JP3890701B2 - Continuous carbon fiber manufacturing process - Google Patents

Description

表中、＊印は耐炎化工程で糸条が通過しない、あるいは糸条通過率が低く炭化処理に供し得なかったものである。また、弛緩比率とは、端部の内側の弛緩率に対する端部の弛緩率の割合を百分率で表したものである。
【００４３】
【発明の効果】
本発明によれば前述した従来法の欠点または問題点、即ち、多フィラメントの有機繊維糸条の焼成時、糸切れないしローラ巻き付き等のトラブルが生じやすく、もしかかるトラブルの修復に時宣を失すると焼成炉内の燃焼等の重大災害に至ること、またそのことが直ちに重大災害に至らぬまでも、糸条通過性が著しく低下し、焼成時の糸切れやローラ巻き付き等を一層助長させるという問題点が解消されるだけではなく、更に次のような多くの優れた効果が得られる。
【００４４】
連続焼成時の品種交換、例えばトータルデニールの変更を容易に行うことができる。即ち、トータルデニールの異なる２種の有機繊維糸条の糸条両端を重ね合わせ、絡合処理することにより両者を容易に接続できる。
【図面の簡単な説明】
【図１】２ヶ所を絡合処理した有機繊維糸条の平面図である。
【図２】本発明におけるＣＦ値測定法を説明するための斜視図である。
【図３】本発明における絡合処理装置の一例を示す斜視図である。
【図４】図３に示す絡合処理装置の縦断面図である。
【図５】図３に示す絡合処理装置の側面図である。
【符号の説明】
１，１’； 交絡部
２ ； 糸条中間部
３ ； 一本の糸条
４，４’： 糸条
５ ； フック
６，７ ； 荷重
８ ； 絡合処理空間
９ ； 糸条挿入口
１０ ； エア噴出孔
Ｌ ； 絡合部長さ
Ｌ’ ； 絡合部と絡合部の間隔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing continuous carbon fibers, and more particularly to a method for producing carbon fibers continuously by efficiently connecting precursor fibers, which are carbon fiber yarns.
[0002]
[Prior art]
In addition to conventional aircraft and sports applications, carbon fiber has begun to be used in construction, civil engineering, and energy-related industrial applications, and demand is growing rapidly. In order to further accelerate this elongation, a lower cost carbon fiber is desired. One way to reduce costs is to fire multifilament yarns at a high density to improve carbon fiber productivity. However, if the yarn density is increased, the yarn itself generates heat during the flameproofing process. Therefore, there is a problem that the oxidation reaction tends to run away. Therefore, when the yarn density is increased, in order to prevent yarn breakage due to runaway reaction, the flameproofing temperature in the flameproofing process is set to a temperature lower than the normal temperature and flameproofing is performed over a long period of time. There is a need. However, if the decrease in the flameproofing temperature is large, the flameproofing time becomes too long, and even if the yarn density is increased, the productivity cannot be improved.
[0003]
Another problem with high yarn density firing is that runaway reactions are more likely to occur because the yarn density at the ends of the fiber bundle ends is higher than the yarn density of the fiber bundle itself. Precursor fiber bundles that are the raw yarn of the firing process are usually rolled up on bobbins, spools, etc. or supplied in a folded and laminated form inside the box, so these precursor fibers are continuously fired and converted to carbon fibers. In order to do this, it is necessary to connect the end portion of the bundle of precursor fibers wound or folded and laminated to the end portion of the precursor fiber before that by some means.
[0004]
As a connecting method, as described in Japanese Patent Publication No. Sho 53-23411, the precursor fiber bundles are made flame-resistant by combining them, and then the knots are cut and removed, and then re-knotted and carbonized. No. 50624, a method for imparting a flame resistant compound to the joint, and both end portions of the precursor fiber bundle described in JP-A-56-37315 are heat-treated in advance, connected by a special knotting method, and fired. And 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 bundle itself, and therefore, burnout due to heat storage, yarn breakage, etc. are likely to occur during the flameproofing treatment.
[0005]
In addition, it is very difficult to perform multifilament yarn joining using the conventional yarn joining method for precursor fiber bundles with a small number of filaments. For example, Japanese Patent Publication No. 1-12850 discloses a method of entanglement by high-speed fluid processing using a precursor fiber bundle having up to 12,000 filaments. It was not suitable for entanglement.
[0006]
As a result of the increase in the number of filaments, troubles such as thread breakage at the entangled part or winding of a roller are likely to occur due to insufficient bond strength (tensile strength) during flameproofing treatment. There was a problem of leading to a serious disaster such as burning.
[0007]
In addition, even if such a serious disaster does not occur, there is a problem that the thread passing property of the connecting portion is remarkably lowered, and yarn breakage and roller winding during firing are further promoted.
[0008]
[Problems to be solved by the invention]
It is an object of the present invention to provide a continuous carbon fiber production method that does not have the above problems.
[0009]
That is, the object of the present invention is to reduce as much as possible yarn breakage or roller wrapping during firing at the connecting portion of the ends of organic fiber yarns when producing carbon fibers, thereby further improving quality and operability. At the same time, it is intended to prevent serious disasters such as combustion in a combustion furnace. Another purpose is to connect the organic fiber yarns with a strong, uniform shape and excellent thread-passability, and workability, operability and productivity, especially for connecting multiple filaments and multiple organic fiber yarns. Thus, it is an object of the present invention to provide a continuous production method that is advantageous when producing carbon fibers in large quantities. Still another object is to provide a production method in which the number of yarns and varieties of organic fiber yarns can be easily changed in a continuous production method of carbon fibers.
[0010]
[Means for Solving the Problems]
The present invention has the following configuration in order to solve the above problems.
[0011]
That is, organic fiber yarns having 24,000 to 30,000 filaments are superposed on each other, and in the superposed portion, 4-5 entangled sites are constrained at both ends, and the entangled sites are relaxed. The rate of 5 to 60% and the rate of relaxation of the entangled sites at both ends is set to 40 to 60 % of the rate of relaxation of the entangled sites on the inside, and the organic fiber yarns are entangled and connected by high-speed fluid treatment. Is a method for producing a carbon fiber, characterized by continuously firing.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
That is, as the organic fiber yarn used in the present invention, an organic type such as an acrylic type or polyvinyl alcohol type fiber, which generates a large amount of heat during firing, particularly when flame resistant, and is likely to cause disconnection of the connection part due to heat storage or generation of tar-like substances. Although it is effective for fiber yarns, it is not limited to these, and it is also effective for connection of pitch-based fiber yarns due to its ease of connection and excellent thread passage properties. Fiber yarns can be used.
[0013]
Furthermore, the single fiber fineness and the number of fibers of these organic fiber yarns are not particularly limited as long as they can be entangled by high-speed fluid treatment described later, and the fineness is 5 denier (d) or less, preferably 0.1 to 0.1. 3d, the number of fibers is is used within the scope of at least 24,000 to 30,000 lines.
[0014]
The feature of the present invention is that the ends of the multifilament organic fiber yarns are superposed on each other, and the high-speed fluid treatment is applied to the superposed portion so that the yarns of the superposed portion are integrally entangled and connected. The tensile strength of the joined portion is usually maintained at 5.5 g / d or more.
[0015]
That is, in the present invention, when the multifilament organic fiber yarns are directly overlapped, there is a tendency that the strength decrease due to thermal oxidation of the fiber yarns constituting the overlapped portion tends to increase, and the overlapping of connected yarns Due to the lack of strength of the mating part, the handleability and workability are lowered, and the overlapped part may be cut particularly in the flameproofing process and the subsequent carbonization process. For this reason, it is sufficient that the tensile strength is maintained at 5.5 g / d or more in the overlapped portion after the entanglement treatment. If the tensile strength is less than 5.5 g / d, the above-mentioned problem due to insufficient strength of the connection portion is caused. May occur.
[0016]
The tensile strength in the present invention is the average denier value of the yarn forming the entangled portion when the point of 2 cm outside the entangled portion is held and pulled at a speed of 20 cm / min at room temperature. Divided by the minimum value of 20 samples or more. For yarns that have been entangled in multiple places, measurement is performed by grasping a point 2 cm outside the farthest entangled part.
[0017]
Here, the entangled portion between the organic fiber yarn and the organic fiber yarn connected by the entanglement treatment used in the present invention will be specifically described with reference to the drawings.
[0018]
FIG. 1 is a plan view showing the structure of an entangled portion of an organic fiber yarn intertwined using air as a high-speed fluid, and is an example in which two points are entangled with a relatively high air pressure. When the entanglement process is performed with a general air treatment apparatus (for example, FIG. 3), strong entanglement between single fibers usually occurs at two locations 1, 1 ′, and the yarns sandwiched between the entanglement portions 1, 1 ′. The intermediate portion 2 exhibits a very weak entanglement state although migration (migration) occurs, and the entangled portions 1, 1 ′ substantially contribute to the strength. In the present invention, entangled portion is constituted from an intermediate portion thereof 2 The entangled portions 1,1 ', you like this entangling unit is present 4-5 places. In FIG. 1, L represents the length of the entangled portion, and L ′ represents the distance between the entangled portion and the entangled portion.
[0019]
It is desirable to have sufficient tensile strength in the entanglement of the fiber with the fluid, and the shape of the connection portion should be as close to the shape of a single yarn as possible. What is to be done is a point related to the thread passing property in the subsequent firing step.
[0020]
Air, water, steam or the like can be applied to the fluid used for the high-speed fluid treatment of the present invention, but it is preferable to use air in terms of workability and economy. The yarn connecting means employs a method in which the two yarns to be connected are aligned with each other and then the fibers of the overlapped portion are entangled using a high-speed fluid ejection nozzle. As such fluid ejection nozzles, various known nozzles can be used. For example, there are nozzles of various structures in Japanese Patent Publication No. 36-10511 and Japanese Patent Publication No. 37-1175. One example is shown in FIGS.
[0021]
The yarns 4, 4 ′ to be connected are inserted into the treatment space 8 from the insertion port 9 and are intertwined by ejecting a high-speed air stream from the air jet port 10. The treatment space 8 has a smooth inner surface that does not cause yarn fluff, and a rectangular one is usually used, but is not limited to a square.
[0022]
Further, the air outlet 10 is not circular in cross section, and may have a slit shape, for example, and the number thereof may be provided at a plurality of locations for one apparatus. The air ejection direction does not have to be perpendicular to the yarn. For example, the air ejection direction may have an angle with respect to the yarn axis in contrast to the two types of ejection ports. In order to facilitate the insertion of the yarn in the yarn insertion port, it is effective for workability to cut the corner of the opening slit to make it round.
[0023]
When multiple filaments are entangled and connected, a larger amount of energy is required for entanglement than in the case of conventional small filaments, so that it is necessary to enlarge the air outlet and the processing space.
[0024]
Moreover, in the entanglement connection of the yarn, it is preferable that the overlapping portion in the entanglement treatment region is in a relaxed state within a range of a relaxation rate of 5 to 60%, preferably 10 to 20%.
[0025]
In the multi-filament entangled connection, the air outlet and the processing space are enlarged as described above in order to sufficiently entangle, and a large amount of air is ejected. When a plurality of locations are intertwined at the same relaxation rate, stress concentrates on the boundary between the overlapped portion of the end and the filament, resulting in a problem that single yarn breakage occurs and tensile strength decreases.
[0026]
Therefore, to loosen the end entangled degree, relaxation rate of the end, it is necessary to 4 0-60% by relative to inner relaxation rate of the end portion.
[0027]
The relaxation rate here is calculated from the length of the yarn that has been loosened with respect to the length of the yarn that has been entangled. For example, the length of the entanglement is 2 cm by one entanglement process. In order to set the relaxation rate to 20% in the apparatus in which the part is obtained, it means that the length of 2.4 cm is relaxed to 2 cm and set to the intertwined part. However, in actual work, it is preferable to perform the entanglement process by gripping the portion of the entangled portion 1 to 2 cm on both sides, and if the outer side is gripped 2 cm, the relaxation rate 20% is a length of 7.2 cm. The thread thus gripped is set to 6.0 cm and set in the entanglement device. In addition, it is extremely preferable in terms of work efficiency that the gripping tool for relaxing and processing the yarn is integrated with the entanglement device and designed so that the desired relaxation rate can be set automatically. is there.
[0028]
In addition, it is possible to grasp the overlapped yarns with both hands without setting with the device as a method of giving a relaxed state, but it is possible to carry out with empirical control, but the entangled state tends to be uneven, It is easy to produce a state defect.
[0029]
In the present invention, when two yarns are connected and then introduced into the flameproofing step, it is necessary to trim the end portion of the yarn entangled and connected by the high-speed fluid so that the yarn smoothly moves through the subsequent steps.
[0030]
When two yarns are intertwined, they are usually overlapped and entangled with a length with enough margin, so there are free parts of several centimeters to 20 cm left on both sides of the intertwined portion. The toe end should be treated after the entanglement treatment so that the yarn is not cut off at a point of 0.2 cm to 0.5 cm from the portion and the yarn is not branched and wound with a roller.
[0031]
The air pressure to be connected to the air nozzle next varies depending on the single yarn fineness, the number of yarn components, the adhesion state of the oil agent, the shape of the air processing nozzle, etc., but at least the gauge pressure is 0 at the inlet to the nozzle. It is better to inject at a pressure of 2 Mpa or more, preferably 0.4 to 0.8 Mpa. When the air pressure is too low, the tensile strength of the entangled portion is small, and when the air pressure is too high, a single yarn breakage is likely to occur in the processing portion, and troubles such as winding of the roller are likely to occur in the subsequent steps.
[0032]
Moreover, the moisture content of the organic fiber yarn to be entangled is preferably 0.5 to 6.0% by weight, and if this moisture content is too low, the entanglement treatment results in poor entanglement and the desired tensile strength. I can't get it. On the other hand, when the moisture content is too high, the heat treatment with flame resistance becomes insufficient. As a result, the yarn passing rate in the subsequent steps is lowered, and the production efficiency is deteriorated.
[0033]
Further, it is desirable that the degree of entanglement of the organic fiber yarn is 40 or less, and if the degree of entanglement is higher than this, the entanglement is poor and the desired tensile strength cannot be obtained. Inefficiency.
[0034]
Here, the entanglement degree of the organic fiber yarn is a value obtained by the following evaluation method.
[0035]
That is, FIG. 2 is a perspective view showing an example of the method for evaluating the degree of entanglement. A single denier 3 is suspended by applying a total denier number / 36 g of load 7, and the total denier number / A hook 5 made of a smooth wire with a surface of 0.5 mm in diameter and having a load 6 of 720 g is inserted and drooped, and the drop distance of the hook is measured. The CF value is calculated from the drop distance using the following equation.
CF value = 100 / fall distance (cm)
The CF value is measured for 50 samples, and the average value of 30 samples obtained by excluding 10 samples from the maximum value and the minimum value is used as the degree of confounding .
[0036]
The organic fiber yarn including the connecting portion of the present invention thus obtained is fired in accordance with known methods for producing various carbon fibers, and converted into carbon fibers or graphitized fibers. For example, the organic fiber yarn is formed into an oxidized fiber in an oxidizing gas atmosphere of about 200 ° C. to 400 ° C., and then heated and carbonized in an inert gas atmosphere of about 800 ° C. to 1500 ° C., and further heated as necessary. A method of heating in an inert gas atmosphere and converting to graphitized fiber is applied.
[0037]
【Example】
Hereinafter, the content of the present invention will be described more specifically with reference to examples.
[0038]
An acrylic long fiber yarn having a single yarn fineness of 1 d / f, a filament number of 12,000, and 24,000 is used with an air entanglement device of the type shown in FIG. Various samples with different binding states with different relaxation rates were prepared.
[0039]
The tensile strength of these samples was measured using a tensile tester, and another entangled spliced yarn prepared under the same conditions was fed at a rate of 1.0 m / min to a flameproofing furnace in which hot air was circulating. After moving to a zigzag by rollers installed at the upper and lower portions and staying for 150 minutes, the yarn passing rate in the oxidation process was measured continuously. Subsequently, the substantial heating part filled with nitrogen gas was introduced into a carbonization furnace having a temperature distribution of 500 to 1400 ° C. at a rate of 1.0 m / min, heat treatment was performed for 1 minute, and the yarn passage rate in the carbonization process was measured.
[0040]
The thread passing rate here is expressed as a percentage of the number of joints that passed without being cut in each step when the yarn joining part was introduced and heat-treated in the oxidation step and carbonization step. is there.
[0041]
The results are shown in Table 1.
[0042]
[Table 1]

In the table, an asterisk (*) indicates that the yarn does not pass through the flameproofing process, or the yarn passing rate is low and cannot be subjected to carbonization. In addition, the relaxation ratio is a percentage of the relaxation rate of the end portion relative to the relaxation rate inside the end portion.
[0043]
【The invention's effect】
According to the present invention, the above-mentioned disadvantages or problems of the conventional method, that is, troubles such as yarn breakage or winding of a roller easily occur when firing a multifilament organic fiber yarn, and it is timeless to repair such trouble. Then, it will lead to a serious disaster such as combustion in the firing furnace, and even if it does not immediately lead to a serious disaster, the thread passing ability will remarkably decrease, further promoting yarn breakage and roller winding at the time of firing. Not only the problem is solved, but also many excellent effects are obtained as follows.
[0044]
Variety exchange during continuous firing, for example, change of total denier can be easily performed. In other words, the two ends of two types of organic fiber yarns having different total deniers can be easily connected by overlapping and entanglement.
[Brief description of the drawings]
FIG. 1 is a plan view of an organic fiber yarn in which two places are entangled.
FIG. 2 is a perspective view for explaining a CF value measuring method in the present invention.
FIG. 3 is a perspective view showing an example of an entanglement processing apparatus according to the present invention.
4 is a longitudinal sectional view of the entanglement processing apparatus shown in FIG.
FIG. 5 is a side view of the entanglement processing device shown in FIG. 3;
[Explanation of symbols]
1, 1 '; Interlaced portion 2; Yarn intermediate portion 3; Single yarn 4, 4': Yarn 5; Hooks 6, 7; Load 8; Entanglement space 9; Yarn insertion port 10; Ejection hole L; Entanglement length L '; Spacing between entanglement and entanglement

Claims (3)

Organic fiber yarns having 24,000 to 30,000 filaments are superposed on each other, and in the superposed part, 4-5 entanglement sites are constrained at both ends, and the relaxation rate of each entanglement site is determined. 5-60%, the relaxation rate of the entangled part at both ends is 40-60 % with respect to the relaxation rate of the inside entangled part, and the organic fiber yarn is continuously connected after entangled and connected by high-speed fluid treatment. A method for producing carbon fiber, characterized by calcination.   The method for producing carbon fiber according to claim 1, wherein the organic fiber yarn has a moisture content of 0.5 to 6% by weight.   The organic fiber yarn is an acrylic fiber yarn, a polyvinyl alcohol fiber yarn or a pitch fiber yarn, and has a moisture content of 0.5 to 1% by weight. Carbon fiber manufacturing method.

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