JP2002309475A - Method for transferring carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for transferring carbon fibers, improved in process passableness in a process for manufacturing the carbon fibers and capable of obtaining carbon fibers having high quality and excellent physical properties such as tensile strength or the like. SOLUTION: The method for transferring carbon fibers comprises a process in which the carbon fibers are transferred by using rollers. The roller has a surface having a fluorine resin layer, and the friction coefficient between the surface of the roller and the carbon fibers is in the range of 0.1-0.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transferring carbon fibers, and more particularly, to a method for transferring carbon fibers having significantly improved process passability in the production of carbon fibers of excellent quality and post-processing of carbon fibers.

[0002]

2. Description of the Related Art Since carbon fiber is excellent in specific strength and specific elastic modulus, it is widely used in general industrial fields such as civil engineering and construction, sporting goods field, and aerospace field, especially in aerospace field. , A very high tensile strength may be required. However, since carbon fibers are inherently brittle materials, if there is a flaw on the surface of the precursor fiber before carbonization to carbon fiber, even if it is minor, it is regarded as carbon fiber. At that time, the scratch becomes a starting point of fracture, and the tensile strength is greatly reduced. Further, in a post-processing step such as the application of a sizing agent after the carbonizing or graphitizing treatment, the above-described fracture may further develop and lower the tensile strength. For this reason, many methods have been proposed for preventing the occurrence of such scratches and defects and for improving the quality of carbon fibers, including the process of producing precursor fibers. For this reason, for example, Japanese Patent Application Laid-Open No. 3-167
Japanese Patent Publication No. 368 discloses a method of wiping off deposits on a roller using an automatic cloth feeder. However, in this method, when the number of yarns is large, the roller length becomes long, and thus the contact between the wiping device and the roller is caused in the roller width direction. In addition, there is a problem that the deposits on the roller cannot be effectively removed. Further, Japanese Patent Publication No. 3-41561 discloses a method in which the tension applied to the fiber bundle in the restricting device is reduced by devising the shape of the yarn path restricting device applied when the fiber bundle is conveyed. . further,
Japanese Patent Application Laid-Open No. 12-73225 discloses a method using a yarn path regulating tool using ceramics having a high level of surface smoothness and hardness. However, in these methods, a sufficient effect for eliminating scratches and defects was not obtained, the tensile strength of the obtained carbon fiber was insufficient, and the operability was not satisfactory. Further, as an attempt to reduce wear, Japanese Patent Application Laid-Open No. 7-278945 discloses a yarn path regulating device made of alumina / zirconia ceramics, but the wear resistance is insufficient and the surface irregularities are large. , It was not practical.

[0003]

SUMMARY OF THE INVENTION In view of the background of the prior art, the present invention is directed to a carbon fiber which has improved processability in the process of producing carbon fiber, has high quality, and has excellent physical properties such as tensile strength. To provide a method for transferring carbon fibers capable of obtaining a carbon fiber.

[0004]

The present invention employs the following means in order to determine such a problem. That is, in the method of transferring carbon fibers of the present invention, in the step of transferring the carbon fibers using a roller, the roller is formed of a surface having a fluororesin layer, and the surface of the roller and the carbon fiber The coefficient of friction is 0.1
０．２0.2.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been made to solve the above-mentioned problem, that is, a carbon fiber which can improve the processability in the carbon fiber production process and can obtain a carbon fiber having high quality and excellent physical properties such as tensile strength. The method for transferring the fibers was studied diligently, and when using a roller having a specific friction coefficient coated with a fluororesin as the roller in the step of transferring the carbon fibers using a roller, it was surprisingly found that such a problem occurred. Was determined to solve all at once.

[0006] As the carbon fiber in the present invention, a precursor fiber to which a silicone-based oil agent has been applied is prepared at 200 to 400 ° C.
Any carbon fiber can be used as long as it is oxidized in an active atmosphere and then carbonized at 300 to 2000 ° C. in an inert atmosphere, and any carbon fiber can be used. , Carbon fibers in an inert atmosphere of nitrogen, argon helium, etc.
The effect is more remarkable in the graphitized fiber having a high elastic modulus after passing through a so-called graphitization step of heating to 0 ° C., and is preferably used.

[0007] As the precursor fiber of such carbon fibers, fibers of acrylic type, rayon type, pitch type or polyvinyl type can be applied. In particular, carbon fibers using acrylic fibers as precursor fibers are preferably used in the present invention because they have excellent mechanical properties.

The step of transferring carbon fibers using a roller in the present invention is a method of guiding carbon fiber yarns in a step of performing some continuous treatment on carbon fibers after a carbonization step. Examples of the process include a process after a carbonizing process in a carbon fiber manufacturing process, a twisting process, an untwisting process, and a yarn transferring process in a carbon fiber reinforced prepreg manufacturing process.

In the twisting step, for example, the carbon fiber is drawn out while applying tension using a creel that is rotated about an axis perpendicular to the longitudinal axis of the bobbin around which the carbon fiber is wound. There is a method of running at a constant speed on a plurality of drive rollers alternately arranged so that the contact angle becomes 180 °, and refers to a process of twisting a desired number of turns. The untwisting step can be performed in a similar manner except that the rotation direction of the creel is opposite to that of the twisting step, and refers to a step of reducing twisting to a desired number of turns. .

In the present invention, the term "roller" means any roller that is in direct contact with the carbon fiber in the carbon fiber production step and the post-processing step.

In the present invention, it is essential that the surface of such a roller is formed of a fluororesin layer. That is, it is necessary to adjust and control the coefficient of friction with the carbon fiber in the range of 0.1 to 0.2 by forming the surface of the roller with such a fluororesin layer. The coefficient of friction between the carbon fiber and the roller surface in the present invention is a coefficient of static friction between the carbon fiber and the roller surface.

Examples of such a fluororesin include polytetrafluoroethylene (hereinafter referred to as PTFE), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, tetrafluoroethylene-ethylene copolymer,
Polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride and the like are preferably used. Among them, polytetrafluoroethylene is desirably used from the viewpoint of the effect of preventing winding.

In the present invention, any method can be used to treat the surface of the roller so that the coefficient of friction with the carbon fiber is in the range of 0.1 to 0.2. How to apply a coating on the surface, how to wind the film, or on the surface of such a film or coating or the roller itself,
A method such as embossing is also preferably used.
Among them, a method of applying a coating treatment to the surface of the roller is preferably adopted because the handleability of the roller is good.

Although any method can be used as a coating method in the present invention, a method of coating with a powder generally used as a method of coating a fluororesin,
Alternatively, a method of applying as an aqueous or organic dispersion is suitably used. In either method, a fluororesin coating film is formed by heating and melting after coating. The thickness of the fluororesin coating layer is 50 to 2
It is preferably in the range of 00 μm. 50 μm thick
If it is less than 1, it is difficult to uniformly coat the roller surface, and processing unevenness is likely to occur, which may cause fraying. On the other hand, if the thickness is 200 μm or more, the influence on the roller diameter is large, so that it is difficult to control the process speed and disadvantageously in terms of cost.

A method of winding the fluororesin film around a roller surface is also suitably used. As the fluororesin film used for such a film, in addition to the film made of the fluororesin alone, it is also possible to use a fluororesin composite film compounded with another polymer film, which is advantageous in cost. Therefore, it is suitably used. Other polymer films to be composited include a polyester film or a polyvinyl chloride film. Further, it is also preferable to perform embossing on the surface of the fluororesin film as long as the quality of the carbon fiber is not affected.

[0016] Thus, a roller in which the fluororesin layer is provided on the surface of the roller for guiding the carbon fiber and the coefficient of friction between the carbon fiber and the roller surface is adjusted in the range of 0.1 to 0.2 is formed. be able to. The friction coefficient is more preferably 0.1 to 0.15.
It is good to be in the range. That is, when the coefficient of friction between the carbon fiber and the roller surface is less than 0.1, the carbon fiber slips on the drive roller, and the surface of the carbon fiber is likely to be damaged or the process speed tends to be unstable. In addition, even on a roller that bends the yarn path of the carbon fiber, the carbon fiber slips, causing loosening, which may cause problems such as detachment of the carbon fiber from the roller. On the other hand, if the coefficient of friction exceeds 0.2, the single yarn is taken up by the roller, causing fluff, deteriorating the quality of the carbon fiber, and possibly causing the yarn to break due to winding.

The transfer method of the present invention can also be used in a yarn transfer step in a carbon fiber reinforced prepreg manufacturing step. That is, as a method for producing such a carbon fiber reinforced prepreg, any of a wet method and a hot melt method may be used, but it is preferably used in a hot melt method in which the volume content of carbon fibers is easily controlled. In particular, in the production of a unidirectional carbon fiber reinforced prepreg, by reducing the generation of fluff, it is possible to provide a carbon fiber reinforced composite material having excellent fiber directional characteristics.

[0018]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto. <Method of Measuring Friction Coefficient> The coefficient of friction, including the examples described later, is measured for a film or coating film of 1
5mmφ mirror round bar guide (20mmφ only for satin guide)
At this time, care is taken so that the bonding portion or the overlapping portion of the film or the coating film is arranged on the guide portion where the carbon fiber described below does not contact. After fixing the film or the coating film on the guide surface in this way, a carbon fiber is hung thereon, a fixed load (T1) is hung on one end of the carbon fiber, and hung on the opposite end. The load (T2) is increased, and the load (T2) when the carbon fiber slides and the contact angle are calculated by the following formula.

Μ = (1 / θ) * ln (T2 / T1) μ: friction coefficient The friction coefficient mentioned here belongs to the category of the so-called static friction coefficient, and the static friction coefficient is generally higher than the dynamic friction coefficient. At the same time, both have a high positive correlation.
Further, the fluctuation range of the coefficient of friction due to the dry / wet state of the fiber bundle, the transport speed and the shape of the effective contact surface is ± 0.0%.
It was controlled to about 2. <Method of measuring the number of windings of carbon fiber> When 150 m of carbon fiber was untwisted at a yarn speed of 5 m / min, a driving roller (6 in total) was used.
The number of times a single yarn was wound on each piece, i.e., the number of times the single yarn was wound. <Method of measuring fuzzing fluff> Five stainless steel rods with a diameter of 10 mm (surface chromium plating, surface roughness 1 to 1.5 ^S ) at 50 mm intervals A rubbing device was used in which the rods were arranged in a zigzag manner so that the carbon fiber yarns could pass through them in parallel with each other and at a contact angle of 120 ° on their surfaces. With this apparatus, a tension of 0.09 g per denier is applied to the entrance side carbon fiber yarn, and the carbon fiber yarn is passed at a yarn speed of 3 m / min.
The number of fluffs when a laser beam is irradiated at right angles to the fiber yarn from the side is counted by a fluff detecting device. <Measurement method of strand strength>
Impregnating a resin composition mixed with KELITE (registered trademark) ERL4221 / 3 boron monoethylamine / acetone = 100/3/4 (parts by weight), and then curing at 130 ° C. for 30 minutes to obtain a resin-impregnated strand; The measurement was carried out by a resin impregnated strand test method (JIS R7601).

Example 1 Acrylonitrile 9 using dimethyl sulfoxide as a solvent
A polymer composed of 8% and 2% of acrylic acid was spun by a dry-wet method to obtain a carbon fiber precursor fiber having a single fiber fineness of 0.11 Tex and a filament number of 12,000. The obtained precursor fiber is twisted at 2.5 turns / m and heat-treated in an oxidizing atmosphere at a temperature of 250 to 270 ° C. and a draw ratio of 1.0 to convert it into oxidized fiber. Temperature 9
Carbon fiber bundles were obtained by carbonization in a low-temperature carbonization furnace at 00 ° C. and a draw ratio of 1.0 and a high-temperature carbonization furnace at a maximum temperature of 1,400 ° C. and a draw ratio. The obtained carbon fiber bundle was subjected to anodizing treatment at 6 coulomb / g-CF in an aqueous sulfuric acid solution, and then washed with water and dried at 150 ° C. to obtain a surface carbon fiber bundle. The obtained surface oxidized carbon fiber bundle was immersed in a bath filled with an aqueous solution of an epoxy-modified polyurethane whose concentration was adjusted so that the amount of adhesion as a sizing agent was 1.0 wt%, and dried at 150 ° C. It was wound on a bobbin via a roller having a surface coated with polytetrafluoroethylene. This carbon fiber bundle,
Similarly, carbon fibers were obtained by untwisting through a roller having a surface coated with polytetrafluoroethylene. In the sizing agent applying step and the untwisting step, the generation of fraying was very slight, and the carbon fiber was excellent in tensile strength. Table 1 shows the results.

Example 2 An embossed polytetrafluoroethylene film (HI-PERFORMANCE) was used as a roller in the sizing agent application step and the untwisting step.
PRODUCT-100 TP-100S, 150μ thickness
m) was wound, and a carbon fiber was obtained in the same manner as in Example 1. Table 1 shows the results.

Example 3 A polytetrafluoroethylene film (HI-PERFORMANCE PRODUC) was formed on the roller surface as a roller in the sizing agent application step and the untwisting step.
Example 1 except that TS Co., Ltd., 50 μm thick) was wound.
A carbon fiber was obtained in the same manner as described above. Table 1 shows the results.

[0023]

[Table 1]

As is clear from Table 1, in Example 1 in which the surface of the roller was subjected to PTFE treatment,
A carbon fiber excellent in quality with few fluffs was obtained.

Comparative Example 1 Carbon fibers were obtained in the same manner as in Example 1 except that a roller subjected to a satin finish on the roller surface was used as a roller in the sizing agent applying step and the untwisting step. Table 2 shows the results.

Comparative Example 2 A roller was used in the sizing agent application step and the untwisting step, except that a tetrafluoroethylene-hexafluoropropylene copolymer film (manufactured by Toray Co., Ltd. 50F, thickness 50 μm) was wound around the roller surface. A carbon fiber was obtained in the same manner as in Example 1. Table 2 shows the results.

Comparative Example 3 Carbon fibers were obtained in the same manner as in Example 1 except that a roller having a mirror-finished surface was used as a roller in the sizing agent applying step and the untwisting step. Table 2 shows the results.

Comparative Example 4 Carbon fibers were prepared in the same manner as in Example 1 except that a polyethylene film (New Poly Wrap, Ube Film Co., Ltd., thickness: 10 μm) was wound around the roller surface as a roller in the sizing agent application step and the untwisting step. I got
Table 2 shows the results.

[0029]

[Table 2]

As is clear from Table 2, in Comparative Example 1 in which the surface of the roller has a satin finish, both the number of windings and the number of fluffs increase, and the strand strength also decreases. Also,
Also in Comparative Example 2 in which the coefficient of friction exceeds 0.2, both the number of windings and the number of fluffs increase, and the strand strength decreases.

[0031]

According to the present invention, in the production of carbon fiber and the post-processing of the carbon fiber, the processability is remarkably improved, and the quality of the carbon fiber is further improved by reducing defects such as fuzzing and yarn breakage. Can be provided.

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Claims (8)

[Claims] In the step of transferring carbon fibers using a roller, the roller is formed of a surface having a fluororesin layer, and the coefficient of friction between the roller surface and the carbon fibers is 0.1%. A method for transferring carbon fibers, wherein the method is in the range of 0.2 to 0.2. 2. The fluororesin layer has a thickness of 50 to 200.
The method for transferring carbon fibers according to claim 1, wherein the diameter is in a range of μm. 3. The method according to claim 1, wherein said fluororesin layer is made of a fluororesin film. 4. The method according to claim 1, wherein the carbon fibers are graphitized fibers. 5. The carbon fiber according to claim 1, wherein the step of transferring the carbon fiber forms part or all of the steps after the sizing agent applying step in the carbon fiber manufacturing step. Fiber transfer method. 6. The carbon fiber transferring step forms part or all of a carbon fiber twisting step.
The method for transferring carbon fibers according to any one of the above. 7. The carbon fiber transferring step forms part or all of a carbon fiber untwisting step.
The method for transferring carbon fibers according to any one of the above. 8. The method of transferring carbon fibers according to claim 1, wherein the step of transferring carbon fibers forms part or all of a step of impregnating a carbon fiber reinforced prepreg.