Conductive rubber composition

Abstract

Provided is an excellent, novel conductive rubber composition that has flexibility, as well as the high conductivity and reinforcing properties required for general conductive applications, and that has greatly improved processability in an unvulcanized state.　The conductive rubber composition is characterized by containing, relative to 100.0 parts by mass of a rubber component, 20.0-60.0 parts by mass carbon black and 1.0-7.0 parts by mass fibrous carbon, and is further characterized in that the carbon black has a nitrogen adsorption specific surface area of 40-80 m2 / g, a DBP absorption quantity of 140-200 mL / 100 g, and a full width at half maximum ΔD of a Raman scattering peak appearing in the range 1340-1360 cm-1 when an excitation wavelength is 532 nm of 200-280 cm-1.

Description

Conductive rubber composition

[0001] The present invention relates to an electrically conductive rubber composition.

[0002] Rubber compositions used as constituent materials for rubber members constituting various automobile parts are required to have high electrical conductivity for anti-static purposes. Known examples of such conductive rubber compositions (conductive rubber compositions) include rubber compositions containing conductive fillers such as ketjen black, acetylene black, graphite powder, carbon fiber, carbon nanotubes, metal powder, and alkali metal salt conductive fillers (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2009-227985

[0004] On the other hand, if a large amount of carbon black is blended into the rubber component to impart high conductivity, the flexibility of the resulting conductive rubber composition decreases, making it difficult to easily attach automotive parts to vehicles.

[0005] Under these circumstances, an object of the present invention is to provide a novel conductive rubber composition that has flexibility, high electrical conductivity and reinforcing properties, and excellent processability in an unvulcanized state.

[0006] As a result of intensive research conducted by the present inventors to solve the above technical problems, they discovered that the desired effects can be achieved by using carbon black having specific physical properties and by using a conductive rubber composition containing specific amounts of the above carbon black and fibrous carbon in the rubber component, and they have completed the present invention based on this finding.

[0007] That is, the present invention provides: (1) a rubber composition containing 20.0 to 60.0 parts by mass of carbon black and 1.0 to 7.0 parts by mass of fibrous carbon per 100.0 parts by mass of a rubber component, wherein the carbon black has a nitrogen adsorption specific surface area of ​​40 to 80 m ２ / g, DBP absorption is 140-200 mL / 100 g, and the excitation wavelength is 532 nm, at 1340-1360 cm －１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 200 to 280 cm －１(2) The conductive rubber composition according to (1) above, which contains 30.0 to 50.0 parts by mass of carbon black and 3.0 to 5.0 parts by mass of fibrous carbon per 100.0 parts by mass of the rubber component; (3) The carbon black has a nitrogen adsorption specific surface area of ​​50 to 70 m ２ / g, DBP absorption is 150-180 mL / 100 g, and the excitation wavelength is 532 nm, at 1340-1360 cm －１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 220 to 260 cm －１ The present invention provides the conductive rubber composition according to the above (1) or (2), which is

[0008] According to the present invention, it is possible to provide a novel conductive rubber composition that has flexibility, high electrical conductivity and reinforcing properties, and excellent processability in an unvulcanized state.

[0009] 1 is an explanatory diagram showing a method for calculating the full width at half maximum ΔD of carbon black in the present application. 2 is a diagram showing an example of a Raman spectrum measurement obtained when calculating the full width at half maximum ΔD of carbon black in the present application. 3 is a schematic diagram of a cross section of an example of a cylindrical reactor for producing carbon black that constitutes the conductive rubber composition according to the present invention. 4 is a conceptual diagram schematically showing a good dispersion state of carbon black and fibrous carbon in rubber in the conductive rubber composition according to the present invention.

[0010] The conductive rubber composition according to the present invention contains 20.0 to 60.0 parts by mass of carbon black and 1.0 to 7.0 parts by mass of fibrous carbon per 100.0 parts by mass of a rubber component, and the carbon black has a nitrogen adsorption specific surface area of ​​40 to 80 m ２ / g, DBP absorption is 140-200 mL / 100 g, and the excitation wavelength is 532 nm, at 1340-1360 cm －１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 200 to 280 cm －１ The present invention is characterized in that:

[0011] In the conductive rubber composition according to the present invention, the carbon black has a nitrogen adsorption specific surface area of ​​40 to 80 m２ The nitrogen adsorption specific surface area of ​​the carbon black is 40 to 80 m / g. ２ / g, homo-agglomeration of carbon black particles can be suitably suppressed, and the conductive rubber composition according to the present invention can easily exhibit high conductivity and reinforcing properties when used as a constituent material for various rubber members. In the conductive rubber composition according to the present invention, the larger the nitrogen adsorption specific surface area of ​​the carbon black, the higher the conductivity and reinforcing properties of the conductive rubber composition when blended with a rubber component. However, if the nitrogen adsorption specific surface area is excessively large, homo-agglomeration of carbon black particles is likely to occur, worsening the dispersibility of the carbon black and reducing the reinforcing properties of the rubber composition and the processability of the rubber in an unvulcanized state. Furthermore, from the viewpoint of imparting the conductivity required for general conductive applications such as antistatic properties while significantly improving the processability of rubber in an unvulcanized state, the nitrogen adsorption specific surface area of ​​the carbon black in the conductive rubber composition according to the present invention is 40 to 80 m ２ / g, and 45 to 75 m ２ / g is preferred, and 50 to 70m ２ / g is more preferred.

[0012] The nitrogen adsorption specific surface area is the specific surface area (m ) calculated from the amount of nitrogen molecules adsorbed per unit mass of carbon black. ２ / g), and in the present application documents, the nitrogen adsorption specific surface area means a value determined in accordance with JIS K6217-7:2013.

[0013] Furthermore, in the conductive rubber composition according to the present invention, the larger the CTAB specific surface area of ​​the carbon black, the higher the conductivity and reinforcing properties of the conductive rubber composition when blended with a rubber component, but the greater the tendency for homo-aggregation of carbon black particles to occur, which significantly deteriorates the dispersibility and processability of the carbon black. Therefore, from the viewpoint of obtaining a conductive rubber composition that suppresses homo-aggregation of carbon black particles, has the conductivity and reinforcing properties required for general conductive applications such as antistatic, and is excellent in processability in an unvulcanized state, the CTAB specific surface area of ​​the carbon black in the conductive rubber composition according to the present invention is 40 to 80 m ２ / g, and 45 to 75m ２ / g, and more preferably 50 to 70m ２ It is more preferable that the saturation coefficient is 1 / g.

[0014] In the present application, the CTAB specific surface area is the specific surface area (m ) calculated from the adsorption amount of CTAB (Cetyl Tri-methyl Ammonium Bromide) molecules per unit mass of carbon black. ２ / g) and means a value determined in accordance with JIS K6217-3:2001.

[0015] In the conductive rubber composition according to the present invention, the DBP absorption of the carbon black is 140 to 200 mL / 100 g. A higher DBP absorption of the carbon black indicates a more developed carbon black structure. A developed carbon black structure improves the proximity and contact between aggregates, thereby increasing the conductivity of the conductive rubber composition when compounded with a rubber component. However, on the other hand, this deteriorates the processability of the rubber in an unvulcanized state. From this perspective, by having the DBP absorption of the carbon black in the conductive rubber composition according to the present invention be 140 to 200 mL / 100 g, when the conductive rubber composition according to the present invention is used as a constituent material for various rubber members, both high conductivity and good processability of the rubber in an unvulcanized state can be achieved. In the conductive rubber composition according to the present invention, the DBP absorption of the carbon black is preferably 145 to 190 mL / 100 g, and more preferably 150 to 180 mL / 100 g or more.

[0016] DBP absorption is a value that expresses the structure of carbon black as the amount of DBP (dibutyl phthalate) absorbed per 100 g of carbon black (mL / 100 g). In this application, DBP absorption refers to a value determined in accordance with JIS K6217-4:2017. The porosity between carbon black aggregates is positively correlated with the carbon black structure. Therefore, a larger DBP absorption value indicates a more developed carbon black structure.

[0017] The carbon black constituting the conductive rubber composition according to the present invention has a viscosity of 1340 to 1360 cm when the excitation wavelength is 532 nm. －１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 200 to 280 cm －１ The carbon black constituting the conductive rubber composition according to the present invention has a viscosity of 1340 to 1360 cm when the excitation wavelength is 532 nm. －１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 200 to 280 cm －１ By using the carbon black as a constituent material of the conductive rubber composition of the present invention, it is possible to easily exhibit excellent conductivity when the conductive rubber composition of the present invention is used as a constituent material of various rubber members while suppressing homo-aggregation of carbon black particles. －１ The smaller the full width at half maximum ΔD of the Raman scattering peak appearing in the range of 1340 to 1360 cm when the excitation wavelength is 532 nm, the higher the conductivity of the conductive rubber composition when the carbon black is blended with the rubber component. However, since the dispersibility of the carbon black and the processability of the rubber in an unvulcanized state (unvulcanized rubber) deteriorate, it is important to control the full width at half maximum ΔD within a predetermined range. －１ The full width at half maximum ΔD of the Raman scattering peak appearing in the range is 200 to 280 cm from the viewpoint of obtaining a conductive rubber composition that has flexibility, high conductivity and reinforcing properties, and simultaneously achieves high levels of carbon black dispersibility and processability in an unvulcanized state.－１ and 210 to 270 cm －１ More preferably, 220 to 260 cm －１ The appropriate range of the full width at half maximum ΔD for balancing the electrical conductivity and reinforcing properties of the conductive rubber composition with the processability in an unvulcanized state varies depending on the range of the specific surface area of ​​the carbon black.

[0018] As shown in FIG. 1 , the carbon black constituting the conductive rubber composition according to the present invention has a peak intensity of 1340 to 1360 cm in a Raman spectrum obtained by measuring at an excitation wavelength of 532 nm by laser Raman spectroscopy. －１ (1350±10cm －１ A peak having a peak top in the range of Dmax (cm) is detected. The measurement wavelength at the peak top position is defined as Dmax (cm). －１ ) and the detection position on the low wavelength (low Raman shift) side having a detection intensity half the peak intensity at Dmax in the obtained spectrum is defined as D50 (cm －１ ), the value calculated by the following formula is the full width at half maximum ΔD (cm －１ ) ΔD = (Dmax - D50) x 2

[0019] In the present application, the full width at half maximum ΔD (cm －１ ) means a value calculated from the Raman spectrum obtained by measuring under the measurement conditions of (Procedure 1) below and then performing data processing of (Procedure 2). (Procedure 1) Using an HR-800 manufactured by Horiba, Ltd. as the laser Raman spectrometer, several grains of the carbon black sample to be measured are placed on a slide glass and rubbed several times with a spatula to flatten the surface, and then measurement is performed under the following measurement conditions: YAG laser (excitation wavelength): 532 nm Number of grooves: 600 gr / mm Filter: D0.6 Objective lens magnification: 100x Exposure time: 150 seconds Number of accumulations: 2 An example of the spectrum obtained at this time is shown in Figure 2. (Procedure 2) Measurement wavelength (RamanShift) of the obtained spectrum: 2100 cm －１The signal intensity at 1350±10 cm was set to 0, and the average value was calculated for each of the 39 adjacent data points constituting the spectrum. Then, smoothing was performed to obtain a spectral curve connecting the average values. －１ The peak top intensity observed in this range is taken as 100. An example of the Raman spectrum obtained in this case is the Raman spectrum shown in FIG.

[0020] In the Raman spectrum, 1340 to 1360 cm －１ (1350±10cm －１ ) corresponds to a peak in the D band of a Raman spectrum. The full width at half maximum ΔD of the D band peak represents the degree of disorder in the crystalline structure on the carbon black surface, i.e., crystallinity. A higher full width at half maximum ΔD of the D band peak is considered to indicate a more disordered crystalline structure (lower crystallinity). High crystallinity is considered to result in fewer edges on the carbon black surface, allowing for free movement of π electrons on the carbon black surface, improving conductivity. At the same time, the number of sites (active sites) where functional groups can be formed on the carbon black surface is reduced, making it difficult for interactions between the rubber component and the carbon black surface to occur. This has the effect of suppressing the hardness of a conductive rubber composition when blended with a rubber component. On the other hand, if the crystallinity of carbon black is too high, homo-aggregation of carbon black particles is likely to occur, which is considered to result in poor processability in the unvulcanized state when blended with a rubber component. Therefore, in the conductive rubber composition according to the present invention, by controlling the full width at half maximum ΔD of the carbon black within a predetermined range, it is thought that homo-agglomeration of carbon black particles can be suppressed, while improving the reinforcing properties of the conductive rubber composition when the carbon black is blended with the rubber component, and that the conductivity can be improved while reducing the hardness of the conductive rubber composition.

[0021] The carbon black constituting the conductive rubber composition according to the present invention can be produced by the production method described below.

[0022] A method for producing the carbon black constituting the conductive rubber composition according to the present invention can include, for example, using a reactor in which a fuel combustion zone and a feedstock oil reaction zone are sequentially provided from upstream to downstream of a gas flow path, introducing an oxygen-containing gas and a fuel into the fuel combustion zone and burning the mixture to generate a high-temperature combustion gas flow, and introducing a feedstock oil into the feedstock oil reaction zone while introducing the high-temperature combustion gas flow to cause a reaction.

[0023] The reactor may be a cylindrical reactor having, as a feedstock oil reaction zone, a reaction zone whose inner diameter gradually converges and then expands in the gas flow direction, in addition to the fuel combustion zone. Specifically, as shown in the cross-sectional view of FIG. 3 , a cylindrical reactor 1 may be mentioned, which has a fuel combustion zone 6, a throat reaction zone 7 which has the same inner diameter from the inlet to the outlet but is smaller than the fuel combustion zone 6, a tapered wide-diameter reaction zone 8 whose inner diameter gradually expands in a tapered manner, and a straight wide-diameter reaction zone 10, which are sequentially provided coaxially and communicate with each other in the furnace axial direction 4.

[0024] In the cylindrical reactor 1 shown in FIG. 3, the fuel combustion zone 6 is formed by introducing oxygen (O ) such as air preheated to 400 to 600° C. from an inlet (In) provided in a direction perpendicular to the furnace axial direction 4 (tangential direction of the furnace head). ２ The furnace is equipped with a wind box 3 equipped with an oxygen-containing gas supply port 2 for introducing oxygen-containing gas, and a double-cylinder fuel oil and feed oil injection nozzle 5 for supplying fuel oil and feed oil in the furnace axial direction 4.

[0025] In the cylindrical reactor 1 shown in FIG. 3, an oxygen-containing gas such as air is supplied from an oxygen-containing gas supply port 2 provided in a wind box 3 and introduced into a fuel combustion region 6 .

[0026] The fuel oil and raw oil injection nozzle 5 having a double-cylinder structure has a coaxial double-cylinder structure having an outer cylinder fuel oil burner 51 which has a water-cooled outer jacket attached in the furnace axial direction 4 and can move back and forth in the furnace axial direction 4, and a central cylinder raw oil nozzle 52 which has a water-cooled outer jacket and is inserted coaxially into the outer cylinder fuel oil burner 51 and can be freely extended and retracted in the furnace axial direction 4.

[0027] In the cylindrical reactor 1 shown in FIG. 3, an oxygen-containing gas such as air is introduced into a fuel combustion region 6 from an oxygen-containing gas supply port 2 provided in a wind box 3, while fuel oil is injected from the external fuel oil burner 51 and mixed and burned to generate a high-temperature combustion gas flow.

[0028] The oxygen-containing gas may be oxygen, air, or a gas consisting of a mixture thereof, and the fuel oil may be one or more selected from hydrogen, carbon monoxide, natural gas, petroleum gas, FCC residual oil, petroleum-based liquid fuels such as heavy oil, and coal-based liquid fuels such as creosote oil.

[0029] In the cylindrical reactor 1 shown in FIG. 3, the feed oil is introduced into the throat reaction zone 7 from the central cylindrical feed oil nozzle 52 while the high-temperature combustion gas flow is being introduced.

[0030] Examples of the feedstock oil include one or more selected from aromatic hydrocarbons such as cyclohexane, benzene, toluene, xylene, naphthalene, and anthracene; coal-based hydrocarbons such as creosote oil and carboxylic acid oil; petroleum-based heavy oils such as ethylene bottom oil (ethylene heavy end oil) and FCC residual oil; acetylenic unsaturated hydrocarbons; ethylenic hydrocarbons; and aliphatic saturated hydrocarbons such as pentane and hexane.

[0031] The feedstock oil introduction position in the throat reaction zone 7 can be changed as needed by extending or retracting the central tubular feedstock oil nozzle 52. This allows the residence time of the product from the feedstock oil introduction position to the outlet of the throat reaction zone 7 (the boundary position with the tapered wide-diameter reaction zone 8, whose inner diameter expands in a tapered manner) to be adjusted within a desired range.

[0032] As described above, the throat reaction zone 7 preferably has a drum-shaped structure (a cylindrical structure) in which the inner diameter is constant from the inlet to the outlet, and as shown in FIG. 3, the throat reaction zone has an inner diameter D and a throat reaction zone length L (the length of the throat reaction zone in the axial direction of the furnace).

[0033] The throat reaction zone 7 has a ratio D / L of the throat reaction zone length L to the throat reaction zone diameter D of preferably 0.12 to 0.18, more preferably 0.12 to 0.17, and even more preferably 0.12 to 0.16.

[0034] In addition, in the throat reaction zone 7, the residence time of the product from the feed oil introduction position to the outlet of the throat reaction zone 7 is preferably controlled to 2.0 to 10.0 msec, more preferably 3.5 to 9.5 msec, and even more preferably 3.0 to 9.0 msec.

[0035] In the present application, the residence time of the product is calculated by the following formula: Residence time of product (msec) = (volume (m) of the space defined by a cross section perpendicular to the furnace axis at the feed oil introduction position, a side surface of the throat reaction zone from the feed oil introduction position to the outlet of the throat reaction zone, and a cross section perpendicular to the furnace axis at the outlet of the throat reaction zone) ３ )) / (the volume of reaction gas per unit time (m) passing through the space defined by the vertical cross section to the furnace axis at the feed oil introduction position, the side surface of the throat reaction zone from the feed oil introduction position to the outlet of the throat reaction zone, and the vertical cross section to the furnace axis at the outlet of the throat reaction zone ３ / sec) × 10 ３ The value calculated by

[0036] By controlling the ratio D / L of the throat reaction zone length L to the throat reaction zone diameter D and the residence time of the product from the feed oil introduction position to the throat reaction zone outlet within the above ranges, the nitrogen adsorption specific surface area, DBP absorption amount, and the 1340 to 1360 cm 3 at an excitation wavelength of 532 nm can be achieved. －１ The carbon black constituting the conductive rubber composition according to the present invention can be easily produced, in which the full width at half maximum ΔD of the Raman scattering peak appearing in the range of 1000 to 10000 and the like are each within the desired range.

[0037] In the cylindrical reactor 1 shown in FIG. 3 , carbon black produced in the throat reaction zone 7 is introduced into the tapered wide-diameter reaction zone 8, where it undergoes particle growth and unreacted organic components on the surface of the carbon black are decomposed and volatilized. This is then reacted in the straight wide-diameter reaction zone 10, which is connected to the tapered wide-diameter reaction zone 8, whereby the feedstock oil is suitably pyrolyzed to produce the desired carbon black. The cylindrical reactor 1 shown in FIG. 3 has a quenching section (reaction termination zone) 11 equipped with a water-cooled quench 9 downstream of the straight wide-diameter reaction zone 10, and a flue 12 connected to the straight wide-diameter reaction zone 10. In the cylindrical reactor 1 shown in FIG. 3 , carbon black particles produced in the straight wide-diameter reaction zone 10 are introduced into the quenching section 11, which is connected to the quenching section 11, where a coolant is sprayed from the water-cooled quench 9 into the quenching section 11, where the reaction is terminated. Examples of the coolant include water, and the carbon black particles suspended in the high-temperature combustion gas are cooled by spraying the coolant.

[0038] In the cylindrical reactor 1 shown in FIG. 3 , the cooled carbon black particles are then passed through a flue 12 and separated and collected at an outlet (Out) by a collection system (separation and collection device) such as a cyclone or a bag filter, thereby allowing the target carbon black to be recovered.

[0039] Next, the fibrous carbon that constitutes the conductive rubber composition according to the present invention will be described.

[0040] The fibrous carbon can be a fibrous carbon nanostructure, which is generally a fibrous structure composed mainly of carbon atoms, and whose radial dimension among its three-dimensional dimensions is in the nanometer range, for example, on the order of several nm to several hundred nm.

[0041] In the conductive rubber composition according to the present invention, the smaller the average diameter of the fibrous carbon, the higher the conductivity of the conductive rubber composition, but this raises concerns about safety for the human body, and deteriorates the dispersibility of the fibrous carbon and the processability of the rubber in an unvulcanized state. Therefore, in the conductive rubber composition according to the present invention, the average diameter of the fibrous carbon is preferably 1 to 200 nm, and from the viewpoint of simultaneously achieving high levels of dispersibility of the fibrous carbon, processability of the rubber in an unvulcanized state, and conductivity of the conductive rubber composition, it is more preferably 5 to 100 nm, and even more preferably 10 to 50 nm.

[0042] In the present application documents, the average diameter of fibrous carbon means a value calculated by measuring the diameter of one fiber at three points, near the tip, near the center, and near the end, using a transmission electron microscope, and arithmetically averaging the fiber diameters measured in the same manner for 30 fibers.

[0043] When the average diameter of the fibrous carbon is 200 nm or less, it becomes easier to obtain a conductive rubber composition with higher conductivity even if the amount of fibrous carbon mixed with the rubber component is small. Also, when the average diameter of the fibrous carbon is 1 nm or more, the safety of the fibrous carbon to the human body is increased, and both the dispersibility of the fibrous carbon and the processability of the rubber in an unvulcanized state can be achieved at a high level, allowing the various properties of the conductive rubber composition of the present invention to be fully exhibited.

[0044] In the conductive rubber composition according to the present invention, the longer the average length of the fibrous carbon, the better the connection with carbon black when blended together with carbon black in a rubber component, and the higher the conductivity. However, since the dispersibility of the fibrous carbon and the processability of the rubber in an unvulcanized state deteriorate, the average length is preferably 10 to 3000 μm, and from the viewpoint of simultaneously achieving high levels of dispersibility of the fibrous carbon, processability of the rubber in an unvulcanized state, and conductivity of the conductive rubber composition, the average length is more preferably 20 to 800 μm, and even more preferably 30 to 300 μm.

[0045] In the present application, the average length of fibrous carbon means a value calculated by measuring and averaging the fiber lengths of 30 fibers in an image measured at a certain magnification using a scanning electron microscope.

[0046] When fibrous carbon is blended into the rubber component together with carbon black, if the average length of the fibrous carbon is 10 nm or more, it will have good connectivity with the carbon black, making it easier to obtain a conductive rubber composition with higher conductivity even with a small amount of fibrous carbon blended.If the average length of the fibrous carbon is 3000 μm or less, it is possible to achieve high levels of both dispersibility of the fibrous carbon and processability of the rubber in an unvulcanized state, and the various properties of the conductive rubber composition of the present invention can be fully exhibited.

[0047] In the conductive rubber composition according to the present invention, the larger the specific surface area of ​​the fibrous carbon, the higher the conductivity of the conductive rubber composition. However, the dispersibility of the fibrous carbon and the processability of the rubber in an unvulcanized state deteriorate. Therefore, from the viewpoint of simultaneously achieving high levels of dispersibility of the fibrous carbon, processability of the rubber in an unvulcanized state, and the conductivity of the conductive rubber composition, the specific surface area should be 100 to 1500 m. ２ / g, and 150 to 1000m ２ / g, and more preferably 200 to 500m ２ It is more preferable that the SiO2 content is 1 / g.

[0048] In the present application, the specific surface area of ​​the fibrous carbon refers to the nitrogen adsorption specific surface area determined by the BET method using a BELSORP-max manufactured by Microtrac-Bell.

[0049] Fibrous carbon is added in small amounts to the rubber component along with carbon black, and by dispersing uniformly, it acts as a bridge connecting aggregates. As a result, when compounded with the rubber component, it does not impair the processability of the rubber in an unvulcanized state, and when producing a conductive rubber composition of a certain hardness, it has the effect of significantly improving conductivity compared to conventional carbon black. Adding fibrous carbon in excess of the specified amount (1.0 to 7.0 parts by mass per 100.0 parts by mass of the rubber component) impairs the processability of the rubber in an unvulcanized state and also deteriorates the reinforcing properties of the conductive rubber composition.

[0050] In the conductive rubber composition according to the present invention, the fibrous carbon nanostructure is not particularly limited, but is preferably a carbon nanotube.

[0051] Carbon nanotubes are substances in which a six-membered ring network formed by carbon forms a single- or multi-layered coaxial tubular (cylindrical) shape. The carbon nanotubes are not particularly limited and can include one or more types selected from single-walled carbon nanotubes and multi-walled carbon nanotubes. The larger the diameter of the carbon nanotubes, the lower the conductivity of the conductive rubber composition when blended with a rubber component. However, the carbon nanotubes are more safe for the human body, and the dispersibility of the carbon nanotubes and the processability of the rubber in an unvulcanized state are improved. Therefore, if the required target conductivity can be achieved, multi-walled carbon nanotubes are preferable to single-walled carbon nanotubes. In the conductive rubber composition according to the present invention, the average diameter of the carbon nanotubes is preferably 1 to 200 nm, more preferably 5 to 100 nm, and even more preferably 10 to 50 nm. From the viewpoint of simultaneously achieving high levels of dispersibility of fibrous carbon, safety to the human body, processability of the rubber in an unvulcanized state, and conductivity of the conductive rubber composition, in the conductive rubber composition according to the present invention, it is more preferable that the diameter of the bundle of multi-walled carbon nanotubes is 0.8 to 15.0 μm, preferably 1.0 to 10.0 μm, and more preferably 2.0 to 7.0 μm. Furthermore, the carbon nanotubes may be vapor-grown carbon fibers (VGCF) obtained by pyrolysis of hydrocarbons.

[0052] When carbon nanotubes are used as the fibrous carbon nanostructures in the conductive rubber composition according to the present invention, the method for producing the carbon nanotubes is not particularly limited, and they can be produced using known synthesis methods such as arc discharge, laser ablation, chemical vapor deposition (CVD), etc. Specifically, fibrous carbon nanostructures containing carbon nanotubes can be efficiently produced, for example, by a method (super-growth method) in which raw material compounds and a carrier gas are supplied onto a substrate having a catalyst layer for carbon nanotube production on its surface, and when carbon nanotubes are synthesized by chemical vapor deposition (CVD), a trace amount of an oxidant (catalyst activator) is made present in the system, thereby dramatically improving the catalytic activity of the catalyst layer.

[0053] The conductive rubber composition according to the present invention contains a rubber component in addition to the carbon black and fibrous carbon according to the present invention.

[0054] The carbon black according to the present invention has a nitrogen adsorption specific surface area of ​​40 to 80 m ２ / g, DBP absorption is 140-200 mL / 100 g, and the excitation wavelength is 532 nm, at 1340-1360 cm －１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 200 to 280 cm －１ This refers to carbon black.

[0055] The rubber component is not particularly limited, but examples thereof include general-purpose rubbers such as natural rubber, styrene butadiene rubber, butadiene rubber, butyl rubber, ethylene propylene rubber, acrylonitrile butadiene rubber, and chloroprene rubber; special rubbers such as acrylic rubber, chlorosulfonated polyethylene rubber, urethane rubber, silicone rubber, and fluororubber; and mixtures thereof.

[0056] The conductive rubber composition according to the present invention contains 20.0 to 60.0 parts by mass of the carbon black according to the present invention, preferably 25.0 to 55.0 parts by mass of the carbon black according to the present invention, and more preferably 30.0 to 50.0 parts by mass of the carbon black according to the present invention, per 100.0 parts by mass of the rubber component.

[0057] In the conductive rubber composition according to the present invention, the greater the content of the carbon black according to the present invention per 100.0 parts by mass of the rubber component, the higher the conductivity of the conductive rubber composition, but the worse the processability of the rubber in an unvulcanized state. Therefore, by having the conductive rubber composition according to the present invention contain 20.0 to 60.0 parts by mass of the carbon black according to the present invention per 100.0 parts by mass of the rubber component, it is possible to impart to the conductive rubber composition both the conductivity and reinforcing properties required for general conductive applications, while also imparting significantly improved processability of the rubber in an unvulcanized state.

[0058] The conductive rubber composition according to the present invention contains 1.0 to 7.0 parts by mass of fibrous carbon per 100.0 parts by mass of the rubber component, preferably 2.0 to 6.0 parts by mass of fibrous carbon, and more preferably 3.0 to 5.0 parts by mass of fibrous carbon. Since fibrous carbon generally disperses poorly in rubber compared to carbon black, a masterbatch prepared by dispersing fibrous carbon in a rubber component in advance may be used, and when kneading with the rubber material, the content relative to the rubber component after kneading may be adjusted to the above-mentioned range.

[0059] In the conductive rubber composition according to the present invention, the greater the content of fibrous carbon per 100.0 parts by mass of the rubber component, the higher the conductivity of the conductive rubber composition, but the worse the processability of the rubber in an unvulcanized state. Therefore, by having the conductive rubber composition according to the present invention contain 1.0 to 7.0 parts by mass of fibrous carbon per 100.0 parts by mass of the rubber component, it is possible to obtain a conductive rubber composition that has flexibility, high conductivity and reinforcing properties, and excellent processability of the rubber in an unvulcanized state.

[0060] In the conductive rubber composition according to the present invention, the higher the content ratio expressed by "fibrous carbon content / carbon black content," the better the connectivity between the carbon black and the fibrous carbon at the micro level in the conductive rubber composition, resulting in higher conductivity, but the worse the mixing and dispersibility of the fibrous carbon and the carbon black. Therefore, it is necessary to set an appropriate content ratio from the viewpoint of achieving both high conductivity of the conductive rubber composition and good mixing and dispersibility of the fibrous carbon and the carbon black. In the conductive rubber composition according to the present invention, the content ratio expressed by "fibrous carbon content / carbon black content" is preferably 0.01 to 0.35, more preferably 0.02 to 0.25, and even more preferably 0.04 to 0.20, by mass.

[0061] In addition, a state in which the fibrous carbon and carbon black are well mixed and dispersible means a state in which the dispersibility of carbon black in the rubber component and the dispersibility of fibrous carbon in the rubber component are both good, and the fibrous carbon and carbon black are uniformly mixed so that the fibrous carbon acts as a bridge to connect aggregates together.

[0062] A conceptual diagram showing a state in which the carbon black and fibrous carbon in the rubber component are well mixed and dispersed in one example of the conductive rubber composition according to the present invention is shown in Fig. 4. As shown in Fig. 4, in the conductive rubber composition according to the present invention, aggregates AG (the smallest unit of carbon black) consisting of a plurality of aggregates of black spherical primary particles and fibrous carbon FC are each suitably dispersed in a matrix made of the rubber component, and it is considered that the fibrous carbon FC and the aggregates AG are uniformly mixed and distributed so that the fibrous carbon FC acts as a bridge connecting the aggregates AG together.

[0063] In the conductive rubber composition according to the present invention, the content ratio expressed by "content of fibrous carbon / content of carbon black" is 0.01 to 0.35 by mass, so that a conductive rubber composition having lower hardness and conductivity required for general conductive applications can be obtained.

[0064] Furthermore, the conductive rubber composition according to the present invention preferably contains 21.0 to 67.0 parts by mass, more preferably 27.0 to 61.0 parts by mass, and even more preferably 33.0 to 55.0 parts by mass of carbon black and fibrous carbon in total per 100.0 parts by mass of the rubber component.

[0065] Furthermore, the conductive rubber composition according to the present invention may contain, in addition to the main components of the rubber component, carbon black, and fibrous carbon, as auxiliary components, components commonly used in this technical field, such as inorganic reinforcing materials, coupling agents, vulcanizing agents, vulcanization accelerators, antioxidants, vulcanization aids, softeners, plasticizers, processing aids, etc. The conductive rubber composition according to the present invention preferably contains 1.0 to 70.0 parts by mass of the auxiliary components in total, per 100.0 parts by mass of the rubber component, more preferably 2.0 to 60.0% by mass, and even more preferably 3.0 to 50.0 parts by mass.

[0066] The conductive rubber composition according to the present invention can be obtained by kneading desired amounts of the rubber component, the carbon black, the fibrous carbon, and, if necessary, desired amounts of an inorganic reinforcing material, a coupling agent, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a vulcanization aid, a softener, a plasticizer, a processing aid, etc. The kneading can be carried out using a kneading machine such as a known mixer or mill.

[0067] As an index showing the flexibility of the conductive rubber composition according to the present invention, hardness determined in accordance with JIS K6253-3: 2012 is used. The hardness of the conductive rubber composition according to the present invention is preferably 55 to 75, and more preferably 60 to 75 from the viewpoint of achieving both flexibility and rubber strength required for practical use.

[0068] Furthermore, Mooney viscosity determined in accordance with JIS K6300-1:2013 is used as an index indicating the processability of rubber in an unvulcanized state (unvulcanized rubber). The conductive rubber composition according to the present invention has a Mooney viscosity in an unvulcanized state of, for example, 10 to 100, preferably 20 to 80, and from the viewpoint of exhibiting excellent processability of the rubber in an unvulcanized state, more preferably 25 to 70, and particularly preferably 25 to 65. The lower the Mooney viscosity, the better the processability, but if it is too low, swelling increases during extrusion, resulting in poor dimensional stability and other processability problems.

[0069] As an index showing the conductivity of the conductive rubber composition according to the present invention, the surface resistance determined in accordance with JIS K7194:1994 is used. The surface resistance of the conductive rubber composition according to the present invention is, for example, 10 6 Ω / □ or less, but 10 4 Ω / □ or less is preferable, and 10 ３ Ω / □ or less is more preferable, and 10 ２ It is more preferable that it is Ω / □ or less, and particularly preferable that it is 1 to 45 Ω / □.

[0070] As an index showing the reinforcing property of the conductive rubber composition according to the present invention, the tensile strength determined according to JIS K6251: 2017, i.e., tensile strength, is used. The tensile strength of the conductive rubber composition according to the present invention is, for example, 7.0 to 35.0 MPa, but from the viewpoint of achieving both the reinforcing property required for general conductive applications such as antistatic properties and excellent processability in an unvulcanized state, the tensile strength is preferably 10.0 to 35.0 MPa, more preferably 12.0 to 35.0 MPa, and particularly preferably 15.0 to 35.0 MPa.

[0071] In order to obtain a conductive rubber composition having flexibility, conductivity and reinforcing properties required for general conductive applications such as antistatic, and excellent processability, the conductive rubber composition according to the present invention has a Mooney viscosity of 25 to 70 in an unvulcanized state, a hardness of 55 to 75, and a surface resistance of 10 ２It is preferable that the conductive rubber composition according to the present invention has a Mooney viscosity in an unvulcanized state of 25 to 65, a hardness of the conductive rubber composition of 60 to 75, a surface resistance of 1 to 45 Ω / □ or less, and a tensile strength of 12.0 to 35.0 MPa.

[0072] According to the present invention, it is possible to provide a novel and excellent conductive rubber composition that has flexibility, conductivity and reinforcing properties required for general conductive applications, and also has significantly improved processability in an unvulcanized state.

[0073] Next, the present invention will be explained in more detail by way of examples, but these are merely illustrative and do not limit the present invention.

[0074] <Preparation of Carbon Blacks 1 to 5 and Carbon Blacks 7 to 13> Carbon Blacks 1 to 13 were measured for nitrogen adsorption specific surface area (N ２ SA), CTAB specific surface area (CTAB), DBP absorption (DBP), 1340-1360 cm when the excitation wavelength is 532 nm －１ The full width at half maximum ΔD (ΔD) of the Raman scattering peak appearing in the range of 1000 to 15000 and the respective production conditions are shown in Tables 1 and 2.

[0075] As shown in Figure 3, a cylindrical reactor 1 was installed, which included a wind box 3 equipped with an oxygen-containing gas supply port 2 at the furnace head, a fuel combustion zone 6 (fuel combustion zone inlet inner diameter 600 mm, furnace axial length 4 800 mm) with a gradually converging downstream outlet, a throat reaction zone 7 (throat reaction zone diameter D 250 mm, throat reaction zone length L adjusted to satisfy the D / L values ​​listed in Tables 1 and 2) coaxially connected to the fuel combustion zone 6, a tapered wide-diameter reaction zone 8 (furnace axial length 4 300 mm) tapering outward, a straight wide-diameter reaction zone 10 (inner diameter 700 mm, furnace axial length 4 4700 mm) of the same diameter, and a quenching section 11 equipped with a water-cooled quench 9 that could be repositioned in the furnace axial direction in Figure 3 downstream of the straight wide-diameter reaction zone 10. A double-cylinder fuel oil and feedstock oil injection nozzle 5 was installed along the furnace central axis from the furnace head. The double-cylinder fuel oil and feedstock oil injection nozzle 5 was adjusted so that the fuel oil introduction point (the nozzle hole of the outer-cylinder fuel oil burner 51) was located in the center of the fuel combustion zone 6, and the feedstock oil introduction point (the nozzle hole of the central-cylinder feedstock oil nozzle 52) was located at a position in the throat reaction zone 7 that satisfied the residence times listed in Tables 1 and 2, respectively. For carbon blacks 1 to 5 and carbon blacks 7 to 13, the amounts of combustion air listed in Tables 1 and 2 were introduced into the fuel combustion zone 6 from the oxygen-containing gas supply port 2. Furthermore, the amounts of fuel oil and feedstock oil listed in Tables 1 and 2 were introduced from the double-cylinder fuel oil and feedstock oil injection nozzle 5, respectively. After reaction in the straight wide-diameter reaction zone 10, the reaction was stopped by injecting a coolant from the water-cooled quench 9 installed in the quenching section 11, and carbon blacks having the properties listed in Tables 1 and 2 were prepared. The fuel oil and feedstock oil used had the properties listed in Table 3.

[0076] <Preparation of Carbon Black 6> As shown in Figure 3, a cylindrical reactor was installed, which had: a wind box 3 equipped with an oxygen-containing gas inlet 2 at the furnace head; a fuel combustion zone 6 (fuel combustion zone inlet inner diameter 600 mm, throat reaction zone length in the furnace axial direction 4 800 mm) whose downstream outlet gradually converged; a drum-shaped throat reaction zone 7 (throat reaction zone inlet inner diameter 200 mm, throat reaction zone outlet inner diameter 170 mm, throat reaction zone length L in the furnace axial direction 4 1430 mm) coaxially connected to the fuel combustion zone 6; a tapered wide-diameter reaction zone 8 (throat reaction zone length 300 mm, throat reaction zone length in the furnace axial direction 4 300 mm) tapered and expanding downstream of the straight wide-diameter reaction zone 10; a straight wide-diameter reaction zone 10 (inner diameter 700 mm, throat reaction zone length 4700 mm) of the same diameter; and a quenching section 11 equipped with a water-cooled quench 9 whose position could be changed in the furnace axial direction in Figure 3 downstream of the straight wide-diameter reaction zone 10. A double-cylinder fuel oil and feedstock oil injection nozzle 5 was installed along the furnace central axis from the furnace head. The double-cylinder fuel oil and feedstock oil injection nozzle 5 was adjusted so that the fuel oil introduction point (the injection hole of the outer-cylinder fuel oil burner 51) was located in the center of the fuel combustion zone 6, and the feedstock oil introduction point (the injection hole of the central-cylinder feedstock oil nozzle 52) was located in the throat reaction zone 7 at a position that satisfied the residence time listed in Table 1. The amount of combustion air listed in Table 1 was introduced into the fuel combustion zone 6 from the oxygen-containing gas supply port 2, and the amounts of fuel oil and feedstock oil listed in Table 1 were introduced from the double-cylinder fuel oil and feedstock oil injection nozzle 5. After reaction in the straight wide-diameter reaction zone 10, the reaction was stopped by injecting a coolant from the water-cooled quench 9 installed in the quenching section 11, thereby preparing carbon black 6 having the properties listed in Table 1. The fuel oil and feedstock oil used had the properties listed in Table 3.

[0077] In Tables 1 and 2, the term "amount of combustion air" refers to the amount of air introduced into the fuel combustion zone 6, the term "amount of fuel oil" refers to the amount of fuel oil introduced from the external fuel oil burner 51, and the term "amount of feed oil" refers to the amount of feed oil introduced from the central axial-cylinder feed oil nozzle 52. In Tables 1 and 2, D / L refers to the ratio D / L of the throat reaction zone diameter D to the throat reaction zone length L. The term "residence time" refers to the residence time of the product from the feed oil introduction position to the throat reaction zone 7 outlet.

[0078]

[0079]

[0080]

[0081] (Examples 1 to 8, Comparative Examples 1 to 11) 100.0 parts by mass of nitrile rubber (high nitrile NBR Nipol (registered trademark) DN4050 manufactured by Nippon Zeon Co., Ltd.) as a rubber component was mixed with either Carbon Black 1 or Carbon Black 6 and carbon nanotubes (multi-walled CNT K-Nanos210T manufactured by Kumho Petrochemical Co., Ltd., average diameter 11 to 13 nm, average bundle diameter 2 to 5 μm, average length 40 to 50 μm, specific surface area 250 to 280 m). ２ / g), a plasticizer bis(2-ethylhexyl) phthalate (DOP), zinc oxide, and stearic acid were weighed out in the amounts shown in Tables 4 and 5, and a closed-type mixer (MIXTRON (registered trademark) BB-2 manufactured by Kobe Steel, Ltd.) was used to mix the nitrile rubber first at a fill factor (total volume of the rubber materials / internal mixer volume) of 0.7 and a rotation speed of 75 rpm. The nitrile rubber was then added and masticated for 30 seconds, and the other ingredients (either carbon black 1 or carbon black 6, carbon nanotubes, bis(2-ethylhexyl) phthalate (DOP), zinc oxide, and stearic acid) were then simultaneously added, mixed for 4 minutes, and discharged to obtain a kneaded mixture A. Note that no carbon black was added in Comparative Examples 7 to 9. Next, each of the above kneaded mixtures A was once cooled to room temperature (23±2°C), and then again charged into an internal mixer (MIXTRON (registered trademark) BB-2, manufactured by Kobe Steel, Ltd.) and kneaded for 10 seconds. Next, sulfur as a vulcanizing agent and N-oxydiethylene-2-benzothiazole sulfenamide as a vulcanization accelerator (ACCEL (registered trademark) NS, manufactured by Kawaguchi Chemical Industry Co., Ltd.) were simultaneously charged in the amounts shown in Tables 4 and 5, respectively, relative to 100.0 parts by mass of nitrile rubber in the kneaded mixture A. The mixture was kneaded for 1 minute at a rotation speed of 50 rpm and then discharged to prepare each of the kneaded mixtures B. The Mooney viscosity of each of the obtained unvulcanized kneaded mixtures B was measured by the method shown below. The results are shown in Tables 4 and 5.

[0082] <Mooney viscosity (ML １＋４ ) > Mooney viscosity (ML) was measured at 125°C using an L-type rotor (MOONEY VISCOMETER AM-3 manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with the provisions of JIS K6300-1:2013. １＋４ ) values ​​were calculated.

[0083] Next, a sample for measuring Mooney viscosity was cut out from the kneaded product B, and the remaining kneaded product was vulcanized in a 53 ton press (manufactured by Dumbbell Co., Ltd.) at 150° C. for 60 minutes to obtain each conductive rubber composition.

[0084] The hardness, tensile strength, and surface resistance of each of the conductive rubber compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 11 were measured by the methods described below. The results are shown in Tables 4 and 5.

[0085] <Hardness> The hardness was measured in accordance with the provisions of JIS K6253-3:2012 using a Type A durometer (Digital Rubber Hardness Tester DD4 manufactured by Kobunshi Keiki Co., Ltd.).

[0086] <Tensile strength> In accordance with the provisions of JIS K6251:2017, the tensile strength was measured using a dumbbell-shaped No. 3 test piece with a tensile tester (STROGRAPH AE-CT manufactured by Toyo Seiki Seisaku-sho, Ltd.).

[0087] <Surface Resistivity> According to JIS K7194:1994, the surface resistance was measured at five points using a test piece measuring 100 mm x 100 mm x 2 mm thick, using a four-terminal four-probe high-precision low resistivity meter (Loresta-GP MCP-T610, manufactured by the former Mitsubishi Chemical Analytech Co., Ltd.).

[0088]

[0089]

[0090] (Examples 9 to 16, Comparative Examples 12 to 22) 100.0 parts by mass of nitrile rubber (high nitrile NBR Nipol (registered trademark) DN4050 manufactured by Nippon Zeon Co., Ltd.) as a rubber component was mixed with any one of the above carbon blacks 1 to 13 and carbon nanotubes (multi-walled CNT K-Nanos210T manufactured by Kumho Petrochemical Co., Ltd., average diameter 11 to 13 nm, average bundle diameter 2 to 5 μm, average length 40 to 50 μm, specific surface area 250 to 280 m). ２ / g), a plasticizer, bis(2-ethylhexyl) phthalate (DOP), zinc oxide, and stearic acid were weighed out so as to obtain the blending amounts shown in Tables 6 and 7, and the nitrile rubber was masticated for 30 seconds using a closed mixer (MIXTRON (registered trademark) BB-2 manufactured by Kobe Steel, Ltd.) under conditions of a fill factor (total volume of the above rubber materials / internal mixer volume) of 0.7 and a rotation speed of 75 rpm, and then the blending materials other than the above nitrile rubber (any of Carbon Black 1 to Carbon Black 13, carbon nanotubes, bis(2-ethylhexyl) phthalate (DOP), zinc oxide, and stearic acid) were simultaneously added, and the mixture was kneaded for 4 minutes and then discharged, thereby obtaining kneaded mixture A. Next, each of the above kneaded mixtures A was once cooled to room temperature (23±2°C) and then again charged into an internal mixer (MIXTRON (registered trademark) BB-2, manufactured by Kobe Steel, Ltd.) and kneaded for 10 seconds. After that, sulfur as a vulcanizing agent and N-oxydiethylene-2-benzothiazole sulfenamide as a vulcanization accelerator (ACCEL (registered trademark) NS, manufactured by Kawaguchi Chemical Industry Co., Ltd.) were simultaneously charged in the amounts shown in Tables 6 and 7 relative to 100.0 parts by mass of nitrile rubber in the kneaded mixture A, and the mixture was kneaded for 1 minute at a rotation speed of 50 rpm and then discharged to prepare each of the kneaded mixtures B. The Mooney viscosity of each of the obtained unvulcanized kneaded mixtures B was measured by the method described above. The results are shown in Tables 6 and 7. Next, a sample for measuring Mooney viscosity was cut out from the kneaded product B, and the remaining kneaded product was vulcanized in a 53 ton press (manufactured by Dumbbell Co., Ltd.) at 150° C. for 60 minutes to obtain each conductive rubber composition.

[0091] The hardness, tensile strength, and surface resistance of each of the conductive rubber compositions obtained in Examples 9 to 16 and Comparative Examples 12 to 22 were measured by the methods described above. The results are shown in Tables 6 and 7. For comparison, the results of Example 3 are also shown in Table 6.

[0092]

[0093]

[0094] As shown in Tables 4 and 6, in Examples 1 to 16, carbon black having a nitrogen adsorption specific surface area of ​​40 to 80 m ２ / g, DBP absorption is 140-200 mL / 100 g, and the excitation wavelength is 532 nm, at 1340-1360 cm －１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 200 to 280 cm －１ While employing the above-mentioned carbon black, 20.0 to 60.0 parts by mass and 1.0 to 7.0 parts by mass of fibrous carbon were blended with 100.0 parts by mass of the rubber component to prepare conductive rubber compositions. Therefore, the conductive rubber compositions obtained in Examples 1 to 16 had hardnesses of 55 to 75, tensile strengths of 15.0 to 20.0 MPa, and surface resistivities of 1 to 30 Ω / □, demonstrating that they possess high tensile strength and the conductivity required for general conductive applications while maintaining excellent flexibility with reduced hardness. Furthermore, as shown in Tables 4 and 6, the conductive rubber compositions obtained in Examples 1 to 16 had Mooney viscosities of 30 to 55 in the unvulcanized state, demonstrating low Mooney viscosities and excellent processability in the unvulcanized state.

[0095] On the other hand, as shown in Table 5, in the conductive rubber compositions obtained in Comparative Examples 1 to 11, either the amount of carbon black per 100.0 parts by mass of the rubber component was outside the predetermined range (Comparative Examples 3 and 4, and Comparative Examples 7 to 9), the amount of fibrous carbon per 100.0 parts by mass of the rubber component was outside the predetermined range (Comparative Examples 1 to 3, 5 to 6, and 9), or the physical properties of the carbon black did not satisfy the predetermined requirements (Comparative Examples 10 to 11). Therefore, as shown in Table 5, the conductive rubber compositions obtained in Comparative Examples 1 to 11 had high surface resistance and poor conductivity (Comparative Examples 1 to 7), low tensile strength and poor reinforcement (Comparative Examples 7 to 9), or high Mooney viscosity and poor processability in the unvulcanized state (Comparative Examples 10 to 11).

[0096] Furthermore, Table 7 shows that the conductive rubber compositions obtained in Comparative Examples 12 to 22 all had high hardness and poor flexibility (Comparative Examples 19 and 20), high surface resistance and poor conductivity (Comparative Examples 12 to 14, 17, and 20 to 22), or low tensile strength and poor reinforcement (Comparative Examples 12 to 14, and 20 to 22), because the physical properties of the carbon black did not satisfy the predetermined specifications. Furthermore, Table 7 shows that the conductive rubber compositions obtained in Comparative Examples 14 to 16 and 18 to 20 all had high Mooney viscosity and poor processability in the unvulcanized state, because the physical properties of the carbon black did not satisfy the predetermined specifications.

[0097] According to the present invention, it is possible to provide a novel and excellent conductive rubber composition that has flexibility, conductivity and reinforcing properties required for general conductive applications, and also has significantly improved processability in an unvulcanized state.

[0098] DESCRIPTION OF SYMBOLS 1 Cylindrical reactor 2 Oxygen-containing gas supply port 3 Wind box 4 Furnace axial direction 51 Outer cylinder fuel oil burner 52 Center cylinder feed oil nozzle 5 Double-cylinder structure fuel oil and feed oil injection nozzle 6 Fuel combustion zone 7 Throat reaction zone 8 Tapered wide-diameter reaction zone 9 Water-cooled quench 10 Straight wide-diameter reaction zone 11 Quenching section 12 Flue D Throat reaction zone diameter L Throat reaction zone length AG Aggregate FC Fibrous carbon

Claims

1. A rubber composition containing 20.0 to 60.0 parts by mass of carbon black and 1.0 to 7.0 parts by mass of fibrous carbon per 100.0 parts by mass of a rubber component, wherein the carbon black has a nitrogen adsorption specific surface area of ​​40 to 80 m ２ / g, DBP absorption is 140-200 mL / 100 g, and the excitation wavelength is 532 nm, at 1340-1360 cm －１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 200 to 280 cm －１ The conductive rubber composition is characterized by:

2. The conductive rubber composition according to claim 1, which contains 30.0 to 50.0 parts by mass of carbon black and 3.0 to 5.0 parts by mass of fibrous carbon per 100.0 parts by mass of the rubber component.

3. The carbon black has a nitrogen adsorption specific surface area of ​​50 to 70 m ２ / g, DBP absorption is 150-180 mL / 100 g, and the excitation wavelength is 532 nm, at 1340-1360 cm －１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 220 to 260 cm －１ 3. The conductive rubber composition according to claim 1, wherein

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