CN113105659A - Polytetrafluoroethylene microporous film and preparation method and application thereof - Google Patents
Polytetrafluoroethylene microporous film and preparation method and application thereof Download PDFInfo
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- CN113105659A CN113105659A CN202110400849.8A CN202110400849A CN113105659A CN 113105659 A CN113105659 A CN 113105659A CN 202110400849 A CN202110400849 A CN 202110400849A CN 113105659 A CN113105659 A CN 113105659A
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- polytetrafluoroethylene
- polytetrafluoroethylene resin
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- 229920001343 polytetrafluoroethylene Polymers 0.000 title claims abstract description 162
- 239000004810 polytetrafluoroethylene Substances 0.000 title claims abstract description 162
- -1 Polytetrafluoroethylene Polymers 0.000 title claims abstract description 151
- 238000002360 preparation method Methods 0.000 title abstract description 47
- 239000011347 resin Substances 0.000 claims abstract description 80
- 229920005989 resin Polymers 0.000 claims abstract description 78
- 239000000463 material Substances 0.000 claims abstract description 77
- 238000005245 sintering Methods 0.000 claims abstract description 49
- 239000002994 raw material Substances 0.000 claims abstract description 14
- 238000001816 cooling Methods 0.000 claims description 29
- 238000010438 heat treatment Methods 0.000 claims description 29
- 238000000034 method Methods 0.000 claims description 26
- 239000012982 microporous membrane Substances 0.000 claims description 23
- 239000002245 particle Substances 0.000 claims description 20
- 238000002844 melting Methods 0.000 claims description 16
- 230000008018 melting Effects 0.000 claims description 16
- 239000000945 filler Substances 0.000 claims description 13
- 238000002156 mixing Methods 0.000 claims description 10
- 238000007514 turning Methods 0.000 claims description 9
- 239000012528 membrane Substances 0.000 claims description 7
- 238000000465 moulding Methods 0.000 claims description 7
- 239000000843 powder Substances 0.000 claims description 7
- 238000007723 die pressing method Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- 229920002313 fluoropolymer Polymers 0.000 claims description 4
- 239000004811 fluoropolymer Substances 0.000 claims description 4
- 230000009467 reduction Effects 0.000 claims description 4
- 238000012216 screening Methods 0.000 claims description 4
- 238000003825 pressing Methods 0.000 claims description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 2
- 239000004812 Fluorinated ethylene propylene Substances 0.000 claims description 2
- HQQADJVZYDDRJT-UHFFFAOYSA-N ethene;prop-1-ene Chemical group C=C.CC=C HQQADJVZYDDRJT-UHFFFAOYSA-N 0.000 claims description 2
- 229910002804 graphite Inorganic materials 0.000 claims description 2
- 239000010439 graphite Substances 0.000 claims description 2
- 238000004806 packaging method and process Methods 0.000 claims description 2
- 229920009441 perflouroethylene propylene Polymers 0.000 claims description 2
- 229920002620 polyvinyl fluoride Polymers 0.000 claims description 2
- 239000000377 silicon dioxide Substances 0.000 claims description 2
- 239000011148 porous material Substances 0.000 abstract description 21
- 238000009826 distribution Methods 0.000 abstract description 7
- 238000011160 research Methods 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 239000004088 foaming agent Substances 0.000 abstract description 3
- 238000010923 batch production Methods 0.000 abstract 1
- 230000035699 permeability Effects 0.000 description 24
- 238000012360 testing method Methods 0.000 description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 12
- 239000000306 component Substances 0.000 description 12
- 230000004907 flux Effects 0.000 description 7
- 239000007788 liquid Substances 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 230000006835 compression Effects 0.000 description 5
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- 229920000295 expanded polytetrafluoroethylene Polymers 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 238000000113 differential scanning calorimetry Methods 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 238000009837 dry grinding Methods 0.000 description 3
- 238000009776 industrial production Methods 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000006229 carbon black Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
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- 239000000835 fiber Substances 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 238000009736 wetting Methods 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 1
- 241000872198 Serjania polyphylla Species 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000007767 bonding agent Substances 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 235000011089 carbon dioxide Nutrition 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
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- 230000000694 effects Effects 0.000 description 1
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- 150000002148 esters Chemical class 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229920006254 polymer film Polymers 0.000 description 1
- 229920006389 polyphenyl polymer Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
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- 238000006467 substitution reaction Methods 0.000 description 1
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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
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- 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
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
-
- 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
- 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
-
- 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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- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
The invention provides a polytetrafluoroethylene microporous film and a preparation method and application thereof, wherein the preparation raw materials of the polytetrafluoroethylene microporous film comprise 20-100 parts by weight of sintering materials and 10-40 parts by weight of first polytetrafluoroethylene resin; the sintering material is obtained by presintering second polytetrafluoroethylene resin; the polytetrafluoroethylene microporous film is prepared by adding a specific part of sintering material into the raw materials, matching a specific part of new polytetrafluoroethylene resin material and combining the advantages of the sintering material and the new polytetrafluoroethylene resin material, and the polytetrafluoroethylene microporous film with adjustable pore size, pore size distribution and porosity is successfully prepared; the preparation method is simple to operate, does not need special equipment and instruments, does not need to additionally add a pore-foaming agent in the preparation process, is environment-friendly and pollution-free, is beneficial to industrial batch production, and has important research value.
Description
Technical Field
The invention belongs to the technical field of polymer films, and particularly relates to a polytetrafluoroethylene microporous film and a preparation method and application thereof.
Background
The battery pack explosion-proof valve is a new energy automobile part and accessory, and aims to maintain the balance of air pressure inside and outside a battery pack, prevent liquid oil stain dust from entering a battery pack shell and timely relieve pressure when the battery is out of control due to heat. The film for the explosion-proof valve is a core component of the whole product, and has the functions of quickly ventilating, balancing internal and external pressure difference, blocking dust and oil stains and participating in explosion-proof pressure relief. In addition to the above functions, the explosion-proof valve film is required to have chemical reagent resistance, high and low temperature resistance, ultraviolet ray resistance, and the like, so as to improve the reliability of the explosion-proof valve when used in a harsh environment. At present, the explosion-proof valve of the mainstream battery pack mainly adopts a Polytetrafluoroethylene (PTFE) microporous membrane as a waterproof and breathable material.
Therefore, many researches and reports on the PTFE microporous membrane and the preparation method thereof have been made, and researches on the mechanical strength, porosity and gas permeability of the PTFE microporous membrane have been mainly focused. CN103722859A discloses a preparation method of an expanded polytetrafluoroethylene sealing film, which comprises the following steps: the method comprises the steps of placing a selected expanded polytetrafluoroethylene microporous film material roll on a unreeling machine, enabling the head end of the expanded polytetrafluoroethylene microporous film to penetrate through a gap between a left traction roller and a right traction roller, enabling the expanded polytetrafluoroethylene microporous film to contact a horizontal operation platform under the traction of the left traction roller and the right traction roller, enabling the left traction roller and the right traction roller and a left compression roller at the left end of the horizontal operation platform or a right compression roller at the right end of the horizontal operation platform to synchronously move back and forth, enabling the pressure of the left compression roller and the right compression roller to be 0.5-2 MPa, enabling the temperature to be 150-250 ℃, enabling the expanded polytetrafluoroethylene microporous film to be rolled, tiled and superposed on a horizontal operation platform layer by layer, uniformly spraying a bonding agent on the upper end face of each layer to be compositely bonded together until the required thickness is achieved, standing the film on the horizontal operation platform at 50-150 ℃ for 24. The invention improves the air permeability of the polytetrafluoroethylene microporous film mainly through the improvement of the process, but the whole preparation process is complex and the operation is complex, thus being not beneficial to large-scale industrial production and use.
CN106832695A discloses a PTFE film for an explosion-proof valve and a preparation method thereof, wherein the PTFE film comprises the following components in parts by weight: 50-65 parts of PTFE resin, 5-20 parts of calcium oxide, 2-10 parts of dry ice, 5-15 parts of polyurethane and 10-20 parts of polyphenyl ester; the preparation method comprises the steps of raw material pretreatment, weighing and material preparation, stirring and mixing, drying, melting, cooling, cutting and film forming. The PTFE film for the explosion-proof valve has the characteristics of excellent performance, high reliability, good stability and low cost. The air permeability of the polytetrafluoroethylene microporous membrane is improved by changing the preparation raw materials of the polytetrafluoroethylene microporous membrane, but the air permeability, the water pressure resistance and the mechanical strength of the obtained PTFE membrane are difficult to be considered simultaneously, and the solvent used in the preparation process also has the problem of environmental pollution.
US5417743 discloses a porous PTFE film with a "fiber/node" microstructure prepared by stretching a PTFE dispersion resin, the pores between the fibers serving the gas permeability function. However, the pore size, pore size distribution, pore size and porosity of the PTFE membrane prepared by the method are difficult to control, and the universality is poor, so that industrial production and application are difficult.
Therefore, the development of a polytetrafluoroethylene microporous membrane with simple preparation process and excellent air permeability is a problem to be solved urgently in the field.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a polytetrafluoroethylene microporous film and a preparation method and application thereof, wherein the raw materials for preparing the polytetrafluoroethylene microporous film comprise a specific part of sintering material, the sintering material is obtained by presintering polytetrafluoroethylene resin, and the specific part of new polytetrafluoroethylene resin material is matched, so that the advantages of the sintering material and the new material are combined, and the polytetrafluoroethylene microporous film with adjustable pore size, pore size distribution and porosity is successfully prepared; the preparation method is simple to operate, does not need special equipment and instruments, does not need to additionally add pore-foaming agents and solvents in the preparation process, is environment-friendly and pollution-free, and is favorable for industrial mass production.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a polytetrafluoroethylene microporous membrane, which comprises the following components in parts by weight: 20-100 parts of sintering material and 10-40 parts of first polytetrafluoroethylene resin;
the sintering material is obtained by presintering the second polytetrafluoroethylene resin.
The frit material may be 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 55 parts by weight, 60 parts by weight, 70 parts by weight, 80 parts by weight, or 90 parts by weight, and specific points therebetween, which are not exhaustive for the invention and included in the range for brevity.
The first polytetrafluoroethylene resin may be 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, or 35 parts by weight, and specific values therebetween are not exhaustive for the invention and for brevity.
The raw materials for preparing the polytetrafluoroethylene microporous film comprise a sintering material and a first polytetrafluoroethylene resin new material in specific parts, wherein the sintering material is obtained by presintering a second polytetrafluoroethylene resin. The particles of the first polytetrafluoroethylene resin new material are soft and easy to compress, and the particles are easy to contact and fuse in the process of die pressing and sintering, so that gaps among the particles are eliminated. Therefore, the product prepared by singly adopting the first polytetrafluoroethylene resin new material has extremely high mechanical strength, but the film prepared by singly using the first polytetrafluoroethylene resin new material has almost no air permeability; on the contrary, if the particles of the sintering material obtained by separately using the second polytetrafluoroethylene resin for pre-sintering are hard and have poor compression performance, the particles are not easy to contact and fuse in the die pressing and sintering processes, so that more pores are left in the product, and the product prepared by separately using the sintering material has good air permeability but poor mechanical strength; according to the invention, the sintering material and the first polytetrafluoroethylene resin (new material) are matched, and the advantages of the sintering material and the first polytetrafluoroethylene resin are combined, so that the polytetrafluoroethylene microporous film with excellent air permeability and strength is successfully prepared, no pore-forming agent is required to be additionally added, and the cost is saved.
The scanning electron microscope image of the polytetrafluoroethylene microporous film provided by the invention is shown in figure 1, and the polytetrafluoroethylene microporous film has a pore structure and further has good air permeability as can be seen from figure 1.
The mass ratio of the sintered material to the first polytetrafluoroethylene resin is preferably 1 (0.2 to 2.5), for example, 1:0.5, 1:0.9, 1:1.3, 1:1.5, 1:1.7, 1:1.9, 1:2.1, 1:2.3, or 1:2.4, and more preferably 1 (0.2 to 0.4).
According to the preparation method of the polytetrafluoroethylene microporous film, the mass ratio of the sintering material to the first polytetrafluoroethylene resin in the raw materials for preparing the polytetrafluoroethylene microporous film is 1 (0.2-2.5), so that the polytetrafluoroethylene microporous film with high strength and excellent air permeability can be obtained, if the content of the sintering material is low, the air permeability of the microporous film is influenced, and if the content of the first polytetrafluoroethylene resin is low, the strength of the microporous film is influenced.
Preferably, the powder density of the first polytetrafluoroethylene resin and the powder density of the second polytetrafluoroethylene resin are respectively 350-450 g/L, such as 360g/L, 370g/L, 380g/L, 390g/L, 400g/L, 410g/L, 420g/L, 430g/L or 440g/L, and specific values therebetween are limited to space and for the sake of brevity, and the invention does not exhaustively enumerate specific values included in the range, and further preferably 350-400 g/L.
Preferably, D of the first polytetrafluoroethylene resin and the second polytetrafluoroethylene resin50The particle diameters are each independently 10 to 100 μm, for example 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm or 90 μm, and specific values therebetween are limited toFor the sake of brevity, the invention does not exhaust the specific points included in the range, and further preferably 20-30 μm.
In the present invention, the particle size and particle size distribution of the first polytetrafluoroethylene resin and the second polytetrafluoroethylene resin have a decisive influence on the air permeability and water pressure resistance of the sample; the more the large-particle-diameter parts of the first polytetrafluoroethylene resin and the second polytetrafluoroethylene resin are, the better the air permeability is, the lower the bubble point pressure is, and the lower the water pressure resistance is; the larger the small particle size, the poorer the air permeability, the higher the bubble point pressure, and the higher the water pressure resistance.
Preferably, the first melting points of the first polytetrafluoroethylene resin and the second polytetrafluoroethylene resin are each independently 340-350 ℃, such as 341 ℃, 342 ℃, 343 ℃, 344 ℃, 345 ℃, 346 ℃, 347 ℃, 348 ℃ or 349 ℃, and the specific values therebetween are limited by space and for the sake of brevity, and the invention is not exhaustive of the specific values included in the ranges.
Preferably, the second melting points of the first polytetrafluoroethylene resin and the second polytetrafluoroethylene resin are each independently 320-330 ℃, such as 321 ℃, 322 ℃, 323 ℃, 324 ℃, 325 ℃, 326 ℃, 327 ℃, 328 ℃ or 329 ℃, and the specific values therebetween are limited by space and for the sake of brevity, and the invention is not exhaustive of the specific values included in the ranges.
Preferably, the shrinkage of the first polytetrafluoroethylene resin and the shrinkage of the second polytetrafluoroethylene resin are each independently less than 5%, for example, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, or 0.5%, and the specific values therebetween are limited by space and for the sake of brevity, and the present invention is not exhaustive list of the specific values included in the ranges, and is further preferably less than 3%.
Preferably, the sinter comprises a fully sintered and/or a semi-sintered.
The fully sintered material is characterized in that the crushed material has only one melting peak within the range of 320-330 ℃ on a primary temperature rise curve of a DSC test; the semi-sintered material refers to the crushed material which has 2 melting peaks on a primary heating curve of a DSC test, wherein one peak is between 320 and 330 ℃, and the other peak is between 340 and 350 ℃. And the first polytetrafluoroethylene resin and the second polytetrafluoroethylene resin only have one melting peak within the range of 340-350 ℃ on a DSC (differential scanning calorimetry) test primary temperature rise curve, and only have one melting peak within the range of 320-330 ℃ on a second temperature rise curve.
Preferably, the pre-sintering temperature is 340-380 ℃, such as 343 ℃, 346 ℃, 349 ℃, 352 ℃, 355 ℃, 358 ℃, 361 ℃, 364 ℃, 369 ℃, 372 ℃, 375 ℃ or 379 ℃, and the specific values therebetween are limited by space and for the sake of brevity, and the invention is not exhaustive of the specific values included in the range.
Preferably, the pre-sintering time is 2-10 h, such as 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h or 9.5h, and specific values therebetween are limited by space and for brevity, and the invention is not exhaustive.
Preferably, the raw materials for preparing the polytetrafluoroethylene microporous membrane also comprise a filler.
As a preferable technical scheme of the invention, the raw materials for preparing the polytetrafluoroethylene microporous membrane provided by the invention are also added with the filler, the filler can improve the mechanical strength of the finally obtained polytetrafluoroethylene microporous membrane, and the type of the filler can be selected according to the requirement of a final product on the strength.
Preferably, the amount of the filler in the raw material for preparing the microporous polytetrafluoroethylene film is 5 to 20 parts by weight, for example, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 12 parts by weight, 14 parts by weight, 16 parts by weight or 18 parts by weight, and specific values therebetween are not exhaustive, and the invention is not limited to the specific values included in the range for brevity.
Preferably, the filler comprises silica and/or graphite.
Preferably, the filler further comprises a further meltable fluoropolymer.
Preferably, the melt-fluoropolymer comprises any one or a combination of at least two of polyvinyl fluoride, fluorinated ethylene propylene copolymer or FPA resin.
In a second aspect, the present invention provides a method for preparing a microporous polytetrafluoroethylene membrane as described in the first aspect, the method comprising: and mixing, molding, sintering and turning the sintering material and the first polytetrafluoroethylene resin to obtain the polytetrafluoroethylene microporous film.
The preparation method of the polytetrafluoroethylene microporous film provided by the invention comprises the following steps of mixing, molding, sintering, turning and the like the first polytetrafluoroethylene resin and the sintering material filler to obtain the polytetrafluoroethylene microporous film; the preparation method has simple process, does not need pore-foaming agent and solvent, and is suitable for large-scale industrial production and application.
Preferably, the mixing further comprises a screening step.
Preferably, the pressure of the molding is 8 to 30MPa, such as 10MPa, 12MPa, 14MPa, 16MPa, 18MPa, 20MPa, 22MPa, 24MPa, 26MPa or 28MPa, and the specific values therebetween are limited by the space and the simplicity, and the invention does not exhaustive list the specific values included in the range, and more preferably 10 to 20 MPa.
Preferably, the molding time is 5-50 min, such as 10min, 15min, 20min, 25min, 30min, 35min, 40min or 45min, and the specific values therebetween are limited by space and for simplicity, and the invention is not exhaustive, and preferably 10-30 min.
Preferably, the sintering is performed under a condition of temperature reduction after temperature increase.
The method for heating and cooling comprises the following steps: heating the system to 300-335 ℃ (e.g. 303 ℃, 306 ℃, 309 ℃, 312 ℃, 315 ℃, 318 ℃, 321 ℃, 324 ℃, 328 ℃ or 332 ℃, etc.), keeping the temperature for 2-4 h (e.g. 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h or 3.8h, etc.), heating to 350-390 ℃ (e.g. 353 ℃, 356 ℃, 359 ℃, 361 ℃, 364 ℃, 368 ℃, 372 ℃, 375 ℃, 378 ℃, 382 ℃, 384 ℃, 388 ℃, or 390 ℃, etc.), keeping the temperature for 4-6 h (e.g. 4.2h, 4.4h, 4.6h, 4.8h, 5h, 5.2h, 5.4h, 5.6h or 5.8h, etc.), cooling to 300-335 ℃ (e.g. 304 ℃, 308 ℃, 312 ℃, 316 ℃, 320 ℃, 324 ℃, 328 ℃, 332 ℃ or 334 ℃, etc.), keeping the temperature for 2-4 h (e.g. 2h, 2.4h, 2.6h, 2.8h, 3.8h, etc.), and the next step.
As a preferred technical scheme, the preparation method comprises the following steps: mixing the sintering material with first polytetrafluoroethylene resin, screening, pressing for 5-50 min under the pressure of 8-30 MPa, sintering under the conditions of first temperature rise and then temperature reduction, and turning to obtain the microporous film; the method for heating and cooling comprises the following steps: and heating the system to 300-335 ℃, preserving heat for 2-4 h, heating to 350-390 ℃, preserving heat for 4-6 h, cooling to 300-335 ℃, preserving heat for 2-4 h, cooling to room temperature, and carrying out the next operation.
In a third aspect, the present invention provides a use of the microporous polytetrafluoroethylene film according to the first aspect in a breathable component, a packaging cover patch or a waterproof and breathable film for an LED vehicle lamp.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the polytetrafluoroethylene microporous film provided by the invention, a sintering material and a new polytetrafluoroethylene resin material which are obtained by adding a specific part of polytetrafluoroethylene resin into a preparation raw material and pre-sintering are combined, and the advantages of the sintering material and the new polytetrafluoroethylene resin material are combined, so that the polytetrafluoroethylene microporous film with excellent mechanical strength and air permeability is successfully prepared; the pore size distribution and pore size of the finally obtained polytetrafluoroethylene microporous film can be controlled by controlling the mass ratio of the sintering material to the new polytetrafluoroethylene resin material; specifically, the air flux of the polytetrafluoroethylene microporous membrane provided by the invention is 80-1200 mL/min/cm2@7 Kpa; the average pore diameter is 0.5-6 μm; a density of 0.7 to 1.7 g/cc; the water pressure resistance is 10 to more than 40 kPa; the thickness is 0.22 mm; the shrinkage rates are all less than 3 percent; the tensile strength is 4.2-17.8 MPa.
(2) The preparation process of the polytetrafluoroethylene microporous film provided by the invention is simple in flow and convenient to operate, special equipment and instruments are not needed, a pore-forming agent and a solvent are not needed to be additionally added in the preparation process, the industrial mass production is facilitated, and the preparation method has important research value.
Drawings
FIG. 1 is a scanning electron microscope image of a microporous polytetrafluoroethylene film according to the present invention.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Preparation example 1
A fully sintered material, D50The particle diameter is 90 mu m and D10Particle diameter of 25 μm, D90The grain diameter is 225 μm;
the preparation method comprises the following steps: and (3) pre-sintering polytetrafluoroethylene resin (Dajin M18) at 380 ℃ for 4h, and crushing by a dry grinding method to obtain the fully sintered material.
Preparation example 2
A fully sintered material, D50Particle size 180 μm, D10Particle size 60 μm, D90The grain diameter is 450 mu m;
the preparation method comprises the following steps: and (3) pre-sintering polytetrafluoroethylene resin (Dajin M18) at 380 ℃ for 8h, and crushing by a dry grinding method to obtain the fully sintered material.
Preparation example 3
A semi-sintered material D50Particle size 70 μm, D10Particle size of 30 μm, D90The grain diameter is 250 mu m;
the preparation method comprises the following steps: and (3) pre-sintering polytetrafluoroethylene resin (Dajin M18) at 340 ℃ for 4h, and crushing by a dry grinding method to obtain the semi-sintered material.
Example 1
A polytetrafluoroethylene microporous membrane is prepared by the following steps: 1600g of the fully sintered material (preparation example 1) and 400g of polytetrafluoroethylene resin (Dajin M18, powder density 400g/L, D)50The particle size is 40 μm, the first melting point is 340.3 deg.C, and the second melting point isThe point is 327.5 ℃), performing mould pressing for 20min under the pressure of 20MPa, and sintering under the condition of firstly heating and then cooling, wherein the method for firstly heating and then cooling comprises the following steps: and (3) heating the system to 300 ℃, preserving heat for 4h, heating to 380 ℃, preserving heat for 5h, cooling to 300 ℃, preserving heat for 2h, cooling to room temperature, and turning to obtain the polytetrafluoroethylene microporous film with the thickness of 0.22mm and the width of 150 mm.
Example 2
A polytetrafluoroethylene microporous membrane which is different from example 1 in that the amount of a completely sintered material is 1000g, the amount of a polytetrafluoroethylene resin is 1000g, and other components, amounts and preparation methods are the same as example 1.
Example 3
A microporous polytetrafluoroethylene film differing from example 1 in that the amount of the perfect sintered material was 580g, the amount of the polytetrafluoroethylene resin was 1420g, and the other components, amounts and preparation methods were the same as example 1.
Example 4
A polytetrafluoroethylene microporous membrane which is different from example 1 in that the amount of a completely sintered material is 500g, the amount of a polytetrafluoroethylene resin is 1500g, and other components, amounts and preparation methods are the same as example 1.
Example 5
A microporous polytetrafluoroethylene film was prepared in the same manner as in example 1 except that the amount of the completely sintered material was 1800g, the amount of the polytetrafluoroethylene resin was 200g, and the other components, amounts and preparation methods were the same as in example 1.
Example 6
A polytetrafluoroethylene microporous membrane is prepared by the following steps: 1520g of the completely sintered material (preparation example 1) and 380g of polytetrafluoroethylene resin (Dajin M18, powder density 0.40g/L, D)50Mixing the carbon black with the grain size of 40 mu m, the first melting point of 340.3 ℃ and the second melting point of 327.5 ℃) and 100g of carbon black, carrying out die pressing for 20min under the pressure of 20MPa, and sintering under the conditions of firstly heating and then cooling, wherein the method for firstly heating and then cooling comprises the following steps: heating the system to 300 ℃, preserving heat for 4h, heating to 380 ℃, preserving heat for 5h, and cooling toKeeping the temperature at 300 ℃ for 2h, cooling to room temperature, and turning to obtain the polytetrafluoroethylene microporous film with the thickness of 0.22mm and the width of 150 mm.
Example 7
A polytetrafluoroethylene microporous membrane is prepared by the following steps: 1600g of semi-sintered material (preparation example 3) and 400g of polytetrafluoroethylene resin (Dajin M18, powder density 0.40g/L, D)50Mixing the materials with the grain diameter of 40 mu m, the first melting point of 340.3 ℃ and the second melting point of 327.5 ℃, carrying out die pressing for 20min under the pressure of 20MPa, and sintering under the condition of firstly heating and then cooling, wherein the method for firstly heating and then cooling comprises the following steps: and (3) heating the system to 335 ℃, preserving heat for 4h, heating to 380 ℃, preserving heat for 4h, cooling to 335 ℃, preserving heat for 2h, cooling to room temperature, and turning to obtain the polytetrafluoroethylene microporous film with the thickness of 0.22mm and the width of 150 mm.
Example 8
A microporous polytetrafluoroethylene membrane differing from example 1 only in that the fully sintered material obtained in preparation example 2 was used in place of the fully sintered material obtained in preparation example 1, and the other components, amounts and preparation methods were the same as in example 6.
Comparative example 1
A polytetrafluoroethylene microporous membrane, the method of polytetrafluoroethylene microporous membrane comprising: 2000g of polytetrafluoroethylene resin (Dajin M18) is molded for 20min under the molding pressure of 20MPa, and is sintered under the condition of firstly heating and then cooling, wherein the method for firstly heating and then cooling comprises the following steps: and (3) heating the system to 300 ℃, preserving heat for 4h, heating to 380 ℃, preserving heat for 4h, cooling to 300 ℃, preserving heat for 4h, cooling to room temperature, and turning to obtain the polytetrafluoroethylene microporous film with the thickness of 0.22mm and the width of 150 mm.
Comparative example 2
A polytetrafluoroethylene microporous film which was different from example 1 only in that the amount of the completely sintered material was 2000g, no polytetrafluoroethylene resin was added, and the other components, amounts and preparation methods were the same as example 1.
Comparative example 3
A polytetrafluoroethylene microporous film was distinguished from example 1 only in that the amount of the completely sintered material was 1900g, the amount of the polytetrafluoroethylene resin was 100g, and the other components, amounts and preparation methods were the same as in example 1.
Comparative example 4
A polytetrafluoroethylene microporous membrane which differs from example 1 only in that the amount of the completely sintered material was 400g, the amount of the polytetrafluoroethylene resin was 1600g, and the other components, amounts and preparation methods were the same as example 1.
And (3) performance testing:
(1) gas flux: testing according to QCT979-2014 test standard;
the testing steps comprise: and installing the cut test sample in a clamping device, installing the clamping device in a closed metal tank, wherein one end of the metal tank is connected with an air tightness tester, and the other end of the metal tank is connected with a gas collecting device by using an air pipe. The gas was collected using a drainage method to test the volume V and the time T required to collect the gas was recorded.
The gas flux of the film was calculated as follows:
wherein K represents the average ventilation flow rate, mL/(cm)2Min); v represents the volume of gas collected, mL;
a represents an effective area, cm2(ii) a T represents the gas collection time, min.
(2) Water pressure resistance: testing according to QCT979-2014 test standard;
installing the cut test sample in a clamping device, and adding a water column with the height of 10mm into a clamp; one end of the clamping device is connected with the air tightness tester; testing the pressure of water drop exudation within 1min under stable air pressure; the initial pressure of the test is 30kPa, and if no water seeps out in each test, the pressure is increased by 1kPa until water seeps out; five samples were tested, and the minimum non-water-seepage air pressure was taken as the test result.
(3) Pore size distribution: testing according to GB/T32361-2015 standard;
wetting of the test samples with a low surface tension liquid ensures that all pores are filled with wetting liquid. The sample was mounted on a jig and vented to increase the gas pressure in steps. As the gas pressure increases, the surface tension of the liquid is overcome until the liquid is drained from the pores, and the relationship between gas pressure and gas flow during this process is recorded, referred to as the "wet" curve. After all the liquid is discharged, recording the relation between the gas pressure and the gas flow, and calling a dry curve; the average pore diameter can be calculated by a dry curve and a wet curve.
(4) Thickness: mechanical gauges measure film thickness.
(5) Density: instead of the sintered cylindrical billet density, the mass of the sintered billet can be divided by the billet volume (calculated from the billet inner diameter, outer diameter and height).
(6) Shrinkage rate: cutting the film into sample pieces with length of about 10cm and width of 1cm, and measuring with ruler to obtain accurate length L0(ii) a Placing in an oven at 200 deg.C for 10min, taking out, and cooling to room temperature. Measuring the length L of the film by a ruler; according to the shrinkage factor of (L-L)0)/L0Calculating the multiplied by 100 percent;
(7) tensile strength: the test was performed according to ASTM D461-87.
The polytetrafluoroethylene microporous films obtained in examples 1 to 8 and comparative examples 1 to 4 were tested according to the above test method, and the test results are shown in table 1:
TABLE 1
As can be seen from the data in table 1: the polytetrafluoroethylene microporous film provided by the invention has excellent mechanical strength and air permeability.
Specifically, the gas flux of the microporous polytetrafluoroethylene film provided in examples 1 to 8 is 80 to 1200mL/min/cm2@7 Kpa; average pore diameter0.5 to 6 μm; a density of 0.7 to 1.7 g/cc; the water pressure resistance is 10 to more than 40 kPa; the thickness is 0.22 mm; the shrinkage rates are all less than 3 percent; the tensile strength is 4.2-17.8 MPa.
Comparing example 1 with comparative example 1, it can be seen that, in the polytetrafluoroethylene microporous membrane directly sintered with polytetrafluoroethylene resin (comparative example 1), neither the gas flux nor the pore size can be measured (shown as n.d.), indicating that the gas permeability is poor.
Comparing example 1, comparative example 2 and comparative example 3, it can be seen that the gas flux of the polytetrafluoroethylene microporous film prepared using 100% of the fully sintered material (comparative example 2) or a large amount of the fully sintered material (comparative example 3) is high, but the water pressure resistance and the tensile strength are both lowered. Comparing example 1 with comparative example 4, it can be seen that, when the amount of the fully sintered material is too low, the gas flux and the average pore diameter of the prepared polytetrafluoroethylene microporous membrane cannot be measured (shown as n.d.), indicating that the permeability is poor.
Further comparing examples 1-5, it can be found that by adjusting the ratio of the fully sintered material to the polytetrafluoroethylene resin, the air permeability, water resistance and mechanical properties of the product can be adjusted to obtain a product suitable for the application of the breathable film; when the ratio of the amount of the completely sintered material to the amount of the polytetrafluoroethylene resin is lower than a predetermined value (example 4), the prepared polytetrafluoroethylene microporous film has poor air permeability; on the contrary, when the ratio of the amount of the completely sintered material to the amount of the polytetrafluoroethylene resin is higher than the predetermined value (example 5), the tensile strength of the microporous polytetrafluoroethylene film obtained is poor.
Comparing example 1 with example 7, it can be found that the air permeability, water resistance and mechanical properties of the prepared polytetrafluoroethylene microporous film can be further improved by adding a filler.
Comparing example 1 and example 8, it can be seen that the particle size and particle size distribution of the fully pre-sintered material have a significant effect on the air permeability and water resistance of the article; the larger the particle size of the completely sintered material is, the larger the pores of the prepared polytetrafluoroethylene microporous film are, the better the air permeability is, but the poorer the water resistance is.
The applicant states that the present invention is illustrated by the above examples to a polytetrafluoroethylene microporous membrane and its preparation method and application, but the present invention is not limited to the above process steps, i.e. it is not meant that the present invention must rely on the above process steps to be carried out. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific modes and the like, which are within the scope and disclosure of the present invention, are contemplated by the present invention.
Claims (10)
1. The polytetrafluoroethylene microporous film is characterized by comprising the following raw materials in parts by weight: 20-100 parts of sintering material and 10-40 parts of first polytetrafluoroethylene resin;
the sintering material is obtained by presintering the second polytetrafluoroethylene resin.
2. The microporous polytetrafluoroethylene membrane according to claim 1, wherein the mass ratio of the sintering material to the first polytetrafluoroethylene resin is 1 (0.2-2.5), preferably 1 (0.2-0.4);
preferably, the powder density of the first polytetrafluoroethylene resin and the powder density of the second polytetrafluoroethylene resin are respectively 350-450 g/L, and more preferably 350-400 g/L;
preferably, D of the first polytetrafluoroethylene resin and the second polytetrafluoroethylene resin50The particle diameters are 10 to 100 μm, preferably 20 to 30 μm;
preferably, the first melting point of the first polytetrafluoroethylene resin and the first melting point of the second polytetrafluoroethylene resin are respectively 340-350 ℃;
preferably, the second melting points of the first polytetrafluoroethylene resin and the second polytetrafluoroethylene resin are respectively 320-330 ℃;
preferably, the shrinkage rates of the first polytetrafluoroethylene resin and the second polytetrafluoroethylene resin are each independently less than 5%, and more preferably less than 3%.
3. Polytetrafluoroethylene microporous membrane according to claim 1 or 2, characterised in that the sinter charge comprises a fully sintered charge and/or a semi-sintered charge;
preferably, the pre-sintering temperature is 340-380 ℃;
preferably, the pre-sintering time is 2-10 h.
4. The microporous polytetrafluoroethylene membrane according to any one of claims 1 to 3, wherein the microporous polytetrafluoroethylene membrane is prepared from raw materials further comprising a filler;
preferably, the content of the filler in the raw materials for preparing the polytetrafluoroethylene microporous film is 5-20 parts by weight;
preferably, the filler comprises silica and/or graphite;
preferably, the filler further comprises a meltable fluoropolymer;
preferably, the melt-fluoropolymer comprises any one or a combination of at least two of polyvinyl fluoride, fluorinated ethylene propylene copolymer or FPA resin.
5. A method for preparing a microporous polytetrafluoroethylene film according to any one of claims 1 to 4, comprising: and mixing, molding, sintering and turning the sintering material and the first polytetrafluoroethylene resin to obtain the polytetrafluoroethylene microporous film.
6. The method of claim 5, further comprising a screening step after the mixing.
7. The production method according to claim 5 or 6, wherein the pressure of the molding is 8 to 30MPa, preferably 10 to 20 MPa;
preferably, the time for the die pressing is 5-50 min, preferably 10-30 min.
8. The production method according to any one of claims 5 to 7, wherein the sintering is performed under a condition of temperature reduction after temperature increase;
the method for heating and cooling comprises the following steps: and heating the system to 300-335 ℃, preserving heat for 2-4 h, heating to 350-390 ℃, preserving heat for 4-6 h, cooling to 300-335 ℃, preserving heat for 2-4 h, cooling to room temperature, and carrying out the next operation.
9. The production method according to any one of claims 5 to 8, characterized by comprising: mixing the sintering material with first polytetrafluoroethylene resin, screening, pressing for 5-50 min under the pressure of 8-30 MPa, sintering under the conditions of first temperature rise and then temperature reduction, and turning to obtain the microporous film; the method for heating and cooling comprises the following steps: and heating the system to 300-335 ℃, preserving heat for 2-4 h, heating to 350-390 ℃, preserving heat for 4-6 h, cooling to 300-335 ℃, preserving heat for 2-4 h, cooling to room temperature, and carrying out the next operation.
10. Use of the microporous polytetrafluoroethylene film according to any one of claims 1 to 4 in breathable components, packaging cover patches or waterproof breathable films for LED vehicle lamps.
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