CARBON FIBER NON-WOVEN CLOTH, METHOD OF PRODUCING CARBON FIBER NON-WOVEN CLOTH, CARBON FIBER MULTI-LAYER CLOTH AND COMPOSITE MATERIAL

Abstract

A carbon fiber non-woven cloth that satisfies at least one of the following (1) to (3): (1) includes a carbon fiber that does not substantially include an organic material, (2) includes a carbon fiber that does not form a strand, or (3) includes a carbon fiber that is a retrieved product from a composite material including the carbon fiber and an organic substance.

Claims

1. A carbon fiber non-woven cloth that satisfies at least one of the following (1) to (3): (1) includes a carbon fiber that does not substantially include an organic material, (2) includes a carbon fiber that does not form a strand, or (3) includes a carbon fiber that is a retrieved product from a composite material including the carbon fiber and an organic substance.

2. The carbon fiber non-woven cloth according to claim 1, wherein a length of the carbon fiber is from 20 mm to 150 mm.

3. The carbon fiber non-woven cloth according to claim 1, further comprising a resin fiber.

4. A method of producing the carbon fiber non-woven cloth according to claim 1, the method comprising, in the following order: a contact process of contacting a processing solution with a composite material, the composite material including a carbon fiber and an organic substance that decomposes in the processing solution; a separation process of separating the processing solution, which includes a decomposition product of the organic substance, from the carbon fiber; and a non-woven cloth producing process of producing a carbon fiber non-woven cloth using the carbon fiber that is obtained through the contact process and the separation process.

5. The method of producing a carbon fiber non-woven cloth according to claim 4, wherein the organic substance comprises a resin including an ester bond.

6. The method of producing a carbon fiber non-woven cloth according to claim 4, wherein the processing solution comprises an organic solvent and a decomposition catalyst.

7. A carbon fiber multi-layer cloth, comprising the carbon fiber non-woven cloth according to claim 1 and a sheet in which carbon fibers are oriented in at least one direction.

8. A composite material, comprising the carbon fiber non-woven cloth according to claim 1, and a resin.

9. A composite material, comprising the carbon fiber multi-layer cloth according to claim 7, and a resin.

Description

EXAMPLES

[0113] In the following, the embodiments are described in further detail by referring to the Examples. However, the embodiments are not limited to the Examples.

Example 1

[0114] A carbon fiber was separated from a composite material under the following conditions.

[0115] As the composite material, a prepreg material including an epoxy resin having an ester bond and a carbon fiber cloth material (thickness: 0.4 mm, resin content: 45% by mass) was used. As the processing solution, a mixture of benzyl alcohol and sodium hydroxide (content of sodium hydroxide: 0.5 mol/L) was used.

[0116] (Contact Process)

[0117] The composite material was cut into square pieces (4 cm4 cm) along the direction of the carbon fiber, and contacted with the processing solution in a container. The container had a tube for the processing solution to flow in and a tube for the processing solution to flow out, and the latter is positioned below the former in a gravitational direction such that the processing solution flows from the bottom to the top in a gravitational direction. The temperature of the processing solution was set at 60 C. for 2 hours at the beginning of the immersion, and subsequently at 190 C. for 5 hours.

[0118] (Separation Process)

[0119] At 7 hours after the beginning of the immersion, the processing solution was drained from the container to separate from the carbon fibers. The temperature of the processing solution at the separation process was set at 60 C. The processing solution after the separation process included a decomposition product of the epoxy resin.

[0120] The observation found that the carbon fibers after the separation included carbon fibers in a state of an independent filament without forming a strand. The content of the organic substance with respect to the total mass of the carbon fibers and the organic substance, calculated by the method as described above using a muffle furnace (Yamato Scientific Co., Ltd., FP311), was 1.3% by mass, indicating that the carbon fiber does not substantially has an organic substance.

[0121] (Preparation of Carbon Fiber Non-Woven Cloth)

[0122] A carbon fiber non-woven cloth was obtained by opening 5.7 kg of the carbon fiber and 4.3 kg of polypropylene fibers as a resin fiber (JNC Corporation, RP-270, fineness: 6.6 Dt, average filament length: 51 mm) with a carding machine. The basis weight of the carbon fiber non-woven cloth was 200 g/m.sup.2. The carbon fiber non-woven cloth had a sufficient flexibility that is applicable for the formation of a three-dimensional object.

[0123] (Preparation of Composite Material)

[0124] A laminate having a basis weight of 2500 g/m.sup.2 was prepared by stacking plural layers of the carbon fiber non-woven cloth. The laminate was subjected to hot pressing by sandwiching with a small hot pressing machine (AS ONE Corporation) with a spacer of 2.7 mm and pressing at 43 kg/cm.sup.2 at 200 C., thereby preparing a composite material.

[0125] (Evaluation of Strength)

[0126] The composite material was cut with a rotating cutter (Makita Corporation) attached with a rotating blade (Tanitec Corporation) to obtain 10 test pieces of 2.5 cm in width and 8 cm in length. The bending strength and the bending elastic modulus of the test pieces were measured by a three-point bending method according to JIS K 7171. The measurement was performed with a universal tester (Shimadzu Corporation, AUTOGRAPH AG-X 1kN). The average of the measured values obtained from the test pieces was 232 MPa (bending strength) and 13 GPa (bending elastic modulus).

Comparative Example 1

[0127] A carbon fiber non-woven cloth and a composite material were prepared in the same manner as Example 1, except that the same amount of carbon fibers with an organic substance (sizing agent) attached to the surface was used as the carbon fibers, and the measurement was performed. The average of the measured values obtained from the test pieces was 190 MPa (bending strength) and 9 GPa (bending elastic modulus).

[0128] The results show that a composite material with excellent formability and strength can be prepared by the embodiment.