High filling screws for plastic extruders

Abstract

The invention discloses a high-filling screw for a plastic extruder, comprising a rod body and screw ribs, wherein the rod body has a feeding section, a compression section, a shearing section and a discharging section connected in sequence from the tail to the head, the screw ribs are arranged on the rod body along the circumferential direction and spirally extend from the feeding section to a part of the discharging section, a screw groove is formed between the spacing of the screw ribs and the rod body, the compression section has a gradually increasing outer diameter, and on the shearing section, a plurality of wavy portions protruding outward in a radial direction are arranged in the screw groove, the plurality of wavy portions are arranged along the direction of the screw groove, each wavy portion has a wave crest away from the rod body in the radial direction and a wave trough close to the rod body in the radial direction, and the depth of the screw groove at the wave trough of the wavy portion is greater than the depth of the screw groove at the wave crest of the wavy portion. After the alternating circulation of the screw grooves at the plurality of wave crests and the plurality of wave troughs, the material can achieve a better plasticizing and mixing effect in the shearing section.

Description

Technical Field

[0001] The invention relates to the technical field of plastic extrusion, in particular to an extrusion screw for a plastic extruder, which is mainly used for the extrusion production of highly filled products such as SPC floors, WPC floors, and PP corrugated pipes. Background Art

[0002] SPC is the abbreviation of Stone Plastic Composites. The main raw material is polyvinyl chloride resin. It is made by extruding the SPC substrate with an extruder combined with a T-die, and heating and laminating the PVC wear-resistant layer, PVC color film and SPC substrate at one time with a three-roll or four-roll calender. No glue is used in the production process. WPC is an emerging composite material, which is characterized by being green and environmentally friendly, using plastic instead of wood. Wood Plastic Composite (WPC) is an emerging material. In the most common sense, the abbreviation WPC represents a wide range of composite materials. These materials are made of pure or recycled plastics and natural fiber fillers. The plastics can be various plastics such as high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS) and polyvinyl chloride (PVC), while the natural fibers include wood powder and linen fibers. Polypropylene, referred to as PP, is a colorless, odorless, non-toxic, translucent solid substance. Polypropylene (PP) is a thermoplastic synthetic resin with excellent performance. It is a colorless, translucent thermoplastic lightweight general-purpose plastic. Polypropylene has chemical resistance, heat resistance, electrical insulation, high-strength mechanical properties and good high wear resistance processing properties. Since its advent, it has been rapidly developed and applied in many fields such as machinery, automobiles, electronics and electrical appliances, construction, textiles, packaging, agriculture, forestry, fishery and food industry.

[0003] A conventional extrusion screw generally includes a rod body and screw fins. The rod body has a feeding section, a compression section, a shearing section, and a discharging section connected in sequence from the tail to the head. The screw fins are arranged circumferentially on the rod body and extend spirally from the tail of the rod body to the head. The spacing between the screw fins and the rod body forms a screw groove. The compression section generally has an outer diameter that gradually increases along its length, so that the depth of the screw groove between the screw and the barrel gradually decreases, thereby extruding the material. Usually, the material is fed through the feeding section and transported from the tail to the head of the rod body, extruded through the compression section, and then plasticized and melted by the shear heat of the shearing section, and finally extruded through the discharging section to form a product. In order to reduce the production cost of plastic products and improve certain properties of plastic products, such as increasing rigidity, reducing shrinkage, and improving coloring effects, a certain proportion of fillers are added to the raw materials for plastic molding. For the extrusion of such highly filled materials, ordinary screw structures have poor plasticizing effects, unstable feeding, high shear temperatures, and easy decomposition of materials. In addition, the extrusion pressure on the materials is relatively large, and the large fluctuations in the materials are not conducive to the plasticizing and mixing of the materials, resulting in a high rate of defective products. Summary of the invention

[0004] In order to solve the above technical problems, the object of the present invention is to provide a high-filling screw for a plastic extruder with better plasticizing and mixing effects.

[0005] In order to achieve the purpose of the above invention, the present invention adopts the following technical solutions:

[0006] A high-filling screw for a plastic extruder comprises a rod body and screw fins, wherein the rod body comprises a feeding section, a compression section, a shearing section and a discharging section which are sequentially connected in a direction from a tail to a head, the screw fins are circumferentially arranged on the rod body and spirally extend from the feeding section to a portion of the discharging section, a screw groove is formed between the spacing of the screw fins and the rod body, the compression section has a gradually increasing outer diameter, and on the shearing section, a plurality of wavy portions protruding outward in a radial direction are arranged in the screw groove, the plurality of wavy portions are arranged along the direction of the screw groove, each of the wavy portions has a crest away from the rod body in a radial direction and a trough close to the rod body in a radial direction, and the depth of the screw groove at the trough of the wavy portion is greater than the depth of the screw groove at the crest of the wavy portion.

[0007] In the above technical scheme, preferably, the discharging section includes a barrier section, a metering section and a mixing section which are connected in sequence from the tail to the head of the rod body, the barrier section is provided with a main edge and a secondary edge extending in a circumferential spiral direction, the main edge and the secondary edge are arranged alternately, and a feed trough and a discharging trough arranged side by side are provided between the main edge and the secondary edge, the main edge and the secondary edge have a height difference in the radial direction, the spiral edge extends to the metering section, and the mixing section is provided with a plurality of rows of pins arranged along its length direction, and each row of pins is arranged along the circumferential direction.

[0008] In the above technical solution, preferably, the ratio of the height difference to the diameter of the high-filling screw is 0.008-0.012:1.

[0009] In the above technical solution, preferably, the length ratio of the feeding section, the compression section, the shearing section, the barrier section, the metering section and the mixing section is 7-8:3-4:10-12:2-3:3-4:2-3.

[0010] In the above technical solution, preferably, the ratio of the diameter of the metering section to the diameter of the high-filling screw is 0.85-0.92:1.

[0011] In the above technical solution, preferably, the ratio of the diameter of the mixing section to the diameter of the high-filling screw is 0.75-0.85:1.

[0012] In the above technical solution, preferably, the maximum height of the wave crest of the wavy portion in the radial direction is smaller than the height of the screw flight in the radial direction.

[0013] In the above technical solution, preferably, two adjacent wavy portions are arranged to be away from each other in the radial direction.

[0014] In the above technical solution, preferably, the ratio of the screw groove depth at the wave crest of the wavy portion to the diameter of the high-filling screw is 0.02-0.05:1.

[0015] In the above technical solution, preferably, the ratio of the depth of the screw groove at the trough of the wavy portion to the diameter of the high-filling screw is 0.05-0.1:1.

[0016] In the above technical solution, preferably, the ratio of the diameter of the feeding section to the diameter of the high-filling screw is 0.6-0.8:1.

[0017] In the above technical solution, preferably, the ratio of the diameter of the shearing section to the diameter of the high-filling screw is 0.85-0.92:1.

[0018] In the above technical solution, preferably, the diameter of the high-filling screw is 65-120 mm.

[0019] The present invention provides a plurality of wavy portions protruding outward in a radial direction in the screw groove on the shearing section, the plurality of wavy portions are arranged along the direction of the screw groove, each wavy portion has a wave crest far away from the rod body in the radial direction and a wave trough close to the rod body in the radial direction, and the depth of the screw groove at the wave trough is greater than the depth of the screw groove at the wave crest, so that the shearing effect on the material in the screw groove at the wave crest is greater than the shearing effect on the material in the screw groove at the wave trough, and the shearing effect on the material in the screw groove at the wave trough is weakened, so that the extrusion pressure on the material is released, the temperature is relaxed, and the material is not subjected to excessive shear heat and decomposed, and after the screw grooves at the plurality of wave crests and the plurality of wave troughs are alternately circulated, the material can achieve better plasticization and mixing effects in the shearing section. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the present invention;

[0021] Figure 2 It is a structural schematic diagram of the shearing section of the present invention;

[0022] Figure 3 yes Figure 2 A local enlarged schematic diagram of the middle A;

[0023] Figure 4 yes Figure 2 Schematic diagram of the cross-section structure along line BB;

[0024] Figure 5 yes Figure 2 Schematic diagram of the cross-sectional structure along the CC line;

[0025] Figure 6 is a schematic structural diagram of a barrier segment of the present invention;

[0026] Figure 7 is a schematic cross-sectional view of a barrier segment of the present invention;

[0027] Figure 8 It is a schematic structural diagram of the mixing section of the present invention;

[0028] Fig. 9 is a cross-sectional schematic diagram of a mixing section of the present invention;

[0029] Among them: 1, rod body; 11, feeding section; 12, compression section; 13, shearing section; 14, barrier section; 15, metering section; 16, mixing section; 111, head; 112, tail;

[0030] 2. Screw edge; 21. Main edge; 22. Secondary edge; 23. Pin;

[0031] 3. Screw groove; 31. Feed chute; 32. Discharge chute;

[0032] 4. wavy portion; 41. wave crest; 42. wave trough. DETAILED DESCRIPTION

[0033] In order to explain the technical content, structural features, objectives and effects of the invention in detail, the following will be described in detail with reference to the embodiments and the accompanying drawings.

[0034] The invention is mainly used on a plastic extruder to perform extrusion operations on highly filled materials.

[0035] like Figure 1 As shown, the high filling screw includes a rod body 1 and screw fins 2. The rod body 1 has a feeding section 11, a compression section 12, a shearing section 13, a barrier section 14, a metering section 15 and a mixing section 16 connected in sequence from the tail 112 to the head 111. Among them, the barrier section 14, the metering section 15 and the mixing section 16 are used as discharge sections. When the material reaches these three sections, it is basically in a molten state to be discharged. A small part of the material that is not completely melted is further plasticized and mixed in these three sections, and finally reaches a molten state. The screw fins 2 are arranged on the rod body 1 along the circumferential direction and extend spirally from the feeding section 11 to part of the discharge section. Specifically, the feeding section 11, the compression section 12, the shearing section 13 and the metering section 15 are all provided with screw fins 2, and the spacing between the screw fins 2 and the rod body 1 forms a screw groove 3. When the high-filling screw is assembled on a plastic extruder, it cooperates with the inner hole of the barrel of the plastic extruder. The material moves along the direction of the screw groove 3 from the tail 112 to the head 111, is extruded in the compression section 12, is sheared in the shear section 13, plasticized, mixed and melted, and finally reaches the discharge section, where it is further completely plasticized and melted to prepare for extrusion of products. In this example, the diameter D of the high-filling screw is 65-120 mm, which is suitable for the extrusion of high-filling materials in extruders of various specifications.

[0036] In order to increase the conveying capacity of high-filling materials and improve feeding efficiency, the structure of the feeding section 11 is a deep groove bottom diameter, that is, the diameter of the rod body 1 in this section is smaller, the depth of the screw groove 3 is larger, and the diameter d1 of the feeding section 11 is 0.6-0.8D.

[0037] The compression section 12 has a gradually increasing outer diameter d2. In this section, the depth of the screw groove 3 gradually decreases from the tail 112 to the head 111 of the rod body 1. The material is squeezed in this section and is gradually compacted.

[0038] like Figure 2 , Figure 3As shown, in the shearing section 13, a plurality of wavy portions 4 protruding outward in the radial direction are provided in the screw groove 3. The plurality of wavy portions 4 are arranged along the direction of the screw groove 3, and two adjacent wavy portions 4 are arranged away from each other in the radial direction. Each wavy portion 4 has a wave crest 41 away from the rod body 1 in the radial direction and a wave trough 42 close to the rod body 1 in the radial direction. The maximum height of the wave crest 41 of the wavy portion 4 in the radial direction is less than the height of the screw ridge 2 in the radial direction, so that a gap is formed between the wave crest 41 of the wavy portion 4 and the screw ridge 2, and the material can pass through the gap between the wave crest 41 and the screw ridge 2, and the shearing effect on the material in the screw groove at the wave crest 41 is aggravated. Figure 4 , Figure 5 As shown, the distance between the crest 41 of the wavy portion 4 and the screw ridge 2 (i.e., the screw groove depth H1 at the crest 41) is smaller than the distance between the trough 42 of the wavy portion 4 and the screw ridge 2 (i.e., the screw groove depth H2 at the trough 42), so that the screw groove depth at the trough 42 of the wavy portion 4 is greater than the screw groove depth at the crest 41 of the wavy portion 4, and the shearing effect on the material in the screw groove at the trough 42 is relatively weakened, so that the extrusion pressure on the material can be released, and the temperature can be moderated, so that the material will not be decomposed due to excessive shear heat. After the alternating cycles of the screw grooves at multiple crests 41 and multiple troughs 42, the material can achieve better plasticization and mixing effects in the shear section 13. The diameter d3 of the shearing section 13 is 0.85-0.92D, the depth H1 of the screw groove at the crest 41 of the wavy portion 4 is 0.02-0.05D, and the depth H2 of the screw groove at the trough 42 of the wavy portion 4 is 0.05-0.1D.

[0039] like Figure 6 , Figure 7 As shown, the barrier section 14 is provided with a main edge 21 and a secondary edge 22 extending in a circumferential spiral direction, and the rotation direction of the main edge 21 and the secondary edge 22 is consistent with the rotation direction of the screw edge 2, the main edge 21 and the secondary edge 22 are arranged in an alternating manner, and a feed trough 31 and a discharge trough 32 arranged side by side are provided between the main edge 21 and the secondary edge 22, and the main edge 21 and the secondary edge 22 have a spacing in the radial direction. When passing through the barrier section 14, the material can enter from the feed trough 31 and flow into the discharge trough 32 across the spacing between the main edge 21 and the secondary edge 22. The incompletely melted material can form a vortex between the feed trough 31 and the discharge trough 32 under the rotation of the high-filling screw, and the flow direction of the vortex is opposite to the direction of travel of the material, so that a small portion of the incompletely melted material can be subjected to a higher shearing effect in this section and further plasticized, while the completely melted material travels along the discharge trough 32 to the metering section 15. The diameter d4 of the barrier section 14 is equal to the diameter D of the high-filling screw, and the height difference δ between the main edge 21 and the secondary edge 22 in the radial direction is 0.008-0.012D.

[0040] The screw 2 extends to the metering section 15, and the ratios of the length L1 of the feeding section 11, the length L2 of the compression section 12, the length L3 of the shearing section 13, the length L4 of the barrier section 14, the length L5 of the metering section 15, and the length L6 of the mixing section 16 are 7-8:3-4:10-12:2-3:3-4:2-3, so that the metering section 15 is designed to be longer, and the material gradually builds up a stable pressure after being transported by the metering section 15, reducing the extrusion vibration. Figure 8 , Fig. 9 As shown, the mixing section 16 is provided with multiple rows of pins 23 arranged along its length direction, and each row of pins 23 is arranged along the circumferential direction. The material is dispersed and mixed by the pins 23, and the molten material is divided into multiple strands and then merged again, which plays a good role in dispersion and mixing. At the same time, the temperature of the melt can be appropriately reduced, eliminating the influence of temperature fluctuations. Among them, the diameter d5 of the metering section 15 is 0.85-0.92D, and the diameter d6 of the mixing section 16 is 0.75-0.85D.

[0041] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-filling screw for a plastic extruder, comprising a rod body (1) and screw fins (2), the rod body (1) having a feeding section (11), a compression section (12), a shearing section (13) and a discharge section sequentially connected in a direction from the tail to the head, the screw fins (2) being arranged on the rod body (1) along the circumferential direction and spirally extending from the feeding section (11) to part of the discharge section, the spacing between the screw fins (2) and the rod body (1) forming a screw groove (3), the compression section (12) having a gradually increasing outer diameter, characterized in that: In the shearing section (13), a plurality of wavy portions (4) protruding outwardly in the radial direction are arranged in the screw groove (3); the plurality of wavy portions (4) are arranged along the direction of the screw groove (3); each of the wavy portions (4) has a wave crest (41) away from the rod body (1) in the radial direction and a wave trough (42) close to the rod body (1) in the radial direction; the depth of the screw groove at the wave trough (42) of the wavy portion (4) is greater than the depth of the screw groove at the wave crest (41) of the wavy portion (4); The maximum height of the wave crest (41) of the portion (4) in the radial direction is smaller than the height of the screw flight (2) in the radial direction, the ratio of the screw groove depth at the wave crest (41) of the wave-shaped portion (4) to the diameter of the high-filling screw is 0.02-0.05:1, and the ratio of the screw groove depth at the wave trough (42) of the wave-shaped portion (4) to the diameter of the high-filling screw is 0.05-0.1:1; the discharge section comprises a barrier section (14), a metering section (15), and a plurality of other sections connected in sequence from the tail to the head of the rod body (1). 5) and a mixing section (16), wherein the length ratios of the feeding section (11), the compression section (12), the shearing section (13), the barrier section (14), the metering section (15) and the mixing section (16) are 7-8:3-4:10-12:2-3:3-4:2-3, wherein the barrier section (14) is provided with main edges (21) and secondary edges (22) extending in a circumferential spiral direction, wherein the main edges (21) and the secondary edges (22) are arranged in an alternating manner, and the main edges (21) and the secondary edges (22) are arranged in an alternating manner. A feed trough (31) and a discharge trough (32) arranged side by side are provided between the ridge (21) and the secondary ridge (22); the main ridge (21) and the secondary ridge (22) have a height difference in the radial direction, and the ratio of the height difference to the diameter of the high-filling screw is 0.008-0.012:1; the screw ridge (2) extends to the metering section (15); and the mixing section (16) is provided with a plurality of rows of pins (23) arranged along its length direction, and each row of the pins (23) is arranged along the circumferential direction.

2. The high filling screw for plastic extruder according to claim 1, characterized in that: The ratio of the diameter of the metering section (15) to the diameter of the high-filling screw is 0.85-0.92:

1.

3. The high filling screw for plastic extruder according to claim 1, characterized in that: The ratio of the diameter of the mixing section (16) to the diameter of the high filling screw is 0.75-0.85:

1.

4. The high filling screw for plastic extruder according to claim 1, characterized in that: Two adjacent wavy portions (4) are arranged to be separated from each other in the radial direction.

5. The high filling screw for plastic extruder according to claim 1, characterized in that: The ratio of the diameter of the feeding section (11) to the diameter of the high filling screw is 0.6-0.8:

1.

6. The high filling screw for plastic extruder according to claim 1, characterized in that: The ratio of the diameter of the shearing section (13) to the diameter of the high-filling screw is 0.85-0.92:

1.

7. The high filling screw for plastic extruder according to claim 1, characterized in that: The diameter of the high filling screw is 65-120 mm.

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