Carbon fiber sheet and method for producing the same

• US 20030027471A1
• Filed: 07/24/2002
• Published: 02/06/2003
• Est. Priority Date: 11/24/2000
• Status: Active Grant

• Current Assignee: Toho Tenax Co., Ltd. (Teijin Limited)
• Original Assignee: Toho Tenax Co., Ltd. (Teijin Limited)
• Inventors: Tanaka, Shintaro, Shimazaki, Kenji
• Granted Patent: US 6,812,171 B2
• Time in Patent Office: Days
• US Class Current: 442/59
• CPC Class Codes: D01F 9/22 from polyacrylonitriles
• CPC Class Codes: D03D 15/46 Flat yarns, e.g. tapes or films
• CPC Class Codes: D10B 2101/12 Carbon; Pitch
• CPC Class Codes: D10B 2321/10 polymers of unsaturated nitriles, e.g. polyacrylonitrile, polyvinylidene cyanide
• CPC Class Codes: D10B 2401/16 antistatic; conductive
• CPC Class Codes: Y10T 428/24 Structurally defined web or sheet [e.g., overall dimension, etc.]
• CPC Class Codes: Y10T 428/30 Self-sustaining carbon mass or layer with impregnant or other layer
• CPC Class Codes: Y10T 442/134 Including a carbon or carbonized fiber
• CPC Class Codes: Y10T 442/20 Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
• CPC Class Codes: Y10T 442/2352 Coating or impregnation functions to soften the feel of or improve the "hand" of the fabric
• CPC Class Codes: Y10T 442/2361 Coating or impregnation improves stiffness of the fabric other than specified as a size
• CPC Class Codes: Y10T 442/2984 Coated or impregnated carbon or carbonaceous fiber fabric
• CPC Class Codes: Y10T 442/611 Cross-sectional configuration of strand or fiber material is other than circular
• CPC Class Codes: Y10T 442/642 Strand or fiber material is a blend of polymeric material and a filler material
• CPC Class Codes: Y10T 442/645 Parallel strand or fiber material is inorganic [e.g., rock wool, mineral wool, etc.]

Abstract

The present invention discloses a process for producing a carbon fiber sheet, which comprises allowing, as necessary, an oxidized polyacrylonitrile fiber sheet to contain 0.2 to 5% by mass of a resin, then subjecting the resin-containing oxidized polyacrylonitrile fiber sheet to a compression treatment in the thickness direction under the conditions of 150 to 300° C. and 5 to 100 MPa (10 to 100 MPa when no resin treatment is made) to obtain a compressed, oxidized fiber sheet having a bulk density of 0.40 to 0.80 g/cm³ and a compression ratio of 40 to 75%, and thereafter subjecting the compressed, oxidized fiber sheet to a carbonizing treatment. The carbon fiber sheet has a thickness of 0.15 to 1.0 mm, a bulk density of 0.15 to 0.45 g/cm³, a carbon fiber content of 95% by mass or more, a compression deformation ratio of 10 to 35%, an electric resistance of 6 mΩ or less and a feeling of 5 to 70 g.

Having a small electric resistance in the thickness direction, the carbon fiber sheet is suitable as an earth material and a conductive material such as battery electrode material or the like.

Claims

1. A carbon fiber sheet having a thickness of 0.15 to 1.0 mm, a bulk density of 0.15 to 0.45 g/cm³, a carbon fiber content of 95% by mass or more, a compression deformation ratio of 10 to 35%, an electric resistance of 6 mΩ

or less and a feeling of 5 to 70 g.

5. A process for producing a carbon fiber sheet set forth in claim 1, by subjecting an oxidized polyacrylonitrile fiber sheet to a carbonizing treatment, which process comprises subjecting an oxidized polyacrylonitrile fiber sheet to a compression treatment in the thickness direction under the conditions of 150 to 300°

C. and 10 to 100 MPa to obtain a compressed, oxidized fiber sheet having a bulk density of 0.40 to 0.80 g/cm³ and a compression ratio of 40 to 75%, and then subjecting the compressed, oxidized fiber sheet to a carbonizing treatment.

6. A process for producing a carbon fiber sheet set forth in claim 1, by subjecting an oxidized polyacrylonitrile fiber sheet to a carbonizing treatment, which process comprises allowing an oxidized polyacrylonitrile fiber sheet to contain 0.2 to 5% by mass of a resin, then subjecting the resin-containing oxidized polyacrylonitrile fiber sheet to a compression treatment in the thickness direction under the conditions of 150 to 300°

C. and 5 to 100 MPa to obtain a compressed, oxidized fiber sheet having a bulk density of 0.40 to 0.80 g/cm³ and a compression ratio of 40 to 75%, and thereafter subjecting the compressed, oxidized fiber sheet to a carbonizing treatment.

2. A carbon fiber sheet wherein the section of single fiber at each intersection between fibers has an oblate shape and the major axis of the section is nearly parallel to the surface of the carbon fiber sheet.

3. A carbon fiber sheet according to claim 2, wherein at each intersection between fibers, the oblateness (L2/L1) of single fiber represented by the maximum diameter (L1) of the section of single fiber and the minimum diameter (L2) of the section of single fiber is 0.2 to 0.7.

4. A carbon fiber sheet according to claim 2, wherein the portion other than the intersections between fibers in single fiber contains at least a part in which the oblateness (L2/L1) is more than 0.7.