JPH11131348A - Production of carbon fiber and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain carbon fiber of high quality without breakage at the jointed part or burning breakage by connecting precursor fiber bundles at their edges by needle-punching through a not-exothermic jointing medium at their flame- resisting temperature and then by firing the connected precursor fiber bundle. SOLUTION: Two of precursor fiber bundles with a filament count of 3,000 or more each are connected at their edge parts by using flame-resisting threads at the flame-resisting treatment (preoxidation) temperature as a non-exothermic jointing medium to flatly open the edge fibers of the crimped precursor fiber bundles into less than 400 filament count/mm so that the filament count F of the flame-resisting yarns and the filament count F of the precursor filament bundle may satisfy the formula: 0.4×G<=F<=1.5 and their edge parts of the precursor fiber bundles are heat-treated to remove their crimps. Then, they are overlapped, needle-punched and a flame-resisting reaction inhibitor as aqueous boric acid is applied to the jointed part and the jointed fiber bundle are fired to give the objective carbon fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing carbon fibers, and more particularly, to a technique for connecting precursor fibers which are raw yarns of carbon fibers.

[0002]

2. Description of the Related Art In addition to conventional aircraft and sports applications, carbon fibers are starting to be used in construction, civil engineering, and energy-related industrial applications, and the demand is growing rapidly. To further accelerate this growth, lower cost carbon fibers are desired. As one of the means of cost reduction, there is a method of firing a multifilament yarn at high density to improve the productivity of carbon fiber.However, if the yarn density is increased, the yarn itself in the flame-proofing process is increased. There is a problem that the oxidation reaction easily runs away due to heat generation. Therefore, when increasing the yarn density,
In order to prevent yarn breakage due to a runaway reaction, it is necessary to set the flame resistance temperature in the flame resistance step to a temperature lower than a normal temperature, and to perform the flame resistance for a long time. However, if the decrease in the oxidization temperature is large, the oxidization time is too long, and even if high yarn density firing is performed, it does not lead to improvement in productivity.

Another problem in high yarn density firing is that runaway reaction is likely to occur because the yarn density at the connection between the ends of the fiber bundle is higher than the yarn density of the fiber bundle itself. It is. The precursor fiber bundle, which is the raw yarn in the firing step, is usually wound up on a bobbin, a spool, or the like, or supplied in a state housed in a box, so that these precursor fibers are continuously fired into carbon fibers. In order to perform the conversion, it is necessary to connect the end portion of the fiber bundle of the precursor fiber wound up or housed in the box to the end portion of the precursor fiber bundle before it by some means.

As a connection method, Japanese Patent Publication No. 53-2341
No. 1, JP-A-54-50624 discloses a method in which precursor fiber bundles are combined and made flame-resistant, then knots are cut and removed, then re-tied and carbonized. A method in which a flame-resistant compound such as silicon grease is applied to the fiber bundle, a method in which both ends of a precursor fiber-resistant fiber bundle described in Japanese Patent Application Laid-Open No. There is a method of entanglement by high-speed fluid treatment described in JP-A-58-208420. However, in any of these methods, the yarn density at the joint portion is considerably higher than the yarn density of the fiber itself, so that burnout due to heat storage, yarn breakage, and the like are likely to occur during the oxidation treatment.

In Japanese Patent Publication No. 60-2407,
In order to suppress heat storage, a flame-resistant yarn or carbon fiber is interposed. However, since the connection method is a knot, the knot is tightened to increase the yarn density and the heat storage suppression effect is small.

[0006] As a method of improving these, Japanese Patent Publication No.
In JP-A No. 12850, a method is described in which the precursor fiber bundles or the precursor fiber bundles and the flame-resistant yarn are entangled by high-speed fluid treatment. FIG. 1 is a diagram showing the embodiment.
This is because the end portions 2a of the fiber bundles to be bonded are simply stacked in a bundle and placed in the processing chamber 4 of the nozzle 1, and about 5 to 60
% Relaxation and then high-speed fluid treatment. Further, in the connection method in which the flame-resistant yarn is interposed, since the flame-resistant yarn hardly generates heat in the flame-proofing step, there is an effect that the heat storage at the connection portion is smaller than in the connection between the precursor fiber bundles.

In the nozzle used in this method, as shown in FIG. 1, a high-speed jet fluid ejected from two nozzle holes 3 provided in a small entanglement processing chamber 4 collides with each other in the entanglement processing chamber. Is generated and the fiber bundle is opened and entangled, so that the fiber bundle having a small number of filaments can be sufficiently opened and entangled.

However, when the number of filaments of the fiber bundle to be entangled increases, the jetting fluid ejected from the nozzle does not hit the entire fiber bundle, the fiber bundle does not mix at the single yarn level, and some small bundles Divided into tangled. When such entanglement of the small bundles occurs unevenly in the joint portion, a portion having a high thread density of the fiber bundle is locally formed, and heat is easily stored. Further, since the entanglement is weak, the bonding strength is also weak.
In each of the examples described in the above-mentioned publications, the measurement was carried out only with a fiber bundle having a filament number of up to 12,000.
Even if the end portions of the precursor fiber bundles are connected directly or connected with a flame-resistant yarn interposed therebetween, they break in the flame-proofing step or burn out due to heat storage for the above-described reason.

In addition, in the case of a multifilament yarn,
To improve handling when unwinding from the stored state,
In some cases, the fiber bundle is crimped to give it a bundle,
Since the crimped fiber bundle is bulky and each single yarn is entangled little by little, the connection between the end portions of the crimped tow-like precursor fiber bundle is described in JP-B-1-125050. It is more difficult to implement using the method. In this case, even if the fiber bundles collected by crimping are overlapped with each other and subjected to high-speed fluid treatment, the fiber bundles do not spread at the single-yarn level due to crimping, and are bulky and cottony. Is suppressed at the single yarn level, and the fiber bundles are not sufficiently mixed with each other. Therefore, the entanglement is uneven and the bonding strength is very low.

[0010]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to improve the bonding strength of a bonding portion when connecting a thick precursor fiber bundle having 30,000 or more filaments. Blending and entanglement of fiber bundles
Achieves suppression of heat storage, allows the process to pass without breaking or burning out the connecting part in the flameproofing process, and the flameproofing treatment of the precursor fiber bundle connection to the flameproofing temperature of the precursor fiber bundle It is an object of the present invention to provide a method and an apparatus for producing carbon fiber, which can reduce the temperature drop.

[0011]

In order to solve the above-mentioned problems, a method for producing a carbon fiber according to the present invention is characterized in that the end portions of a precursor fiber bundle having a filament number of 30,000 or more are connected to each other at an oxidization resistance temperature. In the method, a connection is performed by entanglement with a needle punch through a non-heat-generating connection medium, and then firing is performed.

Here, "non-exothermic at the oxidizing temperature" means that the amount determined by the DSC (differential scanning calorimeter) method at the oxidizing temperature is 500 cal / g or less,
Details will be described later.

As the connection medium which does not generate heat at the oxidizing temperature, for example, oxidizing yarn can be used.

The connection between the end portion of the precursor fiber bundle and the connection medium is performed, for example, by opening each end portion of the precursor fiber bundle so as to have a flat shape, and at the same time, the flame resistance as an example of the connection medium. After opening the ends of the yarn (for example, 4,000 each)
After opening flattened so as to be not more than book / mm), in a state in which the opened flame-resistant yarn and the precursor fiber bundle are overlapped,
A method of connecting by entanglement by a needle punch can be used.

Further, in the method for producing carbon fibers according to the present invention, the end portions of the thick precursor fiber bundle having 30,000 or more filaments are connected to each other without passing through the non-heat-generating connection medium. Direct connection by entanglement with a needle punch, followed by firing.

In this case, the ends of the precursor fiber bundles are connected to each other after the ends of the precursor fiber bundles are flattened (for example, each of them is 4,000 fibers / mm or less). After flattening), a method of connecting by entanglement with a needle punch in a state where the end portions of the spread precursor fiber bundles are overlapped with each other can be used.

Further, when the end portions of the precursor fiber bundles are directly connected to each other, a chemical solution having an effect of suppressing an oxidizing reaction (an oxidizing reaction inhibitor) is used in order to prevent burnout and burnout due to heat storage at the yarn connecting portion. ) Can be applied to the yarn joining portion. Boric acid water can be used as the flame retardant reaction inhibitor used in such a production method.

As the precursor fiber bundle used in the present invention, both a crimped (crimped) fiber bundle and a non-crimped fiber bundle can be used.

Further, as the precursor fiber bundle used in the present invention, a precursor fiber bundle which is a crimped fiber bundle and in which only a connection portion at a terminal portion of the fiber bundle is removed by crimping can be used. For example, before entangling by the needle punch, a method of crimp-removing the end portion of the precursor fiber bundle to be entangled by heat treatment can be used.

Further, according to the present invention, there is provided an apparatus for producing carbon fibers via a non-heat-generating connection medium at a fiber bundle connection portion, wherein the precursor fiber bundle holds the end portions of the precursor fiber bundle in an opened state. The holding means, the connection medium holding means for holding the connection medium in an opened state, and the precursor fiber bundle after the terminal end of the precursor fiber bundle and the terminal end of the connection medium held by both means are overlapped, respectively. And entanglement processing means for performing entanglement processing by needle punching on a portion where the connection medium is superimposed.

Further, according to the present invention, there is provided an apparatus for producing carbon fibers which does not pass through the connecting medium to the fiber bundle connection portion, wherein the end portions of the precursor fiber bundle are directly connected to each other. Precursor fiber bundle holding means for holding the portions in an opened state, and entanglement processing means for performing entanglement processing by needle punching on the portion where the end portions of the precursor fiber bundles are overlapped. It consists of the features.

In the above-mentioned carbon fiber manufacturing apparatus, in addition to the holding means for each end of the precursor fiber bundle to be connected and the entanglement processing means using a needle punch, the precursor fiber bundle to be connected is further provided. May be provided with a crimp removing means for performing a crimp removing process by a heat treatment in advance on a portion where the entanglement process is performed.

By using such an apparatus, the above-described method for producing carbon fibers can be realized.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. First, an embodiment of a carbon fiber manufacturing process in which the (continuous) carbon fiber manufacturing method and manufacturing apparatus according to the present invention can be preferably used will be described. Since the speed of the process for producing the precursor fiber, which is the raw yarn for carbon fiber production, and the speed of the baking process are significantly different, the precursor fiber is usually wound in a bobbin as a fiber bundle or in a box (can). It is supplied to the firing step in a state where it is folded, stacked and accommodated in the inside. Hereinafter, a case where the precursor fibers are supplied in a state of being accommodated in a can will be described.

The precursor fiber bundle as the raw yarn accommodated in the can is drawn out of the can and then subjected to a flame-proof treatment in a flame-proof furnace. In this flame-resistant treatment, the yarn is subjected to a heat treatment at 200 to 500 ° C. in an oxidizing atmosphere to obtain a flame-resistant yarn. The flame-resistant yarn is carbonized in a carbonization furnace to form carbon fibers. The carbon fiber is subjected to a surface treatment such as a sizing agent if necessary in the surface treatment step,
It is wound in a winding step to be a carbon fiber product. When the precursor fiber bundle accommodated in the can comes to the end, the starting end of the precursor fiber bundle accommodated in the next can is connected. That is, the end portions of the precursor fiber bundle are connected to each other. The connected precursor fiber bundles are continuously fired to continuously produce carbon fibers. The present invention, in particular, in a method for producing a carbon fiber using a yarn having a large number of filaments,
An object of the present invention is to improve the method of connecting the yarns before the flame-proofing step while preventing the occurrence of inconvenience in the flame-proofing treatment.

Particularly, a precursor fiber bundle having a filament number of 30,000 or more is targeted. When a precursor fiber bundle fed out of a can comes to an end, a next can is prepared and an end portion of the precursor fiber bundle is prepared. Are connected to each other.

The connection method of the present invention includes a method of connecting each end portion with a connection medium that does not generate heat at the oxidizing temperature, and a method of connecting each end portion directly without the connection medium.

First, a method of connecting the respective end portions of the precursor fiber bundle via a connection medium will be described.

FIG. 2 is a schematic side view showing an example of a method of connecting the respective ends of the precursor fiber bundle 2 by entanglement at the single yarn level via a connection medium. Each end 2a of the precursor fiber bundle 2 is connected via a connection medium 10, as shown in FIG. Reference numeral 12 denotes an entangled portion on which an entanglement process by a needle punch described later has been performed. This connection medium 10
Is a non-heat-generating material at an oxidizing temperature, and for example, an oxidizing yarn can be used as such a connection medium 10.

Here, "non-exothermic at the flame-resistant temperature" means that the calorific value obtained by the DSC (differential scanning calorimeter) method is 500 cal / g or less.

The measuring method is as follows. (1) Measuring device: A differential scanning calorimeter (DSC) is used. (2) Sample preparation: 2 mg of the flame-resistant yarn and the like are ground to about 3 mm and inserted into an aluminum pan. (3) Measurement conditions: Measurement atmosphere; in air (atmosphere). Temperature: The temperature is raised from room temperature to 400 ° C. at a rate of 10 ° C./min. (4) How to Obtain the Heating Value As shown in FIG. 3, a straight line is drawn between the point at 200 ° C. and the point at 400 ° C. of the obtained heating curve, and the area enclosed by the straight line and the heating curve is calculated. The calorific value (cal / g) is used. FIG. 3 shows an example of characteristics of the precursor raw yarn and the oxidized yarn.

The ends of the precursor fiber bundles are connected as follows through the non-heat-generating connection medium as described above. As a preferable connection method, after the end portions of the precursor fiber bundle and the oxidized yarn are each spread flat, in a state where both ends of the connection medium are superimposed on each end portion of the opened precursor fiber bundle. A method of connecting by entanglement with a needle punch can be applied.

The fiber bundle at the portion to be entangled by the needle punch is spread flat in advance and overlapped with each other, so that the precursor fiber bundle and the connecting medium are entangled by the needle punch. The fibers can be uniformly mixed at the single yarn level and sufficiently entangled. At this time, if the fiber bundle is not sufficiently opened, the fiber bundle may be entangled in a bundle state, or the fiber mixture of the precursor fiber bundle and the connection medium may be uneven. For this reason, it is desirable that the fiber end of each fiber bundle be sufficiently opened in advance, and it is particularly desirable that the number of filaments be 4,000 filaments / mm or less.

When oxidized yarn is used as the connection medium, the number of interposed oxidized yarns should be selected in an appropriate range according to the properties, the number of filaments, the form, the breaking strength, etc. of the precursor fiber bundle. Is desirable. Assuming that the number of filaments of the precursor fiber bundle is G, as the number of filaments F of the oxidized yarn used as the connection medium becomes smaller than the number G of filaments of the precursor fiber bundle, the binding force also decreases. In some cases, the connection portion may not be able to withstand the applied tension in the process, which may cause a decrease in the rate of passing through the flameproofing process. Conversely, as the number of filaments F of the oxidized yarn increases with respect to the number G of filaments of the precursor fiber bundle, the connection medium covers the precursor fiber bundle of the connection portion, and the oxidization reaction heat of the precursor fiber bundle is reduced. It becomes difficult to remove heat. As a result, the effect of suppressing the heat storage of the connection portion is reduced. For this reason, in the present invention, the number of filaments of the oxidized yarn interposed as the connecting medium is preferably selected from an appropriate range according to the properties of the precursor fiber bundle to be connected, the number of filaments, the form, the breaking strength, and the like. It is desirable that the number F of filaments of the oxidized yarn interposed as the connection medium is in a relationship of 0.4 × G ≦ F ≦ 1.5 × G with the number G of filaments of the precursor fiber bundle. This is derived from the embodiment described later.

FIG. 4 shows an embodiment of the above-described connection method, in which the end portion 1 of the precursor fiber bundle 11 which is opened in a flat shape is shown.
1 shows a method of connecting the connection media 1a to both ends of the connection medium 10. In this example, the precursor fiber bundle 1 opened in a flat shape is used.
The overlapping portion of the end portion 11a of the first connection medium 10 and the connection medium 10 is
As shown in FIG. 2, they are connected by entanglement by a needle punch. In the example of FIG. 4, the connection medium 10 is arranged only on one side, but alternatively, the connection medium may sandwich the end portion of the precursor fiber bundle from both sides.

In a needle punch, generally, a needle having a barb in a direction perpendicular to a fiber bundle moves up and down, and a fiber bundle caught on the tip of the needle or the barb is pushed in to form a three-dimensional entanglement. In the connection application of the present invention, the number of needle punches, the density, and the shape of the needle can be optimized to obtain a desired binding force.

In addition, any needle-shaped means other than the needle punch can be used as long as the fiber bundles to be connected can be entangled in the same manner as the needle punch.

In the present invention, the fiber bundles that have been opened in a flat shape are overlapped with each other and then entangled by a needle punch. Therefore, even a fiber bundle having a large number of filaments can be uniformly mixed at a single yarn level. , Can be entangled.

The connection via the connection medium as shown in FIG. 4 is performed by using, for example, a method and an apparatus as shown in FIGS. As shown in FIG. 5, precursor fiber bundle holding means 22a, 22 having two pairs of fiber bundle holding portions 21.
b are arranged in series with an interval, and the end portions 1 of each precursor fiber bundle 11 are
1a and 11a (end and start) are held, respectively. The connection medium 10 made of, for example, oxidized yarn is held by the connection medium holding means 24 having two pairs of fiber bundle holding sections 23, and both ends of the held connection medium 10 are each end 11 a of the precursor fiber bundle 11. , 11a.

At this time, in order to strengthen the binding force of the entanglement process by the needle punch and to make the mixing uniform, the end portion 11a of the precursor fiber bundle and the connecting medium 10 are connected to the precursor fiber bundle holding means 22a, 22b and the When holding by the connection medium holding means 24, it is desirable to hold each fiber bundle and the connection medium in a state where they are opened in a flat shape without twisting. In particular, it is desirable that each fiber bundle and the connection medium are spread to 4,000 fibers / mm or less. By doing so, the precursor fiber bundle and the connecting medium can be uniformly mixed at the single yarn level, and the binding power is also improved.

In this state, as shown in FIG. 6, each of the overlapping end portions 11a is placed in the processing chamber of the needle punch.
And the connecting medium 10 are arranged such that the needle punch 2
5 is installed, and the fiber bundles overlapped by the needle punch are entangled to obtain a desired connection state. In this schematic configuration, the structure of the needle punch is a stripper plate 2
While the needle beam 26 is moved up and down with the fiber bundle overlapped between the bed 7 and the bed plate 28, the fiber bundle is entangled, but other structures may be used.

In the connection method as described above, a connection medium that does not generate heat at the oxidization resistance temperature is used as the connection medium. Calorific value is kept small,
Problems such as yarn breakage due to excessive heating are avoided.
As a result, when the joint between the ends of the thick precursor fiber bundle having 30,000 or more filaments is subjected to the flameproofing treatment, the flameproofing can be performed without substantially lowering the flameproofing temperature. Therefore, finally, it becomes possible to continuously produce thick carbon fiber bundles, and it is possible to produce carbon fibers at low cost.

In particular, the method of opening the end portion of the precursor fiber bundle and connecting it by entanglement with a connection medium by a needle punch is similar to the method of tying the fiber bundle or connecting by a high-speed fluid treatment according to the prior art. There are no bumps or twists, and the bindings are not tightened. For this reason, even if the original yarn is a relatively thick fiber bundle, the connection portion can be maintained in a form having a small calorific value per unit area or per unit volume. Together, excessive heat generation and heat storage can be more reliably suppressed. As a result, even if the connection portion is considered to pass through the furnace, the flame-resistance temperature does not need to be set so low, and the thick precursor fiber bundle can be efficiently and stably oxidized to a predetermined state. Thus, carbon fibers can be produced at a low cost with high industrial productivity.

Further, the above-mentioned method of opening the end portion of the precursor fiber bundle and connecting it by entanglement with a connecting medium by a needle punch involves directly connecting the end portions of the precursor fiber bundle without passing through a connecting medium. It can be applied to the connection method.

When trying to connect the end portions of the thick precursor fiber bundle according to the prior art, the number of filaments is too large and, for example, even if fluid treatment is performed, the entanglement is weak and the yarn density becomes non-uniform, and the binding force is reduced. Insufficient heat storage due to local high yarn density
Burnout occurs.

However, according to the method of the present invention, in which the fiber bundles are superposed in an opened state and connected by entanglement with a needle punch, even if the ends of the thick precursor fiber bundles are directly connected to each other, The binding force is greatly improved as compared with the technology, and in the connection portion, connection in a form having a small calorific value per unit area or unit volume can be uniformly performed, and excessive heat generation and heat storage can be suppressed.

The method of opening the ends of the thick precursor fiber bundles and directly connecting them can be basically performed in the same manner as the above-described method of interposing a connection medium.

Specifically, there is a method in which the end portions of the precursor fiber bundles are overlapped in an opened state and connected by entanglement with a needle punch.

As a specific example of the connection form, the end portion 11a (end portion) of the precursor fiber bundle 11 shown in FIG.
In place of the connecting medium connected to the end portion, the terminal portion 11a (start end portion) of the next precursor fiber bundle may be connected.

The connection at this time can be easily carried out by the same connection method and apparatus as those shown in FIGS. 5 and 6 via the connection medium. Specifically, the precursor fiber bundle holding means 22a shown in FIGS. 5 and 6 is caused to hold the terminal end (end) 11a of the precursor fiber bundle.
Then, in place of the connecting medium 10, the terminal end (starting end) 11a of the next precursor fiber bundle is held. In this case, another precursor fiber bundle holding means 22b is not required. Next, as shown in FIG. 6, the precursor fiber bundle (end portion) 11 a and the precursor fiber bundle (start end portion: instead of the connection medium 10) are overlapped and subjected to an entanglement process by a needle punch 25. It is.

At this time, in order to strengthen the entanglement of the entanglement treatment by the needle punch and to uniformize the fibers, the precursor fiber bundle ends (end and start) are flattened without twisting. It is desirable to keep it. In particular, each fiber bundle
It is desirable that the fibers be opened to 4,000 lines / mm or less.

Further, in the above-described method of connecting the end portions of the precursor fiber bundles via a connection medium and the method of directly connecting the end portions of the precursor fiber bundles, the fiber bundles are opened in advance. Since the entanglement process by the needle punch is performed after the arrangement, even if the precursor fiber bundle to be connected is crimped, it can be connected with a certain binding strength.

However, the crimped precursor fiber bundle is
Since the single yarns are entangled in the form of cotton, the fiber bundles to be connected tend to be insufficiently mixed.

As a means for solving this, in the connection method according to the present invention, only the terminal connection portion of the crimped precursor fiber bundle can be subjected to the crimp removal treatment.

Since the crimp removing treatment is intended to strengthen entanglement by needle punching, the crimped and entangled cotton-like fiber bundle is entangled and straightened. It is sufficient that the individual yarns are kept straight and subjected to a short-time heat treatment so that the individual yarns are straight and the single yarns are not entangled.

Therefore, the means for heat treatment is hot air,
Various means such as press with steam and a sheet heater can be applied.

FIG. 7 is a schematic side view showing a specific example of a method and an apparatus for crimping and removing only the end portion of a fiber bundle in a short time. End portion 11 of crimped precursor fiber bundle 11
a is held by the fiber bundle holding means 30a, 30b, and then the precursor fiber bundle holding means 30a, 30b is moved in a way to separate the fiber bundle holding means 30 of the crimped fiber bundle.
The crimp of the end portion 11a of the precursor fiber bundle sandwiched between the a and 30b is stretched and straightened. At this time, the movement of the fiber bundle holding means 30a, 30b may be at a predetermined interval, or the tension applied to the fiber bundle may be at a predetermined load.

Thereafter, the crimp can be removed in a short time by sandwiching the fiber bundle from both upper and lower surfaces with the sheet heater 31.
Specifically, for example, the temperature of the planar heater 31 is 80 to
Pressing at 180 ° C., more preferably about 100 ° C. to 150 ° C. for about 3 to 10 seconds is sufficient.

Since the crimp removing means shown in FIG. 7 is very simple, it can be easily incorporated into the connection methods and connection devices shown in FIGS. 5 and 6 described above.

Incidentally, in the method of directly connecting the precursor fiber bundles described above, the precursor fiber density at the connecting portion is twice as large as the method of connecting via a non-heat-generating connection medium at the oxidization resistance temperature. Therefore, heat is easily stored as compared with the case where a connection medium is interposed.

As a means for alleviating this, in the present invention,
It is possible to adopt a method of applying a flame-resistant reaction inhibitor to a portion where the thick precursor fiber bundles are directly connected to each other.

By providing an antioxidant reaction inhibitor,
Since the exothermic reaction is suppressed, it is possible to suppress the heat storage at the connection portion, and it is possible to avoid inconveniences such as burning and yarn breakage in the flameproofing step. As a flame retardant reaction inhibitor, boric acid water is particularly desirable.

[0063]

The present invention will be described more specifically below with reference to examples. In order to confirm the effects of the present invention,
The following oxidizing furnace running test was performed using the oxidizing furnace in the manufacturing process described above as one embodiment of the carbon fiber manufacturing process. The precursor fiber bundle accommodated in the can is guided to an oxidizing furnace and is oxidized at a predetermined temperature for a predetermined time. Prepare a can containing the next precursor fiber bundle in the place where the can is placed, and use the yarn joining method described later in detail to prepare the end of the precursor fiber bundle accommodated in the can and the next precursor fiber bundle. The beginning was connected. The connection passes through a guide bar and a drive station to enter a hot-air circulation type flameproofing furnace. The oxidizing time was set to 60 minutes, the oxidizing furnace temperature was changed for each level, the upper limit temperature at which the yarn could be passed was measured, and the oxidizing process passage rate at that temperature was measured.
Since there is a fluctuation range in the furnace temperature control, the measurement temperature was set at 5 ° C. intervals.

The connecting portion passing through the oxidizing furnace was subsequently carbonized at 1500 ° C. in a nitrogen atmosphere, and after passing through the carbonizing furnace, was wound up on a bobbin using a winder. Initially, the tension applied to the precursor fiber bundle in the oxidation furnace is about 6 kgf /
In the later stage, the fiber bundle contracted and was about 9 kgf / st.

The precursor fiber bundle to be made flame-resistant is a polyacrylic precursor fiber bundle having 1.5 denier single yarn and 70,000 filaments. The fiber bundle is crimped to make it easy to start up from the can and to pass through the yarn path. Table 1 summarizes the examples and comparative examples.

<Blank> As a blank, the upper limit temperature at which the oxidizing furnace could pass through the precursor fiber bundle having 70,000 filaments (70K) (no connection portion), and the process passage rate were measured. As a result, the upper limit temperature at which oxidization was possible was 235 ° C. When the oxidization temperature was set to 240 ° C., the precursor fiber bundle was burned out. In addition, the flame resistance temperature 23
At 5 ° C., the pass rates of both the oxidization step and the carbonization step were 100%.

<Example 1> 70,000 filaments
The end portions of the precursor fiber bundles of the book were connected to each other with an oxidized yarn interposed therebetween. At this time, the number of filaments of the flameproofing yarn to be interposed was 36,000, 48,000, 60,0.
Four types of connection samples were prepared, with the number being 00 and 100,000.

As the connecting means, the crimp removing means shown in FIG. 7 and the fiber bundle connecting device shown in FIGS. 5 and 6 were used, and the connection was carried out in the form shown in FIG. Entanglement length is about 30c
m. The procedure is shown below.

(1) The end of the precursor fiber bundle is crimped and removed using the crimp removing means shown in FIG. (Surface temperature 100 ° C
The stretched fiber bundle is sandwiched from both sides and pressed for 5 seconds by a sheet heater at ~ 130 ° C. (2) As shown in FIG. 5, the precursor fiber bundle that has been crimped and removed, and the oxidized yarn serving as the connection medium, are each flattened (widened) to a width of 25 mm, and then overlapped and held. (3) As shown in FIG. 6, the overlapping portion is entangled with a needle punch. (4) The remaining obstructive portions at the end portions of the connected precursor fiber bundle and the oxidized yarn are cut and removed so that the connection portion has the form shown in FIG.

The connecting portion produced by the above-described means is an entangled portion formed by a needle punch, in which the fiber bundle is sufficiently mixed and entangled at a single yarn level, and is entangled in such a form as to be twisted by a small bundle. Did not occur.

The connection portion of the precursor fiber bundle thus connected was passed through an oxidizing furnace, and the upper limit temperature at which the fiber bundle could pass was measured. In addition, a joint part of the precursor fiber bundle was prepared under the same conditions, and the passage rate of the joint in the oxidation treatment step and the passage rate of the next carbonization step in a state where the upper limit temperature that can pass through the oxidation furnace were set were measured. did.

As a result, as shown in Table 1, as compared with the blank, the upper limit temperature at which the gas could pass through the oxidizing furnace was equal to or about 5 ° C., and the degree of reduction was extremely small. When the temperature of the oxidizing furnace was set to the upper limit temperature at which the oxidizing furnace could pass, and the connecting portion was run, it passed through the oxidizing step and the carbonizing step, and was wound on a bobbin by a winder. In particular, since the form of the entangled portion by the needle punch is flat and uniformly entangled, it easily fits in the grooved roller.

<Comparative Example 1> 70,000 filaments
The ends of the precursor fiber bundles of the book are separated from each other by
The connection was made by the air entanglement method of the prior art described in Japanese Patent Application Laid-Open No. 0-0. The air entanglement nozzle having the structure shown in FIG. 1 and having a entanglement treatment chamber and a larger nozzle hole diameter for a fiber bundle having a large number of filaments was used. Regarding the number of entanglement points, the air entanglement process was performed at four points at the overlapping portion of the fiber bundles to be connected. The bundle of fiber bundles to be connected was placed in the entanglement processing chamber of the nozzle in a state of being overlapped with each other, and the air entanglement treatment was performed by setting the compressed air pressure supplied to the nozzle to 0.5 MPa. In the air entanglement by the above method, the fiber bundle having a large number of filaments is divided into several small bundles, and the twisted entangled form is obtained.

With respect to the produced connection portion, the upper limit temperature and the process pass rate at which the connection portion can pass through the oxidizing furnace were measured in the same manner as in Example 1. As a result, the air-entangled portion twisted and entangled easily in the oxidizing furnace was liable to heat storage and burn, and the upper limit temperature at which the oxidizing furnace could pass was 220 ° C., which was much lower than that of the blank. In addition, since the binding force was significantly lower than that of Example 1 and the variation was large, in the oxidization test at 220 ° C., the connection portion was likely to come off or break frequently.

<Comparative Example 2> Number of filaments 70,000
The end portions of the precursor fiber bundles of the book are made
The connection was performed by interposing a flame-resistant yarn having 60,000 filaments by the air entanglement method which is a conventional technique described in Japanese Patent Application Laid-Open No. H10-163,086. The connection method was the same as in Comparative Example 1. In the air entanglement by the above method, as in Comparative Example 1, the precursor fiber bundle and the oxidized yarn became separate and entangled into several small bundles.

The upper limit of the temperature at which the connection portion was able to pass through the oxidizing furnace and the process passage rate were measured in the same manner as in Example 1. As a result, in the oxidizing furnace, there was an effect of suppressing heat storage due to the presence of the oxidizing yarn as compared to Comparative Example 1, and the upper limit temperature at which the oxidizing furnace could pass was 225 ° C. Greatly reduced. Also, as in Comparative Example 1, the binding force was significantly weaker than in Example 1, and the dispersion was large.

From Example 1 and Comparative Examples 1 and 2 described above, in the connection method of the present invention, compared to the conventional technique, the binding strength of the joint is improved, and the fiber bundles to be joined are uniformly mixed and entangled. It can be seen that the effect of suppressing heat storage has been achieved. In particular, from the results of (1) to (1) in Example 1, the number of filaments F of the oxidized yarn to be interposed is in the range of 0.4 × G ≦ F ≦ 1.5 × G with respect to the number of filaments G of the precursor fiber bundle. It is preferable that the ratio be in the range of 0.6 × G ≦ F ≦ 1.0 × G.

Example 2 Number of filaments 60,000
The end portions of the precursor fiber bundle having 70,000 filaments (70K) were connected to each other via the (60K) flame-resistant yarn. The connecting means was the same as in Example 1 and was carried out in the above-described procedures (1) to (4), but the width for opening each fiber bundle in (2) was 14 mm instead of 25 mm. In the connection part produced by this connection method, compared to the connection part of Example 1, there was a variation in the mixing and entanglement of the entangled part by the needle punch. As a result, although the upper limit temperature at which the gas can pass through the stabilization furnace and the process passage rate are slightly lower than those of Example 1, it is greatly improved as compared with Comparative Example 2.

In Example 2, as shown in Table 1, the opening width of the end portion of each fiber bundle before the entanglement treatment by the needle punch was larger than 4,000 yarns / mm. In Examples 1, 3, and 4, it was 4,000 fibers / mm or less, and the entanglement treatment by needle punch was performed after sufficiently opening each fiber bundle. From this, in order to carry out the connection method of the present invention by a more preferable method, the opening width of the end portion of each fiber bundle to be connected is set to 4,000 / mm.
It is desirable to open the fibers in a flat shape in advance as described below, and then perform the entanglement treatment by needle punching by overlapping.

<Example 3> 70,000 filaments
The end portions of the precursor fiber bundles of the book were directly connected without intervening the oxidized yarn. The connecting means is the same as in Example 1, but instead of overlapping the precursor fiber bundle and the oxidized yarn,
The end portions of the precursor fiber bundle are overlapped and connected. The length of the entangled portion by the needle punch was about 30 cm. In the connection part manufactured by the above-mentioned means, the entangled part formed by the needle punch was sufficiently uniformly mixed and entangled, and no entanglement in the form of twisting with a small bundle occurred.

The connection thus connected was passed through an oxidizing furnace, and the maximum temperature at which the connection was possible was measured. As a result, since the density of the precursor fiber bundle at the connection portion was increased, the connection portion easily stored heat, and the upper limit temperature at which the material could pass through the oxidizing furnace was 225 ° C. Although decreased as compared with the blank, it was higher and improved as compared with Comparative Example 1. When the connecting portion was run at 225 ° C., it passed through the flameproofing step and the carbonizing step, and was wound up on a bobbin by a winder. In particular, since the form of the entangled portion by the needle punch is flat and uniformly entangled, it easily fits in the grooved roller.

This method has a lower productivity than the method in which the flame-resistant yarn is interposed, but is a simpler method than that in Example 1, and thus can be used under conditions where the temperature in the flame-resistant furnace can be lowered. Is fully applicable to production.

<Example 4> After directly connecting the end portions of the precursor fiber bundle having 70,000 filaments to each other in the same manner as in Example 3, boric acid water was added to the connection portion as an anti-oxidation reaction inhibitor. Granted. As a result, the upper limit temperature that can pass through the oxidizing furnace was 235 ° C., and the sample could be passed through the oxidizing furnace under the same conditions as the blank. However, the portion to which the boric acid solution is applied is suppressed in the reaction and retarded in the flame resistance, and thus burns out even if the carbonization is performed as it is. Therefore, when performing boric acid treatment on the connection portion, after the connection portion has passed through the oxidation furnace, cut and remove the portion with boric acid water,
It is desirable to reconnect.

From the above Examples and Comparative Examples, the connection form of the precursor fiber bundle according to the present invention is extremely effective in industrially producing continuous carbon fibers, particularly, for the oxidizing treatment. You can see that.

[0085]

[Table 1]

[0086]

As described above, according to the present invention,
In particular, when a thick precursor fiber bundle having 30,000 or more filaments is connected by entanglement with a needle punch, the binding strength of the connecting portion is improved, and the uniform fiber mixing and entanglement of the connected fiber bundles, and the heat storage of the heat storage. In the flameproofing process, the connection can be passed without breaking or burning out, and the flameproofing treatment temperature of the precursor fiber bundle connection portion with respect to the flameproofing treatment temperature of the precursor fiber bundle. Can be reduced, and a high-quality carbon fiber can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view of an air-entangled nozzle according to an embodiment of a connection method according to the related art.

FIG. 2 is a schematic side view of a connecting portion between precursor fiber bundles according to the present invention.

FIG. 3 is a characteristic diagram showing how to determine a heat value of a connection medium.

FIG. 4 is a schematic configuration diagram illustrating an example of a connection unit.

FIG. 5 is a schematic perspective view showing an example of a connection method and a connection device.

FIG. 6 is a schematic side view showing a connection method using the method and apparatus of FIG.

FIG. 7 is a schematic side view showing an example of a crimp removing unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conventional entanglement nozzle apparatus 2 Thread consisting of precursor fiber bundle 2a Terminal part of precursor fiber bundle 3 Nozzle hole 4 Processing chamber 10 Connection medium 11 Precursor fiber bundle 11a Terminal part of precursor fiber bundle 12 Needle punch or needle Entangled part by means of shape means 21, 23, 30a, 30b Fiber bundle holding part 22a, 22b Precursor fiber bundle holding means 24 Connecting medium holding means 25 Needle punch or needle-like means 26 Needle beam 27 Stripper plate 28 Bed plate 31 Planar heater

Claims (13)

[Claims] 1. An end portion of a precursor fiber bundle having 30,000 or more filaments is connected by entanglement with a needle punch through a connection medium which is non-heat-generating at an oxidizing temperature, and then fired. A method for producing carbon fiber. 2. The method for producing carbon fibers according to claim 1, wherein the connection medium is a flame-resistant yarn. 3. The flame-resistant yarn and the precursor fiber bundle are flattened so that the ends of the flame-resistant yarn and the precursor fiber bundle each have a thickness of 4,000 / mm or less. 3. The method for producing carbon fibers according to claim 2, wherein the connection is performed by entanglement with a needle punch in the superposed state. 4. The crimp-removed fiber bundle end portion, which is a crimped fiber bundle of the precursor fiber bundle and is subjected to a heat treatment before being entangled by the needle punch. The method for producing carbon fiber according to claim 3, characterized in that: 5. The number of filaments F of the oxidized yarn interposed at the connection of the end portion of the precursor fiber bundle is 0.4 × G ≦ F ≦
The method for producing a carbon fiber according to claim 2, wherein the carbon fiber is in a range of 1.5 × G. 6. A method for producing carbon fibers, comprising connecting the ends of precursor fiber bundles having 30,000 or more filaments by entanglement with a needle punch and then firing. 7. Each of the end portions of the precursor fiber bundle is set to 4,
After opening in a flat shape to be 000 lines / mm or less,
7. The method for producing carbon fibers according to claim 6, wherein the end portions of the opened precursor fiber bundles are connected by entanglement with a needle punch in a state where the end portions are overlapped. 8. The crimped fiber bundle, wherein the precursor fiber bundle is a crimped fiber bundle, and the end portion of the fiber bundle to be entangled is crimped and removed by heat treatment before being entangled by the needle punch. The method for producing a carbon fiber according to claim 6, wherein: 9. The carbon fiber production according to claim 6, wherein after the entanglement by the needle punch is performed, a flame-resistant reaction inhibitor is applied to the entangled portion. Method. 10. The method for producing carbon fiber according to claim 9, wherein said flame-resistant reaction inhibitor is boric acid water. 11. An apparatus for connecting end portions of a precursor fiber bundle with a connection medium interposed therebetween, wherein said precursor fiber bundle holding means holds the end portions of said precursor fiber bundles in an opened state. And, the connection medium holding means for holding the connection medium in an opened state, and after overlapping the ends of the precursor fiber bundles and the end parts of the connection medium respectively held by both means, the precursor fiber bundle and An entanglement processing means for performing entanglement processing using a needle punch on a portion where the connection medium is superimposed, wherein the carbon fiber production apparatus is provided with: 12. An apparatus for directly connecting end portions of a precursor fiber bundle, comprising a precursor fiber bundle holding means for holding the end portions of the precursor fiber bundles in an opened state, respectively, and a precursor fiber. Entanglement processing means for performing entanglement processing using a needle punch on a portion where the end portions of the bundle are overlapped with each other, the method comprising the steps of: 13. A crimp removing means for performing a crimp removing process by a heat treatment in advance at a portion of the precursor fiber bundle to be connected to which the entanglement process is performed using a needle punch. An apparatus for manufacturing a carbon fiber according to 11 or 12.