An aging-resistant silicone tube and its preparation method

Abstract

This invention discloses an aging-resistant silicone tube and its preparation method, belonging to the field of silicone tube manufacturing. The aging-resistant silicone tube formulation of this invention comprises, by weight, 10-15 parts methyl vinyl silicone, 60-90 parts vinyl silicone, 5-10 parts methyl silicone resin, 8-14 parts silica, 1-5 parts vulcanizing agent, 0.2-0.5 parts antioxidant, 0.3-0.8 parts light stabilizer, 20-50 parts co-solvent, and 0.21-0.85 parts reinforcing agent. This preparation method uses xylene as a co-solvent, solving the problem of poor compatibility between additives and main components caused by simple physical mixing in traditional preparation methods. Secondly, dibutyltin diacetate and 3,3'-dichloro-4,4'-diisocyanate biphenyl are used as reinforcing agents. Under the catalysis of dibutyltin diacetate, the light stabilizer 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol undergoes a coupling reaction with 3,3'-dichloro-4,4'-diisocyanate biphenyl, and then crosslinks with the main component of the silicone tube through ester bonds, uniformly fixing the light stabilizer in the silicone tube, thereby extending the aging resistance time of the silicone tube.

Description

Technical Field

[0001] This invention relates to the field of silicone tube manufacturing, and more particularly to an aging-resistant silicone tube and its preparation method. Background Technology

[0002] Silicone tubing is widely used in medical, industrial, and food fields due to its unique material properties. It possesses characteristics such as high temperature resistance, chemical inertness, biocompatibility, insulation, and ease of processing.

[0003] Common polymer organic molecules all undergo aging; even the cells that make up living organisms in everyday plastic products age. Ozone and oxygen environments, as well as ultraviolet radiation, all contribute to the aging of silicone tubing, with the aging process accelerating at high temperatures. Organic molecules exposed to ultraviolet radiation easily generate free radicals, and oxidation from exposure to the natural environment further shortens the lifespan and reduces the performance of silicone tubing.

[0004] In silicone tubing production formulations, additives such as antioxidants and light stabilizers are often used to combat aging. However, simple physical mixing can lead to poor compatibility between the additives and the main components, making it difficult to achieve uniform mixing during the kneading process or resulting in silicone tubing with inconsistent properties and vulnerabilities. On the other hand, while commercially available additives are widely applicable, they often fail to meet the performance requirements of specific products. Products with market performance advantages typically require specific production processes or additive formulations. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide an aging-resistant silicone tube; another purpose of this invention is to provide a method for preparing an aging-resistant silicone tube.

[0006] Technical solution: An aging-resistant silicone tube, the formula of which includes, by weight, 10-15 parts of methyl vinyl silicone, 60-90 parts of vinyl silicone, 5-10 parts of methyl silicone resin, 8-14 parts of silica, 1-5 parts of vulcanizing agent, 0.2-0.5 parts of antioxidant, 0.3-0.8 parts of light stabilizer, 20-50 parts of co-solvent, and 0.21-0.85 parts of reinforcing agent.

[0007] All materials used in this formula are commercially available chemicals, and the sources of these materials are wide-ranging.

[0008] Preferably, the antioxidant is one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1010, or Phosphite A.

[0009] Preferably, the light stabilizer is 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol.

[0010] Preferably, the co-solvent is xylene.

[0011] Preferably, the reinforcing agent is 0.01-0.05 parts of dibutyltin diacetate and 0.2-0.8 parts of 3,3-dichloro-4,4'-diisocyanate biphenyl.

[0012] The method for preparing the aging-resistant silicone tube includes the following steps:

[0013] S1. Add 3,3'-dichloro-4,4'-diisocyanate biphenyl, light stabilizer, dibutyltin diacetate, and cosolvent to the reactor according to the formula. Under inert gas protection, heat to 55-85℃ and stir for 1-2 hours to obtain the modified light stabilizer.

[0014] S2. Add antioxidants and modified light stabilizers to the kneader according to the formula, stir evenly, then add methyl vinyl silica gel, vinyl silica gel, fumed silica and methyl silicone resin, start kneading, when the kneading temperature reaches 155~160℃, start vacuuming, collect the condensed co-solvent through the reflux condenser, and stop vacuuming when about 80% of the co-solvent has been recovered.

[0015] S3. Add the solvent recovered in step S2 back into the kneader and start kneading again. When the kneading temperature reaches 160~165℃, start vacuuming and collect the condensed solvent through the reflux condenser until no more solvent drips out. Continue vacuuming for 20-60 minutes to obtain silica gel material.

[0016] S4. Add the silicone material prepared in S3 to the open mill, add the vulcanizing agent according to the formula, after mixing, sheet it out, cool it to room temperature, and obtain the mixed rubber sheet.

[0017] S5. Add the compounded rubber sheet prepared in step S4 to a silicone extruder and extrude it to obtain an aging-resistant silicone tube.

[0018] Preferably, in steps S2 and S3, the vacuum level during the vacuuming process is lower than -0.08 MPa.

[0019] Preferably, in step S4, the mixing temperature is 152-160℃ and the mixing time is 30-60min.

[0020] Preferably, in step S5, the extrusion temperature is 160-165℃ and the extrusion rate is 3-20m / min.

[0021] Beneficial effects:

[0022] 1. This solution innovatively incorporates xylene as a co-solvent during the kneading process in the silicone tube manufacturing process. This allows for thorough mixing of the antioxidants and light stabilizers in the formulation with the main components of the silicone tube, thereby solving the problem of poor compatibility between additives and main components caused by simple physical mixing in traditional preparation methods mentioned in the background technology. This allows the antioxidants and light stabilizers to play their full role.

[0023] 2. This formulation uses xylene as a co-solvent and dibutyltin diacetate and 3,3'-dichloro-4,4'-diisocyanate biphenyl as reinforcing agents. Under the catalysis of dibutyltin diacetate, the light stabilizer 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol undergoes a coupling reaction with 3,3'-dichloro-4,4'-diisocyanate biphenyl, and then crosslinks with the main component of the silicone tube through ester bonds, uniformly fixing the light stabilizer in the silicone tube, thereby extending the aging resistance time of the silicone tube. In the light aging test, the YI (E313-73) of the silicone tube remained almost unchanged within 240 hours, while the YI value of the silicone tube without the reinforcing agent increased by more than two times. In the thermal aging test, the YI value of the silicone tube prepared by this formulation increased by approximately three times after 3 hours, while the YI value of the silicone tube prepared by the conventional method increased by up to approximately 17 times after 3 hours. Attached Figure Description

[0024] Figure 1 This is the infrared spectrum of the silicone material prepared in Example 1 of this invention;

[0025] Figure 2 This is a SEM image of the surface of the compounded film prepared in Example 1 of this invention;

[0026] Figure 3 This is a SEM image of the surface of the compounded film prepared in Comparative Example 1 of this invention;

[0027] Figure 4 This is a comparison chart of the photoaging test results of this invention;

[0028] Figure 5 This is a comparison chart of the thermal aging test results of this invention. Detailed Implementation

[0029] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] 0.5 kg of 3,3'-dichloro-4,4'-diisocyanate biphenyl, 0.5 kg of light stabilizer 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 0.02 kg of dibutyltin diacetate, and 35 kg of xylene were added to a reactor. Under nitrogen atmosphere, the mixture was heated to 70°C and stirred for 1.5 h. The isocyanate group content of the system was determined to be 18.3% by the hydrochloric acid-di-n-butylamine method, indicating that an ester bond was formed between the reinforcing agent and the light stabilizer. The reaction was stopped to obtain the modified light stabilizer.

[0032] 0.3 kg of antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and modified light stabilizer were added to a kneader and stirred evenly. Then, 12 kg of methyl vinyl silica gel, 75 kg of vinyl silica gel, 10 kg of silica fume, and 8 kg of methyl silicone resin were added, and kneading was started. When the kneading temperature reached 160℃, the isocyanate group content of the system was 1.3% as determined by the hydrochloric acid-di-n-butylamine method, indicating that ester bonds were formed between the modified light stabilizer and the main component of silica gel. The reaction was stopped, and a vacuum was drawn until the vacuum degree was below -0.08 MPa. The distilled vapor was cooled and the co-solvent was recovered by a plate cooling tower. The vacuum was stopped when 28 kg of vapor was collected.

[0033] The received flux was added back to the kneader, and kneading was resumed. When the kneading temperature reached 165℃, vacuum was applied until the vacuum level was below -0.08MPa. The distilled vapor was cooled and the flux was recovered using a plate cooling tower until no flux dripped out. Vacuuming was continued for 40 minutes to obtain silica gel material. 10g of silica gel material was taken and soaked in 100ml of toluene at 50℃ overnight. After filtration, the filter cake was washed three times with toluene, and then vacuum dried to remove the toluene. The sample was subjected to infrared spectroscopy analysis (see attached image). Figure 1 .

[0034] The prepared silicone material was added to a two-roll mill, along with 3 kg of vulcanizing agent. The mixture was then kneaded at 160°C for 45 minutes, sheeted, and cooled to room temperature to obtain the compounded rubber sheet. SEM images of the sheet are attached. Figure 2 .

[0035] The prepared compounded rubber sheet was added to a silicone extruder, and the extrusion temperature was set to 163℃ and the extrusion rate to 10m / min. The aging-resistant silicone tube 1 was obtained by extrusion molding.

[0036] Example 2

[0037] 0.2 kg of 3,3'-dichloro-4,4'-diisocyanate biphenyl, 0.3 kg of light stabilizer 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 0.01 kg of dibutyltin diacetate, and 20 kg of xylene were added to a reactor. Under a carbon dioxide atmosphere, the mixture was heated to 55°C and stirred for 1 hour. The isocyanate group content of the system was determined by the hydrochloric acid-di-n-butylamine method to be 20.1% remaining. The reaction was then stopped to obtain the modified light stabilizer.

[0038] Add 0.2 kg of antioxidant Phosphite A and modified light stabilizer to a kneader and stir evenly. Then add 10 kg of methyl vinyl silica gel, 60 kg of vinyl silica gel, 8 kg of silica fume, and 5 kg of methyl silicone resin. Start kneading. When the kneading temperature reaches 155℃, start vacuuming until the vacuum degree is below -0.08 MPa. Cool the distilled vapor through a reflux condenser to recover the co-solvent. Stop vacuuming when 15.8 kg has been collected.

[0039] The received flux is added back into the kneader, and kneading is started again. When the kneading temperature reaches 155℃, vacuum is started until the vacuum level is below -0.08MPa. The distilled vapor is recovered as flux through the reflux condenser until no flux drips out. Vacuum is continued for 20 minutes to obtain silica gel material.

[0040] Add the prepared silicone material to a two-roll mill, add 1 kg of vulcanizing agent, mix at 152°C for 30 min, sheet out, and cool to room temperature to obtain the mixed rubber sheet.

[0041] The prepared compounded rubber sheet was added to a silicone extruder, and the extrusion temperature was set to 160℃ and the extrusion rate to 3m / min. The aging-resistant silicone tube 2 was obtained by extrusion molding.

[0042] Example 3

[0043] 0.8 kg of 3,3'-dichloro-4,4'-diisocyanate biphenyl, 0.8 kg of light stabilizer 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 0.05 kg of dibutyltin diacetate, and 50 kg of xylene were added to a reactor. Under argon atmosphere protection, the temperature was raised to 85°C and the mixture was stirred for 2 hours. The isocyanate group content of the system was determined by the hydrochloric acid-di-n-butylamine method to be 17.7% remaining. The reaction was then stopped to obtain the modified light stabilizer.

[0044] Add 0.5 kg of antioxidant 1010 and modified light stabilizer to a kneader and stir evenly. Then add 15 kg of methyl vinyl silica gel, 90 kg of vinyl silica gel, 14 kg of silica fume, and 10 kg of methyl silicone resin. Start kneading. When the kneading temperature reaches 160℃, start vacuuming until the vacuum degree is below -0.08 MPa. Cool the distilled vapor through a plate cooling tower to recover the co-solvent. Stop vacuuming when 39 kg is collected.

[0045] The received flux is added back into the kneader, and kneading is started again. When the kneading temperature reaches 155℃, vacuum is started until the vacuum degree is below -0.08MPa. The distilled vapor is recycled to recover the flux through a plate cooling tower until no flux drips out. Vacuum is continued for 60 minutes to obtain silica gel material.

[0046] Add the prepared silicone material to a two-roll mill, add 5 kg of vulcanizing agent, mix at 160°C for 60 min, sheet out, and cool to room temperature to obtain the mixed rubber sheet.

[0047] The prepared compounded rubber sheet was added to a silicone extruder, and the extrusion temperature was set to 165℃ and the extrusion rate to 20m / min. The aging-resistant silicone tube 3 was obtained by extrusion molding.

[0048] Comparative Example 1

[0049] Add 0.5 kg of light stabilizer 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 0.02 kg of dibutyltin diacetate, 0.3 kg of antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 12 kg of methyl vinyl silica gel, 75 kg of vinyl silica gel, 10 kg of silica fume, and 8 kg of methyl silicone resin to a kneader and knead for 2 hours at a kneading temperature of 160℃.

[0050] The prepared silicone material was added to a two-roll mill, along with 3 kg of vulcanizing agent. The mixture was then kneaded at 160°C for 45 minutes, sheeted, and cooled to room temperature to obtain the compounded rubber sheet. SEM images of the sheet are attached. Figure 3 .

[0051] The prepared compounded rubber sheet was added to a silicone extruder, and the extrusion temperature was set to 163℃ and the extrusion rate to 10m / min. The silicone tube 4 was then extruded.

[0052] Comparative Example 2

[0053] Add 0.5 kg of 3,3'-dichloro-4,4'-diisocyanate biphenyl, 0.5 kg of light stabilizer 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 0.02 kg of dibutyltin diacetate, 0.3 kg of antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 12 kg of methyl vinyl silica gel, 75 kg of vinyl silica gel, 10 kg of silica fume, and 8 kg of methyl silicone resin to a kneader and knead for 2 hours at a kneading temperature of 160°C.

[0054] Add the prepared silicone material to a two-roll mill, add 3 kg of vulcanizing agent, mix at 160°C for 45 min, sheet out, and cool to room temperature to obtain the mixed rubber sheet.

[0055] The prepared compounded rubber sheet was added to a silicone extruder, and the extrusion temperature was set to 163℃ and the extrusion rate to 10m / min. The silicone tube 5 was then extruded.

[0056] Comparative Example 3

[0057] 0.5 kg of light stabilizer 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 35 kg of xylene, 0.3 kg of antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 12 kg of methyl vinyl silica gel, 75 kg of vinyl silica gel, 10 kg of silica fume, and 8 kg of methyl silicone resin were kneaded. When the kneading temperature reached 160°C, a vacuum was drawn until the vacuum level was below -0.08 MPa. The distilled vapor was cooled and the co-solvent was recovered by a plate cooling tower. The vacuum was stopped when 28.4 kg was collected.

[0058] The received flux is added back into the kneader, and kneading is started again. When the kneading temperature reaches 165℃, vacuum is started until the vacuum level is below -0.08MPa. The distilled vapor is cooled and the flux is recovered by a plate cooling tower until no flux drips out. Vacuum is continued for 40 minutes to obtain silica gel material.

[0059] Add the prepared silicone material to a two-roll mill, add 3 kg of vulcanizing agent, mix at 160°C for 45 min, sheet out, and cool to room temperature to obtain the mixed rubber sheet.

[0060] The prepared compounded rubber sheet was added to a silicone extruder, and the extrusion temperature was set to 163℃ and the extrusion rate to 10m / min. The silicone tube 6 was then extruded and formed.

[0061] Photoaging test:

[0062] Instrument: Q-LabQUV / Spray UV fluorescence aging test chamber.

[0063] Test parameters: The lamp used is UVA-313, with an irradiance of 0.55W / m². 2 / nm.

[0064] Results Analysis: In accordance with ASTM D1544-2018 standard, the YI (E313-73) of the compounded film sample at a 10° angle was tested using an X-riteCi7600 benchtop colorimeter with a C light source.

[0065] Test process: Results statistics are shown in Table 1, and comparison charts are attached. Figure 4 .

[0066] Table 1: Results of photoaging test

[0067]

[0068] The results in the table above show that silicone tube 4, without the addition of light stabilizers and antioxidants, exhibits a significant increase in YI (E313-73) over time, indicating poor resistance to photoaging. Silicone tube 6, without the addition of reinforcing agents, shows only a slight increase in YI (E313-73) over the first 240 hours, demonstrating some light stability. However, its light stability decreases significantly between 240 and 480 hours. Silicone tube 5, without the addition of co-solvents, shows a better trend in photoaging stability than silicone tube 6, although its light stability decreases after prolonged use. Silicone tubes 1-3 show no significant increase in YI (E313-73) during the test period, indicating good resistance to photoaging.

[0069] The SEM image of the compounded film prepared in Example 1 shows no particles on its surface (see attached image). Figure 1 The SEM image of the compounded film prepared in Comparative Example 1 shows particles on its surface (see attached image). Figure 2 This demonstrates that the use of a co-solvent in the preparation process facilitates the uniform dispersion of light stabilizers and antioxidants, solves the problem of poor compatibility between additives and the main silicone component, and enhances the short-term photo-aging resistance of the silicone tube. Adding a reinforcing agent to the formulation, combined with the co-solvent preparation process of this invention, further improves the photo-aging resistance of the prepared silicone tube, enabling it to maintain good photostability for a longer period.

[0070] In Example 1, during the preparation process, the remaining isocyanate group content of the system was monitored to be 18.3%, indicating that ester bonds were formed between the reinforcing agent and the light stabilizer. During the kneading process, the remaining isocyanate group content of the system decreased to 1.3%, and the infrared spectrum at 2260 cm⁻¹ was [data missing]. -1 No characteristic peaks of isocyanate group stretching vibrations were observed near the wavelength, 1690 cm⁻¹. -1 The presence of characteristic absorption peaks of ester carbonyl groups at the specified wavelength indicates that the addition of reinforcing agents dibutyltin diacetate and 3,3'-dichloro-4,4'-diisocyanate biphenyl in the formulation demonstrates that under the catalysis of dibutyltin diacetate, the light stabilizer 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol undergoes a coupling reaction with 3,3'-dichloro-4,4'-diisocyanate biphenyl, and then crosslinks with the main component of the silicone tube through ester bonds, uniformly fixing the light stabilizer in the silicone tube. Ultimately, this allows the silicone tube to maintain its anti-photoaging performance for a longer period of time.

[0071] Thermal aging test:

[0072] Instrument: LRHS-22-NQ type air exchange aging chamber.

[0073] Test parameters: Aging at 150℃ for 3 hours.

[0074] Results analysis: In accordance with ASTM D1544-2018 standard, the YI (E313-73) of the compounded film sample at a 10° angle was tested every 1 hour using an X-riteCi7600 benchtop colorimeter.

[0075] Test process: Results statistics are shown in Table 2, and comparison charts are attached. Figure 5 .

[0076] Table 2: Results of thermal aging test

[0077]

[0078] The results in the table above show that the high-temperature heat aging resistance (YI) of silicone tubes 1-3, 4, 5, and 6 all increased with the extension of the test time. Silicone tube 6, produced using a solvent mixing process, exhibited improved heat aging resistance. Silicone tube 5, with the addition of reinforcing agents, also showed improved heat aging resistance, but it was still inferior to that of silicone tube 6. This indicates that the solvent mixing process is beneficial for improving heat aging resistance.

[0079] Silicone tubes 1-3 prepared using a solvent mixing process and with added reinforcing agents exhibit the best resistance to heat aging.

[0080] Tensile strength test:

[0081] Instrument: Universal testing machine;

[0082] Sample: Injection molded into type 1A, with dimensions of 25 mm × 5 mm × 1 mm;

[0083] Test: The test rate was 4 mm / min, and the test temperature was 25℃. Each sample was tested three times repeatedly, and the average value was taken. The results are shown in Table 3 below:

[0084] Table 3 Tensile strength test results

[0085]

[0086] The silicone tube 5 formulation did not contain any co-solvents and had slightly lower tensile strength. The tensile strengths of silicone tubes 1-3, 4, and 6 were almost identical, indicating that adding reinforcing agents would not cause a decrease in the strength of the silicone tubes.

[0087] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An aging resistant silicone tube, characterized by: The formula comprises methyl vinyl silicone 10-15 parts by weight, vinyl silicone 60-90 parts by weight, methyl silicone resin 5-10 parts by weight, white carbon black 8-14 parts by weight, vulcanizing agent 1-5 parts by weight, antioxidant 0.2-0.5 parts by weight, light stabilizer 0.3-0.8 parts by weight, cosolvent 20-50 parts by weight, reinforcing agent 0.21-0.85 parts by weight. The cosolvent is dimethylbenzene; the reinforcing agent is dibutyltin diacetate 0.01-0.05 parts by weight and 3,3'-dichloro-4,4'-diisocyanate biphenyl 0.2-0.8 parts by weight.

2. The aging resistant silicone tube according to claim 1, wherein: The antioxidant is one of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester, 1010, and Phosphite A.

3. The aging resistant silicone tube according to claim 1, wherein: The light stabilizer is 2,4-di-tert-butyl-6-(5-chlorobenzotriazole-2-yl)phenol.

4. A process for producing the anti-aging silica gel tube according to any one of claims 1 to 3, characterized by, The method comprises the following steps: S1. According to the formula, 3,3'-dichloro-4,4'-diisocyanate biphenyl, light stabilizer, dibutyltin diacetate, and cosolvent are added to a reactor, and the mixture is stirred under inert gas protection and heated to 55-85°C for 1-2h to obtain a modified light stabilizer; S2. The antioxidant and the modified light stabilizer are added to a kneader according to the formula, and then the methyl vinyl silicone, vinyl silicone, white carbon black, and methyl silicone resin are added after uniform stirring, and kneading is started, and when the kneading temperature reaches 155-160°C, vacuum is started, and the condensed cosolvent is collected through a reflux condenser, and when about 80% of the cosolvent is recovered, the vacuum is stopped; S3. The recovered cosolvent in step S2 is added to the kneader again, and kneading is started again, and when the kneading temperature reaches 160-165°C, vacuum is started, and the condensed cosolvent is collected through a reflux condenser until no cosolvent drops out, and vacuum is continued for 20-60min to obtain a silicone compound; S4. The silicone compound prepared in step S3 is added to an open mill, and the vulcanizing agent is added according to the formula, and after mixing, the mixture is sheeted, and cooled to room temperature to obtain a mixed rubber sheet; S5. The mixed rubber sheet prepared in step S4 is added to a silicone extruder, and extruded to form an aging-resistant silicone tube.

5. The method of claim 4, wherein the aging-resistant silicone tube is prepared by the steps of: In steps S2 and S3, the vacuum degree in the vacuum process is lower than -0.08MPa.

6. The method of claim 4, wherein the aging-resistant silicone tube is prepared by the steps of: In step S4, the mixing temperature is 152-160°C, and the mixing time is 30-60min.

7. The method for preparing the aging-resistant silicone tube according to claim 4, characterized in that, In step S5, the extrusion temperature is 160-165°C, and the extrusion rate is 3-20m / min.

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