A twin-screw extruder for lithium battery separator plastic

Abstract

The application relates to lithium battery diaphragm plastic production equipment, in particular to a double-screw extruder for lithium battery diaphragm plastic, which comprises a machine shell and a screw, the machine shell is formed by sequentially butting a plurality of barrel sections, and two screws are arranged in the machine shell and are arranged side by side in a horizontal plane; an input section, a melting section, a homogenizing section and an output section are sequentially formed between the machine shell and the screw from right to left; the homogenizing section sequentially has a first kneading structure, a granulation stirring structure and a second kneading structure from right to left; the raw material after melting is cooled and preliminarily kneaded at the first kneading structure, is cut into small viscous pieces by the granulation stirring structure and is uniformly stirred, and is then kneaded by the second kneading structure, so that the nucleating agent can be uniformly distributed in the plastic. The application has the beneficial effects that the nucleating agent can be uniformly distributed in the whole material, so that the uniformity of the micro-holes during subsequent stretching can be ensured.

Description

Technical Field

[0001] This invention relates to the technical field of lithium battery material preparation, and in particular to a twin-screw extruder for lithium battery separator plastics. Background Technology

[0002] In lithium-ion batteries, graphite and metal oxides are coated onto copper and aluminum foils, respectively. An organic salt of lithium acts as the electrolyte and is coated onto a separator, which is then placed between the copper and aluminum foils. The separator is typically made of plastic (such as polypropylene), hence it is also called a separator plastic. The separator plastic has micropores that allow lithium electrons to freely move between the positive and negative electrodes, thus forming a current loop.

[0003] The preparation of diaphragm plastics can be carried out using either a dry or wet process. For example, in the dry process (or physical stretching pore formation), small viscous pieces of resin are first heated to a molten state, and then extruded through a special die (twin-screw extruder) to form a thick sheet with a certain crystalline structure. This sheet is then heat-treated (annealed) at a specific temperature, during which the crystalline structure separates, thereby forming narrow micropores along the stretching direction inside the film. Finally, an alkaline heat treatment is performed to fix the microporous structure and prevent it from shrinking back.

[0004] However, in existing dry preparation methods, even when using a twin-screw extruder, it is still impossible to guarantee that the nucleating agent is distributed particularly evenly in the diaphragm plastic. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a twin-screw extruder for lithium battery separator plastics, solving the problem that the nucleating agent is not distributed very evenly in the separator plastic.

[0006] It should be noted that in the dry process of preparing lithium battery separator plastics, a nucleating agent needs to be added to the plastic during extrusion using a twin-screw extruder. This allows the plastic to form a metastable crystalline morphology (i.e., β-crystals) during extrusion. β-crystals have a relatively loose structure and poor stability, making them prone to lamellar separation along specific directions under tensile stress, thus forming micropores. The uniformity of the nucleating agent's distribution in the plastic affects the uniformity of micropores in the subsequently produced separator plastic, thereby impacting the quality of the separator plastic.

[0007] Furthermore, when the powdered nucleating agent is cooled and kneaded with the molten plastic, although the molten plastic is a very viscous substance and the powdered nucleating agent can be evenly distributed in the molten plastic to a certain extent, the nucleating agent still has a certain weight. Therefore, in the twin-screw extruder, when the nucleating agent is kneaded with the molten plastic, the nucleating agent will inevitably sink to a certain extent. In addition, the nucleating agent is also prone to be distributed in the cavity wall under centrifugal force (even if this occurs to a relatively slight degree), which will still affect the uniform distribution of the nucleating agent in the final diaphragm plastic.

[0008] The objective of this invention is achieved through the following technical solution: a twin-screw extruder for lithium battery separator plastic, comprising a housing and screws, wherein the housing is formed by sequentially connecting multiple cylindrical sections, and two screws arranged side by side in a horizontal plane are provided inside the housing;

[0009] The machine housing and the screw are connected from right to left to form an input section, a melting section, a homogenization section, and an output section.

[0010] The homogenization section has a first kneading structure, a granulation and stirring structure, and a second kneading structure from right to left. The molten raw material is cooled and initially kneaded in the first kneading structure, then cut into viscous small pieces by the granulation and stirring structure and stirred evenly, and then kneaded again by the second kneading structure, thus forming a structure in which the nucleating agent can be evenly distributed in the plastic.

[0011] As a preferred technical solution of this application, the first kneading structure includes a kneading part I, a kneading part II, and a rolling part III. From right to left, it has the following features: a spiral A in the shape of an auger on the screw - the two spirals A of the screws at this position form the kneading part I; multiple wide kneading blocks in the shape of ellipses on the screw - the two wide kneading blocks of the screws at this position form the kneading part II; the screw itself is a bent and twisted rod segment of a screw pump structure, and the inner wall of the corresponding cylinder is the shape of the pump wall of a screw pump - the two screws at this position and the inner wall of the corresponding cylinder form the rolling part III;

[0012] After the molten raw material enters the first kneading structure, it is cooled and kneaded in a twisted shape at kneading part I. Then, the twisted plastic is squeezed and kneaded radially at kneading part II, and then rolled at rolling part III.

[0013] As a preferred technical solution of this application, the granulation and mixing structure includes a mesh section IV, a shearing section V, and a mixing section VI. The mesh section IV has a mesh element that is compressed and fixed between two cylindrical sections, and the mesh element has holes for two screws to pass through. The shearing section V has a cutting blade on each screw. The mixing section VI has an auger blade A on each screw, and multiple mixing rod sections are arranged axially on the auger blade A, each mixing rod section located at a different radial position on the auger blade A. When the plastic moves from right to left, it passes through the mesh element and forms multiple strip-shaped materials; the strip-shaped materials are sheared into multiple viscous small pieces by the shearing blade; the multiple viscous small pieces are conveyed by the auger blade A and mixed by the mixing rod sections.

[0014] Furthermore, the right and left ends of the granulation mixing structure respectively have a right conveying structure and a left conveying structure. The right conveying structure and the left conveying structure have the same structure, both having auger blades B on the corresponding screw; the right conveying structure forces the material into the granulation mixing structure, while the left conveying structure forces the stirred viscous lumps of material into the second kneading structure.

[0015] As a preferred technical solution of this application, the second kneading structure is the same as the first kneading structure.

[0016] As a preferred technical solution of this application, the homogenization section also has a third kneading structure; the third kneading structure is located at the left end of the second kneading structure and includes only the corresponding kneading part I and kneading part II.

[0017] As a preferred technical solution of this application, the input section has a conical spiral B in the shape of an auger on the corresponding screw, and a conveying structure is formed between the conical spirals B of the two screws.

[0018] Furthermore, the melting section, from right to left, has a conical spiral C in the shape of an auger, a narrow kneading block, and a fan-shaped rotary cutter on each screw. The spiral spacing of the conical spiral C is smaller than that of the conical spiral B, forming a structure between the conical spirals C of the two screws that allows the material to be squeezed and melted. The fan-shaped rotary cutter cuts and stirs the long chain of molten material. Between the melting section and the input section, there are also reverse auger blades on the corresponding screws, forming a structure that prevents the molten material from flowing backward.

[0019] As a preferred technical solution of this application, the output section has a corresponding spiral D in the shape of an auger on the corresponding screw.

[0020] The present invention has the following advantages: during the homogenization stage, the nucleating agent can be evenly distributed throughout the material (thereby ensuring the uniformity of the distribution of each micropore during subsequent stretching).

[0021] Specifically, after the molten raw material enters the first kneading structure, it is cooled and kneaded in a twisted shape at kneading part I. Then, at kneading part II, the twisted plastic is rolled and kneaded with the screw as the axis. Then, it is rolled and pressed at rolling part III, which increases the uniformity of the nucleating agent distribution in the material.

[0022] Furthermore, at the granulation mixing structure, as the plastic moves from right to left, it forms multiple strips after passing through the mesh (at this point, the strips still stick together, but the adhesion is not particularly thorough); the strips are then sheared into multiple viscous small pieces by the shearing blades (these small pieces still stick together, but the adhesion is not particularly thorough); these viscous small pieces are conveyed by the auger blades, and they are also mixed by the mixing rod sections (changing the position of each viscous small piece, allowing some viscous small pieces with more nucleating agents to mix). It can be relatively well and evenly dispersed in various positions of this pile of viscous lumps, so as to a certain extent, the nucleating agent is evenly distributed (that is, by changing the distribution of viscous lumps, the nucleating agent is evenly distributed to a certain extent). Since the viscous lumps are not completely stuck together, when the stirring rod is stirring, the viscous lumps can be easily stirred from one position to another. The viscous lumps bring the nucleating agent inside them together. After the viscous lumps are remixed, the nucleating agent can be evenly distributed in the entire material. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention;

[0024] Figure 2 This is a structural diagram of the input segment;

[0025] Figure 3 This is a schematic diagram of the molten section.

[0026] Figure 4 A schematic diagram of the narrow kneading block in the melting section;

[0027] Figure 5 This is a schematic diagram of the first kneading structure;

[0028] Figure 6 A schematic diagram of the radial cross-section at the wide kneading block of the first kneading structure;

[0029] Figure 7 A top view showing the axial cross-section of the torsion bar segment of the first kneading structure;

[0030] Figure 8 This is a schematic diagram of the granulation mixing structure, the right conveying structure, and the left conveying structure.

[0031] Figure 9This is a schematic diagram of the second kneading structure;

[0032] Figure 10 This is a schematic diagram of the third kneading structure;

[0033] Figure 11 This is a schematic diagram of the output section;

[0034] In the picture:

[0035] 1001 - Cylindrical section, 20 - Screw;

[0036] 30-Input section, 31-Conical spiral B, 40-Melting section, 4001-Reverse auger blade, 41-Conical spiral C, 42-Narrow kneading block, 43-Rotating cutter, 50-Homogenization section, 51-First kneading structure, 5101-Conical spiral A, 5102-Wide kneading block, 5103-Bent torsion bar section, 52-Right conveying structure, 53-Pelletizing mixing structure, 5301-Grid component, 5302-Shearing blade, 5303-Auger blade A, 5303-1-Stirring rod section, 54-Left conveying structure, 55-Second kneading structure, 56-Third kneading structure, 60-Output section, 61-Conical spiral D. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0038] It should be noted that in existing related technologies, when dry-processing the separator plastic for lithium batteries, a twin-screw extruder is often used to extrude the plastic raw material: through conveying (feeding and initial preheating) - melting / mixing (highest temperature, the material is completely melted and becomes a homogeneous melt) - homogenization / discharging (lowering the temperature to prepare the melt for passing through the die and casting roller, so that the temperature of the melt at this time forms a huge temperature difference with the surface of the casting roller) and other processes - forming the precursor structure for pore formation (in the extruder, the temperature is mainly raised by the "shear heat" generated by the shearing and kneading of the material by the screw, and the heating is also assisted by the electric heating coils set inside the barrel / shell. At the same time, the temperature is lowered by the oil cooling / water cooling circulation formed in the inner cavity of the barrel / shell, thus forming a relatively stable temperature control).

[0039] The problem is that in the melting section, the corresponding material has a low viscosity. Although some stirring is carried out, the nucleating agent is not distributed evenly in the low viscosity plastic material under the action of centrifugal force and gravity. In the subsequent homogenization stage, due to the decrease in temperature and the increase in viscosity of the material, the nucleating agent is unevenly distributed during the initial cooling. Even with stirring, it is difficult to make the nucleating agent evenly distributed in the high viscosity material (because at this time, the fluidity of the entire material and the nucleating agent is very low when stirring).

[0040] This solution addresses the issue through the following approach: a. During the homogenization stage, the viscous material is cut into small, viscous pieces, which are then stirred (this makes stirring easier). Even if the nucleating agent content varies among the small pieces, stirring ensures a more uniform distribution of the nucleating agent within the mass of viscous pieces, allowing for even distribution of the nucleating agent throughout the plastic material. (In simpler terms, nucleating agent particles in molten plastic are not evenly distributed evenly, even with stirring. This solution involves stirring, then turning the molten plastic into a viscous mass, cutting the mass into small, viscous pieces, and then stirring each piece again, thus ensuring a more uniform distribution of the nucleating agent particles throughout the plastic.) b. Furthermore, during the homogenization stage, the viscous material is twisted and kneaded in a spiral shape (like a fried dough twist), rolled and kneaded using a wide kneading block, and then rolled and pressed—these actions ensure a uniform distribution of the nucleating agent throughout the plastic.

[0041] The present invention will be further illustrated below through specific embodiments (it should be noted that, in the absence of conflict, the embodiments and features and technical solutions in the embodiments of the present invention can be combined with each other).

[0042] See Figures 1-11 This specific embodiment discloses a twin-screw extruder for lithium battery separator plastic, including a housing and screws 20. The housing is formed by connecting multiple cylindrical sections 1001 in sequence, and two screws 20 arranged side by side in a horizontal plane are provided inside the housing.

[0043] Along the screw axis from right to left (or from input to output), the housing and the two screws 20 sequentially form an input section 30, a melting section 40, a homogenization section 50, and an output section 60;

[0044] The homogenization section 50 has a first kneading structure 51, a granulation and stirring structure 53, and a second kneading structure 55 from right to left. The molten raw material is cooled and initially kneaded in the first kneading structure 51, then cut into viscous small pieces by the granulation and stirring structure 53 and stirred evenly (this method not only makes stirring easier, but also allows the nucleating agent to be more evenly distributed throughout the viscous material). It is then kneaded by the second kneading structure 55 to form a structure in which the nucleating agent can be evenly distributed in the plastic.

[0045] During operation: ① In the input section 30, the temperature range of 160℃-180℃ is maintained to ensure stable conveying of the material (plastic powder, nucleating agent, and other additives). The material is preheated by friction between materials and between the material and mechanical parts. At this temperature, the material will not melt (existing technology). ② In the melting section, the spacing of the corresponding spirals on the screw is reduced, thereby increasing friction. Furthermore, the use of strong mixing elements such as kneading components generates significant shear heat, raising the temperature to between 200℃-230℃. This causes the plastic in the material to completely melt (the nucleating agent does not melt). During this process, the nucleating agent is dispersed to some extent in the molten plastic (however, due to gravity, centrifugal force, etc., the dispersion is not entirely uniform). ③ The temperature is maintained at 190℃-210℃. a) At this point, cooling occurs, and the molten plastic becomes somewhat viscous. The first kneading structure 51 ensures that the nucleating agent is evenly distributed in the plastic (but may still not be evenly distributed). (a) b) Then, using the granulation mixing structure 53, the material (a viscous mixture of molten plastic and nucleating agent) that has been initially kneaded is cut into multiple viscous small pieces (each viscous small piece contains a corresponding nucleating agent; due to the situation in the melting section mentioned above ②, some viscous small pieces contain a relatively high amount of nucleating agent). Then, the multiple viscous small pieces are stirred (cutting into multiple viscous small pieces and then stirring is easier than directly stirring the viscous material, and this allows the viscous small pieces containing more nucleating agent to be better dispersed throughout the viscous small piece pile, thus indirectly allowing the nucleating agent to present a better distribution throughout the viscous small piece pile). c) Then, it is kneaded by the second kneading structure 55, so that the multiple viscous small pieces that have been cut can be re-adhere (after the actions of b and c, the nucleating agent is distributed very evenly in the plastic after being adhere). ④ Then, the temperature is maintained at 190℃-210℃ and conveyed (after being conveyed out of the extruder, β crystals are induced to form using the flow-extending equipment).

[0046] The following provides further explanation of input segment 30.

[0047] See Figure 2 The input section 30 has a conical spiral B31 in the shape of an auger on the corresponding screw, and a conveying structure is formed between the conical spirals B of the two screws (as per the prior art).

[0048] The following provides further explanation of the melting section 40.

[0049] See Figure 3 For the melting section 40: from right to left, the corresponding screws have a conical spiral C41 in the shape of an auger, a narrow kneading block 42, and a fan-shaped rotating cutting element 43 respectively;

[0050] Among them, the pitch of the conical spiral C41 is smaller than that of the conical spiral B31, and the conical spirals C of the two screws form a force that compresses the material and increases the friction between the materials; in addition, the narrow kneading block 42 can shear the material, thereby generating a large amount of shear heat; furthermore, the fan-shaped rotating cutter 43 cuts and stirs the long chains of molten material, which can also generate corresponding shear heat; by means of compression, increased friction, and shearing, the material is heated, thereby melting the plastic in the material (and the molten material has a large fluidity).

[0051] It should be noted that in the melting section 40, the plastic is melted while the material is also evenly distributed.

[0052] Further, see Figure 3 Between the melting section 40 and the input section 30, there is also a reverse auger blade 4001 on the corresponding screw, forming a structure to prevent the molten material from flowing in the opposite direction.

[0053] Further, see Figure 3 and Figure 4 Multiple narrow kneading blocks 42 are installed on a screw (the included angle between two adjacent narrow kneading blocks 42 on a screw is an acute angle), and the narrow kneading blocks 42 on two screws also form an acute angle, thus ensuring a large shearing force. In addition, the narrow kneading blocks 42 are elliptical in shape.

[0054] The first kneading structure 51 will be further explained below.

[0055] See Figure 5 The first kneading structure 51 includes a kneading part I, a pinching part II, and a rolling part III;

[0056] From right to left, the following are listed: a. See also Figure 5 The screw has a spiral A5101 in a spiral shape. At this position, the spirals A of the two screws form a kneading section I (existing technology). The pitch between adjacent spirals A5101 is smaller than the pitch of the spiral C in the melting section 40; b. In addition, see Figure 5 and Figure 6 The screw has multiple elliptical wide kneading blocks 5102. A kneading section II is formed between the wide kneading blocks of two screws at this location (the wide kneading blocks 5102 in the homogenization stage are unique to this design). The main function of the wide kneading blocks 5102 here is to make the material roll and knead around the screw axis; c. See also Figure 7The screw 20 itself is a bent and twisted rod section 5103 of the screw pump structure, and the inner wall of the corresponding cylinder section 1001 is the shape of the pump wall of the screw pump. At this position, the two screws and the inner wall of the corresponding cylinder section form a rolling section III (the screw pump has a corresponding structure, and this solution applies the structure in the screw pump to the extruder structure, which is unique to this solution). This method can roll and extrude the material forward.

[0057] During operation, after the molten raw material enters the first kneading structure 51, it is cooled and kneaded in a twisted shape at the kneading part I. Then, at the kneading part II, the twisted plastic is rolled and kneaded with the screw as the axis. Finally, it is rolled and pressed at the rolling part III, which increases the uniformity of the nucleating agent distribution in the material.

[0058] The granulation mixing structure 53 will be further explained below.

[0059] See Figure 8 The granulation mixing structure 53 includes a mesh section IV, a shearing section V, and a mixing section VI;

[0060] Among them, the mesh part IV has a mesh element 5301, which is pressed and fixed between two cylindrical sections 1001, and the mesh element 5301 has holes for two mesh rods to pass through.

[0061] Among them, the shearing part V: has a shearing blade 5302 with a cutting edge on the corresponding screw;

[0062] Among them, the stirring part VI: has an auger blade A5303 on the corresponding screw, and multiple stirring rod sections 5303-1 are provided on the auger blade A5303 along the axial direction, with each stirring rod section 5303-1 located at a different radial position of the auger blade A5303;

[0063] During operation, as the plastic moves from right to left, it passes through the mesh 5301 and forms multiple strips (at this point, the strips still stick together, but the sticking is not very thorough). The strips are then cut into small, sticky pieces by the shearing blade 5302 (the sticky pieces still stick together, but the sticking is not very thorough). The sticky pieces are conveyed by the auger blades A5303 and mixed by the stirring rod section 5303-1. Because the sticky pieces are not completely stuck together, when the stirring rod section 5303-1 stirs, the sticky pieces can be easily moved from one position to another. The sticky pieces move along with the nucleating agent inside them. After the sticky pieces are remixed, the nucleating agent is evenly distributed throughout the material.

[0064] Further, see Figure 8The right end and left end of the granulation mixing structure 53 have a right conveying structure 52 and a left conveying structure 54, respectively. The right conveying structure 52 and the left conveying structure 54 have the same structure, and both have auger blades B on the corresponding screw. The right conveying structure 52 forces the material into the granulation mixing structure 53, and the left conveying structure 54 forces the viscous lumps of material after mixing into the second kneading structure 55.

[0065] The second kneading structure 55 will be further explained below.

[0066] See Figure 9 The second kneading structure 55 has the same structure as the first kneading structure 51.

[0067] The homogenization segment 50 will be further explained below.

[0068] See Figure 10 The homogenization section 50 also has a third kneading structure 56; the third kneading structure 56 is located at the left end of the second kneading structure 55 and includes only the corresponding kneading part I and kneading part II; the structure of the kneading part I and kneading part II here is the same as the structure of the corresponding kneading part I and kneading part II in the first kneading structure 51 (except that the rolling part III is missing).

[0069] The following provides further explanation of output segment 60.

[0070] See Figure 11 The output section 60 has a corresponding auger-shaped conical spiral D61 on the corresponding screw.

[0071] It should be noted that the orientation or positional relationship indicated by terms such as "left" and "right" is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, or the orientation or positional relationship in which those skilled in the art would conventionally understand it. Such terms are only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0072] The above embodiments only illustrate preferred implementation methods, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention, and these all fall within the protection scope of this invention.

Claims

1. A double screw extruder for lithium battery separator plastic, comprising a machine housing and a screw (20), the machine housing is formed by sequentially butting a plurality of barrel sections (1001), and two screws (20) are arranged side by side in the horizontal plane in the machine housing, characterized in that: the machine housing and the screw (20) sequentially form an input section (30), a melting section (40), a homogenizing section (50), and an output section (60) from right to left; the homogenizing section (50) sequentially has a first kneading structure (51), a granulation stirring structure (53), and a second kneading structure (55) from right to left; the melted raw material is cooled and preliminarily kneaded at the first kneading structure (51), is then cut into small sticky pieces by the granulation stirring structure (53) and is stirred uniformly, and is then kneaded by the second kneading structure (55), so that the structure of the nucleating agent uniformly distributed in the plastic is formed; the granulation stirring structure (53) comprises a mesh part IV, a shearing part V, and a stirring part VI; the mesh part IV has a mesh piece (5301) fixedly extruded between two barrel sections (1001), and the mesh piece (5301) is provided with holes for the two screws to pass through; the shearing part V has a shearing blade (5302) with a blade on the corresponding screw; the stirring part VI has an auger blade A (5303) on the corresponding screw, and a plurality of stirring rod sections (5303-1) are arranged on the auger blade A (5303) in the axial direction, and each stirring rod section (5303-1) is located at a different radial position of the auger blade A (5303); when the plastic moves from right to left, a plurality of strip-shaped materials are formed after passing through the mesh piece (5301); the strip-shaped materials are cut into a plurality of small sticky pieces after passing through the shearing blade (5302); and the plurality of small sticky pieces are transported by the auger blade A (5303) and are stirred and mixed by the stirring rod sections (5303-1). The first kneading structure (51) comprises a kneading part I, a kneading part II, and a rolling part III from right to left; the kneading part I has a conical screw A (5101) in the shape of an auger on the screw, the conical screws A of the two screws form the kneading part I at this position, a plurality of wide kneading blocks (5102) in the shape of an ellipse are arranged on the screw, the wide kneading blocks of the two screws form the kneading part II between them at this position, the screw (20) itself is a bending and twisting rod section (5103) of a screw pump structure, and the inner wall of the corresponding barrel section (1001) is in the shape of a pump wall of a screw pump, the two screws and the inner wall of the corresponding barrel section form the rolling part III at this position; when the melted raw material enters the first kneading structure (51), it is cooled and twisted in the shape of a twisted dough at the kneading part I, is then radially extruded and kneaded in the shape of a twisted dough at the kneading part II, and is then rolled at the rolling part III. The right end and the left end of the granulation stirring structure (53) respectively have a right conveying structure (52) and a left conveying structure (54). ​ ​ ​ ​ ​ 2. A twin-screw extruder for plastic of lithium battery separator according to claim 1, characterized in that: ​ ​ ​ 3. A twin-screw extruder for plastic of lithium battery separator membrane according to claim 1, characterized in that: ​ The right conveying structure (52) and the left conveying structure (54) are identical in structure and are provided with auger blades B on the corresponding screws; the right conveying structure (52) forces the material to be pressed into the granulating stirring structure (53), and the left conveying structure (54) forces the stirred viscous small pieces of material to be pressed into the second rubbing structure (55).

4. A twin-screw extruder for plastic of lithium battery separator as claimed in claim 2, wherein: The second rubbing structure (55) is identical in structure to the first rubbing structure (51).

5. A twin-screw extruder for plastic of lithium battery separator according to claim 4, characterized in that: The homogenizing section (50) is further provided with a third rubbing structure (56). The third rubbing structure (56) is located at the left end of the second rubbing structure (55) and only includes corresponding rubbing part I and kneading part II.

6. A twin-screw extruder for plastic of lithium battery separator as claimed in claim 1, wherein: The input section (30) is provided with auger-shaped tapered screws B (31) on the corresponding screws, and the tapered screws B between the two screws form a conveying structure.

7. A twin-screw extruder for plastic of lithium battery separator according to claim 6, characterized in that: The melting section (40) is provided with auger-shaped tapered screws C (41), narrow kneading blocks (42) and fan-shaped rotary cutting members (43) on the corresponding screws from right to left. The spiral pitch of the tapered screws C (41) is smaller than that of the tapered screws B (31), and the tapered screws C between the two screws form a structure for extruding and melting the material. The fan-shaped rotary cutting members (43) cut and stir the long chains of the molten material; The input section (30) and the melting section (40) are further provided with reverse auger blades (4001) on the corresponding screws, forming a structure for avoiding the reverse flow of the molten material.

8. A twin-screw extruder for plastic of lithium battery separator membrane according to claim 1, characterized in that: The output section (60) is provided with corresponding auger-shaped tapered screws D (61) on the corresponding screws.

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