JP2507367B2 - Carbon fiber manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing carbon fiber, and more specifically, the production of carbon fiber using a heating furnace configured to prevent the invasion of outside air. It is about the method.

(Prior Art) Generally, in order to produce carbon fibers, an organic polymer such as polyacrylonitrile, cellulose, petroleum-based pitch or coal-based pitch is spun and focused to obtain a fiber tow in an oxidizing atmosphere at 150 to 400. After carrying out flameproofing treatment or infusibilization treatment by heating to ℃, it is heated to 500 to 1500 ℃ in an inert gas to carry out carbonization treatment, and if necessary, in an inert gas.
It is heated to 00-3000 ℃ and graphitized. In a heating furnace that performs these treatments, it is necessary to maintain the inside of the furnace at a predetermined oxidizing gas concentration or an inert atmosphere (fine oxygen concentration) in order to perform the fiber treatment uniformly and stably. is there. Therefore, in a heating furnace, it is important to take preventive measures so that outside air does not enter from the inlet and outlet of the fiber tow, and various sealing methods have been proposed.

For example, in the case of a carbonization furnace, a member having various shapes is provided at the inlet and the outlet, and an inert gas is jetted to the portion (Japanese Patent Publication No. 47-26969, JP-A-49-86635), the inlet and the outlet. Method of immersing the end portion of liquid in a liquid (Japanese Patent Laid-Open No. 48-24031) and a pair of hollow elastic members at the inlet and outlet, a hollow rigid member, an elastic roller or a rigid roller, or a corrugated scraping surface And sliding the fiber tow while pressurizing the fiber tow with these members or rollers (JP-A-48-14820, 53-8).
6896, 57-117624).

(Problems to be solved by the invention) However, the method of sealing with gas complicates the apparatus, requires a large amount of inert gas, and causes the fibers to be disturbed by the jet gas flow, resulting in breakage of single yarns. There are drawbacks such as
In addition, since the sealing liquid adheres to the fiber tow in the liquid sealing method, the liquid is brought into the carbonization furnace to disturb the atmosphere in the furnace when used at the inlet, and the fiber tow is dried when used at the outlet. There are some drawbacks needed. Further, the method of physically pinching the fiber tow causes fluffing and single yarn breakage because the fiber tow comes into contact with the member and the roller, and when a rigid body is used, the fiber tow is inevitably formed on both sides of the fiber tow. However, there is a drawback in that a gap of the thickness occurs and the sealing property is deteriorated.

(Means for Solving Problems) Therefore, the inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, the invasion of outside air into the heating furnace utilizes an effect opposite to the stack effect. This is prevented by lowering the positions of the upper and lower ends of the fiber tow introduction opening and the discharge opening of the heating furnace below the furnace bottom position, and it is possible to significantly reduce the amount of sealing gas used at the inlet and outlet. The present invention has been completed based on the findings.

That is, the gist of the present invention is a method for producing a carbonized fiber by carrying out infusibilizing treatment or flameproofing treatment on the fiber tow, then carbonizing treatment, and further performing graphitizing treatment, if necessary. At least one step is a tunnel furnace having a substantially horizontal straight body part, an opening for introducing fiber tow at one end, and an opening for leading out at the other end, wherein the upper end positions of both openings are the straight body part. A carbon fiber manufacturing method is characterized in that it is carried out by using a furnace which is configured to be located at the same position as or below the position of the floor, and which is equipped with an atmosphere gas introduction pipe in at least the straight body part.

Hereinafter, the present invention will be described in detail. First, the fiber tow as the starting material of the present invention is, for example, polyacrylonitrile,
It is prepared by spinning a cellulose, a petroleum-based pitch or a coal-based pitch by a known method and bundling about 500 to 30,000 fibers obtained.

The heat treatment of the fiber tow is also performed according to a known method. That is, the flame-proofing or infusibilizing treatment of the fiber is carried out by treating the fiber tow with, for example, oxygen, ozone, air, nitrogen oxides, halogen,
It is carried out by heating to 150 to 400 ° C. in an oxidizing atmosphere such as sulfurous acid gas. The carbonization treatment of the fibers is carried out by heating the flame-resistant or infusibilized fiber tow to 500 to 1500 ° C. under an atmosphere of an inert gas such as nitrogen or argon. When graphitizing the fiber as required, carbonize the fiber tow under an inert gas atmosphere at 1500
By heating to ~ 3000 ° C.

 Next, the present invention will be described based on the drawings.

FIG. 1 is an explanatory diagram of an example of a heating furnace used in the present invention. In the figure, 1 is a fiber tow, 2 is a bar, 4 and 16 are openings for introducing and leading out the fiber tow, 6 and 16 are conveyors, and 11 is a straight body part of a tunnel furnace.

The tunnel furnace has a fiber tow introduction opening 4 at one end of a straight body portion 11 installed horizontally and a lead-out opening 16 at the other end,
The upper end positions 5 and 14 of both openings 4 and 16 are the same as or below the position of the floor 9 of the straight body part 11, preferably 0.5.
Configured to be ~ 10m lower. Introductory pipe 10, 10 '
Is a conduit for supplying heating gas and / or atmosphere gas,
It is provided so as to open on the upper surface and / or the side surface of the straight body part 11.

The conveyor 6 is for moving the bar 2 in which the fiber tow 1 is hung in a comb shape from the fiber tow introduction opening 4 into the tunnel furnace.
Erected between the ends of.

The guide rail 12 is for moving the bar 2 from one end of the tunnel furnace to the other end, and is stretched over the straight body portion 11.

The conveyor 19 is for transferring the bar 2 from the fiber tow desorption section B to the fiber tow placing section A, and is installed outside the tunnel furnace between the outlet 17 of the chute 13 of the tunnel furnace and the opening 4.

As the bar 2, well-known ones, for example, rod-shaped ones having a circular cross section or a star shape can be used, but the peripheral shape of the horizontal cut surface is uneven or meandering, and the cross section has a circular or elliptical shape. It is preferable to use shapes, polygons, stars and the like. In the case of using the bar having such a structure, the interdigital surface of the fiber tow becomes uneven rather than flat. Therefore, the gas supplied into the furnace and the gas generated by heating flow in the direction of the arrow from the generated gap, so that a uniform heat treatment can be performed.

(Operation) Next, a method of heating the fiber tow by using the heating furnace configured as described above will be described.

In Fig. 1, the tunnel furnace is shown as an inlet pipe 10, 10 '...
The ambient gas supplied from the openings 4 and 16 is maintained at a predetermined ambient gas concentration, and is maintained at a predetermined temperature by the ambient gas and / or another heat source. The conveyors 6 and 19 are driven in the direction of the arrow. Fiber tow 1
Is fed to the fiber tow placing section A in a state where a plurality of pieces (for example, 20 to 500 pieces) are aligned in the horizontal direction, and at that portion, the bar 2 conveyed by the conveyor 19 is scooped from below. It is folded up and hung on the bar 2 in a blind shape. The bar 2 on which the fiber tow 1 is hung is moved from the conveyor 19 to the conveyor 6 at the intersection 3 of the conveyor 19 and the conveyor 6, and at the end of the straight body part 11 from the conveyor 6 to the guide rail 12 by the pusher 8. Be moved. On the guide rail 12, one bar 2 is moved rightward for each movement of the pusher 8. When the bar 2 reaches the fiber tow detachment section B, the fiber tow 1 is sequentially pulled up by driving the roller 15. The bar 2 from which the fiber tow 1 is detached is dropped into the shout 13 by the operation of the pusher 8 and is locked at the bar lock 18 of the conveyor 19 at the exit 17 of the shout.
It is moved in the direction of the fiber tow rest A.

In FIG. 1, a roller provided with a claw instead of the pusher 8 can be used to move the bar 2 onto the guide rail 12 by the claw. Further, instead of the guide rail 12, it is possible to use one in which the conveyor 6 is extended to the straight body portion 11. In this case, the pusher 8 becomes unnecessary.

Next, another example of the heating furnace used in the present invention will be described with reference to FIG. FIG. 2 shows that both openings 4 and 16 open at the lower ends of the introductory part inclination cylinder 7 and the outlet part inclination cylinder 20, respectively, and their shapes and positions 5 and 14 of the opening upper end are substantially the same, that is, both ends of the tunnel furnace This is an example in which the parts are made symmetrical, and the reverse chimney effect is more effectively exhibited. In FIG. 2, the same numbers and symbols as in FIG. 1 have the same meanings as in FIG.

In FIG. 2, a conveyor 21 is for taking out the bar 2 in which the fiber tow 1 is hung in a comb shape from the inside of the tunnel furnace, and from the end of the straight body part 11 to the opening 16 via the inclined cylinder 20. Erected in.

In the heating furnace shown in FIG. 2, the bar 2 that has moved on the guide rail 12 in the same manner as in the case of FIG. 1 is placed on the conveyor 21 and sent to the fiber tow detachment section B. The speed of the conveyor 21 is the same as or several times as fast as the conveyor 6 (that is, the speed at which the fiber tow is pulled out in the inclined cylinder 20 in a substantially straight line shape). The bar 2 that has reached the fiber tow detachment section B is sequentially pulled up by the drive of the roller 22, and then, at the intersection 23 with the conveyor 19, the bar locking member 18 of the conveyor 19 that rises from the lower side. And is moved in the direction of the fiber tow placing portion A.

In FIG. 2, a roller provided with a claw instead of the pusher 8 can be used to move the bar 2 to the guide rail 12 by the claw. Further, instead of the guide rail 12, it is possible to use a conveyor in which the conveyors 6 and 21 are extended to the straight body portion 11 and integrated. In this case, the pusher 8 becomes unnecessary.

Further, another example of the heating furnace used in the present invention will be described with reference to FIG.

In FIG. 3, the same numbers and symbols as in FIG. 1 have the same meanings as in FIG. In FIG. 3, the heating furnace is an inlet pipe.
The atmosphere gas supplied from 10, 10 ', 10 "and discharged from the openings 4 and 16 maintains a predetermined atmosphere gas concentration,
Further, the gas and / or another heat source keeps the temperature at a predetermined level. The conveyors 19 and 25 are driven in the direction of the arrow. The fiber tow 1 is continuously fed into the heating furnace through the opening 4 in a state where a plurality of fibers (for example, 20 to 500) are arranged in the horizontal direction,
In the fiber tow placement section A, the bar 2 conveyed by the conveyor 19 is folded so as to be scooped from below and is hung on the bar 2 in a comb shape. The bar 2 on which the fiber tow 1 is suspended is placed on the conveyor 25 by the rolling device 24 and moved rightward in the furnace. The bar 2 that has reached the fiber tow detachment section B is moved up from below after the fiber tow 1 is sequentially pulled up by the drive of the roller 15.
It is locked by the bar locking tool 18 of 19 and moved toward the fiber tow mounting portion A. Fiber tow 1 detached from bar 2 is open
It is taken out continuously from 16.

In the apparatus of FIG. 3, the atmospheric gas can be supplied from the side of the heating furnace. Further, instead of the rolling device 24, a roller provided with a pusher or a claw similar to that shown in FIG. 1 can be used. Further, when using a roller provided with a pusher or a claw, the guide rail similar to that shown in FIG. 1 can be used instead of the conveyor 25.

Furthermore, other examples of the heating furnace used in the present invention are shown in FIGS.
It will be described with reference to the drawings. 4 to 7 are schematic explanatory views of the heating furnace for showing only the configurations of the fiber tow introduction opening and the discharge opening, and the same numbers as in FIG. 1 have the same meanings as in FIG. , And all other components are omitted.

FIG. 4 shows the case where the openings 4 and 16 are provided in the straight body portion 11 via the L-shaped tube. FIG. 5 shows a case where the openings 4 and 16 are provided in the straight body portion 11 via a straight cylinder. FIG. 6 shows the heating furnace as shown in FIG. 2 in which the inlet and outlet openings 4 and 16 provided in each inclined cylinder are substantially horizontal. In this way, when an inclined cylinder is used for the inlet or outlet, by making the opening substantially horizontal, the upward flow of outside air that may occur in the lower layer of the inclined cylinder depending on the airflow of outside air such as crosswind. It can prevent better and is suitable,
As shown in FIG. 7, it is desirable that at least the opening of the introduction portion inclined cylinder where the outside air is likely to enter is substantially horizontal.

Further, if the inclination angle of the inclined cylinder with respect to the vertical direction is too large (close to horizontal), infiltration of outside air is likely to occur, so it should generally be 60 degrees or less, more preferably 45 degrees or less. In any case where a tilted cylinder is used, it is also recommended to provide an air flow guide plate with an appropriate position and shape so that the flow of the furnace atmosphere gas flowing out of the cylinder is not biased only to the upper layer of the cylinder. .

The shapes of the above-mentioned introduction part and the derivation part do not necessarily have to be the same, and it is possible to adopt a combination of each shape, but as mentioned above, the introduction part is selected to a shape that can better prevent the infiltration of outside air. Preferably.

As described above, the type of the heating furnace used in the present invention can be variously modified as described in detail, but in any case, the upper ends of the introduction opening and the extraction opening are both below the floor position of the straight body part, More preferably, it is important that it is set below 0.5 to 10 m and that at least a straight body portion is provided with an atmospheric gas introduction pipe in an upper portion and / or a side portion thereof. That is, since the introduced atmospheric gas is much hotter than the outside air, the reverse chimney effect can be obtained even if those openings are considerably large by being discharged from the fiber introduction and discharge openings set below the floor of the straight body part. Therefore, the invasion of outside air into the furnace can be naturally prevented.

The heating furnace used in the present invention may be constructed by connecting two arbitrary types as an infusibilizing furnace or a flameproofing furnace and a carbonizing furnace, or by using a completely different type flameproofing furnace or infusibilizing furnace as a carbonizing furnace. You can also connect. In any case, appropriate exhaust means should be considered so that the atmosphere gas of each furnace does not mix with other furnaces at the contact points.

As described above, the case where the heat treatment is performed while the fiber tow is hung on the bar has been described, but the present invention is a method in which the fiber tow is moved in the heating furnace in a can and a state in which the fiber tow is tensioned. It can also be carried out by a method of moving the inside of the heating furnace.

(Effects of the Invention) As described above, in the present invention, when the heat treatment of the fiber tow is performed, the position of the upper end of the fiber tow is not required to be provided in the heating furnace even if a special sealing mechanism is not provided. Is configured to be located at the same position as or below the floor of the heating furnace, and by introducing an atmosphere gas into at least the straight body part of the furnace, it is possible to effectively prevent outside air from entering the heating furnace. Can be stopped.

Therefore, in the present invention, since there is not much restriction on the conditions (shape, size, amount, etc.) of entering and exiting the fiber into the furnace, it is typically a method of hanging in a comb shape on a bar or a can charging. Not only can it be processed by a method, but even if it is a roll method, a large amount of fibers can always maintain a predetermined atmospheric gas composition, and as a result, it is possible to easily carry out uniform infusibilization, flame resistance, carbonization, graphitization, etc. it can. In particular, since the oxygen concentration in the atmosphere gas can be set to 10 ppm or less during the carbonization treatment and the graphitization treatment, it is useful as a method for producing carbon fibers such that high quality fibers can be obtained.

[Brief description of drawings]

1 to 3 are explanatory views of an example of a heating furnace used in the present invention, and FIGS. 4 to 7 are mainly other examples of the introduction part and the extraction part of the fiber tow in these heating furnaces. It is a schematic explanatory drawing for showing. 1: Fiber tow 4: Fiber tow introduction opening 5: Fiber tow introduction opening 7: Fiber tow introduction part inclined cylinder 9: Tunnel furnace floor 10, 10 ′, 10 ″: Atmosphere gas introduction pipe 11: Tunnel furnace Straight body part 14: Upper end of fiber tow lead-out opening 16: Fiber tow lead-out opening 20: Fiber tow lead-out part Inclined cylinder A: Fiber tow rest part B: Fiber tow release part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliographic references Sho 54-82182 (JP, U) Japanese Patent Sho 40-2709 (JP, B1) Japanese Official Sho 60-30362 (JP, B2)

Claims (7)

(57) [Claims] 1. A method for producing a carbon fiber by subjecting a fiber tow to an infusibilizing treatment or a flameproofing treatment, followed by a carbonization treatment and, if necessary, a graphitization treatment, wherein at least one of the treatment steps is performed. One of the steps is a tunnel furnace having a substantially horizontal straight body part, an opening for introducing fiber tow at one end, and an opening for leading out at the other end, the upper end positions of both openings being the floor of the straight body part. A method for producing carbon fiber, which is characterized in that it is arranged at the same position as or below the position, and is carried out using a furnace equipped with an atmosphere gas introduction pipe at least in the straight body part. 2. The method for producing a carbon fiber according to claim 1, wherein the fiber tow is a pitch fiber tow. 3. The method for producing a carbon fiber according to claim 1, wherein the fiber tow is an infusibilized Pitch fiber tow. 4. The introductory opening and the outgoing opening are opened at the lower ends of the introductory portion inclination tube and the outflowing portion inclination tube, respectively, which are connected to the straight body portion. The method for producing a carbon fiber according to any one of 1) to (3). 5. The carbon fiber according to claim 4, wherein at least the introduction opening is substantially horizontal among the introduction opening and the extraction opening. Manufacturing method. 6. The method for producing carbon fiber according to claim 5, wherein both the introduction opening and the outlet opening are opened substantially horizontally. 7. The carbon fiber according to claim 4, wherein the introductory-portion slanting cylinder and the lead-out slanting cylinder are inclined at an angle of 60 degrees or less with respect to a vertical direction. Manufacturing method.