JP2001200096A - Electroconductive thermoplastic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electroconductive thermoplastic resin composition, cheap and light, excellent in electroconductivity, stable in a corrosive environment, excellent in processability, mechanical characteristics, surface smoothness, or the like, and capable of favorably used specifically for the purpose of antistatic and as a shield to an electromagnetic wave. SOLUTION: This electroconductive thermoplastic resin composition contains a minute carbon fiber, the minute carbon fiber contains boron or a boron compound at 0.1-3 wt.% as boron atom to the carbon in the minute carbon fiber, the diameter of the minute carbon fiber is 0.01-5 μm and the aspect ratio is 10 or higher, and the content of the minute carbon fiber is 0.1-50 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive thermoplastic resin composition which has excellent conductivity, is excellent in antistatic and electromagnetic wave shielding, and is also excellent in economy, mechanical properties and the like.

[0002]

2. Description of the Related Art With the development of electronics technology, a material having a light weight and high conductivity has been required as a material for shielding electromagnetic waves and preventing static electricity. As the conductive material used for such a purpose, a resin composite material in which a conductive material such as powdered or fibrous metal or carbon such as carbon black or carbon fiber is blended with a synthetic resin such as rubber or plastic is used. Has begun to be used.

[0003]

However, those using a metal as a conductive material are disadvantageous in that they are expensive and heavy, and their conductivity is unstable in a corrosive environment.
There is a problem that the use of a noble metal having good corrosion resistance is extremely expensive. In addition, carbon-based conductive materials have a drawback that they have low conductivity compared to metals and do not provide sufficient performance.If the compounding amount is increased to compensate for this, workability and mechanical properties are reduced. Problems arise. In addition, when carbon fibers are used, there is a problem that the surface smoothness is lowered when the amount of the carbon fibers is increased.

Accordingly, the present invention provides a conductive thermoplastic resin composition which is inexpensive, light, has excellent conductivity, is stable even in a corrosive environment, and has excellent workability, mechanical properties, surface smoothness and the like. The purpose is to provide.

[0005]

The inventor of the present invention has conducted intensive studies to achieve the above object, and as a result, has a diameter of 0.01 to 5 μm.
m, an aspect ratio of 10 or more, a conductive thermoplastic resin composition using 0.1 to 50% by weight of fine carbon fiber containing 0.1 to 3% by weight of boron is inexpensive and light,
The inventors have found that they have excellent conductivity, are stable even in a corrosive environment, and are excellent in workability, mechanical properties, and surface smoothness, and have completed the present invention.

That is, the present invention relates to a conductive thermoplastic resin composition containing fine carbon fibers, wherein the fine carbon fibers contain boron or a boron compound with respect to the carbon content of the fine carbon fibers. 0.1 to 3% by weight in terms of boron atom
The conductive material is characterized in that the fine carbon fiber has a diameter of 0.01 to 5 μm and an aspect ratio of 10 or more, and the content of the fine carbon fiber is 0.1 to 50% by weight. The present invention provides a thermoplastic resin composition.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The fine carbon fiber used in the present invention is preferably prepared by adding boron or a boron compound as a raw material to the fine carbon fiber in an amount of preferably 1 atom in terms of boron atom with respect to the carbon content of the fine carbon fiber.
It is obtained by blending 0% by weight or less, particularly preferably 5% by weight or less, and can be produced by containing boron in its crystal and highly crystallization by its catalytic action. When boron or a boron compound is added in an amount of more than 10% by weight in terms of boron atom with respect to the carbon content of the fine carbon fiber, not only the processing cost is increased, but also it is easy to melt and sinter in the heat treatment stage, and the fiber is hardened. It is not preferable because filler properties may be lost, for example, the surface may be coated to increase electric resistance. Further, the amount of carbon that can be doped with boron is generally 3% by weight or less, and considering the reaction rate, it is not preferable to add more than 10% by weight from this point as well. The amount of boron or boron compound in the carbon fiber when the heat treatment is performed to effectively crystallize the carbon fiber is 0.1 to 3% by weight in terms of boron atoms based on the carbon amount of the fine carbon fiber. It is necessary that
3% by weight is preferred. The boron or boron compound may be present in the above amount when the heat treatment is performed to highly crystallize the carbon fiber. If the content is not less than 0.1% by weight, then the heat treatment may be further performed with higher heat. The concentration of boron may be lower than the amount of boron added.

The fine carbon fiber used in the present invention has a diameter of 0.01 to 5 μm, preferably 0.01 to 1 μm, and an aspect ratio of 10 or more, preferably 50 or more. When the diameter is less than 0.01 μm, the strength of the fiber is weak, and when used as a filler, the fiber is frequently cut, and the function as the fiber is easily impaired. On the other hand, when the diameter is larger than 5 μm, the number of fibers becomes too small when the addition ratio (% by weight) as a filler is fixed,
The function of the fiber as a filler is not sufficiently exhibited. Further, since the productivity of the fiber itself is significantly reduced, the cost is industrially high. If the aspect ratio is less than 10, the function as a fiber is not sufficient.

The length of the fiber itself is not particularly limited, and the lower limit is preferably a length determined from the lower limit of the aspect ratio. For example, when the aspect ratio is 50 or more, the diameter is 0.01 μm.
For m, the fiber length is preferably 0.5 μm or more, and for 1 μm diameter, the length is preferably 50 μm or more. However, the length of the fiber is preferably 400 μm or less, more preferably 100 μm or less, because if the length is too long, problems may occur in the dispersibility as a filler due to entanglement of the fiber or the like, and irregularities may easily occur on the surface of the resin molded product. .

The fine carbon fiber used in the present invention has an interplanar spacing d _{002 of} carbon of 3.385 ° or less as measured by X-ray diffraction, and a thickness Lc in the c-axis direction of the crystal of 400 ° or less. Further, d ₀₀₂ is less 3.385A, and together with Lc is less than 400 Å, the absorption intensity I _G of R value of Raman absorption spectrum (1580 cm ^-1 1360
It is characterized in that the ratio (R = I _D / I _G ) of the absorption intensity _ID at cm ⁻¹ is 0.5 or more.

The fine carbon fiber used in the present invention has a powder resistance of 0.01 Ω · c at a bulk density of 0.8 g / cm ^3.
m, particularly preferably 0.005 Ω · cm or less.

Next, a method for producing fine carbon fibers used in the present invention will be described. -Carbon fiber as starting material-
As the carbon fiber as a starting material, fine carbon fiber grown in a gas phase by thermally decomposing an organic compound such as benzene can be used. This carbon fiber is used, for example, in JP-A-7-150419, JP-A-5-321039, JP-A-60-215816, and JP-A-61-7.
0014, Japanese Patent Publication No. 5-36521, Japanese Patent Publication No. 3-61768, and the like.

Although the crystallinity of this fine carbon fiber can be improved to some extent by heat treatment, d ₀₀₂ is 3.38.
5% is the limit, and to further improve the crystallinity,
It is necessary to add boron or boron compounds.

Various studies have been made on increasing the crystallinity of ordinary carbon materials by heat treatment by adding boron (for example, "Carbon" 1996, N0172, 89-94).
Page, JP-A-3-245458, JP-A-5-251
080, JP-A-5-266880, JP-A-7-73898, JP-A-8-31422,
JP-A-8-306359, JP-A-9-63584
JP-A-9-63585, etc.). However, there is no example in which boron is introduced into fine vapor-grown carbon fibers having a diameter of 5 μm or less to improve the characteristics. The reason is that, as shown below, graphitization using boron is difficult to be performed due to the shape characteristics, and the catalytic effect of boron is difficult to exert because the fiber has a special structure.
(A) Vapor-grown carbon fiber is an onion-like fiber in which the crystal structure of the cut surface of the fiber has developed concentrically. (A) The length of the fiber varies depending on the manufacturing conditions, but is, for example, 0.01 to
In the case of a fiber having a diameter of about 0.5 μm, not only a single fiber but also a large number of branched fibers are present, so it is difficult to specify clearly. However, when the straight line portion is measured with a scanning electron microscope, the average is 5 μm or more. Is the most. (C) In addition, since these fibers include fine fibers branched in addition to long fibers, not only long fibers but also short fibers of about 5 μm have a size of at least 10 μm or more, in some cases. A large floc of 100 μm or more tends to be formed. (D) Therefore, the bulk density of the aggregate is small, 0.05 g / cm ³ or less, usually 0.01 g / cm ³ or less.
g / cm ³ or less. Moreover, it has a floc-like three-dimensional structure, making it difficult to contact with the graphitization catalyst.
It is difficult to uniformly borate. (E) Also, since the fine carbon fibers are covered with a solid surface of beesalbrain (a hexagonal network structure plane), even if they are graphitized using boron, they are crystalline due to steric hindrance during polygonization. Improvement is hindered.

In order to dope boron, as a raw material fine carbon fiber, a low-temperature treated product which is easy to dope and has little crystal growth, preferably 1500 ° C.
The heat-treated carbon fiber is used below. Even in the case of low-temperature-treated carbon fiber, it is finally heated to the graphitization temperature during the treatment using boron or a boron compound as a catalyst (boronation treatment). Can be used enough. 2000 ° C or higher, further 230
Carbon fiber that has been graphitized at a temperature of 0 ° C or higher can be used, but it is not necessary to perform graphitization in advance from the viewpoint of energy reduction. It is preferable to work.
Further, there is a report that the temperature at which the content of boron in carbon is the highest and the doping is easy is 2000 to 2300 ° C., and a material which is treated at a higher temperature and crystallized has a small catalytic effect.

The fine carbon fiber used as the raw material may be crushed or crushed in advance for easy handling, but crushing and crushing are sufficient if the crushing and crushing are performed to such an extent that boron or a boron compound can be mixed. It is. In other words, after the boration treatment, a filler treatment such as crushing, pulverization, and classification is performed, so that it is not necessary to make the filler a proper length before the boration treatment. Diameter of about 0.01 to 5 μm and length of 0.5 to 400 generally obtained by vapor phase growth
Carbon fibers of about μm can be used as they are. These may be flocked. The raw fiber may be a heat-treated fiber, but the heat treatment temperature is preferably 1500 ° C. or lower.

-Boration treatment-Boration treatment is 2000
Since it is carried out at a temperature of at least 2000 ° C., a substance which does not evaporate even by decomposition before reaching at least 2000 ° C.
Elemental Bow element, B ₂ 0 _3, boric acid, B ₄ C, BN, it is preferred to use other boron compounds. When boric acid or the like is used, a method of adding water as an aqueous solution and evaporating water in advance, or a method of evaporating water in a heating process can be used. If the aqueous solution is uniformly mixed, the boron compound can be uniformly attached to the fiber surface after water evaporation.

The fine carbon fiber has a three-dimensional structure and is easy to form a floc shape, and has a very small bulk density and a very large porosity. Moreover, since the amount of boron to be added is as small as 10% by weight or less, preferably 5% by weight or less, it is difficult to make uniform contact only by mixing both. In order to efficiently carry out the boron introduction reaction, it is preferable to mix the carbon fiber and boron or the boron compound well, and to contact both as uniformly as possible. For this purpose, it is preferable to use boron or boron compound particles having the smallest possible particle size.
If the particles are large, a high-concentration region is partially generated, and it is easy to consolidate.
m, more preferably 50 μm
The thickness is particularly preferably 20 μm or less.

Fine carbon fibers produced by the gas phase method
Since the bulk density is very small, the carbon fiber and boron or boron compound may be mixed and heat-treated as it is. However, it is necessary to increase the density of the mixture and to maintain (fix) the state as much as possible and to heat-treat the mixture. Is preferred. As a preferable method, for example, there is a method in which the mixture is mixed, and then the mixture is compressed by applying pressure to thereby increase the density and immobilize the mixture. Mixing of carbon fiber and boron or boron compound,
Any method may be used as long as uniformity can be maintained. As the mixer, any of commercially available mixers can be used,
Since the fine carbon fibers tend to form flocs, a Henschel mixer type having a chopper for crushing the fine fibers is more preferable. The raw carbon fiber to be used may be as manufactured as described above,
A processed product at a temperature of 00 ° C. or less may be used. However, it is preferable to use it as it is manufactured economically. As a method of densifying the mixture of carbon fiber and boron or boron compound and fixing them so that they do not separate, molding method, granulation method, or putting the mixture in a crucible and compressing it into a certain shape and filling it Any method may be used. In the case of the molding method, the shape of the molded body is cylindrical, plate-like, rectangular parallelepiped, or the like.
Any shape may be used.

[0020] The carbon fiber thus added with boron or boron compound to increase the bulk density is then heat-treated. The processing temperature required for introducing boron into the carbon crystal is preferably 2000 ° C. or higher, particularly preferably 2300 ° C. or higher.
If the treatment temperature is lower than 2000 ° C., the reactivity between boron and carbon tends to be poor, and it becomes difficult to introduce boron. In order to further promote the introduction of boron and improve the crystallinity of carbon, and particularly to reduce d ₀₀₂ to 3.385 ° or less,
It is preferable to keep the temperature at 2300 ° C. or higher. Although there is no particular limitation on the heat treatment temperature, it is preferably about 3200 ° C. or less due to limitations of the apparatus and the like. The heat treatment furnace used is 2000
Any furnace can be used as long as it can be maintained at a temperature of not less than 2 ° C., preferably not less than 2300 ° C., and any device such as an ordinary Acheson furnace, a resistance furnace or a high-frequency furnace may be used. In some cases, a method in which the powder or the molded body is directly energized and heated may be used. The heat treatment atmosphere is preferably a non-oxidizing atmosphere, particularly a rare gas atmosphere such as argon. The heat treatment time is preferably as short as possible from the viewpoint of productivity. In particular, when heating is performed for a long time, the sintering proceeds, so that the yield also decreases. Therefore, a holding time of one hour or less is sufficient after the temperature of the central part of the molded body or the like reaches the target temperature.

When heat-treated, carbon fibers densified by compression molding or the like partially sinter to form blocks. Therefore, since the form is not suitable as a filler as it is, it is preferable to crush the molded body. Therefore, this block is crushed, crushed, classified, etc., and processed so as to be suitable as a filler, and at the same time, non-fibrous materials are separated. At that time, if the pulverization is too much, the filler performance is deteriorated, and if the pulverization is insufficient, the mixing with the resin composition base material does not work well, and the addition effect is hardly obtained. In order to obtain a desirable form as a filler, for example, it is preferable to first crush the heat-treated block into a size of 2 mm or less, and then pulverize it with a pulverizer. As the crusher, a commonly used device such as an ice crusher or a rotoplex can be used. As a pulverizer, a pulverizer or a free pulverizer of an impact type pulverizer, or a pulverizer such as a micro jet can be used. Classification for separating non-fibrous materials can be performed by an airflow classifier or the like. The conditions for pulverization and classification vary depending on the type and operation conditions of the pulverizer. However, in order to exhibit filler characteristics, the fiber length is preferably 5 to 400 μm.
The high density after the pulverization classification is 0.001 to 0.2 g /
cm ³ is preferable, and more preferably 0.005 to 0.1
5 g / cm ³ , particularly preferably 0.01 to 0.1 g / c
m is ^3. If the bulk density exceeds 0.2 g / cm ³ , the length of the fiber may be as short as 5 μm or less depending on the diameter, and the filler effect tends to be reduced. 0.001 g / cm ³
If it is smaller, it will be longer than 400 μm depending on the diameter, and clogging as a filler will be poor.
The bulk density is a tapping bulk density determined from the volume and weight when the container is filled with fibers and vibrated to reach a substantially constant volume.

The fine carbon fiber containing boron in the fiber produced by the method described above has a bulk density of 0.8 g /
The powder resistance at cm ³ is 0.01 Ω · cm or less. On the other hand, fine carbon fibers of the same shape and formed by a vapor growth method containing no boron in the fibers have a bulk density of 0.8 g / c.
The powder resistance at m ³ is about 0.01 to 0.03 Ωcm. This is because when boron is added as a catalyst during graphitization, crystallinity is improved, and as a result, conductivity is improved. As described above, the use of the fine carbon fiber whose conductivity is improved by about one digit compared to the conventional technology has a low electric resistance and is suitable for the purpose of preventing static electricity and shielding electromagnetic waves. A resin composition can be obtained.

-Resin component- The thermoplastic resin used in the present invention is not particularly limited as long as it is a resin used in the field of molding. For example, polyolefin resins such as polyethylene and polypropylene, and styrenes such as polystyrene, ABS and AS resins. System resins, polyamide resins such as nylon 6, nylon 66 and nylon 12, engineering plastics such as polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyphenylene sulfite, polysulfone, polyether ketone, polyether sulfone, and the like. In the present invention, these thermoplastic resins can be used alone or in combination of two or more. Further, various additives usually used, such as antioxidants, lubricants, plasticizers, stabilizers, and the like, may be previously added to these thermoplastic resins.

In blending and dispersing fine carbon fibers into such a thermoplastic resin, a usual thermoplastic resin blending method can be used, but such a method is generally used. A kneading machine such as a Banbury mixer or a kneader can also be used. The conductive thermoplastic resin composition of the present invention can be produced according to a conventional method after blending and dispersing fine carbon fibers into the thermoplastic resin.

The conductive thermoplastic resin composition of the present invention thus obtained preferably has a resistance value of 0.01 Ω · cm or less, in order to secure sufficient conductivity.
It is particularly preferred that the resistance is not more than 05 Ω · cm. From such a viewpoint, the content of the fine carbon fibers in the conductive thermoplastic resin composition of the present invention needs to be 0.1% by weight or more, and preferably 1% by weight or more. 0.
If the amount is less than 1% by weight, a coagulated structure to the extent that conductivity can be imparted in the resin is not formed, and the conductivity as a molded article is not sufficient. On the other hand, if the content is too large, the fluidity at the time of melting decreases, and molding becomes difficult. In addition, even if it is contained at a high filling rate, no improvement in conductivity corresponding to the high filling rate level is observed. From the above viewpoints, the content of fine carbon fibers in the conductive thermoplastic resin composition of the present invention needs to be 0.1 to 50% by weight, and 1 to 50% by weight. Is preferred.

The conductive thermoplastic resin composition of the present invention comprises:
Various known additives can be added, if necessary, as long as the object of the present invention is not hindered. Examples of the additive include an antioxidant, an ultraviolet absorber, a plasticizer, a stabilizer, a filler, a reinforcing agent, a flame retardant, a lubricant, a solvent, and a processing aid. Further, a metal-based or other carbon-based conductive material or the like can be added and used in combination.

The conductive thermoplastic resin composition of the present invention is selected from various molding methods such as extrusion molding, injection molding, transfer molding, and press molding, by selecting an appropriate method according to the shape of the base resin and the molded product. Then, by molding, an intended molded product can be obtained. In particular,
Low resistance band such as facsimile, uncharged conveyor belt, conductive tire, IC storage case, roll for copy machine,
Examples include a heating element, an overcurrent / overheat prevention element, an electromagnetic wave shielding housing, a keyboard switch, and a connector element.

[0028]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

Examples 1 to 4 and Comparative Examples 1 to 2
Some fine carbon fibers are metallized with transition metals
Known method of pyrolyzing benzene in the presence of a compound
(See, for example, JP-A-7-150419)
The raw fibers were further heat-treated at 1200 ° C. Obtained
Carbon fibers were flocculated, but were broken up
And the bulk density is 0.02 g / cm ^Three, Fiber length is 10
The thickness was 100 μm. Most fiber diameter is 0.5μm or less
(The average fiber diameter observed by electron micrograph is 0.2μ
m). Surface of carbon by X-ray diffraction of this carbon fiber
Interval d₀₀₂Is 3.407 ° and the thickness L of the crystal in the c-axis direction is
c was 56 °. The average particle size of 2.88 kg of this fiber
15 μm B_FourC powder 120g, add
Mix well with Kisa. 50 liters of this mixture
Into a cylindrical graphite crucible and compress it to reduce bulk density.
0.075g / cm^ThreeAnd Compress with a graphite pressure plate
The lid was closed, and placed in an Acheson furnace for heat treatment. this
The temperature at that time is 2900 ° C.
And heated for 60 minutes. After heat treatment, cool,
Take out the raw fiber, pulverize it with a bantam mill, and then
The fibrous material was separated by an air classifier. The obtained fiber diameter is
Mostly 0.5μ as before heat treatment at 2900 ° C
m, length is 5 to 30 μm, and bulk density is 0.04 g / c.
m^ThreeMet. The fiber has a boron content of 1.0.
3% by weight, d₀₀₂, Lc are 3.380 ° and 29, respectively.
It was 0 °. In addition, bulk density 0.8 g / cm^ThreeAt the time
The powder resistance was 0.003Ω · cm.

Next, using the fine carbon fibers, a conductive thermoplastic resin composition (pellet) was produced as follows. That is, polypropylene (SMA410 manufactured by Nippon Polyolefin Co., Ltd.) and the fine vapor-grown carbon fibers containing boron were blended in the ratio shown in Table 1 and melt-kneaded with an extruder to obtain pellets.

Comparative Examples 3 and 4 3.0 kg of the fine carbon fibers used in Example 1 were packed in a cylindrical graphite crucible having a capacity of 50 liters and compressed to obtain a bulk density of 0.075 g / cm.
^{It was set to 3} . While being compressed with a graphite pressing plate, the lid was closed, and the plate was placed in an Acheson furnace and heat-treated. The temperature at this time is 290
The temperature was 0 ° C, and heating was performed for 60 minutes after the temperature reached 2900 ° C. After the heat treatment, the mixture was cooled, the carbon fiber was taken out of the crucible, pulverized by a bantam mill, and then the non-fibrous material was separated by a gas classifier. The fiber diameter obtained was the same as before the heat treatment at 2900 ° C., mostly 0.5 μm or less, the length was 5 to 30 μm, and the bulk density was 0.04 g / cm ³ . Further, d ₀₀₂ and Lc of this fiber are 3.3, respectively.
It was 88 ° and 280 °, and the powder resistance at a bulk density of 0.8 g / cm ³ was 0.013 Ω · cm. Then
Pellets were obtained in the same manner as described above, using the above-mentioned polypropylene and with the composition shown in Table 1.

Comparative Example 5 Pellets were obtained in the same manner as in Example 1 except that carbon black was used instead of fine vapor grown carbon fiber.

Test Example 1 Each of the pellets obtained above was press-molded under the usual polypropylene molding conditions to obtain a test piece. For each of the obtained test pieces, the volume resistivity was measured using a surface resistance meter manufactured by Mitsubishi Chemical Corporation. Table 1 shows the results. The surface smoothness was measured by a surface roughness meter (finger touch type).

[0034]

[Table 1]

As is clear from Table 1, the conductive thermoplastic resin compositions of Examples 1 to 4 exhibited excellent conductivity.
Further, the conductive thermoplastic resin compositions of Examples 1 to 4 all had good surface smoothness, but the conductive thermoplastic resin composition of Comparative Example 2 had excellent conductivity. The surface smoothness was reduced. The conductive thermoplastic resin compositions of Comparative Examples 3 to 5 had low conductivity. Further, as is clear from Example 3 and Comparative Example 4, when the addition amount of the fine carbon fibers is the same, the resistance value of the conductive thermoplastic resin composition of the present invention is set to 1/2 or less of the conventional one. be able to.

[0036]

The conductive thermoplastic resin composition of the present invention comprises:
Fine carbon fibers with high conductivity are uniformly dispersed in the resin while contacting at many contact points, so they have extremely high conductivity, and are inexpensive, light, and stable even in a corrosive environment. Has excellent workability, mechanical properties, surface smoothness, etc. Therefore, it can be suitably used for the purpose of preventing static electricity and shielding electromagnetic waves.

Continued on front page F term (reference) 4J002 BB031 BB121 BC031 BC061 BN151 CB001 CF061 CF071 CH091 CL011 CL031 CN011 CN031 DA016 DK007 FA046 FB076 FD106 FD116 GQ00 4L037 AT02 AT05 CS03 FA02 FA03 FA05 FA12 DA04 DD02 DA02 DA02 DA02 DA02

Claims (4)

[Claims] 1. A conductive thermoplastic resin composition containing fine carbon fibers, wherein said fine carbon fibers convert boron or a boron compound into boron atoms in terms of the amount of carbon in said fine carbon fibers. And the fine carbon fiber has a diameter of 0.01 to 5 μm and an aspect ratio of 1
0 or more, and the content of the fine carbon fibers is 0.1
The conductive thermoplastic resin composition is characterized by being in an amount of from 50 to 50% by weight. 2. A fine carbon fibers, according to claim interplanar spacing d _{00 2} carbons as measured by X-ray diffractometry is not more than 3.385A, and the thickness Lc of the c-axis direction of the crystal is not more than 400Å 2. The conductive thermoplastic resin composition according to 1. 3. The conductive thermoplastic resin composition according to claim 1, wherein the powder resistance of the fine carbon fibers is 0.01 Ω · cm or less when the bulk density is 0.8 g / cm ³ . 4. The conductive thermoplastic resin composition according to claim 1, which has a resistance value of 0.01 Ω · cm or less.