JP2022086911A - Carbon nanotube dispersion, and method of producing elastomer composition - Google Patents

Abstract

To provide a carbon nanotube dispersion capable of providing an elastomer crosslinked product which exerts sufficient rubber performance even under a high temperature exceeding 300°C.SOLUTION: The carbon nanotube dispersion of the present invention includes: an elastomer solution; and a carbon nanotube dispersed in the elastomer solution, and satisfies at least one of the following conditions (1)-(4). (1) A preparation dispersion is made by preparing so that a carbon nanotube concentration is 0.008 mass%, and a coverage of 1.5 mm×1 mm is observed using an optical microscope, then the area ratio as a proportion occupied by CNT aggregates generated by aggregating carbon nanotubes in the coverage is 1.0% or less. (2) the average value of areas of the CNT aggregates is 60 μm2 or less. (3) the average value of vertical direction Feret's diameters of the CNT aggregates is 6 μm or less. (4) the median diameter of the carbon nanotube is 9 μm or less.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a carbon nanotube dispersion liquid and an elastomer composition, and in particular, a carbon nanotube dispersion liquid and an elastomer crosslinked product capable of exhibiting sufficient rubber performance even at a high temperature of over 300 ° C. The present invention relates to a method for producing an elastomer composition.

Conventionally, an elastomer composition obtained by blending a carbon material with an elastomer has been used as a material having excellent properties such as conductivity, thermal conductivity, and strength. In recent years, carbon nanotubes (hereinafter, may be abbreviated as "CNT") have been attracting attention as carbon materials having a high effect of improving the characteristics.

Although each CNT has excellent characteristics, it has a small outer diameter, so that it is easy to bundle (easily bundle) by Van der Waals force when it is used as a bulk material. Therefore, when producing a molded product using an elastomer composition containing an elastomer and CNT, it is required to defibrate the CNT aggregate in which CNTs are aggregated and to disperse CNTs well in the matrix which is an elastomer. Has been done. In the present invention, it is shown that the carbon nanotube (CNT) contains a plurality of carbon nanotubes.

On the other hand, fluorine-containing elastomers have the property of being able to provide crosslinked articles with excellent heat resistance, chemical resistance, weather resistance, etc., and are therefore used in various fields such as automobiles, industrial machinery, OA equipment, and electrical and electronic equipment. Has been done. For example, Patent Document 1 contains a copolymer having a unit based on perfluoro (alkyl vinyl ether) as a fluorine-containing elastomer and CNT, and can suppress deterioration of rubber performance even when placed at a high temperature. It is disclosed that it can be done.

Japanese Unexamined Patent Publication No. 2019-189702

However, the technique of the preceding document 1 is not always sufficient, and there is a demand for an elastomer crosslinked product that exhibits sufficient rubber performance even in an environment at a higher temperature of, for example, exceeding 300 ° C.

An object of the present invention is to provide a carbon nanotube dispersion liquid and an elastomer composition capable of providing an elastomer crosslinked product that exhibits sufficient rubber performance even at a high temperature of more than 300 ° C.

The present inventor has made diligent studies for the purpose of solving the above problems. Then, the present inventors prepare an elastomer composition using a carbon nanotube dispersion liquid which comprises an elastomer solution in which a fluorine-containing elastomer is dissolved in a solvent and carbon nanotubes dispersed in the elastomer solution and satisfies a predetermined condition. For example, they have found that it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at high temperatures, and completed the present invention.

That is, the present invention aims to advantageously solve the above problems, and the carbon nanotube dispersion liquid of the first embodiment of the present invention includes an elastomer solution in which a fluorine-containing elastomer is dissolved in a solvent and the above-mentioned elastomer. A carbon nanotube dispersion liquid comprising a carbon nanotube dispersed in a solution, wherein the carbon nanotube dispersion liquid is prepared so that the carbon nanotube concentration is 0.008% by mass, and the preparation dispersion liquid is prepared. When the prepared dispersion is observed in a range of 1.5 mm × 1 mm using an optical microscope, the area ratio as a proportion of the CNT aggregates in which the carbon nanotubes are aggregated is 1.0% or less in the range. It is characterized by being. According to the carbon nanotube dispersion liquid having such a structure, it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at a high temperature.

Further, the carbon nanotube dispersion liquid of the second embodiment of the present invention is a carbon nanotube dispersion liquid comprising an elastomer solution in which a fluorine-containing elastomer is dissolved in a solvent and carbon nanotubes dispersed in the elastomer solution, and is the carbon. As the nanotube dispersion, a prepared dispersion prepared so that the carbon nanotube concentration was 0.008 mass% was prepared, and the prepared dispersion was observed in a range of 1.5 mm × 1 mm using an optical microscope. The average value of the area of the CNT aggregate in which the carbon nanotubes are aggregated is 60 μm ² or less within the above range. According to the carbon nanotube dispersion liquid having such a structure, it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at a high temperature.

Further, the carbon nanotube dispersion liquid of the third embodiment of the present invention is a carbon nanotube dispersion liquid comprising an elastomer solution in which a fluorine-containing elastomer is dissolved in a solvent and carbon nanotubes dispersed in the elastomer solution, and is the carbon. As the nanotube dispersion, a prepared dispersion prepared so that the carbon nanotube concentration was 0.008 mass% was prepared, and the prepared dispersion was observed in a range of 1.5 mm × 1 mm using an optical microscope. In the meantime, within the above range, the average value of the vertical ferret diameter of the CNT aggregate in which the carbon nanotubes are aggregated is 6 μm or less. According to the carbon nanotube dispersion liquid having such a structure, it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at a high temperature.

Further, the carbon nanotube dispersion liquid of the fourth embodiment of the present invention is a carbon nanotube dispersion liquid comprising an elastomer solution in which a fluorine-containing elastomer is dissolved in a solvent and carbon nanotubes dispersed in the elastomer solution. It is characterized in that the median diameter of the carbon nanotubes in the nanotube dispersion is 9 μm or less. According to the carbon nanotube dispersion liquid having such a structure, it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at a high temperature.

Here, in the carbon nanotube dispersion liquid of the present invention, for example, the fluorine-containing elastomer is a perfluoroelastomer (FFKM).

Further, in the carbon nanotube dispersion liquid of the present invention, it is preferable that the carbon nanotube contains a single-walled carbon nanotube. When single-walled carbon nanotubes are used as carbon nanotubes, the characteristics (for example, conductivity, thermal conductivity, strength, etc.) of the obtained molded product of the elastomer crosslinked product can be improved.

Further, in the carbon nanotube dispersion liquid of the present invention, it is preferable that the carbon nanotubes are contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the fluorine-containing elastomer. When the content of carbon nanotubes in the carbon nanotube dispersion liquid is within the above range, the carbon nanotubes can be satisfactorily dispersed in the obtained molded product of the elastomer crosslinked product.

Further, in the carbon nanotube dispersion liquid of the present invention, the solvent is preferably a fluorine-based solvent.

The present invention aims to advantageously solve the above problems, and the method for producing an elastomer composition according to the first aspect of the present invention is an elastomer containing a fluorine-containing elastomer and carbon nanotubes. A method for producing a composition, which is a dispersion step of mixing and dispersing the fluorine-containing elastomer, the carbon nanotubes, and a solvent capable of dissolving the fluorine-containing elastomer to obtain a carbon nanotube dispersion liquid. A drying step of removing the solvent from the carbon nanotube dispersion liquid to obtain a dried product is provided, and the dispersion step is such that the obtained carbon nanotube dispersion liquid has a carbon nanotube concentration of 0.008% by mass. When the prepared prepared dispersion was prepared and the prepared dispersion was observed in a range of 1.5 mm × 1 mm using an optical microscope, the area of the CNT aggregate in which the carbon nanotubes were aggregated within the range. It is characterized in that the dispersion processing is performed so that the rate is 1.0% or less. According to the method for producing an elastomer composition having such a structure, it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at high temperatures.

Further, the method for producing an elastomer composition according to the second aspect of the present invention is a method for producing an elastomer composition containing a fluorine-containing elastomer and carbon nanotubes, wherein the fluorine-containing elastomer, the carbon nanotubes, and the like. A dispersion step of mixing and dispersing a solvent capable of dissolving the fluorine-containing elastomer to obtain a carbon nanotube dispersion liquid, and a drying step of removing the solvent from the obtained carbon nanotube dispersion liquid to obtain a dried product are performed. In the dispersion step, a prepared dispersion prepared so that the obtained carbon nanotube dispersion has a carbon nanotube concentration of 0.008% by mass is prepared, and an optical microscope is used for the prepared dispersion. When observed in a range of 1.5 mm × 1 mm, the dispersion treatment is performed so that the average value of the area of the CNT aggregate in which the carbon nanotubes are aggregated is 60 μm ² or less within the range. .. According to the method for producing an elastomer composition having such a structure, it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at high temperatures.

Further, the method for producing an elastomer composition according to the third aspect of the present invention is a method for producing an elastomer composition containing a fluorine-containing elastomer and carbon nanotubes, wherein the fluorine-containing elastomer, the carbon nanotubes, and the like. A dispersion step of mixing and dispersing a solvent capable of dissolving the fluorine-containing elastomer to obtain a carbon nanotube dispersion liquid, and a drying step of removing the solvent from the obtained carbon nanotube dispersion liquid to obtain a dried product are performed. In the dispersion step, a prepared dispersion prepared so that the obtained carbon nanotube dispersion has a carbon nanotube concentration of 0.008% by mass is prepared, and an optical microscope is used for the prepared dispersion. When observed in a range of 1.5 mm × 1 mm, the dispersion treatment is performed so that the average value of the vertical ferret diameter of the CNT aggregate in which the carbon nanotubes are aggregated is 6 μm or less within the range. And. According to the method for producing an elastomer composition having such a structure, it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at high temperatures.

Further, the method for producing an elastomer composition according to a fourth aspect of the present invention is a method for producing an elastomer composition containing a fluorine-containing elastomer and carbon nanotubes, wherein the fluorine-containing elastomer, the carbon nanotubes, and the like. A dispersion step of mixing and dispersing a solvent capable of dissolving the fluorine-containing elastomer to obtain a carbon nanotube dispersion liquid, and a drying step of removing the solvent from the obtained carbon nanotube dispersion liquid to obtain a dried product. The dispersion step is characterized in that the dispersion treatment is performed so that the median diameter of the carbon nanotubes in the obtained carbon nanotube dispersion liquid is 9 μm or less. According to the method for producing an elastomer composition having such a structure, it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at high temperatures.

Here, in the method for producing an elastomer composition of the present invention, for example, the fluorine-containing elastomer is a perfluoroelastomer (FFKM).

Further, in the method for producing an elastomer composition of the present invention, it is preferable that the carbon nanotubes contain single-walled carbon nanotubes. When single-walled carbon nanotubes are used as carbon nanotubes, the characteristics (for example, conductivity, thermal conductivity, strength, etc.) of the obtained molded product of the elastomer crosslinked product can be improved.

Further, in the method for producing an elastomer composition of the present invention, the carbon nanotube dispersion liquid preferably contains the carbon nanotubes in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the fluorine-containing elastomer. When the content of carbon nanotubes in the carbon nanotube dispersion liquid is within the above range, the carbon nanotubes can be satisfactorily dispersed in the obtained molded product of the elastomer crosslinked product.

Further, in the method for producing an elastomer composition of the present invention, the solvent is preferably a fluorine-based solvent.

The method for producing an elastomer composition of the present invention may further include a kneading step of mixing the dried product and a cross-linking agent to obtain a cross-linking composition after the drying step.

Further, the method for producing an elastomer composition of the present invention can further include a cross-linking step of cross-linking the cross-linking composition obtained in the kneading step to obtain an elastomer cross-linked product.

According to the method for producing a carbon nanotube dispersion liquid and an elastomer composition of the present invention, it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at a high temperature of over 300 ° C.

(Carbon nanotube dispersion liquid)
Hereinafter, the carbon nanotube dispersion liquid of the present invention will be described in detail.
The carbon nanotube dispersion liquid of the present invention includes an elastomer solution in which a fluorine-containing elastomer is dissolved in a solvent, and carbon nanotubes (or carbon nanotube aggregates) dispersed in the elastomer solution.

<Fluorine-containing elastomer>
As the fluorine-containing elastomer, a known fluorine rubber can be used without particular limitation. Specifically, examples of the fluorine-containing elastomer include vinylidene fluoride rubber (FKM), ethylene tetrafluoroethylene-propylene rubber (FEPM), and ethylene tetrafluoroethylene-perfluoroalkyl vinyl ether rubber as a perfluoroelastomer. (FFKM), tetrafluoroethylene rubber (TFE) and the like can be mentioned. These may be used alone or in combination of two or more.

Here, vinylidene fluoride rubber (FKM) is a fluororubber containing vinylidene fluoride as a main component and having excellent heat resistance, oil resistance, chemical resistance, solvent resistance, processability and the like. The FKM is not particularly limited, and is, for example, a binary copolymer composed of vinylidene fluoride and hexafluoropropylene, a ternary copolymer composed of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, and vinylidene fluoride. A quaternary copolymer composed of hexafluoropropylene, tetrafluoroethylene, and a sulfide site monomer can be mentioned. Examples of commercially available products include "Baiton (registered trademark)" of Chemours Company, Inc. and "Daiel (registered trademark) G" of Daikin Industries, Ltd. Of these, a quaternary copolymer composed of vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, and a vulcanized site monomer is preferable. The quaternary copolymer is available, for example, as a commercially available product "Byton GBL-200S" (manufactured by The Chemours Company, Inc.). In the present specification, "main component of vinylidene fluoride" means that the unit of vinylidene fluoride contained in the vinylidene fluoride rubber is 50% by mass or more, preferably more than 50% by mass.

Fluorinated ethylene-propylene rubber (FEPM) is a fluororubber that is based on an alternating copolymer of tetrafluoroethylene and propylene and has excellent heat resistance, chemical resistance, polar solvent resistance, steam resistance, and the like. .. The FEPM is not particularly limited, but is, for example, a binary copolymer composed of tetrafluoroethylene and propylene, a ternary copolymer composed of tetrafluoroethylene, propylene and vinylidene fluoride, and cross-linking with tetrafluoroethylene and propylene. Examples thereof include a ternary copolymer composed of a point monomer. Examples of commercially available products of the binary copolymer composed of tetrafluoroethylene and propylene include "Afras (registered trademark) 100" and "Afras 150" of AGC Inc. As a commercially available product of a ternary copolymer composed of tetrafluoroethylene, propylene and vinylidene fluoride, for example, "Afras 200" of AGC Inc. can be mentioned. As a commercially available product of a ternary copolymer composed of tetrafluoroethylene, propylene and a cross-linking point monomer, for example, "Afras 300" of AGC Inc. can be mentioned.

In the tetrafluoroethylene-perfluoroalkyl vinyl ether-based rubber (FFKM), the hydrogen atom (H) bonded to the carbon atom constituting the main chain carbon (C) -carbon (C) bond is completely fluorinated. Fluorine rubber, which has excellent heat resistance, chemical resistance, and plasma resistance, and can be suitably used as a sealing member for semiconductor devices. Examples of the FFKM include a copolymer containing a constituent unit derived from tetrafluoroethylene (TFE) and a constituent unit derived from perfluoroalkyl vinyl ether (PAVE) or perfluoroalkoxyalkyl vinyl ether (PAOVE). The FFKM may further include a structural unit having a cross-linking site in addition to the above two structural units.

As the perfluoroalkyl vinyl ether (PAVE), those having an alkyl group having 1 to 5 carbon atoms can be used, for example, perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), perfluoropropyl vinyl ether (PPVE). ) Etc. can be mentioned.

Perfluoroalkoxyalkyl vinyl ether (PAOVE) can have 3 to 11 carbon atoms in the group bonded to the vinyl ether group (CF ₂ = CFO-), for example CF ₂ = CFOCF ₂ CF (CF ₃ ) OC _n F. _{2n + 1} ,
CF ₂ = CFO (CF ₂ ) ₃ OC _n F _{2n + 1} ,
CF ₂ = CFO CF ₂ CF (CF ₃ ) O (CF ₂ O) _m C _n F _{2n + 1} or CF ₂ = CFO (CF ₂ ) ₂ OC _n F _{2n + 1}
Can be mentioned. Here, n is, for example, an integer of 1 to 5, and m is, for example, an integer of 1 to 3.

FFKM includes, for example, "Afras (registered trademark) PM1100" and "Afras PM3000" and "Afras PM4000" of AGC Co., Ltd., "Carletz (registered trademark)" series of DuPont, and "Daiel (registered trademark)" of Daikin Industries, Ltd. Examples include the "Perflo" series, Solvay's "Technoflon (registered trademark) PFR" series, and 3M's "DuPont (registered trademark)" series.

<Solvent>
The solvent is not particularly limited as long as it is a solvent capable of dissolving the fluorine-containing elastomer. Examples of such a solvent include ketones such as methyl ethyl ketone and acetone, ethers such as tetrahydrofuran, and a fluorine-based solvent, and among these, a fluorine-based solvent is preferable.

As the fluorine-based solvent, a solvent having a perfluorohydrocarbon group can be used. The perfluorohydrocarbon group may be a chain-type perfluorohydrocarbon group or a ring-type perfluorohydrocarbon group.

The chain-type perfluorohydrocarbon group may be linear or branched. Examples of the chain type perfluorohydrocarbon group include a perfluoroalkyl group, a perfluoroalkylene group, a perfluorovinylalkyl group, and a perfluorovinylalkylene group. The number of carbon atoms of the perfluorohydrocarbon group having the largest number of carbon atoms in the perfluorohydrocarbon group is 3 to 7. When the number of carbon atoms is 3 or more, the solubility of the fluorine-containing elastomer in the fluorine-based solvent is excellent. When the number of carbon atoms is 7 or less, it is easy to obtain a fluorine-based solvent. Further, when the number of carbon atoms is 6 or less, the boiling point of the fluorine-based solvent tends to be low, and it is easy to remove.

The boiling point of the fluorinated solvent is preferably 50 to 160 ° C. When the boiling point of the fluorinated solvent is 50 ° C. or higher, the dispersion treatment can be stably performed. When the boiling point of the fluorinated solvent is 160 ° C. or lower, it is easy to remove the fluorinated solvent. As the fluorine-based solvent, at least one selected from the group consisting of a fluorine-containing compound having a nitrogen atom, a hydrofluorocarbon, and a hydrofluoro ether is preferable. When the fluorine-based solvent is at least one selected from the group consisting of a fluorine-containing compound having a nitrogen atom, hydrofluorocarbon, and hydrofluoroether, the solubility of the fluorine-containing elastomer in the fluorine-based solvent tends to be excellent. The solvent may be used alone or in combination of two or more at any ratio.

Specific examples of the fluorine-based solvent having a nitrogen atom include Fluorinert (registered trademark) FC-770 manufactured by 3M.
Specific examples of hydrofluorocarbons include 1,1,1,2,2,3,3,4,4-nonafluorohexane, 1,1,1,2,2,3,3,4,4,5. 5,6,6-Tridecafluorohexane, 1,1,1,2,2,3,3,4,5,5,6-Tridecafluorooctane are exemplified. Asahi Kulin (registered trademark) AC-2000, 1 manufactured by AGC Inc. as a commercially available product of 1,1,1,2,2,3,4,4,5,5,6,6-tridecafluorohexane, 1 , 1,1,2,2,3,3,4,5,5,6,6-Tridecafluorooctane is exemplified by Asahi Kulin (registered trademark) AC-6000 manufactured by AGC. To.
Specific examples of the hydrofluoroether include Novec® 7300 manufactured by 3M.

<Carbon nanotube>
As the carbon nanotube (CNT), for example, those of the first aspect and those of the second aspect described later can be used. The CNTs may be in a state of being defibrated one by one, or may be in a state of being configured as an aggregate of carbon nanotubes in which a plurality of CNTs are formed in a bundle shape.

<< About the first aspect >>
Examples of the CNTs according to the first aspect include the following.
The type of CNT is not particularly limited, and includes single-walled carbon nanotubes and multi-walled carbon nanotubes. Further, the plurality of CNTs preferably mainly contain carbon nanotubes from a single layer to five layers, and more preferably contain single-walled carbon nanotubes. This is because the inclusion of CNTs having a relatively small number of layers, particularly single-walled CNTs, improves the characteristics (for example, conductivity, thermal conductivity, strength, etc.) of the molded product even if the blending amount is small. The above-mentioned "mainly included" means that more than half of the total number of the plurality of carbon nanotubes is included.

The average diameter of the CNTs is preferably 1 nm or more, preferably 60 nm or less, more preferably 30 nm or less, and even more preferably 10 nm or less. When the average diameter of CNTs is within the above range, the characteristics of the molded product (for example, conductivity, thermal conductivity, strength, etc.) can be sufficiently improved. Here, in the present invention, the "average diameter" of CNTs is determined by measuring the diameter (outer diameter) of 20 CNTs on a transmission electron microscope (TEM) image and calculating the number average value. You can ask.

As the CNT, a CNT in which the ratio (3σ / Av) of the value (3σ) obtained by multiplying the standard deviation (σ: sample standard deviation) of the diameter by 3 with respect to the average diameter (Av) is more than 0.20 and less than 0.80. It is preferably used, more preferably a CNT having a 3σ / Av greater than 0.25, and even more preferably a CNT having a 3σ / Av greater than 0.50. When 3σ / Av is in the above range, the characteristics of the molded product (for example, conductivity, thermal conductivity, strength, etc.) can be further improved. The average diameter (Av) and standard deviation (σ) of CNTs may be adjusted by changing the manufacturing method and manufacturing conditions of CNTs, or by combining a plurality of types of CNTs obtained by different manufacturing methods. You may.

As the CNTs, those having a normal distribution when plotted with the diameter measured as described above on the horizontal axis and the frequency on the vertical axis and approximated by Gaussian are usually used.

The average length of CNTs is preferably 10 μm or more, more preferably 50 μm or more, further preferably 80 μm or more, preferably 600 μm or less, and even more preferably 550 μm or less. , 500 μm or less is more preferable. When the average length of CNTs is within the above range, the characteristics of the molded product (for example, conductivity, thermal conductivity, strength, etc.) can be sufficiently improved. In the present invention, the "average length" of CNTs can be obtained by measuring the lengths of, for example, 20 CNTs on a scanning electron microscope (SEM) image and calculating the number average value. can.

CNTs usually have an aspect ratio of more than 10. For the aspect ratio of CNTs, the diameter and length of 20 randomly selected CNTs were measured using a scanning electron microscope or a transmission electron microscope, and the ratio of diameter to length (length / diameter) was measured. It can be obtained by calculating the average value.

The CNT has a BET specific surface area preferably 600 m ² / g or more, more preferably 800 m ² / g or more, preferably 2000 m ² / g or less, and 1800 m ² / g or less. Is more preferable, and 1600 m ² / g or less is further preferable. When the BET specific surface area of CNT is 600 m ² / g or more, the characteristics of the molded product (for example, conductivity, thermal conductivity, strength, etc.) can be sufficiently enhanced with a small blending amount. Further, when the BET specific surface area of CNT is 2000 m ² / g or less, the bundle structure of CNT can be defibrated satisfactorily. In the present invention, the "BET specific surface area" refers to the nitrogen adsorption specific surface area measured by the BET method.

For CNTs, it is preferable that the t-plot obtained from the adsorption isotherm shows an upwardly convex shape. The "t-plot" can be obtained by converting the relative pressure into the average thickness t (nm) of the nitrogen gas adsorption layer in the adsorption isotherm of CNT measured by the nitrogen gas adsorption method. That is, the conversion is performed by obtaining the average thickness t of the nitrogen gas adsorption layer corresponding to the relative pressure from a known standard isotherm obtained by plotting the average thickness t of the nitrogen gas adsorption layer with respect to the relative pressure P / P0. To obtain a t-plot of CNT (t-plot method by de Boer et al.). The CNTs obtained from the adsorption isotherms whose t-plot shows an upwardly convex shape are preferably CNTs that have not been subjected to opening treatment.

Here, in a substance having pores on the surface, the growth of the nitrogen gas adsorption layer is classified into the following processes (1) to (3). Then, the slope of the t-plot changes due to the following processes (1) to (3).
(1) Single-molecule adsorption layer formation process of nitrogen molecules on the entire surface (2) Multi-molecule adsorption layer formation and accompanying condensate-filling process of capillaries in pores (3) Apparent pores filled with nitrogen Process of forming a multi-molecular adsorption layer on a non-porous surface

In the t-plot showing an upwardly convex shape, the plot is located on a straight line passing through the origin in the region where the average thickness t of the nitrogen gas adsorption layer is small, whereas when t is large, the plot is below the straight line. It will be in a position shifted to. The 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 a large number of openings are formed in the carbon nanostructures constituting the CNT.

The bending point of the CNT t-plot is preferably in the range of 0.2 ≦ t (nm) ≦ 1.5, and preferably in the range of 0.45 ≦ t (nm) ≦ 1.5. Is more preferable, and it is further preferable that the range is 0.55 ≦ t (nm) ≦ 1.0. As long as the bending point of the CNT t-plot is within such a range, the characteristics of the molded product (for example, conductivity, thermal conductivity, strength, etc.) can be enhanced with a small blending amount. The "position of the bending point" is the intersection of the approximate straight line A of the process of (1) described above and the approximate straight line B of the process of (3) described above.

Incidentally, 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 by, for example, "BELSORP (BELSORP), which is a commercially available measuring device. It can be performed using "registered trademark) -mini" (manufactured by Nippon Bell Co., Ltd.).

The CNTs preferably have a RadialBreathing Mode (RBM) peak when evaluated using Raman spectroscopy. It should be noted that RBM does not exist in the Raman spectrum of three or more multi-walled CNTs.

Further, in the CNT, the ratio (G / D ratio) of the G band peak intensity to the D band peak intensity in the Raman spectrum is preferably 0.5 or more and 5.0 or less, and can be 1.0 or more. It may be 4.0 or less. When the G / D ratio is 0.5 or more and 5.0 or less, the characteristics of the molded product (for example, conductivity, thermal conductivity, strength, etc.) can be further improved.

The CNT can be produced by using a known CNT synthesis method such as an arc discharge method, a laser ablation method, and a chemical vapor deposition method (CVD method) without particular limitation. Specifically, CNTs are used, for example, when a raw material compound and a carrier gas are supplied onto a substrate having a catalyst layer for CNT production on the surface, and CNTs are synthesized by a chemical gas phase growth method (CVD method). , According to the method of dramatically improving the catalytic activity of the catalyst layer by the presence of a trace amount of oxidizing agent (catalyst activator) in the system (Super Growth Method; see International Publication No. 2006/011655). It can be manufactured efficiently. In the following, the CNT obtained by the super growth method may be referred to as "SGCNT". The CNTs produced by the super growth method may be composed of SGCNTs alone, or may contain other carbon nanostructures such as non-cylindrical carbon nanostructures in addition to SGCNTs.

<< Second aspect >>
Examples of the CNTs according to the second aspect include the following.
The CNT aggregate composed of CNTs according to the second aspect satisfies at least one of the following conditions (1) to (3) and has excellent dispersibility in a matrix (fluorine-containing elastomer in the present invention). be.
Conditions (1) The plasmon of the carbon nanotube dispersion in the spectrum obtained by Fourier transform infrared spectroscopic analysis of the carbon nanotube dispersion obtained by dispersing the carbon nanotube aggregate so that the bundle length is 10 μm or more. There is at least one resonance-based peak in the range of wavenumbers above 300 cm ^-1 and above 2000 cm ^-1 .
Condition (2) The maximum peak in the differential pore volume distribution measured for the carbon nanotube aggregate is in the range of the pore diameter of more than 100 nm and less than 400 nm.
-Conditions (3) At least one peak of the two-dimensional spatial frequency spectrum of the electron microscope image of the carbon nanotube aggregate exists in the range of 1 μm ^-1 or more and 100 μm ^-1 or less.

The reason why the CNT aggregate satisfying at least one of the above conditions (1) to (3) is excellent in dispersibility is not clear, but it is presumed to be as follows. That is, the CNTs constituting the CNT aggregate satisfying at least one of the above conditions (1) to (3) have a wavy structure. It is presumed that the interaction between the CNTs constituting the CNT aggregate can be suppressed due to the "wavy structure". If the interaction between the CNTs is suppressed, it is possible to suppress the tight bundling and aggregation of the CNTs contained in the CNT aggregate. This may make it possible to easily disperse the CNT aggregate. Further, if the CNT aggregate can be easily dispersed, there is an effect that the ease of secondary processing of the CNT aggregate is improved.

-Condition (1)-
In the condition (1), the wave number is in the range of 300 cm ^-1 to 2000 cm ^-1 or less, preferably in the range of 500 cm ^-1 or more and 2000 cm ^-1 or less, and more preferably in the range of 700 cm ^-1 or more and 2000 cm ^-1 or less. If a peak based on the plasmon resonance of the CNT is present, the CNT can exhibit good dispersibility.

In the spectrum obtained by Fourier transform infrared spectroscopy, in addition to the relatively gentle peak based on the plasmon resonance of the carbon nanotube dispersion, the wave number is around 840 cm ^-1 and around 1300 cm ^-1 and around 1700 cm ^-1 . Sharp peaks may be seen. These sharp peaks do not correspond to "peaks based on plasmon resonance of carbon nanotube dispersion", and each corresponds to infrared absorption derived from a functional group. More specifically, the sharp peak near 840 cm ^-1 wavenumber is due to the CH out-of-plane angular vibration; the sharp peak near 1300 cm ^-1 wavenumber is due to the epoxy three-membered ring expansion and contraction vibration; 1700 cm wavenumber. The sharp peak near ^-1 is due to C = O expansion and contraction vibration.

Here, under the condition (1), in order to acquire the spectrum by Fourier transform infrared spectroscopic analysis, it is necessary to obtain the carbon nanotube dispersion by dispersing the carbon nanotube aggregate so that the bundle length is 10 μm or more. be. Here, for example, carbon nanotube aggregates, water, and a surfactant (for example, sodium dodecylbenzene sulfonate) are blended in an appropriate ratio and stirred with ultrasonic waves or the like for a predetermined time to bring them into water. It is possible to obtain a dispersion liquid in which carbon nanotube dispersions having a bundle length of 10 μm or more are dispersed.

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

-Condition (2)-
The differential pore volume distribution of the carbon nanotube aggregate can be obtained from the adsorption isotherm of liquid nitrogen at 77K based on the BJH (Barrett-Joiner-Halenda) method. The BJH method is a measurement method for obtaining the pore diameter distribution on the assumption that the pores are cylindrical. The fact that the peak in the differential pore volume distribution measured for the carbon nanotube aggregate is in the range of more than 100 nm means that in the carbon nanotube aggregate, there are voids of a certain size between the CNTs, and the CNTs are excessively dense. It means that it is not in an aggregated state. The upper limit of 400 nm is the measurement limit of the measuring device (BELSORP-mini II) used in the examples.

Here, from the viewpoint of further enhancing the dispersibility, the value of the differential pore volume at the maximum peak in the differential pore volume distribution of the CNT aggregate is preferably 2 cm ³ / g or more.

-Condition (3)-
Satisfiability of such a condition can be determined as follows.
First, the CNT aggregate to be determined is magnified and observed (for example, 10,000 times) using an electron microscope (for example, an electrolytic radiation scanning electron microscope), and a plurality of electron microscope images are obtained in a 1 cm square field (for example). For example, 10 sheets) will be acquired. The obtained plurality of electron microscope images are subjected to a fast Fourier transform (FFT) process to obtain a two-dimensional spatial frequency spectrum. The two-dimensional spatial frequency spectra obtained for each of the plurality of electron microscope images are binarized, and the average value of the peak positions appearing on the highest frequency side is obtained. When the average value of the obtained peak positions was within the range of 1 μm ^-1 or more and 100 μm ^-1 or less, it was determined that the condition (3) was satisfied. Here, as the "peak" used in the above determination, a clear peak obtained by performing an isolated point extraction process (that is, a reverse operation of removing isolated points) is used. Therefore, if a clear peak cannot be obtained within the range of 1 μm ^-1 or more and 100 μm ^-1 or less when the isolated point extraction process is performed, it is determined that the condition (3) is not satisfied.

Here, from the viewpoint of further enhancing the dispersibility, 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.

From the viewpoint of further enhancing the dispersibility, the carbon nanotube aggregate of the present invention preferably satisfies at least two of the above conditions (1) to (3), and satisfies all of the conditions (1) to (3). It is more preferable to meet.

-Characteristics of CNT aggregate according to the second aspect-
The CNT aggregate according to the second aspect preferably has, for example, the following properties.
The total specific surface area of the CNT aggregate by the BET method is preferably 600 m ² / g or more, more preferably 800 m ² / g or more, preferably 2600 m ² / g or less, and more preferably 1400 m ² / g or less. .. Further, in the case of the opening-treated one, it is preferably 1300 m ² / g or more. In the CNT aggregate having a high specific surface area, there are gaps between the CNTs constituting the aggregate, and the CNTs are not excessively bundled. Therefore, the individual CNTs are loosely bonded to each other and can be easily dispersed. The CNT aggregate may contain mainly single-walled CNTs, and may contain two-walled CNTs and multi-walled CNTs to the extent that the functions are not impaired. The total specific surface area of CNTs by the BET method can be measured, for example, by using a BET specific surface area measuring device compliant with JIS Z8830.

When CNTs are produced using a carrier by the method for producing CNTs described later, the average height of CNTs constituting the CNT aggregate from the surface of the carrier is preferably 10 μm or more and 10 cm or less, preferably 100 μm or more. It is more preferably 2 cm or less. When the average height of the CNTs constituting the CNT aggregate is 10 μm or more, it is possible to prevent aggregation with the adjacent CNT bundle and easily disperse the CNTs. When the average height of the CNTs constituting the CNT aggregate is 100 μm or more, it becomes easy to form a network between CNTs, and it can be suitably used in applications requiring conductivity or mechanical strength such as electrode formation. .. When the average height of the CNTs constituting the CNT aggregate is 10 cm or less, the formation can be performed in a short time, so that the adhesion of carbon-based impurities can be suppressed and the specific surface area can be improved. If the average height of the CNTs constituting the CNT aggregate is 2 cm or less, it can be more easily dispersed. The average height of CNTs can be determined by measuring the height of 100 randomly selected CNTs using a scanning electron microscope (SEM).

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. Since the CNT aggregates in such a density range do not excessively strengthen the bonds between the CNTs, they are excellent in dispersibility and can be molded into various shapes. When the tap bulk density of the CNT aggregate is 0.2 g / cm ³ or less, the bond between the CNTs is weakened, so that when the CNT aggregate is stirred with a solvent or the like, it becomes easy to disperse it uniformly. 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 the handling becomes easy. The tap bulk density is the apparent bulk density in a state where the powdery CNT aggregate is filled in a container, the voids between the powder particles are reduced by tapping or vibration, and the containers are tightly packed.

Further, the average diameter of the CNTs constituting the CNT aggregate is preferably 0.5 nm or more, more preferably 1.0 nm or more, preferably 15.0 nm or less, and 10.0 nm or less. It is more preferably present, and further preferably 5.0 nm or less. When the average diameter of CNTs is 1.0 nm or more, bundling between CNTs can be reduced and a high specific surface area can be maintained. When the average diameter of CNTs is 5.0 nm or less, the ratio of multi-walled CNTs can be reduced and a high specific surface area can be maintained. Here, the average diameter of CNTs can be determined by measuring the diameter (outer diameter) of 100 randomly selected CNTs using a transmission electron microscope (TEM). The average diameter (Av) and standard deviation (σ) of CNTs may be adjusted by changing the manufacturing method and manufacturing conditions of CNTs, or by combining a plurality of types of CNTs obtained by different manufacturing methods. May be good.

The G / D ratio of the CNT aggregate is preferably 1 or more and 50 or less. It is considered that the CNT aggregate having a G / D ratio of less than 1 has low crystallinity of single-walled CNTs, has a lot of stains such as amorphous carbon, and has a high content of multi-walled CNTs. On the other hand, CNT aggregates having a G / D ratio of more than 50 have high linearity, and CNTs tend to form bundles with few gaps, which may reduce the specific surface area. The G / D ratio is an index generally used for evaluating the quality of CNTs. Vibration modes called G band (around 1600 cm ^-1 ) and D band (around 1350 cm ^-1 ) are observed in the Raman spectrum of CNTs measured by a Raman spectroscope. The G band is a vibration mode derived from the hexagonal lattice structure of graphite, which is the cylindrical surface of CNT, and the D band is a vibration mode derived from an amorphous portion. Therefore, the higher the peak intensity ratio (G / D ratio) between the G band and the D band, the higher the crystallinity (linearity) of the CNT.

In order to obtain a high specific surface area, it is desirable that the purity of the CNT aggregate is as high as possible. The term "purity" as used herein is carbon purity, and is a value indicating what percentage of the mass of the CNT aggregate is composed of carbon. Although there is no upper limit to the purity for obtaining a high specific surface area, it is difficult to obtain a CNT aggregate of 99.9999% by mass or more in manufacturing. If the purity is less than 95% by mass, it becomes difficult to obtain a specific surface area of more than 1000 m ² / g in the unopened state. Further, if the carbon purity is less than 95% by mass including the metal impurities, the metal impurities react with oxygen in the opening treatment and hinder the opening of the CNTs, and as a result, it becomes difficult to increase the specific surface area. From these points, the purity of the single-walled CNT is preferably 95% by mass or more.
The purity of the CNT aggregate is usually 98% by mass or more, preferably 99.9% by mass or more, even without purification treatment. Almost no impurities are mixed in the CNT aggregate, and the original characteristics of CNT can be fully exhibited. The carbon purity of the CNT aggregate can be obtained from elemental analysis using fluorescent X-rays, thermogravimetric analysis (TGA), or the like.

The carbon nanotube aggregate according to the second aspect can be produced by using a CNT synthesis step according to known methods such as a fluidized bed method, a mobile layer method and a fixed bed method. Here, the fluidized bed method means a synthesis method for synthesizing CNTs while fluidizing a granular carrier carrying a catalyst for synthesizing CNTs (hereinafter, also referred to as a granular catalyst carrier). Further, the moving layer method and the fixed layer method mean a synthetic method for synthesizing CNTs without flowing a carrier (particulate carrier or plate-like carrier) carrying a catalyst.

<< CNT content >>
In the carbon nanotube dispersion liquid of the present invention, the CNT is preferably contained in an amount of 0.1 part by mass or more, more preferably 1 part by mass or more, and more preferably 2 parts by mass or more with respect to 100 parts by mass of the fluorine-containing elastomer. More preferably, it may contain 3 parts by mass or more. Further, in the carbon nanotube dispersion liquid of the present invention, the CNT is preferably contained in an amount of 10 parts by mass or less, more preferably 8 parts by mass or less, and more preferably 7 parts by mass or less with respect to 100 parts by mass of the fluorine-containing elastomer. More preferably, it may contain 6 parts by mass or less. When the content of CNTs in the carbon nanotube dispersion is within the above range, CNTs can be more satisfactorily dispersed in the fluorine-containing elastomer in the molded product obtained by the elastomer composition described later.

<< Preparation method of CNT dispersion liquid >>
The CNT dispersion liquid of the present invention can be obtained by the following method.
The method for producing a CNT dispersion liquid includes a step (dispersion step) of mixing and dispersing the fluorine-containing elastomer, the carbon nanotubes, and a solvent capable of dissolving the fluorine-containing elastomer. Here, the dispersion step includes a dissolution step of obtaining an elastomer solution in which the fluorine-containing elastomer is dissolved in a solvent, and a dispersion treatment step of mixing carbon nanotubes in the elastomer solution and performing a dispersion treatment.

The dissolution step may be carried out by a known method, as long as the fluorine-containing elastomer is dissolved in the solvent. Further, in the dispersion treatment step, it is sufficient that the CNTs can be dispersed in the elastomer solution, and a known dispersion treatment can be used. Examples of such a dispersion treatment include a dispersion treatment by shear stress, a dispersion treatment by collision energy, and a dispersion treatment in which a cavitation effect can be obtained. According to such a distributed processing, the distributed processing can be carried out relatively easily.

Examples of the apparatus that can be used for the dispersion treatment by shear stress include a two-roll mill and a three-roll mill. Examples of the device that can be used for the dispersion processing by the collision energy include a bead mill, a rotor / stator type disperser, and the like. Examples of the device that can be used for the dispersion processing that can obtain the cavitation effect include a jet mill and an ultrasonic disperser. The conditions for the dispersion processing are not particularly limited, and can be appropriately set, for example, within the range of normal dispersion conditions in the above-mentioned apparatus.

<< Area ratio of CNT aggregate >>
For the carbon nanotube dispersion liquid of the first embodiment of the present invention, a prepared dispersion liquid prepared so that the carbon nanotube concentration is 0.008% by mass is prepared, and the prepared dispersion liquid is prepared using an optical microscope. When observed in a range of 5 mm × 1 mm, the area ratio as a ratio of the carbon nanotube aggregates (CNT aggregates) in which carbon nanotubes are aggregated is 1.0% or less in the range. With such a configuration, the elastomer crosslinked product formed by the carbon nanotube dispersion has further excellent CNT dispersibility, and even when stored at a higher temperature, the hardness change is as low as ± 6 points or less, which is sufficient. Can ensure high heat resistance. From the viewpoint of further improving the heat resistance of the crosslinked elastomer, the area ratio is preferably 0.5% or less.

<Average value of the area of CNT aggregate>
Further, as the carbon nanotube dispersion liquid of the second embodiment of the present invention, a prepared dispersion liquid prepared so that the carbon nanotube concentration is 0.008% by mass is prepared, and the prepared dispersion liquid is prepared using an optical microscope. When observed in the range of 1.5 mm × 1 mm, the average value of the area of the CNT aggregate in which the carbon nanotubes are aggregated is 60 μm ² or less in the range. With such a configuration, the elastomer crosslinked product formed by the carbon nanotube dispersion has further excellent CNT dispersibility, and even when stored at a higher temperature, the hardness change is as low as ± 6 points or less, which is sufficient. Can ensure high heat resistance. From the viewpoint of further improving the heat resistance of the crosslinked elastomer, the average value of the above areas is preferably 40 μm ² or less.

<Average value of vertical ferret diameter of CNT aggregate>
Further, for the carbon nanotube dispersion liquid of the third embodiment of the present invention, a prepared dispersion liquid prepared so that the carbon nanotube concentration is 0.008% by mass is prepared, and the prepared dispersion liquid is prepared using an optical microscope. When observed in the range of 1.5 mm × 1 mm, the average value of the vertical ferret diameter of the CNT aggregate in which carbon nanotubes are aggregated is 6 μm or less in the range. With such a configuration, the elastomer crosslinked product formed by the carbon nanotube dispersion has further excellent CNT dispersibility, and even when stored at a higher temperature, the hardness change is as low as ± 6 points or less, which is sufficient. Can ensure high heat resistance. From the viewpoint of further improving the heat resistance of the crosslinked elastomer, the average value of the vertical ferret diameter of the CNT aggregate is preferably 4.5 μm or less.

Here, in the present invention, the area ratio, the average value of the area, and the average value of the ferret diameter can be measured by, for example, the following method. That is, the dispersion obtained in the dispersion step of mixing and dispersing the fluorine-containing elastomer, the carbon nanotubes and the solvent is diluted with the solvent used in the dispersion treatment so that the carbon nanotube concentration becomes 0.008% by mass. A diluted solution having a carbon nanotube concentration of 0.008% by mass was dropped onto a slide glass, covered with a cover glass, sealed, and used with a digital microscope (product name "VHX-900" manufactured by Keyence) to 1.5 mm. An image is obtained by observing a field of view of × 1 mm (magnification 200 times) with side-illuminated illumination. After binarizing the obtained image using image processing software (manufactured by Mitani Shoji Co., Ltd., product name "WinROOF2015"), the area of the CNT aggregate in which carbon nanotubes are aggregated in the image is measured, and 1.5 mm × The total area (Sc) of the CNT aggregate is obtained within the range of 1 mm. Then, as shown in the following formula, the area ratio (S) of the CNT aggregate can be obtained by calculating the ratio of the total area (Sc) of the CNT aggregate to the observation visual field area (St) as a percentage.
S = (Sc / St) x 100 (%)
Further, the area of 800 or more CNT aggregates can be measured, and the average value thereof can be obtained as the average value of the areas.
Further, 800 or more vertical ferret diameters of the CNT aggregate can be measured, and the average value can be obtained as the average value of the vertical ferret diameters. The vertical ferret diameter refers to the ferret diameter in the direction perpendicular to the long axis of the object by obtaining the circumscribing rectangle in the long axis direction of the object.

<Median diameter D50>
Here, in the carbon nanotube dispersion liquid of the fourth embodiment of the present invention, the median diameter of the carbon nanotubes in the carbon nanotube dispersion liquid is 9 μm or less. With such a configuration, the elastomer crosslinked product formed by the carbon nanotube dispersion has further excellent CNT dispersibility, and even when stored at a higher temperature, the hardness change is as low as ± 6 points or less, which is sufficient. Can ensure high heat resistance. From the viewpoint of further improving the heat resistance of the crosslinked elastomer, the median diameter of the carbon nanotubes is preferably 5 μm or less. Here, in the present invention, the median diameter can be measured by, for example, the following method. That is, the dispersion liquid obtained in the dispersion step of mixing and dispersing the fluorine-containing elastomer, carbon nanotubes, and solvent was used with a laser diffraction type particle size distribution measuring device (manufactured by HORIBA, product name "LA-950"). The transmittance at a wavelength of 630 nm is adjusted to 88%, and the particle size distribution is measured. Then, the median diameter D50 of the carbon nanotubes in the carbon nanotube dispersion can be calculated from the particle diameter of 50% of the cumulative particle size distribution obtained.

(Manufacturing method of elastomer composition)
The method for producing an elastomer composition of the present invention comprises a dispersion step of mixing and dispersing a fluorine-containing elastomer, carbon nanotubes, and a solvent capable of dissolving the fluorine-containing elastomer to obtain the carbon nanotube dispersion liquid of the present invention described above. The present invention comprises a drying step of removing the solvent from the obtained carbon nanotube dispersion liquid of the present invention to obtain an elastomer composition as a dried product. Therefore, the obtained elastomer composition contains a fluorine-containing elastomer, carbon nanotubes, and optionally a cross-linking agent, an additive, and the like. Here, the dispersion step can be carried out by using the method for preparing the CNT dispersion liquid described above. Further, in the drying step, it is sufficient that the solvent can be removed, and for example, known methods such as a coagulation method, a casting method, and a drying method can be used.

<Crosslinking agent>
The cross-linking agent is not particularly limited, but a known cross-linking agent capable of cross-linking the fluorine-containing elastomer in the elastomer composition can be used. Examples of such a cross-linking agent include a peroxide-based cross-linking agent, a bisphenol-based cross-linking agent, a diamine-based cross-linking agent, a triazine-based cross-linking agent, an oxazole-based cross-linking agent, an imidazole-based cross-linking agent, and a thiazole-based cross-linking agent. The cross-linking agent may be used alone or in combination of two or more. Further, the content of the cross-linking agent in the elastomer composition is not particularly limited, and can be an amount usually used in a known elastomer composition.

<Additives>
The additive is not particularly limited, and is not particularly limited, and is a dispersant, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a pigment, a colorant, a foaming agent, an antioxidant, a flame retardant, a lubricant, and a softening agent. Examples thereof include agents, tackifiers, plasticizers, mold release agents, deodorants, and fragrances. More specific additives include, for example, carbon black, silica, talc, barium sulfate, calcium carbonate, clay, magnesium oxide, calcium hydroxide and the like. The additive may be used alone or in combination of two or more. The content of the additive in the elastomer composition is not particularly limited, and can be an amount normally used in a known elastomer composition. For example, the content of the additive in the elastomer composition can be 5 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the fluorine-containing elastomer.

<Kneading process>
The method for producing an elastomer composition of the present invention can include, after the drying step, a kneading step of mixing the dried product with a cross-linking agent or an arbitrary additive to obtain a cross-linking composition. That is, in the kneading step, a crosslinkable composition can be obtained by kneading the dried product, the crosslinking agent, and any additive. The kneading step can be performed using, for example, a mixer, a uniaxial kneader, a biaxial kneader, a roll, a pressure kneader, a lavender (registered trademark), an extruder and the like.

<Crosslinking process>
Further, the method for producing an elastomer composition of the present invention can include a cross-linking step of cross-linking the cross-linking composition obtained in the kneading step to obtain an elastomer cross-linked product. In the cross-linking step, the cross-linking reaction can be carried out by heating the cross-linking composition to obtain an elastomer cross-linked product. In the cross-linking step, for example, the cross-linking composition can be put into a mold having a desired shape and heated, so that the press molding and the cross-linking step can be performed at the same time. Further, by putting the crosslinkable composition into a mold having a desired shape and heating it, press molding and primary crosslinking are performed at the same time, and then the obtained primary crosslinked product is heated again by a heating device such as a gear oven. By doing so, secondary cross-linking can also be performed. Conditions such as the temperature and time of the crosslinking reaction can be appropriately set.

<Molding process>
In addition, the method for producing an elastomer composition of the present invention can include a molding step for obtaining a molded product in which the shape of the crosslinked elastomer is fixed. The molding step can be carried out by any method such as injection molding, extrusion molding, press molding, roll molding and the like. The molded product obtained in the molding step is excellent in properties such as conductivity, thermal conductivity, and strength because CNTs are well dispersed in the fluorine-containing elastomer.

<Use of molded product>
The molded body includes, for example, automobile parts, air conditioning equipment, control equipment, water / hot water supply equipment, high temperature steam equipment, semiconductor equipment, food processing equipment, analysis / physics and chemistry equipment, liquid storage equipment and pressure switch equipment, paint / painting equipment. , Printing / coating equipment, OA equipment, fuel cell peripheral equipment, and various parts that require high tensile strength and high elongation in high temperature environments, which are used in fields such as oil drilling and medical fields. Can be done. Specifically, the molded body can be used as a hose, a sealing material, a belt, a vibration-proof rubber, a diaphragm, a hollow rubber molded body, a roll, a tube, or the like.

The hose is not particularly limited, and for example, a fuel hose, a turbo air hose, an oil hose, a radiator hose, a heater hose, a water hose, a vacuum brake hose, a control hose, an air conditioner hose, a brake hose, a power steering hose, and an air hose. , Marine hoses, risers, flow lines and other hoses can be mentioned.

The sealing material is not particularly limited, and for example, various seals such as О-ring, packing, oil seal, shaft seal, bearing seal, mechanical seal, well head seal, seal for electric / electronic equipment, and seal for pneumatic equipment. Can be mentioned.
The belt is not particularly limited, and examples thereof include various belts such as a power transmission belt and a conveyor belt.
The vibration-proof rubber is not particularly limited, and examples thereof include various vibration-proof rubbers such as vibration-proof rubbers for automobiles.

The diaphragm is not particularly limited, and for example, a diaphragm for an automobile engine such as a fuel system, an exhaust system, a brake system, a drive system, and an ignition system; a diaphragm for a pump; a diaphragm for a valve; a diaphragm for a filter press; a diaphragm for a blower; Various diaphragms such as can be mentioned.

The hollow rubber molded body is not particularly limited, and for example, various bladder such as a tire manufacturing bladder and a tire vulcanizing bladder; various joints such as a flexible joint and an expansion joint; joint boots, rack and pinion steering boots, and pin boots. , Various boots such as piston boots; various valves such as primer valves; and the like.

The roll is not particularly limited, and examples thereof include a print roll; a coating roll; a copy roll such as a printer; and the like.

The tube is not particularly limited, and is, for example, a tube for analytical instruments; a tube for pumps, reactors, stirrers, mixers; a tube for inks such as printers; a tube for pumps for semiconductor manufacturing equipment; for fuel cells. Tubes; tubes that require high corrosive gas properties; etc. can be mentioned.

The crosslinked elastomer composed of the elastomer composition preferably has a hardness of 70 to 90, and particularly preferably has a small change in hardness of ± 6 points or less even after being allowed to stand at 330 ° C. for 70 hours.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, "%" and "part" representing quantities are based on mass unless otherwise specified.

In this example and the comparative example, the median diameter D50 of the laser diffraction type particle size distribution, the area ratio of the carbon nanotube aggregate (CNT aggregate) obtained by image processing, the average value of the area, the average value of the vertical ferret diameter, The change in hardness of the crosslinked elastomer was measured or evaluated using the following methods, respectively.

<D50 of laser diffraction type particle size distribution>
A dispersion liquid obtained in a dispersion step of mixing and dispersing a fluorine-containing elastomer, carbon nanotubes, and a solvent is prepared using a laser diffraction type particle size distribution measuring device (manufactured by HORIBA, product name "LA-950") at a wavelength of 630 nm. The transmittance was adjusted to 88% and the particle size distribution was measured. Then, the median diameter D50 was calculated from the particle size of the cumulative 50% of the obtained particle size distribution.

<Area ratio of carbon nanotube aggregate, average value of area, average value of vertical ferret diameter>
The dispersion obtained in the dispersion step of mixing and dispersing the fluorine-containing elastomer, the carbon nanotubes and the solvent was diluted with the solvent used in the dispersion treatment so that the carbon nanotube concentration was 0.008 wt%. A diluted solution having a carbon nanotube concentration of 0.008 wt% was dropped onto a slide glass, covered with a cover glass, sealed, and used with a digital microscope (product name "VHX-900" manufactured by Keyence), 1.5 mm ×. An image was obtained by observing a 1 mm field of view (magnification 200 times) with side-illuminated illumination. After binarizing the obtained image using image processing software (manufactured by Mitani Shoji Co., Ltd., product name "WinROOF2015"), the area of the carbon nanotube aggregate (CNT aggregate) in which the carbon nanotubes in the image are aggregated is measured. Then, the total area (Sc) of the CNT aggregates within the range of 1.5 mm × 1 mm was obtained. Then, as shown in the following formula, the area ratio (S) of the CNT aggregate can be obtained by calculating the ratio of the total area (Sc) of the CNT aggregate to the observation visual field area (St) as a percentage.
S = (Sc / St) x 100 (%)
The area of 800 or more CNT aggregates was measured, and the average value was obtained as the average value of the area.
800 or more vertical ferret diameters of the CNT aggregate were measured, and the average value was obtained as the average value of the vertical ferret diameters. The vertical ferret diameter refers to the ferret diameter in the direction perpendicular to the long axis of the object by obtaining the circumscribing rectangle in the long axis direction of the object.

<Hardness change>
The sheet-shaped elastomer crosslinked products obtained in Examples and Comparative Examples were punched into dumbbell test pieces (JIS No. 3) to prepare test pieces. Using an automatic rubber hardness tester (manufactured by Polymer Meter Co., Ltd., product name "Automatic rubber hardness tester P1-A type"), in accordance with JIS K6253-3: 2012, under the conditions of test temperature 23 ° C and test humidity 50%. The normal hardness _HA was measured by measuring the hardness with. The dumbbell test piece was heat-treated in an oven at 330 ° C. (manufactured by Koyo Thermo System Co., Ltd., model "INH-9CD-S") for 70 hours in the atmosphere to prepare a test piece after heat aging. The test piece after heat aging was used with an automatic rubber hardness tester (manufactured by Polymer Meter Co., Ltd., product name "automatic rubber hardness tester P1-A type"), and the test temperature was 23 ° C. in accordance with JIS K6253-3: 2012. By measuring the hardness under the condition of the test humidity of 50%, the hardness _HB after heat aging at 330 ° C. was measured. Then, as shown in the following formula, the hardness change ΔH was calculated from the difference between the normal hardness _HA and the hardness H _B after heat aging at 330 ° C.
ΔH = H _B - _HA

(Example 1)
<Preparation of carbon nanotube dispersion liquid>
<< Dispersion process >>
Add 100 parts (100 g) of FFKM (trade name "Aflas PM-1100" manufactured by AGC) as a fluorine-containing elastomer to 1899 g of Novec (registered trademark) 7300 manufactured by 3M as a solvent, and 12 at a temperature of 20 ° C. The fluorine-containing elastomer was dissolved by stirring for a time to obtain a fluorine-containing elastomer solution (dissolution step).

Next, for the fluorine-containing elastomer solution, SGCNT as a carbon nanotube (manufactured by Zeon Nanotechnology, product name "ZEONANO SG101", average diameter: 3.4 nm, BET specific surface area: 1350 m ² / g, t-plot is above. 1 part (1 g) was added, and the mixture was stirred at a temperature of 20 ° C. for 30 minutes using a stirrer (manufactured by PRIMIX, Lab Solution (registered trademark), stirring part: homodisper). Further, a bead mill (manufactured by Asada Iron Works Co., Ltd., trade name "Nanomill NM-G1.4L", zirconia beads (average diameter of dispersed media: 0.65 mm) as a dispersed medium was used, and a fluorine-containing elastomer solution containing SGCNT was added to the temperature. A 3-pass dispersion treatment was performed at 40 ° C. (dispersion treatment conditions: peripheral speed 12.5 m / s, discharge rate 74 g / min) to obtain a carbon nanotube dispersion liquid (dispersion treatment step).

Using the obtained dispersion treatment liquid, laser diffraction type particle size distribution measurement of the dispersion liquid, digital microscope observation and image processing were performed, the median diameter D50 of the carbon nanotubes in the dispersion liquid, and the carbon nanotube aggregate obtained by the image processing. The area ratio, the average value of the area, and the average value of the vertical ferret diameter were obtained. The results are shown in Table 1.

<Drying process>
Then, the obtained dispersion was added dropwise to 2000 g of methyl ethyl ketone (MEK) and coagulated to obtain a black solid. The obtained black solid was dried under reduced pressure at 120 ° C. for 12 hours to obtain a mixture of a fluorine-containing elastomer and SGCNT (drying step).

<Kneading process>
Using an open roll at 50 ° C., 101 parts of the mixture, 3 parts of triallyl isocyanurate (manufactured by Nihon Kasei Co., Ltd., product name "TAIC (registered trademark)") and 2,5-dimethyl-2,5 as a cross-linking agent. -Di (t-butylperoxy) hexane (manufactured by Nihon Kasei Co., Ltd., trade name "Perhexa (registered trademark) 25B-40" was kneaded with 2 parts to obtain a crosslinkable composition (kneading step).

<Elastomer crosslinked product>
The obtained crosslinkable composition was put into a mold and crosslinked at a temperature of 150 ° C. and a pressure of 10 MPa for 20 minutes to form a sheet-like crosslinked product after primary vulcanization (length: 150 mm, width: 150 mm, thickness:: 2 mm) was obtained. Then, it was heat-treated in a gear oven (manufactured by Toyo Seiki Co., Ltd., model "S60") at 250 ° C. for 4 hours to obtain a sheet-shaped elastomer crosslinked product after secondary vulcanization. The hardness change of this elastomer crosslinked product after heat aging at 330 ° C. for 70 hours was determined. The results are shown in Table 1.

(Example 2)
Example 1 except that the amount of SGCNT added to the fluorine-containing elastomer solution was changed to 4 parts (4 g), and the average diameter of the dispersed media of zirconia beads, which is the dispersed medium of the bead mill, was changed to 0.50 mm. In the same manner as above, a dispersion liquid and a sheet-shaped elastomer crosslinked product were prepared. Various measurements were made in the same manner. The results are shown in Table 1.

(Example 3)
A dispersion and a sheet-shaped crosslinked elastomer were prepared in the same manner as in Example 2 except that the amount of SGCNT added to the fluorine-containing elastomer solution was changed to 1 part (1 g). Various measurements were made in the same manner. The results are shown in Table 1.

(Comparative Example 1)
The same as in Example 1 except that the dispersion treatment (dispersion treatment conditions: pressure 100 MPa, number of passes 7 times) was performed using a jet mill (manufactured by Yoshida Kikai Kogyo Co., Ltd., trade name "L-ES007") instead of the bead mill. To prepare a dispersion liquid and a sheet-shaped elastomer crosslinked product. Various measurements were made in the same manner. The results are shown in Table 1.

(Comparative Example 2)
When preparing a fluorine-containing elastomer solution, 100 parts (100 g) of FKM (manufactured by Chemers, product name "Viton GBL600S") and 1899 g of methyl ethyl ketone (MEK, manufactured by Fujifilm Wako Junyaku Co., Ltd.) were used as the fluorine-containing elastomer. Further, the obtained dispersion was dropped onto 4000 g of 2-propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and solidified to obtain a black solid, but the dispersion and the dispersion were obtained in the same manner as in Example 2. A sheet-shaped elastomer crosslinked product was prepared. Various measurements were made in the same manner. The results are shown in Table 1.

From Table 1, the elastomer crosslinked product produced using the carbon nanotube dispersions of Examples 1 to 3 satisfying the predetermined median diameter D50, the area ratio of the carbon nanotube aggregate, the average value of the area, and the average value of the vertical ferret diameter. Is an elastomer bridge produced using the carbon nanotube dispersions of Comparative Examples 1 and 2 that do not satisfy any of the predetermined median diameter D50, the area ratio of the carbon nanotube aggregate, the average value of the area, and the average value of the vertical ferret diameter. It can be seen that the change in hardness after heat aging at a temperature of 330 ° C. is smaller than that of the product.

According to the method for producing a carbon nanotube dispersion liquid and an elastomer composition of the present invention, it is possible to provide an elastomer crosslinked product that exhibits sufficient rubber performance even at a high temperature of over 300 ° C.

Claims (18)

A carbon nanotube dispersion liquid comprising an elastomer solution in which a fluorine-containing elastomer is dissolved in a solvent and carbon nanotubes dispersed in the elastomer solution.
For the carbon nanotube dispersion liquid, prepare a preparation dispersion liquid prepared so that the carbon nanotube concentration is 0.008% by mass, and use an optical microscope to prepare the preparation dispersion liquid in a range of 1.5 mm × 1 mm. A carbon nanotube dispersion having an area ratio of 1.0% or less as a proportion of CNT aggregates in which the carbon nanotubes are aggregated within the above range when observed. A carbon nanotube dispersion liquid comprising an elastomer solution in which a fluorine-containing elastomer is dissolved in a solvent and carbon nanotubes dispersed in the elastomer solution.
For the carbon nanotube dispersion liquid, prepare a prepared dispersion liquid prepared so that the carbon nanotube concentration is 0.008 mass%, and use an optical microscope to prepare the prepared dispersion liquid in a range of 1.5 mm × 1 mm. A carbon nanotube dispersion having an average value of 60 μm ² or less in the area of the CNT aggregate in which the carbon nanotubes are aggregated within the above range when observed. A carbon nanotube dispersion liquid comprising an elastomer solution in which a fluorine-containing elastomer is dissolved in a solvent and carbon nanotubes dispersed in the elastomer solution.
For the carbon nanotube dispersion liquid, prepare a preparation dispersion liquid prepared so that the carbon nanotube concentration is 0.008% by mass, and use an optical microscope to prepare the preparation dispersion liquid in a range of 1.5 mm × 1 mm. A carbon nanotube dispersion having an average value of 6 μm or less in the vertical ferret diameter of the CNT aggregate in which the carbon nanotubes are aggregated within the above range when observed. A carbon nanotube dispersion liquid comprising an elastomer solution in which a fluorine-containing elastomer is dissolved in a solvent and carbon nanotubes dispersed in the elastomer solution.
A carbon nanotube dispersion liquid in which the median diameter of the carbon nanotubes in the carbon nanotube dispersion liquid is 9 μm or less. In the carbon nanotube dispersion liquid according to any one of claims 1 to 4.
The fluorine-containing elastomer is a carbon nanotube dispersion liquid which is a perfluoroelastomer (FFKM). In the carbon nanotube dispersion liquid according to any one of claims 1 to 5.
The carbon nanotube is a carbon nanotube dispersion liquid containing a single-walled carbon nanotube. In the carbon nanotube dispersion liquid according to any one of claims 1 to 6.
The carbon nanotube is a carbon nanotube dispersion liquid contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the fluorine-containing elastomer. In the carbon nanotube dispersion liquid according to any one of claims 1 to 7.
The solvent is a carbon nanotube dispersion liquid which is a fluorine-based solvent. A method for producing an elastomer composition containing a fluorine-containing elastomer and carbon nanotubes.
A dispersion step of mixing and dispersing the fluorine-containing elastomer, the carbon nanotubes, and a solvent capable of dissolving the fluorine-containing elastomer to obtain a carbon nanotube dispersion liquid.
A drying step of removing the solvent from the obtained carbon nanotube dispersion liquid to obtain a dried product is provided.
In the dispersion step, a prepared dispersion prepared so that the obtained carbon nanotube dispersion has a carbon nanotube concentration of 0.008% by mass is prepared, and the prepared dispersion is prepared using an optical microscope. A method for producing an elastomer composition, wherein the dispersion treatment is performed so that the area ratio of the CNT aggregates in which the carbon nanotubes are aggregated is 1.0% or less in the range when observed in the range of .5 mm × 1 mm. .. A method for producing an elastomer composition containing a fluorine-containing elastomer and carbon nanotubes.
A dispersion step of mixing and dispersing the fluorine-containing elastomer, the carbon nanotubes, and a solvent capable of dissolving the fluorine-containing elastomer to obtain a carbon nanotube dispersion liquid.
A drying step of removing the solvent from the obtained carbon nanotube dispersion liquid to obtain a dried product is provided.
In the dispersion step, a prepared dispersion prepared so that the obtained carbon nanotube dispersion has a carbon nanotube concentration of 0.008% by mass is prepared, and the prepared dispersion is prepared using an optical microscope. A method for producing an elastomer composition, wherein the dispersion treatment is performed so that the average value of the area of the CNT aggregates in which the carbon nanotubes are aggregated is 60 μm ² or less when observed in the range of .5 mm × 1 mm. .. A method for producing an elastomer composition containing a fluorine-containing elastomer and carbon nanotubes.
A dispersion step of mixing and dispersing the fluorine-containing elastomer, the carbon nanotubes, and a solvent capable of dissolving the fluorine-containing elastomer to obtain a carbon nanotube dispersion liquid.
A drying step of removing the solvent from the obtained carbon nanotube dispersion liquid to obtain a dried product is provided.
In the dispersion step, a prepared dispersion prepared so that the obtained carbon nanotube dispersion has a carbon nanotube concentration of 0.008% by mass is prepared, and the prepared dispersion is prepared using an optical microscope. An elastomer composition that is subjected to dispersion treatment so that the average value of the vertical ferret diameter of the CNT aggregates in which the carbon nanotubes are aggregated is 6 μm or less when observed in a range of .5 mm × 1 mm. Production method. A method for producing an elastomer composition containing a fluorine-containing elastomer and carbon nanotubes.
A dispersion step of mixing and dispersing the fluorine-containing elastomer, the carbon nanotubes, and a solvent capable of dissolving the fluorine-containing elastomer to obtain a carbon nanotube dispersion liquid.
A drying step of removing the solvent from the obtained carbon nanotube dispersion liquid to obtain a dried product is provided.
The dispersion step is a method for producing an elastomer composition, wherein the dispersion treatment is performed so that the median diameter of the carbon nanotubes in the obtained carbon nanotube dispersion liquid is 9 μm or less. In the method for producing an elastomer composition according to any one of claims 9 to 12.
The method for producing an elastomer composition, wherein the fluorine-containing elastomer is a perfluoroelastomer (FFKM). In the method for producing an elastomer composition according to any one of claims 9 to 13.
The carbon nanotube is a method for producing an elastomer composition containing a single-walled carbon nanotube. In the method for producing an elastomer composition according to any one of claims 9 to 14.
The method for producing an elastomer composition, wherein the carbon nanotube dispersion liquid contains the carbon nanotubes in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the fluorine-containing elastomer. In the method for producing an elastomer composition according to any one of claims 9 to 15.
A method for producing an elastomer composition, wherein the solvent is a fluorine-based solvent. In the method for producing an elastomer composition according to any one of claims 9 to 16.
A method for producing an elastomer composition, further comprising a kneading step of mixing the dried product and a cross-linking agent to obtain a cross-linking composition after the drying step. In the method for producing an elastomer composition according to claim 17.
A method for producing an elastomer composition, further comprising a cross-linking step of cross-linking the cross-linking composition obtained in the kneading step to obtain an elastomer cross-linked product.