JP3535972B2 - Highly conductive carbon fiber and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a highly conductive carbon fiber and a method for producing the same. More specifically, the present invention relates to a resin-bonded carbon fiber reinforced plastic (CF).
The present invention relates to a highly conductive carbon fiber obtained from RP) having a desired fiber length distribution useful as a reinforcing material for a molding material, a filler, and the like, and a method for producing the same.

[0002]

2. Description of the Related Art CFRP is used for aviation, space applications, sports equipment such as baseball bats, golf shafts, and tennis rackets because it has excellent specific strength and elastic modulus. Further, carbon fiber has not only mechanical properties but also functions such as conductivity and heat resistance, and it has come to be widely used for general industrial applications by utilizing these functions. When carbon fiber is used for a structure, the shape also varies depending on the required characteristics. That is, when high strength and high rigidity are required, a material impregnated with a resin called a prepreg in which fibers are arranged in parallel in one direction, or a material obtained by applying fibers in a plain weave or satin weave is used. Further, regarding application to conventional mechanical parts, resin is filled with fibers of various fiber lengths to impart weight reduction, conductivity, and the like.

[0003]

Generally, carbon fibers are obtained by firing polyacrylonitrile fibers at a high temperature of 1000 ° C. to 3000 ° C. and producing them as continuous fibers. However, in order to cut a continuous carbon fiber, it is usual to subject the fiber to a surface treatment with a sizing agent to form a fiber, but it is generally difficult to make a fiber length of 3 mm or less, and moreover, when cutting the fiber. When used as a filler due to the remaining surface treatment agent such as the sizing agent, these surface treatment agents act as a binder, and a sufficient dispersion state cannot be obtained unless these are removed. On the other hand, milled fibers that are crushed without surface treatment have high production costs and also have the problem that the fibers agglomerate into a cotton shape and the dispersibility becomes extremely poor when used as a filler. Furthermore, with the milled fiber, fine ones of 1 mm or less can be obtained, but the fiber lengths are not uniform. The so-called whiskers generally have a fiber diameter of less than 100 μm.

Therefore, especially in the industry, 100 μ
It was difficult to obtain a fiber having an arbitrary fiber length in the range of m to 3 mm and according to the required performance. In addition, although a considerable amount of energy is consumed in the production of carbon fiber because an expensive raw material is fired at a high temperature, the continuous continuous carbon fiber obtained can be cut and used depending on the intended use. ,
The high-strength and high-rigidity characteristics of carbon fiber are lost, and a large energy loss occurs. On the other hand, when the carbon fiber and CFRP obtained by spending such a large amount of energy are discarded, the carbon fiber is non-combustible and does not corrode, and therefore, at present, there is no choice but to rely on landfill treatment, which causes environmental problems.

[0005] In order to solve the above problems, studies have been made on the use of CFRP waste materials. For example, JP-A-4-3230
No. 09 has CFRP above the decomposition point of the matrix resin,
By treating at a temperature equal to or lower than the decomposition point of the carbon fiber, a carbon fiber mass integrated (bound) with the decomposition product of the matrix resin is obtained. Although this carbon fiber lump can be decomposed into single fibers by cutting or the like, it cannot be cut into pieces having an arbitrary fiber length in the range of 100 μm to 3 mm and according to the required performance.

Crushed CF is disclosed in JP-A-6-99160.
RP at 300 to 600 at an oxygen concentration of 3 to 18% by volume
A method is disclosed in which carbon fibers are recovered by pyrolyzing the plastic of the matrix by treating without burning at 0 ° C. However, the purpose of crushing is to make good contact with the atmospheric gas, and the crushing degree is 3 to 50 cm.
Carbon fibers having an arbitrary fiber length distribution in the range of 00 μm to 3 mm and according to the required performance are not recovered. Further, in this method, the oxygen concentration decreases as the reaction progresses, so it is said that oxygen is constantly introduced to control the oxygen concentration.

Japanese Patent Laid-Open No. 7-33904 discloses a method in which CFRP is dry-distilled to convert a plastic into a carbide, which is then heated at 300 to 1000 ° C. at an oxygen concentration of 0.1 to 25% by volume without being burned to oxidize and decompose the carbide. To obtain carbon fiber. Even in this method, it is good to crush the CFRP beforehand, but this is to prevent the carbon fiber in the CFRP from being damaged by the oxidation reaction, and the crushing degree is 3 to 10 cm.
However, carbon fibers having an arbitrary fiber length distribution in the above range of 100 μm to 3 mm and according to required performance are not recovered. Further, even in this method, the oxygen concentration is lowered as the reaction progresses, so it is said that oxygen is constantly introduced to control the oxygen concentration.

Japanese Unexamined Patent Publication (Kokai) No. 7-118440 discloses a method in which CFRP is crushed into scales and then 300 times in a substantially non-oxidizing atmosphere.
The carbon fiber mass integrally bonded by the thermal decomposition product of the matrix resin obtained by dry distillation at ˜1000 ° C. will be described. Again, crushing is because the efficiency of carbonization is high.
It is about 0 mm. Although this carbon fiber lump can also be decomposed into single fibers by cutting or the like, it cannot be cut into pieces having an arbitrary fiber length in the range of 100 μm to 3 mm and according to the required performance.

The object of the present invention is to provide a highly conductive carbon fiber having a desired fiber length in accordance with the required performance, that is, a highly conductive carbon fiber having a desired fiber length over a wide range, and moreover, it occurs during the production of CFRP as a raw material. An object of the present invention is to provide a highly conductive carbon fiber which can use waste materials and waste CFRP products and is excellent in environmental protection, and a method for producing the same.

[0010]

The present invention is a resin-bonded structure.
Crushed carbon fiber into fibers in the range of 100 μm to 3 mm
After that, classify and adjust the fiber length, and 1 or 2 or more of each classified product
The upper part is in the range of 300-600 ℃ under the decomposition gas filled with crushed material.
Containing resin carbide obtained by heating in a room
Highly conductive carbon fiber having a fiber length of 400 to 1
The present invention relates to a highly conductive carbon fiber containing graphite and a resin carbide obtained by heating in an inert gas atmosphere at 000 ° C. and having a desired fiber length.

The present invention also provides a resin-bonded carbon fiber.
After pulverizing into fibers in the range of 100 μm to 3 mm, classify and
Align the length and crush one or more of each classified product
Obtained by heating in the range of 300-600 ℃ under the decomposition gas
Contains the carbide of the resin and has the desired fiber length
That the highly conductive carbon fibers, further in an inert gas atmosphere at 400 to 1000 ° C., wherein the carbide graphite and resin, characterized by heating, and the production of highly conductive carbon fibers having a desired fiber length According to the method. According to the invention, 100
It is possible to obtain a highly conductive carbon fiber having a desired fiber length distribution in which the fiber length is adjusted within the range of μm to 3 mm and within which the required performance is satisfied.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, for example, resin-bonded carbon fibers are used as a raw material. Examples of the binder resin include epoxy resin, unsaturated polyester resin,
Examples thereof include thermosetting resins such as phenol resins, and thermoplastic resins such as nylon resins, polyester resins, polycarbonate resins and acrylic resins. In addition to this, the raw material may contain a catalyst, a filler, a metal powder, and the like. To give an example, the waste material of CFRP containing a pipe-shaped or flat-plate epoxy resin as a matrix should be crushed using a rigid crusher, coarsely crushed, and then re-crushed to pass a screen diameter of 1 to 5 mm. To obtain a pulverized product.

In the present invention, when the above crushed material is decomposed by heating, the fiber length is adjusted to some extent by changing the screen mesh. Further, this pulverized product is sorted into a desired length by a classifier such as a sieving machine to make the fiber length uniform. In the present invention, the fiber length of the pulverized product is 100 μm to
Within the range of 3 mm, in particular, since classification is carried out in advance before thermal decomposition, those having a fluctuation range of ± 50% of the average fiber length can be obtained. Of course, by increasing the classification accuracy, particles with even more granularity can be obtained, but the classification operation becomes complicated,
The above fiber length distribution can sufficiently withstand practical use.

Here, the average fiber length is a weight average fiber length (lw) and is calculated by the following formula. lw = ΣWi · li / Wi lw = Σα · Ni · li ² / Σα · Ni · li lw = ΣNi · li ² / ΣNi · li α is πr ² ρ (2r = fiber diameter, ρ = density) and Ni is length
The number of fibers in li.

As a raw material for producing the carbon fiber of the present invention, for example, recycled products of CFRP, waste materials produced during the production of CFRP, etc. can be used, and they are excellent in environmental protection. In the present invention, as described above, by crushing the recycled product of CFRP and the waste material generated at the time of CFRP production, a desired fiber length within a range of 100 μm to 3 mm and a desired performance in accordance with the required performance can be obtained. A pulverized product having a fiber length distribution can be obtained. In the present invention, by classifying the pulverized product in advance, it is possible to easily obtain a product having a regular fiber length, and the generally-known number average fiber length lm / lw is 1.05 to 1.50, which is close to 1 and has monodispersity. It is an excellent thing to have.

On the other hand, in the past, continuous carbon fibers have been surface-treated with a sizing agent to form fibers, but it is generally difficult to obtain a fiber length of 3 mm or less, skill is required, and fiber length control is required. Was difficult. In addition, milled fibers that are crushed without surface treatment are expensive to manufacture, and the fibers are aggregated in a cotton shape, and fine fibers of 1 mm or less can be obtained, but the fiber lengths are not uniform. The so-called whiskers generally have a fiber diameter of less than 100 μm.

As described above, conventionally, it has been extremely difficult to obtain a fiber having an arbitrary fiber length in the range of 100 μm to 3 mm and having a required performance. The present invention, as described above, uses C
This problem is solved all at once by crushing and classifying the recycled material of FRP and the waste material generated during the production of CFRP. In the present invention, each of the classified products in which the fiber length is adjusted by crushing and classifying is individually heated and decomposed at 350 to 500 ° C. under the filled decomposition gas of the crushed product to have a desired fiber length distribution. A carbon fiber can be obtained. Further, it is possible to produce fibers having a fiber length / fiber diameter (aspect ratio) as required. For milling, for example, a cutter mill (hard type) mill, a rotary mill mill, a hammer mill mill, or the like can be used. Examples of the decomposition gas include CO, methane, benzene, toluene, and derivatives thereof.

The heating of the crushed product under the decomposition gas is, for example, a method of heating the crushed product in a closed state, a method of filling the crushed product in a container at a high filling rate and heating. Examples of the container include a crucible, and a high filling rate is, for example, 50 to 100%, preferably 80 to 9%.
A filling rate of about 9% can be mentioned. In the present invention,
Since the crushed material is heated and decomposed while being filled with the decomposed gas, it is not necessary to prepare oxygen gas, air, nitrogen gas, or the like, and no complicated operation of constantly controlling the oxygen gas concentration is necessary.

In the present invention, since the resin is carbonized under the filling of the decomposed gas of the pulverized material, the decomposition of the fiber is suppressed, and the fiber containing the carbide is obtained. The thermal decomposition is 300 to 60
It is preferably carried out in the range of 0 ° C. The thermal decomposition time depends on the temperature, but is usually 30 minutes to 8 hours, preferably 2 to
It takes about 5 hours. By this operation, a highly conductive carbon fiber containing a resin carbide and having a desired fiber length can be obtained. The amount of the carbide of the resin can be appropriately selected depending on the intended conductivity, but it is preferably about 0.01 to 25% by weight.

Further, by heating the fiber containing the resin carbide in an inert gas atmosphere at 400 to 1000 ° C., the resin carbide and / or the carbon fiber is graphitized, and further excellent high conductivity is obtained. It is possible to obtain a carbon fiber containing graphite powder and resin carbide. 400-1000
Efficient treatment is possible by heating in the range of ° C. The heat treatment time depends on the temperature, but is usually 10 minutes to 2 minutes.
The time is preferably about 30 minutes to 1 hour. The amount of graphite can be appropriately selected depending on the desired conductivity, but it is 0.05
It is preferably about 20% by weight.

The carbon fiber obtained in the present invention has a size of 100 μm
Since it has a desired fiber length distribution within the range of 3 mm and in which any fiber length is arranged according to the required performance, it can be used for various purposes as it is. The carbon fiber obtained in the present invention can be used as, for example, a filler, a reinforcing material, a conductive agent, or the like. When mixing with other materials such as filler,
Epoxy resin-based sizing treatment, chemical vapor deposition (CVD), electroplating, to improve adhesion with materials
Surface treatment such as silane coupling treatment or oxidation treatment may be performed.

[0022]

EXAMPLES The present invention will be further described below with reference to Examples and Comparative Examples.
Will be explained in detail. Example 1(However, it corresponds to the reference example) FRP golf ball using epoxy resin as matrix
The shaft diameter is roughly crushed by a hard crusher and the screen diameter is
After passing 12 mm, re-grind it and screen diameter 1 mm
Carbon fiber with epoxy resin attached by passing through
We have been obtained. This pulverized product is 250-3000 μm
The fiber length is adjusted by classifying with a sieving machine of different sizes
Each classified product of carbon fiber was obtained. Next, for each of these classified products
Fill the crucible at a filling rate of 80% by volume, and use an electric furnace to
It is heated and decomposed at 0 ° C for 3 hours under a gas filled with decomposition gas.
Have a desired fiber length distribution within the range of 250 μm to 3 mm
I got a fiber. Initially the resin content was 33 wt% due to thermal decomposition
What was there was 6 wt% (resin carbide). Fu
Average fiber length and size of commercially available milled fiber according to size
A long distribution is shown.

[0023]

[Table 1]

From the above results, the fibers regenerated from the FRP waste material according to the present invention are pulverized and classified in a state where the epoxy resin is adhered, so that the fiber length distribution has less variation as compared with the commercially available milled fibers, and It is possible to easily obtain a carbon fiber having a desired length. The pulverized product to which the epoxy resin was attached was heated and decomposed in a crucible at a filling rate of 90% by volume under a condition of 400 ° C. for 2 hours under a decomposition gas filled condition to obtain a carbon fiber containing a resin carbide. The initial amount of the resin by heat decomposition was 33% by weight, but it became 8% by weight (resin carbide).

Example 2 Further, the carbon fiber containing the resin carbide obtained in Example 1 was heated to 700 L while feeding nitrogen gas at 2 L / min.
Graphitization was performed under conditions of 30 ° C. and 30 minutes. The amount of resin carbide was 4 wt% due to the graphitization treatment. The amount of graphite was 2 wt%. Further, no fiber length change was observed even after this graphitization treatment, which was within ± 50% of the average fiber length. Carbon fiber containing graphite and resin carbide obtained by this treatment was added to nylon 66 resin at 10 wt% and 20 wt%.
% And 30 wt%, and pellets were prepared by kneading and extruding. Then, this pellet is injection molded and the thickness is 2m.
The sample was molded into a plate shape of m, length, width, and 150 mm, and the volume resistivity of this sample was measured by the ASTM D-257 method. For comparison, the volume resistivity was measured in the same manner (Comparative Example 1) except that a commercially available milled fiber was used instead of the carbon fiber containing the above graphite and resin carbide.

[0026]

[Table 2]

From the above results, it is understood that the carbon fiber and / or the resin carbide is graphitized by the treatment in the inert gas atmosphere, and not only the fiber is contacted to give the conductivity, but also the graphite and the carbide are present. The conductivity was 10 ² to 10 ³ times higher.

[0028]

INDUSTRIAL APPLICABILITY In the present invention, a waste material produced during CFRP production or a waste CFRP product can be used as a raw material, and a method for producing a highly conductive carbon fiber excellent in environmental protection can be provided. The carbon fiber obtained by the present invention is 100 μm
It has a desired fiber length distribution within the range of up to 3 mm and an arbitrary fiber length according to the required performance, and is obtained by contacting carbon fibers by heat treatment under the decomposition gas filling of the crushed material. In addition to the electroconductivity obtained, the resin carbide dispersed in the carbon fiber also has electroconductivity, so that it can be used for various purposes. Further, by subjecting the fiber containing the resin carbide to a heat treatment at 400 to 1000 ° C. in an atmosphere of an inert gas, the resin carbide and / or the carbon fiber is graphitized, and graphite having further higher conductivity is obtained. A carbon fiber containing powder and resin carbide is obtained.

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-7-118440 (JP, A) JP-A-5-309753 (JP, A) JP-A-11-50338 (JP, A) JP-A-4- 323009 (JP, A) JP 6-99160 (JP, A) JP 7-33904 (JP, A) JP 11-290822 (JP, A) JP 6-298993 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29B 17/00-17/02 C08J 11/00-11/28 D01F 9/08-9/32

Claims (2)

(57) [Claims] 1. A resin-bonded carbon fiber having a thickness of 100 μm.
After pulverizing to a fiber shape within the range of ~ 3 mm, classify to adjust the fiber length.
E, 1 or 2 or more of each classified product is decomposed gas of crushed material
Obtained by heating in the range of 300 to 600 ° C. under filling,
A high-conductivity carbon fiber containing a resin carbide and having a desired fiber length is further heated in an inert gas atmosphere at 400 to 1000 ° C. to obtain graphite and a resin carbide, and the desired fiber Highly conductive carbon fiber with long length. 2. A resin-bonded carbon fiber having a thickness of 100 μm.
After pulverizing to a fiber shape within the range of ~ 3 mm, classify to adjust the fiber length.
E, 1 or 2 or more of each classified product is decomposed gas of crushed material
Obtained by heating in the range of 300 to 600 ° C. under filling,
A highly conductive carbon fiber containing a resin carbide and having a desired fiber length is further heated in an inert gas atmosphere at 400 to 1000 ° C., containing graphite and a resin carbide, and A method for producing a highly conductive carbon fiber having a fiber length of 1.