JPH02169727A - Oven for infusing pitch fiber - Google Patents

Abstract

PURPOSE:To produce the homogeneous flow of an oxidizable heated gas in a pitch fiber mat by disposing a conveyor equipped with a pitch fiber-three- dimentionally holding mechanism above an air-permeable carrying conveyor for carrying the pitch fiber mat in the oxidizable gas atmosphere. CONSTITUTION:A pitch fiber mat is carried with an air-permeable carrying conveyor 1 in the direction of the arrow 3 and heated in the respective chambers 5 of an infusion oven in a state wherein the fiber mat is floated with an oxidizable heated gas 7 supplied from the lower direction. An conveyor 11 which moves at the same direction as the carrying conveyor and is equipped with a mechanism for holding the pitch fibers three-dimensionally is disposed above the carrying conveyor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infusible furnace for bulky mat-like pitch fibers.

Prior art and its problems As a method for continuous infusibility of bulky mat-like pitch fibers (hereinafter simply referred to as fiber mat unless otherwise required) obtained by melt-spinning naphtha pitch or coal tar pitch, it is possible to A method has been proposed in which an oxidizing gas is forced to pass through the thickness of a placed fiber mat (Japanese Patent Application Laid-open No. 167928/1983). However, in this method, when the fiber mat is bulky (about 30 to 300 mm thick), the temperature difference in the vertical direction of the fiber mat becomes large and uniform infusibility cannot be achieved. In order to reduce the temperature difference in the vertical direction,
As the circulation rate of heated gas increases, the gas blown from above to below presses the fiber mat onto the conveyor, increasing the bulk density of the mat, which may cause fibers to fuse together or cause reactions due to heat generation. This may make it easier for people to go out of control. In such a case, there is also the problem that the fibers are damaged and the physical properties of the carbonized fibers are reduced.

JP-A-62-33823 proposes a method of making a fiber mat infusible while suspended on a bar. However, in the case of bulky fiber mats, the pitch fibers are relatively poorly entangled with each other, causing the fiber mats suspended on the bars to stretch or break. In addition, it is also possible to secure enough air volume to cause forced convection inside the fiber mat.
There is also the problem that it is difficult in practice.

Means for Solving the Problems As a result of extensive research in view of the current state of the art as described above, the inventor of the present invention has discovered that a fiber mat placed on a conveyor made of an air permeable belt is By providing a mechanism that holds the fiber mat three-dimensionally above the conveyor made of the air-permeable belt, a uniform oxidizing heated gas is forced into the fiber mat. It has been found that the problems of the prior art are greatly alleviated when the flow is generated.

That is, the present invention provides an infusibility furnace as follows: Bulky mat-like pitch fibers are placed on a conveyor made of an air-permeable belt, and the pitch fibers are heated from below with an oxidizing heated gas. ” An infusibility furnace that infusifies pitch fibers by moving them through an oxidizing atmosphere while blowing them up in both directions,
An infusibility furnace characterized in that a conveyor equipped with a three-dimensional holding mechanism for pitch fibers is provided above the conveyor.

■A part of the oxidizing heated gas that is blown from below upwards to make the pitch fibers infusible should not be allowed to pass through the pitch fibers (the heated gas that passes through the pitch fibers should be bypassed and released upwards). The infusibility furnace according to item 0 above, which is provided with a wind foot adjustment mechanism for adjusting the amount of.

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

FIG. 1 is a longitudinal sectional view showing an outline of the infusibility furnace according to the present invention. The fiber mat is placed on a conveyor (1) made of a breathable belt and sent in the direction of the arrow (3). The infusibility furnace is divided into multiple chambers (5) and (5) by partitions.
)... are divided into... Inside each room (5),
The oxidizing heating gas (7) flowing from the bottom to the top inside the fiber mat pierces the fiber mat and heats it in a floating state, and then moves the side of the conveyor (1) in the direction of the arrow (9). and then cycle again in the same way. A conveyor (11) is provided above the conveyor (1), which moves in the same direction as the conveyor (1) and is equipped with a mechanism for three-dimensionally holding the pitch fibers.

Moreover, (13) shows an exhaust system.

In this specification, the expression "holding the pitch fibers three-dimensionally" means simply holding the upper surface of the pitch fiber mat flatly or two-dimensionally by the oxidizing heated gas circulating from below upwards. This means that it is not held by pressing, but also held from within the fiber mat. The temperature of the oxidizing heating gas is preferably about 50 to 350°C.

Below, the mechanism for three-dimensionally holding the fiber mat will be described in detail.

FIG. 2 shows an example of a conveyor (11) with a mechanism for holding pitch fibers in three dimensions. The entire surface of the conveyor (11) has a needle-like fixture (17) with multiple small protrusions.
) are provided. This needle-shaped fixture (17) penetrates the inside of the fiber mat (1) and is lifted up by the heated gas (7) flowing from below to upward. By holding the fiber mat against the force, the fiber mat remains uniformly dense. Thus, unlike the prior art, fiber pine) (19) is forcibly heated under uniform conditions throughout, which prevents the fusion of fibers with each other and runaway reaction due to internal heat storage of infusible reaction heat. No failure will occur. Note that the form of the conveyor (11) is not particularly limited, and for example, as shown in the figure, needle-like fixing tools are attached to bars (21) provided at regular intervals in a direction perpendicular to the traveling direction of the fiber mat (19). (17
), or a net conveyor with a similar needle-shaped fixture (not shown). Further, the needle-like fixture (17) is not particularly limited as long as it can penetrate into the inside of the fiber mat and hold the fiber mat against the force of the fluid oxidizing heated gas.

FIG. 3 shows another example of a conveyor equipped with a three-dimensional holding mechanism for pitch fibers. In this case, the conveyor includes a plurality of rotating rollers (23), (23) fixed at a fixed position.
)... These rollers have small protrusions on their outer peripheral surfaces. In this case, the contact point between the transported fiber mat (19) and the rotating roller is constantly moving, so the fiber mat is not consolidated.
It is always sent forward in an unraveled state, and problems such as nonuniform heating due to local increases in bulk density, fusion of fibers to each other, and runaway reactions due to local overheating do not occur.

The three-dimensional holding mechanism for the fiber mat is not particularly limited, and any mechanism other than the above embodiments can be used as long as it can hold the fiber mat in an unraveled state without compressing it.

FIG. 4 shows a cross-sectional view of one partitioned chamber (5) shown in FIG. (25) is an oxidizing heating gas circulation path equipped with a blower (27), (31), (31)...
- indicates a heater. In the present invention, the air volume adjustment mechanism (33
), (33), and the width of the opening for passing the heated gas (
By adjusting 35) and (35), a balance is achieved between the circulation of the oxidizing heated gas and the forced air flow rate within the fiber mat, thereby suppressing the pressing of the fiber mat (19) against the conveyor (11) and reducing the amount of fiber mat. It is possible to achieve a moderate level of levitation. Adjustment of this opening width is usually performed using fiber mats (
19) is the full width of A, and the aperture width (width of the aperture (35), (
35)) is B/Ax100 (
It is preferable to perform this so that the aperture ratio defined in %) is 0 to 10%.

The fiber mat treated by the infusibility furnace of the present invention can be subsequently carbonized in accordance with a conventional method to form carbon fibers, or further subjected to graphite treatment to form carbonized fibers.

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

(b) By providing a three-dimensional holding mechanism for the fiber mat, the bulk density of the fiber mat will not become uneven, so the oxidizing heating gas will be uniformly supplied into the fiber mat, and the reaction heat will also be reduced. easily removed.

Therefore, problems such as local overheating of the fiber mat, mutual fusion of the fibers, and runaway reaction due to internal storage of heat of the infusible reaction, which were observed in the prior art, do not occur.

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

(b) Since the fiber mat is forcibly conveyed by a three-dimensional holding mechanism, it is less likely to be cut or meandered than in the prior art, and stable production is possible.

(c) By adjusting the size of the openings on both sides of the conveyor, it is possible to balance the circulation amount of oxidizing heating gas with the amount of forced air passing through the fiber mat. No need to apply wind pressure.

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

Example 1 Coal tar based near blown pitch (softening point 280°C
, 0140%) was blown fiber-spun by the eddy current method, deposited on an air-permeable mesh conveyor, and collected by suction to form a bulky continuous fiber mat. The thickness of this fiber mat is 150mm, and the basis weight is 1000g/ry.
It was i'.

The obtained fiber mat is sent to a hot air circulation type infusibility furnace of the type shown in Fig. 1, and while the fiber mat is held three-dimensionally by a conveyor equipped with a needle-shaped fixing device of the type shown in Fig. 2,
The temperature was raised from 150° C. to 325° C. over 65 minutes in an air atmosphere under the conditions of a circulating wind speed of 0.8 m/see and an aperture ratio of −0% to make it infusible.

At this time, the fiber mat was lifted by the wind force and was sufficiently pierced by the needle-like fixture above the conveyor. When the pressure difference below was measured on the fiber mat in this state, it was found that the water column was approximately 5 mm. there were.

In addition, the temperature difference between the second side and the bottom side of fiber pine at temperatures of 200°C, 250°C and 300°C during infusibility is 7°C, 9.5°C and 12°C, respectively. It was small.

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

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

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

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

Table 1 Measurement Diameter Strength Elongation Elastic modulus location (μ
m) (kgf/ll1m2) (%) (tf/
ll1m2) Upper 13.0 89 2.2
5 4. 0 Chubu 13.0 83 2.1
0 4. 0 lower part 13.0 80 2.0
0 4. As is clear from the results shown in Table 1, the physical properties of the obtained carbon fibers are almost constant regardless of the position of the mat. This indicates that the fiber mat was uniformly infusible.

Example 2 Continuous infusibility of a fiber mat was carried out in the same manner as in Example 1 except that the circulating air volume was 2.4 m/see and the aperture ratio was 8%.

At this time, the fiber mat was lifted by the wind force and was sufficiently pierced by the needle-like fixture above the conveyor. When the pressure difference between the upper and lower parts of the fiber mat was measured in this state, it was found to be approximately 5 mm in water column. .

Furthermore, the temperature differences between the upper and lower surfaces of the fiber mat at temperatures of 200°C, 1250°C and 300°C during infusibility were 2°C, 3.5°C and 5°C, respectively, in Example 1.
It was much smaller than.

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

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

Comparative Example 1 A fiber mat similar to that used in Example 1 was infusible according to Example 1 without using a conveyor equipped with needle-like fixtures. However, in addition to setting the circulating wind speed to 0.2 m/see, the pressure difference between the top and bottom of the fiber mat should be set to 0.5 m in the water column to prevent the fiber mat from being lifted up by the wind force.
It was set as m.

The temperature difference between the upper and lower surfaces of the fiber mat at the infusibility setting temperature of 200°C, 250°C and 300°C is 14°C, respectively.
℃, 20℃ and 27℃, which were extremely large.

Furthermore, the oxygen content of the infusible fibers obtained by setting the infusible temperature to 325°C was 6.5%, 8.1%, and 7.4% in the upper, middle, and lower parts of the mat, respectively.
There was a large variation.

This occurs because the reaction heat generated during infusibility is not sufficiently removed.

Although the fiber mat was infusible for 7 consecutive days in this manner, runaway reactions due to heat generation frequently occurred from the beginning, and the mat broke frequently.

Infusible fiber obtained above (infusibility set temperature 325°C)
was carbonized in a continuous carbonization furnace in the same manner as in Example 1 to obtain carbon fibers.

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

Measurement in Table 2 Diameter Strength Elongation Elastic modulus location (μ
m) (kgf/m+n2) (%) (tf/
mm2) Upper 13.0 57 L, 45
4. 0 Chubu 13.0 71 1.80
4. 0 lower part 13.0 76 1,90
4. As is clear from the results shown in Table 1, the obtained carbon fibers had larger variations in strength and elongation and lower values than the carbon fibers of Example 1. These results also indicate that the fiber mat was not uniformly infusible.

Example 3 A fiber mat similar to that used in Example 1 was heated with circulating air fi1.
．． The temperature was increased from 150° C. to 325° C. over 35 minutes in an air atmosphere containing 1% nitrogen dioxide under conditions of 2 m/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 sufficiently pierced by the needle-like fixture above the conveyor. When the pressure difference between the top and bottom of the fiber mat was measured in this state, it was found that the water column was approximately 5 cm. Ta.

Furthermore, the temperature difference between the upper and lower surfaces of the fiber mat at temperatures of 200°C, 250°C, and 300°C during infusibility is as follows:
The temperatures were 5°C, 7°C and 10.5°C, respectively.

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

In this way, the fiber mat was made infusible continuously for 70 days, but no problems such as diversion reactions due to heat generation or mat breakage occurred, and stable operation was possible.

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

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

Measurement in Table 3 Diameter Strength Elongation Elastic modulus location (μ
m) (kgf/mm2) (%) (tf/m
m”) Upper 13.0 83 2.30
3. 6 Chubu 13.0 86 2.40
3. 6 lower part 13.0 85 2J5
3. 6 The obtained carbon fiber has homogeneous physical properties and is particularly excellent in elongation as compared to the product of Example 1.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing an outline of the apparatus of the present invention. FIG. 2 is a drawing showing an example of a conveyor equipped with a three-dimensional holding mechanism for pitch fibers used in the present invention. FIG. 3 is a drawing showing another example of a conveyor equipped with a three-dimensional holding mechanism for pitch fibers used in the present invention. FIG. 4 is a cross-sectional view showing an outline of the device of the present invention. (1) Conveyor (3) Direction of movement of fiber mat (7), (9) Heated gas (11) Conveyor (13) Exhaust system (17) ... Needle-like fixture (19) ... Fiber mat (21) ... Bar (23) ... Roller (25) ... Oxidizing heating gas circulation path (27) ...
Blower (31)...Heater (33)...Air volume adjustment mechanism (35)...Opening for passage of oxidizing heated gas Fig. 1 Fig. 3 Fig. 4 Fig. 2

Claims (2)

[Claims] (1) Bulky mat-like pitch fibers are placed on a conveyor made of an air-permeable belt, and the pitch fibers are blown up from below to above by oxidizing heated gas while being moved through an oxidizing atmosphere. An infusibility furnace that performs melting,
An infusibility furnace characterized in that a conveyor equipped with a three-dimensional holding mechanism for pitch fibers is provided above the conveyor. (2) Adjust the amount of heated gas that passes through the pitch fibers so that a portion of the oxidizing heated gas that is blown upward from below to infusibility the pitch fibers bypasses the pitch fibers and escapes upwards. The infusibility furnace according to claim 1, further comprising an air volume adjustment mechanism for controlling the air volume.