CN112808011A - Anti-stripping composite PVDF ultrafiltration membrane - Google Patents
Anti-stripping composite PVDF ultrafiltration membrane Download PDFInfo
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- CN112808011A CN112808011A CN202011561568.2A CN202011561568A CN112808011A CN 112808011 A CN112808011 A CN 112808011A CN 202011561568 A CN202011561568 A CN 202011561568A CN 112808011 A CN112808011 A CN 112808011A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/14—Ultrafiltration; Microfiltration
- B01D61/145—Ultrafiltration
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
- B01D71/34—Polyvinylidene fluoride
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/24—Mechanical properties, e.g. strength
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Abstract
The invention discloses an anti-stripping composite PVDF ultrafiltration membrane, which comprises the following required materials: polyvinylidene fluoride monomer; dimethyl sulfoxide; a dispersant; an oil soluble initiator; a chain transfer agent and deionized water. By adding the quaternary ammonium base alcohol solution, the styrene solution and the dichloromethane solution into the polyvinylidene fluoride during polymerization, the polymer of the polyvinylidene fluoride is modified, so that the oxidation resistance of the polyvinylidene fluoride is improved, the bond energy between fluorine and carbon in the polyvinylidene fluoride is also improved, the tensile strength and the compressive strength of the polyvinylidene fluoride ultrafiltration composite membrane are greatly improved, and the peeling resistance of the polyvinylidene fluoride ultrafiltration membrane is improved.
Description
Technical Field
The invention relates to the technical field of ultrafiltration membranes, in particular to an anti-stripping composite PVDF ultrafiltration membrane.
Background
PVDF membrane (polyvinylidene fluoride) is a solid phase support commonly used in Western blotting, and the key point of ultrafiltration is the membrane. The membranes are of various types and sizes and can be selected according to the requirements of the job. Early membranes were isotropic, homogeneous membranes, i.e., microporous membranes commonly used today, with pore sizes of typically 0.05mm and 0.025 mm. Several anisotropic asymmetric ultrafiltration membranes have been produced in recent years, one of which consists of a very thin porous "skin layer" (about 0.1mm to 1.0mm thick) of a certain pore size, and a relatively much thicker (about 1mm) more permeable "sponge layer" as a support. The skin layer determines the selectivity of the membrane, while the sponge layer adds mechanical strength. In fact, in the ultrafiltration membrane of our daily water purification industry, the majority of the ultrafiltration membranes adopt the PVDF ultrafiltration membrane component, and the filtration mode of the PVDF ultrafiltration membrane component also tends to adopt full-flow filtration, wherein a discharge valve is periodically opened for pollution discharge or cross-flow filtration, and 5% -10% of sewage is discharged by opening a sewage valve while water is produced. The ultrafiltration membrane, the last river basin PVDF milipore filter, the membrane element, it is good to accept automatic control contrast usually. So that a pre-treatment which is not critically necessary is typically a 50-100 μm filtration precision. The existing PVDF ultrafiltration membrane has a serious problem that the tensile resistance and the compressive strength of the polyvinylidene fluoride ultrafiltration composite membrane are influenced because the energy required for breaking the bonds of the fluorine-carbon functional groups among molecules is low during the preparation.
Disclosure of Invention
The invention provides an anti-stripping composite PVDF ultrafiltration membrane aiming at the technical defects of the traditional Chinese medicine formula for preventing and treating diabetes and the like.
In order to solve the technical defects, the invention adopts a modified technical scheme, and the anti-stripping composite PVDF ultrafiltration membrane is prepared from the following required materials: polyvinylidene fluoride monomer; dimethyl sulfoxide; a dispersant; an oil soluble initiator; a chain transfer agent and deionized water.
As a preferred embodiment of the present invention, the preparation method is as follows:
1S: prefabricating: adding dimethyl sulfoxide, deionized water and a dispersing agent which are prepared in advance into a stainless steel autoclave with stirring, sealing the autoclave, vacuumizing, filling nitrogen to replace oxygen, stirring, and heating to 50 ℃;
2S: polymerized polyvinylidene fluoride: adding a polyvinylidene fluoride monomer, raising the pressure of the kettle to 3.5MPa, keeping the temperature in the kettle at 30 ℃, adding an oil-soluble initiator and a chain transfer agent, and starting a polymerization reaction; continuously adding a polyvinylidene fluoride monomer and an oil-soluble initiator and a chain transfer agent in a corresponding proportion at a certain speed, and maintaining the temperature and the pressure in the reaction kettle; stopping stirring until the polyvinylidene fluoride monomer is added and the pressure is reduced from 3.5MPa to 2.8MPa, and finishing the polymerization reaction;
3S: preparing an ultrafiltration membrane: centrifuging, washing and drying the polymerization product to obtain a dry film;
4S: preparing a composite membrane: soaking the dry film in 0.1-0.5 mol L of quaternary ammonium base alcohol solution at room temperature for 2-4 h to obtain a polyvinylidene fluoride modified film with a darkened color; preparing a styrene solution, wherein the volume ratio of styrene to tetrahydrofuran is 4: 1; and then mixing the modified film with a styrene solution in a mass ratio of 0.1-0.5: 1, adding a certain amount of oil-soluble initiator into a styrene solution, carrying out grafting reaction for 8-10 h at the temperature of 60-80 ℃ in a nitrogen atmosphere, adding a dichloromethane solution into the solution after the reaction, taking out the membrane after the reaction is expanded, and washing the membrane for several times by using deionized water to obtain a composite membrane; and sulfonating the composite membrane in concentrated sulfuric acid at 70-80 ℃ for 2-4 h, taking out the composite membrane after reaction, and washing with deionized water to obtain the composite polyvinylidene fluoride membrane.
In a preferred embodiment of the present invention, the oil-soluble initiator is diisopropyl peroxydicarbonate or di-2-ethylhexyl peroxydicarbonate, and the polyvinylidene fluoride monomer is subjected to suspension polymerization.
As a preferred embodiment of the present invention, the dispersant is cellulose ethers or polyvinyl alcohols, such as methyl cellulose and hydroxyethyl cellulose, and the main functions of the dispersant are: the polymer is adsorbed on the surface of the polyvinylidene fluoride monomer liquid drop to keep the stability of the polymer; preventing coalescence between the polymer particles.
In a preferred embodiment of the present invention, the chain transfer agent is acetone, and the molar mass of polyvinylidene fluoride is estimated by testing the melt mass flow rate and the intrinsic viscosity, so that the molar mass of the polymer can be effectively controlled, and simultaneously, the initiator can be used in a sufficient amount to ensure a high reaction rate without adverse effect on the thermal stability of the polymer.
As a preferred embodiment of the invention, the polymerization kettle is a 130L stainless steel autoclave with the rotating speed of 88r/min, the sealing performance of the polymerization system is firstly checked, then the autoclave is vacuumized and filled with nitrogen to discharge oxygen, and the steps are repeated for several times until the oxygen content of the polymerization system reaches the requirement.
In a preferred embodiment of the present invention, the amount of the dispersant is 0.01 to 1% by mass, preferably 0.05 to 0.4% by mass, based on the mass of the polyvinylidene fluoride monomer.
As a preferred embodiment of the invention, the modified membrane is washed by deionized water, dried and weighed, and then is put into a prepared mixed solution, and then is put into a reaction kettle, and N is introduced2Reacting for 12 hours; after the reaction is finished, sticky styrene homopolymer is adhered to the surface of the film, the film can be taken out only by repeatedly extracting the sticky styrene homopolymer for about 4 hours by using dichloromethane, and the sticky styrene homopolymer is cleaned, dried and weighed again; the content of styrene in the film is expressed in terms of its mass percentage (Gy): gy ═ W-Wo)/W0x100％。
The invention has the following beneficial effects: by adding the quaternary ammonium base alcohol solution, the styrene solution and the dichloromethane solution into the polyvinylidene fluoride during polymerization, the polymer of the polyvinylidene fluoride is modified, so that the oxidation resistance of the polyvinylidene fluoride is improved, the bond energy between fluorine and carbon in the polyvinylidene fluoride is also improved, the tensile strength and the compressive strength of the polyvinylidene fluoride ultrafiltration composite membrane are greatly improved, and the peeling resistance of the polyvinylidene fluoride ultrafiltration membrane is improved.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
The anti-stripping composite PVDF ultrafiltration membrane is characterized in that the required materials are as follows: polyvinylidene fluoride monomer; dimethyl sulfoxide; a dispersant; an oil soluble initiator; a chain transfer agent and deionized water.
The preparation method comprises the following steps:
1S: prefabricating: adding dimethyl sulfoxide, deionized water and a dispersing agent which are prepared in advance into a stainless steel autoclave with stirring, sealing the autoclave, vacuumizing, filling nitrogen to replace oxygen, stirring, and heating to 50 ℃;
2S: polymerized polyvinylidene fluoride: adding a polyvinylidene fluoride monomer, raising the pressure of the kettle to 3.5MPa, keeping the temperature in the kettle at 30 ℃, adding an oil-soluble initiator and a chain transfer agent, and starting a polymerization reaction; continuously adding a polyvinylidene fluoride monomer and an oil-soluble initiator and a chain transfer agent in a corresponding proportion at a certain speed, and maintaining the temperature and the pressure in the reaction kettle; stopping stirring until the polyvinylidene fluoride monomer is added and the pressure is reduced from 3.5MPa to 2.8MPa, and finishing the polymerization reaction;
3S: preparing an ultrafiltration membrane: centrifuging, washing and drying the polymerization product to obtain a dry film;
4S: preparing a composite membrane: soaking the dry film in 0.1-0.5 mol L of quaternary ammonium base alcohol solution at room temperature for 2-4 h to obtain a polyvinylidene fluoride modified film with a darkened color; preparing a styrene solution, wherein the volume ratio of styrene to tetrahydrofuran is 4: 1; and then mixing the modified film with a styrene solution in a mass ratio of 0.1-0.5: 1, adding a certain amount of oil-soluble initiator into a styrene solution, carrying out grafting reaction for 8-10 h at the temperature of 60-80 ℃ in a nitrogen atmosphere, adding a dichloromethane solution into the solution after the reaction, taking out the membrane after the reaction is expanded, and washing the membrane for several times by using deionized water to obtain a composite membrane; and sulfonating the composite membrane in concentrated sulfuric acid at 70-80 ℃ for 2-4 h, taking out the composite membrane after reaction, and washing with deionized water to obtain the composite polyvinylidene fluoride membrane.
The oil-soluble initiator is diisopropyl peroxydicarbonate or di-2-ethylhexyl peroxydicarbonate, and the polyvinylidene fluoride monomer is subjected to suspension polymerization.
The dispersant is cellulose ether or polyvinyl alcohol, such as methyl cellulose and hydroxyethyl cellulose, and has the main functions of: the polymer is adsorbed on the surface of the polyvinylidene fluoride monomer liquid drop to keep the stability of the polymer; preventing coalescence between the polymer particles.
The chain transfer agent is acetone, the molar mass of the polyvinylidene fluoride is estimated by testing the melt mass flow rate and the intrinsic viscosity, the molar mass of the polymer can be effectively controlled, and meanwhile, the sufficient amount of the initiator can be allowed to be used, so that the higher reaction rate is ensured, and the thermal stability of the polymer is not adversely affected.
The polymerization kettle is a 130L stainless steel autoclave with the rotating speed of 88r/min, the sealing performance of the polymerization system is firstly checked, then the autoclave is vacuumized and filled with nitrogen to discharge oxygen, and the operation is repeated for a plurality of times until the oxygen content of the polymerization system meets the requirement.
The dosage of the dispersant is 0.01 to 1 percent of the mass of the polyvinylidene fluoride monomer, and the proper dosage is 0.05 to 0.4 percent of the mass of the monomer.
Cleaning the modified membrane with deionized water, drying, weighing, adding into the prepared mixed solution, adding into a reaction kettle, and introducing N2Reacting for 12 hours; after the reaction is finished, sticky styrene homopolymer is adhered to the surface of the film, the film can be taken out only by repeatedly extracting the sticky styrene homopolymer for about 4 hours by using dichloromethane, and the sticky styrene homopolymer is cleaned, dried and weighed again; the content of styrene in the film is expressed in terms of its mass percentage (Gy): gy ═ W-Wo)/W0x100％。
Example 1
The preparation method comprises the following steps:
1S: prefabricating: adding dimethyl sulfoxide, deionized water and a dispersing agent which are prepared in advance into a stainless steel autoclave with stirring, sealing the autoclave, vacuumizing, filling nitrogen to replace oxygen, stirring, and heating to 50 ℃;
2S: polymerized polyvinylidene fluoride: adding a polyvinylidene fluoride monomer, raising the pressure of the kettle to 3.5MPa, keeping the temperature in the kettle at 30 ℃, adding an oil-soluble initiator and a chain transfer agent, and starting a polymerization reaction; continuously adding a polyvinylidene fluoride monomer and an oil-soluble initiator and a chain transfer agent in a corresponding proportion at a certain speed, and maintaining the temperature and the pressure in the reaction kettle; stopping stirring until the polyvinylidene fluoride monomer is added and the pressure is reduced from 3.5MPa to 2.8MPa, and finishing the polymerization reaction;
3S: preparing an ultrafiltration membrane: centrifuging, washing and drying the polymerization product to obtain a dry film;
4S: preparing a composite membrane: soaking the dry film in 0.1-0.5 mol L of quaternary ammonium base alcohol solution at room temperature for 2-4 h to obtain a polyvinylidene fluoride modified film with a darkened color; preparing a styrene solution, wherein the volume ratio of styrene to tetrahydrofuran is 4: 1; and then mixing the modified film with a styrene solution in a mass ratio of 0.1-0.5: 1, adding a certain amount of oil-soluble initiator into a styrene solution, carrying out grafting reaction for 8-10 h at the temperature of 60-80 ℃ in a nitrogen atmosphere, adding a dichloromethane solution into the solution after the reaction, taking out the membrane after the reaction is expanded, and washing the membrane for several times by using deionized water to obtain a composite membrane; and sulfonating the composite membrane in concentrated sulfuric acid at 70-80 ℃ for 2-4 h, taking out the composite membrane after reaction, and washing with deionized water to obtain the composite polyvinylidene fluoride membrane.
| Type of membrane | MPa | Break-strain(％) |
| PVDF composite membrane | 26.720 | 60.33 |
| Modified membrane | 0.935 | 36.15 |
The existence of the supporting layer greatly improves the strength of the obtained composite membrane, mechanical experiments are carried out on the modified membrane and the PVDF homogeneous membrane, the maximum tensile strength of the PVDF composite membrane is 26.720MPa, the breaking elongation is 60.33%, the tensile strength of the modified membrane is only 0.935MPa, the breaking elongation is 36.15%, the tensile strength of the PVDF composite membrane is 28.5 times of that of the modified membrane, and the breaking elongation is 1.11 times of that of the modified membrane.
Example 2
The preparation method comprises the following steps:
1S: prefabricating: adding dimethyl sulfoxide, deionized water and a dispersing agent which are prepared in advance into a stainless steel autoclave with stirring, sealing the autoclave, vacuumizing, filling nitrogen to replace oxygen, stirring, and heating to 50 ℃;
2S: polymerized polyvinylidene fluoride: adding a polyvinylidene fluoride monomer, raising the pressure of the kettle to 3.5MPa, keeping the temperature in the kettle at 30 ℃, adding an oil-soluble initiator and a chain transfer agent, and starting a polymerization reaction; continuously adding a polyvinylidene fluoride monomer and an oil-soluble initiator and a chain transfer agent in a corresponding proportion at a certain speed, and maintaining the temperature and the pressure in the reaction kettle; stopping stirring until the polyvinylidene fluoride monomer is added and the pressure is reduced from 3.5MPa to 2.8MPa, and finishing the polymerization reaction;
3S: preparing an ultrafiltration membrane: centrifuging, washing and drying the polymerization product to obtain a dry film;
4S: preparing a composite membrane: soaking the dry film in 0.1-0.5 mol L of quaternary ammonium base alcohol solution at room temperature for 2-4 h to obtain a polyvinylidene fluoride modified film with a darkened color; preparing a styrene solution, wherein the volume ratio of styrene to tetrahydrofuran is 4: 1; and then mixing the modified film with a styrene solution in a mass ratio of 0.1-0.5: 1, adding a certain amount of oil-soluble initiator into a styrene solution, carrying out grafting reaction for 8-10 h at the temperature of 60-80 ℃ in a nitrogen atmosphere, adding a dichloromethane solution into the solution after the reaction, taking out the membrane after the reaction is expanded, and washing the membrane for several times by using deionized water to obtain a composite membrane; and sulfonating the composite membrane in concentrated sulfuric acid at 70-80 ℃ for 2-4 h, taking out the composite membrane after reaction, and washing with deionized water to obtain the composite polyvinylidene fluoride membrane.
The oil-soluble initiator is diisopropyl peroxydicarbonate or di-2-ethylhexyl peroxydicarbonate, and the polyvinylidene fluoride monomer is subjected to suspension polymerization.
The dosage of the oil-soluble initiator has great influence on the polymerization rate and the PVDF performance, the dosage of the initiator is 0.05-1.50% of the monomer mass, and as the dosage of the initiator is increased, the more primary free radicals are generated, and the faster the polymerization rate is; on the other hand, the chance of terminating free radicals is too many, which causes unstable polymerization reaction, yield reduction and poor polymer performance, and the proper dosage is 0.3-0.85% of the monomer mass.
Example 3
The preparation method comprises the following steps:
1S: prefabricating: adding dimethyl sulfoxide, deionized water and a dispersing agent which are prepared in advance into a stainless steel autoclave with stirring, sealing the autoclave, vacuumizing, filling nitrogen to replace oxygen, stirring, and heating to 50 ℃;
2S: polymerized polyvinylidene fluoride: adding a polyvinylidene fluoride monomer, raising the pressure of the kettle to 3.5MPa, keeping the temperature in the kettle at 30 ℃, adding an oil-soluble initiator and a chain transfer agent, and starting a polymerization reaction; continuously adding a polyvinylidene fluoride monomer and an oil-soluble initiator and a chain transfer agent in a corresponding proportion at a certain speed, and maintaining the temperature and the pressure in the reaction kettle; stopping stirring until the polyvinylidene fluoride monomer is added and the pressure is reduced from 3.5MPa to 2.8MPa, and finishing the polymerization reaction;
3S: preparing an ultrafiltration membrane: centrifuging, washing and drying the polymerization product to obtain a dry film;
4S: preparing a composite membrane: soaking the dry film in 0.1-0.5 mol L of quaternary ammonium base alcohol solution at room temperature for 2-4 h to obtain a polyvinylidene fluoride modified film with a darkened color; preparing a styrene solution, wherein the volume ratio of styrene to tetrahydrofuran is 4: 1; and then mixing the modified film with a styrene solution in a mass ratio of 0.1-0.5: 1, adding a certain amount of oil-soluble initiator into a styrene solution, carrying out grafting reaction for 8-10 h at the temperature of 60-80 ℃ in a nitrogen atmosphere, adding a dichloromethane solution into the solution after the reaction, taking out the membrane after the reaction is expanded, and washing the membrane for several times by using deionized water to obtain a composite membrane; and sulfonating the composite membrane in concentrated sulfuric acid at 70-80 ℃ for 2-4 h, taking out the composite membrane after reaction, and washing with deionized water to obtain the composite polyvinylidene fluoride membrane.
The chain transfer agent was acetone and the molar mass of polyvinylidene fluoride was estimated by measuring the melt mass flow rate, intrinsic viscosity.
In the polymerization process, the dosage of the chain transfer agent is increased, the mass flow rate of the melt is increased, the intrinsic viscosity is reduced, and the molar mass of PVDF is reduced; when the amount of the chain transfer agent is too small, the molar mass is high, but the polymerization reaction is not stable and difficult to control, and the polymerization is terminated early, resulting in a decrease in productivity.
While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (8)
1. The anti-stripping composite PVDF ultrafiltration membrane is characterized in that the required materials are as follows: polyvinylidene fluoride monomer; dimethyl sulfoxide; a dispersant; an oil soluble initiator; a chain transfer agent and deionized water.
2. The anti-stripping composite PVDF ultrafiltration membrane according to claim 1, wherein the preparation method is as follows:
1S: prefabricating: adding dimethyl sulfoxide, deionized water and a dispersing agent which are prepared in advance into a stainless steel autoclave with stirring, sealing the autoclave, vacuumizing, filling nitrogen to replace oxygen, stirring, and heating to 50 ℃;
2S: polymerized polyvinylidene fluoride: adding a polyvinylidene fluoride monomer, raising the pressure of the kettle to 3.5MPa, keeping the temperature in the kettle at 30 ℃, adding an oil-soluble initiator and a chain transfer agent, and starting a polymerization reaction; continuously adding a polyvinylidene fluoride monomer and an oil-soluble initiator and a chain transfer agent in a corresponding proportion at a certain speed, and maintaining the temperature and the pressure in the reaction kettle; stopping stirring until the polyvinylidene fluoride monomer is added and the pressure is reduced from 3.5MPa to 2.8MPa, and finishing the polymerization reaction;
3S: preparing an ultrafiltration membrane: centrifuging, washing and drying the polymerization product to obtain a dry film;
4S: preparing a composite membrane: soaking the dry film in 0.1-0.5 mol L of quaternary ammonium base alcohol solution at room temperature for 2-4 h to obtain a polyvinylidene fluoride modified film with a darkened color; preparing a styrene solution, wherein the volume ratio of styrene to tetrahydrofuran is 4: 1; and then mixing the modified film with a styrene solution in a mass ratio of 0.1-0.5: 1, adding a certain amount of oil-soluble initiator into a styrene solution, carrying out grafting reaction for 8-10 h at the temperature of 60-80 ℃ in a nitrogen atmosphere, adding a dichloromethane solution into the solution after the reaction, taking out the membrane after the reaction is expanded, and washing the membrane for several times by using deionized water to obtain a composite membrane; and sulfonating the composite membrane in concentrated sulfuric acid at 70-80 ℃ for 2-4 h, taking out the composite membrane after reaction, and washing with deionized water to obtain the composite polyvinylidene fluoride membrane.
3. The anti-stripping composite PVDF ultrafiltration membrane as claimed in claim 2, wherein the oil-soluble initiator is diisopropyl peroxydicarbonate or di-2-ethylhexyl peroxydicarbonate, and the polyvinylidene fluoride monomer undergoes suspension polymerization.
4. The anti-stripping composite PVDF ultrafiltration membrane as claimed in claim 2, wherein the dispersant is cellulose ether or polyvinyl alcohol, such as methyl cellulose and hydroxyethyl cellulose.
5. The stripping resistant composite PVDF ultrafiltration membrane as claimed in claim 2, wherein the chain transfer agent is acetone, and the molar mass of polyvinylidene fluoride is estimated by measuring the melt mass flow rate and the intrinsic viscosity.
6. The anti-stripping composite PVDF ultrafiltration membrane as claimed in claim 2, wherein the polymerization kettle is a 130L stainless steel autoclave with a rotation speed of 88r/min, the sealing performance of the polymerization system is firstly checked, then the autoclave is vacuumized and filled with nitrogen to discharge oxygen, and the steps are repeated for several times until the oxygen content of the polymerization system reaches the requirement.
7. The anti-stripping composite PVDF ultrafiltration membrane as claimed in claim 2, wherein the amount of dispersant is 0.01-1% of the mass of polyvinylidene fluoride monomer, preferably 0.05-0.4% of the mass of monomer.
8. The anti-stripping composite PVDF ultrafiltration membrane as claimed in claim 2, wherein the modified membrane is washed with deionized water, dried, weighed, put into a prepared mixed solution, put into a reaction kettle, and N is introduced2Reacting for 12 hours; after the reaction is finished, sticky styrene homopolymer is adhered to the surface of the film, the film can be taken out only by repeatedly extracting the sticky styrene homopolymer for about 4 hours by using dichloromethane, and the sticky styrene homopolymer is cleaned, dried and weighed again; the content of styrene in the film is expressed in terms of its mass percentage (Gy): gy ═ W-Wo)/W0x100％。
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