A preparation method of easy-to-tear polytetrafluoroethylene tube

Abstract

The present invention discloses a method for preparing an easy-tear polytetrafluoroethylene tube, relating to the technical field of PTFE tubes. The method comprises the following steps: mixing a sieved PTFE dispersed resin with a certain amount of a lubricating agent, mixing in a mixing device, and then aging at a set temperature. The aging PTFE resin is sieved and preformed under a certain pressure. The PTFE extruded tube is then sintered at a high temperature, cooled, and cut to obtain a finished product. The cut PTFE tube is then stretched to a certain extent and then cut to obtain a tearable PTFE tube.

Description

Technical Field

[0001] The invention relates to the technical field of PTFE tubes, in particular to a method for preparing an easy-to-tear polytetrafluoroethylene tube. Background Art

[0002] Due to its excellent performance, PTFE has found widespread application in various fields of social development. This is particularly evident in the semiconductor, medical, and aerospace industries, where its products are used as protective components for precision devices, micro-nano probes, and superconducting media. PTFE products take on different forms depending on the application scenario. PTFE is often used as a protective sleeve. However, as development demands, protective sleeves are often removed after their intended function, allowing the protected device to fully function and function. However, due to the structural characteristics of PTFE, the prepared protective sleeves are difficult to tear by hand. Even using a knife to scratch and then tear them requires considerable time and effort, and may damage the protected device. However, through process modifications or post-processing, PTFE protective sleeves can be made tearable, allowing for easy removal after use. This is crucial for specialized applications such as precision control and high-speed connection.

[0003] Currently, tearable PTFE protective sleeves are mostly achieved through blending modification or by creating weld lines during the extrusion process to alter the molecular structure of the sleeve. Blending modification often involves adding a small amount of a fluororesin with a similar molecular structure, creating differences in intermolecular aggregation energy. This creates differences in the fluororesin's compatibility and, consequently, tearability. Weld lines are primarily created by modifying the extrusion die structure, causing the resin flow to temporarily branch as it passes through the die foot during extrusion, forming weld lines along the length of the extruded tube and imparting a degree of tearability.

[0004] However, achieving the tearability of the sleeve through blending modification or the generation of weld marks not only has certain limitations in material selection, but also has high requirements for equipment and processes. Only in this way can the stability of the tearability of the protective sleeve be achieved, which is particularly evident in mass production. Blending modification not only has strict requirements on the blending formula composition, the degree of blending, and the impact on the subsequent extrusion process, but may also cause the precipitation of blended particles, which cannot be ignored in the fields of medicine and semiconductors. By generating weld marks, the impact of process fluctuations often causes the resulting protective sleeve to lack obvious tearability. Moreover, the use of weld marks is often seen in melt extrusion. Due to the high melt viscosity of PTFE, the use of this method requires extremely high requirements for mold design and process control, making it difficult to meet the conditions for mass production. Summary of the Invention

[0005] The present invention provides a method for preparing an easy-to-tear polytetrafluoroethylene tube. Since PTFE has a very high melt viscosity and its insolubility, it can only be processed by a molding process similar to powder metallurgy. PTFE dispersion resin is an important component of PTFE and its most important product form. A high-strength protective sleeve is usually prepared by extrusion through a dedicated extruder. After the extruded sleeve is stretched to a certain degree, the extruded sleeve then exhibits certain tearability. This is because after the PTFE extruded tube is stretched to a certain degree, the orientation degree of the PTFE molecular chains is significantly improved, and the PTFE molecular chains are preferentially oriented and arranged along the direction of the external force, reducing the degree of cross-linking of the molecular chains. When an external force tears the stretched PTFE tube, the main intermolecular force between the molecular chains with a higher degree of orientation is the van der Waals force, which is just perpendicular to the direction of the tearing force. Since the van der Waals force between the PTFE molecular chains is relatively weak, it is relatively easy to tear and it is relatively easy to obtain a relatively regular straight line.

[0006] In order to achieve the above-mentioned invention object, this method proposes the following solutions:

[0007] A method for preparing an easy-to-tear polytetrafluoroethylene tube, the operating steps of which are:

[0008] S1: Mix the sieved PTFE dispersion resin with a certain amount of lubricating additive in a mixing device for 20-35 minutes, and then mature at a set temperature for 8 to 24 hours;

[0009] S2: Screening the matured PTFE resin and preforming it under a certain pressure;

[0010] S3: Place the preformed PTFE blank into the PTFE extruder, calculate the specifications of the product according to the needs, and select appropriate equipment and mold for extrusion;

[0011] S4: Under certain extrusion speed conditions, the PTFE extruded tube is sintered at high temperature, cooled, and cut to obtain the finished product;

[0012] S5: The cut PTFE tube is stretched to a certain extent, and then selectively cut to obtain a PTFE tearable tube.

[0013] The amount of the lubricating auxiliary agent added is 18% to 25% of the PTFE dispersed resin.

[0014] The preparation method of the lubricating agent is as follows:

[0015] K1: Add 3-6 parts of hexafluoropolyether triethoxysilane (CAS: 1052667-99-8), 100-120 parts of molybdenum trioxide, and 1000-1500 parts of DMF to reactor 1, by weight, stir at 40-50°C for 100-150 minutes, filter, and dry to obtain molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane;

[0016] K2: Add 2-5 parts of lithium 2-aminoadipate, 5-10 parts of perfluoropolyether methacrylate, 30-60 parts of amino-terminated hyperbranched polyamide, 200-300 parts of DMF, and 0.5-2 parts of triethylamine to reactor 2 by weight, and stir at 70-90°C for 30-100 minutes;

[0017] K3: Add 0.005-0.05 parts of molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane to the reactor 2, stir vigorously for 100-150 minutes, and distill off DMF to obtain a lubricating agent.

[0018] The amino-terminated hyperbranched polyamide is a commercially available product, such as HyPer N101, HyPer N102 and HyPer N103.

[0019] The aging temperature is 30°C to 40°C.

[0020] The preforming conditions are 2-3 MPa, 3-8 min.

[0021] The angle of the extrusion die is 20 to 50 degrees.

[0022] The range of L / D of the extrusion die is 10 to 50.

[0023] The extrusion speed is 2-4 m / min.

[0024] The sintering temperature is 300-400°C.

[0025] The reaction mechanism of the lubricating agent:

[0026] 2-Aminoadipate lithium and perfluoropolyether methacrylate undergo amino-acrylic acid addition reaction to obtain product 1; amino-terminated hyperbranched polyamide and perfluoropolyether methacrylate undergo amino-acrylic acid addition reaction to obtain product 2. Products 1 and 2 are mixed with molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane to obtain a lubricating agent.

[0027] The stretching design device of this process:

[0028] By fixing the two ends of a certain length of PTFE tube on a mobile fixture and a fixed fixture respectively, the specific arrangement quantity is made according to needs (considering factors such as the size of the equipment, ease of operation, and production efficiency). The fixed fixture and the mobile fixture tighten the PTFE tube and confirm that the distance between the two fixtures meets the requirements. The positions of the caliper measurement and control points at both ends are set on the control panel. During the stretching process, the caliper will move to the relevant position with the movement of the telescopic rod, and will return to the initial position after the stretching operation is completed. Enter the specifications of the pipe, the required specifications of the pipe or the trigger conditions for the end of stretching, whether the pipe needs to be cut, etc. on the control panel. Start stretching. When the end conditions are triggered during the stretching process of the pipe or the relevant set requirements are met, the stretching action stops. According to requirements, the personnel operate the sliding rod and the cutting tool to cut the stretched pipe. After confirming that the cutting operation is completed, the stretching device automatically returns to the initial state to prepare for a new stretching operation.

[0029] Please see the figure below.

[0030] 1. The entire stretching device is placed on a platform with a ruler and slide rails;

[0031] 2. The fixed fixture and the movable fixture are used in conjunction with each other. Both the fixed fixture and the movable fixture have a serrated structure that matches the upper and lower parts to prevent the tightened PTFE tube from slipping during the stretching process. The fixed fixture is generally operated in a fixed position during the operation, and the movable fixture gradually moves away from the fixed fixture at a set speed during the stretching process.

[0032] 3. The movable slide bar is used in conjunction with the cutting tool. The cutting tool can cut PTFE and other pipes. The movable slide bar is controlled in real time with the operation and can slide left and right, move up and down, and extend and retract forward and backward. According to the control, the position is determined. At the location where the pipe needs to be cut, the movable slide bar slides and retracts on the slide rail to position the tool above the pipe. After moving up and down and limiting, the pipe is placed on the cutting edge. The pipe is cut according to the control.

[0033] 4. The caliper is used in conjunction with a telescopic rod. The telescopic rod can adjust the position of the caliper in the stretching direction so as to measure the pipe size at different stretching positions. The caliper adopts an infrared dual-axis caliper.

[0034] 5. As the control component of the entire stretching device, the control system has multiple functions, including parameter setting, data integration, program import control, and alarm feedback. First, the control system can control the stretching process, setting the trigger conditions for the end of stretching or the required pipe size, the original pipe specifications, and the strength limit. Second, the control system can display the stretching process in real time, showing the tensile strength, elongation at break, displacement, elastic modulus, the outer diameter of the pipe at three points after stretching, and the effective length of the pipe after stretching. Finally, the control system can provide real-time control based on operator operation, such as the sliding and retracting of the slider and the cutting of the tool.

[0035] Technical effects:

[0036] Compared with traditional methods, this method has the following advantages:

[0037] 1. The technical principle is simple, the operation is convenient, and batch production can be realized quickly;

[0038] 2. The process is stable and is almost unaffected by process parameters and other aspects.

[0039] 3. Small investment and low cost. Appropriate investment can be used for large-scale production;

[0040] 4. High production efficiency and easy automation transformation;

[0041] 5. Low safety risk, there is almost no safety risk for operators.

[0042] 6. Improved Lubricity: The lithium complex and molybdenum trioxide treated with hexafluoropolyether triethoxysilane disperse evenly within the polymer matrix, filling voids and forming a uniform lubricating film on the friction surface, effectively reducing the coefficient of friction. Lithium ion interaction with the PTFE matrix: Lithium ions may weakly interact with electronegative atoms (such as fluorine) in the PTFE molecular chain, improving the compatibility between the lithium complex and PTFE, thereby enhancing the overall performance of the composite. Perfluoropolyether forms a low-friction surface inside the PTFE protective sleeve, significantly reducing internal friction. This is crucial for ensuring easy operation in complex environments. This lubricity also prevents material damage caused by friction and extends product life. Perfluoropolyether molecules may interact with PTFE molecules through London dispersion forces. Because both perfluoropolyether and PTFE have highly fluorinated structures, they are highly compatible, allowing the perfluoropolyether to effectively wet the PTFE surface and enhance lubrication. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0044] Figure 1 This is the design drawing of the stretching design device, including: 1. Support platform; 2. Fixed fixture; 3. PTFE tube; 4. Ruler; 5. Cutting tool; 6. Mobile fixture; 7. Telescopic rod; 8. Mobile slide rod; 9. Diameter gauge; 10. Slide rail; 11. Control system. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0046] Lubricating agent preparation example 1

[0047] K1: Add 3 g of hexafluoropolyether triethoxysilane (CAS: 1052667-99-8), 100 g of molybdenum trioxide, and 1000 g of DMF to reactor 1, stir at 40°C for 100 min, filter, and dry to obtain molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane;

[0048] K2: Add 2 g of lithium 2-aminoadipate, 5 g of perfluoropolyether methacrylate, 30 g of amino-terminated hyperbranched polyamide, 200 g of DMF, and 0.5 g of triethylamine to reactor 2, and stir at 70°C for 30 min.

[0049] K3: Add 0.005 g of molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane to the reactor 2, stir vigorously for 100 min, and distill off DMF to obtain a lubricating agent.

[0050] The amino-terminated hyperbranched polyamide is a commercially available product, namely HyPerN101.

[0051] Lubricating agent preparation example 2

[0052] K1: Add 4.5 g of hexafluoropolyether triethoxysilane (CAS: 1052667-99-8), 110 g of molybdenum trioxide, and 1250 g of DMF to reactor 1, stir at 45°C for 125 min, filter, and dry to obtain molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane;

[0053] K2: Add 3.5 g of lithium 2-aminoadipate, 7.5 g of perfluoropolyether methacrylate, 45 g of amino-terminated hyperbranched polyamide, 250 g of DMF, and 1.5 g of triethylamine to reactor 2, and stir at 80°C for 60 min.

[0054] K3: Add 0.03 g of molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane to the reactor 2, stir vigorously for 1250 min, and distill off DMF to obtain a lubricating agent.

[0055] The amino-terminated hyperbranched polyamide is a commercially available product, namely HyPerN102.

[0056] Lubricating agent preparation example 3

[0057] K1: Add 6 g of hexafluoropolyether triethoxysilane (CAS: 1052667-99-8), 120 g of molybdenum trioxide, and 1500 g of DMF to reactor 1, stir at 50°C for 150 min, filter, and dry to obtain molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane;

[0058] K2: Add 5 g of lithium 2-aminoadipate, 10 g of perfluoropolyether methacrylate, 60 g of amino-terminated hyperbranched polyamide, 300 g of DMF, and 2 g of triethylamine to reactor 2, and stir at 90°C for 100 min.

[0059] K3: Add 0.05 g of molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane into the reactor 2, stir vigorously for 150 min, and distill off DMF to obtain a lubricating agent.

[0060] The amino-terminated hyperbranched polyamide is a commercially available product, namely HyPerN103.

[0061] Example of test results for this process:

[0062] The sieved PTFE dispersion resin is mixed with 22wt% of a lubricating agent, mixed in a mixing device, and then aged at 35°C for 16 hours; the aged PTFE resin is sieved and preformed under a certain pressure, with the preforming conditions being 2.5MPa and 5min; the preformed PTFE billet is placed in a PTFE extruder, and the specifications of the prepared product are calculated according to demand, and suitable equipment and molds are selected for extrusion; under a certain extrusion speed, the PTFE extruded tube is sintered at a high temperature, cooled, and cut to obtain a finished product; the cut PTFE tube is stretched to a certain degree, and then selected and cut to obtain a PTFE tearable tube.

[0063] Example 1

[0064] In this example, using a lubricating agent to prepare Example 1, a PTFE tube with a size of 1.65×1.3 mm and a pitch of 20 mm was prepared. After 700% stretching, the tube was cut at a relatively uniform location midway through the stretching. The resulting outer diameter ranged from 0.93 to 0.96 mm, the inner diameter ranged from 0.66 to 0.69 mm, and the length of the uniform section was approximately 40 mm. The tear force was reduced from 2.55 N to 0.6 N. This demonstrates that the dimensions of the stretched tube product can be controlled within a certain range, and the product length has doubled compared to the stretching pitch. Most notably, the product tear force was significantly reduced, to approximately 23.5% of the original tube, demonstrating excellent tearability.

[0065] Example 2

[0066] In this example, a lubricating agent was used to prepare Example 1, and a PTFE tube with a specification of 2.68×1.92 mm and a spacing of 400 mm was prepared. After 100% stretching, the tube was cut at a position with relatively uniform dimensions in the middle after stretching. The outer diameter of the tube measured after cutting was in the range of 2.13 to 2.15 mm, the inner diameter was in the range of 1.52 to 1.54 mm, the length of the uniform section of the tube was about 600 mm, and the tearing force was reduced from the original 5.43 N to 3.4 N, which is about 62.6% of the original tube.

[0067] Example 3

[0068] In this example, a lubricating agent was used to prepare Example 2, and a PTFE tube with a specification of 2.9×2.1 mm and a spacing of 20 mm was prepared. After being stretched by 600%, the tube was cut at a position with relatively uniform dimensions in the middle after stretching. The outer diameter of the tube measured after cutting was in the range of 1.62 to 1.67 mm, and the inner diameter was in the range of 1.01 to 1.06 mm. The length of the uniform section of the tube was about 40 mm, and the tearing force was reduced from the original 8.38 N to 1.41 N, which is about 16.8% of the original tube.

[0069] Example 4

[0070] In this example, a lubricating agent was used to prepare Example 2. PTFE tubing with a size of 3.2 x 1.6 mm and a spacing of 20 mm was prepared. After 300% stretching, the tubing was cut at a relatively uniform location midway through the stretching. The cut tubing had an outer diameter range of 2.37 to 2.4 mm, an inner diameter range of 1.09 to 1.12 mm, and a uniform length of approximately 40 mm. The tear force was reduced from 18.92 N to 11.35 N, approximately 60% of the original tubing. After 400% stretching, the outer diameter ranged from 2.19 to 2.23 mm, the inner diameter ranged from 1.03 to 1.08 mm, and the uniform length of approximately 43 mm. The tear force was reduced from 18.92 N to 10.31 N, approximately 54.5% of the original tubing. After 600% stretching, the outer diameter range of the pipe changed to 1.91-1.94mm, the inner diameter range changed to 0.89-0.92mm, the length of the uniform section of the pipe was about 45mm, and the tearing force was reduced from the original 18.92N to 8.69N, which is about 45.9% of the original pipe.

[0071] Example 5

[0072] In this example, a lubricating agent was used to prepare Example 3, and a PTFE tube with a specification of 3.36×2.76 mm and a spacing of 100 mm was prepared. After 200% stretching, the tube was cut at a position with relatively uniform dimensions in the middle after stretching. The outer diameter of the tube measured after cutting was in the range of 2.23 to 2.26 mm, the inner diameter was in the range of 1.80 to 1.83 mm, the length of the uniform section of the tube was about 180 mm, and the tearing force was reduced from the original 5.34 N to 1.65 N, which is about 30.9% of the original tube.

[0073] Example 6

[0074] In this example, a lubricating agent was used to prepare Example 3, and a PTFE tube with a specification of 3.93×3.16 mm and a spacing of 200 mm was prepared. After 250% stretching, the tube was cut at a position with relatively uniform dimensions in the middle after stretching. The outer diameter of the tube measured after cutting was in the range of 2.36 to 2.39 mm, the inner diameter was in the range of 1.84 to 1.87 mm, the length of the uniform section of the tube was about 420 mm, and the tear force was reduced from the original 20.48 N to 9.02 N, which is about 44% of the original tube.

[0075] Example 7

[0076] In this example, a lubricating agent was used to prepare Example 3, and a PTFE tube with a specification of 8.49×7.47 mm and a spacing of 20 mm was prepared. After 600% stretching, the tube was cut at a position with relatively uniform dimensions in the middle after stretching. The outer diameter of the tube measured after cutting was in the range of 4.95 to 5.27 mm, the inner diameter was in the range of 4.35 to 4.64 mm, the length of the uniform section of the tube was about 60 mm, and the tear force was reduced from the original 20.15 N to 6.56 N, which is about 32.6% of the original tube.

[0077] From the above specific implementation scheme, it can be seen that the tearing force of the PTFE tube after stretching is significantly reduced, and there is no obvious correlation between the tearing forces of tubes of different specifications after stretching to different degrees. This is the result that this process is not affected by the brand of PTFE dispersed resin.

[0078] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements, or modifications based on the present invention to solve substantially the same technical problems and achieve substantially the same technical effects are all within the scope of protection of the present invention.

Claims

1. A method for preparing an easy-to-tear polytetrafluoroethylene tube, comprising the following steps: S1: Mix the sieved PTFE dispersion resin with a certain amount of lubricating additive in a mixing device for 20-35 minutes, and then mature at a set temperature for 8 to 24 hours; S2: Screening the matured PTFE resin and preforming it under a certain pressure; S3: Place the preformed PTFE blank into the PTFE extruder, calculate the specifications of the product according to the needs, and select appropriate equipment and mold for extrusion; S4: Under certain extrusion speed conditions, the PTFE extruded tube is sintered at high temperature, cooled, and cut to obtain the finished product; S5: stretching the cut PTFE tube to a certain extent, and then cutting it to obtain a PTFE tearable tube; The amount of the lubricating agent added is 18% to 25% of the PTFE dispersion resin; The preparation method of the lubricating agent is as follows: K1: Add 3-6 parts of hexafluoropolyether triethoxysilane, 100-120 parts of molybdenum trioxide, and 1000-1500 parts of DMF to a reactor 1, stirring at 40-50°C for 100-150 minutes, filtering, and drying to obtain molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane; K2: Add 2-5 parts of lithium 2-aminoadipate, 5-10 parts of perfluoropolyether methacrylate, 30-60 parts of amino-terminated hyperbranched polyamide, 200-300 parts of DMF, and 0.5-2 parts of triethylamine to the second reactor by weight, and stir at 70-90°C for 30-100 minutes; K3: Add 0.005-0.05 parts of molybdenum trioxide surface-treated with hexafluoropolyether triethoxysilane to the second reactor, stir vigorously for 100-150 minutes, and distill off DMF to obtain a lubricating agent.

2. The method for preparing an easily tearable polytetrafluoroethylene tube according to claim 1, wherein: The aging temperature in the step S1 is 30°C to 40°C.

3. The method for preparing an easily tearable polytetrafluoroethylene tube according to claim 1, wherein: The preforming conditions are 2-3 MPa, 3-8 min.

4. The method for preparing an easily tearable polytetrafluoroethylene tube according to claim 1, wherein: The extrusion speed is 2-4 m / min.

5. The method for preparing an easily tearable polytetrafluoroethylene tube according to claim 1, characterized in that: The temperature of the high-temperature sintering in the step S4 is 300-400°C.

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