JPH0737690B2 - Pitch fiber infusible furnace - Google Patents

Description

TECHNICAL FIELD The present invention relates to an infusibilizing furnace for bulky matt pitch fibers.

Prior art and its problems As a continuous infusibilizing method for bulky matt pitch fibers obtained by melt spinning naphtha pitch or coal tar pitch (hereinafter simply referred to as fiber mat unless otherwise required) A method has been proposed in which an oxidizing gas is forcibly passed through in the thickness direction of the laid fiber mat (JP-A-60-167928). However, in this method, the fiber mat is bulky (thickness
In the case of about 30 to 300 mm), the temperature difference in the vertical direction of the fiber mat becomes large and uniform infusibilization cannot be performed. In order to reduce the temperature difference in the vertical direction, when the circulation amount of the heating gas is increased, the fiber mat is pressed onto the conveyor by the gas blown downward from above, and the bulk density of the mat increases, The fibers are fused to each other, and runaway reaction due to heat generation is likely to be induced. In such a case, there is a problem that the fiber is damaged and the physical property value of the carbonized fiber is lowered.

JP-A-62-33823 proposes a method of infusibilizing a fiber mat suspended on a bar. However,
In the case of a bulky fiber mat, the entanglement of pitch fibers with each other is relatively insufficient, so that the fiber mat suspended on the bar stretches or breaks. There is also a problem in that it is practically difficult to secure an air volume that causes forced convection inside the fiber mat.

Means for Solving the Problems As a result of intensive studies in view of the current state of the art as described above, the present inventor has blown a fiber mat placed on a conveyer conveyor made of a breathable belt from below to above. By moving in an oxidizing atmosphere while raising, and by providing a mechanism for holding the fiber mat three-dimensionally above the conveying conveyor made of the breathable belt, a uniform oxidizing heating gas flow is forcibly provided in the fiber mat. It has been found that the problems of the prior art are greatly alleviated if they occur.

That is, the present invention provides an infusible furnace as follows: A bulky matt pitch fiber is placed on a conveyor made of a breathable belt, and the pitch fiber is moved upward from below by an oxidizing heating gas. An infusible furnace for infusibilizing pitch fibers by moving them in an oxidizing atmosphere while blowing them up, characterized in that a conveyor provided with a three-dimensional holding mechanism for pitch fibers is provided above the conveyor. And infusible furnace.

To adjust the amount of heating gas that passes through the pitch fiber so that a portion of the oxidizing heating gas blown upward from below to infusibilize the pitch fiber is bypassed and escaped upward without passing through the pitch fiber. The infusible furnace according to the above item, which is provided with the air flow rate adjusting mechanism.

The present invention will be described in more detail below with reference to the embodiments shown in the drawings.

FIG. 1 is a vertical sectional view showing an outline of an infusible furnace according to the present invention. The fiber mat is sent in the direction of the arrow (3) while being placed on the conveyor (1) made of a breathable belt. The infusible furnace is divided into a plurality of chambers (5),
(5) It is divided into ... In each chamber (5), the oxidative heating gas (7) flowing from the lower side to the upper side in the fiber mat is heated while penetrating the fiber mat and floating it, and then the side of the conveyor (1). One descends in the direction of the arrow (9) and circulates again in the same manner. Above the transfer conveyor (1), provided is a conveyor (11) that moves in the same direction as the transfer conveyor and has a mechanism for holding the pitch fibers three-dimensionally. Moreover, (13) shows an exhaust system.

In the present specification, the expression "holding the pitch fibers three-dimensionally" simply holds the upper surface of the fiber mat lifted by the oxidative heating gas circulating from the lower side to the upper side in a planar or two-dimensional manner. It means to hold from the inside of the fiber mat as well. The temperature of the oxidizing heating gas is preferably about 50 to 250 ° C.

The mechanism for holding the fiber mat in three dimensions will be described in detail below.

FIG. 2 shows an example of a conveyor (11) having a mechanism for holding pitch fibers three-dimensionally. A needle-like fixture (17) having a plurality of small protrusions is provided on the entire surface of the conveyor (11). The needle-like fixture (17) penetrates into the fiber mat lifted by the heating gas (7) flowing through the fiber mat (19) from the lower side to the upper side, and resists the force generated by the fluid oxidizing heating gas. Then, since the fiber mat is held, the fiber mat is held at a uniform bulk density. Thus, unlike the prior art, the fiber mat (19) is forcibly heated under uniform conditions, so that fusion of the fibers with each other, runaway of reaction due to internal heat storage of infusible reaction heat, etc. No failure occurs. The conveyor (1
The form of 1) is not particularly limited, and, for example, as shown in the drawing, the needle-like fixtures (17) are attached to the bars (21) provided at regular intervals in the direction perpendicular to the traveling direction of the fiber mat (19). Examples thereof include those attached, or those in which a similar needle-like fixing device is attached to the net conveyor (not shown). Also,
The needle-like fixing device (17) is not particularly limited as long as it can enter the inside of the fiber mat and can hold the fiber mat against the force of the flowing oxidative heating gas.

The three-dimensional holding mechanism for the fiber mat is not particularly limited, and any one other than the above examples can be used as long as it can hold the fiber mat in a disentangled state without compaction.

FIG. 4 shows a cross-sectional view of the single compartment (5) shown in FIG. Reference numeral (25) represents an oxidizing heated gas circulation path equipped with a blower (27), and (31), (31), etc. represent heaters. In the present invention, as also shown in FIG. 3, forcible air flow rate adjusting plates (33) that can move in a direction orthogonal to the traveling direction of the conveyor (11) are moved to provide heating gas bypasses provided on both sides. By adjusting the widths of the openings (35) and (35) of the fiber to control the air volume passing through both sides, the circulation volume of the oxidizing heating gas and the forced air volume in the fiber mat are balanced, and the fiber mat It is possible to suppress the pressing of (19) against the conveyor (11) and to appropriately float the fiber mat. This adjustment of the opening width is usually B / A × 100 (%) when the total width of the fiber mat (19) is A and the opening width (total value of the widths of the openings (35) and (35)) is B. It is preferable that the aperture ratio is defined as 0 to 10%.

The fiber mat treated by the infusibilizing furnace of the present invention can be subsequently carbonized according to a conventional method to form carbon fiber, or further subjected to graphite treatment to form carbonized fiber.

Effects of the Invention According to the present invention, the following remarkable effects are achieved.

(A) Since the three-dimensional holding mechanism of the fiber mat is provided, the bulk density of the fiber mat does not become non-uniform, so that the oxidizing heated gas is uniformly supplied into the fiber mat,
Also, the heat of reaction is easily removed. Therefore, problems such as local overheating of the fiber mat, fusion of the pitch fibers to each other, runaway reaction due to internal heat storage of the infusible reaction heat, etc., which are seen in the prior art, do not occur.

As a result, stable continuous operation is performed and mass production becomes possible.

(B) Since the fiber mat is forcibly conveyed by the three-dimensional holding mechanism, it is less likely to cause cutting, meandering, etc. as compared with the conventional technique, and stable production is possible.

(C) By adjusting the size of the openings provided on both sides of the conveyor, it is possible to balance the circulation amount of the oxidizing heating gas and the forced air flow in the fiber mat.
There is no need to apply excessive wind pressure.

Examples Examples will be shown below to further clarify the features of the present invention.

Example 1 Coal tar-based air blown pitch (softening point 280 ° C., QI4
(0%) was blown by a vortex method, deposited on a breathable mesh conveyor, and suctioned to collect a bulky continuous fiber mat. This fiber mat had a thickness of 150 mm and a basis weight of 1000 g / m ² .

The obtained fiber mat is fed into a hot air circulation type infusible furnace of the type shown in FIG. 1, while the fiber mat is three-dimensionally held by a conveyor equipped with a needle-shaped fixture of the type shown in FIG.
The temperature was raised from 150 ° C. to 325 ° C. over 65 minutes in an air atmosphere under the conditions of a circulating wind velocity of 0.8 m / sec and an opening ratio of 0% to infusibilize it.

At this time, the fiber mat was lifted by the wind force and was in a state of being sufficiently pierced into the needle-shaped fixture above the conveyor, and when the pressure difference between the upper and lower sides of the fiber mat was measured in this state, it was about 5 mm of water column. .

The temperature difference between the upper surface and the lower surface of the fiber mat at the temperature of 200 ° C, 250 ° C, and 300 ° C during the infusibilization is 7
It was extremely small at ℃, 9.5 ℃ and 12 ℃.

Furthermore, the oxygen content of the obtained infusible fiber is 6.8% in the upper, middle and lower parts of the mat, respectively.
It was 7.2% and 7.0%.

In this way, the fiber mat was made infusible for 7 consecutive days, but no problems such as runaway reaction due to heat generation and mat breakage occurred at all, and stable operation was possible.

The infusible fiber obtained above was heated to 930 ° C. in a continuous carbonization furnace in a nitrogen atmosphere (residual oxygen concentration of 50 ppm or less) over 23 minutes to obtain a carbon fiber.

Table 1 shows the mechanical properties of the obtained carbon fibers.

As is clear from the results shown in Table 1, the physical properties of the carbon fibers obtained are almost constant regardless of the position of the mat. This indicates that the infusibilization of the fiber mat was performed uniformly.

Example 2 The continuous infusibilization of the fiber mat was performed in the same manner as in Example 1 except that the circulating air flow rate was 2.4 m / sec and the aperture ratio was 8%.

At this time, the fiber mat was lifted by the wind force and was in a state of being sufficiently pierced into the needle-shaped fixture above the conveyor, and when the pressure difference between the upper and lower sides of the fiber mat was measured in this state, it was about 5 mm of water column. .

The temperature difference between the upper surface and the lower surface of the fiber mat at the temperature of 200 ° C, 250 ° C and 300 ° C during the infusibilization is 2 respectively.
C., 3.5.degree. C., and 5.degree. C., which were smaller than those in Example 1.

Furthermore, the oxygen content of the obtained infusible fiber is 6.9% in the upper, middle and lower parts of the mat, respectively.
It was 7.1% and 7.0%.

In this way, the fiber mat was made infusible for 7 consecutive days, but no problems such as breakage of the runaway reaction mat due to heat generation occurred at all, and stable operation was possible.

Comparative Example 1 The same fiber mat as used in Example 1 was infusibilized according to Example 1 without the use of a conveyor equipped with needle-shaped fixtures. However, the circulating air volume was 0.2 m / sec, and the pressure difference between the upper and lower sides of the fiber mat was about 0.5 mm so that the fiber mat would not be lifted by the wind force.

The temperature difference between the fiber mat and the upper and lower surfaces at the infusibilizing temperature settings of 200 ℃, 250 ℃ and 300 ℃ is 14 ℃ and 20 ℃, respectively.
And was extremely large at 27 ° C.

Further, the oxygen content of the infusibilized fiber obtained at the infusibilizing set temperature of 325 ° C. varied greatly at 6.5%, 8.1% and 7.4% in the upper part, middle part and lower part of the mat, respectively. This is because the reaction heat generated during infusibilization is not sufficiently removed.

In this way, the fiber mat was made infusible for 7 consecutive days, but the runaway reaction due to heat generation frequently occurred from the beginning, and the mat was often broken.

The infusible fiber obtained above (infusible setting temperature 325 ° C.) is carbonized in the continuous carbonization furnace in the same manner as in Example 1,
Carbon fiber was obtained.

Table 2 shows the mechanical properties of the obtained carbon fiber.

As is clear from the results shown in Table 1, the carbon fibers obtained have large variations in strength and elongation as compared with the carbon fibers of Example 1, and their values are also low. These results also show that the infusibilization of the fiber mat was not performed uniformly.

Example 3 A fiber mat similar to that used in Example 1 was circulated with an air flow of 1.2 m.
The temperature was raised from 150 ° C. to 325 ° C. over 35 minutes in an air atmosphere containing 1% of nitrogen dioxide under the conditions of / sec and an aperture ratio of 2% to make it infusible.

At this time, the fiber mat was lifted by the wind force and was in a state of being sufficiently pierced into the needle-shaped fixture above the conveyor, and when the pressure difference between the upper and lower sides of the fiber mat was measured in this state, it was about 5 mm of water column. .

In addition, the temperature difference between the upper surface and the lower surface of the fiber mat at temperatures of 200 ° C, 250 ° C and 300 ° C during the infusibilization is 5 respectively.
℃, 7 ℃ and 10.5 ℃.

Furthermore, the oxygen content of the infusible fiber obtained is 7.3% in the upper, middle and lower parts of the mat, respectively.
7.6% and 7.5%. In this example, since the infusibilization was carried out in the air atmosphere containing 1% of nitrogen dioxide as the oxidizing agent, the oxygen content was high although the time was shortened.

In this way, the fiber mat was made infusible for seven consecutive days, but no problems such as runaway reaction due to heat generation and mat breakage occurred at all, and stable operation was possible.

The infusible fiber obtained above was carbonized in a continuous carbonization furnace in the same manner as in Example 1 to obtain a carbon fiber.

Table 3 shows the mechanical properties of the obtained carbon fibers.

The obtained carbon fiber has uniform physical properties and is particularly excellent in elongation as compared with the product of Example 1.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing the outline of the device of the present invention. FIG. 2 is a drawing showing an example of a conveyor having a three-dimensional holding mechanism for pitch fibers used in the present invention. FIG. 3 is a schematic view (viewed from the top of the apparatus) showing an example of a mechanism for adjusting the widths of the heated gas bypass openings (35) and (35) by the forced passage air flow rate adjusting plate (33). FIG. 4 is a cross-sectional view showing the outline of the device of the present invention. (1) …… Conveyor (3) …… Fiber mat moving direction (7), (9) …… Heating gas (11) …… Conveyor (13) …… Exhaust system (17) …… Needle-shaped fixture (19) …… Fiber mat (21) …… Bar (25) …… Oxidizing heated gas circulation path (27) …… Blower (31) …… Heater (33) …… Forced flow rate adjustment plate (35)… ... Aperture for passage of heated oxidizing gas

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kenji Okuda, 4-17 Jonan-cho, Izumiotsu-shi, Osaka (72) Inventor Keihachiro Tanaka 4-32-11 Kasugaoka, Itami-shi, Hyogo

Claims (2)

[Claims] 1. A bulky matt pitch fiber is placed on a conveyor made of an air permeable belt, and the pitch fiber is blown upward from below by an oxidizing heating gas while being moved in an oxidizing atmosphere. An infusibilizing furnace for performing infusibilization, comprising a conveyor provided with a three-dimensional pitch fiber holding mechanism above the conveyor. 2. An amount of heating gas passing through the pitch fiber so that a part of the oxidizing heating gas blown upward from below for infusibilizing the pitch fiber is bypassed without passing through the pitch fiber and escaped upward. The infusible furnace according to claim 1, further comprising an air flow rate adjusting mechanism for adjusting the temperature.