit excellent extensibility at high temperatures, and a fluororubber composition that can form the molded article.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.
Here, the fluororubber composition of the present invention can be used for forming the molded article of the present invention. And the molded article of the present invention is formed using the fluororubber composition of the present invention.

(Fluoro-rubber composition)
The fluororubber composition of the present invention contains at least fluororubber and single-walled carbon nanotubes, and optionally at least one selected from the group consisting of multi-walled carbon nanotubes, reinforcing fillers, cross-linking agents, and other components. further includes

Here, the fluororubber composition of the present invention has a complex elastic modulus of G ^* When _L (kPa) and G ^* _H (kPa) is the complex elastic modulus at a dynamic strain of 630%, the following formula (I):
γG ^* =G ^* _L /G ^* _H (I)
γG ^* calculated by is 20 or more. If a fluororubber composition having a γG ^* of 20 or more, which is calculated as the ratio of the complex elastic modulus at a dynamic strain of 0.1% to the complex elastic modulus at a dynamic strain of 630%, is used, A molded article having excellent extensibility can be obtained.

The reason why the γG ^* of the fluororubber composition is equal to or higher than the above-described value can improve the extensibility of the molded article at high temperatures is presumed as follows.
First, the extensibility of the molded body at high temperatures is excellent in a network structure composed of single-walled CNTs, multi-walled CNTs, and reinforcing fillers (hereinafter collectively referred to as “single-walled CNTs, etc.”). It is thought that it will be improved by being formed. According to the study of the present inventor, it is possible to use γG ^* as a factor that correlates with the degree of formation of this network structure. Specifically, in a dynamic viscoelasticity test, a network structure composed of single-walled CNTs or the like is maintained when the dynamic strain is small (eg, 0.1%), while the dynamic strain is large (eg, 630 %) in which case it will be destroyed. That is, the complex elastic modulus at a dynamic strain of 0.1% corresponds to the complex elastic modulus when the network structure is maintained, and the complex elastic modulus at a dynamic strain of 630% corresponds to that when the network structure is destroyed. corresponds to the complex elastic modulus in the flattened state. Therefore, if γG ^* , which is calculated as the ratio of the complex elastic modulus (dynamic strain: 0.1%) to the complex elastic modulus (dynamic strain: 630%), is 20 or more, the network structure is maintained. The complex elastic modulus (dynamic strain: 0.1%) is sufficiently larger than the complex elastic modulus (dynamic strain: 630%) in the state where the network structure is destroyed, and the single-walled CNT etc. in the fluororubber composition It can be judged that the network structure composed of is well formed. It is believed that the molded article formed from the fluororubber composition can exhibit excellent extensibility at high temperatures due to the favorable network structure of single-walled CNTs and the like.

<Fluoro rubber>
The fluororubber is not particularly limited, and examples thereof include tetrafluoroethylene-propylene rubber (FEPM), vinylidene fluoride rubber (FKM), tetrafluoroethylene-perfluoromethyl vinyl ether rubber (FFKM), tetrafluoro Ethylene-based rubber (TFE) can be mentioned. Among these, vinylidene fluoride rubber (FKM) and tetrafluoroethylene-propylene rubber (FEPM) are preferable, and vinylidene fluoride rubber (FKM) is more preferable.
In addition, fluororubber may be used individually by 1 type, and may be used in combination of 2 or more types.

Here, the vinylidene fluoride rubber (FKM) is a fluororubber that has vinylidene fluoride as its main component and is excellent in heat resistance, oil resistance, chemical resistance, solvent resistance, workability, and the like. Examples of FKM include, but are not limited to, a binary copolymer of vinylidene fluoride and hexafluoropropylene, a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene, and vinylidene fluoride. , hexafluoropropylene, tetrafluoroethylene, and a vulcanization site monomer. Commercially available products include, for example, "Viton (registered trademark)" manufactured by Chemours Co., Ltd., and "Dai-El (registered trademark) G" manufactured by Daikin Industries, Ltd. Among them, a quaternary copolymer composed of vinylidene fluoride, hexafluoropyrene, tetrafluoroethylene and a vulcanization site monomer is preferred. The quaternary copolymer is available, for example, as a commercial product "Viton GBL-600S" (manufactured by Chemours Corporation).

Polytetrafluoroethylene-propylene rubber (FEPM) is a fluororubber based on an alternating copolymer of tetrafluoroethylene and propylene, and has excellent heat resistance, chemical resistance, polar solvent resistance, and steam resistance. is. Examples of FEPM include, but are not limited to, a binary copolymer consisting of tetrafluoroethylene and propylene, a terpolymer consisting of tetrafluoroethylene, propylene and vinylidene fluoride, and tetrafluoroethylene, propylene and a cross-linking point. a terpolymer consisting of a monomer and the like. Examples of commercially available binary copolymers of tetrafluoroethylene and propylene include "AFRAS (registered trademark) 100" and "AFRAS 150" manufactured by AGC Corporation. Commercially available terpolymers composed of tetrafluoroethylene, propylene and vinylidene fluoride include, for example, "AFRAS 200" manufactured by AGC Corporation. Commercially available terpolymers composed of tetrafluoroethylene, propylene, and cross-linking monomers include, for example, "Afras 300" manufactured by AGC Corporation.

The content of the fluororubber in the fluororubber composition is preferably 80% by mass or more, more preferably 85% by mass or more, with the mass of the entire fluororubber composition being 100% by mass. It is more preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. If the content of the fluororubber in the fluororubber composition is within the range described above, the extensibility of the molded article at high temperatures can be sufficiently improved while ensuring the workability of the fluororubber composition.

<Single-walled carbon nanotube>
The fluororubber composition of the present invention contains at least single-walled CNTs as CNTs.
Here, the average diameter of single-walled CNTs is preferably 0.5 nm or more, more preferably 1 nm or more, preferably 15 nm or less, more preferably 10 nm or less, and 5 nm or less. is more preferable, and 3.5 nm or less is particularly preferable. If the average diameter (Av) of the single-walled CNTs is within the range described above, it is possible to further improve the extensibility at high temperatures of the molded article formed using the fluororubber composition.

In addition, single-walled CNTs preferably show an upward convex shape in the t-plot obtained from the adsorption isotherm. Among them, it is more preferable that the single-walled CNTs are not subjected to the opening treatment and that the t-plot exhibits an upwardly convex shape. If single-walled CNTs exhibiting a convex shape in the t-plot obtained from the adsorption isotherm are used, the extensibility at high temperatures of the molded article formed using the fluororubber composition can be further improved. can.

Here, adsorption is generally a phenomenon in which gas molecules are removed from the gas phase onto a solid surface, and is classified into physical adsorption and chemisorption according to the cause. And the nitrogen gas adsorption method used to obtain the t-plot utilizes physical adsorption. Normally, if the adsorption temperature is constant, the number of nitrogen gas molecules adsorbed on CNT increases as the pressure increases. In addition, the relative pressure on the horizontal axis (the ratio of the adsorption equilibrium state pressure P and the saturated vapor pressure P0) and the nitrogen gas adsorption amount on the vertical axis are called "isothermal lines", and nitrogen gas adsorption is performed while increasing the pressure. The case where the amount is measured is called the "adsorption isotherm", and the case where the nitrogen gas adsorption amount is measured while decreasing the pressure is called the "desorption isotherm".

Then, the t-plot is obtained by converting the relative pressure to the average thickness t (nm) of the nitrogen gas adsorption layer in the adsorption isotherm measured by the nitrogen gas adsorption method. That is, the average thickness t of the nitrogen gas adsorption layer corresponding to the relative pressure is obtained from a known standard isotherm obtained by plotting the average thickness t of the nitrogen gas adsorption layer against the relative pressure P/P0, and the above conversion is performed. gives a t-plot of CNTs (t-plot method by de Boer et al.).

Here, in a sample having pores on its surface, the growth of the nitrogen gas adsorption layer is classified into the following processes (s-1) to (s-3). Then, the slope of the t-plot changes due to the following processes (s-1) to (s-3).
(s-1) Process of forming a monomolecular adsorption layer of nitrogen molecules on the entire surface (s-2) Formation of a polymolecular adsorption layer and accompanying capillary condensation filling process within the pores (s-3) Pores are filled with nitrogen Formation process of polymolecular adsorption layer on apparently non-porous filled surface

Then, the t-plot showing an upwardly convex shape is located on a straight line passing through the origin in a region where the average thickness t of the nitrogen gas adsorption layer is small, whereas when t becomes large, the plot is on the straight line. position shifted downward from A CNT having such a t-plot shape has a large ratio of the internal specific surface area to the total specific surface area of the CNT, indicating that many openings are formed in the CNT.

Note that the t-plot inflection point of the single-walled CNTs used in the present invention preferably falls within a range that satisfies 0.2 ≤ t (nm) ≤ 1.5, and 0.45 ≤ t (nm) ≤ 1.5. 5, more preferably 0.55≦t(nm)≦1.0. When the position of the inflection point of the t-plot is within the above range, the properties of the single-walled CNTs are further improved, so that the extensibility at high temperatures of the molded body formed using the fluororubber composition is further improved. can be done.
Here, the "position of the inflection point" is the intersection of the approximate straight line A in the process (s-1) described above and the approximate straight line B in the process (s-3) described above in the t-plot. .

Furthermore, in the single-walled CNTs used in the present invention, the ratio (S2/S1) of the internal specific surface area S2 to the total specific surface area S1 obtained from the t-plot is preferably 0.05 or more, and 0.06 or more. It is more preferably 0.08 or more, and preferably 0.30 or less. If S2/S1 is 0.05 or more and 0.30 or less, the properties of the single-walled CNTs can be further improved, so that the extensibility at high temperatures of the molded body formed using the fluororubber composition can be improved. can be further enhanced.

By the way, the measurement of the adsorption isotherm of CNT, the creation of the t-plot, and the calculation of the total specific surface area S1 and the internal specific surface area S2 based on the analysis of the t-plot can be performed, for example, by using a commercially available measurement device "BELSORP (registered (trademark)-mini” (manufactured by Bell Japan).

Here, as a single-walled CNT, the ratio (3σ/Av) of the value (3σ) obtained by multiplying the standard deviation (σ) of the diameter by 3 to the average diameter (Av) is single It is preferable to use layered CNTs, more preferably to use single-walled CNTs with 3σ/Av of more than 0.25, even more preferably to use single-walled CNTs with 3σ/Av of more than 0.40, and 3σ/Av of It is particularly preferred to use single-walled CNTs greater than 0.50. By using single-walled CNTs with a 3σ/Av of more than 0.20 and less than 0.80, it is possible to further improve the elongation at high temperatures of the molded article formed using the fluororubber composition.
In addition, "average diameter of CNT (Av)" and "standard deviation of diameter of CNT (σ: sample standard deviation)" are the diameters of 100 CNTs randomly selected using a transmission electron microscope (outer diameter ) can be obtained by measuring The average diameter (Av) and standard deviation (σ) of CNTs may be adjusted by changing the CNT production method or production conditions, or by combining multiple types of CNTs obtained by different production methods. You may
The single-walled CNTs used in the present invention preferably have a BET specific surface area of 600 m ² /g or more, more preferably 800 m ² /g or more, preferably 2000 m ² /g or less, and 1600 m 2 /g or more. ² /g or less is more preferable. When the BET specific surface area of the single-walled CNT is 600 m ² /g or more, the physical properties of the compact can be further improved. Moreover, when the BET specific surface area of the single-walled CNTs is 2000 m ² /g or less, the single-walled CNTs can be satisfactorily dispersed in the compact. Therefore, if the BET specific surface area of the single-walled CNTs is within the above range, it is possible to further improve the extensibility at high temperatures of the molded article formed using the fluororubber composition.

The average length of the single-walled CNTs used in the present invention is preferably 10 µm or longer, more preferably 15 µm or longer, and even more preferably 20 µm or longer. If the average length of the single-walled CNTs is 10 μm or more, it is possible to further improve the extensibility at high temperatures of the molded article formed using the fluororubber composition. Although the upper limit of the average length of single-walled CNTs is not particularly limited, it is usually 800 μm or less.
Here, the average length of single-walled CNTs can be obtained by measuring the length of 100 single-walled CNTs and calculating the average value thereof. A scanning electron microscope (SEM) or known image processing can be used for observation of single-walled CNTs.
In particular, the average length of the single-walled CNTs contained in the fluororubber composition is obtained by measuring the length of 100 single-walled CNTs as described above after removing the rubber component such as the fluororubber from the fluororubber composition. , can be obtained as the average value. The method for removing the rubber component from the fluororubber composition is not particularly limited. For example, after burning the rubber component in the fluororubber composition, a solvent is added to the resulting ash to elute the single-walled CNTs, and the individual single-walled CNTs are obtained by coating the surface of the substrate for observation. Observable state.

Single-walled CNTs having the properties described above can be produced, for example, by chemical vapor deposition (CVD) by supplying a raw material compound and a carrier gas onto a substrate having a catalyst layer for CNT production on its surface. A method of dramatically improving the catalytic activity of the catalyst layer by allowing a small amount of oxidizing agent (catalyst activating substance) to exist in the system when synthesizing CNTs (super-growth method; International Publication No. 2006/011655 ), the formation of the catalyst layer on the substrate surface by a wet process enables efficient production. In addition, below, the carbon nanotube obtained by the super growth method may be called "SGCNT."

In addition, the content of single-walled CNTs in the fluororubber composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, per 100 parts by mass of the fluororubber. It is more preferably 2 parts by mass or more, particularly preferably 2 parts by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 6 parts by mass or less. It is preferably 4 parts by mass or less, and particularly preferably 4 parts by mass or less. If the content of the single-walled CNTs in the fluororubber composition is 0.1 parts by mass or more per 100 parts by mass of the fluororubber, the extensibility of the molded article at high temperatures can be further improved. On the other hand, if the content of the single-walled CNTs in the fluororubber composition is 10 parts by mass or less per 100 parts by mass of the fluororubber, it is possible to suppress the increase in viscosity of the fluororubber composition and to ensure sufficient workability.

<<CNT aggregate>>
Carbon nanotubes in the form of CNT aggregates may also be used. As the CNTs in the form of CNT aggregates, for example, CNT aggregates satisfying at least one of conditions (1) to (3) described later can be used.

Here, as the CNT aggregate used when forming the fluororubber composition, it is preferable to use a CNT aggregate that satisfies at least one of the following conditions (1) to (3).

(1) A spectrum obtained by Fourier transform infrared spectroscopic analysis of a carbon nanotube dispersion obtained by dispersing a carbon nanotube aggregate so that the bundle length is 10 μm or more, the plasmon resonance of the carbon nanotube dispersion There is at least one peak in the wave number range of more than 300 cm ⁻¹ to 2000 cm ⁻¹ or less.
(2) For carbon nanotube aggregates, from the adsorption isotherm of liquid nitrogen at 77 K, based on the Barrett-Joyner-Halenda method, in the pore distribution curve showing the relationship between the pore diameter and the Log differential pore volume The largest peak is in the range of pore sizes greater than 100 nm and less than 400 nm.
(3) At least one peak in the two-dimensional spatial frequency spectrum of the electron microscope image of the aggregate of carbon nanotubes exists in the range of 1 μm ⁻¹ to 100 μm ⁻¹ .

Each of the above conditions (1) to (3) will be described in detail.

[Condition (1)]
The condition (1) is "a carbon nanotube dispersion obtained by dispersing aggregates of carbon nanotubes so that the bundle length is 10 μm or more. In the spectrum obtained by Fourier transform infrared spectroscopic analysis, the carbon nanotube dispersion At least one peak based on the plasmon resonance of is present in the wavenumber range of more than 300 cm ⁻¹ and 2000 cm ⁻¹ or less.”. Here, a strong absorption characteristic in the far-infrared region has been widely known as an optical characteristic of CNTs. Such strong absorption properties in the far-infrared region are believed to be due to the diameter and length of CNTs. The absorption characteristics in the far-infrared region, more specifically, the relationship between the peak based on plasmon resonance of CNT and the length of CNT, is described in non-patent literature (T. Morimoto et al., "Length-Dependent Plasmon Resonance in Single-Walled Carbon Nanotubes”, pp 9897-9904, Vol.8, No.10, ACS NANO, 2014).

In condition (1), the peak based on the plasmon resonance of CNT preferably exists in the wave number range of more than 2000 cm ^-1 ^or less, more preferably in the wave number range of 500 cm ^-1 or more and 2000 cm ^-1 or less. It is more preferable that the wave number is in the range of 700 cm ⁻¹ or more and 2000 cm ⁻¹ or less.

In the spectrum obtained by Fourier transform infrared spectroscopic analysis of the CNT aggregate, wavenumbers around 840 cm ⁻¹ , 1300 cm ⁻¹ , and 1700 cm ⁻¹ in addition to relatively gentle peaks based on the plasmon resonance of the CNT dispersion , a sharp peak may be observed. These sharp peaks do not correspond to "peaks based on plasmon resonance of carbon nanotube dispersion", and each corresponds to infrared absorption derived from functional groups. More specifically, the sharp peak near wavenumber 840 ^cm is attributed to CH out-of-plane bending vibration; the sharp peak near wavenumber 1300 ^cm is attributed to epoxy three-membered ring stretching vibration; wavenumber 1700 cm. The sharp peak near ^-1 is attributed to C=O stretching vibration. In addition, in the region of wave numbers exceeding 2000 cm ⁻¹ , apart from the plasmon resonance, the above-mentioned T.M. As mentioned in the non-patent literature by Morimoto et al., a peak similar to the S1 peak is detected, so the upper limit for determining the presence or absence of a peak based on plasmon resonance of the CNT dispersion under condition (1) is 2000 ^-1 cm or less. can be

Here, in condition (1), in obtaining a spectrum by Fourier transform infrared spectroscopy, it is necessary to obtain a CNT dispersion by dispersing the CNT aggregates so that the bundle length is 10 μm or more. Here, for example, a CNT aggregate, water, and a surfactant (for example, sodium dodecylbenzenesulfonate) are blended in an appropriate ratio, and stirred for a predetermined period of time using ultrasonic waves or the like to form a bundle in water. A dispersion liquid in which CNT dispersions having a length of 10 μm or more are dispersed can be obtained.

The bundle length of the CNT dispersion can be obtained by analyzing it with a wet image analysis type particle size measuring device. Such a measuring device calculates the area of each dispersion from the image obtained by photographing the CNT dispersion, and the diameter of the circle having the calculated area (hereinafter also referred to as the ISO area diameter). ) can be obtained. In this specification, the bundle length of each dispersion is defined as the value of the ISO circle diameter thus obtained.

[Condition (2)]
Condition (2) defines that "the maximum peak in the pore distribution curve is in the range of pore diameters greater than 100 nm and less than 400 nm." The pore size distribution of the aggregate of carbon nanotubes can be determined based on the Barrett-Joyner-Halenda method (BJH method) from the adsorption isotherm of liquid nitrogen at 77K. The fact that the peak in the pore distribution curve obtained by measuring the carbon nanotube aggregate is in the range of more than 100 nm means that there are voids of a certain size between the CNTs in the carbon nanotube aggregate, and the CNTs are It means that it is not in an excessively densely agglomerated state. Note that the upper limit of 400 nm is the measurement limit when, for example, BELSORP-mini II is used as a measurement device.

[Condition (3)]
Condition (3) stipulates that "at least one peak in the two-dimensional spatial frequency spectrum of the electron microscope image of the aggregate of carbon nanotubes exists in the range of 1 μm ^-1 to 100 μm ^-1 ". The sufficiency of such conditions can be determined in the following manner. First, the CNT aggregate to be determined is magnified (e.g., 10,000 times) using an electron microscope (e.g., field emission scanning electron microscope), and a plurality of electron microscope images ( For example, 10 sheets) are obtained. A plurality of electron microscope images obtained are subjected to fast Fourier transform (FFT) processing to obtain a two-dimensional spatial frequency spectrum. A two-dimensional spatial frequency spectrum obtained for each of a plurality of electron microscope images is binarized to obtain an average value of peak positions appearing on the highest frequency side. If the average value of the obtained peak positions is within the range of 1 μm ⁻¹ or more and 100 μm ⁻¹ or less, it can be determined that the condition (3) is satisfied. Here, as the "peak" used in the above determination, a clear peak obtained by executing the isolated point extraction process (that is, the inverse operation of the isolated point removal) is used. Therefore, if a clear peak is not obtained within the range of 1 μm ⁻¹ to 100 μm ⁻¹ when performing the isolated point extraction process, it can be determined that the condition (3) is not satisfied.

Here, it is preferable that the peak of the two-dimensional spatial frequency spectrum exists in the range of 2.6 μm ⁻¹ or more and 100 μm ^{−1 or} less. The CNT aggregate preferably satisfies at least two of the above conditions (1) to (3), and more preferably satisfies all of the conditions (1) to (3).

[Other properties]
The CNT aggregate that can be used in producing the fluororubber composition of the present invention preferably has the following properties in addition to the above conditions (1) to (3).

The tap bulk density of the CNT aggregate is preferably 0.001 g/cm ³ or more and 0.2 g/cm ³ or less. A CNT aggregate having such a density range does not excessively strengthen the bonds between CNTs, so that it is excellent in dispersibility and can be molded into various shapes. If the tapped bulk density of the CNT aggregate is 0.2 g/cm ³ or less, the bonds between the CNTs become weak, so that when the CNT aggregate is stirred in a solvent or the like, it becomes easy to uniformly disperse it. Further, when the tap bulk density of the CNT aggregate is 0.001 g/cm ³ or more, the integrity of the CNT aggregate is improved and handling is facilitated. The tapped bulk density is the apparent bulk density in a state in which the powdery CNT aggregate is filled in a container, and then the voids between the powder particles are reduced by tapping or vibration, etc., to close-pack.

[Method for producing CNT aggregate]
A method for producing a CNT aggregate is not particularly limited, and production conditions can be adjusted according to desired properties. For example, a CNT aggregate that satisfies at least one of the above conditions (1) to (3) can be produced, for example, according to the method described in WO2021/172078.

<Multi-walled carbon nanotube>
The fluororubber composition of the present invention preferably contains, as CNTs, multi-walled CNTs in addition to the single-walled CNTs described above. A fluororubber composition containing both single-walled CNTs and multi-walled CNTs ensures sufficient processability, and according to the fluororubber composition, it is possible to form a molded article that can exhibit even better extensibility at high temperatures. can be done.

Here, the multilayer CNT preferably has a BET specific surface area of 50 m ² /g or more, more preferably 150 m ² /g or more, preferably 800 m ² /g or less, and 500 m ² /g or less. It is more preferable to have If the BET specific surface area of the multi-layered CNT is within the above range, it is possible to further improve the extensibility at high temperatures of the molded article formed using the fluororubber composition.

Then, multilayer CNTs having the properties described above can be produced by known methods.

Here, the content of the multilayer CNT in the fluororubber composition is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and 3 parts by mass or more per 100 parts by mass of the fluororubber. more preferably 4 parts by mass or more, particularly preferably 5 parts by mass or more, preferably 15 parts by mass or less, more preferably 12 parts by mass or less, It is more preferably 8 parts by mass or less, and particularly preferably 6 parts by mass or less. If the content of multi-walled CNTs in the fluororubber composition is 0.5 parts by mass or more per 100 parts by mass of the fluororubber, the extensibility of the molded article at high temperatures can be further improved. On the other hand, if the content of multi-walled CNTs in the fluororubber composition is 15 parts by mass or less per 100 parts by mass of the fluororubber, thickening of the fluororubber composition can be suppressed to ensure sufficient workability.

In addition, the ratio of the multi-walled CNTs to the total CNTs in the fluororubber composition is 40% by mass or more, with the mass of the entire CNTs (that is, the sum of the mass of the single-walled CNTs and the multi-walled CNTs) being 100% by mass. preferably 50% by mass or more, more preferably 60% by mass or more, particularly preferably 70% by mass or more, preferably 95% by mass or less, 91% by mass % or less, more preferably 90 mass % or less, even more preferably 85 mass % or less, and particularly preferably 80 mass % or less. If the proportion of multilayer CNTs in the total CNTs is 40% by mass or more, the extensibility of the molded article at high temperatures can be further improved. On the other hand, if the ratio of multi-walled CNTs to the total CNTs is 95% by mass or less, it is possible to suppress thickening of the fluororubber composition and sufficiently ensure workability.

<Reinforcing filler>
The fluororubber composition of the present invention preferably contains a reinforcing filler from the viewpoint of further improving the extensibility of the molded article at high temperatures.

Examples of reinforcing fillers include carbon black, graphene, graphite, and silica. Among these, carbon black and silica are preferable from the viewpoint of further improving the extensibility of the molded article at high temperatures. Carbon black is more preferable from the viewpoint of further improving extensibility of molded articles at high temperatures while sufficiently ensuring workability by suppressing thickening of the fluororubber composition.
The reinforcing filler may be used singly or in combination of two or more.

Examples of carbon black include furnace black, acetylene black, thermal black, channel black, and ketjen black. The particle size of carbon black is not particularly limited, and can be within the known particle size range of carbon black.

Examples of silica include colloidal silica, wet silica, amorphous silica, fumed silica, silica sol, and silica gel. The surface of silica may be modified with functional functional groups such as hydrophilicity and hydrophobicity. In addition, the particle size of silica is not particularly limited, and can be within the range of known silica particle sizes.

Here, the content of the reinforcing filler in the fluororubber composition is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and 6 parts by mass or more per 100 parts by mass of the fluororubber. more preferably 8 parts by mass or more, preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 30 parts by mass or less. If the content of the reinforcing filler in the fluororubber composition is 1 part by mass or more per 100 parts by mass of the fluororubber, the extensibility of the molded article at high temperatures can be further improved. On the other hand, if the content of the reinforcing filler in the fluororubber composition is 40 parts by mass or less per 100 parts by mass of the fluororubber, thickening of the fluororubber composition can be suppressed to ensure sufficient workability.

<Crosslinking agent>
The cross-linking agent that the fluororubber composition of the present invention may optionally contain is not particularly limited. Specifically, as the cross-linking agent, a known cross-linking agent capable of cross-linking the fluororubber contained in the fluororubber composition can be used. More specifically, examples of cross-linking agents include peroxide-based cross-linking agents (2,5-dimethyl-2,5-di(t-butylperoxy)hexane, etc.), triallyl isocyanurate, bisphenol AF (4, 4'-(Hexafluoroisopropylidene)diphenol), bisphenol A and the like can be used.
In addition, these crosslinking agents may be used individually by 1 type, and may be used in combination of 2 or more type. The content of the cross-linking agent in the fluororubber composition of the present invention is not particularly limited, but is preferably 1 part by mass or more, more preferably 3 parts by mass or more per 100 parts by mass of the fluororubber. , more preferably 5 parts by mass or more, preferably 15 parts by mass or less, and more preferably 10 parts by mass or less.

<Other ingredients>
Components other than the fluororubber, single-walled CNTs, multi-walled CNTs, reinforcing fillers, and cross-linking agents (other components) that the fluororubber composition of the present invention may optionally contain include, for example, rubbers other than fluororubbers, Additives are included.
Rubber other than fluororubber is not particularly limited. Rubber (IR), natural rubber (NR), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), and their hydrides (hydrogenated acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-isoprene rubber, hydrogenated acrylonitrile- butadiene-isoprene rubber, hydrogenated styrene-butadiene rubber, hydrogenated butadiene rubber, hydrogenated isoprene rubber, hydrogenated natural rubber, hydrogenated ethylene-propylene-diene rubber, hydrogenated butyl rubber). The content of the rubber other than the fluororubber in the fluororubber composition is not particularly limited, and can be appropriately set according to the use of the fluororubber composition.
Examples of additives include, but are not limited to, cross-linking aids, acid acceptors, dispersants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, pigments, colorants, foaming agents, and antistatic agents. , flame retardants, lubricants, softeners, tackifiers, plasticizers, mold release agents, deodorants, perfumes, and other known additives that can be blended in fluororubber compositions can be used. The content of the additive in the fluororubber composition is not particularly limited, and may be the amount normally used in known fluororubber compositions.
Moreover, the fluororubber composition of the present invention may contain a compound A described later as another component.
In addition, another component may be used individually by 1 type, and may be used in combination of 2 or more type.

<γG ^* >
As described above, the fluororubber composition of the present invention has a γG ^* calculated as a ratio of a complex elastic modulus (dynamic strain: 0.1%) to a complex elastic modulus (dynamic strain: 630%) of 20 or more. It is preferably 24 or more, more preferably 30 or more, and even more preferably 35 or more. If γG ^* is less than 20, it is presumed that the network structure composed of single-walled CNTs and the like is not well formed in the fluororubber composition, and the extensibility of the molded article at high temperatures is reduced. . Although the upper limit of γG ^* is not particularly limited, it can be set to 150 or less, for example.
Here, γG ^* of the fluororubber composition can be controlled by changing the type and/or content of the fluororubber, single-walled CNTs, multi-walled CNTs, and/or reinforcing filler in the fluororubber composition. can. In addition, γG ^* of the fluororubber composition can be improved by producing the fluororubber composition using the method described later in the section <Production method of fluororubber composition>.

<Tensile strength ratio>
Further, when the fluororubber composition of the present invention contains a reinforcing filler and a cross-linking agent, the tensile strength T _X (MPa) of the cross-linked rubber sheet X obtained by cross-linking the rubber composition, and the carbon A test rubber composition excluding nanotubes and a reinforcing filler (that is, a fluororubber composition containing at least a fluororubber, CNTs, a reinforcing filler, and a cross-linking agent, excluding CNTs and a reinforcing filler. The ratio of the tensile strength T _Y (MPa) of the crosslinked rubber sheet Y obtained by crosslinking the material) is expressed by the following formula (II):
Tensile strength ratio = T _X /T _Y (II)
The tensile strength ratio calculated by is preferably 3.0 or more, more preferably 3.5 or more, even more preferably 4.0 or more, especially 4.5 or more preferable. As described above, the tensile strength ratio calculated by the above formula (II) is the ratio of the tensile strength of the crosslinked rubber sheet containing CNTs and reinforcing filler to the tensile strength of the crosslinked rubber sheet not containing CNTs and reinforcing filler. The higher the tensile strength ratio, the higher the durability of the molded article obtained using the fluororubber composition. In addition, since the durability is improved, it becomes possible to reduce the size of various members composed of the molded article.
Although the upper limit of the tensile strength ratio calculated by the above formula (II) is not particularly limited, it can be, for example, 10.0 or less.
Here, the tensile strength ratio of the fluororubber composition can be controlled by changing the types and/or contents of single-walled CNTs, multi-walled CNTs, and/or reinforcing fillers in the fluororubber composition. Further, the tensile strength ratio of the fluororubber composition can be improved by producing the fluororubber composition using the method described later in the section <Production method of fluororubber composition>.

<Method for producing fluororubber composition>
The fluororubber composition of the present invention, which contains at least fluororubber and single-walled CNTs and has γG ^* equal to or greater than the above-mentioned value, contains, for example, fluororubber and single-walled CNTs, and optionally compound A described later. A step of preparing a masterbatch (masterbatch preparation step), and optionally selected from the group consisting of the masterbatch, multi-walled CNTs, reinforcing fillers, cross-linking agents, and other components (excluding compound A) Through a step of kneading at least one of them (kneading step), it can be produced efficiently.

<<Master batch preparation process>>
The masterbatch is preferably prepared by the following preparation method (i) or (ii). Since single-walled CNTs have a small outer diameter, they are easily bundled (easily bundled). On the other hand, by using the following preparation method (i) or (ii), the bundle structure of single-walled CNTs can be fibrillated and the single-walled CNTs can be well dispersed in the fluororubber. By dispersing the single-walled CNTs, it is speculated that a network structure such as the above-described single-walled CNTs can be formed satisfactorily.
(i) A method of subjecting a composition containing fluororubber, single-walled CNTs and a solvent to dispersion treatment using a bead mill and removing the solvent from the composition after dispersion treatment.
(ii) A method of mixing single-walled CNTs with compound A and subjecting a composition containing the resulting mixture and fluororubber to dispersion treatment.
Here, compound A has a Hansen Solubility Parameter distance R1 of 6.0 MPa ^1/2 or less from single-walled CNT, a Hansen Solubility Parameter distance R2 of fluororubber greater than R1, and a freezing point of 40°C. The following are organic compounds.

[Masterbatch preparation method (i)]
In preparation method (i), as described above, a composition containing fluororubber, single-walled CNTs and a solvent is subjected to dispersion treatment using a bead mill, and the dispersion medium is removed from the composition after dispersion treatment to obtain a master. get a batch.
When obtaining a composition containing fluororubber, single-walled CNTs and a solvent, the multi-walled CNTs, reinforcing filler, cross-linking agent and/or other components (excluding compound A) may optionally be added to the fluororubber and single-walled CNTs. and a solvent to be contained in the composition, but these are preferably added to the masterbatch in the kneading step described later.

As the solvent used in the preparation method (i), a solvent capable of dissolving the fluororubber and dispersing the single-walled CNTs is preferably used. Methyl ethyl ketone is preferred as such a solvent. In addition, a solvent may be used individually by 1 type, and may be used in combination of 2 or more type.

The fluororubber and single-walled CNTs are added to the above solvent, and the resulting composition is subjected to dispersion treatment by bead building. The conditions of the dispersion treatment (the number of passes, the properties of the dispersion media to be used, etc.) are not particularly limited, and can be appropriately set from the viewpoint of dispersing the single-walled CNTs well in the solvent.
When preparing a composition containing fluororubber, single-walled CNTs, and a solvent, it is preferable to dissolve the fluororubber in a solvent to prepare a fluororubber solution, and then add the single-walled CNTs to the fluororubber solution.

The method for removing the solvent from the composition after dispersion treatment is not particularly limited, and known methods such as coagulation, casting, and drying can be used.

[Masterbatch preparation method (ii)]
In the preparation method (ii), as described above, the single-walled CNTs and the compound A are mixed to prepare a mixture, and the composition containing the obtained mixture and the fluororubber is subjected to a dispersion treatment to prepare a masterbatch. get

Here, compound A has a freezing point of 40° C. or lower. Further, the distance R1 of the Hansen solubility parameter between the single-walled CNT and the compound A is 6.0 MPa ^1/2 or less, and the distance R2 of the Hansen solubility parameter between the fluororubber and the compound A is larger than R1. A masterbatch in which single-walled CNTs are satisfactorily dispersed can be obtained by setting the freezing point of compound A to the above value or less, and having the above relationship between the single-walled CNTs, the fluororubber, and the Hansen solubility parameter of compound A. . The reason for this is not clear, but is presumed to be as follows.
First, compound A has sufficient fluidity because it has a freezing point of 40° C. or lower. Then, since the value of R1 is equal to or less than the predetermined value, the compound A has excellent affinity with the single-walled CNT, and the compound A, which has excellent fluidity, is impregnated inside the bundle structure of the single-walled CNT. Promotes disentanglement of the bundle structure. In addition, since the value of R2 is larger than the value of R1, compound A can have a better affinity with single-walled CNTs than fluororubber, and the presence of fluororubber causes the above-mentioned compound A to excessively defibrate the bundle structure. It does not interfere with Therefore, it is considered that the bundle structure of single-walled CNTs can be sufficiently fibrillated and the single-walled CNTs can be well dispersed in the fluororubber.

-freezing point-
The “freezing point” of compound A must be 40° C. or lower as described above, and is preferably 35° C. or lower from the viewpoint of ensuring the fluidity of compound A more sufficiently.
Although the lower limit of the freezing point of compound A is not particularly limited, it can be, for example, 5°C or higher.
In addition, the "freezing point" of compound A is a value measured by the following method.
That is, the sample is sealed in an aluminum cell, the aluminum cell is inserted into a sample holder of a differential scanning calorimeter (manufactured by Hitachi High-Tech Science, product name "DSC7000X"), and the sample holder is heated at 10 ° C. in a nitrogen atmosphere. An endothermic peak is observed while heating up to 150° C./min, and the obtained endothermic peak can be taken as the freezing point of the sample.

-Distance R1 of Hansen Solubility Parameter-
The distance R1 of the Hansen solubility parameter between compound A and single-walled CNTs must be 6.0 MPa ^1/2 or less as described above, preferably 5.5 MPa ^1/2 or less. It is more preferably 0 MPa ^1/2 or less, further preferably 4.5 MPa ^1/2 or less, even more preferably 4.0 MPa ^1/2 or less, and 3.5 MPa ^1/2 or less. is particularly preferred. It is speculated that if R1 is 6.0 MPa ^1/2 or less, the affinity of compound A with single-walled CNTs is improved, and compound A easily impregnates inside the bulk structure of single-walled CNTs. Layer CNTs can be well dispersed in the fluororubber.
The lower limit of the value of R1 is not particularly limited, but it is preferably 0.5 MPa ^1/2 or more, more preferably 1.0 MPa ^1/2 or more.

The distance R1 (MPa ^1/2 ) of the Hansen solubility parameter between single-walled CNT and compound A can be calculated using the following formula (III).
R1={4×(δ _d3 −δ _d2 ) ² +(δ _p3 −δ _p2 ) ² +(δ _h3 −δ _h2 ) ² } ^1/2 (III)
δ _d2 : Dispersion term of compound A δ _d3 : Dispersion term of single-walled CNT δ _p2 : Polarity term of compound A δ _p3 : Polarity term of single-walled CNT δ _h2 : Hydrogen bond term of compound A δ _h3 : Single-walled CNT hydrogen bond term

-Distance R2 of Hansen Solubility Parameter-
Moreover, the distance R2 of the Hansen solubility parameter between the compound A and the fluororubber must be larger than R1 as described above. If R2 is R1 or more, compound A does not excessively increase affinity with the fluororubber, and it is presumed that the inside of the CNT bulk structure is easily impregnated. can be well dispersed in

Specifically, R2 is preferably 4.0 MPa ^1/2 or more, more preferably 4.5 MPa ^{1/2 or} more, and still more preferably more than 5.5 MPa ^1/2 . It is more preferably 0 MPa ^1/2 or more, particularly preferably 7.0 MPa ^1/2 or more, preferably 16.0 MPa ^1/2 or less, and preferably 9.0 MPa ^1/2 or less. more preferred. If R2 is within the above range, the single-walled CNTs can be dispersed more favorably in the fluororubber.

The distance R2 of the Hansen solubility parameter between the fluororubber and the compound A can be calculated using the following formula (IV).
R2={4×(δ _d1 −δ _d2 ) ² +(δ _p1 −δ _p2 ) ² +(δ _h1 −δ _h2 ) ² } ^1/2 (IV)
δ _d1 : Dispersion term of fluororubber δ _d2 : Dispersion term of compound A δ _p1 : Polarity term of fluororubber δ _p2 : Polarity term of compound A δ _h1 : Hydrogen bond term of fluororubber δ _h2 : Hydrogen bond term of compound A

The definition and calculation method of the Hansen solubility parameter are described in the following document. Charles M. Hansen, "Hansen Solubility Parameters: A Users Handbook", CRC Press, 2007.

For substances whose literature value of Hansen solubility parameter is unknown, the Hansen solubility parameter can be easily estimated from the chemical structure by using computer software (Hansen Solubility Parameters in Practice (HSPiP)).
Specifically, for example, using HSPiP version 3, the values are used for compounds registered in the database, and the estimated values are used for compounds that are not registered.

-Specific examples of compound A-
Here, the compound A is not particularly limited as long as it has a freezing point equal to or lower than the above-described value and satisfies the above-described conditions regarding the distance of the Hansen Solubility Parameter, and any organic compound can be used. As the compound A, for example, an ester compound having a cyclic hydrocarbon (a compound having a cyclic hydrocarbon and an ester group) is preferable, an ester compound having an aromatic ring is more preferable, and an ester compound having a benzene ring is still more preferable. Phenyl ester compounds are more preferred.
Specific examples of compounds having cyclic hydrocarbons include methyl p-toluate (methyl 4-methylbenzoate), methyl o-toluate (methyl 2-methylbenzoate), methyl benzoate, and benzoic acid. benzoic acid ester compounds such as benzyl and phenyl benzoate; alkyl 3-phenylpropionates such as methyl 3-phenylpropionate; and ethyl cinnamate.
Among these, methyl o-toluate is particularly preferred.
In addition, compound A can be used individually by 1 type or in mixture of 2 or more types.

- Amount of compound A used -
Although the amount of compound A used is not particularly limited, it should be 0.1 parts by mass or more per 100 parts by mass of the fluororubber used for preparing the masterbatch from the viewpoint of better dispersing the single-walled CNTs in the fluororubber. is preferably 1 part by mass or more, more preferably 5 parts by mass or more, particularly preferably 10 parts by mass or more, preferably 60 parts by mass or less, and 40 parts by mass or less is more preferably 35 parts by mass or less, and particularly preferably 30 parts by mass or less.

- Mixture of single-walled CNT and compound A -
When mixing single-walled CNTs and compound A to obtain a mixture, optionally, multi-walled CNTs, reinforcing fillers, cross-linking agents and/or other components (excluding compound A) are mixed with single-walled CNTs and compound A. These may be added to the mixture as a mixture, but it is preferable to add them to the masterbatch in the kneading step described later.
In addition, single-walled CNTs and compound A are usually mixed in the absence of fluororubber.

Here, the mixing of the single-walled CNT and the compound A is not particularly limited. Any mixing method such as application of A or spraying of compound A onto single-walled CNTs can be used. Above all, from the viewpoint of better dispersing the single-walled CNTs in the later-described dispersion treatment, it is preferable to mix the single-walled CNTs with the compound A by impregnating the single-walled CNTs with the compound A.

The time for which the compound A is impregnated into the single-walled CNTs can be any time, but from the viewpoint of dispersing the single-walled CNTs even better in the dispersion treatment described later, it is preferably at least 1 hour, and at least 10 hours. more preferred.
Moreover, the temperature at which the single-walled CNTs are impregnated with the compound A is not particularly limited.
Impregnation of single-walled CNTs with compound A is not particularly limited, but is usually performed under normal pressure (1 atm).

- Distributed processing -
A dispersion treatment is applied to a composition containing the mixture obtained by mixing the single-walled CNTs and the compound A as described above and the fluororubber.
In the dispersion treatment, the composition may optionally contain multi-walled CNTs, reinforcing fillers, cross-linking agents and/or other components (excluding compound A). It is preferably added to a masterbatch.

The dispersion treatment is not particularly limited as long as the single-walled CNTs can be dispersed in the fluororubber, and any known dispersion treatment can be used. Such dispersion treatment includes, for example, dispersion treatment by shear stress, dispersion treatment by collision energy, and dispersion treatment by which a cavitation effect is obtained.

Apparatuses that can be used for dispersion treatment using shear stress include a two-roll mill, a three-roll mill, a kneader, a rotor/stator type disperser, and the like.
Apparatuses that can be used for dispersion treatment by collision energy include bead mills, ball mills, and the like.
A jet mill, an ultrasonic disperser, and the like can be used as devices that can be used for the dispersion treatment to obtain the cavitation effect.

The conditions for the dispersion processing are not particularly limited, and can be set as appropriate within the range of normal dispersion conditions for the above-described apparatus, for example.

<< Kneading process >>
The masterbatch obtained in the above masterbatch preparation step may be used as it is as the fluororubber composition of the present invention, but in addition to single-walled CNTs and fluororubber, multi-layered CNTs, a cross-linking agent, and / or other components ( When preparing a fluororubber composition containing the above-described compound A), it is preferable to knead these components with the masterbatch obtained as described above. Further, in the kneading step, a fluororubber may be additionally added to the masterbatch.
For kneading, for example, a mixer, single-screw kneader, twin-screw kneader, roll, Brabender, extruder, or the like can be used. Kneading conditions can be appropriately adjusted.
In the kneading step, when multi-layer CNT and/or reinforcing filler and a cross-linking agent are used, the masterbatch and multi-layer CNT and/or reinforcing filler are first kneaded, and then the resulting mixture and cross-linking agent are mixed. is preferable from the viewpoint that γG ^* can be well controlled within the desired range.

(Molded body)
The molded article of the present invention is formed using the fluororubber composition of the present invention containing the cross-linking agent described above. And since the molded article of the present invention is formed from the fluororubber composition of the present invention, it is excellent in extensibility at high temperatures.
Here, the use of the molded article of the present invention is not particularly limited. The molded article of the present invention can be suitably used, for example, as a sealing material for oil gas or as an engine peripheral member. Further, the shape of the molded article of the present invention can be appropriately set according to the application.

The molding method for obtaining a molded article by molding the fluororubber composition is not particularly limited, and any molding method such as injection molding, extrusion molding, press molding, roll molding, etc. may be used. can be done.

EXAMPLES The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.
In the examples and comparative examples, various measurements and evaluations were performed as follows.

<γG ^* >
The obtained fluororubber composition was measured using a dynamic viscoelasticity measuring device "Rubber Process Analyzer" (manufactured by Alpha Technology, model: Premier RPA) under the conditions of measurement frequency: 1 Hz and measurement temperature: 40 ° C. A viscoelasticity test was performed. Then, the complex elastic modulus G ^* _L (kPa) at a dynamic strain of 0.1% and the complex elastic modulus G ^* _H (kPa) at a dynamic strain of 630% were measured.
Using the obtained G ^* _L and G ^* _H , the following formula (I)
γG ^* =G ^* _L /G ^* _H (I)
to calculate γG ^* .
<Tensile strength ratio>
The obtained fluororubber composition was subjected to primary cross-linking at a temperature of 160° C. and a pressure of 10 MPa for 20 minutes. Then, it was heated in a gear oven at 232° C. for 2 hours for secondary crosslinking to obtain a crosslinked rubber sheet X (length: 150 mm, width: 150 mm, thickness: 2 mm).
This crosslinked rubber sheet X was punched into a dumbbell test piece (JIS No. 3) to prepare a test piece X. Using a tensile tester (Strograph VG, manufactured by Toyo Seiki Co., Ltd.), in accordance with JIS K6251: 2010, test temperature: 200 ° C., test humidity: 50%, tensile speed: 500 ± 50 mm / min Tensile test. and measured the tensile strength (value obtained by dividing the maximum tensile force (N) recorded when the test piece was pulled to break by the initial cross-sectional area (m ² ) of the test piece). This tensile strength was defined as T _X (MPa).
Separately, the fluororubber, the crosslinker, and the additive (acid acceptor) are mixed at the same mass ratio as the mass ratio of the fluororubber: crosslinker: additive (acid acceptor) contained in the above-described fluororubber composition. ) to prepare a test rubber composition. That is, the test rubber composition corresponds to a composition obtained by removing the CNTs and the reinforcing filler from the fluororubber composition containing the cross-linking agent.
The resulting test rubber composition was subjected to primary cross-linking and secondary cross-linking in the same manner as in the preparation of the cross-linked rubber sheet X to obtain a cross-linked rubber sheet Y.
This crosslinked rubber sheet Y was punched into a dumbbell test piece (JIS No. 3) to prepare a test piece Y. The tensile strength of the test piece Y was measured in the same manner as when the tensile strength T _X of the test piece X was measured. This tensile strength was defined as T _Y (MPa).
Using the obtained tensile strength T _X and tensile strength T _Y , the following formula (II):
Tensile strength ratio = T _X /T _Y (II)
to calculate the tensile strength ratio.
<Extensibility at high temperature (tensile strength)>
It was evaluated by the tensile strength T _X in the "tensile strength ratio" described above. The larger the value of the tensile strength _TX , the more excellent the extensibility at high temperatures of the molded article formed using the fluororubber composition.
<Workability (viscosity)>
The complex viscosity at the complex elastic modulus G ^* _L (kPa) at a dynamic strain of 0.1% obtained in deriving γG ^* was evaluated as viscosity (kPa·s). The smaller the viscosity value, the more excellent the processability of the fluororubber composition.

(Example 1)
<Preparation of single-walled CNT>
SGCNTs ("ZEONANO SG101" manufactured by Nippon Zeon Co., Ltd.) were prepared as single-walled CNTs.
In the measurement of SGCNTs with a Raman spectrophotometer, a radial breathing mode (RBM) spectrum was observed in the low wavenumber region of 100 to 300 cm ⁻¹ characteristic of single-walled CNTs. Further, the BET specific surface area of SGCNT measured using a BET specific surface area meter (BELSORP (registered trademark)-max, manufactured by Bell Japan Co., Ltd.) was 1325 m ² /g (unopened). Furthermore, the diameter and length of 100 randomly selected SGCNTs were measured using a transmission electron microscope, and the average diameter (Av) of the SGCNTs, the standard deviation of the diameter (σ) and the average length were obtained. , the average diameter (Av) is 3.5 nm, the standard deviation (σ) multiplied by 3 (3σ) is 2.1 nm, their ratio (3σ/Av) is 0.6, and the average The length was 450 μm. Furthermore, when the t-plot of SGCNT was measured using “BELSORP (registered trademark)-mini” manufactured by Bell Japan Co., Ltd., the t-plot was curved in a convex shape. S2/S1 was 0.09, and the bending point position t was 0.6 nm.
<Preparation of fluororubber composition>
[Preparation of masterbatch]
A masterbatch was prepared as follows by the preparation method (i) described above.
To 1900 g of methyl ethyl ketone as a solvent, 100 g of a vinylidene fluoride rubber (FKM, manufactured by Chemours, product name "Viton GBL-600S") as a fluororubber was added and stirred for 24 hours to dissolve the fluororubber.
Next, 4 g of the above SGCNT was added to the obtained fluororubber solution, and the mixture was stirred for 15 minutes using a stirrer (manufactured by PRIMIX, product name “Labo Solution (registered trademark)”). Furthermore, a bead mill (manufactured by Asada Iron Works, product name “Nanomill (registered trademark) NM-G1.4L”), zirconia beads as dispersion media (Vickers hardness: 1250, filling rate of dispersion media: 52%, average of dispersion media SGCNT-added fluororubber solution was dispersed at a temperature of 45° C. for 6 passes under conditions of a peripheral speed of 12 m/s and a discharge amount of 65 g/min. After that, the resulting dispersed liquid was air-dried to obtain a black solid. The resulting black solid was dried under reduced pressure at 60° C. for 12 hours to obtain a masterbatch, which is a mixture of fluororubber and SGCNT.
[Kneading]
After that, using an open roll at 20 ° C., 104 g of the masterbatch obtained above (fluororubber: 100 g, SGCNT: 4 g), 3 g of zinc white (two types of zinc white) as an acid acceptor, and 3 g of triallyl isocyanurate (manufactured by Mitsubishi Chemical Corporation, "TAIC (registered trademark)") and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (manufactured by NOF Corporation, trade name "Perhexa 25B40") 2 g, and after adjusting the roll interval to 2 mm, the rubber kneaded product is wound around a roll, and after performing left and right turning three times each, sheeting is performed to obtain a fluororubber composition containing a cross-linking agent. got This fluororubber composition was subjected to a dynamic viscoelasticity test to determine γG ^* and viscosity. Table 1 shows the results.
<Preparation of molding (crosslinked rubber sheet)>
The resulting fluororubber composition containing a cross-linking agent was cross-linked under the conditions described above in the <Tensile strength ratio> section to prepare a cross-linked rubber sheet X as a molded article, and the tensile strength _TX was measured. Table 1 shows the results of tensile strength _TX .
Separately, as a fluororubber composition obtained by excluding single-walled CNTs from a fluororubber composition containing a cross-linking agent, vinylidene fluoride-based rubber as a fluororubber, zinc white as an acid acceptor, and triallyl as a cross-linking agent A test rubber composition containing isocyanurate and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane in the same weight ratio as the fluororubber composition containing the cross-linking agent was prepared. The test rubber composition was crosslinked under the conditions described above in the section <Tensile strength ratio> to prepare a crosslinked rubber sheet Y, and the tensile strength _TY was measured. Then, the tensile strength ratio was calculated. Table 1 shows the tensile strength ratio results.

(Example 2)
<Preparation of single-walled CNT>
SGCNTs (Hansen solubility parameters: δ _d3 =19.4, δ _p3 =6.0, δ _h3 =4.5) similar to those in Example 1 were prepared.
<Preparation of fluororubber composition>
[Preparation of masterbatch]
A masterbatch was prepared as follows by the preparation method (ii) described above.
After weighing 26.4 g of single-walled CNTs (4 parts by mass when 660 g of fluororubber described later is taken as 100 parts by mass) in a glass bottle, 158.4 g of methyl o-toluate (freezing point: −50° C. or less) as compound A. Dripped. Then, the single-walled CNTs were allowed to stand in an oven at 40° C. for 12 hours, and the single-walled CNTs were impregnated with o-methyl toluate to obtain a mixture containing the single-walled CNTs and methyl o-toluate.
Next, vinylidene fluoride rubber (FKM, manufactured by Chemours, product name “Viton GBL-600S”, Hansen solubility parameters: δ _d1 =14.7, δ _p1 =9.0, δ _h1 =2. 7)) Add 660 g of the mixture containing the single-walled CNTs and methyl o-toluate to Wonder Kneader (registered trademark) whose jacket temperature is set to 25 ° C., knead (disperse) for 60 minutes, A composite of fluororubber, single-walled CNT and methyl o-toluate was obtained. The resulting composite was cut into pieces of 1 cm square and then dried in a vacuum dryer at 150° C. overnight to obtain a masterbatch.
Note that the distance R1 of the Hansen solubility parameter between the single-walled CNT (SGCNT) and the compound A (methyl o-toluate) is 6.0 MPa ^1/2 or less, and the fluororubber (FKM) and the compound A (methyl o-toluate) ) was greater than the distance R1 of the Hansen solubility parameter.
[Kneading]
A fluororubber composition containing a cross-linking agent was obtained in the same manner as in Example 1 except that the masterbatch obtained above (fluororubber: 100 g, SGCNT: 4 g, the total amount of the masterbatch was adjusted to contain 4 g) was used. rice field. This fluororubber composition was subjected to a dynamic viscoelasticity test to determine γG ^* and viscosity. Table 1 shows the results.
<Preparation of molding (crosslinked rubber sheet)>
The obtained fluororubber composition containing the cross-linking agent was cross-linked in the same manner as in Example 1 to prepare a cross-linked rubber sheet X as a molded article, and the tensile strength _TX was measured. Table 1 shows the results of tensile strength _TX .
Separately, the crosslinked rubber sheet Y prepared in the same manner as in Example 1 was measured to measure the tensile strength _TY . Then, the tensile strength ratio was calculated. Table 1 shows the tensile strength ratio results.

(Example 3)
<Preparation of single-walled CNT>
SGCNTs similar to those in Example 1 were prepared.
<Preparation of fluororubber composition>
[Preparation of masterbatch]
A masterbatch, which is a mixture of fluororubber and SGCNT, was obtained in the same manner as in Example 1.
[Kneading]
Then, using an open roll at 20 ° C., 104 g of the master batch obtained above (fluororubber: 100 g, SGCNT: 4 g) and carbon black as a reinforcing filler (manufactured by Cancarb, product name "Thermax (registered Trademark) MT”) 30 g was kneaded, and the roll interval was adjusted to 2 mm. Furthermore, using an open roll at 20 ° C., 134 g of the sheet obtained above (fluororubber: 100 g, SGCNT: 4 g, carbon black: 30 g) and zinc white (two types of zinc white) as an acid acceptor 3 g , 3 g of triallyl isocyanurate as a cross-linking agent (manufactured by Mitsubishi Chemical Corporation, "TAIC (registered trademark)") and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (manufactured by NOF Corporation, (trade name “Perhexa 25B40”)), and after adjusting the roll interval to 2 mm, the rubber kneaded product is wound around a roll, and after turning left and right three times each, the sheet is taken out to contain a cross-linking agent. A fluororubber composition was obtained. This fluororubber composition was subjected to a dynamic viscoelasticity test to determine γG ^* and viscosity. Table 1 shows the results.
<Preparation of molding (crosslinked rubber sheet)>
The obtained fluororubber composition containing the cross-linking agent was cross-linked in the same manner as in Example 1 to prepare a cross-linked rubber sheet X as a molded article, and the tensile strength _TX was measured. Table 1 shows the results of tensile strength _TX .
Separately, the crosslinked rubber sheet Y prepared in the same manner as in Example 1 was measured to measure the tensile strength _TY . Then, the tensile strength ratio was calculated. Table 1 shows the tensile strength ratio results.

(Example 4)
Single-walled CNTs were prepared in the same manner as in Example 3, except that silica (hydrophobic, manufactured by Evonik, product name "Aerosil (registered trademark) R972V") was used instead of carbon black as the reinforcing filler. A fluororubber composition and a molded article were produced and various evaluations were performed. Table 1 shows the results.

(Example 5)
<Preparation of single-walled CNT>
SGCNTs similar to those in Example 1 were prepared.
<Preparation of fluororubber composition>
[Preparation of masterbatch]
A masterbatch, which is a mixture of fluororubber and SGCNT, was obtained in the same manner as in Example 1.
[Kneading]
Then, using an open roll at 20 ° C., 52 g of the master batch obtained above (fluororubber: 50 g, SGCNT: 2 g) and carbon black as a reinforcing filler (manufactured by Cancarb, product name "Thermax (registered Trademark) MT”) and 50 g of vinylidene fluoride rubber (FKM, manufactured by Chemours, product name “Viton GBL-600S”) as a fluororubber are kneaded, and after adjusting the roll interval to 2 mm, the rubber is kneaded. The material was wound around a roll, and the sheet was taken out after the right and left turnover was performed three times each. Furthermore, using an open roll at 20 ° C., 132 g of the sheet obtained above (fluororubber: 100 g, SGCNT: 2 g, carbon black: 30 g) and 3 g of zinc white (two types of zinc white) as an acid acceptor , 3 g of triallyl isocyanurate as a cross-linking agent (manufactured by Mitsubishi Chemical Corporation, "TAIC (registered trademark)") and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (manufactured by NOF Corporation, (trade name “Perhexa 25B40”)), and after adjusting the roll interval to 2 mm, the rubber kneaded product is wound around a roll, and after turning left and right three times each, the sheet is taken out to contain a cross-linking agent. A fluororubber composition was obtained. This fluororubber composition was subjected to a dynamic viscoelasticity test to determine γG ^* and viscosity. Table 1 shows the results.
<Preparation of molding (crosslinked rubber sheet)>
The obtained fluororubber composition containing the cross-linking agent was cross-linked in the same manner as in Example 1 to prepare a cross-linked rubber sheet X as a molded article, and the tensile strength _TX was measured. Table 1 shows the results of tensile strength _TX .
Separately, the crosslinked rubber sheet Y prepared in the same manner as in Example 1 was measured to measure the tensile strength _TY . Then, the tensile strength ratio was calculated. Table 1 shows the tensile strength ratio results.

(Example 6)
In the same manner as in Example 5, except that 5 g of multi-layered CNT (manufactured by KUMHO, product name “K-nanos 100P”; BET specific surface area: 260 m ² /g) was used instead of 30 g of carbon black as a reinforcing filler. Single-walled CNTs were prepared, fluororubber compositions and moldings were produced, and various evaluations were performed. Table 1 shows the results.

(Example 7)
<Preparation of CNT2>
CNT2 was produced in the CNT synthesis process by a method of supplying raw material gas while continuously conveying a particulate catalyst support by rotating a screw. Specifically, one manufactured in the same manner as in Example 1 of International Publication No. 2021/172078 was used.
The produced CNT2 includes single-walled CNT, and its characteristics are tap bulk density: 0.01 g/cm ³ , CNT average length: 200 μm, BET specific surface area: 800 m ² /g, average outer diameter: 4.0 nm. , carbon purity of 99.6%, and Hansen solubility parameters (δ _d3 =18.7, δ _p3 =4.9, δ _h3 =3.1).
When the obtained CNT aggregate was evaluated in the same manner as in Example 1 of WO 2021/172078,
(1) In the spectrum obtained by Fourier transform infrared spectroscopic analysis of the carbon nanotube dispersion obtained by dispersing it so that the bundle length is 10 μm or more, the peak based on the plasmon resonance of the carbon nanotube dispersion is at a wavenumber of 830 cm. observed at ^-1 ,
(2) For carbon nanotubes, the maximum maximum in the pore distribution curve showing the relationship between the pore diameter and the Log differential pore volume obtained from the adsorption isotherm of liquid nitrogen at 77 K based on the Barrett-Joyner-Halenda method A peak exists within a pore diameter range of more than 100 nm and less than 400 nm,
(3) The peak of the two-dimensional spatial frequency spectrum of the electron microscope image of the carbon nanotube was present at the position of 3.0 μm ⁻¹ .

A masterbatch was obtained in the same manner as in Example 2 except that the above CNT2 was used as the single-walled CNT, a fluororubber composition and a molded body were produced, and various evaluations were performed. Table 1 shows the results.

(Comparative example 1)
<Preparation of single-walled CNT>
Single-walled CNTs similar to those in Example 1 were prepared.
<Preparation of fluororubber composition>
[Preparation of masterbatch]
100 parts by mass of vinylidene fluoride rubber (FKM, manufactured by Chemours, product name “Viton GBL-600S”) as a fluororubber is wound around a water-cooled open roll, and 4 parts by mass of the above-described single-walled CNTs are kneaded (dispersed). , got the masterbatch.
[Kneading]
A fluororubber composition containing a cross-linking agent was obtained in the same manner as in Example 1, except that the masterbatch obtained above was used. This fluororubber composition was subjected to a dynamic viscoelasticity test to determine γG ^* and viscosity. Table 1 shows the results.
<Preparation of molding (crosslinked rubber sheet)>
The obtained fluororubber composition containing the cross-linking agent was cross-linked in the same manner as in Example 1 to prepare a cross-linked rubber sheet X as a molded article, and the tensile strength _TX was measured. Table 1 shows the results of tensile strength _TX .
Separately, a crosslinked rubber sheet Y prepared in the same manner as in Example 1 was measured, and the tensile strength _TY was measured. Then, the tensile strength ratio was calculated. Table 1 shows the tensile strength ratio results.

(Comparative example 2)
Single-walled CNTs were prepared in the same manner as in Example 1 except that the amount of single-walled CNTs was changed from 4 g to 2 g during [preparation of masterbatch], and a fluororubber composition and a molded article were produced, Various evaluations were performed. Table 1 shows the results.

(Comparative Example 3)
<Preparation of fluororubber composition>
Using an open roll at 20° C., 100 g of vinylidene fluoride rubber (Viton GBL-600S, manufactured by Chemours), 3 g of zinc oxide (zinc oxide) as an acid acceptor, and triallyl isocyanate as a cross-linking agent. 3 g of Nurate (manufactured by Mitsubishi Chemical Corporation, "TAIC (registered trademark)") and 2 g of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (manufactured by NOF Corporation, trade name "Perhexa 25B40") , 45 g of carbon black (manufactured by Cancarb, product name "Thermax (registered trademark) MT") as a reinforcing filler, and after adjusting the roll interval to 2 mm, the rubber kneaded product is wound around the roll and turned left and right. 3 times, the sheet was taken out to obtain a fluororubber composition containing a cross-linking agent. This fluororubber composition was subjected to a dynamic viscoelasticity test to determine γG ^* and viscosity. Table 1 shows the results.
<Preparation of molding (crosslinked rubber sheet)>
The obtained fluororubber composition containing the cross-linking agent was cross-linked in the same manner as in Example 1 to prepare a cross-linked rubber sheet X as a molded article, and the tensile strength _TX was measured. Table 1 shows the results of tensile strength _TX .
Separately, the crosslinked rubber sheet Y prepared in the same manner as in Example 1 was measured to measure the tensile strength _TY . Then, the tensile strength ratio was calculated. Table 1 shows the tensile strength ratio results.

(Comparative Example 4)
<Preparation of fluororubber composition>
Using an open roll at 20° C., 100 g of vinylidene fluoride rubber (Viton GBL-600S, manufactured by Chemours), 3 g of zinc oxide (zinc oxide) as an acid acceptor, and triallyl isocyanate as a cross-linking agent. 3 g of Nurate (manufactured by Mitsubishi Chemical Corporation, "TAIC (registered trademark)") and 2 g of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (manufactured by NOF Corporation, trade name "Perhexa 25B40") After kneading and adjusting the roll interval to 2 mm, the rubber kneaded product was wound around a roll, and after performing left and right turning 3 times each, sheeting was performed to obtain a fluororubber composition containing a cross-linking agent. This fluororubber composition was subjected to a dynamic viscoelasticity test to determine γG ^* and viscosity. Table 1 shows the results.
<Preparation of molding (crosslinked rubber sheet)>
The obtained fluororubber composition containing the cross-linking agent was cross-linked in the same manner as in Example 1 to prepare a cross-linked rubber sheet X as a molded article, and the tensile strength _TX was measured. Table 1 shows the results of tensile strength _TX .

From Table 1, in Examples 1 to 7 using a fluororubber composition containing fluororubber and single-walled CNTs and having a γG ^* of a predetermined value or more, a molded body capable of exhibiting excellent extensibility at high temperatures was obtained. It can be seen that it has been produced.
On the other hand, ^{from Table 1, Comparative Examples 1 and 2 using a fluororubber composition containing fluororubber and single-walled CNT but having γG*} ^less than a predetermined value, Comparative Example 3 using a fluororubber composition containing no single-walled CNTs, and a comparison using a fluororubber composition containing fluororubbers but not containing single-walled CNTs and having γG ^* less than a predetermined value In Example 4, it can be seen that the extensibility of the molded article obtained at high temperatures is low.

Claims

A fluororubber composition containing a fluororubber and a carbon nanotube,
the carbon nanotubes comprise single-walled carbon nanotubes, and
In a dynamic viscoelasticity test performed under the conditions of measurement frequency: 1 Hz, measurement temperature: 40 ° C., the complex elastic modulus when the dynamic strain is 0.1% is G * L (kPa), and the dynamic strain is 630%. When the complex elastic modulus of is G * H (kPa), the following formula (I):
γG * =G * L /G * H (I)
A fluororubber composition having a γG * of 20 or more, as calculated by
The fluororubber composition according to claim 1, wherein the carbon nanotubes further include multi-walled carbon nanotubes.
The fluororubber composition according to claim 1, further comprising a reinforcing filler other than the carbon nanotubes.
The fluororubber composition according to claim 3, wherein the reinforcing filler contains at least one of carbon black and silica.
The fluororubber composition according to claim 1, wherein the content of the single-walled carbon nanotubes is 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the fluororubber.
The fluororubber composition according to claim 1, further comprising a cross-linking agent.
The fluororubber composition according to claim 3,
The fluororubber composition further comprises a cross-linking agent,
Regarding the crosslinked rubber sheet X formed from the fluororubber composition containing the crosslinking agent, test temperature: 200 ° C., test humidity: 50%, tensile speed: 500 ± 50 mm / min in accordance with JIS K6251: 2010 Let T X (MPa) be the tensile strength measured under
Regarding the crosslinked rubber sheet Y formed from the test rubber composition obtained by removing the carbon nanotubes and the reinforcing filler from the fluororubber composition containing the crosslinking agent, the test temperature was 200°C in accordance with JIS K6251:2010. , test humidity: 50%, tensile speed: 500 ± 50 mm / min. When the tensile strength measured under the conditions is T Y (MPa), the following formula (II):
Tensile strength ratio = T X /T Y (II)
A fluororubber composition having a tensile strength ratio of 3.0 or more.
A molded article formed using the fluororubber composition according to claim 6 or 7.