JPH10121337A - Carbon fiber and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain carbon fibers which are rich in micropores and useful for purifying a industrial liquid waste by carbonizing waste cotton fallen from the gauge of a carding machine without discarding the waste cotton. SOLUTION: Cotton fibers and/or fiber groups mainly containing cotton fibers less than 20mm long, occurring during the process of opening and picking or carding, are carbonized. The carbonized fibers in blocks can be readily converted to a variety of forms and can be readily mixed with pulp. The cotton fibers are indirectly heated at a temperature-increasing rate of 2-3 deg.C/min up to the maximum temperature of <=700 deg.C at a fill factor of 5-10 in a stationary bed type furnace whereby the fibers can be carbonized in uniform blocks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In the case of cotton-based industries, such as absorbent cotton manufacturing, the Japanese Pharmaceutical Affairs Law restricts 100% of cotton and the absence of foreign substances. Too much of the elimination causes the cotton fibers to fall off.

[0002] The amount of fallen waste that does not become a product is
It reaches about 15%, depending on the locality. We examined various uses, but most of them are incinerated or disposed of. TECHNICAL FIELD The present invention relates to carbon fibers obtained by carbonizing tow which has been treated as a nuisance and a method for producing the carbon fibers.

[0003]

The production method relating to carbonization is as follows.
It has a long history, such as producing charcoal from wood and using it as fuel, and many technologies have been inherited.

[0004] In recent years, a large number of products have been found in a continuous production format or using pitch-based or acrylic fibers as raw materials.

[0005] In the present invention, the fixed hearth type was selected instead of the continuous type and the effective utilization of cotton-based tochiwa.

The reason why cotton is used as a raw material is that cotton naturally has pores called lumens and has a high specific surface area. It has the ability to retain water vapor and the like. It is used for underwear because it adsorbs human sweat. In addition to that, it is also from the environmental point of view of effective use of waste.

[0007] The reason why the fixed hearth type is adopted is that the continuous product has the same shape as the carbonized product. For example, a thread-like object is a thread, and a cloth-like object is a cloth.

[0008] For that purpose, if it is to be changed to another shape, it is necessary to once break the prototype. For example, when blending with pulp, labor such as breaking down the carbonized fibers of the thread-like cloth and mixing with the pulp is required.

[0009] In the case of the fixed hearth type, since it is formed in a lump, it is easy to arbitrarily convert it into various shapes. However, in the case of the fixed hearth type, there is a problem as to whether heat conduction to the raw material is uniform.

[0010] To solve this problem, indirect heating, filling ratio,
The present invention has been completed by taking measures such as a heating rate and a maximum temperature.

[0011]

The present inventor has studied the uniform heat conduction in the carbonization process based on the above-mentioned problem awareness, and has completed the present invention.

The gist of the present invention is as described in the appended claims.

[0013] In the present invention, the cotton tail is
Cotton that does not fall out of the machine during the process of blended cotton or carding and does not become a product. Things are mostly.

The indirect heating is to put a container filled with waste into a furnace and to heat the container from the outside with a heat source such as gas.

The container can be easily taken out of the furnace. The pressure of the gas is designed so that it can be variously changed depending on the position of the container.

When the amount of filling the container is increased, the temperature distribution varies greatly, and when the amount is decreased, the yield of carbon fibers is deteriorated. Most preferably, as described in the claims of the present application, the space ratio is 5 to 1 for the foreground 1.
In the range of 0, the yield is good and a carbon fiber having a large specific surface area can be obtained.

Theoretically, the yield of carbon is about 40%, judging from the molecular weight, but the most preferable yield could be obtained in the range of 1: 5 to 10, more precisely 1: 8. .

Another factor that affects the yield and the specific surface area is the rate of temperature rise. When the temperature in the vessel is rapidly increased, the pores collapse and the yield is significantly deteriorated, and in an atmosphere of indirect heating in which the specific surface area is reduced, the rate of temperature increase is an important factor, as described in the claims of the present application. It is desirable to raise the temperature as slowly as possible at 2 ° C./min to 3 ° C./min.

The maximum temperature in the container is desirably 700 ° C. or lower as described in the claims of the present application.
When the temperature reaches from 250C to 250C, it is desirable to stop the temperature rise for a certain period of time and then gradually raise the temperature.

By doing so, many micropores are formed, and a carbon fiber having a large specific surface area and a high yield can be obtained.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

[Example 1] The filling ratio (the ratio of the inner volume of the container to the weight of the container 1) of the container in the hearth of the fixed hearth furnace was 1: 3, 1: 5, and 1: Fill the container so as to obtain four levels of 8, 1:10, put the container in a furnace, and raise the temperature to 2
The carbon fiber was manufactured under the manufacturing conditions of 700 ° C./min and the maximum temperature of 700 ° C. (or more).

The product test results were evaluated in terms of yield and specific surface area.

In the test method, the yield was determined from the difference between the weight before heating and the weight after heating.

The specific surface area was calculated by applying a BET method to a nitrogen adsorption isotherm at a liquid nitrogen temperature using a specific surface area pore distribution analyzer Model 2100-02 manufactured by Micromeritix Corporation. Table 1 shows the results.

[0025]

[Table 1]

Example 2 In the same manner as in Example 1, the temperature was raised at a rate of 2 ° C./min, 3 ° C./min, 5
° C / min, 8 ° C / min, filling ratio 1: 8, maximum temperature 70
Carbon fibers were manufactured under the manufacturing conditions of 0 ° C. (or more constant). Table 2 shows the results.

[0027]

[Table 2]

Example 3 Carbon fibers were produced in the same manner as in Example 1, but in Example 3, the temperature was raised for 30 minutes when a certain temperature was reached during carbonization, and thereafter, An experiment was conducted in which carbonization was continued up to the maximum temperature.

As the factors, the temperature at which the temperature increase was temporarily stopped, and the level was 150 ° C., 200 ° C., 250 ° C., 300 ° C.
° C, filling ratio 1: 8, heating rate 2 ° C, maximum temperature 70
0 ° C. was kept constant. Table 3 shows the results of the carbon fibers manufactured under the above manufacturing conditions.

[0030]

[Table 3]

[Embodiment 4] In the same manner as in Embodiment 1, the highest temperature was used as a factor, and the temperature was set at 250 ° C., 400 ° C., 55
0 ° C, 700 ° C, filling ratio 1: 8, heating rate 2 ° C /
The carbon fiber was manufactured under the manufacturing conditions of a minute (or more constant). Table 4 shows the results.

[0032]

[Table 4]

[0033]

The carbon fiber of the present invention relates to the effective use of tochiwata, which has been disposed of as waste in the cotton industry, and carbonized carbon fiber is used for coloring wastewater and reducing the concentration of organic matter. Contact with high factory wastewater is effective in decoloring, reducing BOD, and removing harmful gases.

[0034] The waste, which has been regarded as a troublesome thing, is a useful invention that has been recycled into a natural environment-friendly product.

Claims (7)

[Claims] A carbon fiber obtained by carbonizing cotton having a fiber length of 20 mm or less and / or a fiber group mainly composed of cotton. 2. The carbon fiber according to claim 1, wherein the carbon fiber is not a continuous shape but is a mass that easily collapses. 3. The carbon fiber according to claim 1, wherein the carbon fiber is indirectly heated and carbonized in a volume ratio of a container for filling the fiber group with respect to a weight of 1 of the fiber group within a range of 5 to 10. Manufacturing method. 4. The method for producing carbon fiber according to claim 3, wherein the carbonization is performed while maintaining the temperature rise rate of carbonization at 2 ° C./min to 3 ° C./min. 5. The method for producing carbon fibers according to claim 3, wherein the carbonization is performed at a maximum temperature of 700 ° C. or less. 6. A method for detecting the oxygen concentration in a container filled with a fiber group, opening and closing a fan door in contact with outside air based on the detection result, and carbonizing while controlling the oxygen concentration in the container. A method for producing a carbon fiber according to any one of claims 3 to 5, characterized in that: 7. The method for producing carbon fibers according to claim 3, wherein the temperature rise is temporarily stopped when the carbonization temperature reaches 150 ° C. to 250 ° C.