High-speed mixing device

Abstract

The present invention provides a high shear mixing device comprising a mixing screw and a housing for accommodating the mixing screw; the housing includes a nozzle provided at a tip and a hopper communicating with the inside; the mixing screw includes a rotating shaft and blades provided on an outer circumferential surface of the rotating shaft; the rotating shaft includes, in this order, a first tapered section whose outer diameter gradually increases in the direction of the nozzle, a kneading section whose outer diameter is maintained the same or gradually increases in the direction of the nozzle, and a second tapered section whose outer diameter gradually decreases in the direction of the nozzle; the blades include a first helical blade disposed on the outer circumferential surface of the first tapered section, a second helical blade disposed on the outer circumferential surface of the kneading section, and a third helical blade disposed on the outer circumferential surface of the second tapered section.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0121462, filed on September 26, 2022, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a high shear mixer, and more particularly to a high shear mixer used in the manufacture of dry electrodes for secondary batteries. [Background technology]

[0003] Mixers are used to finely mix various paste manufacturing equipment and chemical raw materials, such as inks, pigments, paints, cosmetics, pharmaceuticals, and coating materials, with various coating agents, abrasives, ceramic or metal powders, or various electronic materials (PZT, dielectrics, MLCC, Ferrite, display materials), etc. As the mixer, planetary mixers and twin screw extruders, which use blades and rotors to mix high-viscosity materials in a container, are particularly used as equipment for mixing high-viscosity materials.

[0004] Meanwhile, with the expansion and development of secondary battery applications, there is a continuous demand for improvements in electrodes, such as lower resistance, higher capacity, improved mechanical properties, and improved productivity, which has led to an increasing need for high shear mixing for electrode manufacturing mixtures. Specifically, a technology for manufacturing dry electrode films by mixing a binder and a conductive material without a liquid medium such as a solvent or dispersion medium, and then passing the powder mixture through a rolling mill, is being actively developed, and high shear mixing is being applied to the manufacture of such electrodes.

[0005] In the high shear mixing method, binders called "fibrillizable binders" or "fibril-forming binders" are used, and when high shear mixing is applied to a mixture containing such binders, the binders are fibrillated to bind the active material and conductive material.

[0006] As the high shear mixing method, a conventional planetary mixer, a twin screw extruder, or the like is used.

[0007] However, during this high-shear mixing process, the fiberizable polymer becomes like chewing gum, placing a heavy load on the planetary mixer or twin-screw extruder, which frequently results in damage to the equipment. While methods for reducing the shear force have been considered to prevent such equipment damage, these methods often result in poor fiberization of the fiberizable polymer. Therefore, it is extremely difficult to build a large-capacity mass production system for manufacturing dry electrodes for secondary batteries using conventional high-shear mixing devices. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 2011-0117902 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been devised to solve the above-mentioned problems of the prior art, and aims to provide a high shear mixer that can efficiently mix materials without causing overload when mixing materials with high shear force.

[0010] In particular, the object of the present invention is to provide a high-shear mixer that can efficiently microfiberize a polymer without generating an overload when high-shear mixing a mixture for manufacturing a dry electrode that contains a fiberizable polymer as a binder. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention a high shear mixing unit including a mixing screw and a housing containing said mixing screw; the housing includes a nozzle at a tip end and a hopper in communication with the interior; The mixing screw includes a rotating shaft and a blade provided on the outer circumferential surface of the rotating shaft, the rotating shaft includes, in this order, a first tapered section whose outer diameter gradually increases toward the nozzle, a kneading section whose outer diameter is maintained constant or gradually increases toward the nozzle, and a second tapered section whose outer diameter gradually decreases toward the nozzle, The blades provide a high shear mixer including a first spiral blade arranged on the outer peripheral surface of the first tapered section, a second spiral blade arranged on the outer peripheral surface of the kneading section, and a third spiral blade arranged on the outer peripheral surface of the second tapered section.

[0012] In one embodiment of the present invention, the first helical blade and the second helical blade may be formed independently, the pitch of the first helical blade may be larger than the pitch of the second helical blade, and the first helical blade and the second helical blade may be wound helically in the same direction around the rotation axis.

[0013] In one embodiment of the present invention, based on the acute angle formed by the cross section perpendicular to the central axis of the rotation shaft and the spiral blade, the acute angle of the second spiral blade may be formed to be larger than the acute angle of the first spiral blade.

[0014] In one embodiment of the present invention, the second spiral blade may be three or more independent blades provided so as to overlap on the outer circumferential surface of the kneading section.

[0015] In one embodiment of the present invention, the second helical blade and the third helical blade may be wound helically in the same direction around the rotation axis.

[0016] In one embodiment of the present invention, the third spiral blade may be three or more independent blades provided so as to overlap the outer circumferential surface of the second tapered portion.

[0017] In one embodiment of the present invention, the second helical blade and the third helical blade may be provided independently of each other.

[0018] In one embodiment of the present invention, the second spiral blade may extend to the outer circumferential surface of the second tapered portion to form a third spiral blade.

[0019] In one embodiment of the present invention, a separation section can be positioned between the second spiral blade and the third spiral blade, the separation section being located between the end of the kneading section of the rotating shaft and the tip of the second tapered section.

[0020] In one embodiment of the present invention, the three or more independent blades provided on the second tapered portion may be formed up to the outer periphery of the tip surface of the second tapered portion in the nozzle direction.

[0021] In one embodiment of the present invention, the diameter of the tip surface of the second tapered portion of the rotating shaft facing the nozzle may be 0.5 to 1 time, preferably 0.7 to 0.9 times the inner diameter of the nozzle.

[0022] In one embodiment of the present invention, the rotating shaft may have a first tapered section whose outer diameter gradually increases toward the nozzle, a kneading section whose outer diameter gradually increases or maintains the same from the maximum outer diameter of the first tapered section, and a second tapered section whose outer diameter gradually decreases from the end of the kneading section.

[0023] In one embodiment of the present invention, the space between the outer surface of the first tapered portion of the rotating shaft and the housing may gradually decrease as it moves toward the nozzle, the space between the outer surface of the kneading portion and the housing may gradually decrease or be maintained uniformly as it moves toward the nozzle, and the space between the second tapered portion and the housing may be maintained uniformly or may gradually decrease.

[0024] In one embodiment of the present invention, the length of the first tapered portion, the length of the kneading portion, and the length of the second tapered portion of the rotating shaft may be formed in a ratio of 1:0.1-0.3:0.2-0.45.

[0025] In one embodiment of the present invention, the acute angle of the second spiral blade may be smaller than or equal to the acute angle of the third spiral blade, based on the acute angle formed by the spiral blade and a cross section perpendicular to the central axis of the rotation shaft.

[0026] In one embodiment of the present invention, the third spiral blade may have a maximum pitch at the start point of the second tapered section that contacts the kneading section, a minimum pitch at the tip surface of the second tapered section toward the nozzle, and a pitch that gradually decreases as it goes toward the nozzle.

[0027] In one embodiment of the present invention, a vertical cross section of the first spiral blade relative to the direction in which it is wound around the rotation shaft includes two height-forming sides, and one of the height-forming sides in the nozzle direction may form an acute angle of 30 degrees to 80 degrees, preferably 50 degrees to 70 degrees, with the central axis of the rotation shaft in the direction opposite to the nozzle.

[0028] In one embodiment of the present invention, a vertical cross section of the second spiral blade relative to the direction of winding around the rotation shaft includes two height-forming sides, and one of the height-forming sides in the nozzle direction may form an acute angle of 40 degrees to 80 degrees, preferably 50 degrees to 70 degrees, with the central axis of the rotation shaft in the direction opposite the nozzle.

[0029] In one embodiment of the present invention, a vertical cross section of the third spiral blade relative to the direction of winding around the rotation shaft includes two height-forming sides, and one of the height-forming sides in the nozzle direction may form an acute angle of 40 degrees to 80 degrees, preferably 50 degrees to 70 degrees, with the central axis of the rotation shaft in the direction opposite to the nozzle.

[0030] In one embodiment of the present invention, the high shear mixer is used for high shear mixing of a mixture for manufacturing a dry electrode containing a fiberizable polymer as a binder, and can be used to microfibrillate the fiberizable polymer. [Effects of the Invention]

[0031] The high shear mixer of the present invention provides the effect of efficiently mixing materials without overloading when mixing materials using high shear force, and also minimizes damage to the device, making it possible to configure the device with a large capacity.

[0032] In particular, the high shear mixer of the present invention provides the effect of efficiently microfibrillating the polymer without generating an overload when high shear mixing a mixture for manufacturing a dry electrode containing a fiberizable polymer as a binder. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a diagram showing a schematic diagram of one embodiment of the high shear mixer of the present invention. FIG. [Figure 2] FIG. 1 is a diagram showing one embodiment of a high shear mixing unit provided in the high shear mixing apparatus of the present invention. [Figure 3]FIG. 1 is a diagram showing one embodiment of a high shear mixing unit provided in the high shear mixing apparatus of the present invention. [Figure 4] FIG. 1 is a diagram showing one embodiment of a high shear mixing unit provided in the high shear mixing apparatus of the present invention. [Figure 5] FIG. 2 is a diagram showing specific material sources of the high shear mixing unit provided in the high shear mixing apparatus of the present invention. [Figure 6] 1 is a diagram showing a schematic view of a vertical cross section of each partial blade provided in the high shear mixer of the present invention, with respect to the direction in which the blade is wound around the rotation shaft. [Figure 7] 1 is a diagram showing the shape and material source of each partial blade provided in the high shear mixing device of the present invention. FIG. [Figure 8] 1 is a photograph showing the shape of a single screw installed in a conventional mixer and the results of high shear mixing using the same. [Figure 9] 1 is a photograph showing the configuration of a conventional twin screw kneader. [Figure 10] 1 is a photograph showing the configuration of a single screw used in conventional polymer mixing applications and the state of use thereof. [Figure 11] FIG. 1 is a diagram schematically illustrating the mixing mechanism in the form of a first spiral blade provided in a high shear mixer of the present invention and a conventional mixer. [Figure 12] FIG. 2 is a diagram showing a schematic configuration of a third spiral blade provided in the high shear mixer of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily understand the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. The same reference numerals are used throughout the specification to refer to similar parts.

[0035] FIG. 1 is a perspective view showing one embodiment of the high shear mixer (500) of the present invention, and FIGS. 2 to 4 are cross-sectional views showing embodiments of the high shear mixing unit (100) provided in the high shear mixer (500) of the present invention.

[0036] The high shear mixer (500) of the present invention, as shown in FIGS. 1 and 2, a high shear mixing unit (100) including a mixing screw (10) and a housing (20) containing said mixing screw; The housing (20) includes a nozzle (22) at its tip and a hopper (24) communicating with its interior, The mixing screw (10) includes a rotating shaft (12) and blades (14) provided on the outer circumferential surface of the rotating shaft, the rotating shaft (12) includes, in this order, a first tapered section (12a) whose outer diameter gradually increases toward the nozzle (22), a kneading section (12b) whose outer diameter is maintained constant or gradually increases toward the nozzle, and a second tapered section (12c) whose outer diameter gradually decreases toward the nozzle; The blade (14) is characterized by including a first spiral blade (14a) arranged on the outer peripheral surface of the first tapered portion (12a), a second spiral blade (14b) arranged on the outer peripheral surface of the kneading portion (12b), and a third spiral blade (14c) arranged on the outer peripheral surface of the second tapered portion (12c).

[0037] The high shear mixer (500) of the present invention has a simple single-screw structure, which allows for low-cost manufacturing and simplifies process management and maintenance. Furthermore, compared to twin-screw mixers, it has the advantage of providing more stable drive characteristics.

[0038] In particular, the high shear mixer (500) of the present invention includes an improved mixing screw (10), which significantly improves the compression and discharge force for the fiberizable binder (e.g., PTFE) powder, providing the advantage of easily adjusting the degree of fiberization and powder compression ratio for the fiberizable binder.

[0039] In one embodiment of the present invention, the length of the first tapered section (12a), the length of the kneading section (12b), and the length of the second tapered section (12c) of the rotating shaft (12) can be formed in a ratio of 1:0.1-0.3:0.2-0.45, preferably 1:0.15-0.25:0.3-0.4.

[0040] When the length ratio of each part constituting the rotating shaft (12) satisfies the above-mentioned range, it is preferable because the dispersibility of the materials to be mixed and the high shear mixing efficiency are increased.

[0041] In particular, if the length ratio of the kneading section exceeds 0.3, it is not preferable because the materials to be mixed may stagnate.

[0042] Specifically, for example, the length of the first tapered section (12a) may be 100 mm to 200 mm, preferably 120 mm to 160 mm. The length of the kneading section (12b) may be 20 mm to 40 mm, preferably 25 mm to 35 mm. If the length of the kneading section is too short, the rotation motion will deteriorate and the material to be mixed will not be able to be pumped up to the upper part. Conversely, if the length of the kneading section is too long, the material to be mixed will get stuck and stagnate.

[0043] The length of the second tapered portion (12c) may be 30 mm to 70 mm, preferably 40 mm to 60 mm, and more preferably 45 mm to 55 mm. The length of the nozzle portion (22) may be 40 mm to 80 mm, and preferably 50 mm to 70 mm.

[0044] In one embodiment of the present invention, as shown in Figure 5, the first tapered portion (12a) may be tapered to form an angle of 3 to 6 degrees, preferably 4 to 5 degrees, with the central axis of the rotating shaft (12). If the tapered angle is too large, the powder will change phase and its passage through the compression section will be delayed, causing the material to be mixed to get caught between the blades and become stagnant.

[0045] The second tapered portion (12c) may be tapered to form an angle of 15 to 22 degrees, preferably 16 to 20 degrees, with the central axis of the rotating shaft (12). If the angle formed by the second tapered portion (12c) and the central axis of the rotating shaft (12) is outside the above range, the material to be mixed (e.g., electrode active material composition) is not discharged, and fiberization is difficult to achieve.

[0046] In one embodiment of the present invention, the first helical blade (14a) and the second helical blade (14b) may be formed independently, as shown in FIG. 3, the pitch (P) of the first helical blade (14a) may be larger than the pitch of the second helical blade (14b), and the first helical blade and the second helical blade may be wound helically in the same direction around the rotation axis.

[0047] The first spiral blade 14a functions to transport and mix the material to be mixed (e.g., electrode active material composition) supplied to the hopper 24 toward the nozzle. During the mixing and transport toward the nozzle, the material to be mixed passes over the wide, inclined spiral blade surface, and the applied shear force activates the fiberization binder, thereby progressing the initial fiberization stage (pre-fibrillation).

[0048] The pitch (P) between the first helical blades 14a can be relatively large, while the pitch (P) between the second helical blades 14b can be relatively small, which is effective since kneading and high shear mixing are performed in the second helical blades 14b.

[0049] In one embodiment of the present invention, the pitch (P) of the first helical blade (14a) may be 20 mm to 60 mm, and preferably 35 mm to 50 mm.

[0050] If the pitch (P) of the first spiral blade (14a) is less than the above-mentioned range, the material to be mixed may become caught in the space between the pitches, hindering its transport, making it difficult for the material to pass over the first spiral blade, and initial fiberization may not be carried out efficiently, which is not desirable.

[0051] The pitch (P) of the second helical blade (14b) may be 8 mm to 25 mm, and preferably 10 mm to 17 mm.

[0052] If the pitch (P) of the second spiral blade (14b) is less than the above range, it is not preferable because the device may be overloaded during high shear mixing, and if it exceeds the above range, it is not preferable because the drawback of insufficient kneading may occur.

[0053] The maximum pitch (P) of the third helical blade (14c) may be 8 mm to 25 mm, preferably 10 mm to 17 mm, and the minimum pitch (P) may be 5 mm to 12 mm, preferably 6 mm to 10 mm.

[0054] The third spiral blade 14c has a pitch that gradually decreases toward the nozzle. That is, the third spiral blade 14c may have a maximum pitch at the start of the second tapered portion that contacts the kneading portion, and a minimum pitch at the tip end of the second tapered portion toward the nozzle.

[0055] When the pitch (P) of the third spiral blade (14c) satisfies the above-mentioned range, the free volume also gradually decreases as the pitch gradually decreases, which results in additional compression of the mixed material, and the mixed material passing over the third spiral blade, resulting in further increased fiberization.

[0056] Meanwhile, the pitch (P) of the fourth spiral blade (14d) provided on the outer circumferential surface of the distal shaft portion (12d) may be 30 mm to 50 mm, preferably 35 mm to 45 mm. When the pitch of the fourth spiral blade satisfies the above range, it is possible to smoothly discharge the material to be mixed and additional fiberization can also be performed, which is preferable.

[0057] In one embodiment of the present invention, it may be preferable that the acute angle (α in FIG. 3) formed between the cross section perpendicular to the central axis of the rotation shaft 12 and the helical blade 14 is larger than the acute angle of the first helical blade 14a. This is because the first helical blade 14a performs the function of mixing while transporting the material to be mixed (e.g., electrode active material composition) supplied to the hopper 24 toward the nozzle, so the acute angle of the first helical blade 14a can be formed relatively small. On the other hand, since the second helical blade 14b performs kneading and high-shear mixing, if the acute angle of the second helical blade 14b is relatively large, it can apply a large pressure to the material to be mixed, thereby enabling effective kneading and mixing.

[0058] Specifically, as shown in FIG. 3, it may be preferable that the acute angle of the second spiral blade (14b) is 1.5 to 3 times, more preferably 2 to 2.5 times, larger than the acute angle of the first spiral blade (14a).

[0059] For the same reason, the acute angle of the third spiral blade (14c) may be larger or the same as the acute angle of the second spiral blade (14b) in the adjacent portion of the second spiral blade (14b), and may be such that the acute angle becomes increasingly larger as it progresses from the adjacent portion of the second spiral blade (14b) to the portion adjacent to the tip surface of the second tapered portion.

[0060] In the present invention, the acute angle is defined as the angle formed by a line connecting two center points on the outer circumferential surface of the spiral blade (14) and a cross section perpendicular to the central axis of the rotation shaft (12), as shown in Figure 3.

[0061] Specifically, in one embodiment of the present invention, the acute angle of the first spiral blade (14a) can be formed to be 10 degrees to 40 degrees, preferably 14 degrees to 20 degrees, and the acute angle of the second spiral blade (14b) can be formed to be 30 degrees to 55 degrees, preferably 33 degrees to 41 degrees.

[0062] The acute angle of the third spiral blade 14c may be 30 to 55 degrees, preferably 35 to 45 degrees, at the portion adjacent to the second spiral blade 14b, and may be gradually increased from the portion adjacent to the second spiral blade 14b to the portion adjacent to the tip surface of the second tapered portion.Finally, the acute angle at the portion adjacent to the tip surface of the second tapered portion may be 40 to 60 degrees, preferably 45 to 55 degrees.

[0063] In the present invention, the acute angles of the helical blades 14 generally increase from the first helical blade 14a to the second helical blade 14b and the third helical blade 14c. If the acute angles were gradually reduced, clogging of the mixing unit could occur.

[0064] In particular, within the third helical blade (14c), the acute angle may gradually increase as it progresses toward the tip surface of the second tapered portion.

[0065] If the acute angle of each blade (14) does not satisfy the above range, kneading and high shear mixing will not be performed sufficiently, which is not preferable.

[0066] In addition, the fourth spiral blade (14d) may have an acute angle of 45 to 55 degrees. If the fourth spiral blade is not provided, nozzle clogging may occur, and if the acute angle is too small, nozzle clogging may occur. If the acute angle is too large, clogging may occur due to a decrease in axial motion and an increase in rotational motion, and further fiberization may be difficult to achieve.

[0067] In one embodiment of the present invention, a vertical cross section of the first spiral blade 14a in the direction of winding around the rotating shaft 12 includes two height-forming edges, as shown in FIG. 6. One edge toward the nozzle 22 forms an acute angle (β) of 30 to 80 degrees, preferably 50 to 70 degrees, and more preferably 55 to 65 degrees, with the central axis of the rotating shaft 12 in the direction away from the nozzle (see FIG. 3). Forming such an acute angle (β) is preferable because the material to be mixed (e.g., an electrode active material composition) is squeezed while passing over the edge having the acute angle (β) (leakage flow), thereby effectively achieving fiberization. However, if the acute angle (β) is formed below the above range, leakage flow does not occur, resulting in insufficient preliminary fiberization. If the angle (β) is formed beyond the above range, the material to be mixed cannot pass over the edge and is simply transported, resulting in insufficient squeezing and insufficient fiberization, as shown in FIG. 11. That is, in this case, the phenomenon occurs in which only the surface is fibrillated, which is not preferable.

[0068] Furthermore, as shown in Figure 6, one of the two height-forming sides forms an angle of 60 to 90 degrees, preferably 80 to 90 degrees, with the central axis of the rotating shaft (12) toward the nozzle. Forming such an angle is preferable because it maximizes pre-fiberization by preventing stagnation of the materials to be mixed and circulating them through leakage flow. An angle of more than 90 degrees is undesirable because it can cause the materials to be mixed (e.g., electrode active material composition) to become trapped, hindering leakage flow circulation. An angle of less than 60 degrees is undesirable because it does not generate high shear force.

[0069] Meanwhile, a vertical cross section of the first spiral blade (14a) in the direction of winding around the rotation axis (12) may include the two height-forming edges as well as one terminal edge connected to the two height-forming edges, as shown in Figure 6. The terminal edge may be formed to a length of 4mm to 10mm, preferably 5mm to 8mm. If the terminal edge is formed to be shorter than the above range, it may be difficult to effectively compress the materials to be mixed, and if it exceeds the above range, it may be undesirable because an overload may be placed on the equipment.

[0070] In one embodiment of the present invention, the vertical cross section of the second spiral blade (14b) in the direction of winding around the rotating shaft (12) includes two height-forming edges, as shown in Figure 6. One edge toward the nozzle (22) forms an acute angle (β) of 40 to 80 degrees, preferably 50 to 70 degrees, and more preferably 55 to 65 degrees, with the central axis of the rotating shaft (12) in the direction away from the nozzle. Forming such an acute angle (β) is preferable because the material to be mixed (e.g., an electrode active material composition) passes over the edge having the acute angle (β) and is squeezed, resulting in effective fiberization. However, if the acute angle (β) is less than the above range, leakage flow does not occur, which is undesirable, resulting in insufficient preliminary fiberization. If the angle (β) is greater than the above range, the material to be mixed does not pass over the edge and is simply transported, resulting in insufficient squeezing and insufficient fiberization. That is, in this case, only the surface of the material to be mixed is fiberized, which is undesirable.

[0071] The side of the nozzle 22 may be curved. In this case, the acute angle β is set based on a tangent line passing through the midpoint of the length of the curve. Specifically, the curve may have an R of 3 mm to 5 mm.

[0072] Also, one side of the nozzle (22) may be formed with a straight lower portion and a curved upper portion, as shown in Fig. 6. In this case, the acute angle (β) is set based on the angle formed by the straight portion. Specifically, the curved portion may have an R of 3 mm to 5 mm. When such an R value is formed, it is preferable because the material to be mixed can smoothly pass over the blade.

[0073] Of the two height-forming sides, one side opposite the nozzle (22) forms an angle of 60 to 90 degrees, preferably 80 to 90 degrees, with the central axis of the rotating shaft (12) toward the nozzle.

[0074] Meanwhile, when one side of the second spiral blade 14b in the direction of the nozzle 22 is formed as a straight line, a cross section perpendicular to the direction of winding around the rotation shaft 12 may further include one terminal side connected to the two height-forming sides in addition to the two height-forming sides. The terminal side may be formed to a length of 0.3 mm to 0.8 mm, preferably 0.4 mm to 0.7 mm. If the terminal side is formed to be shorter than the above range, the shear force generated on the materials to be mixed may be insufficient, and if it exceeds the above range, the thickness of the second spiral blade 14b may be too thick, which may cause clogging.

[0075] When one side in the nozzle (22) direction is formed in a curved line or a combination of a curved line and a straight line as described above, the end side can be omitted and the two sides forming the height can be directly connected as shown in FIG. 6.

[0076] In one embodiment of the present invention, a vertical cross section of the third spiral blade (14c) in the direction of winding around the rotating shaft (12) includes two height-forming edges, as shown in FIG. 6. One edge toward the nozzle (22) forms an acute angle (β) of 40 to 70 degrees, preferably 55 to 65 degrees, with the central axis of the rotating shaft (12) (see FIG. 3) in the direction away from the nozzle. Forming such an acute angle (β) is preferable because the material to be mixed (e.g., an electrode active material composition) passes over the edge having the acute angle (β) and is squeezed, resulting in effective fiberization. However, if the acute angle (β) is less than the above range, leakage flow does not occur, resulting in insufficient preliminary fiberization. If the angle (β) is greater than the above range, the material to be mixed does not pass over the edge and is simply transported, resulting in insufficient squeezing and insufficient fiberization. That is, this is undesirable because only the surface is fiberized.

[0077] When such an R value is formed, the material to be mixed can smoothly pass over the blade, which may be preferable.

[0078] One side of the nozzle 22 may be curved. In this case, the acute angle β is set based on a tangent line passing through the midpoint of the length of the curve. Specifically, the curve may have an R of 3 mm to 5 mm. When such an R value is formed, it is preferable because the material to be mixed can smoothly pass over the blade.

[0079] Also, one side of the nozzle 22 may be formed with a straight lower portion and a curved upper portion as shown in Fig. 6. In this case, the acute angle β is set based on the angle formed by the straight portion. Specifically, the curved portion may have an R of 3mm to 5mm.

[0080] Of the two height-forming sides, one side opposite the nozzle (22) forms an angle of 60 to 90 degrees, preferably 80 to 90 degrees, with the central axis of the rotating shaft (12) toward the nozzle.

[0081] Meanwhile, when one side of the third spiral blade (14c) in the direction of the nozzle (22) is formed as a straight line, a cross section perpendicular to the direction of winding around the rotation shaft (12) may further include one terminal side connected to the two height-forming sides in addition to the two height-forming sides. The terminal side may be formed to a length of 0.3 mm to 0.8 mm, preferably 0.4 mm to 0.7 mm. If the terminal side is formed to be shorter than the above range, the shear force generated on the materials to be mixed may be insufficient, and if it exceeds the above range, the thickness of the second spiral blade (14c) may be too thick, which may cause clogging.

[0082] When the side in the nozzle (22) direction is formed in a curved line or a combination of a curved line and a straight line as described above, the end side may not be formed, and the two sides forming the height may be directly connected, as shown in FIG. 6.

[0083] In one embodiment of the present invention, the vertical cross section of the fourth spiral blade (14d) relative to the direction of winding around the rotating shaft (12) includes two height-forming edges. One edge of the edge facing the nozzle (22) forms an acute angle (β) of 25 to 50 degrees, preferably 30 to 40 degrees, with the central axis of the rotating shaft (12) in the direction away from the nozzle. Forming such an acute angle (β) is preferable because the material to be mixed (e.g., an electrode active material composition) passes over the edge with the acute angle (β) and is squeezed, effectively achieving fiberization. However, if the acute angle (β) is less than the above range, leakage flow does not occur, resulting in insufficient preliminary fiberization. If the angle (β) is greater than the above range, the material to be mixed fails to pass over the edge and is simply transported, resulting in insufficient squeezing and insufficient fiberization. In other words, this is undesirable because only the surface is fiberized.

[0084] The side of the nozzle 22 may have a lower straight portion and an upper curved portion, as shown in Fig. 6. In this case, the acute angle β is set based on the angle formed by the straight portion. Specifically, the curved portion may have an R of 0.4mm to 0.6mm.

[0085] Of the two height-forming sides, one side opposite the nozzle (22) forms an angle of 60 to 90 degrees, preferably 80 to 90 degrees, with the central axis of the rotating shaft (12) toward the nozzle.

[0086] Meanwhile, in the fourth spiral blade (14d), the cross section perpendicular to the direction of winding around the rotary shaft (12) may be connected by a curve of which the R value of the two height forming sides is 0.4 mm to 0.6 mm.

[0087] In one embodiment of the present invention, the first spiral blade 14a may be provided in the form of a single spiral blade continuously wound around the outer circumferential surface of the first tapered portion 12a. In this case, the single spiral blade may be formed in a form of continuously wound around the outer circumferential surface of the first tapered portion 12a for 2 to 7 turns, preferably 3 to 5 turns. If the single spiral blade is wound around the outer circumferential surface of the first tapered portion 12a beyond the above range, the initial fiberization of the materials to be mixed may not be performed, and the pitch may be too small, causing problems such as the materials to be mixed being pinched and unable to be transported.

[0088] In one embodiment of the present invention, the second spiral blade (14b) may be provided with three or more independent blades overlapping on the outer circumferential surface of the kneading section (12b). The number of second spiral blades (14b) may vary depending on the size of the high shear mixer, but generally, it may be 3 to 10, preferably 4 to 8, and more preferably 4 to 6. Increasing the number of blades can enhance the fiberization of the fiberizable binder. However, having too many blades is undesirable because it reduces the free volume and causes stagnation due to the blades interfering with the transport of the materials to be mixed.

[0089] When three or more independent blades are provided overlapping on the outer peripheral surface of the kneading section (12b) as described above, each spiral blade can be formed to have a length of 1 / 4 to 1 turn, preferably 1 / 4 to 1 / 2 turn, and more preferably 1 / 4 to 2 / 5 turn, around the outer peripheral surface of the kneading section (12b), as shown in Figure 2. The length of the turn can be affected by the length of the kneading section (12b) and the acute angle of the blade.

[0090] When three or more independent blades are provided overlapping on the outer periphery of the kneading section 12b as described above, three or more spiral blades are wound spirally on the outer periphery of the kneading section 12b from the start point of the kneading section 12b and extend to the end point of the kneading section 12b, as shown in Figure 2. At this time, it may be preferable to form a regular interval between each blade.

[0091] In one embodiment of the present invention, the second helical blade (14b) and the third helical blade (14c) may be helically wound in the same direction around the rotation shaft (12).

[0092] In one embodiment of the present invention, the third spiral blade (14c) may be three or more independent blades arranged to overlap on the outer circumferential surface of the second tapered portion (12c). The number of third spiral blades (14c) may vary depending on the size of the high shear mixer, but generally, 3 to 10 blades, preferably 4 to 8, and more preferably 4 to 6 blades may be provided. Increasing the number of blades can enhance the fiberization of the fiberizable binder. However, using too many blades is undesirable because it reduces the free volume and causes stagnation due to the impediment to the transport of the materials to be mixed.

[0093] When three or more independent blades are provided overlapping on the outer peripheral surface of the second tapered portion 12c as described above, each spiral blade may be formed to have a length of 1 / 4 to 1 turn, preferably 2 / 5 to 3 / 5 turns, around the outer peripheral surface of the second tapered portion 12c, as shown in Figure 2. The length of the turn may be affected by the length of the second tapered portion 12c and the acute angle of the blade.

[0094] When three or more independent blades are arranged overlappingly around the outer periphery of the second tapered portion 12c, as shown in FIG. 2, three or more spiral blades are wound spirally around the outer periphery of the second tapered portion 12c from the start point of the second tapered portion 12c and extend to the end point of the second tapered portion 12c. In this case, it is preferable to form a constant spacing between each blade. However, because the end point of the second tapered portion 12c has a narrow cross section as the taper end, the three or more spiral blades can be formed with gradually narrower spacing as they approach the end point. This gradually narrowing spacing reduces the pitch and free volume, resulting in increased fiberization as the mixed material attempts to leave the channel for additional squeezing and mixing. This allows for more effective high-shear mixing.

[0095] In one embodiment of the present invention, the second helical blade (14b) and the third helical blade (14c) may be provided independently of each other, as shown in FIG.

[0096] In one embodiment of the present invention, the second spiral blade (14b) may be extended to the outer peripheral surface of the second tapered portion (12c) to form a third spiral blade (14c), as shown in FIG.

[0097] In one embodiment of the present invention, a separation portion may be provided between the second spiral blade (14b) and the third spiral blade (14c), as shown in Fig. 2, between the end of the kneading portion (12b) and the front end of the second tapered portion (12c) of the rotating shaft (12). When a separation portion is provided in this manner, materials to be mixed can move through the separation portion, thereby reducing the torque applied to the second tapered portion.

[0098] In one embodiment of the present invention, the three or more independent blades provided on the second tapered portion 12c may be formed up to the outer periphery of the tip surface of the second tapered portion 12c facing the nozzle 22. When the blades are formed up to the outer periphery of the tip surface of the second tapered portion 12c facing the nozzle 22, kneading and high shear mixing are performed more effectively, and the materials to be mixed can be more easily transferred to the nozzle 22, which is preferable.

[0099] In one embodiment of the present invention, the diameter of the tip end surface of the second tapered portion (12c) of the rotating shaft (12) facing the nozzle (22) may be 0.5 to 1 times the inner diameter of the nozzle. Also, the maximum diameter of the second tapered portion (12c) may be 2.1 to 7.1 times, preferably 3.1 to 5.1 times the inner diameter of the nozzle.

[0100] In one embodiment of the present invention, the maximum diameter of the first tapered portion (12a) of the rotating shaft (12) may be 2 to 7 times, preferably 3 to 5 times, the inner diameter of the nozzle, and the minimum diameter may be 1 to 4 times, preferably 1.5 to 2.5 times.

[0101] In one embodiment of the present invention, the maximum diameter of the kneading section (12b) of the rotating shaft (12) may be 2.1 to 7.1 times, preferably 3.1 to 5.1 times, the inner diameter of the nozzle, and the minimum diameter may be 2 to 7 times, preferably 3 to 5 times. In this case, when the outer diameter of the kneading section (12b) is formed uniformly, it can be formed within the above-mentioned range of the minimum diameter.

[0102] In one embodiment of the present invention, the height of the first blade 14a protruding from the outer circumferential surface of the first tapered portion 12a may be 10 mm to 20 mm, preferably 13 mm to 18 mm. The outer circumferential portion of the first blade 14a may be spaced from the inner surface of the housing by a distance of 0.2 mm to 3 mm, preferably 0.3 mm to 0.7 mm.

[0103] In one embodiment of the present invention, the height of the second blade (14b) protruding from the outer circumferential surface of the kneading section (12b) may be 1 mm to 5 mm, preferably 2 mm to 4 mm. The outer circumferential portion of the second blade (14b) may be spaced from the inner surface of the housing by a distance of 0.2 mm to 3 mm, preferably 0.3 mm to 0.7 mm.

[0104] In one embodiment of the present invention, the height of the third blade (14c) protruding from the outer peripheral surface of the second tapered portion (12c) may be 1 mm to 5 mm, preferably 2 mm to 3.5 mm. The outer peripheral portion of the third blade (14c) may be spaced from the inner surface of the housing by a distance of 0.3 mm to 3 mm, preferably 0.5 mm to 1.1 mm.

[0105] In one embodiment of the present invention, the height of the fourth blade 14d protruding from the outer circumferential surface of the tip shaft 12d may be 0.5 mm to 3 mm, preferably 0.7 mm to 1.3 mm. The outer circumferential portion of the fourth blade 14d may be spaced from the inner surface of the housing by a distance of 0.8 mm to 3 mm, preferably 1 mm to 2 mm.

[0106] In the above, if the distance between each blade and the inner surface of the housing is too small, the materials to be mixed cannot be squeezed while passing through, making it difficult to perform fiberization effectively. That is, there is a possibility that only the surface will be fiberized. On the other hand, if the distance is too large, it is undesirable because the squeezing efficiency will decrease.

[0107] In one embodiment of the present invention, the rotating shaft 12 may further include a front shaft portion 12d extending from the front end of the second tapered portion 12c toward the nozzle 22 into the nozzle, as shown in Figure 1. The rotating shaft 12 may also further include a rear shaft portion 12e extending from the end surface of the first tapered portion 12a opposite the nozzle.

[0108] At least one of the front shaft portion 12d and the rear shaft portion 12e may be connected to a driving unit to transmit power to the mixing screw.

[0109] In one embodiment of the present invention, the inner surface of the housing may have a roughness (roughness) of 3 μm to 30 μm, preferably 5 μm to 15 μm. When the roughness is formed in the above range, it is preferable because the transfer efficiency and fiberization efficiency of the material to be mixed can be improved.

[0110] In one embodiment of the present invention, the rotating shaft (12) may comprise, in succession, a first tapered section (12a) whose outer diameter gradually increases toward the nozzle, a kneading section (12b) whose outer diameter is maintained at the same level or gradually increases from the maximum outer diameter of the first tapered section, and a second tapered section (12c) whose outer diameter gradually decreases from the end of the kneading section (12b).

[0111] In one embodiment of the present invention, the space between the outer peripheral surface of the first tapered portion (12a) of the rotating shaft and the housing (20) gradually decreases toward the nozzle (22), the space between the outer peripheral surface of the kneading portion (12b) and the housing (20) gradually decreases toward the nozzle or is maintained uniform, and the space between the second tapered portion (12c) and the housing (20) may be maintained uniform or gradually decreases.

[0112] In the above, it may be more preferable that the space between the outer peripheral surface of the kneading portion 12b and the housing 20 is maintained uniform as it goes toward the nozzle, and it may be more preferable that the space between the second tapered portion 12c and the housing 20 is maintained uniform.

[0113] In one embodiment of the present invention, the high shear mixer (500) effectively disperses the materials to be mixed and effectively fiberizes a fiberizable polymer, such as PTFE, contained in the materials. Furthermore, the fiberization process of a fiberizable polymer, such as PTFE, does not place a heavy load on the mixer. Therefore, the high shear mixer of the present invention having the above-described structure can be preferably used for high shear mixing in the manufacture of dry electrodes for secondary batteries, enabling the construction of large-capacity mass production equipment.

[0114] In particular, when a dry freestanding electrode is manufactured by high-shear mixing a mixture containing an active material, a conductive material, and a fiberizable binder such as PTFE, and rolling the mixture, the tensile strength of the freestanding electrode is significantly improved, and such a dry freestanding electrode provides the effect of significantly improving the lifespan of a secondary battery.

[0115] In one embodiment of the present invention, the high shear mixer (500) may further include a drive unit (200) for providing power to the rotating shaft (12) in addition to the above-described components, as shown in Figure 1, and may further include, without limitation, components that are applicable to known high shear mixers among components not mentioned above. The known components are obvious to those skilled in the art, so a description thereof will be omitted.

[0116] In addition, the high shear mixer (500) of the present invention may further include a film forming device (300) installed in association with the nozzle (22), as shown in Figure 1. The film forming device (300) is not particularly limited, and may be, for example, a device including a pair of squeeze rollers.

[0117] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the examples detailed below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0118] Example 1: Production of free-standing film using a high-shear mixer and evaluation of its physical properties (1) Freestanding film manufacturing A primary mixture for a freestanding electrode was prepared by mixing 95.5 wt % or 97 wt % NCM powder (product name: GL80, LG Chem), which is a positive electrode active material particle with an average particle size of 10 μm, 1.5 wt % Li250 (Denka) as a conductive material, and 1.5 wt % or 3 wt % PTFE as a binder.

[0119] The high shear mixer of the present invention (including the mixer screw of FIG. 5) and the conventional mixer were operated under the conditions shown in Table 1 to prepare a dough-like secondary mixture.

[0120] The dough-like secondary mixture was roll-pressed at 100° C. using a two-roll mill (MR-3, Inoue Co.) to produce a free-standing film with a thickness of 200 μm.

[0121] Test Example 1: Evaluation of free-standing film properties (1) Thickness deviation measurement The thickness of the freestanding films prepared in the Examples and Comparative Examples was measured using an electrode thickness measuring device, Millimar (manufactured by Mahr). The freestanding films were punched out in the MD direction to a size of 6 cm wide and 6 cm long, and the thickness was measured at a total of 25 points spaced 1 cm apart. The measurements were performed on four freestanding film samples each, and the thickness deviation for each sample was calculated. The average thickness deviation is shown in Table 1 below.

[0122] (2) Tensile strength measurement The freestanding films prepared in the examples and comparative examples were cut into samples of 20 mm width and 20 mm length, and the tensile strength was measured at 50 mm / min using a 180° peel test method using a LLOYD UTM device. The maximum force applied until the film did not break during the test was evaluated as the strength of the freestanding film, and the measurement results are shown in Table 1 below.

[0123] (3) Battery life characteristics evaluation 1. Lithium secondary battery manufacturing The free-standing films prepared in the Examples and Comparative Examples were placed on one side of a 20 μm-thick primer-coated aluminum foil (manufactured by Dongwon Systems) current collector, and bonded using a lamination roll maintained at 120° C. to prepare positive electrodes.

[0124] A coin-type half cell was fabricated using the prepared cathode, lithium metal as a counter electrode, and an electrolyte containing 1M LiPF6 in a solvent of EC:DMC:DEC (volume ratio 1:2:1).

[0125] 2. Capacity retention evaluation of lithium secondary batteries The prepared coin-type half battery was charged and discharged 100 times at 25°C under the conditions of a voltage range of 3 to 4.3 V and a current rate of 0.33 C, and then the discharge capacity retention rate of 100 times relative to the discharge capacity of one time was calculated. The results are shown in Table 1 below.

[0126] [Table 1]

[0127] Although the present invention has been described in connection with the preferred embodiment above, various modifications and variations can be made without departing from the spirit and scope of the invention, and it is therefore intended by the appended claims to cover all such modifications and variations as fall within the spirit and scope of the invention. [Explanation of symbols]

[0128] 10: Mixing screw 12: Rotating shaft 12a: First tapered section 12b: Kneading section 12c: Second tapered section 12d: Tip shaft 12e: Rear shaft 14: Blade 14a: First spiral blade 14b: Second spiral blade 14c: Third spiral blade 14d: Fourth spiral blade 20: Housing 22: Nozzle 24: Hopper 100: High shear mixing unit 200: Driving unit 300: Film forming device 500: High shear mixing equipment

Claims

1. a high shear mixing unit including a mixing screw and a housing containing said mixing screw; the housing includes a nozzle at a tip end and a hopper in communication with the interior; The mixing screw includes a rotating shaft and a blade provided on the outer circumferential surface of the rotating shaft, the rotating shaft includes, in this order, a first tapered section whose outer diameter gradually increases toward the nozzle, a kneading section whose outer diameter is maintained constant or gradually increases toward the nozzle, and a second tapered section whose outer diameter gradually decreases toward the nozzle, The blades include a first spiral blade arranged on the outer peripheral surface of the first tapered portion, a second spiral blade arranged on the outer peripheral surface of the kneading portion, and a third spiral blade arranged on the outer peripheral surface of the second tapered portion, the pitch of the first helical blade is greater than the pitch of the second helical blade; a high shear mixer, wherein the acute angle of the second helical blade is larger than the acute angle of the first helical blade, based on the acute angle formed by the helical blade and a cross section perpendicular to the central axis of the rotation shaft;

2. 2. The high shear mixing device according to claim 1, wherein the first helical blade and the second helical blade are formed independently, and the first helical blade and the second helical blade are wound helically in the same direction around the rotation axis.

3. 3. The high shear mixer according to claim 2, wherein the second spiral blade comprises three or more independent blades that are overlapped on the outer circumferential surface of the kneading section.

4. 4. The high shear mixer according to claim 3, wherein the second and third helical blades are wound helically in the same direction around the rotation axis.

5. 5. The high shear mixer according to claim 4, wherein the third spiral blade comprises three or more independent blades that are overlapped on the outer circumferential surface of the second tapered portion.

6. 6. The high shear mixer according to claim 5, wherein the second spiral blade and the third spiral blade are provided independently of each other.

7. 6. The high shear mixer of claim 5, wherein the second helical blade extends to the outer periphery of the second tapered section to form a third helical blade.

8. 8. The high shear mixer according to claim 7, wherein a separation section is located between the second spiral blade and the third spiral blade, the separation section being located between the end of the kneading section of the rotating shaft and the tip of the second tapered section.

9. 6. The high shear mixer according to claim 5, wherein the three or more independent blades provided on the second tapered portion are formed up to an outer periphery of a tip surface of the second tapered portion in a nozzle direction.

10. 10. The high shear mixer according to claim 9, wherein the diameter of the tip end surface of the second tapered portion of the rotating shaft facing the nozzle is 0.5 to 2 times the inner diameter of the nozzle.

11. 2. The high shear mixer of claim 1, wherein the rotating shaft comprises a first tapered section whose outer diameter gradually increases toward the nozzle, a kneading section whose outer diameter gradually increases or remains constant from a maximum outer diameter of the first tapered section, and a second tapered section whose outer diameter gradually decreases from an end of the kneading section.

12. 2. The high shear mixer of claim 1, wherein the space between the outer circumferential surface of the first tapered section of the rotating shaft and the housing gradually decreases toward the nozzle, the space between the outer circumferential surface of the kneading section and the housing gradually decreases or is uniformly maintained toward the nozzle, and the space between the second tapered section and the housing is uniformly maintained or gradually decreases.

13. 2. The high shear mixer according to claim 1, wherein the ratio of the length of the first tapered section, the length of the kneading section, and the length of the second tapered section in the rotating shaft is 1:0.1-0.3:0.2-0.

45.

14. 6. The high shear mixer of claim 5, wherein the acute angle of the second helical blade is equal to or smaller than the acute angle of the third helical blade, based on the acute angle formed by the helical blade and a cross section perpendicular to the central axis of the rotation shaft.

15. 6. The high shear mixer according to claim 5, wherein the third spiral blade has a maximum pitch at a starting point of the second tapered section contacting the kneading section, a minimum pitch at a tip end surface of the second tapered section facing the nozzle, and the pitch gradually decreases toward the nozzle.

16. 6. The high shear mixer of claim 5, wherein a cross section of the first spiral blade perpendicular to a direction of winding around the rotation shaft includes two height-forming sides, and one of the height-forming sides in the nozzle direction forms an acute angle of 30 degrees to 80 degrees with the central axis of the rotation shaft in a direction away from the nozzle.

17. 17. The high shear mixer of claim 16, wherein a cross section of the second spiral blade perpendicular to a direction of winding around the rotation shaft includes two height-forming sides, and one of the height-forming sides in the nozzle direction forms an acute angle of 40 degrees to 80 degrees with the central axis of the rotation shaft in a direction away from the nozzle.

18. 18. The high shear mixer of claim 17, wherein a cross section of the third spiral blade perpendicular to a direction of winding around the rotation shaft includes two height-forming sides, and one of the height-forming sides in the nozzle direction forms an acute angle of 40 degrees to 80 degrees with the central axis of the rotation shaft in a direction away from the nozzle.

19. 2. The high shear mixing device according to claim 1, characterized in that it is used for high shear mixing of a mixture for manufacturing a dry electrode containing a fiberizable polymer as a binder, and for microfibrillating the fiberizable polymer.

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