Polytetrafluoroethylene extruder

Abstract

The utility model discloses a polytetrafluoroethylene extruder which comprises an extrusion cylinder body and a plunger prepressing module, a plunger prepressing cavity and a screw plasticizing cavity which are sequentially communicated are arranged in the extrusion cylinder body, the plunger prepressing cavity is connected with the plunger prepressing module, an extrusion outlet is arranged at one end of the screw plasticizing cavity deviating from the plunger prepressing cavity, a short screw is arranged in the screw plasticizing cavity, and the short screw is connected with the plunger prepressing module. The axis of the short screw is parallel to the propelling direction of the plunger prepressing module, the end, away from the plunger prepressing module, of a screw shaft of the short screw extends out of the extrusion barrel, and the extending end of the screw shaft of the short screw is connected with a side driving module. According to the technical scheme, through a composite plunger-screw collaborative extrusion structure, on the basis that the plunger pre-pressing module is kept to densify unmodified PTFE powder at high pressure, the short screw plasticizing cavity is introduced to perform low-temperature low-shear plasticizing on a pre-pressed blank, so that the fluidity of paste and the filling uniformity of the mold are remarkably improved, and the production efficiency is improved. And high-efficiency continuous production of complex profiled bars (such as multi-cavity pipes and thin-wall sealing strips) is realized.

Description

Technical Field

[0001] This utility model relates to the field of polytetrafluoroethylene (PTFE) extruder technology, and particularly to a PTFE extruder. Background Technology

[0002] Polytetrafluoroethylene (PTFE) is widely used in sealing, insulation, and corrosion protection due to its excellent chemical resistance, high temperature resistance, and extremely low coefficient of friction. Currently, PTFE extrusion processing mainly relies on two types of equipment: plunger extruders and screw extruders.

[0003] Plunger extruders pre-compress PTFE mixtures into PTFE billets using hydraulic or mechanical pressure and push them into a heating section, forming profiles using the paste extrusion principle. While this technology maintains the original properties of PTFE, it is limited by intermittent operation, resulting in low production efficiency and is only suitable for producing simple cross-sections (such as rods and pipes). Screw extruders achieve continuous plasticizing and extrusion through screw rotation, theoretically capable of processing complex profiles. However, PTFE melt viscosity is extremely high, making it difficult for traditional screws to achieve effective shearing and melt transport. Chemical modification of PTFE (such as introducing comonomers to reduce crystallinity) is necessary to adapt to processing requirements, leading to a significant decrease in core properties such as temperature resistance and chemical inertness. Plunger extruders are inefficient and have limited molding capacity, while screw extruders are highly dependent on material modification; neither can simultaneously meet the high performance and complex structural requirements of PTFE products. Furthermore, the lubricant residue problem in plunger processes and the high-temperature decomposition risk in screw processes further restrict product quality and safety. Utility Model Content

[0004] The main purpose of this invention is to provide a polytetrafluoroethylene (PTFE) extruder that balances the requirements for high performance and complex structure of PTFE products.

[0005] To achieve the above objectives, this utility model proposes a polytetrafluoroethylene extruder, including an extrusion barrel and a plunger pre-compression module. The extrusion barrel is provided with a plunger pre-compression chamber and a screw plasticizing chamber connected in sequence. The plunger pre-compression chamber is connected to the plunger pre-compression module. The end of the screw plasticizing chamber opposite to the plunger pre-compression chamber is provided with an extrusion outlet. A short screw is provided in the screw plasticizing chamber. The axis of the short screw is parallel to the propulsion direction of the plunger pre-compression module. The end of the short screw shaft opposite to the plunger pre-compression module extends out of the extrusion barrel. The end of the short screw shaft extending out of the extrusion barrel is connected to a side-mounted drive module.

[0006] In one possible implementation, the side-mounted drive module includes a gearbox and a drive motor. The output shaft of the gearbox is connected to the screw shaft of the short screw via a transmission component, and the input shaft of the gearbox is fixedly connected to the output shaft of the drive motor.

[0007] In one possible implementation, the gearbox is a right-angle gearbox, the input shaft of which is coaxially connected to the output shaft of the drive motor, the transmission component is a coupling or a spline, and the output shaft of the right-angle gearbox is connected to the screw shaft of the short screw via a coupling or a spline.

[0008] In one possible implementation, a sealing ring is provided between the screw shaft of the short screw and the extrusion barrel, and the sealing ring is a graphite-filled sealing ring.

[0009] In one possible implementation, the length of the short screw is 3-5 times the screw diameter, and the surface of the short screw is plated with a hard chromium layer or a nickel-based alloy layer.

[0010] In one possible implementation, the extrusion cylinder is provided with a segmented heating structure, which includes a preheating zone, a melting zone, and a homogenizing zone. The preheating zone and the melting zone are both located outside the plunger pre-compression chamber, and the homogenizing zone is located outside the spiral plasticizing chamber. The preheating zone, the melting zone, and the homogenizing zone are all equipped with electromagnetic induction heaters.

[0011] The working principle and beneficial effects of this utility model are as follows:

[0012] This utility model's technical solution utilizes a composite plunger-screw co-extrusion structure. While retaining the plunger pre-compression module for high-pressure compaction of unmodified PTFE powder, it introduces a short screw plasticizing chamber for low-temperature, low-shear plasticization of the pre-compressed billet. This significantly improves the paste flowability and mold filling uniformity, enabling efficient and continuous production of complex profiles (such as multi-cavity tubes and thin-walled sealing strips). It solves the problems of low efficiency and limited molding capacity of traditional plunger extruders. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art 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 the structures shown in these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the structure of this utility model;

[0015] Figure 2 This is the right view of the present invention;

[0016] Figure 3 This is a top view of the present invention;

[0017] Figure 4 for Figure 3 Sectional view at point AA.

[0018] Explanation of reference numerals: 1. Extrusion barrel; 2. Plunger pre-compression module; 3. Plunger pre-compression chamber; 4. Screw plasticizing chamber; 5. Side-mounted drive module; 11. Extrusion outlet; 12. Preheating zone; 13. Melting zone; 14. Immersion zone; 41. Short screw; 51. Gearbox; 52. Drive motor.

[0019] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] like Figures 1-4 As shown, this embodiment proposes a polytetrafluoroethylene extruder, including an extrusion barrel 1 and a plunger pre-compression module 2. The extrusion barrel 1 is provided with a plunger pre-compression chamber 3 and a screw plasticizing chamber 4 connected in sequence. The plunger pre-compression chamber 3 is connected to the plunger pre-compression module 2. The end of the screw plasticizing chamber 4 opposite to the plunger pre-compression chamber 3 is provided with an extrusion outlet 11. A short screw 41 is provided in the screw plasticizing chamber 4. The axis of the short screw 41 is parallel to the pushing direction of the plunger pre-compression module 2. The end of the screw shaft of the short screw 41 opposite to the plunger pre-compression module 2 extends out of the extrusion barrel 1. The end of the screw shaft of the short screw 41 is connected to a side-mounted drive module 5.

[0022] The extrusion barrel 1, as the main structure of the equipment, supports the plunger pre-compression chamber 3, the screw plasticizing chamber 4, and other functional modules, ensuring overall rigidity and stability. By separating the plunger pre-compression chamber 3 and the screw plasticizing chamber 4, it achieves a continuous "pre-compression → plasticizing → extrusion" process for PTFE processing. The partitioned design matches the processing characteristics of PTFE (pre-compression compaction + low-temperature plasticizing), avoiding the problem of uneven pressure transmission in traditional single-chamber systems; the segmented barrel structure facilitates later maintenance or upgrades. The plunger pre-compression module 2 is used to provide pressure via hydraulic or mechanical drive to compress the PTFE powder and lubricant mixture into a high-density billet (density ≥ 2.1 g / cm³). 3The short screw 41 reduces particle gaps and pushes the preform into the screw plasticizing chamber 4. The connection between the plunger pre-compression chamber 3 and the screw plasticizing chamber 4 allows the pre-compressed preform to directly enter the screw plasticizing chamber 4, avoiding material loss or contamination caused by intermediate transfer. The short screw 41 is used to apply slight shearing to the preform at low temperature, reducing the flow resistance of the paste; the rotation of the short screw 41 evenly pushes the plasticized paste to the extrusion outlet 11, ensuring continuous discharge. The short screw 41 shears and breaks the van der Waals forces between PTFE particles, reducing the viscosity of the paste and improving the filling capacity of complex profiles; at the same time, the low-temperature operation of the short screw 41 can prevent the generation of toxic gases (such as PFIB). The side-mounted drive module 5 is used to provide power to the short screw 41 and drive the short screw 41 to rotate.

[0023] In this embodiment, the side-mounted drive module 5 includes a gearbox 51 and a drive motor 52. The output shaft of the gearbox 51 is connected to the screw shaft of the short screw 41 via a transmission component, and the input shaft of the gearbox 51 is fixedly connected to the output shaft of the drive motor 52. The gearbox 51 is a right-angle gearbox 51, and the input shaft of the right-angle gearbox 51 is coaxially connected to the output shaft of the drive motor 52. The transmission component is a coupling or a spline, and the output shaft of the right-angle gearbox 51 is connected to the screw shaft of the short screw 41 via a coupling or a spline.

[0024] The right-angle gearbox 51 converts the horizontal rotational motion of the drive motor 52 into a rotational direction perpendicular to the motor shaft (or transmits power at a set angle), adapting to the spatial layout requirements of the side-mounted drive module 5; and reduces the output speed and increases the torque through the gear reduction ratio, matching the low-speed, high-torque requirements of the short screw 41. The right-angle steering avoids interference between the drive module and the extrusion barrel 1 and the discharge path, ensuring equipment compactness; the high reduction ratio design meets the high-resistance shearing requirements of PTFE paste extrusion, avoiding motor overload; the drive motor 52 provides the mechanical energy required for the rotation of the short screw 41, and can be a servo motor or a frequency converter motor, supporting precise speed control; the coupling or spline (not shown in the figure) transmits the rotational motion of the output shaft of the gearbox 51 to the shaft of the short screw 41, ensuring lossless torque transmission. The overall design of the side-mounted drive module 5 places the drive system on the side of the extrusion barrel 1, effectively avoiding conflict with the plunger pre-compression module 2 or the discharge direction;

[0025] In this embodiment, a sealing ring is provided between the screw shaft of the short screw 41 and the extrusion barrel 1, and the sealing ring is a graphite-filled sealing ring. The length of the short screw 41 is 3-5 times the screw diameter, and the surface of the short screw 41 is coated with a hard chrome layer or a nickel-based alloy layer.

[0026] The sealing ring (not shown in the diagram) prevents PTFE paste and lubricant from leaking from the screw plasticizing chamber 4 into the external environment during screw shaft rotation; it also withstands the high pressure transmitted by the plunger pre-compression, ensuring stable pressure within the barrel. Graphite filler is heat-resistant up to 500℃ and adapts to PTFE processing temperatures (250-380℃), preventing leakage due to seal failure; the low coefficient of friction between graphite and the screw shaft reduces wear. A short screw 41, 3-5 times the screw diameter, applies moderate shear to the PTFE paste within a short stroke, reducing flow resistance while preventing excessive shearing that could lead to material decomposition; a 3-5 times length-to-diameter ratio (L / D) effectively balances shear force and conveying efficiency, reduces paste viscosity, and improves flow uniformity. The short-stroke design adapts to the "paste extrusion" characteristics of PTFE, avoiding torque overload caused by high viscosity in traditional long screws (L / D > 10). A hard chrome plating or nickel-based alloy coating resists friction and wear between PTFE particles and the screw surface, extending service life. At the same time, it prevents the chemical corrosion of the screw by lubricant evaporation residues (such as acidic decomposition products).

[0027] In this embodiment, the extrusion cylinder 1 is provided with a segmented heating structure, which includes a preheating zone 12, a melting zone 13, and a soaking zone 14. The preheating zone 12 and the melting zone 13 are both located outside the plunger pre-compression chamber 3, and the soaking zone 14 is located outside the spiral plasticizing chamber. The preheating zone 12, the melting zone 13, and the soaking zone 14 are all electromagnetic induction heaters.

[0028] The preheating zone 12 is located outside the plunger pre-compression chamber 3, near the raw material inlet. It is used to gradually heat the PTFE powder and lubricant mixture from room temperature to 150-200℃, initially softening the particle surface; promoting the uniform penetration of lubricants such as paraffin oil into the gaps between PTFE particles, reducing subsequent extrusion resistance. The melting zone 13 is located outside the plunger pre-compression chamber 3, immediately downstream of the preheating zone 12. It is used to soften the PTFE particles at 280-320℃, forming a semi-molten "paste state"; reducing material viscosity and providing a basis for shear flow in the plasticizing section of the short screw 41. The soaking zone 14 is located outside the screw plasticizing chamber 4. It is used to eliminate the internal temperature gradient of the paste at 340-360℃, ensuring uniform material flow; partially crystallizing the PTFE molecular chains, improving the initial strength of the extruded profile. The electromagnetic induction heater directly heats the metal barrel (non-contact type) through electromagnetic induction, and the eddy current effect causes the barrel surface to heat up instantaneously. The temperature control accuracy of the electromagnetic induction heater is ±1℃ (compared to ±5℃ for traditional resistance heating), which can effectively prevent local overheating and decomposition of PTFE (decomposition temperature > 380℃).

[0029] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this application, it should be understood that if terms such as "upper," "lower," "left," and "right" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the accompanying drawings are only for illustrative purposes and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0030] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A polytetrafluoroethylene extruder comprising an extrusion barrel (1), a plunger pre-pressing module (2), characterized in that, The extrusion barrel (1) is provided with a plunger pre-pressing cavity (3) and a screw plasticizing cavity (4) which are communicated in sequence, the plunger pre-pressing cavity (3) is connected with a plunger pre-pressing module (2), one end of the screw plasticizing cavity (4) away from the plunger pre-pressing cavity (3) is provided with an extrusion outlet (11), the screw plasticizing cavity (4) is provided with a short screw (41), the axis of the short screw (41) is parallel to the pushing direction of the plunger pre-pressing module (2), one end of the screw shaft of the short screw (41) away from the plunger pre-pressing module (2) extends out of the extrusion barrel (1), and one end of the screw shaft of the short screw (41) extending out is connected with a side-mounted driving module (5).

2. A polytetrafluoroethylene extruder according to claim 1, wherein The side-mounted driving module (5) comprises a gear box (51) and a driving motor (52), the output shaft of the gear box (51) is connected with the screw shaft of the short screw (41) through a transmission component, and the input shaft of the gear box (51) is fixedly connected with the output shaft of the driving motor (52).

3. A polytetrafluoroethylene extruder according to claim 2, wherein The gear box (51) is a right-angle gear box (51), the input shaft of the right-angle gear box (51) is coaxially connected with the output shaft of the driving motor (52), the transmission component is a shaft coupling or a spline, and the output shaft of the right-angle gear box (51) is connected with the screw shaft of the short screw (41) through the shaft coupling or the spline.

4. A polytetrafluoroethylene extruder as claimed in claim 1, wherein A sealing ring is arranged between the screw shaft of the short screw (41) and the extrusion barrel (1), and the sealing ring is a graphite packing ring.

5. A polytetrafluoroethylene extruder as claimed in claim 1, wherein, The length of the short screw (41) is 3-5 times of the screw diameter, and the surface of the short screw (41) is plated with a hard chromium layer or a nickel-based alloy layer.

6. A polytetrafluoroethylene extruder as claimed in claim 1, wherein The extrusion barrel (1) is provided with a segmented heating structure, the segmented heating structure comprises a preheating zone (12), a melting zone (13) and a soaking zone (14), the preheating zone (12) and the melting zone (13) are located outside the plunger pre-pressing cavity (3), the soaking zone (14) is located outside the screw plasticizing cavity, and the preheating zone (12), the melting zone (13) and the soaking zone (14) all adopt electromagnetic induction heaters.

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