JP2016164313A - Method for producing carbon fiber woven fabric and carbon fiber woven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carbon fiber woven fabric that has excellent mechanical characteristics (strength, flexibility) and a high carbonization yield, and to provide a carbon fiber woven fabric produced by the producing method.SOLUTION: There is provided a method for producing a carbon fiber woven fabric including the steps of: (a) preparing a woven fabric that comprises a cellulosic fiber; (b) impregnating the woven fabric with an organic sulfonic acid; (c) subjecting the woven fabric impregnated with the organic sulfonic acid to heat treatment in the temperature range of 500°C to 2600°C in an inert gas atmosphere; and (d) subjecting the woven fabric that is impregnated with the organic sulfonic acid and is subjected to the heat treatment to re-heating treatment in the temperature range of 2200°C to 3200°C in an inert gas atmosphere.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a carbon fiber fabric in which a fabric composed of cellulosic fibers is carbonized using an organic sulfonic acid catalyst.

  Since carbon fibers are excellent in specific strength and specific elastic modulus, they are being widely used from sports and leisure goods to aerospace applications. When carbon fiber is used as such a structural material, there is a method in which a prepreg obtained by impregnating a thermosetting resin into a woven fabric obtained by weaving a carbon fiber tow is used as a carbon fiber reinforced plastic obtained by molding and curing. It is common.

  Currently, in this field, fabrics woven from polyacrylonitrile (PAN) carbon fiber and pitch-based carbon fiber tows are generally used, but the carbon fiber as the material is very expensive. The cost is high, which is an obstacle to widespread use.

  Therefore, carbon materials using cheap cellulosic substances, which are the largest biomass on the earth, have been attracting attention. Originally, the UCC company of the United States produced using rayon carbon fiber as a carbon fiber made from cellulosic material. Patent Documents 1 and 2 disclose a method for carbonizing cellulose fibers. However, the carbonization yield decreases due to the thermal decomposition of cellulose, and mechanical properties (strength, flexibility) are compared with PAN-based carbon fibers. ) Did not appear.

  For these problems, a cellulose-based fiber fabric is impregnated with a silicone-based polymer solution and a mineral-based additive solution to suppress the thermal decomposition of cellulose (Patent Document 3). A carbonization method (Patent Document 4) has been proposed in which an organic sulfonic acid is impregnated and the carbonization yield is improved using the yield as a catalyst.

U.S. Pat. No. 3,053,775 U.S. Pat. No. 3,107,152 Japanese Patent No. 5271887 WO2013 / 183668

  However, in the method of Patent Document 3, process control is considerably complicated in order to perform stable carbonization while suppressing thermal decomposition of cellulose, and in the carbon fiber sheet obtained by the method described in Patent Document 4, mechanical characteristics are obtained. There was a problem that (strength, flexibility) was insufficient.

  Then, an object of this invention is to provide the carbon fiber fabric manufactured by the manufacturing method of the carbon fiber fabric excellent in mechanical characteristics (strength, flexibility) and a high carbonization yield, and the method.

The present invention provides the following (1) to (7) inventions.
(1) A method for producing a carbon fiber fabric, comprising the following steps (a) to (d):
(A) A step of preparing a fabric composed of cellulosic fibers (b) A step of impregnating the fabric with organic sulfonic acid (c) A fabric impregnated with the organic sulfonic acid in an inert gas atmosphere at 500 ° C. Step of heat treatment at a temperature of ˜2600 ° C. (d) Reheating treatment step at 2200 ° C. to 3200 ° C. in an inert gas atmosphere for the woven fabric impregnated with the organic sulfonic acid (2) The method for producing a carbon fiber fabric according to (1), wherein the cellulosic fiber is at least one selected from cupra ammonium rayon, viscose rayon, and purified cellulose fiber.
(3) The method for producing a carbon fiber fabric according to any one of (1) to (2), wherein the organic sulfonic acid is methanesulfonic acid.
(4) Any one of (1) to (3), wherein the concentration of the organic sulfonic acid impregnated in the fabric composed of the cellulosic fibers is 0.1 mol / L to 2.0 mol / L. The manufacturing method of the carbon fiber fabric as described in a term.
(5) A carbon fiber woven fabric produced by the method according to any one of (1) to (4) and having a basis weight of 50 g / m ^{2 to} 400 g / m ² .
(6) A composite material using a carbon fiber fabric produced by the method according to any one of (1) to (4).
(7) A gas diffusion layer for a fuel cell, wherein the carbon fiber fabric produced by the method according to any one of (1) to (4) is used.

According to the present invention, it is possible to provide a method for producing a carbon fiber fabric having excellent mechanical properties (strength and flexibility) and a high carbonization yield, and a carbon fiber fabric produced by the method.

  In the method for producing a carbon fiber fabric of the present invention, a fabric composed of cellulosic fibers (hereinafter sometimes referred to as “fabric”) is impregnated with an organic sulfonic acid, and then is heated to 500 ° C. in an inert gas atmosphere. Carbon having excellent mechanical properties (strength and flexibility) by heat treatment at a temperature of ˜2600 ° C. and further reheating treatment at 2200 ° C. to 3200 ° C. in an inert gas atmosphere A high-yield carbon fiber fabric can be produced.

(Cellulose fiber)
In the present invention, the cellulosic fiber is a long fibrous regenerated cellulosic material obtained by subjecting a plant cellulosic material obtained from a tree or the like and / or a plant cellulosic material (cotton, pulp, etc.) to chemical treatment and dissolving. It is the fiber comprised from the substance, and components, such as lignin and hemicellulose, may be contained in this fiber.

  As raw materials for cellulosic fibers (vegetable cellulose materials, regenerated cellulose materials), cotton (for example, short fiber cotton, medium fiber cotton, long fiber cotton, super long cotton, super-long cotton), hemp, bamboo, etc. Recycled cellulose fibers such as cellulose made from vegetative cellulose fibers such as bananas and bananas, copper-ammonia method rayon, viscose method rayon, polynosic rayon, bamboo, organic solvents (N-methylmorpholine N oxide) ) Examples include purified cellulose fibers to be spun and acetate fibers such as diacetate and triacetate. Among these, at least one selected from cupra ammonium rayon, viscose rayon, and purified cellulose fiber is preferable from the viewpoint of availability.

In the present invention, the diameter of the single fibers constituting the cellulosic fibers 5Myuemu～75myuemu, it is preferable density of 1.4m ³ /g~1.9m ³ / g.

  The form of the cellulosic fiber is not limited and can be adjusted to raw yarn (unprocessed yarn), false twisted yarn, dyed yarn, single yarn, double twisted yarn, covering yarn and the like according to the purpose. Moreover, when a cellulosic fiber contains 2 or more types of raw materials, it can be set as a blended yarn, a blended yarn, etc. Furthermore, the above-mentioned various forms of raw materials can be used alone or in combination of two or more as the cellulose fiber. Among these, a non-twisted yarn is preferable in terms of both the moldability of the composite material and the mechanical strength.

  In the present invention, the method for weaving the cellulosic fibers is not particularly limited, and a general method can be used, and the woven structure of the woven fabric is not particularly limited, and may be plain weave, twill weave or satin weave. Mihara organization is mentioned.

In the woven fabric made of cellulosic fibers, the gap between the warp and weft of the cellulosic fibers is preferably 0.1 mm to 0.8 mm, more preferably 0.2 mm to 0.6 mm, and more preferably 0.25 mm to More preferably, it is 0.5 mm. Furthermore, it is preferred that the basis weight of the fabric consisting of cellulosic fibers is ^{50g / m 2 ~400g / m 2} , and more preferably 100g / m2~300g / m2.

  By setting the cellulosic fiber and the fabric composed of cellulosic fibers in the above range, the carbon fiber fabric obtained by heat-treating the fabric has high strength and excellent resin impregnation properties.

  In the carbon fiber woven fabric of the present invention, the gap between the warps and wefts of carbon fibers constituting the carbon fiber woven fabric is preferably 0.1 mm to 0.8 mm, more preferably 0.15 mm to 0.6 mm. More preferably, it is 0.2 mm to 0.5 mm. If the gap between the yarns is too small, the impregnation of the resin into the carbon fiber fabric may be hindered. On the other hand, if the gap between the yarns is too large, there is a problem that the mechanical properties of the composite material deteriorate when a fiber reinforced plastic (composite material) made of a carbon fiber fabric and a resin is molded.

Preferably the basis weight of the carbon fiber woven fabric of the present invention is ^{50g / m 2 ~400g / m 2} , and more preferably ^{100g / m 2 ~300g / m 2} . When the basis weight of the carbon fiber is less than 50 g / m ² , it is preferable from the viewpoint of the resin impregnation property. However, since the number of laminated layers increases in order to express the required strength, the workability of the resin impregnation operation is increased. In addition, the drapeability of the resulting composite material decreases, and the workability also deteriorates. On the other hand, when the basis weight of the carbon fiber exceeds 400 g / m ² , there arises a problem that work efficiency is lowered due to deterioration of resin impregnation property and flexibility is lowered due to increase in thickness and weight.

(Organic sulfonic acid)
In the present invention, the organic sulfonic acid impregnated in the fabric may be any organic compound as long as it has a sulfo group (one or more) bonded to the carbon skeleton. Although compounds having various sulfo groups of aromatic and aromatic groups can be used, low molecular weight is preferable from the viewpoint of handling.

  Specific examples of the sulfonic acid include, for example, R—SO 3 H (wherein R is a linear / branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or 6 to 6 carbon atoms). 20 aryl groups, and the alkyl group, cycloalkyl group, and aryl group may be substituted with an alkyl group, a hydroxyl group, and a halogen group, respectively. For example, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, 1-hexanesulfonic acid, vinylsulfonic acid, cyclohexanesulfonic acid, p-toluenesulfonic acid, p-phenolsulfonic acid, naphthalenesulfonic acid, benzenesulfonic acid, camphor Examples thereof include sulfonic acid. Of these, methanesulfonic acid is preferably selected. Moreover, organic sulfonic acid may be used individually by 1 type, and may use 2 or more types together.

In the present invention, the fabric is impregnated with organic sulfonic acid and subjected to a heat treatment, so that water from the cellulose molecules ((C ₆ (H ₂ O) 5) _n ) constituting the fabric (cellulosic fibers) and water Only (H ₂ O) can be removed. For this reason, it is considered that there is almost no generation of hydrocarbon gas accompanying normal pyrolysis, and almost no carbon component in the cellulose molecule is lost, so that it is possible to prevent a decrease in the amount of the remaining carbon substance.

  In the method for producing a carbon fiber fabric of the present invention, when the organic sulfonic acid is used as an aqueous solution, its concentration is preferably 0.1 mol / L to 2.0 mol / L, preferably 0.1 mol / L to 1. 0.0 mol / L is more preferable.

  The method for causing the woven fabric to absorb the organic sulfonic acid is not particularly limited. For example, (1) A method in which a fabric is dipped in an aqueous solution of organic sulfonic acid in a concentration of 0.1 mol / L to 2.0 mol / L for 5 to 30 minutes and then pulled up from the solution and dried. (2) Organic A method of applying a necessary amount of organic sulfonic acid diluted with sulfonic acid or some solvent and / or water to a concentration of 0.1 mol / L to 2.0 mol / L, and (3) vapor of organic sulfonic acid And a method of bringing the fabric into contact with each other. Among these, (1) is preferred.

  The amount adsorbed on the woven fabric is usually 10 to 80%, preferably 20 to 60%, based on the weight of the original woven fabric. The amount of organic sulfonic acid absorbed can be adjusted as appropriate. It is preferable that the amount is such that a decrease in carbonization yield can be suppressed and a carbon fiber woven fabric with good handling properties can be prepared.

  In the present invention, a silicone polymer solution can be impregnated into a woven fabric in order to suppress thermal decomposition of cellulose and perform carbonization more stably. Examples of the silicone polymer include polysiloxane (PS), polydimethylsiloxane (Polydimethylsiloxane), room temperature curing silicone (RTV), polymethylphenylsiloxane (Poly Phenyl Siloxane: PMPS), polysilazane ( Polysilazane). In the silicone polymer solution, a polar solvent is used. Examples of the polar solvent include acetone (Acetone), perchloroethylene, tetrahydrofuran (Tetrahydrofurane: THF), methyl ethyl ketone (Methyl ethyl ketone). : MEK), ethyl alcohol, methyl alcohol and the like.

(Carbonization treatment)
In the present invention, the fabric that has absorbed the organic sulfonic acid is heat-treated (carbonized). Carbonization is performed in an inert gas atmosphere. Examples of the inert gas include argon and nitrogen.

In the present invention, a fabric impregnated with organic sulfonic acid is heat-treated in an inert gas atmosphere at a temperature of 500 ° C. to 2600 ° C., and then the fabric impregnated with organic sulfonic acid is heat-treated. It is important to perform reheating treatment (graphitization step) at 2200 ° C. to 3200 ° C. in the atmosphere.
In addition, the temperature in the case of the said heat processing is 500 to 2600 degreeC, Preferably it is 500 to 1000 degreeC. Thereby, the carbon fiber fabric in which the shape of the fabric is maintained can be obtained. When the heat treatment temperature is less than 500 ° C., the carbon content of the carbon fiber fabric is 80% or less and the carbonization is insufficient. On the other hand, when the temperature exceeds 2600 ° C., the carbonization state almost no longer changes. Further, the carbonization treatment may be performed continuously or in a batch state.

  Further, when the reheating treatment temperature is less than 2200 ° C., the progress of graphitization (crystallization) hardly occurs. On the other hand, when it exceeds 3200 ° C., the degree of graphitization hardly changes.

  The specific carbonization method is described below.

  First, the woven fabric that has undergone the sulfonic acid absorption step is heat-treated within the above range in a nitrogen or argon atmosphere using an electric furnace while maintaining the form. At this time, the heat treatment time is preferably 0.5 to 1 hour, although it depends on the heat treatment temperature. The temperature raising time from room temperature to the predetermined heat treatment temperature is preferably 3 to 8 ° C./min. In the heat treatment process, a high-temperature furnace in an inert gas atmosphere such as a tubular furnace or an electric furnace can be used. In this case, the inert gas exhaust pipe is filled with an adsorbent such as activated carbon and is generated from sulfonic acid. It is preferable to desulfurize a small amount of sulfur-based gas.

Next, as a reheating treatment step (partial graphitization step), preferably, the fabric heat-treated in the above step is once returned to room temperature, and then reheated at a temperature of 2200 ° C. to 3200 ° C. in an inert gas atmosphere. Thereby, the carbon fiber fabric partially graphitized while maintaining the initial form can be obtained.
In the present invention, during reheating treatment, the graphite crystals are efficiently oriented in the fiber axis direction of the carbon fiber by stretching in a direction parallel to the warp and / or in a direction crossing the warp of the fabric. Therefore, the strength of the carbon fiber fabric is improved.

  By the method for producing a carbon fiber fabric of the present invention, a carbon fiber fabric can be obtained while maintaining the form of the fabric composed of cellulosic fibers. Theoretically, when all the carbon contained in the cellulose constituting the fabric remains as a carbonized product, the carbonization yield becomes 44.4% by weight, whereas according to the production method of the present invention, 30% by weight or more. In some cases, the carbonization yield is as high as 40% by weight or more.

  Next, the present invention will be described in more detail than Examples and Comparative Examples, but the present invention is not limited thereto.

(Production Example 1)
Using a non-twisted rayon fiber (Omikeshi: 120d / 44f raw yarn) as the warp, and a non-twisted rayon fiber (Omikeshi: 120d / 44f raw yarn) as the weft, a warp density of 94 yarns / 2.54 cm, A twill fabric having a weft density of 135 / 2.54 cm and a basis weight of 154 g / m ² was woven in an air jet loom.

(Production Example 2)
Using Bemberg (Asahi Kasei Fiber Co., Ltd .: Cupra, 100d / 45f raw yarn) as the warp yarn and Bemberg (Asahi Kasei Fibers Co., Ltd .: Cupra, 75d / 45f raw yarn) as the weft yarn, warp density 150 / 2.54 cm, weft density 86 pieces / 2.54 cm plain woven fabric, 88 g / m ² of fabric weight were woven in an air jet loom.

Example 1
The rayon fabric obtained in Production Example 1 was cut to a size of 80 × 100 mm, and then immersed in a 1.0 mol / L aqueous methanesulfonic acid solution at room temperature for 5 minutes. Thereafter, the rayon fabric was taken out from the aqueous solution and naturally dried at room temperature for 24 hours to obtain a fabric having an absorption amount of methanesulfonic acid of 50% by weight (based on the solid content of rayon fabric). This fabric is sandwiched between two carbon plates, heated in an electric furnace in an argon gas atmosphere at a rate of temperature rise of 5.2 ° C./minute from room temperature to 800 ° C., and heated at the same temperature for 1 hour. Turned into. Then, it cooled to room temperature and took out the test material. Using this test material, a partially graphitized carbon fiber fabric was prepared by reheating to 2900 ° C. and treating at that temperature for 1 hour.

(Example 2)
A carbon fiber fabric was prepared in the same manner as in Example 1 except that p-toluenesulfonic acid was used using the rayon fabric obtained in Production Example 1.

(Example 3)
Using the cupra fabric obtained in Production Example 2, a partially graphitized carbon fiber fabric was prepared by the same procedure as Example 1.

(Comparative Example 1)
A carbon sheet was obtained according to Example 1 except that a sheet made of wood pulp was used.

(Comparative Example 2)
Using the rayon fabric obtained in Production Example 1, a carbon fiber fabric was prepared in the same manner as in Example 1 except that the immersion treatment in an aqueous methanesulfonic acid solution was omitted.

(Comparative Example 3)
Using the rayon fabric obtained in Production Example 1, a carbon fiber fabric was prepared in the same manner as in Example 1, except that a 1 mol / L ammonium sulfate solution was used instead of the methanesulfonic acid aqueous solution.

(Evaluation test)
Table 1 shows the results of performance evaluation of the carbon materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

<Evaluation method>
1) Carbon content The carbon content was determined by conducting an elemental analysis of the carbon fiber fabric.
2) Carbon yield The carbon yield was calculated by the following formula.
Carbon yield = Carbon fiber fabric weight after (carbonization + overheat treatment) / Cellulosic fiber fabric weight (including moisture)
3) Weight per unit area The weight per unit area was determined by measuring the weight of a carbon fiber woven fabric 50 mm × 50 mm.
4) Interval between warp and weft The distance between the warp and the weft was determined by measuring the distance between 10 arbitrary points with calipers.
5) Specific strength The bending specific strength was measured using a universal testing machine (Tensilon RTG-1210).
6) Flexibility The flexibility when an external force is applied to the carbon fiber fabric was determined by sensory evaluation.

○: The carbon fiber fabric is well bent and extremely flexible. △: The carbon fiber fabric is not very flexible and slightly inflexible. ×: The carbonized paper is not bent at all and is extremely inflexible.

Claims (7)

The manufacturing method of the carbon fiber fabric characterized by including the process of following (a)-(d).
(A) A step of preparing a fabric composed of cellulosic fibers (b) A step of impregnating the fabric with organic sulfonic acid (c) A fabric impregnated with the organic sulfonic acid in an inert gas atmosphere at 500 ° C. Step (d) of heat treatment at a temperature of ˜2600 ° C. (d) Reheating treatment step at 2200 ° C. to 3200 ° C. in an inert gas atmosphere for the woven fabric impregnated with the organic sulfonic acid and subjected to the heat treatment The method for producing a carbon fiber fabric according to claim 1, wherein the cellulosic fiber is at least one selected from cupra ammonium rayon, viscose rayon and purified cellulose fiber. The said organic sulfonic acid is a methanesulfonic acid, The manufacturing method of the carbon fiber fabric as described in any one of Claims 1-2 characterized by the above-mentioned. The density | concentration of the organic sulfonic acid impregnated in the textile fabric comprised from the said cellulosic fiber is 0.1 mol / L-2.0 mol / L, It is any one of Claims 1-3 characterized by the above-mentioned. Carbon fiber fabric manufacturing method. Claims 1 produced by the method according to any one of claims 4, carbon fiber woven fabric having a basis weight is ^{50g / m 2 ~400g / m 2} . A composite material using a carbon fiber fabric produced by the method according to any one of claims 1 to 4. A gas diffusion layer for a fuel cell, wherein the carbon fiber fabric produced by the method according to any one of claims 1 to 4 is used.