JP2003155629A - Heat treatment apparatus for making carbon fiber flameproof and method for producing carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat treatment apparatus for making a carbon fiber flameproof, simultaneously satisfying equation of heat treatment for fireproof and improvement of productivity with an extremely small installation cost without damaging operability in a heat treatment chamber on the occurrence of abnormality such as yarn break. SOLUTION: This heat treatment apparatus for making the carbon fiber flameproof has an inside wall in the inside of a furnace wall to form the furnace wall into a double structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flameproofing heat treatment apparatus for carbon fibers for subjecting continuously running yarns to flameproofing heat treatment in an oxidizing atmosphere, and particularly to a uniform temperature distribution in the flameproof treatment chamber. The present invention relates to a flameproofing heat treatment device for carbon fibers, which is capable of uniformly treating a yarn with flameproofing treatment.

[0002]

2. Description of the Related Art Carbon fibers, particularly carbon fibers produced from acrylonitrile-based synthetic fibers as raw materials, can be made extremely high in tensile strength of 500 kg / mm ² or more and elongation of 2% or more. Therefore, application development as a material for aviation and space is in progress.

In order to produce such a carbon fiber, it is first necessary to subject the acrylonitrile-based synthetic fiber to flame resistance treatment in a heat treatment furnace in an oxidizing atmosphere at 200 to 300 ° C. This flameproofing process is the most time-consuming process in the carbon fiber manufacturing process, and in order to improve the productivity of the carbon fiber process, improving the productivity of the flameproofing process is an important matter.

A multi-step heat treatment is a generally used method for efficiently performing the flameproofing treatment, and a target treatment time can be obtained in a limited space by folding each roller through a plurality of rollers. . In addition, as the demand for carbon fibers has increased in recent years, the size of carbon fiber manufacturing equipment has been remarkably increased, and it has become necessary to dramatically increase the number of treated yarns in order to improve productivity.

This increase in the number of stages and the increase in size are likely to cause unevenness in the treatment temperature for the flameproofing treatment, which is a cause of nonuniformity of the flameproofing treatment. The unevenness of the flameproofing treatment temperature directly leads to non-uniform quality, which is an extremely important problem in the manufacturing process.

For this reason, many proposals have been made so far regarding improvement of productivity in the flameproofing process and flameproofing uniform treatment. For example, in the flame-proof treatment furnace disclosed in Japanese Patent Laid-Open No. 59-137510, multiple yarns are arranged in strips and placed on rolls to run in multiple stages in the flame-proof treatment furnace while hot air is blown into the heat treatment furnace. Is introduced in parallel with the traveling direction of the yarn, and hot air guide plates are arranged at each stage of the yarn, and the hot air is blown in zigzag with respect to the traveling direction of the yarn.

In addition to the above publication, Japanese Patent Application No. 10-3
In Japanese Patent No. 57138, it is proposed to provide a hot air inlet and a hot air outlet in the flameproofing furnace, and to provide a plurality of hot air circulation chambers and a heat retaining area on four sides of the furnace to make the processing temperature uniform.

[0008]

However, the heat treatment furnace disclosed in the above-mentioned Japanese Patent Laid-Open No. 59-137510 has a gas guide plate in a narrow processing chamber, so that the operability of the yarn is poor and the yarn breakage occurs. When an abnormality occurs, there is a problem that the hot air guide plate is damaged and sufficient treatment cannot be performed. Further, in Japanese Patent Application No. 10-357138, there is no operability problem, but there are a plurality of problems. Since the hot-air circulation chamber and the heat-retaining area are provided, the structure of the furnace becomes complicated, resulting in a new problem that enormous equipment cost is required for upsizing.

The present invention is intended to solve such a conventional problem and to make uniform the flameproof heat treatment without impairing the operability in the heat treatment chamber when an abnormality such as a yarn breakage occurs and at an extremely small equipment cost. It is an object of the present invention to provide a flameproof heat treatment apparatus that can satisfy both the improvement of productivity and the improvement of productivity.

[0010]

Means for Solving the Problems As a result of intensive studies made by the present inventors in order to achieve the above object, another wall is provided on the inner wall of the conventional heat treatment furnace to secure a passage for hot air. The fins that block the heat radiation from the outer wall of the furnace to prevent the temperature drop of the wall part and preferably change the direction of the hot air on the inner wall are provided at 90 ° with respect to the traveling direction of the hot air. It is preferable to install them in a direction so that hot air is blown between the stages.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a schematic vertical sectional view showing a flameproof heat treatment furnace apparatus which is a preferred embodiment of the present invention, and FIG. 2 is a schematic top plan view of the apparatus shown in FIG.

FIG. 3 is a schematic vertical sectional view showing a conventional flameproof heat treatment apparatus, and FIG. 4 is a schematic top plan view of the apparatus shown in FIG.

By the heater 4 and the circulation fan 5, the yarn 7 is heat-treated in multiple stages through each roller group 6 against the hot air circulating flow flowing from the upper stage to the lower stage to obtain the necessary flameproofing treatment time. However, in this case, if the number of treatment stages is increased for the purpose of improving productivity, the resistance of the yarn decreases the wind velocity of the hot air circulation to the lower stage, resulting in a difference in wind velocity between the upper and lower stages, resulting in heat generation due to flame resistance. There is a problem that a sufficient heat removing effect by the wind for suppressing the reaction cannot be obtained. If the exothermic reaction prevails against the heat removal effect by the wind, the yarn will break due to the runaway reaction, so the processing temperature will inevitably be lowered, leading to a deterioration in productivity. . Further, there is a problem that the progress of flameproofing is lowered due to the temperature drop in the furnace wall portion with respect to the central portion of the furnace due to heat radiation from the furnace wall (outer wall) 2. That is, it is important to solve these problems in multi-step heat treatment and increase in the number of yarns for improving productivity, and it is a difficult task.

On the other hand, in the flame-proof heat treatment furnace of the present invention, the inner wall 3 of the conventional outer wall is further installed to form a double wall so that the above two problems can be simultaneously satisfied at low cost. It is the one.

That is, when the inner side wall 3 is installed, a part of the circulating hot air flows between the inner side wall 3 and the conventional furnace wall (outer side wall) 2 to form a heat insulating layer by air.
It is possible to prevent the temperature drop of%. Further, the inside of the furnace side wall 2, that is, the roller group 6 side (the yarn running side)
By providing the fins 8 oriented in the direction of preferably 90 ° on the wall surface of the inner side wall 2 of the multi-stage, the circulating hot air from the upper part generates a flow which is converted to the direction between the multi-stage layers by the fins 8, and the multi-stage is produced. It became possible to prevent the wind speed from decreasing in the upper and lower stages due to the treatment. As a result, the wind speed can be secured to obtain the sufficient heat removal effect required during the yarn heat treatment, the production efficiency is significantly improved, and the temperature distribution in the heat treatment furnace is more uniform than in the conventional heat treatment furnace. Can be

The distance between the outer wall 2 and the inner wall 3 is 10
If it is cm or more, it is effective as a heat insulating effect, but if it is smaller than that, a sufficient heat insulating effect cannot be obtained. Further, the circulating air velocity of the furnace may be maintained as it is at the normal flameproofing air velocity, and it is not necessary to apply special conditions.

Furthermore, since the temperature unevenness is improved by installing the fins 8 on the inner wall 3 of the double wall furnace, the fins 8 are provided.
Is preferred. Its shape is 5 depending on the number of processing stages
The effect is exhibited by installing with a width of not less than cm, and the temperature difference between the upper and lower stages is improved by 0.3 ° C in each stage as compared with the case without fins. The 5 cm width in this case means the length of the fin protruding from the inner wall 3 to the yarn running side.

In the apparatus shown in FIGS. 1 and 2, the flame-proof heat treatment apparatus shows an example in which multiple yarns run in a horizontal sheet form. The running direction of the yarns may be horizontal or vertical, but the horizontal direction is preferred from the standpoint of ease of treatment when an abnormality such as winding of the yarns in the heat treatment furnace occurs. In this case, the circulation fan 5 allows high-temperature hot air to flow from the top to the bottom of the heat treatment chamber. The hot air is discharged from the heat treatment chamber, heated to a required treatment temperature by the heater 4 in the path, and is again guided by the circulation fan 5 to the heat treatment furnace 1 ′ to form a circulating hot air system.

A seal circulating flow having a wind direction opposite to the circulating flow of the heat treatment furnace main body is made to flow into the inlet and outlet of the multi-filament to prevent the main body circulating hot air from leaking out of the furnace. The treated yarn that has been subjected to hot air treatment in the furnace is folded back by the rollers arranged outside the seal circulation flow and guided again into the furnace, and is subjected to multi-stage flame-proof heat treatment by repeating this procedure. In this case, the traveling direction of the yarn may be either upwards → downwards or downwards → upwards, but in order to avoid the temperature at which the flameproof runaway reaction occurs, the lower part, which has a lower temperature than the upper part, is used as the yarn entrance It can be said that it is more efficient.

In the flame-resistant heat treatment apparatus, a double wall having a 5 cm fin on the yarn side is installed on the entire inner wall from the uppermost yarn path portion to the lowermost yarn path portion inside the inner wall 3 of the furnace. .

The fins 8 provided on the inner wall are arranged between each stage (between the rollers) so that the number of stages is the same as the number of stages, and the circulating airflow from the upper part is caused by the fins of each stage. A sufficient flameproofing heat treatment temperature can be obtained by changing the direction of the horizontal direction and entering.

When the circulating hot air of the flame-proof heat treatment apparatus is supplied from the upper part in a direction perpendicular to the yarn through the circulation duct, a part of the hot air flows between the double wall consisting of the outer wall 2 and the inner wall 3. Form a heat insulating layer with flowing air. Due to this heat insulating effect, heat radiation from the outer wall is reduced, and uniform flameproof heat treatment can be realized.

[0024]

EXAMPLES Examples of the present invention will be specifically described below with reference to comparative examples. The common conditions in the examples and comparative examples are: [common conditions] (1): heat treatment furnace type cross-flow hot air circulation furnace (2): heat treatment length length per stage of the heat treatment furnace in the running direction of the yarn. The length is 10 m and a total of 30 stages are processed. Total effective length is 300
m.

(3): Width of heat treatment furnace 3 m (4): Wind direction Vertical direction to yarn running direction (5): Heat treatment temperature 250 ° C. (6): Temperature measurement JIS K thermocouple (7): Wind velocity measurement Anemomaster hot wire anemometer (8) made by "Japan Kanomax Co., Ltd.": treated yarn single yarn denier 1.1 decitex (1 denier) 12000 filament yarn (9): treating speed 8.0 m / min [Example 1] In the flame-resistant heat treatment apparatus shown in FIGS. 1 and 2, the temperature and wind speed near the center of the furnace were 250 ° C. and
It was set to 1.0 m / s. Similarly, the temperature of the seal circulation and the wind speed were set to 250 ° C. and 2.0 m / s, and the temperature distribution in the flameproof furnace was measured. As a result, the temperature unevenness in the width direction of the heat treatment for flameproofing was within ± 2 ° C with respect to the average value in the entire width. Further, the temperature difference between the uppermost stage and the lowermost stage was within 6 ° C. The heat-treated flame-resistant yarn had a substantially uniform density in the entire width direction.

[Example 2] The same heat treatment furnace as in Example 1 was used except that the fins inside the double-walled furnace were removed.
As a result of performing the same heat treatment as in Example, the temperature unevenness in the full width direction was as small as within 2 ° C. with respect to the average value, but the temperature difference between the uppermost stage and the lower stage in the furnace was 8 ° C., but was treated. The density of the flameproof yarn could satisfy the target level value.

[Embodiment 3] The distance between the outer wall and the double wall is 5 cm.
Using a heat treatment furnace similar to the example except set to
As a result of performing the same heat treatment as in the example, the temperature difference between the uppermost stage and the lower stage in the furnace was as small as 6 ° C, but the temperature unevenness in the entire width direction was as large as 3.5 ° C with respect to the average value, and the treated flame resistance was high. The density unevenness of the synthetic yarn was slightly large.

[Comparative Example 1] In the same heat treatment furnace as in Example 1, a heat treatment furnace in which only the double wall was removed was used and the same treatment as in Example 1 was performed. As a result, the temperature unevenness in the entire width direction was averaged. The value was as large as 4 ° C, and the temperature difference between the uppermost layer and the lower layer was 10 ° C. The flame-resistant yarn obtained by this treatment had large density unevenness and the target density could not be obtained, so the treatment speed had to be reduced.

[0029]

The effect of the present invention is that even when an abnormality such as a yarn breakage occurs in the flame-proof heat treatment process of carbon fiber, the operability in the heat treatment chamber is not impaired, and the flame-proof heat treatment can be performed uniformly at an extremely small equipment cost. It will be possible to realize both productivity and productivity improvement at the same time.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a flameproof heat treatment apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic top plan view of the flameproof heat treatment apparatus of FIG.

FIG. 3 is a schematic vertical sectional view of a conventional flameproofing heat treatment apparatus.

FIG. 4 is a schematic top plan view of the flameproof heat treatment apparatus of FIG.

[Explanation of symbols]

1, 1 ': Flameproof heat treatment equipment 2: Outer wall 3: Double wall 4: heater 5: Circulation fan 6: Roller group 7: Treated yarn 8: Double wall fin

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4L037 CS02 CS03 CT11 CT12 CT40                       PA53

Claims (4)

[Claims] 1. A flameproofing furnace for carbon fibers, wherein an inner side wall is further provided inside the furnace wall, and the furnace wall has a double structure. 2. The flameproof heat treatment apparatus for carbon fiber according to claim 1, wherein the temperature decrease in the roller axial direction is 2 ° C. or less. 3. The carbon fiber according to claim 1, wherein a distance between the furnace wall and the inner wall is 10 cm or more, and fins for changing the direction of hot air are installed on the inner wall. Flame resistant heat treatment equipment. 4. A method for producing a flameproof yarn for carbon fibers, which comprises using the flameproofing heat treatment device for carbon fibers according to claim 1.