JP2005248343A - Method for producing carbon fiber, and woven fabric of carbon fiber, using the obtained carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a carbon fiber from which a woven fabric of the carbon fiber having good quality of appearance can be obtained; and to provide the woven fabric of the carbon fiber having the good quality of the appearance. <P>SOLUTION: The method for producing the carbon fiber involves regulating the tension added to the fiber under a carbonization treatment so as to be ≤0.2 g-weight/dTex when carrying out the carbonization treatment of a flame-resistant fiber obtained by subjecting an acrylic fiber to a flame-resisting treatment in an oxidative atmosphere, in an inert atmosphere of 1,200-1,800°C maximum temperature. In another aspect, the method for producing the carbon fiber involves regulating the tension added to the fiber under the carbonization treatment so as to be ≤0.2 g-weight/dTex when carrying out the carbonization treatment of a carbon fiber fiber obtained by subjecting the acrylic fiber to the flame-resisting treatment in an oxidative atmosphere, and subjecting the flame-resistant fiber to a carbonization treatment in an inert atmosphere of 550-800°C maximum temperature, in the inert atmosphere of 1,200-1,800°C maximum temperature. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a carbon fiber having a good appearance quality and suitable for a carbon fiber fabric, and a carbon fiber fabric having a good appearance quality.

  Carbon fiber is widely used as a reinforcing material for aerospace, leisure goods, industrial materials and the like because of its high specific strength and specific elasticity. The appearance quality of a carbon fiber fabric is very important because it often appears as it is in the appearance of a molded product using the carbon fiber fabric. The appearance quality of the carbon fiber woven fabric cannot be solved simply by the weaving method, and it is necessary to control the convergence of the carbon fiber. For example, Patent Document 1 discloses the shape of the cross section of the single fiber constituting the carbon fiber. A technique for improving the convergence of carbon fiber and resin impregnation by controlling the amount of Si is disclosed.

  However, the appearance quality of the carbon fiber woven fabric using the carbon fiber is not yet satisfactory, and the development of a carbon fiber capable of obtaining a carbon fiber woven fabric having a better appearance quality is desired.

JP2002-242027

  The objective of this invention is providing the manufacturing method of the carbon fiber which can obtain the carbon fiber fabric with a favorable external appearance quality. Another object of the present invention is to provide a carbon fiber woven fabric having good appearance quality.

  The first gist of the present invention is that when a flameproof fiber obtained by flameproofing an acrylic fiber in an oxidizing atmosphere is carbonized in an inert atmosphere having a maximum temperature of 1200 to 1800 ° C., There exists in the manufacturing method of the carbon fiber which makes the tension concerning a fiber 0.2 g weight / dTex or less.

  In addition, the second gist of the present invention is that after the flame-resistant fiber obtained by flame-treating acrylic fiber in an oxidizing atmosphere is carbonized in an inert atmosphere having a maximum temperature of 550 to 800 ° C., the maximum temperature is 1200 to In the carbon fiber production method, the tension applied to the fiber during the carbonization treatment is 0.2 g weight / dTex or less when the carbonization treatment is performed in an inert atmosphere at 1800 ° C.

  The third gist of the present invention is a carbon fiber fabric using the carbon fiber obtained by the above-described carbon fiber production method as a warp and / or a weft, and the tow width unevenness of the warp and / or the weft is 4 It is in the carbon fiber fabric which is 5% or less.

  According to the carbon fiber manufacturing method of the present invention, it is possible to obtain a carbon fiber capable of obtaining a carbon fiber fabric having good appearance quality.

Hereinafter, the configuration of the present invention will be sequentially described.
<Acrylic fiber>
The acrylonitrile polymer constituting the acryl used in the present invention includes acrylonitrile and vinyl monomers copolymerizable with acrylonitrile, such as acrylic acid, methacrylic acid, itaconic acid and alkali metal salts, ammonium salts and lower alkyl esters thereof. , Acrylamide and its derivatives, allyl sulfonic acid, methallyl sulfonic acid and their salts or alkyl esters. If the copolymerization component exceeds 10 mol%, adhesion between single yarns is likely to occur in the flameproofing step described later, which is not preferable.

  As a polymerization method for the acrylonitrile-based polymer, conventionally known solution polymerization, suspension polymerization, emulsion polymerization and the like can be applied. As the solvent used in the acrylic polymer solution, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, an aqueous zinc chloride solution, nitric acid, or the like can be used.

  As the spinning method, a wet spinning method, a dry wet spinning method, a dry spinning method, or the like can be employed. The obtained coagulated yarn is made into a precursor acrylic fiber having a predetermined fineness by performing conventionally known water washing, bath drawing, application of process oil, drying densification, steam drawing and the like.

<Flame resistance>
In the present invention, the flameproofing condition of the acrylic fiber is not particularly limited as long as it is a known method and condition, but the density is preferably 1.25 g in an oxidizing atmosphere at 200 to 300 ° C. under tension or stretching conditions. / Cm ³ or higher, more preferably 1.32 g / cm ³ or higher.

  If the flame resistance is insufficient, adhesion between single yarns is likely to occur during pre-carbonization. As the atmosphere, a known oxidizing atmosphere such as air, oxygen, and nitrogen dioxide can be adopted, but air is preferable from the viewpoint of economy.

<Treatment in an inert atmosphere with a maximum temperature of 550 to 800 ° C.>
In the present invention, the flame-resistant fiber is tensioned in an inert atmosphere having a maximum temperature of 550 to 800 ° C., and the temperature rising rate is 500 ° C./min or less, preferably 300 ° C./min or less in a temperature range of 300 to 500 ° C. It is effective to improve the mechanical properties of the final carbon fiber (hereinafter referred to as pre-carbonized fiber).

  As the inert atmosphere, a known inert atmosphere such as nitrogen, argon, or helium can be adopted, but nitrogen is desirable from the viewpoint of economy.

<Carbonization>
In the present invention, the flame-resistant fiber or the pre-carbonized fiber is heat-treated in an inert atmosphere having a maximum temperature of 1200 to 1800 ° C. At this time, in the temperature range of 1000 to 1200 ° C., it is effective in order to improve the mechanical properties of the carbon fiber to perform carbonization treatment at a heating rate of 500 ° C./min or less, preferably 300 ° C./min or less. .

  As the inert atmosphere, a known inert atmosphere such as nitrogen, argon, or helium can be adopted, but nitrogen is desirable from the viewpoint of economy.

  The tension applied to the fiber treated by carbonization needs to be 0.2 g weight / dTex or less, and more preferably 0.1 g weight / dTex or less. In carbonization, the weight of the treated fiber is reduced. In this case, the tension is estimated by (tension of the treated fiber / total fineness of the treated fiber).

  When the tension at the time of carbonization exceeds 0.2 g weight / dTex, the fiber bundles are aligned, and the appearance quality of the woven fabric when woven is lowered.

<Treatment after carbonization>
The obtained carbon fiber is subjected to electrolytic oxidation treatment in a conventionally known electrolytic solution, or is subjected to oxidation treatment in a gas phase or liquid phase, so that the affinity and adhesion between the carbon fiber and the matrix resin in the composite material It is preferable to improve.

  Furthermore, a sizing agent can be provided by a conventionally known method as necessary.

<Carbon fiber fabric>
The carbon fiber fabric of the present invention can be woven using a conventionally known rapier loom, projectile loom, air jet loom, water jet loom, shuttle loom or the like.

  The woven structure of the carbon fiber fabric is plain weave, twill weave or satin weave, which improves the workability when forming the structural material of the carbon fiber fabric by the hand lay-up method and the mechanical properties of the carbon fiber fabric molding. It is preferable for improvement.

The basis weight of the carbon fiber woven fabric is 400 g / m ² or less, preferably 350 g / m ² or less, more preferably 300 g / m ² or less. When the basis weight of the carbon fiber woven fabric is 400 g / m ² or more, the bending of the carbon fiber bundle becomes large, and the mechanical properties of the molded product using the carbon fiber woven fabric are inferior.

Further, the number of carbon fiber filaments constituting the carbon fiber fabric is preferably 8000 or less. When the basis weight of the carbon fiber woven fabric is 400 g / m ² or less and the number of filaments of the carbon fibers constituting the carbon fiber woven fabric is 8000 or more, the gap between the carbon fibers constituting the carbon fiber woven fabric is increased and the appearance quality is deteriorated. .

(Example)
Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, the evaluation was based on the following method.

(Resin impregnated strand characteristics)
The strand strength and strand elastic modulus of the carbon fiber were measured in accordance with a test method described in JIS R7601.

(Uneven toe width of carbon fiber fabric)
Measure 100 tow widths of the warp and weft constituting the carbon fiber fabric,
Fluctuation rate (%) = standard deviation ÷ average x 100
The tow width unevenness of the carbon fiber woven warp and weft.

(Appearance grade of carbon fiber fabric)
The carbon fiber fabric was visually observed and judged as ◎, ○, and × in order from the fabric having a uniform fabric.

  A dimethylacetamide (DMAc) solution having a concentration of 20% by mass was prepared using a copolymer consisting of 96 mol% of acrylonitrile units / 3 mol% of acrylamide units / 1 mol% of itaconic acid units.

  This solution was coagulated in a DMAc aqueous solution having a temperature of 35 ° C. and a concentration of 67% by mass through a spinneret having a pore diameter of 60 μm and a hole number of 3000. The coagulated yarn was washed with water and then stretched in a bath to give a silicone-based oil, and then stretched in pressurized steam to obtain an acrylic fiber having a single fiber fineness of 1.2 dTex and a total fineness of 3600 dTex.

This acrylic fiber is heated to tension in air at 230 to 260 ° C. to be converted to a flame-resistant fiber having a density of 1.36 g / cm ³ , and further subjected to pre-carbonization treatment by tension in nitrogen at 700 ° C. Carbonized fiber was used. The heating rate at 300 to 500 ° C. in the pre-carbonization treatment was 200 ° C./min.

The pre-carbonized fiber was carbonized at 1500 ° C. and a tension of 0.15 g weight / dTex to obtain a carbon fiber having a total fineness of 2000 dTex, and a sizing agent was applied after the surface treatment. The heating rate at 1000 to 1200 ° C. was 400 ° C./min.
The evaluation results are shown in Table 1.

The precarbonized fiber obtained in Example 1 was carbonized at 1550 ° C. and a tension of 0.09 g weight / dTex to obtain a carbon fiber having a total fineness of 2030 dTex, and a sizing agent was applied after the surface treatment. The heating rate at 1000 to 1200 ° C. was 400 ° C./min.
The evaluation results are shown in Table 1.

The pre-carbonized fiber obtained in Example 1 was carbonized at 1450 ° C. and a tension of 0.15 g weight / dTex to obtain a carbon fiber having a total fineness of 1980 dTex, and a sizing agent was applied after the surface treatment. The heating rate at 1000 to 1200 ° C. was 400 ° C./min.
The evaluation results are shown in Table 1.
(Comparative Example 1)

The precarbonized fiber obtained in Example 1 was carbonized at 1450 ° C. and a tension of 0.25 g weight / dTex to obtain a carbon fiber having a total fineness of 1960 dTex, and a sizing agent was applied after the surface treatment. The heating rate at 1000 to 1200 ° C. was 400 ° C./min.
The evaluation results are shown in Table 1.

  The DMAc solution of the acrylic copolymer obtained in Example 1 was coagulated in a DMAc solution at a temperature of 35 ° C. and a concentration of 67% through a spinneret having a pore diameter of 60 μm and a hole number of 6000. The coagulated yarn was washed with water, bath-drawn, and a silicone-based oil agent was applied. Then, the coagulated yarn was drawn in pressurized steam to obtain acrylic fibers having a single fiber fineness of 1.2 dTex and a total fineness of 7200 dTex.

This acrylic fiber is heated to tension in the air at 230 to 260 ° C. to convert to a flame resistant fiber having a density of 1.36 g / cm ³ , and pre-carbonization is performed by pre-carbonization treatment for tension in a nitrogen atmosphere at 700 ° C. Made of fiber. The temperature rising rate at 300 to 500 ° C. was 200 ° C./min.

This pre-carbonized fiber was carbonized at 1500 ° C. at a tension of 0.15 g weight / dTex to obtain a carbon fiber having a total fineness of 3980 dTex, and a sizing agent was applied after the surface treatment. The heating rate at 1000 to 1200 ° C. was 400 ° C./min.
The evaluation results are shown in Table 1.
(Comparative Example 2)

The pre-carbonized fiber obtained in Example 4 was carbonized at 1450 ° C. and a tension of 0.25 g weight / dTex to obtain a carbon fiber having a total fineness of 3940 dTex, and a sizing agent was applied after the surface treatment. The heating rate at 1000 to 1200 ° C. was 400 ° C./min.
The evaluation results are shown in Table 1.

Claims (6)

  When the flame-resistant fiber obtained by flame-treating acrylic fiber in an oxidizing atmosphere is carbonized in an inert atmosphere having a maximum temperature of 1200 to 1800 ° C., the tension applied to the fiber being carbonized is 0.2 g weight. / DTex or less carbon fiber production method.   After the flame-resistant fiber obtained by flame-treating acrylic fiber in an oxidizing atmosphere is carbonized in an inert atmosphere having a maximum temperature of 550 to 800 ° C., the carbonization treatment is performed in an inert atmosphere having a maximum temperature of 1200 to 1800 ° C. A carbon fiber manufacturing method in which the tension applied to the fiber during carbonization is 0.2 g weight / dTex or less.   The method for producing a carbon fiber according to claim 1 or 2, wherein the number of filaments of the flame resistant fiber is 8000 or less.   4. A carbon fiber woven fabric using carbon fibers obtained by the carbon fiber manufacturing method according to claim 1 as warps and / or wefts, wherein the tow width unevenness of the warps and / or wefts is 4. Carbon fiber fabric that is 5% or less. The carbon fiber fabric according to claim 4, wherein the fabric basis weight is 400 g / m ² or less.   The carbon fiber woven fabric according to claim 4 or 5, wherein the woven fabric is a plain weave, twill weave or satin weave.