JP2002105766A - Method for flame resisting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stably producing carbon fibers in excellent productivity, while preventing the breakage of the fibers due to the storage of heat. SOLUTION: This method for allowing the substantially non-twisted polyacrylonitrile-based carbon fiber precursors totally comprising >=10,000 filaments to resist to flame, characterized by using a heat-treating oven which has openings for charging and discharging the fibers to be treated in a heat- treating chamber and in which plural nozzles for blowing out a hot gas along a fiber-passing route and plural nozzles for sucking the hot gas are disposed on both the sides of the fiber-passing route, and blowing the hot gas between the suction openings of the hot gas-sucking nozzles and the fiber to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a stable and highly productive carbon fiber.

[0002]

2. Description of the Related Art As a method for making a polyacrylonitrile precursor fiber flame-resistant, a method disclosed in Japanese Patent Application Laid-Open No. Hei 10-237723 is known. It has a structure with a hot air outlet and a suction port above and below the yarn passage, and blows out hot air into the heat treatment chamber in a direction parallel to the yarn transfer direction. Is a heat treatment furnace having extremely uniform temperature controllability by providing the seal chamber. However, when performing flame resistance by the method, the fluff of the single fiber of the fiber bundle generated inside the acrylic precursor fiber bundle and in the heat treatment furnace is deposited at the suction port,
As a result, there is a problem that the shape of the fiber bundle, that is, the maximum thickness of the fiber bundle is changed by entanglement with the fiber bundle. Since the flame-resistant reaction is an exothermic reaction, when the maximum thickness of the fiber bundle is increased, heat is stored inside the fiber bundle, the temperature inside the fiber bundle becomes extremely high with respect to the processing temperature, and a runaway reaction occurs to cause yarn breakage. For this reason, there is a problem that production must be performed by lowering the temperature in the heat treatment furnace, and it takes time to obtain oxidized fibers having sufficiently advanced oxidization. Further, there is a problem that the accumulated fluff is entangled with the adjacent multi-fiber bundles, and the multi-fiber bundles are liable to be broken at a time due to heat storage, and it is difficult to perform long-term continuous operation.

[0003] As a method of reducing the accumulated fluff to the suction port, it is conceivable to increase the distance between the suction nozzle and the fiber bundle and increase the distance between the fiber bundle and the nozzle. In such a case, it is necessary to increase the heat treatment, which increases the equipment cost of the heat treatment furnace and, consequently, the production cost.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention reduces yarn breakage due to heat storage,
It is an object of the present invention to provide a method for producing a stable and highly productive carbon fiber.

[0005]

The present invention employs the following means in order to solve the above-mentioned problems. That is, in the method for producing a carbon fiber of the present invention, in the method for flame-proofing a polyacrylonitrile-based carbon fiber precursor having a total filament count of 10,000 or more and being substantially untwisted, an object to be treated is taken in and out of a heat treatment chamber. Heat treatment furnace having a plurality of nozzles, each having a plurality of nozzles for blowing hot air in a direction along the workpiece passage, and a plurality of nozzles for sucking the hot air on both sides of the workpiece passage. The hot air is blown between the suction port of a nozzle for sucking the hot air and the object to be treated to make it flame-resistant.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is directed to a method for producing a stable and highly productive carbon fiber by reducing the above problem, that is, yarn breakage due to heat storage, and conducting a heat treatment in a specific heat treatment furnace. Hot air was blown between the circulating air suction port in the furnace and the fiber bundle to make it flame-resistant, and it was found that such a problem could be solved at once.

That is, the total number of filaments is 10,000.
More than 30,000 to 100,000 polyacrylonitrile-based precursor fiber bundles are made substantially non-twisted in a heat treatment furnace at a temperature of 200 to 300 ° C. while being turned by a guide roll to flame resistance. In the method for producing carbonized carbon fibers, hot air is blown between a circulating air suction port in a heat treatment furnace and a fiber bundle to reduce fluff deposited at the suction port to 0.2 g / 7 tons or less of a flameproofing treatment. , Reduce the entanglement of the fluff with the fiber bundle, and always keep the maximum thickness of the fiber bundle at 5,500 to 11,000 dtex /
mm.

[0008] In the present invention, the fiber bundle in the process of flame resistance is controlled to a substantially twistless state. Here, the state of substantially no twist means that the twist is usually 0.1 turns or less per 1 m between the guide rolls. Further, the cross-sectional shape is kept substantially rectangular, and the apparent average fineness per 1 mm width of the precursor fiber bundle is from 5,500 to 11,000 dtex.
It is a state that is kept.

[0009] The suction nozzle is generally located in the heat treatment furnace, and is disposed above and below the workpiece. Accordingly, the cross-sectional area of the suction nozzle port is smaller than the total cross-sectional area of the heat treatment furnace on the suction port side. Accordingly, the circulating wind speed near the suction port is substantially higher than the average wind speed in the heat treatment furnace, and the accumulation of single yarn fluff in the single fiber bundle increases. In order to reduce the accumulation of fluff, it is preferable that the suction port has a large sectional area.

The shape of the suction nozzle opening is preferably a round or elliptical shape in order to prevent the single yarn fluff from being caught. Further, in order to prevent the surface from being caught, it is preferable that the metal is subjected to mirror plating or satin-like plating.

The hot air supplied between the suction port and the fiber bundle is preferably supplied with heated outside air, and preferably has a structure in which the temperature and flow rate of the heated outside air can be freely set.

[0012] The spray angle is 90 ° with respect to the suction port.
~ 270 ° is preferred. More preferably 120 ° -24
The range is 0 °.

When the temperature of the blown hot air exceeds the average temperature in the heat treatment chamber, a part of the fiber bundle is abnormally heated, the temperature inside the fiber bundle becomes extremely high, a runaway reaction occurs, and the yarn breaks. The temperature is preferably lower than the internal average temperature. On the other hand, when the temperature is lower than the average temperature in the heat treatment furnace, decomposed products of polyacrylonitrile and decomposed products of oil agent are condensed and adhere to the suction port. Therefore, the temperature of the blown hot air is preferably in the range of −50 ° C. to 0 ° C., more preferably in the range of −20 ° C. to 0 ° C., with respect to the average temperature in the heat treatment room.

Since the blowing hot air speed is opposite to the circulating wind speed in the heat treatment room, a wind speed higher than the circulating wind speed is required. Since the object of the present invention is hot air blowing for floating the single yarn fluff in contact with the suction port from the surface of the suction port so as not to cause breakage of the single yarn, the wind speed is preferably higher than the circulation wind speed in the heat treatment chamber immediately near the fiber bundle. In the immediate vicinity of the blowing nozzle,
It is preferable to blow a wind speed 1 to 7 times the wind speed in the heat treatment room. More preferably, the range is 2 to 5 times. Here, the wind speed is 20 m from the outlet of the spray nozzle.
At the position of m, a general-purpose anemometer, for example, ANEMOMASTER, Model 6162 manufactured by Kanomax Japan, was used to measure five points in the width direction at room temperature, and the average value was used.

The amount of hot air blown is not particularly limited,
Supplying the heated outside air into the heat treatment chamber results in formation of unevenness in wind speed and a non-wind portion in the heat treatment chamber. Therefore, the amount of hot air supplied is 0.1 to 5% by volume based on the total circulation amount in the heat treatment chamber.
Is preferably small. Here, the blowing hot air volume was calculated by multiplying the wind speed from the blowing nozzle by the cross-sectional area of the nozzle.

The present invention will be described below with reference to the drawings.

FIG. 1 is a schematic structural view showing one example of a heat treatment furnace used in the present invention. The heat treatment chamber 2 has an opening 7 for taking in and out the object 5 and a heat treatment chamber 5 for heat treating the object 5. This is a heat treatment furnace incorporating a device for circulating hot air. This heat treatment furnace 1 has a fan 9 for circulating hot air,
A heater 8 for heating hot air, a blowing nozzle 3 for flowing hot air into the heat treatment chamber 2, a suction nozzle 4,
It consists of ducts connecting them. Heat treatment furnace 1
The guide rolls 6 are arranged on both sides of the yarn, and the precursor fiber bundle 5 is passed through the heat treatment furnace in a zigzag shape, and a hot air outlet and a suction hole are provided above and below the yarn passage. In this method, hot air is blown out in a direction parallel to the transfer direction, and hot air is blown from a hot air blowing nozzle 10 to the suction nozzle 4 as shown in FIG.

FIG. 2 is an enlarged cross-sectional view of the periphery of the suction nozzle 4 of the present invention which has been blown with hot air, as viewed from the side.

[0019]

The present invention will be described below in more detail with reference to examples. Example 1 Single yarn denier 1.5d, number of filaments 50,000,
A polyacrylonitrile fiber bundle having a total denier of 75,000 was placed in a heat treatment furnace having a circulation air velocity of 5 m / sec and a total circulation amount of 200 m ³ / min in the heat treatment furnace at a distance of 20 mm between the suction port and the fiber bundle. From the spray nozzle 11 shown in FIG.
Hot air was blown from 12 shown in FIG. 2 at a blowing rate of 210 m / sec, a blowing flow rate of 0.5 m ³ / min, and a blowing angle of 210 °.
When a 7-ton oxidization treatment was continuously performed at 20 ° C. for 20 minutes and at 250 ° C. for 20 minutes, the fluff deposited on the suction port became 0.2 g, and the fluff entangled with the fiber bundle and the maximum thickness increased. As a result, no heat storage outage occurred at all. Example 2 The same polyacrylonitrile fiber bundle as in Example 1 was blown between the inlet and the fiber bundle with hot air having a temperature of 170 ° C., a blowing speed of 13 m / s, and a blowing flow rate of 0.5 m ³ / min. After performing the flame resistance treatment,
The decomposed product of polyacrylonitrile and the decomposed gas of the oil agent are condensed and adhered to the suction port, and the fuzz deposited at the suction port becomes 5.2 g. The number of cuts could be reduced to almost half as compared with the four fiber bundles and the comparative example 1. Example 3 The same polyacrylonitrile fiber as in Example 1 was introduced at a temperature of 210 ° C. between the inlet and the fiber bundle, and the wind speed immediately after the blowing was 7
When hot air was blown at a flow rate of 0.3 m ³ / min at a flow rate of 0.3 m ³ / min and the same flame resistance treatment was performed as in Example 1, the fluff deposited at the suction port became 1.5 g, and fluff entanglement in the fiber bundle occurred. The heat storage breakage due to the increase in the maximum thickness could be reduced to one fiber bundle and 1/7 of that in Comparative Example 1. Comparative Example 1 The same polyacrylonitrile-based fiber bundle as in Example 1 was subjected to the same flame-proof treatment as in Example 1 without blowing hot air between the suction port and the fiber bundle, and the fluff deposited at the suction port was 7. The fiber bundle became 0 g and fluff was entangled with the fiber bundle, and the heat storage cutoff due to the increase in the maximum thickness resulted in seven fiber bundles.

The results of Examples 1, 2, 3 and Comparative Example 1 are summarized in Table 1.

[0021]

[Table 1]

[0022]

According to the present invention, particularly when the polyacrylonitrile precursor fiber bundle having a total filament number of 30,000 or more is made to be flame-resistant, the fuzz deposited on the suction port is reduced, and the thickness of the fiber bundle due to the fuzz is reduced. The factor of increasing the size of the fiber bundle can be eliminated, so that the thickness of the fiber bundle can be stably maintained at 5,500 to 11,000 dtex per 1 mm. Smooth and quick flameproofing treatment. Provided is a method for producing a carbon fiber in which single fiber fluff deposited in a heat treatment furnace is reduced, yarn breakage due to heat storage in the heat treatment furnace can be reduced, and productivity is improved through a stable process. .

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a heat treatment furnace used in the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing one example of a suction nozzle peripheral portion of a heat treatment furnace used in the present invention which has been blown with hot air.

[Explanation of symbols]

 1: Heat treatment furnace 2: Heat treatment chamber 3: Blow nozzle 4: Suction nozzle 5: Workpiece (fiber bundle) 6: Guide roller 7: Opening for taking in and out the work 8: Heater 9: Hot air circulation fan 10: Hot air blowing nozzle 11: Hot air blowing

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F073 AA12 BA18 BB01 DA01 GA01 GA11 HA11 4L037 CS02 CS03 CT10 CT11 CT12 CT31 FA01 FA03 PA53 PS02 PS10 PS20

Claims (6)

[Claims] 1. A method for making a substantially non-twisted polyacrylonitrile-based carbon fiber precursor having a total number of filaments of 10,000 or more and flame-resistant, comprising an opening through which an object to be treated is put in and out of a heat treatment chamber. And, a nozzle that blows out hot air in a direction along the workpiece passage and a nozzle that sucks the hot air, on both sides of the workpiece passage, using a heat treatment furnace provided with a plurality of each, and A flameproofing method, characterized in that hot air is blown between a suction port of a nozzle for sucking the hot air and the object to be treated to make it flameproof. 2. The maximum thickness of the fiber bundle is from 5,500 to 1,
2. The flameproofing method according to claim 1, wherein the method is maintained at 1,000 dtex / mm. 3. The method as claimed in claim 1, wherein the temperature of the blown hot air is in the range of −50 to 0 ° C. with respect to the average temperature in the heat treatment room. 4. The flame resistance according to claim 1, wherein the wind speed of the hot air blown is in the range of 1 to 7 times the circulating wind speed in the vicinity of the spray nozzle and the circulation wind speed of the heat treatment chamber. Method. 5. The flameproofing method according to claim 1, wherein an amount of the hot air blown is in a range of 0.1 to 5% by volume with respect to a total circulation amount of the heat treatment chamber. . 6. The method according to claim 1, wherein the total number of filaments of the polyacrylonitrile-based carbon fiber precursor is in the range of 30,000 to 10,000. .