Agitation tank and agitation device

Abstract

To provide an agitation tank and an agitation device in which material attached to an inner wall can be easily and surely returned to the material that is an object to be agitated.SOLUTION: An agitation tank is given in which surface roughness at an upper part of an inner wall in a height direction is greater than that at a lower part thereof.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a stirring vessel and a stirring device. [Background technology]

[0002] In the manufacturing process of secondary batteries such as lithium-ion secondary batteries, a negative electrode paste containing a negative electrode active material and a positive electrode paste containing a positive electrode active material are prepared, and the respective pastes are applied to a negative electrode current collector foil and a positive electrode current collector foil, etc., to produce a negative electrode and a positive electrode. Patent Document 1 describes a method of preparing a paste by mixing an active material and a dispersant to prepare a powder mixture, adding water as a dispersion medium to the powder mixture, and kneading the mixture (coarse kneading step and hard kneading step). Patent Document 1 also discloses a technology that enables quality control of the paste by determining the manufacturing conditions for the hard kneading step of paste production, such as the optimal amount of dispersion medium to be added and the optimal time for the hard kneading step.

[0003] Furthermore, Patent Document 2 discloses an agitation device for various raw materials, which is a mechanical agitation type high-speed flow mixer with a vertical rotation axis, and which can easily clean raw materials adhering to the agitation vessel and / or agitation blades, and a method for simply and reliably discharging residual raw materials remaining after the raw materials have been discharged. Patent Document 2 discloses forming a coating layer on the inner surface of the agitation vessel and / or the surface of the agitation blades to improve the release of raw materials. According to Patent Document 2, the provision of the coating layer makes it possible to easily discharge adhering raw materials.

[0004] Furthermore, Patent Document 3 discloses a disperser for dispersing a pigment in a liquid, which is equipped with a spraying device that sprays the liquid upward into a stirring tank with a lid, onto the inner surface of the lid. According to Patent Document 3, it is possible to prevent the pigment or the like from adhering to and remaining on the inner surface of the lid, thereby reducing the effective content of the pigment or the like in the liquid and causing material loss of the pigment or the like. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-257653 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-100197 [Patent Document 3] Japanese Patent Application Publication No. 7-328407 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technology disclosed in Patent Document 2 is effective when removing the paste after mixing and kneading the materials. Furthermore, the technology disclosed in Patent Document 3 washes away materials adhering to the lid and the inner wall of the tank, but it relies on a mechanism that sprays up the liquid inside the mixing tank, which is only applicable to low-viscosity liquids, and it is necessary to consider the possibility that the sprayed-up liquid will adhere to the inside of the mixing tank. Until now, no mixing tank or mixing device has been known that can easily and reliably return materials adhering to the inner wall of the mixing tank to the materials being mixed during the material mixing stage.

[0007] Therefore, in view of the above-mentioned circumstances, the present disclosure aims to provide a stirring tank and a stirring device that can easily and reliably return material adhering to the inner wall to the material to be stirred. [Means for solving the problem]

[0008] The present disclosure, which achieves the above-mentioned objectives, includes the following. <1> An agitation vessel in which the upper part of the inner wall in the height direction has a greater surface roughness than the lower part. <2> The region with high surface roughness is above 50% of the height of the inner wall, where the height of the inner wall is 100%. <1> The stirring tank according to claim 1. <3> The region with high surface roughness has an inner wall with irregularities. <1> or <2> The stirring tank according to claim 1. <4> The length between the convex portions of the concave and convex portions is 0.1 μm or more and 15 μm or less. <3> The stirring tank according to claim 1. <5> <1> ~ <4> 1. A stirring device comprising: a stirring vessel according to any one of the above items; a stirring blade disposed inside the stirring vessel; and a drive device for driving the stirring blade. <6> The upper limit of the material input is set to a height position where the surface roughness of the inner wall of the stirring tank becomes large. <5> The stirring device according to claim 1. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a stirring tank and a stirring device that can easily and reliably return material adhering to the inner wall to the material to be stirred. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram illustrating a stirring tank according to the present disclosure. FIG. [Figure 2] FIG. 2 is a schematic diagram illustrating the length between convex portions of the unevenness formed on the inner wall of the stirring vessel. [Figure 3] 1 is a schematic diagram illustrating a configuration of a stirring device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described. The description is for illustrating the embodiments and is not intended to limit the scope of the present disclosure.

[0012] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0013] In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0014] In this specification, when an embodiment is described with reference to drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of components in each drawing are conceptual, and the relative size relationships between components are not limited to these.

[0015] [Mixing tank] In the stirred tank of the present disclosure, the surface roughness is greater at the top of the inner wall in the height direction than at the bottom. In the stirred tank of the present disclosure, the surface roughness is greater above a predetermined position in the height direction than below that position. In the stirred tank of the present disclosure, material adhering to the inner wall, which has a high surface roughness, peels off from the inner wall due to its own weight or slight vibration and returns to the mass of material being mixed or kneaded below. This avoids the need for tedious work such as peeling off material adhering to the inner wall and prevents deterioration in quality and productivity due to material adhering to the inner wall. Surface roughness is synonymous with the so-called "average length of cross-sectional curve element: PSm," "average length of roughness curve element: RSm," and "average length of waviness curve element: WSm," and the definitions specified in JIS B 0601-2001 can be adopted.

[0016] FIG. 1 shows an example of a stirring vessel according to the present disclosure. The stirring vessel 1 shown in FIG. 1 has a generally cylindrical shape with an open top surface, and is characterized in that the surface roughness of the vessel's inner wall 2 is greater above a predetermined height position T and smaller below position T. Here, position T is not particularly limited, but can be set to the same height as or higher than the materials (solids, dispersion medium, and other components) introduced into the vessel. Typically, materials are introduced into the stirring vessel 1 up to approximately the center of the height (approximately 50% of the height). Therefore, it is preferable that the predetermined position T be set at a height of 50% of the height of the inner wall, where the height of the inner wall is 100%.

[0017] By setting the predetermined position T at a position that is 50% of the height of the inner wall 2, assuming that the height of the inner wall 2 is 100%, the surface below the position T can be made the same as that of the inner wall of a normal mixing vessel. As an example, the inner wall 2 of the mixing vessel 1 below the position T can be mirror-finished. This allows materials to be mixed or kneaded while applying a desired shear force between the stirring blades of the mixing device described below and the inner wall 2 of the mixing vessel 1.

[0018] In particular, it is preferable that the inner wall 2 above position T in the stirring tank 1 has irregularities. That is, by forming irregularities above position T on the inner wall of the stirring tank 1, the surface roughness can be increased above position T and decreased below position T. For example, the inner wall 2 above position T can have irregularities, and the inner wall 2 below position T can have a mirror finish. Here, the irregularities are not particularly limited, but refer to a structure in which, when a paste or the like obtained by kneading the introduced materials adheres, the contact area is smaller than that of a mirror finish. That is, with the irregularities formed on the inner wall 2, the paste or the like comes into contact with the convex portions, and therefore the adhered paste or the like is more likely to peel off than when it adheres to a mirror finish.

[0019] The irregularities on the inner wall 2 are not particularly limited, but may include at least one shape selected from the group consisting of dimples, which are spherical depressions; embossments, which are spherical protrusions; polygonal pyramidal or other conical recesses; polygonal pyramidal or other conical protrusions; linear (straight, curved, or jagged) recesses; and linear (straight, curved, or jagged) protrusions, or a combination thereof. Such irregularities can be formed by, for example, dimple processing, embossing, square pyramidal recess processing, square pyramidal protrusion processing, needle processing, knurling (cross-knurling, flat knurling, oblique knurling, or square knurling), and jagged processing. These processes can be performed using, for example, an ultrashort pulse laser, a precision processing machine such as a CNC (Computer Numerical Control) processing device, or a micromilling processing device.

[0020] In particular, the length between convex portions of the unevenness of the inner wall 2 is preferably 0.1 μm or more and 15 μm or less. Here, the length between convex portions can be a value calculated by the arithmetic mean of the distances between adjacent convex portions (D1, D2, ... in FIG. 2), as shown in FIG. 2. The length between convex portions in the unevenness of the inner wall 2 can be measured by image analysis of an image of the uneven region of the inner wall 2 taken with a scanning electron microscope. By setting the length between convex portions in the unevenness of the inner wall 2 to 0.1 μm or more and 15 μm or less, the adhered paste can be easily peeled off from the inner wall by its own weight or slight vibration.

[0021] [Mixing device] The stirring device of the present disclosure also includes the above-described stirring vessel, a stirring blade disposed inside the stirring vessel, and a drive device for driving the stirring blade. Because the stirring device of the present disclosure includes the above-described stirring vessel, materials such as paste adhering to the inner wall of the stirring vessel, which has a high surface roughness, peel off from the inner wall due to their own weight or slight vibration and are returned to the mass of material being mixed or kneaded below. Thus, by using the stirring device of the present disclosure, it is possible to avoid the cumbersome task of peeling off materials adhering to the inner wall and to prevent deterioration in quality and productivity due to materials adhering to the inner wall.

[0022] An example of the stirring apparatus of the present disclosure is shown in Figure 3. The stirring apparatus 3 shown in Figure 3 includes the stirring vessel 1 shown in Figure 1, a stirring blade 4 disposed inside the stirring vessel 1, and a drive unit 5 that drives the stirring blade 4. The stirring apparatus 3 shown in Figure 3 is a so-called planetary mixer that mixes and kneads materials 6 introduced into the stirring vessel 1 by the planetary motion of the stirring blade 4. However, the stirring apparatus of the present disclosure is not limited to a planetary mixer, and may be an apparatus in which stirring blades such as propeller blades, turbine blades, paddle blades, anchor blades, or ribbon blades are attached to one rotating shaft.

[0023] In the agitator 3, the agitator blade 4 is composed of a dispersing blade 7 and mixing blades 8A and 8B. The dispersing blade 7 and mixing blades 8A and 8B are attached to a planetary gear unit 9. Specifically, the dispersing blade 7 is attached to a sun gear (not shown) of the planetary gear unit 9, and the mixing blades 8A and 8B are attached to planetary gears (not shown) of the planetary gear unit 9. The dispersing blade 7 includes a first rotating shaft 10 and blades 11, such as propeller blades, turbine blades, paddle blades, anchor blades, or ribbon blades, attached to the tip of the first rotating shaft 10. The mixing blades 8A and 8B each include a second rotating shaft 12 and a frame-type blade 13 attached to the second rotating shaft 12. The agitator 3 has a motor as a drive unit 5, and the rotational force from the motor is transmitted to the first rotating shaft 10 and the second rotating shaft 12 via the sun gear and planetary gears of the planetary gear unit 9.

[0024] The stirring device of the present disclosure may include the above-described stirring vessel in a detachable manner or in a fixed manner. That is, in the stirring device 3 shown in Fig. 3, the stirring vessel 1 may be detachable or fixed. Furthermore, the stirring device 3 shown in Fig. 3 may include a drive device (not shown) that positions the stirring blades 4 inside the stirring vessel 1.

[0025] By using the stirring device of the present disclosure configured as described above, materials introduced into a stirring tank can be mixed or kneaded. The materials introduced into the stirring tank are not particularly limited, but are preferably materials containing solids and a dispersion medium. The stirring device of the present disclosure can produce a desired paste by mixing and kneading materials containing solids and a dispersion medium. The stirring device of the present disclosure is particularly suitable for stirring high-viscosity materials. Hereinafter, as an example, a process for producing a negative electrode paste used in a secondary battery using the stirring device 3 shown in FIG. 3 will be described. A positive electrode paste can also be produced in the same manner as the negative electrode paste. Furthermore, the stirring device 3 can also be used to produce pastes other than negative and positive electrode pastes that are used for purposes other than secondary batteries.

[0026] First, carbon powder (5 μm to 30 μm at D50) as the active material, CMC (carboxymethyl cellulose) powder as the dispersant, and CNT (carbon nanotube) powder as the conductive additive are charged into the stirring tank 1 as materials 6. With these powders charged into the stirring tank 1, the motor of the driving device 5 is driven, and the powders alone are mixed by the dispersing blade 7 and the mixing blades 8A and 8B. Next, water as the dispersion medium is charged into the stirring tank 1. Note that it is preferable to add only half of the water required for the desired negative electrode paste rather than all of it. In this state, the motor of the driving device 5 is driven, and the dispersion medium and powder charged into the stirring tank 1 are kneaded by the dispersing blade 7 and the mixing blades 8A and 8B (rough kneading process). In this rough kneading process, the viscosity is high until the remaining powders are dispersed to a certain extent. Therefore, in order to prevent malfunction of the driving device 5 motor, it is preferable to knead at a relatively low rotation speed until the dispersion of the powders progresses and the viscosity settles.

[0027] Next, the motor rotation speed is increased to carry out a stiffening step. Stiffening is a step in which the powder particles of material 6, which have been dispersed to a certain extent by kneading, are further rubbed together to dissolve any powder lumps and further promote dispersion. After the stiffening step is completed, the remainder of the dispersion medium is added to the stirring tank 1, and kneading is continued while maintaining the rotation speed used in the stiffening step. Thereafter, styrene butadiene rubber is added to the stirring tank 1 as a binder, and while maintaining the rotation speed and continuing kneading, kneading is continued until the added binder is uniformly dispersed, and finally, a viscosity of, for example, 5000 Pa·s to 500,000 Pa·s (shear rate: 0.1 s -1 ) negative electrode paste is completed.

[0028] As described above, the stirring device 3 can produce the desired negative electrode paste. During this process, the material 6 mixed and kneaded by the stirring blades 4 gradually changes into a paste, but may adhere to the inner wall 2 as it is stirred. However, because the surface roughness is high above position T on the inner wall 2 of the stirring vessel 1, the adhered material 6 peels off from the inner wall due to its own weight or slight vibration and returns to the mass of material 6 being mixed or kneaded below. Therefore, the stirring device 3 does not require the complicated task of peeling off the material 6 adhered to the inner wall 2, and can prevent deterioration in quality and productivity due to the material 6 adhering to the inner wall 2.

[0029] In particular, in the stirring device 3, it is preferable to set the upper limit of the material input up to the height position T at which the surface roughness of the inner wall 2 of the stirring tank 1 becomes large. In the above-described example of producing a negative electrode paste, at the stage where the binder is finally input, all of the material 6 in the stirring tank 1 is set to a height below the height position T at which the surface roughness of the inner wall 2 of the stirring tank 1 becomes large. Note that the height of the material 6 input into the stirring tank 1 is measured in an unstirred state. In this way, by setting the height of the material 6 input into the stirring tank 1 below the position T at which the surface roughness of the inner wall 2 becomes large, an appropriate shear force can be applied to the material 6 by the stirring blades 4. [Explanation of symbols]

[0030] 1...mixing vessel, 2...inner wall, 3...mixing device, 4...mixing blade, 5...driving device, 6...material, 7...dispersing blade, 8A and 8B...mixing blade, 9...planetary gear device, 10...first rotating shaft, 11...blade, 12...second rotating shaft, 13...frame-type blade

Claims

1. An agitation vessel in which the upper part of the inner wall in the height direction has a greater surface roughness than the lower part.

2. 2. The stirred tank according to claim 1, wherein the region with high surface roughness is located above 50% of the height of the inner wall, where the height of the inner wall is 100%.

3. The stirred tank according to claim 1 , wherein the region with high surface roughness has an uneven inner wall.

4. 4. The stirring tank according to claim 3, wherein a length between convex portions of the irregularities is 0.1 μm or more and 15 μm or less.

5. The stirring tank according to any one of claims 1 to 4, a stirring blade disposed inside the stirring tank; a drive device that drives the stirring blade; A stirring device comprising:

6. 6. The stirring device according to claim 5, wherein the upper limit of the material feeding amount is set to a height position at which the surface roughness of the inner wall of the stirring tank becomes large.

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