CN218701133U - External mold structure for improving surface smoothness of polytetrafluoroethylene extruded tube - Google Patents

Abstract

The patent provides an improve outer die structure of polytetrafluoroethylene extrusion pipe surface finish, and the tubulose polytetrafluoroethylene surface that uses this outer die to extrude basically does not have crackle, and the finish is high, and the polytetrafluoroethylene extrusion pipe surface roughness that this tubulose polytetrafluoroethylene obtained after technologies such as follow-up sintering, crystallization is less. The die cavity of the outer die structure comprises a conical extrusion area, a uniform-section forming area and a conical off-die expansion buffering area, wherein the extrusion direction is taken as the front, the front of the conical extrusion area is small, the back of the conical extrusion area is large, and the front of the conical off-die expansion buffering area is large and the back of the conical off-die expansion buffering area is small.

Description

External mold structure for improving surface finish degree of polytetrafluoroethylene extruded tube

Technical Field

This patent belongs to the processing and manufacturing technical field of polytetrafluoroethylene extrusion pipe, specifically speaking relates to the external mold of extrusion tubulose polytetrafluoroethylene.

Background

Polytetrafluoroethylene (PTFE), commonly known as "plastic king," has a high melt viscosity due to its high molecular weight, and does not have good fluidity in the molten state as conventional plastics, and the surface of the processed product has a high degree of finish as long as the surface of the mold is controlled to have a high degree of finish during processing.

Referring to fig. 1, a hydraulic station 1 supplies hydraulic oil to a pushing cylinder 2, the pushing cylinder 2 pushes mixture ingredients containing polytetrafluoroethylene and the like in a mold barrel 3 to an outer mold 5, the ingredients pass through a taper angle alpha extrusion area in the periphery of a core mold 4 and an outer mold and a molding area with an inner hole diameter of A and the like section to form tubular polytetrafluoroethylene 10, the tubular polytetrafluoroethylene 10 is extruded out of the outer mold 5, and then the tubular polytetrafluoroethylene 10 is sequentially dried, sintered and crystallized by a drying furnace 6, a sintering furnace 7 and a crystallizing furnace 8 to form a polytetrafluoroethylene tube, and the polytetrafluoroethylene tube is wound by a winding device 9.

Due to the particularity of the polytetrafluoroethylene tube manufacturing process, the surface finish of the polytetrafluoroethylene extruded tube is influenced by the following two factors: (1) In the extrusion process, the raw pipe blank is subjected to extrusion shrinkage in a die cavity of an outer die (shown in figures 2 and 3) to generate fibrosis, and then is subjected to die-releasing expansion instantly when being discharged from a die orifice, and the die orifice generates a certain shearing force on the surface of a pipe at the moment, so that microscopic transverse cracks 11 appear on the surface of the pipe; (2) In the sintering process, the pipe expands along with the rise of temperature, the generation of surface transverse cracks is aggravated, and finally the surface of the produced pipe has obvious rough feeling.

The existing technical means for improving the surface finish of the polytetrafluoroethylene tube is basically improved from the aspect of tube material preparation, the conventional method generally adjusts and adds an extrusion aid in the tube material preparation, and selects different types and dosage, however, the improvement method still has limited improvement on the surface finish of the polytetrafluoroethylene tube, and the obtained tube green compact (tubular polytetrafluoroethylene) still generates die release expansion and generates transverse cracks in the subsequent sintering process, and the generated dimensional change generates irreparable adverse effects on the surface finish of the final polytetrafluoroethylene tube.

The low finish of the prior polytetrafluoroethylene tube severely limits the application field thereof. For example, semiconductors are important as electronic materials in the development of society, and semiconductor technology is widely used in various fields such as industry, agriculture, commerce, transportation, aviation, information, and communication. Particularly, with the rapid development of 5G information technology, photoelectric application, etc., the third generation semiconductor industry is also developing vigorously.

Because of the particularity of semiconductor materials, which have extremely high requirements on manufacturing processes during the manufacturing process, polytetrafluoroethylene materials can meet such requirements to a certain extent. The semiconductor material is very critical in pollution resistance, but due to the limitation of the processing technology of the existing polytetrafluoroethylene material, the surface smoothness of the processed polytetrafluoroethylene tube cannot meet the requirement, and if the existing polytetrafluoroethylene tube is used in the field of semiconductor materials, the semiconductor material is easy to cause the residue of chemical reagents in the preparation, use or cleaning processes and is difficult to clean. It can be seen that the low finish problem limits the use of ptfe tubing in the semiconductor field.

Disclosure of Invention

This patent provides an improve polytetrafluoroethylene extrusion pipe surface finish's external mold structure to polytetrafluoroethylene extrusion pipe surface finish's not enough problem, uses the tubulose polytetrafluoroethylene surface that this external mold extruded to basically not have the crackle, and the finish is high, and this tubulose polytetrafluoroethylene obtains behind processes such as follow-up sintering, crystallization polytetrafluoroethylene extrusion pipe surface roughness less.

This patent improve polytetrafluoroethylene extrusion pipe surface finish's outer die structure, its die cavity includes conical extrusion region, the shaping region of uniform cross-section, conical off-mold expansion buffer area to the extrusion direction is the place ahead, and big end back before the conical extrusion region, big end back before the conical off-mold expansion buffer area.

In the outer mold structure, the taper angle beta of the tapered off-mold expansion buffer area is 2-6 degrees.

In the outer mold structure, the diameter of the large-end outlet of the conical mold-release expansion buffer area is B, the maximum outer diameter of the tubular polytetrafluoroethylene after mold-release expansion is C, and C is less than B.

In the outer die structure, the diameter of an inner hole of a forming area with an equal section is A, and A is less than C.

In the external mold structure, the taper angle alpha of the tapered extrusion area is 20-30 degrees.

The beneficial effect of this patent:

this patent is for conventional external mold, the separation die inflation buffer zone of toper has been increased in its die cavity, make the tubulose polytetrafluoroethylene who comes out from the shaping region of uniform cross section can not produce great inflation in the twinkling of an eye and the microcrack appears, but the tubulose polytetrafluoroethylene who comes out from the shaping region of uniform cross section gets into separation die inflation buffer zone, make tubulose polytetrafluoroethylene slow expansion in separation die inflation buffer zone, slow down the internal stress release process of tubulose polytetrafluoroethylene, avoid its great inflation of production in the twinkling of an eye and produce the microcrack, thereby improve tubulose polytetrafluoroethylene surface finish greatly. The tubular polytetrafluoroethylene is sintered and other conventional processes to obtain the polytetrafluoroethylene tube with high smoothness.

Drawings

FIG. 1 is a schematic view of the production of an extruded polytetrafluoroethylene tube

FIG. 2 is a view showing the structure of a conventional outer mold

FIG. 3 is a schematic view showing crack generation

FIG. 4 is a partial enlarged view of FIG. 3

FIG. 5 is a view showing the structure of the outer mold of this patent

FIG. 6 is a partial enlarged view of FIG. 5

FIG. 7 is a schematic view of the extrusion of polytetrafluoroethylene in the form of a tube according to the present patent

In the figure, a hydraulic station 1, a pushing cylinder 2, a mold barrel 3, a core mold 4, an outer mold 5, a drying furnace 6, a sintering furnace 7, a crystallizing furnace 8, a winding device 9, tubular polytetrafluoroethylene 10 and a transverse crack 11.

Detailed Description

The outer die 5 described in this patent contains four critical dimensions, the extrusion angle α (taper angle α of the tapered extrusion zone), the bore diameter a (small end diameter of the tapered extrusion zone, bore diameter of the uniform cross-section molding zone, small end diameter of the tapered die swell buffer zone), the exit angle β (taper angle α of the tapered extrusion zone), the exit diameter B (large end diameter of the tapered die swell buffer zone). (see FIGS. 5 and 6)

This patent polytetrafluoroethylene extrusion pipe has a critical dimension, the biggest external diameter C after the inflation of tubulose polytetrafluoroethylene demolding in the forming process. (see FIG. 7)

The dimensional relationship is as follows: a is more than C and less than B.

The proper range of the external mold extrusion angle alpha is 20-30 degrees.

The suitable range of the external mold outlet angle beta is 2-6 degrees.

Compared with a conventional extrusion outer die, the outer die increases a conical die-stripping expansion buffer area with an outlet angle beta, reasonably sets an outlet diameter B, increases the buffer area when the tubular polytetrafluoroethylene expands from the die, prevents the tubular polytetrafluoroethylene from forming instant large-size expansion at the outlet of the outer die to generate micro cracks, and slows down the release of the internal stress of the tubular polytetrafluoroethylene by slow expansion, thereby greatly improving the surface finish. The tubular polytetrafluoroethylene is dried, sintered, crystallized and the like in a subsequent conventional drying furnace, a sintering furnace and a crystallizing furnace to prepare the high-finish polytetrafluoroethylene extrusion pipe.

This patent reasonable in design extrudes external mold upgrading with the conventionality and reforms transform, has improved product quality and practicality greatly.

Claims (5)

1. Improve polytetrafluoroethylene extrusion pipe surface finish's exterior mold structure, characterized by: the die cavity comprises a conical extrusion area, a uniform-section forming area and a conical off-die expansion buffering area, the extrusion direction is taken as the front, the front of the conical extrusion area is small, the back of the conical extrusion area is large, and the front of the conical off-die expansion buffering area is large and the back of the conical extrusion area is small.

2. The exterior mold structure of claim 1, wherein: the taper angle beta of the tapered off-mold expansion buffer area is 2-6 degrees.

3. The exterior mold structure of claim 1, wherein: the diameter of a large-end outlet of the conical demolding expansion buffer area is B, the maximum outer diameter of the tubular polytetrafluoroethylene subjected to demolding expansion is C, and C is smaller than B.

4. The exterior mold structure according to claim 3, wherein: the diameter of the inner hole of the forming area with the uniform section is A, and A is less than C.

5. The exterior mold structure of claim 1, wherein: the taper angle alpha of the tapered extrusion region is 20-30 deg.

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