JP7680319B2 - Conductive resin composition sheet, conductive resin composition, method for producing conductive resin composition, and method for producing conductive resin composition sheet - Google Patents

Description

The present disclosure relates to an electrically conductive resin composition, a sheet, and a method for producing the electrically conductive resin composition.

Patent Documents 1 and 2 disclose conductive resin compositions containing multi-walled carbon nanotubes.
Patent Document 3 discloses a conductive resin composition containing dumpling-like carbon nanotubes or carbon nanotubes having a bundle structure.
Patent Document 4 discloses a method for producing a conductive resin composition by kneading a predetermined polyolefin and carbon nanotubes with an open roll.

JP 2010-024261 A JP 2010-235675 A JP 2016-108524 A JP 2017-186440 A

However, conventional conductive resin compositions containing conductive carbon have the problem that the electrical resistance value cannot be precisely controlled.

The present disclosure aims to provide a conductive resin composition having good electrical properties. The present disclosure can be realized in the following forms:

A conductive resin composition comprising a thermoplastic resin and a carbon nanostructure containing branched carbon nanotubes.

The present disclosure provides a conductive resin composition with good electrical properties.

FIG. 2 is a cross-sectional view of a sheet of a conductive resin composition. FIG. 2 is a diagram showing a schematic diagram of a phase separation structure. FIG. 1 is a diagram illustrating a carbon nanostructure.

Here, a preferred example of the present disclosure is given.
The conductive resin composition has a content of the carbon nanostructure of more than 0 mass % and not more than 5 mass % when the entire conductive resin composition is taken as 100 mass %.
- A conductive resin composition, wherein the thermoplastic resin comprises a first thermoplastic resin and a second thermoplastic resin of a different type from the first thermoplastic resin, the first thermoplastic resin and the second thermoplastic resin have a phase-separated structure in which the first thermoplastic resin and the second thermoplastic resin are phase-separated, and the carbon nanostructures are unevenly distributed in the first thermoplastic resin.
- A conductive resin composition in which the content of the carbon nanostructure is greater than 0 mass% and not more than 5 mass%, when the total of the first thermoplastic resin and the carbon nanostructure is 100 mass%.
A sheet of the above conductive resin composition, which has a surface resistance value of 1.0×10 ⁴ Ω/□ or more and 1.0×10 ⁸ Ω/□ or less.
A method for producing a conductive resin composition, comprising kneading a carbon nanostructure containing branched carbon nanotubes into a first thermoplastic resin to form a master batch, and kneading the master batch with a second thermoplastic resin of a different type from the first thermoplastic resin.

The present disclosure is described in detail below. In this specification, when a numerical range is described using "-", it is meant to include the lower limit and the upper limit unless otherwise specified. For example, the description "10-20" is meant to include both the lower limit "10" and the upper limit "20". In other words, "10-20" has the same meaning as "10 or more and 20 or less".

1. Conductive resin composition 10
The conductive resin composition 10 of this embodiment contains a thermoplastic resin and a carbon nanostructure 14 containing branched carbon nanotubes. Fig. 1 is a cross-sectional view of a sheet 20 of the conductive resin composition 10. In Fig. 1, the carbon nanostructure 14 is omitted.

(1) Thermoplastic resin The thermoplastic resin is not particularly limited. Examples of the thermoplastic resin include polyolefin resin, polystyrene resin, polyamide resin, saturated polyester resin, polyacetal resin, polyphenylene sulfide (PPS), polyphenylene ether (PPE), modified PPE resin modified by blending or graft polymerization with other resins (polypropylene, nylon, acrylonitrile-butadiene-styrene copolymer, etc.), polystyrene resin, polymethacrylic resin, polyvinyl chloride resin, thermoplastic elastomer, etc. From the viewpoint of moldability and cost reduction, the thermoplastic resin is preferably a polyolefin resin.

Examples of polyolefin resins include polyethylene resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-α-olefin copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methacrylate copolymer; polypropylene resins such as polypropylene, propylene-ethylene copolymer, and propylene-1-butene copolymer; ionomers; and polybutene.
The thermoplastic resin may be one type or two or more types.

(1.1) Thermoplastic resin A and thermoplastic resin B
It is preferable that the thermoplastic resin contains a first thermoplastic resin (also referred to as thermoplastic resin A) and a second thermoplastic resin (also referred to as thermoplastic resin B) of a type different from thermoplastic resin A, and has a phase-separated structure in which thermoplastic resin A and thermoplastic resin B are phase-separated.

The carbon nanostructures 14 are preferably unevenly distributed in the thermoplastic resin A. "Unevenly distributed in the thermoplastic resin A" means that the carbon nanostructures 14 are more present in the phase containing thermoplastic resin A than in the phase containing thermoplastic resin B.

There are no particular limitations on the thermoplastic resin A and the thermoplastic resin B. A combination of two types of resins capable of forming a phase separation structure can be appropriately selected as the thermoplastic resin A and the thermoplastic resin B. In addition, the thermoplastic resin A and the thermoplastic resin B can be appropriately selected so that the carbon nanostructures 14 are unevenly distributed in the thermoplastic resin A, taking into account the affinity of the carbon nanostructures 14 to the resin.
An example of a combination of thermoplastic resin A and thermoplastic resin B is a combination of a polyethylene resin and a polypropylene resin.

From the viewpoint of dispersibility and affinity of the carbon nanostructures 14, the thermoplastic resin A is preferably a polyethylene-based resin, and more preferably low-density polyethylene.
The MFR (melt flow rate) of the polyethylene resin is not particularly limited. The MFR (JIS K7210, 190°C, load 2.16 kg) of the polyethylene resin is preferably 0.1 g/10 min to 15 g/10 min, more preferably 0.5 g/10 min to 12 g/10 min, and even more preferably 3 g/10 min to 10 g/10 min.
The melting point of the polyethylene resin is not particularly limited. The melting point of the polyethylene resin is preferably 80° C. to 140° C., more preferably 90° C. to 130° C., and further preferably 100° C. to 120° C. The melting point of the polyethylene resin is measured by a differential scanning calorimeter (DSC method).
The density of the polyethylene resin is not particularly limited and is preferably 0.88 g/cm ³ to 0.94 g/cm ³ , more preferably 0.90 g/cm ³ to 0.935 g/cm ³ , and even more preferably 0.91 g/cm ³ to 0.93 g/cm ³ .

From the viewpoint of suppressing migration of the carbon nanostructures 14, the thermoplastic resin B is preferably a polypropylene-based resin, and more preferably a propylene-ethylene copolymer.
The MFR of the polypropylene resin is not particularly limited. The MFR of the polypropylene resin (JIS K7210, 230°C, load 2.16 kg) is preferably 0.1 g/10 min to 15 g/10 min, more preferably 0.2 g/10 min to 10 g/10 min, and further preferably 0.3 g/10 min to 7 g/10 min.
The melting point of the polypropylene-based resin is not particularly limited. The melting point of the polypropylene-based resin is preferably higher than the melting point of the thermoplastic resin A, for example, 150° C. to 165° C. The melting point of the polypropylene-based resin is measured by a differential scanning calorimeter (DSC method).

The mass ratio of thermoplastic resin A:thermoplastic resin B is not particularly limited. The mass ratio of thermoplastic resin A:thermoplastic resin B is preferably 10:90-100:0, more preferably 10:90-90:10, even more preferably 15:85-75:25, and even more preferably 20:80-60:40. When an ethylene-based resin having an MFR of 3 g/10 min-10 g/10 min is used as thermoplastic resin A, the mass ratio of thermoplastic resin A:thermoplastic resin B may be 20:80-40:60. By setting the mass ratio of thermoplastic resin A:thermoplastic resin B in the above range, good electrical properties can be achieved.

(1.2) Phase-separated structure Examples of the phase-separated structure include a cocontinuous structure, a sea-island structure, a continuous spherical structure, a composite dispersed structure, and a composite structure of two or more of these.
The co-continuous structure is a structure in which a plurality of resin phases each form a continuous phase. Fig. 2 shows a schematic diagram of a co-continuous structure in which a first phase 11 containing a thermoplastic resin A and a second phase 12 containing a thermoplastic resin B each form a continuous phase. Each of the first phase 11 and the second phase 12 has a three-dimensional network shape.
The sea-island structure is a structure in which the dispersed phase is dispersed in the continuous phase, and particulate or spherical dispersed phase is dispersed in the continuous phase. The continuous spherical structure is a structure in which roughly spherical dispersed phase is connected and dispersed in the continuous phase. The composite dispersed structure is a structure in which the dispersed phase is dispersed in the continuous phase, and the resin that constitutes the continuous phase is further dispersed in the dispersed phase.

The phase separation structure is preferably a structure having a continuous phase, and more preferably a co-continuous structure. By distributing the carbon nanostructures 14 unevenly in the resin contained in the continuous phase, the uniformity of the surface resistance value can be favorably improved. In addition, the amount of the carbon nanostructures 14 can be reduced while suppressing an increase in the surface resistance value.
The phase separation structure can be realized by appropriately adjusting the types and compounding ratio of the thermoplastic resin A and the thermoplastic resin B, and the manufacturing conditions of the conductive resin composition 10 (the kneading method, the kneading temperature, etc.).

Whether or not thermoplastic resin A and thermoplastic resin B form a phase separation structure can be confirmed, for example, as follows. A cross section of the molded conductive resin composition 10 is observed using a transmission electron microscope (TEM) to obtain an observation image. The observation image is analyzed to determine the presence or absence of a phase separation structure from the contrast difference based on the differences in composition and density.

(2) Carbon nanostructure 14
The carbon nanostructure 14 contains branched carbon nanotubes. Carbon nanotubes are carbon materials in which graphene layers are in the form of single or multiple coaxial tubes. A branched carbon nanotube refers to a carbon nanotube in which one main axis is split into multiple parts along the way, or a carbon nanotube in which a secondary axis is split from the main axis. FIG. 3 shows a schematic drawing of a carbon nanotube in which one main axis is split into two parts along the way to form a Y-shape. In FIG. 3, the contact points between the branched carbon nanotubes are indicated by black circles.

The size and structure of the branched carbon nanotubes are not particularly limited. The average diameter of the branched carbon nanotubes is usually 1 μm or less, for example, 1 nm to 100 nm, 5 nm to 20 nm. The diameter of the branched carbon nanotubes can be determined as the outer diameter of the main axis. The average length of the branched carbon nanotubes is, for example, 50 μm to 100 μm. The length of the branched carbon nanotubes can be determined as the length of the longest main axis. The average number of layers of the branched carbon nanotubes is, for example, 2 to 6 layers, and may be 3 to 5 layers.
The average diameter, average length and average number of walls of the branched carbon nanotubes can be determined as the average values measured by observing, for example, 20 branched carbon nanotubes with a transmission electron microscope (TEM).

Such carbon nanostructures 14 can be obtained, for example, by suitable shearing of flakes of cross-linked carbon nanotubes, which can be obtained by growing carbon nanotubes on a fibrous support by a chemical vapor deposition (CVD) process under rapid (e.g., 2 μm/s-10 μm/s) elongation conditions.
A specific example of the carbon nanostructure 14 is "ATHLOS (registered trademark)" (manufactured by Cabot Corporation).

The carbon nanostructure 14 may contain components other than branched carbon nanotubes. Examples of such components include unbranched carbon nanotubes, carbon nanotubes that share some walls (graphene layers), and additives such as resins. Even when carbon nanostructure 14 contains components other than carbon (additives, etc.), the carbon content in carbon nanostructure 14 is preferably 90% by mass or more, and more preferably 95% by mass or more.

The content of the carbon nanostructure 14 is not particularly limited. From the viewpoint of reducing the surface resistance value, the content of the carbon nanostructure 14 is preferably more than 0 mass%, 0.1 mass% or more, 0.2 mass% or more, 0.3 mass% or more, or 0.4 mass% or more, when the entire conductive resin composition 10 is taken as 100 mass%. From the viewpoint of cost, the content of the carbon nanostructure 14 is preferably 5 mass% or less, more preferably 2 mass% or less, 1.5 mass% or less, 1 mass% or less, or 0.5 mass% or less. From these viewpoints, the content of the carbon nanostructure 14 is preferably more than 0 mass% and 5 mass% or less, and can be set to a range that appropriately combines the above lower limit and upper limit.
The carbon nanostructures 14 may be unevenly distributed in a specific portion or may be dispersed throughout the conductive resin composition 10. The content of the carbon nanostructures 14 can be calculated from the blending ratio of the carbon nanostructures 14 to the thermoplastic resin A.

In the case where the carbon nanostructure 14 is unevenly distributed in the thermoplastic resin A, the content of the carbon nanostructure 14 relative to the total of the thermoplastic resin A and the carbon nanostructure 14 is not particularly limited. From the viewpoint of reducing the surface resistance value, the content of the carbon nanostructure 14 is preferably more than 0 mass%, 0.2 mass% or more, 0.4 mass% or more, 0.6 mass% or more, 0.8 mass% or more, or 1.0 mass% or more, when the total of the thermoplastic resin A and the carbon nanostructure 14 is 100 mass%. From the viewpoint of cost, the content of the carbon nanostructure 14 is preferably 5 mass% or less, more preferably 2 mass% or less, 1.8 mass% or less, or 1.5 mass% or less. From these viewpoints, the content of the carbon nanostructure 14 is preferably more than 0 mass% and 5 mass% or less, and can be a range that appropriately combines the above lower limit and upper limit.
The content of the carbon nanostructures 14 can be calculated from the blending ratio of the carbon nanostructures 14 to the thermoplastic resin A.

(3) Other Components The conductive resin composition 10 may contain other components in addition to the thermoplastic resin and the carbon nanostructures 14. Examples of the other components include an ultraviolet absorber, a stabilizer such as an antioxidant, a pigment, a dye, a filler, a plasticizer, a function-imparting agent, a flame retardant, and the like.

2. Sheet 20
The sheet 20 of the present disclosure is a sheet 20 of the conductive resin composition 10. The sheet 20 maintains the phase-separated structure of the conductive resin composition 10 described above.
The thickness of the sheet 20 can be set according to the application, and can be, for example, 0.2 mm to 0.5 mm, or 1 mm to 2 mm. The sheet 20 may be composed of the conductive resin composition 10 alone, or may be composed including a material other than the conductive resin composition 10. Even when the sheet 20 is composed of a material other than the conductive resin composition 10, it is preferable that the surface layer of the sheet 20 is composed of the conductive resin composition 10.

The surface resistance value of the sheet 20 is not particularly limited and can be set according to the application. From the viewpoint of protecting electronic components, the surface resistance value of the sheet 20 is preferably 1.0×10 ⁴ Ω/□ or more, more preferably 1.0×10 ⁵ Ω/□ or more, and even more preferably 1.0×10 ⁶ Ω/□ or more. From the viewpoint of antistatic, the surface resistance value of the sheet 20 is preferably 1.0×10 ⁸ Ω/□ or less, more preferably 5.0×10 ⁷ Ω/□ or less, and even more preferably 1.0×10 ⁷ Ω/□ or less. From these viewpoints, the surface resistance value of the sheet 20 is preferably 1.0×10 ⁴ Ω/□ or more and 1.0×10 ⁸ Ω/□ or less, more preferably 1.0×10 ⁵ Ω/□ or more and 5.0×10 ⁷ Ω/□ or less, and even more preferably 1.0×10 ⁶ Ω/□ or more and 1.0×10 ⁷ Ω/□ or less. The surface resistance value is a value measured as follows.
<Measurement of surface resistance>
A square sheet sample of 25 cm x 25 cm with a thickness of 0.5 mm-2 mm is prepared. A surface resistance value measuring instrument F-109 manufactured by Hozan Corporation is used for the measurement. The applied voltage is 10 V when the measurement object has a resistance of less than 1 x 10 ⁶ Ω/□, and 100 V when the measurement object has a resistance of 1 x 10 ⁶ Ω/□ or more. The distance between the pair of electrodes is 15 cm. Measurements are performed at the upper edge, lower edge, left edge, and right edge of the sample. The measured value 15 seconds after the start of the measurement is read as the surface resistance value of the measurement site. The average of the measured surface resistance values of the upper edge, lower edge, left edge, and right edge is calculated and used as the surface resistance value of the sample.

From the viewpoint of stably exerting performance, the surface resistance value of the sheet 20 is preferably uniform throughout the sheet 20. Specifically, the surface resistance values of the upper edge, lower edge, left edge, and right edge of the sheet 20 are preferably 5.0×10 ⁴ Ω/□ or more and 5.0×10 ⁶ Ω/□ or less at two or more locations, more preferably 5.0×10 ⁴ Ω/□ or more and 5.0×10 ⁶ Ω/□ or less at three or more locations, and even more preferably 5.0×10 ⁴ Ω/□ or more and 5.0×10 ⁶ Ω/□ or less at four locations.

The uses of the sheet 20 are not particularly limited. Because the sheet 20 has good electrical properties, it is suitable as a mat for electronic devices and as a housing for electronic devices.

3. Manufacturing method of conductive resin composition 10 and sheet 20 The manufacturing method of the conductive resin composition 10 is not particularly limited. In the manufacturing method of the conductive resin composition 10, all components may be mixed at once, or the carbon nanostructures 14 may be mixed in advance with a part of the thermoplastic resin to prepare a master batch, and then the remaining thermoplastic resin (also referred to as a diluent resin) may be mixed. The thermoplastic resin of the master batch and the diluent resin may be the same type or different types.

The manufacturing method of the conductive resin composition 10 preferably includes a step of melt-kneading the thermoplastic resin and the carbon nanostructures 14. It is presumed that melt-kneading the thermoplastic resin and the carbon nanostructures 14 can form bridge-like conductive paths in the thermoplastic resin, as described below. In this case, the carbon nanostructures 14 can be suitably dispersed by using a polyethylene resin with an MFR (190°C, 2.16 kg) of 3 g/10 min-10 g/10 min as the thermoplastic resin.

When carbon nanostructures 14 are to be unevenly distributed in thermoplastic resin A, conductive resin composition 10 can be manufactured as follows. The method for manufacturing conductive resin composition 10 is, for example, to knead carbon nanostructures 14 into thermoplastic resin A to form a master batch, and then knead the master batch with thermoplastic resin B of a different type from thermoplastic resin A.

When kneading the carbon nanostructures 14 into the thermoplastic resin A, it is preferable to use a multi-screw kneading extruder such as a twin-screw extruder from the viewpoint of dispersibility of the carbon nanostructures 14. When kneading the thermoplastic resin B and the master batch, it is preferable to use a kneader or a single-screw extruder from the viewpoint of forming a phase separation structure. In other words, when kneading the carbon nanostructures 14 into the thermoplastic resin A, it is preferable to use a shear force stronger than the shear force used to knead the thermoplastic resin B and the master batch.

The mixture (kneaded product) of each component is molded to obtain the conductive resin composition 10. The method for molding the conductive resin composition 10 is not particularly limited and can be appropriately selected depending on the application. The sheet 20 of the conductive resin composition 10 can be molded, for example, by a heat press method.

4. Effects of the Present Embodiment The conductive resin composition 10 of the present embodiment has good electrical properties. Hereinafter, the reasons why the conductive resin composition 10 has good electrical properties will be explained, but the present disclosure is not limited to these reasons.
The electrical properties required for a product vary depending on its application. For example, when used as a mat for electronic devices, the surface resistance is required to be 1.0×10 ⁴ Ω/□ or more and 1.0×10 ⁸ Ω/□ or less, and the surface resistance is required to be highly uniform. In a conductive resin composition in which conductive carbon is blended with a thermoplastic resin, the surface resistance at the percolation threshold may be included within the above-mentioned range of surface resistance. The percolation threshold refers to the concentration of conductive carbon at the inflection point where the electrical resistance of the conductive resin composition changes significantly. In other words, in a conductive resin composition, a small change in the conductive carbon concentration greatly affects the surface resistance, and there is a concern that the electrical resistance cannot be precisely controlled.

The conductive resin composition 10 of this embodiment includes a carbon nanostructure 14 containing branched carbon nanotubes. The branched carbon nanotubes are thought to form a conductive path with a bridge-like structure as shown in FIG. 3. In FIG. 3, the contact points between the branched carbon nanotubes are represented by black circles. On the other hand, conductive carbon such as Ketjen Black is thought to form a conductive path with a point contact structure between particles. The conductive path of the branched carbon nanotube has a lower frequency of conductive parts due to contact than the conductive path of Ketjen Black, and can achieve stable conductivity, so it is presumed that the uniformity of the surface resistance value is high. In addition, the branched carbon nanotube can form a conductive path with a small amount compared to conductive carbon such as Ketjen Black, so it is presumed that the surface resistance value can be reduced with a small amount of compounding.

When the carbon nanostructures 14 are unevenly distributed in the thermoplastic resin A, the uniformity of the surface resistance value can be further improved. This is presumably because the carbon nanostructures 14 are localized in the thermoplastic resin A, making it easier for bridge-like conductive paths to form than when the carbon nanostructures 14 are dispersed throughout the conductive resin composition 10.

The following provides a more detailed explanation using examples.

1. Preparation of conductive resin composition sheets A master batch was prepared according to the blending ratio in Table 1, and the master batch and dilution resin were blended according to the blending ratio in Table 1 to prepare sheets of the conductive resin composition of Examples 1 to 5 and Comparative Example 1. Details of the main raw materials listed in Table 1 are shown below.
Polyethylene resin 1: low density polyethylene, MFR 5.0 (190°C, 2.16 kg), density 0.922 g/cm ³ , melting point (DSC method) 110°C
Polyethylene resin 2: low density polyethylene, MFR 0.4 (190°C, 2.16 kg), density 0.921 g/cm ³ , melting point (DSC method) 111°C
Polypropylene resin: propylene-ethylene block copolymer, MFR 0.5 (230°C, 2.16 kg), density 0.90 g/ ^cm3
Carbon nanostructure: carbon nanostructure containing branched carbon nanotubes, carbon content 97% by mass, manufactured by Cabot Corporation, ATHLOS 200
・Ketjen Black: Special oil furnace carbon, carbon content 98% or more by mass, manufactured by Lion Specialty Chemicals, EC300J

In Table 1, the resin in the "Masterbatch" column corresponds to the "First Thermoplastic Resin (Thermoplastic Resin A)". The resin in the "Diluted Resin" column corresponds to the "Second Thermoplastic Resin (Thermoplastic Resin B)".
The carbon content was calculated from the blending ratio of the carbon nanostructure or Ketjen black when the entire conductive resin composition was taken as 100 mass %.

Specifically, the sheets of each conductive resin composition were prepared as follows.
Each component of the master batch was mixed in the mixing ratio shown in Table 1 and fed into a unidirectional twin screw extruder (HYPERKTX30MX, manufactured by Kobe Steel, Ltd.). The mixture was kneaded under conditions of a rotation speed of 600 rpm, a cylinder temperature of 110°C, and a discharge rate of 20 kg/h, and cut with a pelletizer to obtain pellets (master batch). The obtained pellets and diluted resin were mixed in the mass ratio shown in Table 1 and fed into a kneader. After kneading under conditions of 120°C, 50 rpm, and 5 minutes, the mixture was hot pressed under conditions of a temperature of 200°C, a time of 3 minutes, and a thickness of 2.0 mm to obtain sheets of the conductive resin compositions of Examples 1-5 and Comparative Example 1.

2. Evaluation Method The surface resistance value (average value) was measured by the method of "Measurement of surface resistance value" described in the embodiment.
The variation in surface resistance represents the number of portions of the upper edge, lower edge, left edge, and right edge of the sheet that have a surface resistance of 5.0×10 ⁴ Ω/□ or more and 5.00×10 ⁶ Ω/□ or less. For example, when the surface resistances of all four portions of the upper edge, lower edge, left edge, and right edge are within the above range, the variation in surface resistance is set to 4. That is, a variation of surface resistance of "4" represents the smallest variation from 5.0×10 ⁵ Ω/□ and the high uniformity of the surface resistance. The smaller the value of the variation in surface resistance, the larger the variation from 5.0×10 ⁵ Ω/□ and the lower the uniformity of the surface resistance.

Based on the surface resistance value (average value) and the variation in the surface resistance value, the electrical properties of the sheets of the conductive resin composition of Examples 1-5 and Comparative Example 1 were judged according to the following criteria: A: excellent electrical properties; B: electrical properties inferior to A, but practical; C: poor electrical properties, difficult to use.
"A": The surface resistance value is 1.0×10 ⁶ Ω/□ or more and 1.0×10 ⁷ Ω/□ or less, and the variation in the surface resistance value is 4.
"B": Except for cases falling under A, the surface resistance is 1.0 x 10 ⁴ Ω/□ or more and 1.0 x 10 ⁸ Ω/□ or less, and the variation in the surface resistance is 3 or 4.
"C": The surface resistance value is less than 1.0×10 ⁴ Ω/□ or exceeds 1.0×10 ⁸ Ω/□. Alternatively, the variation in the surface resistance value is 0, 1, or 2.

3. Results The results are shown in Table 1.
(1) Satisfaction of Each Requirement in Examples 1 to 5 and Comparative Example 1 The conductive resin compositions of Examples 1 to 5 satisfy all of the following requirements (a) to (b).
Requirement (a): Contains a thermoplastic resin.
Requirement (b): The carbon nanostructure contains a branched carbon nanotube.
In contrast, the conductive resin composition of Comparative Example 1 does not satisfy the requirement (b).

Moreover, the conductive resin compositions of Examples 1 to 5 satisfy the following requirements.
Requirement (c): The content of the carbon nanostructure is more than 0 mass % and 5 mass % or less, when the entire conductive resin composition is taken as 100 mass %.

Among the rubbers of the conductive resin compositions of Examples 1 to 5, the conductive resin compositions of Examples 1 and 2 satisfy the following requirements.
- Requirement (d): The thermoplastic resin contains a first thermoplastic resin and a second thermoplastic resin of a type different from the first thermoplastic resin, has a phase-separated structure in which the first thermoplastic resin and the second thermoplastic resin are phase-separated, and the carbon nanostructures are unevenly distributed in the first thermoplastic resin.
Requirement (e): The content of the carbon nanostructure is more than 0% by mass and 5% by mass or less, based on 100% by mass of the first thermoplastic resin.

(2) Results and Observations The conductive resin compositions of Examples 1 to 5 were judged as A or B. In contrast, the conductive resin composition of Comparative Example 1 was judged as C. This suggests that when requirements (a) and (b) are satisfied, the composition has good electrical properties.
Moreover, the conductive resin composition of Example 1-5 satisfies the requirement (c) in addition to the requirements (a) and (b). It was found that Example 1-5 has good electrical properties with the incorporation of a small amount of carbon nanostructures.

The conductive resin compositions of Examples 1 and 2 were rated as A, and had better electrical properties than those of Examples 3 to 5. It was suggested that when requirement (d) is satisfied in addition to requirements (a) and (b), the composition has even better electrical properties.
Moreover, the conductive resin compositions of Examples 1 and 2 satisfy requirement (e) in addition to requirements (a), (b), and (d). It was found that Examples 1 and 2 have good electrical properties even when a small amount of carbon nanostructure is blended.

5. Effects of the Examples According to the above examples, a conductive resin composition having good electrical properties can be provided.

This disclosure is not limited to the embodiments detailed above, and various modifications and variations are possible.

REFERENCE SIGNS LIST 10: Conductive resin composition 11: First phase 12: Second phase 14: Carbon nanostructure 20: Sheet

Claims (6)

A sheet of a conductive resin composition comprising a thermoplastic resin and a carbon nanostructure containing branched carbon nanotubes ,
The thermoplastic resin includes a first thermoplastic resin and a second thermoplastic resin different from the first thermoplastic resin, and has a phase-separated structure in which the first thermoplastic resin and the second thermoplastic resin are phase-separated;
the carbon nanostructures are unevenly distributed in the first thermoplastic resin,
A sheet of a conductive resin composition having a surface resistance value of 1.0×10 ⁴ Ω/□ or more and 1.0×10 ⁸ Ω/□ or less. A conductive resin composition comprising a thermoplastic resin and a carbon nanostructure containing branched carbon nanotubes,
The thermoplastic resin includes a first thermoplastic resin and a second thermoplastic resin different from the first thermoplastic resin,
the first thermoplastic resin is a polyethylene-based resin,
The conductive resin composition, wherein the second thermoplastic resin is a polypropylene-based resin. A conductive resin composition comprising a thermoplastic resin and a carbon nanostructure containing branched carbon nanotubes,
The thermoplastic resin includes a first thermoplastic resin and a second thermoplastic resin different from the first thermoplastic resin, and has a phase-separated structure in which the first thermoplastic resin and the second thermoplastic resin are phase-separated;
The carbon nanostructure is a conductive resin composition unevenly distributed in the first thermoplastic resin (wherein at least one elastomer component selected from the group consisting of an elastomeric polymer (A) having a side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and/or a nitrogen-containing heterocycle and having a glass transition point of 25° C. or lower, and an elastomeric polymer (B) containing a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety in a side chain and having a glass transition point of 25° C. or lower;
Paraffin oil and
Branched multi-walled carbon nanotubes,
and the content ratio of the paraffin oil is 1 to 65 mass % based on the total amount of the composition). A method for producing a conductive resin composition, comprising kneading a carbon nanostructure containing branched carbon nanotubes into a first thermoplastic resin to form a master batch, and kneading a second thermoplastic resin different from the first thermoplastic resin with the master batch under a shear force weaker than a shear force used to knead the carbon nanostructure into the first thermoplastic resin,
The first thermoplastic resin and the second thermoplastic resin have a phase-separated structure,
A method for producing a conductive resin composition, wherein the carbon nanostructures are unevenly distributed in the first thermoplastic resin. The method includes a step of kneading a carbon nanostructure containing branched carbon nanotubes into a first thermoplastic resin to prepare a master batch, and kneading a second thermoplastic resin different from the first thermoplastic resin with the master batch.
A method for producing a sheet of a conductive resin composition having a surface resistivity of 1.0×10 ⁴ Ω/□ or more and 1.0×10 ⁸ Ω/□ or less. A conductive resin composition comprising: a first thermoplastic resin and a carbon nanostructure containing branched carbon nanotubes to form a master batch; and a second thermoplastic resin different from the first thermoplastic resin and the master batch, the conductive resin composition comprising at least one elastomer component selected from the group consisting of an elastomeric polymer (A) having a side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and/or a nitrogen-containing heterocycle and having a glass transition point of 25° C. or lower; and an elastomeric polymer (B) having a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety in a side chain and having a glass transition point of 25° C. or lower;
Paraffin oil and
Branched multi-walled carbon nanotubes,
and the content ratio of the paraffin oil is 1 to 65 mass% based on the total amount of the composition .

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