JP2014080719A - Carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon fiber superior in quality and grade.SOLUTION: A carbon fiber is obtained by burning an acrylic fiber tow with the total denier of 60,000-1,000,000 dtex. In the carbon fiber, single yarn breakage does not occur, and the number of fuzz occurrence places is 3 or less per 1 m.

Description

  The present invention relates to carbon fibers.

The carbon fiber is usually composed of a small number of filaments having 1,000 to 30,000 filaments, and the packaging form of the acrylic fiber tow which is a precursor thereof is generally bobbin wound. Therefore, in the carbon fiber production process, after the precursor wound on the bobbin is unwound from the bobbin, the filament density is regulated by a comb guide or a groove roll so that the filament density becomes 110 to 5,500 dtex / mm. There has been proposed a method of supplying to a firing step including a conversion step.
In order to reduce the production cost of carbon fiber, it is effective to increase the production capacity by using so-called large tow, which generally has 40,000 or more filaments. However, since large tow is difficult to wind with a bobbin, the large tow is generally transferred and packed into a storage container while traversing.

Conventionally, as a technique for pulling up the tow from the storage container, it is common to use a toning technique used in the field of fiber tow for clothing. In the trimming tow technique, it is only necessary that the tows are stacked substantially in parallel along the longitudinal direction and can be supplied to the cutting process, and it is not necessary to uniformly spread the tows into a sheet or to divide them into small tows. .
However, when the tow used as the carbon fiber precursor is pulled up from the storage container, twisting (twisting), bending, tow thickness unevenness, and the like may occur when the above-described toning technique is used. As a result, there was a problem that the tow was partially damaged due to accumulation of reaction heat in the flameproofing process, and the roll was wound by the fragments.

Therefore, for example, in Patent Document 1, twisting (twisting) is defined by defining the relationship between the traverse width X in the storage container and the rising height Y from the storage container to the toe guide in the toe starting process. There has been disclosed a method for obtaining a carbon fiber having excellent quality without causing breakage.
Patent Document 2 discloses the maximum tension to be added, the total contact angle with the guide, and the number of guides for the tow that is taken out of the storage container and supplied to the flameproofing furnace through the guide. By defining, a method for obtaining a carbon fiber with good quality is disclosed.

Japanese Patent Laid-Open No. 11-229241 JP 2007-154371 A

However, the method described in Patent Document 1 cannot always stably suppress torsion and breakage of the tow. In particular, when the tow is a non-crimped yarn, it has been difficult to stably suppress twisting and bending of the tow.
Further, with the method described in Patent Document 2, it has been difficult to stably suppress torsion and bending of the tow.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the carbon fiber excellent in quality and quality.

  The carbon fiber of the present invention is a carbon fiber obtained by firing an acrylic fiber tow having a total fineness of 60,000 to 1,000,000 dtex, has no single yarn breakage, and has three occurrences of fluff per 1 m. It is characterized by the following.

  The carbon fiber of the present invention is excellent in quality and quality.

It is the schematic which shows an example of the manufacturing apparatus of the carbon fiber used for this invention. It is a schematic side view which shows an example of the rising part of the acrylic fiber tow from a storage container for demonstrating the traverse width of an acrylic fiber tow.

Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to FIG.
FIG. 1 is a schematic view showing an example of a carbon fiber production apparatus used in the present invention. The carbon fiber manufacturing apparatus 1 of this example includes a pulling means 30 for pulling up the acrylic fiber tow 20 traversed and stored in the storage container 10 in the vertical direction, and a baking means 40 for baking the acrylic fiber tow 30.
In the present invention, the “vertical direction” refers to both the upward direction in the vertical direction and the downward direction in the vertical direction, and “pick up in the vertical direction” means to pull up in the vertical direction.

The storage container 10 is not particularly limited as long as it can store the acrylic fiber tow 20. The storage container 10 in which the acrylic fiber tow 20 is stored is transferred from the precursor manufacturing stage to the carbon fiber manufacturing stage through the firing process, and is placed directly, or transferred to a cart, pellets, or the like and left still.
The number of storage containers 10 is not particularly limited, and may be one or two or more.

The acrylic fiber tow 20 used in the present invention is used as a carbon fiber precursor, and 0.1 to 10 other monomer units copolymerizable with acrylonitrile with respect to 90 to 99.9% by mass of acrylonitrile units. It is obtained by spinning an acrylonitrile copolymer copolymerized at a mass percentage.
Examples of other monomers copolymerizable with acrylonitrile include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid or salts thereof, methyl acrylate, ethyl acrylate, methyl methacrylate, acrylamide, methacrylamide, 2-hydroxy Examples include ethylacrylonitrile and chloroacrylonitrile.

As the acrylic fiber tow 20, a single tow shape can be used. Further, it is used as an acrylic fiber tow that can be divided into two or more small tows while maintaining a single tow form, or as a flame resistant fiber obtained after passing through a flameproof furnace (not shown) of the firing means 40. Acrylic fiber tow can also be used. In particular, as an acrylic fiber tow that can be divided into a plurality of small tows, a tow formed by a predetermined number of a plurality of yarn groups in parallel is weakly entangled with each other at the side ends (ear portions) of each yarn group. The sheet is preferably held in the form of a sheet.
Furthermore, as the acrylic fiber tow 20, it is preferable to use a tow having a total fineness of 14,000 to 9,900,000 dtex.

Although the storage method of the acrylic fiber tow 20 is not particularly limited, it is preferable that the acrylic fiber tow 20 is traversed and stored.
In the present invention, “to be traversed and stored” means to be transferred to the storage container while being swung in the front-rear direction of the storage container and also in the left-right direction.

The pulling means 30 includes a trimming toe guide 31 having one or more guides, and among the trimming tow guides 31, a guide to which the pulled acrylic fiber tow 20 first comes in contact with the acrylic fiber tow (that is, a guide). The guide located in the uppermost stream) is pulled up to A in the vertical direction. The driving of the guide A at that time is not limited.
By applying vibration to the acrylic fiber tow, even if the tow is a non-crimped yarn, the tow can be pulled up from the storage container while suppressing the torsion, bending, and thickness unevenness of the tow. .
In the present invention, the term “vibration” means that an acrylic fiber tow at an arbitrary position moves periodically while alternately repeating a movement that moves from that position in a predetermined direction and a movement that moves in the opposite direction. That is.

The trimming tow guide 31 trims the acrylic fiber tow 20 pulled up from the storage container 10 and sends it to the firing means 40.
The toning guide 31 has one or more guides and is provided with a guide that reciprocates and vibrates the acrylic fiber tow in the uppermost stream.

  The reciprocating motion of the guide A located in the uppermost stream among the towing guides 31 is performed by the periodic movement of the guide A. For example, as illustrated in FIG. 1, the periodic movement of the guide A is an arbitrary position in which the guide A at the fixed position is upward in the vertical direction when the position of the guide A when the reciprocation is stopped is set as the fixed position. It shows that the movement of moving to the fixed position and the movement of the moved guide A ′ returning to the fixed position are repeated alternately. In the present invention, the case of reciprocating in such a direction is referred to as “vertically upward”. Further, a case where the reciprocating motion is performed in the direction opposite to the vertical upward direction (that is, the case where the guide A at the fixed position moves downward in the vertical direction to an arbitrary position) is referred to as “vertical downward direction”.

  The direction of reciprocation of the guide A is not particularly limited, and may be any of a vertical direction (vertically upward and vertically downward), a horizontal direction, and an oblique direction, but the same direction as the pulling-out direction of the acrylic fiber tow is preferable. As shown in FIG. 1, when the acrylic fiber tow is pulled up in the vertical direction, the direction of reciprocation of the guide A is vertical or horizontal in that stable vibration can be applied without applying an excessive force to the acrylic fiber tow. The direction is preferable, and the vertical upward direction is more preferable.

  The fixed position of the guide A is equal to the length of pulling out the acrylic fiber tow 20 (in the case of FIG. 1, the lifting height H), the total fineness and pulling speed of the acrylic fiber tow 20 pulled up from the storage container 10, the acrylic fiber tow is When traversed and stored in the storage container 10, the traverse width X (see FIG. 2) and the number of storage containers 10 are appropriately set. Specifically, it is preferable to set the height at which the acrylic fiber tow 20 is pulled up from the storage container 10 and reaches the guide A so that vibrations of 5 to 1000 times can be applied.

  Further, the movement distance (hereinafter referred to as “vibration amplitude Y”) when the guide A moves from the fixed position vertically upward or downward or horizontally is preferably 0.5 to 10 cm, and more preferably 1 It is -8cm, More preferably, it is 1-5cm. If the vibration amplitude Y is 0.5 cm or more, vibration can be efficiently applied to the acrylic fiber tow. Accordingly, the tow can be pulled up from the storage container while effectively preventing the tow from being twisted, bent, and thick spots. As a result, the reaction heat is more difficult to accumulate in the flameproofing process, so that partial breakage of the tow such as yarn breakage and fluff generation can be suppressed. Therefore, it is possible to prevent winding by fragments. On the other hand, if the vibration amplitude Y is 10 cm or less, the effect on equipment investment is easily obtained efficiently.

  The reciprocating motion of the guide A can be performed by using a known cam mechanism (mainly a mechanism for converting the rotation of the driving node into the linear reciprocating motion or the swinging motion of the driven node). As a cam mechanism, for example, when rotating around a point at a certain distance from the center, the disc rotates eccentrically, and at this time, the follower node provided on the circumferential surface of the disc is rotated periodically. A disc cam that gives motion, a plate cam that has a follower on the circumferential side of the rotating disc, a positive cam that forcibly drives the reciprocating motion of a follower that is used in an engine camshaft, etc. Examples thereof include a three-dimensional cam that drives a follower node using displacement due to the surface of a sphere or a three-dimensional shape, and a flat cam that applies displacement to a follower node using grooves and protrusions provided in a plane portion of a rotating body.

Examples of the guide constituting the adjusting tow guide 31 include a guide bar and a guide roll. Examples of the guide bar include a flat guide bar 32 that is linear with respect to the axial direction as shown in FIG. 2, a yarn path regulating guide bar, and the like.
The straightening toe guide 31 preferably uses both a flat guide bar and a yarn path regulating guide bar as a guide. In particular, it is preferable that the guide A located at the uppermost stream is a flat guide bar. If the guide A is a flat guide bar, vibration can be smoothly applied to the acrylic fiber tow 20, and the acrylic fiber tow 20 can be stably fed to the baking means 40.

The adjusting tow guide 31 shown in FIG. 1 has five guides A to E, and each guide A to E includes a flat guide bar and a yarn path regulating guide bar. For example, the guides A to C are flat guide bars and the guides D to E are yarn path regulation guide bars. The guides A, C, and E are flat guide bars, and the guides B and D are yarn path regulation guides. Examples of combinations include bars, but are not limited thereto.
In the example shown in FIG. 1, guides A, C, and E are flat guide bars, and guides B and D are yarn path regulating guide bars. As shown in FIG. 1, the yarn path regulating guide bar includes curved guide bars (guide bars curved with a certain curvature with respect to the axial direction) B1 and D1, and auxiliary guide bars (upstream of the curved guide bars). It is composed of linear guide bars B2 and D2 with respect to the axial direction.

When the yarn path regulating guide bar is composed only of a curved guide bar, when the acrylic fiber tow is supplied, the toe side part is broken due to the tension difference of the acrylic fiber tow at the curved guide bar, or the firing means 40 is fed with acrylic fiber. It is difficult to supply tow stably. In order to prevent the tow from breaking, the tension of the acrylic fiber tow in the adjusting tow guide may be increased. However, it is necessary to increase the tension of the entire acrylic fiber tow, which is likely to cause fluff.
If the yarn path regulating guide bar is composed of a curved guide bar and an auxiliary guide bar located upstream thereof, the tension of the acrylic fiber tow can be increased while suppressing the occurrence of fuzz, so that the tow breakage is effective. Can be prevented.

  The distance between the curved guide bar and the auxiliary guide bar is preferably 50 to 500 mm, more preferably 100 to 400 mm, and still more preferably 200 to 300 mm. If the distance between both guide bars is within the above range, uniform tension can be locally applied to the tow. Therefore, since the tension of the acrylic fiber tow can be increased while suppressing the generation of fluff, the tow can be prevented from breaking.

The number of guides of the adjusting toe guide 31 is not limited to that shown in FIG. 1, and the number of the guides may be determined as appropriate based on the running state of the tows.
The material of each guide is not particularly limited, but considering durability and cost, metals such as iron and stainless steel and ceramics are preferable.
Further, the size of each guide is not particularly limited, but a guide having a diameter of about 10 to 50 mm is preferable.

  The firing means 40 is a means for firing the acrylic fiber tow 20 pulled up from the storage container 10 by the drawer means 30. As the firing means 40, a known firing means used in the production of carbon fibers can be used, and usually includes a flameproofing furnace and a carbonization furnace (both not shown).

  The carbon fiber manufacturing apparatus used in the present invention is not limited to the one shown in FIG. May be.

In the carbon fiber manufacturing method using the carbon fiber manufacturing apparatus 1 shown in FIG. 1, first, the pulling means 30 vertically moves to the guide A while applying vibration to the acrylic fiber tow 20 traversed and stored in the storage container 10. Pull up in the direction.
By applying vibration to the acrylic fiber tow 20, even if the tow is a non-crimped yarn, the tow can be pulled up from the storage container while suppressing torsion, bending, and thickness unevenness of the tow due to the impact at that time. it can. As a result, reaction heat is unlikely to accumulate in the flameproofing step, so that yarn breakage and fluff generation can be suppressed and winding can be prevented.

  The vibration direction of the acrylic fiber tow is not particularly limited, and may be any of a vertical direction, a horizontal direction, and an oblique direction. However, it is particularly preferable to vibrate in the vertical direction from the viewpoint that the tow can be efficiently impacted and vibration can be imparted without applying an excessive force to the tow.

The application of vibration to the acrylic fiber tow 20 can be achieved by reciprocating the guide A. The guide A shown in FIG. 1 is located on the vertical line of the storage container 10 and is the guide with which the acrylic fiber tow 20 that has been pulled up first contacts among the tow guides 31, so that the guide A reciprocates. The acrylic fiber tow 20 vibrates in conjunction with the movement.
As described above, the guide A preferably reciprocates in the same direction as the pulling direction of the acrylic fiber tow. As shown in FIG. 1, when the acrylic fiber tow is pulled up in the vertical direction, the guide A preferably reciprocates in the vertical direction (vertically upward and vertically downward), more preferably vertically upward. As the guide A reciprocates in the vertical direction, the acrylic fiber tow 20 vibrates in the vertical direction in conjunction with the movement.

The reciprocating speed of the guide A is the total fineness of the acrylic fiber tow 20 pulled up from the storage container 10, and when the acrylic fiber tow is traversed and stored in the storage container 10, the traverse width X (see FIG. 2) and storage. It is determined appropriately according to the number of containers 10.
In the present invention, “traversed and stored” means that, as described above, the container is swung into the storage container while being swung in the front-rear direction and also in the left-right direction. When the acrylic fiber tow stored in this manner is pulled out of the storage container, the acrylic fiber tow travels in the front-rear direction, and the left-right direction at this time is defined as the “traverse width”. In the case of the example shown in FIGS. 1 and 2, the width direction of the side surface of the storage container 10 in FIG. 2 (the same direction as the axial direction of the flat guide bar 32) is the “left-right direction, that is, the traverse width X”. The width direction of the front surface of the container 10 is the “front-rear direction”.

  Specifically, as shown in FIG. 1, when the reciprocation of the guide A is vertically upward, the guide A when the fixed position guide A moves vertically upward to the position of the guide A ′ and pulls up the acrylic fiber tow 20. The moving speed of A is not particularly limited, and may be set in a range that does not damage the tow by squeezing the guide A and the acrylic fiber tow.

On the other hand, the moving speed of the guide A when the guide A returns from the position of the guide A ′ to the home position and the acrylic fiber tow 20 falls by its own weight is preferably a speed near free fall. If the speed is in the vicinity of free fall, the acrylic fiber tow can be impacted efficiently, and it becomes easy to suppress the occurrence of twisting and bending.
Here, the velocity V [m / s] when the object in the free fall motion due to gravity g falls the distance h [m] can be obtained by the following equation (1) when the air resistance is ignored. In the present invention, the “velocity in the vicinity of free fall” is a speed of 30% or more of the value calculated by the following formula (1), preferably 50% or more, more preferably 100% (that is, Free fall speed).

  When the acrylic fiber tow 20 is pulled out, it is preferable that 5 to 1000 vibrations are applied to the acrylic fiber tow 20 until it reaches the guide A, more preferably 30 to 800 times. More preferably, it is 60 to 600 times. If the frequency | count of a vibration is 5 times or more, a vibration can be efficiently provided to an acrylic fiber tow. Therefore, the tow can be pulled out from the storage container while effectively preventing the tow from being twisted, bent, and thick spots. As a result, reaction heat is more difficult to accumulate in the flameproofing step, so that yarn breakage and fluff generation can be suppressed and winding can be prevented. On the other hand, if the number of vibrations is 1000 times or less, it is easy to efficiently obtain an effect on equipment investment.

  The period of vibration applied to the acrylic fiber tow 20 is preferably 0.1 to 20 times / second, more preferably 0.5 to 15 times / second, and further preferably 1 to 10 times. Times. If the period of vibration is 0.1 times / second or more, vibration can be efficiently applied to the acrylic fiber tow. Therefore, the tow can be pulled out from the storage container while effectively preventing the tow from being twisted, bent, and thick spots. As a result, reaction heat is more difficult to accumulate in the flameproofing step, so that yarn breakage and fluff generation can be suppressed and winding can be prevented. On the other hand, if the period of vibration is 20 times / second or less, the effect on equipment investment can be easily obtained efficiently.

Moreover, 0.5-10 cm is preferable, as for the amplitude of the vibration provided to the acrylic fiber tow 20, 1-8 cm is more preferable, and 1-5 cm is further more preferable. If the amplitude of vibration is 0.5 cm or more, vibration can be efficiently imparted to the acrylic fiber tow. Therefore, the tow can be pulled out from the storage container while effectively preventing the tow from being twisted, bent, and thick spots. As a result, reaction heat is more difficult to accumulate in the flameproofing step, so that yarn breakage and fluff generation can be suppressed and winding can be prevented. On the other hand, if the amplitude of vibration is 10 cm or less, an effect on equipment investment can be easily obtained efficiently.
Since the vibration applied to the acrylic fiber tow 20 is interlocked with the reciprocation of the guide A, the amplitude of the vibration applied to the acrylic fiber tow 20 is such that the guide A is vertically upward or downward from a fixed position. Or it is the same as the moving distance (vibration amplitude Y) when moving in the horizontal direction.

  The acrylic fiber tow 20 pulled up by the pulling means 30 is adjusted by passing through the adjusting tow guide 31. The tension of the conditioned acrylic fiber tow 20 is preferably 0.1 to 3.5 kg / piece, more preferably 0.3 to 3.0 kg / piece, and still more preferably 0.5 to 2.5 kg / piece. It is a book. If the tension is within the above range, a toning effect is easily obtained and fluff is less likely to occur.

The acrylic fiber tow 20 trimmed by the trimming tow guide 31 is sent to the calcining means 40 and calcined to become carbon fiber.
As a firing method, a method of performing a flameproofing treatment in a flameproofing furnace (not shown) and then pre-carbonizing and carbonizing treatment in a carbonizing furnace (not shown) can be used.

  In the carbon fiber manufacturing method described above, the direction in which the acrylic fiber tow stored in the storage container is pulled out is not particularly limited, and may be any direction, for example, downward in the vertical direction, horizontal direction, or diagonal direction. However, from the viewpoint of efficiently pulling out the acrylic fiber tow and applying vibration, the pulling direction is preferably upward in the vertical direction as shown in FIG.

In the present invention, if necessary, after adjusting the tow of the acrylic fiber tow 20 with the adjusting tow guide 31, and before baking with the baking means 40, the acrylic fiber tow 20 using a pin guide (not shown) or the like. You may provide the process of dividing | segmenting into small tow | toe units.
Moreover, you may provide the process of surface-treating the carbon fiber obtained by the baking means 40. FIG. By performing the surface treatment, excellent adhesion to the matrix resin can be imparted to the carbon fiber. Examples of the surface treatment method include a dry method such as ozone oxidation, and a wet method in which an electrolytic surface treatment is performed in an electrolytic solution.
Furthermore, if necessary, a step of coating the surface-treated carbon fiber with a sizing agent may be provided. By carrying out the coating treatment, the handleability of the carbon fibers and the affinity with the matrix resin can be improved. Examples of the sizing agent include epoxy resins, polyether resins, epoxy-modified urethane resins, and polyester resins.

As described above, according to the present invention, the acrylic fiber tow is pulled out while applying vibration, so that even if the tow is a non-crimped yarn, the tow is prevented from being twisted, broken, or uneven in thickness. In addition, the tow can be pulled out of the storage container. As a result, reaction heat is unlikely to accumulate in the flameproofing step, so that yarn breakage and fluff generation can be suppressed and winding can be prevented.
Therefore, according to the present invention, carbon fiber excellent in quality, quality, and physical properties can be produced from acrylic fiber tow with high productivity. Specifically, it is possible to produce a carbon fiber having no single yarn breakage and having 10 or less fluff generation sites per meter with high productivity.
Furthermore, the present invention can also be applied to acrylic fiber tows that are non-crimped yarns and acrylic fiber tows that have a splitting ability in the width direction that can be split into a plurality of small tows.

  Further, the carbon fiber of the present invention has no single yarn breakage, and the number of occurrences of fluff is 10 or less per 1 m, and is excellent in quality and quality. Therefore, it can be particularly suitably used for industrial materials such as aerospace, automobiles, architecture, sports / leisure, and pressure vessels that are required to have high quality and high quality.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.
In addition, the manufacturing apparatus of carbon fiber and each evaluation method which were used by each Example, the reference example, and the comparative example are as follows.

<Carbon fiber manufacturing equipment>
As the manufacturing apparatus, the carbon fiber manufacturing apparatus shown in FIG. 1 was used. As the towing guide 31, guides A, C, and E are flat guide bars (surface roughness: Ra = 3.2a), and guides B and D are yarn path regulating guide bars. The guides B and D are respectively composed of curved guide bars (curvature radius: 600 mm, surface roughness: Ra = 3.2a) B1, D1, and auxiliary guide bars (surface roughness: Ra = 3.2a) B2, D2. The distance between the curved guide bar and the auxiliary guide bar is 0.3 m.
The acrylic fiber tow 20 used was traversed and stored in the storage container 10. Moreover, it adjusted so that the tension | tensile_strength of the acrylic fiber tow 20 which passed the adjusting tow guide 31 may be 1.0 kg / piece.

<Evaluation>
(Evaluation of process passability)
During the process of pulling out 10,000m acrylic fiber tow from the storage container by the pulling means and baking by the baking means, count the number of times torsion (twisting) or bending of the tow is supplied to the flameproofing furnace of the baking means. Evaluation was made according to the following evaluation criteria.
A: Less than 2 times.
○: 3 to 5 times.
Δ: 6 to 10 times.
X: 11 times or more.

(Product quality evaluation)
About the obtained carbon fiber, the occurrence of fluff and the presence or absence of single yarn breakage were visually observed and evaluated according to the following evaluation criteria.
A: Single yarn breakage is not confirmed, but the occurrence of fluff is 3 or less per 1 m of carbon fiber.
○: Single yarn breakage is not confirmed, but generation of fluff is 4 to 10 per 1 m of carbon fiber.
Δ: Single yarn breakage is not confirmed, but generation of fluff is 11 or more per 1 m of carbon fiber.
X: Single thread breakage was confirmed.

(Comprehensive evaluation)
From the evaluation of process passability and product quality, the following evaluation criteria were used.
A: Evaluation of process passability and evaluation of product quality are both “A”.
○: At least one of “Evaluation of process passability” and “Evaluation of product quality” has “◯” or “Δ”, and neither has “X”.
X: There are one or more “x” in the process passability evaluation and the product quality evaluation.

<Reference Example 1>
The acrylic fiber tow 20 having a total fineness of 14,400 dtex was transferred and stored in the storage container 10 shown in FIG. 2 so that the traverse width X was 1.5 m.
Next, the acrylic fiber tow 20 was pulled up from the storage container 10 in the vertical direction under the pulling conditions shown in Table 1 to produce carbon fibers. The results are shown in Table 1.
“Speed” shown in Table 1 is an apparent tow pulling speed in consideration of toe vibration, “Vibration direction” is the direction of reciprocation of guide A, and “Falling speed” is determined by guide A. This is the speed when returning from the guide A ′ to the fixed position. Further, the drop speed of Reference Example 1 is “free fall”.

<Reference Examples 2 to 4 and Examples 5 to 12>
Carbon fibers were produced in the same manner as in Reference Example 1 except that the total fineness of the acrylic fiber tow, the traverse width X, the number of storage containers relative to the guide A, and the drawing conditions were changed as shown in Tables 1 and 2. The results are shown in Tables 1 and 2. In addition, the drop speed of Reference Examples 2 to 4 and Examples 5 to 12 is “free fall”.

<Reference Examples 13-17>
An acrylic fiber tow with a total fineness of 72,000 dtex, which can be divided into two small tows with a total fineness of 36,000 dtex, is transferred to the storage container 10 so that the traverse width X becomes 0.72 m. Carbon fibers were produced in the same manner as in Reference Example 1 except that the number of storage containers and the drawing conditions were changed as shown in Table 2. The results are shown in Table 2. In addition, the drop speed of Reference Examples 13 to 17 is “free fall”.

<Examples 18 to 21>
An acrylic fiber tow with a total fineness of 180,000 dtex, which can be divided into three small tows with a total fineness of 60,000 dtex, is transferred to the storage container 10 so that the traverse width X becomes 0.72 m. Carbon fibers were produced in the same manner as in Reference Example 1 except that the number of storage containers and the drawing conditions were changed as shown in Tables 2 and 3. The results are shown in Tables 2 and 3. In addition, the fall speed of Examples 18 to 21 is “free fall”.

<Examples 22-24, 29, 31, Reference Examples 25-28, 30, 32>
Carbon fibers were produced in the same manner as in Reference Example 1 except that the total fineness of the acrylic fiber tow, the traverse width X, the number of storage containers relative to the guide A, and the drawing conditions were changed as shown in Tables 3 and 4. The results are shown in Tables 3 and 4. In addition, the drop speed of Examples 23, 24, 29, and 31 and Reference Examples 30 and 32 is “free fall”.

<Comparative Examples 1-5>
Except that vibration was not applied to the acrylic fiber tow 20, and the total fineness of the acrylic fiber tow, the traverse width X, the number of storage containers for the guide A, and the drawing conditions were changed as shown in Table 4, the same as in Reference Example 1 Carbon fiber was manufactured. The results are shown in Table 4.

As apparent from Tables 1 to 4, Examples 5 to 12, 18 to 24, 29 and 31, Reference Examples 1 to 4, 13 to 17, 25 to 28, 30, and 32 have good process passability. The carbon fibers obtained in each example were excellent in product quality and quality.
In particular, when the vibration direction is vertically upward (Example 7), when the vibration direction is vertically downward (Reference Example 25), and when the vibration direction is horizontal (Reference Example 26), the vibration direction is vertically upward. In the case, the evaluation result was the best, and then it was the case where it was turned vertically downward.
Moreover, when the fall speed is set to free fall (Example 7), when it is set to 40% of free fall (Reference Example 27), and when it is set to 10% of free fall (Reference Example 28), the drop is compared. The evaluation results were the best when the speed was set to free fall, and then 40% of the free fall.
Moreover, when the vibration period is 3 times / second (Example 7) and 0.05 times / second (Reference Example 30), the evaluation result is 3 times / second. Was good.
Further, when the vibration amplitude was set to 1.5 cm (Example 7) and the case where the vibration amplitude was set to 0.2 cm (Reference Example 32), the evaluation result was better in the case of 1.5 cm. .
Furthermore, the number of storage containers for the guide A is increased (Examples 7 and 11, Examples 8 and 12), or an acrylic fiber tow having a dividing ability in the width direction that can be divided into a plurality of small tows (reference). Even in Examples 13 to 17 and Examples 18 to 21), it was possible to obtain carbon fibers having good process passability and excellent product quality and quality.

  On the other hand, Comparative Examples 1 to 5 in which the acrylic fiber tow was pulled up in the vertical direction without applying vibration decreased the process passability, and the carbon fiber obtained in each comparative example had a product quality / quality compared to each example. It was inferior.

1: Carbon fiber production equipment,
10: Storage container,
20: Acrylic fiber tow,
30: Drawer means,
31: Toning guide,
40: firing means,
A to E: Guide,
X: Traverse width,
Y: vibration amplitude,
H: Raised height.

Claims (1)

A carbon fiber obtained by firing an acrylic fiber tow having a total fineness of 60,000 to 1,000,000 dtex,
Carbon fiber having no single yarn breakage and no more than 3 occurrences of fluff per meter.

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