JP5133112B2 - Carbon fiber bundle manufacturing method - Google Patents

Description

  The present invention relates to a method for flameproofing a large number of multifilament polyacrylonitrile-based precursor fiber bundles.

  As a method for making the acrylic precursor fiber bundle flame resistant, as shown in FIG. 1, folding rolls 2 are arranged on both sides of the flame resistant furnace 1, and the precursor fiber bundle yarn 3 is zigzag-shaped in the flame resistant furnace. The method of passing is common. In such a flameproofing process, as a method of preventing entanglement between the treated yarns, overcoming the guide roll, processing spots, etc., a number of grooved rolls are used, and the precursor fiber bundle is guided into the groove of the roll. The yarns are separated and made independent.

  However, in such a method, when the number of filaments per one processed yarn increases, when the cross-sectional shape is circular, the maximum thickness of the yarn becomes large, and a problem that yarn breakage due to heat accumulation tends to occur. .

Patent Document 1 discloses a method for controlling the average flatness and average fineness of a polyacrylonitrile-based precursor fiber bundle having a substantially rectangular cross section by defining the groove shape of a grooved roll disposed on both sides of a flameproofing furnace. Is described. As a result, a flame-resistant fiber bundle having a uniform progress of flame resistance can be obtained, and no fluffing, yarn damage or the like in the subsequent carbonization process occurs, and a high-quality, high-quality carbon fiber bundle can be obtained.
Japanese Patent No. 3733688

  By the way, in the method of Patent Document 1, since the radius of roundness at the corner of the groove bottom is small, particularly when the average flatness defined by the yarn width / thread thickness ratio is large and the apparent average fineness per unit width is small, The end of the precursor fiber bundle thread that is kept in a substantially rectangular shape when passing through the grooved roll may break or become thick, and then enter the flameproofing furnace to break the flame due to flameproof spots or heat accumulation. Cause. In addition, when the running position of the yarn in the groove is shifted to the slope of the mountain on one side, the radius of the roundness at the corner of the groove bottom is small, so the yarn is likely to break at the corner and travels. This causes a problem that the shape of the yarn becomes unstable. Moreover, in the method of patent document 1, since the grooved roll is used for the return | turnback roll, replacement | exchange of a grooved roll is not easy.

  The present invention has been made for the purpose of solving such various conventional problems. Specifically, when the multifilament polyacrylonitrile-based precursor fiber bundle is flameproofed, the running position of the yarn is restricted. And a method for producing a carbon fiber bundle in which a groove shape capable of maintaining a substantially rectangular shape as much as possible is defined, thereby preventing breakage and thickness unevenness of the yarn when passing through the groove member and easy replacement of the groove member Is to provide.

  In the present invention, a polyacrylonitrile-based precursor fiber bundle having a total fineness of 40,000 dtex or more is passed through a flame-proofing furnace in a zigzag shape with a folding roll and passed through a flameproofing treatment at 200 to 300 ° C., and then exceeds 600 ° C. In the method for producing a carbon fiber bundle that is carbonized at a temperature, a groove member that satisfies the following formulas (1) to (3) is disposed between the flameproofing furnace and the folding roll, and passes through the groove member. This is a method for producing a carbon fiber bundle in which the apparent average fineness per 1 mm width of the subsequent polyacrylonitrile-based precursor fiber bundle is maintained at 2,400 to 5,000 dtex.

0.6 ≦ b / a ≦ 0.9 (1)
0.2 × a ≦ h ≦ 0.5 × a (2)
1 × (ab) ≦ R ≦ 2 × (ab) (3)
(Where, a is the width of the groove top (mm), b is the width of the groove bottom (mm), h is the depth of the groove (mm), and R is the radius (mm) of the round corner of the groove bottom)
Furthermore, it is preferable that the groove member is disposed on the entry side of the folding roll, and a center-to-center distance between the groove member and the folding roll is 250 mm or more.

  Moreover, it is preferable that the said groove member is arrange | positioned at the exit side of the folding | turning roll, and the distance between the centers of the said groove member and the said folding | turning roll is 400 mm or more.

  According to the method for producing a carbon fiber bundle of the present invention, when the multifilament polyacrylonitrile-based precursor fiber bundle having a total fineness of 40,000 dtex or more is made flame resistant, the precursor is defined by defining the groove shape of the groove member. It is possible to control the running position of the fiber bundle yarn and control the form of the yarn. In particular, as an effect of defining the radius of roundness at the corners of the groove bottom portion, it leads to prevention of form defects such as yarn breakage and thickness unevenness when passing through the groove member, and can be maintained in a substantially rectangular sheet shape. That is, it leads to suppression of yarn breakage and fluff during the flameproofing process, and high-quality carbon fiber bundles can be produced by a stable process. In addition, by disposing the groove member between the flameproofing furnace and the folding roll, the groove member can be easily replaced, and workability can be improved.

  The precursor fiber bundle yarn subjected to flame resistance treatment in the present invention is a polyacrylonitrile-based precursor fiber bundle having a total fineness of 40,000 dtex or more. In particular, it is suitable for flameproofing a polyacrylonitrile-based precursor fiber bundle having a total fineness of 50,000 to 60,000 dtex. In the present invention, a carbon fiber bundle can be produced by subjecting this polyacrylonitrile-based precursor fiber bundle to flameproofing treatment at 200 to 300 ° C. and then carbonizing treatment at a temperature exceeding 600 ° C.

  In the present invention, the cross-sectional shape of the precursor fiber bundle yarn subjected to the flameproofing treatment is maintained in a substantially rectangular shape, and the average flatness is controlled in the range of 15 to 70. Here, “substantially rectangular” refers to a shape surrounded by two sets of substantially parallel straight lines, and the corners may be curved.

  The average flatness of the substantially rectangular yarn cross section was defined as follows. Stop driving the running yarn, measure it at a rate of 1 point in the width direction of the yarn at 10 ms using a generally known laser displacement meter, average it to the yarn thickness A, and the width of the yarn Was measured by averaging 5 points at 5 cm intervals in the longitudinal direction using calipers, and B was obtained, and B divided by A was taken as the average flatness.

  When the average flatness is less than 15, the yarn thickness increases, and yarn breakage or the like is likely to occur due to heat accumulation by reaction in the flameproofing process. Moreover, since the yarn width increases when the average flatness ratio exceeds 70, the number of treated yarns with respect to the flameproofing furnace width decreases, and the equipment productivity decreases. Therefore, the average flatness is preferably in the range of 15 to 70, and more preferably in the range of 25 to 50.

  When the apparent average fineness per 1 mm width of the substantially rectangular precursor fiber bundle is less than 2,400 dtex, the number of treated yarns decreases, and the equipment productivity decreases. Further, when the apparent average fineness exceeds 5,000 dtex, the thickness increases, and fuzzing and yarn breakage are likely to occur due to heat accumulation by the flameproofing reaction, and it is necessary to lower the flameproofing treatment temperature to suppress it. , Productivity decreases. Therefore, the apparent average fineness of the treated yarn in flame resistance is preferably in the range of 2,400 to 5,000 dtex, and more preferably in the range of 2,700 to 4,000 dtex.

  In order to achieve the above average flatness and apparent average fineness, the precursor fiber bundle is passed through the flameproofing furnace in a zigzag manner, for example, a zigzag so as to reciprocate several times in the horizontal direction. A groove member having the following shape may be disposed between the two.

  And the said groove member uses what satisfies following formula (1)-(3).

0.6 ≦ b / a ≦ 0.9 (1)
0.2 × a ≦ h ≦ 0.5 × a (2)
1 × (ab) ≦ R ≦ 2 × (ab) (3)
Where a is the width of the groove top (mm), b is the width of the groove bottom (mm), h is the depth of the groove (mm), and R is the radius (mm) of the round corner of the groove bottom. Show. Here, the width of the groove bottom means the width when the inflection point between the rounded radius portion of the corner of the groove bottom and the slope of the mountain forming the groove is the end. Each dimension in the cross section of the groove | channel 4 which the groove member 5 has is shown in FIG.

  In order to keep the cross-sectional shape of the precursor fiber bundle yarn in a flat, substantially rectangular sheet shape, it is necessary to give a width to the groove bottom. When the ratio b / a of the width a of the groove top part to the width b of the groove bottom part is less than 0.6, the groove shape becomes nearly V-shaped and cannot be maintained in a substantially rectangular sheet shape. If b / a exceeds 0.9, the slope of the slope of the mountain forming the groove becomes larger than the bottom of the groove, and it is highly possible that the end of the running precursor fiber bundle yarn will break. The form maintainability of the strip is reduced. Preferably, 0.75 ≦ b / a ≦ 0.85.

  When the groove depth h is less than 0.2 times the width a of the groove top, a part of the running yarn may get over the groove, and the adjacent yarn may get tangled and cause fluffing. In addition, when the groove depth h exceeds 0.5 times the width a of the groove top, the ratio of the cross-sectional area of the substantially rectangular sheet to the groove cross-sectional area is reduced, which increases the processing cost and is economical. Absent. Therefore, the groove depth h is set to a range of 0.2 to 0.5 times the width a of the groove top. Preferably, 0.3 × a ≦ h ≦ 0.4 × a.

  When the radius R of the roundness at the corner of the groove bottom is less than 1 × (ab), the thickness is uneven at the end of the precursor fiber bundle yarn that is substantially rectangular, or at the radius of the roundness at the corner of the groove bottom Is likely to occur. Further, when the radius R of the round corner of the groove bottom portion is larger than 2 × (ab), the radius portion of the round corner of the groove bottom portion in the width of the groove bottom portion becomes large, so that it is easy to get over the groove, and the adjacent yarn The strip may get tangled and fluffy. Also, if the radius of the round corner of the groove bottom is increased, the slope of the groove peak and the groove bottom cannot be smoothly connected as the groove shape, causing the end of the precursor fiber bundle yarn to break There is a possibility. Therefore, the radius R of the roundness at the corner of the groove is set to a range of 1 × (ab) ≦ R ≦ 2 × (ab). Preferably, 1.3 × (ab) ≦ R ≦ 1.7 × (ab).

  Further, the groove bottom may not be a flat bottom but may be a groove shape with an arc. By attaching an arc to the bottom of the groove, it is possible to suppress the run-out of the precursor fiber bundle yarn in the width direction and improve the running position controllability.

  In FIG. 3, the example which showed the arrangement | positioning relationship of the groove member 5 and the folding | turning roll 2 with respect to the flame-proofing furnace 1 is shown. The precursor fiber bundle yarn 3 exiting the flameproofing furnace 1 is changed in direction by the folding roll 2 which is a flat roll through the groove member 5 and enters the flameproofing furnace again.

  Here, as shown in FIG. 3, when the groove member is on the side of the folding roll, the interval between the groove member and the folding roll is preferably 250 mm or more. This interval is a distance (center distance) between the center of the groove member and the center of the folding roll. Since the precursor fiber bundle yarn has a shape along the groove when passing through the groove member, when the distance between the groove member and the folding roll is less than 250 mm and the gap is small, the yarn reaches the folding roll with the width of the yarn narrowed. Then, it may be put into a flameproofing furnace. The center distance is more preferably 300 mm or more. The center-to-center distance may be long as long as the groove member is disposed outside the flameproofing furnace, but is preferably 550 mm or less.

  Although not shown, the groove member can be disposed on the exit side of the folding roll. In this case, the distance between the groove member and the folding roll is preferably 400 mm or more. This interval is a distance (center distance) between the center of the groove member and the center of the folding roll. When controlling the yarn on the exit side of the folding roll, since the binding force in the width direction of the yarn is strong, if the distance between the groove member and the folding roll is less than 400 mm, there is a high possibility that the groove will jump. The center distance is more preferably 450 mm or more. The center-to-center distance may be long as long as the groove member is disposed outside the flameproofing furnace, but is preferably 700 mm or less.

  The groove member 5 may be a grooved roll or a grooved plate obtained by processing the groove on the plate, and may be anything as long as it has a groove shape satisfying the above formulas (1) to (3).

If the tension applied to the yarn conveyed into the flameproofing furnace is less than 6.6 × 10 ⁻² g / dtex, the yarn will be suspended and rubbing will occur at the bottom of the flameproofing furnace, resulting in subsequent carbonization There is a risk of degrading the quality of the carbon fiber bundle obtained in the process and lowering the tensile strength. On the other hand, if the tension is greater than 2 × 10 ⁻¹ g / dtex, fluffing due to single yarn breakage in the flameproofing process increases, and there is a risk of winding on the roll. Therefore, in order to obtain a desired flameproof fiber bundle in a stable flameproofing process, the tension applied to the yarn is preferably 6.6 × 10 ⁻² to 2 × 10 ⁻¹ g / dtex, preferably 1 × 10. ^{-1 to} 1.7 × 10 ^-1 g / dtex is more preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not restrict | limited by these Examples.

Example 1
A polyacrylonitrile-based precursor fiber bundle having a total fineness of 60,000 dtex is placed at a position of 450 mm on the entry side of the folding roll, a = 20 mm, b = 17 mm, h = 6 mm, R = 5.0 mm [ie, b / a = 0.85, h = 0.30 × a, R = 1.67 × (a−b)], a grooved roll A is installed, and the thread form after passing through the grooved roll A Was observed. At this time, the average flatness is 50, the apparent average fineness for a yarn width of 1 mm is 2,900 dtex, the tension applied to the yarn is 0.7 × 10 ⁻¹ g / dtex, and the precursor after passing through the grooved roll A The form of the body fiber bundle yarn was controlled.

(Example 2)
The same polyacrylonitrile-based precursor fiber bundle yarn as in Example 1 was placed at the same position as in Example 1 at a = 17.5 mm, b = 13 mm, h = 6.5 mm, R = 5.0 mm [ie, b / a = 0.74, h = 0.37 × a, R = 1.1 × (a−b)] in which the grooved roll B having a groove shape is installed, and the thread form after passing the grooved roll B Was observed. At this time, the average flatness ratio is 20, the apparent average fineness for a yarn width of 1 mm is 4,600 dtex, and the tension applied to the yarn is 1.4 × 10 ⁻¹ g / dtex. The form of the body fiber bundle yarn was controlled.

(Example 3)
A polyacrylonitrile-based precursor fiber bundle yarn similar to that in Example 1 is installed with a grooved plate A having the same groove shape as in Example 2 at the same position as in Example 1, and after passing through the grooved plate A The yarn morphology was observed. At this time, the average flatness ratio, the apparent average fineness with respect to the yarn width of 1 mm, and the tension applied to the yarn are the same as in Example 2, and the form of the precursor fiber bundle yarn after passing through the grooved plate A is controlled. It was.

  The results of Examples 1 to 3 are summarized in Table 1.

  When the running position and form of the precursor fiber bundle yarn are controlled by a grooved roll having a shape satisfying the formulas (1) to (3) as in Examples 1 and 2, the end fold and thickness of the yarn are controlled. Troubles such as spots and grooves did not occur. Moreover, the result of Table 1 has shown that the thread form controllability of the grooved roll and grooved plate which have the same groove shape is equivalent, and there is no big difference by the member which processes a groove | channel.

Next, in order to grasp the influence of the radius of roundness at the corner of the groove bottom portion on the traveling precursor fiber bundle yarn, the same polyacrylonitrile-based precursor fiber bundle yarn as in Example 1 was placed on the entry side of the folding roll. The grooved roll shown below was installed in the position of 250 mm, and the thread form after passing through the grooved roll was observed. At this time, the average flatness of the yarn before passing through the grooved roll was 30, the apparent average fineness with respect to the yarn width of 1 mm was 4,000 dtex, and the tension applied to the yarn was 1.0 × 10 ⁻¹ g / dtex. .

Example 4
Using the same grooved roll A as in Example 1, the form of the precursor fiber bundle yarn was controlled after passing through the grooved roll A and observing the form of the yarn on the folding roll. Moreover, although the installation position of the roll A with a groove | channel was shifted in the width direction of the thread | yarn and it was made to run by making it contact with the slope part of a groove mountain, the form of the thread was controllable.

(Example 5)
Using the same grooved roll B as in Example 2, the shape of the yarn after passing through the grooved roll B and on the folding roll was observed, and the form of the precursor fiber bundle yarn was controlled. Moreover, although the installation position of the roll B with a groove | channel was shifted in the width direction of the thread | yarn, and it was made to run by making it contact with the slope part of a groove mountain, the form of the thread was controllable.

(Comparative Example 1)
a = 20 mm, b = 17.9 mm, h = 6 mm, R = 5.0 mm [ie, b / a = 0.90, h = 0.30 × a, R = 2.4 × (ab)] The shape of the precursor fiber bundle yarn was controlled after the passage of the grooved roll C and the shape of the yarn on the folding roll was observed using the grooved roll C having the shape of When the installation position of the grooved roll C was shifted in the width direction of the strip and was allowed to run on the sloping portion of the groove mountain, the end of the yarn became thick and thickness spots were generated.

(Comparative Example 2)
a = 20 mm, b = 17.6 mm, h = 5 mm, R = 2.0 mm [ie, b / a = 0.88, h = 0.25 × a, R = 0.83 × (a−b)] The shape of the precursor fiber bundle yarn was controlled when the shape of the yarn was observed after passing through the grooved roll D and on the folding roll using the grooved roll D having the shape of When the installation position of the grooved roll D was shifted in the width direction of the strip and was allowed to run on a sloping portion of the groove mountain, the result was that the end of the yarn passed through the folding roll in a broken state.

  The results of Examples 4 and 5 and Comparative Examples 1 and 2 are summarized in Table 2.

  Even if the groove shape satisfies the formulas (1) and (2), if the radius is not the radius of the round corner of the groove bottom that smoothly connects the slope of the groove and the bottom of the groove, the yarn will not touch Troubles such as breaking the end of the thread. Therefore, the radius of the roundness of the corner of the groove bottom must be within a range satisfying the expression (3).

Next, a groove member is arranged on the entry side of the folding roll, and the same polyacrylonitrile-based precursor fiber bundle yarn as in Example 1 is folded back with the groove member using the same grooved roll B as in Example 2. The distance between the centers of the rolls was changed, and the shape of the yarn after passing through the grooved roll B and on the folding roll and the presence or absence of trouble were confirmed. At this time, the average flatness of the yarn before passing through the grooved roll was 40, the apparent average fineness for a yarn width of 1 mm was 3,300 dtex, and the tension applied to the yarn was 0.7 × 10 ⁻¹ g / dtex. .

(Example 6)
When the distance between the center of the folding roll and the groove member was set to 300 mm, the running position and form of the yarn could be controlled without any trouble.

(Example 7)
When the distance between the center of the folding roll and the groove member was set to 250 mm, the running position and form of the yarn could be controlled without any trouble.

(Comparative Example 3)
When the distance between the centers of the folding roll and the groove member is set to 200 mm, the width of the yarn on the folding roll is about 0.8 to 0.9 times that when the groove member is not installed, and the width of the yarn is As a result, it passed in a reduced state.

(Comparative Example 4)
When the distance between the center of the folding roll and the groove member is set to 150 mm, the width of the yarn on the folding roll is about 0.8 to 0.9 times that when the groove member is not installed. As a result, it passed in a reduced state.

  The results of Examples 6 and 7 and Comparative Examples 3 and 4 are summarized in Table 3.

  When the groove member is arranged on the entry side of the folding roll, the precursor fiber bundle yarn has a shape along the groove when passing through the groove member, and travel position regulation and yarn shape control are performed. Then, after passing through the groove member, it returns to a substantially rectangular shape and passes through the folding roll. However, when the distance between the groove member and the folding roll is small, the shape of the yarn does not return to a substantially rectangular shape, the end of the yarn has a thickness, reaches the folding roll in a narrowed state, and then the flameproofing furnace Will be thrown into. In order to prevent this, the distance between the centers of the folding roll and the groove member needs to be 250 mm or more.

Next, a groove member is arranged on the exit side of the folding roll, and the polyacrylonitrile-based precursor fiber bundle yarn similar to that in Example 1 is used as the groove member and the folding roll using the same grooved roll B as in Example 2. The center distance was changed, and the form of the yarn after passing the grooved roll B and the presence or absence of trouble were confirmed. At this time, the average flatness of the yarn before passing through the grooved roll was 40, the apparent average fineness for a yarn width of 1 mm was 3,000 dtex, and the tension applied to the yarn was 0.74 × 10 ⁻¹ g / dtex. .

(Example 8)
When the distance between the centers of the folding roll and the groove member was set to 450 mm, the running position and form of the yarn could be controlled without any trouble.

Example 9
When the distance between the center of the folding roll and the groove member was set to 400 mm, the running position and form of the yarn could be controlled without any trouble.

(Comparative Example 5)
When the distance between the centers of the folding roll and the groove member was set to 350 mm, in the precursor fiber bundle yarn that hits the slant portion of the groove mountain, the end of the precursor fiber bundle yarn was bent.

(Comparative Example 6)
When the distance between the centers of the folding roll and the groove member was set to 300 mm, the traveling position controllability was poor, resulting in the occurrence of groove skipping.

  The results of Examples 8 and 9 and Comparative Examples 5 and 6 are summarized in Table 4.

  When the groove member is arranged on the exit side of the folding roll, the precursor fiber bundle yarn is constrained by the folding roll, so that the interval is made longer than when the groove member is arranged on the entry side of the folding roll. There must be. When the distance between the folding roll and the groove member is small, it is difficult to restrict the travel position by the groove member, and there is a high possibility that the groove jumps. Moreover, in order to enable the shape control of the precursor fiber bundle yarn having a substantially rectangular shape, it is indicated that the gap between the groove member and the folding roll needs to be 400 mm or more.

It is the schematic which shows arrangement | positioning of a flame-resistant furnace and a folding | turning roll. It is sectional drawing of the groove part which a groove member has. It is the schematic which shows arrangement | positioning of the return | turnback roll and a groove member with respect to a flameproofing furnace.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flame-resistant furnace 2 Folding roll 3 Precursor fiber bundle yarn 4 Groove 5 Groove member

Claims (3)

A polyacrylonitrile-based precursor fiber bundle having a total fineness of 40,000 dtex or more is passed through a flame-proofing furnace in a zigzag manner with a folding roll, passed through a flame-resistant treatment at 200 to 300 ° C., and then carbonized at a temperature exceeding 600 ° C. In the method for producing a carbon fiber bundle to be treated,
Between the flameproofing furnace and the folding roll, a groove member that satisfies the following formulas (1) to (3) is arranged,
A method for producing a carbon fiber bundle, wherein an apparent average fineness per 1 mm width of the polyacrylonitrile-based precursor fiber bundle after passing through the groove member is maintained at 2,400 to 5,000 dtex.
0.6 ≦ b / a ≦ 0.9 (1)
0.2 × a ≦ h ≦ 0.5 × a (2)
1 × (ab) ≦ R ≦ 2 × (ab) (3)
(Wherein, a is the groove top width (mm), b is the groove bottom width (mm), h is the groove depth (mm), and R is the radius (mm) of the round corner of the groove bottom. )   2. The method for producing a carbon fiber bundle according to claim 1, wherein the groove member is disposed on an entry side of the folding roll, and a center-to-center distance between the groove member and the folding roll is 250 mm or more.   The method for producing a carbon fiber bundle according to claim 1, wherein the groove member is disposed on the exit side of the folding roll, and a center-to-center distance between the groove member and the folding roll is 400 mm or more.

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