Method for producing conductive resin composition, conductive resin composition, conductive resin molded body, and use of conductive resin molded body

Abstract

A method for producing a conductive resin composition according to the present invention comprises: a mixing dispersion step for mixing components including an aqueous medium to obtain a mixture; a kneading solvent-removal step for removing the aqueous medium while kneading the obtained mixture with an extruder to obtain a primary kneaded product; and a re-kneading step for shearing, melting, and kneading the obtained primary kneaded product with a Banbury mixer.

Description

Method for producing conductive resin composition, conductive resin composition, conductive resin molded article, and use of conductive resin molded article

[0001] The present invention relates to a method for producing a resin composition that exhibits excellent mechanical properties by highly dispersing a fibrous carbon compound in a thermoplastic resin.

[0002] Thermoplastic resins are indispensable materials in our daily lives, but when used alone, they are colorless, have low mechanical strength, and are insulating. Accordingly, resin compositions imparted with functionality by using various fillers depending on applications have been actively developed. For applications requiring conductivity, carbon black or the like is generally used as a conductive material, and is used as a resin composition having an antistatic function in the field of electronic components and the like. However, in fields such as the automobile industry, high conductivity, mechanical properties and moldability are often required, and there have been many cases that cannot be achieved with carbon black.

[0003] In recent years, carbon nanotubes have attracted attention as a material that can impart high conductivity while maintaining other physical properties. A carbon nanotube has a structure formed by rolling a flat graphene sheet into a cylindrical shape, has a high aspect ratio with a diameter of several nanometers to several tens of nanometers and a length of several micrometers. Due to its structure, it exhibits extremely high mechanical strength, electrical conductivity and thermal conductivity, and is expected to be applied in various fields.

[0004] On the other hand, the application of carbon nanotubes has been difficult for the following reasons. This is because carbon nanotubes are elongated in shape and have large van der Waals forces, so they strongly aggregate with each other, making dispersion extremely difficult. In the field of thermoplastic resins, studies have been conducted to improve mechanical properties by dispersing carbon nanotubes in resins, but mechanical properties cannot be enhanced unless carbon nanotubes are uniformly dispersed. This is because if carbon nanotubes are not uniformly dispersed, stress applied to the resin composition concentrates near aggregates of carbon nanotubes, leading to easy fracture. Therefore, uniformly dispersing carbon nanotubes, which have strong cohesive force, has been a challenge.

[0005] Against this backdrop, methods are being investigated for uniformly dispersing fibrous carbon compounds such as carbon nanotubes and cellulose fibers using kneaders with high production speeds. One such method involves a hydrolysis method in which the material is pretreated with a wetting agent and kneaded in a twin-screw extruder, enabling high dispersion of carbon nanotubes (Patent Document 1).

[0006] Japanese Patent Publication No. 2013-201117

[0007] The method described in Patent Document 1 significantly improves conductivity and mechanical properties compared to not pre-treating the material. However, this method still has its challenges; while it improves dispersibility in olefin-based resins, such as polypropylene resin, it does not achieve a sufficiently dispersed state.

[0008] The present invention aims to provide a method for producing a conductive resin composition, a conductive resin composition, a conductive resin molded article, and a method for using a conductive resin molded article, particularly when using carbon nanotubes, by highly dispersing fibrous carbon compounds in a thermoplastic resin, thereby exhibiting superior mechanical properties compared to conventional techniques.

[0009] [1] A method for producing a conductive resin composition containing a thermoplastic resin and a fibrous carbon compound, comprising the following steps 1, 2, and 3: Step 1: A step of mixing a thermoplastic resin having an average particle size of 0.01 mm or more and 3 mm or less, a fibrous carbon compound in an amount of 0.3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the thermoplastic resin, and an aqueous medium in an amount of 10 parts by mass or more and 500 parts by mass or less per 100 parts by mass of the fibrous carbon compound to obtain a mixture. Step 2: A step of melt-kneading the mixture using a single-screw or twin-screw extruder at a peripheral speed of 5 m / min or more and 150 m / min or less, and removing the aqueous medium to obtain a primary kneaded product. Step 3: A step of shear-melt kneading the primary kneaded product using a Banbury mixer at a temperature set to or below the melting point or softening point of the thermoplastic resin, at a screw peripheral speed of 1 m / min or more and 150 m / min or less, to obtain a secondary kneaded product. Step 4: A step to obtain a conductive resin composition by melt-kneading the secondary kneaded material at a temperature set to be above the melting point or softening point of the thermoplastic resin to obtain a homogenized conductive resin composition. [2] A method for producing a conductive resin composition according to [1], wherein the fibrous carbon compound is a carbon nanotube. [3] A method for producing a conductive resin composition according to [1] or [2], wherein the aqueous medium is at least one selected from the group consisting of water and a hydrophilic organic solvent. [4] A method for producing a conductive resin composition according to any one of [1] to [3], wherein the thermoplastic resin is at least one selected from the group consisting of polypropylene resin, low-density polyethylene resin, linear low-density polyethylene resin, and thermoplastic polyurethane. [5] A conductive resin composition produced by a method for producing a conductive resin composition according to any one of [1] to [4]. [6] A conductive resin composition according to [5], further containing a surfactant. [7] A conductive resin composition according to [6], wherein the surfactant is at least one selected from the group consisting of acetylene glycol compounds and alkane sulfonic acid compounds. [8] A conductive resin molded article using the conductive resin composition according to [5]. [9] A conductive resin molded article using the conductive resin composition described in [6] or [7].

[10] Use of the conductive resin molded article described in [8] for automotive parts, building material parts, machine parts, electrical parts, electronic parts, furniture parts, home appliance parts, containers, or packaging materials.

[11] Use of the conductive resin molded article described in [9] for automotive parts, building material parts, machine parts, electrical parts, electronic parts, furniture parts, home appliance parts, containers, or packaging materials.

[0010] According to the present invention, by highly dispersing fibrous carbon compounds in a thermoplastic resin, it is possible to provide a method for producing a conductive resin composition that exhibits superior mechanical properties compared to those obtained using conventional techniques, a conductive resin composition, a conductive resin molded article, and a method for using the conductive resin molded article.

[0011] The embodiments of the present invention will be described below, but the present invention is not limited to the embodiments described below, and various modifications are possible without departing from the spirit of the invention.

[0012] <Method for Manufacturing Conductive Resin Composition> The method for manufacturing a conductive resin composition according to this embodiment comprises: step 1 (hereinafter also referred to as the "mixing and dispersion step"), which involves mixing each component containing an aqueous medium to obtain a mixture; step 2 (hereinafter also referred to as the "kneading and solvent removal step"), which involves kneading the obtained mixture in an extruder while removing the aqueous medium to obtain a primary kneaded product; and step 3 (hereinafter also referred to as the "re-kneading step"), which involves kneading the obtained primary kneaded product in a Banbury mixer. The details thereof will be described below. In addition, in the method for manufacturing a conductive resin composition according to this embodiment, the step of kneading a fibrous carbon compound into a thermoplastic resin was investigated to enable high dispersion of the fibrous carbon compound. Furthermore, compared to the case using conventional technology, the mechanical properties of the obtained conductive resin molded article were significantly improved.

[0013] (Step 1 (Mixing and Dispersion Step)) In the mixing and dispersion step, a mixture is obtained by mixing a thermoplastic resin with an average particle size of 0.01 mm or more and 3 mm or less, a fibrous carbon compound in an amount of 1 to 30 parts by mass per 100 parts by mass of the thermoplastic resin, and at least one aqueous medium selected from the group consisting of 10 to 500 parts by mass per 100 parts by mass of the fibrous carbon compound and a hydrophilic organic solvent.

[0014] In the mixing and dispersion process, it is also preferable to use dispersers such as Henschel mixers, super mixers, ultrasonic homogenizers, spiral mixers, planetary mixers, dispersers, hybrid mixers, and kneaders. Two or more dispersers may be used in combination. In particular, from the viewpoint of dispersing carbon nanotubes in thermoplastic resin or suppressing damage to carbon nanotubes, it is preferable to use a Henschel mixer, super mixer, or ultrasonic homogenizer. Furthermore, as necessary, within a range that does not damage the carbon nanotubes, the mixture may be further dispersed using a ball mill, vibration mill, sand mill, or roll mill.

[0015] As the thermoplastic resin, it is necessary to use a powder or pellet form with an average particle size of 0.01 mm or more and 3 mm or less. By using a thermoplastic resin with the above average particle size, the fibrous carbon compound is easily loosened by the thermoplastic resin, and the kneading process becomes easier. The average particle size of the thermoplastic resin can be measured using a microscope or a digital microscope. As the thermoplastic resin, those commonly used in various molding methods such as injection molding and extrusion molding can be used. Examples of thermoplastic resins include polyethylene resins, polypropylene resins, polystyrene resins, acrylic resins, polyolefin resins, acrylonitrile-butadiene-styrene copolymers (ABS resins), polyamide resins, polycarbonate resins, and thermoplastic polyurethane resins. These resins can be used individually or in combination of two or more. Examples of polyethylene resins include ethylene homopolymers (high-density polyethylene, low-density polyethylene, linear low-density polyethylene), ethylene-propylene copolymers, and ethylene-vinyl acetate copolymers. Examples of polypropylene resins include propylene homopolymers (polypropylene resins) and propylene-butene copolymers. Examples of polystyrene resins include styrene homopolymers, acrylonitrile-styrene copolymers, and styrene-butadiene copolymers. Examples of acrylic resins include acrylic acid ester homopolymers, methyl methacrylate homopolymers, and ethylene-ethyl acrylate copolymers. Examples of polyolefin resins include α-olefin homopolymers and ethylene-α-olefin copolymers, among which low-density polyethylene, linear low-density polyethylene, polypropylene resin, or thermoplastic polyurethane resin is preferred.

[0016] Thermoplastic resins may contain additives. Examples of additives that can be used include primary antioxidants, secondary antioxidants, lubricants, UV absorbers, light stabilizers, weather resistance enhancers, fluidity enhancers, plasticizers, mold release agents, flame retardants, nucleating agents, foaming agents, antibacterial agents, antifungal agents, or surfactants.

[0017] As fibrous carbon compounds, carbon nanotubes, carbon nanofibers, cellulose nanofibers, cellulose microfibers, chitin-chitosan nanofibers, or chitin-chitosan microfibers can be used from the viewpoint of improving the strength of the resin composition. Among these, carbon nanotubes or carbon nanofibers are preferred from the viewpoint of improving conductivity. Two or more of these materials can also be used in combination.

[0018] Any known carbon nanotube (hereinafter also referred to as "CNT") can be used as appropriate. The amount of carbon nanotube must be 0.3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of thermoplastic resin. If the amount of carbon nanotube is less than 0.3 parts by mass per 100 parts by mass of thermoplastic resin, the conductivity will be low. On the other hand, if the amount of carbon nanotube exceeds 30 parts by mass per 100 parts by mass of thermoplastic resin, the dispersibility will decrease, and depending on the mixing apparatus, it may not be possible to obtain a conductive resin composition, which is undesirable. Preferably, the amount of carbon nanotube is 0.5 parts by mass or more and 25 parts by mass or less per 100 parts by mass of thermoplastic resin, and more preferably 1 part by mass or more and 20 parts by mass or less.

[0019] Cellulose microfibers function as reinforcing materials when dispersed in a resin matrix. Such cellulose fibers are obtained by defibrating and finely milling cellulose-containing fiber raw materials (e.g., various types of pulp). Suitable defibration equipment used in the defibration process includes high-speed defibrators, grinders (stone mill type pulverizers), high-pressure homogenizers or ultra-high-pressure homogenizers, high-pressure impact pulverizers, ball mills, bead mills, disc refiners, conical refiners, twin-screw kneaders, vibrating mills, homomixers under high-speed rotation, ultrasonic dispersers, or beaters, or wet grinding equipment. Cellulose microfibers can be used alone, but it is preferable to use them in combination with CNTs to improve conductivity. When using cellulose microfibers as a fibrous carbon compound, the amount blended is preferably 1 to 70 parts by mass per 100 parts by mass of thermoplastic resin.

[0020] The aqueous medium is preferably at least one selected from the group consisting of water and a hydrophilic organic solvent. The aqueous medium is preferably mainly water (50% or more of the total) and further contains a hydrophilic organic solvent. As water, it is preferable to use ion-exchanged water, distilled water, and purified water. As the hydrophilic organic solvent, it is preferable to use one that has a boiling point that evaporates easily in the subsequent kneading and solvent removal step and does not remain in the resulting conductive resin composition. Considering the impact on the working environment, cost, and handling ease, an alcohol-based solvent or a glycol-based solvent can be used, with ethanol being particularly preferred. The amount of the aqueous medium should be greater than or equal to the amount that can disperse the carbon nanotubes, and less than or equal to the amount that can be removed by kneading. The amount of the aqueous medium must be 10 parts by mass or more and 500 parts by mass or less, and preferably 20 parts by mass or more and 400 parts by mass or less, per 100 parts by mass of carbon nanotubes.

[0021] In the mixing and dispersion step, it is preferable to further mix the surfactant to obtain a mixture. By adding a surfactant, the aqueous medium containing the surfactant can easily penetrate the entangled aggregates of fibrous carbon compounds, thereby improving the effect of loosening the fibrous carbon compounds. As surfactants, ionic surfactants such as anionic surfactants, cationic surfactants, and amphoteric surfactants, as well as nonionic surfactants, can be used. Examples of anionic surfactants include sulfate ester type, phosphate ester type, and sulfonic acid type surfactants. Examples of cationic surfactants include quaternary ammonium salt type surfactants. Examples of amphoteric surfactants include alkyl betaine type, amide betaine type, and amine oxide type surfactants. Examples of nonionic surfactants include fatty acid esters and sorbitan fatty acid esters. Among these, the use of acetylene glycol-based compounds or alkane sulfonic acid-based compounds is preferred because they have a high effect in loosening carbon nanotubes. Examples of acetylene glycol compounds include the Surfinol series (manufactured by Nisshin Chemical Industry Co., Ltd.), the Orfin series (manufactured by Nisshin Chemical Industry Co., Ltd.), and the Acetyleneol series (manufactured by Kawaken Fine Chemical Co., Ltd.). Examples of alkanesulfonic acid compounds include HOSTAPUR SAS93 (manufactured by Clariant Japan Co., Ltd.) and Latemul PS (manufactured by Kao Corporation).

[0022] The amount of surfactant should be within a range that does not degrade the physical properties of the resulting conductive resin composition. Specifically, the amount of surfactant may be 0 parts by mass, more than 0 parts by mass but 40 parts by mass or less, or 0.02 parts by mass or more but 10 parts by mass or less, per 100 parts by mass of the total of the fibrous carbon compound and the surfactant.

[0023] The conductive resin composition may optionally contain other components besides those mentioned above. Examples of other components include flame retardants, fillers, plasticizers, antioxidants, ultraviolet absorbers, light stabilizers, dispersants, antistatic agents, conductivity imparters, mold release agents, lubricants, dyes, and pigments.

[0024] (Step 2 (Mixing and Solvent Removal Step)) In the mixing and solvent removal step, the solvent in the mixture obtained in the mixing and dispersion step is removed while the mixture is being mixed. Then, a conductive resin composition (primary mixture) in the form of pellets or flakes can be obtained by granulation as needed. Alternatively, the raw resin may be mixed in a predetermined ratio with a high-concentration product (masterbatch) that has a high content of fibrous carbon compounds, and then granulated using a mixer such as an extruder or roll press.

[0025] In this process, it is necessary to remove the aqueous medium, so a single-screw or twin-screw extruder (hereinafter also referred to as "extruder") is required for kneading the mixture. Kneading may also be performed twice, in which case different equipment may be combined. For example, it is preferable to first use a pressure kneader to remove some of the aqueous medium under reduced pressure, and then remove the aqueous medium with an extruder, as this allows for better dispersion of the fibrous carbon compound. If a Banbury mixer or a kneader without a vacuum function is used first, the heating is limited to the jacket section, making it difficult to heat the mixture and resulting in a longer removal of the aqueous medium. This is undesirable because it can cause the thermoplastic resin to yellow. Furthermore, the presence of the aqueous medium makes it difficult to apply shear force to the mixture, hindering dispersion, which is also undesirable. The processing temperature and pressure should be appropriately set according to the type of thermoplastic resin and aqueous medium. However, high temperatures are preferable for solvent removal, and while the appropriate temperature varies depending on the thermoplastic resin used, it is generally preferable to process at 100°C to 370°C.

[0026] The extruder must have a peripheral speed of 5 m / min or more and 150 m / min or less, preferably 20 m / min or more and 100 m / min or less. If the peripheral speed is below the lower limit, the resulting resin composition will yellow. If the peripheral speed is above the upper limit, the amount of heat generated due to shearing will increase, causing the resulting resin composition to burn and yellow.

[0027] (Step 3 (Re-mixing Step)) In the re-mixing step, the mixture obtained in the mixing and solvent removal step is re-mixed using a Banbury mixer. Then, a conductive resin composition (secondary mixture) in the form of pellets or flakes can be obtained by granulation as needed using a two-roll or square pelletizer. In this step, the fibrous carbon compound is loosened and dispersed in the thermoplastic resin by melt-mixing with shear force. In order to perform shear-melt mixing, it is necessary that the temperature range is from when the thermoplastic resin begins to melt or soften until just before it is completely melted or softened. This allows for shear-melt mixing while maintaining a high viscosity state, and enables efficient loosening of the fibrous carbon compound. If the temperature is significantly exceeded, the viscosity decreases, and the shear force also decreases, so even if melt-mixing is done for a long time, the fibrous carbon compound will not loosen and will remain aggregated. In a Banbury mixer, shear heat occurs during shear-melt mixing, causing a natural temperature rise even without heating. Therefore, it is important to cool the mixture as needed to maintain the aforementioned temperature range. In a high-viscosity state, the shear-melt mixing time required in the Banbury mixer (capacity 1.7 L) used in this invention is approximately 2 to 5 minutes. The optimal shear-melt mixing time varies depending on the size of the apparatus, and the optimal time increases or decreases in proportion to the capacity. For example, if the capacity increases, the required mixing time increases. For crystalline resins, the melting point is used as a guideline for management, and for amorphous resins, the softening point is used as a guideline.

[0028] For re-mixing the compound, for example, a Banbury mixer can be used. Banbury mixers (internal mixers) include tangential types where the rotating circles of the left and right rotors do not overlap, and meshing types where the rotating circles overlap. In this embodiment, it is preferable to use the meshing type, which provides a greater shear force.

[0029] The processing temperature and pressure can be set appropriately depending on the type of thermoplastic resin. However, in order to achieve proper dispersion, it is preferable to knead at the lowest possible temperature, specifically at a temperature below the melting point of the thermoplastic resin. By heating with shear heat and kneading at a temperature near the melting point of the thermoplastic resin, kneading can be performed in a high-viscosity state, thereby improving the dispersibility of the fibrous carbon compound.

[0030] In step 3, the peripheral speed of the screw in the kneading machine, such as a Banbury mixer, must be 1 m / min or more and 150 m / min or less, preferably 5 m / min or more and 130 m / min or less, more preferably 8 m / min or more and 100 m / min or less, even more preferably 9 m / min or more and 80 m / min or less, even more preferably 10 m / min or more and 70 m / min or less, and particularly preferably 11 m / min or more and 50 m / min or less. If the peripheral speed is less than 1 m / min, no shear force is applied and dispersibility decreases. If the peripheral speed is greater than 150 m / min, the fibrous carbon compound is fragmented, dispersibility deteriorates, and conductivity or mechanical properties decrease.

[0031] The mixing time in the Banbury mixer may be 1 minute or more, 1 minute or more and 30 minutes or less, 2 minutes or more and 15 minutes or less, or 3 minutes or more and 10 minutes or less.

[0032] (Step 4 (Homogenization Step)) The homogenization step is necessary to uniformly disperse the fibrous carbon compound in the thermoplastic resin in a melted or softened state at a temperature setting above the melting point or softening point. For homogenization of the kneaded material, for example, a two-roll kneader, a kneader, an extruder, or a Banbury mixer can be used. In Step 4, the peripheral speed of the screw in the kneader, extruder, or Banbury mixer used for kneading is preferably 1 m / min or more and 150 m / min or less, more preferably 5 m / min or more and 130 m / min or less, even more preferably 8 m / min or more and 100 m / min or less, even more preferably 9 m / min or more and 80 m / min or less, even more preferably 10 m / min or more and 70 m / min or less, and particularly preferably 11 m / min or more and 50 m / min or less. If the peripheral speed is less than 1 m / min, there will be no force applied to the kneading and the dispersibility will decrease. If the peripheral speed exceeds 150 m / min, the fibrous carbon compound will fragment, worsening its dispersibility and reducing its conductivity or mechanical properties.

[0033] According to the method for producing a conductive resin composition of this embodiment, it is possible to disperse fibrous carbon compounds in a good state without impairing the inherent physical properties of the thermoplastic resin, such as its mechanical strength, and to produce a conductive resin composition with excellent conductivity while maintaining the inherent physical properties of the thermoplastic resin, such as its mechanical strength.

[0034] <Conductive Resin Composition and Conductive Resin Molded Article> The conductive resin composition according to this embodiment is prepared by the method for manufacturing the conductive resin composition according to this embodiment as described above. The conductive resin molded article according to this embodiment is made using the conductive resin composition according to this embodiment as described above. Furthermore, the conductive resin molded article according to this embodiment can be suitably used for automobile parts, building material parts, machine parts, electrical parts, electronic parts, furniture parts, home appliance parts, containers, or packaging materials. The thickness of films and sheets is defined in JIS Z0108:2012, and in this application, a film is defined as a plastic membrane with a thickness of less than 0.25 mm (less than 250 μm), and a sheet is defined as a thin plastic plate with a thickness of 0.25 mm or more (250 μm or more).

[0035] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" refer to mass unless otherwise specified. The average particle size of the thermoplastic resin was obtained by observing 30 randomly selected particles using a digital microscope (Keyence Corporation, model number VHX-600) at a magnification of 100x and averaging the result.

[0036] <Preparation of Conductive Resin Composition> (Example 1) 1.5 parts of carbon nanotubes (product name "Knanos 100T", manufactured by Kunho Petrochemical) and 98.5 parts of polypropylene powder (PP, product name "Prime Polypro J229E", manufactured by Prime Polymer) with an average particle size of 0.05 to 1.1 mm were placed in a mixer and stirred and mixed for 3 minutes at 25°C. 5 parts of a 1% surfactant aqueous solution prepared by diluting acetylene glycol-based surfactant (product name "Surfinol #465", manufactured by Nisshin Chemical Co., Ltd.) with water were added and stirred and mixed for 2 minutes at 25°C to obtain a mixture. Using a twin-screw extruder (product name "TEX30", manufactured by Japan Steel Works, Ltd.), the obtained mixture was melt-kneaded at a peripheral speed of 38 m / min and a processing temperature of 200°C, while the solvent (water) was evaporated and removed from the vent of the twin-screw extruder to obtain a pellet-shaped primary kneaded product. Using a Banbury mixer, the primary mixture was melt-kneaded at a peripheral speed of 20 m / min and a processing temperature of 160°C. After confirming the sound of gas escaping at the start of melting, mixing was continued while cooling water was flowed through the jacket to obtain a conductive resin composition (secondary mixture). The obtained secondary mixture was kneaded using a two-roll mixer (product name "MX-0X12", manufactured by Inoue Seisakusho Co., Ltd.) at a processing temperature of 25°C to produce a 1 cm thick sheet. The obtained sheet was then used with a square pelletizer (product name "GHP-220", manufactured by Tomoki Iron Works Co., Ltd.) to obtain a square pellet-shaped secondary mixture.

[0037] (Examples 2-21 and Comparative Examples 9-12) Conductive resin compositions were obtained in the same manner as in Example 1, except that the formulations were changed as shown in Tables 1-4. Details of the materials used are shown below.

[0038] ・LLDPE: Linear low-density polyethylene (average particle size 0.01-1.2 mm, product name "US370GN", manufactured by Nippon Polyethylene Co., Ltd.) ・LDPE: Low-density polyethylene (average particle size 0.01-1.0 mm, product name "Suntec F2270", manufactured by Asahi Kasei Chemicals Corporation) ・TPU: Thermoplastic polyurethane (average particle size 0.01-1.0 mm, product name "Rezamin P-880" pulverized product, manufactured by Dainichi Seika Kogyo Co., Ltd.) ・FT9000: Carbon nanotube (product name "FT9000", manufactured by Canano Inc.) ・VGCF-X: Carbon nanotube (product name "VGCF-X", manufactured by Showa Denko Corporation) ・B800: Cellulose microfiber (product name "ARBOCEL B800", manufactured by Rettenmeyer GmbH) • Hostapure SAS93: Alkanesulfonic acid-based surfactant (product name "HostaPure SAS93", manufactured by Clariant Japan Co., Ltd.)

[0039] (Comparative Example 1) 95.5 parts of polypropylene powder (product name "Prime PolyPro J229E", manufactured by Prime Polymer Co., Ltd.) with an average particle size of 0.05 to 1.1 mm were mixed with 4.5 parts of carbon nanotubes (product name "Knanos 100T", manufactured by Kunho Petrochemical Co., Ltd.), and the mixture was stirred and mixed in the same manner as in Example 1 to obtain a mixture. Using a twin-screw extruder, the obtained mixture was melt-kneaded at a peripheral speed of 38 m / min and a processing temperature of 200°C, while the water was evaporated and removed from the vent of the twin-screw extruder to obtain a pellet-shaped kneaded product.

[0040] (Comparative Examples 2-4, 7, 8, and 13-20) Conductive resin compositions were obtained in the same manner as in Comparative Example 1, except that the formulations were changed as shown in Tables 1-4.

[0041] (Comparative Example 5) A conductive resin composition was obtained in the same manner as in Example 2, except that step 2 was performed using a Banbury mixer and step 3 using a twin-screw extruder.

[0042] (Comparative Example 6) A conductive resin composition was obtained in the same manner as in Example 2, except that both steps 2 and 3 were performed using a twin-screw extruder.

[0043] (Reference Examples A to D) For the four types of thermoplastic resins used in the Examples and Comparative Examples, namely polypropylene resin, linear low-density polyethylene resin, low-density polyethylene resin, and thermoplastic polyurethane resin, the same type of physical property evaluation was performed on each individual resin. The results are shown in Table 4 as Reference Examples A to D.

[0044] <Evaluation> (Surface Resistivity) Using an extruder equipped with a belt die (trade name "NV-20", manufactured by Mars Seiki Co., Ltd.), the obtained conductive resin composition was molded to prepare an evaluation sheet having a thickness of about 0.1 mm and a width of 50 mm. Then, using a low resistivity meter (trade name "Loresta GP", manufactured by Mitsubishi Chemical Corporation) and a high resistivity meter (trade name "Hiresta UP", manufactured by Mitsubishi Chemical Corporation), the surface resistivity (Ω / □) of the produced evaluation sheet was measured. The results are shown in Tables 1 to 4. In the tables, "3.5E+05" and the like represent "3.5×10 ５ " and the like.

[0045] (Dispersion State) The conductive resin composition was sheet-pressed to obtain a sheet of about 20 µm. Then, the dispersion state of carbon nanotubes in the obtained sheet was observed at a magnification of 100 times using an optical microscope or a digital microscope, and the dispersion state of carbon nanotubes was evaluated according to the evaluation criteria shown below. The results are shown in Tables 1 to 4. [Evaluation Criteria for Dispersion State]: S: No aggregate having a size of 1 µm or more exists A: Aggregate size is 1 µm or more and less than 5 µm B: Aggregate size is 5 µm or more and less than 10 µm C: Aggregate size is 10 µm or more and less than 20 µm D: Aggregate size is 20 µm or more and less than 50 µm E: Aggregate size is 50 µm or more

[0046] (Elongation at break) In accordance with ASTM D638, for the obtained conductive resin composition, after molding dumbbells with an injection molding machine, the elongation at break was measured using a tensile testing machine. Then, the elongation at break was evaluated for each type of thermoplastic resin according to the evaluation criteria shown below. The results are shown in Tables 1 to 4. [Evaluation criteria for elongation at break] - For PP: S: Elongation at break of 400% or more; A: Elongation at break of 300% or more and less than 400%; B: Elongation at break of 200% or more and less than 300%; C: Elongation at break of 150% or more and less than 200%; D: Elongation at break of 100% or more and less than 150%; E: Elongation at break of less than 100%. - For LLDPE: S: Elongation at break of 500% or more; A: Elongation at break of 400% or more and less than 500%; B: Elongation at break of 300% or more and less than 400%; C: Elongation at break of 200% or more and less than 300%; D: Elongation at break of 100% or more and less than 200%; E: Elongation at break of less than 100%. - For LDPE: S: Elongation at break of 600% or more; A: Elongation at break of 500% or more and less than 600%; B: Elongation at break of 400% or more and less than 500%; C: Elongation at break of 300% or more and less than 400%; D: Elongation at break of 200% or more and less than 300%; E: Elongation at break of less than 200%. - For TPU: S: Elongation at break of 750% or more; A: Elongation at break of 650% or more and less than 750%; B: Elongation at break of 550% or more and less than 650%; C: Elongation at break of 450% or more and less than 550%; D: Elongation at break of 350% or more and less than 450%; E: Elongation at break of less than 350%

[0047]

[0048]

[0049]

[0050]

[0051] (Application Example 1: Use as a Masterbatch) 20 parts of the square pellet-shaped secondary compound obtained in Example 6 and 80 parts of polypropylene powder (product name "Prime Polypro J229E", manufactured by Prime Polymer Co., Ltd.) with an average particle size of 0.05 to 1.1 mm were placed in a mixer and stirred and mixed at 25°C for 3 minutes. Next, using a twin-screw extruder (product name "TEX30", manufactured by Japan Steel Works Co., Ltd.), the obtained mixture was melt-kneaded at a peripheral speed of 38 m / min and a processing temperature of 200°C to obtain a pellet-shaped compound. When the obtained compound was evaluated, the dispersion state was B, the tensile elongation at break was A, and the conductivity was excellent, similar to Example 2.

[0052] (Application Example 2: T-die method) The compound prepared in Example 19 was extruded at 200°C using a Laboplast Mill (manufactured by Toyo Seiki Co., Ltd.) equipped with a T-die to produce a sheet-like evaluation sample with a thickness of approximately 50 μm and a width of 100 mm. The volume resistivity of the produced evaluation sample was measured using a Loresta GX-11 (manufactured by Nitto Seiko Analytech Co., Ltd.). The volume resistivity was 8.2 × 10⁻⁶. ３ The film was confirmed to have high conductivity in Ω·cm.

[0053] (Application Example 3: Inflation Molding Method) An inflation film with a thickness of 20 μm was fabricated from the compound prepared in Example 4 using an inflation molding machine (manufactured by Thermoplastics Industry Co., Ltd.) at a molding temperature of 230°C. The volume resistivity of the manufactured evaluation sample was measured using a Loresta GX-11 (manufactured by Nitto Seikou Analytech Co., Ltd.). The volume resistivity was 1.2 × 10⁻⁶. ２ The film was confirmed to have high conductivity in Ω·cm.

Claims

1. A method for producing a conductive resin composition containing a thermoplastic resin and a fibrous carbon compound, comprising the following steps 1, 2, and 3: Step 1: A step of mixing a thermoplastic resin having an average particle size of 0.01 mm or more and 3 mm or less, a fibrous carbon compound in an amount of 0.3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the thermoplastic resin, and an aqueous medium in an amount of 10 parts by mass or more and 500 parts by mass or less per 100 parts by mass of the fibrous carbon compound to obtain a mixture. Step 2: A step of melt-kneading the mixture using a single-screw or twin-screw extruder at a peripheral speed of 5 m / min or more and 150 m / min or less, and removing the aqueous medium to obtain a primary kneaded product. Step 3: A step of shear-melt kneading the primary kneaded product using a Banbury mixer at a temperature set to or below the melting point or softening point of the thermoplastic resin, and at a screw peripheral speed of 1 m / min or more and 150 m / min or less to obtain a secondary kneaded product. Step 4: A step to obtain a conductive resin composition by melt-kneading the secondary kneaded material at a temperature set to be above the melting point or softening point of the thermoplastic resin and making it homogenized.

2. The method for producing a conductive resin composition according to claim 1, wherein the fibrous carbon compound is a carbon nanotube.

3. The method for producing a conductive resin composition according to claim 1, wherein the aqueous medium is at least one selected from the group consisting of water and hydrophilic organic solvents.

4. The method for producing a conductive resin composition according to claim 1, wherein the thermoplastic resin is at least one selected from the group consisting of polypropylene resin, low-density polyethylene resin, linear low-density polyethylene resin, and thermoplastic polyurethane.

5. A conductive resin composition prepared by the method for producing a conductive resin composition according to any one of claims 1 to 4.

6. The conductive resin composition according to claim 5, further comprising a surfactant.

7. The conductive resin composition according to claim 6, wherein the surfactant is at least one selected from the group consisting of acetylene glycol compounds and alkanesulfonic acid compounds.

8. A conductive resin molded article using the conductive resin composition described in claim 5.

9. A conductive resin molded article using the conductive resin composition according to claim 6 or claim 7.

10. Use of the conductive resin molded article according to claim 8 in automobile parts, building material parts, machine parts, electrical parts, electronic parts, furniture parts, home appliance parts, containers, or packaging materials.

11. Use of the conductive resin molded article according to claim 9 in automobile parts, building material parts, machine parts, electrical parts, electronic parts, furniture parts, home appliance parts, containers, or packaging materials.

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