JP2001200211A - Electroconductive coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide electroconductive coating materials which have a low electrical resistance and withstand long-term service and are suitably used particularly in destaticizing and electromagnetic wave shielding. SOLUTION: The electroconductive coating materials comprise 70-99.8 mass% thermoplastic resin or thermosetting resin and 30-0.2 mass% fine carbon fibers having a diameter of 0.01-5 μm and an aspect ratio of >=10 and containing 0.1-3 mass% boron therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
It is related to conductive paint that can withstand long-term use,
Especially for the purpose of electrostatic painting, static electricity prevention and electromagnetic wave shielding,
Alternatively, the present invention relates to a conductive paint suitably used for a conductive ink for a resistor, a circuit, a roll of a copying machine, and the like.

[0002]

2. Description of the Related Art Recently, in fields where electromagnetic wave shielding properties, antistatic properties, and antistatic properties are required for electronic devices and the like,
Conductive paints have been used. In these paints, metal powders such as silver, aluminum and copper, carbon powders and the like are used as fillers. Further, a paint having good conductivity is also required as a base paint for electrostatic coating.

[0003]

However, silver has the disadvantage that it is expensive and has a high specific gravity, and the conductivity of other metal powders is reduced due to oxidation, corrosion and the like. On the other hand, carbon powder is inexpensive and has few problems like metal powder, but has drawbacks such as insufficient conductivity. This is because the conductivity of the carbon powder itself is lower than that of the metal powder and the aspect ratio (length / diameter) is small. For this reason, in this field, an inexpensive filler having high conductivity, low specific gravity, high aspect ratio, and low conductivity is desired.

Accordingly, graphitizable carbonaceous fibers having a unique structure with a small fiber diameter and a large aspect ratio disclosed in Japanese Patent Publication No. Hei 6-39576,
No. 97, there is proposed a filler which improves the above-mentioned disadvantages, such as a carbon fibril material comprising an aggregate in which fine thread-like carbon fibrils are entangled with each other. However, in order to obtain sufficient conductivity, it is necessary to add a large amount of several tens of mass% to these fillers, which not only leads to a considerable increase in cost, but also complicates handling when mixed with the resin, A problem arises in that the fluidity of the paint after mixing is reduced and application becomes difficult.

Accordingly, an object of the present invention is to provide a conductive paint which has high conductivity, is chemically stable, and is inexpensive.

[0006]

SUMMARY OF THE INVENTION The present inventors have previously disclosed in Japanese Patent Application No. 11-81260 a fine carbon fiber having high crystallinity and a method for producing the same, which could not be obtained conventionally.
And a battery electrode having higher performance using the fiber as a filler. The carbon fiber has a diameter of 0.01 to 5 μm.
m, the aspect ratio is 10 or more, and boron is contained in the fiber in an amount of 0.
A fine carbon fiber containing 1 to 3% by mass and having a carbon spacing d ₀₀₂ of 3.385 ° or less and a thickness Lc in the c-axis direction of the crystal of 400 ° or less determined by X-ray diffraction. It is.

The fine carbon fibers have high crystallinity and are therefore excellent in conductivity. Therefore, the present inventors have studied the fine carbon fiber in order to improve the drawbacks of the conventional conductive paint, and as a result, have found that a conductive paint having high conductivity can be obtained with a small amount of addition. I found it. Further, they have found that the resistance value can be reduced to half or less of the conventional value with the same addition amount.

Thus, according to the present invention, 70 to 99.8 parts by mass of a thermoplastic resin or a thermosetting resin,
Fine carbon fibers having an aspect ratio of 10 to 5 μm and containing boron in the fiber in an amount of 0.1 to 3% by mass.
Provided is a conductive paint characterized by containing 2 parts by mass. The plane distance d _{002 of} carbon of fine carbon fibers obtained by X-ray diffraction can be 3.385 ° or less, and the thickness Lc in the c-axis direction of the crystal can be 400 ° or less.

The powder resistance of the fine carbon fiber is 0.01 Ω · cm or less when the bulk density is 0.8 g / cm ³ , and the resistance value of the obtained dry paint is 0.01 Ω · cm or less. Can be.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION (Fine carbon fibers) The carbon fibers to be added to the conductive paint of the present invention have a diameter of 0.01 to 5 μm.
It is a fine carbon fiber having an aspect ratio of 10 or more. When the fiber 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 addition rate (mass%) of the fiber is fixed, the number of fibers decreases as the diameter increases, and the function of the fiber as a filler is not sufficiently exhibited. On the other hand, when the diameter is larger than 5 μm, the productivity of the fiber itself is remarkably reduced, so that the cost becomes industrially high. For these reasons, the fiber diameter is 0.01-5 μm. Those having a fiber diameter of 1 μm or less are preferred.

When the aspect ratio of the fiber is less than 10, the conductivity of the paint when carbon fiber is added to the paint is not sufficient. Preferably, the aspect ratio is 50 or more. The length of the fine carbon fiber is not particularly limited, and the lower limit is preferably a length determined from the lower limit of the aspect ratio. If the length of the fiber is too long, problems may occur in the dispersibility as a filler due to entanglement of the fiber, or irregularities may easily occur on the surface of the coating film. Therefore, the upper limit is preferably 400 μm, more preferably 100 μm. Therefore, for example, when the aspect ratio is 50 or more, when the fiber diameter is 0.01 μm, the fiber length is 0.5 μm or more, and when the fiber diameter is 1 μm, the length is 50 μm.
m or more is preferable. The upper limit of each is preferably 40
It is 0 μm, more preferably 100 μm.

The fine carbon fiber used in the present invention is characterized in that its crystal contains boron. The present inventors have succeeded in obtaining desired properties such as conductivity by incorporating boron into fine carbon fiber crystals. Although the production method will be described later, high crystallization, that is, high conductivity is effectively achieved at a boron content of 0.1 to 3% by mass. Preferably, it contains 0.2 to 3% by mass of boron. However, boron only needs to be present at the time of crystallization of the fiber in the heat treatment, and after high crystallization, the boron is volatilized by treatment at a higher temperature or the like, and the content is 0.1% by mass.
The concentration may be lower than the addition amount as long as it does not fall below the range.

Further, the fine carbon fiber containing boron in the crystal used in the present invention has high crystallinity, the plane spacing d ₀₀₂ determined by the X-ray diffraction method is 3.385 ° or less, and the c-axis of the crystal is The thickness Lc in the direction can be in the range of 400 ° or less. Conventionally, it has not been possible to reduce the interplanar spacing d ₀₀₂ to 3.385 ° or less in fine carbon fibers.
Further, although the fine carbon fiber has a small d ₀₀₂ , the thickness Lc of the crystal in the c-axis direction can be 400 ° or less, which is an unconventional feature. This fine carbon fiber contains boron, and d ₀₀₂ and Lc
Value is within the above range, and (ratio R = I _D / I _G of the absorption intensity I _D of the absorption intensity I _G and 1360 cm ^-1 in 1580 cm ^-1) R value of Raman absorption spectrum of 0.5 or more It has the following features.

Further, the powder resistance of the fine carbon fiber can be 0.01 Ω or less when the bulk density is 0.8 g / cm ³ . When the fine carbon fibers have such high conductivity, the conductivity of the paint containing the fine carbon fibers is also improved. (Preparation method of fine carbon fiber) The fine carbon fiber used in the present invention incorporates boron into the crystal structure of the fiber,
It can be produced by its catalytic action. As described above, the content of boron effective for high crystallization is generally 0.1 to 3% by mass, preferably 0.2 to 3% by mass.

As the carbon fiber used as a starting material, fine carbon fiber grown in the gas phase by thermal decomposition of an organic compound such as benzene can be used. This carbon fiber is used, for example, in JP-A-7-150419 and JP-A-5-321039.
JP-A-60-215816, JP-A-60-215816
It can be manufactured by the method described in Japanese Patent Application Publication No. -70014, Japanese Patent Publication No. 5-36521, Japanese Patent Publication No. 3-61768, and the like. If the fiber diameter is 0.01 μm or more, fine fibrous substances called carbon nanotubes or carbon nanofibers having the same annual ring structure can be used. Accordingly, carbon nanotubes, carbon nanofibers, and the like having a multi-structure manufactured by an arc discharge method, a laser method, or the like can be used.

[0016] a study of the present inventors, such fine carbon fibers, although it is possible to improve the crystallinity by a heat treatment, the d ₀₀₂ only heat treatment is limit 3.385A, crystalline than It turned out that no improvement could be expected.
Then, as a result of further study on a graphitization catalyst for high crystallization, boron was particularly effective. Regarding ordinary carbon materials, various studies have been made on adding boron to a heat treatment to increase crystallinity. ("Carbon" 199
6, No. 172, pp. 89-94, JP-A-3-24545
8, JP-A-5-251080, JP-A-5-251080
266880, JP-A-7-73898, JP-A-8-31422, JP-A-8-306359, JP-A-9-63584, JP-A-9-635
No. 85) However, there is no example in which the properties of fine vapor grown carbon fibers having a diameter of 5 μm or less have been improved by introducing boron. The reason is that graphitization using boron is hard to be easily performed due to the shape characteristics as described below, and the catalytic effect of boron cannot be expected because the fiber has a special structure.

The vapor grown carbon fiber is an onion-like fiber in which the crystal structure of the cut surface of the fiber has developed concentrically. Although the length of the fiber varies depending on the manufacturing conditions, for example, in the case of a fiber having a diameter of about 0.01 to 0.5 μm, not only a single fiber but also a large number of branched fibers exist, so it is difficult to clearly define the straight part. In most cases, the average is at least 5 μm or more as measured by a scanning electron microscope.

In addition, since the 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, and in some cases, A large floc having a size of 100 μm or more tends to be formed. Therefore, the bulk density as an aggregate is small,
05g / cm ³ or less, usually is 0.01g / cm ³ or less. In addition, since it has a floc-shaped three-dimensional structure, it is difficult to contact with a graphitization catalyst, and it is difficult to uniformly boronize.

In addition, since the fine carbon fibers are covered with a solid basal plane (a hexagonal network structure), the surface of the fine carbon fibers is sterically hindered even during graphitization using boron. Is inhibited. The present inventors have found that high crystallization can be achieved by doping fine carbon fibers with boron.

In order to dope boron, it is preferable to use, as the fine carbon fiber as a raw material, a low-temperature-treated product which is easy to dope and has little crystal development, preferably a carbon fiber which has been heat-treated at 1500 ° C. or lower. Even low-temperature-treated carbon fibers are finally heated to the graphitization temperature during the treatment using boron as a catalyst (boronation treatment), so that even untreated heat-treated products with undeveloped crystals can be used. . 2000 ° C. or higher, preferably 2300
It is not impossible to use carbon fibers that have been graphitized at a temperature of ℃ or higher.However, it is not necessary to graphitize in advance from the viewpoint of energy savings. It is preferable to act on the catalyst simultaneously with the conversion.

Further, there is a report that the temperature at which the content of boron in carbon is the largest and the doping is easy is 2000 to 2300 ° C., and a material crystallized by treatment at a higher temperature has a small catalytic effect. Fine carbon fibers as raw materials that have been crushed and pulverized in advance for easy handling can be used, but the crushing and pulverization are sufficient as long as they can be mixed with boron or a boron compound. That is,
Even after the boration treatment, a filler treatment such as crushing, pulverization, and classification is finally performed, so that it is not necessary to make the filler as a proper length before the boration treatment. Thickness (diameter) generally obtained by a vapor growth method is about 0.01 to 5 μm,
Carbon fibers having a length of about 0.5 to 400 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.

As a boron source used for doping boron, a substance which does not evaporate by decomposition or the like before reaching at least 2000 ° C., for example, elemental boron,
B ₂ O _3, boron, B ₄ C, BN, it is preferred to use other boron compounds. The amount of carbon that can be doped with boron is generally 3% by mass or less. When the boron content is 0.1 to 3% by mass, high crystallization is effectively achieved, that is, high conductivity is achieved. Preferably, it contains 0.2 to 3% by mass of boron. However, boron only needs to be present at the time of crystallization of the fiber in the heat treatment, and after high crystallization, the boron is volatilized by, for example, treatment at a higher temperature, so that the content is not more than 0.1% by mass. The concentration may be lower than that.

Therefore, the addition amount of boron or boron compound at the time of compounding is sufficient to be not more than 10% by mass in terms of boron atom with respect to the carbon amount in consideration of the reaction rate. If the amount of boron used is large, not only the processing cost is increased, but also the filler properties are lost, such as easy melting and sintering at the heat treatment stage and increase in electrical resistance by hardening or coating the fiber surface.

In order to efficiently carry out the boron introduction reaction, it is necessary to mix the carbon fiber and boron or boron compound well and to make the contact as uniform as possible. Fine carbon fibers have a three-dimensional three-dimensional structure and are not only easily formed in a floc shape, but also have 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 mass or less, preferably 5% by mass or less, it is difficult to make uniform contact only by mixing both. Therefore, it is necessary that the carbon fiber and the boron compound be brought into contact as uniformly as possible by using particles of boron or boron compound having the smallest possible particle size. In addition, when the particles are large, a high concentration region is partially generated, which may cause solidification. Specifically, the particle size is 100 μm in average particle size.
Or less, preferably 50 μm or less, more preferably 20 μm
m or less.

Although carbon fibers and boron or a boron compound can be uniformly mixed and heat-treated as it is, fine carbon fibers obtained by a gas phase method have a very low bulk density.
Preferably, the heat treatment is performed while the density is increased and the state is maintained (fixed) as much as possible. As a preferred method,
After mixing both, there is a method of applying pressure to the mixture, compressing the mixture, densifying the mixture, and fixing the mixture.

Mixing of the carbon fiber with boron or a boron compound may be performed by any method as long as uniformity can be maintained.
As the mixer, any of commercially available mixers may be used. However, since fine carbon fibers tend to form flocs, it is more preferable to use a Henschel mixer type with a chopper to break the fine fibers. 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 a mixture of carbon fiber and boron or a boron compound and fixing the mixture so that the two are not separated, a molding method, a granulation method, or a method in which the mixture is put into a crucible and compressed into a predetermined shape. Any method may be used, such as a method of stuffing. In the case of the molding method, the shape of the molded body may be any shape such as a columnar shape, a plate shape, and a rectangular parallelepiped. The carbon fiber to which the boron or the boron compound has been added to increase the bulk density is then heat-treated.

The processing temperature required to introduce boron into the carbon crystal is generally above 2000 ° C., preferably 2 ° C.
300 ° C. or higher. If the treatment temperature is lower than 2000 ° C., the reactivity between boron and carbon is poor, and it is difficult to introduce boron. In order to further promote the introduction of boron and improve the crystallinity of carbon, in particular, to reduce d ₀₀₂ to 3.385 ° or less, 23
It is preferable to keep the temperature at 00 ° C or higher. There is no particular upper limit for the heat treatment temperature, but it is about 3200 ° C. due to limitations of the apparatus and the like.

The heat treatment furnace to be used may be any furnace capable of maintaining a target temperature of 2000 ° C. or higher, preferably 2300 ° C. or higher, and may be any of ordinary devices such as an Acheson furnace, a resistance furnace, and a high frequency furnace. In some cases, a method in which the powder or the molded body is directly energized and heated may be used.
The atmosphere for the heat treatment is a non-oxidizing atmosphere, preferably 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.

The carbon fiber densified by compression molding or the like partially sinters and becomes block-shaped when heat-treated, so that it is desirable to crush the molded body to obtain a form suitable as a filler. Therefore, this block is crushed, crushed,
At the same time, the non-fibrous material is separated while being classified and treated to be suitable as a filler. At that time, if the pulverization is too much, the filler performance is deteriorated. If the pulverization is insufficient, the mixing with the paint base agent does not work well, and the addition effect may not be obtained.

In order to obtain a desirable form as a filler, the block-like material after the heat treatment is first crushed into a size of 2 mm or less, and further crushed by a crusher. 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 aspect ratio is preferably 10 or more, more preferably 50 or more.

The bulk density after pulverization and classification is 0.001.
0.2 g / cm ³ , preferably 0.005 to 0.15 g
/ Cm ³ , more preferably 0.01 to 0.1 g / cm ³ . When the bulk density is 0.2 g / cm ³ or more, the length of the fiber becomes as short as 5 μm or less depending on the diameter, and the filler effect is reduced. On the other hand, if the diameter is less than 0.001 g / cm ³ , the diameter becomes longer than 400 μm depending on the diameter, and clogging as a filler becomes worse. What is bulk density?
This is the tapping bulk density determined from the volume and mass 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 above method has a bulk density of 0.8 g / cm ^3.
, The powder resistance can be 0.01 Ω · cm or less. On the other hand, fine carbon fibers of the same shape and produced by a vapor growth method containing no boron in the fibers have a bulk density of 0.8 g.
/ Cm ³ , the powder resistance is about 0.01 to 0.03 Ω · cm. 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 conductive paint of the present invention, which has a low electric resistance and is preferably used for purposes such as prevention of static electricity and electromagnetic wave shielding, is provided by using fine carbon fibers whose conductivity is improved by almost one digit compared to the related art. can do.

(Resin) As a thermoplastic resin or a thermosetting resin which can be used for the conductive paint of the present invention, examples of the thermoplastic resin include polyamide resin, polyurethane resin, vinyl chloride resin and ethylene-vinyl acetate. Polymers, acrylic resins, cellulose resins, butyral resins, and the like, as thermosetting resins, phenolic resins, epoxy resins, urea resins, melamine resins, xylene resins, furan resins, unsaturated polyester resins, silicon resins, and the like, These precursors can also be used.

For these resins, if necessary, known curing agents and curing assistants, curing catalysts and activators can be used. For example, an amine or mercaptan compound or an acid anhydride can be used as a curing agent for an epoxy resin. The above resin can be used as an emulsion or a latex, but it is preferable to dissolve it in a solvent and use it as a solution.

The solvent is not particularly limited as long as it dissolves or disperses the resin. For example, toluene, hydrocarbons such as xylene, dichloroethane, halogenated hydrocarbons such as trichloroethane, isopropyl alcohol,
Alcohols such as butanol, methyl ethyl ketone,
Ketones such as methyl isobutyl ketone, ethyl acetate,
Esters such as ethyl propylate, ethers such as methyl ether of ethylene glycol and dimethyl ether of diethylene glycol, and water can be used.

(Composition of conductive paint) In the present invention, the content of fine carbon fibers in the thermoplastic resin or thermosetting resin is 30 to 0.2% by mass, preferably 10 to 0.5% by mass. % By mass. If the carbon fiber content exceeds 30% by mass with respect to the resin, problems such as a decrease in fluidity, difficulty in uniform coating, a decrease in coating film strength, and a decrease in substrate adhesion will occur. On the other hand, when the content does not reach 0.2% by mass, the effect of the carbon fiber is poor, and the conductivity when used in a paint is not sufficient.

The amount of the solvent is not particularly limited.
It may be determined in consideration of the storage property, coating property, drying property and the like.
In the conductive paint of the present invention, an additive for improving paint properties can be used as necessary. For example,
Dispersant for increasing the dispersibility of carbon fiber as a filler, other fibrous substances and inorganic substances, powders and flakes such as metals,
Leveling agents for improving printability, stabilizers against heat, oxidation, and light, coupling agents, thickeners, pigments, plasticizers, crosslinking agents, fillers, and the like can be mixed.

In order to further improve the conductivity, it can be used by mixing with another conductive powder.
Other conductive powders include acetylene black, carbon black such as Ketjen black, graphite powder,
Various carbon fibers, powders or fibers of gold, silver, nickel, aluminum, and the like, metal-coated glass fibers, and the like are included.

(Production of Paint) The conductive paint of the present invention can be usually produced by mixing a solution of the resin with fine carbon fibers. As the mixing device, a normal device such as a three-roll mill or a ball mill can be used. The conductive paint of the present invention can be applied by a usual method such as brushing, roller coating, spraying and the like.

The conductive paint of the present invention thus produced can have a resistance value of 0.01 Ω · cm or less after being applied and dried.

[0042]

The conductive paint of the present invention is a paint having extremely high conductivity because fine carbon fibers having high conductivity are uniformly dispersed in the resin while contacting at many contact points. . Further, the strength of the coating film is excellent due to the reinforcing effect of the carbon fiber, and there is no decrease in conductivity due to oxidation, corrosion, and the like over a long period of use, unlike a metal filler. Therefore, it can be applied to various base materials such as concrete, metal, wood, and plastic, and can be suitably used for the purpose of preventing static electricity and shielding electromagnetic waves.

[0043]

The present invention will be described below in detail with reference to examples. (Examples 1 to 4 and Comparative Examples 1 and 2) Fine carbon fibers as a starting material are prepared by a known method of thermally decomposing benzene in the presence of an organometallic compound containing a transition metal (for example, 7-150419) was further heat-treated at 1200 ° C. The obtained carbon fibers were flocculated, but were crushed to give a bulk density of 0.02 g / cm ³ and a fiber length of 10 to 100 μm. The fiber diameter was mostly 0.5 μm or less (average fiber diameter observed by electron micrograph was 0.2 μm). The plane distance d ₀₀₂ of carbon of the carbon fiber by X-ray diffraction was 3.
At 407 °, the thickness Lc of the crystal in the c-axis direction was 56 °.

To 2.88 kg of the fiber, 120 g of B ₄ C powder having an average particle size of 15 μm was added, and thoroughly mixed with a Henschel mixer. The mixture was packed in a cylindrical graphite crucible having a capacity of 50 liters and compressed to a bulk density of 0.075.
g / cm 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. At this time, the heating time after reaching 2900 ° C. and 2900 ° C. is 6
0 minutes.

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 diameter of the obtained fiber is 2900
As in the case before the heat treatment at ° C., the majority was 0.5 μm or less, the length was 5 to 30 μm, and the bulk density was 0.04 g / cm ³ . The fiber had a boron content of 1.03% by mass and d ₀₀₂
Was 3.380 ° and Lc was 290 °. The powder resistance at a bulk density of 0.8 g / cm ³ is 0.003 Ω · cm.
Met.

Next, a conductive paint was prepared using the fine carbon fibers as follows. The fine carbon fibers were mixed with a 20% by mass solution of phenol resin in methyl ethyl ketone at a mass ratio shown in Table 1 using three rolls to obtain each conductive paint. This was applied on a glass plate, and after the solvent was dried, the coating film was peeled off from the glass, and the volume resistivity and tensile strength were measured. Table 1 shows the results. (Comparative Examples 3 and 4) 3.0 kg of the fine carbon fibers as the starting material shown in the examples 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 ^3.
And 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 2900
The heating time after reaching 2900 ° C. was 60 minutes. 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 diameter of the obtained fiber was 2900 ° C. before heat treatment.
Mainly 0.5μm or less, length is 5-30μ
m, bulk density is 0.04 g / cm^ThreeMet. Also, this fiber
D ₀₀₂Was 3.388 ° and Lc was 280 °.
In addition, bulk density 0.8 g / cm^ThreePowder resistance is 0.0
It was 13 Ω · cm. Conducted using this fine carbon fiber
In the same manner as in the examples, paints were prepared at the mass ratios shown in Table 1,
The product specific resistance and tensile strength were measured. Table 1 shows the results.
Shown in (Comparative Example 5) Acetylene bra instead of fine carbon fiber
A paint is prepared in the same manner as in the example except that a paint is used.
Then, the volume resistivity and the tensile strength were measured. as a result
Are shown in Table 1.

[0048]

[Table 1]

As is clear from Table 1, the conductive paints of Examples 1 to 4 exhibited excellent conductivity, and no decrease in the strength of the paint was observed. In addition, Example 3, Comparative Example 3, and Example 4
As is clear from the comparison between Comparative Example 4 and Comparative Example 4, when the addition amount of the fine carbon fibers is the same, the resistance value of the conductive paint of the present invention can be reduced to 以下 or less of the conventional one.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J038 BA021 CB051 CD021 CE071 CG001 DA031 DA131 DA141 DB001 DC011 DD181 DG001 DH001 DL001 HA026 KA12 KA19 NA03 NA11 NA19 NA20 PB09 PC02 PC04 PC06 PC08

Claims (4)

[Claims] 1. A thermoplastic or thermosetting resin 70 to
99.8 parts by mass, a diameter of 0.01 to 5 μm, an aspect ratio of 10 or more, and 0.1 to 3% by mass of boron in the fiber
A conductive paint comprising 30 to 0.2 parts by mass of fine carbon fibers contained therein. 2. The fine carbon fiber is determined by X-ray diffraction.
Plane spacing d of carbon ₀₀₂Is less than 3.385 °,
The thickness Lc in the c-axis direction is 400 ° or less.
Conductive paint. 3. The conductive paint 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 obtained dry paint has a resistance value of 0.05Ω.
The conductive paint according to any one of claims 1 to 3, wherein the conductive paint is not more than cm.