JP2628658B2 - Method and apparatus for infusibilizing pitch-based carbon fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention enables uniform infusibilization treatment in the production of general-purpose carbon fibers using petroleum-based and coal-based pitch as raw materials, and has high production efficiency and high energy efficiency. The present invention relates to an economical method and apparatus for infusing pitch-based carbon fibers.

(Prior Art) Conventionally, when producing a carbon fiber by melt-spinning a petroleum-based or coal-based pitch, an infusibilization treatment is performed before firing the spun pitch fiber.

Examples of the infusibilizing method include a method of winding spun pitch fibers with a roller and a method of suspending fibers on a tray having a U-shaped cross section (Japanese Patent Publication No. 58-53085 and Japanese Patent Application Laid-Open No. 59-150114).
Japanese Patent Application Laid-Open No. 58-5019) or a net conveyor system in which an infusibilization reaction is carried out while transferring a net conveyor on which pitch fibers are deposited (Japanese Patent Application Laid-Open No. 58-5019). 55-90621 and JP-A-60-1
67928) and the like.

(Problems to be Solved by the Invention) However, in the roller winding method, since the pitch fiber after melt spinning is weak and weak in both strength and elongation, the winding (running) speed cannot be increased. There are problems that the production efficiency is poor and that it takes time and effort to repair when the yarn breaks.

Further, the above-mentioned JP-B-58-53085 and JP-A-59-150114
In the known technique disclosed in the above-mentioned publication, a bar is passed over a tray having a U-shaped cross section, pitch fibers are suspended from these bars, and the tray is sequentially put into an infusibilizing furnace and a firing furnace. In addition, since the permeation of the processing gas into the fiber is only a diffusion action, the bulk density of one tow fiber cannot be large, and the oxidation unevenness due to the temperature distribution of the tray unless the gas flow inside the tray is made uniform. Therefore, it is necessary to leave a gas flow path (space) inside the tray, and the amount of fiber that can be filled in the tray is at most 3 kg /
there is a problem that becomes smaller and m ^3. Furthermore,
In addition to deteriorating the properties of the fiber portion in contact with the bar, there is also the problem that the handling of applying the fiber to the bar requires extra time and expense.

Further disclosed in the above-mentioned JP-A-58-5019,
In a known technique, a spun pitch fiber is filled into a container having an air hole at a high bulk density, and the container is sequentially put into an infusibilizing furnace and a firing furnace. When the pressure loss due to the ventilation increases, there is a problem that the damage to the lower part of the fiber layer and the poor oxidation state become remarkable. Further, since the heating amount of the container itself is not negligible, neither the production efficiency nor the energy efficiency is high.

Furthermore, Japanese Patent Application Laid-Open No. 55-90621 and Japanese Patent Application Laid-Open
No. 67928, disclosed in, for example, in the known technology of sequentially depositing the pitch fibers on a continuously running net conveyor and passing through an infusibilizing furnace and a firing furnace, a wave is applied to the pitch fibers in a net shape and There is a problem that the density of the fiber group is increased by gravity (self-weight), and in addition to local damage, the oxidation state is generally poor. This tendency becomes more remarkable when a measure such as suction of an oxidizing gas through the fiber layer is taken to increase production efficiency by forcibly ventilating the fiber layer.

As described above, according to the prior art, in order to obtain a uniform product, both the production efficiency and the energy efficiency have to be lowered, and the resulting carbon fiber must be expensive.

Therefore, an object of the present invention is to provide a technique for uniformly infusifying pitch fibers with high production efficiency and energy efficiency.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the inventors of the present invention set the concentration of the oxidized state failure and damage due to gravity (self-weight) and ventilation pressure under the fiber layer during the infusibilizing treatment in the conventional technique. As a result of intensive examination focusing on the point that, by inverting the fiber layer at regular time intervals and by uniformly blowing the processing gas to the fiber layer at least in the processing stage after the fiber layer mat formation processing stage from above and below It has been found that the ventilation pressure becomes uniform up and down with respect to the fiber layer, and that the contact wear of the fiber layer with the net conveyor surface is minimized, and as a result, uniform infusibilization treatment and improvement in production efficiency can be achieved. Thus, the present invention has been completed.

That is, the present invention, when subjecting pitch fibers obtained by melt-spinning petroleum-based or coal-based pitches to infusibilization treatment, depositing the pitch fibers on a horizontal net conveyor,
Simultaneously applying an oxidizing gas to the fiber layer from above and below at least in a processing stage after the fiber layer mat forming processing stage, while continuously moving the formed fiber layer to be processed into the infusibilizing furnace. A method for infusibilizing pitch-based carbon fibers, or depositing the pitch fibers on a horizontal net conveyor and forming at least a fiber layer mat while continuously advancing the formed fiber layer to be treated in an infusibilizing furnace. In a processing stage after the processing stage, an oxidizing gas is simultaneously blown from above and below to the fiber layer, and the fiber layer is inverted at least once in a furnace. It relates to a melting method.

Further, the present invention provides an apparatus for performing infusibilization treatment on pitch fibers obtained by melt-spinning petroleum or coal pitch, wherein the infusible furnace heating chamber and the pitch fibers are deposited and run in the heating chamber. And a nozzle capable of simultaneously spraying an oxidizing gas to the upper surface and the lower surface of the fiber layer in a heating chamber at a processing stage after the fiber layer mat forming processing stage. An infusibilizing device for pitch-based carbon fibers, characterized in that, or at least two or more infusibilizing furnace heating chambers in the vertical direction, and run through each heating chamber by depositing the pitch fibers,
And a net conveyor arranged so that the formed fiber layer to be processed is reversed for each heating chamber, and at least a heating chamber in a processing stage after the fiber layer mat forming processing stage, The present invention relates to an apparatus for infusibilizing pitch-based carbon fibers, comprising: a nozzle capable of simultaneously blowing an oxidizing gas from a lower surface.

The infusibilizing treatment of the carbon fiber of the present invention will be described in more detail below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing the process of the present invention. In this figure, pitch fibers 2 continuously formed from a spinning nozzle 1 of a melt spinning machine are deposited on a belt conveyor 3 provided at a lower portion of the spinning machine to form a fiber layer 4. The fiber layer 4 enters the infusibilizing furnace heating chamber 7 by the net conveyor 6 and thereafter passes through each heating chamber while the fiber layer 4 is smoothly inverted by the guide 8 as the net conveyor 6 is sequentially inverted. The infusible fiber layer 14 having an oxidized state is sent to a subsequent baking furnace by a transfer conveyor 15.

The atmosphere in the infusibilizing furnace is used alone or mixed with air, NOx, SOx, and other oxidizing gases, and the temperature is 100
Within the range of ~ 400 ° C. By making the fiber layer 4 stay in the infusibilizing furnace for 1 to 6 hours, infusibilization of the pitch-based carbon fibers can be performed.

FIG. 2 shows a detailed view of the infusibilizing apparatus according to the preferred embodiment of the present invention. In FIG. 2, the fiber layer 4 transferred to the infusibilizing furnace inlet 5 is moved through the heating chamber by the net conveyor 6 and is blown from the blowing nozzles 9 installed above and below the net conveyor 6 on the upper and lower surfaces of the mat-like fiber layer 4. At the same time, the gas is blown by the oxidizing gas. However, in the first stage, only the upper blowing nozzle is provided for forming the fiber layer mat. The movement of the fiber layer for each stage can be smoothly performed by the guide 8. Further, the speed of the net conveyor 6 at each stage can be adjusted by the driving roller 10 and the rotating roller 11 so that a predetermined residence time is obtained.

FIG. 3 is a cross-sectional view of the infusibilizing device shown in FIG. 2 perpendicular to the flow direction. The oxidizing gas sent from the fan box 13 shown in this figure is preheated to a predetermined temperature by a heat exchanger (not shown) installed in a blow-out box 13 installed above and below the chamber to be heated, The air is rectified from the blowing nozzle 9 and blown onto the fiber layer 4.

(Operation) Since the fiber infused as described above is inverted at each stage, the bulk density of the lower layer is not increased by its own weight, and a uniform bulk density state is maintained. In addition, since the oxidizing gas is blown from above and below at least in the processing stage after the fiber layer mat forming processing stage, the penetration and diffusion of this gas into the fiber are prompt, and the difference between the oxidation state of the fiber surface and the inside is also reduced. In addition, the contact between the lower surface of the fiber layer and the net conveyor is minimized by the gas flow from below, and no local damage of the lower part of the fiber layer is observed. The characteristics of the carbon fiber obtained by firing the infusible fiber are smaller than those of the conventional net conveyor system, especially when the basis weight of the fiber layer is increased, and the dispersion of the infusibilize in the upper, middle and lower layers is small. It is.

The bulk density and thickness of the fiber layer can be arbitrarily selected by the operation before charging the infusibilizing furnace. However, if these are too small, the production efficiency is reduced. Runaway reaction and local fusion phenomenon are likely to occur. Therefore, specifically, the bulk density is 10-30
It is preferable that the thickness be in the range of 10 to 100 mm in kg / m ³ .

The net conveyor running in the furnace can perform infusibility treatment only on the lower side where the fiber layer is loaded, but the fiber layer for blowing the oxidizing gas from the vertical direction may be locally disturbed, It is preferable to install a net conveyor on the upper side of the fiber layer in order to smoothly move the fiber layer, and to carry out the treatment while sandwiching the fiber layer between two net conveyors.

(Examples) Next, the present invention will be described with reference to Examples and Comparative Examples.

Example 1 Thermal reforming of coal tar pitch was performed, and the softening point was 248 ° C.
Was obtained. Using this pitch, the number of holes
The melt spinning was performed by a distant spinning machine having 360. The spun pitch fibers were sequentially deposited to obtain a fiber layer having a bulk density of 20 kg / m ³ and a thickness of 50 mm. The fiber layer was kept at 100 to 320 ° C. for 2 hours in an air atmosphere containing 1% by volume of NO ₂ using the infusibilizing apparatus of the present invention, during which the fiber layer was inverted three times.

The infusibilized fiber layer thus obtained is introduced into a conventional belt-conveyor-type sintering furnace, sintering is performed at 400 to 950 ° C. for 1 hour in an N ₂ atmosphere, and then cooled to 200 ° C. and then out of the furnace Sent out.

The carbon fiber obtained in this manner has no fusion of the fiber layer, no local damage or pressure bonding, and the average single yarn properties are 18 mm in diameter.
The strength is 72 kg / mm ² and the elastic modulus is 3.3 ton / mm ² at μm. Also, as shown in Table 1 below, the dispersion of the physical properties of the upper, middle and lower parts of the fiber layer is small, and the average single yarn strength is high. 5kg / mm
^It was within ^two .

Comparative Example 1 The same type of pitch fiber layer as in Example 1 was introduced into a conventional net conveyor type infusibilizing furnace, and was infusibilized under the same conditions as in Example 1, followed by firing.

In the carbon fiber thus obtained, the crimping phenomenon at the lower part of the fiber layer was remarkably observed, and the net conveyor wave was left as a trace. The physical properties of the single yarn showed a strength of 63 kg / mm ² and an elastic modulus of 3.2 ton / mm ² at an average yarn diameter of 18 μm. However, as shown in Table 1, the dispersion between the upper and lower portions of the fiber layer was large, and the average single yarn strength was high. A difference of about 20 kg / mm ² was observed.

Examples 2 and 3 Pitch fibers obtained in the same manner as in Example 1 were sequentially deposited, and a fiber layer having a bulk density of 100 kg / m ³ and a thickness of 5 mm and a bulk density of 10 k were used.
A fiber layer having a thickness of g / m ³ and a thickness of 100 mm was obtained. Using the infusibilizer of the present invention, these fiber layers were allowed to stay at a temperature of 100 to 320 ° C. for 2 hours in an air atmosphere containing 2% by volume of NO ₂ , during which the fiber layers were inverted three times. .

The infusible fiber layer thus obtained was carbonized in the same manner as in Example 1. Example 2 is shown in Table 2 below.
4 shows the results of single-filament physical property measurement of the carbon fibers obtained in Examples 1 and 2.

As is clear from Table 2, Examples 2 and 3 were used.
As in Example 1, the physical properties of the fiber layer showed little variation in the upper, middle, and lower portions of the fiber layer, and the average single yarn strength was 5 kg / mm ^2.
Within the range.

(Effects of the Invention) By supplementing the disadvantages of the net conveyor type infusibilizing furnace, which does not require the most means for transporting fibers, with the method and apparatus of the present invention, it becomes possible to produce uniform carbon fibers with good production efficiency. Was. Also, as compared with a method using a breathable container or a U-shaped toilet, it is possible to save the trouble of filling the container or the toilet with the fiber and taking out the fiber, and also reduce the amount of heat absorbed by the container or the toilet. Furthermore, since the furnace volume should be large enough to process the fiber layer, the furnace volume can be made smaller than when using a container or toilet, and the furnace itself can be made compact. It is very advantageous from the viewpoint.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the infusibilizing process of the present invention, FIG. 2 is a cross-sectional view along a flow direction showing a preferred embodiment of the infusibilizing apparatus of the present invention, and FIG. 3 is a flow of the apparatus shown in FIG. It is sectional drawing perpendicular to a direction. DESCRIPTION OF SYMBOLS 1 ... Spinning nozzle, 2 ... Pitch fiber 3 ... Belt conveyor, 4 ... Fiber layer 5 ... Infusible furnace inlet, 6 ... Net conveyor 7 ... Infusible furnace heating chamber, 8 ... Guide 9 ... ... Blow-out nozzle, 19 ... Driving roller 11 ... Rotating roller, 12 ... Blow-out box 13 ... Fan box, 14 ... Infusible fiber layer 15 ... Transfer conveyor

Continuing on the front page (72) Inventor Minoru Yoshida 1 Kawasaki-cho, Chiba-shi, Chiba Pref. Kawasaki Steel Corporation Research and Technology Headquarters (72) Inventor Susumu Nakai 1- Kawasaki-cho, Chiba-shi Chiba Pref. Within the headquarters (72) Inventor: Mamoru Kanshita 1 Kawasaki-cho, Chiba-shi, Chiba Pref. Kawasaki Steel Corporation Research and Technology Headquarters (72) Inventor: Shigeru Kinomoto 1-6-6, Shimokosaka, Higashi-Osaka-shi, Osaka Hajime Oura 1-127 Yaogi, Yao-shi, Osaka (56) References JP-A-62-177217 (JP, A) JP-A-62-177226 (JP, A)

Claims (6)

(57) [Claims] When a pitch fiber obtained by melt-spinning a petroleum or coal pitch is subjected to an infusibilizing treatment, the pitch fiber is deposited on a horizontal net conveyor, and the formed fiber layer to be treated is continuously formed. The pitch-based carbon fiber, characterized in that the oxidizing gas is simultaneously blown from above and below to the fiber layer at least in a processing stage after the fiber layer mat forming processing stage while being advanced into the infusibilizing furnace. Infusibilization method. 2. A pitch fiber obtained by melt-spinning a petroleum-based or coal-based pitch, in which the pitch fiber is deposited on a horizontal net conveyor, and the formed fiber layer to be processed is continuously formed. Oxidizing gas is simultaneously blown from above and below to the fiber layer at least in the processing stage after the fiber layer mat forming processing stage while being advanced into the infusibilizing furnace, and at least once in the furnace. A method for infusing pitch-based carbon fibers, comprising inverting a fiber layer. 3. The bulk density of the fiber layer to be treated is 10 to 100 kg / m ^3.
3. The method according to claim 1, wherein said thickness is 3 to 100 mm. 4. An apparatus for subjecting pitch fibers obtained by melt-spinning petroleum or coal pitch to infusibilization treatment,
An infusibilizing furnace heating chamber, a net conveyor that is arranged to deposit the pitch fibers and run in the heating chamber, and in the heating chamber, at least a fiber layer mat forming processing step and a processing step after the fiber layer mat forming step. And a nozzle capable of simultaneously blowing an oxidizing gas onto the upper surface and the lower surface. 5. An apparatus for subjecting pitch fibers obtained by melt-spinning petroleum or coal pitch to infusibilization treatment,
At least two or more infusibilizing furnace heating chambers in the vertical direction, and are arranged so that the pitch fibers are deposited and run in each heating chamber, and the formed fiber layer to be processed is inverted for each heating chamber. And a nozzle capable of simultaneously blowing an oxidizing gas from the upper and lower surfaces of the fiber layer to be processed in a heating chamber in a processing stage at least after the fiber layer mat forming processing stage. An infusibilizing device for pitch-based carbon fibers. 6. The apparatus according to claim 4, wherein the net conveyor running in each heating chamber has a double structure sandwiching the fiber layer to be processed from above and below.