CN117304550B - High-strength waterproof polytetrafluoroethylene porous membrane and preparation method and application thereof - Google Patents
High-strength waterproof polytetrafluoroethylene porous membrane and preparation method and application thereof Download PDFInfo
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- CN117304550B CN117304550B CN202311584843.6A CN202311584843A CN117304550B CN 117304550 B CN117304550 B CN 117304550B CN 202311584843 A CN202311584843 A CN 202311584843A CN 117304550 B CN117304550 B CN 117304550B
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- 229920001343 polytetrafluoroethylene Polymers 0.000 title claims abstract description 139
- 239000004810 polytetrafluoroethylene Substances 0.000 title claims abstract description 139
- 239000012528 membrane Substances 0.000 title claims abstract description 99
- -1 polytetrafluoroethylene Polymers 0.000 title claims abstract description 91
- 238000002360 preparation method Methods 0.000 title abstract description 8
- 241000258957 Asteroidea Species 0.000 claims abstract description 11
- 239000013354 porous framework Substances 0.000 claims abstract description 5
- 238000012986 modification Methods 0.000 claims description 67
- 230000004048 modification Effects 0.000 claims description 67
- 239000011148 porous material Substances 0.000 claims description 43
- 239000000463 material Substances 0.000 claims description 36
- 239000006185 dispersion Substances 0.000 claims description 30
- 238000005238 degreasing Methods 0.000 claims description 27
- 238000005245 sintering Methods 0.000 claims description 26
- 238000000034 method Methods 0.000 claims description 23
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- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 13
- 238000005507 spraying Methods 0.000 claims description 11
- 229920000642 polymer Polymers 0.000 claims description 10
- 238000005096 rolling process Methods 0.000 claims description 10
- 239000011248 coating agent Substances 0.000 claims description 9
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- 239000012752 auxiliary agent Substances 0.000 claims description 5
- 238000000465 moulding Methods 0.000 claims description 5
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 4
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- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
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- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
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- CNPVJWYWYZMPDS-UHFFFAOYSA-N 2-methyldecane Chemical compound CCCCCCCCC(C)C CNPVJWYWYZMPDS-UHFFFAOYSA-N 0.000 description 1
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
- B01D71/36—Polytetrafluoroethene
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D7/00—Producing flat articles, e.g. films or sheets
- B29D7/01—Films or sheets
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/12—Chemical modification
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
- C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
- C08J2327/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C08J2327/18—Homopolymers or copolymers of tetrafluoroethylene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2427/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
- C08J2427/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
- C08J2427/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C08J2427/18—Homopolymers or copolymers of tetrafluoroethylene
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- C08J2429/02—Homopolymers or copolymers of unsaturated alcohols
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- C08J2433/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
- C08J2433/24—Homopolymers or copolymers of amides or imides
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- C08J2439/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a single or double bond to nitrogen or by a heterocyclic ring containing nitrogen; Derivatives of such polymers
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Abstract
The invention discloses a high-strength waterproof polytetrafluoroethylene porous membrane, a preparation method and application thereof, wherein the high-strength waterproof polytetrafluoroethylene porous membrane has a high-strength porous framework structure, the microstructure of the high-strength waterproof polytetrafluoroethylene porous membrane is in a non-oriented rich and compact spider-web structure, a thick starfish structure or a round hole structure, and the true waterproof capacity of the high-strength waterproof polytetrafluoroethylene porous membrane in the absence of a support is not lower than 0.35MPa. The invention changes the porous skeleton structure of the polytetrafluoroethylene porous membrane, and changes the traditional dotted porous structure into a compact reticular structure, a high-strength starfish structure and a round hole structure, the microscopic appearance of the membrane is not a bulked structure, the surface layer, the internal density and the strength of the membrane are improved, the membrane is not easy to delaminate, and the membrane has high elastic modulus, high strength, small deformation and easy recovery of deformation.
Description
Technical Field
The invention relates to the technical field of polymer porous membranes, in particular to a high-strength waterproof polytetrafluoroethylene porous membrane, and a preparation method and application thereof.
Background
The existing Polytetrafluoroethylene (PTFE) porous membrane preparation technology is mainly prepared by mixing PTFE dispersion resin and an auxiliary agent, pre-pressing and molding, pushing and extruding, calendaring, removing the auxiliary agent, longitudinal stretching (MD) and transverse stretching (TD), and sintering and shaping. Because of the thermal sensitivity and creep property of polytetrafluoroethylene materials, uneven stretching phenomenon often exists in the expanding process, the porous pore diameter is wide in distribution range and poor in uniformity, the preparation difficulty of small pore diameter is high, and the thickness difference of different areas of the membrane is large. Meanwhile, the prepared membrane has a porous morphology of a bulked reticular structure formed by nodes and microfibers, and the microfibers forming the membrane porous structure are too fine and weak, so that deformation or fracture easily occurs in the use process, the pore diameter of the membrane is increased, and the protection capability and the separation performance are reduced. When the pore diameter is reduced by the stretching process, the porosity of the membrane is synchronously reduced, and the membrane is soft and light, so that the mechanical strength of the membrane is low, the membrane is easy to deform and scratch, the usability is influenced, and the bulked structure is low in cohesive force, is easy to delaminate and is unfavorable for subsequent processing.
Patent publication numbers CN201080002329.1 and CN201710063655.7, the invention discloses a waterproof sound-transmitting membrane, the surface density of PTFE porous membrane is 1-20g/m 2 Adopts a mode of multilayer superposition and compoundingThe pore diameter of the membrane is regulated and controlled by a multilayer stretching and sticking mode, and the waterproof sound-transmitting membrane is obtained by roasting at the temperature above the melting point of polytetrafluoroethylene after stretching.
The patent CN201880036006.0 uses polytetrafluoroethylene resin with large molecular weight to press and mold, roasting into a nonporous film, then stretching, regulating the porous quantity of the section of the film, regulating the pore diameter of the film, improving the cohesion and the puncture strength, and ensuring that the average pore diameter is in the range of 0.03-0.2 mu m, and the porosity is more than 25% and less than 90%.
Patent CN202080082140.1 discloses a method of preparing a polytetrafluoroethylene film with small pore size and high strength, wherein polytetrafluoroethylene with ultra-high molecular weight is selected, pre-pressed, extruded, molded, stretched in the extrusion direction at a certain speed at a molding temperature of 300 ℃, and sintered at a temperature higher than the melting point of polytetrafluoroethylene, so that the polytetrafluoroethylene film with small pore size and high strength is prepared, the bubble point under isopropanol is 400kPa or more, and the tensile strength is 50MPa or more.
The pore diameter and the strength of the membrane are regulated and controlled in the above research, but the porous structure is unchanged, and is a single-layer or multi-layer composite bulked structure, which is composed of nodes and fibrils, and has the problems of loose surface layer, poor mechanical strength, easy deformation, scratch and layering, low mechanical strength of the membrane product, easy deformation and fracture of the microfibers, difficult maintenance of the porous structure and the like. In the waterproof capability test, due to the deformation problem caused by low strength, a stainless steel wire mesh is often required to be arranged on the opposite side of the membrane pressing surface, and the measurement is carried out in a state of inhibiting deformation, so that a large gap is formed between the stainless steel wire mesh and the practical application process.
The patent CN20201029100. X prepares a PTFE porous membrane with needle-like and slit-like structural characteristics by adding thermoplastic perfluoropolymer powder and sintering the PTFE parison twice. The PTFE body is partially melted by adding thermoplastic perfluoropolymer powder for a first high-temperature short-time sintering treatment, the melting proportion is 0.5-55wt%, a novel porous structure is molded, the shaping and solidification of the porous structure of the body after stretching pore-forming are realized by a second sintering treatment, the hand hardness, namely the mechanical strength, of the PTFE porous membrane is effectively improved, but the porosity is lower under a small pore diameter, mixing is uneven due to the fact that powder is added, and the product yield is reduced.
Therefore, how to adjust the micro-morphology structure of the membrane by process control, improve the mechanical strength of the membrane, change the problem of easy deformation and fracture of the membrane, and prepare the porous membrane with high strength, thin layer, small pore diameter and high porosity, thereby realizing the waterproof and sound-transmitting effects of the porous membrane, which is a technical problem to be solved by the technicians in the field.
Disclosure of Invention
The invention aims to provide a polytetrafluoroethylene porous membrane with high strength and true waterproof capability aiming at the defect that the polytetrafluoroethylene porous membrane in the prior art is poor in mechanical strength and easy to deform and break.
Another object of the present invention is to provide a method for preparing the high-strength waterproof polytetrafluoroethylene porous membrane.
Another object of the present invention is to provide the use of the high-strength waterproof polytetrafluoroethylene porous membrane.
The technical scheme adopted for realizing the purpose of the invention is as follows:
the high-strength waterproof polytetrafluoroethylene porous membrane is provided with a high-strength porous framework structure, the microstructure of the high-strength waterproof polytetrafluoroethylene porous membrane is in a non-oriented rich and compact spider-web structure, a thick and dense 'starfish' structure or a round hole structure, the spider-web structure is a node-free rich and compact network structure, the 'starfish' structure is formed by connecting thick microfibrils with adjacent island-shaped areas in a divergent state, and the round hole structure is a round hole structure without nodes and obvious fiber structures;
the high-strength waterproof polytetrafluoroethylene porous membrane has a true waterproof capability of not less than 0.35MPa in the absence of a support.
In the technical scheme, the maximum pore diameter range of the high-strength waterproof polytetrafluoroethylene porous membrane is 20 nm-400 nm, the pore diameter distribution is more than 90%, and the thickness of the high-strength waterproof polytetrafluoroethylene porous membrane is 2-70 mu m.
In the technical scheme, the tensile breaking strength of the high-strength waterproof polytetrafluoroethylene porous membrane is 10-200 MPa, and the breaking elongation of the high-strength waterproof polytetrafluoroethylene porous membrane is less than 300%.
In another aspect of the present invention, there is provided a method for preparing the high-strength waterproof polytetrafluoroethylene porous membrane, comprising the steps of:
step 1, mixing and pre-pressing forming: mixing the dispersion resin with the auxiliary agent oil, and performing prepressing molding to obtain a cylindrical or cylindric PTFE rod blank;
step 2, pushing extrusion: pushing and extruding the rod blank obtained in the step 1 through horizontal or vertical pushing and extruding equipment to obtain a rod-shaped or cylindrical PTFE parison;
step 3, calendaring: rolling the rod-shaped or cylindrical PTFE parison obtained in the step 2 into a base material belt by a double-roller calender;
step 4, degreasing treatment: heating the base material belt prepared in the step 3 to remove auxiliary oil;
step 5, surface modification treatment: carrying out surface modification treatment on the base material belt subjected to degreasing treatment in the step 4, and coating a surface modification solution on the base material belt; then high-temperature treatment is carried out, and a double-roller calender is carried out for two times or more times to obtain a rolled base band;
step 6, longitudinal stretching: longitudinally stretching the rolled base band subjected to surface modification treatment;
step 7, transverse stretching: and transversely stretching the longitudinally stretched film sample to obtain a PTFE (polytetrafluoroethylene) body with a porous structure, wherein the PTFE body with the porous structure is the high-strength waterproof polytetrafluoroethylene porous film.
In the technical scheme, the extrusion speed in the step 2 is 40mm/min-200mm/min;
the diameter of the roller of the double-roller calender in the step 3 is 600mm-1000mm, and the thickness of the base material belt is 20 mu m-400 mu m;
the degreasing treatment in the step 4 is carried out at a treatment temperature of 150-280 ℃ for 5-30 min.
In the above technical solution, the surface modification solution in the step 5 includes 50% -80% of polytetrafluoroethylene dispersion and 20% -50% of aqueous polymer solution, the concentration of the polytetrafluoroethylene dispersion is 30% -60% by weight, the concentration of the aqueous polymer solution is 3% -10% by weight, preferably, the aqueous polymer is one or more of polyvinyl alcohol PVA, polyacrylamide PAM, polyacrylic acid PAA, polyethylene oxide PEO or polyvinylpyrrolidone PVP;
the surface modification treatment mode in the step 5 is dipping, spraying, electrostatic spinning coating or preset coating; the high temperature treatment temperature of the high temperature furnace in the step 5 is 230-360 ℃, and the thickness of the rolled base band is 10-50 mu m.
In the technical scheme, the stretching temperature of the longitudinal stretching in the step 6 is 40-300 ℃, the stretching multiplying power is 50-1000%, and the stretching interval is 20-200 mm;
the stretching temperature of the transverse stretching in the step 7 is 20-300 ℃, the stretching multiplying power is 50-2000%, and the stretching interval is 20-200 mm.
In the above technical solution, further includes:
step 8, sintering and shaping: and (3) sintering and shaping the PTFE body with the porous structure obtained by stretching in the step (7) under the action of maintaining tension to obtain the high-strength waterproof polytetrafluoroethylene porous membrane.
In the technical scheme, the sintering temperature of the sintering shaping is 330-450 ℃, and the treatment time of the sintering shaping is 0.5-10 min.
In another aspect, the invention provides application of the high-strength waterproof polytetrafluoroethylene porous membrane as a waterproof breathable membrane and a sound-permeable audio membrane in the field of consumer electronics.
With the widespread use of electronic devices such as mobile phones, interphones, electronic watches, bluetooth headsets, outdoor monitors and the like in life, in order to reduce damages to the electronic devices caused by water sports on water, outdoor environments and daily life water, waterproof breathable films are generally assembled at microphone holes, balance breathable holes and barometer breathable holes which are communicated with the outside in the inner cavities of the electronic devices for protection; for acoustic components such as speakers, microphones, and handsets, a waterproof sound-transmitting membrane is required for isolation. For example, a typical sports watch or bracelet has higher requirements for the waterproof capability of a waterproof breathable and waterproof sound-permeable membrane, a 30m (0.3 MPa) waterproof watch can be used in daily toilet or rain, i.e. water drops are only splashed on the surface without any water pressure being applied to the watch; the 50-meter waterproof meter can be suitable for swimming and general housework; the 100-meter waterproof meter can be used for underwater work such as swimming, diving and the like. The water resistance is expressed as a value of the water pressure resistance test. For example, a water pressure resistance of 1MPa is required for a membrane used for an electronic device or the like that is 100m waterproof, and a pore diameter of a membrane having a water pressure resistance of 1MPa is required to be several tens of nanometers or less. The high-strength waterproof polytetrafluoroethylene porous membrane has a thin layer, high tensile strength, small elongation at break and high waterproof capacity, and is suitable for the application.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the high-strength waterproof polytetrafluoroethylene porous membrane, the surface layer modification treatment is carried out on the base material belt, and then the high-temperature low-multiplying power longitudinal stretching and the middle-high-temperature low-multiplying power transverse stretching are carried out, so that the porous framework structure of the membrane is changed, the traditional dotted linear porous structure is changed into a compact net structure, a high-strength starfish structure and a round hole structure, the surface layer and the inner density and the strength of the membrane are improved, layering is not easy, the membrane has high elastic modulus, the strength is high, the deformation quantity is small, and the deformation is easy to recover. The sintering heat setting process can be omitted after the film is stretched, the process flow is simplified, the influence on the film morphology structure and pore diameter distribution condition due to the temperature gradient and stress release difference in the sintering setting process is avoided, the uniformity and stability of the film finished product are improved, the mechanical strength, deformation resistance and true waterproof capability of the film surface layer and the porous framework structure are effectively improved, and the dense porous structure is enriched, so that the film is not easy to deform, delaminate and scratch.
2. The high-strength waterproof polytetrafluoroethylene porous membrane can avoid compression deformation in the application process, can keep the self porous structure, and achieves high-strength true waterproof capability.
Drawings
FIG. 1 is a flow chart of a preparation method of the high-strength waterproof polytetrafluoroethylene porous membrane.
Fig. 2 is a scanning electron microscope image of the degreasing baseband i.
Fig. 3 is a scanning electron microscope image of the surface layer of the base band corresponding to sample 1# after the surface layer modification treatment.
Fig. 4 is a scanning electron microscope image of sample 1#.
Fig. 5 is a scanning electron microscope image of sample No. 2.
Fig. 6 is a scanning electron microscope image of sample 3#.
Fig. 7 is a scanning electron microscope image of sample No. 4.
Fig. 8 is a scanning electron microscope image of PTFE baseband after the surface layer modification treatment corresponding to sample No. 5.
Fig. 9 is a scanning electron microscope image of sample No. 5.
Fig. 10 is a pore size distribution diagram of sample 5#, sample 6# and sample 7#.
Fig. 11 is a scanning electron microscope image of sample 6#.
Fig. 12 is a scanning electron microscope image of sample 7#.
Fig. 13 is a scanning electron microscope image of sample 8#.
Fig. 14 is a scanning electron microscope image of sample 9#.
Fig. 15 is a scanning electron microscope image of sample 10#.
FIG. 16 is a pore size distribution plot of PTFE flat porous membranes of samples # 8, # 9 and # 10.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The tensile breaking strength and the breaking elongation of the high-strength waterproof polytetrafluoroethylene porous membrane are tested by an electronic universal tensile machine (Instron 5965), and the method is based on GB/T1040.3-2006, the ambient temperature is 20 ℃, the humidity is 45% RH, the sample width is 20mm, the tensile spacing is 150mm, and the tensile speed is 150mm/min. The true waterproof capability is according to GB/T4208-2017, the test effective area phi is 2mm, the test duration is one hour, and the test effective area has no support, substrate or backboard. The porous morphology and structural characteristics of the membrane are characterized by adopting a freeze scanning electron microscope (HITACHIE S8200), and the PTFE porous membrane is subjected to vacuum ion sputtering metal spraying treatment before testing. The pore size of the PTFE porous membrane is measured by a capillary pore size analyzer (POROMETER POROLUX 1000), the measuring method is referred to as CN 201510569827.9, and the pore size distribution, the maximum pore size, the average pore size and the minimum pore size are measured by a dry-wet curve by utilizing a gas-liquid displacement principle. The stretching equipment is a high-temperature film biaxial stretching instrument.
Example 1
A high strength waterproof polytetrafluoroethylene porous membrane, as shown in fig. 1, prepared by the following method:
step 1, mixing and pre-pressing forming: 80 parts of Dajin F104 dispersion resin is added into a mixing device, 20 parts of Isopar G auxiliary oil of Exxon Mobil is uniformly mixed in a spraying mode, cured for 24 hours at 50 ℃, then filled into pre-pressing forming equipment with phi of 150mm, the pressure is set to 3.5MPa, and the pressure is maintained for 10 minutes, so that a cylindrical PTFE rod blank is prepared.
Step 2, pushing extrusion: the rod-shaped or cylindrical PTFE parison is extruded by a horizontal or vertical extrusion device, the extrusion die size phi is 15mm, and the extrusion speed is 50mm/min.
Step 3, calendaring: the rod-shaped or cylindrical PTFE parison was rolled into a base stock tape by a twin-roll calender having a roll diameter of 600mm at a calendering speed of 20m/min (calendering speed, which is used in the subsequent examples of the present invention), and the base stock tape had a thickness of 60. Mu.m.
Step 4, degreasing treatment: and (3) conveying the base material belt prepared in the step (3) into a high-temperature box for heating treatment, removing auxiliary oil in the molded body, wherein the treatment temperature is 230 ℃, and the treatment time is 30min, so that a degreasing base belt I is obtained, and the microscopic morphology of the degreasing base belt I is shown in figure 2.
Step 5-8, surface finishing treatment, longitudinal stretching, transverse stretching and sintering shaping:
sample 1#: the surface modification treatment of the base band is realized by carrying out the surface modification treatment on the degreasing base band I. Coating the surface modification solution on a base material belt in an electrostatic spinning mode, and carrying out high-temperature treatment by a high-temperature furnace; and then, carrying out secondary rolling by a double-roller rolling machine to obtain a rolled base band, wherein the thickness of the rolled base band is 50 mu m. The surface modification solution comprises polytetrafluoroethylene dispersion liquid with the proportion of 50% and PVP solution with the proportion of 50%, wherein the concentration of the polytetrafluoroethylene dispersion liquid is 60wt%, and the concentration of the PVP solution is 5wt%; the temperature of the high-temperature treatment is 260 ℃. The microscopic morphology of the surface modification treated baseband is shown in fig. 3. Firstly longitudinally stretching the base material belt subjected to surface layer modification treatment by adopting a film biaxial stretching device, wherein the stretching temperature is 250 ℃, the stretching multiplying power is 800%, and the stretching interval is 150mm; and transversely stretching the longitudinally stretched film sample at 40 ℃ with a stretching multiplying power of 200%, sintering and shaping the stretched PTFE (polytetrafluoroethylene) body with the porous structure under the action of maintaining tension at 330 ℃ for 5min, and obtaining a high-strength waterproof polytetrafluoroethylene porous film sample 1# with the thickness of 37 mu m.
Sample # 2: the surface modification treatment of the base band is realized by carrying out the surface modification treatment on the degreasing base band I. Coating the surface modification liquid on a base material belt in an electrostatic spinning mode, and carrying out high-temperature treatment by a high-temperature furnace; the surface modification solution comprises polytetrafluoroethylene dispersion liquid with the proportion of 60% and PVP solution with the proportion of 40%, wherein the concentration of the polytetrafluoroethylene dispersion liquid is 60% by weight, and the concentration of the PVP solution is 5% by weight; the temperature of the high-temperature treatment is 270 ℃, the film thickness after secondary compression is 50 mu m, and other baseband treatment conditions are the same as those of sample No. 1. Stretching the base material belt subjected to surface layer modification treatment by adopting a film biaxial stretching device, and firstly performing longitudinal stretching at the stretching temperature of 250 ℃, the stretching multiplying power of 800% and the stretching interval of 150mm; and transversely stretching the longitudinally stretched film sample at 40 ℃, stretching multiplying power of 400%, stretching interval of 150mm, sintering and shaping the PTFE body with the porous structure obtained by stretching under the action of maintaining tension, wherein the sintering temperature is 330 ℃, and the treatment time is 10min, so that the high-strength waterproof polytetrafluoroethylene porous film sample No. 2 with the thickness of 40 mu m is obtained.
Sample 3#: the same treatment mode as that of sample No. 1 is adopted, the surface modification solution comprises polytetrafluoroethylene dispersion liquid with the proportion of 70% and PVA solution with the proportion of 30%, the concentration of the polytetrafluoroethylene dispersion liquid is 60% by weight, the concentration of the PVA solution is 4% by weight, the high temperature is 280 ℃, and the film thickness after secondary compression is 50 μm. Firstly longitudinally stretching the base material belt subjected to surface layer modification treatment by adopting a film biaxial stretching device, wherein the stretching temperature is 250 ℃, the stretching multiplying power is 1000%, the stretching interval is 150mm, and the stretching speed is 150mm/min; and transversely stretching the longitudinally stretched film sample at 40 ℃, stretching multiplying power of 200%, stretching interval of 150mm and stretching speed of 150mm/min, and sintering and shaping the stretched PTFE body with the porous structure under the action of maintaining tension at 335 ℃ for 10min to obtain a high-strength waterproof polytetrafluoroethylene porous film sample No. 3 with the thickness of 35 mu m.
Sample # 4: the same treatment mode as that of sample No. 1 is adopted, the surface modification solution comprises polytetrafluoroethylene dispersion liquid with the proportion of 80% and PVA solution with the proportion of 20%, the concentration of the polytetrafluoroethylene dispersion liquid is 60wt%, the concentration of the PVA solution is 3wt%, the high temperature is 300 ℃, and the film thickness after secondary compression is 50 μm. Firstly longitudinally stretching the base material belt subjected to surface layer modification treatment by adopting a film biaxial stretching device, wherein the stretching temperature is 250 ℃, the stretching multiplying power is 600%, the stretching interval is 150mm, and the stretching speed is 150mm/min; and transversely stretching the longitudinally stretched film sample at the stretching temperature of 60 ℃, the stretching multiplying power of 300%, the stretching interval of 150mm and the stretching speed of 150mm/min, and sintering and shaping the stretched PTFE (polytetrafluoroethylene) body with the porous structure under the action of maintaining the tension, wherein the sintering temperature is 335 ℃, and the treatment time is 5min, so that the high-strength waterproof polytetrafluoroethylene porous film sample No. 4 with the thickness of 38 mu m is obtained.
Sample 1# -sample 4# the high strength waterproof polytetrafluoroethylene porous membrane has morphology structure shown in figures 4-7, the porous structure is in a spider-web structure, the fibers are thick, and no obvious nodes and orientation are generated. The test data of sample 1# -sample 4# are shown in Table 1.
Comparing the morphology graph (figure 2) of the degreasing base band with the morphology graph (figure 3) of the base band subjected to surface modification treatment in the embodiment 1, the degreasing base band can be found to be in a loose structure with orderly arranged microscopic particles, the base band is coated with surface modification liquid, subjected to high-temperature treatment and subjected to secondary compression, the surface modification liquid and polytetrafluoroethylene dispersion resin are fused into a whole, the pores of the integral structure of the base band after the secondary compression are reduced and are more compact, the surface strength of the membrane is improved, and a high-strength multi-layer skeleton structure can be formed. The structural morphology of the membrane in the embodiment 1 of the invention is shown in figures 4-7, the membrane is prepared into a rich, multi-layer structure and node-free spider-web structure after the surface layer modification treatment of the base band is subjected to longitudinal stretching (MD), transverse stretching (TD) and sintering setting, the fiber is thick and strong, no obvious directivity is generated, the pore size is smaller, the longitudinal tensile strength and the transverse tensile strength are higher, the membrane thickness is about 30-40 mu m, and the true waterproof capability of the membrane can reach more than 0.35MPa.
Compared with the invention, the film structure prepared by the prior stretching technology is mostly a fibrous bulked structure, and the small pore structure is difficult to prepare; the fiber is thin and weak, has poor mechanical strength and large elongation at break, has weak deformation resistance, is easy to deform, and is difficult to bear membrane deformation and breakage caused by high-pressure liquid impact.
Table 1 various test data for sample 1# -sample 4#
Example 2
A high-strength waterproof polytetrafluoroethylene porous membrane is prepared by the following method:
step 1, adding 79 parts of large gold company F104 dispersion resin into a mixing device, uniformly mixing 21 parts of Isopar M auxiliary oil of Exxon Mobil in a spraying manner, curing for 24 hours at 50 ℃, filling into phi 130mm pre-pressing forming equipment, setting the pressure to 3.5MPa, and maintaining the pressure for 10 minutes to obtain a cylindrical PTFE rod blank.
Step 2, pushing and extruding the bar blank through horizontal or vertical pushing and extruding equipment, wherein the extrusion die has the size phi of 17.5mm and the extrusion speed of 100mm/min, so as to prepare a bar-shaped or cylindrical PTFE parison;
and 3, rolling the rod-shaped or cylindrical PTFE parison into a base material belt with the thickness of 50 mu m by a double-roller calender and the diameter of a roller of 800mm, wherein the thickness is measured by an infrared on-line analysis thickness sensor.
And 4, heating the base material belt to remove auxiliary oil in the molded body, wherein the treatment temperature is 260 ℃ and the treatment time is 30min, so as to obtain a degreasing base belt II.
And 5, performing surface modification treatment on the degreasing base band II to realize surface modification treatment on the base band. Spraying the surface modification solution on a base material belt in a high-pressure air gun spraying mode, and carrying out high-temperature treatment by a high-temperature furnace; and then, carrying out secondary rolling by a double-roller calender to obtain a rolled base band with the thickness of 30 mu m. The surface modification solution comprises polytetrafluoroethylene dispersion liquid with the proportion of 60% and PVA solution with the proportion of 40%, wherein the concentration of the polytetrafluoroethylene dispersion liquid is 60% by weight, and the concentration of the PVA solution is 3% by weight; the temperature of the high-temperature treatment is 330 ℃. The microscopic morphology of the surface modification treatment baseband is shown in fig. 8, no obvious resin particles are arranged on the surface of the baseband, the secondary resin particles are integrated, and the gaps in the visual field range of the surface of the baseband are further reduced;
step 6, longitudinally stretching the base material belt subjected to surface modification treatment at a stretching temperature of 260 ℃ and a stretching multiplying power of 200%, wherein the stretching interval is 100mm;
and 7, transversely stretching the longitudinally stretched film sample at the temperature of 200 ℃, stretching multiplying power of 300%, and stretching the film sample at the interval of 100mm to obtain a high-strength waterproof polytetrafluoroethylene porous film sample No. 5 with the thickness of 35 mu m.
The average pore diameter and pore diameter distribution of the porous membrane of the PTFE flat plate were tested, and the result of the pore diameter distribution of sample No. 5 is shown in FIG. 10. The morphology structure of sample 5# is shown in fig. 9, the concentration of the surface layer modification treatment liquid is increased, the high-temperature treatment temperature is increased, and the porous structure of the membrane is in a starfish structure. The test data for sample 5# are detailed in table 2.
Example 3
Step 1, adding 79 parts of large gold company F106 dispersion resin into a mixing device, uniformly mixing 21 parts of Isopar M auxiliary oil of Exxon Mobil in a spraying manner, curing for 24 hours at 50 ℃, filling into phi 150mm pre-pressing forming equipment, setting the pressure to 3.5MPa, and maintaining the pressure for 10 minutes to obtain a cylindrical PTFE rod blank.
Step 2, pushing and extruding the bar blank through horizontal or vertical pushing and extruding equipment, wherein the extrusion die has the size phi of 15mm and the extrusion speed of 100mm/min, so as to prepare a bar-shaped or cylindrical PTFE parison;
and 3, rolling the rod-shaped or cylindrical PTFE parison into a base material belt with the thickness of 40 mu m by a double-roller calender and the roller diameter of 800mm, wherein the thickness is measured by an infrared online analysis thickness sensor.
And 4, heating the base material belt to remove auxiliary oil in the molded body, wherein the treatment temperature is 260 ℃ and the treatment time is 30min, so as to obtain a degreasing base belt III.
Step 5-7:
sample 6#: step 5, carrying out surface modification treatment on the degreasing base band III to realize surface modification treatment on the base band, uniformly spraying a surface modification solution on a base band in a preset coating mode, and carrying out high-temperature treatment on the base band by a high-temperature furnace; and then, carrying out secondary rolling by a double-roller calender to obtain a rolled base band, wherein the thickness of the base band is 30 mu m. The surface modification solution comprises polytetrafluoroethylene dispersion liquid with the proportion of 40% and PVA solution with the proportion of 60%, wherein the concentration of the polytetrafluoroethylene dispersion liquid is 60% by weight, and the concentration of the aqueous polymer solution is 3% by weight; the temperature of the high-temperature treatment is 335 ℃;
step 6, longitudinally stretching the base material belt subjected to surface modification treatment at a stretching temperature of 260 ℃ and a stretching multiplying power of 200%, wherein the stretching interval is 100mm;
and 7, transversely stretching the longitudinally stretched film sample at the temperature of 230 ℃, stretching multiplying power of 200%, and stretching the film sample at the interval of 100mm to obtain a high-strength waterproof polytetrafluoroethylene porous film sample No. 6 with the thickness of 25 mu m.
Sample # 7: step 5, carrying out surface modification treatment on the degreasing base band III to realize surface modification treatment on the base band, uniformly spraying a surface modification solution on a base band in a dipping mode, and carrying out high-temperature treatment on the base band by a high-temperature furnace; and then, carrying out secondary rolling by a double-roller calender to obtain the base band with the thickness of 30 mu m. The surface modification solution comprises polytetrafluoroethylene dispersion liquid with the proportion of 60% and PVA solution with the proportion of 40%, wherein the concentration of the polytetrafluoroethylene dispersion liquid is 60% by weight, and the concentration of the aqueous polymer solution is 3% by weight; the high temperature is 340 ℃;
step 6, longitudinally stretching the base material belt subjected to surface modification treatment at a stretching temperature of 260 ℃ and a stretching multiplying power of 200%, wherein the stretching interval is 100mm;
and 7, transversely stretching the longitudinally stretched film sample at 260 ℃, stretching multiplying power of 200%, and stretching interval of 100mm to obtain a high-strength waterproof polytetrafluoroethylene porous film sample No. 7 with thickness of 17 mu m.
The average pore size and pore size distribution of sample 6# and sample 7# were tested, and the pore size distribution results are shown in fig. 10. Morphology of samples 6# and 7# as in fig. 11 and 12, the porous structure was a unique circular hole structure structurally characterized by a node-free fibrous structure. The test data for sample 6# and sample 7# are detailed in table 2.
As can be seen from comparing the degreasing baseband topography map (fig. 2) with the baseband topography map (fig. 8) after the surface layer modification treatment of the embodiment 2, the surface layer modification liquid of the embodiment 2 is coated more uniformly by adopting a spraying mode; the surface modifying liquid and the resin are melted into a whole through high-temperature treatment above the melting point of the material, and loose resin particles gradually tend to a compact surface state without obvious gaps; the secondary calendaring is carried out to a thinner thickness, the secondary orientation of the modification layer also ensures that the combination between the modification layer and the base band is more compact, molecular chains are entangled and crosslinked together, and the degree of freedom of molecular movement is reduced, so that a high-strength starfish-shaped pore structure is formed after biaxial stretching, as shown in figure 9, the thick microfibrils are connected with adjacent island-shaped areas in a non-oriented divergence state, the average pore diameter is further reduced to 115.9 and nm, the mechanical strength is improved (the longitudinal tensile strength reaches 39.2 MPa, the transverse tensile strength reaches 11.5 MPa), and the true water-proof capacity of the membrane is improved to 1.0MPa.
In example 3, the surface layer finishing liquid with higher concentration and the treatment temperature are further adopted, the thickness of the surface layer finishing liquid is reduced to be 30 mu m, the volume density of the base band is further improved, after biaxial stretching, the thickness of the film can be reduced to be 17 mu m, the appearance structure of the film, as shown in figures 11-12, is a unique round hole-shaped small hole structure without fiber, holes are not connected by fiber any more, but are connected by island-island, the average pore diameter is further reduced to 66.7nm, the mechanical strength is higher (the longitudinal tensile strength reaches 70.2 MPa, the transverse tensile strength reaches 50.5 MPa), the tensile strength and the waterproof capability are synchronously improved, and the true waterproof capability is improved to be 1.5 MPa.
On the other hand, in order to eliminate the internal stress in the stretching process, the prior art needs to perform sintering setting treatment, and the process can widen the pore size distribution of the membrane, which is unfavorable for the concentration of the pore size distribution and the uniformity of the membrane. According to the invention, after the surface layer modification treatment and the biaxial stretching film preparation are carried out in the embodiment 2 and the embodiment 3, the sintering shaping step is not needed, and the morphological structure of the film in the fig. 9, the fig. 11 and the fig. 12 shows that the stretched film after the surface layer modification treatment has regular pore channel structure, concentrated pore size distribution, high mechanical strength and strong true waterproof capability.
Table 2 various test data for sample 5# -sample 7#
Comparative example 1
The degreasing base band I is subjected to biaxial stretching, longitudinal stretching is firstly performed, the stretching temperature is 250 ℃, the stretching multiplying power is 500%, and the stretching interval is 150mm; and transversely stretching the longitudinally stretched film sample at the temperature of 250 ℃, stretching multiplying power of 500%, and stretching the film sample at the interval of 100mm to obtain a PTFE flat porous film sample 8# with the thickness of 30 mu m.
Comparative example 2
The degreasing base band I is subjected to biaxial stretching, longitudinal stretching is firstly performed, the stretching temperature is 250 ℃, the stretching multiplying power is 250%, and the stretching interval is 150mm; and transversely stretching the longitudinally stretched film sample at the temperature of 250 ℃, the stretching multiplying power of 200%, and the stretching interval of 150mm to obtain a PTFE flat porous film sample 9# with the thickness of 35 mu m.
Comparative example 3
The degreasing base band III is subjected to biaxial stretching, longitudinal stretching is firstly performed, the stretching temperature is 250 ℃, the stretching multiplying power is 250%, and the stretching interval is 150mm; and transversely stretching the longitudinally stretched film sample at the temperature of 250 ℃, stretching multiplying power of 400%, and stretching the film sample at the interval of 100mm to obtain a PTFE flat porous film sample 10# with the thickness of 37 mu m.
Comparative example 4
Casting the surface modification liquid onto a glass plate, and separating the formed polytetrafluoroethylene material belt from the glass plate after high-temperature treatment by a high-temperature furnace. The surface modification solution comprises polytetrafluoroethylene dispersion with the proportion of 60% and PVA solution with the proportion of 40%, wherein the concentration of the polytetrafluoroethylene dispersion is 60% by weight, the concentration of the aqueous polymer solution is 3% by weight, and the temperature of the high-temperature treatment is 330 ℃. Stretching is carried out on the polytetrafluoroethylene material belt, the material belt is broken, and the polytetrafluoroethylene material belt cannot be stretched into a film.
The scanning electron microscope and the pore size distribution of the PTFE flat porous membrane are tested, the morphology structures of the PTFE flat porous membrane prepared by samples 8# and 9# and 10# are shown in figures 13, 14 and 15, and the porous structure is a bulk fiber structure with the structural characteristics of loose; the pore size distribution results are shown in FIG. 16. The test data of sample 8# -sample 10# are shown in Table 3.
Table 3 various test data for sample 8# -10# in comparative examples 1-3
As can be seen from comparing the degreasing baseband morphology graph (fig. 2) with the surface layer modified baseband morphology graph (fig. 3 and 8), the degreasing baseband resin is in a granular compact arrangement of secondary particles, the morphology structure of the film prepared in comparative example 1 is a bulging structure of small nodes and fine fibers, the morphology of the film after stretching in comparative example 2 is a bulging structure of large nodes and fibers, and comparative example 3 is a directed fiber node-shaped structure. Comparative example 4 was unable to stretch into a film because the tape strength was too low.
Comparing the microscopic morphology patterns of sample 1# -and sample 4# in the comparative example and the example 1, it can be found that the porous PTFE membrane prepared by biaxial stretching has a rich network structure with the increase of the concentration of the aqueous polytetrafluoroethylene dispersion in the surface layer modification solution, and the fibers are thick, rich and dense. In the embodiment 2 and the embodiment 3, the concentration of the polytetrafluoroethylene aqueous phase dispersion liquid in the surface layer modification solution and the high-temperature treatment temperature are further increased, and then the surface layer of the base band is in a void-free compact structure after the surface layer modification treatment, the microscopic morphology of the sample No. 5 is in a high-strength starfish shape, the starfish shape structure is formed by connecting thick microfibrils with adjacent island-shaped areas in a divergent state, and the fibers are in a multi-layer staggered structure; samples 6# and 7# are round hole structures which are uniformly distributed, and the round hole structures are round hole-shaped structures without nodes and obvious fiber structures. From the tensile strength test results, the starfish structure and the round hole structure have higher mechanical strength and smaller elongation at break.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. The high-strength waterproof polytetrafluoroethylene porous membrane is characterized by having a high-strength porous framework structure, wherein the microstructure of the high-strength waterproof polytetrafluoroethylene porous membrane is in a non-oriented rich and compact spider-web structure, a thick and strong 'starfish' structure or a round hole structure, the spider-web structure is a non-node rich and compact network structure, the 'starfish' structure is formed by connecting thick microfibrils with adjacent island-shaped areas in a divergent state, and the round hole structure is a round hole structure without nodes and obvious fiber structures;
the high-strength waterproof polytetrafluoroethylene porous membrane has the true waterproof capability of not less than 0.35MPa when no support exists,
the high-strength waterproof polytetrafluoroethylene porous membrane is prepared by the following method:
step 1, mixing and pre-pressing forming: mixing the dispersion resin with the auxiliary agent oil, and performing prepressing molding to obtain a cylindrical or cylindric PTFE rod blank;
step 2, pushing extrusion: pushing and extruding the rod blank obtained in the step 1 through horizontal or vertical pushing and extruding equipment to obtain a rod-shaped or cylindrical PTFE parison;
step 3, calendaring: rolling the rod-shaped or cylindrical PTFE parison obtained in the step 2 into a base material belt by a double-roller calender;
step 4, degreasing treatment: heating the base material belt prepared in the step 3 to remove auxiliary oil;
step 5, surface modification treatment: carrying out surface modification treatment on the base material belt subjected to degreasing treatment in the step 4, and coating a surface modification solution on the base material belt; then high-temperature treatment is carried out, and a double-roller calender is carried out for two times or more times to obtain a rolled base band;
step 6, longitudinal stretching: longitudinally stretching the rolled base band subjected to surface modification treatment;
step 7, transverse stretching: transversely stretching the longitudinally stretched film sample to obtain a PTFE (polytetrafluoroethylene) body with a porous structure, wherein the PTFE body with the porous structure is a high-strength waterproof polytetrafluoroethylene porous film;
wherein the surface modification solution in the step 5 comprises 50% -80% of polytetrafluoroethylene dispersion and 20% -50% of aqueous polymer solution, the concentration of the polytetrafluoroethylene dispersion is 30% -60% by weight, the concentration of the aqueous polymer solution is 3% -10% by weight, and the aqueous polymer is one or more of polyvinyl alcohol PVA, polyacrylamide PAM, polyacrylic acid PAA, polyethylene oxide PEO or polyvinylpyrrolidone PVP.
2. The high-strength waterproof polytetrafluoroethylene porous membrane according to claim 1, wherein the high-strength waterproof polytetrafluoroethylene porous membrane has a maximum pore diameter ranging from 20 nm to 400 nm, and a thickness ranging from 2 μm to 70 μm.
3. The high-strength waterproof polytetrafluoroethylene porous membrane according to claim 1, wherein the tensile breaking strength of the high-strength waterproof polytetrafluoroethylene porous membrane is 10 MPa to 200 MPa, and the elongation at break of the high-strength waterproof polytetrafluoroethylene porous membrane is less than 300%.
4. A method for preparing the high-strength waterproof polytetrafluoroethylene porous membrane according to any one of claims 1 to 3, comprising the steps of:
step 1, mixing and pre-pressing forming: mixing the dispersion resin with the auxiliary agent oil, and performing prepressing molding to obtain a cylindrical or cylindric PTFE rod blank;
step 2, pushing extrusion: pushing and extruding the rod blank obtained in the step 1 through horizontal or vertical pushing and extruding equipment to obtain a rod-shaped or cylindrical PTFE parison;
step 3, calendaring: rolling the rod-shaped or cylindrical PTFE parison obtained in the step 2 into a base material belt by a double-roller calender;
step 4, degreasing treatment: heating the base material belt prepared in the step 3 to remove auxiliary oil;
step 5, surface modification treatment: carrying out surface modification treatment on the base material belt subjected to degreasing treatment in the step 4, and coating a surface modification solution on the base material belt; then high-temperature treatment is carried out, and a double-roller calender is carried out for two times or more times to obtain a rolled base band;
step 6, longitudinal stretching: longitudinally stretching the rolled base band subjected to surface modification treatment;
step 7, transverse stretching: and transversely stretching the longitudinally stretched film sample to obtain a PTFE (polytetrafluoroethylene) body with a porous structure, wherein the PTFE body with the porous structure is the high-strength waterproof polytetrafluoroethylene porous film.
5. The method according to claim 4, wherein the extrusion speed in the step 2 is 40mm/min to 200mm/min;
the diameter of the roller of the double-roller calender in the step 3 is 600mm-1000mm, and the thickness of the base material belt is 20 mu m-400 mu m;
the degreasing treatment in the step 4 is carried out at a treatment temperature of 150-280 ℃ for 5-30 min.
6. The method of claim 4, wherein the surface modification treatment in step 5 is dipping, spraying, electrospinning or coating of a predetermined amount; the temperature of the high-temperature treatment in the step 5 is 230-360 ℃, and the thickness of the rolled base band is 10-50 mu m.
7. The method according to claim 4, wherein the stretching temperature in the longitudinal stretching in the step 6 is 40 ℃ to 300 ℃, the stretching multiplying power is 50% to 1000%, and the stretching interval is 20mm to 200mm;
the stretching temperature of the transverse stretching in the step 7 is 20-300 ℃, the stretching multiplying power is 50-2000%, and the stretching interval is 20-200 mm.
8. The method of manufacturing as set forth in claim 4, further comprising:
step 8, sintering and shaping: and (3) sintering and shaping the PTFE body with the porous structure obtained by stretching in the step (7) under the action of maintaining tension to obtain the high-strength waterproof polytetrafluoroethylene porous membrane.
9. The method of claim 8, wherein the sintering temperature of the sintering is 330 ℃ to 450 ℃ and the treatment time of the sintering is 0.5min to 10min.
10. Use of a high strength waterproof polytetrafluoroethylene porous membrane as claimed in any one of claims 1-3 as a waterproof breathable membrane, a sound-permeable audio membrane in the field of consumer electronics.
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