CN114011256B - PEI modified PVDF organic solvent-resistant film and preparation method thereof - Google Patents
PEI modified PVDF organic solvent-resistant film and preparation method thereof Download PDFInfo
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- 239000002033 PVDF binder Substances 0.000 title claims abstract description 45
- 229920002981 polyvinylidene fluoride Polymers 0.000 title claims abstract description 45
- 239000003960 organic solvent Substances 0.000 title claims abstract description 39
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 238000006243 chemical reaction Methods 0.000 claims abstract description 20
- 238000000034 method Methods 0.000 claims description 9
- 238000010992 reflux Methods 0.000 claims description 9
- 239000012528 membrane Substances 0.000 abstract description 37
- 238000004090 dissolution Methods 0.000 abstract description 6
- 239000011148 porous material Substances 0.000 abstract description 4
- 239000010408 film Substances 0.000 description 70
- 229920002873 Polyethylenimine Polymers 0.000 description 68
- 239000000243 solution Substances 0.000 description 24
- 238000010438 heat treatment Methods 0.000 description 17
- 230000004048 modification Effects 0.000 description 16
- 238000012986 modification Methods 0.000 description 16
- 230000000694 effects Effects 0.000 description 13
- 238000005260 corrosion Methods 0.000 description 9
- 230000007797 corrosion Effects 0.000 description 9
- 230000014759 maintenance of location Effects 0.000 description 9
- 238000002791 soaking Methods 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 239000011241 protective layer Substances 0.000 description 5
- 239000004693 Polybenzimidazole Substances 0.000 description 4
- 229920002480 polybenzimidazole Polymers 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000002351 wastewater Substances 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000004132 cross linking Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 238000001728 nano-filtration Methods 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- JWUJQDFVADABEY-UHFFFAOYSA-N 2-methyltetrahydrofuran Chemical compound CC1CCCO1 JWUJQDFVADABEY-UHFFFAOYSA-N 0.000 description 2
- 238000012695 Interfacial polymerization Methods 0.000 description 2
- 239000004809 Teflon Substances 0.000 description 2
- 229920006362 Teflon® Polymers 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000008280 blood Substances 0.000 description 2
- 210000004369 blood Anatomy 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000003628 erosive effect Effects 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- NOWKCMXCCJGMRR-UHFFFAOYSA-N Aziridine Chemical compound C1CN1 NOWKCMXCCJGMRR-UHFFFAOYSA-N 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 229920009405 Polyvinylidenefluoride (PVDF) Film Polymers 0.000 description 1
- 238000001237 Raman spectrum Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- CJPIDIRJSIUWRJ-UHFFFAOYSA-N benzene-1,2,4-tricarbonyl chloride Chemical compound ClC(=O)C1=CC=C(C(Cl)=O)C(C(Cl)=O)=C1 CJPIDIRJSIUWRJ-UHFFFAOYSA-N 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 239000003431 cross linking reagent Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 125000001153 fluoro group Chemical group F* 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 235000013372 meat Nutrition 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- 238000006011 modification reaction Methods 0.000 description 1
- 230000000051 modifying effect Effects 0.000 description 1
- 239000002114 nanocomposite Substances 0.000 description 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 239000002798 polar solvent Substances 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920005597 polymer membrane Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- PYWVYCXTNDRMGF-UHFFFAOYSA-N rhodamine B Chemical compound [Cl-].C=12C=CC(=[N+](CC)CC)C=C2OC2=CC(N(CC)CC)=CC=C2C=1C1=CC=CC=C1C(O)=O PYWVYCXTNDRMGF-UHFFFAOYSA-N 0.000 description 1
- 229940043267 rhodamine b Drugs 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000002352 surface water Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
- B01D71/82—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74 characterised by the presence of specified groups, e.g. introduced by chemical after-treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0081—After-treatment of organic or inorganic membranes
- B01D67/0088—Physical treatment with compounds, e.g. swelling, coating or impregnation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
- B01D71/34—Polyvinylidene fluoride
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/30—Chemical resistance
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention provides a preparation method of a PEI modified PVDF organic solvent resistant film, which comprises the following steps: fully immersing PEI into the surface of the PVDF membrane and the membrane pore canal; step two, putting the film prepared in the step one into an oven for reaction, so that the modified PVDF film has the performance of resisting organic solvents; the PEI modified PVDF organic solvent-resistant membrane provided by the invention solves the technical problem that the conventional PVDF modified membrane is not resistant to organic solvent dissolution.
Description
Technical Field
The invention belongs to the field of polymer membrane separation materials, and particularly relates to a PEI modified PVDF organic solvent-resistant membrane and a preparation method thereof.
Background
In recent years, the membrane technology has been widely used for treating various kinds of sewage and wastewater. Along with the continuous expansion of the application fields of the membrane separation technology, the membrane technology is found to have outstanding advantages in the aspects of treatment, separation, recovery and the like of acid wastewater, alkaline wastewater, wastewater containing organic solvents and the like. Among them, polyvinylidene fluoride (PVDF) film has wide application space and great application value due to its excellent mechanical strength, tensile property and chemical stability.
The erosion rate of the organic solvent to PVDF is far greater than that of an acid-base solution, and the PVDF film can completely lose mechanical property and permeability after being soaked in pure NMP for ten seconds, so that the PVDF film can be completely dissolved within two minutes. The simple blending modification can not achieve the effect of fully covering the surface of the whole film. Shi et al deposited ultra-thin Teflon AF2400 membranes on commercially available PE porous supports, developed novel Teflon AF2400/PE membranes for nanofiltration of organic solvents. The membrane surface with PI supporting layer is deposited with mZIF-8 nano particles by Yang et al, and then a novel sandwich type thin film nano composite (TFN) polyamide membrane is prepared by an interfacial polymerization method, cross-linking and solvent activation, and the nanofiltration membrane has the performance of resisting organic solvents; the interception rate of rhodamine B dye (RDB) of the modified film after being soaked in DMF for 120h at 80 ℃ is almost unchanged, which shows that the film still has very good resistance under the environment of a strong polar solvent and is hopefully applied to practical industrial production, but the method has more steps and is more complicated, the adopted mZIF-8 nano particles are required to be prepared by a hydrothermal synthesis method, the thickness and uniformity of a deposition layer have a certain influence on subsequent interfacial polymerization, and finally the corrosion resistance of the film is obviously influenced. Davood et al crosslinked the integral skin asymmetric PBI membrane with trimellitic chloride and 2-methyltetrahydrofuran solution to prepare a high flux polybenzimidazole membrane for organic solvent nanofiltration. In 96 hours of continuous testing, polybenzimidazole membranes maintained stable OSN overall, but crosslinking of PBI membranes was highly demanding in terms of crosslinking reaction conditions, requiring TMC as a crosslinking agent and dissolution in anhydrous THF or anhydrous 2-methyltetrahydrofuran solution.
In view of the above, a preparation method of a PEI (polyethyleneimine) -modified PVDF organic solvent resistant film needs to be developed.
Disclosure of Invention
In view of the above-described drawbacks of the prior art, an object of the present invention is to provide a method for preparing a modified PVDF film to achieve the purpose of resistance of the modified PVDF film to dissolution by an organic solvent;
in order to achieve the above and other related objects, the present invention provides a method for preparing a PEI modified PVDF membrane resistant to organic solvents, comprising the steps of firstly, immersing PEI fully into the surface of the PVDF membrane and into the membrane pore canal; and step two, putting the film prepared in the step one into an oven for reaction, so that the modified PVDF film obtains the performance of resisting the organic solvent.
Preferably, the method comprises the following steps:
pouring PEI solution into a three-neck flask with a condensing reflux pipe, condensing and refluxing at 90 ℃, placing a PVDF pure film into a reaction device, and taking out the film after reaction;
and step two, rapidly draining the PEI solution on the surface of the film prepared in the step one, putting the film into a 90 ℃ oven, and taking out the prepared modified PVDF film from the oven after the reaction.
Preferably, the method comprises the following steps:
pouring PEI solution into a three-neck flask with a condensing reflux pipe, condensing and refluxing at 90 ℃, placing a PVDF pure film into a reaction device, and taking out the PVDF film after 17h of reaction;
and step two, rapidly draining the PEI solution on the surface of the film prepared in the step one, putting the film into a 90 ℃ oven, reacting for 3 hours, and taking the prepared modified PVDF film out of the oven.
Preferably, the PEI solution is an aqueous PEI solution, the mass fraction of the PEI is 1-15%, and the molecular weight of the PEI is 600-10000 g/mol, 10000-10W g/mol or 10W-75W g/mol.
Preferably, the PEI has a molecular weight of one or more of 600, 7W and 75W g/mol and the total mass fraction of PEI in the PEI solution is 4% or 6%.
Preferably, the molecular weight of PEI contained in the PEI solution is 600, 7W and 75W g/mol, and the mass fraction of PEI with different molecular weights in the PEI solution is 1.33-1.34%.
Preferably, the molecular weight of PEI contained in the PEI solution is 600, 7W and 75W g/mol, and the mass fraction of the PEI solution and the PEI contained in the PEI solution is 2%.
Preferably, the PEI solution contains PEI having a molecular weight of 600 and 75W g/mol, both in a mass fraction of 2% in the PEI solution.
Preferably, the humidity in the oven in step two is vacuum, 70% or 99%.
The PEI modified PVDF organic solvent resistant film prepared by the preparation method.
The preparation method of the PEI modified PVDF organic solvent resistant film has the following beneficial effects:
1) According to the invention, PEI with different molecular weights is used as a co-heating solution for the first time, and a protective layer is formed on the surface of the PVDF film under a certain reaction condition, so that the protective layer can effectively prevent the erosion of an organic solvent to the PVDF skeleton, and the corrosion resistance of the film is improved.
2) The preparation method has the advantages of few operation steps, simple operation and easy control;
3) The preparation method of the invention improves the organic solvent corrosion resistance of the modified PVDF film to the organic solvent.
Drawings
FIG. 1 is an SEM front view of a PEI modified organic solvent resistant film of the present invention of different components;
FIG. 2 shows the mass retention of PEI modified organic solvent resistant films of different components of the present invention after immersion in NMP;
FIG. 3 shows M prepared at different common heating times according to the invention 600+7W+75W Mass retention after NMP soaking;
FIG. 4 is a schematic diagram of the M of the present invention 600+7W+75W Is a spectrogram of (2);
FIG. 5 is a three-necked flask with a condensate return tube used in the present invention.
Wherein, 1-three-neck flask; 2-condensing reflux pipe; 3-a condensate inlet; 4-a condensate outlet; 5-heating the stirrer.
Detailed Description
Example 1:
step one, pouring PEI solution into a three-neck flask 1 (an open reactor or an open reaction kettle can be arranged in an up-down separable way, as shown in fig. 5) with a condensing reflux pipe 2, heating to 90 ℃ under the action of a heating stirrer 5, and continuously stirring; the condensed water flows in and out from the condensed water inlet 3, the condensed water return pipe body and the condensed water outlet 4 circularly to condense and return the heated PEI solution, (the upper cover of the three-neck flask 1 is opened), the PVDF pure film is placed in a reaction device, and the PVDF film is taken out after 17 hours of reaction;
and step two, rapidly draining the PEI solution on the surface of the film prepared in the step one, putting the film into a 90 ℃ oven, reacting for 3 hours, and taking the prepared modified PVDF film out of the oven.
Modified films were prepared according to the preparation method using PEI of different relative molecular masses and different mass fractions using the PEI modified PVDF organic solvent resistant film of example 1, and were numbered as shown in Table 1: PEI with mw=600 was a solid powder, while mw=7w and 75W respectively were 50% aqueous solutions of PEI mass fraction.
TABLE 1 relative molecular masses and mass fractions of PEI used to modify films
The changes of the conditions such as common heating time, common heating temperature, oven humidity and the like in the technical process of the PEI modified PVDF film have obvious influence on the wrapping degree and corrosion resistance of the modified film.
Maintaining the total heating temperature at 90deg.C and humidity at 70%, mixing M 600+7W+75W Is set to 3h, 10h, 17h and 24h, respectively, as can be seen from FIG. 3, M prepared by co-heating for 3h 600+7W+75W After soaking in NMP for one day, the mass retention rate is less than 70%; m prepared by co-heating for 10h 600+7W+75W After soaking in NMP for one day, the mass retention rate is less than 90%; m prepared by co-heating for 17h and co-heating for 24h 600+7W+75W After soaking in NMP for 7 days, the mass retention rate is still above 90% (90% and 90.6% respectively), which shows that the modification effect is better and the stability can be maintained for a longer time under the common heating time, and simultaneously shows that the PEI coating amount is positively correlated with the modification effect of the organic solvent resistance.
Since the PEI solution used in the co-thermal reaction is an aqueous solution, the co-thermal temperature of 90 ℃ can cause rapid evaporation of water in the solution, so that a condensing reflux device is required to be externally connected with the reaction device. The temperature drop can lead to the rise of the viscosity of the fluid, in order to avoid 17 hours of insufficient PEI solution viscosity rise to enable PEI to completely permeate into the grooves and the internal pores of the surface of the membrane, the concurrent heating time is set to be 24 hours and 36 hours, and the concurrent heating temperature is simultaneously reduced to 45 ℃ and 60 ℃, and whether the concurrent heating temperature can be reduced by testing the organic solvent resistance of the modified membrane or not is tested. The results showed that the modified film M after the reaction was heated at 60℃for 36 hours 600+7W+75W Soaking in 50% NMP for 7 days, decreasing the quality by more than 50%, completely losing the basic structure of membrane, and filteringPerformance. Due to excessive corrosion, the film cannot be collected completely and the quality of the corroded film cannot be measured accurately. The modification method is that the higher the temperature is, the longer the common heating time is, and the better the modification effect is. The modified film prepared under the conditions of 45 ℃ and 24 hours has poorer corrosion resistance, is soaked in NMP, excessively corroded, and cannot be completely collected to obtain accurate data.
The scheme is that a vacuum drying box and a constant temperature and humidity test box are used, and the second reaction condition of the modification reaction step is respectively set to be vacuum, 70% humidity and 99% humidity, so that the influence of the humidity of an oven on the modification effect is explored; the results show that: although the modified film dried under vacuum (vacuum drying oven) has certain organic solvent tolerance, the toughness of the film is extremely poor, the assembly of the film component can not be carried out, and the film can not be applied to actual production; under the condition of 99% humidity, the organic solvent resistant modification effect is weaker than the drying effect in an oven with 70% humidity, M 600+7W+75W After drying in an oven with the humidity of 99%, soaking in NMP with the mass fraction of 50% for 7 days, wherein the mass retention rate is 85%, and after changing the humidity of the oven to 70%, the mass retention rate reaches 90%.
The influence of different PEI components on the modification effect is critical, the scheme adopts better modification conditions, the common heat temperature is kept at 90 ℃, the humidity is kept at 70%, the common heat time is kept at 17h, and the modified PVDF film is obtained by changing the PEI components.
As can be seen from FIG. 1, the modified film M 600+7W+75W 、M 6％ And M 600+75W The film surface of the modified film also shows excellent corrosion resistance to organic solvents in corrosion resistance experiments, while the modified film M is relatively dense 75W The coating layer on the surface of the membrane is obviously low in compactness, only a 'protective framework' is generated, and the exposed PVDF structure is easy to corrode in an organic solvent such as NMP, so that the corrosion resistance is low. M with best modification effect 600+7W+75W Since most parts of the surface of the membrane are wrapped by a protective layer, the pores of the membrane are reduced, and the permeability of the membrane is affected to a certain extent.
The PEI modified organic solvent resistant film with different components is subjected to water contact angle, filtering performance and mechanical performanceAs can be seen from table 2, the PEI wrap modification resulted in lower water contact angle, lower membrane flux and increased maximum tensile stress on the membrane surface. The coating modification only generates a protective layer on the inner surface and the outer surface of the film, the macroscopic structure of the film is hardly affected, the mechanical strength of the film is increased, M 600+7W+75W The maximum tensile stress of (2) can reach 5.60MPa. PEI on the surface of the film has the effect of hydrophilic modification to a certain extent, so that the surface water contact angle of the modified film is reduced.
TABLE 2 basic Properties of PVDF raw film and organic solvent resistant film modified by PEI of different Components
As shown in fig. 2, the different modified films showed a continuous dissolution phenomenon when immersed in NMP, and showed a trend of faster and faster dissolution rate during the immersion for 7 days. This is due to the increasing contact area of the modified membrane with NMP as dissolution proceeds; the PEI components are different, the modification effect is greatly influenced, M 6％ 、M 600+7W+75W 、M 600+75W After soaking in NMP with mass fraction of 50% for one week, the mass retention rate can still reach more than 90%, while M 7W+75W 、M 7W 、M 75W The mass retention of (2) is only less than 70%. This is due to the resistance to organic solvents through branched amino groups (-NH) in PEI 2 ) The PEI with large molecular weight is obtained by reacting as active groups to form a coating layer, and the branching degree of the PEI with large molecular weight is relatively low, so that the reaction sites capable of forming an organic solvent resistant structure are less caused, the membrane surface can not be well coated by PEI with large molecular weight, and part of PVDF is exposed on the membrane surface and is directly contacted with NMP. Small molecular weight PEI (M) W Pei=600) has no problem of insufficient branching degree due to the short chain itself, but the PEI molecules can only be connected through hydrogen bonds, no covalent bond is formed into a "skeleton", and the best modifying effect cannot be achieved only by the PEI with small molecular weight. When both high molecular weight PEI and low molecular weight PEI are added, the high molecular weight PEI acts as a "boneThe rack wraps the surface of the membrane, and the part of the membrane exposed outside is filled by the PEI with small molecular weight as blood flesh, and meanwhile, the problem of low branching degree of the PEI with large molecular weight is solved. The framework and the blood meat are connected through hydrogen bonds to form complete package on the membrane, and the two components act together to achieve the best modification effect.
XPS analysis is carried out on the surface of the modified film, as shown in fig. 4, the surface of the modified film contains H, C, N, O, F elements, wherein O element is new element introduced after the surface of the film is wrapped. The chemical bond and the functional group of the film are tested and analyzed through infrared spectrum and Raman spectrum, the chemical bond of the oxygen element contained on the surface of the film has C-O bond and C=O bond, wherein C, N element is PEI wrapped on the surface of the modified film, C, F element is PVDF, and O element is the reactive group on the surface of the film and oxygen-containing gas (CO) 2 ) The reaction results in; whereas the film surface N atom ratio is much higher than F atoms, the mass ratio of PEI to PVDF in the previous test modified film was about 1:10, this shows that PEI is mainly distributed on the surface of the membrane, and the PVDF is isolated from direct contact with the organic solvent by forming a 'protective layer' on the surface of the membrane, so that a better organic solvent resistant effect is achieved.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (2)
1. A preparation method of PEI modified PVDF organic solvent resistant film is characterized in that,
the method comprises the following steps:
pouring PEI solution into a three-neck flask with a condensing reflux pipe, condensing and refluxing at 90 ℃, placing a PVDF pure film into a reaction device, and taking out the PVDF film after 17h of reaction;
step two, rapidly draining the PEI solution on the surface of the film prepared in the step one, putting the film into a 90 ℃ oven, reacting for 3 hours, and taking the prepared modified PVDF film out of the oven;
the PEI solution is an aqueous PEI solution, wherein,
the molecular weight of PEI contained in the PEI solution is 600, 7W and 75Wg/mol, and the mass fraction of PEI with different molecular weights in the PEI solution is 1.33-1.34%;
or the molecular weight of PEI contained in the PEI solution is 600, 7W and 75W g/mol, and the mass fraction of the PEI solution and the PEI solution is 2%;
or the molecular weight of PEI contained in the PEI solution is 600 and 75W g/mol, and the mass fraction of PEI contained in the PEI solution is 2%;
the humidity in the oven in the second step is vacuum, 70% or 99%.
2. The PEI modified PVDF organic solvent resistant film is characterized in that the PEI modified PVDF organic solvent resistant film prepared by the preparation method of claim 1.
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