Yarn twisting device and yarn twisting method

Abstract

To provide a novel yarn twisting machine and a yarn twisting method, capable of more stabilizing the shape of a carbon fiber bundle.SOLUTION: A yarn twisting machine comprises a yarn twisting part for twisting long carbon fibers in the yarn twisting direction, with an axial direction being the feed-out direction of a plurality of the carbon fibers, a solvent application part for applying a specified solvent to the twisted carbon fiber bundle, a formation part for forming a viscous fluid on the carbon fiber bundle after application of the solvent, and a drying part for drying the viscous fluid formed on the carbon fiber bundle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present specification discloses a yarn twisting device and a yarn twisting method. [Background technology]

[0002] Conventionally, a twisting device has been proposed that includes, for example, an applicator that feeds out a plurality of carbon fibers in a feed direction and rotates in a twisting direction with the feed direction as the axial direction to form a viscous fluid on the twisted carbon fiber bundle, and a dryer that dries the viscous fluid applied to the carbon fiber bundle (see, for example, Patent Document 1). This twisting device can twist the carbon fibers together to control their diameter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-63319 Summary of the Invention [Problem to be solved by the invention]

[0004] In the twisting device disclosed in Patent Document 1, the carbon fibers are twisted by rotating them in the twisting direction, and then a binder as a viscous fluid is formed on the surface of the fibers, which is then dried to fix the carbon fiber bundle. The long carbon fiber bundle is then wound around a bobbin while controlling the diameter. In this case, for example, when the carbon fibers to be fed are flat, the flat fiber bundle can be twisted as is and fixed with a binder to approximate a circular bundle in appearance. However, when twisting flat carbon fiber bundles, the fibers at the ends of the length and those near the center move more significantly during twisting, which can result in shape variations and lead to fraying and breakage of individual fibers. Thus, there has been a demand for improved shape stability of carbon fiber bundles.

[0005] The present disclosure has been made in consideration of such problems, and a main object of the present disclosure is to provide a novel twisting device and twisting method that can make the shape of carbon fiber bundles more stable. [Means for solving the problem]

[0006] As a result of intensive research to achieve the above-mentioned object, the present inventors have found that applying a solvent to the carbon fiber bundles after twisting allows the carbon fibers to move more smoothly among themselves, and makes it possible to make the shape of the carbon fiber bundles more stable, and have thus completed the invention disclosed in this specification.

[0007] That is, the yarn twisting device disclosed in this specification is a twisting unit that twists the carbon fibers in a twisting direction whose axial direction is the feed direction of the plurality of carbon fibers as the long object; a solvent application unit that applies a predetermined solvent to the twisted carbon fiber bundle; a forming unit that forms a viscous fluid on the carbon fiber bundle after the solvent is applied; a drying section that dries the viscous fluid formed on the carbon fiber bundle; It is equipped with the following.

[0008] The twisting method disclosed in this specification comprises: a twisting step of twisting the carbon fibers in a twisting direction whose axial direction is the feed direction of the plurality of carbon fibers as a long object; a solvent application step of applying a predetermined solvent to the twisted carbon fiber bundle; a forming step of forming a viscous fluid on the carbon fiber bundle after the solvent is applied; a drying step of drying the viscous fluid formed on the carbon fiber bundle; It includes: [Effects of the Invention]

[0009] The present disclosure can provide a novel twisting device and twisting method that can make the shape of carbon fiber bundles more stable. The reason for this effect is presumed to be as follows: For example, if carbon fibers to be twisted are supplied in a flattened state, the fibers at the ends of the length are more likely to move during twisting than the fibers near the center, which can easily cause shape variations and result in a deformed carbon fiber bundle. In this case, if a solvent is applied to the fiber bundles while twisting, the fiber bundles will loosen, and the individual fibers will attract each other due to surface tension, allowing the deformed and solidified state to be transformed into a fiber bundle that is close to circular. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing an example of a yarn twisting device 10. [Figure 2] 1A and 1B are side and front views of a yarn twisting device 10. [Figure 3] FIG. 2 is an explanatory diagram showing an example of a secondary battery structure 14. [Figure 4] FIG. 2 is an explanatory diagram showing an example of a supply unit 20 and a yarn twisting unit 30. [Figure 5] FIG. 3 is an explanatory diagram showing an example of a solvent application unit 50. [Figure 6] FIG. 3 is an explanatory diagram showing an example of a forming section 60. [Figure 7] FIG. 2 is an explanatory diagram showing an example of a drying section 70. [Figure 8] FIG. 4 is an explanatory diagram showing an example of a winding section 80. [Figure 9] FIG. 1 is an explanatory diagram of a test to confirm the circularization effect when flat carbon fiber bundles are twisted. [Figure 10] The results of an investigation into the relationship between the presence or absence of solvent application and the diameter of the carbon fiber bundle. [Figure 11] FIG. 1 is an explanatory diagram of a test in which flat carbon fiber bundles are twisted and then fixed with a binder. [Figure 12] The results of an investigation into the relationship between the presence or absence of solvent application and the diameter of the immobilized carbon fiber bundle. DETAILED DESCRIPTION OF THE INVENTION

[0011] This embodiment will be described below with reference to the drawings. FIG. 1 is a perspective view showing an example of a yarn twisting device 10. FIG. 2 is a side view (FIG. 2A) and a front view (FIG. 2B) of the yarn twisting device 10. FIG. 3 is an explanatory diagram showing an example of a secondary battery structure 14. FIG. 4 is an explanatory diagram showing an example of a supply unit 20 and a yarn twisting unit 30, where FIG. 4A is a front view, FIG. 4B is a perspective view of the yarn twisting unit 30, and FIG. 4C is an explanatory diagram of a first support roller 31. FIG. 5 is an explanatory diagram showing an example of a solvent application unit 50. FIG. 6 is an explanatory diagram showing an example of a forming unit 60. FIG. 7 is an explanatory diagram showing an example of a drying unit 70. FIG. 8 is an explanatory diagram showing an example of a winding unit 80, where FIG. 8A is a perspective view of the winding unit 80, FIG. 8B is a perspective view of the winding roller 81 and wheel 87, FIG. 8C is an explanatory diagram of the winding unit 80, FIG. 8D is an explanatory diagram of a pivot support fixing unit 83, and FIG. 8E is an explanatory diagram of removing the wheel 87.

[0012] As shown in FIGS. 1 and 2 , the twisting device 10 is an apparatus for pulling out a long material L, which has been arranged flat and wound into a sheet, in a feed direction A and twisting it in a twisting direction R to produce a long material L with a circular cross section. The twisting device 10 includes a control unit 19, a supply unit 20, a twisting unit 30, a support / feed unit 40, a solvent application unit 50, a forming unit 60, a drying unit 70, and a winding unit 80. The long material L may be, for example, carbon fiber that can be used as a negative electrode active material in secondary batteries, as shown in FIG. 3 . Here, the up-down, left-right, and front-to-back directions of the twisting device 10 are shown in FIGS. 1 and 2 as examples, and the feed direction A is described as a downward direction, and the twisting direction R is described as a rotational direction around the up-down direction. The twisting direction R may be either counterclockwise or clockwise.

[0013] Here, a product using the long material L produced by the twisting device 10 will be described. As shown in FIG. 3, the long material L produced by the twisting device 10 is a carbon fiber bundle and is used as the negative electrode 16 of a secondary battery 15. The secondary battery 15 has a structure in which an insulating and ion-conductive separator 17 is formed on the surface of a cylindrical negative electrode 16, and a positive electrode 18 is further formed on the surface of the separator 17. The secondary battery structure 14 has a structure in which multiple secondary batteries 15 are bundled together. Furthermore, the long material L may be twisted and fixed with a binder. In this secondary battery structure 14, since the cylindrical long material L is used as the negative electrode 16, ions can be absorbed and released from the outer periphery. This allows for superior response speed and energy density compared to flat laminated electrodes, resulting in improved output characteristics. The carbon fiber may have any length, and its diameter d may be, for example, in the range of 5 μm to 100 μm. When the diameter d of the carbon fiber is 5 μm or more, higher strength can be ensured, and when it is 100 μm or less, flexibility can be ensured. The diameter d of the carbon fiber is more preferably in the range of 20 μm or less. The carbon fiber bundle as the long material L may have a diameter D (μm) in the range of 30 μm or more and 1000 μm or less. When the diameter D is 30 μm or more, the amount of active material can be ensured, and when it is 1000 μm or less, an increase in ion diffusion resistance in the electrode can be further suppressed, which is preferable. The diameter D is preferably 50 μm or more, more preferably 100 μm or more. Furthermore, the diameter D is preferably 600 μm or less, more preferably 500 μm or less. The diameters d and D may be empirically selected appropriately depending on the characteristics required of the secondary battery 15.

[0014] The separation membrane 17 has, for example, ion conductivity of the carrier (e.g., lithium ions) and may be a solid electrolyte or a gel electrolyte. The separation membrane 17 is preferably made of a polymer having ion conductivity and insulating properties, such as polyvinylidene fluoride (PVdF), a copolymer of PVdF and hexafluoropropylene (HFP), polymethyl methacrylate (PMMA), and a copolymer of PMMA and an acrylic polymer. Examples of binders that fix the elongated material L include the above-mentioned PVdF, PVdF-HFP copolymer, PMMA, and PMMA-acrylic polymer copolymer, as well as fluorine-containing resins such as polytetrafluoroethylene (PTFE) and fluororubber, thermoplastic resins such as polypropylene and polyethylene, ethylene-propylene-diene mer (EPDM), sulfonated EPDM, and natural butyl rubber (NBR), either alone or in a mixture of two or more thereof. The positive electrode 18 may be made of, for example, a material used in a general secondary battery (e.g., a lithium-ion secondary battery), or may be a positive electrode composite containing a positive electrode active material, a conductive material, and a binder. The conductive material may be, for example, a carbonaceous material such as acetylene black, carbon black, or ketjen black, or a mixture of one or more metals (e.g., copper, nickel, aluminum, silver, or gold). The binder serves to bind the active material particles and the conductive material particles together to maintain a predetermined shape, and may be, for example, polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVdF). Examples of the positive electrode active material include compounds containing alkali metals and transition metals, such as oxides containing alkali metals and transition metal elements, and phosphate compounds containing alkali metals and transition metal elements. The secondary battery 15 may have a diameter of, for example, 0.2 mm or more and 0.5 mm or less. The cross-sectional shape of the secondary battery 15 may be polygonal, circular, or elliptical. Examples of polygonal shapes include triangles, squares, pentagons, hexagons, and octagons, with hexagons being preferred.

[0015] The control unit 19 (see FIG. 1) is configured as a controller centered around a CPU (not shown) and controls the entire device. This control unit 19 is electrically connected to the supply unit 20, forming unit 60, drying unit 70, winding unit 80, etc., and receives signals from these units and outputs control signals to these units. This control unit 19 is equipped with a flash memory that stores various processing programs and setting values ​​for each unit, and a RAM that temporarily stores data.

[0016] The supply unit 20 is configured to feed the long material L in a feed direction A and to rotate in a twisting direction R with the feed direction A as its axial direction. As shown in FIG. 4, the supply unit 20 is disposed on top of a first housing 11, which has a rectangular parallelepiped frame with a space in the central region. The supply unit 20 includes a supply roller 21, a roller support unit 22, a rotation drive unit 23, and a support member 24. The long material L is arranged in a sheet-like manner and wound around the supply roller 21. A predetermined rotation brake is applied to the supply roller 21 so that the supply roller 21 rotates in accordance with the winding of the long material L by the winding unit 80. The roller support unit 22 rotatably supports the supply roller 21 around a horizontal axis of rotation and is rotatably supported on the top plate 13 of the first housing 11 around a vertical axis of rotation. The roller support unit 22 is rotatably suspended from the center of the top plate 13. The roller support 22 removably supports the supply roller 21, and when the long material L is consumed, the used supply roller 21 is removed and a new supply roller 21 is installed. The rotation drive 23 is a motor connected to the roller support 22 and drives the roller support 22 to rotate. The rotation drive 23 is supplied with power from the control unit 19 according to the twist degree of the long material L, and is driven to rotate. The driving force of the rotation drive 23 causes the supply roller 21, roller support 22, support member 24, and twisting unit 30 to rotate together in the twisting direction R. The rotation speed in the twisting direction R can be set, for example, in a range of 0 rpm to 300 rpm. Furthermore, if the twist degree is defined as the number of turns per unit length when the unit length of the long material L is 10 cm, the twist degree is preferably set in a range of 10 turns / 10 cm to 20 turns / 10 cm. Since the degree of twisting can be adjusted by the relationship between the delivery speed and the winding speed, it is sufficient to set the optimum rotation speed, delivery speed, and winding speed depending on the characteristics of the long material L being used. The support member 24 is a U-shaped member fixed to a stay disposed on the side of the roller support part 22, and the twisting part 30 is disposed at the center of its lower end. The support member 24 is disposed on the stay so that the distance between the supply roller 21 and the twisting part 30 can be changed according to the width of the supply roller 21, the flexibility of the long material L, etc.

[0017] The twisting unit 30 supports the long material L so that it rotates in the twisting direction R and continuously delivers the long material L in the delivery direction A. The twisting unit 30 is fixed to a support member 24 disposed in the supply unit 20 and rotates integrally with the supply unit 20 in the twisting direction R. The twisting unit 30 includes a support roller 31 and slide units 36 and 37. The support roller 31 rotates in the delivery direction A and clamps the long material L to prevent it from rotating in the twisting direction R. The support roller 31 consists of a pair of rollers: a convex roller 32 and a concave roller 33. As shown in FIG. 4B , the convex roller 32 is fixed to the center of a rotating shaft 34, which is rotatably supported at the tip of the slide unit 36. The concave roller 33 is fixed to the center of a rotating shaft 35, which is rotatably supported at the tip of the slide unit 37. The convex roller 32 is a roller whose outer circumferential surface is formed in a convex shape at the center, and the concave roller 33 is a roller whose outer circumferential surface is formed in a concave shape at the center. One rubber ring is fitted into the convex portion of the convex roller 32, and two rubber rings are fitted into the concave portion of the concave roller 33, with the long material L passing continuously between these rubber rings. The slide sections 36, 37 rotatably support the convex roller 32 and the concave roller 33 of the support roller 31 and move them between a clamping position where the long material L is clamped and a release position where the clamping of the long material L is released. The slide sections 36, 37 are fixed to the support member 24 by fixtures (not shown), and the gripping force of the long material L can be adjusted by adjusting the center distance between the convex roller 32 and the concave roller 33. The slide portions 36, 37 may be configured so that an elastic body such as a spring (not shown) biases the convex roller 32 and the concave roller 33 in the direction of approaching each other, and when the fixing device is released, the convex roller 32 and the concave roller 33 can be separated. Alternatively, the slide portions 36, 37 may move the convex roller 32 and the concave roller 33 toward and away from each other by the driving force of a motor or the like.

[0018] As shown in FIGS. 1 and 2 , the support and feed unit 40 is disposed downstream of the twisting unit 30, between the drying unit 70 and the winding unit 80, and supports the long material L so that the long material L is continuously fed in the feed direction A without rotating in the twisting direction R. The support and feed unit 40 is fixed to a second housing 12 that is separate from the first housing 11. As shown in FIG. 2B , the support and feed unit 40 has a support roller 41 that rotates in the feed direction A and clamps the long material L, and a slide unit 42 that rotatably supports the support roller 41 and moves it between a clamping position and an open position. Note that the support roller 41 and the slide unit 42 have the same configuration as the support roller 31 and the slide units 36 and 37, except that they are fixed to the stationary second housing 12, and a detailed description thereof will be omitted.

[0019] The solvent application section 50 is a unit that applies a predetermined solvent to the carbon fiber bundles twisted in the twisting section 30. This solvent application section 50 is provided with a removal section 55 that removes the applied solvent. As shown in FIG. 5 , the solvent application section 50 is provided between the twisting section 30 and the support and feeding section 40, particularly between the twisting section 30 and the forming section 60. The solvent application section 50 is provided at a position a predetermined solvent removal distance X away from the forming section 60. Note that the solvent removal distance X may be empirically determined, for example, so that it is a distance that allows the applied solvent to be sufficiently removed from the long material L.

[0020] In the solvent application section 50, the supply rate of the solvent may be appropriately determined according to the supply rate of the long material L. The supply rate of the solvent may be, for example, in the range of 0.020 mL / m or more and 0.1 mL / m or less per unit length of the long material L, or may be 0.025 mL / m or more, 0.03 mL / m or more, or 0.04 mL / m or more. It may also be 0.05 mL / m or less. If the application amount is small, the effect of improving the shape stability of the carbon fiber bundle is small, and if the application amount is large, the solvent is not sufficiently removed. Therefore, the supply rate of the solvent may be determined taking into consideration the effect and removability.

[0021] Furthermore, the solvent application unit 50 preferably uses a solvent such as water that is not harmful to the product of the long material L, and can be appropriately selected depending on properties such as wettability and surface tension. The solvent application unit 50 preferably uses a highly volatile solvent. This is because it is preferable to minimize the presence of solvent when forming a viscous fluid on the surface of the carbon fiber bundle in the next process. For example, the boiling point of this solvent is preferably higher than room temperature but lower, preferably 90°C or lower, and may be 80°C or lower. Higher volatility of the solvent facilitates removal, making it preferable. For example, the solvent preferably has a high affinity with the carbon fiber bundle. For example, either water or an organic solvent may be used, with organic solvents being preferred. Using an aqueous solvent requires high removal energy but simplifies post-processing. On the other hand, using an organic solvent may require recovery or other processing after removal, but reduces removal energy and shortens removal time. The solvent may be a polar or nonpolar solvent. Furthermore, the solvent may be a protic or aprotic solvent. Nonpolar solvents include hydrocarbon solvents such as hexane, benzene, toluene, and cyclohexane, halogenated solvents such as chloroform, and ether solvents such as diethyl ether. Aprotic polar solvents include ketone solvents including acetone, as well as dichloromethane, tetrahydrofuran, ethyl acetate, and acetonitrile. Protic polar solvents include alcohol solvents including ethanol, carboxylic acid solvents including formic acid and acetic acid, and nitromethane. Among these, the solvent is preferably at least one of an alcohol solvent and a ketone solvent. Examples of alcohol solvents include methanol, ethanol, propanol, and butanol, among which ethanol is preferred due to its ease of handling. Examples of ketone solvents include acetone and diethyl ketone, among which acetone is preferred.

[0022] The solvent application unit 50 includes an application unit 51 and a removal unit 55. The application unit 51 includes a main body 52 having a passage 52a through which carbon fiber bundles serving as the long material L pass, and a discharge unit 53 that supplies solvent to the carbon fiber bundles passing through the passage 52a. The main body 52 is a block body that fixes the discharge unit 53 and allows the long material L to pass through. The passage 52a is a hole through which the long material L passes, and is formed on the underside of the center of the main body 52. ​​The discharge unit 53 applies the solvent supplied from outside to the long material L. The discharge unit 53 may include, for example, a syringe that temporarily stores the solvent and a needle-shaped discharge tube that is connected to the tip of the syringe, has an outer diameter smaller than the syringe, and has a discharge port 54 at its tip. The discharge unit 53 may also include a piston that presses against the syringe to forcibly discharge the solvent. A tube (not shown) is connected to this discharge part 53, and the solvent supplied via the tube is supplied from the discharge port 54 to the outer circumferential surface of the carbon fiber bundle. The discharge parts 53 are arranged at four locations on the outer periphery of the main body part 52, and supply the solvent to the carbon fiber bundle from four directions. Note that, as long as the solvent can be supplied sufficiently to the long material L, the number of discharge parts 53 may be four or less, or may be any of three to one.

[0023] The removal section 55 removes the solvent from the carbon fiber bundle to which the solvent has been applied. The removal section 55 may also remove the solvent from the long material L by circulating heated gas. The removal section 55 includes a drying space 56, a supply pipe 57, a discharge pipe 58, and a temperature sensor 59. The removal section 55 may also be disposed at a position after the solvent has sufficiently stabilized the shape of the long material L. Here, the removal section 55 is disposed adjacent to the application section 51 and immediately downstream of the application section 51 through which the long material L moves. Examples of the heated gas include heated air. The heated gas supplied to the removal section 55 may be heated by a heater (not shown). The drying space 56 is a space for drying the long material L, disposed immediately downstream of the application section 51. A supply pipe 57 and a discharge pipe 58 are connected to the drying space 56. The supply pipe 57 is a pipe for supplying heated gas. The discharge pipe 58 is a pipe that discharges the heated gas after heating the long material L. The removal unit 55 may also be equipped with a collection unit that traps the solvent that has evaporated at the end of the discharge pipe 58. The temperature sensor 59 measures the temperature inside the drying space 56, and may be, for example, a thermocouple. The control unit 19 adjusts the temperature and supply amount of the heated gas based on the temperature measured by the temperature sensor 59.

[0024] The forming unit 60 is disposed downstream of the twisting unit 30 and forms a viscous fluid on the twisted elongated material L. Examples of the viscous fluid include a binder that binds carbon fibers and a resin that serves as a separator membrane with ionic conductivity and insulating properties for carrier ions in an electricity storage device. The binder or resin may be dissolved in, for example, an aqueous solvent or an organic solvent. Examples of organic solvents that can be used include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran. The twisting device 10 may include a plurality of forming units 60 and drying units 70 to form a plurality of types of viscous fluids on the elongated material L. For example, the first coating unit may cause a resin that will serve as a binder to penetrate into the interior of the elongated material L, and the first drying unit may dry it, the second coating unit may form a resin that will serve as a separation membrane on the outer surface of the elongated material L, and the second drying unit may then dry it, after which the third coating unit may form a viscous fluid of an electrode mixture containing an electrode active material on the surface of this separation membrane, and the third drying unit may dry it to further form an electrode mixture layer. Here, for ease of explanation, the twisting device 10 will be described as including a forming unit 60 that forms a binder and a drying unit 70.

[0025] As shown in FIG. 6 , the forming unit 60 includes an inner member 61, an outer member 65, and a supply pipe 69. The forming unit 60 applies a viscous fluid from a cavity 67 formed by the outer surface of the inner nozzle 62 and the inner surface of the outer nozzle 66 to the elongated material L passing through the central hole of the inner nozzle 62. The viscous fluid is ejected onto the elongated material L from a circumferential slit formed by the tip of the outer nozzle 66 and the tip of the inner nozzle 62. The inner member 61 has a central hole formed therein and an inner nozzle 62 protruding in the application direction. The inner member 61 has a conical inner nozzle 62 formed on the lower surface of its plate-like body. The inner nozzle 62 has a conical supply space 63 formed therein through which the elongated material L passes, and a central hole formed at its tip. The outer member 65 has an outer nozzle 66 formed therein and protruding in the application direction, concentrically accommodating the inner nozzle 62. The outer member 65 has a cylindrical body and a conical space formed therein into which the inner nozzle 62 is inserted. An outer nozzle 66 is formed on the underside of the outer member 65, protruding downward, and has a central hole formed in its center. The outer member 65 is fixed to the inner member 61 by positioning it using a positioning unit so that the central holes of the inner member 61 and the outer member 65 are concentric. The forming unit 60 can adjust the amount of viscous fluid discharged onto the elongated material L by changing the distance between the inner member 61 and the outer member 65. A supply pipe 69 communicating with the cavity 67 is connected to the side of the outer member 65. The supply pipe 69 is supplied with viscous fluid from a tank (not shown) via a pump.

[0026] The drying section 70 dries the viscous fluid formed on the long material L. As shown in FIG. 7, the drying section 70 includes air heaters 71 and 73, temperature measurement units 72 and 74, an air cooling unit 75, and a cover member 76. The drying section 70 has two combinations of air heaters and temperature measurement units. The air heater 71 is disposed at an angle toward the discharge direction A of the long material L and discharges heated air as a heating gas onto the long material L. It is preferable that the discharge direction of the heated gas from the air heaters 71 and 73 is at an acute angle rather than perpendicular to the discharge direction A. The drying section 70 includes a pair of air heaters 71 disposed in the left-right or front-back direction. Heated air is supplied from the pair of air heaters 71 to solidify the viscous fluid on the long material L or to vaporize and remove the solvent contained in the viscous fluid. The flow rate and heating temperature of the heated air depend on the type and amount of the long material L and the viscous fluid to be dried, and appropriate values ​​can be empirically set accordingly. The temperature measurement unit 72 measures the temperature of the long material L and may be, for example, a thermocouple. The temperature measurement unit 72 is located immediately downstream of the air heater 71 supplying heated air, at a position where it measures the vicinity of the long material L moving in the discharge direction A. The temperature measurement unit 72 indirectly obtains the temperature of the long material L by measuring the temperature in the vicinity of the long material L. The temperature measurement unit 72 may directly contact the long material L or may directly measure the temperature using a non-contact thermosensor. The air heater 73 has a configuration similar to that of the air heater 71 and is located downstream of the air heater 71. The air heater 73 may supply heated air to the long material L at a higher temperature than the air heater 71. This is preferable because it makes it easier to heat the long material L. The temperature measurement unit 74 has a similar configuration to the temperature measurement unit 72 and is arranged downstream of the temperature measurement unit 72. The air heater 73 and the temperature measurement unit 74 have the same configuration as the air heater 71 and the temperature measurement unit 72, so their description will be omitted. The control unit 19 acquires the measured values ​​of the temperature measurement units 72 and 74 and controls the temperature and flow rate of the heated air of the air heaters 71 and 73 so that the actual measured values ​​match the set values. The air cooling unit 75 supplies cooling air to the long material L after heating and has a cooling nozzle.The cover member 76 is a structure having a passage space through which the long material L passes. From the upstream side, an air heater 71, a temperature measurement unit 72, an air heater 73, and a temperature measurement unit 74 are fixed to the cover member 76, which supply heated air into the passage space and measure its temperature.

[0027] The winding unit 80 winds up the long material L heated and cooled in the drying unit 70. As shown in FIG. 8 , the winding unit 80 includes a winding roller 81, a axial support fixing unit 83, a support plate 84, a fixing member 85, a swinging unit 86, a wheel 87, a winding drive unit 88, and a swinging drive unit 89. The winding roller 81 is a roller that winds up the produced long material L and is configured to rotate around a winding shaft 82 as a central axis. In this winding roller 81, the winding shaft 82 is axially supported by the axial support fixing unit 83. This winding roller 81 may have a relatively large diameter to prevent defects in the long material L itself, as well as the separation membrane and electrode composite layer formed on the long material L. Note that FIGS. 1, 2, and 8 show an example of the winding roller 81 that winds up the long material L after the separation membrane and electrode composite layer have been formed. For example, if the long material L is fixed with a binder, the winding roller 81 may have a relatively small diameter, similar to the supply roller 21. The winding roller 81 is driven to rotate by a winding drive unit 88 at a rotational speed that corresponds to the time required for the entire device to process the long material L. The winding speed of the long material L may be, for example, 20 m / min or less. The axial support fixing unit 83 is a member that axially supports the winding roller 81 in a removably manner. The axial support fixing unit 83 is a member that axially supports the winding shaft 82 that protrudes from the winding roller 81, and includes a support plate 84 and a fixing member 85. The support plate 84 is a plate-shaped member disposed on both sides of the winding roller 81. The support plate 84 has a notch formed therein to accommodate the winding shaft 82. By fixing the fixing member 85, the winding shaft 82 is axially supported on the support plate 84 in a non-removable manner. An operator can remove the winding roller 81 from the winding unit 80 by removing the fixed member 85 fixed to the support plate 84 (see FIG. 8E). A plurality of rotatable roller followers are arranged on the support plate 84, and these roller followers come into contact with and support the winding shaft 82. Roller followers are also arranged on the fixed member 85. The winding drive unit 88 is a motor that drives the rotation of the winding roller 81, and is connected to the winding shaft 82 via a gear. The swinging unit 86 swings the winding roller 81 in a direction along the rotation axis of the winding roller 81.The swinging unit 86 swings the entire winding roller 81, the shaft support fixing unit 83, the wheel 87, and the winding drive unit 88 (see FIG. 8C). The swinging unit 86 causes the long material L to be wound onto the winding roller 81 so that it is uniformly flat along the outer circumferential surface of the winding roller 81. The swinging unit 86 swings the swinging unit 86 in a direction along the rotation axis of the winding roller 81 by the swinging drive unit 89. The wheel 87 is a gear that applies tension to the winding roller 81 similar to that of the supply roller 21, and is fixed to the side of the winding roller 81. The winding roller 81 and the wheel 87 may be detachable or may be integrated.

[0028] The support and feed section 40, solvent application section 50, forming section 60, drying section 70, and winding section 80 are disposed within the space inside the first housing 11 and are disposed inside the second housing 12, which is a rectangular parallelepiped frame with a space in the central region. To bind the elongated material L, it is useful to uniformly apply a viscous fluid concentrically around the elongated material L in the forming section 60 and dry it. On the other hand, it is preferable to prevent vibrations caused by rotation in the twisting direction R for twisting the elongated material L from being transmitted to the forming section 60. For this reason, in the twisting device 10, the supply section 20 and twisting section 30 are disposed in the first housing 11, and the support and feed section 40, solvent application section 50, forming section 60, drying section 70, and winding section 80 are disposed in the second housing 12, which is separate from the first housing 11 (see FIG. 1).

[0029] Next, the operation of the twisting device 10 configured as described above will be described. First, the supply roller 21, around which carbon fiber as the long material L is wound, is set in the supply unit 20. The long material L is then pulled out and its leading end is fixed to the take-up roller 81. Next, the take-up roller 81 is rotationally driven by the winding drive unit 88 to move the long material L in the delivery direction A, and the rotation drive unit 23 rotates the supply unit 20 and the twisting unit 30 in the twisting direction R to twist the long material L between the twisting unit 30 and the solvent application unit 50. The twisted long material L is supported in a twisted state by the twisting unit 30 and the support and feeding unit 40 and passes successively through the solvent application unit 50, the forming unit 60, and the drying unit 70. At this time, a solvent is applied to the long material L in the solvent application unit 50, and the shape of the long material L1, which is unstable, is stabilized to a shape of the long material L2 (see FIG. 5). In addition, a viscous fluid of a binder that binds the elongated material L is formed on the elongated material L in the forming section 60, and the elongated material L is dried and cooled in the drying section 70. Because the binder is a resin and the carbon fiber is flexible, it is not damaged when wound around the winding roller 81. The twisted carbon fiber bundles as the elongated material L are fixed by the binder. The twisted carbon fiber bundles are loaded together with the winding roller 81 into the supply section 20, and a separation membrane material, which is a viscous fluid, is applied to their surfaces by the forming section 60, and the bundles are then wound up by the winding section 80. After the elongated material L that has been fixed in a shape-stable state is loaded into the supply section 20, solvent application in the solvent application section 50 is unnecessary and is therefore omitted. The carbon fiber bundles on which the separation membrane 17 has been formed are loaded together with the winding roller 81 into the supply section 20, and a viscous fluid electrode mixture is applied to their surfaces by the forming section 60, and the bundles are then wound up by the winding section 80. Thereafter, the obtained long material L is pulled out from the winding roller 81 and cut to the length of the secondary battery 15 with the positive electrode 18 formed on the separator 17. A predetermined number of the cut secondary batteries 15 are grouped together and press-molded into a secondary battery structure 14.

[0030] (Twisting method) The twisting method is a method for producing a carbon fiber bundle with improved shape stability by twisting a plurality of carbon fibers as a long object. This twisting method may include the processes performed by the twisting device 10 described above. This twisting method may include a twisting step, a solvent application step, a forming step, and a drying step. This twisting method may also include a winding step in which the long material L is wound up after the drying step. This twisting method may use the processing conditions and members described for the twisting device 10 as appropriate, and detailed description thereof will be omitted. In the twisting step, a process is performed in which the carbon fibers as the long object L are twisted in a twisting direction whose axial direction is the feed direction of the plurality of carbon fibers. In the twisting step, the processing conditions described for the supply unit 20 and the twisting unit 30 may be used as appropriate. In the solvent application step, a predetermined solvent is applied to the twisted carbon fiber bundle. In the solvent application step, the processing conditions and solvent type described for the solvent application unit 50 may be used as appropriate. In the forming step, a process of forming a viscous fluid on the carbon fiber bundles after the solvent has been applied is carried out. In the forming step, the process conditions and type of viscous fluid described in the forming section 60 can be used as appropriate. In the drying step, a process of drying the viscous fluid formed on the carbon fiber bundles is carried out. In the drying step, the process conditions described in the drying section 70 can be used as appropriate. In this twisting method, by carrying out the solvent application step, the shape of the carbon fiber bundles as the long material L can be made more stable.

[0031] Here, the correspondence between the components of this embodiment and the components of the present disclosure will be clarified. The twisting unit 30 of this embodiment corresponds to the twisting unit of the present disclosure, the solvent application unit 50 corresponds to the solvent application unit, the forming unit 60 corresponds to the forming unit, and the drying unit 70 corresponds to the drying unit. Furthermore, the main body unit 52 of the solvent application unit 50 corresponds to the main body unit, the passage opening 52a corresponds to the passage opening, the discharge unit 53 corresponds to the discharge unit, and the removal unit 55 corresponds to the removal unit. Note that this embodiment also clarifies an example of the twisting method of the present disclosure by explaining the operation of the twisting device 10.

[0032] The twisting device 10 and twisting method described above can provide a novel twisting device and twisting method that can more stabilize the shape of carbon fiber bundles. The reason for this effect is presumed to be as follows: For example, if the carbon fibers to be twisted are supplied in a flattened state, the fibers at the ends of the length are more likely to move during twisting than the fibers near the center, which can easily cause shape variations and result in a deformed carbon fiber bundle (see long material L1 in FIG. 5). In this case, if a solvent is applied to the fiber bundles while twisting, the carbon fiber bundles will loosen and the individual fibers will attract each other due to surface tension, resulting in a carbon fiber bundle that is closer to a circle than the deformed state (see long material L2 in FIG. 5). In this way, the carbon fiber twisting device 10 can more stabilize the shape of the carbon fiber bundles by applying and removing a solvent to the long material L.

[0033] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.

[0034] For example, in the above-described embodiment, the solvent application unit 50 has the removal unit 55, but is not limited to this, and the removal unit 55 may be omitted. In this case, the solvent application unit 50 may be disposed at a solvent removal distance X from the formation unit 60 so that the solvent can be removed. Furthermore, the solvent application unit 50 may use a solvent with higher volatility, or a solvent that does not have much effect on the formation of a viscous fluid on the elongated material L even if it remains on the elongated material L. [Example]

[0035] The following describes, as an example, a specific example of fabricating the above-described twisting device 10 and solvent application unit 50. Here, the twisting device 10 shown in Figures 1 to 8 was fabricated, a flat long material L was supplied, and the shape of the twisted material was examined depending on whether or not a solvent was applied.

[0036] (Circularization effect confirmation test) The effect of solvent application on the production of carbon fiber columnar components was investigated. Flat fiber bundles were supplied as raw materials, twisted into long materials with circular cross sections, and continuously wound up to produce carbon fiber columnar components. The twisting device had a supply section, twisting section, solvent application section, forming section, drying section, and winding section, as shown in Figures 1 to 8. The solvent removal distance X between the solvent application section and the forming section was 12.5 cm. The carbon fiber bundle used as raw material was a 400 m long bundle with a carbon fiber diameter d of 7 μm, 400 fibers, a width of 1 mm, and a thickness of 0.03 mm, wound up in a flat shape. The feed rate of the long material was 2 m / min. The solvent application was performed by injecting the solvent into a nozzle with a hole diameter of 0.5 mm as the discharge section at a rate of 0.025 mL / m to 0.05 mL / m, and impregnating the carbon fiber bundle as it was wound downward. The solvent was removed by supplying heated air at 150°C to 170°C at 25 L / min through the removal section. Evaluation tests were carried out for two levels, with and without twisted yarn, and with and without solvent, with ethanol application, and with acetone application.

[0037] FIG. 9 is an explanatory diagram of a test to confirm the circularization effect when flattened carbon fiber bundles are twisted, where FIG. 9A is a table of solvent application conditions, FIGS. 9B and 9C are explanatory diagrams of the treatment configuration, and FIG. 9D is an explanatory diagram of winding the carbon fiber bundle after twisting. As shown in FIG. 9D, when winding the carbon fiber bundle, a polystyrene case was placed on an octagonal winding bobbin to prevent deformation of the carbon fiber bundle, and the carbon fiber bundle was wound in a floating state as much as possible. The twisted and wound carbon fiber bundle was pulled out, and the outer diameters of 100 randomly selected points were measured using a digital microscope. For example, when the cross section of the carbon fiber bundle is elliptical, the outer diameter was taken as its major diameter.

[0038] Figure 10 shows the results of an investigation into the relationship between the presence or absence of solvent application and the diameter of the carbon fiber bundle. As shown in Figure 10, when no twisting was performed, the cross-sectional shape of the supplied carbon fiber was flat, and therefore, without the application of a solvent, the diameter was in the range of 400 to 850 μm, and the fiber bundle diameter varied greatly. On the other hand, when the solvent was applied and removed without twisting, the diameter was in the range of 160 to 350 μm with ethanol and 150 to 300 μm with acetone, and the fiber bundle diameter varied little. It was presumed that the carbon fibers loosened and each moved to a state close to a perfect circle. Similarly, when twisting was performed, the diameter was in the range of 160 to 320 μm without the application of a solvent, and the variation was large. On the other hand, the diameter was in the range of 150 to 220 μm with ethanol and 150 to 260 μm with acetone, and the variation in fiber bundle diameter was further reduced when the solvent was applied and removed. Regarding the type of solvent, both ethanol and acetone have a high effect of stabilizing the shape, and it was presumed that ethanol is particularly preferable.

[0039] Next, we investigated the circularization effect of forming a binder on the surface of the carbon fiber bundles in the forming section after twisting them and fixing the fiber bundles. The conditions for twisting the carbon fiber bundles were the same as those shown in Figure 9. A solution of a copolymer of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP) was used as the binder, and it was applied to the surface of the twisted carbon fiber bundles at a rate of 0.02 mL / min to 0.15 mL / min, and then dried at 170 °C in the drying section. The resulting fixed carbon fiber bundle was wound in the same manner as in Figure 9D, and its diameter was measured at 100 random locations. Figure 11 is an explanatory diagram of a test in which flat carbon fiber bundles were twisted and then fixed with a binder. Figure 12 shows the results of an investigation into the relationship between the presence or absence of solvent application and the diameter of the fixed carbon fiber bundles. As shown in Figure 12, the diameters of the long fibers bound with a binder after twisting without applying a solvent ranged from 150 to 280 μm, with large variations. On the other hand, the diameters of the carbon fiber bundles to which ethanol was applied and removed after twisting were in the range of 150 to 190 μm, with small variations. Similarly, the diameters of the carbon fiber bundles to which acetone was applied and removed after twisting were in the range of 150 to 200 μm, with small variations. Thus, it was revealed that applying and removing a solvent after twisting the carbon fiber bundles and before forming the viscous fluid can result in carbon fiber bundles that are closer to circular, and can be formed into columnar electrodes for electricity storage devices with a stable shape. [Industrial Applicability]

[0040] The present disclosure is applicable to the technical field of twisting and fixing elongated materials. [Explanation of symbols]

[0041] 10 twisting device, 11 first housing, 12 second housing, 13 top plate, 14 secondary battery structure, 15 secondary battery, 16 negative electrode, 17 separation membrane, 18 positive electrode, 19 control unit, 20 supply unit, 21 supply roller, 22 roller support unit, 23 rotation drive unit, 24 support member, 30 twisting unit, 31 support roller, 32 convex roller, 33 concave roller, 34 rotating shaft, 35 rotating shaft, 36 slide unit, 37 slide unit, 40 support feed unit, 41 support roller, 42 slide unit, 50 solvent application unit, 51 application unit, 52 main body unit, 52a passage port, 53 discharge unit, 54 discharge port, 55 removal unit, 56 drying space, 57 supply pipe, 58 discharge pipe, 59 temperature sensor, 60 forming unit, 61 inner member, 62 Inner nozzle, 63 supply space, 65 outer member, 66 outer nozzle, 67 cavity, 69 supply pipe, 70 drying section, 71 air heater, 72 temperature measurement section, 73 air heater, 74 temperature measurement section, 75 air cooling section, 76 cover member, 80 winding section, 81 winding roller, 82 winding shaft, 83 shaft support fixing section, 84 support plate, 85 fixing member, 86 swinging section, 87 wheel, 88 winding drive section, 89 swinging drive section, A delivery direction, L, L1, L2 long material, R twisting direction, d diameter, D diameter, X solvent removal distance.

Claims

1. a twisting unit that twists the carbon fibers in a twisting direction whose axial direction is the feed direction of the plurality of carbon fibers as the long object; a solvent application unit that applies a predetermined solvent, which is a polar or non-polar organic solvent or an aqueous solvent that does not contain a binder or a resin, to the twisted carbon fiber bundle; a forming unit that forms a viscous fluid containing a binder that binds the carbon fibers and a resin that serves as a separation membrane having ion conductivity and insulation properties for carrier ions of an electricity storage device on the carbon fiber bundle after the solvent has been applied; a drying section that dries the viscous fluid formed on the carbon fiber bundle; A yarn twisting device comprising:

2. 2. The yarn twisting device according to claim 1, wherein the solvent application unit includes: a main body having a passage opening through which the carbon fiber bundle passes; and a discharge unit that supplies the solvent to the carbon fiber bundle passing through the passage opening.

3. The yarn twisting device according to claim 1 or 2, wherein the solvent application unit includes a removal unit that removes the solvent from the carbon fiber bundle to which the solvent has been applied.

4. The yarn twisting device according to any one of claims 1 to 3, wherein the solvent application unit applies at least one of an alcohol-based solvent and a ketone-based solvent to the carbon fiber bundle.

5. The yarn twisting device according to any one of claims 1 to 4, wherein the solvent application unit is disposed at a predetermined solvent removal distance from the forming unit.

6. The yarn twisting device according to any one of claims 1 to 5, wherein the solvent applicator applies the solvent to the carbon fiber bundle in a range of 0.020 mL / m or more and 0.1 mL / m or less.

7. a twisting step of twisting the carbon fibers in a twisting direction whose axial direction is the feed direction of the plurality of carbon fibers as a long object; a solvent application step of applying a predetermined solvent, which is a polar or non-polar organic solvent or an aqueous solvent, containing no binder or resin, to the twisted carbon fiber bundle; a forming step of forming a viscous fluid containing a binder that binds the carbon fibers and a resin that serves as a separation membrane having ionic conductivity and insulating properties for carrier ions of an electricity storage device on the carbon fiber bundle after the solvent has been applied; a drying step of drying the viscous fluid formed on the carbon fiber bundle; A yarn twisting method comprising:

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