JP2018174081A - Heating method, carbon fiber manufacturing method, carbonization apparatus and carbon fiber manufacturing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating method and the like, capable of increasing the heating of an object to be heated, and also capable of adjusting the energy intensity of a microwave that is imparted on the way of traveling.SOLUTION: In a heating method, an object 1b to be heated traveling along a tube axis of a heating tube 15 in the heating tube 15 is heated by an electric field of a TE mode microwave A that propagates in the heating tube 15 with a rectangular cross-sectional shape, the heating tube having a pair of short side walls and a pair of long side walls 15c, 15d. The intensity of an electric field of the microwave A is adjusted by changing the internal area in a cross section of the heating tube 15, along a traveling direction of the object 1b to be heated.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a heating method using microwaves.

The carbon fiber is produced by heating a precursor fiber produced from polyacrylonitrile fiber, rayon fiber, cellulose fiber, pitch fiber, or the like. For example, heating of a precursor fiber produced from polyacrylonitrile fiber is referred to as a flame-proofing step in which the precursor fiber is heated in an oxygen-containing atmosphere (in a flameproofing furnace) and a fiber that has undergone a flameproofing step (hereinafter referred to as “flameproof fiber”). ) Through a carbonization step of heating in an inert atmosphere (carbonization furnace). In addition, the said heating is performed because a fiber passes (runs) through a flame-proofing furnace and a carbonization furnace. Further, the fiber here is in the form of a bundle of a plurality of filaments.
As heating for carbonizing the precursor fibers, methods using microwaves have been proposed in addition to conventional electric heaters (for example, Patent Documents 1 and 2). The method described in Patent Literature 2 heats an object to be heated that travels in the heating tube by microwaves in a TE mode that propagates in a heating tube having a square cross section having a pair of short side walls and a pair of long side walls, The object to be heated is supplied so as to cross the pair of short side walls.
In addition, the heating of patent document 2 is what is called an electric field heating heated when an electric field becomes perpendicular | vertical with respect to a to-be-heated material.

Patent 6063045 JP-A-2006-195021

However, in the technique of Patent Document 2, since the object to be heated crosses the pair of short side walls, the heating length of the object to be heated is shortened. For this reason, in order to ensure the energy to provide, it is necessary to slow down the traveling speed of a to-be-heated object, or enlarge a heating pipe and lengthen a short side wall, and it is difficult to apply to a production machine.
In addition, as described in paragraph 80 of Patent Document 1, when the precursor fiber is heated, the reaction proceeds due to heat storage and the precursor fiber is cut, so that energy (electric field) applied to the object to be heated is being traveled. However, it is difficult to adjust the energy by the method of Patent Document 2.
In addition to the thread-like conductive material, these problems may also occur in a heated object that is transported in the waveguide by a film-like material or transporting means.
An object of the present invention is to provide a heating method, a carbon fiber manufacturing method, and the like that can lengthen the heating of an object to be heated and can adjust the energy intensity of a microwave applied during traveling. To do.

In order to achieve the above object, a heating method according to one embodiment of the present invention includes a TE-mode microwave electric field propagating in a heating tube having a square cross section having a pair of short side walls and a pair of long side walls. In the heating method of heating the object to be heated that travels along the tube axis of the heating tube in the heating tube, the strength of the electric field of the microwave is in the cross section of the heating tube along the traveling direction of the object to be heated. It is adjusted by changing the internal area.
In order to achieve the above object, a heating method according to one embodiment of the present invention includes a TE-mode microwave electric field propagating in a heating tube having a square cross section having a pair of short side walls and a pair of long side walls. In the heating method for heating an object to be heated that travels along the tube axis of the heating tube in the heating tube, the heating tube has a slit for introducing a microwave generated from a microwave generator in the traveling direction. And the strength of the electric field of the microwave is adjusted by changing the dimension of the slit in the traveling direction.

In order to achieve the above object, a carbon fiber manufacturing method according to an aspect of the present invention is a carbon fiber manufacturing method in which a precursor fiber is heated to manufacture a carbon fiber. The heating method described above is included.
In order to achieve the above object, a carbonization apparatus according to one aspect of the present invention heats a precursor fiber that travels along a tube axis in a heating tube having a rectangular cross section by a TE-mode microwave electric field. The carbonization apparatus which carbonizes is equipped with the adjustment means which adjusts the strength of the electric field of the said microwave along the running direction of the said precursor fiber.
In order to achieve the above object, a carbonization apparatus according to an aspect of the present invention is a carbon fiber manufacturing apparatus that manufactures carbon fibers by heating precursor fibers, and carbon that heats and carbonizes the precursors. The carbonization apparatus described above is included as the carbonization apparatus.

  A heating method, a carbon fiber manufacturing method, a carbonization apparatus, and a carbon fiber manufacturing apparatus according to an aspect of the present invention heat a heated object that heats the heated object traveling along the tube axis of the heating pipe. It is possible to adjust the energy intensity of the microwave applied during traveling by changing the internal area of the cross section of the heating tube or changing the dimension of the slit in the traveling direction.

(A) shows the conceptual diagram of the electric field strength distribution in the cross section of the heating tube which a microwave propagates, (b) shows the mode of the microwave which propagates a heating tube. (A) is a figure which shows the introduction hole provided in the long side wall by the side of the waveguide in a heating tube, (b) is a figure which shows the strength of the electric field in which the introduction hole of (a) is provided. . It is a figure explaining the heating tube which adjusts the electric field strength of a microwave, (a) is a figure which shows the mode of the microwave which propagates a heating tube, (b) is distribution of the intensity of the electric field of a microwave (C) is a figure which shows the strength of the electric field of a microwave. (A) is a figure which shows distribution of the electric field in the cross section of the heating tube in the A position shown to (b) of FIG. 3, (b) is a figure of the heating tube in the B position shown in (b) of FIG. It is a figure which shows distribution of the electric field in a cross section, (c) is a figure which shows distribution of the electric field in the cross section of a heating tube in the C position shown by (b) of FIG. It is the schematic which shows the manufacturing process of carbon fiber. It is the schematic of a heating apparatus. It is a figure which shows the temperature change of the surface of the flame resistant fiber which drive | works the inside of a heating pipe. (A) shows a step-like height adjustment member, (b) shows a slope-like height adjustment member. It is a figure which shows the example which adjusts the intensity | strength of the electric field of a microwave by adjusting the space | interval of a pair of short side wall.

<Overview>
A heating method according to one embodiment of the present invention includes a heating tube in which a cross-sectional shape having a pair of short side walls and a pair of long side walls has a square shape, and utilizes TE-mode microwaves that propagate in the heating tube. The object to be heated running in the pipe is heated.
Here, although TE10 is demonstrated as an example of TE mode, other TE modes, for example, TE20, may be sufficient. The object to be heated travels in a direction perpendicular to the rectangular cross section (the tube axis direction of the heating tube). The tube axis direction is the direction in which the tube axis of the heating tube extends.

  Microwave A propagates in a direction orthogonal to the paper surface in FIG. 1A, and microwave A propagates in the tube axis direction of heating tube 15 as shown in FIG. In FIG. 1A, the side walls 15a and 15b extending in the vertical direction are referred to as “short side walls”, and the side walls 15c and 15d extending in the left and right direction are referred to as “long side walls”.

  The object to be heated 1b is supplied so as to travel in the tube axis direction of the heating tube 15 as shown in FIG. FIG. 1 shows a precursor fiber that is an example of the object to be heated 1b, and the precursor fiber travels in parallel with the pair of long side walls 15c and 15d. Note that an inlet of the object to be heated 1b is provided on the upstream end wall 15e in the tube axis direction of the heating pipe 15, and an outlet of the object to be heated 1b is provided on the downstream end wall 15f.

  In consideration of productivity, a plurality of objects to be heated 1b may be supplied to the heating tube 15. In FIG. 1A, there are two. In consideration of heating spots, heating efficiency, and electric field intensity unevenness of the plurality of objects to be heated 1b, it is preferable to pass through a position that is line-symmetric with respect to a virtual line connecting the midpoints of the long side walls 15c and 15d (FIG. 1). (See (a)). The supplied heated object 1b is preferably a dielectric.

The microwave A in the heating tube 15 may be directly introduced from a microwave oscillator provided at one end of the heating tube 15, or may be introduced into the heating tube 15 from a waveguide provided with the microwave oscillator at one end. The microwave leaking from the hole in the side wall of the waveguide may be introduced into the heating tube 15.
When utilizing the microwave leaked from the waveguide, the waveguide (102) is provided with the heating tube 15 as shown in FIG. 6, for example, and has a leakage introduction hole (106) on the opposite side wall. Configured as follows.

Depending on the object to be heated 1b, it may be preferable to adjust the energy (electric field) of the microwave in the tube axis direction of the heating tube 15. For example, as described in “Problems to be Solved by the Invention”, the precursor fiber is cut by heat storage.
Hereinafter, the adjustment of the energy of the microwave will be described.

(1) In the case where microwave leaked from the waveguide is used A description will be given mainly with reference to FIG.
In the case where the heating tube 15 having a rectangular cross section and long in the direction perpendicular to the cross section is used and the microwave leaking from the waveguide is introduced into the inside through the introduction hole 106, the introduction hole 106 of the heating tube 15 is used. The intensity of the microwave electric field can be adjusted by changing the size of. The introduction holes 106 having different sizes correspond to an example of the adjusting means in the present invention.

For example, when the strength of the electric field is increased, the introduction hole 106 may be enlarged, and when the strength of the electric field is decreased, the introduction hole 106 may be reduced.
A plurality (even number) of introduction holes 106 are provided at intervals along the propagation direction of the microwave A in the heating tube 15.
The pitch L of the introduction holes 106 is λg when the waveguide wavelength of the microwave A waveguide is λg.
L = λg / 2 × n
(Where n is an integer).
The introduction holes 106 are provided as a pair. That is, a plurality of introduction holes 106 are provided, with two introduction holes 106 as one set.

The introduction hole 106 is constituted by, for example, a rectangular slit. In addition, the code | symbol of a slit is also set to "106." The length a which is a dimension of the slit 106 in the direction orthogonal to the tube axis direction of the heating tube 15 is given by It is fixed with a dimension larger than 1/2. Note that there is a possibility that the cutoff frequency is 1/2.
The width b of the slit 106 in the tube axis direction of the heating tube 15 may be a size smaller than the in-tube wavelength λg in the heating tube 15.
In FIG. 2, the length a of the plurality of slits 106 is the same, and the width b of each set of slits 106 is the same from the upstream end to the middle in the tube axis direction (for example, the slit 106 </ b> A). Thereafter, it is provided so as to gradually become smaller (for example, slits 106B and 106C) as it moves downstream. As a result, as shown in FIG. 5B, the intensity of the electric field of the microwave is substantially constant halfway and becomes weaker as it progresses from the middle to the downstream side.
In this way, in the plurality of sets of slits 106 formed at intervals in the tube axis direction, the width b of each set is reduced as it moves downstream, so that the electric field increases as the tube axis direction moves downstream. Can weaken the strength.

(2) When Using Microwave Propagating in Heating Tube This will be described mainly with reference to FIGS.
The microwave A described here may be directly introduced from a microwave oscillator provided at one end of the heating tube 15, or may be introduced from a waveguide provided at one end of the microwave oscillator. The microwave leaking from the introduction hole in the side wall of the waveguide may be introduced.
Adjustment of the electric field strength of the microwave A is performed by changing the internal area in the cross section of the heating tube 15 along the traveling direction of the article to be heated 1b. The change in the internal area here is made by the change in the distance between the pair of facing surfaces that form a space existing between the pair of long side walls 15c, 15d facing each other in the direction parallel to the pair of short side walls 15a, 15b.
For example, when the height adjusting member 151 is disposed on at least one long side wall 15c of the pair of long side walls 15c and 15d, the inner surface of the other long side wall 15 and the surface facing the other long side wall of the height adjusting member 151 And a pair of opposing surfaces, and the height of the height adjusting member 151 is changed to change the distance between the pair of opposing surfaces.
For example, when the heating tube 15 is configured so that the distance between the pair of long side walls 15 is different, the inner surfaces of the long side walls 15c and 15d become a pair of opposing surfaces.
Note that the opposing surfaces having different intervals correspond to an example of the adjusting means in the present invention.

The height adjusting member 151 is configured to weaken the strength of the microwave electric field in two stages on the downstream side in the tube axis direction of the heating tube 15 in the traveling direction of the article to be heated 1b.
As shown in FIGS. 3 and 4, the height adjusting member 151 heats the first height portion 151a having the first height H1 and the second height portion 151b having the second height H2. It has along the pipe-axis direction of the pipe | tube 15. In addition, the length of the 1st height part 151a is set to L1, and the length of the 2nd height part 151b is set to L2. Further, a length where the height adjusting member 151 does not exist is set to L3. If there is a member in the portion where the height adjusting member 151 does not exist, the height H3 is 0, which can be said to be the third height portion (151c).
About each height of the height part,
H1>H2> H3 = 0
There is a relationship.

Here, in the heating tube 15, the height adjusting member 151 is provided, assuming that the electric field strength at position A in FIG. 3 is E1, the electric field strength at position B is E2, and the electric field strength E3 at position C. Thereby, the internal space area in the cross section of the heating tube 15 changes, and the strength of the electric field of the microwave A also changes. Note that the strength of the electric field increases as the internal area decreases.
Therefore, the strength of the electric field of the microwave A inside the heating tube 15 is as shown in (c) of FIG.
E1>E2> E3
It becomes.
Thus, the energy of the microwave A can be sufficiently imparted by running the article to be heated 1b along the tube axis direction of the heating tube 15. In addition, the strength of the electric field of the microwave A can be adjusted using one heating tube 15 by causing the object to be heated 1 b to travel along the tube axis direction of the heating tube 15.

When the height adjusting member 151 is provided in the heating tube 15, as shown in FIG. 3B, the electric field strength distribution is higher in the adjusting member 151 than in the C position. Accordingly, the peak portion tends to be flat. That is, the electric field distribution extends in the tube axis direction of the heating tube 15. By flattening the peak portion, the microwave A having a strong energy can be applied to the heated object 1b traveling in the tube axis direction for a long time.
Further, as shown in FIG. 4, the distribution of the electric field in the cross section of the heating tube 15 has a tendency that the peak portion becomes flat as the height adjusting member 151 becomes higher than the distribution at the position C. . Thereby, in the cross section in the heating pipe | tube 15, distribution spreads in the width direction (the left-right direction in a figure), and the number of the to-be-heated objects 1b inserted in the heating pipe | tube 15 can be increased.

When the width that is the distance between the inner surfaces of the short side walls 15a and 15b of the heating tube 15 is W and the width of the height adjusting member 151 is s,
0.3 × W ≦ s ≦ 0.6 × W
Satisfy the relationship. When this relationship is satisfied, the strength of the electric field in the heating tube 15 can be adjusted without greatly changing the impedance in the heating tube 15. Note that when the impedance changes greatly, the wavelength of the microwave changes, and it becomes difficult for a standing wave to be generated, or a reflected wave is likely to be generated by the height adjusting member 151.

When the length of the nth height portion of the height adjusting member 151 is Ln (n = 2 in FIG. 3),
Ln = (λg / 4) × (2k−1)
Is preferred. Note that λg is the guide wavelength, and k is a natural number.
Thereby, the influence of the reflected wave which the microwave A reflects on the standing surface of the height adjustment member 151 can be offset.
In addition, the direction in which the height of the height adjusting member 151 decreases, that is, the direction in which the distance between the pair of opposing surfaces increases is preferably the direction opposite to the traveling direction of the microwave A. This is to reduce the influence of the reflected wave. In FIG. 3, the traveling wave of the microwave A is directed from the downstream side to the upstream side of the heating tube 15, and the arrow in FIG. 3 indicates the traveling direction of the object to be heated 1b.

<Embodiment>
1. Overall Hereinafter, a method for producing a carbon fiber using microwave heating will be described with reference to FIG.
The carbon fiber is manufactured using a precursor which is a precursor fiber. One precursor is a bundle of a plurality of filaments, for example, 24,000 filaments. In some cases, it may be a precursor fiber bundle or a carbon fiber bundle.

The precursor 1a is obtained by spinning a spinning solution obtained by polymerizing a monomer containing 90% by mass or more of acrylonitrile in a wet spinning method or a dry wet spinning method, and then washing, drying, and stretching. In addition, as a monomer to be copolymerized, alkyl acrylate, alkyl methacrylate, acrylic acid, acrylamide, itaconic acid, maleic acid, or the like is used.
Usually, the speed for producing the precursor 1a is different from the speed for producing carbon fiber by carbonizing the precursor 1a. For this reason, the manufactured precursor 1a is once accommodated in a carton or wound around a bobbin.

As shown in FIG. 5, for example, the carbon fiber is pulled out from the bobbin 30, travels toward the downstream side, is subjected to various treatments, and is wound around the bobbin 39.
As shown in FIG. 3, the carbon fiber is referred to as a flameproofing step for making the precursor 1 a flameproof and a flameproofed fiber (hereinafter referred to as “flameproof fiber”, which corresponds to an example of the “precursor fiber” of the present invention. .) Carbonization step of carbonizing 1b while stretching, surface treatment step of improving the surface of carbonized fiber (hereinafter also referred to as “fiber after carbonization”) 1d, and surface improved It is manufactured through a sizing process in which a resin is adhered to the fiber 1e and a drying process in which the fiber 1f to which the resin is adhered is dried.

1 g of the dried fiber is wound around the bobbin 39 as 1 g of carbon fiber. In addition, although the fiber which finished each process is distinguished like the flame resistant fiber 1b, for example, "1" is used for the code | symbol at the time of only describing as a "fiber."
Here, the treatment for making the precursor 1a flame resistant is the flameproofing treatment, the treatment for carbonizing the flame resistant fiber 1b is carbonized, the treatment for improving the surface of the fiber 1d after carbonization is the surface treatment, and the fiber whose surface is improved The process of attaching the resin to 1e is referred to as a sizing process, and the process of drying the fiber 1f to which the resin is attached is referred to as a drying process. Hereinafter, processes and processes will be described.

(1) Flame resistance process (flame resistance treatment)
The flameproofing step is performed using the flameproofing furnace 3 in which the inside of the furnace is set to an oxidizing atmosphere of 200 [° C.] to 350 [° C.]. Specifically, the flame resistance is performed by the precursor 1a passing through the flame resistance furnace 3 in an air atmosphere a plurality of times. Note that the oxidizing atmosphere may contain oxygen, nitrogen dioxide, or the like.
The precursor 1a in the flameproofing process is stretched with a predetermined tension in accordance with the carbon fiber to be manufactured. The draw ratio in the flameproofing step is, for example, in the range of 0.7 to 1.3. The precursor 1a is stretched by the two rollers 5, 7 at the entrance of the flameproofing furnace 3 and the three rollers 9, 11, 13 at the exit.

(2) Carbonization process (carbonization process)
A carbonization process is a process of producing a thermal decomposition reaction by heating the flame resistant fiber 1b and performing carbonization. Carbonization is performed by the flame resistant fiber 1 b passing through the first carbonization furnace 15 and the fiber 1 c passing through the first carbonization furnace 15 passing through the second carbonization furnace 17. The carbonization here is performed by passing through at least the first carbonization furnace 15 and the second carbonization furnace 17.
Here, the carbonization performed in the first carbonization furnace 15 is referred to as “first carbonization” or “first carbonization treatment”, and this step is referred to as a first carbonization step. The fiber that has been subjected to the carbonization treatment (from the first carbonization furnace 15) is referred to as “fiber after the first carbonization treatment”.

Similarly, the carbonization performed in the second carbonization furnace 17 is referred to as “second carbonization” or “second carbonization treatment”, and this step is referred to as a second carbonization step. The fiber that has been subjected to the carbonization treatment (exited from the second carbonization furnace 17) is referred to as “fiber after the second carbonization treatment” or “fiber after carbonization”.
The plurality of carbonization furnaces are provided in an independent form. Here, the first carbonization furnace 15 and the second carbonization furnace 17 are provided independently of each other, and the tension of the fiber is adjusted between the first carbonization furnace 15 and the second carbonization furnace 17. Adjustment means can be provided.

A roller 19 is provided outside the first carbonization furnace 15 at the inlet side, and a roller 21 is provided between the first carbonization furnace 15 and the second carbonization furnace 17, and the second carbonization furnace. A roller 23 is provided on the outer side of 17 and on the outlet side.
The carbonization in the carbon process includes a first carbonization process in which the flame resistant fiber 1b is heated in the first carbonization furnace 15 using a microwave to cause a thermal decomposition reaction, and the fiber 1c heated in the microwave is subjected to a first decomposition. And a second carbonization step in which carbonization is advanced by rapid and uniform heating using plasma while stretching in the second carbonization furnace 17. The first carbonization furnace corresponds to an example of the carbonization apparatus of the present invention.

  The first carbonization step is performed by a heating apparatus using microwaves that propagate through the inside of a heating tube having a square cross-sectional shape. The flame resistant fiber 1b travels in the heating tube 15 along the tube axis direction of the heating tube 15 and is heated. At this time, electric field energy serving as a heating source is introduced from the waveguide through which the microwave propagates to the heating tube 15 via the introduction hole, and the electric field is matched between the pair of introduction holes. The heating device used for the first carbonization step will be described in detail later. Note that the second carbonization step may be heated by a heating means other than plasma.

(3) Surface treatment process (surface treatment)
The surface treatment step is performed by passing the carbonized fiber 1d through the surface treatment apparatus 25. A roller 26 is provided at the outlet of the surface treatment device 25. In addition, by making surface treatment, when it is set as a composite material using 1g of carbon fibers, the affinity and adhesiveness of 1g of carbon fibers and matrix resin improve.
The surface treatment is generally performed by oxidizing the surface of the carbon fiber. As the surface treatment, for example, there is a treatment in a liquid phase or a gas phase. The treatment in the liquid phase includes industrial oxidation such as chemical oxidation by immersing the carbonized fiber 1d in an oxidizer, and anodic electrolytic oxidation by energizing in an electrolytic solution in which the carbonized fiber 1d is immersed. Used for.
The treatment in the gas phase can be performed by passing the carbonized fiber 1d through an oxidizing gas or spraying active species generated by discharge or the like.

(4) Sizing process (sizing process)
The sizing process is performed when the fiber 1 e passes through the resin liquid 29. The resin liquid 29 is stored in the resin bath 27. In addition, the convergence property of the surface-treated fiber 1e increases by a sizing process.
The fibers 1e in the sizing process pass through the resin liquid 29 while changing the traveling direction by a plurality of rollers 31, 33 and the like disposed inside the resin bath 27 and around the resin bath 27. As the resin liquid 29, for example, a liquid or emulsion liquid in which an epoxy resin, a urethane resin, a phenol resin, a vinyl ester resin, an unsaturated polyester resin, or the like is dissolved in a solvent is used.

(5) Drying process (drying process)
The drying process is performed by passing the fiber 1 f through the drying furnace 35. Note that 1 g of the dried fiber is wound around the bobbin 39 via the roller 37 on the downstream side of the drying furnace 35 (winding process).

2. Heating device (first carbonization furnace)
(1) Outline A heating apparatus will be described with reference to FIG.
The heating apparatus 100 has a heating tube having a square cross section. This heating tube is the first carbonization furnace 15 in FIG. In the following description, the reference numeral of the heating tube is “15”.

The heating tube 15 has a pair of short side walls 15a and 15b and a pair of long side walls 15c and 15d. Microwave A is in TE mode. Here, the TE10 mode is used. The flame resistant fiber 1b travels inside the heating tube 15 along the tube axis. The end walls 15e and 15f at both ends in the tube axis direction of the heating tube 15 are provided with an inlet and an outlet for the flame resistant fiber 1b (see FIG. 6).
The microwave A is introduced into the heating tube 15 by the waveguide 102. The waveguide 102 has a rectangular cross section similar to the heating tube 15 in order to propagate the microwave B transmitted from a microwave oscillator described later in the TE mode.

  The waveguide 102 is provided in a state where the tube axis of the waveguide 102 is parallel to the tube axis of the heating tube 15 and the inside of the heating tube 15 communicates with the inside of the waveguide 102. Here, the heating tube 15 and the waveguide 102 are integrated, and a heating space (which is an internal space of the heating tube 15) and a waveguide space (which is an internal space of the waveguide 102). It is partitioned by a partition wall 104. Here, the partition wall 104 is a long side wall (15 c) on the waveguide 102 side in the heating tube 15.

The partition wall 104 has an introduction hole 106. Here, the introduction hole 106 is provided in a slit shape extending in a direction perpendicular to each tube axis of the heating tube 15 and the waveguide 102. The microwave B in the waveguide 102 leaks from the introduction hole (slit) 106 to the heating tube 15 side.
As the microwave oscillator 108, for example, a microwave electron tube such as a klystron and a magnetron, a microwave semiconductor element using a diode, or the like can be used. The output of the microwave oscillator 108 can be appropriately selected depending on the number, speed, carbon degree, and the like of the flame resistant fibers 1b that travel inside the heating tube 15. In addition, the frequency of the microwave transmitted from the microwave oscillator 108 is 0.3 [GHz] to 140 [GHz].

The microwave oscillator 108 is connected to one end 102 a of the waveguide 102 via the connection waveguide 110. A fixed short-circuit plate 112 is provided at the other end 102 b of the waveguide 102. The fixed short-circuit plate 112 is for reflecting the microwave B propagating from the one end 102a of the waveguide 102 to the other end 102b toward the one end 102a. It can make a standing wave.
The standing wave (B) in the waveguide 102 leaks to the heating tube 15 through the introduction hole 106 of the partition wall 104 and propagates in the heating tube 15.

  A plurality (even numbers) of the introduction holes 106 are provided at intervals along the propagation direction of the microwave A in the partition wall 104. In the case of a normal standing wave, the size of the introduction hole 106 is the same.

A fixed short-circuit plate 114 is also provided at one end of the heating tube 15, and a variable short-circuit plate 116 is provided at the other end via a connection waveguide 115.
The fixed short-circuit plate 114 at one end reflects the microwave A leaking from the introduction hole 106 and propagating toward the one end toward the other end 15f. Thereby, the microwave A can be used effectively. The variable short-circuit plate 116 at the other end 15f propagates the inside of the heating tube 15 and reflects the microwave A reaching the other end 15f to one end side. In the case of the apparatus configuration of FIG. It is for making it in a resonance state between. Thereby, as shown in FIG.1 and FIG.6, a standing wave can be caused in the heating tube 15. FIG.

  The connecting waveguide 110 that connects the microwave oscillator 108 and the waveguide 102 is provided with an isolator 118, a directional coupler 120, and a sleeving tuner 122 from the microwave oscillator 108 side. The isolator 118 prevents the microwave oscillator 108 from being damaged by the microwave B reflected by the other end 102 b of the waveguide 102.

The directional coupler 120 measures incident power (microwave toward the other end 102b of the waveguide 102) and reflected power (microwave reflected at the other end and directed to the microwave transmitter). To do. The three-stub tuner 122 is for adjusting the impedance matching in the waveguide 102. This matching enables efficient microwave heating.
The heating tube 15 has a plurality of temperature measurement windows 124 along the traveling direction for measuring the temperature of the flame resistant fiber 1b traveling in the tube. The temperature measurement window 124 is provided with a lid for preventing oxygen from flowing in.

The heating tube 15 or the waveguide 102 is provided with a gas inlet 128 for making the inside of the tube an inert gas atmosphere, an exhaust port 126 for exhausting the gas generated when the flame resistant fiber 1b is heated, and the like. ing. As the inert gas, for example, nitrogen can be used, and argon or the like can be used.
The heating tube 15 is connected to the variable short-circuit plate 116 through the connection waveguide 115 at the other end 15f. A directional coupler 130 is provided in the connection waveguide 115. This directional coupler 130 propagates in the heating tube 15 toward the other end 15f, and is reflected by the variable short-circuit plate 116 and propagates toward one end of the electric power of the microwave A that is not absorbed by the flame resistant fiber 1b. The power of microwave A is measured.

(2) Adjustment of microwave When an electric field having a certain strength is applied to the flame resistant fiber 1b, heat may be stored and cut. For this reason, the intensity of the electric field of the microwave A is weakened (adjusted) in the heating tube 15 as it moves from the middle of the traveling direction of the flame resistant fiber 1b to the downstream side. Hereinafter, a method for adjusting the strength of the electric field and a means for adjusting the strength will be described.

(2-1) Introduction hole The slit 106 can be used as an example of the introduction hole. Usually, the size of the slit 106 is the same. However, the strength of the electric field can be adjusted by changing the size of the slit 106.
Here, as shown in FIG. 2A, the width b of the slit 106 is reduced as it proceeds from the middle in the tube axis direction of the heating tube 15 to the downstream side. Thereby, as shown in FIG. 2B, the strength of the electric field can be reduced as it proceeds from the middle in the tube axis direction of the heating tube 15 to the downstream side.

(2-2) Area of internal space By adjusting the distance between the pair of opposed surfaces facing the internal space of the heating tube 15, the area of the internal space changes, and the strength of the electric field can be adjusted. Here, a height adjusting member 151 is disposed in the heating tube 15 as shown in FIG. The distance between the height adjusting member 151 and the long side wall 15d is increased as the distance from the middle in the tube axis direction of the heating tube 15 proceeds to the downstream side. As a result, as shown in FIG. 3C, the strength of the electric field can be reduced as it proceeds from the middle in the tube axis direction of the heating tube 15 toward the downstream side.

3. Example An example of the embodiment will be described below.
The heating device 100 heats the supplied flame resistant fiber 1b with the microwave A.
The flame resistant fiber 1b used has a density of 1.36 [g / cm ³ ]. The supply of the flame resistant fiber 1b to the heating tube 15 of the heating apparatus 100 is two, and the flame resistant fiber 1b is supplied along the tube axis direction of the heating tube 15. The number of filaments of the flame resistant fiber 1b is 24,000 [pieces].
The microwave A used in the heating apparatus 100 has a wavelength in the range of 0.705 [m] to 0.00737 [m] and a frequency in the range of 425 [MHz] to 40680 [MHz].

The width of the waveguide 102 and the heating tube 15 (the dimension between the pair of short side walls 15a and 15b) is in the range of 0.5 [m] to 16 [m]. The height of the waveguide 102 and the heating tube 15 (the dimension between the pair of long side walls 15c and 15d) is in the range of 0.2 [m] to 10 [m].
The output of the microwave A is in the range of 0.1 [kW] to 1000 [kW]. The traveling speed of the flame resistant fiber 1b is in the range of 0.01 [m / min] to 50 [m / min]. The inside of the heating tube 15 is maintained at 91000 [Pa] to 122000 [Pa] in a nitrogen atmosphere. In the first carbonization step, the flame resistant fiber 1b is carbonized until the density becomes, for example, 1.50 [g / cm ³ ] to 1.60 [g / cm ³ ].
In addition, in the heating apparatus using the conventional electric heater, the temperature in the furnace is heated by about 7 [min] to 10 [min] at 500 [° C.] to 800 [° C.].

4). Heating test A heating test was performed using the heating device 100.
(1) Test 1
In Example 1, the traveling speed of the flame resistant fiber 1b is 0.3 [m / min]. In this case, the residence time of the flame resistant fiber 1b inside the heating tube 15 is about 8 [minutes]. The output of the microwave A is 1.0 [kW].
The width b of the slit 106 is 14 [mm], 10 [mm], 8 [mm], and 6 [mm], and is provided at an interval of 37 [mm] in the traveling direction of the flame resistant fiber 1b. A pair of slits 106 having the same width are provided adjacent to each other, and a total of eight slits 106 are provided. Here, the “i” -th slit (here “i” is a natural number from 1 to 8) from the upstream side in the traveling direction of the flame resistant fiber 1 b is defined as the i-th slit. "Is a slit number.
A change in the temperature of the surface of the flame resistant fiber 1b traveling in the heating tube 15 is shown by a solid line in FIG. In addition, the measurement of the surface temperature of the flame resistant fiber 1b uses the radiation thermometer.

In Example 1, the energy (electric field strength) of the microwave A is reduced along the traveling direction of the flame resistant fiber 1b by reducing the slit width b along the traveling direction of the flame resistant fiber 1b.
The flame resistant fiber 1b is heated (heated) by the energy of the microwave A and is carbonized. At this time, as shown by the solid line in FIG. 7, the temperature of the flame-resistant fiber 1 b peaks at the fourth slit position after entering the heating tube 15 and gradually decreases thereafter.
As described above, since the electric field strength of the microwave A is weakened along with the progress of carbonization of the flame resistant fiber 1b, the amount of heat stored in the flame resistant fiber 1b is reduced, and troubles such as cutting in the running flame resistant fiber 1b are caused. Did not occur.

(2) Experiment 2
The height adjusting member 151 is arranged inside using the heating tube 15 provided with the slit 106 having the slit width b described in the first embodiment. The output of the microwave A is 0.75 [W].
The height adjusting member 151 adjusts the distance (space height) between the pair of opposed surfaces of the heating tube 15. The interval (height) is 11 [mm], 16 [mm], and 21 [mm] from the upstream side. In addition, the space | interval (height) here subtracts the height of the height adjustment member 151 shown to (a) of FIG. 3 from the distance between long side walls 15c and 15d.

A change in the temperature of the surface of the flame resistant fiber 1b running in the heating tube 15 is indicated by a dashed line in FIG.
In Example 2, the electric field energy of the microwave A is weakened along the traveling direction of the flame resistant fiber 1b by widening the interval between the opposing surfaces (the height of the space between the long side walls) along the traveling direction of the flame resistant fiber 1b. (The effect of the slit 106 is also included).
The temperature of the flame resistant fiber 1b in the heating tube 15 gradually increases as it travels (moves downstream) as shown by the one-dot chain line in FIG. This is because although the output of the microwave A is lower than that of the first embodiment, the energy (density) of the microwave A is increased because the space between the long side walls 15c and 15d is narrowed.
Thereafter, the energy of the microwave A is weakened while increasing the interval (space height) between the opposing surfaces. As a result, the temperature of the flame resistant fiber 1b gradually rose, the runaway reaction of the flame resistant fiber 1b could be suppressed, and the flame resistant fiber 1b was not cut during running.

(3) Comparative Example For comparison, heating was performed with microwave A using a heating tube 15 having a constant slit width b. The traveling speed, number, and microwave output of the flame resistant fiber 1b are the same as those in the first embodiment. The slit width b in the comparative example is 10 [mm], and four sets (eight) are provided in the tube axis direction of the heating tube. The pitch L of the slits 106 is the same as that in the first embodiment.

A change in the temperature of the surface of the flame resistant fiber 1b traveling in the heating tube 15 is indicated by a broken line in FIG.
The temperature of the flame resistant fiber 1b in the heating tube 15 is lower than the temperatures of the first and second embodiments until entering the heating tube 15 and reaching the fifth slit position as shown by the broken line in FIG. It has become. This is because in Example 1 and Example 2, the energy of the microwave A is set higher on the upstream side of the heating tube 15 than on the downstream side, but in the comparative example, energy adjustment is not performed. This is because energy is low.
The temperature of the flame resistant fiber 1b of the comparative example enters the heating tube 15 and the temperature gradient becomes higher from about the third slit position, and the temperature becomes higher than that of the first and second embodiments at about the sixth slit position. ing. This is because the runaway reaction has started due to heat storage of the flame resistant fiber 1b, and the flame resistant fiber 1b may be cut during running.

(4) Summary As described above, the adjustment (Example 1) by changing the slit width b and the adjustment (Example 2) by changing the distance between the pair of opposing surfaces (the height of the space) are the energy of the microwave A. For example, the carbonization step of the flame resistant fiber 1b can be performed stably (without cutting).
Further, as shown in the second embodiment, even when the low-power microwave A is used, energy equivalent to that of the high-power microwave A can be given by increasing the energy upstream in the traveling direction.

<Modification>
As described above, the present invention is not limited to the embodiment. For example, any of the embodiments and modifications described below may be combined as appropriate, or a plurality of modifications may be combined as appropriate.

1. Precursor Fiber In the embodiment, the flame resistant fiber having 24,000 filaments has been described. However, the number of filaments is 3,000, 6,000, 12,000, 36,000, etc. It can also be applied to flame resistant fibers.
In the embodiment, the carbon fiber manufacturing method including the carbonization step has been described. However, for example, the graphitization treatment may be further performed before the surface treatment step. That is, in the embodiment, the heating method of the present invention was used for the first carbonization in the production of the general-purpose product (carbon fiber having an elastic modulus of 240 [GPa]. It can also be used for the first carbonization of precursor fibers for high-performance products such as elastic high-strength products.

2. Heating by microwave (1) Temperature In the test, the surface temperature of the fiber was heated to 400 [° C.] to 800 [° C.], but it may be set to a temperature according to carbonization. The temperature can be adjusted, for example, by adjusting the output of the microwave, adjusting the traveling speed of the precursor fiber, changing the dimensions of the heating tube, and changing the TE mode of the microwave.

(2) TE mode In the embodiment, the microwave mode is TE10, but other modes may be used. Other modes include a TE20 mode and a TE30 mode. That is, the microwave mode is a TEm0 mode (where “m” is a natural number and “0” is the number zero) in which the electric field strength at the short side wall is 0 (lower). Good.
When “m” is 2 or more, in the heating tube, two regions (two regions where the electric field strength is positive and negative) sandwiching a virtual plane connecting the centers of the pair of short side walls are sandwiched. The precursor fiber traveling region can be used, and the number of precursor fibers supplied can be doubled compared to the TE10 mode in which the precursor fiber traveling region is one. However, when the microwave output is the same, the electric field strength of the TE20 mode is half of the electric field strength of the TE10 mode.

(3) Traveling wave, standing wave Although the microwave A of the embodiment is mainly described as a standing wave, it may be a traveling wave. In this case, when the height adjusting member is disposed in the heating tube, it is preferably disposed in a direction that reduces the influence of the reflected wave.
For example, in the case of the height adjusting member 151 as shown in FIG. 3A, it is preferable to introduce the microwave from the upstream side. On the contrary, when the height adjusting member (151) as shown in FIG. 3 (a) is arranged at the center of the heating tube 15, it proceeds from the lower side of the height portion (downstream side of the heating tube). It is preferable to introduce waves.

(4) Electric field / magnetic field The heating in the embodiment uses the electric field component of the microwave. For example, the object to be heated may be heated using the magnetic field component, or the electric field component and the magnetic field component may be heated. You may heat a to-be-heated material using both components.

3. Heating tube Although the cross-sectional shape of the heating tube of the embodiment is rectangular, other shapes may be used. Examples of other shapes include a circular shape and an elliptical shape. In the case of these shapes, the microwave propagation mode is a TM mode such as TM01, for example.
In the embodiment, the height adjusting member 151 is disposed in the heating tube 15. However, for example, a heating tube having a shape having an internal space when the height adjusting member 151 is disposed may be used.

4). Height Adjustment Member The height adjustment member of the embodiment has a step shape as shown in FIG. However, the height adjusting member only needs to be able to adjust the distance between the opposing surfaces of the height adjusting member and the heating tube. For example, the height adjusting member may have a slope shape as shown in FIG. The upper surface constituting the slope (the surface facing the heating tube) may be linear or curved in the longitudinal section.

5. Strength Adjustment In one example of the embodiment, the strength of the microwave electric field is adjusted by a height adjustment member. However, for example, in the case of a heating tube having a square cross section, the distance between the pair of short side walls may be adjusted as shown in FIG.
In FIG. 9, the distance between the pair of short side walls 15Aa and 15Ab of the heating tube 15A gradually increases, and an adjustment member 151A is arranged inside the heating tube 15A. The adjustment member 151A has a first height portion 151Aa and a second height portion 151Ab. The first height portion 151Aa is higher than the second height portion 151Ab. The width of the adjustment member 151A gradually increases corresponding to the pair of short side walls 15Aa and 15Ab.
Also in this case, the microwave energy density changes, and the intensity of the microwave energy in the heating tube can be adjusted.
In addition, although adjustment of the space area of a heating pipe | tube utilizes the height adjustment member in embodiment, as mentioned above, it is good also as a shape which matched the shape of the heating pipe | tube with the height adjustment member. That is, the strength adjustment may be performed using an adjustment member, or may have an adjustment function so that the heating tube can be freely adjusted.

DESCRIPTION OF SYMBOLS 1 Fiber 1a Precursor 1b Flame resistant fiber 1c 1st carbonized fiber 15 1st carbonization furnace (heating tube)
15a, 15b Short side wall 15c, 15d Long side wall 151 Height adjustment member

Claims (9)

A TE-mode microwave electric field propagating in a heating tube having a square cross section having a pair of short side walls and a pair of long side walls heats an object to be heated traveling along the tube axis of the heating tube in the heating tube. In the heating method to
The intensity of the electric field of the microwave is adjusted by changing the internal area in the cross section of the heating tube along the traveling direction of the object to be heated. The heating method according to claim 1, wherein the change in the internal area of the cross section of the heating tube is performed by a change in an interval between opposing surfaces facing each other in a direction parallel to the pair of short side walls. The heating method according to claim 2, wherein the change in the interval is performed by arranging a height adjusting member on one long side wall. A TE-mode microwave electric field propagating in a heating tube having a square cross section having a pair of short side walls and a pair of long side walls heats an object to be heated traveling along the tube axis of the heating tube in the heating tube. In the heating method to
The heating tube has a plurality of slits for introducing a microwave generated from a microwave generator at intervals in the traveling direction,
The intensity of the electric field of the microwave is adjusted by changing the dimension in the traveling direction of the slit. In the carbon fiber manufacturing method of manufacturing the carbon fiber by heating the precursor fiber,
The heating method for heating the precursor includes the heating method according to any one of claims 1 to 4. A carbon fiber manufacturing method. In a carbonization apparatus for heating and carbonizing a precursor fiber that travels along a tube axis in a heating tube having a square cross section by a TE-mode microwave electric field,
A carbonization apparatus comprising adjustment means for adjusting the intensity of the electric field of the microwave along the traveling direction of the precursor fiber. The carbonization apparatus according to claim 6, wherein the adjustment unit changes an internal area in a cross section of the heating tube. The heating tube has a plurality of slits for introducing microwaves at intervals in the traveling direction,
The carbonization apparatus according to claim 6, wherein the adjustment unit includes the plurality of slits having different dimensions in the traveling direction in the slit. In the carbon fiber manufacturing apparatus for manufacturing the carbon fiber by heating the precursor fiber,
A carbon fiber manufacturing apparatus including the carbonization apparatus according to any one of claims 6 to 8 as a carbonization apparatus for heating and carbonizing the precursor.

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