JP2006241600A - Method for producing carbon fiber sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a carbon fiber sheet without forming a distortion on calcinating and satisfying physical properties such as a good ventilating property, sufficient strength, etc. <P>SOLUTION: This carbon fiber sheet is produced by heat compression-treating an oxidized fiber crude sheet obtained by blending/containing the following 3 components, A, B, C, wherein, A: an oxidized fiber having 2.0-25.0 mm fiber length; B: an organic polymer having 30-70 mass% residual carbon ratio; and C: an organic polymer having 0.5-20.0 mass% residual carbon ratio, by 50-95 pts.mass blended amount of the A component, 50-5 pts.mass blended amount of the B component, and 0.3-5.0 (C)/(B) blending ratio of the C component to the B component under 100-350°C temperature and 0.30-20 MPa pressure to obtain an oxidized fiber sheet having 1.0-0.2 g/cm<SP>3</SP>bulk density, and then calcinating the same under an inert gas atmosphere, at 1,300-2,500°C temperature for carbonizing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a carbon fiber sheet by firing an oxidized fiber sheet.

  Carbon materials are excellent in heat resistance, corrosion resistance, chemical resistance, and have conductivity, and are therefore used as electrode materials and electromagnetic shielding materials. In particular, a sheet excellent in gas or liquid permeability is desired for use as an electrode material.

  When the carbon material is in the form of a sheet, workability, workability, and handleability are good. As the sheet-like carbon material, there is a carbon fiber sheet such as a carbon fiber reinforced material sheet (C / C paper).

  C / C paper is a mixture of carbon fiber and binder fiber such as polyvinyl alcohol, and the resulting carbon fiber paper is impregnated with a thermosetting resin such as a phenol resin, cured, and then subjected to a nitrogen atmosphere. It can be obtained by firing at a temperature around 2000 ° C.

  In the production process of the C / C paper, the sheet after impregnated with a thermosetting resin and hot-pressed is generally hardened, and the flexibility and / or strength is lowered. When the suppleness and / or strength is reduced, the sheet becomes difficult to be wound on a roll, so the form of the sheet must be a single sheet, and the baking becomes a batch type. As a result, the production efficiency is reduced and the manufacturing cost is very high.

  As means for solving these problems, a method of controlling the surface area ratio of carbon fibers within a specific range (for example, see Patent Document 1), a method of using an endless belt at the time of firing (for example, see Patent Document 2), a resin impregnation amount For example, a method of controlling the carbon fiber within an appropriate range (for example, see Patent Document 3), a method of combining two or more types of carbon fibers (for example, see Patent Document 4), and the like have been proposed.

  However, nothing satisfying the suppleness and / or strength reduction prevention and the production cost reduction has been obtained.

  As a method for producing a carbon fiber sheet other than the above, there is a method for producing a carbon fiber sheet using oxidized fiber as a papermaking raw material (see, for example, Patent Documents 5 and 6). Oxidized fibers have higher fiber elongation than carbon fibers and good processability during paper making. Therefore, the oxidized fiber sheet before the carbonization treatment can be easily manufactured.

However, the method for producing a carbon fiber sheet of Patent Document 5 requires a phenol resin impregnation after the paper making process, and the process is complicated. Moreover, the carbon fiber sheet manufactured by the manufacturing method of Patent Document 6 cannot obtain sufficient strength. Moreover, this carbon fiber sheet does not have sufficient air permeability.
JP 2003-183994 A (claims, paragraph numbers [0005] to [0008]) JP 2004-259711 A (paragraph numbers [0043], [0072]) JP 2002-302557 A (Claims, paragraph number [0026]) JP 2001-283878 A (Claims, paragraph numbers [0011] to [0024]) JP 2004-183164 A (claims, paragraph numbers [0031] to [0036]) JP 2004-27435 A (claims, paragraph numbers [0047] to [0053])

  The research group to which the inventor belongs has invented an oxidized fiber mixed paper (oxidized fiber sheet) having excellent fiber dispersibility and excellent flame retardancy, and a method for producing the same, and has filed an application earlier (Japanese Patent Application No. 2003-195642). ). However, some of the carbon fiber sheets obtained by firing the oxidized fiber sheet are likely to be distorted during firing. Also, the physical properties such as good air permeability and insufficient strength were not satisfactory.

  While various studies have been made by the present inventor to solve the above problems, the A component of the oxidized fiber having a predetermined fiber length, the B component of the organic polymer having a high residual carbon ratio, and the low residual carbon ratio are obtained. By firing the oxidized fiber sheet obtained by mixing and containing the C component of the organic polymer having a predetermined blending ratio, physical properties such as no distortion during firing and good air permeability and sufficient strength are obtained. It was learned that a satisfactory carbon fiber sheet can be obtained.

  Further, the sheet after firing and after firing has appropriate flexibility and / or strength, and can be easily wound up on a roll, so that firing can be continuous. As a result, the present inventor has learned that production efficiency may be improved and manufacturing costs may be reduced, and the present invention has been completed.

  Accordingly, an object of the present invention is to provide a method for producing a carbon fiber sheet that solves the above-described problems.

  The present invention for achieving the above object is described below.

[1] The following three components A, B, C
A: Oxidized fiber having a fiber length of 2.0 to 15.0 mm B: Organic polymer having a residual carbon ratio of 30 to 70% by mass C: Organic polymer having a residual carbon ratio of 0.5 to 20.0% by mass A rough oxidized fiber sheet comprising 50 to 95 parts by mass of component A, 50 to 5 parts by mass of component B, and C / B 0.3 to 5.0 in proportion of component C to component B , Under a temperature of 100 to 350 ° C. under a pressure of 0.30 to 20 MPa, an oxide fiber sheet having a bulk density of 1.0 to 0.2 g / cm ³ is obtained, and then this is treated with an inert gas atmosphere. Below, the manufacturing method of the carbon fiber sheet baked and carbonized at the temperature of 1300-2500 degreeC.

  [2] The method for producing a carbon fiber sheet according to [1], wherein the component A is an oxidized fiber having a fiber thickness of 0.8 to 3.3 dtex and a fiber length of 2.0 to 15.0 mm.

  [3] The method for producing a carbon fiber sheet according to [1], wherein the B component is an aromatic polyamide.

  [4] The method for producing a carbon fiber sheet according to [1], wherein the C component is a polyester fiber.

  The method for producing a carbon fiber sheet of the present invention comprises an A component of oxidized fibers having a predetermined fiber length, an organic polymer B component having a high carbon residue, and an organic polymer C component having a low carbon residue. A carbon fiber sheet characterized by firing an oxidized fiber sheet obtained by mixing and containing at a predetermined blending ratio, which does not cause distortion at the time of firing and has satisfactory physical properties such as good air permeability and sufficient strength. can get.

  In addition, the carbon fiber sheet obtained by the production method of the present invention has appropriate flexibility and / or strength at the time of firing, and can be easily wound up on a roll, so that continuous firing is possible. Thus, according to the carbon fiber sheet manufacturing method of the present invention, the production efficiency can be improved and the manufacturing cost can be reduced.

  The carbon fiber sheet produced in the present invention has high conductivity, heat resistance, and easy air permeability control, so it is particularly suitable for electrode materials such as fuel cells, redox flow batteries, zinc bromine batteries, zinc chlorine batteries, and salt electrolysis. Is suitable.

  Hereinafter, the manufacturing method of the carbon fiber sheet of this invention is demonstrated in detail.

[Raw material oxidized fiber sheet]
The raw material oxidized fiber sheet for producing the carbon fiber sheet of the present invention includes an A component of an oxidized fiber having a predetermined fiber length, an organic polymer B component having a high residual carbon ratio, and an organic material having a low residual carbon ratio. It is an oxidized fiber sheet formed by mixing and containing a polymer C component.

[Component A]
The component A is obtained by, for example, a flameproofing treatment in which a commercially available polyacrylonitrile (PAN) fiber is treated in air at a high temperature to cause a cyclization reaction and increase the amount of oxygen bonds to make it infusible and flame retardant. Oxidized fibers can be used.

  The PAN-based fiber is prepared by spinning, washing, drying, or drawing a spinning solution containing a homopolymer of acrylonitrile or a copolymer obtained by polymerizing a monomer containing 95% by mass or more of acrylonitrile in a wet or dry-wet spinning method. It can be obtained by performing such processing. As the monomer to be copolymerized, methyl acrylate, itaconic acid, methyl methacrylate, acrylic acid and the like are preferable.

  In addition to the PAN-based oxidized fibers, the oxidized fibers considered as the component A include pitch-based, phenol-based, rayon-based oxidized fibers, etc., but the PAN-based oxidized fibers have the highest strength oxidized fiber sheet and carbon fiber. A sheet is obtained.

  The compounding quantity of the oxidized fiber which is A component is 50-95 mass parts with respect to 100 mass parts of total compounding quantities of A component and below-mentioned B component, Preferably it is 60-85 mass parts.

  When the blending amount of the component A is less than 50 parts by mass, the carbon fiber sheet obtained by firing the oxidized fiber sheet has large voids and good air permeability. However, since the carbon fiber component is derived from the A component, when the blending amount of the A component is less than 50 parts by mass, the carbon fiber component in the carbon fiber sheet is reduced, so that the strength of the carbon fiber sheet is weakened.

  When the blending amount of the A component exceeds 95 parts by mass, the pyrolytic carbon derived from the B component is reduced accordingly. This pyrolytic carbonaceous material contributes to bonding carbon fibers in the carbon fiber sheet. From this, when the compounding quantity of A component exceeds 95 mass parts, the intensity | strength of a carbon fiber sheet does not express. Moreover, when the compounding quantity of A component exceeds 95 mass parts, since the number of carbon fibers increases correspondingly, the space | gap in a carbon fiber sheet becomes small and air permeability worsens.

  The fiber length (cut length) of the oxidized fiber which is the component A is 2.0 to 15.0 mm. When the fiber length is less than 2.0 mm, the strength of the resulting oxidized fiber sheet is lowered, which is not preferable. When the fiber length exceeds 15.0 mm, the dispersibility of the fibers in the resulting oxidized fiber sheet is lowered, which is not preferable.

  The fiber length is measured according to JIS R 3420.

  The fiber thicknesses of the A component and the C component described later are determined by measuring the fiber before cutting according to JIS L 1013.

  The specific gravity of the oxidized fiber as the component A is preferably 1.20 to 1.60.

  Although the fiber thickness of the oxidized fiber which is A component is not specifically limited, The thing of 0.8-3.3 dtex can be used.

[B component]
The B component is an organic polymer having a residual carbon ratio of 30 to 70% by mass. This organic polymer has a high residual carbon ratio compared to the C component described later, and is excellent in strength retention of the sheet because it acts as a binder component during and after carbonization.

  The residual carbon ratio can be measured by the weight reduction rate after heating to 1000 ° C. in a nitrogen atmosphere using a thermal analyzer. In this example, the flow rate of nitrogen at the time of measurement is 200 ml / min, and the heating rate is 10 ° C./min.

  As the organic polymer binder, it is possible to use organic polymers such as aromatic polyamide (aramid), phenol resin, polyimide, PAN, etc., such as powder, pellet, short fiber, and pulp.

  Among these shapes, pulp-like and fibrid-like materials are preferable in consideration of dispersibility during papermaking, thickness unevenness, distortion and strength of the carbon fiber sheet after firing. In addition, a pulp-like thing is preferable for the purpose of improving the homogeneity of the oxidized fiber sheet. Further, for the purpose of improving the strength of the oxidized fiber sheet or carbon fiber sheet, a fibrid product is preferable, and a meta-polyamide fibrid is particularly preferable.

  Fibrid is a general term for thin leaf-like, scaly pieces having fine fibrils, or short microfibers randomly fibrillated. For example, a fibrid produced by mixing an organic polymer solution in a system in which a precipitant and a shearing force are generated, as described in JP-B-35-11851, JP-B-37-5732, and the like, Five fibrillated randomly by applying mechanical shearing force such as beating to a molded article having molecular orientation formed from a polymer solution having optical anisotropy described in JP-B-59-603 A lid is exemplified.

  The pulp form is a fine fiber obtained by crushing a fibrous material to form a fibril.

  As the shape used for the B component, the one based on the former manufacturing method is particularly optimal.

  The compounding quantity of the organic polymer binder which has the said remaining carbon ratio of B component is 50-5 mass parts with respect to 100 mass parts of total compounding quantities of A component and B component, Preferably it is 40-15 mass parts.

  When the blending amount of component B exceeds 50 parts by mass, the carbon fiber sheet obtained by firing the oxidized fiber sheet as described above has a large gap and good air permeability, but the carbon fiber component in the carbon fiber sheet is Since it decreases, the strength of the carbon fiber sheet becomes weak.

  When the compounding quantity of B component is less than 5 mass parts, the intensity | strength of a carbon fiber sheet does not express as mentioned above. In addition, as the number of carbon fibers increases, the voids in the carbon fiber sheet are reduced, and air permeability is deteriorated.

  When the organic polymer having the above-mentioned residual carbon ratio of the component B is fibrous, the fiber length is preferably 0.8 to 2.0 mm. When the fiber length of the B component exceeds 2.0 mm, the B component remains in a granular state after firing, which is a cause of occurrence of thickness unevenness and distortion of the carbon fiber sheet after firing. When the fiber length of the component B is less than 0.8 mm, it is not preferable because it causes a decrease in strength and a decrease in yield in the oxidized fiber sheet after papermaking.

[C component]
Component C is an organic polymer having a residual carbon ratio of 0.5 to 20.0% by mass. As the organic polymer having a low residual carbon ratio as compared with the component B, polyester fibers, polyolefin fibers, and the like can be used. Examples of the polyester fiber include polyethylene terephthalate (PET) fiber, polybutyl terephthalate (PBT) fiber, polyarylate (PAT) fiber, and a composite fiber made of a similar copolymer. Examples of the polyolefin fibers include polypropylene (PP) fibers and composite fibers made of a copolymer similar thereto.

  These C component fibers include undrawn polyester fibers, core / sheath composite fibers composed of polyester / polyester copolymers, polypropylene fibers, and the processability during papermaking, heat treatment, and function as a binder during firing. In addition, a composite fiber having a core / sheath structure made of polypropylene / polyethylene and a similar copolymer is preferable. Although it can select suitably from these fibers and can use it as a binder at the time of baking, an unstretched polyester fiber is especially preferable.

  The compounding ratio C / B of the C component to the B component is 0.3 to 5.0, preferably 0.5 to 2.5.

  When the blending ratio C / B of the C component with respect to the B component exceeds 5.0, the action of the B component that contributes to bonding the carbon fibers to each other is reduced, so that the strength of the obtained carbon fiber sheet is preferably reduced. Absent.

  When the blending ratio C / B of the C component to the B component is less than 0.3, the action of the B component that contributes to bonding the carbon fibers becomes too strong, so a coating is formed on the resulting carbon fiber sheet. This is not preferable because it reduces air permeability and strength.

  In the case where the organic polymer having the carbon residue rate of component C is fibrous, the fiber length is preferably 2.0 to 15.0 mm.

  The thickness of the organic polymer fiber that is the component C is not particularly limited, but 0.1 to 3.3 dtex can be used.

[Paper]
The above-mentioned A component, B component, and C component are made into, for example, wet paper making into an oxidized fiber coarse sheet.

[Heat compression treatment]
The above-mentioned oxidized fiber coarse sheet is subjected to a homogenization process by a thermal compression process at a temperature of 100 to 350 ° C. and a pressure of 0.30 to 20 MPa to obtain an oxidized fiber sheet. By this thermal compression treatment, the bulk density of the oxidized fiber sheet after the homogenization treatment is controlled to 1.0 to 0.2 g / cm ³ .

  The homogenization process by the heat compression process can be performed by, for example, calendar processing or press processing.

[Carbonization treatment]
The oxidized fiber sheet is baked and carbonized at 1300 to 2500 ° C. via 500 ° C. in an inert gas atmosphere such as nitrogen to obtain a carbon fiber sheet. In the course of reaching a temperature of 1300 ° C., it is preferable to raise the temperature over a certain period of time. It is preferable to raise the temperature appropriately, linearly, stepwise, and further in a curved line.

  The carbon fiber sheet obtained by the above production method has an average pore diameter of 10 to 35 μm, an air permeability of 10,000 ml / min or more, a film-like carbide is not formed on the surface, and a bending strength of 10 MPa or more. It is.

The carbon fiber sheet is controlled to have a thickness of 50 to 400 μm, a basis weight of 20 to 180 g / m ² , and a bulk density of 0.2 to 0.6 g / cm ³ .

  The present invention is described in detail by the following examples and comparative examples.

  Carbon fiber sheets were produced under the conditions of the following examples and comparative examples. Various physical properties of the A component, the B component, the C component, and the carbon fiber sheet were measured by the above-described method or the following method.

  Specific gravity of component A: measured by Archimedes method (solvent acetone).

  Carbon fiber sheet thickness: The thickness when a load of 1.2 N was applied with a disk-shaped pressure plate having a diameter of 5 mm was measured.

  Carbon fiber sheet weight: The mass per unit area was calculated from the mass of a 100 mm square sheet dried at 120 ° C. for 1 hour.

  Carbon fiber sheet bulk density: Calculated from the thickness and basis weight measured under the above conditions.

  Air permeability of carbon fiber sheet: Measured according to ISO 2965-1997.

  Average pore diameter of carbon fiber sheet: Measured according to JIS K 3832-1990.

Bending strength of carbon fiber sheet: A load when fractured under the condition of a bending length of 1 mm according to ISO 2493-1992 was measured, and a bending stress calculation method described in JIS K 7171-1994 (σ = 3FL / bh ² , Where σ is the bending strength, F is the load at break, L is the distance between fulcrums (1 mm), b is the width of the test piece, and h is the thickness of the test piece).

  Winding property of carbon fiber sheet to paper tube: Evaluated by whether or not it can be wound on a 6 inch paper tube (outer diameter 150 mm).

Example 1
Component A (fiber thickness 1.3 dtex, specific gravity 1.35, PAN-based oxidized fiber having a fiber length of 5.0 mm), and component B (residual carbon ratio 50 mass%, fiber length 1.20 mm aramid fibrid), Component C (residual carbon ratio: 17.0% by mass, fiber thickness: 2.50 dtex, fiber length: 5.0 mm PET fiber) is mixed at the blending ratio shown in Table 1, wet papermaking, and a PAN-based oxidized fiber coarse sheet Got. The rough sheet was compressed under the conditions of a temperature of 120 ° C. and a pressure of 0.5 MPa to obtain oxidized fiber sheets shown in Table 1. The oxidized fiber sheet was baked in a nitrogen gas atmosphere at 500 ° C. for 10 minutes and at 2000 ° C. for 10 minutes to obtain carbon fiber sheets shown in Table 1. The residual carbon ratio was adjusted by the molecular weight of the fiber and the amount of the crosslinking component.

  The obtained carbon fiber sheet was a carbon fiber sheet with good physical properties as shown in Table 1.

Example 2
Except for mixing the A component, the B component, and the C component at the blending ratios shown in Table 1, wet papermaking and compression treatment were performed in the same manner as in Example 1 to obtain an oxidized fiber sheet shown in Table 1, and this was then used. The carbon fiber sheet shown in Table 1 was obtained by firing.

  The obtained carbon fiber sheet was a carbon fiber sheet with good physical properties as shown in Table 1.

Example 3
PAN-based oxidized fiber having a fiber thickness of 2.2 dtex, a specific gravity of 1.42, and a fiber length of 5.0 mm was used as the A component, and the A component, the B component, and the C component were mixed at a blending ratio shown in Table 1. In the same manner as in Example 1, wet papermaking and compression treatment were performed to obtain an oxidized fiber sheet shown in Table 1, and then this was fired to obtain a carbon fiber sheet shown in Table 1.

  The obtained carbon fiber sheet was a carbon fiber sheet with good physical properties as shown in Table 1.

Example 4
Except for using PAN-based oxidized fiber having a fiber thickness of 2.2 dtex, a specific gravity of 1.42 and a fiber length of 5.0 mm as the A component, wet papermaking and compression treatment are performed as shown in Table 1 in the same manner as in Example 2. A sheet was obtained and then fired to obtain a carbon fiber sheet shown in Table 1.

  The obtained carbon fiber sheet was a carbon fiber sheet with good physical properties as shown in Table 1.

Example 5
Oxidized fibers shown in Table 1 after wet papermaking and compression treatment as in Example 2 except that PAN-based oxidized fibers having a fiber thickness of 3.3 dtex, a specific gravity of 1.43, and a fiber length of 5.0 mm were used as the A component. A sheet was obtained and then fired to obtain a carbon fiber sheet shown in Table 1.

  The obtained carbon fiber sheet was a carbon fiber sheet with good physical properties as shown in Table 1.

比較例１
Ａ成分と、Ｂ成分と、Ｃ成分とを表２に示す配合割合で混合した以外は、実施例１と同様に湿式抄紙、圧縮処理して表２に示す酸化繊維シートを得、次いでこれを焼成して表２に示す炭素繊維シートを得た。

Comparative Example 1
Except for mixing the A component, the B component, and the C component in the mixing ratio shown in Table 2, wet papermaking and compression treatment were performed in the same manner as in Example 1 to obtain an oxidized fiber sheet shown in Table 2, and then The carbon fiber sheet shown in Table 2 was obtained by firing.

  The composition of the oxidized fiber sheet deviates from the composition of the present invention in the blending amount of the A component, the blending amount of the B component, and the blending ratio C / B of the C component with respect to the B component.

  As shown in Table 2, the obtained carbon fiber sheet was insufficient in air permeability and strength. Moreover, it was not able to wind up to a 6 inch paper tube (outer diameter 150 mm), and was not a carbon fiber sheet having good physical properties.

Comparative Example 2
Except that the A component, B component, and C component were mixed at the blending ratio shown in Table 2, wet papermaking and compression treatment were performed in the same manner as in Example 3 to obtain an oxidized fiber sheet shown in Table 2, and then The carbon fiber sheet shown in Table 2 was obtained by firing.

  The composition of the oxidized fiber sheet deviates from the composition of the present invention in the blending amount of the A component, the blending amount of the B component, and the blending ratio C / B of the C component with respect to the B component.

  As shown in Table 2, the obtained carbon fiber sheet had insufficient air permeability, and its strength was so low that it could not be measured. Moreover, it was not able to wind up to a 6 inch paper tube (outer diameter 150 mm), and was not a carbon fiber sheet having good physical properties.

Comparative Example 3
Except for mixing the A component, the B component, and the C component in the mixing ratio shown in Table 2, wet papermaking and compression treatment were performed in the same manner as in Example 4 to obtain an oxidized fiber sheet shown in Table 2, and then The carbon fiber sheet shown in Table 2 was obtained by firing.

  In the configuration of the oxidized fiber sheet, the blending ratio C / B of the C component to the B component deviates from the configuration of the present invention.

  As shown in Table 2, the obtained carbon fiber sheet was insufficient in strength. Moreover, it was not able to wind up to a 6 inch paper tube (outer diameter 150 mm), and was not a carbon fiber sheet having good physical properties.

Comparative Example 4
Except for mixing the A component, the B component, and the C component at the blending ratio shown in Table 2, wet papermaking and compression treatment were performed in the same manner as in Example 2 to obtain an oxidized fiber sheet shown in Table 2, and then The carbon fiber sheet shown in Table 2 was obtained by firing.

  The composition of the oxidized fiber sheet differs from the composition of the present invention in the amount of component A and the amount of component B.

  As shown in Table 2, the obtained carbon fiber sheet had such a low strength that it could not be measured. Moreover, it was not able to wind up to a 6 inch paper tube (outer diameter 150 mm), and was not a carbon fiber sheet having good physical properties.

実施例６
Ａ成分に繊維太さ２．２ｄｔｅｘ、比重１．４２、繊維長３．０ｍｍのＰＡＮ系酸化繊維を用いた以外は、実施例４と同様に湿式抄紙、圧縮処理して表３に示す酸化繊維シートを得、次いでこれを焼成して表３に示す炭素繊維シートを得た。

Example 6
Except for using PAN-based oxidized fiber having a fiber thickness of 2.2 dtex, a specific gravity of 1.42, and a fiber length of 3.0 mm as the A component, wet papermaking and compression treatment are performed as shown in Table 3 in the same manner as in Example 4. A sheet was obtained and then fired to obtain a carbon fiber sheet shown in Table 3.

  The obtained carbon fiber sheet was a carbon fiber sheet with good physical properties as shown in Table 3.

Example 7
Oxidized fibers shown in Table 3 after wet papermaking and compression treatment as in Example 4 except that PAN-based oxidized fibers having a fiber thickness of 2.2 dtex, a specific gravity of 1.42, and a fiber length of 14.0 mm were used as the A component. A sheet was obtained and then fired to obtain a carbon fiber sheet shown in Table 3.

  The obtained carbon fiber sheet was a carbon fiber sheet with good physical properties as shown in Table 3.

Comparative Example 5
Except for using PAN-based oxidized fibers having a fiber thickness of 2.2 dtex, a specific gravity of 1.42, and a fiber length of 1.5 mm as the A component, wet papermaking and compression treatment are performed as shown in Table 3 in the same manner as in Example 4. A sheet was obtained and then fired to obtain a carbon fiber sheet shown in Table 3.

  As shown in Table 3, the obtained carbon fiber sheet had poor air permeability and low bending strength. Moreover, it was not able to wind up to a 6 inch paper tube (outer diameter 150 mm), and was not a carbon fiber sheet having good physical properties.

Comparative Example 6
Oxidized fibers shown in Table 3 after wet papermaking and compression treatment as in Example 4 except that PAN-based oxidized fibers having a fiber thickness of 2.2 dtex, a specific gravity of 1.42, and a fiber length of 16.0 mm were used as the A component. A sheet was obtained and then fired to obtain a carbon fiber sheet shown in Table 3.

  As shown in Table 3, the obtained carbon fiber sheet was poor in fiber dispersibility, and thus produced air spots and had low bending strength. Moreover, it was not able to wind up to a 6 inch paper tube (outer diameter 150 mm), and was not a carbon fiber sheet having good physical properties.

実施例８
Ｂ成分に残炭率３５質量％、繊維長５．０ｍｍのＰＡＮ系繊維を用いた以外は、実施例４と同様に湿式抄紙、圧縮処理して表４に示す酸化繊維シートを得、次いでこれを焼成して表４に示す炭素繊維シートを得た。

Example 8
Except for using a PAN-based fiber having a residual carbon ratio of 35 mass% and a fiber length of 5.0 mm as the B component, wet papermaking and compression treatment were performed in the same manner as in Example 4 to obtain an oxidized fiber sheet shown in Table 4, and then Were fired to obtain a carbon fiber sheet shown in Table 4.

  The obtained carbon fiber sheet was a carbon fiber sheet having good physical properties as shown in Table 4.

Example 9
Except for using a phenol novolac fiber having a residual carbon ratio of 65 mass% and a fiber length of 5.0 mm as the B component, wet papermaking and compression treatment were performed in the same manner as in Example 4 to obtain an oxidized fiber sheet shown in Table 4, and then Were fired to obtain a carbon fiber sheet shown in Table 3.

  The obtained carbon fiber sheet was a carbon fiber sheet having good physical properties as shown in Table 4.

Comparative Example 7
Except for using a phenol novolac fiber having a residual carbon ratio of 25% by mass and a fiber length of 5.0 mm as the B component, wet papermaking and compression treatment were performed in the same manner as in Example 4 to obtain an oxidized fiber sheet shown in Table 4, and then Were fired to obtain a carbon fiber sheet shown in Table 4.

  As shown in Table 4, the obtained carbon fiber sheet had poor air permeability and low bending strength. Moreover, it was not able to wind up to a 6 inch paper tube (outer diameter 150 mm), and was not a carbon fiber sheet having good physical properties.

Comparative Example 8
Except for using a phenol novolac fiber having a residual carbon ratio of 75 mass% and a fiber length of 5.0 mm as the B component, wet papermaking and compression treatment were performed in the same manner as in Example 4 to obtain an oxidized fiber sheet shown in Table 4, and then Were fired to obtain a carbon fiber sheet shown in Table 4.

  The obtained carbon fiber sheet had a low bending strength as shown in Table 4. Moreover, it was not able to wind up to a 6 inch paper tube (outer diameter 150 mm), and was not a carbon fiber sheet having good physical properties.

実施例１０
Ｃ成分に残炭率７．０質量％、繊維太さ２．１１ｄｔｅｘ、繊維長５．０ｍｍのポリビニルアルコール系繊維を用いた以外は、実施例４と同様に湿式抄紙、圧縮処理して表５に示す酸化繊維シートを得、次いでこれを焼成して表５に示す炭素繊維シートを得た。

Example 10
Table 5 shows wet papermaking and compression treatment in the same manner as in Example 4 except that polyvinyl alcohol fibers having a residual carbon ratio of 7.0% by mass, a fiber thickness of 2.11 dtex, and a fiber length of 5.0 mm were used as the C component. The carbon fiber sheet shown in Table 5 was obtained by baking this and then firing this.

  The obtained carbon fiber sheet was a carbon fiber sheet with good physical properties as shown in Table 5.

Comparative Example 9
Table 5 shows wet papermaking and compression treatment in the same manner as in Example 4 except that polyethylene fiber having a residual carbon ratio of 0.3 mass%, a fiber thickness of 2.15 dtex, and a fiber length of 5.0 mm was used as the C component. An oxidized fiber sheet was obtained and then fired to obtain a carbon fiber sheet shown in Table 5.

  As shown in Table 5, the obtained carbon fiber sheet had high air permeability and an increased average pore diameter, but was brittle and generated a lot of carbon powder with low bending strength. Moreover, it was not able to wind up to a 6 inch paper tube (outer diameter 150 mm), and was not a carbon fiber sheet having good physical properties.

Comparative Example 10
Table 5 shows wet papermaking and compression treatment in the same manner as in Example 4 except that a phenol novolac fiber having a residual carbon ratio of 25.0 mass%, a fiber thickness of 2.00 dtex, and a fiber length of 5.0 mm was used as the C component. The obtained oxidized fiber sheet was obtained and then fired to obtain the carbon fiber sheet shown in Table 5.

  As shown in Table 5, the obtained carbon fiber sheet had low air permeability, low bending strength, and was unmeasurable. Moreover, it was not able to wind up to a 6 inch paper tube (outer diameter 150 mm), and was not a carbon fiber sheet having good physical properties.

Claims (4)

The following three components A, B, C
A: Oxidized fiber having a fiber length of 2.0 to 15.0 mm B: Organic polymer having a residual carbon ratio of 30 to 70% by mass C: Organic polymer having a residual carbon ratio of 0.5 to 20.0% by mass A rough oxidized fiber sheet comprising 50 to 95 parts by mass of component A, 50 to 5 parts by mass of component B, and C / B 0.3 to 5.0 in proportion of component C to component B , Under a temperature of 100 to 350 ° C. under a pressure of 0.30 to 20 MPa, an oxide fiber sheet having a bulk density of 1.0 to 0.2 g / cm ³ is obtained, and then this is treated with an inert gas atmosphere. Below, the manufacturing method of the carbon fiber sheet baked and carbonized at the temperature of 1300-2500 degreeC. The method for producing a carbon fiber sheet according to claim 1, wherein the component A is an oxidized fiber having a fiber thickness of 0.8 to 3.3 dtex and a fiber length of 2.0 to 15.0 mm. The method for producing a carbon fiber sheet according to claim 1, wherein the component B is an aromatic polyamide. The method for producing a carbon fiber sheet according to claim 1, wherein the component C is a polyester fiber.