JP6972517B2 - Method for manufacturing conductive resin composition and molded product - Google Patents

Description

The present invention relates to a method for producing a conductive resin composition using carbon nanotubes.

As a packaging material for electronic devices and electronic parts using ICs and LSIs, trays formed of thermoplastic resins, embossed carrier tapes, and the like are known. As the base material of the tray or the embossed carrier tape, a resin molded product such as a resin sheet is generally used. Since the resin itself is not conductive, resin molded products (hereinafter referred to simply as "molded bodies") prevent problems such as dielectric breakdown of electronic components due to static electricity and functional deterioration of electronic components due to adhesion of dust. By kneading conductive particles such as carbon black into the molded body, antistatic performance and static electricity diffusion performance are imparted. Further, since electronic devices and electronic parts are often handled in a clean room at the time of manufacture, clean performance is also required in which foreign substances such as fillers are less likely to fall off from the molded product. Further, in the fields of electronic parts and automobiles, molded bodies are being used as a substitute for metal parts, and there is a demand for a level of conductivity that cannot be achieved with carbon black.

Under these circumstances, carbon nanotubes are used for electronics (transistor elements, wiring, etc.), energy (electrode materials for fuel cells, solar power generation equipment, gas storage, etc.), electron emission (flat panel equipment, etc.), and chemistry (adsorption). It is expected to be applied in various fields such as agents, catalysts, sensors, etc.), composite materials (conductive plastics, reinforced materials, flame-retardant nanocomposites, etc.), and among these, it is expected to be applied to conductive applications. It is known that carnon nanotubes can exhibit conductive performance with a lower addition as compared with carbon black used in the same conductive application, and thus can suppress the amount of filler dropped off. However, carbon nanotubes exist as primary aggregates in which individual carbon nanotubes (primary particles) are intricately entwined, and usually, secondary aggregates in which the primary aggregates are entangled with each other are also mixed. .. Since it is extremely difficult to disperse the mixture of the primary aggregate and the secondary aggregate to the primary particles in the resin, it is difficult to bring out the original performance of the carbon nanotube. Further, if a large number of secondary aggregates are present in the molded body, foreign matter may be formed on the surface of the molded body, which causes a problem that the appearance of the molded body is deteriorated, the molded body is dropped, and the like.

As a technique for dispersing carbon nanotubes in a resin, Patent Document 1 discloses a method in which carbon nanotubes are treated with plasma to disentangle and disperse the carbon nanotubes in a resin. Further, Patent Document 2 discloses a method of exhibiting conductivity using an ionic liquid and carbon nanotubes as main components.

Further, in Patent Document 3, a method in which a polymer alloy containing two kinds of resins is selectively blended with carbon nanotubes in a continuous layer having a sea-island structure or a co-continuous state, so that conductivity can be obtained even at a low concentration of carbon nanotubes. Is disclosed. Further, Patent Document 4 discloses a method of adding a thermoplastic resin after dispersing carbon nanotubes in an elastomer.

Japanese Unexamined Patent Publication No. 2003-30607 Japanese Unexamined Patent Publication No. 2004-255481 Japanese Unexamined Patent Publication No. 2005-187811 Japanese Unexamined Patent Publication No. 2007-154157

However, the conventional plasma treatment is expensive and difficult to spread. Further, when the ionic liquid is used, there is a problem that the ionic liquid bleeds out on the surface of the molded body. Further, the method of Patent Document 3 requires that the two types of resins are incompatible with each other, so that there is a problem that the mechanical properties of the molded product are significantly deteriorated. Further, in the method of Patent Document 4, it is difficult for the carbon nanotubes in the elastomer to be uniformly dispersed in the thermoplastic resin, and since the elastomer has low heat resistance, it is necessary to knead at a low temperature, so that a high torque is applied to the kneading device and the device is broken. There were many things. Further, when an elastomer is used, the conductive resin composition has high elasticity and ductility, so that it cannot be pulverized and it is difficult to process it into powder or pellets, which causes a problem of poor handling.

INDUSTRIAL APPLICABILITY According to the present invention, carbon nanotubes can be highly dispersed without the need for special manufacturing equipment, and since they have good pulverizability, they can be made into powders, pellets, etc., and a conductive resin having a good appearance can be obtained. An object of the present invention is to provide a method for producing a composition.

The method for producing a conductive resin composition of the present invention is a method ^{for kneading a polyolefin having a density of 0.88 to 0.94 g / cm 3} and a weight average molecular weight of 2500 to 130000 and carbon nanotubes with an open roll.
It contains 15 to 70 parts by mass of carbon nanotubes with respect to 100 parts by mass of the polyolefin.

According to the present invention described above, when a specific amount of carbon nanotubes is blended with a polyolefin having a specific density and molecular weight and kneaded with an open roll, the carbon nanotubes can be highly dispersed in the polyolefin, so that the kneaded product has pulverizability. It is good and can be pelletized. In addition, the molded product molded using the obtained pellets had the effect of having good appearance and pulverizability. In addition, the obtained molded product has a good appearance without agglomerates of carbon nanotubes and high conductivity.

INDUSTRIAL APPLICABILITY According to the present invention, carbon nanotubes can be highly dispersed without the need for special manufacturing equipment, and since they have good pulverizability, they can be made into powders, pellets, etc., and a conductive resin having a good appearance can be obtained. A method for producing a composition can be provided.

The method for producing a conductive resin composition of the present invention is a method ^{for kneading a polyolefin having a density of 0.88 to 0.94 g / cm 3} and a weight average molecular weight of 2500 to 130000 and carbon nanotubes with an open roll.
It contains 15 to 70 parts by mass of carbon nanotubes with respect to 100 parts by mass of the polyolefin.

The open roll used in the present invention is an open-type kneading device that rotates two or more horizontal roll rods, adds a material between the roll rods, and kneads them by shearing force. The open roll is sometimes called a mixing roll. Further, the open roll is also used when the open roll is covered for convenience and when the closed roll is kneaded at atmospheric pressure.

The number of rolls contained in the kneading device is generally two rolls or three rolls, but the number of rolls may be further increased as long as the problem of the present invention can be solved. As the rotation direction of the plurality of rolls, both the same direction rotation and the different direction rotation can be used, and the different direction rotation is preferable because a large shear force can be applied to the material more efficiently.

The conditions for kneading in the present invention are not limited as long as the polyolefin and carbon nanotubes can be sufficiently mixed. However, if the kneading with an open roll is performed at 50 ° C. or higher, the carbon nanotubes can be more highly dispersed in the polyolefin. The upper limit of the kneading temperature is not particularly limited as long as it is higher than the melting point of the polyolefin and lower than the temperature at which the polyolefin does not decompose or vaporize. Considering the torque load of the kneader, the wrapping of the conductive resin composition around the rolls, and the processability around the banks between the rolls, the kneading temperature is preferably 10 ° C. or higher higher than the melting point of the polyolefin. A temperature higher than ° C. is more preferable.

Further, the clearance between the plurality of rolls of the open roll should be as narrow as possible in order to apply a strong shearing force to the mixture, preferably 0.01 mm to 1 mm, and more preferably 0.05 mm to 0.5 mm. ..

Further, the number of kneading times and the kneading time using the open roll can be arbitrarily adjusted as long as the material is not significantly deteriorated.

<Polyolefin>
The polyolefin used in the present invention is a polyolefin having a density of 0.88 to 0.94 g / cm ³ and a weight average molecular weight of 2500 to 130000.
When carbon nanotubes having a polyolefin density of 0.94 g / cm ³ or less are blended, it is difficult to make the viscosity extremely high, so that kneading becomes easy. Further, when the density is 0.88 g / cm ³ or more, the melt viscosity of the polyolefin is maintained in an appropriate range, and an appropriate shearing force can be applied to the carbon nanotubes during kneading, so that the dispersibility is further improved. The density of the polyolefin is preferably ^{0.88~0.92g / cm 3, 0.88~0.91g / cm} 3 is more preferable.

When the weight average molecular weight of the polyolefin is 25,000 or more, the mechanical properties of the molded product are improved. Further, during molding, the conductive resin composition is less likely to be drawn down, and the moldability is further improved. In addition, since an appropriate shearing force is likely to be applied during kneading, carbon nanotubes in an aggregated state can be appropriately unraveled. Further, when the weight average molecular weight is 130000 or less, the kneading device can be kneaded without excessive load. The weight average molecular weight of the polyolefin is preferably 40,000 to 100,000, more preferably 50,000 to 80,000.

The polyolefin is not particularly limited as long as it satisfies the above density and the above weight average molecular weight. Polyolefins are polymers obtained by polymerizing olefin monomers alone or in combination of two or more. The polyolefin is preferably polyethylene and polypropylene.
Polyethylene is, for example, a polyethylene homopolymer, an ethylene copolymer: a copolymer of ethylene and an unsaturated monomer having 4 to 30 carbon atoms;
Polypropylene is a polypropylene homopolymer, a copolymer of propylene and an unsaturated monomer having 4 to 30 carbon atoms;
Copolymer of ethylene and propylene;
Polymers of olefin monomers with 4 or more carbon atoms (polybutene, poly-4-methylpentene-1, polystyrene, etc.);
Multiple copolymers in which the above olefin monomers are combined; and the like can be mentioned.

Unsaturated monomers having 4 to 30 carbon atoms include ptene (for example, 1-butene) and α-olefins having 5 to 30 carbon atoms (for example, 1-hexene, 4-methylpentene-1, 1-decene, 1-). Dodecene and the like), vinyl acetate, (meth) acrylic acid, (meth) acrylic acid alkyl ester and the like.
Among these polyolefins, polyethylene is preferable when low temperature physical properties are important. When polyethylene is synthesized using a metallocene-based catalyst, it is easy to adjust the weight average molecular weight to a predetermined range.

<Carbon nanotubes>
The carbon nanotube used in the present invention is a tubular substance having a structure in which a graphene sheet is rolled into a cylindrical shape. The carbon nanotubes include single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), and each carbon nanotube (primary particles) can be observed with an electron microscope or the like. The carbon nanotubes are preferably multi-walled carbon nanotubes in terms of cost and strength. Further, the side wall of the carbon nanotube may be a carbon nanotube having an amorphous structure instead of the graphite structure. In general, it is difficult to synthesize carbon nanotubes having a uniform graphite structure, and those having a partially amorphous structure on the side surface are generally used.
Further, in carbon nanotubes, primary particles are aggregated and entangled to form a primary aggregate, but the primary aggregate may further aggregate to form a secondary aggregate.

The carbon nanotubes preferably have an average fiber diameter of 0.5 to 50 nm, more preferably 1 to 40 nm, and even more preferably 5 to 20 nm. When the average fiber diameter is set to an appropriate range , it becomes difficult for the carbon nanotubes to take in the olefin inside during kneading, so that the viscosity of the conductive resin composition can be easily maintained in an appropriate range and the carbon nanotubes can be easily dispersed. The average fiber diameter is the diameter of carbon nanotubes, and is a value obtained by averaging about 20 fibers obtained from a magnified image with an electron microscope.

Carbon nanotubes can generally be produced by a laser ablation method, an arc discharge method, a chemical vapor deposition method (CVD method), a combustion method, or the like, but if the problem of the present invention can be solved, the production method is not particular. Among these production methods, the CVD method usually uses iron or iron on a carrier such as silica, alumina, magnesium oxide, titanium oxide, silicate, diatomaceous earth, alumina silica, silica titania, and zeolite at a high temperature of 400 to 1000 ° C. It is preferable to bring the catalyst fine particles carrying a metal catalyst such as silica into contact with the carbon-containing gas as a raw material because carbon nanotubes can be produced in large quantities at low cost.

The carbon nanotubes preferably contain 15 to 70 parts by mass of carbon nanotubes with respect to 100 parts by mass of polyolefin, more preferably 20 to 60 parts by mass, still more preferably 25 to 50 parts by mass. By containing 15 parts by mass or more of the carbon nanotubes, the conductive resin composition can be easily pulverized, so that it can be easily processed into fine particles. Further, when the content is 70 parts by mass or less, the dispersibility of the carbon nanotubes is further improved, and foreign substances derived from the carbon nanotubes are less likely to be generated on the surface of the molded body.

<Conductive resin composition>
The conductive resin composition of the present invention contains, if necessary, an oxidation-resistant stabilizer, a weather-resistant stabilizer, an antistatic agent, a dye, a pigment, a dispersant, a coupling agent, a crystal nucleating agent, a resin filler, and the like. It may contain an agent.
The conductive resin composition of the present invention has a tensile elongation rate of 30% or less, more preferably 20% or less. By setting the above values, it is easy to crush even with various crushers, and it is easy to mold into a desired shape. The lower limit of the tensile elongation is about 0%.

The conductive resin composition of the present invention is obtained by kneading a polyolefin having a density of 0.88 to 0.94 g / cm ³ and a weight average molecular weight of 2500 to 130000 with an open roll and then powdering it with a hammer mill crusher. In order to facilitate handling during molding, it is preferable to perform melt kneading (diluting step) with a kneading machine to mold into a desired shape. This shape is preferably in the form of pellets, powder, granules, beads, or the like, more preferably in the form of powder or pellets, and even more preferably in the form of pellets. Pelletizers are usually used for pelletization.

According to the method of using the conductive resin composition of the present invention, a desired molded product can be produced by molding as it is. Alternatively, the conductive resin composition may be mixed with a thermoplastic resin as a diluting resin and kneaded, and then formed into a desired shape (for example, pellets, powder, granules, beads, etc.).
The conductive resin composition preferably contains 1 to 1400 parts by mass, more preferably 2 to 900 parts by mass, and even more preferably 10 to 500 parts by mass with respect to 100 parts by mass of the diluted resin. When the above range is satisfied, the conductive resin composition can be easily distributed in the molded product.
By using the diluted resin, a resin that is not thermally deteriorated as compared with the polyolefin used when dispersing the carbon nanotubes is added, and the elasticity and tensile characteristics of the molded product are further improved.
Where polyolefin is preferable, the diluted resin may be a resin other than polyolefin, such as polyester or polycarbonate, as long as it is compatible with a predetermined polyolefin. Examples of the polyolefin include polyethylene and polypropylene.
The kneading can be performed by appropriately selecting an open roll or another known mixing device.

<Molded body>
The molded product of the present invention can be produced by melt-kneading and molding the conductive resin composition. At the time of the melt-kneading, it is preferable to further add a thermoplastic resin for dilution and mix it with the conductive resin composition. The conductivity of the molded product can be adjusted by the amount of the thermoplastic resin for dilution added.
The carbon nanotube content in the molded product may be appropriately adjusted depending on the degree of conductivity, if desired. For example, the carbon nanotubes are preferably 1 to 6% by mass, more preferably 2 to 5% by mass in 100% by mass of the molded product for antistatic film applications.

Molding is performed by putting the composition after melt-kneading into a molding machine usually set at 50 ° C. to 350 ° C. to prepare a molded product having a desired shape and cooling the molded product.
Examples of the molding method include extrusion molding, injection molding, blow molding, compression molding, transfer molding, film molding such as T-die molding and inflation molding, calendar molding, spinning and the like.

In the molded product of the present invention, the carbon nanotubes in the conductive resin composition used are highly dispersed and a specific polyolefin is used, so that drawdown, which is a problem when molding a film or a sheet, is suppressed. Therefore, as the molding method, T-die molding and inflation molding are preferable, and inflation molding is more preferable, where various methods can be used. The thermoplastic resin for dilution is preferably polyolefin, but it ^{does not necessarily have to satisfy a density of 0.88 to 0.94 g / cm 3} and a weight average molecular weight of 2500 to 130000. Further, a resin other than the polyolefin such as polyester or polycarbonate may be used as long as it is compatible with the predetermined polyolefin.

Examples of the shape of the molded product include plates, rods, fibers, tubes, pipes, bottles, sheets, films and the like. Among these, sheets and films are preferable because they do not have agglomerates of carbon nanotubes and can produce a molded product having a smooth surface.
The molded product of the present invention is preferably used for antistatic applications because the carbon nanotubes are highly dispersed. More specifically, it is preferably used for trays for transporting semiconductors and the like, protective sheets used for packing semiconductors and the like, protective bags and the like. In addition, it can be used for various purposes in which foreign matter is to be prevented from adhering due to static electricity.
In the present invention, a sheet having a molded body thickness of less than 250 μm is used as a film. Further, a sheet having a thickness of 250 μm to 1000 μm is called a sheet, and a sheet having a thickness of more than 1000 μm is called a plate. preferable.

The present invention will be described in more detail with reference to the following examples, but the following examples do not limit the present invention in any way. In the examples, unless otherwise specified, "parts" represents "parts by mass" and "%" represents "% by mass".

Tables 1 and 2 show the physical property values of the polyolefins and carbon nanotubes used in Examples and Comparative Examples.

The raw materials used in the examples are as follows.
<Polyolefin (A)>
(A1) Polyethylene (kernel KJ-640T, manufactured by Japan Polyethylene Corporation) Melting point: 58 ° C., Density: 0.88 g / mL, Weight average molecular weight: 43300 :, Molecular weight distribution: 2.2
(A2) Polyethylene (Novatec UF-420, manufactured by Japan Polyethylene Corporation) Melting point: 123 ° C., Density: 0.90 g / mL, Weight average molecular weight: 113000, Molecular weight distribution: 3.9
(A3) Polyethylene (Suntech LD M2270, manufactured by Japan Polyethylene Corporation) Melting point: 92 ° C., Density: 0.92 g / mL, Weight average molecular weight: 53300 :, Molecular weight distribution: 6.8
(A4) Polypropylene of Production Example 1 below, melting point 110 ° C., density: 0.90 g / mL, weight average molecular weight 55000 :, molecular weight distribution: 7
(A5) Polyethylene (Suntech HD B770, manufactured by Japan Polyethylene Corporation) Softening point: 127 ° C., Density: 0.96 g / mL, Weight average molecular weight: 203000 :, Molecular weight distribution: 28
(A6) Polypropylene of Production Example 2 below, melting point 161 ° C., density: 0.93 g / mL, weight average molecular weight 301000 :, molecular weight distribution: 22
The molecular weight distribution is a numerical value obtained by dividing the weight average molecular weight by the number average molecular weight.

<Carbon nanotube (B)>
(B1) Carbon nanotubes of Production Example 1 (B2) Carbon nanotubes of Production Example 2 (B3) Carbon nanotubes manufactured by Showa Denko KK (product name: VGCF-H)

(Polypropylene Production Example 1)
A stainless reactor with an internal volume of 5 L equipped with a stirrer was mixed with 1 L / h of toluene, 5 mmol / h of triisobutylaluminum, and 6 μmol / h of Ziegler-Natta catalyst, and the reaction temperature was set to 70 ° C. for the reaction. Propylene was continuously supplied and the polymerization reaction was carried out so that the hydrogen concentration in the gas phase portion of the reactor was maintained at 0.8 mol% and the total pressure in the reactor was maintained at 0.75 MPa · G. Polypropylene was obtained by removing toluene as a solvent and washing the polymer with a tetrahydrofuran solution. Polyolefin (A4) was obtained by setting the reaction temperature to 110 ° C. and the total pressure in the reactor to 0.9 MPa · G.

(Polypropylene production example 2)
Polypropylene polyolefin (A5) was obtained by setting the reaction temperature to 110 ° C. and the total pressure in the reactor to 0.9 MPa · G with the formulation shown in Production Example 1 of polypropylene.

An example of manufacturing carbon nanotubes will be described below.

(Production example 3 of carbon nanotube (B1))
72 g of cobalt hydroxide / tetrahydrate, 172 g of magnesium acetate / tetrahydrate, and 125 g of ascorbic acid were weighed in a beaker, 1000 g of purified water was added, and the mixture was stirred until completely dissolved. The mixture was transferred to a heat-resistant container, dried in an electric oven at an ambient temperature of 170 ± 5 ° C. for 120 minutes to evaporate the water content, and then pulverized in a mortar to obtain a precursor of the catalyst (c). 400 g of the obtained precursor (c) precursor was weighed in a heat-resistant container, calcined in an air at 500 ° C. ± 5 ° C. for 30 minutes in a muffle furnace, and then pulverized in a mortar to obtain a catalyst (c). .. Next, a quartz glass bakeware sprayed with 1.0 g of the catalyst (c) was installed in the center of a horizontal reaction tube having an internal volume of 10 liters, which could be pressurized and heated by an external heater. Exhaust was performed while injecting argon gas, and the air in the reaction tube was replaced with argon gas to reduce the oxygen concentration in the horizontal reaction tube to 1% by volume or less. It was heated by an external heater, and the central part of the horizontal reaction tube was heated to 750 ° C. Subsequently, hydrogen was introduced, and the catalyst was activated at 0.1 liter per minute for 1 minute, and then acetylene gas was injected at a rate of 1 liter per minute and reacted for 4 hours to produce carbon nanotubes. After completion of the reaction, the gas in the reaction tube was replaced with argon gas, and the mixture was taken out at a temperature of 100 ° C. or lower to obtain carbon nanotube aggregates. The obtained carbon nanotube agglomerates were pulverized and filtered through an 80-mesh wire mesh to obtain carbon nanotubes (B1).

(Production example 4 of carbon nanotube (B2))
200 g of cobalt acetate / tetrahydrate, 172 g of magnesium acetate / tetrahydrate and 125 g of ascorbic acid were weighed in a beaker, 1000 g of purified water was added, and the mixture was stirred until completely dissolved. The mixture was transferred to a heat-resistant container, dried in an electric oven at an ambient temperature of 170 ± 5 ° C. for 120 minutes to evaporate the water content, and then pulverized in a mortar to obtain a precursor of the catalyst (a). 400 g of the obtained catalyst (a) precursor was weighed in a heat-resistant container, fired in a muffle furnace in an atmosphere of 500 ° C. ± 5 ° C. for 30 minutes, and then pulverized in a mortar to obtain a catalyst (a). .. Next, a quartz glass bakeware sprayed with 1.0 g of the catalyst (a) was installed in the center of a horizontal reaction tube having an internal volume of 10 liters, which could be pressurized and heated by an external heater. Exhaust was performed while injecting argon gas, and the air in the reaction tube was replaced with argon gas to reduce the oxygen concentration in the horizontal reaction tube to 1% by volume or less. It was heated by an external heater, and the central part of the horizontal reaction tube was heated to 750 ° C. Subsequently, hydrogen was introduced at 0.1 liter per minute for 1 minute to activate the catalyst, and then acetylene gas was injected at a rate of 1 liter per minute and reacted for 4 hours to produce carbon nanotubes. After completion of the reaction, the gas in the reaction tube was replaced with argon gas, and the mixture was taken out at a temperature of 100 ° C. or lower to obtain carbon nanotube aggregates. The obtained carbon nanotube agglomerates were pulverized and filtered through an 80-mesh wire mesh to obtain carbon nanotubes (B2).

Hereinafter, a method for measuring the physical property values of each raw material will be shown.

(Density measurement)
The density of the polyolefin was measured by the method A of JIS7112-1999. The test piece to be measured was processed into a sheet having a thickness of 1 cm by a press machine heated to 160 ° C. in order to remove air bubbles in the resin composition as much as possible, and then measured.

(Weight average molecular weight)
The molecular weight distribution curve was measured by a gel permeation chromatograph (GPC) method using a Prominence GPC system manufactured by Shimadzu Corporation, and the weight average molecular weight (Mw) and the number average molecular weight (Mn) were calculated from polystyrene-equivalent values. The molecular weight distribution (Mw / Mn) was calculated from the obtained weight average molecular weight and number average molecular weight values. As the standard polystyrene used for polystyrene conversion, polystyrene manufactured by VARIAN was used, TSKgelGMH-HT manufactured by Tosoh Co., Ltd. was used as the column, and orthodichlorobenzene was used as the carrier at the time of measurement. The column temperature was 140 ° C. and the carrier flow rate was 1.0 mL.

(Volume resistivity)
The volume resistivity (Ω · cm) was measured using the powder resistivity system MCP-PD51 (manufactured by Mitsubishi Chemical Analytech). Specifically, 1.2 g of carbon nanotube powder was weighed, and the value under a load of 20 kN was taken as the volume resistivity.

(Average fiber diameter)
Carbon nanotubes were observed at an acceleration voltage of 5 kV using a scanning electron microscope (JSM-6700M, manufactured by JEOL Ltd.), and an image (number of pixels: 1024 x 1280) of 50,000 times was taken. Next, the minor axis lengths of each of the 20 arbitrary carbon nanotubes were measured in the captured image, and the number average value of the minor axis lengths was taken as the average diameter of the carbon nanotubes.

Hereinafter, an example of manufacturing the conductive resin composition will be shown.

[Example 1]
(Manufacturing of Conductive Resin Composition C1)
75% of polyolefin (A1) and 25% of carbon nanotubes (B1) were mixed with a pressure kneader to obtain a massive resin mixture. Next, the mixture was put into an open roll kneader (three rolls, manufactured by IMEX) and kneaded repeatedly at 130 ° C. three times to obtain a kneaded product. Next, the obtained kneaded material was pulverized with a hammer mill to obtain a powdery conductive resin composition (C1) having a diameter of about 1 mm. Next, 75% of the powdery polyolefin (A3) and 25% of the powdery conductive resin composition (C1) are mixed, put into a twin-screw extruder, melt-kneaded at 180 ° C., and cut with a pelletizer to pellet. Got

<Tensile elongation rate>
The obtained conductive resin composition (C1) is put into a hot press sheet molding machine and heated to 200 ° C. to prepare a press sheet having a length of 200 mm, a width of 200 mm and a thickness of 1.5 mm, and then hit into a No. 2 dumbbell mold. It was pulled out and used as a test piece. Next, the tensile fracture point elongation rate was measured according to JIS K-7127 under the condition of a tensile speed of 100 mm / min. Further, the tensile fracture point elongation rate is 100% for the dumbbell piece before the test, and when the length is 120% from that state, the elongation rate is 20%. The lower the tensile fracture point elongation rate, the less extensibility and the better the pulverizability. The tensile elongation is preferably 30% or less, and if it is higher than 30%, the conductive resin composition is stretched at the time of pulverization, which makes pulverization difficult or the shape of the produced pulverized material becomes non-uniform. Occurs.

<Roll workability>
The operability during open roll kneading in the production of the conductive resin composition (C1) was evaluated according to the following criteria. The poor processability means that the resin composition does not wrap around the roll during kneading and cannot be kneaded or partially peeled off. Further, good processability means that the resin composition can be sufficiently kneaded without peeling from the roll.
◯: Good workability ×: Poor workability

<Crushability>
The resin lump of the obtained conductive resin composition (C1) is cut into a cube (one side: 1 cm), 10 pieces are put into a small hammer mill (manufactured by Labnext), and a screen (mesh opening: 1 mm) is opened in 1 minute. The crushed material that passed was evaluated. For the observation of the crushed material, the surface was observed at a magnification of 300 times using a video microscope "VHX-900" (manufactured by KEYENCE CORPORATION). The evaluation criteria are shown below. Good pulverizability means that the size of the powder of the produced pulverized product is substantially uniform. The more uniform the size of the powder (W × D × H), the more the resin composition is pulverized without stretching during pulverization. Note that uniform means that the magnification of the higher value and the lower value of any of the three dimensions is less than 5 times. Poor crushability means that the resin composition is stretched at the time of crushing, and the ratio of the higher value or the lower value of any of the three dimensions is 5 times or more, or the resin composition is crushed after 1 minute has passed. It means that the mass of the resin lump remaining in the mill is 20% or more of the input mass.
◯: Powder with uniform dimensions (good)
×: Cannot be crushed (cannot be used)

(Manufacturing of molded product E1)
The obtained pellets were heated at 200 ° C. using an inflation molding machine (manufactured by PLACO Co., Ltd.) for inflation molding to obtain a tubular molded body (E1) having a length of 100 cm, a width of 15 cm, and a thickness of 30 μm.
(Manufacturing of molded product F1)
The obtained pellets are heated at 200 ° C. using a T-die sheet molding machine (manufactured by Toyo Seiki Co., Ltd.) to form a sheet, whereby a sheet-shaped molded product (F1) having a length of 300 cm, a width of 15 cm, and a thickness of 100 μm is formed. Got

The following evaluations were performed on the obtained molded product (E1) and the molded product (F1), respectively.

<Surface resistance value>
Resistivity meter "Loresta GP" (Loresta GP MCP-T610 type resistivity meter, JIS-K7194 compliant, 4-terminal 4-probe method constant current application method, manufactured by Mitsubishi Chemical Analytech) (4-terminal probe with 0.5 cm intervals) The surface resistivity value (Ω / □) of the molded product was measured using.

<Appearance evaluation>
The surface of the molded body was observed with a video microscope "VHX-900" (manufactured by KEYENCE) at a magnification of 500 times, and a foreign substance having a length and width of 30 μm or more on the surface of the molded body cut into a length of 50 cm and a width of 15 cm. Was measured and evaluated according to the following criteria. The smaller the number of foreign substances, the better.
◯: Less than 10 foreign substances (good)
×: 10 or more foreign substances (defective)

[Examples 2-9] and [Comparative Examples 10-19]
The conductive resin composition (the conductive resin composition) was carried out in the same manner as in Example 1 except that the polyolefin (A) and the carbon nanotube (B) of Example 1 were changed to the raw materials and blending amounts shown in Tables 2 and 3. C2) to (C15) were prepared. Only the conductive resin composition (C15) was kneaded by setting the kneading temperature of the open roll to 170 ° C.

Using the obtained conductive resin compositions (C2) to (C15), the molded product E2 was carried out in the same manner as in Example 1 except that the blending amounts of the raw materials shown in Tables 5 and 6 were changed. ~ F15 and molded products F2 to F15 were prepared and evaluated in the same manner as in Example 1.

From the results of Tables 3 and 4, Examples 1 to 9 have better roll processability and pulverizability of the conductive resin composition as compared with Comparative Examples 10 to 11. Further, as compared with Comparative Examples 12 to 13, the pulverizability of the carbon nanotubes is good when the predetermined average fiber diameter is within a specific range. Further, as compared with Comparative Examples 14 to 15, it can be seen that when the molecular weight and density of the polyolefin are within the range of the present invention, the roll processability is excellent.

Further, from the results of Tables 7 and 8, the molded bodies E1 to E9 and the molded bodies F1 to F9 of Examples 1 to 9 are more than the molded bodies E11 to 15 and the molded bodies F11 to 15 of Comparative Examples 11 to 15. It can be seen that the carbon nanotubes are highly dispersed in the resin because the surface resistance value is clearly low and the appearance is good with few bumps.

Claims (5)

A method for producing a conductive resin composition, wherein a polyolefin having a density of 0.88 to 0.94 g / cm ³ and a weight average molecular weight of 2500 to 130000 and carbon nanotubes are kneaded with an open roll.
The average fiber diameter of the carbon nanotubes is 0.5 to 50 nm, and the carbon nanotubes have an average fiber diameter of 0.5 to 50 nm.
The carbon nanotubes are contained in an amount of 15 to 70 parts by mass with respect to 100 parts by mass of the polyolefin.
A method for producing a conductive resin composition, wherein the tensile elongation rate under the following measurement conditions is 30% or less.

Measurement of tensile elongation; Put the conductive resin composition into a hot press sheet molding machine and heat it to 200 ° C to make a press sheet with a length of 200 mm, a width of 200 mm, and a thickness of 1.5 mm, and then hit it into a No. 2 dumbbell mold. Remove it to make a test piece. Then, the measurement is performed according to JIS K-7127 under the condition of a tensile speed of 100 mm / min. The method for producing a conductive resin composition according to claim 1, wherein the kneading with an open roll is performed at 50 ° C. or higher. A method for producing a molded product, which comprises molding the conductive resin composition obtained by the production method according to claim 1 or 2. The method for manufacturing a molded product according to claim 3, wherein the molding is inflation molding. A conductive resin composition which is a kneaded product of polypropylene having a density of 0.88 to 0.94 g / cm ³ and a weight average molecular weight of 2500 to 130000 and carbon nanotubes.
The average fiber diameter of the carbon nanotubes is 0.5 to 50 nm, and the carbon nanotubes have an average fiber diameter of 0.5 to 50 nm.
It contains 15 to 70 parts by mass of carbon nanotubes with respect to 100 parts by mass of the polypropylene.
A conductive resin composition having a tensile elongation of 30% or less under the following measurement conditions.

Measurement of tensile elongation; Put the conductive resin composition into a hot press sheet molding machine and heat it to 200 ° C to make a press sheet with a length of 200 mm, a width of 200 mm, and a thickness of 1.5 mm, and then hit it into a No. 2 dumbbell mold. Remove it to make a test piece. Then, the measurement is performed according to JIS K-7127 under the condition of a tensile speed of 100 mm / min.