JP3035787B2 - How to clean carbon fiber - Google Patents

Description

The present invention relates to a method for cleaning a carbon fiber bundle. More specifically, the present invention relates to a method of effectively cleaning a carbon fiber bundle without damaging the carbon fiber bundle. Here, the carbon fiber bundle generally refers to a filament bundle made of carbon fiber or graphite fiber.

<< Prior Art and Problems >> In general, carbon fibers have excellent mechanical properties, for example, high specific strength and specific elasticity, and therefore, light-weight structural materials in various fields, mainly in the aerospace field, and sports / recreation fields. Widely used in Particularly in the field of structural materials, the quality stability of the carbon fiber bundle is an important factor of the carbon fiber bundle.

Carbon fiber bundles are often used as a composite with a resin, and it is necessary to improve the adhesion between the carbon fiber bundle and the matrix resin in order to improve the mechanical properties of the composite.
For this purpose, a method of performing a surface treatment on a carbon fiber bundle is usually employed.

As the surface treatment, an oxidation treatment in a liquid phase or a gas phase is known. As the liquid phase oxidation treatment, an electrolytic surface treatment is generally used.

When the carbon fiber bundle is subjected to surface treatment, it is necessary to remove the electrolyte adhering to the treated carbon fiber bundle. Examples of the electrolyte include inorganic acids such as sulfuric acid, nitric acid, phosphoric acid, boric acid, and carbonic acid; organic acids such as acetic acid, butyric acid, oxalic acid, and maleic acid; and alkali metal salts and ammonium salts thereof, or a mixture of two or more thereof. There is.

Even in the liquid phase surface treatment other than the electrolytic surface treatment, various chemicals such as permanganate, hypochlorite, and caustic soda are attached, and it is necessary to remove these from the carbon fiber surface by washing with water or the like.

When these chemicals remain on the carbon fiber surface,
This is because the mechanical properties, heat resistance and thermal oxidation resistance of the composite material are reduced.

As a method for cleaning the carbon fiber to which such a chemical solution has adhered, a bath method, a vibro method, a shower method,
A combination of these methods is known.

However, in these cleaning methods, generally, the cleaning water is directly applied to the fiber, so that the fiber is greatly damaged, and there is a problem that a single fiber of the carbon fiber bundle breaks, that is, the fluff of the carbon fiber bundle occurs. In addition, each of these methods has the following problems.

In the bath system, there is a problem that a sufficient cleaning bath length must be adopted to obtain a desired cleaning effect, and the amount of cleaning water increases.

In the vibro system, although the cleaning effect of the carbon fiber bundle is large, the impact on the carbon fiber bundle due to vibration is large, and this has caused fluffing of the carbon fiber bundle.

In the shower method, the area for obtaining the cleaning effect can be smaller than that in the bath method, but since the shower water is directly applied to the fibers, the damage to the fibers is large, and the single fiber of the carbon fiber bundle is cut, that is, the carbon fiber bundle is cut. It caused fluff.

[Object of the invention]

An object of the present invention is to effectively clean a carbon fiber bundle without damaging the carbon fiber bundle.

[Configuration of the invention]

 The present invention has the following configurations.

(1) A method for cleaning a carbon fiber bundle, comprising contacting water applied to a roller with the carbon fiber bundle on the roller surface when cleaning the carbon fiber.

(2) The cleaning method according to (1), wherein the tension of the carbon fiber bundle is set to 0.03 to 0.5 g / d.

(3) The cleaning method according to (1), wherein the amount of water is 10 to 100 ml / g of carbon fiber bundle.

(4) The cleaning method according to (1), wherein a multi-stage roller is used.

(5) The cleaning method according to (1), wherein the temperature of the cleaning water is 15 to 60 ° C.

(6) The contact between the carbon fiber bundle and the roller is set to 90 degrees or less at the center angle of the roller.
Cleaning method.

ADVANTAGE OF THE INVENTION According to this invention, it can wash effectively, without damaging a carbon fiber bundle.

In the present invention, the carbon fiber is an acrylic carbon fiber,
Rayon-based carbon fibers, pitch-based carbon fibers, and the like.

As the washing water, ion-exchanged water, distilled water, well water and the like are used.

The roller is usually a metal roller coated with ceramic or plastic,
The corrosion-resistant metal roller can be used as it is.

A groove into which each carbon fiber bundle is inserted can be provided on the surface of the roller, but a flat roller having a flat surface may be used.

For the contact between the roller and the carbon fiber bundle, it is necessary to consider the diameter of the roller, the tension of the carbon fiber bundle, the contact angle with the roller, and the like.

For this reason, the diameter of the roller should be 30 to 50 in consideration of the contact area with the carbon fiber bundle, the amount of washing water, washing efficiency, workability, etc.
It is preferable to set the range to 0 mm.

In particular, when the contact angle between the roller and the carbon fiber bundle is increased, the fluff of the carbon fiber bundle is increased, which is not preferable. The contact angle is preferably 90 degrees or less. In particular, it is preferably 30 degrees or less. The contact angle between the roller and the carbon fiber bundle is desired not only for the roller that is being supplied with water but also for the roller that is adjacent to and being supplied with water.

The tension of the carbon fiber is preferably set to 0.03 to 0.5 g / d from the viewpoint of the cleaning efficiency of the carbon fiber bundle and the prevention of damage. Particularly preferably, it is 0.04 to 0.3 g / d.

Wash water for the roller is applied onto the roller from a pipe provided in the axial direction of the roller. At this time, care is taken so that the washing water flowing out of the pipe does not directly hit the carbon fiber bundle. This is performed by adjusting the diameter of the roller, the distance between the roller and the pipe for supplying water, and the area of the hole or slit for jetting the washing water provided on the pipe.

Wash water supplied to the roller from the water supply pipe is usually 10 to 100 ml per gram of carbon fiber. The temperature of the washing water is preferably 15 to 60 ° C. from the viewpoint of the washing effect and the workability.
Particularly preferably, the water supply amount is 10 to 80 ml per 1 g of carbon fiber,
The temperature is 30-50 ° C.

This is preferable in terms of cleaning efficiency, prevention of damage to carbon fibers, and work environment.

 The present invention will be described with reference to the drawings.

FIG. 1 is a conceptual side view showing the steps of the method of the present invention (when one cleaning roller is used). Fig. 2
Side view conceptual diagram (when two cleaning rollers are used)
It is.

1 and 2, 1 is a carbon fiber bundle, 2 is a cleaning roller, 3 is a cleaning water supply pipe, 4 is a roller that is not supplied, 5 is cleaning water, and α is a contact angle between the cleaning roller and the carbon fiber bundle. Show.

〔The invention's effect〕

According to the present invention, the cleaning water flows on the roller surface as a water film, and the carbon fiber bundle comes in contact with the water film, and the carbon fiber bundle is cleaned.
In addition, the cleaning is performed by flowing water, and the cleaning water once in contact with the carbon fiber bundle does not contact the carbon fiber bundle again, so that effective cleaning can be performed.

(Examples and Comparative Examples)

Example 1 A polyacrylonitrile-based carbon fiber bundle (12,000 filaments) carbonized in a carbonization furnace set at a maximum temperature of 1450 ° C. was used as a raw material.

100 carbon fiber bundles are arranged in parallel at 5 mm intervals, and the processing speed is set using a bathtub type (bathtub length 4 m) surface treatment bath.
Electrolytic surface treatment was performed using 8% by weight sodium sulfate as an electrolyte solution at 2 m / min. Processing electricity is 10.1 coulomb / g
And

The thus treated carbon fiber bundle was washed by a multi-stage washing apparatus similar to that shown in FIG. The overall length of this cleaning device is 1.5 m. The number of washing rollers is 3,
The cleaning roller is a flat roller with a diameter of 100 mm, and the contact angle (α) between each cleaning roller and the carbon fiber bundle is 25 degrees,
The tension applied to the fiber bundle was 0.1 g / d.

Cleaning water was supplied to each cleaning roller at 15 ml / carbon fiber 1 g (total 45 ml / carbon fiber 1 g), a water film was formed on the surface of the cleaning roller, and the water film-like cleaning water was brought into contact with the carbon fiber bundle. .

 As the washing water, ion exchange water at 35 ° C. was used.

As a result, the sulfate concentration in the carbon fiber bundle was 1 ppm
It became.

 Next, it was dried at 110 ° C. and wound around a bobbin.

The number of thread cuts per 1 m of the fiber bundle was measured by the following method for measuring the number of fluffs and found to be as good as 14 pieces / m.

The number of fluff is measured by immersing 12,000 filament strands in acetone to dissolve and remove the sizing agent.
Count between 1m.

Comparative Example 1 A carbon fiber bundle whose surface treatment was completed under the same conditions as in Example 1.
100 were washed using a washing bath of a bathtub type (tub length 5 m, depth 30 mm). The supply amount of the washing water was 45 ml per 1 g of the carbon fiber bundle, and the washing water was in a countercurrent to the running of the carbon fiber bundle.

As a result, when the fluff of this carbon fiber bundle was measured by the fluff number measurement method, it was good at 38 pieces / m, but the concentration of sulfate contained in the carbon fiber bundle was 83 ppm.

Comparative Example 2 Under the same conditions as in Example 1, 100 carbon fiber bundles that had been subjected to the electrolytic surface treatment were maintained at a tension of 0.1 g / d, and the washing water was 45 ml / g.
Was applied directly in the shower at a rate of, and washed. The carbon fiber bundle and the shower water are approximately 15
It was applied so as to make contact at an angle of degrees. As a result, the residual salt concentration was 1 ppm or less, and the number of fluff was 150 / m.

COMPARATIVE EXAMPLE 3 Under the same conditions as in Example 1, 100 carbon fiber bundles having been subjected to electrolytic surface treatment were run at a tension of about 0.1 g / d while running, and an outer cylinder was placed in a bathtub having a depth of 400 mm. Using a 300 mm diameter vibro washer, immersion length 1.5 m, washing water 45 ml / g
And washed. As a result, the residual salt concentration was 1 ppm or less, and the number of fluff was 300 pieces / m or more.

Example 2 The results of a test performed in Example 1 while changing the cleaning conditions are shown in Table 1 below. As evident in Table 1, the tension is 0.
03-0.5g / d, washing water temperature 15-60 ° C, washing water amount 10-100ml /
g, when the contact angle was 90 ° or less, a carbon fiber having good performance was obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual side view showing the steps of the method of the present invention (when one cleaning roller is used). FIG. 2 is a conceptual view of the same side (when two cleaning rollers are used). Description of reference numerals in the drawings 1: carbon fiber bundle, 2: cleaning roller, 3: cleaning water supply pipe,
4: Roller not supplied, 5: Cleaning water, α: Contact angle between cleaning roller and carbon fiber bundle

Claims (6)

(57) [Claims] 1. A method for cleaning carbon fiber bundles, comprising contacting water applied to a roller with a carbon fiber bundle on the roller surface when cleaning the carbon fiber. 2. The cleaning method according to claim 1, wherein the tension of the carbon fiber bundle is set to 0.03 to 0.5 g / d. 3. The method according to claim 1, wherein the amount of water is 10 to 100 ml / g of carbon fiber bundle. 4. The cleaning method according to claim 1, wherein a multi-stage roller is used. 5. The cleaning method according to claim 1, wherein the temperature of the cleaning water is 15 to 60 ° C. 6. The cleaning method according to claim 1, wherein the contact between the carbon fiber bundle and the roller is 90 degrees or less at the center angle of the roller.