A preparation method and application of PEO-modified PTFE film

Abstract

The invention discloses a preparation method and application of a PEO-modified PTFE film, belonging to the technical field of polymer material processing, including S1. selecting PEO raw materials, adding to 1,2-dichloroethane as a solvent, and finally adding water, stirring at high speed to obtain a mixed solution; S2. selecting PTFE dispersion material, and obtaining a uniaxially stretched PTFE low-density microporous belt through mixing, blank making, pushing, calendering, deoiling, stretching, and shaping operations; S3. putting the PEO / 1,2-dichloroethane / water mixed solution obtained by S1 into a water bath sealed heating box of a surface treatment device, and the water bath temperature is within the range of 25-55°C; S4. placing the PTFE low-density microporous belt obtained by S2 at the unwinding end of the PTFE low-density microporous belt of the surface treatment device, and traction into the water bath sealed heating box for surface treatment. The defect of poor bonding effect of PTFE membrane and TPU material is solved, while avoiding the aging and slag problem caused by traditional glue compounding, with higher bonding strength and long-term stability.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material processing, and in particular to a preparation method of a PEO-modified PTFE film and application thereof. Background Art

[0002] Polytetrafluoroethylene (PTFE) is a polymer compound made of tetrafluoroethylene. Its products have excellent chemical stability, corrosion resistance, sealing, self-lubrication, electrical insulation and good aging resistance. This material is almost insoluble in all solvents, and has the characteristics of acid and alkali resistance and resistance to various organic solvents. At the same time, it has good temperature resistance and can be used for a long time at -180--260℃. The decomposition index is as high as 400℃, and the friction coefficient is extremely low. It is widely used as a wrapping product in industrial wire production. However, due to its own extreme stability, polytetrafluoroethylene film is extremely difficult to compound with other products. Thermoplastic polyurethane (TPU) is a polymer material with good temperature resistance. It can work for a long time at -50℃--120℃. It has high strength and good plasticity and can maintain its shape and performance in extreme environments; it has corrosion resistance, good elasticity and softness, good transparency, and excellent wear resistance and tortuosity resistance. It can effectively resist damage caused by physical friction and scratches and can maintain stable performance under repeated cyclic stress. Therefore, it is widely used in the field of drag chain cables. However, due to its high friction coefficient, the friction is large when used alone to prepare drag chain cables, and the dust-free level cannot meet the requirements of modern workshops.

[0003] How to combine the advantages of polytetrafluoroethylene film (PTFE) and thermoplastic polyurethane (TPU) to obtain a material with tortuosity resistance, self-lubrication, wear resistance and good cleanability has been the focus of research in the drag chain cable industry in recent years. Currently, there are two commonly used technologies. The first is to bond the polytetrafluoroethylene film to the thermoplastic polyurethane material with glue, but this process has the risk of glue leakage and adds a new interlayer, resulting in weakened performance; the second is to directly hot-press the polytetrafluoroethylene film and thermoplastic polyurethane. The advantage of this production process is that no glue is used, which maintains the stability of the performance of the composite material to the greatest extent, but this process has a widespread problem of weak bonding.

[0004] Polyethylene oxide (PEO), also known as polyethylene oxide, is a crystalline, thermoplastic, water-soluble polymer with excellent bonding properties to thermoplastic polyurethane (TPU) materials. Therefore, polyethylene oxide (PEO) can be used to surface treat polytetrafluoroethylene film (PTFE) to improve the bonding effect with thermoplastic polyurethane (TPU) and achieve the purpose of effective bonding. Patent application No. 201610367113.4 "Method for preparing polytetrafluoroethylene nanofiber porous membrane by PEO template sacrificial method" also uses PEO to modify PTFE, which enhances the thermal stability, chemical resistance and mechanical properties of the nanofiber porous membrane prepared by PTFE. However, the nanofiber porous membrane prepared by this method using electrostatic spinning after mixing PTFE emulsion with PEO solution is too expensive and has low strength.

[0005] Therefore, there is an urgent need for a method for preparing a PEO-modified PTFE film to effectively solve the bonding problem when the PTFE film is composited with a TPU material, thereby obtaining a composite material with excellent performance for use in the field of electrical insulation materials. Summary of the invention

[0006] To this end, the present invention provides a preparation method of a PEO-modified PTFE film and its application, so as to solve the problem of weak bonding between the PTFE film and the TPU material during hot pressing in the prior art, while avoiding the defects caused by the use of glue.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] According to a first aspect of the present invention, there is provided a method for preparing a PEO-modified PTFE film, comprising the following steps:

[0009] S1. Select PEO raw material, add it to 1,2-dichloroethane as a solvent, and finally add water, stir at high speed to obtain a mixed solution;

[0010] S2. Select PTFE dispersion, and obtain uniaxially stretched PTFE low-density microporous tape by mixing, blanking, pressing, calendering, deoiling, stretching and shaping operations;

[0011] S3. The PEO / 1,2-dichloroethane / water mixed solution obtained in S1 is placed in a sealed water bath heating box of the surface treatment equipment, and the water bath temperature is in the range of 25-55 ℃;

[0012] S4. The PTFE low-density microporous tape obtained in S2 is placed at the PTFE low-density microporous tape unwinding end of the surface treatment equipment, pulled into a water bath sealed heating box for surface treatment and passed through a first drying box, a cleaning tank, a second drying box and a cooling roller, and finally wound up at the finished product winding end.

[0013] Furthermore, in S1, the PEO / 1,2-dichloroethane / water mixed solution has a mixing temperature of 25-55° C. and a mixing ratio of (1-20):100:(10-30).

[0014] Furthermore, the molecular weight of the PEO material in S1 is 200,000-10 million, and the purity of 1,2-dichloroethane is 90-99%.

[0015] Furthermore, the specific operations of mixing, blanking, pushing, calendering, deoiling, stretching and shaping in S2 are as follows:

[0016] Mixing process: 1-4kg of polytetrafluoroethylene dispersion resin raw material is sieved into the mixing barrel through an 8-16 mesh screen, and auxiliary oil is added at a ratio of 230-300g / kg of raw material and mixed thoroughly, and then placed in a maturation box at a temperature of 40-60℃ for 10-18h;

[0017] Blank making process: Place the matured raw materials in a temperature of 40-60℃ with a diameter of In a billet making machine, the billet is pressed into a cylindrical billet;

[0018] Pushing process: put the billet into a pusher of corresponding size at a temperature of 40-60℃ and push it into a diameter of sticks;

[0019] Calendering process: Place the rods in a calender at a temperature of 40-60°C and calender them into an oil-containing base tape with a thickness of 230-260μm;

[0020] Deoiling process: the oil-containing base tape is passed through a deoiling machine at a temperature of 150-250°C at a speed of 1-3m / min to obtain a degreased base tape;

[0021] Stretching process: The degreased base tape is passed through a stretching box at a temperature of 250-350°C at a speed of 1-3m / mim. There are 2-13 stretching rollers in the stretching box. The speed of each stretching roller is controlled independently, and the total stretching ratio is 2-4 times;

[0022] Forming process: The stretched base tape enters a forming machine at a temperature of 300-380°C at a stretching speed of 0.95-1.2 times for forming, and finally a uniaxially stretched PTFE low-density microporous tape is obtained.

[0023] Furthermore, the PTFE low-density microporous tape in S2 has a thickness of 0.03-0.3 mm and a density of 0.3-1 g / cm 3 .

[0024] Furthermore, the water bath sealed heating box of the surface treatment equipment in S3 has a water bath temperature of 25-55°C.

[0025] Furthermore, in S4, the temperature in the first drying box is 50-80°C, the water temperature in the cleaning pool is 30-80°C, the temperature in the second drying box is 100-170°C, and the temperature of the cooling roller is 40-80°C.

[0026] Further,

[0027] The pulling length of the PTFE low-density microporous belt in the water bath sealed heating box is 5-9m;

[0028] The pulling length of the PTFE low-density microporous belt in the first drying box is 2-6m;

[0029] The pulling length of the PTFE low-density microporous belt in the cleaning tank is 1-5m;

[0030] The pulling length of the PTFE low-density microporous belt in the second drying box is 6-12m;

[0031] The contact length between the PTFE low-density microporous belt and the cooling roller is about 0.5-2.5 m.

[0032] Furthermore, the processing speed in S4 is 1.5-5.5 m / min.

[0033] According to a second aspect of the present invention, there is provided application of the PEO-modified PTFE film prepared by the above-mentioned method for preparing the PEO-modified PTFE film in the field of electrical insulating materials.

[0034] The present invention has the following advantages:

[0035] 1. In the present application, the PTFE low-density microporous belt is surface-treated with PEO, and the surface of the treated PTFE low-density microporous belt is attached with PEO material. Therefore, when the PEO-modified PTFE low-density microporous belt is compounded with the TPU material by hot pressing, the hydroxyl groups react and are tightly combined together, making the PEO-modified PTFE low-density microporous belt and the TPU material more firmly bonded.

[0036] 2. After the PTFE low-density microporous belt is surface treated with PEO, the temperature required for hot pressing the PEO-modified low-density microporous belt and the TPU material is lower than that before modification, so the TPU material in contact with the hot roller can be effectively protected to prevent the TPU material from overheating and deformation.

[0037] 3. The technical solution of the present application does not introduce glue, thus avoiding the adverse phenomena caused by factors such as aging and falling of glue during the use of glue composite products. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0039] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0040] Figure 1 A process flow chart of the surface treatment equipment provided by the present invention;

[0041] In the figure: 1. Unwinding end of PTFE low-density microporous tape; 2. Water bath sealed heating box; 3. First drying box; 4. Cleaning tank; 5. Second drying box; 6. Cooling roller; 7. Finished product winding end. DETAILED DESCRIPTION

[0042] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] The present invention provides a method for preparing a PEO-modified PTFE film, comprising the following steps:

[0044] S1. Select PEO raw material, add it to 1,2-dichloroethane as a solvent, and finally add water, stir at high speed to obtain a mixed solution;

[0045] S2. Select PTFE dispersion, and obtain uniaxially stretched PTFE low-density microporous tape by mixing, blanking, pressing, calendering, deoiling, stretching and shaping operations;

[0046] S3. The PEO / 1,2-dichloroethane / water mixed solution obtained in S1 is placed in a sealed water bath heating box of the surface treatment equipment, and the water bath temperature is in the range of 25-55 ℃;

[0047] S4. The PTFE low-density microporous tape obtained in S2 is placed at the unwinding end of the PTFE low-density microporous tape of the surface treatment equipment, pulled into a water bath sealed heating box for surface treatment and passed through a first drying box, a cleaning tank, a second drying box and a cooling roller, and finally wound at the winding end of the finished product, such as Figure 1 shown.

[0048] Specifically, the PEO / 1,2-dichloroethane / water mixed solution in S1 has a mixing temperature of 25-55° C. and a mixing ratio of (1-20):100:(10-30).

[0049] Specifically, the molecular weight of the PEO material in S1 is 200,000-1000,000, and the purity of 1,2-dichloroethane is 90-99%.

[0050] Among them, the specific operations of mixing, blank making, pushing, calendering, deoiling, stretching and shaping in S2 are as follows:

[0051] Mixing process: 1-4kg of polytetrafluoroethylene dispersion resin raw material is sieved into the mixing barrel through an 8-16 mesh screen, and auxiliary oil is added at a ratio of 230-300g / kg of raw material and mixed thoroughly, and then placed in a maturation box at a temperature of 40-60℃ for 10-18h;

[0052] Blank making process: Place the matured raw materials in a temperature of 40-60℃ with a diameter of In a billet making machine, the billet is pressed into a cylindrical billet;

[0053] Pushing process: put the billet into a pusher of corresponding size at a temperature of 40-60℃ and push it into a diameter of sticks;

[0054] Calendering process: Place the rods in a calender at a temperature of 40-60°C and calender them into an oil-containing base tape with a thickness of 230-260μm;

[0055] Deoiling process: the oil-containing base tape is passed through a deoiling machine at a temperature of 150-250°C at a speed of 1-3m / min to obtain a degreased base tape;

[0056] Stretching process: The degreased base tape is passed through a stretching box at a temperature of 250-350°C at a speed of 1-3m / mim. There are 2-13 stretching rollers in the stretching box. The speed of each stretching roller is controlled independently, and the total stretching ratio is 2-4 times;

[0057] Forming process: The stretched base tape enters a forming machine at a temperature of 300-380°C at a stretching speed of 0.95-1.2 times for forming, and finally a uniaxially stretched PTFE low-density microporous tape is obtained.

[0058] Among them, the thickness of PTFE low-density microporous tape in S2 is 0.03-0.3mm and the density is 0.3-1g / cm 3 .

[0059] Among them, the water bath sealed heating box of the surface treatment equipment in S3 has a water bath temperature of 25-55°C.

[0060] Specifically, in S4, the temperature in the first drying box is 50-80°C, the water temperature in the cleaning pool is 30-80°C, the temperature in the second drying box is 100-170°C, and the temperature of the cooling roller is 40-80°C.

[0061] Specifically,

[0062] The pulling length of the PTFE low-density microporous belt in the water bath sealed heating box is 5-9m;

[0063] The pulling length of the PTFE low-density microporous belt in the first drying box is 2-6m;

[0064] The pulling length of the PTFE low-density microporous belt in the cleaning tank is 1-5m;

[0065] The pulling length of the PTFE low-density microporous belt in the second drying box is 6-12m;

[0066] The contact length between the PTFE low-density microporous belt and the cooling roller is about 0.5-2.5 m.

[0067] Specifically, the processing speed in S4 is 1.5-5.5 m / min.

[0068] The present invention provides the application of the PEO-modified PTFE film prepared by the preparation method of the PEO-modified PTFE film in the field of electrical insulation materials.

[0069] Example 1

[0070] This embodiment provides a method for preparing a PEO-modified PTFE film, comprising the following specific steps:

[0071] S1. Select 8 million molecular weight PEO raw material, use 95% 1,2-dichloroethane as solvent, then add water to make the mixing ratio of PEO, 1,2-dichloroethane and water be 3:100:11, stir at high speed at 35°C to obtain a mixed solution;

[0072] S2. Select PTFE dispersion, and obtain 0.2mm uniaxially stretched PTFE low-density microporous tape after mixing, blanking, pushing, calendering, deoiling, stretching and shaping operations;

[0073] The specific operations are:

[0074] Mixing process: 4 kg of polytetrafluoroethylene dispersion resin raw material is sieved into the mixing barrel through an 8-mesh screen, and auxiliary oil is added at a ratio of 260 g / kg of raw material and mixed thoroughly, and then placed in a maturation box at a temperature of 50°C for 14 hours;

[0075] Blank making process: The ripened raw materials are placed in a blank making machine with a temperature of 50°C and a diameter of φ140mm, and pressed into cylindrical blanks;

[0076] Pushing process: put the blank into a pusher of corresponding size at a temperature of 50℃ and push it into a rod with a diameter of φ22mm;

[0077] Calendering process: the rods are placed in a calender at a temperature of 50°C and calendered into an oil-containing base tape with a thickness of 245 μm; deoiling process: the oil-containing base tape is passed through a deoiling machine at a temperature of 190°C at a speed of 1.5 m / min to obtain a degreased base tape;

[0078] Stretching process: The degreased base tape is passed through a stretching box at a temperature of 290°C at a speed of 2m / min. There are three stretching rollers in the stretching box, and the speed of each stretching roller is controlled independently. The total stretching ratio is 2.5 times;

[0079] Forming process: The stretched base tape enters a forming machine at a temperature of 370°C at a stretching speed 1.1 times that of the stretching speed for final forming, and finally obtains a 0.2mm uniaxially stretched PTFE low-density microporous tape;

[0080] Among them, the processing speed of S4 is 3.5m / min, which is adjusted according to the thickness, density of the PTFE low-density microporous belt and the ratio of PEO / 1,2-dichloroethane / water mixed solution. The traction length of the PTFE low-density microporous belt in the water bath sealed heating box is about 7m; the traction length in the first drying box is about 4m; the traction length in the cleaning tank is about 3m; the traction length in the second drying box is about 9m; and the contact length with the cooling roller is about 1.57m.

[0081] Among them, the stretching ratio of the PTFE low-density microporous belt in S2 is 2-6 times, the deoiling temperature is 100-250℃, and the setting temperature is 200-390℃.

[0082] S3. The PEO / 1,2-dichloroethane / water mixed solution obtained in S1 is placed in a sealed water bath heating box of the surface treatment equipment;

[0083] S4. The PTFE low-density microporous belt obtained in S2 is placed on the unwinding end of the PTFE low-density microporous belt of the surface treatment equipment, and is pulled into a water bath sealed heating box for surface treatment. The water bath temperature of the water bath sealed heating box is 35°C, so that the PEO / 1,2-dichloroethane / water mixed solution is fully in contact with the PTFE low-density microporous belt to complete the surface treatment operation, and then enters a first drying box with a set temperature of 65°C for drying, while removing the 1,2-dichloroethane remaining on the surface of the surface-treated PTFE low-density microporous belt, and then washes off the PEO crystals on the membrane surface in a 50°C cleaning tank, enters a second drying box for drying at 150°C, removes the water remaining on the surface of the PEO-modified PTFE low-density microporous belt, and finally passes through a 45°C cooling roller to quickly cool the PEO-modified PTFE low-density microporous belt to enhance the chemical stability of the product and facilitate the winding operation, and finally is wound at the winding end of the finished product to obtain a natural color (white) PEO-modified 0.2 mm PTFE low-density microporous belt.

[0084] S4. Finally, the modified PTFE low-density microporous belt and the TPU membrane material are placed in a pressing mold, the pressure is set to 1 MPa, the temperature is set to 140°C, and the PTFE-TPU composite membrane is obtained after compounding for 30 minutes.

[0085] Among them, the water bath sealed heating box and the top of the first drying box are also provided with waste gas treatment devices to render the volatilized 1,2-dichloroethane harmless.

[0086] An exhaust gas processor is also provided on the top of the second drying box to collect and process the evaporated water vapor.

[0087] Example 2

[0088] This embodiment provides a method for preparing a PEO-modified PTFE film, comprising the following specific steps:

[0089] S1. Select 8 million molecular weight PEO raw material, use 95% pure n-butanol as solvent, then add water to make the mixing ratio of PEO, n-butanol and water 3:100:11, stir at high speed at 35°C to obtain a mixed solution;

[0090] S2. Select PTFE dispersion, and obtain 0.2mm uniaxially stretched PTFE low-density microporous tape after mixing, blanking, pushing, calendering, deoiling, stretching and shaping operations;

[0091] The specific operations are:

[0092] Mixing process: 4 kg of polytetrafluoroethylene dispersion resin raw material is sieved into the mixing barrel through an 8-mesh screen, and auxiliary oil is added at a ratio of 260 g / kg of raw material and mixed thoroughly, and then placed in a maturation box at a temperature of 50°C for 14 hours;

[0093] Blank making process: The ripened raw materials are placed in a blank making machine with a temperature of 50°C and a diameter of φ140mm, and pressed into cylindrical blanks;

[0094] Pushing process: put the blank into a pusher of corresponding size at a temperature of 50℃ and push it into a rod with a diameter of φ22mm;

[0095] Calendering process: the rods are placed in a calender at a temperature of 50°C and calendered into an oil-containing base tape with a thickness of 245 μm; deoiling process: the oil-containing base tape is passed through a deoiling machine at a temperature of 190°C at a speed of 1.5 m / min to obtain a degreased base tape;

[0096] Stretching process: The degreased base tape is passed through a stretching box at a temperature of 290°C at a speed of 2m / min. There are three stretching rollers in the stretching box, and the speed of each stretching roller is controlled independently. The total stretching ratio is 2.5 times;

[0097] Forming process: The stretched base tape enters a forming machine at a temperature of 370°C at a stretching speed 1.1 times that of the stretching speed for final forming, and finally obtains a 0.2mm uniaxially stretched PTFE low-density microporous tape;

[0098] Among them, the processing speed of S4 is 2m / min, which is adjusted according to the thickness, density of the PTFE low-density microporous belt and the ratio of the PEO / n-butanol / water mixed solution. The traction length of the PTFE low-density microporous belt in the water bath sealed heating box is about 7m; the traction length in the first drying box is about 4m; the traction length in the cleaning tank is about 3m; the traction length in the second drying box is about 9m; and the contact length with the cooling roller is about 1.57m.

[0099] S3. The PEO / n-butanol / water mixed solution obtained in S1 is placed in a sealed water bath heating box of the surface treatment equipment;

[0100] S4. The PTFE low-density microporous belt obtained in S2 is placed on the unwinding end of the PTFE low-density microporous belt of the surface treatment equipment, and is pulled into a water bath sealed heating box for surface treatment. The water bath temperature of the water bath sealed heating box is 35°C, so that the PEO / n-butanol / water mixed solution is fully in contact with the PTFE low-density microporous belt to complete the surface treatment operation, and then enters a first drying box with a set temperature of 130°C for drying, while removing the 1,2-dichloroethane remaining on the surface of the surface-treated PTFE low-density microporous belt, and then washes off the PEO crystals on the membrane surface in a 50°C cleaning tank, enters a second drying box for drying at 150°C, removes the water remaining on the surface of the PEO-modified PTFE low-density microporous belt, and finally passes through a 45°C cooling roller to quickly cool the PEO-modified PTFE low-density microporous belt to enhance the chemical stability of the product and facilitate the winding operation, and finally is wound at the winding end of the finished product to obtain a natural color (white) PEO-modified 0.2 mm PTFE low-density microporous belt.

[0101] S4. Finally, the modified PTFE low-density microporous belt and the TPU membrane material are placed in a pressing mold, the pressure is set to 1 MPa, the temperature is set to 140°C, and the PTFE-TPU composite membrane is obtained after compounding for 30 minutes.

[0102] Among them, the water bath sealed heating box and the top of the first drying box are also provided with waste gas treatment devices to render the volatilized 1,2-dichloroethane harmless.

[0103] An exhaust gas processor is also provided on the top of the second drying box to collect and process the evaporated water vapor.

[0104] Example 3

[0105] This embodiment provides a method for preparing a PEO-modified PTFE film, comprising the following specific steps:

[0106] S1. Select 8 million molecular weight PEO raw material, use 95% 1,2-dichloroethane as solvent, then add water to make the mixing ratio of PEO, 1,2-dichloroethane and water be 3:100:11, stir at high speed at 35°C to obtain a mixed solution;

[0107] S2. Select PTFE dispersion, and obtain 0.1mm PTFE low-density microporous tape after mixing, blanking, pressing, calendering, degreasing, stretching and shaping operations;

[0108] The specific operations are:

[0109] Mixing process: 4 kg of polytetrafluoroethylene dispersion resin raw material is sieved into the mixing barrel through an 8-mesh screen, and auxiliary oil is added at a ratio of 280 g / kg of raw material and mixed thoroughly, and then placed in a maturation box at a temperature of 50°C for 14 hours;

[0110] Blank making process: The ripened raw materials are placed in a blank making machine with a temperature of 50°C and a diameter of φ140mm, and pressed into cylindrical blanks;

[0111] Pushing process: put the blank into a pusher of corresponding size at a temperature of 50℃ and push it into a rod with a diameter of φ18mm;

[0112] Calendering process: Place the rod in a calender at 50°C and calender it into an oil-containing base tape with a thickness of 150μm;

[0113] Deoiling process: the oily base tape is passed through a deoiling machine at a temperature of 190°C at a speed of 2m / min to obtain a degreased base tape;

[0114] Stretching process: The degreased base tape is passed through a stretching box at a temperature of 290°C at a speed of 3m / min. There are three stretching rollers in the stretching box, and the speed of each stretching roller is controlled independently. The total stretching ratio is 2.5 times;

[0115] Forming process: The stretched base tape enters a forming machine at a temperature of 370°C at a stretching speed 1.1 times that of the stretching speed for forming, and finally obtains a PTFE low-density microporous tape with a thickness of 0.1 mm;

[0116] Among them, the processing speed of S4 is 4m / min, which is adjusted according to the thickness, density of the PTFE low-density microporous belt and the ratio of the PEO / 1,2-dichloroethane / water mixed solution. The traction length of the PTFE low-density microporous belt in the water bath sealed heating box is about 7m; the traction length in the first drying box is about 4m; the traction length in the cleaning tank is about 3m; the traction length in the second drying box is about 9m; and the contact length with the cooling roller is about 1.57m.

[0117] S3. The PEO / 1,2-dichloroethane / water mixed solution obtained in S1 is placed in a sealed water bath heating box of the surface treatment equipment;

[0118] S4. The PTFE low-density microporous belt obtained in S2 is placed on the unwinding end of the PTFE low-density microporous belt of the surface treatment equipment, and is pulled into a water bath sealed heating box for surface treatment. The water bath temperature of the water bath sealed heating box is 35°C, so that the PEO / 1,2-dichloroethane / water mixed solution is fully in contact with the PTFE low-density microporous belt to complete the surface treatment operation, and then enters a first drying box with a set temperature of 60°C for drying, while removing the 1,2-dichloroethane remaining on the surface of the surface-treated PTFE low-density microporous belt, and then washes off the PEO crystals on the membrane surface in a 50°C cleaning tank, enters a second drying box for drying at 140°C, removes the residual water on the surface of the PEO-modified PTFE low-density microporous belt, and finally passes through a 45°C cooling roller to quickly cool the PEO-modified PTFE low-density microporous belt to enhance the chemical stability of the product and facilitate the winding operation, and finally is wound at the winding end of the finished product to obtain a natural color (white) PEO-modified 0.1mm PTFE low-density microporous belt.

[0119] S4. Finally, the modified PTFE low-density microporous belt and the TPU membrane material are placed in a pressing mold, the pressure is set to 1 MPa, the temperature is set to 140°C, and the PTFE-TPU composite membrane is obtained after compounding for 30 minutes.

[0120] Among them, the water bath sealed heating box and the top of the first drying box are also provided with waste gas treatment devices to render the volatilized 1,2'-dichloroethane harmless.

[0121] An exhaust gas processor is also provided on the top of the second drying box to collect and process the evaporated water vapor.

[0122] Example 4

[0123] This embodiment provides a method for preparing a PEO-modified PTFE film, comprising the following specific steps:

[0124] S1. Select 8 million molecular weight PEO raw material, use 95% 1,2-dichloroethane as solvent, then add water to make the mixing ratio of PEO, 1,2-dichloroethane and water be 5:100:5, stir at high speed at 35°C to obtain a mixed solution;

[0125] S2. Select PTFE dispersion, and obtain 0.2mm uniaxially stretched PTFE low-density microporous tape after mixing, blanking, pushing, calendering, deoiling, stretching and shaping operations;

[0126] The specific operations are:

[0127] Mixing process: 4 kg of polytetrafluoroethylene dispersion resin raw material is sieved into the mixing barrel through an 8-mesh screen, and auxiliary oil is added at a ratio of 260 g / kg of raw material and mixed thoroughly, and then placed in a maturation box at a temperature of 50°C for 14 hours;

[0128] Blank making process: The ripened raw materials are placed in a blank making machine with a temperature of 50°C and a diameter of φ140mm, and pressed into cylindrical blanks;

[0129] Pushing process: put the blank into a pusher of corresponding size at a temperature of 50℃ and push it into a rod with a diameter of φ22mm;

[0130] Calendering process: the rods are placed in a calender at a temperature of 50°C and calendered into an oil-containing base tape with a thickness of 245 μm; deoiling process: the oil-containing base tape is passed through a deoiling machine at a temperature of 190°C at a speed of 1.5 m / min to obtain a degreased base tape;

[0131] Stretching process: The degreased base tape is passed through a stretching box at a temperature of 290°C at a speed of 2m / min. There are three stretching rollers in the stretching box, and the speed of each stretching roller is controlled independently. The total stretching ratio is 2.5 times;

[0132] Forming process: The stretched base tape enters a forming machine at a temperature of 370°C at a stretching speed 1.1 times that of the stretching speed for final forming, and finally obtains a 0.2mm uniaxially stretched PTFE low-density microporous tape;

[0133] Among them, the processing speed of S4 is 4m / min, which is adjusted according to the thickness, density of the PTFE low-density microporous belt and the ratio of the PEO / 1,2-dichloroethane / water mixed solution. The traction length of the PTFE low-density microporous belt in the water bath sealed heating box is about 7m; the traction length in the first drying box is about 4m; the traction length in the cleaning tank is about 3m; the traction length in the second drying box is about 9m; and the contact length with the cooling roller is about 1.57m.

[0134] S3. The PEO / 1,2-dichloroethane / water mixed solution obtained in S1 is placed in a sealed water bath heating box of the surface treatment equipment;

[0135] S4. The PTFE low-density microporous belt obtained in S2 is placed on the unwinding end of the PTFE low-density microporous belt of the surface treatment equipment, and is pulled into a water bath sealed heating box for surface treatment. The water bath temperature of the water bath sealed heating box is 50°C, so that the PEO / 1,2-dichloroethane / water mixed solution is fully in contact with the PTFE low-density microporous belt to complete the surface treatment operation, and then enters a first drying box with a set temperature of 65°C for drying, while removing the 1,2-dichloroethane remaining on the surface of the surface-treated PTFE low-density microporous belt, and then washes off the PEO crystals on the membrane surface in a 50°C cleaning tank, enters a second drying box and dries at 150°C, removes the residual water on the surface of the PEO-modified PTFE low-density microporous belt, and finally passes through a 45°C cooling roller to quickly cool the PEO-modified PTFE low-density microporous belt to enhance the chemical stability of the product and facilitate the winding operation, and finally is wound at the finished product winding end to obtain a natural color (white) PEO-modified 0.2 mm PTFE low-density microporous belt.

[0136] S4. Finally, the modified PTFE low-density microporous belt and the TPU membrane material are placed in a pressing mold, the pressure is set to 1 MPa, the temperature is set to 140°C, and the PTFE-TPU composite membrane is obtained after compounding for 30 minutes.

[0137] Among them, the water bath sealed heating box and the top of the first drying box are also provided with waste gas treatment devices to render the volatilized 1,2-dichloroethane harmless.

[0138] An exhaust gas processor is also provided on the top of the second drying box to collect and process the evaporated water vapor.

[0139] Comparative Example 1: This example is used as a comparative example of Example 1.

[0140] 1. According to the production process of polytetrafluoroethylene wrapping tape, 0.2mm PTFE low-density microporous tape is obtained through mixing, blanking, pushing, calendering, deoiling, stretching and shaping operations.

[0141] 2. The PTFE low-density microporous belt and the TPU membrane material are placed in a pressing mold, the pressure is set to 1 MPa, the temperature is 140°C, and the composite time is 30 min to obtain a PTFE-TPU composite membrane.

[0142] The bonding performance test was performed on Examples 1-4 and Comparative Example 1. The test results are shown in Table 1:

[0143] Table 1 Performance analysis of PTFE-TPU composite membranes prepared from different raw materials

[0144]

[0145] It can be seen from the data in the table that 1. when the PEO-modified PTFE low-density microporous belt is compounded with TPU (Examples 1, 3, and 4), the bonding strength of the composite film is relatively high, which is manifested as "strong bonding and difficult to peel off"; when the unmodified PTFE low-density microporous belt is compounded with TPU (Comparative Example 1), the bonding strength of the composite film is relatively low, which is manifested as "low bonding strength and easy to peel off".

[0146] 2. 1,2-Dichloroethane: When 1,2-dichloroethane is used as the solvent (Examples 1, 3, and 4), the bonding strength of the composite film is relatively high; when n-butanol is used as the solvent (Example 2), the bonding strength of the composite film is relatively low.

[0147] 3. The thickness of the PTFE low-density microporous belt in Example 3 is 0.21 mm, and the composite membrane still exhibits a relatively high bonding strength, indicating that within a certain range, the thickness has little effect on the bonding strength; the thickness of the PTFE low-density microporous belt in Examples 1, 4 and Comparative Example 1 is 0.40 mm, but the bonding strength of the modified composite membrane is significantly better than that of the unmodified one.

[0148] 4. When the PEO-modified PTFE low-density microporous belt is compounded with TPU, the required hot pressing temperature is relatively low, which can effectively protect the TPU material and prevent overheating and deformation; while when the unmodified PTFE low-density microporous belt is compounded with TPU, the hot pressing temperature is relatively high, which causes the TPU material to overheat and deform, affecting the wear resistance of the composite material.

[0149] In summary, the PEO-modified PTFE low-density microporous belt significantly improves the bonding strength with the TPU composite material, showing the characteristics of strong adhesion and difficulty in peeling. The PEO modification treatment significantly improves the bonding strength between the PTFE film and the TPU composite material. Even if the film thickness is the same, the modified composite film shows a higher bonding strength. Moreover, the modification treatment of the technical solution is suitable for composite materials of different thicknesses, and the bonding performance is stable. The composite material can maintain a high bonding strength at different thicknesses, ensuring that the material can also ensure the quality and performance of the composite material in a larger thickness range. When the PEO-modified PTFE low-density microporous belt is compounded with TPU, the required hot pressing temperature is low, which can effectively protect the TPU material and prevent overheating and deformation. In short, when the PEO-modified PTFE low-density microporous belt is compounded with TPU, the bonding strength of the composite film can be significantly improved, while the hot pressing temperature is reduced, avoiding the problem of overheating and deformation of the TPU material. In addition, the method of not introducing glue in the technical solution avoids the problem of aging and falling off of glue, improves the long-term stability of the composite material, and further improves the stability and service life of the composite material.

[0150] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for preparing a PEO-modified PTFE film, characterized in that: The following steps are involved: S1. Select PEO raw material, add it to 1,2-dichloroethane as a solvent, and finally add water, stir at high speed to obtain a mixed solution; S2. Select PTFE dispersion, and obtain uniaxially stretched PTFE low-density microporous tape by mixing, blanking, pressing, calendering, deoiling, stretching and shaping operations; S3. The PEO / 1,2-dichloroethane / water mixed solution obtained in S1 is placed in a sealed water bath heating box of the surface treatment equipment, and the water bath temperature is in the range of 25-55 ℃; S4. The PTFE low-density microporous tape obtained in S2 is placed at the PTFE low-density microporous tape unwinding end of the surface treatment equipment, pulled into a water bath sealed heating box for surface treatment and passed through a first drying box, a cleaning tank, a second drying box and a cooling roller, and finally wound up at the finished product winding end.

2. The method for preparing a PEO-modified PTFE film according to claim 1, wherein In S1, the PEO / 1,2-dichloroethane / water mixed solution has a mixing temperature of 25-55° C. and a mixing ratio of (1-20):100:(10-30).

3. The method for preparing a PEO-modified PTFE film according to claim 2, wherein The molecular weight of the PEO material in S1 is 200,000-10 million, and the purity of 1,2-dichloroethane is 90-99%.

4. The method for preparing a PEO-modified PTFE film according to claim 1, wherein The specific operations of mixing, blanking, pushing, calendering, deoiling, stretching and shaping in S2 are as follows: Mixing process: 1-4kg of polytetrafluoroethylene dispersion resin raw material is sieved into the mixing barrel through an 8-16 mesh screen, and auxiliary oil is added at a ratio of 230-300g / kg of raw material and mixed thoroughly, and then placed in a maturation box at a temperature of 40-60℃ for 10-18h; Blank making process: Place the ripened raw materials in a blank making machine with a temperature of 40-60℃ and a diameter of φ80-150mm, and press them into cylindrical blanks; Pushing process: put the blank into a pusher of corresponding size at a temperature of 40-60℃ and push it into a rod with a diameter of φ6-30mm; Calendering process: Place the rods in a calender at a temperature of 40-60°C and calender them into an oil-containing base tape with a thickness of 230-260μm; Deoiling process: the oil-containing base tape is passed through a deoiling machine at a temperature of 150-250°C at a speed of 1-3m / min to obtain a degreased base tape; Stretching process: The degreased base tape is passed through a stretching box at a temperature of 250-350°C at a speed of 1-3m / mim. There are 2-13 stretching rollers in the stretching box. The speed of each stretching roller is controlled independently, and the total stretching ratio is 2-4 times; Forming process: The stretched base tape enters a forming machine at a temperature of 300-380°C at a stretching speed of 0.95-1.2 times for forming, and finally a uniaxially stretched PTFE low-density microporous tape is obtained.

5. The method for preparing a PEO-modified PTFE film according to claim 1, wherein The PTFE low-density microporous tape in S2 has a thickness of 0.03-0.3 mm and a density of 0.3-1 g / cm 3 .

6. The method for preparing a PEO-modified PTFE film according to claim 1, wherein The water bath sealed heating box of the surface treatment equipment in S3 has a water bath temperature of 25-55°C.

7. The method for preparing a PEO-modified PTFE film according to claim 1, wherein In S4, the temperature in the first drying box is 50-80°C, the water temperature in the cleaning pool is 30-80°C, the temperature in the second drying box is 100-170°C, and the temperature of the cooling roller is 40-80°C.

8. The method for preparing a PEO-modified PTFE film according to claim 7, wherein: The pulling length of the PTFE low-density microporous belt in the water bath sealed heating box is 5-9m; The pulling length of the PTFE low-density microporous belt in the first drying box is 2-6m; The pulling length of the PTFE low-density microporous belt in the cleaning tank is 1-5m; The pulling length of the PTFE low-density microporous belt in the second drying box is 6-12m; The contact length between the PTFE low-density microporous belt and the cooling roller is 0.5-2.5 m.

9. The method for preparing a PEO-modified PTFE film according to claim 1, wherein The processing speed in S4 is 1.5-5.5 m / min.

10. Application of the PEO-modified PTFE film obtained by the preparation method of the PEO-modified PTFE film according to any one of claims 1 to 9 in the field of electrical insulating materials.

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