Elliptical-opening extrusion die head for PTFE (Polytetrafluoroethylene) filaments

Abstract

The oval opening extrusion die head of the PTFE filament comprises a die head body, a through hole is formed in the die head body, the through hole comprises a guide-in section and an extrusion section, the guide-in section is in an oval hollow cone shape, and the extrusion section is in an oval tube shape. When a PTFE material is extruded through the extrusion die head, the cross section of a PTFE filament is in an oval shape, the problem that the PTFE filament expands after being demolded can be effectively solved, the stability of the PTFE filament after being demolded is improved, the calendering stress distribution is more uniform when the PTFE filament is subjected to calendering, and therefore the uniformity of a film is improved.

Description

Technical Field

[0001] This application relates to an extrusion die head for wire extrusion, and mainly relates to an elliptical orifice extrusion die head for PTFE filaments. Background Art

[0002] Polytetrafluoroethylene (PTFE) material is one of the important varieties of engineering plastics, with excellent corrosion resistance, hydrophobicity, thermal stability, electrical insulation and anti-aging properties. It is currently widely used in dust filtration, biomedicine, functional clothing, metallurgical smelting and other fields, and can be prepared into different forms such as PTFE tubes, rods, tapes, plates, films, etc. according to the usage requirements. Among them, PTFE films are generally made from polytetrafluoroethylene dispersion resin through special processes such as premixing, compacting, wire extrusion, and calendering. In the entire preparation process flow, the extrusion die head, as a forming tool, plays an important role in the quality of the final calendered product.

[0003] Chinese Patent CN202297886U discloses a die head for extruding polytetrafluoroethylene fiber monofilaments, including an introduction section and extrusion fine holes. The introduction section is in the shape of an elongated frustum of a cone as a whole, and the extrusion fine holes are circular orifices. When the material is extruded through the extrusion die head, it is in a round bar shape, and it is easy to have uneven transverse stress distribution during subsequent calendering, resulting in poor film uniformity. Chinese Patent CN205553140U discloses an extrusion die head for high-efficiency polytetrafluoroethylene films, including a die head body and a through hole penetrating the die head body. The through hole includes a feed port section and a discharge port section connected thereto. The feed port section is a funnel-shaped flow channel with a flat-shaped necking, and the discharge port section is a flat-shaped frustum of a pyramid. When the material is extruded through the extrusion die head, it is in a sheet shape, but this shape is easily affected by die swell, and instead, an extrusion material with uniform thickness cannot be obtained.

[0004] In summary, it is necessary to develop an extrusion die head that does not affect the film-forming uniformity of PTFE films. Summary of the Utility Model

[0005] Aiming at the technical problem of poor calendered film uniformity in the prior art, this application proposes an elliptical orifice extrusion die head for PTFE filaments.

[0006] To achieve the above object, this application adopts the following technical solutions:

[0007] An elliptical orifice extrusion die head for PTFE filaments, including a die head body. The die head body has a through hole inside. The through hole includes an introduction section and an extrusion section. The introduction section is in the shape of an elliptical hollow cone, and the extrusion section is in the shape of an elliptical tube. The filaments extruded by this die head are elliptical in shape, and can make the transverse stress distribution more uniform during calendering, reduce the influence brought by die swell, and thus improve the film uniformity.

[0008] Preferably, the introduction section and the extrusion section are connected by a smooth transition through a chamfered R angle. The design of the chamfered R angle can make the material evenly stressed, so that the extrudate fluid can flow smoothly inside the mold, reduce the resistance of the extrudate, and reduce energy loss.

[0009] Preferably, the inlet cross section of the introduction section and the outlet cross section of the extrusion section are parallel The same inlet and outlet shapes are conducive to better connection between the introduction section and the extrusion section, and are conducive to the smooth flow of the extruded fluid inside the mold.

[0010] Preferably, the ratio of the major axis to the minor axis of the inlet cross section of the introduction section and the outlet cross section of the extrusion section is 2-5:1.

[0011] Preferably, the ratio of the area of ​​the inlet cross section of the introduction section to the outlet cross section of the extrusion section is 40-100:1.

[0012] Preferably, the lead-in section The cone angle θ of the long axis section of the circular hollow cone is 30°-120°.

[0013] Preferably, the ratio of the length of the extrusion section to the average diameter of the outlet cross section is 2-10:1.

[0014] Compared with the prior art, this application has the following beneficial effects:

[0015] When the PTFE material is extruded through the extrusion die of the present application, the cross-section of the PTFE filament is elliptical, which can effectively alleviate the problem of PTFE filament expansion after demolding, increase the stability of the PTFE filament after demolding, and make the calendering stress distribution of the PTFE filament more uniform during calendering, thereby improving the uniformity of the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and are used together with the description to explain the principles of the present application. It will be easy to recognize other embodiments and many expected advantages of the embodiments because they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale with each other. The same reference numerals refer to corresponding similar parts.

[0017] Figure 1 This is a cross-sectional view of an elliptical major axis section of an extrusion die head according to an embodiment of the present application;

[0018] Figure 2 A top view of an extrusion die according to an embodiment of the present application;

[0019] In the figure, 1 is the introduction section, 2 is the extrusion section, 3 is the inlet section of the introduction section, 4 is the outlet section of the extrusion section, R is the transition R angle between the introduction section and the extrusion section, and θ is the cone angle of the major axis section of the ellipse of the introduction section. DETAILED DESCRIPTION

[0020] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the contents of the relevant application, rather than to limit the application. It is also necessary to explain that, for ease of description, only the parts related to the relevant application are shown in the accompanying drawings.

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] Example 1

[0023] An elliptical mouth extrusion die head for PTFE filaments, such as Figure 1 As shown, it includes a die body, wherein the die body has a through hole inside, and the through hole includes an introduction section 1 and an extrusion section 2, wherein the introduction section 1 is in the shape of an elliptical hollow cone, and the extrusion section 2 is in the shape of an elliptical tube. The filaments extruded by this die are elliptical strips, which can make the lateral stress distribution more uniform during calendering, reduce the influence of the die expansion, and thus improve the uniformity of the film.

[0024] Specifically, the introduction section 1 and the extrusion section 3 are smoothly connected by a chamfered R angle. The design of the chamfered R angle can make the material evenly stressed, so that the extrudate fluid can flow smoothly inside the mold, reduce the resistance of the extrudate, and reduce energy loss.

[0025] Specifically, Figure 2 As shown, the inlet section 3 of the introduction section 1 and the outlet section 4 of the extrusion section 2 are parallel. The same inlet and outlet shapes are conducive to better connection between the introduction section 1 and the extrusion section 2, and are conducive to the smooth flow of the extruded fluid inside the mold.

[0026] Specifically, the ratio of the major axis to the minor axis of the inlet section 3 of the introduction section and the outlet section 4 of the extrusion section are both 2-5:1.

[0027] Specifically, the area ratio of the inlet cross section 3 of the introduction section to the outlet cross section 4 of the extrusion section is 40-100:1.

[0028] Specifically, the introduction section 1 The cone angle θ of the long axis section of the circular hollow cone is 30° to 120°.

[0029] Specifically, the ratio of the length of the extrusion section 2 to the average diameter of the outlet cross section 4 is 2 to 10:1.

[0030] Example 2

[0031] The invention discloses an elliptical mouth extrusion die head for PTFE filaments, comprising a die head body, a through hole inside the die head body, and an introduction section 1 and an extrusion section 2, wherein the introduction section 1 is in the shape of an elliptical hollow cone, and the extrusion section 2 is in the shape of an elliptical tube. The filaments extruded by the die head are in the shape of elliptical strips, which can make the transverse stress distribution more uniform during calendering, reduce the influence of the die expansion, and thus improve the uniformity of the film.

[0032] Specifically, the introduction section 1 and the extrusion section 2 are smoothly connected by a chamfered R angle. The design of the chamfered R angle can make the material evenly stressed, so that the extrudate fluid can flow smoothly inside the mold, reduce the resistance of the extrudate, and reduce energy loss.

[0033] Specifically, the inlet section 3 of the introduction section 1 and the outlet section 4 of the extrusion section 2 are parallel. The same inlet and outlet shapes are conducive to better connection between the introduction section 1 and the extrusion section 2, and are conducive to the smooth flow of the extruded fluid inside the mold.

[0034] Specifically, the length of the introduction section is 60 mm, the length of the extrusion section is 50 mm, the major axis of the extrusion port ellipse is 20 mm, and the minor axis is 10 mm.

[0035] Specifically, the ratio of the major axis to the minor axis of the inlet cross section of the introduction section and the outlet cross section of the extrusion section is 2:1.

[0036] Specifically, the ratio of the area of ​​the inlet cross section of the introduction section to the outlet cross section of the extrusion section is 49:1.

[0037] Specifically, the import section The cone angle of the long axis section of the circular hollow cone is θ = 90°.

[0038] Specifically, the ratio of the length of the extrusion section to the average diameter of the outlet cross section is 4:1.

[0039] The above describes the specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An elliptical mouth extrusion die for PTFE filaments, comprising a die body, wherein the die body has a through hole inside, characterized in that: The through hole comprises an introduction section (1) and an extrusion section (2); the introduction section (1) is in the shape of an elliptical hollow cone, and the extrusion section (2) is in the shape of an elliptical tube.

2. The elliptical mouth extrusion die head of a PTFE filament according to claim 1, characterized in that: The introduction section (1) and the extrusion section (2) are connected in a smooth transition via a chamfered R angle.

3. The elliptical mouth extrusion die head of a PTFE filament according to claim 1, characterized in that: The inlet cross section of the introduction section (1) and the outlet cross section of the extrusion section (2) are parallel. round.

4. The elliptical mouth extrusion die head of a PTFE filament according to claim 3, characterized in that: The ratio of the major axis to the minor axis of the inlet cross section of the introduction section (1) and the outlet cross section of the extrusion section (2) is 2-5:

1.

5. The elliptical mouth extrusion die head of a PTFE filament according to claim 3, characterized in that: The ratio of the area of ​​the inlet cross section of the introduction section (1) to the outlet cross section of the extrusion section (2) is 40-100:

1.

6. The elliptical mouth extrusion die head of a PTFE filament according to claim 1, characterized in that: The introduction section (1) The cone angle θ of the long axis section of the circular hollow cone is 30°-120°.

7. The elliptical mouth extrusion die head of a PTFE filament according to claim 1, characterized in that: The ratio of the length of the extrusion section (2) to the average diameter of the outlet cross section is 2-10:1.

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