A preparation process of ultra-clean fusible polytetrafluoroethylene tube

Abstract

The invention relates to a preparation process of an ultra-clean fusible polytetrafluoroethylene tube, and belongs to the technical field of fusible polytetrafluoroethylene tubes. In the invention, the raw materials are pre-treated to remove impurities on the surface of the raw materials and dried, the whole environment of the equipment is made oxygen-free by high-purity nitrogen treatment, the raw materials are extracted from bottom to top by a vacuum suction machine to enter a single-screw extruder to avoid contamination by impurities during the feeding process, extrusion, cooling and shaping, cutting and purging, and the ultra-clean fusible polytetrafluoroethylene tube is obtained. The process steps of the invention are simple, and the prepared ultra-clean fusible polytetrafluoroethylene tube has good tensile strength and cleanliness, and can be used for the transportation of high-purity chemicals.

Description

Technical Field

[0001] The invention belongs to the technical field of fusible polytetrafluoroethylene tubes and relates to a preparation process of an ultra-clean fusible polytetrafluoroethylene tube. Background Art

[0002] PFA, also known as fusible polytetrafluoroethylene, is a relatively new fluoroplastic that can be melt-processed. The chemical properties of PFA, FEP (fluoroethylene propylene copolymer), and PTFE (polytetrafluoroethylene) are similar, but FEP can only be used below 200 degrees and PTFE cannot be injection molded. The molecular structure of PFA allows melt processing, so PFA can be manufactured through traditional single-step processes such as injection molding.

[0003] Ultrapure PFA is widely used in the semiconductor industry, especially in wet processes, whether it is wet etching, chemical mechanical polishing, cleaning, photolithography or chemical supply systems. PFA is resistant to strong acids and alkalis, high temperatures and high pressures, and can be formed into a variety of shapes through thermal processing. It is an ideal material for chemical delivery in semiconductor manufacturing.

[0004] According to the SEMI F57 standard, the measured number of metal ion precipitation is within the specified range, that is, it has reached "ultra-clean". When PFA materials are produced in a high-specification clean room, the possibility of introducing contaminants during the manufacturing process is extremely low, and even metal ion precipitation can be achieved at the ppt level (one trillionth). During injection molding, PFA materials will produce a layer of skin on the surface of the material, resulting in an almost unmeasurable surface roughness. The average surface roughness Ra is 0.05 to 0.10µm (B-1), which meets the B-1 SPI standard of the Society of Plastics Industry or higher standards. It is 98.4% smoother than PTFE equivalent products and is the best candidate material for preventing particle generation. Summary of the invention

[0005] The invention aims to provide a preparation process of an ultra-clean fusible polytetrafluoroethylene tube, which has the characteristics of simple preparation process and high cleanliness.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A preparation process of an ultra-clean fusible polytetrafluoroethylene tube comprises the following steps:

[0008] S1. Raw material pretreatment: In a dust-free clean workshop, the fusible polytetrafluoroethylene PFA particles are purged with high-purity N2 at 70-80°C to remove impurities, and then dried at 90-100°C for 5-6 hours to obtain dry PFA particles;

[0009] S2. Environmental treatment: First, high-purity nitrogen is introduced from the inlet pipe of the hopper to ensure an oxygen-free environment;

[0010] S3, feeding: the dried PFA particles are directly extracted from the storage hopper through a pipeline by a vacuum suction machine and passed into the discharge port of the single screw extruder from bottom to top;

[0011] S4, extrusion: PFA raw material particles are melted and extruded by a single screw extruder, and the temperature of each section in the single screw extruder is set as follows: feed port 200-220°C, barrel zone 1 275-285°C, barrel zone 2 345-355°C, barrel zone 3 355-365°C, barrel zone 4 365-375°C, barrel zone 5 375-385°C, flange temperature zone 385-395°C, mold zone 1 395-405°C, mold zone 2 385-395°C, wherein the screw speed is 1-10r / min;

[0012] S5, cooling and shaping: the PFA tube after step S4 is gradually cooled by the copper sizing sleeve through the traction machine at a traction speed of 1000~3500mm / min, and then cooled and solidified by the low-temperature cooling box under vacuum environment, wherein the sizing sleeve is gradually cooled by vacuuming and cooling liquid alternately, the first cooling zone uses 150℃ high-temperature and high-pressure steam, the pressure is 5~8KPa, and the cooling time is 100~130s, the second cooling zone uses 80℃ cooling water, the cooling time is 100~130s, and the third cooling zone uses 20~25℃ cooling water, the cooling time is 100~150s;

[0013] S6, cutting: cutting the PFA pipe after step S5 into the required length by a pipe cutting machine;

[0014] S7, purging: Use high-purity nitrogen to purge the inside of the PFA tube to obtain an ultra-clean fusible polytetrafluoroethylene tube.

[0015] As a preferred technical solution of the present invention, in step S1, the nitrogen gas is 99.999% pure nitrogen gas, the nitrogen gas flow rate is 1500-2500 sccm, and the time is 10-15 min.

[0016] As a preferred technical solution of the present invention, in step S2, when the nitrogen is introduced, the purity of the nitrogen is 99.999%, the nitrogen flow rate is 2000-3000 sccm, and the time is 10-15 min.

[0017] As a preferred technical solution of the present invention, in step S3, the environment in which the feeding hopper and the vacuum suction machine are located is a Class 100 clean room of the US Federal Standard FS-209E.

[0018] As a preferred technical solution of the present invention, in step S4, the material of the screw, barrel and extrusion head of the single-screw extruder is Hastelloy 276 alloy.

[0019] As a preferred technical solution of the present invention, in step S5, the copper sizing sleeve is made of beryllium copper or tungsten copper alloy.

[0020] As a preferred technical solution of the present invention, in step S6, the environment of the pipe cutting machine is a Class 100 clean room of the US federal standard FS-209E, and the pipe cutting machine is connected to a strong suction hood.

[0021] Beneficial effects of the present invention:

[0022] In the present invention, the PFA particles are first purged with high-purity nitrogen in a dust-free clean workshop, so that the dirt, grease and moisture on the surface of the PFA particles can be effectively removed. Since the nitrogen molecules are small, they can quickly pass through gaps and obstacles to form a strong airflow to wash away the impurities and residues on the surface of the PFA particles. This non-contact cleaning method has a very important effect on the preparation of ultra-clean plastic pipes. At the same time, high-purity nitrogen is a dry gas with good buffering and inertness. Through the high-purity nitrogen purging, the original oxygen and other active gases in the PFA particles are replaced, which helps to prevent corrosion, degradation or unwanted chemical reactions. The high-purity nitrogen purging can also remove static electricity from the surface of the object to prevent the increase of the content of migrants in the raw materials due to electrostatic adsorption of impurities.

[0023] Use high-purity nitrogen to purge the entire equipment to ensure an oxygen-free environment, ensuring that the purity and quality of the reactants are not affected during the purge process. High-purity nitrogen can quickly evaporate and take away the solvent and moisture on the surface of the liquid without heating. By effectively removing the solvent and moisture in the reaction, the decomposition and oxidation of the reactants can be prevented, protecting the effectiveness of the reactants.

[0024] The material is directly extracted from the storage hopper by vacuum extraction and enters the feeding port of the single screw extruder from bottom to top. This feeding method can effectively prevent the pre-treated PFA raw materials from being contaminated by the external environment during the feeding process, thus ensuring the purity of the feeding process;

[0025] By adjusting the temperature in different zones during the extrusion process, the extrusion process can be precisely controlled. First, the feed port temperature is set to 200~220℃, which can soften the PFA raw material and avoid excessive friction on the screw barrel due to the PFA raw material being too hard, which causes the metal ions in the screw barrel to precipitate into the PFA material. At the same time, this temperature just prevents PFA from agglomerating. The temperature of the first zone of the barrel is 275~285℃, which can further soften the PFA raw material while still having a certain toughness, and further extrude it forward with the screw. The temperature of the second zone of the barrel is 345~355℃, and the PFA raw material reaches a molten state. Temperature, begins to enter the melting compression zone; the temperature of the barrel zone is designed to increase gradually, and the temperature of the compression section is slightly lower, which can reduce the extrusion wear of PFA material and screw barrel leading to metal ion precipitation, and ensure a certain toughness to facilitate the forward transportation of PFA material; the temperature of the homogenization section ensures that the PFA melt has sufficient plasticization degree to be transported forward; the temperature of the mold zone 1 is 395~405℃, which is further increased than the temperature in the barrel, thereby ensuring the plasticization degree of PFA and smooth melt flow, the mold zone 2 is 385~395℃, which is slightly lower than the temperature of the mold zone 1, so that the PFA material in the extrusion mold body produces a certain back pressure, thereby improving the dimensional precision.

[0026] The screw, barrel, extrusion head and die core rod used in the present invention are made of Hastelloy 276 alloy, and the high temperature corrosion resistance of Hastelloy 276 alloy is better than that of common alloy materials.

[0027] The copper sizing sleeve is made of beryllium copper or tungsten copper alloy. It has better thermal conductivity, corrosion resistance and wear resistance than ordinary copper sizing sleeves and has a longer service life. If ordinary copper sizing sleeves are used, the inside of the sizing sleeve will be damaged due to wear and corrosion in two to three days. At this time, it is necessary to re-polish or replace a new sizing sleeve. If beryllium copper or tungsten copper alloy sizing sleeves are used, the time for replacing the sizing sleeve is doubled, which improves production efficiency and reduces the loss caused by replacing the sizing sleeve.

[0028] The sizing sleeve can avoid insufficient vacuum adsorption caused by too fast cooling during the sizing process by alternating between vacuuming and cooling liquid, and avoid excessive size fluctuations during PFA tube forming; slowing down the cooling process of the PFA tube can release stress and obtain large crystals with good crystal form. Rapid cooling may lead to poor crystal growth, produce more grains, and make it difficult to form large crystals. At the same time, more grains will increase the precipitation of microparticles. By adjusting the water temperature of the copper sizing sleeve, the outer diameter of the PFA tube can be fine-tuned without replacing the sizing sleeve. The first cooling zone uses 150℃ high-temperature and high-pressure steam. At this time, the pipe has just started to cool down, the temperature is high and it is relatively soft. Through the evaporation and heat absorption of the high-temperature and high-pressure steam, it can fully exchange heat with the pipe surface in a short time, accelerate the cooling process, and the steam can be evenly distributed to avoid local overcooling or overheating, and reduce the deformation of the PFA tube during the molding process; the second cooling zone uses 80℃ cooling water to further cool the PFA tube after the first cooling, and the third cooling zone uses 20~25℃ cooling water to thoroughly cool the PFA tube. This gradual cooling method can avoid the shrinkage of the PFA tube caused by a sudden drop in temperature and maintain dimensional stability; and gradual cooling means that the PFA stays in the sizing sleeve for a longer time, which can be more fully heat exchanged and cooled, thereby reducing subsequent thermal stress.

[0029] The pipe cutting machine of the present invention is connected with a strong air suction hood to ensure that the debris and dust generated during the cutting process are sucked away in time, thereby ensuring cleanliness. DETAILED DESCRIPTION

[0030] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0031] In the following examples and comparative examples:

[0032] PFA particles: purchased from Daikin Fluorochemical (China) Co., Ltd., brand AP-231SH;

[0033] The storage hopper and vacuum suction machine are located in a Class 100 clean room of the U.S. federal standard FS-209E.

[0034] The screw, barrel and extrusion head of the single screw extruder used are made of Hastelloy 276 alloy;

[0035] The material of the copper sizing sleeve is beryllium copper or tungsten copper alloy;

[0036] The environment of the tube cutting machine used for cutting PFA tubes is a Class 100 clean room of the US Federal Standard FS-209E, and the tube cutting machine is connected to a strong suction hood;

[0037] The purity of the nitrogen used is 99.999%.

[0038] The following embodiments and comparative examples take 1 / 2 inch tube as an example, and the dimensions have tolerances ranging from inner diameter: 9.53±0.10 mm, outer diameter: 12.70±0.12 mm, and thickness: 1.59±0.10 mm.

[0039] Example 1

[0040] S1. Raw material pretreatment: In a dust-free clean room, the PFA particles are purged with high-purity N2 at 70°C to remove impurities, and then dried at 90°C for 6 hours to obtain dry PFA particles, wherein the nitrogen flow rate is 1500 sccm and the time is 10 minutes;

[0041] S2. Environmental treatment: First, high-purity nitrogen is introduced from the inlet pipe of the hopper to ensure an oxygen-free environment;

[0042] S3, feeding: the dried PFA particles are directly extracted from the storage hopper through a pipeline by a vacuum suction machine and passed into the discharge port of the single screw extruder from bottom to top;

[0043] S4, extrusion: PFA raw material particles are melted and extruded by a single screw extruder, and the temperature of each section in the single screw extruder is set as follows: feed port 200°C, barrel zone 1 275°C, barrel zone 2 345°C, barrel zone 355°C, barrel zone 4 365°C, barrel zone 5 375°C, flange temperature zone 385°C, mold zone 1 395°C, mold zone 2 385°C, wherein the screw speed is 1r / min;

[0044] S5, cooling and shaping: the PFA tube after step S4 is gradually cooled through the copper sizing sleeve by a traction machine at a traction speed of 1000mm / min, the vacuum pressure of the copper sizing sleeve is 0.01KPa, and the sizing sleeve is cooled and solidified in a low-temperature cooling box under a vacuum environment, wherein the sizing sleeve is gradually cooled by alternately vacuuming and cooling liquid, the first cooling zone uses 150℃ high-temperature and high-pressure steam, the pressure is 5KPa, and the cooling time is 100s, the second cooling zone uses 80℃ cooling water, the cooling time is 100s, and the third cooling zone uses 20℃ cooling water, the cooling time is 100s;

[0045] S6, cutting: cutting the PFA tube obtained in step S5 into a desired length by a tube cutting machine, and the obtained PFA tube has an inner diameter of 9.53 mm, an outer diameter of 12.70 mm, a length of 3 m, and a thickness of 1.60 mm;

[0046] S7, purging: Use high-purity nitrogen to purge the inside of the PFA tube to obtain an ultra-clean fusible polytetrafluoroethylene tube.

[0047] Example 2

[0048] S1. Raw material pretreatment: In a dust-free clean room, the PFA particles are purged with high-purity N2 at 75°C to remove impurities, and then dried at 95°C for 5.5 hours to obtain dry PFA particles, wherein the nitrogen flow rate is 2000 sccm and the time is 12 minutes;

[0049] S2. Environmental treatment: First, high-purity nitrogen is introduced from the inlet pipe of the hopper to ensure an oxygen-free environment;

[0050] S3, feeding: the dried PFA particles are directly extracted from the storage hopper through a pipeline by a vacuum suction machine and passed into the discharge port of the single screw extruder from bottom to top;

[0051] S4, extrusion: PFA raw material particles are melted and extruded by a single screw extruder, and the temperature of each section in the single screw extruder is set as follows: feed port 210°C, barrel zone 1 280°C, barrel zone 2 350°C, barrel zone 360°C, barrel zone 4 370°C, barrel zone 5 380°C, flange temperature zone 390°C, mold zone 1 400°C, mold zone 2 390°C, wherein the screw speed is 5r / min;

[0052] S5, cooling and shaping: the PFA tube after step S4 is gradually cooled through the copper sizing sleeve by a traction machine at a traction speed of 1500mm / min, the vacuum pressure of the copper sizing sleeve is 0.05KPa, and the sizing sleeve is cooled and solidified in a low-temperature cooling box under a vacuum environment, wherein the sizing sleeve is gradually cooled by vacuuming and cooling liquid alternately, the first cooling zone uses 150℃ high-temperature and high-pressure steam, the pressure is 6KPa, and the cooling time is 110s, the second cooling zone uses 80℃ cooling water, the cooling time is 11s, and the third cooling zone uses 22℃ cooling water, the cooling time is 120s;

[0053] S6, cutting: cutting the PFA tube obtained in step S5 into the required length by a tube cutting machine, and the obtained PFA tube has an inner diameter of 9.56 mm, an outer diameter of 12.75 mm, a length of 3 m, and a thickness of 1.60 mm;

[0054] S7, purging: Use high-purity nitrogen to purge the inside of the PFA tube to obtain an ultra-clean fusible polytetrafluoroethylene tube.

[0055] Example 3

[0056] S1. Raw material pretreatment: In a dust-free clean room, the PFA particles are purged with N2 at 80°C to remove impurities, and then dried at 100°C for 6 hours to obtain dried PFA particles, wherein the nitrogen flow rate is 2500 sccm and the time is 15 minutes;

[0057] S2. Environmental treatment: First, high-purity nitrogen is introduced from the inlet pipe of the hopper to ensure an oxygen-free environment;

[0058] S3, feeding: the dried PFA particles are directly extracted from the storage hopper through a pipeline by a vacuum suction machine and passed into the discharge port of the single screw extruder from bottom to top;

[0059] S4, extrusion: PFA raw material particles are melted and extruded by a single screw extruder, and the temperature of each section in the single screw extruder is set as follows: feed port 220°C, barrel zone 1 285°C, barrel zone 2 355°C, barrel zone 3 365°C, barrel zone 4 375°C, barrel zone 5 385°C, flange temperature zone 395°C, mold zone 1 405°C, mold zone 2 395°C, wherein the screw speed is 10r / min;

[0060] S5, cooling and shaping: the PFA tube after step S4 is gradually cooled through the copper sizing sleeve by a traction machine at a traction speed of 3500mm / min, the vacuum pressure of the copper sizing sleeve is 0.08KPa, and the sizing sleeve is cooled and solidified in a low-temperature cooling box under a vacuum environment, wherein the sizing sleeve is gradually cooled by vacuuming and cooling liquid alternately, the first cooling zone uses 150℃ high-temperature and high-pressure steam, the pressure is 8KPa, and the cooling time is 130s, the second cooling zone uses 80℃ cooling water, the cooling time is 130s, and the third cooling zone uses 25℃ cooling water, the cooling time is 150s;

[0061] S6, cutting: cutting the PFA tube obtained in step S5 into the required length by a tube cutting machine, and the obtained PFA tube has an inner diameter of 9.55 mm, an outer diameter of 12.73 mm, a length of 3 m, and a thickness of 1.59 mm;

[0062] S7, purging: Use high-purity nitrogen to purge the inside of the PFA tube to obtain an ultra-clean fusible polytetrafluoroethylene tube.

[0063] Comparative Example 1

[0064] The difference between Comparative Example 1 and Example 1 is that in step S1 of Comparative Example 1, high-purity nitrogen gas purging treatment is not performed, and the other operations are the same.

[0065] Comparative Example 2

[0066] The difference between Comparative Example 2 and Example 1 is that the feeding method in step S3 of Comparative Example 2 is directly pouring into the single-screw extruder, and the other operations are the same.

[0067] Comparative Example 3

[0068] The difference between Comparative Example 3 and Example 1 is that in step S5 of Comparative Example 3, the sizing sleeve is not cooled gradually but directly cooled rapidly by cooling water, and the other operations are the same.

[0069] Comparative Example 4

[0070] The difference between Comparative Example 4 and Example 1 is that in step S5 of Comparative Example 4, high-temperature and high-pressure steam at 150° C. is not used, and the other operations are the same.

[0071] Performance Test:

[0072] 1. The tensile strength, yield strength and elongation at break are all based on the standard GB / T 8804.1-2003. The tubes with a diameter of 1 / 2 inch or more (including 1 / 2 inch) are cut into dumbbell shapes. The test results are shown in Table 1:

[0073] Table 1

[0074]

[0075] 2. The PFA tubes prepared in the examples and comparative examples were treated as follows: ultrapure water was filled into the PFA tubes and retained for 2 minutes, the filling water was removed and drained, this step was repeated 10 times, and then 36% hydrochloric acid was used to fill the PFA tubes, both ends of the tubes were sealed with high-purity PFA plugs, and the number of metal ions precipitated from the immersion liquid was tested after heating and insulation at 85°C for 7 days. The instrument used was ICP-MS / MS, the reference method was SEMI F57, the method detection limit (MDL) was 0.01, and the unit was ug / m 2 ND means not detected, the result is less than the detection limit, the results are shown in Table 2:

[0076] Table 2

[0077]

[0078] According to Table 2, referring to the standard SEMI F57, when the number of metal ions precipitated by Al, Fe, Mn, and Zn is ≤5 ug / m 2 , the number of metal ions released from As, Mg, Ti, and V is ≤2 ug / m 2 , the number of metal ions released from Cr, Pb, Ni, Ag, and Mo is ≤1 ug / m 2 , the number of metal ions released from Cu, K, and Na is ≤10 ug / m 2 , the number of metal ions precipitated from Co, Ga, Sr, Zr, and Pt is ≤0.5 ug / m 2 The ultra-clean requirements are met when the ultra-clean PFA tube is used. The test data of embodiments 1 to 3 all comply with the standard SEMI F57, and thus can meet the ultra-clean PFA tube requirements.

[0079] 3. The PFA tubes prepared in the examples and comparative examples were treated as follows: ultrapure water was filled into the PFA tube and retained for 2 minutes, the filling water was removed and drained. This step was repeated 10 times. The PFA tube was filled with 36% hydrochloric acid, and both ends of the tube were sealed with high-purity PFA plugs. After heating and keeping warm at 85°C for 7 days, the number of microparticles precipitated from the immersion liquid was tested. The instrument used was LPC, the reference method was SEMI F57, and the method detection limit (MDL) was 1, where the test items (0.1um, 0.2um, 0.3um, 0.4um, 0.5um) refer to the particle size of the microparticles. The results are shown in Table 3:

[0080] Table 3

[0081]

[0082] It can be seen from the above table that the quality of the PFA tube can be effectively improved by vacuuming the sizing sleeve and gradually cooling the coolant. The ultra-clean soluble polytetrafluoroethylene tube prepared by the present invention has a low number of particles and metal ion precipitation, so it has high cleanliness and can be used for the transportation of high-purity chemicals.

[0083] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A process for preparing an ultra-clean fusible polytetrafluoroethylene tube, characterized in that: The following steps are involved: S1. Raw material pretreatment: In a dust-free clean workshop, the fusible polytetrafluoroethylene PFA particles are purged with high-purity N2 at 70-80°C to remove impurities, and then dried at 90-100°C for 5-6 hours to obtain dry PFA particles; S2. Environmental treatment: First, high-purity nitrogen is introduced from the inlet pipe of the hopper to ensure an oxygen-free environment; S3, feeding: the dried PFA particles are directly extracted from the storage hopper through a pipeline by a vacuum suction machine and passed into the discharge port of the single screw extruder from bottom to top; S4, extrusion: PFA raw material particles are melted and extruded by a single screw extruder, and the temperature of each section in the single screw extruder is set as follows: feed port 200-220°C, barrel zone 1 275-285°C, barrel zone 2 345-355°C, barrel zone 3 355-365°C, barrel zone 4 365-375°C, barrel zone 5 375-385°C, flange temperature zone 385-395°C, mold zone 1 395-405°C, mold zone 2 385-395°C, wherein the screw speed is 1-10r / min; S5, cooling and shaping: the PFA tube after step S4 is gradually cooled by the copper sizing sleeve through the traction machine at a traction speed of 1000~3500mm / min, and then cooled and solidified by the low-temperature cooling box under vacuum environment, wherein the sizing sleeve is gradually cooled by vacuuming and cooling liquid alternately, the first cooling zone uses 150℃ high-temperature and high-pressure steam, the pressure is 5~8KPa, and the cooling time is 100~130s, the second cooling zone uses 80℃ cooling water, the cooling time is 100~130s, and the third cooling zone uses 20~25℃ cooling water, the cooling time is 100~150s; S6, cutting: cutting the PFA pipe after step S5 into the required length by a pipe cutting machine; S7, purging: Use high-purity nitrogen to purge the inside of the PFA tube to obtain an ultra-clean fusible polytetrafluoroethylene tube.

2. The process for preparing the ultra-clean fusible polytetrafluoroethylene tube according to claim 1, characterized in that: In step S1, the nitrogen gas is 99.999% pure nitrogen gas, the nitrogen gas flow rate is 1500-2500 sccm, and the time is 10-15 min.

3. The preparation process of the ultra-clean fusible polytetrafluoroethylene tube according to claim 1, characterized in that: In step S2, when the nitrogen is introduced, the purity of the nitrogen is 99.999%, the nitrogen flow rate is 2000-3000 sccm, and the time is 10-15 min.

4. The process for preparing the ultra-clean fusible polytetrafluoroethylene tube according to claim 1, characterized in that: In step S3, the environment in which the vacuum suction machine is located is a Class 100 clean room of the U.S. federal standard FS-209E.

5. The process for preparing the ultra-clean fusible polytetrafluoroethylene tube according to claim 1, characterized in that: In step S4, the screw, barrel and extrusion head of the single screw extruder are made of Hastelloy 276 alloy.

6. The process for preparing the ultra-clean fusible polytetrafluoroethylene tube according to claim 1, characterized in that: In step S5, the copper sizing sleeve is made of beryllium copper or tungsten copper alloy.

7. The process for preparing the ultra-clean fusible polytetrafluoroethylene tube according to claim 1, characterized in that: In step S6, the environment of the pipe cutting machine is a Class 100 clean room of the US federal standard FS-209E, and the pipe cutting machine is connected to a strong suction hood.

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