A twin-screw structure of a plastic pellet extruder

Abstract

The utility model belongs to the technical field of plastic particle extruder, disclose a kind of double screw structure of plastic particle extruder, including barrel, driven screw and driving screw are arranged in parallel in barrel, driving screw and driven screw are mutually meshed and concentric rotation, the thread element of driving screw is large lead deep groove structure, the thread element of driven screw is small lead shallow groove structure, the lead of large lead deep groove structure is greater than the lead of small lead shallow groove structure, the ratio of the lead of driving screw and the lead of driven screw is 1.5:1 to 2.5:1, the meshing area profile of driving screw and driven screw is asymmetric design, the helix angle of the thread top of driving screw is greater than the helix angle of the thread root of driven screw.The utility model is through the synergies of asymmetric lead, multi-start thread and sectional design, forms the flow field of strong shear and weak shear alternation, to solve the problem of traditional symmetric screw mixing uneven, especially suitable for high viscosity or high filling material.

Description

Technical Field

[0001] This utility model relates to the field of plastic pellet extruder technology, and in particular to a twin-screw structure for a plastic pellet extruder. Background Technology

[0002] Twin-screw extruders are core equipment in polymer material processing and are widely used in plastic mixing, plasticizing, degassing, homogenization and granulation. Their working principle is that two intermeshing screws rotate in the barrel to convey, shear, mix and extrude plastic materials, and finally form a stable melt through the die.

[0003] Existing co-rotating twin-screw extruders typically employ a symmetrical or near-symmetrical design for their two screws. While this design offers certain advantages in conveying stability, it also presents the following problems: 1) Uneven mixing effect: The shear field and flow field distribution of symmetrical screws are relatively uniform. For materials that require alternating strong and weak shear zones to achieve good dispersion and mixing, the mixing effect is not ideal, and "dead zones" or mixing dead angles are easily generated. 2) Limited self-cleaning ability: The traditional symmetrical meshing zone has a relatively simple scraping effect on the root of the screw. For some highly viscous melts, a small amount of material may still remain. Therefore, we propose a twin-screw structure for a plastic granule extruder. Utility Model Content

[0004] In view of the problems of uneven mixing effect and limited self-cleaning ability of the existing twin-screw structure of plastic pellet extruders, this utility model is proposed.

[0005] To solve the above-mentioned technical problems, this utility model provides the following technical solution: A twin-screw structure for a plastic granule extruder includes a barrel, in which a driving screw and a driven screw are arranged in parallel. The driving screw and the driven screw mesh with each other and rotate concentrically. The threaded element of the driving screw is a deep groove structure with a large lead, and the threaded element of the driven screw is a shallow groove structure with a small lead. The lead of the deep groove structure with a large lead is greater than the lead of the shallow groove structure with a small lead.

[0006] As a technical solution for the twin-screw structure of the plastic granule extruder described in this utility model, the ratio of the lead of the driving screw to the lead of the driven screw is 1.5:1 to 2.5:1.

[0007] As a technical solution for the twin-screw structure of the plastic granule extruder described in this utility model, the meshing area profile of the driving screw and the driven screw is asymmetrically designed, and the helix angle at the top of the thread of the driving screw is greater than the helix angle at the root of the thread of the driven screw.

[0008] As a technical solution for the twin-screw structure of the plastic granule extruder described in this utility model, the entire length of the driving screw is divided into a feeding section, a compression section, a mixing section and a homogenization section, wherein the mixing section is mainly located on the driven screw.

[0009] As a technical solution for the twin-screw structure of the plastic granule extruder described in this utility model, the driven screw has at least one set of multi-start threaded sections spaced apart on the mixing section.

[0010] As a technical solution of the twin-screw structure of the plastic granule extruder described in this utility model, the number of threads in the multi-threaded section is three or four.

[0011] As a technical solution for the twin-screw structure of the plastic granule extruder of this utility model, the compression section of the twin-screw structure is formed by synchronously reducing the thread lead of the driving screw and the driven screw, and the lead reduction gradient of the driven screw is greater than the lead reduction gradient of the driving screw.

[0012] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This utility model, through the synergistic effect of asymmetric lead, multi-start thread and segmented design, forms a flow field with alternating strong and weak shear, so as to solve the problem of uneven mixing in traditional symmetrical screws, and is especially suitable for high viscosity or high filler materials.

[0013] 2. This utility model, through the design of asymmetric meshing zone profile and lead gradient difference, can reduce material retention and screw wear. Combined with the segmented flexible adjustment design, it can be adapted to the processing needs of different plastics. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Among them: Figure 1 This is a schematic diagram of the main structure of this utility model.

[0015] Figure 2 This is a schematic diagram of the internal structure of the barrel of this utility model in half section.

[0016] Figure 3 This is a bottom view of the structure of the present invention, showing the active screw and driven screw in a parallel and meshed state.

[0017] Explanation of reference numerals in the attached figures: In the diagram: 1. Barrel; 2. Driving screw; 201. Large lead deep groove structure; 202. Feeding section; 203. Compression section; 204. Mixing section; 205. Homogenization section; 3. Driven screw; 301. Small lead shallow groove structure; 302. Multi-start threaded area. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0019] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0020] Meanwhile, the meaning of "and / or" or "and / or" appearing throughout the text is that it includes three options. Taking "A and / or B" as an example, it includes option A, option B, or an option that satisfies both A and B.

[0021] Furthermore, in this utility model, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.

[0022] Reference Figures 1-3 A twin-screw structure for a plastic granule extruder is provided. The twin-screw structure of the plastic granule extruder includes a barrel 1, in which a driving screw 2 and a driven screw 3 are arranged in parallel. The driving screw 2 and the driven screw 3 mesh with each other and rotate concentrically. An independent temperature control system can be set in the high-shear section of the barrel 1 corresponding to the driven screw 3. The threaded element of the driving screw 2 is a large-lead deep-groove structure 201 (e.g., lead range 30-50mm), and the threaded element of the driven screw 3 is a small-lead shallow-groove structure 301 (e.g., lead range 15-25mm). The lead of the large-lead deep-groove structure 201 is greater than that of the small-lead shallow-groove structure 301. In application, through the asymmetric lead design, the large lead of the driving screw 2 enhances the conveying capacity, and the small lead of the driven screw 3 strengthens the shearing action, forming a differentiated flow field distribution. This avoids the mixing dead zone problem of traditional symmetrical screws. At the same time, the deep-groove structure can increase the melt residence time to improve plasticization uniformity.

[0023] Reference Figure 2 and Figure 3 The ratio of the lead of the driving screw 2 to the lead of the driven screw 3 is 1.5:1 to 2.5:1 (e.g., the lead of the driving screw 2 is 40mm and the lead of the driven screw 3 is 20mm, the ratio is 2:1). In application, the design of a lead ratio of 1.5:1 to 2.5:1 optimizes the balance between conveying and shearing. If the lead ratio is too small, it may lead to insufficient shearing, and if it is too large, it may easily cause melt backflow. This ratio can improve the mixing efficiency.

[0024] Reference Figure 2 and Figure 3 The meshing area profiles of the driving screw 2 and the driven screw 3 are asymmetrically designed. The helix angle at the top of the thread of the driving screw 2 (e.g., 25°) is greater than the helix angle at the root of the thread of the driven screw 3 (e.g., 12°). In application, the larger helix angle at the top of the thread of the driving screw 2 enhances the dragging ability of the material, while the smaller helix angle at the root of the driven screw 3 strengthens the reverse scraping action, reduces the residue of sticky material, and improves self-cleaning performance.

[0025] Reference Figure 3 The entire length of the driving screw 2 is divided into a feeding section 202 (if a maximum lead of 50 mm is used), a compression section 203, a mixing section 204, and a homogenization section 205 (if the lead is stable). The mixing section 204 is mainly set on the driven screw 3. In application, the feeding section 202 conveys materials quickly with a large lead, the compression section 203 increases pressure through lead gradient changes, the mixing section 204 relies on the small lead multi-start thread of the driven screw 3 to enhance dispersion and mixing, and the homogenization section 205 stably extrudes materials, thus achieving process adaptability.

[0026] Reference Figure 2 and Figure 3At least one set of multi-start threaded sections 302 are spaced apart on the mixing section of the driven screw 3. The number of threads in the multi-start threaded sections 302 is three or four, and the number of threads is selected according to the viscosity of the material: high viscosity materials (such as TPU) use four-start threads to enhance shearing, and ordinary plastics (such as PP and PE) use three-start threads to balance mixing and conveying. Applicable materials include PVC, TPU, and high-filled composite materials. Working parameters: screw speed: 200-400 rpm, barrel 1 temperature: controlled in sections according to the melting characteristics of the material (such as 150℃ in the feeding section and 200℃ in the homogenization section), compression ratio: controlled at 2.5:1-3:1 by adjusting the lead gradient. In application, the three-start or four-start threads form multi-channel shearing in the mixing section, breaking the laminar flow, which is especially suitable for the dispersion of high-filled or nano-composite materials.

[0027] Reference Figure 2 and Figure 3 The compression section of the twin-screw structure is formed by the synchronous reduction of the thread lead of the driving screw 2 and the driven screw 3 (e.g., gradually reducing from 50mm to 30mm). The lead reduction gradient of the driven screw 3 is greater than that of the driving screw 2 (e.g., from 25mm to 10mm). In application, the lead of the driven screw 3 decreases faster, forming a gradual compression, avoiding overheating or degradation caused by a sudden increase in melt pressure, which is suitable for heat-sensitive materials.

[0028] This invention provides a twin-screw structure for a plastic granule extruder. Through the synergistic effect of asymmetric lead, multi-start screw, and segmented design, it forms an alternating flow field of strong and weak shear to solve the problem of uneven mixing in traditional symmetrical screws. It is especially suitable for high-viscosity or high-filled materials. At the same time, through the asymmetric meshing zone profile and lead gradient difference design, it reduces material retention and screw wear. Combined with the segmented flexible adjustment design, it can be adapted to the processing needs of different plastics.

[0029] It should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of the technical solution of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A twin-screw structure for a plastic granule extruder, comprising a barrel (1), wherein a driving screw (2) and a driven screw (3) are arranged in parallel within the barrel (1), the driving screw (2) and the driven screw (3) meshing with each other and rotating concentrically, characterized in that: The threaded element of the driving screw (2) is a large-lead deep groove structure (201), and the threaded element of the driven screw (3) is a small-lead shallow groove structure (301). The lead of the large-lead deep groove structure (201) is greater than the lead of the small-lead shallow groove structure (301).

2. The twin-screw structure of the plastic pellet extruder according to claim 1, characterized in that: The ratio of the lead of the driving screw (2) to the lead of the driven screw (3) is 1.5:1 to 2.5:

1.

3. The twin-screw structure of the plastic pellet extruder according to claim 2, characterized in that: The meshing area profile of the active screw (2) and the driven screw (3) is asymmetrically designed, and the helix angle at the top of the thread of the active screw (2) is greater than the helix angle at the root of the thread of the driven screw (3).

4. The twin-screw structure of the plastic pellet extruder according to claim 1, characterized in that: The entire length of the active screw (2) is divided into a feeding section (202), a compression section (203), a mixing section (204) and a homogenization section (205), wherein the mixing section (204) is mainly located on the driven screw (3).

5. The twin-screw structure of the plastic pellet extruder according to claim 1, characterized in that: The driven screw (3) has at least one set of multi-start threaded sections (302) spaced apart on the mixing section.

6. The twin-screw structure of the plastic pellet extruder according to claim 5, characterized in that: The number of threaded starts in the multi-start threaded area (302) is three or four.

7. The twin-screw structure of the plastic pellet extruder according to claim 1, characterized in that: The compression section of the twin-screw structure is formed by synchronously reducing the thread lead of the driving screw (2) and the driven screw (3), and the lead reduction gradient of the driven screw (3) is greater than the lead reduction gradient of the driving screw (2).

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