Twin-screw extruder for preparing thermoplastic vulcanized rubber

Abstract

The utility model belongs to the technical field of double-screw extruders, and particularly relates to a double-screw extruder for preparing thermoplastic vulcanized rubber, the double-screw extruder comprises a machine barrel and a double-screw system arranged in the machine barrel, the double-screw system comprises two screws, and the double-screw system at least comprises a first section, a second section and a third section in the axial direction of the screws, the thread pitches of the screws in the first section, the second section and the third section are a1, a2 and a3 in sequence; in the first section, the second section and the third section, the minimum distance between the screw and the inner wall of the machine barrel is d1, d2 and d3 in sequence, a1 > a2 > a3, and d1 > d3 > d2. According to the preparation method, the process linkage of melting plasticizing, shearing dispersion and dynamic vulcanization and the process link collaboration in the TPV manufacturing process can be realized, so that the mechanical property stability of the TPV product can be optimized, and the problem of performance fluctuation of TPV prepared by a traditional double-screw extruder can be solved.

Description

Technical Field

[0001] This application belongs to the technical field of twin-screw extruders, specifically relating to a twin-screw extruder for preparing thermoplastic vulcanized rubber. Background Technology

[0002] A screw extruder is a mechanical device that uses two rotating screws to achieve material conveying, plasticizing, mixing, and extrusion. It is widely used in the plastics, rubber, food, and pharmaceutical industries. In the processing of thermoplastic vulcanizates (TPV), twin-screw extruders are commonly used. However, due to the special ratio of the rubber and plastic phases in TPV materials and the stringent requirements of dynamic vulcanization processes for shear dispersion and multi-stage synergy, traditional twin-screw extruders have revealed numerous material problems in actual production, resulting in poor product performance stability and difficulty in meeting the processing requirements of high-quality TPV. Utility Model Content

[0003] In view of the technical problems existing in the background art, this application provides a twin-screw extruder for preparing thermoplastic vulcanizates, specifically including the following:

[0004] This application discloses a twin-screw extruder for preparing thermoplastic vulcanizates, comprising a barrel and a twin-screw system disposed within the barrel. The twin-screw system includes two screws, each screw including a screw mandrel and threads disposed outside the screw mandrel. The twin-screw system includes at least a first section, a second section, and a third section along the axial direction of the screws. The thread pitch (i.e., pitch) of the screws in the first, second, and third sections is a1, a2, and a3, respectively. The minimum distance between the screws in the first, second, and third sections and the inner wall of the barrel is d1, d2, and d3, respectively, where a1 > a2 > a3, and d1 > d3 > d2.

[0005] This application includes at least the following beneficial effects: Through a gradient and synergistic design of the thread pitch and the minimum distance between the screw and the inner wall of the barrel in the three-stage structure of a twin-screw extruder, a composite shear field highly adapted to the TPV preparation process is formed. In the first stage, a larger thread pitch and a larger distance between the screw and the inner wall of the barrel provide a high volumetric efficiency during the initial material conveying stage, achieving rapid filling and uniform preheating, avoiding local overheating caused by premature compression, and ensuring that the rubber phase is fully melted and infiltrated in the plastic matrix. In the second stage, a reduced screw pitch and a minimum distance between the screw and the inner wall of the barrel create a high-intensity shear zone, breaking down the rubber phase. Simultaneously, shear heat generation raises the material temperature to the decomposition temperature of the vulcanizing agent, creating a dispersion basis for dynamic vulcanization. In the third stage, a further reduced screw pitch, combined with a medium distance between the screw and the inner wall of the barrel, provides a stable residence time while maintaining micro-scale shearing, allowing the rubber phase to complete the vulcanization reaction in a fully dispersed state. This stabilizes the degree of crosslinking while avoiding excessive shearing that could lead to the breakage of the crosslinking network. Therefore, the process integration and energy matching of melt plasticization, shear dispersion, and dynamic vulcanization in TPV manufacturing can be achieved. By controlling shear strength, material residence time, and gap flow field, the uniformity of rubber phase dispersion, consistency of vulcanization reaction, and synergy of process steps can also be improved, thereby optimizing the mechanical property stability of TPV products and solving the performance fluctuation problem of TPV produced by traditional twin-screw extruders. Furthermore, depending on actual needs, the device described in this application can also be used for the preparation of other materials; its application in the processing of other materials is not excluded.

[0006] In some embodiments, in the first segment, the thread height of the screw is 15%-20% of the screw mandrel diameter, the ratio of thread pitch to screw mandrel diameter a1 is 1.2-1.8, and the minimum distance d1 between the screw and the inner wall of the barrel is 0.2mm-0.4mm; in the second segment, the thread height of the screw is 25%-35% of the screw mandrel diameter, the ratio of thread pitch to screw mandrel diameter a2 is 0.7-1.0, and the minimum distance d2 between the screw and the inner wall of the barrel is 0.15mm-0.2mm; in the third segment, the thread height of the screw is 20%-25% of the screw mandrel diameter, the ratio of thread pitch to screw mandrel diameter a3 is 0.3-0.6, and the minimum distance d3 between the screw and the inner wall of the barrel is 0.2mm-0.25mm. This allows for further improvement in the process synergy of the twin-screw extruder at different stages of TPV production, and further optimization of the mechanical property stability of TPV products. It should be noted that the screw mandrel diameter refers to the outer diameter of the screw mandrel.

[0007] In some embodiments, in the first section, the thread height of the screw is 16%-18% of the screw mandrel diameter, and / or, the ratio of the thread pitch to the screw mandrel diameter, a1, is 1.4-1.6, and / or, the minimum distance d1 between the screw and the inner wall of the barrel is 0.25mm-0.35mm; and / or, in the second section, the thread height of the screw is 25%-30% of the screw mandrel diameter, and / or, the ratio of the thread pitch to the screw mandrel diameter, a1, is 1.4-1.6, a1, and a2, a1, is 1.4-1.6, a1, and a2, a1, is 0.25mm-0.35mm; and / or, in the second section, the thread height of the screw is 25%-30% of the screw mandrel diameter, and / or, the ratio of the thread pitch to the screw mandrel diameter, a1, is 1.4-1.6, a1, and a2, a1, is 0.25mm-0.35mm. The ratio of the screw shaft diameter a2 is 0.7-0.9, and / or the minimum distance d2 between the screw and the inner wall of the barrel is 0.15mm-0.18mm; and / or, in the third section, the thread height of the screw is 22%-24% of the screw mandrel diameter, and / or the ratio of the thread pitch to the screw mandrel diameter a3 is 0.4-0.6, and / or the minimum distance d3 between the screw and the inner wall of the barrel is 0.2mm-0.23mm. Therefore, the process synergy of the twin-screw extruder at different stages of TPV production can be further improved, and the stability of the mechanical properties of TPV products can be further optimized.

[0008] In some implementations, in the first segment, the ratio of thread pitch to screw mandrel diameter a1 is 1.5, and / or, the minimum distance d1 between the screw and the inner wall of the barrel is 0.3 mm; and / or, in the second segment, the ratio of thread pitch to screw mandrel diameter a2 is 0.8, and / or, the minimum distance d2 between the screw and the inner wall of the barrel is 0.15 mm; and / or, in the third segment, the ratio of thread pitch to screw mandrel diameter a3 is 0.5, and / or, the minimum distance d3 between the screw and the inner wall of the barrel is 0.2 mm. This further improves the process synergy of the twin-screw extruder at different stages of TPV production and further optimizes the mechanical property stability of TPV products.

[0009] In some implementations, the length ratio of the first, second, and third segments is (2-3.5):(6-8):)(2.5-3.5). This can further improve the process synergy of the twin-screw extruder at different stages of TPV production and further optimize the mechanical property stability of TPV products.

[0010] In some implementations, the two screws in the double-helix system are arranged parallel to each other.

[0011] In some embodiments, the threads of the two screws in the twin-helix system mesh with each other. In TPV production, parallel meshing co-directional twin screws are preferred (screw axes are parallel, and screw edges mesh with each other). Of course, the meshing method, rotation direction, and speed of the two screws in the twin-helix system can be adjusted according to actual production needs; this application does not impose excessive restrictions in this regard. Attached Figure Description

[0012] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application; irrelevant details have been omitted for clarity. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0013] Figure 1 This is a front structural schematic diagram of the twin-screw extruder disclosed in this application.

[0014] In the diagram: 1. Barrel; 11. First section; 12. Second section; 13. Third section; 2. Screw spindle; 3. Drive motor; 31. Gearbox; 32. Feed hopper. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments shown below are not intended to limit the scope of the invention as described in the claims. Furthermore, the complete contents of the configurations shown in the embodiments below are not limited to those necessary for the solution of the invention as described in the claims.

[0016] refer to Figure 1 The figure shows a " / " symbol indicating a thread. This application discloses a twin-screw extruder for preparing thermoplastic vulcanizates, including a barrel 1 and a twin-screw system disposed within the barrel 1. The twin-screw system includes two screws, each screw including a screw mandrel and a thread disposed outside the screw mandrel. The twin-screw system includes at least a first section 11, a second section 12, and a third section 13 along the axial direction of the screws. Figure 1 The dashed lines in the diagram represent the segmentation of the twin-screw system and are not actual lines within the device. The thread pitch (i.e., the distance between the screw threads in the first segment 11, the second segment 12, and the third segment 13) is a1, a2, and a3, respectively. The minimum distance between the screw threads and the inner wall of the barrel 1 (i.e., the minimum distance between the outer edge of the thread and the inner wall of the barrel 1) in the first segment 11, the second segment 12, and the third segment 13 is d1, d2, and d3, respectively, where a1 > a2 > a3, and d1 > d3 > d2. It should be noted that... Figure 1The twin screws are positioned on the same horizontal plane, so when viewed from the front, the two screws overlap, and only one screw is visible. Furthermore, the twin-screw extruder described in this application may also include a drive motor 3, a reduction gearbox 31 connected to the drive motor 3 and the twin-screw system respectively, and a feed hopper 32 and a discharge device (not shown) mounted on the barrel 1, among other necessary components. Since these components are conventionally installed, they are not described in detail in this application. In this application, the thread pitch (i.e., the screw length) refers to the distance between two adjacent thread teeth on the same screw along the axis of the screw mandrel 2 (i.e., the axial distance between corresponding points of adjacent thread teeth measured along the axis of the screw mandrel 2). Additionally, this application does not limit the specific dimensions of the screw mandrel; they can be set according to actual needs. For example, the diameter of the screw mandrel can be constant at 72 mm. Of course, the diameter of the mandrel can also be set to other constant or variable dimensions as needed.

[0017] This application utilizes a gradient-based synergistic design of the thread pitch and the minimum distance between the screw and the inner wall of the barrel 1 in a three-section structure of a twin-screw extruder to create a composite shear field highly adapted to the TPV preparation process. In the first section 11, a larger thread pitch and a larger distance between the screw and the inner wall of the barrel provide a high volumetric efficiency during the initial material conveying stage, enabling rapid filling and uniform preheating. This avoids localized overheating caused by premature compression and ensures the rubber phase is fully melted and wetted in the plastic matrix. In the second section 12, a reduced screw pitch and a minimum distance between the screw and the inner wall of the barrel create a high-intensity shear zone, breaking down the rubber phase. Simultaneously, shear heat generation raises the material temperature to the decomposition temperature of the vulcanizing agent, creating a dispersion basis for dynamic vulcanization. In the third section 13, a further reduced screw pitch, combined with a medium distance between the screw and the inner wall of the barrel, provides a stable residence time while maintaining micro-scale shearing. This allows the rubber phase to complete the vulcanization reaction in a fully dispersed state, stabilizing the degree of crosslinking while preventing excessive shearing that could lead to the breakage of the crosslinking network. This achieves seamless integration and energy matching of the melting and plasticizing, shear dispersion, and dynamic vulcanization processes in TPV manufacturing. Furthermore, by controlling shear strength, material residence time, and gap flow field, it improves the uniformity of rubber phase dispersion, consistency of vulcanization reaction, and synergy of process steps. As a result, it can optimize the mechanical property stability of TPV products and solve the performance fluctuation problem of TPV produced by traditional twin-screw extruders.

[0018] It should be noted that the barrel 1 of the device described in this application can be made of wear-resistant alloy, or the inner wall of the barrel 1 can be coated with a wear-resistant coating, or both. This application does not limit the specific material of the barrel 1. In addition, if necessary, a temperature control component can be provided in the device described in this application, such as cooling channels can be provided in the screw. This application does not limit this.

[0019] In some embodiments, in the first segment 11, the thread height of the screw is 15%-20% of the diameter of the screw mandrel 2, the ratio a1 of the thread pitch to the diameter of the screw mandrel 2 is 1.2-1.8, and the minimum distance d1 between the screw and the inner wall of the barrel 1 is 0.2mm-0.4mm; in the second segment 12, the thread height of the screw is 25%-35% of the diameter of the screw mandrel 2, the ratio a2 of the thread pitch to the diameter of the screw mandrel 2 is 0.7-1.0, and the minimum distance d2 between the screw and the inner wall of the barrel 1 is 0.15mm-0.2mm; in the third segment 13, the thread height of the screw is 20%-25% of the diameter of the screw mandrel 2, the ratio a3 of the thread pitch to the diameter of the screw mandrel 2 is 0.3-0.6, and the minimum distance d3 between the screw and the inner wall of the barrel 1 is 0.2mm-0.25mm. This application, taking into account the characteristics of TPV production technology, further limits the specific parameters of the first section 11, the second section 12, and the third section 13 to the aforementioned range. This can further improve the process synergy of the twin-screw extruder at different stages of TPV production and further optimize the mechanical property stability of TPV products. Specifically, the ratio a1 of the screw thread pitch to the screw mandrel 2 diameter in the first section 11 is further limited to 1.2-1.8, and the minimum distance d1 between the screw 2 and the inner wall of the barrel 1 is 0.2mm-0.4mm, further forming a high-volume material conveying space. This setting can further achieve rapid filling in the initial material feeding stage, further ensure that the rubber phase is uniformly preheated and fully melted and wetted in the plastic matrix, and lay a stable material mixing foundation for the subsequent shearing and dispersion stages. The ratio a2 of the thread pitch of the second section 12 to the diameter of the screw mandrel 2 is further limited to 0.7-1.0, while the minimum distance d2 between the screw and the inner wall of the barrel 1 is controlled at 0.15mm-0.2mm. This shortening of the thread pitch and narrowing of the distance between the screw and the inner wall of the barrel creates a high-intensity shearing zone. This parameter range can further effectively break the rubber phase down to the submicron level, while also utilizing shear heat generation to precisely raise the material temperature to the vulcanizing agent reaction temperature. This provides the necessary temperature conditions for the dynamic vulcanization reaction and, through strong shearing, constructs a uniformly dispersed microstructure, further avoiding rubber phase agglomeration due to insufficient shearing or temperature control deviations caused by excessive distance between the screw and the inner wall of the barrel. The third section 13 further reduces the ratio a3 of the thread pitch to the diameter of the screw mandrel 2 to 0.3-0.6, and sets the minimum distance d3 between the screw and the inner wall of the barrel 1 to 0.2mm-0.25mm. While maintaining microscale shearing action, the material residence time is controlled by the flow field through the medium distance between the inner walls of the barrel: the smaller thread pitch ensures continuous shearing of the dispersed phase to suppress agglomeration, and the medium distance between the inner walls of the barrel avoids the excessive shearing that may be caused by the extremely small distance between the inner walls of the barrel in the second section 12, which may damage the crosslinking network. At the same time, it provides a stable residence time so that the rubber phase can complete the vulcanization reaction in the submicron dispersion state.This setting allows for more precise control of the degree of crosslinking within the ideal range, avoiding insufficient vulcanization or excessive crosslinking. It forms a gradient synergy with the melting, plasticizing, and shear dispersion stages in the first two stages, further ensuring energy matching and seamless connection between each process stage in the TPV preparation process, thereby significantly improving the stability and uniformity of the product's mechanical properties.

[0020] Specifically, in this embodiment, in the first paragraph 11: the thread height of the screw 2 can be 15%, 16%, 17%, 18%, 19%, 20%, etc., or any two of the above values; the ratio a1 of the thread pitch to the diameter of the screw spindle 2 can be 1.2, 1.3, 1.4, 1.45, 1.5, 1.55, 1.6, 1.7, 1.8, etc., or any two of the above values; the minimum distance d1 between the screw and the inner wall of the barrel 1 can be 0.2mm, 0.22mm, 0.25mm, 0.26mm, 0.27mm, 0.28mm, 0.3mm, 0.32mm, 0.35mm, 0.38mm, 0.4mm, etc., or any two of the above values. In the second section 12, the thread height of the screw is 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% of the diameter of the screw mandrel 2, or any two of the above values; the ratio a2 of the thread pitch to the diameter of the screw mandrel 2 is 0.7-1.0, specifically 0.7, 0.75, 0.8, 0.85, 0.9, 1.0, or any two of the above values; the minimum distance d2 between the screw 2 and the inner wall of the barrel 1 can be 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.2mm, or any two of the above values. In the third section 13, the thread height of the screw 2 is 20%, 21%, 22%, 23%, 24%, 25% of the diameter of the screw mandrel 2, or any two of the above values; the ratio a3 of the thread pitch to the diameter of the screw mandrel 2 can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, or any two of the above values; the minimum distance d3 between the screw and the inner wall of the barrel 1 can be 0.20mm, 0.21mm, 0.22mm, 0.24mm, 0.25mm, or any two of the above values.

[0021] In some embodiments, in the first section 11, the thread height of the screw 2 is 16%-18% of the diameter of the screw mandrel 2, and / or, the ratio a1 of the thread pitch to the diameter of the screw mandrel 2 is 1.4-1.6, and / or, the minimum distance d1 between the screw and the inner wall of the barrel 1 is 0.25mm-0.35mm; and / or, in the second section 12, the thread height of the screw 2 is 25%-30 .... The ratio a2 of the diameter of the mandrel 2 is 0.7-0.9, and / or the minimum distance d2 between the screw and the inner wall of the barrel 1 is 0.15mm-0.18mm; and / or, in the third section 13, the thread height of the screw is 22%-24% of the diameter of the screw mandrel 2, and / or the ratio a3 of the thread pitch to the diameter of the screw mandrel 2 is 0.4-0.6, and / or the minimum distance d3 between the screw and the inner wall of the barrel 1 is 0.20mm-0.23mm. Therefore, the process synergy of the twin-screw extruder at different stages of TPV production can be further improved, and the stability of the mechanical properties of TPV products can be further optimized.

[0022] In some implementations, in the first segment 11, the ratio a1 of the thread pitch to the diameter of the screw mandrel 2 is 1.5, and / or, the minimum distance d1 between the screw and the inner wall of the barrel 1 is 0.3 mm; and / or, in the second segment 12, the ratio a2 of the thread pitch to the diameter of the screw mandrel 2 is 0.8, and / or, the minimum distance d2 between the screw and the inner wall of the barrel 1 is 0.15 mm; and / or, in the third segment 13, the ratio a3 of the thread pitch to the diameter of the screw mandrel 2 is 0.5, and / or, the minimum distance d3 between the screw and the inner wall of the barrel 1 is 0.2 mm. This further improves the process synergy of the twin-screw extruder at different stages of TPV production and further optimizes the mechanical property stability of TPV products.

[0023] In some implementations, the length ratio of the first segment 11, the second segment 12, and the third segment 13 is (2-3.5):(6-8):)(2.5-3.5). This further improves the process synergy of the twin-screw extruder at different stages of TPV production and optimizes the mechanical property stability of TPV products. For example, the length ratio of the first segment 11, the second segment 12, and the third segment 13 can be 2:7:3, 2:6:2.5, 3:8:3.5, 3.5:7:3.5, 2.5:7:3, 3.5:8:3.5, or any range between two of these values.

[0024] In some implementations, the two screws in the double-helix system are arranged parallel to each other.

[0025] In some embodiments, the threads of the two screws in the twin-helix system mesh with each other. In TPV production, a parallel meshing co-directional twin-screw system is preferred (the screw mandrels 2 have parallel axes, and the thread edges mesh with each other). Of course, the engagement method, rotation direction, and speed of the two screws in the twin-screw system can be adjusted according to actual production needs; this application does not impose excessive restrictions on this.

[0026] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A twin-screw extruder for preparing thermoplastic vulcanizates, comprising a barrel and a twin-screw system disposed within the barrel, the twin-screw system comprising two screws, each screw comprising a screw mandrel and a thread disposed outside the screw mandrel, characterized in that, The twin-screw system includes at least a first section, a second section, and a third section along the axial direction of the screws, wherein the thread pitches of the screws in the first, second, and third sections are a1, a2, and a3, respectively; and the minimum distances between the screws in the first, second, and third sections and the inner wall of the barrel are d1, d2, and d3, respectively, wherein a1 > a2 > a3, and d1 > d3 > d2.

2. The twin-screw extruder for preparing thermoplastic vulcanizates according to claim 1, characterized in that, In the first section, the thread height of the screw is 15%-20% of the screw mandrel diameter, the ratio a1 of the thread pitch to the screw mandrel diameter is 1.2-1.8, and the minimum distance d1 between the screw and the inner wall of the barrel is 0.2mm-0.4mm; In the second section, the thread height of the screw is 25%-35% of the screw mandrel diameter, the ratio a2 of the thread pitch to the screw mandrel diameter is 0.7-1.0, and the minimum distance d2 between the screw and the inner wall of the barrel is 0.15mm-0.2mm; In the third section, the thread height of the screw is 20%-25% of the screw mandrel diameter, the ratio a3 of the thread pitch to the screw mandrel diameter is 0.3-0.6, and the minimum distance d3 between the screw and the inner wall of the barrel is 0.2mm-0.25mm.

3. The twin-screw extruder for preparing thermoplastic vulcanizates according to claim 2, characterized in that, In the first section, the thread height of the screw is 16%-18% of the screw mandrel diameter, and / or, the ratio a1 of the thread pitch to the screw mandrel diameter is 1.4-1.6, and / or, the minimum distance d1 between the screw and the inner wall of the barrel is 0.25mm-0.35mm; and / or, In the second section, the thread height of the screw is 25%-30% of the screw mandrel diameter, and / or, the ratio a2 of the thread pitch to the screw mandrel diameter is 0.7-0.9, and / or, the minimum distance d2 between the screw and the inner wall of the barrel is 0.15mm-0.18mm; and / or, In the third section, the thread height of the screw is 22%-24% of the screw mandrel diameter, and / or the ratio a3 of the thread pitch to the screw mandrel diameter is 0.4-0.6, and / or the minimum distance d3 between the screw and the inner wall of the barrel is 0.2mm-0.23mm.

4. The twin-screw extruder for preparing thermoplastic vulcanizates according to claim 2 or 3, characterized in that, In the first segment, the ratio a1 of the thread pitch to the diameter of the screw mandrel is 1.5, and / or, the minimum distance d1 between the screw and the inner wall of the barrel is 0.3 mm; and / or, In the second section, the ratio a2 of the thread pitch to the diameter of the screw mandrel is 0.8, and / or, the minimum distance d2 between the screw and the inner wall of the barrel is 0.15 mm; and / or, In the third section, the ratio a3 of the thread pitch to the diameter of the screw mandrel is 0.5, and / or the minimum distance d3 between the screw and the inner wall of the barrel is 0.2 mm.

5. The twin-screw extruder for preparing thermoplastic vulcanizates according to claim 2 or 3, characterized in that, The length ratio of the first segment, the second segment, and the third segment is (2-3.5):(6-8):)(2.5-3.5).

6. The twin-screw extruder for preparing thermoplastic vulcanizates according to any one of claims 1-3, characterized in that, The two screws in the twin-screw system are arranged in parallel to each other.

7. The twin-screw extruder for preparing thermoplastic vulcanizates according to claim 6, characterized in that, The threads of the two screws in the twin-screw system mesh with each other.

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