JP5274044B2 - Carbon fiber sheet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long carbon fiber sheet which can reduce the effect of warps formed on thermal treatments, and to provide a method for producing the same. <P>SOLUTION: Provided is the carbon fiber sheet in which the final end portion of a carbon fiber sheet (a) is bound to the starting end portion of a carbon fiber sheet (b), wherein two corner portions in at least one of the terminal end portion of the carbon fiber sheet (a) and the initial end portion of the carbon fiber sheet (b) are cut down. Provided also is a method for producing the carbon fiber sheet, which includes a step of binding the final end portion of a carbon fiber sheet precursor (A) to the starting end portion of a carbon fiber sheet precursor (B); a step of cutting down two corner portions in at least one of the final end portion of a carbon fiber sheet precursor (A) and the starting end portion of a carbon fiber sheet precursor (B); and a step of carbonizing the bound carbon fiber sheet precursor. Thereby, the carbon fiber sheet can suitably be produced. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention is a carbon fiber sheet in which a plurality of carbon fiber sheets are joined together and a method for producing the same. The carbon fiber sheet of the present invention is suitable for various uses such as a heat insulating material, a heat-resistant protective material, an electrode material such as a fuel cell, and a current-carrying material.

  Since carbon fiber is excellent in heat resistance, it is used as a heat insulating material and heat-resistant protective material, and because it has electrical conductivity, it is applied and developed as an electrode material and current-carrying material for fuel cells. Is also underway.

  Carbon fiber is generally used in a state of being processed into a carbon fiber sheet such as a woven fabric, a nonwoven fabric, or a paper. A carbon fiber sheet is produced by carbonizing a carbon fiber sheet precursor, but when this carbon fiber sheet is used for the above-mentioned purposes, a heat treatment at about 150 to 400 ° C. may be performed again. In order to continuously perform the heat treatment again, there is a demand to lengthen the carbon fiber sheet.

  In Patent Document 1, the carbon fiber sheets are overlapped with each other, and the carbon fiber sheets are joined by connecting the end sides with a spun yarn or filament bundle made of polyacrylonitrile-based oxidized fiber having predetermined physical properties. A lengthening method is described. Specifically, a method is described in which a woven carbon fiber sheet is sewn using a needle.

On the other hand, when producing a carbon fiber sheet, the carbon fiber sheet precursor is carbonized by running in a heat treatment furnace set at a predetermined temperature. However, since the carbon fiber sheet precursor is not endless, the temperature of the heat treatment furnace is temporarily lowered for each carbon fiber sheet precursor, and a new carbon fiber sheet precursor is placed in the traveling line, and the temperature of the heat treatment furnace is raised again. There is a need. Since the temperature of the heat treatment furnace is very high, these processes take a long time, and as a result, the operation efficiency of the heat treatment furnace is greatly reduced. Therefore, there is also a desire to lengthen the carbon fiber sheet precursor. For example, in accordance with the method described in Patent Document 1, a method of elongating the carbon fiber sheet precursor by sewing the ends of the carbon fiber sheet precursor using a needle is conceivable.
JP 2004-176233 A

  However, when heat-treating a long carbon fiber sheet or carbon fiber sheet precursor, the side edges of the sheet may warp, and the carbon fiber sheet or carbon fiber sheet precursor may crack or bend. Sometimes get stuck in the heat treatment furnace.

  Then, an object of this invention is to provide the carbon fiber sheet which can reduce the influence by the curvature which generate | occur | produces when heat-processing, and its manufacturing method.

The present invention is a carbon fiber sheet in which the end portion of the carbon fiber sheet (a) and the start end portion of the carbon fiber sheet (b) are joined together by stitching one place or two places or more with a joining thread (l). There,
The total denier of the tether (l) is 400 to 4000 tex,
It is a carbon fiber sheet in which two corners in at least one of a terminal portion of the carbon fiber sheet (a) and a starting end portion of the carbon fiber sheet (b) are cut off.

Moreover, this invention is the process of stitching together the termination | terminus part of a carbon fiber sheet precursor (A), and the start end part of a carbon fiber sheet precursor (B) by one or two or more places by a stitching thread (L). ;
Cutting off two corners of at least one of a terminal portion of the carbon fiber sheet precursor (A) and a starting end portion of the carbon fiber sheet precursor (B); and carbonizing the joined carbon fiber sheet precursor. the step of possess the total denier of the connecting thread (L) is a carbon fiber sheet obtained by the manufacturing method and the manufacturing method thereof of the carbon fiber sheet is 400～4000Tex.

  ADVANTAGE OF THE INVENTION According to this invention, the influence by the curvature which generate | occur | produces when heat-treating the carbon fiber sheet and carbon fiber sheet precursor which were lengthened can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Carbon fiber sheet>
FIG. 1 is a top view showing an embodiment of the carbon fiber sheet of the present invention. In the carbon fiber sheet 10, the end portion of the carbon fiber sheet (a) 11 and the start end portion of the carbon fiber sheet (b) 12 are straightly connected in the length direction in a state where both end portions are aligned with each other. Yes. In addition, the carbon fiber sheet may be connected by the required number according to a use, and the form of joining in each joining location can be set independently.

The carbon fiber sheets (a) 11 and (b) 12 are sheets containing carbon fibers, and may be any of a woven shape, a nonwoven fabric shape, and a paper shape. The length, thickness, and basis weight of the carbon fiber sheets (a) 11 and (b) 12 can be appropriately set according to the purpose of use. For example, the length is 1-1500 m, the thickness is 0.1-10 mm, The basis weight is preferably 10 to ²⁰⁰ g / m2.

  As a kind of carbon fiber contained in the carbon fiber sheets (a) 11 and (b) 12, it is possible to use polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, phenol-based carbon fiber, or the like. it can. Since the bending strength and tensile strength of the obtained carbon fiber sheet are increased, it is preferable to use a PAN-based carbon fiber or a pitch-based carbon fiber, and it is more preferable to use a PAN-based carbon fiber. The carbon fibers are preferably short fibers having a length of 1 to 100 mm and an average diameter of 4 to 8 μm.

  The carbon fiber sheets (a) 11 and (b) 12 are preferably carbon fiber sheets in which carbon fibers are bound by carbon. Such a carbon fiber sheet can be obtained by carbonizing a carbon fiber sheet precursor comprising carbon fibers and a carbon precursor resin.

  As shown in FIG. 1, the carbon fiber sheet 10 may be joined in a state in which the end of the carbon fiber sheet (a) 11 and the start of the carbon fiber sheet (b) 12 are in contact with each other, as shown in FIG. 2. Thus, it is preferable that the end part of the carbon fiber sheet (a) 11 and the start end part of the carbon fiber sheet (b) 12 are connected in an overlapping state. By forming the overlapping portion in this way, it is possible to suppress a crack from occurring in the joined portion, or to prevent the joined portion from being divided due to the progress of the crack.

  The length L of the overlap portion 20 in which the end portion of the carbon fiber sheet (a) 11 and the start end portion of the carbon fiber sheet (b) 12 are overlapped with each other is obtained by connecting the carbon fiber sheets (a) 11 and (b) 12 with a connecting thread. Although it can set suitably in the range which can be bound, 100-500 mm is preferable and 220-350 mm is more preferable.

  As an example of the embodiment in which the end portion of the carbon fiber sheet (a) 11 and the start end portion of the carbon fiber sheet (b) 12 are joined together, as shown in FIGS. The state where it is sewed using is mentioned. The number of places connected by the connecting thread (1) 30 may be one, or two or more. For example, in the carbon fiber sheet shown in FIGS. 1 and 2, the carbon fiber sheets are stitched together at three locations by the joining thread (l) 30.

  The connecting yarn (l) 30 can be appropriately selected in consideration of the subsequent process. For example, carbon fiber, flame resistant fiber, aramid fiber, phenol fiber and the like can be used.

  The total denier of the tether (l) 30 is preferably 400 to 4000 tex, and more preferably 800 to 2400 tex. If the total denier is less than 400 tex, the tow strength may be insufficient. In addition, the yarn strength tends to decrease during the high-temperature treatment in the subsequent process. When the total denier exceeds 4000 tex, the yarn becomes thick, so that the sheet thickness of the joint portion increases, and it is likely to be caught by a guide or the like in the subsequent process or clogging of the gap. In addition, the single fibers become rigid during the high-temperature treatment in the subsequent process, and the single fibers are cut off at the connecting portions, so that cracks are likely to occur.

  The tow strength of the connecting yarn (l) 30 is preferably 1 kg or more. When the toe strength is less than 1 kg, the connecting portion is easily cut. Although there is no particular problem with the high tow strength of the connecting yarn (l) 30, a connecting yarn having a tow strength of 4 kg or less is usually used.

  The elongation of the connecting yarn (l) 30 is preferably 0.3 to 30%. When the elongation exceeds 30%, the connecting yarn is easily stretched by tension, so that the connecting portion is not sufficiently fixed, and the connecting portion is likely to be deformed (wrinkled, swelled).

  The specific gravity of the tether (l) 30 can be selected from 1.6 to 2.2, which is the specific gravity of pitch-based carbon fibers available as a commercial product, for example.

  On the other hand, two corners in at least one of the end portion of the carbon fiber sheet (a) 11 and the start end portion of the carbon fiber sheet (b) 12 are cut off. In the embodiment of FIGS. 1 and 2, two corners at the start end of the carbon fiber sheet (b) 12 are cut off. Since the warp of the side end portion of the carbon fiber sheet is likely to occur at the corner portion, the influence of the warp can be reduced by cutting off the corner portion.

  Even if the two corners at the terminal end of the carbon fiber sheet (a) 11 are cut off instead of the two corners at the starting end of the carbon fiber sheet (b) 12, the influence of the warp can be reduced. . When the two corners at the end of the carbon fiber sheet (a) 11 and the start of the carbon fiber sheet (b) 12 are cut off, the influence of warpage can be further reduced.

  The corners can be cut off with a cutter, for example. The range to be cut off can be set as appropriate so that the influence of warpage can be effectively reduced, but it is preferable to cut off linearly at positions where the distances L8 and L9 from the apex are 30 to 90 mm.

  Moreover, as an example of embodiment by which the terminal part of the carbon fiber sheet (a) 11 and the start part of the carbon fiber sheet (b) 12 are joined together, as shown in FIG. 3, the carbon fiber sheet (a) 11 A plurality of through holes (x) 21 are formed in the overlapping portion 20 between the end portion and the start end portion of the carbon fiber sheet (b) 12, and the connecting threads (m) are formed in the plurality of through holes (x) 21. 22 is passed, and the connecting thread (m) 22 is bound between the plurality of through-holes (x) 21 so that the connected state is mentioned. The connecting yarn (m) 22 may be one or two or more.

  Non-woven fabric and paper-like carbon fiber sheets are more fragile than woven fabrics, and when stitched with a needle, there is a high possibility that a crack will occur at the point where the needle is stabbed. There was a possibility that the mating part would be divided. However, as in the embodiment shown in FIG. 3, the gap between the plurality of through-holes (x) 21 is bound by the connecting thread (m) 22 so that the quality is long even in a non-woven or paper shape. It becomes a carbon fiber sheet of the scale.

  The connecting yarn (m) 22 can be appropriately selected in consideration of the subsequent process, and the same one as the connecting yarn (l) 30 can be used.

  The size of the through hole (x) 21 can be appropriately set in consideration of the strength of the carbon fiber sheets (a) 11 and (b) 12 and the number and thickness of the connecting yarns (m) 22. 2-10 mm is preferable and 4-7 mm is more preferable.

  The through hole (x) 21 can be formed using a drill or the like. However, cracks may occur in the carbon fiber sheet when using a type of hole that is pushed in to make a hole, and particularly in the case of a non-woven fabric or paper-like carbon fiber sheet, the crack occurs. Probability is high. Therefore, it is preferable to use a so-called corrugated drill, which is a drill of a type that opens a hole from the center to the outer peripheral side. By using a corrugated sheet, even if it is a nonwoven fabric-like or paper-like carbon fiber sheet, it becomes difficult to crack.

  When the through hole (x) 21 is formed, the carbon fiber sheets (a) 11 and (b) 12 can be prevented from shifting by temporarily fixing both side ends of the overlapping portion 20 with a clip or the like.

  The position at which the through hole (x) 21 is formed can be appropriately set in consideration of binding between the plurality of through holes (x) 21 by the connecting thread (m) 22.

  The number of the through holes (x) 21 may be plural, and may be two or four, for example. It is preferable that the number of the through holes (x) 21 is an even number because the connecting hole (x) 21 is bound to the through hole (x) 21 through the connecting thread (m) 22. The thread (m) 22 may be threaded through the plurality of through holes (x) 21 as long as the plurality of through holes (x) 21 are bound together. For example, a state in which the connecting thread (m) 22 is passed so as to reciprocate between the two through holes (x) 21 can be mentioned.

  When four through-holes (x) 21 are formed, as shown in FIG. 3, the tethers (m) 22 are passed through the four through-holes (x) 21 in the form of tearing. Is preferred. Although the connecting thread (m) 22 may be passed through the two through holes (x) 21 so as to reciprocate, the connecting thread (m) 22 is passed through in the form of tearing. As a result, a wide region is bound, so that the carbon fiber sheet is less likely to be cracked, and further, wrinkles and twists are less likely to occur in the overlapping portion 20.

  As the four through holes (x) 21, as shown in FIG. 3, it is preferable that two sets of two through holes (x) 21 arranged in parallel in the width direction are formed. And it is preferable that the joining thread (m) 22 is passed in parallel in the width direction in each of the two through holes (x) 21 arranged in parallel in the width direction. Further, it is preferable that none of the tethers (m) 22 passed between any two of the four through holes (x) 21 are parallel to the length direction. In general, the carbon fiber sheet is easily cracked in the length direction, but is difficult to crack in the width direction and the oblique direction. Also, the progress of cracks is easy to proceed in the length direction, and difficult to proceed in the width direction and the oblique direction. Therefore, the generation and progression of cracks can be suppressed by passing the connecting yarn (m) 22 as described above.

  The distances L1 and L2 between the two through holes (x) 21 arranged in parallel in the width direction are appropriately determined in consideration of binding between the four through holes (x) 21 by the connecting thread (m) 22. Although it can set, 17 to 84% of the width of carbon fiber sheets (a) 11 and (b) 12 is preferred, and 30 to 70% is more preferred. Further, as described above, since it is preferable that the tether (m) 22 passed between any two of the four through holes (x) 21 is not parallel to the length direction, L1 and L2 is preferably different.

  The distance L3 between the two sets of two through holes (x) 21 arranged in parallel in the width direction takes into account that the four through holes (x) 21 are bound by the connecting thread (m) 22. Although it can set suitably, 20 to 150% of the shorter one of L1 and L2 is preferable, and 33 to 67% is more preferable.

  The distance L4 between the two ends of the two through-holes (x) 21 arranged in parallel in the width direction and the start end or the end close to the start end or the end can be appropriately set so that the start end or the end does not get caught. 10 to 60 mm is preferable, and 25 to 40 mm is more preferable.

  FIG. 4 is a top view showing an embodiment of the carbon fiber sheet in which two or more sets of the plurality of through holes (x) 21 are formed and the space between them is bound. In FIG. 4, the through hole (x) 21 is omitted. In this way, two or more sets of the plurality of through holes (x) 21 may be formed, and each set may be bound by the connecting thread (m) 22. What is necessary is just to arrange | position each set so that carbon fiber sheet (a) 11 and (b) 12 can fully be bound. When two or more sets of four through holes (x) 21 are formed, the total of L1 and L2 preferably satisfies the above condition, and the shortest distance among L4 preferably satisfies the above condition.

  The connecting yarn (m) 22 may not be tied unless it is removed from the through hole (x) 21, but as shown in FIG. 3, the ends of the joining yarn (m) 22 are tied together. Is preferred.

  An embodiment in which at least one corner of at least one of the terminal end of the carbon fiber sheet (a) 11 and the start end of the carbon fiber sheet (b) 12 is cut off and a plurality of penetrations by the connecting yarn (m) 22 The embodiment in which the gaps between the holes (x) 21 are bound can be combined independently.

  Moreover, as an example of embodiment by which the terminal part of the carbon fiber sheet (a) 11 and the start part of the carbon fiber sheet (b) 12 are joined together, as shown in FIG. A through hole (y) 26 is formed at a side end portion of the overlapping portion 20 between the end portion and the start end portion of the carbon fiber sheet (b) 12, and a connecting thread (n) 27 is formed in the through hole (y) 26. , And the connecting yarn (n) 27 is bound between the through hole (y) 26 and the side edge of the overlapping portion 20, so that the connected state can be mentioned. The connecting yarn (n) 27 may be one or two or more.

  In the past, when the carbon fiber sheet was heat-treated again, the side ends of the carbon fiber sheet were warped, and the carbon fiber sheet was sometimes cracked or bent and caught in a heat treatment furnace. However, as in the embodiment shown in FIG. 5, the effect of warpage is reduced by binding the through hole (y) 26 and the side edge of the overlapping portion 20 by the connecting thread (n) 27. Can do.

  The connecting yarn (n) 27 can be appropriately selected in consideration of the subsequent steps, and the same one as the connecting yarn (l) 30 can be used.

  The size of the through hole (y) 26 can be appropriately set in consideration of the strength of the carbon fiber sheets (a) 11 and (b) 12 and the number and thickness of the connecting yarns (n) 27. 2-10 mm is preferable and 4-7 mm is more preferable.

  The through hole (y) 26 can be formed using a drill or the like. For the same reason as described above, it is preferable to use a corrugated sheet.

  When the through hole (y) 26 is formed, the carbon fiber sheets (a) 11 and () are formed by temporarily fixing the positions where the through hole (y) 26 is not formed at both end portions of the overlapping portion 20 with a clip or the like. b) The displacement of 12 can be prevented.

  The position where the through hole (y) 26 is formed can be appropriately set in consideration of binding between the side ends of the overlapping portion 20. The distance L5 between the through hole (y) 26 and the side edge of the overlapping portion 20 is preferably 20 to 30 mm because the influence of warpage can be effectively reduced.

  The number of through holes (y) 26 can be set to 1 to 10, for example. In addition, since the phenomenon that the side edges of the carbon fiber sheet warp is likely to occur at both ends, the same number of through holes (y) 26 are formed at both ends of the overlapping portion 20. It is preferable. Therefore, the total number of through holes (y) 26 to be formed is preferably an even number. For example, in the carbon fiber sheet shown in FIG. 5, three through-holes (y) 26 are formed at both end portions of the overlapping portion 20.

  When a plurality of through-holes (y) 26 are formed at one end, the distance L6 between the plurality of through-holes (y) 26 can be set as appropriate so that no warpage occurs between them. -450 mm is preferable, and 100-300 mm is more preferable. The distance L7 between the through hole (y) closest to the start end or the end of the plurality of through holes (y) 26 formed in one side end and the start end or the end is appropriately set so that the start end or the end is not caught. However, 10 to 90 mm is preferable, and 20 to 70 mm is more preferable.

  As shown in FIG. 5, the thread (n) 27 is passed through the through hole (y) 26 by reciprocating between the through hole (y) 26 and the side end of the overlapping portion 20. Is preferred. By being in this state, the connection thread (n) 27 is in a state where the through hole (y) 26 and the side end of the overlapping portion 20 are bound. The connecting yarn (n) 27 is preferably parallel to the width direction between the through hole (y) 26 and the side end of the overlapping portion 20.

  The connecting yarn (n) 27 may not be tied unless it is removed from the through hole (y) 26, but as shown in FIG. 5, the ends of the joining yarn (n) 27 are tied together. Is preferred.

  The embodiment in which two corners in at least one of the end portion of the carbon fiber sheet (a) 11 and the start end portion of the carbon fiber sheet (b) 12 are cut off, and the connecting thread (n) 27 has a through hole ( y) The embodiment in which the space between 26 and the side edge of the overlapping portion 20 is bound can be combined independently.

  Moreover, as an example of the embodiment in which the end portion of the carbon fiber sheet (a) 11 and the start end portion of the carbon fiber sheet (b) 12 are joined together, the states of FIGS. 3 and 5 are combined as shown in FIG. State. In this case, an embodiment in which at least one corner of at least one of the terminal end of the carbon fiber sheet (a) 11 and the start end of the carbon fiber sheet (b) 12 is cut off, and the connecting yarn (m) 22 provides a plurality of The embodiment in which the space between the through holes (x) 21 is bound and the embodiment in which the space between the through hole (y) 26 and the side edge of the overlapping portion 20 is bound by the connecting thread (n) 27 are: Can be combined independently.

  The carbon sheet of the present invention is suitable for various uses such as a heat insulating material, a heat-resistant protective material, an electrode material such as a fuel cell, and a current-carrying material.

<Method for producing carbon fiber sheet>
The carbon fiber sheet of the present invention, for example, after producing the carbon fiber sheet (a) and the carbon fiber sheet (b), connects the end portion of the carbon fiber sheet (a) and the start end portion of the carbon fiber sheet (b). It can be manufactured by combining and cutting off two corners in at least one of them. At this time, the order of both processes is not ask | required.

  Moreover, the carbon fiber sheet of this invention connects the terminal part of a carbon fiber sheet precursor (A), and the start part of a carbon fiber sheet precursor (B), and cuts off two corners in at least one of them. Moreover, it can also be produced by carbonizing the joined carbon fiber sheet precursor. Hereinafter, this method will be described.

  First, the terminal part of a carbon fiber sheet precursor (A) and the start part of a carbon fiber sheet precursor (B) are joined together. In addition, the carbon fiber sheet precursor may be connected by the required number according to the use of the manufactured carbon fiber sheet, and the form of joining in each joining place can be set independently.

The carbon fiber sheet precursors (A) and (B) become carbon fiber sheets by being carbonized, and may be any of a woven shape, a nonwoven fabric shape, and a paper shape. The length, thickness and basis weight of the carbon fiber sheet precursors (A) and (B) can be appropriately set according to the purpose of use of the produced carbon fiber sheet. For example, the length is 1 to 1500 m and the thickness. Is preferably 0.1 to 10 mm, and the basis weight is preferably 10 to ²⁰⁰ g / m ² .

  Examples of the carbon fiber sheet precursors (A) and (B) include a carbon fiber sheet precursor including carbon fibers and a carbon precursor resin. By carbonizing this carbon fiber sheet precursor, a carbon fiber sheet in which carbon fibers are bound by carbon is obtained.

  As a kind of carbon fiber, polyacrylonitrile (PAN) type carbon fiber, pitch type carbon fiber, rayon type carbon fiber, phenol type carbon fiber, etc. can be used. Since the bending strength and tensile strength of the obtained carbon fiber sheet are increased, it is preferable to use a PAN-based carbon fiber or a pitch-based carbon fiber, and it is more preferable to use a PAN-based carbon fiber. The carbon fibers are preferably short fibers having a length of 1 to 100 mm and an average diameter of 4 to 8 μm.

  The carbon precursor resin is used for the purpose of binding between carbon fibers. For example, a thermoplastic resin such as polyvinyl alcohol (PVA), a thermosetting resin such as a phenol resin, pitch, starch, or the like is used. be able to. Among these, phenol resin and pitch become carbide by heat treatment for carbonization, and exhibit a function of binding between carbon fibers in the carbon fiber sheet. Moreover, starch and PVA exhibit the function which improves the passage property in obtaining a carbon fiber sheet precursor.

  In the case of a carbon fiber sheet precursor comprising carbon fiber and a carbon precursor resin, the content ratio of the carbon fiber is preferably 10 to 90% by mass, more preferably 20 to 60% by mass, and further 30 to 50% by mass. preferable. When the content ratio of the carbon fiber is less than 10% by mass, the tensile strength of the obtained carbon fiber sheet tends to be reduced or the carbon fiber sheet tends to be brittle and easily broken. On the other hand, if the carbon fiber content exceeds 90 wt%, the resulting carbon fiber sheet tends to be bulky, and the tensile strength and compressive strength tend to decrease. For example, it may not be suitable for use in fuel cell electrodes.

  The carbon fiber sheet precursor comprising carbon fiber and carbon precursor resin may contain carbon powder, metal powder, inorganic powder, metal fiber, inorganic fiber, etc. in addition to carbon fiber and carbon precursor resin. When the obtained carbon fiber sheet is used as a fuel cell electrode base material, it is preferable to contain carbon powder in order to improve conductivity and reduce impurities.

  As a method for producing the carbon fiber sheet precursor, a paper making method such as a wet method in which carbon fiber is dispersed in a liquid medium for paper making or a dry method in which carbon fiber is dispersed in air to be deposited can be applied. Of these, the wet method is preferred. In order to help the carbon fibers disperse into the single fibers and to prevent the dispersed single fibers from converging again, it is preferred to wet paper with an appropriate amount of carbon precursor resin.

  As a method of mixing the carbon fiber and the carbon precursor resin, there are a method of stirring and dispersing in water and a method of directly mixing, but a method of stirring and dispersing in water is preferable for uniform dispersion. By mixing the carbon precursor resin with the carbon fiber in this way, the strength of the carbon fiber sheet precursor is maintained, and the carbon fiber is peeled off from the carbon fiber sheet precursor during the production, or the orientation of the carbon fiber is changed. Can be prevented.

  The production of the carbon fiber sheet precursor may be performed continuously or in a batch manner. From the viewpoint of productivity and mechanical strength, it is preferable to carry out continuously.

  In the carbon fiber sheet precursor, carbon fibers are preferably dispersed in a two-dimensional plane. Here, “dispersion in a two-dimensional plane” means that the carbon fibers lie so as to form a single plane. Thereby, breakage of the carbon fiber can be prevented. The orientation direction of the carbon fibers in the two-dimensional plane may be substantially random, or the orientation in a specific direction may be high.

  As will be described later, when the carbon fiber sheet precursors (A) and (B) are heat-treated at a plurality of temperatures, the sheet that has been heat-treated to an intermediate stage is also converted into the carbon fiber sheet precursors (A) and (B). Shall be included.

  According to the embodiment of the carbon fiber sheet shown in FIG. 1, the carbon fiber sheet precursor (A) and the carbon fiber sheet precursor (B) may be joined together in a state where the end of the carbon fiber sheet precursor (A) is in contact with the carbon fiber sheet precursor (B). According to the embodiment of the carbon fiber sheet shown in FIG. 2, it is preferable that the terminal portion of the carbon fiber sheet precursor (A) and the start end portion of the carbon fiber sheet precursor (B) are overlapped and joined in that state. By forming the overlapping portion in this way, it is possible to suppress a crack from occurring in the joined portion, or to prevent the joined portion from being divided due to the progress of the crack.

  The length of the overlapping part formed by overlapping the terminal part of the carbon fiber sheet precursor (A) and the starting part of the carbon fiber sheet precursor (B) connects the carbon fiber sheet precursors (A) and (B). Although it can set suitably in the range which can be bound with a thread | yarn, 100-500 mm is preferable and 220-350 mm is more preferable.

  At this time, from the viewpoint of preventing catching in the heat treatment furnace, it is preferable that the preceding carbon fiber sheet precursor is placed on the lower side and the subsequent carbon fiber sheet precursor is placed on the upper side.

  As an example of a method for joining the end portion of the carbon fiber sheet precursor (A) and the start end portion of the carbon fiber sheet precursor (B), according to the embodiment of the carbon fiber sheet shown in FIGS. (L) includes a method of sewing using a needle. The number of places to be sewn with the connecting thread (L) may be one, or two or more. For example, according to the embodiment of the carbon fiber sheet shown in FIGS. 1 and 2, the seam can be sewn at three places by the connecting thread (L).

  The connecting yarn (L) can be appropriately selected in consideration of the subsequent steps. For example, carbon fiber, flame resistant fiber, aramid fiber, phenol fiber and the like can be used.

  The total denier of the connecting yarn (L) is preferably 400 to 4000 tex, more preferably 800 to 2400 tex. If the total denier is less than 400 tex, the tow strength may be insufficient. In addition, the yarn strength tends to decrease during the high-temperature treatment in the subsequent process. When the total denier exceeds 4000 tex, the yarn becomes thick, so that the sheet thickness of the joint portion increases, and it is likely to be caught by a guide or the like in the subsequent process or clogging of the gap. In addition, the single fibers become rigid during the high-temperature treatment in the subsequent process, and the single fibers are cut off at the connecting portions, so that cracks are likely to occur.

  The tow strength of the connecting yarn (L) is preferably 1 kg or more. When the toe strength is less than 1 kg, the connecting portion is easily cut. There is no particular problem with the high tow strength of the tether (L), but usually a tether having a tow strength of 4 kg or less is used.

  The elongation of the connecting yarn (L) is preferably 0.3 to 30%. When the elongation exceeds 30%, the connecting yarn is easily stretched by tension, so that the connecting portion is not sufficiently fixed, and the connecting portion is likely to be deformed (wrinkled, swelled).

  The specific gravity of the connecting yarn (L) can be selected from, for example, 1.6 to 2.2, which is the specific gravity of a carbon fiber pitch system available as a commercial product.

  On the other hand, according to the embodiment of the carbon fiber sheet shown in FIGS. 1 and 2, the two corners in at least one of the terminal portion of the carbon fiber sheet precursor (A) and the starting end portion of the carbon fiber sheet precursor (B) are Cut off. Since the warp of the side end portion of the carbon fiber sheet precursor is more likely to occur at the corner portion, the influence of the warp can be reduced by cutting off the corner portion.

  Even if the two corners at the terminal end of the carbon fiber sheet precursor (A) are cut off or the two corners at the starting end of the carbon fiber sheet precursor (B) are cut off, the influence of warpage can be reduced. it can. When two corners are cut off at the end portion of the carbon fiber sheet precursor (A) and the start end portion of the carbon fiber sheet precursor (B), the influence of warpage can be further reduced.

  The corners can be cut off with a cutter, for example. The range to be cut off can be set as appropriate so that the influence of the warp can be effectively reduced, but it may be cut off linearly at positions where the distances L8 and L9 (according to FIGS. 1 and 2) from the apex are 30 to 90 mm, respectively. preferable.

  The step of joining the carbon fiber sheet precursor (A) and the carbon fiber sheet precursor (B), the terminal portion of the carbon fiber sheet precursor (A), and the starting end portion of the carbon fiber sheet precursor (B). The order of the step of cutting off the two corners in at least one of them does not matter.

  In addition, as an example of a method for joining the end portion of the carbon fiber sheet precursor (A) and the start end portion of the carbon fiber sheet precursor (B), according to the embodiment of the carbon fiber sheet shown in FIG. The carbon fiber sheet precursor (A) and the plurality of through-holes (X) are bound to the plurality of through-holes (X) through the connecting threads (M). A method of joining (B) is mentioned. The connecting yarn (M) may be one or two or more.

  Non-woven fabric and paper-like carbon fiber sheet precursors are more fragile than woven fabrics, and when stitched with a needle, there is a high possibility that the needle will puncture, and the crack will progress. As a result, there is a possibility that the joining portion will be divided. However, according to the embodiment of the carbon fiber sheet shown in FIG. 3, by binding between the plurality of through-holes (X) with the connecting yarn (M), a long and high quality even in a non-woven or paper shape It becomes a carbon fiber sheet precursor for obtaining a carbon fiber sheet.

  The connecting yarn (M) can be appropriately selected in consideration of subsequent steps, and the same as the connecting yarn (L) can be used.

  The size of the through hole (X) can be appropriately set in consideration of the strength of the carbon fiber sheet precursors (A) and (B), the number and thickness of the connecting yarns (M), etc. 10 mm is preferable and 4-7 mm is more preferable.

  The through hole (X) can be formed using a drill or the like. However, cracks may occur in the carbon fiber sheet precursor when using a type of drill that pushes in to make a hole, especially in the case of a nonwoven or paper-like carbon fiber sheet precursor. There is a high possibility of cracking. Therefore, it is preferable to use a so-called corrugated drill, which is a drill of a type that opens a hole from the center to the outer peripheral side. By using the corrugated sheet, even if it is a non-woven fabric or paper-like carbon fiber sheet precursor, cracks are difficult to enter.

  When the through hole (X) is formed, the carbon fiber sheet precursors (A) and (B) can be prevented from shifting by temporarily fixing both side ends of the overlapping portion with a clip or the like.

  The position where the through hole (X) is formed can be appropriately set in consideration of binding between the plurality of through holes (X) by the connecting thread (M).

  The number of through holes (X) may be plural, and may be two, for example, or four. It is preferable that the number of the through holes (X) is an even number because the connecting thread (M) is bound through the through holes (X). The method for threading the connecting thread (M) into the plurality of through holes (X) may be any method that binds between the plurality of through holes (X). For example, a method of passing the connecting thread (M) so as to reciprocate between the two through holes (X) can be mentioned.

  When four through-holes (X) are formed, according to the embodiment of the carbon fiber sheet shown in FIG. 3, the connecting thread (M) can be passed through the four through-holes (X) in the form of tearing. preferable. Although it is possible to pass the connecting thread (M) so as to reciprocate between each of the two through holes (X), it is possible to bind a wide area by passing the connecting thread (M) in the form of a brush, Cracks and the like are less likely to occur in the carbon fiber sheet precursor, and further, wrinkles and twists are less likely to occur in the overlapping portion.

  As the four through holes (X), it is preferable to form two sets of two through holes (X) arranged in parallel in the width direction in accordance with the embodiment of the carbon fiber sheet shown in FIG. And it is preferable to pass the connecting thread (M) parallel to the width direction in each of the two through holes (X) arranged in parallel to the width direction. Further, the connecting yarns (M) passed between any two of the four through holes (X) are connected to the four through holes (X) so that none of them is parallel to the length direction ( M) is preferred. In general, the carbon fiber sheet precursor is easily cracked in the length direction, but is not easily cracked in the width direction or the oblique direction. Also, the progress of cracks is easy to proceed in the length direction, and difficult to proceed in the width direction and the oblique direction. Therefore, by causing the connecting yarn (M) to pass through as described above, the occurrence and progress of cracks can be suppressed. Furthermore, in this case, from the viewpoint of preventing the catching in the heat treatment furnace, it is preferable that the portion parallel to the width direction is passed upward.

  The distances L1 and L2 (similar to FIG. 3) between two through-holes (X) arranged in parallel in the width direction are considered to be bound between the four through-holes (X) by the connecting thread (M). However, 17 to 84% of the width of the carbon fiber sheet precursors (A) and (B) is preferable, and 30 to 70% is more preferable. In addition, as described above, since it is preferable that the tethers (M) passed between any two of the four through holes (X) are not parallel to the length direction, L1 and L2 are Preferably they are different.

  The distance L3 (similar to FIG. 3) between two sets of two through-holes (X) arranged in parallel in the width direction means that the four through-holes (X) are bound by the connecting thread (M). Although it can set suitably in consideration, 20 to 150% of the shorter one of L1 and L2 is preferable, and 33 to 67% is more preferable.

  The distance L4 (according to FIG. 3) between the two ends of the two through holes (X) arranged in parallel in the width direction and closer to the start or end and the start or end does not catch the start or end. However, 10 to 60 mm is preferable and 25 to 40 mm is more preferable.

  Two or more sets of through-holes (X) may be formed, and each set may be bound by a connecting thread (M). What is necessary is just to arrange | position each set so that carbon fiber sheet precursor (A) and (B) can fully be bound. For example, the carbon fiber sheet precursors (A) and (B) can be bound according to the embodiment of the carbon fiber sheet shown in FIG. What is necessary is just to arrange | position each set so that carbon fiber sheet precursor (A) and (B) can fully be bound. When two or more sets of four through holes (X) are formed, the total of L1 and L2 preferably satisfies the above condition, and the shortest distance among L4 preferably satisfies the above condition.

  The connecting thread (M) may be tied as long as it is not detached from the through hole (X), but it is preferable that the ends of the joining thread (M) are tied together. However, from the viewpoint of preventing catching in the heat treatment furnace, it is preferable to tie the knot at a position on the upper side.

  In addition, an embodiment in which two corners in at least one of the terminal end of the carbon fiber sheet precursor (A) and the start end of the carbon fiber sheet precursor (B) are cut off, and the through hole (Y) by the connecting yarn (N) And the embodiment of binding between the side edges of the overlapping portion can be combined independently.

  In addition, as an example of a method for joining the end portion of the carbon fiber sheet precursor (A) and the start end portion of the carbon fiber sheet precursor (B), according to the embodiment of the carbon fiber sheet shown in FIG. There is a method in which a through hole (Y) is formed in a side end portion of the portion, and a space between the through hole (Y) and a side end of the overlapping portion is bound to the through hole (Y) through a connecting thread (N). The connecting yarn (N) may be one or two or more.

  Until now, when the carbon fiber sheet precursor is heat treated again, the side end of the carbon fiber sheet precursor is warped, the carbon fiber sheet precursor is cracked or bent and caught in the heat treatment furnace. was there. However, according to the embodiment of the carbon fiber sheet shown in FIG. 5, the effect of warpage can be reduced by binding between the through hole (Y) and the side end of the overlapping portion with the connecting yarn (N). .

  The connecting yarn (N) can be appropriately selected in consideration of subsequent steps, and the same as the connecting yarn (L) can be used.

  The size of the through hole (Y) can be appropriately set in consideration of the strength of the carbon fiber sheet precursors (A) and (B), the number and thickness of the connecting yarns (N), etc. 10 mm is preferable and 4-7 mm is more preferable.

  The through hole (Y) can be formed using a drill or the like. For the same reason as described above, it is preferable to use a corrugated sheet.

  When the through hole (Y) is formed, the carbon fiber sheet precursors (A) and (B) are temporarily fixed with clips or the like at positions where the through hole (Y) is not formed at both end portions of the overlapping portion. Can be prevented.

  The position where the through hole (Y) is formed can be appropriately set in consideration of binding between the side edges of the overlapping portion. Since the influence by the warp can be effectively reduced, the distance L5 (similar to FIG. 5) between the through hole (Y) and the side edge of the overlapping portion is preferably 20 to 30 mm.

  The number of through-holes (Y) can be 1-10, for example. In addition, since the phenomenon that the side edges of the carbon fiber sheet precursor warp is likely to occur at both ends, it is possible to form the same number of through holes (Y) at both ends of the overlapping portion. preferable. Therefore, the total number of through holes (Y) to be formed is preferably an even number. For example, according to the embodiment of the carbon fiber sheet shown in FIG. 5, three through holes (Y) can be formed at both end portions of the overlapping portion.

  When a plurality of through-holes (Y) are formed at one side end, the distance L6 (similar to FIG. 5) between the plurality of through-holes (Y) should be prevented from warping therebetween. However, it is preferably 50 to 450 mm, more preferably 100 to 300 mm. The distance L7 (similar to FIG. 5) between the through hole (Y) closest to the start end or the end of the plurality of through holes (Y) formed at the one side end and the start end or the end is determined by the start or end being pulled. Although it can set suitably so that it may not exist, 10-90 mm is preferable and 20-70 mm is more preferable.

  The method of reciprocating between the through hole (Y) and the side edge of the overlapping portion is performed in accordance with the embodiment of the carbon fiber sheet shown in FIG. 5 in order to pass the connecting thread (N) to the through hole (Y). Is preferred. By doing so, it is possible to bind between the through hole (Y) and the side edge of the overlapping portion by the connecting thread (N). It is preferable to pass the connecting thread (N) between the through hole (Y) and the side end of the overlapping portion in parallel to the width direction.

  The connecting yarn (N) may not be tied unless it is removed from the through hole (Y), but it is preferable that the ends of the joining yarn (N) are tied together. However, from the viewpoint of preventing catching in the heat treatment furnace, it is preferable to tie at a position where the knot is at the side end or the upper side.

  In addition, an embodiment in which two corners in at least one of the terminal end of the carbon fiber sheet precursor (A) and the start end of the carbon fiber sheet precursor (B) are cut off, and the through hole (Y) by the connecting yarn (N) And the embodiment of binding between the side edges of the overlapping portion can be combined independently.

  Moreover, as an example of a method for joining the terminal portion of the carbon fiber sheet precursor (A) and the starting end portion of the carbon fiber sheet precursor (B), the methods of FIGS. 3 and 5 were combined as shown in FIG. A method is mentioned. In this case, an embodiment in which at least one of the end portion of the carbon fiber sheet precursor (A) and the start end portion of the carbon fiber sheet precursor (B) is cut off, and through the connecting yarn (M). The embodiment in which the gap between the hole (X) and the side edge of the overlapping portion is bound and the embodiment in which the gap between the through hole (Y) and the side edge of the overlapping portion is bound by the connecting thread (N) are combined independently. be able to.

  After joining the carbon fiber sheet precursors (A) and (B) as described above, the joined carbon fiber sheet precursor is carbonized. Carbonization can be performed by running the joined carbon fiber sheet precursor in a heat treatment furnace.

  Carbonization of the joined carbon fiber sheet precursor is preferably performed by heat treatment at a plurality of temperatures. Carbonization of the carbon fiber sheet precursor obtained by joining the carbon fiber sheet precursors (A) and (B) that have been heat-treated to an intermediate stage may be performed by subsequent heat treatment.

  As the first heat treatment, the carbon fiber sheet precursor is preferably oxidized at a temperature of 200 ° C. or higher and lower than 300 ° C. By this oxidation treatment, the carbon fibers can be further fused with the carbon precursor resin, and the carbonization rate of the carbon precursor resin can be improved. The temperature of the oxidation treatment is more preferably 240 to 270 ° C. The oxidation treatment is preferably performed in an air atmosphere. The time for the oxidation treatment is preferably 10 minutes to 2 hours, more preferably 10 minutes to 90 minutes.

  As a second heat treatment, the carbon fiber sheet precursor is carbonized at a temperature of 1000 ° C. or higher. By this carbonization treatment, the carbon precursor resin is carbonized, and a carbon fiber sheet can be obtained. The carbonization treatment temperature is preferably 1000 to 3000 ° C, and more preferably 1000 to 2200 ° C. The carbonization treatment is preferably performed in an inert atmosphere. The carbonization treatment time is preferably 10 minutes to 1 hour.

  Prior to the second heat treatment (carbonization treatment), the carbon fiber sheet precursor may be pre-carbonized at a temperature of 300 to 800 ° C. The precarbonization treatment is preferably performed in an inert atmosphere.

  Since heat treatment is preferably performed at a plurality of temperatures as described above, the heat treatment furnace for performing carbonization preferably has a plurality of regions that can be set to different temperatures. The plurality of regions may be installed in one heat treatment furnace, or a plurality of heat treatment furnaces may be combined.

  It is preferable that a bending member is provided in the heat treatment furnace. And it is preferable to drive the inside of a heat treatment furnace, making a carbon fiber sheet precursor contact a bending member. By doing so, wrinkles and irregularities are less likely to occur in the obtained carbon fiber sheet.

  The bending member can be provided, for example, in the hearth in the heat treatment furnace, the hearth ceiling, or between the hearth and the hearth ceiling. In order to bring the full width of the carbon fiber sheet precursor and the bending member into contact with each other, it is preferable to provide the carbon fiber sheet precursor in a direction crossing the traveling direction of the carbon fiber sheet precursor. From this point of view, a rod-like bending member is preferable, but a plate-like bending member may be used. In addition, suppose that the ratio of the major axis and minor axis of a cross section is less than 4 times with rod shape. By setting it as a rod shape, the height of the bending member can be lowered, the contact length with the carbon fiber sheet precursor can be shortened, and wear of the carbon fiber sheet precursor can be prevented. As a material for the bending member, it is preferable to use a material made of carbon that is inexpensive and chemically stable in an inert atmosphere.

  Moreover, it is preferable to heat-press mold the carbon fiber sheet precursor at a temperature of less than 200 ° C. before the first heat treatment (oxidation treatment). By carrying out like this, carbon fiber can be fuse | fused with carbon precursor resin, and the thickness nonuniformity of the carbon fiber sheet obtained can be reduced. The heat press molding may be any technique that can uniformly heat press mold the carbon fiber sheet precursor. For example, it may be a method of hot pressing with smooth rigid plates from both upper and lower surfaces, using a continuous belt press device. The method of performing may be used.

  When the joined carbon fiber sheet precursors are heated and pressed, a method using a continuous belt press apparatus is preferable. As a pressing method in the continuous belt apparatus, a method of applying pressure to the belt by a roll press or a press by a surface pressure by a hydraulic head press may be used, but the latter can obtain a smoother carbon fiber sheet. This is preferable.

  In order to effectively smooth the surface, the heating temperature is preferably less than 200 ° C, more preferably 120 to 190 ° C. Regarding the molding pressure, when the ratio of the carbon precursor resin is large, it is easy to smooth the surface of the carbon fiber sheet precursor even if the molding pressure is low. If the press pressure is increased more than necessary at this time, problems such as destruction of the carbon fibers at the time of molding and excessively dense structure of the obtained carbon fiber sheet may occur. Therefore, it is preferable to pressurize at a pressure of 20 kPa to 10 MPa. The heating and pressing time is preferably 30 seconds to 10 minutes.

  When the carbon fiber sheet precursor is heat-pressed with a continuous belt device sandwiched between rigid plates, either apply a release agent in advance so that the carbon precursor resin does not adhere to the rigid plate or belt, It is preferable that the release paper is sandwiched between the carbon fiber sheet precursor and the rigid plate or belt.

It is a top view which shows one Embodiment of the carbon fiber sheet of this invention. It is a top view which shows one Embodiment of the carbon fiber sheet of this invention. It is a top view which shows one Embodiment of the carbon fiber sheet of this invention. It is a top view which shows embodiment of the carbon fiber sheet in which two or more places were bound by the connecting thread (m). It is a top view which shows one Embodiment of the carbon fiber sheet of this invention. It is a top view which shows one Embodiment of the carbon fiber sheet of this invention.

Explanation of symbols

10 Carbon fiber sheets 11 joined together Carbon fiber sheet (a)
12 Carbon fiber sheet (b)
20 Overlapping part 21 Through hole (x)
22 Tether (m)
26 Through hole (y)
27 Tether (n)
30 Tying thread (l)

Claims (8)

The carbon fiber sheet (a) and the carbon fiber sheet (b) have a carbon fiber sheet in which one end or two or more ends of the carbon fiber sheet (b) are stitched together by a connecting thread (l) .
The total denier of the tether (l) is 400 to 4000 tex,
A carbon fiber sheet in which two corners in at least one of a terminal portion of the carbon fiber sheet (a) and a starting end portion of the carbon fiber sheet (b) are cut off.   The carbon fiber sheet according to claim 1, wherein a terminal portion of the carbon fiber sheet (a) and a start portion of the carbon fiber sheet (b) are overlapped.   The carbon fiber sheet according to claim 1 or 2, wherein both of the carbon fiber sheets (a) and (b) are carbon fibers bound by carbon. A step of joining the terminal portion of the carbon fiber sheet precursor (A) and the starting end portion of the carbon fiber sheet precursor (B) by one or two or more stitches with a connecting thread (L) ;
Cutting off two corners of at least one of a terminal portion of the carbon fiber sheet precursor (A) and a starting end portion of the carbon fiber sheet precursor (B); and carbonizing the joined carbon fiber sheet precursor. the step of possess a total denier process for producing a carbon fiber sheet is 400~4000tex of the connecting thread (L). The method for producing a carbon fiber sheet according to claim 4 , further comprising a step of overlapping a terminal portion of the carbon fiber sheet precursor (A) and a starting end portion of the carbon fiber sheet precursor (B).   A bending member is provided in a heat treatment furnace for carbonizing the joined carbon fiber sheet precursor, and the inside of the heat treatment furnace is caused to travel while the joined carbon fiber sheet precursor is in contact with the bent member. The manufacturing method of the carbon fiber sheet of description.   The carbon fiber sheet precursors (A) and (B) both comprise carbon fibers and a carbon precursor resin, and the method for producing a carbon fiber sheet according to any one of claims 4 to 6.   The carbon fiber sheet obtained by the manufacturing method of the carbon fiber sheet in any one of Claims 4-7.

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