Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
  • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
  • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
  • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
  • D01F9/32—Apparatus therefor
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs
  • C08J5/248—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs using pre-treated fibres
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D11/00—Other features of manufacture
  • D01D11/02—Opening bundles to space the threads or filaments from one another
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F11/00—Chemical after-treatment of artificial filaments or the like during manufacture
  • D01F11/10—Chemical after-treatment of artificial filaments or the like during manufacture of carbon
  • D01F11/14—Chemical after-treatment of artificial filaments or the like during manufacture of carbon with organic compounds, e.g. macromolecular compounds
• • D—TEXTILES; PAPER
  • D02—YARNS; MECHANICAL FINISHING OF YARNS OR ROPES; WARPING OR BEAMING
  • D02J—FINISHING OR DRESSING OF FILAMENTS, YARNS, THREADS, CORDS, ROPES OR THE LIKE
  • D02J1/00—Modifying the structure or properties resulting from a particular structure; Modifying, retaining, or restoring the physical form or cross-sectional shape, e.g. by use of dies or squeeze rollers
  • D02J1/18—Separating or spreading

Definitions

• the present invention mainly relates to a method of producing a partially split carbon fiber bundle.
• Patent Document 2 proposes to partially split the carbon fiber bundle by intermittently piercing a plate or a needle into the carbon fiber bundle and to use the carbon fiber bundle for producing SMC.
• the partial-split denotes a process of partially splitting one original continuous fiber bundle into a plurality of sub-bundles.
• An object of the present invention is to provide enhancement of a method of producing a partially split carbon fiber bundle. More specifically, the object of the present invention includes the following.
• a method of producing a partially split carbon fiber bundle comprising: continuously supplying a carbon fiber bundle from a carbon fiber production line to a partial-split line connected to the carbon fiber production line; and performing a partial-split treatment on the carbon fiber bundle in a partial-split section provided in the partial-split line.
• a method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, wherein the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the protruding portion is formed of a needle, and the needle is inclined to fall to a downstream side of the carbon fiber bundle in a traveling direction in a case where the needle pierces into the carbon fiber bundle.
• a method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, wherein the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the protruding portion is formed of a plate, in a case where the plate pierces into the carbon fiber bundle, in a part of the plate that pierces into the carbon fiber bundle, an edge of the plate facing an upstream side of the carbon fiber bundle in a traveling direction is inclined to fall to a downstream side of the carbon fiber bundle in the traveling direction.
• a method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, wherein the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the protruding portion is formed of a plate, the protruding portion having a plate shape has at least one convex corner with an inner angle of 90° or greater and does not have a convex corner with an inner angle of less than 90°, and in the partial-split treatment, the number of convex corners of the protruding portion with an inner angle of 90° or greater that are in a state of piercing into the carbon fiber bundle does not exceed 1.
• a method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, wherein the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the protruding portion is formed of a plate, the protruding portion having a plate shape has two right angle corners, and in the partial-split treatment, only one of the two right angle corners pierces into the carbon fiber bundle.
• a method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, wherein the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the protruding portion is formed of a rectangular plate, and in the partial-split treatment, only one of four right angle corners of the rectangular plate pierces into the carbon fiber bundle.
• a method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, wherein the partial-split treatment includes swinging a split jig having a protruding portion and intermittently piercing the protruding portion into the carbon fiber bundle that travels in the longitudinal direction of the carbon fiber bundle.
• a method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, wherein the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in the longitudinal direction of the carbon fiber bundle, and the method includes blowing compressed air to the protruding portion of the split jig in a case where the partial-split treatment is performed.
• a method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, wherein the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the split jig has (n + 1) or more pieces of the protruding portions, and in the partial-split treatment, the carbon fiber bundle is partially split into n or (n + 1) sub-bundles, where n represents an integer of 2 or greater.
• One embodiment of the present invention relates to a method of producing a partially split carbon fiber bundle.
• a partial-split line 2 having a partial-split section 1 is prepared as shown in FIG. 1 .
• an unsplit carbon fiber bundle 3 which is a starting material, is unwound from a spool and supplied to the partial-split section 1.
• the bundle size of the carbon fiber bundle 3, that is, the number of carbon fiber filaments constituting the carbon fiber bundle 3 is usually 12K or greater and may be 15K or greater, 24 or greater, 36K or greater, 48K or greater, or the like, and is usually 120K or less and may be 100K or less, 80K or less, 60K or less, or the like, but the present invention is not limited thereto.
• K is a symbol indicating 1000, and for example, 12K denotes 12,000 and 120K denotes 120,000.
• the carbon fiber bundle 3 is subjected to a partial-split treatment to obtain a partially split carbon fiber bundle 4.
• the partial-split treatment can be performed, for example, by intermittently piercing a needle or a plate into the carbon fiber bundle 3 that travels in a longitudinal direction (fiber direction), but other tools may be used.
• the partial-split treatment of the carbon fiber bundle 3 in the partial-split section can be performed using a slitter roll in which a defective portion is provided on a slit blade provided on a circumferential surface.
• FIG. 22 shows an example of such a slitter roll.
• a defective portion 53 is provided on a slit blade 52 provided on a circumferential surface 51.
• the partially split carbon fiber bundle 4 that has exited the partial-split section is wound around another spool.
• the carbon fiber production line 5 and the partial-split line 2 are connected, and the unsplit carbon fiber bundle 3 is continuously supplied from the carbon fiber production line 5 to the partial-split line 2.
• the carbon fiber production line 5 includes, in order from the upstream side, a calcining section 7 in which a precursor fiber bundle 6 formed of polyacrylonitrile is calcined to form a carbon fiber bundle, a surface treatment section 8 in which a surface treatment for introducing a functional group into a carbon fiber surface is performed, and a sizing section 9 in which the carbon fiber bundle is sized.
• the calcining section 7 usually includes a flame-resistant section and a carbonization section as subsections, and may further include a graphitization section.
• the precursor fiber bundle 6 may be twisted at, for example, 5 to 20 turns/m.
• the unsplit carbon fiber bundle 3 is preferably untwisted to be in a twistless state on a downstream side of the calcining section 7. It is preferable that the untwisting is performed until the sizing is completed, and in an example, the untwisting may be performed on an upstream side of the surface treatment section 8.
• the unsplit carbon fiber bundle 3 is supplied to the partial-split line 2 without being wound around a spool after being produced in the carbon fiber production line 5 and is partially split in the partial-split section 1 of the partial-split line 2, and thus the partially split carbon fiber bundle 4 is obtained.
• the partially split carbon fiber bundle 4 is wound around a spool.
• Not winding the carbon fiber bundle produced in the carbon fiber production line around a spool before the partial split is advantageous in stabilizing the quality of the partially split carbon fiber bundle. This is because the posture of the carbon fiber bundle is stabilized in a case where the carbon fiber bundle travels in the partial-split section without having a winding habit before being supplied to the partial-split line.
• the reason why the carbon fiber bundle is likely to have a winding habit is that the carbon fiber has plasticity, and more specifically, the reason is that a resin containing a low-molecular-weight compound, which is referred to as a sizing agent, is used to bond the carbon fibers to each other. Therefore, for example, even in a case where a packaging container is charged with the carbon fiber bundle by applying a method disclosed in Japanese Unexamined Patent Application, First Publication No. 2012-188773 , instead of winding the carbon fiber bundle around a spool, the carbon fiber bundle has a winding habit. In general, since the carbon fiber bundle that is once packaged before being supplied to the partial-split line has a winding habit, the posture of the carbon fiber bundle during traveling the partial-split section is unstable.
• the posture of the carbon fiber bundle during traveling the partial-split section is particularly unstable in a case where the carbon fiber bundle that is traversely wound around a spool is used by being unwound.
• the carbon fiber bundle is likely to be locally twisted in a case where the movement direction of a traverse guide is reversed, and the twisting of the carbon fiber bundle does not completely return to the original state even after unwinding from the spool.
• the partial-split step in a case where a part in a state where the carbon fiber bundle is twisted is processed with a tool such as a needle or a plate, a large number of carbon fibers are cut, and thus there is a problem in that the carbon fiber bundle after the partial-split is severely fuzzed.
• the carbon fiber bundle that does not almost have a twisted part can be supplied to the partial-split line, and thus the fuzzing of the carbon fiber bundle in the partial-split step is also suppressed.
• the carbon fiber bundle is sized before being supplied to the partial-split line.
• the carbon fiber bundle is subjected to a partial-split treatment without being sized, a large amount of broken fibers are generated, and the carbon fiber bundle is significantly fuzzed.
• both of the following two frictional forces are greatly increased by introducing a functional group into the surface of the carbon fiber by performing a surface treatment.
• One of the two frictional forces is a frictional force acting between carbon fibers adjacent to each other in the bundle, and the other is a frictional force acting between a tool such as a needle or a plate used for the partial-split treatment and the carbon fibers.
• the reason why the fuzzing caused by the partial-split treatment is suppressed in the sized carbon fiber bundle is that the sizing agent introduced into the carbon fiber bundle by carrying out sizing acts as a lubricant that reduces the frictional forces.
• the carbon fiber bundle passes through a sizing bath and then dried. Since the carbon fibers are fixed to each other by the sizing, it is desirable that in the sizing section 9, the carbon fibers are sufficiently aligned by applying a high tension to the carbon fiber bundle using, for example, a tension applying mechanism such as a dancer roll.
• a high tension is also applied to the carbon fiber bundle 3 on the partial-split line 2 such that a tool such as a needle or a plate reliably pierces into the carbon fiber bundle 3.
• a single tension applying mechanism may serve as both the tension applying mechanism for the sizing section 9 and the tension applying mechanism for the partial-split line 2.
• the force generated by the contraction of the precursor fiber bundle 6 due to the calcination in the calcining section 7 can also be used for applying a tension to the carbon fiber bundle in the sizing section 9 and the partial-split line 2.
• the carbon fiber bundle is partially split in the partial-split section provided on the partial-split line.
• the partial-split treatment is performed by piercing a needle or a plate into the carbon fiber bundle passing through the partial-split section.
• the carbon fiber bundle supplied to the partial-split section has a flat shape, and thus has a width direction and a thickness direction in addition to a longitudinal direction (fiber direction).
• the width direction and the thickness direction are each perpendicular to the longitudinal direction and are perpendicular to each other.
• a tension is applied to the carbon fiber bundle that travels in the partial-split section such that the longitudinal direction is parallel to a first direction and the width direction is parallel to a second direction orthogonal to the first direction. That is, the carbon fiber bundle passes through the partial-split section in a state of being substantially straightened in the first direction without being twisted and floating in the air.
• the first direction is referred to as an x direction in the partial-split section
• the second direction is referred to as a y direction in the partial-split section
• a direction perpendicular to both the x direction and the y direction is referred to as a z direction.
• the x direction may be perpendicular, inclined, or parallel to the direction in which gravity acts.
• the y direction may be perpendicular, inclined, or parallel to the direction in which gravity acts.
• the carbon fiber bundle vibrates in a case of traveling in a state of floating in the air. Therefore, even in a case where the longitudinal direction of the carbon fiber bundle is parallel to the x direction in a case where the carbon fiber bundle passes through the partial-split section, the longitudinal direction is not constantly strictly parallel to the x direction. Similarly, the width direction of the carbon fiber bundle traveling in the partial-split section and the y direction are not constantly strictly parallel to each other.
• a split jig having a protruding portion formed of a needle or a plate is installed in the partial-split section.
• the carbon fiber bundle supplied to the partial-split line is partially split by intermittently piercing by the protruding portion of the split jig while passing through the partial-split section.
• the number of protruding portions of one split jig is typically 2 or greater, but may be 1.
• FIGS. 4 , 5, and 6 show an example of a split jig in which the protruding portion is formed of a needle.
• a split jig 20A shown in FIGS. 4 , 5, and 6 includes a base 21 and eight needles 22 fixed to the base 21.
• the eight needles are parallel to each other and extend in the u direction shown in the drawings.
• the eight needles are also arranged at equal intervals in a t direction orthogonal to the u direction. All the eight needles have the same length, and a straight line formed by connecting the tips of the needles is parallel to the t direction.
• the material of the needles is typically a metal.
• metals steel typified by stainless steel is preferable, but the present invention is not limited thereto.
• the needle has at least a body.
• the body is a part where the shape and the area of a transverse cross section are constant.
• the shape of the body is preferably a cylinder, and may be an elliptical cylinder, a triangular prism, a quadrangular prism, a hexagonal prism, or other prisms.
• the cross-sectional shape of the elliptical cylinder may be an ellipse or an oval.
• the tip of a needle is tapered to easily pierce into the carbon fiber bundle.
• FIG. 7 shows an example of the shape that the tip of a tapered needle can have.
• needles each having a conical tip 22a-1, a flat surface tapered tip 22a-2, a double flat surface tapered tip 22a-3, and a hemispherical tip 22a-4 in order from the left are shown as an example.
• the diameter of the body of the needle is preferably 1 mm or less, more preferably 0.9 mm or less, and still more preferably 0.8 mm or less.
• the diameter of the body decreases, but in a case where the diameter is extremely small, the rigidity is lowered, and the needle does not pierce into the carbon fiber or is easily bent. Therefore, the diameter of the body is preferably 0.3 mm or greater and more preferably 0.4 mm or greater, and may be 0.5 mm or greater. In a case where the body is not cylindrical, the minimum width of the body is regarded as the diameter.
• the tip of the needle is hemispherical.
• the end of the tapered tip other than the hemispherical shape may be rounded, or an end surface perpendicular to an axial direction may be provided.
• the split jig 20A shown in FIGS. 4 , 5, and 6 can be produced by preparing the base 21 in which a plurality of holes 21a are formed, inserting the root of the needle 22 into each hole 21a one by one, and then adhering and fixing the base 21 and the needle 22.
• the split jig 20A shown in FIGS. 4 , 5, and 6 is merely an example of a split jig having a plurality of needles that are arranged in parallel with each other and fixed to each other.
• the method of producing the split jig is not limited to the method in which a plurality of needles are arranged in parallel and fixed to each other.
• the needle 22 may be fixed with a screw 25 by being sandwiched between two plates 24.
• FIGS. 10, 11, and 12 show an example of the split jig in which the protruding portion is formed of a plate.
• a split jig 20B shown in FIGS. 10, 11, and 12 has seven spacers 31 and eight plates 32 that are alternately arranged and fixed to each other.
• the eight plates 32 have the same length, width, and thickness, and the shape of the main surfaces (surfaces orthogonal to the thickness direction) thereof is rectangular.
• the eight plates 32 are parallel to each other, and the long sides of the main surfaces of the plates 32 are further parallel to the u direction shown in the drawings.
• the eight plates are arranged at equal intervals in the t direction orthogonal to the u direction.
• the seven spacers 31 are alternately laminated with the eight plates 32 on a -u side of the split jig 20B. A +u side of each plate 32 protrudes with respect to the spacer 31.
• the material of the plate 32 is typically a metal. Steel typified by stainless steel is preferable, but the present invention is not limited thereto.
• a method of fixing the spacer 31 and the plate 32 to each other is not limited, and for example, various methods such as adhesion, clamping, and screwing can be appropriately applied.
• the thickness of the plate is preferably 1 mm or less, and may be 0.9 mm or less, 0.8 mm or less, 0.7 mm or less, 0.6 mm or less, 0.5 mm or less, 0.4 mm or less, 0.3 mm or less, or the like. As the thickness of the plate decreases, the plate is more likely pierce into the carbon fiber bundle, and the carbon fiber bundle is easily split into sub-bundles having a small bundle size. From this viewpoint, it is preferable that the thickness of the plate decreases, but in a case where the plate is extremely thin, the rigidity is lowered, and the plate does not pierce anything into the carbon fiber bundle or is easily bent. Therefore, the thickness of the plate is preferably 0.1 mm or greater and more preferably 0.2 mm or greater.
• the edge of the plate may be tapered.
• the split jig 20B shown in FIGS. 10, 11, and 12 shows one suitable example, and the plate 32 is rectangular, that is, a quadrangle having four right angle corners (corners with an inner angle of 90°), and the protruding portion includes two of the four right angle corners.
• the plate 32 may have a polygonal shape other than a quadrangle, such as a triangle, a pentagon, or a hexagon, may have a concave polygonal shape, or may have a shape that does not have a corner, such as an ellipse.
• the plate 32 has preferably a polygonal shape, more preferably a quadrangular shape, and particularly preferably a rectangular shape.
• the partial-split treatment of the carbon fiber bundle using the split jig is performed as follows.
• FIGS. 13, 14, and 15 each show an example in which the split jig having a protruding portion formed of a needle is used.
• the traveling direction of the carbon fiber bundle 11 is a direction from left to right in the drawing, and the same applies to FIGS. 16, 17 , 19, 20 , and 21 described below.
• the actuator 40 causes the split jig 20A to reciprocate linearly, and thus the needle 22 intermittently pierces into the traveling carbon fiber bundle 11.
• the split jig 20A is disposed such that a t direction of the split jig 20A is parallel to the y direction.
• the split jig 20A swings about the shaft 45 by an actuator (not shown), and the needle 22 intermittently pierces into the traveling carbon fiber bundle 11.
• the shaft 45 is parallel to the y direction.
• the split jig 20A is disposed such that the t direction of the split jig 20A is parallel to the y direction, and the longitudinal direction of the needle 22 is parallel to the radial direction of the cylinder in a case of assuming a cylinder having the shaft 45 as a center.
• This example may be modified such that the split jig 20 rotates instead of swinging.
• the split jig 20 swings about the shaft 45 by an actuator (not shown), and the needle 22 intermittently pierces into the traveling carbon fiber bundle 11.
• the shaft 45 is parallel to the y direction.
• the split jig 20A is disposed such that the t direction of the split jig 20A is parallel to the y direction, and the longitudinal direction of the needle 22 is inclined with respect to the radial direction of the cylinder in a case of assuming a cylinder having the shaft 45 as a center.
• both the x direction and the y direction may be horizontal, and in this case, the carbon fiber bundle 11 may be pierced by the needle 22 from below or may be pierced by the needle 22 from above.
• the carbon fiber bundle 11 is split by allowing the split jig 20A to remain stationary for a certain period of time in a state where the needle 22 pierces into the traveling carbon fiber bundle 11.
• the needle 22 in a state of piercing into the carbon fiber bundle 11 is not perpendicular to the traveling direction of the carbon fiber bundle 11, and is inclined (angle ⁇ is less than 90°) to fall to the downstream side (+x direction side) of the carbon fiber bundle 11 in the traveling direction. In this manner, carbon fiber scraps are difficult to accumulate on the split jig 20, which is convenient.
• FIGS. 16 and 17 each show an example in which the split jig having a protruding portion formed of a plate is used.
• the actuator 40 causes the split jig 20B to reciprocate linearly, and thus the plate 32 intermittently pierces into the traveling carbon fiber bundle 11.
• the split jig 20B is disposed such that a t direction of the split jig 20B is parallel to the y direction.
• the carbon fiber bundle 11 is split by allowing the split jig 20B to remain stationary for a certain period of time in a state where the plate 32 pierces into the traveling carbon fiber bundle 11.
• the split jig 20B swings about the shaft 45 by an actuator (not shown), and thus the plate 32 intermittently pierces into the traveling carbon fiber bundle 11.
• the shaft 45 is parallel to the y direction.
• the split jig 20B is disposed such that the t direction of the split jig 20B is parallel to the y direction, and the carbon fiber bundle 11 is split by allowing the split jig 20B to remain stationary for a certain period of time in a state where the plate 32 pierces into the traveling carbon fiber bundle 11.
• the present invention is not limited to a case where the protruding portion is formed of a rectangular plate, and in a case where the protruding portion of the split jig has a plate shape and has a plurality of convex corners (corners in which an inner angle is a convex angle), the same effect can be obtained by setting the number of convex corners in a state of piercing into the carbon fiber bundle among the plurality of convex corners not to exceed 1 while the partial-split treatment is performed.
• the number of convex corners of the protruding portion having a plate shape may be set to only one.
• the above-described effect is more significant, preferably by setting the inner angle of the convex corner that pierces into the carbon fiber bundle to 90° or greater. From the viewpoint that the protruding portion easily pierces into the carbon fiber bundle, the inner angle is preferably 120° or less.
• the movement of the split jig is reciprocation instead of rotation regardless of the kind of the protruding portion.
• Examples of the reciprocation include linear reciprocation and swinging.
• the reason why reciprocation is preferable is that winding does not occur in a case where a trouble of breakage of the carbon fiber bundle (the entirety or a part of sub-bundles) occurs. In a case where winding occurs, it is necessary to stop the production line, and it takes a long time to recover from the winding.
• a suitable example of the actuator for reciprocating the split jig is an air cylinder, but the present invention is not limited thereto, and an electric motor may be used.
• the split jig swings such that the protruding portion moves in a direction opposite to the traveling direction of the carbon fiber bundle in a case where the protruding portion pierces into the carbon fiber bundle, and the protruding portion moves in the direction same as the traveling direction of the carbon fiber bundle in a case where the protruding portion is released from the carbon fiber bundle.
• a slit is formed in the carbon fiber bundle.
• the formation of the slit is interrupted.
• FIG. 18 is a plan view of the partially split carbon fiber bundle 4 as viewed in the thickness direction.
• first slit row R S1 a first slit row R S1 , a second slit row R S2 , a third slit row R S3 , and a fourth slit row R S4 are formed in the partially split carbon fiber bundle 4.
• the first slit row R S1 is formed of a plurality of first slits S1 arranged in the longitudinal direction of the partially split carbon fiber bundle 4.
• the second slit row R S2 is formed of a plurality of second slits S2 arranged in the longitudinal direction of the partially split carbon fiber bundle 4.
• the third slit row R S3 is formed of a plurality of third slits S3 arranged in the longitudinal direction of the partially split carbon fiber bundle 4.
• the fourth slit row R S4 is formed of a plurality of fourth slits S4 arranged in the longitudinal direction of the partially split carbon fiber bundle 4.
• a gap length L G between slits which is the length of the gap G S between the slits in each of the first to fourth slit rows R S1 , R S2 , R S3 , and R S3 , is substantially a product of the time from when the protruding portion is released from the carbon fiber bundle to when the protruding portion pierces into the subsequent carbon fiber bundle and the traveling speed of the carbon fiber bundle.
• the slit length L S and the gap length L G between slits are constant in any slit row, and are common to all the slit rows.
• the slit length L S is preferably 20 cm or greater, more preferably 40 cm or greater, and still more preferably 60 cm or greater. As the slit length L S increases, it is advantageous since the chopped carbon fiber bundle obtained in a case where the split carbon fiber bundle 4 is cut in order to produce SMC includes a large number of bundles having the same bundle size as the sub-bundles.
• the fiber length of the chopped carbon fiber bundle may be preferably 5 to 60 mm, more preferably 10 to 30 mm, and still more preferably 20 mm or less. From this viewpoint, the upper limit of the slit length L S is not particularly limited.
• the slit length L S increases, a problem (for example, winding around the roll) that occurs in a case where the sub-bundles are broken in the partial-split line or in the line for producing SMC using or the partially split carbon fiber bundle 4 is likely to be serious.
• the slit length L S is preferably 300 cm or less, more preferably 200 cm or less, and still more preferably 150 cm or less.
• the slit length L S can be set to, for example, 60 cm or greater and less than 100 cm, 100 cm or greater and less than 150 cm, 150 cm or greater and less than 200 cm, 200 cm or greater and less than 250 cm, or 250 cm or greater and 300 cm or less.
• the gap length L G between slits is preferably 1 cm or less, more preferably 5 mm or less, and still more preferably 2 mm or less, and may be 1 mm or less.
• the description of the slit length L S and the gap length L G between slits is not limited to the partially split carbon fiber bundle that is partially split into five sub-bundles, and also applies to the partially split carbon fiber bundle that is partially split into four or less or six or more sub-bundles.
• the bundle size of the sub-bundle formed by the partial-split treatment is not particularly limited.
• the bundle size of the sub-bundles in a case where the carbon fiber bundles having a bundle size of 12 to 24K is subjected to the partial-split treatment is set to preferably 6K or less, more preferably 4K or less, still more preferably 3K or less, and even still more preferably 2K or less.
• the size of the sub-bundles in a case where the carbon fiber bundles having a bundle size of 36K to 120K are subjected to the partial-split treatment is preferably set to 18K or less, and may be, for example, 15K or less, 12K or less, 9K or less, 6K or less, 4K or less, 3K or less, 2K or less, or the like.
• the bundle size of the sub-bundles is preferably 0.5K or greater and more preferably 1K or greater.
• the split jig In order to partially split the carbon fiber bundle into n (n represents an integer of 2 or greater) sub-bundles, it is necessary to simultaneously form (n - 1) slits in the carbon fiber bundle, and for that purpose, the split jig must have at least (n - 1) pieces of protruding portions. Further, the split jig is required to be disposed in the partial-split section such that (n - 1) pieces of protruding portions can simultaneously pierce into the carbon fiber bundle.
• a guide roller with a groove having a groove width corresponding to the width of the carbon fiber bundle may be used.
• the number of protruding portions of the split jigs may be set to (n + 1) or greater instead of splitting the carbon fiber bundle into n sub-bundles using the split jig having exactly (n - 1) pieces of protruding portions, and the carbon fiber bundle may be partially split into at least n sub-bundles.
• variation in the position of the carbon fiber bundle in the y direction in the partial-split section is allowed to some extent so that the traveling speed of the carbon fiber bundle does not need to be lowered, and even in a case where variation in the position of the carbon fiber bundle in the y direction occurs, the number of protruding portions that pierce into the carbon fiber bundle is not allowed to be less than (n - 1) at the same time.
• FIGS. 20 and 21 show an example in which n is 9 and the split jig has (n + 1), that is, 10 needles as protruding portions.
• the number of protruding portions that pierce into the subsequent carbon fiber bundle 11 is nine due to a slight shift in the position of the carbon fiber bundle 11 in the y direction. In such a case, the number of sub-bundles increases from 9 to 10, but a sub-bundle having an abnormally large bundle size is not formed.
• the position of the carbon fiber bundle 11 in the y direction is largely shifted after the eight protruding portions (needles 22) of the split jig 20A pierce into the carbon fiber bundle 11 are released, and therefore, the number of protruding portions piercing into the subsequent carbon fiber bundle 11 is still eight. Even in such a case, the sub-bundle having an abnormally large bundle size is not formed.
• the longitudinal direction of the needle 22 in a case of piercing into the carbon fiber bundle 11 is parallel to the z direction, but the present invention is not limited thereto.
• the needle 22 may be inclined to fall to the downstream side of the carbon fiber bundle 11 in the traveling direction in a case where the needle 22 pierces into the carbon fiber bundle 11.
• the number of protruding portions of the split jig that simultaneously pierce into the carbon fiber bundle is set such that the bundle size of the sub-bundles to be formed is a predetermined upper limit or less. Therefore, in a case where the bundle size of the carbon fiber bundle before a partial-split treatment is 15K and the upper limit of the bundle size of the sub-bundles is about 5K, the number of protruding portions of the split jig to simultaneously pierce may be set to 2 or 3.
• the number of protruding portions of the split jig that simultaneously pierce into the carbon fiber bundle may be set to 4 or 5.
• Fiber scraps generated by cutting an extremely small part of the carbon fibers in the step on the upstream side may be attached to the carbon fiber bundle supplied to the partial-split section.
• the carbon fibers may be cut by the partial-split treatment in the partial-split section, and the fiber scraps may be generated.
• Such fiber scraps are likely to be caught in the protruding portion of the split jig.
• the fiber scraps are accumulated so that large cotton waste is formed and attached to the partially split carbon fiber bundle, there is a concern that the quality of the SMC produced using the partially split carbon fiber bundle deteriorates.
• the caught fiber scraps and/or cotton waste may be blown off by blowing compressed air to the protruding portion of the split jig.
• the blowing of the compressed air may be continuous or intermittent.
• a suction nozzle is installed in the vicinity of the split jig, and the fiber scraps and/or the cotton waste blown by the compressed air are removed to prevent the fiber scraps and/or the cotton waste from being attached to the partially split carbon fiber bundle.
• Preferable embodiments of the present invention include the following but are not limited thereto.
• a method of producing a partially split carbon fiber bundle including: continuously supplying a carbon fiber bundle from a carbon fiber production line to a partial-split line connected to the carbon fiber production line; and performing a partial-split treatment on the carbon fiber bundle in a partial-split section provided in the partial-split line.
• Embodiment A2 The method according to Embodiment A1, in which the carbon fiber production line includes a sizing section, and the carbon fiber bundle is sized in the sizing section and supplied to the partial-split line.
• Embodiment A3 The method according to Embodiment A2, in which a single tension applying mechanism serves as both a tension applying mechanism for the sizing section and a tension applying mechanism for the partial-split line.
• Embodiment A4 The method according to any one of Embodiments A1 to A3, in which a force generated as a precursor fiber bundle in the carbon fiber production line contracts is used for applying a tension to the carbon fiber bundle in the partial-split line.
• Embodiment A5 The method according to any one of Embodiments A1 to A4, in which the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle.
• Embodiment A6 The method according to Embodiment A5, in which the protruding portion is formed of a needle.
• Embodiment A7 The method according to Embodiment A6, in which the needle is inclined to fall to a downstream side of the carbon fiber bundle in a traveling direction in a case where the needle pierces into the carbon fiber bundle.
• Embodiment A8 The method according to Embodiment A5, in which the protruding portion is formed of a plate.
• Embodiment A9 The method according to Embodiment A8, in which in a part of the protruding portion having a plate shape that pierces into the carbon fiber bundle, in a case where the protruding portion pierces into the carbon fiber bundle, an edge of the protruding portion facing an upstream side of the carbon fiber bundle in a traveling direction is inclined to fall to a downstream side of the carbon fiber bundle in the traveling direction.
• Embodiment A10 The method according to Embodiment A8 or A9, in which the protruding portion having a plate shape has at least one convex corner, and in the partial-split treatment, the number of convex corners of the protruding portion that are in a state of piercing into the carbon fiber bundle does not exceed 1.
• Embodiment A11 The method according to any one of Embodiments A8 to A10, in which the protruding portion having a plate shape has at least one convex corner with an inner angle of 90° or greater and does not have a convex corner with an inner angle of less than 90°, and in the partial-split treatment, the number of convex corners of the protruding portion with an inner angle of 90° or greater that are in a state of piercing into the carbon fiber bundle does not exceed 1.
• Embodiment A12 The method according to any one of Embodiments A8 to A11, in which the protruding portion having a plate shape has two right angle corners, and in the partial-split treatment, only one of the two right angle corners of the protruding portion pierce into the carbon fiber bundle.
• Embodiment A13 The method according to any one of Embodiments A8 to A12, in which the protruding portion is formed of a rectangular plate, and in the partial-split treatment, only one of four right angle corners of the rectangular plate pierces into the carbon fiber bundle.
• Embodiment A14 The method according to any one of Embodiments A5 to A13, in which in the partial-split treatment, the split jig reciprocates to have e the protruding portion intermittently pierce into the carbon fiber bundle, and the reciprocation may be linear reciprocation or swinging reciprocation.
• Embodiment A15 The method according to any one of Embodiments A5 to A14, in which in the partial-split treatment, the split jig swings to have the protruding portion intermittently pierce into the carbon fiber bundle.
• Embodiment A16 The method according to Embodiment A15, in which the protruding portion moves in a direction opposite to a traveling direction of the carbon fiber bundle in a case where the protruding portion pierces into the carbon fiber bundle, and the protruding portion moves in a direction same as the traveling direction of the carbon fiber bundle in a case where the protruding portion is released from the carbon fiber bundle.
• Embodiment A17 The method according to Embodiment A15 or A16, in which the partial-split section has an x direction, a y direction, and a z direction orthogonal to each other, and in a case where the longitudinal direction and a width direction of the carbon fiber bundle are each parallel to the x direction and the y direction while the carbon fiber bundle passes through the partial-split section, the split jig swings about an axis parallel to the y direction.
• Embodiment A18 The method according to any one of Embodiments A5 to A17, further including: blowing compressed air to the protruding portion of the split jig in a case where the partial-split treatment is performed.
• Embodiment A19 The method according to any one of Embodiments A5 to A18, in which the split jig has exactly (n - 1) pieces of the protruding portions, and in the partial-split treatment, the carbon fiber bundle is partially split into n sub-bundles, where n represents an integer of 2 or greater.
• Embodiment A20 The method according to any one of Embodiments A5 to A18, in which the split jig has (n + 1) or more pieces of the protruding portions, and in the partial-split treatment, the carbon fiber bundle is partially split into n or (n + 1) sub-bundles, where n represents an integer of 2 or greater.
• Embodiment A21 The method according to Embodiment A19 or A20, in which a bundle size of each of the sub-bundles is 18k or less, preferably 15k or less, more preferably 12k or less, and still more preferably 9k or less, and may be 6k or less, 4k or less, 3k or less, or 2k or less.
• Embodiment A22 The method according to any one of Embodiments A1 to A18, in which the carbon fiber bundle is partially split into a plurality of sub-bundles by the partial-split treatment, and a bundle size of each of the plurality of sub-bundles is 18k or less, preferably 15k or less, more preferably 12k or less, and still more preferably 9k or less, and may be 6k or less, 4k or less, 3k or less, or 2k or less.
• Embodiment A23 The method according to any one of Embodiments A1 to A22, in which in the partial-split treatment, a slit row formed of a plurality of slits arranged in a longitudinal direction of the carbon fiber bundle is formed in the carbon fiber bundle, and a length of the plurality of slits is 20 cm or greater, preferably 40 cm or greater, and more preferably 60 cm or greater, and may be, for example, 60 cm or greater and less than 100 cm, 100 cm or greater and less than 150 cm, 150 cm or greater and less than 200 cm, 200 cm or greater and less than 250 cm, or 250 cm or greater and 300 cm or less.
• Emodiment B1 A method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, in which the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the protruding portion is formed of a needle, and the needle is inclined to fall to a downstream side of the carbon fiber bundle in a traveling direction in a case where the needle pierces into the carbon fiber bundle.
• Embodiment B2 A method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, in which the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the protruding portion is formed of a plate, in a case where the protruding portion having a plate shape pierces into the carbon fiber bundle, in a part of the protruding portion that pierces into the carbon fiber bundle, an edge of the protruding portion facing an upstream side of the carbon fiber bundle in a traveling direction is inclined to fall to a downstream side of the carbon fiber bundle in the traveling direction.
• Embodiment B3 The method according to Embodiment B2, in which the protruding portion having a plate shape has at least one convex corner, and in the partial-split treatment, the number of convex corners of the protruding portion that are in a state of piercing into the carbon fiber bundle does not exceed 1.
• Embodiment B4 The method according to Embodiment B2 or B3, in which the protruding portion having a plate shape has at least one convex corner with an inner angle of 90° or greater and does not have a convex corner with an inner angle of less than 90°, and in the partial-split treatment, the number of convex corners of the protruding portion with an inner angle of 90° or greater that are in a state of piercing into the carbon fiber bundle does not exceed 1.
• Embodiment B5 The method according to any one of Embodiments B2 to B4, in which the protruding portion having a plate shape has two right angle corners at an end in a protruding direction, and in the partial-split treatment, only one of the two right angle corners of the protruding portion pierces into the carbon fiber bundle.
• Embodiment B6 The method according to any one of Embodiments B2 to B5, in which the protruding portion is formed of a rectangular plate, and in the partial-split treatment, only one of four right angle corners of the rectangular plate pierces into the carbon fiber bundle.
• Embodiment B7 A method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, in which the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the protruding portion is formed of a plate, the protruding portion having a plate shape has at least one convex corner with an inner angle of 90° or greater and does not have a convex corner with an inner angle of less than 90°, and in the partial-split treatment, the number of convex corners of the protruding portion with an inner angle of 90° or greater that are in a state of piercing into the carbon fiber bundle does not exceed 1.
• Emodiment B8 A method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, in which the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the protruding portion is formed of a plate, the protruding portion having a plate shape has two right angle corners, and in the partial-split treatment, only one of the two right angle corners pierces into the carbon fiber bundle.
• Emodiment B9 A method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, in which the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the protruding portion is formed of a rectangular plate, and in the partial-split treatment, only one of four right angle corners of the rectangular plate pierces into the carbon fiber bundle.
• Embodiment B10 The method according to any one of Embodiments B1 to B9, in which in the partial-split treatment, the split jig reciprocates to have the protruding portion intermittently pierce into the carbon fiber bundle, and the reciprocation may be linear reciprocation or swinging reciprocation.
• Embodiment B11 The method according to any one of Embodiments B1 to B10, in which in the partial-split treatment, the split jig swings to have the protruding portion intermittently pierce into the carbon fiber bundle.
• Embodiment B12 The method according to Embodiment B11, in which the protruding portion moves in a direction opposite to the traveling direction of the carbon fiber bundle in a case where the protruding portion pierces into the carbon fiber bundle, and the protruding portion moves in a direction same as the traveling direction of the carbon fiber bundle in a case where the protruding portion is released from the carbon fiber bundle.
• Embodiment B13 The method according to Embodiment B11 or B12, in which a space where the partial-split treatment is performed has an x direction, a y direction, and a z direction orthogonal to each other, and in a case where the longitudinal direction and a width direction of the carbon fiber bundle are each parallel to the x direction and the y direction while the carbon fiber bundle passes through the space, the split jig swings about an axis parallel to the y direction.
• Embodiment B14 The method according to any one of Embodiments B1 to B13, including: blowing compressed air to the protruding portion of the split jig in a case where the partial-split treatment is performed.
• Embodiment B15 The method according to any one of Embodiments B1 to B14, in which the split jig has exactly (n - 1) pieces of the protruding portions, and in the partial-split treatment, the carbon fiber bundle is partially split into n sub-bundles, where n represents an integer of 2 or greater.
• Embodiment B16 The method according to any one of Embodiments B1 to B14, in which the split jig has (n + 1) or more pieces of the protruding portions, and in the partial-split treatment, the carbon fiber bundle is partially split into n or (n + 1) sub-bundles, where n represents an integer of 2 or greater.
• Embodiment B17 The method according to Embodiment B15 or B16, in which a bundle size of each of the sub-bundles is 18k or less, preferably 15k or less, more preferably 12k or less, and still more preferably 9k or less, and may be 6k or less, 4k or less, 3k or less, or 2k or less.
• Embodiment B18 The method according to any one of Embodiments B1 to B14, in which the carbon fiber bundle is partially split into a plurality of sub-bundles by the partial-split treatment, and a bundle size of each of the plurality of sub-bundles is 18k or less, preferably 15k or less, more preferably 12k or less, and still more preferably 9k or less, and may be 6k or less, 4k or less, 3k or less, or 2k or less.
• Embodiment B19 The method according to any one of Embodiments B1 to B18, in which in the partial-split treatment, a slit row formed of a plurality of slits arranged in the longitudinal direction of the carbon fiber bundle is formed in the carbon fiber bundle, and a length of the plurality of slits is 20 cm or greater, preferably 40 cm or greater, and more preferably 60 cm or greater, and may be, for example, 60 cm or greater and less than 100 cm, 100 cm or greater and less than 150 cm, 150 cm or greater and less than 200 cm, 200 cm or greater and less than 250 cm, or 250 cm or greater and 300 cm or less.
• Emodiment C1 A method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, in which the partial-split treatment includes swinging a split jig having a protruding portion and intermittently piercing the protruding portion into the carbon fiber bundle that travels in the longitudinal direction of the carbon fiber bundle.
• Embodiment C2 The method according to Embodiment C1, in which the protruding portion moves in a direction opposite to a traveling direction of the carbon fiber bundle in a case where the protruding portion pierces into the carbon fiber bundle, and the protruding portion moves in a direction same as the traveling direction of the carbon fiber bundle in a case where the protruding portion is released from the carbon fiber bundle.
• Embodiment C3 The method according to Embodiment C1 or C2, in which a space where the partial-split treatment is performed has an x direction, a y direction, and a z direction orthogonal to each other, and in a case where the longitudinal direction and a width direction of the carbon fiber bundle are each parallel to the x direction and the y direction while the carbon fiber bundle passes through the space, the split jig swings about an axis parallel to the y direction.
• Embodiment C4 The method according to any one of Embodiments C1 to C3, in which the protruding portion is formed of a needle.
• Embodiment C5 The method according to any one of Embodiments C1 to C3, in which the protruding portion is formed of a plate.
• Embodiment C6 The method according to any one of Embodiments C1 to C5, including: blowing compressed air to the protruding portion of the split jig in a case where the partial-split treatment is performed.
• Embodiment C7 The method according to any one of Embodiments C1 to C6, in which the split jig has exactly (n - 1) pieces of the protruding portions, and in the partial-split treatment, the carbon fiber bundle is partially split into n sub-bundles, where n represents an integer of 2 or greater.
• Embodiment C8 The method according to any one of Embodiments C1 to C6, in which the split jig has (n + 1) or more pieces of the protruding portions, and in the partial-split treatment, the carbon fiber bundle is partially split into n or (n + 1) sub-bundles, where n represents an integer of 2 or greater.
• a bundle size of each of the sub-bundles is 18k or less, preferably 15k or less, more preferably 12k or less, and still more preferably 9k or less, and may be 6k or less, 4k or less, 3k or less, or 2k or less.
• Embodiment C10 The method according to any one of Embodiments C1 to C6, in which the carbon fiber bundle is partially split into a plurality of sub-bundles by the partial-split treatment, and a bundle size of each of the plurality of sub-bundles is 18k or less, preferably 15k or less, more preferably 12k or less, and still more preferably 9k or less, and may be 6k or less, 4k or less, 3k or less, or 2k or less.
• Embodiment C11 The method according to any one of Embodiments C1 to C10, in which in the partial-split treatment, a slit row formed of a plurality of slits arranged in the longitudinal direction of the carbon fiber bundle is formed in the carbon fiber bundle, and a length of the plurality of slits is 20 cm or greater, preferably 40 cm or greater, and more preferably 60 cm or greater, and may be, for example, 60 cm or greater and less than 100 cm, 100 cm or greater and less than 150 cm, 150 cm or greater and less than 200 cm, 200 cm or greater and less than 250 cm, or 250 cm or greater and 300 cm or less.
• Emodiment D1 A method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, in which the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in the longitudinal direction of the carbon fiber bundle, and the method includes blowing compressed air to the protruding portion of the split jig in a case where the partial-split treatment is performed.
• Embodiment D2 The method according to Embodiment D1, in which the protruding portion is formed of a needle.
• Embodiment D3 The method according to Embodiment D1, in which the protruding portion is formed of a plate.
• Embodiment D4 The method according to any one of Embodiments D1 to D3, in which the split jig has exactly (n - 1) pieces of the protruding portions, and in the partial-split treatment, the carbon fiber bundle is partially split into n sub-bundles, where n represents an integer of 2 or greater.
• Embodiment D5 The method according to any one of Embodiments D1 to D3, in which the split jig has (n + 1) or more pieces of the protruding portions, and in the partial-split treatment, the carbon fiber bundle is partially split into n or (n + 1) sub-bundles, where n represents an integer of 2 or greater.
• Embodiment D6 The method according to Embodiment D4 or D5, in which a bundle size of each of the sub-bundles is 18k or less, preferably 15k or less, more preferably 12k or less, and still more preferably 9k or less, and may be 6k or less, 4k or less, 3k or less, or 2k or less.
• Embodiment D7 The method according to any one of Embodiments D1 to D3, in which the carbon fiber bundle is partially split into a plurality of sub-bundles by the partial-split treatment, and a bundle size of each of the plurality of sub-bundles is 18k or less, preferably 15k or less, more preferably 12k or less, and still more preferably 9k or less, and may be 6k or less, 4k or less, 3k or less, or 2k or less.
• Embodiment D8 The method according to any one of Embodiments D1 to D7, in which in the partial-split treatment, a slit row formed of a plurality of slits arranged in the longitudinal direction of the carbon fiber bundle is formed in the carbon fiber bundle, and a length of the plurality of slits is 20 cm or greater, preferably 40 cm or greater, and more preferably 60 cm or greater, and may be, for example, 60 cm or greater and less than 100 cm, 100 cm or greater and less than 150 cm, 150 cm or greater and less than 200 cm, 200 cm or greater and less than 250 cm, or 250 cm or greater and 300 cm or less.
• Embodiment E1 A method of producing a partially split carbon fiber bundle by performing a partial-split treatment on a carbon fiber bundle, in which the partial-split treatment includes intermittently piercing a protruding portion of a split jig having the protruding portion into the carbon fiber bundle that travels in a longitudinal direction of the carbon fiber bundle, the split jig has (n + 1) or more pieces of the protruding portions, and in the partial-split treatment, the carbon fiber bundle is partially split into n or (n + 1) sub-bundles, where n represents an integer of 2 or greater.
• Embodiment E2 The method according to Embodiment E1, in which a bundle size of each of the sub-bundles is 18k or less, preferably 15k or less, more preferably 12k or less, and still more preferably 9k or less, and may be 6k or less, 4k or less, 3k or less, or 2k or less.
• Embodiment E3 The method according to Embodiment E1 or E2, in which the protruding portion is formed of a needle.
• Embodiment E4 The method according to Embodiment E1 or E2, in which the protruding portion is formed of a plate.
• Embodiment E5 The method according to any one of Embodiments E1 to E4, in which in the partial-split treatment, a slit row formed of a plurality of slits arranged in a longitudinal direction of the carbon fiber bundle is formed in the carbon fiber bundle, and a length of the plurality of slits is 20 cm or greater, preferably 40 cm or greater, and more preferably 60 cm or greater, and may be, for example, 60 cm or greater and less than 100 cm, 100 cm or greater and less than 150 cm, 150 cm or greater and less than 200 cm, 200 cm or greater and less than 250 cm, or 250 cm or greater and 300 cm or less.
• a slitter roll in which a slit blade provided on the circumferential surface was provided with a defective portion was installed in the partial-split section.
• the partially split carbon fiber bundle could be stably produced.
• the carbon fiber bundle was significantly fuzzed due to the partial-split treatment, and a carbon fiber in a single filament state was generated by the partial-split treatment causing a part of the carbon fiber bundle to be unraveled. There was a concern that the carbon fiber in this single filament state was entangled in the guide roll.
• a split jig (the same as the split jig used in Experiment 3 described below) having a plurality of needles arranged in parallel and fixed to each other as shown in FIGS. 4 to 6 was installed in the partial-split section as means for the partial-split treatment.
• the split jig was allowed to swing about a swinging axis provided in parallel with the width direction of the carbon fiber bundle traveling in the partial-split section to have the needle intermittently pierce into the carbon fiber bundle.
• the partial-split line shown in FIG. 1 was prepared, and a carbon fiber bundle (TR50S15L, manufactured by Mitsubishi Chemical Corporation) having 15K filaments, which was produced in the carbon fiber production line (including a sizing section) separate from the partial-split line and wound around a bobbin, was pulled out from the bobbin and subjected to a partial-split treatment.
• a carbon fiber bundle TR50S15L, manufactured by Mitsubishi Chemical Corporation
• a split jig having a plurality of protruding portions each formed of a needle was installed in the partial-split section.
• the needle was made of stainless steel (SUS304), the tip was hemispherical, and the body was a cylinder having a diameter of 0.8 mm.
• the split jig as in the examples shown in FIGS. 4 to 6 , more than 15 needles were arranged in parallel at a constant pitch of 1 mm.
• the orientation of the split jig was adjusted such that a straight line connecting the tips of the needles was parallel to the width direction of the traveling carbon fiber bundle. Since the width of the unsplit carbon fiber bundle was about 7 mm, the number of needles that could simultaneously pierce into the carbon fiber bundle was about 6.
• the reciprocation direction of the split jig was perpendicular to both the traveling direction and the width direction of the carbon fiber bundle. That is, the split jig was moved in parallel with the z direction in FIG. 3 .
• the angle ( ⁇ in the example of FIG. 13 ) between the longitudinal direction of the needle and the traveling direction of the carbon fiber bundle was set to 90°.
• the needle was moved in a direction opposite to the traveling direction of the carbon fiber bundle in a case where the needle pierces into the carbon fiber bundle, and the needle was moved in the direction same as the traveling direction of the carbon fiber bundle in a case where the needle was released from the carbon fiber bundle.
• the angle ( ⁇ in the example of FIG. 14 ) between the longitudinal direction of the needle and the traveling direction of the carbon fiber bundle was set to 45°. That is, during the stationary period, the needle was inclined to fall at an angle of 45° on the downstream side of the carbon fiber bundle in the traveling direction.
• the partial-split of the carbon fiber bundle was attempted in the same manner as in Experiment 3, and there was no problem in the stability of the partial-split treatment.
• the amount of carbon fiber scraps accumulated in the split jig by the partial-split treatment for the same time was less than the amount of carbon fiber scrapes in Experiment 3, as shown in FIG. 24 .
• the split jigs used in Experiment 6 each had a plurality of protruding portions formed of a rectangular plate.
• the rectangular plate was made of stainless steel (SUS304) and had a thickness of 0.2 mm.
• the split jig In the split jig, more than 15 sheets of rectangular plates were alternately laminated with spacers having a thickness of 0.6 mm, and were arranged in parallel at a constant pitch of 0.8 mm.
• the position of the split jig in the stationary period for 4.2 seconds was adjusted such that the orientation of the split jig was adjusted such that a straight line connecting corners between different rectangular plates was parallel to the width direction of the traveling carbon fiber bundle and such that only one corner of each rectangular plate pierced into the carbon fiber bundle. Since the width of the unsplit carbon fiber bundle was about 7 mm, the number of rectangular plates that could simultaneously pierce into the carbon fiber bundle was about 8.
• the angle ( ⁇ in the example of FIG. 16 ) between the edge of the rectangular plate facing the upstream side of the carbon fiber bundle in the traveling direction and the traveling direction in a part where the rectangular plate pierces into the carbon fiber bundle during the stationary period for 4.2 seconds was set to three types of 30°, 45°, and 60°, there was no problem in the stability of the partial-split treatment in all the cases.
• the angle increased, the amount of carbon fiber scraps accumulated on the split jig by the partial-split treatment for the same time increased.
• FIG. 25 is a photograph of the split jig after the partial-split treatment is performed by setting the angle to 60°.
• FIG. 26 is a photograph of the split jig after the partial-split treatment is performed by setting the angle to 30° for the same time.

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