JP4412656B2 - Carbon fiber manufacturing method - Google Patents

Description

  The present invention is a precursor for obtaining a carbon fiber having excellent quality and physical properties, particularly a method for producing carbon fiber using a splittable acrylic fiber tow (hereinafter sometimes referred to simply as tow). The present invention relates to a method for supplying tow stably to a carbon fiber manufacturing process, which is excellent in drawability from a storage container when acrylic fiber tow is made of non-crimped yarn. More specifically, it is a method for producing carbon fiber using acrylic fiber tow that is low in production cost, excellent in productivity, low in yarn breakage and fluff generation, and can be divided, and is uniform in the flameproofing step, and The present invention also relates to a method for producing a carbon fiber capable of stably performing a flameproofing treatment.

  Carbon fibers are usually composed of a small number of filaments having 1,000 to 30,000 filaments, and the packaging form of acrylic fiber tow which is a precursor thereof is generally bobbin wound. Therefore, in the carbon fiber manufacturing process, after the precursor wound on the bobbin is unwound from the bobbin, the filament density is regulated to 100 to 5,000 denier / mm with a comb guide or groove roller and supplied to the flameproofing process. The method to do is adopted. In order to reduce the production cost of carbon fiber, it is generally effective to increase the production capacity by using so-called large tow with 40,000 or more filaments, but it is difficult to bobbin large tow. Generally, it is packed in a container.

  Conventionally, as a technique for pulling up the tow from the storage container, the toning technique used in the fiber tow for clothing is generally used, but the requirement at that time is that it is not necessary to spread the tow uniformly and in the form of a sheet. There is no need to divide into small tows, and it suffices if the tows can be supplied to the cutting process in a substantially parallel manner along the longitudinal direction. On the other hand, when the tow as a carbon fiber precursor is pulled up from the storage container, when the tow is conditioned and fired by this method, heat of reaction accumulates in the flameproofing process if uneven tow thickness or twist (twist) occurs. There are problems such as yarn breakage due to heat storage, a lot of fluff partially occurring, and winding of the roller.

  As a conventional technique, a method for disposing a tow from a storage container and arranging a toe guide at a predetermined pulling height is disclosed (see, for example, Patent Document 1). It is necessary to release the twist (twist) before feeding, and in particular, when the tow is a non-crimped yarn, the twist cannot be stably released.

Japanese Patent Laid-Open No. 11-229241

  In the carbon fiber manufacturing process, the carbon fiber manufacturing process further applies a tension to the tow that is pulled up vertically from the storage container, and the tow that is pulled up while traversing from the uppermost surface of the tow that is transferred into the storage container is bent or twisted ( It is intended to produce carbon fibers from acrylic fiber tow with high productivity by preventing pulling without causing unevenness in thickness, preventing yarn breakage in the firing process, and winding due to generation of fuzz.

The present invention is a method for producing carbon fiber by vertically feeding an acrylic fiber tow stored in a storage container while traversing it to a firing process, and the relationship between the traverse width X and the lifting height Y is 2X. ≦ Y ≦ 10X When pulling in the vertical direction and making contact with the adjusting tow guide to adjust the tow, the tow lifted vertically immediately above the storage container has a tension of 0.8 times its own weight or calculated by the following formula. The carbon fiber manufacturing method is characterized by further applying a tension equal to or greater than the larger numerical tension.
f ≧ 4.5 × 10 ⁻⁴ × F
(Here, f is the tension (g) that is further applied to the dead weight immediately above the storage container, and F is the total fineness (denier).)

  According to the present invention, in the carbon fiber manufacturing process, further tension is applied to the tow that is pulled up vertically from the storage container, and the tow that is pulled up while traversing from the uppermost surface of the tow that is transferred into the storage container is bent or twisted. The twisted tow guide can be supplied without causing (twisting), yarn breakage in the firing step can be prevented, and the productivity of the carbon fiber can be improved.

Hereinafter, embodiments of the present invention will be described in detail.
In the present invention, the acrylic fiber tow, which is a carbon fiber precursor, is traversed in the form of a sheet, and is transferred into the storage container while being shaken back and forth and left and right. The storage container in which the tow is stored is transferred from the precursor manufacturing process to the carbon fiber manufacturing process that goes through the flameproofing process. For example, the storage container is placed directly, or transferred to a cart, pallet, etc. It is lifted vertically from the container and trimmed.

  In the carbon fiber manufacturing method in which the acrylic fiber tow traversed and stored in the storage container is pulled up and fired in the vertical direction, the relationship between the traverse width X and the pulling height Y is pulled up in the 2X ≦ Y ≦ 10X vertical direction, Touch the adjusting tow guide to adjust the tow. Here, the lifting height refers to the distance from the top layer surface of the tow in the storage container to the toning guide. In the present invention, when the tow is lifted, in order to prevent torsion and twisting of the tow from being fed to the adjusting tow guide, means for applying a downward tension to the tow between the adjusting tow guide and the storage container directly above Is provided.

As means for applying tension to the tow that is being pulled up, a method by contacting at least three fixed bars or rolls, a method in which the tow passes between slits, and tension is obtained by contact friction at that time, downward For example, a method of obtaining tension by frictional resistance with the air flow obtained by passing through the air flow flowing through the air flow can be employed.
As the simplest equipment as the tension applying means, there is a method of contacting at least three fixed bars or rolls. In this method, since there is a change in the contact state such as a winding angle associated with the traverse of the tow, a tension is continuously applied by simply passing between two guide bars arranged in the horizontal direction adjacent to each other. In addition, when trying to pass the tow with a small clearance, that is, when the clearance is to be passed, it passes through an interval very close to the thickness of the tow, which is not only difficult to adjust, but also twisted. If it is supplied, it will become caught. Furthermore, a method in which the tow is passed in an S shape or at least two bars or rolls are arranged in a vertical direction can be considered, but depending on the traversed arrangement state of the tow in the box, the contact state accompanying the traverse Fluctuations in the tension applied by friction due to the change in size are large, which is not preferable.

  The firing process for producing carbon fibers from acrylic fiber tows usually comprises a flameproofing process followed by a carbonization process. The acrylic fiber tow to be used is an acrylic fiber tow that can be divided into two or more small tows while maintaining the shape of one tow, and a tow provided mainly as a flame resistant fiber obtained after passing through the flame resistance process. It is. More specifically, it is preferable that a predetermined number of a plurality of yarn groups are intertwined weakly at the side ends (ear portions) of each yarn group and held in a sheet shape.

  Acrylic fiber tow, which is a precursor of carbon fiber, is an acrylonitrile copolymer obtained by copolymerizing other copolymerizable monomer units at a ratio of 0.1 to 10% by mass with respect to 90 to 99.9% by mass of acrylonitrile units. This is an acrylic fiber tow obtained by spinning the coalescence. Other monomers copolymerizable with acrylonitrile include, for example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid or salts thereof, methyl acrylate, ethyl acrylate, methyl methacrylate, acrylamide, methacrylamide, 2-hydroxyethylacrylonitrile. Chloroacrylonitrile and the like.

Next, description will be made based on the attached drawings. As shown in FIG. 1, the lifting height of the tow 3 refers to a distance Y (m) from the top layer surface of the tow in the storage container 1 to the toning guide 2. At this time, the lifting height of the tow 3 needs to be set so that the relationship with the tow traverse width X (m) in the storage container 1 is 2X ≦ Y ≦ 10X as shown in FIG.
The toning guide 2 is composed of at least two, usually three or more guide bars. Such a guide bar may be a flat guide bar or a curved guide bar. As shown as an example in FIG. 3, the tow 3 is passed through the next process while being alternately brought into contact with the guide bar.
FIG. 3 shows an example of the arrangement of the guide bars A to E. The guide bars A to E are composed of a flat guide (linear guide) and a curved guide (guide curved with a curvature in the longitudinal direction). In this case, a combination in which A to C are flat guides and D to E are curved guides, or a combination in which A, C, and E are flat guides, and B and D are curved guides is used. FIG. 3 shows an example of a toning guide composed of five guide bars. However, the number is not necessarily limited to five, and the number of components may be determined as appropriate based on the running state of the tow. .

  In the present invention, when the above-described lifting height Y of the tow is larger than 10X, the installation height of the adjusting tow guide 2 is high and the workability such as threading is bad, and the creel equipment needs to be enlarged and the manufacturing cost increases. It is not preferable. On the other hand, if it is smaller than 2X, yarn swaying is likely to occur on the guide bars A to C constituting the straightening tow guide 2, and the running yarn is offset on the curved guides D to E or the toe side end is bent. In addition, twisting (twisting) is likely to occur. In addition, since the yarn sway increases, it is necessary to secure an interval between the adjacent storage containers so that the tows pulled up from the adjacent storage containers do not come into contact with each other, which increases the creel equipment area and increases the manufacturing cost. There's a problem.

  Next, FIG. 4 shows an embodiment using three bars arranged in the vertical direction. FIG. 4 shows the relationship between the orientation of the storage container 1 and the adjusting tow guide 2 provided on the top thereof. A flat guide bar is used as the guide bar 4 attached immediately above the storage container. In addition, although the material of the guide bar 4 may be any, if durability and cost are considered, metals, such as iron and stainless steel, or a ceramic is preferable. The diameter of the guide bar 4 is not particularly limited, but considering that it is often attached directly to the storage container 1, a diameter of about 15 mm to 50 mm is preferable. Further, the mounting interval of the plurality of flat guide bars is not particularly limited, and when it is desired to increase the tension to be applied, it may be adjusted as appropriate by increasing the winding angle by reducing the mounting interval.

  FIG. 5 shows an embodiment in the case of passing between the slits 5. FIG. 5 shows the relationship between the direction of the slit 5 and the orientation of the storage container 1 and the adjusting tow guide 2 provided at the top. Any material may be used for the slit portion, but a metal plate such as stainless steel is preferable in consideration of durability and cost. The clearance of the slit 5 is preferably 2 to 8 mm and the length of the slit is preferably 20 to 100 mm, but the slit length and the slit clearance are further adjusted in consideration of the threading property and the tension to be applied. It is possible to make adjustments or make appropriate adjustments after confirmation in advance.

Furthermore, FIG. 6 shows an embodiment in the case of passing through the downward air flow.
The air flow (indicated by arrows) is preferably an air curtain flow, and is preferably installed so that the air flow strikes the tow at an angle of 15 ° to 45 ° in order to efficiently apply tension to the tow. FIG. 6 also shows the relationship between the direction of the air curtain flow and the orientation of the container 1 and the toning guide 2 provided at the top.

  The form of the acrylic fiber tow used in the present invention can be divided into small tows having a denier of 150,000 to 1,500,000 and can be divided into small tows having a denier of 50,000 to 250,000 denier. Is preferred. Furthermore, the present invention provides an acrylic fiber that is obtained after passing through a flameproofing step of a carbon fiber manufacturing process that cannot be divided into small tows having a total fineness of 150,000 to 9,000,000 denier and is used as a flameproof fiber. It is also possible to use.

  It is preferable to regulate the yarn density of the tow after trimming to 2,000 to 7,500 denier / mm. Here, the yarn density refers to the number of filaments per 1 mm of the yarn width, and is usually calculated by the number of filaments (KD) / yarn width (mm). In the carbon fiber manufacturing process, by controlling the yarn density sent from the creel to the flameproofing process, parallel operation of multiple yarns becomes possible, and the manufacturing cost can be reduced, but the yarn density is 7,500 denier / mm. If it exceeds, thickness unevenness is likely to occur in the tow, so that there is a high possibility that heat storage by reaction heat will occur in the flameproofing step, and problems such as yarn breakage may occur. On the other hand, if the yarn density is less than 2,000 denier / mm, the creel equipment will be greatly increased, resulting in an increase in production cost.

In the present invention, it is preferable to use three or more flat guide bars and two or more curved guide bars as the adjusting tow guide 2 as described above. Moreover, about the structure of the toning guide 2, it is good to arrange | position a guide bar so that the side edge part of a tow | toe may bend and to have the effect of suppressing twisting (twisting).
Moreover, in this invention, it is also possible to provide the process divided | segmented into small toe units, such as a pin guide, after adjustment tow if needed.

Next, examples of the present invention will be described in more detail.
[Example 1]
An acrylic fiber tow 3 having a total fineness of 150,000 denier that can be divided into three small tows of 50,000 denier was stored in the storage container 1 with a tow traverse width X of 0.72 m.
Next, as shown in FIG. 4, a guide bar 4 directly above the box in which three stainless steel round bars having a diameter of 20 mm are arranged vertically at a pitch of 50 mm between the storage containers 1 in which the tows 3 are stored. I installed it.
The configuration of the adjusting tow guide 2 that regulates the tow density to 2,000 to 7,500 denier / mm is as shown in FIG. 2 and the traverse width X (m) in the storage container 1 and as shown in FIG. The ratio of the height Y (m) from the top toe layer surface to the first straightening tow guide 2 was set to Y = 3.3X. Further, the toe guide 2 has three flat guide bars (surface roughness: Ra 3.2a) A, C and E, and a curved guide bar (curvature radius: 600 mm, surface roughness: Ra 3.2a) B. , D2 was used to configure as shown in FIG.
Through this process, tow 3 was supplied to the carbon fiber firing process at a speed of 250 m / hr. While the weight of the tow 3 pulled up from the storage container 1 is 44 g, the tension applied by the vertical guide bar 4 immediately above the storage container 1 varies in the contact state, but in the range of 100 to 130 g. Yes, the range was larger than the tow's own weight. The carbon fiber could be stably produced without feeding twist (twist) over 50 hours.
[Comparative Example 1]

Carbon fiber was produced in the same manner as in Example 1 except that the vertical guide bar 4 directly above one storage container was not installed in Example 1. The tension of the tow 3 in this example is only for its own weight. As a result, twisting (twisting) was fed to the carbon fiber production process 4 hours after the tow supply was started, and the production process was stopped because yarn breakage occurred in the flameproofing process.
[Comparative Example 2]

As shown in FIG. 7, carbon fiber was produced in the same manner as in Example 1 except that two on-box guide bars 7 were arranged in parallel in the storage container 1 with an interval of 50 mm. The tension applied by the guide bar 7 provided immediately above the storage container 1 at this time was different depending on the contact state between the tow and the guide bar 7, but the range was 0 to 60 g. As a result, twisting (twisting) was fed to the carbon fiber production process 4 hours after the tow supply was started, and the production process was stopped because yarn breakage occurred in the flameproofing process.
[Comparative Example 3]

Except that the ratio of the traverse width X (m) in the storage container 1 shown in FIG. 2 to the height Y (m) from the uppermost surface of the tow to the first toe guide is Y = 1.5X. In the same manner as in No. 1, carbon fiber was produced. The tension applied by the guide bar 4 provided immediately above the storage container was 100 to 130 g as in Example 1. When the tow 3 was fed in this way, the twist (twist) that passed through the guide just above the storage container 15 minutes after the start of tow supply was not fully released and passed through the tow guide 2 as it was, and the carbon fiber. Since the yarn breakage occurred in the flameproofing process, the manufacturing process was stopped.
[Example 2]

Instead of attaching the guide bar 4 directly above the storage container 1 in the first embodiment, a stainless steel slit 5 having a slit clearance of 3 mm and a slit length of 100 mm is installed as shown in FIG. Carbon fiber was manufactured. The tension applied by contact with the slit was 120 to 140 g. As a result, as in Example 1, twisting (twisting) was not fed over 50 hours, and it was possible to produce carbon fibers stably.
[Example 3]

Instead of attaching the guide bar 4 directly above the storage container 1 in Example 1, as shown in FIG. 6, an air curtain flow (arrow) was sprayed on the tow 3 to produce carbon fibers. The air curtain flow generator uses two air blow nozzles (MODEL40S-800-1.0) 6 manufactured by Takezuna Manufacturing Co., Ltd., and the jet angle of air to the raised tow is 30 °. The jet velocity was 20 m / min, and the clearance through which the tow between the two air blow nozzles 6 passed was 30 mm. At this time, the tension applied to the tow by the resistance of the air flow was 75 to 95 g. As a result, as in Example 1, twisting was not fed over 50 hours, and carbon fibers could be produced stably.
The results of Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3 are summarized in Table 1.

It is a conceptual diagram which shows the height to a storage container and the tow guide of the tow | toe raised. Indicates the traverse width of the tow stored in the storage container. It is a conceptual diagram in which a tow passes the adjusting tow guide bar. The tension | tensile_strength to the tow | tow pulled up by the three guide bars arranged in the perpendicular direction is shown. It shows the application of tension to the tow pulled up by the slit. It shows the application of tension to the tow pulled up by blowing the downward air nozzle. The tension applied to the tow pulled up by the parallel guide bar is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Storage container 2 Adjusting tow guide 3 Toe 4 Vertical guide bar 5 Slit 6 Air blow nozzle 7 Box guide bar AE Adjusting toe guide bar

Claims (6)

A method of producing a carbon fiber by pulling up an acrylic fiber tow stored while traversing in a storage container in a vertical direction to a firing process, wherein the relationship between the traverse width X and the lifting height Y is 2X ≦ Y ≦ 10X When the tow is pulled up in the vertical direction and brought into contact with the adjusting tow guide to adjust the tow, the tow pulled up directly above the storage container is 0.8 times its own weight or the tension calculated by the following formula, whichever is greater A method for producing carbon fiber, further comprising applying a tension equal to or greater than the tension of the other numerical value.
f ≧ 4.5 × 10 ⁻⁴ × F
(Here, f is the tension (g) that is further applied to the dead weight immediately above the storage container, and F is the total fineness (denier).) The method for producing carbon fiber according to claim 1, wherein the acrylic fiber tow is a non-crimped yarn. The carbon fiber manufacturing method according to claim 1 or 2, wherein the tension further applied immediately above the acrylic fiber tow storage container is in contact with at least three fixed bars or rolls.  The method for producing carbon fiber according to claim 3, wherein at least three bars or rolls are arranged in a vertical direction. The carbon fiber production method according to claim 1 or 2, wherein the tension further applied immediately above the acrylic fiber tow storage container is obtained by contact friction when the tow passes between the slits. The carbon fiber manufacturing method according to claim 1 or 2, wherein the tension further applied immediately above the acrylic fiber tow storage container is a tension obtained by passing through a downwardly flowing air flow.

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