JP7757822B2 - Yarn twisting device and yarn twisting method - Google Patents

Description

This specification discloses a yarn twisting device and a yarn twisting method.

Conventionally, a twisting device has been proposed that includes, for example, an applicator that delivers multiple carbon fibers in a delivery direction and rotates in a twisting direction with the delivery direction as its 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.

Japanese Patent Application Laid-Open No. 2021-63319

In the twisting device disclosed in Patent Document 1, the carbon fibers are twisted together by rotating them in the twisting direction, and then a binder is formed on the surface as a viscous fluid. The carbon fiber bundle is then fixed by drying, and the long carbon fiber bundle is wound onto a bobbin while controlling the diameter. In this case, for example, when the carbon fibers being fed are flat, the flat fiber bundle can be twisted as is and fixed with a binder, resulting in an appearance that approaches a circular bundle. However, when twisting flat carbon fiber bundles, for example, 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 is a need for greater shape stability in carbon fiber bundles.

The present disclosure has been made in consideration of these issues, and its primary objective is to provide a new twisting device and twisting method that can more consistently produce carbon fiber bundles.

After extensive research to achieve the above-mentioned objectives, the inventors discovered that applying a solvent to the carbon fiber bundles after twisting facilitates smooth movement of the carbon fibers and makes the shape of the carbon fiber bundles more stable, leading to the completion of the invention disclosed in this specification.

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.

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:

The present disclosure provides 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 the carbon fibers to be twisted are supplied in a flattened state, the fibers at the ends of the length tend to move more when twisted 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 bundle while it is being twisted, the fiber bundle 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.

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

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 the 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 of 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 the shaft support fixing unit 83, and FIG. 8E is an explanatory diagram of removing the wheel 87.

As shown in Figures 1 and 2, the twisting device 10 is an apparatus that pulls out a long material L, which has been arranged flat and wound into a sheet, in a feed direction A and twists 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 and feeding unit 40, a solvent application unit 50, a forming unit 60, a drying unit 70, and a winding unit 80. Examples of the long material L include carbon fiber, which can be used as a negative electrode active material in secondary batteries, as shown in Figure 3. Here, the up-down, left-right, and front-to-back directions of the twisting device 10 are shown in Figures 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.

Here, we will explain a product using the long material L produced by the twisting device 10. As shown in Figure 3, the long material L produced by the twisting device 10 is a bundle of carbon fibers 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, the cylindrical long material L is used as the negative electrode 16, allowing ion absorption and desorption 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. A carbon fiber diameter d of 5 μm or greater ensures higher strength, while a diameter d of 100 μm or less ensures better flexibility. The diameter d of the carbon fiber is preferably 20 μm or less. The carbon fiber bundles serving as the long material L may have a diameter D (μm) of 30 μm or greater and 1000 μm or less. A diameter D of 30 μm or greater ensures the amount of active material, while a diameter D of 1000 μm or less is preferable because it further suppresses the increase in ion diffusion resistance in the electrode. The diameter D is preferably 50 μm or greater, more preferably 100 μm or greater. 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.

The separation membrane 17 has ionic conductivity for the carrier (e.g., lithium ions) and may be a solid electrolyte or a gel electrolyte. Suitable materials for the separation membrane 17 include polymers with ionic conductivity and insulating properties, such as polyvinylidene fluoride (PVdF), copolymers of PVdF and hexafluoropropylene (HFP), polymethyl methacrylate (PMMA), and copolymers of PMMA and acrylic polymers. Examples of binders for immobilizing the elongated material L include the aforementioned 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 combination. The positive electrode 18 may be made of, for example, a material used in a typical 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 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 thickness 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, rectangles, pentagons, hexagons, and octagons, with hexagons being preferred.

The control unit 19 (see Figure 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.

The supply unit 20 is configured to feed the long material L in a feed direction A and rotate in a twisting direction R, with the feed direction A serving as the axial direction. As shown in FIG. 4, the supply unit 20 is disposed on top of the first housing 11, which has a rectangular parallelepiped frame with a central space. 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 wound around the supply roller 21 in a sheet-like arrangement. A predetermined rotational brake is applied to the supply roller 21, so that the supply roller 21 rotates in response to 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 itself 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 unit 23 is a motor connected to the roller support unit 22 and drives the roller support unit 22 to rotate. The rotation drive unit 23 receives 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 unit 23 causes the supply roller 21, roller support unit 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 to, for example, 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, then the twist degree is preferably set to a range of 10 turns/10 cm to 20 turns/10 cm. The degree of twisting can be adjusted by adjusting the relationship between the delivery speed and the winding speed, so the optimal rotation speed, delivery speed, and winding speed can be set depending on the characteristics of the long material L being used. The support member 24 is a U-shaped member fixed to a stay attached to the side of the roller support portion 22, with the twisting portion 30 located at the center of its lower end. The support member 24 is attached to the stay so that the distance between the supply roller 21 and the twisting portion 30 can be changed to suit the width of the supply roller 21 and the flexibility of the long material L, etc.

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 arranged in the supply unit 20 and rotates integrally with the supply unit 20 in the twisting direction R. The twisting unit 30 has 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 Figure 4B, the convex roller 32 is fixed to the center of the rotation shaft 34, which is rotatably supported at the tip of the slide unit 36. The concave roller 33 is fixed to the center of the rotation 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 portions 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 they clamp the long material L and an open position where they release the clamping of the long material L. The slide portions 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 slides 36, 37 may be configured so that the convex roller 32 and the concave roller 33 are biased toward each other by an elastic body such as a spring (not shown), and the convex roller 32 and the concave roller 33 can be separated when the fixing device is released. Alternatively, the slides 36, 37 may be configured to 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.

As shown in Figures 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 it is continuously fed in the feed direction A without rotating the long material L in the twisting direction R. The support and feed unit 40 is fixed to the second housing 12, which is separate from the first housing 11. As shown in Figure 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 slide unit 42 have the same configuration as the support roller 31 and slide units 36 and 37, except that they are fixed to the stationary second housing 12, and detailed description thereof will be omitted.

The solvent application unit 50 is a unit that applies a predetermined solvent to the carbon fiber bundles twisted in the twisting unit 30. This solvent application unit 50 is provided with a removal unit 55 that removes the applied solvent. As shown in FIG. 5, the solvent application unit 50 is disposed between the twisting unit 30 and the support feed unit 40, particularly between the twisting unit 30 and the forming unit 60. The solvent application unit 50 is disposed at a predetermined solvent removal distance X from the forming unit 60. Note that the solvent removal distance X may be empirically determined, for example, to be a distance sufficient to allow the applied solvent to be sufficiently removed from the long material L.

In the solvent application section 50, the solvent supply rate may be appropriately determined according to the supply rate of the long material L. This solvent supply rate 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 solvent supply amount should be determined taking into account the effect and removability.

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 selected appropriately 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 subsequent 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 post-removal processing such as recovery, 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 such as acetone, as well as dichloromethane, tetrahydrofuran, ethyl acetate, and acetonitrile. Protic polar solvents include alcohol solvents such as ethanol, carboxylic acid solvents such as 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, with ethanol being easy to handle and preferred. Examples of ketone solvents include acetone and diethyl ketone, with acetone being preferred.

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 secures 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 solvent supplied from an external source to the long material L. The discharge unit 53 may include, for example, a syringe unit that temporarily stores the solvent and a needle-shaped discharge tube connected to the tip of the syringe unit, with an outer diameter smaller than the syringe and 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 unit 53, and the solvent supplied via the tube is fed from the discharge port 54 to the outer surface of the carbon fiber bundle. These discharge units 53 are arranged in four locations on the outer periphery of the main body 52, and supply the solvent to the carbon fiber bundle from four directions. Note that as long as a sufficient amount of solvent can be supplied to the long material L, the number of discharge units 53 may be four or less, or may be any number from three to one.

The removal unit 55 removes the solvent from the carbon fiber bundle to which the solvent has been applied. This removal unit 55 may also remove the solvent from the long material L by circulating heated gas. The removal unit 55 includes a drying space 56, a supply pipe 57, an exhaust pipe 58, and a temperature sensor 59. The removal unit 55 may be located at a position after the solvent has sufficiently stabilized the shape of the long material L. Here, the removal unit 55 is located adjacent to the application unit 51, immediately downstream of the application unit 51 where the long material L moves. Examples of heated gas include heated air. The heated gas supplied to the removal unit 55 may be heated by a heater (not shown). The drying space 56 is located immediately downstream of the application unit 51 and is used to dry the long material L. A supply pipe 57 and an exhaust pipe 58 are connected to the drying space 56. The supply pipe 57 is a pipe that supplies 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 volatilized solvent 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.

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 viscous fluids include binders that bind carbon fibers together and resins that form separation membranes that are ionic conductive and insulating for carrier ions in energy storage devices. These binders and resins may be dissolved in, for example, aqueous solvents or organic solvents. 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 have multiple forming units 60 and drying units 70 to form multiple types of viscous fluids on the elongated material L. For example, the first applicator penetrates the resin that will serve as the binder into the interior of the elongated material L, and the first dryer dries it. The second applicator forms the resin that will serve as the separation membrane on the outer surface of the elongated material L, and the second dryer dries it. After that, the third applicator forms a viscous fluid of an electrode mixture containing an electrode active material on the surface of this separation membrane, and the third dryer dries it to further form an electrode mixture layer. For ease of explanation, the twisting device 10 will be described as including a binder forming unit 60 and a drying unit 70.

As shown in FIG. 6 , the forming unit 60 comprises 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 through 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 underside 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 housing the inner nozzle 62. The outer member 65 has a cylindrical body with a conical space formed inside, into which the inner nozzle 62 is inserted. A downwardly protruding outer nozzle 66 is formed on the underside of the outer member 65, with a central hole formed in its center. The outer member 65 is positioned using a positioning unit to secure the inner member 61 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 dispensed 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. Viscous fluid is supplied to the supply pipe 69 via a pump from a tank (not shown).

The drying section 70 dries the viscous fluid formed on the long material L. As shown in Figure 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 arranged 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 direction in which the heated gas is discharged 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 arranged left and right or front and rear. 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 elongated material L and the viscous fluid to be dried, and therefore, appropriate values can be empirically set to suit these factors. The temperature measurement unit 72 measures the temperature of the elongated 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 that measures the vicinity of the elongated material L moving in the discharge direction A. The temperature measurement unit 72 indirectly obtains the temperature of the elongated material L by measuring the temperature in the vicinity of the elongated material L. The temperature measurement unit 72 may directly contact the elongated 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 elongated material L at a higher temperature than the air heater 71. This is preferable because it makes it easier to heat the elongated material L. The temperature measurement unit 74 has a similar configuration to the temperature measurement unit 72 and is disposed 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, and therefore their description is 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 from 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 heated long material L 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, the air heater 71, the temperature measurement unit 72, the air heater 73, and the temperature measurement unit 74 are fixed to the cover member 76, and these supply heated air into the passage space and measure its temperature.

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 shaft 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 winds up the manufactured long material L and is configured to rotate around a winding shaft 82. In this winding roller 81, the winding shaft 82 is supported by the shaft support fixing unit 83. This winding roller 81 may have a relatively large diameter to prevent defects in the separation membrane and electrode composite layer formed on the long material L, including the long material L itself. Note that FIGS. 1, 2, and 8 show an example of a 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 take-up roller 81 may have a relatively small diameter, similar to the supply roller 21. The take-up roller 81 is driven to rotate by a take-up drive unit 88 at a rotational speed that corresponds to the time required for the entire device to process the long material L. The take-up 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 take-up roller 81 in a removably manner. This axial support fixing unit 83 is a member that axially supports the take-up shaft 82 that protrudes from the take-up 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 take-up roller 81. The support plate 84 has a notch formed therein to accommodate the take-up shaft 82. By fixing the fixing member 85, the take-up 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 contact 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 rotates the winding roller 81 and is connected to the winding shaft 82 via a gear. The swing unit 86 swings the winding roller 81 in a direction along the rotational axis of the winding roller 81. The swing unit 86 swings the winding roller 81, the axial support fixed unit 83, the wheel 87, and the winding drive unit 88 as a whole (see FIG. 8C). The swing unit 86 allows the long material L to be wound onto the winding roller 81 in a uniform, flat state along the outer circumferential surface of the winding roller 81. The swinging unit 86 is swung in a direction along the rotation axis of the winding roller 81 by a 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 wheel 87 may be detachable or may be integrated.

The support and feeding unit 40, solvent application unit 50, forming unit 60, drying unit 70, and winding unit 80 are arranged within the space inside the first housing 11 and inside the second housing 12, which has a rectangular parallelepiped skeleton with a central space. To bind the long material L, it is useful to apply a viscous fluid uniformly and concentrically around the long material L in the forming unit 60 and dry it. On the other hand, it is preferable to prevent rotational vibrations in the twisting direction R for twisting the long material L from being transmitted to the forming unit 60. For this reason, in the twisting device 10, the supply unit 20 and twisting unit 30 are arranged in the first housing 11, and the support and feeding unit 40, solvent application unit 50, forming unit 60, drying unit 70, and winding unit 80 are arranged in the second housing 12, separate from the first housing 11 (see Figure 1).

Next, the operation of the twisting device 10 configured as described above will be described. First, the supply roller 21, on 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 secured to the take-up roller 81. Next, the take-up roller 81 is rotated by the take-up 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 its twisted state by the twisting unit 30 and the support and feed unit 40 and passes successively through the solvent application unit 50, the forming unit 60, and the drying unit 70. At this time, solvent is applied to the long material L in the solvent application unit 50, stabilizing the shape of the long material L1 from an unstable state to a stable state of the long material L2 (see Figure 5). In addition, a viscous fluid binder that binds the long material L is formed on the long material L in the forming section 60, and the material 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 on the winding roller 81. The twisted carbon fiber bundles as the long 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 then wound up by the winding section 80. After the shape-stable, fixed long material L is loaded into the supply section 20, solvent application in the solvent application section 50 is unnecessary and is omitted. The carbon fiber bundles with the separation membrane 17 formed thereon 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 then wound up by the winding section 80. The resulting long material L is then 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.

(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 appropriately use the processing conditions and members described for the twisting device 10, and detailed descriptions thereof will be omitted. In the twisting step, a process is performed to twist the carbon fibers in a twisting direction whose axial direction is the feed direction of the plurality of carbon fibers as the long object L. In the twisting step, the processing conditions described for the supply unit 20 and the twisting unit 30 may be appropriately used. 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 appropriately used. In the forming process, a process of forming a viscous fluid on the carbon fiber bundles after the solvent has been applied is carried out. In the forming process, the process conditions and type of viscous fluid described in the forming unit 60 can be used as appropriate. In the drying process, a process of drying the viscous fluid formed on the carbon fiber bundles is carried out. In the drying process, the process conditions described in the drying unit 70 can be used as appropriate. In this twisting method, by carrying out the solvent application process, the shape of the carbon fiber bundles as the long material L can be made more stable.

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.

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 tend to move more when twisted 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 Figure 5). In this case, if a solvent is applied to the fiber bundle while twisting, the carbon fiber bundle loosens and the individual fibers 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 Figure 5). In this way, the carbon fiber twisting device 10 can more stabilize the shape of the carbon fiber bundle by applying and removing solvent from the long material L.

It goes without saying that the present disclosure is in no way 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.

For example, in the above-described embodiment, the solvent application unit 50 includes a removal unit 55, but this 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, even if it remains on the elongated material L, has little effect on the formation of a viscous fluid on the elongated material L.

The following describes an example in which the above-mentioned twisting device 10 and solvent application unit 50 were specifically fabricated. Here, the twisting device 10 shown in Figures 1 to 8 was fabricated, a flat elongated material L was supplied, and the shape of the material after twisting was examined depending on whether or not a solvent was applied.

(Circularization effect confirmation test)
The effect of solvent application on the production of carbon fiber columnar components was examined. 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 bundles used as raw materials were 400 m long, wound up in a flat shape with a carbon fiber diameter d of 7 μm, 400 fibers, a width of 1 mm, and a thickness of 0.03 mm. The feed rate of the long material was 2 m/min. Solvent application was performed by injecting 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, so that the solvent was impregnated into the carbon fiber bundles being wound downward. The solvent was removed by supplying heated air at 150°C to 170°C at 25 L/min through the removal section. The evaluation test was carried out in three ways: without solvent, with ethanol applied, and with acetone applied, for two levels: with and without twisted yarn.

Figure 9 is an explanatory diagram of a test to confirm the circularization effect when flattened carbon fiber bundles are twisted. Figure 9A is a table of solvent application conditions, Figures 9B and 9C are explanatory diagrams of the processing configuration, and Figure 9D is an explanatory diagram of winding the carbon fiber bundle after twisting. As shown in Figure 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 diameter was measured at 100 random locations using a digital microscope. For example, if the cross section of the carbon fiber bundle is elliptical, the outer diameter was taken as its major axis.

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 without solvent application, the diameter ranged from 400 to 850 μm, resulting in large variations in fiber bundle diameter. On the other hand, when no twisting was performed and the solvent was applied and removed, the diameter ranged from 160 to 350 μm with ethanol and from 150 to 300 μm with acetone, resulting in small variations in fiber bundle diameter. It is presumed that the carbon fibers loosen and move toward a nearly perfect circle. Similarly, when twisting was performed, the diameter ranged from 160 to 320 μm without solvent application, resulting in large variations. However, the diameter ranged from 150 to 220 μm with ethanol and from 150 to 260 μm with acetone. The application and removal of the solvent further reduced the variations in fiber bundle diameter. In terms of solvent type, both ethanol and acetone have a high shape stabilization effect, with ethanol being particularly preferable.

Next, we investigated the circularization effect of twisting carbon fiber bundles and then applying a binder to their surfaces in the forming section to fix the fiber bundles. The carbon fiber bundles were twisted under the same conditions as 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. The bundles were then dried at 170°C in the drying section. The resulting fixed carbon fiber bundles were wound in the same manner as in Figure 9D, and their diameters were 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 diameter of the fixed carbon fiber bundles and the presence or absence of solvent application. 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 a stable shape when used to form columnar electrodes for electricity storage devices.

This disclosure can be used in the technical field of twisting and fixing long materials.

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 Rotation shaft, 35 Rotation shaft, 36 Slide unit, 37 Slide unit, 40 Support and feed unit, 41 Support roller, 42 Slide unit, 50 Solvent application unit, 51 Application unit, 52 Main body, 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 (7)

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: The yarn twisting device described in 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. The 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. The 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. The yarn twisting device described in any one of claims 1 to 4, wherein the solvent application unit is arranged with a predetermined solvent removal distance between it and the forming unit. The twisting device described in any one of claims 1 to 5, wherein the solvent application unit 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. 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: