Modified polytetrafluoroethylene tube and method for producing the same

Abstract

The application belongs to the technical field of polytetrafluoroethylene pipe preparation, and particularly relates to a modified polytetrafluoroethylene pipe and a preparation method thereof. The modified polytetrafluoroethylene pipe is composed of the following raw materials in percentage by mass: polytetrafluoroethylene resin 74-76%, modified red mud 4-5%, modified nano lanthanum phosphate and magnesium borate whisker mixture 3.0-4.0%, and extrusion aid 16-18%. The modified polytetrafluoroethylene pipe has high tensile strength and low water vapor permeability due to the synergistic effect of the raw materials.

Description

Technical Field

[0001] This invention belongs to the field of polytetrafluoroethylene (PTFE) tube preparation technology, specifically relating to a modified PTFE tube and its preparation method. Background Technology

[0002] In recent years, to improve production efficiency, there is a need to transport chemically active and corrosive liquids or steam at higher temperatures. However, traditional pipe materials not only suffer from insufficient crack resistance and chemical resistance but also exhibit significant chemical solution penetration. Polytetrafluoroethylene (PTFE), as a fluoropolymer with high chemical resistance, possesses outstanding corrosion resistance, a wide operating temperature range, good solvent resistance, and insulation properties, enabling its use in various environments. Therefore, PTFE has been widely used in high-end industries such as aerospace, power generation, pharmaceuticals, and semiconductors.

[0003] However, polytetrafluoroethylene (PTFE) materials have high melt viscosity and poor flowability during processing, which prevents them from fully filling tiny pores. Pipes produced by extruding PTFE dispersion resin paste have high permeability, making them unsuitable for applications requiring strict chemical reagent permeability. Furthermore, traditional PTFE pipes also have performance limitations, such as insufficient mechanical strength, which restricts their use in more demanding environments.

[0004] In practical applications, especially in the chemical and petroleum industries, pipes need to possess both good low permeability and sufficient mechanical strength. The performance balance of existing PTFE pipes in these aspects still needs improvement. Current methods often only target improvements to a specific property, failing to comprehensively improve the mechanical properties, acid and alkali corrosion resistance, and permeability of PTFE pipes. Furthermore, in some cases, these modification methods may introduce new problems, such as increased processing complexity, higher costs, or short-lived modification effects. Therefore, it is necessary to explore a new type of modified PTFE pipe. Summary of the Invention

[0005] The purpose of this invention is to provide a modified polytetrafluoroethylene (PTFE) tube. The modified PTFE tube exhibits high tensile strength and low water vapor permeability. Furthermore, this invention also provides a method for its preparation.

[0006] The modified polytetrafluoroethylene (PTFE) pipe of this invention is composed of the following raw materials by mass percentage: 74-76% PTFE resin, 4-5% modified red mud, 3.0-4.0% mixture of modified nano-lanthanum phosphate and magnesium borate whiskers, and 16-18% extrusion aid; the preparation method of the modified red mud consists of the following steps: ① mixing red mud and water evenly, heating to 53-57℃ under stirring, then adding hydrochloric acid to adjust the pH of the reaction system to 6.5-7.0, and maintaining the temperature for 1.5 hours. Immediately after completion, the red mud is pumped into a plate and frame filter press for filtration and pulping to prepare dealkalized red mud; ② The dealkalized red mud is placed in a roasting furnace for roasting, and then the roasted red mud is cooled to room temperature in the furnace and then pulverized to prepare red mud powder; ③ The red mud powder prepared in step ② is mixed with anhydrous ethanol and deionized water, and then acetic acid is added to adjust the pH of the slurry to 4.3. Tridecafluorooctyltriethoxysilane is added dropwise to react. After the reaction is completed, vacuum filtration is performed, and the resulting filter cake is vacuum dried to prepare modified red mud.

[0007] The extrusion aid is Isopar G, manufactured by ExxonMobil.

[0008] The red mud mentioned in step ① has the following chemical composition by mass percentage: CaO 22.54%, Al2O3 24.75%, SiO2 22.38%, Fe2O3 18.54%, TiO2 5.04%, Na2O 0.61%, and loss on ignition 6.14%.

[0009] The step ① of adjusting the pH of the reaction system to 6.5-7.0 by adding hydrochloric acid specifically involves first adding hydrochloric acid accounting for 30% of the mass of the red mud, and then adding hydrochloric acid dropwise to adjust the pH of the reaction system to 6.5-7.0. The mass concentration of the hydrochloric acid is 30%.

[0010] In step ①, the mass ratio of red mud to water is 1:3.

[0011] In step ①, the stirring speed is 150 r / min and the pressure of the plate and frame filter press is 0.8 MPa.

[0012] In step ①, the pulping process involves mixing the filter cake obtained after pressure filtration with deionized water at a mass ratio of 1:2, re-pulping, stirring at room temperature for 20 minutes, and then pressure filtration again. This pulping-pressure filtration cycle is repeated 3-4 times, and the final filter cake is the dealkalized red mud. In step ②, the calcination process involves heating to 700℃ at a rate of 5℃ / min and calcining for 30 minutes in an air atmosphere.

[0013] The pulverization process described in step ② involves first pulverizing the material to d50=1.5µm using a steam kinetic mill (0.8MPa superheated steam), and then classifying it to d90=4µm using a horizontal turbine classifier to obtain red mud powder.

[0014] In step ③, the mass ratio of red mud powder, anhydrous ethanol, and deionized water is 1:1:0.02.

[0015] In step ③, the mass of tridecafluorooctyltriethoxysilane accounts for 1.0% of the mass of red mud powder.

[0016] The dropping time for the tridecafluorooctyltriethoxysilane in step ③ is 5 min.

[0017] The stirring speed during the entire reaction process in step ③ is 1000 r / min.

[0018] In step ③, the reaction temperature is 65℃, the reaction time is 30 min, the vacuum drying temperature is 80℃, the vacuum drying time is 2 h, and the vacuum drying pressure is -0.09 MPa.

[0019] The preparation method of the modified nano-lanthanum phosphate and magnesium borate whiskers comprises the following steps: dispersing nano-lanthanum phosphate and magnesium borate whiskers in isopropanol solution, sonicating at room temperature, and then shearing at high speed; then adding tridecafluorooctyltriethoxysilane; adding acetic acid to adjust the pH of the reaction system to 3.5; hydrolyzing at 50-53℃ for 30 min; and finally filtering and vacuum drying to obtain the modified nano-lanthanum phosphate and magnesium borate whiskers mixture.

[0020] The mass ratio of nano-lanthanum phosphate to magnesium borate whiskers is 2:3.

[0021] The mass of nano-lanthanum phosphate and magnesium borate whiskers is 10% of the mass of the isopropanol solution.

[0022] The ultrasonic treatment time at room temperature is 5-7 minutes, the high-speed shearing speed is 800 r / min, and the high-speed shearing time is 5-7 minutes.

[0023] The addition time for tridecafluorooctyltriethoxysilane was 8 minutes.

[0024] The rotation speed during the hydrolysis reaction was 800 r / min.

[0025] The mass of tridecafluorooctyltriethoxysilane accounts for 1.5-2% of the total mass of nano-lanthanum phosphate and magnesium borate whiskers.

[0026] The vacuum drying temperature is 80℃, the vacuum drying time is 3h, and the vacuum drying pressure is -0.08MPa.

[0027] The method for preparing the modified polytetrafluoroethylene tube of the present invention comprises the following steps:

[0028] (1) A mixture of modified red mud, modified nano lanthanum phosphate and magnesium borate whiskers was added to anhydrous ethanol and ultrasonically dispersed, then sheared at high speed, and finally filtered and vacuum dried to prepare a composite filler.

[0029] (2) The composite filler prepared in step (1) and polytetrafluoroethylene resin are added to a high-speed mixer and mixed evenly, and then sieved to prepare a mixture;

[0030] (3) Spray extrusion aid into the mixture for high-speed mixing, then sieve, seal and mature, add the mixture to the paste extruder for extrusion, and prepare modified PTFE pipe green blank. Vacuum degass and pre-dry the modified PTFE pipe green blank.

[0031] (4) The pre-dried modified PTFE tube blank is heated to 200℃ at a heating rate of 30℃ / h, then heated to 320℃ at a heating rate of 40℃ / h, and finally heated to 380-385℃ at a heating rate of 50℃ / h and held for 30min. Finally, it is cooled to 80℃ in the furnace and taken out of the furnace. It is then naturally cooled to room temperature to obtain the modified polytetrafluoroethylene tube.

[0032] In step (1), the mass ratio of the mixture of modified nano lanthanum phosphate and magnesium borate whiskers to the modified red mud and the mass of anhydrous ethanol is 1:1.

[0033] In step (1), the ultrasonic dispersion time is 10-15 min, the ultrasonic dispersion temperature is room temperature, the rotation speed during high-speed shearing is 1000 r / min, and the high-speed shearing time is 5-7 min.

[0034] In step (1), the vacuum drying temperature is 80-83℃, the vacuum drying pressure is -0.09MPa, and the vacuum drying time is 2h.

[0035] In step (2), the mixing speed in the high-speed mixer is 1000-1200 r / min, and the mixing time is 3-5 min.

[0036] The sieving process described in step (2) involves passing the material through an 80-mesh sieve and repeating the sieving process twice to ensure that there is no agglomeration.

[0037] In step (3), the high-speed mixing speed is 1000-1200 r / min, the mixing time is 3 min, and the mixture is passed through a 30-mesh sieve and then sealed and aged at room temperature for 12 h.

[0038] In step (3), the extrusion pressure of the paste extruder is 55 MPa and the extrusion time is 10 min.

[0039] The vacuum degassing in step (3) is performed at 80°C and -0.09MPa for 30 minutes. The pre-drying temperature is 120°C and the pre-drying time is 30 minutes.

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] (1) The modified polytetrafluoroethylene pipe of the present invention uses polytetrafluoroethylene resin as the matrix resin and a mixture of modified red mud and modified nano-lanthanum phosphate and magnesium borate whiskers as fillers. The modified red mud is first de-alkalied, and then calcined in air at 700°C to densify the particles and generate hard microcrystals; subsequently, it is instantaneously cooled by a steam kinetic mill to generate thermal shock cracks, which facilitates subsequent peeling. Ultrafine grinding to d 90 After reaching a particle size of 4µm, the particles can be arranged in parallel within the PTFE matrix, extending the penetration path and significantly reducing the water permeation rate. Finally, fluorosilane coupling modification improves dispersibility and interfacial compatibility, hydrophobizing the particle surface and reducing interfacial adhesion, thereby reducing the wear rate. In the modified nano-lanthanum phosphate and magnesium borate whisker mixture, the nano-lanthanum phosphate particles fill the gaps between the primary PTFE particles, suppressing cold flow and reducing wear, while the magnesium borate whiskers form a three-dimensional needle-like network, achieving load-bearing and crack deflection through a bridging-pull-out mechanism, thus improving the flexural modulus and tensile strength of the PTFE tube. The nano-lanthanum phosphate and magnesium borate whiskers together constitute a "nanopinion-micron bridging" dual-scale architecture, enhancing the tensile strength and dimensional stability of the prepared modified PTFE tube. Furthermore, the dual-scale filler increases density and suppresses microcracks, thereby extending corrosion fatigue life.

[0042] (2) The preparation method of the modified polytetrafluoroethylene tube of the present invention has easy process parameters to control and is easy to realize industrial production. The modified polytetrafluoroethylene tube prepared by this method has high tensile strength and low water vapor permeability. Detailed Implementation

[0043] Example 1

[0044] The modified polytetrafluoroethylene (PTFE) tube described in Example 1 is composed of the following raw materials by mass percentage: 75% PTFE resin, 4.5% modified red mud, 3.5% mixture of modified nano-lanthanum phosphate and magnesium borate whiskers, and 17% extrusion aid. The preparation method of the modified red mud consists of the following steps: ① Mix red mud and water evenly, heat to 55°C under stirring, then add hydrochloric acid to adjust the pH of the reaction system to 6.8, keep the reaction at this temperature for 1.5 hours, and immediately pump the mixture into a plate and frame filter press for filtration and pulping to obtain dealkalized red mud; ② Place the dealkalized red mud in a roasting furnace for roasting, then cool the roasted red mud to room temperature with the furnace and pulverize it to obtain red mud powder; ③ Mix the red mud powder obtained in step ②, anhydrous ethanol, and deionized water evenly, then add acetic acid to adjust the pH of the slurry to 4.3, add tridecafluorooctyltriethoxysilane dropwise for reaction, and after the reaction is complete, perform vacuum filtration. The resulting filter cake is then vacuum dried to obtain modified red mud.

[0045] The extrusion aid is Isopar G, manufactured by ExxonMobil.

[0046] The red mud mentioned in step ① has the following chemical composition by mass percentage: CaO 22.54%, Al2O3 24.75%, SiO2 22.38%, Fe2O3 18.54%, TiO2 5.04%, Na2O 0.61%, and loss on ignition 6.14%.

[0047] In step ①, the addition of hydrochloric acid to adjust the pH of the reaction system to 6.8 specifically involves first adding hydrochloric acid accounting for 30% of the mass of the red mud, and then adding hydrochloric acid dropwise to adjust the pH of the reaction system to 6.8. The mass concentration of the hydrochloric acid is 30%.

[0048] In step ①, the mass ratio of red mud to water is 1:3.

[0049] In step ①, the stirring speed is 150 r / min and the pressure of the plate and frame filter press is 0.8 MPa.

[0050] The pulping process described in step ① involves mixing the filter cake obtained after pressure filtration with deionized water at a mass ratio of 1:2, re-pulping, stirring at room temperature for 20 minutes, and then pressure filtration again. This pulping-pressure filtration cycle is repeated 3 times, and the final filter cake is the dealkalized red mud.

[0051] The calcination in step ② is carried out by heating to 700℃ at a rate of 5℃ / min and calcining for 30 minutes in an air atmosphere.

[0052] The pulverization process described in step ② involves first pulverizing the material to d using a steam kinetic mill (0.8 MPa superheated steam). 50 =1.5µm, then the airflow is further classified to d by a horizontal turbine classifier.90 =4µm, to obtain red mud powder.

[0053] In step ③, the mass ratio of red mud powder, anhydrous ethanol, and deionized water is 1:1:0.02.

[0054] In step ③, the mass of tridecafluorooctyltriethoxysilane accounts for 1.0% of the mass of red mud powder.

[0055] The dropping time for the tridecafluorooctyltriethoxysilane in step ③ is 5 min.

[0056] The stirring speed during the entire reaction process in step ③ is 1000 r / min.

[0057] In step ③, the reaction temperature is 65℃, the reaction time is 30 min, the vacuum drying temperature is 80℃, the vacuum drying time is 2 h, and the vacuum drying pressure is -0.09 MPa.

[0058] The preparation method of the modified nano-lanthanum phosphate and magnesium borate whiskers comprises the following steps: dispersing nano-lanthanum phosphate and magnesium borate whiskers in isopropanol solution, sonicating at room temperature, and then shearing at high speed; then adding tridecafluorooctyltriethoxysilane; adding acetic acid to adjust the pH of the reaction system to 3.5; hydrolyzing at 51°C for 30 min; and finally filtering and vacuum drying to obtain the modified nano-lanthanum phosphate and magnesium borate whiskers mixture.

[0059] The mass ratio of nano-lanthanum phosphate to magnesium borate whiskers is 2:3.

[0060] The mass of nano-lanthanum phosphate and magnesium borate whiskers is 10% of the mass of the isopropanol solution.

[0061] The room temperature ultrasonic time was 6 minutes, the high-speed shearing speed was 800 r / min, and the high-speed shearing time was 6 minutes.

[0062] The addition time for tridecafluorooctyltriethoxysilane was 8 minutes.

[0063] The rotation speed during the hydrolysis reaction was 800 r / min.

[0064] The mass of tridecafluorooctyltriethoxysilane accounts for 1.7% of the total mass of nano-lanthanum phosphate and magnesium borate whiskers.

[0065] The vacuum drying temperature is 80℃, the vacuum drying time is 3h, and the vacuum drying pressure is -0.08MPa.

[0066] The preparation method of the modified polytetrafluoroethylene tube described in Example 1 consists of the following steps:

[0067] (1) A mixture of modified red mud, modified nano lanthanum phosphate and magnesium borate whiskers was added to anhydrous ethanol and ultrasonically dispersed, then sheared at high speed, and finally filtered and vacuum dried to prepare a composite filler.

[0068] (2) The composite filler prepared in step (1) and polytetrafluoroethylene resin are added to a high-speed mixer and mixed evenly, and then sieved to prepare a mixture;

[0069] (3) Spray extrusion aid into the mixture for high-speed mixing, then sieve, seal and mature, add the mixture to the paste extruder for extrusion, and prepare modified PTFE pipe green blank. Vacuum degass and pre-dry the modified PTFE pipe green blank.

[0070] (4) The pre-dried modified PTFE tube blank is heated to 200°C at a heating rate of 30°C / h, then heated to 320°C at a heating rate of 40°C / h, and finally heated to 383°C at a heating rate of 50°C / h and held for 30 min. Finally, it is cooled to 80°C in the furnace and taken out of the furnace. It is then naturally cooled to room temperature to obtain the modified polytetrafluoroethylene tube.

[0071] In step (1), the mass ratio of the mixture of modified nano lanthanum phosphate and magnesium borate whiskers to the modified red mud and the mass of anhydrous ethanol is 1:1.

[0072] In step (1), the ultrasonic dispersion time is 12 min, the ultrasonic dispersion temperature is room temperature, the high-speed shearing speed is 1000 r / min, and the high-speed shearing time is 6 min.

[0073] In step (1), the vacuum drying temperature is 81℃, the vacuum drying pressure is -0.09MPa, and the vacuum drying time is 2h.

[0074] In step (2), the mixing speed in the high-speed mixer is 1100 r / min and the mixing time is 4 min.

[0075] The sieving process described in step (2) involves passing the material through an 80-mesh sieve and repeating the sieving process twice to ensure that there is no agglomeration.

[0076] In step (3), the high-speed mixing speed is 1100 r / min, the mixing time is 3 min, and the mixture is passed through a 30-mesh sieve and then sealed and aged at room temperature for 12 h.

[0077] In step (3), the extrusion pressure of the paste extruder is 55 MPa and the extrusion time is 10 min.

[0078] The vacuum degassing in step (3) is performed at 80°C and -0.09MPa for 30 minutes. The pre-drying temperature is 120°C and the pre-drying time is 30 minutes.

[0079] The modified polytetrafluoroethylene (PTFE) tube prepared in Example 1 was subjected to performance tests: tensile properties were tested on a universal testing machine according to GB / T 1040.1-2006 "Determination of tensile properties of plastics - Part 1: General rules"; water vapor permeability was tested according to GB / T 1037-2021 "Determination of water vapor permeability of plastic films and sheets - Cup method for gain and loss of weight". The results showed that its tensile strength was 49.3 MPa and its water vapor permeability was 0.35 g / (m²). 2 ·d).

[0080] Example 2

[0081] The modified polytetrafluoroethylene (PTFE) tube described in Example 2 is composed of the following raw materials by mass percentage: 74% PTFE resin, 5% modified red mud, 3.0% mixture of modified nano-lanthanum phosphate and magnesium borate whiskers, and 18% extrusion aid. The preparation method of the modified red mud consists of the following steps: ① Mix red mud and water evenly, heat to 57°C under stirring, then add hydrochloric acid to adjust the pH of the reaction system to 7.0, keep the reaction at this temperature for 1.5 hours, and immediately pump the mixture into a plate and frame filter press for filtration and pulping to prepare dealkalized red mud; ② Place the dealkalized red mud in a roasting furnace for roasting, then cool the roasted red mud to room temperature with the furnace and pulverize it to prepare red mud powder; ③ Mix the red mud powder prepared in step ②, anhydrous ethanol, and deionized water evenly, then add acetic acid to adjust the pH of the slurry to 4.3, add tridecafluorooctyltriethoxysilane dropwise for reaction, and after the reaction is complete, perform vacuum filtration. The resulting filter cake is then vacuum dried to prepare modified red mud.

[0082] The extrusion aid is Isopar G, manufactured by ExxonMobil.

[0083] The red mud mentioned in step ① has the following chemical composition by mass percentage: CaO 22.54%, Al2O3 24.75%, SiO2 22.38%, Fe2O3 18.54%, TiO2 5.04%, Na2O 0.61%, and loss on ignition 6.14%.

[0084] The step ① of adjusting the pH of the reaction system to 7.0 by adding hydrochloric acid specifically involves first adding hydrochloric acid accounting for 30% of the mass of the red mud, and then adding hydrochloric acid dropwise to adjust the pH of the reaction system to 7.0. The mass concentration of the hydrochloric acid is 30%.

[0085] In step ①, the mass ratio of red mud to water is 1:3.

[0086] In step ①, the stirring speed is 150 r / min and the pressure of the plate and frame filter press is 0.8 MPa.

[0087] The pulping process described in step ① involves mixing the filter cake obtained after pressure filtration with deionized water at a mass ratio of 1:2, re-pulping, stirring at room temperature for 20 minutes, and then pressure filtration again. This pulping-pressure filtration cycle is repeated 4 times, and the final filter cake is the dealkalized red mud.

[0088] The calcination in step ② is carried out by heating to 700℃ at a rate of 5℃ / min and calcining for 30 minutes in an air atmosphere.

[0089] The pulverization process described in step ② involves first pulverizing the material to d using a steam kinetic mill (0.8 MPa superheated steam). 50 =1.5µm, then the airflow is further classified to d by a horizontal turbine classifier. 90 =4µm, to obtain red mud powder.

[0090] In step ③, the mass ratio of red mud powder, anhydrous ethanol, and deionized water is 1:1:0.02.

[0091] In step ③, the mass of tridecafluorooctyltriethoxysilane accounts for 1.0% of the mass of red mud powder.

[0092] The dropping time for the tridecafluorooctyltriethoxysilane in step ③ is 5 min.

[0093] The stirring speed during the entire reaction process in step ③ is 1000 r / min.

[0094] In step ③, the reaction temperature is 65℃, the reaction time is 30 min, the vacuum drying temperature is 80℃, the vacuum drying time is 2 h, and the vacuum drying pressure is -0.09 MPa.

[0095] The preparation method of the modified nano-lanthanum phosphate and magnesium borate whiskers comprises the following steps: dispersing nano-lanthanum phosphate and magnesium borate whiskers in isopropanol solution, sonicating at room temperature, and then shearing at high speed; then adding tridecafluorooctyltriethoxysilane; adding acetic acid to adjust the pH of the reaction system to 3.5; hydrolyzing at 50°C for 30 min; and finally filtering and vacuum drying to obtain the modified nano-lanthanum phosphate and magnesium borate whiskers mixture.

[0096] The mass ratio of nano-lanthanum phosphate to magnesium borate whiskers is 2:3.

[0097] The mass of nano-lanthanum phosphate and magnesium borate whiskers is 10% of the mass of the isopropanol solution.

[0098] The room temperature ultrasonic time was 5 minutes, the high-speed shearing speed was 800 r / min, and the high-speed shearing time was 5 minutes.

[0099] The addition time for tridecafluorooctyltriethoxysilane was 8 minutes.

[0100] The rotation speed during the hydrolysis reaction was 800 r / min.

[0101] The mass of tridecafluorooctyltriethoxysilane accounts for 1.5% of the total mass of nano-lanthanum phosphate and magnesium borate whiskers.

[0102] The vacuum drying temperature is 80℃, the vacuum drying time is 3h, and the vacuum drying pressure is -0.08MPa.

[0103] The preparation method of the modified polytetrafluoroethylene tube described in Example 2 consists of the following steps:

[0104] (1) A mixture of modified red mud, modified nano lanthanum phosphate and magnesium borate whiskers was added to anhydrous ethanol and ultrasonically dispersed, then sheared at high speed, and finally filtered and vacuum dried to prepare a composite filler.

[0105] (2) The composite filler prepared in step (1) and polytetrafluoroethylene resin are added to a high-speed mixer and mixed evenly, and then sieved to prepare a mixture;

[0106] (3) Spray extrusion aid into the mixture for high-speed mixing, then sieve, seal and mature, add the mixture to the paste extruder for extrusion, and prepare modified PTFE pipe green blank. Vacuum degass and pre-dry the modified PTFE pipe green blank.

[0107] (4) The pre-dried modified PTFE tube blank is heated to 200°C at a heating rate of 30°C / h, then heated to 320°C at a heating rate of 40°C / h, and finally heated to 380°C at a heating rate of 50°C / h and held for 30 min. Finally, it is cooled to 80°C in the furnace and taken out of the furnace. It is then naturally cooled to room temperature to obtain the modified polytetrafluoroethylene tube.

[0108] In step (1), the mass ratio of the mixture of modified nano lanthanum phosphate and magnesium borate whiskers to the modified red mud and the mass of anhydrous ethanol is 1:1.

[0109] In step (1), the ultrasonic dispersion time is 15 min, the ultrasonic dispersion temperature is room temperature, the high-speed shearing speed is 1000 r / min, and the high-speed shearing time is 5 min.

[0110] In step (1), the vacuum drying temperature is 80℃, the vacuum drying pressure is -0.09MPa, and the vacuum drying time is 2h.

[0111] In step (2), the mixing speed in the high-speed mixer is 1200 r / min and the mixing time is 3 min.

[0112] The sieving process described in step (2) involves passing the material through an 80-mesh sieve and repeating the sieving process twice to ensure that there is no agglomeration.

[0113] In step (3), the high-speed mixing speed is 1200 r / min, the mixing time is 3 min, and the mixture is passed through a 30-mesh sieve and then sealed and aged at room temperature for 12 h.

[0114] In step (3), the extrusion pressure of the paste extruder is 55 MPa and the extrusion time is 10 min.

[0115] The vacuum degassing in step (3) is performed at 80°C and -0.09MPa for 30 minutes. The pre-drying temperature is 120°C and the pre-drying time is 30 minutes.

[0116] The modified polytetrafluoroethylene (PTFE) tube prepared in Example 2 was subjected to performance tests. Tensile properties were tested on a universal testing machine according to GB / T 1040.1-2006 "Determination of Tensile Properties of Plastics Part 1: General Rules". Water vapor permeability was tested according to GB / T 1037-2021 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Method (Gain and Loss Method)". The results showed a tensile strength of 48.5 MPa and a water vapor permeability of 0.38 g / (m²). 2 ·d).

[0117] Example 3

[0118] The modified polytetrafluoroethylene tube described in Example 3 is composed of the following raw materials by mass percentage: 76% polytetrafluoroethylene resin, 4% modified red mud, 4.0% mixture of modified nano lanthanum phosphate and magnesium borate whiskers, and 16% extrusion aid. The preparation method of the modified red mud consists of the following steps: ① Mix red mud and water evenly, heat to 53°C under stirring, then add hydrochloric acid to adjust the pH of the reaction system to 6.5 and keep the reaction at this temperature for 1.5 hours. After the reaction is completed, immediately pump the mixture into a plate and frame filter press for filtration and pulping to prepare dealkalized red mud; ② Place the dealkalized red mud in a roasting furnace for roasting, then cool the roasted red mud to room temperature with the furnace and pulverize it to prepare red mud powder; ③ Mix the red mud powder prepared in step ②, anhydrous ethanol and deionized water evenly, then add acetic acid to adjust the pH of the slurry to 4.3, add tridecafluorooctyltriethoxysilane dropwise for reaction, and after the reaction is completed, perform vacuum filtration. The resulting filter cake is then vacuum dried to prepare modified red mud.

[0119] The extrusion aid is Isopar G, manufactured by ExxonMobil.

[0120] The red mud mentioned in step ① has the following chemical composition by mass percentage: CaO 22.54%, Al2O3 24.75%, SiO2 22.38%, Fe2O3 18.54%, TiO2 5.04%, Na2O 0.61%, and loss on ignition 6.14%.

[0121] In step ①, the addition of hydrochloric acid to adjust the pH of the reaction system to 6.5 specifically involves first adding hydrochloric acid accounting for 30% of the mass of the red mud, and then adding hydrochloric acid dropwise to adjust the pH of the reaction system to 6.5. The mass concentration of the hydrochloric acid is 30%.

[0122] In step ①, the mass ratio of red mud to water is 1:3.

[0123] In step ①, the stirring speed is 150 r / min and the pressure of the plate and frame filter press is 0.8 MPa.

[0124] The pulping process described in step ① involves mixing the filter cake obtained after pressure filtration with deionized water at a mass ratio of 1:2, re-pulping, stirring at room temperature for 20 minutes, and then pressure filtration again. This pulping-pressure filtration cycle is repeated 3 times, and the final filter cake is the dealkalized red mud.

[0125] The calcination in step ② is carried out by heating to 700℃ at a rate of 5℃ / min and calcining for 30 minutes in an air atmosphere.

[0126] The pulverization process described in step ② involves first pulverizing the material to d using a steam kinetic mill (0.8 MPa superheated steam). 50 =1.5µm, then the airflow is further classified to d by a horizontal turbine classifier. 90 =4µm, to obtain red mud powder.

[0127] In step ③, the mass ratio of red mud powder, anhydrous ethanol, and deionized water is 1:1:0.02.

[0128] In step ③, the mass of tridecafluorooctyltriethoxysilane accounts for 1.0% of the mass of red mud powder.

[0129] The dropping time for the tridecafluorooctyltriethoxysilane in step ③ is 5 min.

[0130] The stirring speed during the entire reaction process in step ③ is 1000 r / min.

[0131] In step ③, the reaction temperature is 65℃, the reaction time is 30 min, the vacuum drying temperature is 80℃, the vacuum drying time is 2 h, and the vacuum drying pressure is -0.09 MPa.

[0132] The preparation method of the modified nano-lanthanum phosphate and magnesium borate whiskers comprises the following steps: dispersing nano-lanthanum phosphate and magnesium borate whiskers in isopropanol solution, sonicating at room temperature, and then shearing at high speed; then adding tridecafluorooctyltriethoxysilane; adding acetic acid to adjust the pH of the reaction system to 3.5; hydrolyzing at 53°C for 30 min; and finally filtering and vacuum drying to obtain the modified nano-lanthanum phosphate and magnesium borate whiskers mixture.

[0133] The mass ratio of nano-lanthanum phosphate to magnesium borate whiskers is 2:3.

[0134] The mass of nano-lanthanum phosphate and magnesium borate whiskers is 10% of the mass of the isopropanol solution.

[0135] The room temperature ultrasonic time was 7 minutes, the high-speed shearing speed was 800 r / min, and the high-speed shearing time was 7 minutes.

[0136] The addition time for tridecafluorooctyltriethoxysilane was 8 minutes.

[0137] The rotation speed during the hydrolysis reaction was 800 r / min.

[0138] The mass of tridecafluorooctyltriethoxysilane accounts for 2% of the total mass of nano-lanthanum phosphate and magnesium borate whiskers.

[0139] The vacuum drying temperature is 80℃, the vacuum drying time is 3h, and the vacuum drying pressure is -0.08MPa.

[0140] The preparation method of the modified polytetrafluoroethylene tube described in Example 3 consists of the following steps:

[0141] (1) A mixture of modified red mud, modified nano lanthanum phosphate and magnesium borate whiskers was added to anhydrous ethanol and ultrasonically dispersed, then sheared at high speed, and finally filtered and vacuum dried to prepare a composite filler.

[0142] (2) The composite filler prepared in step (1) and polytetrafluoroethylene resin are added to a high-speed mixer and mixed evenly, and then sieved to prepare a mixture;

[0143] (3) Spray extrusion aid into the mixture for high-speed mixing, then sieve, seal and mature, add the mixture to the paste extruder for extrusion, and prepare modified PTFE pipe green blank. Vacuum degass and pre-dry the modified PTFE pipe green blank.

[0144] (4) The pre-dried modified PTFE tube blank is heated to 200°C at a heating rate of 30°C / h, then heated to 320°C at a heating rate of 40°C / h, and finally heated to 385°C at a heating rate of 50°C / h and held for 30 min. Finally, it is cooled to 80°C in the furnace and taken out of the furnace. It is then naturally cooled to room temperature to obtain the modified polytetrafluoroethylene tube.

[0145] In step (1), the mass ratio of the mixture of modified nano lanthanum phosphate and magnesium borate whiskers to the modified red mud and the mass of anhydrous ethanol is 1:1.

[0146] In step (1), the ultrasonic dispersion time is 10 min, the ultrasonic dispersion temperature is room temperature, the rotation speed during high-speed shearing is 1000 r / min, and the high-speed shearing time is 7 min.

[0147] In step (1), the vacuum drying temperature is 83℃, the vacuum drying pressure is -0.09MPa, and the vacuum drying time is 2h.

[0148] In step (2), the mixing speed in the high-speed mixer is 1000 r / min and the mixing time is 5 min.

[0149] The sieving process described in step (2) involves passing the material through an 80-mesh sieve and repeating the sieving process twice to ensure that there is no agglomeration.

[0150] In step (3), the high-speed mixing speed is 1000 r / min, the mixing time is 3 min, and the mixture is passed through a 30-mesh sieve and then sealed and aged at room temperature for 12 h.

[0151] In step (3), the extrusion pressure of the paste extruder is 55 MPa and the extrusion time is 10 min.

[0152] The vacuum degassing in step (3) is performed at 80°C and -0.09MPa for 30 minutes. The pre-drying temperature is 120°C and the pre-drying time is 30 minutes.

[0153] The modified polytetrafluoroethylene (PTFE) tube prepared in Example 3 was subjected to performance tests. Tensile properties were tested on a universal testing machine according to GB / T 1040.1-2006 "Determination of Tensile Properties of Plastics - Part 1: General Rules". Water vapor permeability was tested according to GB / T 1037-2021 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Method (Gain and Loss Method)". The results showed a tensile strength of 49.0 MPa and a water vapor permeability of 0.32 g / (m²). 2 ·d).

[0154] Comparative Example 1

[0155] The preparation method of the modified polytetrafluoroethylene (PTFE) tube described in Comparative Example 1 is the same as that in Example 1, except that the raw material composition of the modified PTFE tube is different. The modified PTFE tube described in Comparative Example 1, by mass percentage, consists of the following raw materials: 79.5% PTFE resin, 3.5% a mixture of modified nano-lanthanum phosphate and magnesium borate whiskers, and 17% extrusion aid.

[0156] The modified polytetrafluoroethylene (PTFE) tube prepared in Comparative Example 1 was subjected to performance tests. Tensile properties were tested on a universal testing machine according to GB / T 1040.1-2006 "Determination of Tensile Properties of Plastics - Part 1: General Rules". Water vapor permeability was tested according to GB / T 1037-2021 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Method (Gain and Loss Method)". The results showed a tensile strength of 42.3 MPa and a water vapor permeability of 0.44 g / (m²). 2 ·d).

[0157] Comparative Example 2

[0158] The preparation method of the modified polytetrafluoroethylene (PTFE) tube described in Comparative Example 2 is the same as that in Example 1, except that the raw material composition of the modified PTFE tube is different. The modified PTFE tube described in Comparative Example 2 is composed of the following raw materials by mass percentage: 78.5% polytetrafluoroethylene resin, 4.5% modified red mud, and 17% extrusion aid.

[0159] The modified polytetrafluoroethylene (PTFE) tube prepared in Comparative Example 2 was subjected to performance tests. Tensile properties were tested on a universal testing machine according to GB / T 1040.1-2006 "Determination of Tensile Properties of Plastics Part 1: General Rules". Water vapor permeability was tested according to GB / T 1037-2021 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Method (Gain and Loss Method)". The results showed a tensile strength of 43.8 MPa and a water vapor permeability of 0.42 g / (m²). 2 ·d).

[0160] In summary, the above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A modified polytetrafluoroethylene (PTFE) pipe, characterized in that: The mixture, by mass percentage, comprises the following raw materials: 74-76% polytetrafluoroethylene resin, 4-5% modified red mud, 3.0-4.0% mixture of modified nano-lanthanum phosphate and magnesium borate whiskers, and 16-18% extrusion aid; the preparation method of the modified red mud consists of the following steps: ① Mixing red mud and water evenly, heating to 53-57℃ under stirring, then adding hydrochloric acid to adjust the pH of the reaction system to 6.5-7.0 and maintaining the temperature for 1.5 hours. After the reaction is completed, immediately pumping the mixture into a plate. ① The red mud is prepared by pressing and slurrying in a frame filter press to obtain dealkalized red mud; ② The dealkalized red mud is placed in a roasting furnace for roasting, and then the roasted red mud is cooled to room temperature in the furnace and then crushed to obtain red mud powder; ③ The red mud powder obtained in step ② is mixed with anhydrous ethanol and deionized water, and then acetic acid is added to adjust the pH of the slurry to 4.

3. Tridecafluorooctyltriethoxysilane is added dropwise to react. After the reaction is completed, vacuum filtration is performed, and the resulting filter cake is vacuum dried to obtain modified red mud; The preparation method of the modified nano-lanthanum phosphate and magnesium borate whiskers comprises the following steps: dispersing nano-lanthanum phosphate and magnesium borate whiskers in isopropanol solution, sonicating at room temperature, and then shearing at high speed; then adding tridecafluorooctyltriethoxysilane; adding acetic acid to adjust the pH of the reaction system to 3.5; hydrolyzing at 50-53℃ for 30 min; and finally filtering and vacuum drying to obtain the modified nano-lanthanum phosphate and magnesium borate whiskers mixture.

2. The modified polytetrafluoroethylene pipe according to claim 1, characterized in that: The extrusion aid is Isopar G.

3. The modified polytetrafluoroethylene pipe according to claim 1, characterized in that: The red mud mentioned in step ① has the following chemical composition by mass percentage: CaO 22.54%, Al2O3 24.75%, SiO2 22.38%, Fe2O3 18.54%, TiO2 5.04%, Na2O 0.61%, and loss on ignition 6.14%. In step ①, adjusting the pH of the reaction system to 6.5-7.0 with hydrochloric acid involves first adding hydrochloric acid at a concentration of 30% of the red mud mass, and then adding hydrochloric acid dropwise to adjust the pH of the reaction system to 6.5-7.

0. The mass concentration of the hydrochloric acid is 30%. In step ①, the mass ratio of red mud to water is 1:3; In step ①, the stirring speed is 150 r / min and the pressure of the plate and frame filter press is 0.8 MPa. The pulping process described in step ① involves mixing the filter cake obtained after pressure filtration with deionized water at a mass ratio of 1:2, re-pulping, stirring at room temperature for 20 minutes, and then pressure filtration again. This pulping-pressure filtration cycle is repeated 3-4 times, and the final filter cake is the dealkalized red mud.

4. The modified polytetrafluoroethylene pipe according to claim 1, characterized in that: The calcination described in step ② involves heating to 700℃ at a rate of 5℃ / min and calcining for 30 minutes in an air atmosphere. The pulverization process described in step ② involves first pulverizing the material to d using a steam kinetic mill. 50 =1.5µm, then the airflow is further classified to d by a horizontal turbine classifier. 90 =4µm, to obtain red mud powder.

5. The modified polytetrafluoroethylene pipe according to claim 1, characterized in that: In step ③, the mass ratio of red mud powder, anhydrous ethanol, and deionized water is 1:1:0.

02. In step ③, the mass of tridecafluorooctyltriethoxysilane accounts for 1.0% of the mass of the red mud powder; The dropping time for the tridecafluorooctyltriethoxysilane in step ③ is 5 min; The stirring speed during the entire reaction process in step ③ is 1000 r / min; In step ③, the reaction temperature is 65℃, the reaction time is 30 min, the vacuum drying temperature is 80℃, the vacuum drying time is 2 h, and the vacuum drying pressure is -0.09 MPa.

6. The modified polytetrafluoroethylene pipe according to claim 1, characterized in that: In the preparation method of the modified nano lanthanum phosphate and magnesium borate whiskers, the mass ratio of nano lanthanum phosphate to magnesium borate whiskers is 2:

3. In the preparation method of the modified nano-lanthanum phosphate and magnesium borate whiskers, the mass of nano-lanthanum phosphate and magnesium borate whiskers accounts for 10% of the mass of the isopropanol solution. In the preparation method of the modified nano lanthanum phosphate and magnesium borate whiskers, the room temperature ultrasonic time is 5-7 min, the high-speed shearing speed is 800 r / min, and the high-speed shearing time is 5-7 min. In the preparation method of the modified nano lanthanum phosphate and magnesium borate whiskers, the time for adding tridecafluorooctyltriethoxysilane is 8 min. In the preparation method of the mixture of modified nano-lanthanum phosphate and magnesium borate whiskers, the rotation speed during the hydrolysis reaction is 800 r / min; In the preparation method of the modified nano-lanthanum phosphate and magnesium borate whiskers, the mass of tridecafluorooctyltriethoxysilane accounts for 1.5-2% of the total mass of nano-lanthanum phosphate and magnesium borate whiskers; In the preparation method of the modified nano-lanthanum phosphate and magnesium borate whiskers, the vacuum drying temperature is 80℃, the vacuum drying time is 3h, and the vacuum drying pressure is -0.08MPa.

7. A method for preparing the modified polytetrafluoroethylene pipe according to claim 1, characterized in that: It consists of the following steps: (1) A mixture of modified red mud, modified nano lanthanum phosphate and magnesium borate whiskers was added to anhydrous ethanol and ultrasonically dispersed, then sheared at high speed, and finally filtered and vacuum dried to prepare a composite filler. (2) The composite filler prepared in step (1) and polytetrafluoroethylene resin are added to a high-speed mixer and mixed evenly, and then sieved to prepare a mixture; (3) Spray extrusion aid into the mixture for high-speed mixing, then sieve, seal and mature, add the mixture to the paste extruder for extrusion, and prepare modified PTFE pipe green blank. Vacuum degass and pre-dry the modified PTFE pipe green blank. (4) The pre-dried modified PTFE tube blank is heated to 200℃ at a heating rate of 30℃ / h, then heated to 320℃ at a heating rate of 40℃ / h, and finally heated to 380-385℃ at a heating rate of 50℃ / h and held for 30min. Finally, it is cooled to 80℃ in the furnace and taken out of the furnace. It is then naturally cooled to room temperature to obtain the modified polytetrafluoroethylene tube.

8. The method for preparing the modified polytetrafluoroethylene tube according to claim 7, characterized in that: In step (1), the mass ratio of the mixture of modified nano lanthanum phosphate and magnesium borate whiskers to the modified red mud and the mass of anhydrous ethanol is 1:

1. In step (1), the ultrasonic dispersion time is 10-15 min, the ultrasonic dispersion temperature is room temperature, the rotation speed during high-speed shearing is 1000 r / min, and the high-speed shearing time is 5-7 min; In step (1), the vacuum drying temperature is 80-83℃, the vacuum drying pressure is -0.09MPa, and the vacuum drying time is 2h. In step (2), the mixing speed in the high-speed mixer is 1000-1200 r / min, and the mixing time is 3-5 min; The sieving process described in step (2) involves passing the material through an 80-mesh sieve, and the sieving is repeated twice.

9. The method for preparing the modified polytetrafluoroethylene tube according to claim 7, characterized in that: In step (3), the high-speed mixing speed is 1000-1200 r / min, the mixing time is 3 min, and the mixture is passed through a 30-mesh sieve and then sealed and aged at room temperature for 12 h. In step (3), the extrusion pressure of the paste extruder is 55 MPa and the extrusion time is 10 min; The vacuum degassing in step (3) is performed at 80°C and -0.09MPa for 30 minutes. The pre-drying temperature is 120°C and the pre-drying time is 30 minutes.