CN115957562B - Composite filter material and preparation method thereof - Google Patents
Composite filter material and preparation method thereof Download PDFInfo
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- CN115957562B CN115957562B CN202211564920.7A CN202211564920A CN115957562B CN 115957562 B CN115957562 B CN 115957562B CN 202211564920 A CN202211564920 A CN 202211564920A CN 115957562 B CN115957562 B CN 115957562B
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- 239000000463 material Substances 0.000 title claims abstract description 39
- 239000002131 composite material Substances 0.000 title claims abstract description 25
- 238000002360 preparation method Methods 0.000 title abstract description 11
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims abstract description 86
- 239000004810 polytetrafluoroethylene Substances 0.000 claims abstract description 86
- VYFYYTLLBUKUHU-UHFFFAOYSA-N dopamine Chemical compound NCCC1=CC=C(O)C(O)=C1 VYFYYTLLBUKUHU-UHFFFAOYSA-N 0.000 claims abstract description 58
- 239000012528 membrane Substances 0.000 claims abstract description 43
- 239000011148 porous material Substances 0.000 claims abstract description 40
- 229960003638 dopamine Drugs 0.000 claims abstract description 29
- 230000004048 modification Effects 0.000 claims abstract description 24
- 238000012986 modification Methods 0.000 claims abstract description 24
- 238000000034 method Methods 0.000 claims description 24
- 238000003490 calendering Methods 0.000 claims description 19
- 238000005238 degreasing Methods 0.000 claims description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 14
- 238000002156 mixing Methods 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 9
- 238000000643 oven drying Methods 0.000 claims description 7
- 239000011347 resin Substances 0.000 claims description 7
- 229920005989 resin Polymers 0.000 claims description 7
- 239000011248 coating agent Substances 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 4
- 239000000758 substrate Substances 0.000 claims description 4
- 230000001476 alcoholic effect Effects 0.000 claims description 2
- 239000000243 solution Substances 0.000 claims 3
- 239000007864 aqueous solution Substances 0.000 claims 1
- 230000008595 infiltration Effects 0.000 claims 1
- 238000001764 infiltration Methods 0.000 claims 1
- 238000004140 cleaning Methods 0.000 abstract description 3
- 230000007547 defect Effects 0.000 abstract description 3
- 239000002585 base Substances 0.000 description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 21
- 229920001690 polydopamine Polymers 0.000 description 20
- 239000004745 nonwoven fabric Substances 0.000 description 16
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 15
- 239000000843 powder Substances 0.000 description 15
- 239000002994 raw material Substances 0.000 description 15
- 230000008569 process Effects 0.000 description 12
- 239000010410 layer Substances 0.000 description 11
- 229920004933 Terylene® Polymers 0.000 description 10
- 239000003795 chemical substances by application Substances 0.000 description 10
- 238000004132 cross linking Methods 0.000 description 10
- 239000000203 mixture Substances 0.000 description 10
- 239000005020 polyethylene terephthalate Substances 0.000 description 10
- 239000010865 sewage Substances 0.000 description 10
- 238000007493 shaping process Methods 0.000 description 10
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 8
- 230000004907 flux Effects 0.000 description 8
- 239000000126 substance Substances 0.000 description 7
- 239000012752 auxiliary agent Substances 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 238000001125 extrusion Methods 0.000 description 6
- 238000006116 polymerization reaction Methods 0.000 description 6
- 238000005507 spraying Methods 0.000 description 6
- 230000006835 compression Effects 0.000 description 5
- 238000007906 compression Methods 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- 238000001514 detection method Methods 0.000 description 5
- 238000007599 discharging Methods 0.000 description 5
- 238000010030 laminating Methods 0.000 description 5
- 238000003475 lamination Methods 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 238000005096 rolling process Methods 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 229920000295 expanded polytetrafluoroethylene Polymers 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 239000003350 kerosene Substances 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 238000010170 biological method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000003208 petroleum Substances 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 239000007888 film coating Substances 0.000 description 2
- 238000009501 film coating Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000012982 microporous membrane Substances 0.000 description 2
- 230000001699 photocatalysis Effects 0.000 description 2
- 238000007146 photocatalysis Methods 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- -1 Polytetrafluoroethylene Polymers 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000001471 micro-filtration Methods 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 102000004169 proteins and genes Human genes 0.000 description 1
- 108090000623 proteins and genes Proteins 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 150000003384 small molecules Chemical class 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
- Y02A50/2351—Atmospheric particulate matter [PM], e.g. carbon smoke microparticles, smog, aerosol particles, dust
Landscapes
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention discloses a composite filter material and a preparation method thereof, wherein the filter material is a multi-layer composite membrane and at least comprises a base material and a hydrophilic modified PTFE porous material compounded on the base material, wherein the hydrophilic modified PTFE porous material is prepared by taking a porous PTFE membrane as a main body, and sequentially carrying out dopamine modification and PVA modification, and the dopamine modification is a first modified membrane. The film product has good structural performance, effectively overcomes the defect of poor combination of PTFE films, and realizes a product with stable structure and cleaning resistance.
Description
Technical Field
The invention relates to a PTFE composite filter material suitable for water treatment, in particular to a composite filter material and a preparation method thereof.
Background
Along with the rapid expansion of manufacturing industry and the frequent occurrence of the sewage substandard discharge accidents of chemical enterprises, the discharge of heavy metal ions, organic dyes and sewage containing toxic and harmful organic matters has seriously threatened the ecological system and human health. In addition, the problem of global water resource shortage is also becoming more serious, and how to treat sewage efficiently becomes a problem that sewage discharge enterprises have to face.
The traditional sewage treatment method mainly comprises a biological method, an electrolytic method, a chemical method and a photocatalysis method. The biological method has large occupied area, narrow application range and unsatisfactory effect; although the electrolytic method has better effect than the biological method, the energy consumption is large and the popularization is difficult; the chemical method is easy to cause secondary pollution while decomposing pollutants, organic matters cannot be completely converted into nontoxic and harmless small molecules, and the photocatalysis method is one of methods for carrying out substance conversion by utilizing light energy, can degrade organic matter macromolecules into carbon dioxide or other small molecular organic matters and water, has low cost and no secondary pollution, but has the problem of lower light quantum efficiency and light activity. Besides, the sewage treatment method in the prior art has the defects of more or less expensive special equipment, high energy consumption, difficult recovery, separation and recycling and high operation cost, and is particularly a heavy burden for small enterprises.
The membrane separation technology has the advantages of low energy consumption, low oil content of effluent, high separation efficiency and recoverable concentrated solution, and is considered as a new technology with the most potential in the field of sewage treatment. However, the sewage treatment membrane material in the prior art has the problems of single function, easiness in pollution, low service life, and corrosion caused by corrosive sewage, and the membrane is often corroded, so that the working quality and the working efficiency are greatly reduced.
Polytetrafluoroethylene (PTFE) was synthesized in the united states in the 30 s of the 20 th century, has excellent chemical stability, aging resistance, high and low temperature resistance, lubricity, non-tackiness, electrical insulation, radiation resistance, and the like, enjoys the reputation of "plastic king", and has wide application in the fields of chemical industry, textile industry, papermaking, aerospace, petroleum, construction, food, medicine, machinery, and marine operation. In the 70 s of the 20 th century, the Gore company in the United states developed a PTFE biaxially oriented microporous membrane by using a biaxially oriented technology, and the conventional PTFE microporous membrane has a pore diameter of 0.1-10 microns and a porosity of more than 75%, is an excellent separation filter material, and is widely applied to the field of air filtration;
because the surface energy of the PTFE material is relatively low, the contact angle of water is between 120 and 140 degrees, so that water is difficult to pass through the micropores of the ePTFE, and meanwhile, the thickness of the ePTFE film is generally between 1 and 100 microns, so that the PTFE material is soft, has poor mechanical strength and is limited in application in the water treatment industry.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.
Disclosure of Invention
The invention aims to provide a composite filter material and a preparation method thereof, which solve the problems of poor acid and alkali resistance and salt resistance and low service life of the existing water treatment membrane by utilizing an ePTFE composite micro-filtration membrane with higher filtration precision, mechanical strength and water flux and a production process.
To achieve the above object, an embodiment of the present invention provides a composite filter material, which is a multi-layer composite membrane, and at least includes a substrate and a hydrophilically modified PTFE porous material composited onto the substrate, wherein the hydrophilically modified PTFE porous material is obtained by using the porous PTFE membrane as a main body and sequentially performing dopamine modification and PVA modification, and wherein the dopamine modification results in a first modified membrane (note that the two modifications are not necessarily adjacent).
In one or more embodiments of the present invention, dopamine is modified to submerge the infiltrated porous PTFE membrane in 0.3-1wt.% aqueous dopamine solution under first treatment conditions, and then dried to obtain a first modified membrane, where the first treatment conditions satisfy: the pH of the solution is 7.5-10 (dopamine is easy to undergo self-polymerization reaction in weak alkaline environment), the temperature is 25-30 ℃ and the time is 1-3min.
In one or more embodiments of the present invention, the drying is at a temperature of 60-80 ℃ for 3-5min.
In one or more embodiments of the invention, PVA is modified to be coated with a PVA alcoholic solution having a concentration of 3 to 4.5wt.% of pH3 to 4 on a first modified film and dried under the following coating conditions: the PVA alcohol solution has a coating weight of 20-60g/m 2 Standing for 5-10 min.
In one or more embodiments of the present invention, the drying is: oven drying at 50deg.C for 3-5min.
In one or more embodiments of the present invention, the porous PTFE membrane is obtained by mixing and curing a PTFE resin having a molecular weight of 800 to 1000 ten thousand, preforming, pressing, calendaring, degreasing, and then performing pore-forming by a first stretching and a second stretching, wherein the stretching directions of the first stretching and the second stretching are not identical. Preferably, the pushing is performed by extruding the preform at a rate of 1-3m/min and a pressure of 5-10 MPa. Further preferably, the pressing temperature is 50℃and the compression ratio is 75-85. Preferably, the calendering conditions are: the calendaring speed is 2.5m/min, the temperature is 53 ℃, and the thickness of the film baseband after extrusion is 0.2mm
In one or more embodiments of the invention, the conditions for the first stretching are: the stretching temperature is 260-300 ℃, the stretching speed is 1.5-3m/min, and the stretching multiplying power is 5-8 times.
In one or more embodiments of the invention, the conditions for the second stretching are: the stretching temperature is 260-300 ℃, the stretching speed is 1.5-3m/min, and the stretching multiplying power is 9-14 times.
In one or more embodiments of the present invention, a method of preparing a composite filter includes the steps of: A. preparing a base material and a porous PTFE film, wherein the porous PTFE film is obtained by pore-forming of a PTFE base film through first stretching and second stretching, and the stretching directions of the first stretching and the second stretching are inconsistent; B. the porous PTFE membrane is soaked by alcohol, and then is subjected to dopamine modification and PVA modification to obtain a hydrophilic modified PTFE porous material; C. the hydrophilic modified PTFE porous material is compounded with the base material.
In the implementation process of the scheme of the invention, the composite filter material comprising the composite filter material can be used for equipment or systems such as a water purifier, a sewage filtering device and the like.
Compared with the prior art, the composite filter material and the preparation method thereof according to the embodiment of the invention have good uniformity of the composite membrane, the average pore size is 0.1 mu m, the maximum pore size is not more than 0.15 mu m, and the retention rate is more than 99.0% under the filtration pressure difference of 13.3-26.6 kPa. The bubble point method tests that 90% of the pores have a diameter of less than 0.09 μm.
The composite membrane (ePTFE membrane) after surface hydrophilic treatment effectively reduces the surface water contact angle from 134 degrees to 33 degrees, improves the water flux, and ensures that the pure water flux is reduced from 0.5L/(m) under the pressure of 0.3MPa 2 * h) Lifting to 140-320L/(m) 2 *h)。
On the basis that PTFE has extremely strong corrosion resistance, the modified PVA is introduced to carry out hydrophilic modification, so that the protein pollution resistance is improved: adsorption rate of BSA is from 30g/m 2 Reduced to 7.4g/m 2 。
Meanwhile, the composite film of the invention effectively improves the combination property of the product through optimization, and has high film coating fastness and strength reaching 0.6MPa.
The composite membrane has good structural performance, effectively overcomes the defect of poor combination of PTFE films, and realizes a product with stable structure and cleaning resistance. Compared with a single-layer film material, the rupture strength of the non-woven fabric filter paper reaches 1.2-2.5MPa, and meanwhile, the film coating fastness can reach 0.6MPa, so that the structure can be maintained stable in the process of back flushing and cleaning, and the service life is long.
Detailed Description
The following describes specific embodiments of the present invention in detail with reference to examples, but it should be understood that the scope of the present invention is not limited by the specific embodiments.
Throughout the specification and claims, unless explicitly stated otherwise, the term "comprise" or variations thereof such as "comprises" or "comprising", etc. will be understood to include the stated element or component without excluding other elements or components.
Example 1
Step one, selecting a base material: nonwoven fabric
Materials: terylene
Gram weight: 130gsm
Minimum burst strength: 1.2MPa
Tensile strength: 510N/5cm
Step two, PTFE membrane preparation process flow:
raw material selection: PTFE resin powder having a molecular weight of 800 ten thousand was selected, and the particle diameter was 10. Mu.m.
And (3) mixing and curing: PTFE powder and aviation kerosene are mixed according to a proportion (the mass ratio is 100:10), and the mixture is placed for 12 hours at 40 ℃ after the mixing is finished, so that the raw materials are more uniform, the auxiliary agent is absorbed more fully, and the uniformity of the performance and the uniformity of the appearance of the extruded molded product are ensured.
The auxiliary agent is an organic solvent which is easy to wet and absorb, easy to diffuse, free from chemical change, easy to volatilize and free from residue after volatilization, such as petroleum ether, 120# solvent oil, aviation kerosene and the like.
Preforming: and (3) placing the cured raw materials into a cylinder barrel, extruding at the pressure of 6MPa and 15m/min, and discharging air between the powder materials to form a compact columnar blank.
Pushing: the preform was fed into an extruder for extrusion, the die shape was circular, the rate was 1m/min, and the pressure was 5MPa.
Calendering: the rod blank is pressed into a film base band by a double-roller calender, the calendering speed is 2.5m/min, the temperature is 53 ℃, and the thickness of the pressed film base band is 0.2mm.
Degreasing: degreasing the base band by using a roller at 180 ℃ to obtain a dry film, wherein the degreasing purpose is to volatilize, remove and recycle auxiliary oil in the calendaring base band.
Stretching in the longitudinal direction: stretching the dried film in the length direction to pore the porous film to obtain a longitudinal stretched film: stretching temperature 260 ℃, stretching speed 1.5m/min and stretching multiplying power 5 times.
And (5) transverse drawing and shaping: the longitudinal drawn film is stretched in the width direction (the conditions are that the stretching temperature is 260 ℃, the stretching speed is 1.5m/min, and the stretching multiplying power is 9 times), a porous film with high porosity and uniform pore diameter is formed, and then the porous PTFE film with stable structure size is prepared through shaping treatment at 280 ℃.
Step three, hydrophilic treatment
The porous PTFE membrane was sprayed with absolute ethanol to completely wet it.
3g of dopamine was dissolved in 1L of pure water, and the pH was adjusted to 7.5 by adding a small amount of NaOH (dopamine readily undergoes self-polymerization in a weakly alkaline environment).
Immersing the wetted PTFE membrane in a dopamine solution, keeping the temperature at 25 ℃, and taking out after 1 min.
Oven drying at 60deg.C for 3min with air blower. The hydrophilic treatment of the polydopamine layer is completed, and the polydopamine layer provides a platform for the next PVA molecule to be subjected to cross-linking reaction while improving the water flux.
30g of PVA was dissolved in 1L of absolute ethanol, and the mixture was heated to 80℃with stirring to completely dissolve the PVA, thereby obtaining a hydrophilic agent. Cooling to 30deg.C, and standing for 25min.
The PH is regulated to 3 by dilute sulfuric acid (because polydopamine is easy to fall off in alkaline environment), the prepared hydrophilic agent is sprayed on the PTFE membrane by adopting a spraying process, and the dosage is 20g/m 2 Standing for 5 minutes, and crosslinking PVA on a secondary platform built by polydopamine.
And drying the sprayed film for 3min at 50 ℃ to finish PVA hydrophilic modification treatment, thus obtaining the hydrophilic modified PTFE porous material.
Step four, hydrophilic modified PTFE porous material and non-woven fabric filter paper covering process flow:
the terylene non-woven fabric filter paper and the hydrophilically modified PTFE porous material which is hydrophilically treated are unreeled on a laminating machine. The filter paper and the film were simultaneously laminated at a speed of 300m/h by passing through a heated roll at 220℃under a lamination pressure of 2kg. And (5) rolling and film forming detection.
Example 2
Step one, selecting a base material: nonwoven fabric
Materials: terylene
Gram weight: 180gsm
Minimum burst strength: 1.5MPa
Tensile strength: 510N/5cm
Step two, PTFE membrane preparation process flow:
raw material selection: PTFE resin powder having a molecular weight of 850 ten thousand was selected, and the particle diameter was 30. Mu.m.
And (3) mixing and curing: PTFE powder and aviation kerosene are mixed according to a proportion (the mass ratio is 100:13), and the mixture is placed for 12 hours at 40 ℃ after the mixing is finished, so that the raw materials are more uniform, the auxiliary agent is absorbed more fully, and the uniformity of the performance and the uniformity of the appearance of the extruded molded product are ensured.
Preforming: and (3) placing the cured raw materials into a cylinder barrel, extruding at the pressure of 6.5MPa and the pressure of 20m/min, and discharging air between the powder materials to form a compact columnar blank.
Pushing: the preform was fed into an extruder for extrusion, the die shape was circular, the diameter was 16mm, the compression ratio was 75, the temperature was 50 ℃, the rate was 1.5m/min, and the pressure was 6MPa.
Calendering: the rod blank is pressed into a film base band by a double-roller calender, the calendering speed is 2.5m/min, the temperature is 53 ℃, and the thickness of the pressed film base band is 0.2mm.
Degreasing: degreasing the base band by using a roller at 180 ℃ to obtain a dry film, wherein the degreasing purpose is to volatilize, remove and recycle auxiliary oil in the calendaring base band.
Stretching in the longitudinal direction: stretching the dried film in the length direction to pore the porous film to obtain a longitudinal stretched film: stretching temperature 270 ℃, stretching speed 2.3m/min and stretching multiplying power 6 times.
And (5) transverse drawing and shaping: the longitudinal drawn film is stretched in the width direction (the conditions are that the stretching temperature is 270 ℃, the stretching speed is 1.7m/min, and the stretching multiplying power is 10 times), a porous film with high porosity and uniform pore diameter is formed, and the porous PTFE film with stable structure size is prepared by shaping treatment at 290 ℃.
Step three, hydrophilic treatment
The porous PTFE membrane was sprayed with absolute ethanol to completely wet it.
5g of dopamine was dissolved in 1L of pure water, and the pH was adjusted to 8.5 by adding a small amount of NaOH (dopamine readily undergoes self-polymerization in a weakly alkaline environment).
Immersing the wetted PTFE membrane in a dopamine solution, keeping the temperature at 26 ℃, and taking out after 1.5 min.
Oven-drying at 65deg.C for 3.5min. The hydrophilic treatment of the polydopamine layer is completed, and the polydopamine layer provides a platform for the next PVA molecule to be subjected to cross-linking reaction while improving the water flux.
35g of PVA was dissolved in 1L of absolute ethanol, and the mixture was heated to 80℃with stirring to completely dissolve the PVA, thereby obtaining a hydrophilic agent. Cooling to 33deg.C, and standing for 25min.
The PH is regulated to 3.5 by dilute sulfuric acid (because polydopamine is easy to fall off in alkaline environment), the prepared hydrophilic agent is sprayed on the PTFE membrane by adopting a spraying process, and the dosage is 30g/m 2 Standing for 7 minutes, and crosslinking PVA on a secondary platform built by polydopamine.
And drying the sprayed film at 50 ℃ for 3.5min to finish PVA hydrophilic modification treatment, thus obtaining the hydrophilic modified PTFE porous material.
Step four, hydrophilic modified PTFE porous material and non-woven fabric filter paper covering process flow:
the terylene non-woven fabric filter paper and the hydrophilically modified PTFE porous material which is hydrophilically treated are unreeled on a laminating machine. The filter paper and the film were simultaneously laminated at a speed of 350m/h by passing through a heated roll at 230℃under a lamination pressure of 3kg. And (5) rolling and film forming detection.
Example 3
Step one, selecting a base material: nonwoven fabric
Materials: terylene
Gram weight: 200gsm
Minimum burst strength: 1.8MPa
Tensile strength: 510N/5cm
Step two, PTFE membrane preparation process flow:
raw material selection: a PTFE resin powder having a molecular weight of 900 ten thousand was selected, and the particle diameter was 50. Mu.m.
And (3) mixing and curing: PTFE powder and aviation kerosene are mixed according to a proportion (the mass ratio is 100:15), and the mixture is placed for 12 hours at 40 ℃ after the mixing is finished, so that the raw materials are more uniform, the auxiliary agent is absorbed more fully, and the uniformity of the performance and the uniformity of the appearance of the extruded molded product are ensured.
Preforming: and (3) placing the cured raw materials into a cylinder barrel, extruding at 7MPa and 25m/min, and discharging air between the powder materials to form a compact columnar blank.
Pushing: the preform was fed into an extruder for extrusion, the die shape was circular, the diameter was 16mm, the compression ratio was 80, the temperature was 50 ℃, the rate was 2m/min, and the pressure was 8MPa.
Calendering: the rod blank is pressed into a film base band by a double-roller calender, the calendering speed is 2.5m/min, the temperature is 53 ℃, and the thickness of the pressed film base band is 0.2mm.
Degreasing: degreasing the base band by using a roller at 180 ℃ to obtain a dry film, wherein the degreasing purpose is to volatilize, remove and recycle auxiliary oil in the calendaring base band.
Stretching in the longitudinal direction: stretching the dried film in the length direction to pore the porous film to obtain a longitudinal stretched film: stretching temperature 280 ℃, stretching speed 2m/min and stretching multiplying power 7 times.
And (5) transverse drawing and shaping: stretching the longitudinal film in the width direction (the conditions are that the stretching temperature is 280 ℃, the stretching speed is 2m/min and the stretching multiplying power is 12 times), forming a porous film with high porosity and uniform pore diameter, and then shaping at 300 ℃ to obtain the porous PTFE film with stable structural dimension.
Step three, hydrophilic treatment
The porous PTFE membrane was sprayed with absolute ethanol to completely wet it.
7g of dopamine was dissolved in 1L of pure water, and the pH was adjusted to 8 by adding a small amount of NaOH (dopamine was easily subjected to self-polymerization in a weakly alkaline environment).
Immersing the wetted PTFE membrane in a dopamine solution, keeping the temperature at 27 ℃, and taking out after 2 min.
Oven drying at 70deg.C for 4min with a blower. The hydrophilic treatment of the polydopamine layer is completed, and the polydopamine layer provides a platform for the next PVA molecule to be subjected to cross-linking reaction while improving the water flux.
37g of PVA was dissolved in 1L of absolute ethanol, and the mixture was heated to 80℃with stirring to completely dissolve the PVA, thereby obtaining a hydrophilic agent. Cooling to 35deg.C, and standing for 25min.
Adjusting pH to 4 with dilute sulfuric acid (due to the fact that polydopamine is easy to fall off in alkaline environment), spraying the obtained hydrophilic agent on PTFE membrane by spraying process at an amount of 40g/m 2 Standing for 8 minutes, and crosslinking PVA on a secondary platform built by polydopamine.
And (3) drying the sprayed film for 4min at 50 ℃ to finish PVA hydrophilic modification treatment, thus obtaining the hydrophilic modified PTFE porous material.
Step four, hydrophilic modified PTFE porous material and non-woven fabric filter paper covering process flow:
the terylene non-woven fabric filter paper and the hydrophilically modified PTFE porous material which is hydrophilically treated are unreeled on a laminating machine. The filter paper and the film were simultaneously laminated at a speed of 400m/h by passing through a heated roll at 235℃under a lamination pressure of 3kg. And (5) rolling and film forming detection.
Example 4
Step one, selecting a base material: nonwoven fabric
Materials: terylene
Gram weight: 240gsm
Minimum burst strength: 2.2MPa
Tensile strength: 510N/5cm
Step two, PTFE membrane preparation process flow:
raw material selection: PTFE resin powder having a molecular weight of 950 ten thousand was selected, and the particle diameter was 80. Mu.m.
And (3) mixing and curing: PTFE powder and petroleum ether are mixed according to a proportion (the mass ratio is 100:18), and the mixture is placed for 12 hours at 40 ℃ after the mixing is finished, so that the raw materials are more uniform, the auxiliary agent is absorbed more fully, and the uniformity of the performance and the uniformity of the appearance of the extruded molded product are ensured.
Preforming: and (3) placing the cured raw materials into a cylinder barrel, extruding at 7.5MPa and 22m/min, and discharging air between the powder materials to form a compact columnar blank.
Pushing: the preform was fed into an extruder for extrusion, the die shape was circular, the diameter was 16mm, the compression ratio was 82, the temperature was 50 ℃, the rate was 2.5m/min, and the pressure was 9MPa.
Calendering: the rod blank is pressed into a film base band by a double-roller calender, the calendering speed is 2.5m/min, the temperature is 53 ℃, and the thickness of the pressed film base band is 0.2mm.
Degreasing: degreasing the base band by using a roller at 180 ℃ to obtain a dry film, wherein the degreasing purpose is to volatilize, remove and recycle auxiliary oil in the calendaring base band.
Stretching in the longitudinal direction: stretching the dried film in the length direction to pore the porous film to obtain a longitudinal stretched film: stretching temperature is 290 ℃, stretching speed is 2.5m/min, and stretching multiplying power is 8 times.
And (5) transverse drawing and shaping: stretching the longitudinal film in the width direction (the conditions are that the stretching temperature is 290 ℃, the stretching speed is 2.5m/min, and the stretching multiplying power is 13 times), forming a porous film with high porosity and uniform pore diameter, and then shaping at 310 ℃ to obtain the porous PTFE film with stable structure and size.
Step three, hydrophilic treatment
The porous PTFE membrane was sprayed with absolute ethanol to completely wet it.
9g of dopamine was dissolved in 1L of pure water, and the pH was adjusted to 9 by adding a small amount of NaOH (dopamine readily undergoes self-polymerization in a weakly alkaline environment).
Immersing the wetted PTFE membrane in a dopamine solution, keeping the temperature at 29 ℃, and taking out after 2.5 min.
Oven-drying at 75deg.C for 4.5min. The hydrophilic treatment of the polydopamine layer is completed, and the polydopamine layer provides a platform for the next PVA molecule to be subjected to cross-linking reaction while improving the water flux.
40g of PVA was dissolved in 1L of absolute ethanol, and the mixture was heated to 80℃with stirring to completely dissolve the PVA, thereby obtaining a hydrophilic agent. Cooling to 38deg.C, and standing for 25min.
The PH is regulated to 3 by dilute sulfuric acid (because polydopamine is easy to fall off in alkaline environment), the prepared hydrophilic agent is sprayed on the PTFE membrane by adopting a spraying process, and the dosage is 50g/m 2 Standing for 9 minutes, and crosslinking PVA on a secondary platform built by polydopamine.
And drying the sprayed film at 50 ℃ for 4.5min to finish PVA hydrophilic modification treatment, thus obtaining the hydrophilic modified PTFE porous material.
Step four, hydrophilic modified PTFE porous material and non-woven fabric filter paper covering process flow:
the terylene non-woven fabric filter paper and the hydrophilically modified PTFE porous material which is hydrophilically treated are unreeled on a laminating machine. The filter paper and the film were simultaneously laminated at a speed of 450m/h by passing through a heated roll at 240℃under a lamination pressure of 4kg. And (5) rolling and film forming detection.
Example 5
Step one, selecting a base material: nonwoven fabric
Materials: terylene
Gram weight: 260gsm
Minimum burst strength: 2.5MPa
Tensile strength: 510N/5cm
Step two, PTFE membrane preparation process flow:
raw material selection: PTFE resin powder having a molecular weight of 1000 ten thousand was selected, and the particle diameter was 100. Mu.m.
And (3) mixing and curing: PTFE powder and 120# solvent oil are mixed according to a proportion (the mass ratio is 100:20), and the mixture is placed for 12 hours at 40 ℃ after the mixing is finished, so that the raw materials are more uniform, the auxiliary agent is absorbed more fully, and the uniformity of the performance and the uniform appearance of the extruded molded product are ensured.
Preforming: and (3) placing the cured raw materials into a cylinder barrel, extruding at 8MPa and 30m/min, and discharging air between the powder materials to form a compact columnar blank.
Pushing: the preform was fed into an extruder for extrusion, the die shape was circular, the diameter was 16mm, the compression ratio was 85, the temperature was 50 ℃, the rate was 3m/min, and the pressure was 10MPa.
Calendering: the rod blank is pressed into a film base band by a double-roller calender, the calendering speed is 2.5m/min, the temperature is 53 ℃, and the thickness of the pressed film base band is 0.2mm.
Degreasing: degreasing the base band by using a roller at 180 ℃ to obtain a dry film, wherein the degreasing purpose is to volatilize, remove and recycle auxiliary oil in the calendaring base band.
Stretching in the longitudinal direction: stretching the dried film in the length direction to pore the porous film to obtain a longitudinal stretched film: stretching temperature 300 ℃, stretching speed 3m/min and stretching multiplying power 6 times.
And (5) transverse drawing and shaping: stretching the longitudinal film in the width direction (the conditions are that the stretching temperature is 300 ℃, the stretching speed is 3m/min and the stretching multiplying power is 14 times), forming a porous film with high porosity and uniform pore diameter, and then shaping at 320 ℃ to obtain the porous PTFE film with stable structural dimension.
Step three, hydrophilic treatment
The porous PTFE membrane was sprayed with absolute ethanol to completely wet it.
10g of dopamine was dissolved in 1L of pure water, and the pH was adjusted to 10 by adding a small amount of NaOH (dopamine was easily subjected to self-polymerization in a weakly alkaline environment).
Immersing the wetted PTFE membrane in a dopamine solution, keeping the temperature at 30 ℃, and taking out after 3min.
Oven drying at 80deg.C with blower for 5min. The hydrophilic treatment of the polydopamine layer is completed, and the polydopamine layer provides a platform for the next PVA molecule to be subjected to cross-linking reaction while improving the water flux.
45g of PVA was dissolved in 1L of absolute ethanol, and the mixture was heated to 80℃with stirring to completely dissolve the PVA, thereby obtaining a hydrophilic agent. Cooling to 40deg.C, and standing for 25min.
Adjustment of P with dilute sulfuric acidH to 4 (because polydopamine is easy to fall off in alkaline environment), the prepared hydrophilic agent is sprayed on PTFE film by adopting a spraying process, and the dosage is 60g/m 2 Standing for 10 minutes, and crosslinking PVA on a secondary platform built by polydopamine.
And drying the sprayed film at 50 ℃ for 5min to finish PVA hydrophilic modification treatment, thus obtaining the hydrophilic modified PTFE porous material.
Step four, hydrophilic modified PTFE porous material and non-woven fabric filter paper covering process flow:
the terylene non-woven fabric filter paper and the hydrophilically modified PTFE porous material which is hydrophilically treated are unreeled on a laminating machine. The filter paper and the film were simultaneously laminated at a speed of 500m/h by passing through a heated roll at 245℃under a lamination pressure of 5kg. And (5) rolling and film forming detection.
Comparative example 1
This comparative example differs from example 1 only in that: the hydrophilic treatment is improved by only dopamine, and the subsequent PVA modification is not adopted.
Comparative example 2
This comparative example differs from example 1 only in that: the hydrophilic treatment is improved by PVA only, and dopamine modification is not used as transition.
The foregoing descriptions of specific exemplary embodiments of the present invention are presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application to thereby enable one skilled in the art to make and utilize the invention in various exemplary embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.
Claims (6)
1. A composite filter material is a multilayer composite film and at least comprises a substrate and hydrophilic modified PTFE compounded on the substrate
The porous material is prepared by taking a porous PTFE membrane as a main body, and sequentially carrying out dopamine modification and PVA modification, wherein the dopamine modification is that the porous PTFE membrane after infiltration treatment is immersed in 0.3-1wt.% of dopamine aqueous solution under a first treatment condition, and then the porous material is dried to obtain a first modified membrane, and the first treatment condition is as follows: the pH of the solution is 7.5-10, the temperature is 25-30 ℃ and the time is 1-3min, the PVA is modified to be that PVA alcohol solution with the concentration of 3-4.5wt.% and the pH of 3-4 is coated on the first modified film and dried, and the coating conditions are as follows: the PVA alcoholic solution has a coating weight of 20-60g/m 2 And standing for 5-10 minutes, wherein the porous PTFE membrane is obtained by mixing and curing PTFE resin with the molecular weight of 800-1000 ten thousand, preforming, pushing, calendaring and degreasing, and then carrying out primary stretching and secondary stretching for pore forming, wherein the stretching directions of the primary stretching and the secondary stretching are inconsistent.
2. The composite filter material of claim 1, wherein the drying is at a temperature of 60-80 ℃ for 3-5min.
3. The composite filter according to claim 1, wherein the drying is: oven drying at 50deg.C for 3-5min.
4. The composite filter of claim 1, wherein the first stretching conditions are: stretching temperature
260-300 ℃, the stretching speed is 1.5-3m/min, and the stretching multiplying power is 5-8 times.
5. The composite filter of claim 1, wherein the conditions for the second stretching are: stretching temperature
260-300 ℃, the stretching speed is 1.5-3m/min, and the stretching multiplying power is 9-14 times.
6. The method for preparing a composite filter according to any one of claims 1 to 5, comprising the steps of:
A. preparing a base material and a porous PTFE film, wherein the porous PTFE film is obtained by pore-forming of a PTFE base film through first stretching and second stretching, and the stretching directions of the first stretching and the second stretching are inconsistent;
B. the porous PTFE membrane is soaked by alcohol, and then is subjected to dopamine modification and PVA modification to obtain a hydrophilic modified PTFE porous material;
C. the hydrophilic modified PTFE porous material is compounded with the base material.
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