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 dated September 26, 2022, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

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

[0003] The agitator is used to finely mix various paste manufacturing equipment and chemical raw materials, such as ink, pigment, paint, cosmetics, medicine, and paint, with various coating agents, abrasives, ceramic or metal powder, or various electronic materials (PZT, dielectric, MLCC, Ferrite, display materials), etc. As the agitator, a planetary mixer or twin screw extruder that uses blades and rotors to agitate a high-viscosity material in a container is used as equipment for agitating a high-viscosity material.

[0004] Meanwhile, with the expansion and development of applications of secondary batteries, there is a continuous demand for improvements in electrodes, such as lower resistance, higher capacity, improved mechanical properties, and improved productivity, and this has led to an increased need for high shear mixing for mixtures used in electrode production. Specifically, a technology for producing a dry electrode film 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 roll, has been actively developed, and high shear mixing is applied to the production 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 the 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, which places a heavy load on the planetary mixer or twin screw extruder, often resulting in damage to the equipment. In order to prevent such damage to the equipment, methods for reducing the shear force have been considered, but in this case, the fiberizable polymer is not successfully fiberized. Therefore, it is very 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 capable of efficiently microfibrillating a polymer without generating an overload during high shear mixing of a mixture for manufacturing a dry electrode, which mixture 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 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 in the direction toward the nozzle, a kneading section whose outer diameter is maintained constant or gradually increases in the direction toward the nozzle, and a second tapered section whose outer diameter gradually decreases in the direction toward the nozzle, The blade provides a high shear mixer including a first helical blade arranged on the outer peripheral surface of the first tapered section, a second helical blade arranged on the outer peripheral surface of the kneading section, and a third helical 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 are formed independently, the pitch of the first helical blade is greater 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 axis of rotation.

[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 helical blade, the acute angle of the second helical blade may be formed to be larger than the acute angle of the first helical blade.

[0014] In one embodiment of the present invention, the second helical blade may be three or more independent blades provided so as to overlap with each other 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 helically wound in the same direction on the rotation axis.

[0016] In one embodiment of the present invention, the third spiral blade may be provided such that three or more independent blades 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 helical blade may extend to an outer circumferential surface of the second tapered portion to form a third helical blade.

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

[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 an outer periphery of a 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 times, 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 successively include a first tapered section whose outer diameter gradually increases in the direction of 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 peripheral surface of the first tapered portion of the rotating shaft and the housing gradually decreases as it moves toward the nozzle, the space between the outer peripheral surface of the kneading portion and the housing gradually decreases or is maintained uniformly as it moves toward the nozzle, and the space between the second tapered portion and the housing may be maintained uniformly or gradually decreases.

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

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

[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 in the nozzle direction, and the pitch may gradually decrease as it moves 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 the nozzle.

[0028] In one embodiment of the present invention, a vertical cross section of the second 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 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 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 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.

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

[0031] The high shear mixer of the present invention provides an effect of efficiently mixing materials without overloading when mixing materials with high shear force, and also has a feature that the device can be configured with a large capacity because damage to the device is minimized due to this effect.

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

[0033] [Figure 1] FIG. 1 is a schematic diagram showing one embodiment of a high shear mixer of the present invention. [Diagram 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. [Diagram 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. [Diagram 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] FIG. 2 is a schematic diagram showing 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] FIG. 2 is a diagram showing the shape and material source of each partial blade provided in the high shear mixing device of the present invention. [Figure 8] 3 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 a conventional polymer mixing application and the state of use thereof. [Figure 11] FIG. 2 is a schematic diagram showing the mixing mechanism according to the first helical blade configuration provided in the high shear mixer of the present invention and the conventional high shear mixer. [Figure 12] FIG. 2 is a schematic diagram showing the configuration of a third spiral blade provided in the high shear mixer of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in many 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 FIG. 1 and FIG. 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 the interior thereof, The mixing screw (10) includes a rotating shaft (12) and a blade (14) provided on the outer circumferential surface of the rotating shaft, the rotating shaft (12) includes, in this order, a first taper section (12a) whose outer diameter gradually increases in a direction toward the nozzle (22), a kneading section (12b) whose outer diameter is maintained constant or gradually increases in the direction toward the nozzle, and a second taper section (12c) whose outer diameter gradually decreases in the direction toward the nozzle; The blade (14) is characterized by including a first helical blade (14a) arranged on the outer circumferential surface of the first tapered portion (12a), a second helical blade (14b) arranged on the outer circumferential surface of the kneading portion (12b), and a third helical blade (14c) arranged on the outer circumferential surface of the second tapered portion (12c).

[0037] The high shear mixer (500) of the present invention has a simple structure of a single screw, and therefore has the advantages of being inexpensive to manufacture, easy to manage in the process, and easy to maintain. In addition, it has the advantage of having more stable drive characteristics than a twin screw.

[0038] In particular, the high shear mixer (500) of the present invention includes an improved mixing screw (10) that 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 taper portion (12a), the length of the kneading portion (12b), and the length of the second taper portion (12c) in 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, the dispersibility of the materials to be mixed and the high shear mixing efficiency are increased, which is preferable.

[0041] In particular, when 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 taper 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 material to be mixed cannot be pumped up to the upper part due to deterioration of the rotation motion, and conversely, if it is too long, the material to be mixed gets stuck and stagnates.

[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, the first tapered portion (12a) may be tapered to form an angle of 3 degrees to 6 degrees, preferably 4 degrees to 5 degrees, with the central axis of the rotating shaft (12), as shown in Fig. 5. If the tapered angle is too large, the powder will undergo a phase change and its passage through the squeezing section will be delayed, causing the material to be mixed to get caught between the blades and stagnate.

[0045] In addition, the second tapered portion (12c) may be tapered to form an angle of 15 degrees to 22 degrees, preferably 16 degrees to 20 degrees, with the central axis of the rotating shaft (12). If the angle between 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, making it difficult to perform fiberization appropriately.

[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 greater 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 (e.g., electrode active material composition) supplied to the hopper 24 toward the nozzle. During mixing and transporting toward the nozzle, the material passes over the wide inclined spiral blade surface, and the fiberization binder begins to be activated by the applied shear force, thereby proceeding with the initial fiberization stage (pre-fibrillation).

[0048] The pitch (P) between the first helical blades (14a) can be relatively large, whereas 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 from 20 mm to 60 mm, and preferably from 35 mm to 50 mm.

[0050] If the pitch (P) of the first spiral blade (14a) is less than the aforementioned range, the materials to be mixed may get caught in the space between the pitches, hindering their transport, making it difficult for the materials to get over the first spiral blade, and initial fiberization may not be carried out efficiently, which is undesirable.

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

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

[0053] The maximum pitch (P) of the third helical blade (14c) may be from 8 mm to 25 mm, preferably from 10 mm to 17 mm, and the minimum pitch (P) may be from 5 mm to 12 mm, preferably from 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) is formed to have a maximum pitch at the start point of the second tapered portion that contacts the kneading portion, and the third spiral blade (14c) may have a minimum pitch at the tip surface of the second tapered portion in the nozzle direction.

[0055] When the pitch (P) of the third spiral blade (14c) satisfies the above-mentioned range, as the pitch gradually decreases, the free volume also gradually decreases, thereby providing additional compression to the mixed material, and as the mixed material passes over the third spiral blade, the fiberization is further increased.

[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-mentioned range, it is preferable because the mixed material can be discharged smoothly and additional fiberization can be performed.

[0057] In one embodiment of the present invention, based on the acute angle (α in FIG. 3) formed by the cross section perpendicular to the central axis of the rotating shaft (12) and the helical blade (14), it may be preferable that the acute angle of the second helical blade (14b) is larger than the acute angle of the first helical blade (14a). Since the first helical blade (14a) functions to mix the material to be mixed (e.g., electrode active material composition) supplied to the hopper (24) while transporting it toward the nozzle, the acute angle of the first helical blade (14a) may be formed relatively small. Meanwhile, 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, a large pressure can be applied to the material to be mixed, thereby enabling effective kneading and mixing.

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

[0059] For the same reason, the acute angle of the third helical blade (14c) may be greater than or equal to the acute angle of the second helical blade (14b) at the adjacent portion of the second helical blade (14b), and may be such that the acute angle becomes increasingly greater as it progresses from the adjacent portion of the second helical 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 straight line connecting two center points of 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 degrees to 55 degrees, preferably 35 degrees to 45 degrees, at the portion adjacent to the second spiral blade (14b), and may be in a form in which the acute angle becomes larger as it progresses 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 may be 40 degrees to 60 degrees, preferably 45 degrees to 55 degrees, at the portion adjacent to the tip surface of the second tapered portion.

[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 to 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 one progresses toward the tip surface of the second tapered portion.

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

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

[0067] In one embodiment of the present invention, the vertical cross section of the first spiral blade (14a) with respect to the direction of winding around the rotating shaft (12) includes two height forming sides as shown in FIG. 6. At this time, one side in the direction of the nozzle (22) forms an acute angle (β) of 30 degrees to 80 degrees, preferably 50 degrees to 70 degrees, more preferably 55 degrees to 65 degrees with the central axis of the rotating shaft (12) in the direction opposite to the nozzle (see FIG. 3). When such an acute angle (β) is formed, it is preferable because the mixed material (e.g., electrode active material composition) is squeezed while passing over the side having the acute angle (β) (leakage flow), and fiberization is effectively performed. However, when the acute angle (β) is formed below the above range, there is a drawback that leakage flow does not occur and sufficient preliminary fiberization does not occur, and when it is formed beyond the above range, as shown in FIG. 11, the mixed material does not pass over the side and is simply transported, and squeezing is not performed sufficiently, and fiberization is not performed smoothly. That is, in this case, a phenomenon occurs in which only the surface is fibrillated, which is not preferable.

[0068] In addition, one of the two height forming sides opposite the nozzle (22) forms an angle of 60 degrees to 90 degrees, preferably 80 degrees to 90 degrees, with the central axis of the rotating shaft (12) in the direction of the nozzle, as shown in Fig. 6. When the above angle is formed, the mixture is not stagnated, and the preliminary fiberization is maximized by circulation due to leakage flow, which is preferable. When the angle exceeds 90 degrees, the mixture (e.g., electrode active material composition) may be pinched, which is not preferable because leakage flow circulation is hindered, and when the angle is formed less than 60 degrees, high shear force is not generated, which is not preferable.

[0069] Meanwhile, the vertical cross section of the first spiral blade (14a) with respect to the direction of winding around the rotation shaft (12) may further include one end edge connected to the two height forming edges, in addition to the two height forming edges, as shown in Fig. 6. The end edge may be formed to a length of 4mm to 10mm, preferably 5mm to 8mm. If the end edge is formed to be less than the above range, it is difficult to effectively squeeze the materials to be mixed, and if it exceeds the above range, it is not preferable since the equipment is overloaded.

[0070] In one embodiment of the present invention, the vertical cross section of the second spiral blade (14b) with respect to the direction of winding around the rotating shaft (12) includes two height forming sides as shown in FIG. 6. At this time, one side in the direction of the nozzle (22) forms an acute angle (β) of 40 degrees to 80 degrees, preferably 50 degrees to 70 degrees, more preferably 55 degrees to 65 degrees, with the central axis of the rotating shaft (12) in the direction opposite to the nozzle. When such an acute angle (β) is formed, the mixture (e.g., electrode active material composition) is squeezed while passing over the side having the acute angle (β), which is preferable because fiberization is effectively performed. However, when the acute angle (β) is formed below the above range, leakage flow does not occur, which is not preferable because sufficient preliminary fiberization does not occur, and when it is formed beyond the above range, the mixture does not pass over the side, is simply transported, and is not squeezed sufficiently, which prevents smooth fiberization. That is, in this case, a phenomenon occurs in which only the surface is fiberized, which is not preferable.

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

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

[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 vertical cross section with respect to the direction of winding around the rotating shaft (12) may further include one end side connected to the two height forming sides in addition to the two height forming sides. The end side may be formed to a length of 0.3mm to 0.8mm, preferably 0.4mm to 0.7mm. If the end side is formed below 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 become too thick, which may cause clogging.

[0075] When one side in the nozzle (22) direction is formed as a curve or a combination of a curve 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.

[0076] In one embodiment of the present invention, the vertical cross section of the third spiral blade (14c) with respect to the direction of winding around the rotating shaft (12) includes two height forming sides as shown in FIG. 6. At this time, one side in the direction of the nozzle (22) forms an acute angle (β) of 40 degrees to 70 degrees, preferably 55 degrees to 65 degrees, with the central axis of the rotating shaft (12) (see FIG. 3) in the direction opposite to the nozzle. When such an acute angle (β) is formed, the mixture (e.g., electrode active material composition) is squeezed while passing over the side having the acute angle (β), which is preferable because fiberization is effectively performed. However, when the acute angle (β) is formed below the above range, leakage flow does not occur, and sufficient preliminary fiberization is not performed, and when it is formed beyond the above range, the mixture does not pass over the side and is simply transported, and squeezing is not performed sufficiently, so fiberization is not performed smoothly. That is, in this case, a phenomenon occurs in which only the surface is fiberized, which is not preferable.

[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 in the nozzle (22) direction 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 may be 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 lower part formed in a straight line and an upper part formed in a curved line, as shown in Fig. 6. In this case, the acute angle (β) is set based on the angle formed by the straight line part. Specifically, the curved part may have an R of 3mm to 5mm.

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

[0081] Meanwhile, in the case where one side of the third spiral blade (14c) in the direction of the nozzle (22) is formed as a straight line, the vertical cross section with respect to the direction of winding around the rotating 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 0.3mm to 0.8mm, preferably 0.4mm to 0.7mm. If the terminal side is formed below the above range, the generation of shear force 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 become too thick, which may cause clogging.

[0082] When the side in the nozzle (22) direction is formed as a curve or a combination of a curve 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) with respect to the direction of winding around the rotating shaft (12) includes two height forming sides. At this time, one side in the direction of the nozzle (22) forms an acute angle (β) of 25 degrees to 50 degrees, preferably 30 degrees to 40 degrees, with the central axis of the rotating shaft (12) in the direction opposite to the nozzle. When such an acute angle (β) is formed, it is preferable because the mixed material (e.g., electrode active material composition) is squeezed while passing over the side having the acute angle (β), and fiberization is effectively performed. However, when the acute angle (β) is formed below the above range, there is a drawback that leakage flow does not occur and sufficient preliminary fiberization does not occur, and when it is formed beyond the above range, the mixed material does not pass over the side and is simply transported, and squeezing is not performed sufficiently, and fiberization is not performed smoothly. That is, in this case, it is not preferable because a phenomenon occurs in which only the surface is fiberized.

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

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

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

[0087] In one embodiment of the present invention, the first helical blade (14a) may be provided in a form in which one helical blade is continuously wound around the outer circumferential surface of the first tapered portion (12a). At this time, the one helical blade may be formed in a form in which it is continuously wound around the outer circumferential surface of the first tapered portion (12a) 2 to 7 times, preferably 3 to 5 times. If the one helical blade is wound around the outer circumferential surface of the first tapered portion (12a) beyond the above range, there is a possibility that the initial fiberization of the mixed materials is not performed, and the pitch is too fine, so that the mixed materials are pinched and cannot 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 the second spiral blades (14b) may vary depending on the size of the high shear mixer, but generally, 3 to 10 blades may be provided, preferably 4 to 8 blades, and more preferably 4 to 6 blades. When the number of blades is increased, the effect of increasing the fiberization of the fiberizable binder can be obtained. However, when the number of blades is too large, it is not preferable because the blades reduce the free volume and cause stagnation due to the transport obstruction of the mixed material.

[0089] When three or more independent blades are provided so as to overlap 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 Fig. 2. The length of the turn can be influenced by the length of the kneading section (12b) and the acute angle of the blade.

[0090] When three or more independent blades are provided so as to overlap on the outer circumferential surface of the kneading section (12b) as described above, three or more spiral blades are wound in a spiral shape on the outer circumferential surface of the kneading section (12b) from the start point of the kneading section (12b) and are extended to the end point of the kneading section (12b) as shown in Fig. 2. At this time, it may be preferable that each blade forms a certain interval.

[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 on the rotating shaft (12).

[0092] In one embodiment of the present invention, the third spiral blade (14c) may be three or more independent blades that are provided to overlap the outer circumferential surface of the second tapered portion (12c). The number of the third spiral blades (14c) may vary depending on the size of the high shear mixer, but generally, 3 to 10 blades may be provided, preferably 4 to 8 blades, and more preferably 4 to 6 blades. When the number of blades is increased, the effect of increasing the fiberization of the fiberizable binder can be obtained. However, when the number of blades is too large, it is not preferable because the blades reduce the free volume and cause stagnation due to the transport obstruction of the mixed material.

[0093] When three or more independent blades are provided so as to overlap the outer peripheral surface of the second tapered portion (12c) as described above, each spiral blade may be formed to have a length that wraps around the outer peripheral surface of the second tapered portion (12c) 1 / 4 to 1 turn, preferably 2 / 5 to 3 / 5 turns, as shown in Figure 2. The wrapping length 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 provided to overlap the outer circumferential surface of the second tapered portion (12c) as described above, as shown in FIG. 2, three or more spiral blades are wound in a spiral shape from the start point of the second tapered portion (12c) to the end point of the second tapered portion (12c), and are extended and wound to the end point of the second tapered portion (12c). At this time, it may be preferable that each blade is spaced apart from the other blades. However, since the end point of the second tapered portion (12c) is a taper end portion and has a narrow cross section, the three or more spiral blades may be formed so that the spacing between them gradually decreases as they approach the end point. When the spacing gradually decreases, the pitch and free volume are reduced, which results in an effect of increasing fiberization as the additional compression and mixed materials try to leave the channel. That is, high shear mixing can be performed more effectively.

[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 helical blade (14b) may be extended to the outer circumferential surface of the second tapered portion (12c) to form a third helical blade (14c) as shown in FIG.

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

[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) in the direction of the nozzle (22). In this manner, when the blades are formed up to the outer periphery of the tip surface of the second tapered portion (12c) in the direction of 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 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. In addition, 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) in 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 portion (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 circumferential surface of the second tapered portion (12c) may be 1 mm to 5 mm, preferably 2 mm to 3.5 mm. The outer circumferential 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 mixed materials cannot be squeezed while passing through, making it difficult to effectively fiberize the materials. That is, there is a possibility that only the surface is fiberized. On the other hand, if the distance is too large, the efficiency of squeezing the materials decreases, which is not preferable.

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

[0108] At least one of the front shaft portion 12d and the rear shaft portion 12e may be connected to a driving portion and may function 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 transport efficiency and fiberization efficiency of the mixed material can be improved.

[0110] In one embodiment of the present invention, the rotating shaft (12) may include a first tapered section (12a) whose outer diameter gradually increases toward the nozzle, a kneading section (12b) whose outer diameter gradually increases or remains the same 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 or is maintained uniformly toward the nozzle, and the space between the second tapered portion (12c) and the housing (20) may be maintained uniformly or gradually decreases.

[0112] In the above, it may be more preferable that the space between the outer circumferential surface of the kneading portion (12b) and the housing (20) is maintained uniform in the direction 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 performs fiberization of a fiberizable polymer such as PTFE contained in the materials to be mixed. In addition, the fiberization process of a fiberizable polymer such as PTFE does not place a large load on the device. Therefore, the high shear mixer of the present invention having the above-mentioned structure can be preferably used for high shear mixing for manufacturing dry electrodes for secondary batteries, and makes it possible to construct a large-capacity mass production equipment.

[0114] In particular, when a mixture containing an active material, a conductive material, and a fiberizable binder such as PTFE is mixed under high shear and the mixture is rolled to produce a dry freestanding electrode, the tensile strength of the freestanding electrode is significantly improved, and such a dry freestanding electrode provides the effect of significantly improving the life 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-mentioned components as shown in Fig. 1, and may further include, without limitation, components that are applicable to known high shear mixers among the components not mentioned above. The above-mentioned known components are obvious to those of ordinary skill in the art, so the 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 in order to specifically explain the present invention. 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 having average knowledge in the art.

[0118] Example 1: Production of free-standing film using high shear mixer and evaluation of 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 produce 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: Freestanding Film Characterization (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), and the freestanding films were punched out to a size of 6 cm in width and 6 cm in length in the MD direction, and the thickness was measured at a total of 25 points spaced at a distance of 1 cm. The measurement was performed on four freestanding film samples each, and the thickness deviation was calculated for each sample, and the average thickness deviation was shown in Table 1 below.

[0122] (2) Tensile strength measurement The freestanding films prepared in the examples and comparative examples were cut into samples with a width of 20 mm and a length of 20 mm, and the tensile strength was measured at 50 mm / min using a 180 degree 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. Manufacturing of lithium secondary batteries The free-standing films prepared in the Examples and Comparative Examples were placed on one side of a primer coated aluminum foil (manufactured by Dongwon Systems) current collector having a thickness of 20 μm, and bonded through a lamination roll maintained at 120° C. to prepare a positive electrode.

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

[0125] 2. Capacity retention rate evaluation of lithium secondary batteries The prepared coin-type half cell was charged and discharged 100 times at 25° C. under a voltage range of 3 to 4.3 V and a current rate of 0.33 C, and the 100-cycle discharge capacity retention rate relative to the 1-cycle discharge capacity 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 above preferred embodiment, various modifications and variations can be made without departing from the spirit and scope of the invention. Therefore, the appended claims are intended to cover 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 taper section 12b: Kneading section 12c: Second taper section 12d: Tip shaft 12e: Rear shaft 14: Blade 14a: First helical blade 14b: Second helical blade 14c: 3rd helical blade 14d: 4th helical blade 20: Housing 22: Nozzle 24: Hopper 100: High shear mixing unit 200: Driving section 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 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 in the direction toward the nozzle, a kneading section whose outer diameter is maintained constant or gradually increases in the direction toward the nozzle, and a second tapered section whose outer diameter gradually decreases in the direction toward the nozzle, The blade is a high shear mixer including a first helical blade arranged on the outer peripheral surface of the first tapered section, a second helical blade arranged on the outer peripheral surface of the kneading section, and a third helical blade arranged on the outer peripheral surface of the second tapered section.

2. 2. The high shear mixing device of claim 1, wherein the first helical blade and the second helical blade are formed independently, the pitch of the first helical blade is greater than the pitch of the second helical blade, and the first helical blade and the second helical blade are wound helically in the same direction on the rotation axis.

3. 3. The high shear mixer according to claim 2, 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 cross section perpendicular to the central axis of the rotation shaft and the helical blade.

4. The high shear mixer according to claim 3, wherein the second spiral blade comprises three or more independent blades arranged to overlap each other on the outer circumferential surface of the kneading section.

5. 5. The high shear mixing device according to claim 4, wherein the second and third helical blades are wound helically in the same direction on the rotation axis.

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

7. 7. The high shear mixer according to claim 6, wherein the second and third helical blades are provided independently of each other.

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

9. 9. The high shear mixer according to claim 8, 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.

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

11. 11. The high shear mixer according to claim 10, wherein a diameter of a tip 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.

12. 2. The high shear mixer according to claim 1, wherein the rotating shaft comprises a first tapered section whose outer diameter gradually increases in the direction of the nozzle, a kneading section whose outer diameter gradually increases or remains the same from the 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.

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

14. 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 1:0.1-0.4:0.2-0.

5.

15. 7. The high shear mixer according to claim 6, 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 cross section perpendicular to the central axis of the rotation shaft and the helical blade.

16. The third spiral blade has a maximum pitch at a start point of the second tapered section contacting the kneading section, a minimum pitch at a tip surface of the second tapered section in the nozzle direction, and the pitch gradually decreases toward the nozzle direction.

17. 7. The high shear mixer according to claim 6, wherein a cross section of the first spiral blade perpendicular to a direction in which the first spiral blade is wound around the rotation shaft includes two height forming sides, and one side of the height forming sides in a nozzle direction forms an acute angle of 30 degrees to 80 degrees with a central axis of the rotation shaft in a direction opposite to the nozzle.

18. 18. The high shear mixer of claim 17, 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 side of the height forming sides in the nozzle direction forms an acute angle of 40 degrees to 80 degrees with a central axis of the rotation shaft in a direction away from the nozzle.

19. 20. The high shear mixer of claim 18, 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 side of the height forming sides in the nozzle direction forms an acute angle of 40 degrees to 80 degrees with a central axis of the rotation shaft in a direction away from the nozzle.

20. 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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