JP2733568B2 - Fluorinated graphite fiber and its manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to carbon fibers suitable for use in conductive composite materials and the like.

[Conventional technology]

Since carbon fibers are lightweight, have excellent mechanical strength, and have good conductivity, they are used as composite materials by combining metals, plastics, carbon materials, and the like, and used in various application fields.

By the way, since carbon materials are inferior in conductivity to metal materials, studies to improve the conductivity of carbon materials are being conducted, and various molecules, atoms, ions, etc., such as nitric acid, etc., are present between graphite crystal layers. Is known to obtain an interlayer compound having improved conductivity. Furthermore, the covalent intercalation compound obtained by reacting graphite and fluorine is said to exhibit insulating properties, but reacts flake or powdered graphite such as natural graphite or artificial graphite with fluorine. It is also known that a conductive interlayer compound can be obtained. However, such an intercalation compound is in a powder form, and when it is made into a composite material, it is difficult to obtain uniform and stable conductivity, and there is a problem that the strength is reduced.

On the other hand, pitch-based graphite fibers and PAN-based graphite fibers do not develop much crystal structure, and have not been able to obtain a compound with excellent conductivity as an interlayer compound and achieve uniform dispersion as a composite material. It is difficult. Further, on the other hand, a graphite fiber obtained by graphitizing a vapor-grown carbon fiber whose crystal structure is more complete is used, and for example, nitric acid, metal chloride, bromine, etc. are reacted with this. However, there is a drawback that the electrical resistance increases over time due to poor properties, and that the devices and the like in contact therewith are corroded by decomposition products.

[Problems to be solved by the invention]

Accordingly, the present invention provides a graphite layer compound fiber which is extremely excellent in stability and thermal stability in the atmosphere, has good conductivity, and is easily blended with a thermoplastic resin or the like and is suitable for use in a conductive composite material. The purpose was to provide.

[Means for solving the problem]

An object of the present invention as described above is to form an intercalation compound of graphite fiber and fluorine having a three-dimensional crystal structure in which a carbon hexagonal net plane is substantially parallel to a fiber axis and oriented in a ring shape, and This is achieved by a fluorinated graphite fiber characterized in that the length of the repetition period in the c-axis direction is mixed in the range of 5 to 24 angstroms.

The fluorinated graphite fiber of the present invention is obtained by graphitizing a vapor-grown carbon fiber obtained by thermally decomposing a hydrocarbon compound in a non-oxidizing atmosphere in the presence of a catalyst supported on a substrate to form a carbon hexagonal mesh. By obtaining a graphite fiber having a three-dimensional crystal structure substantially parallel to the fiber axis and oriented in a ring shape, and then contacting with a fluorine gas having a pressure of 300 to 1500 Torr at a temperature of -10 to 120 ° C. Can be manufactured. Further, the vapor-grown carbon fiber obtained by contacting the ultrafine metal catalyst suspended in the high temperature zone with the hydrocarbon compound is graphitized so that the carbon hexagonal mesh plane is substantially parallel to the fiber axis, A graphite fiber having a three-dimensional crystal structure oriented in a ring shape is obtained, and then a pressure of 300 to 1500 Torr fluorine gas and -10 to 1
It can also be produced by contact at a temperature of 20 ° C.

Carbon fiber as a material of the fluorinated graphite fiber of the present invention,
Using hydrocarbon compounds such as aromatic hydrocarbons such as toluene, benzene and naphthalene, and aliphatic hydrocarbons such as propane, ethane and ethylene, preferably benzene or naphthalene as a raw material, and gasifying such raw material to produce a carrier gas such as hydrogen Together with a catalyst made of ultrafine metal, for example, iron, nickel, iron-nickel alloy having a particle size of 100 to 300 angstroms in a reaction zone at 900 to 1500 ° C. and decomposed.

The carbon fiber thus obtained is 1500 to 3500 ° C., preferably
At a temperature of 2500 to 3000 ° C., for 3 to 120 minutes, preferably 30 to 6
By heat-treating for 0 minutes in an atmosphere of an inert gas such as argon, a graphite fiber having a three-dimensional crystal structure in which carbon hexagonal planes are substantially parallel to the fiber axis and oriented in a ring shape is obtained. In this case, if the heat treatment temperature is lower than 1500 ° C,
The crystal structure of carbon is not sufficiently developed, and even if it exceeds 3500 ° C., the effect is not particularly enhanced and it is not economical. If the heat treatment time is shorter than 10 minutes, the effect of the heat treatment is not sufficient, and the degree of development of the crystal structure varies greatly. On the other hand, if the heat treatment time exceeds 120 minutes, no further improvement is observed.

The carbon fiber thus obtained may be subjected to a purification treatment before or after the heat treatment for graphitization, if necessary, and may be pulverized using a ball mill, a rotor speed mill, a cutting mill, or another appropriate pulverizer. May be. Although such pulverization is not essential, it is preferable to carry out the pulverization because the ease of formation of an intercalation compound and the dispersibility at the time of compounding with another material are improved.

In fluorinating the graphite fiber thus obtained, at a temperature of 200 ° C. or less, preferably at −10 to 120 ° C.,
A method of contacting with fluorine gas at a pressure of 100 Torr or more, preferably 300 to 1500 Torr for at least 48 minutes and preferably for 48 to 72 hours is used. At this time, a catalyst such as silver fluoride can be used to promote fluorination.

In promoting the above fluorination, if the contact temperature between the graphite fiber and the fluorine gas exceeds 200 ° C., covalent bond type fluorinated graphite is generated, and a fiber having excellent conductivity cannot be obtained.
Further, the pressure of the fluorine gas needs to be at least 100 Torr, and if it is lower than this, the desired fluorinated intercalation compound cannot be obtained. Further, the contact time between the graphite fiber and fluorine needs to be 10 minutes or more, and depending on the reaction temperature and pressure, for example, 40 hours or more at room temperature and normal pressure is appropriate. However, if the reaction time becomes longer, the crystal structure becomes out of the intended range, and as a result, the conductivity is lowered, which is not desirable.

The fluorinated graphite fiber obtained by applying the production conditions as described above has a composition of C ₅ F to C ₃₀ F, and the length of the repetition period I _c of the crystal in the c-axis direction is 5
~ 24 angstroms.

[Example 1] A liquid obtained by dispersing metal iron catalyst particles having a particle size of 300 Å or less in alcohol was coated on a mullite ceramic plate, and a substrate on which a catalyst was dispersed and adhered was placed in a horizontal tubular electric furnace. Then, the temperature was adjusted to 1000 to 1100 ° C., and a mixed gas of benzene and hydrogen was introduced to perform catalytic decomposition to obtain carbon fibers having a length of 2 to 30 mm and a diameter of 5 to 50 μm.

Next, the carbon fiber was placed in an electric furnace, and kept at 2950 to 3000 ° C. for 30 minutes in an argon atmosphere to be graphitized. The obtained graphite fiber X has a three-dimensional crystal structure in which a carbon hexagonal mesh plane is parallel to the fiber axis and is oriented in an annual ring shape by an X-ray diffractometer and an electron microscope, and the lattice constant d ₀₀₂ is 3.36 Å, It was confirmed that the crystal size L _c (002) in the c-axis direction was 1000 Å or more.

Lightly mix the graphite fiber X1g thus obtained and powdered silver fluoride (about 1mg) into a nickel boat in a nickel reaction tube, sufficiently evacuate the mixture, and introduce high-purity fluorine gas at room temperature. At 760 Torr for 72 hours. Thereafter, while introducing argon into the reaction tube to replace the internal gas, fluorine was guided to the alumina-filled adsorption tower to be adsorbed, and the fluorinated graphite fiber A was recovered.

Upon elemental analysis of the obtained fluorinated graphite fiber A,
It was found to have a composition of C _8.3 F. Also, when the length I _c of the repetition period in the c-axis direction of the crystal was measured by the X-ray diffraction method, values of 9.42 angstroms and 12.6 angstroms were obtained, and the number of stages of the intercalation compound was a mixture of two and three. I understood.

Next, the electric resistance of the fluorinated graphite fiber A was measured by a direct current four-terminal method, and after standing in the air for three months, the electric resistance was measured again to examine the stability. Also 25
The high temperature stability was determined by measuring the electrical resistance 30 minutes and 3 hours after holding at 0 ° C.

These measurement results are shown in Table 1 in comparison with the measurement results for the untreated graphite fiber X.

Example 2 Metallic iron catalyst particles having a particle size of about 300 angstroms were suspended in a vertical tubular electric furnace controlled at a temperature of 1000 to 1100 ° C. while flowing hydrogen from below, and mixed with benzene and hydrogen. Gas is introduced from below and catalytically decomposed to a length of 0.
Carbon fibers having a diameter of from 0.1 to 1 mm and a diameter of from 0.1 to 0.5 μm were obtained. Next, this carbon fiber was ground using a planetary ball mill (Fritsch Japan KK, P-5 type) at a rotation speed of 500 rpm for 20 minutes.

This ground carbon fiber was placed in an electric furnace, and kept at 2960 to 3000 ° C. for 30 minutes in an argon atmosphere to be graphitized. The obtained fiber has a three-dimensional crystal structure in which a carbon hexagonal net plane is parallel to the fiber axis and oriented in a ring shape by an X-ray diffractometer and an electron microscope, and has a lattice constant d ₀₀₂ of 3.37 to 3.40 angstroms, It was confirmed that the graphite fiber was excellent in orientation and had a crystal size c-axis direction L _c (002) of 310 Å.

The graphite fiber Y thus obtained was fluorinated in the same procedure as in Example 1, and the fluorinated graphite fiber B was recovered.

Upon elemental analysis of the obtained fluorinated graphite fiber B,
It was found to have a composition of C _8.3 F. Also, when the length I _c of the repetition period in the c-axis direction of the crystal was measured by the X-ray diffraction method, values of 9.42 angstroms and 12.6 angstroms were obtained, and the number of stages of the intercalation compound was a mixture of two and three. I understood.

1 g of such a powder of the fluorinated graphite fiber B is placed in a cylinder made of an insulating material having a diameter of 1 cm, sandwiched between brass electrodes from above and below, and compressed under a pressure of 1 t / cm ² to obtain an electric resistance between the upper and lower electrodes. Was measured, and the volume resistivity when the packing density was 1.6 g / cm ³ was determined. Furthermore, after being left in the air for three months, the electric resistance was measured again to examine the stability. The electrical resistance was measured after 30 minutes and 3 hours at 250 ° C., and the high-temperature stability was examined.

These measurement results are shown in Table 2 in comparison with the measurement results for the untreated graphite fiber Y.

Example 3 Metallic iron catalyst particles having a particle size of about 100 angstroms were suspended in a vertical tubular electric furnace controlled at a temperature of 1000 to 1100 ° C., and benzene, hydrogen, carbon monoxide and carbon dioxide were mixed therein. Gas is introduced from below and catalytically decomposed to a length
Carbon fibers having a diameter of 0.01 to 3 mm and a diameter of 1 to 5 μm were obtained. Next, the carbon fiber was pulverized and graphitized in the same manner as in Example 2 to obtain a graphite fiber Z, and further fluorinated to obtain a powder of a fluorinated graphite fiber C.

The composition and crystal structure of the powder of the fluorinated graphite fiber C were exactly the same as those of the fluorinated graphite fiber B obtained in Example 2.

Further, the volume resistivity of the powder of the fluorinated graphite fiber C was measured in the same manner as in Example 2, and the stability in air and the stability at high temperature were examined.

Table 2 shows a comparison of these measurement results with the measurement result of the untreated graphite fiber Z.

[Example 4] Using the graphite fiber X obtained by the same procedure as in Example 1, fluorination was performed in the same manner as in Example 1, except that the reaction was performed for 48 hours while maintaining the pressure of fluorine at 700 Torr. A fluorinated graphite fiber D was obtained.

Upon elemental analysis of the obtained fluorinated graphite fiber D,
It was found to have a composition of C _20.2 F. The Measurement of the length I _c of the repetition period of the crystal c-axis direction by X-ray diffraction method, obtained a value of 16.42 Å and 19.80 Å, that the number of stages of the intercalation compound is a mixture of 4 and 5 understood.

Next, the electrical resistance of the fluorinated graphite fiber D was measured by the same DC four-terminal method as in Example 1.

The measurement results are shown in Table 3 in comparison with the measurement results for the fluorinated graphite fiber A and the untreated graphite fiber X.

[Comparative Example 1] Using the graphite fiber X obtained by the same procedure as in Example 1, fluorinated by the same method as in Example 1 except that the reaction was carried out for 24 hours while maintaining the pressure of fluorine at 760 Torr, A fluorinated graphite fiber E was obtained.

Upon elemental analysis of the obtained fluorinated graphite fiber E,
It was found to have a composition of C _40.3 F. Further, when the length I _c of the repetition period in the c-axis direction of the crystal was measured by the X-ray diffraction method, the structure of the graphite fiber X remained strong, and formation of an intercalation compound having a periodic structure could not be confirmed.

Further, the electric resistance of the fluorinated graphite fiber E was measured in Example 1.
Table 3 also shows the results of the measurement by the DC four-terminal method similar to the above.

[Example 5] Using the graphite fiber X obtained by the same procedure as in Example 1, fluorination was carried out in the same manner as in Example 1, except that the reaction was carried out at room temperature for 144 hours while maintaining the pressure of fluorine at 760 Torr. Thus, a fluorinated graphite fiber F was obtained.

Elemental analysis of the obtained fluorinated graphite fiber F showed that C
It was found to have a composition of _5.7 F. When the repetition period I _c of the crystal in the c-axis direction was measured by X-ray diffraction, very strong values of 5.14 angstroms and weak 9.38 angstroms were obtained. It was found that a small number of stages 2 were mixed.

The results of measuring the electrical resistance of this fluorinated graphite fiber F by the same direct current four-terminal method as in Example 1 are shown in Table 3.

Example 6 A fluorinated graphite fiber G was obtained by using the graphite fiber Y obtained by the same procedure as in Example 2 and fluorinating it by the same method as in Example 4.

When the obtained fluorinated graphite fiber G was subjected to elemental analysis,
It was found to have a composition of C _22.5 F. When the repetition period length I _c of the crystal in the c-axis direction was measured by X-ray diffraction, values of 13.6, 17.1 and 20.8 angstroms were obtained. I found it to be.

The electrical resistance of the fluorinated graphite fiber G was measured by the same powder method as in Example 2, and the volume resistivity when the packing density was 1.6 g / cm ³ was determined by the fluorinated graphite fiber B and the untreated graphite fiber Y. The results are shown in Table 4 in comparison with the measurement results.

Example 7 A fluorinated graphite fiber H was obtained by using the graphite fiber Y obtained by the same procedure as in Example 2 and fluorinating it by the same method as in Example 5.

Upon elemental analysis of the obtained fluorinated graphite fiber H,
It was found to have a composition of C _6.3 F. The Measurement of the length I _c of the repetition period of the c-axis direction of the crystal by X-ray diffraction method, obtained a peak strong peaks and 9.41 and 12.78 Å weak 5.17 angstroms,
It was found that most of the intercalation compounds had two or three stages, and a small number of stages were mixed.

The electrical resistance of the fluorinated graphite fiber H was measured by the same powder method as in Example 2, and the results are shown in Table 4.

Example 8 A fluorinated graphite fiber I was obtained by using the graphite fiber Z obtained by the same procedure as in Example 3 and performing fluorination in the same manner as in Example 4.

Upon elemental analysis of the obtained fluorinated graphite fiber I,
It was found to have a composition of C _19.8 F. When the repetition period length I _c of the crystal in the c-axis direction was measured by X-ray diffraction, values of 16.4 Å and 19.8 Å were obtained, and the number of stages of the intercalation compound was a mixture of 4 and 5. understood.

The electrical resistance of the fluorinated graphite fiber I was measured by the same powder method as in Example 2, and the results were compared with the measurement results for the fluorinated graphite fiber C and the untreated graphite fiber Z. Indicated according to

[Effect of the Invention] The fluorinated graphite fiber of the present invention is lighter than metal and has higher conductivity than conventional carbon materials, and maintains higher stability than conventional graphite intercalation compounds. Moreover, it has good dispersibility in synthetic resins and the like, and can effectively impart conductivity even in a small amount, and is suitable for use in composite materials and the like.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hidenori Yamanashi 252 Kawashimada, Gotemba-shi, Shizuoka Prefecture Inside Yazaki Parts Co., Ltd. (56) References JP-A-58-191221 (JP, A) JP-A-62-235204 (JP) , A)

Claims (3)

(57) [Claims] 1. An intercalation compound of fluorine and graphite fiber having a three-dimensional crystal structure in which a hexagonal carbon plane of a carbon is substantially parallel to a fiber axis and oriented in an annual ring shape, wherein the crystal is repeated in the c-axis direction. A fluorinated graphite fiber characterized in that the cycle length is mixed in the range of 5 to 24 angstroms. 2. A vapor-grown carbon fiber obtained by thermally decomposing a hydrocarbon compound in a non-oxidizing atmosphere in the presence of a catalyst supported on a substrate is graphitized so that the carbon hexagonal mesh plane is oriented with respect to the fiber axis. A graphite fiber having a three-dimensional crystal structure which is substantially parallel and oriented in a ring shape is obtained, and is then brought into contact with fluorine gas having a pressure of 300 to 1500 Torr at a temperature of -10 to 120 ° C. A process for producing a fluorinated graphite fiber having the properties described in item (1). 3. A vapor-grown carbon fiber obtained by contacting an ultrafine metal catalyst suspended in a high-temperature zone with a hydrocarbon compound is graphitized so that the carbon hexagonal mesh is substantially parallel to the fiber axis. A graphite fiber having a three-dimensional crystal structure oriented in an annual ring shape is obtained, and then fluorine gas at a pressure of 300 to 1500 Torr and −1
The method for producing a fluorinated graphite fiber having the properties described in claim (1), wherein the fiber is contacted at a temperature of 0 to 120 ° C.