CN109621742A - A kind of method that vinylidene fluoride copolymers resin prepares perforated membrane - Google Patents
A kind of method that vinylidene fluoride copolymers resin prepares perforated membrane Download PDFInfo
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- CN109621742A CN109621742A CN201910035260.5A CN201910035260A CN109621742A CN 109621742 A CN109621742 A CN 109621742A CN 201910035260 A CN201910035260 A CN 201910035260A CN 109621742 A CN109621742 A CN 109621742A
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- vinylidene fluoride
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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
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
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- Chemical Kinetics & Catalysis (AREA)
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- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention discloses a kind of methods that vinylidene fluoride copolymers resin prepares perforated membrane, have the macromolecule casting film liquid system of lower critical solution temperature by preparing, are film-made using phase separation method, obtain the vinylidene fluoride copolymers perforated membrane that structure is easy to regulate and control.Macromolecule casting solution of the invention is homogeneous stability at low temperature, but occur mutually to separate at high temperature, corresponding filming technology is different from traditional filming technology, there is no epidermis compacted zone by vinylidene fluoride copolymers resin perforated membrane prepared by twice difference coagulation bath process and aftertreatment technology appropriate, main body is the spongy pore structure of high porosity, near symmetrical, suitable for the application requirement of membrane distillation, there is the characteristic that flux is big, resistance is low, hydrophobicity is strong.
Description
Technical field
The invention belongs to polymeric membrane separation technology fields, and in particular to a kind of vinylidene fluoride copolymers resin prepares porous
The method of film.
Background technique
Membrane distillation (MD) is to utilize dewatering microporous film, using film two sides steam pressure difference as the membrane separating process of mass transfer force,
Wherein the film two sides of directly contact membrane distillation (DCMD) are directly contacted with high temperature feed liquid and low temperature osmotic liquid respectively, and steam penetrates film
Hole is simultaneously directly condensed in penetrating fluid side.Membrane distillation almost retains the non-volatile components such as inorganic salts, macromolecular, and can benefit
With the cheap energy such as solar energy, industrial exhaust heat, application prospect is extensive in terms of high-salt wastewater, high value component.Inclined fluorine
Ethylene copolymer is one kind by least one of vinyl fluoride, tetrafluoroethene, hexafluoropropene, chlorotrifluoroethylene and vinylidene shape
At copolymer.The perforated membrane hydrophobicity prepared with vinylidene fluoride copolymers resin is strong, and high temperature resistant, solvent resistant, acid and alkali-resistance have
Outstanding advantage is highly suitable for membrane distillation process, receives significant attention.The method that vinylidene fluoride copolymers resin prepares perforated membrane
Predominantly phase separation method.Phase separation method is commonly divided into phase separation method (Nonsolvent induced phase
Separation, NIPS) and thermally induced phase separation (Thermally induced phase separation, TIPS).NIPS
The solvent that method is formed using concentration difference is exchanged with non-solvent causes Polymer Solution to be separated into film as mechanism, and TIPS method is with temperature
It is mechanism that differential thermal, which causes Polymer Solution to be separated into film,.Currently used for preparing vinylidene fluoride copolymers perforated membrane
TIPS method, Polymer Solution are usually upper criticalsolution temperatures (UCST) system, i.e. Polymer Solution temperature is dropped to from high temperature
When its critical solution temperature, mutually separation occurs and is further formed perforated membrane；And lower critical solution temperature in contrast
(LCST) system when that is, Polymer Solution temperature is raised to its critical solution temperature from low temperature, occurs mutually separation and forms inclined fluorine second
This system of alkene copolymer perforated membrane has no document report.In consideration of it, the present invention provides one kind based on low critical molten
The method that the vinylidene fluoride copolymers resin casting film liquid system of solution temperature (LCST) prepares perforated membrane.
Summary of the invention
The purpose of the present invention is being directed to the deficiency of the existing porous membrane preparation technology of vinylidene fluoride copolymers resin, one kind is provided
The method that vinylidene fluoride copolymers resin prepares perforated membrane mainly has the vinylidene of lower critical solution temperature by preparing
Copolymer resin Polymer Solution system, is film-made using phase separation method, and what acquisition structure was easy to regulate and control is suitable for membrane distillation application
Vinylidene fluoride copolymers perforated membrane.
The technical scheme of the invention to solve the technical problem is: a kind of vinylidene fluoride copolymers resin preparation is more
The method of pore membrane, it is characterised in that the following steps are included:
1) it prepares the vinylidene fluoride copolymers resin casting solution with lower critical solution temperature: pressing vinylidene fluoride copolymers tree
Rouge mass percentage is 5%-40%, and second of high molecular mass percentage is 1%-20%, and solvent quality percentage contains
Amount is 50%-85%, and the mass percentage of small molecule pore-foaming agent is the vinylidene copolymerization that 1%-20% configures suitable concentration
Small molecule pore-foaming agent is dissolved completely in solvent by resin casting solution first, later be added vinylidene fluoride copolymers resin and
Second of macromolecule, agitating and heating dissolve that form vinylidene being completely dissolved, with lower critical solution temperature (LCST) total
Copolymer resin casting film liquid system, standing and defoaming are stand-by；
2) by above-mentioned prepared vinylidene fluoride copolymers resin casting solution knifing at a certain temperature, in glass plate
On, it is then put into the first of certain temperature rapidly at certain thickness nascent state film, then by nascent state diaphragm plate with knifing machine striking
It 5-20 seconds in coagulation bath, places into the second coagulation bath of room temperature, the generation of nascent state film mutually separates, from liquid phase film-forming；
3) by film be placed in water further in film solvent and the dissolution completely such as small molecule pore-foaming agent, it is later that film is used
Ammonium sulfate solution is heat-treated under certain temperature, then with distilled water immersion, is finally freeze-dried film to get this hair is arrived
Bright vinylidene fluoride copolymers resin perforated membrane.
Vinylidene fluoride copolymers resin casting solution in the step 1) has lower critical solution temperature (LCST), low
At a temperature of the LCST, which is uniform Polymer Solution, and when being higher than the LCST temperature, originally uniform fluorine second partially
Alkene copolymer resin solution generation mutually separate, the lower critical solution temperature (LCST) between 1 DEG C -125 DEG C, preferably 35 DEG C -
80℃。
Vinylidene fluoride copolymers resin casting solution in the step 1) is quaternary and the system that the above component is constituted, packet
Vinylidene fluoride copolymers resin, second of macromolecule, solvent and small molecule pore-foaming agent are included, small molecule pore-foaming agent must chloride containing
Magnesium, but other small molecule compounds can be added simultaneously, the small molecule pore-foaming agent magnesium chloride can be anhydrous magnesium chloride,
It is also possible to the magnesium chloride containing the crystallization water.
Second of macromolecule in the step 1) is the height for having preferable compatibility with vinylidene fluoride copolymers resin
Molecular material can be water-insoluble macromolecule, be also possible to water soluble polymer, the height with carbonyl in preferred structure unit
Molecule such as polyvinylpyrrolidone (PVP), it is without being limited thereto.
Solvent in the step 1) is the solvent that can dissolve vinylidene fluoride copolymers resin, such as dimethylformamide
(DMF), dimethyl acetamide (DMAc), N-Methyl pyrrolidone (NMP), are also possible to the mixed solvent containing the solvent, no
It is limited to this, there is carbonyl in solvent preferred structure unit, electron donor-donor phase can occur with small molecule pore-foaming agent magnesium chloride
The solvation magnesium that interaction forms multi-solvent molecule closes ionic structure such as [Mg (DMAc)6]2+And with vinylidene fluoride copolymers resin
Between solubility parameter difference Δ δs-pLess than 3MPa0.5Organic solvent, such as dimethyl acetamide (DMAc).
Small molecule pore-foaming agent magnesium chloride in the step 1) can be copolymerized with the vinylidene in the step 1)
Resin and second of macromolecule generate electron donor-donor interaction effect.
Heating for dissolving temperature in the step 1) is lower than 130 DEG C, while can be higher than LCST temperature, but preferably shorter than
The dissolution of LCST temperature, the macromolecule casting solution temperature after being completely dissolved are maintained at stand-by lower than LCST temperature.
Knifing under certain temperature in the step 2), this temperature is lower than LCST temperature to keep casting solution to be in heating power
Learn stable state, preferably shorter than 5-10 DEG C of LCST temperature.
The first coagulation bath in the step 2) is polyethylene glycol 200, and temperature is in 90-140 DEG C of section and is higher than LCST
Temperature, the second coagulation bath are the non-solvents of vinylidene fluoride copolymers resin, such as water, ethyl alcohol, solvent-laden aqueous solution, are not limited to
This.
The phase separating mechanism that nascent state film in the step 2) occurs in the first coagulation bath for being higher than LCST temperature
Based on TIPS mechanism, i.e., nascent state film is integrally rapid under the action of thermal difference between the first coagulation bath temperature and casting solution temperature
Thermal inactive occurs, later the film-forming in the second coagulation bath.
Ammonium persulfate mass percentage in ammonium persulfate aqueous solution in the step 3) is 8-10%, heat treatment
For temperature in 75-85 DEG C of section, heat treatment time carried out freeze-drying molding at 3-4 hours.
The vinylidene fluoride copolymers resin film that the step 3) obtains be perforated membrane, the thickness of film at 20 μm -200 μm,
Average pore size is at 0.1 μm -1.0 μm, at a temperature of being higher than LCST successively after twice difference coagulation bath process and ammonium persulfate
The vinylidene fluoride copolymers resin perforated membrane of processing preparation does not have epidermis compacted zone, and main body is the sea of high porosity, near symmetrical
Continuous shape pore structure, while hydrophobicity is strong, is suitable for membrane distillation application.
Compared with prior art, the features of the present invention and advantage are:
1. the present invention is using a kind of vinylidene fluoride copolymers resin casting film for being based on lower critical solution temperature (LCST)
Liquid system has not yet to see the report with lower critical solution temperature (LCST).The present invention is by a kind of simultaneously including inclined fluorine second
Alkene copolymer resin, second of macromolecule, specific small molecule pore-foaming agent magnesium chloride and matched solvent quaternary system at
Function formed it is a kind of there is LCST casting film liquid system, be based on this, open a kind of vinylidene fluoride copolymers resin perforated membrane for preparing
New way.
2. one kind of the invention is based on the vinylidene fluoride copolymers resin casting film liquid system of lower critical solution temperature (LCST),
Its mechanism for forming lower critical solution temperature does not rely on system hydrogen bond action phase caused by temperature elevation process is destroyed
Separation, nor due to temperature sensitive high molecular presence, but because magnesium chloride can be high with the specific solvent of system and second
Electron donor-donor interaction can occur for molecule, wherein the solvation magnesium of the specific multi-solvent molecule formed closes ion in temperature
Degree when increasing can recurring structure changes and the interaction of different components is caused in the quaternary system to change, to reduce macromolecule
Solvability in the system promotees the generation that phases were separated.The casting film liquid system with lower critical solution temperature (LCST),
If replacing magnesium chloride with lithium chloride or zinc chloride etc., and other components are constant, then there is no low in foregoing temperature range for new system
Critical solution temperature (LCST)；In addition, becoming three from quaternary system if removing second of macromolecule or magnesium chloride from the system
First system, then lower critical solution temperature (LCST) is also not present in foregoing temperature range in ternary system.
3. the method that a kind of vinylidene fluoride copolymers resin of the invention prepares perforated membrane, TIPS involved in film-forming process
Split-phase is different from traditional TIPS phase process.Traditional TIPS phase process, vinylidene fluoride copolymers solution is in the condition of high temperature
Under be it is stable, occur mutually to separate at low temperature, corresponding UCST system；And TIPS phase process involved in the present invention, inclined fluorine
Ethylene copolymer solution be under low-temperature condition it is stable, occur mutually to separate at high temperature, corresponding LCST system, is a kind of difference
In the vinylidene fluoride copolymers filming technology of conventional method.
4. the method that a kind of vinylidene fluoride copolymers resin of the invention prepares perforated membrane, with single NIPS legal system film phase
Than not needing numerous technological parameters, but aperture is easier to；Compared with single traditional TIPS method film, it is not required to
The casting solution for the melting temperature (up to 180 DEG C or more) for being higher than vinylidene fluoride copolymers resin is operated, low energy consumption and technique
Simply.Successively by the vinylidene fluoride copolymers resin perforated membrane of twice difference coagulation bath process preparation at a temperature of being higher than LCST
There is no epidermis compacted zone, main body is the spongy pore structure of high porosity, near symmetrical, suitable for the application requirement of membrane distillation,
Characteristic big with flux, resistance is low, hydrophobicity is strong.
Detailed description of the invention
Fig. 1 is the cross section structure SEM figure of vinylidene fluoride copolymers resin perforated membrane prepared by the embodiment of the present invention 1.
Specific embodiment
Present invention is further described in detail with reference to embodiments.
Embodiment 1
By vinylidene fluoride copolymers resin ----Kynoar-hexafluoropropene (PVDF-HFP) mass percentage is
12%, the mass percentage of second of high molecular polythene pyrrolidones (PVP) is 12%, solvent dimethyl acetamide
(DMAc) mass percentage is 68%, and the mass percentage of small molecule pore-foaming agent magnesium chloride is 8% configuration PVDF-HFP casting
Magnesium chloride is dissolved completely in DMAc by film liquid first, and PVDF-HFP and PVP is added later, and agitating and heating is molten in 45 DEG C of constant temperature
Solution forms the PVDF-HFP casting solution of substantially uniformity, standing and defoaming.Later, by above-mentioned casting solution at 45 DEG C knifing, in glass
It in glass plate, then with knifing machine striking at nascent state film, and is put into rapidly in 97 DEG C of polyethylene glycol 200 15 seconds, then is transferred to often
In warm water, the generation of nascent state film is mutually separated, from liquid phase film-forming；By film be placed in water further in film solvent and small point
Sub- pore-foaming agent etc. dissolves out completely, and film is heat-treated 4 at 80 DEG C with the ammonium persulfate aqueous solution that mass percentage is 9% later
Hour, then with distilled water immersion one day, film is freeze-dried at -50 DEG C finally and is copolymerized to get to vinylidene of the invention
Resin perforated membrane.The lower critical solution temperature (LCST) of the PVDF-HFP casting film liquid system is 52 DEG C.First coagulation bath temperature
It is 45 DEG C higher than LCST temperature.The membrane structure of preparation is the spongy pore structure without cortex, as shown in Figure 1.Film with a thickness of 80 μm,
87 ° of contact angle, average pore size is 0.2 μm.Above-mentioned perforated membrane is placed in direct contact membrane distillation device, is contained with quality percentage
Amount is feed liquid for 3.5% sodium-chloride water solution, and 60 DEG C of feed liquid temperature, per-meate side is passed through 20 DEG C of pure water, measures membrane distillation process
Pure water permeation flux be 38L/m2.hr, salt-stopping rate is greater than 99.9%.
Embodiment 2
By vinylidene fluoride copolymers resin ----PVDF-HFP mass percentage is the mass percentage of 16%, PVP
It is 4%, solvent DMAc mass percentage is 72%, and the mass percentage of small molecule pore-foaming agent magnesium chloride is 8% configuration
Magnesium chloride, is dissolved completely in DMAc by PVDF-HFP casting solution first, later be added PVDF-HFP and PVP, agitating and heating in
47 DEG C of constant temperature dissolve the PVDF-HFP casting solution to form substantially uniformity, standing and defoaming.Later, above-mentioned casting solution is scraped at 47 DEG C
Film then with knifing machine striking at nascent state film, and is put into rapidly in 110 DEG C of polyethylene glycol 200 8 seconds on glass plate,
It is transferred in normal-temperature water again, the generation of nascent state film mutually separates, from liquid phase film-forming；Film is placed in water further molten in film
Agent and small molecule pore-foaming agent etc. completely dissolve out, later by film mass percentage be 10% ammonium persulfate aqueous solution in 85 DEG C
Lower heat treatment 3 hours, then with distilled water immersion one day, be finally freeze-dried film at -50 DEG C to get inclined fluorine of the invention is arrived
Ethylene copolymer resin perforated membrane.The lower critical solution temperature (LCST) of the PVDF-HFP casting film liquid system is 52 DEG C.First is solidifying
Glue bath temperature ratio LCST temperature is 58 DEG C high, and the membrane structure of preparation is the spongy pore structure without cortex.Film with a thickness of 90 μm, put down
Equal aperture is 0.12 μm.Above-mentioned perforated membrane is placed in direct contact membrane distillation device, is 3.5% with mass percentage
Sodium-chloride water solution is feed liquid, and 70 DEG C of feed liquid temperature, per-meate side is passed through 20 DEG C of pure water, and the pure water infiltration for measuring membrane distillation process is logical
Amount is 67L/m2.hr, salt-stopping rate is greater than 99.9%.
Embodiment 3
By vinylidene fluoride copolymers resin ----polychlorotrifluoroethylene-vinylidene fluoride copolymers P (VDF-CTFE) quality hundred
Dividing the mass percentage that content is 13%, PVP is 3%, and solvent N-methyl pyrilidone (NMP) mass percentage is
74%, the mass percentage of small molecule pore-foaming agent magnesium chloride is 10% configuration P (VDF-CTFE) casting solution, first by magnesium chloride
It is dissolved completely in NMP, adds P (VDF-CTFE) and PVP, agitating and heating dissolves the P (VDF- for forming substantially uniformity in 70 DEG C
CTFE) casting solution, standing and defoaming.Later, by above-mentioned casting solution, at 70 DEG C then knifing on glass plate uses knifing machine
Striking is put into rapidly in 130 DEG C of polyethylene glycol 200 10 seconds, then be transferred in normal-temperature water at nascent state film, and nascent state film occurs
It mutually separates, from liquid phase film-forming；By film be placed in water further in film solvent and the dissolution completely such as small molecule pore-foaming agent,
Later by film mass percentage be 8% ammonium persulfate aqueous solution be heat-treated 3.5 hours at 75 DEG C, then with distill water logging
Film is finally freeze-dried to get vinylidene fluoride copolymers resin perforated membrane of the invention is arrived by bubble one day at -50 DEG C.The P
(VDF-CTFE) lower critical solution temperature (LCST) of casting film liquid system is 75 DEG C.First coagulation bath temperature ratio LCST temperature is high by 55
DEG C, the membrane structure of preparation is the spongy pore structure without cortex.Film with a thickness of 100 μm, average pore size is 0.3 μm.It will be above-mentioned
Perforated membrane is placed in direct contact membrane distillation device, and the sodium-chloride water solution for being 3.5% using mass percentage is feed liquid, material
80 DEG C of liquid temperature, per-meate side is passed through 20 DEG C of pure water, and the pure water permeation flux for measuring membrane distillation process is 87L/m2.hr, salt-stopping rate
Greater than 99.9%.
Comparative example 1
Nascent state film is directly placed into the water-bath of unique coagulation bath i.e. 20 DEG C, remaining is with embodiment 1 with when step system
Standby polyvinylidene fluoride film.The lower critical solution temperature (LCST) of the vinylidene fluoride copolymers casting film liquid system is 52 DEG C.Coagulation bath
Temperature ratio LCST temperature is 32 DEG C low.Due to gel, no TIPS split-phase, the vinylidene fluoride copolymers of preparation at a temperature of being lower than LCST
Film only has NIPS phase process, and the membrane structure of preparation is typical finger-like pore structure.Film with a thickness of 90 μm, average pore size is
0.03 μm, the pure water permeation flux of membrane distillation process is only the 23% of the film that embodiment 1 obtains.
Comparative example 2
Nascent state film is directly placed into the water-bath of unique coagulation bath i.e. 30 DEG C, and without ammonium persulfate processing, remaining is same
Embodiment 1 prepares polyvinylidene fluoride film with when step.The low Critical Solution temperature of the vinylidene fluoride copolymers casting film liquid system
Spending (LCST) is 52 DEG C.Coagulation bath temperature ratio LCST temperature is 22 DEG C low.Due to gel at a temperature of being lower than LCST, no TIPS divides
Phase, the vinylidene fluoride copolymers film of preparation only have NIPS phase process, and the membrane structure of preparation is typical finger-like pore structure.Film
With a thickness of 90 μm, chlorination sodium leakage occurs for membrane distillation process.
Comparative example 3
It is 12% by PVDF-HFP mass percentage, the quality hundred of second of high molecular polythene pyrrolidones (PVP)
Dividing content is 0%, and solvent DMAc mass percentage is 80%, and the mass percentage of small molecule pore-foaming agent magnesium chloride is 8%
Vinylidene fluoride copolymers casting solution is configured, remaining forms the vinylidene fluoride copolymers of substantially uniformity with 1 step of embodiment through dissolving
Casting solution.Lower critical solution temperature (LCST) is not present between 1 DEG C -125 DEG C in the vinylidene fluoride copolymers casting film liquid system, should
Ternary system cannot form LCST system of the invention.
Comparative example 4
It is 12% by PVDF-HFP mass percentage, the quality hundred of second of high molecular polythene pyrrolidones (PVP)
Dividing content is 12%, and solvent DMAc mass percentage is 76%, and the mass percentage of small molecule pore-foaming agent magnesium chloride is 0%
Vinylidene fluoride copolymers casting solution is configured, remaining forms the vinylidene fluoride copolymers of substantially uniformity with 1 step of embodiment through dissolving
Casting solution.Lower critical solution temperature (LCST) is not present between 1 DEG C -125 DEG C in the vinylidene fluoride copolymers casting film liquid system, should
Ternary system cannot form LCST system of the invention.
Comparative example 5
It is 12% by P (VDF-CTFE) mass percentage, the quality of second of high molecular polythene pyrrolidones (PVP)
Percentage composition is 11.5%, and solvent DMAc mass percentage is 68%, and small molecule pore-foaming agent uses lithium chloride, quality percentage instead
Content is 8.5% configuration vinylidene fluoride copolymers casting solution, remaining forms the inclined fluorine of substantially uniformity with 1 step of embodiment through dissolving
Ethylene copolymer casting solution.Low Critical Solution temperature is not present in the vinylidene fluoride copolymers casting film liquid system between 1 DEG C -125 DEG C
It spends (LCST), which cannot form LCST system of the invention.
Comparative example 6
It is 12% by P (VDF-CTFE) mass percentage, the quality of second of high molecular polythene pyrrolidones (PVP)
Percentage composition is 12, and solvent DMAc mass percentage is 71%, and small molecule pore-foaming agent uses zinc chloride, mass percentage instead
For 5% configuration vinylidene fluoride copolymers casting solution, remaining is total with the vinylidene that 1 step of embodiment forms substantially uniformity through dissolution
Polymers casting solution.Lower critical solution temperature is not present in the vinylidene fluoride copolymers casting film liquid system between 1 DEG C -125 DEG C
(LCST), which cannot form LCST system of the invention.
Claims (9)
1. a kind of method that vinylidene fluoride copolymers resin prepares perforated membrane, it is characterised in that the following steps are included:
1) it prepares the vinylidene fluoride copolymers resin casting solution with lower critical solution temperature: pressing vinylidene fluoride copolymers resinite
Amount percentage composition is 5%-40%, and second of high molecular mass percentage is 1%-20%, and solvent quality percentage composition is
50%-85%, the mass percentage of small molecule pore-foaming agent are the vinylidene fluoride copolymers tree that 1%-20% configures suitable concentration
Small molecule pore-foaming agent is dissolved completely in solvent by rouge casting solution first, and vinylidene fluoride copolymers resin and second is added later
Kind macromolecule, agitating and heating dissolve to form vinylidene fluoride copolymers being completely dissolved, with lower critical solution temperature (LCST)
Resin casting film liquid system, standing and defoaming are stand-by；
2) by above-mentioned prepared vinylidene fluoride copolymers resin casting solution knifing at a certain temperature, on glass plate, so
It uses knifing machine striking at certain thickness nascent state film afterwards, then nascent state diaphragm plate is put into rapidly to the first coagulation bath of certain temperature
It is 5-20 seconds middle, it places into the second coagulation bath of room temperature, the generation of nascent state film mutually separates, from liquid phase film-forming；
3) by film be placed in water further in film solvent and the dissolution completely such as small molecule pore-foaming agent, later by film persulfuric acid
Aqueous ammonium is heat-treated under certain temperature, then with distilled water immersion, and finally film is freeze-dried to get to of the invention
Vinylidene fluoride copolymers resin perforated membrane.
2. the method that a kind of vinylidene fluoride copolymers resin according to claim 1 prepares perforated membrane, which is characterized in that step
It is rapid 1) in vinylidene fluoride copolymers resin casting solution have lower critical solution temperature (LCST), be lower than the LCST at a temperature of,
The casting solution is uniform Polymer Solution, and when being higher than the LCST temperature, originally uniform vinylidene fluoride copolymers solution hair
Raw mutually separation becomes cloudy, and the lower critical solution temperature (LCST) is between 1 DEG C -125 DEG C, preferably at 35 DEG C -80 DEG C.
3. the method that a kind of vinylidene fluoride copolymers resin according to claim 1 prepares perforated membrane, which is characterized in that step
It is rapid 1) in vinylidene fluoride copolymers casting solution be system that quaternary and the above component are constituted, including vinylidene fluoride copolymers tree
Rouge, second of macromolecule, solvent and small molecule pore-foaming agent, small molecule pore-foaming agent must contain magnesium chloride, but can add simultaneously
Other small molecule compounds, the small molecule pore-foaming agent magnesium chloride, can be anhydrous magnesium chloride, are also possible to containing the crystallization water
Magnesium chloride.
4. the method that a kind of vinylidene fluoride copolymers resin according to claim 1 prepares perforated membrane, which is characterized in that step
It is rapid 1) in second of macromolecule be with vinylidene fluoride copolymers have preferable compatibility high molecular material, can be non-aqueous
Property macromolecule, be also possible to water soluble polymer, with the macromolecule such as polyvinylpyrrolidone of carbonyl in preferred structure unit
(PVP), without being limited thereto.
5. the method that a kind of vinylidene fluoride copolymers resin according to claim 1 prepares perforated membrane, which is characterized in that step
It is rapid 1) in solvent be the solvent that can dissolve vinylidene fluoride copolymers, such as dimethylformamide (DMF), dimethyl acetamide
(DMAc), N-Methyl pyrrolidone (NMP) is also possible to the mixed solvent containing the solvent, without being limited thereto, solvent preferred structure
There is carbonyl in unit, can interact to form multi-solvent point with small molecule pore-foaming agent magnesium chloride generation electron donor-donor
The solvation magnesium of son closes ionic structure such as [Mg (DMAc)6]2+And the solubility parameter difference Δ δ between vinylidene fluoride copolymerss-p
Less than 3MPa0.5Organic solvent, such as dimethyl acetamide (DMAc).
6. the method that a kind of vinylidene fluoride copolymers resin according to claim 1 prepares perforated membrane, which is characterized in that step
It is rapid 2) in certain temperature under knifing, this temperature lower than LCST temperature to keep casting solution to be in thermodynamics stable state, preferably shorter than
5-10 DEG C of LCST temperature, first coagulation bath are polyethylene glycol 200, and temperature is in 90-140 DEG C of section and is higher than LCST temperature
Degree, the second coagulation bath is the non-solvent of vinylidene fluoride copolymers resin, without being limited thereto such as water, ethyl alcohol, solvent-laden aqueous solution.
7. the method that a kind of vinylidene fluoride copolymers resin according to claim 1 prepares perforated membrane, which is characterized in that step
It is rapid 2) in nascent state film in the first coagulation bath for being higher than LCST temperature the phase separating mechanism that occurs with Thermal inactive mechanism
Based on, i.e., thermotropic phase integrally occurs rapidly for nascent state film under the action of thermal difference between the first coagulation bath temperature and casting solution temperature
It separates, later the film-forming in the second coagulation bath.
8. the method that a kind of vinylidene fluoride copolymers resin according to claim 1 prepares perforated membrane, which is characterized in that step
It is rapid 3) in ammonium persulfate aqueous solution in ammonium persulfate mass percentage be 8-10%, heat treatment temperature is in 75-85 DEG C of area
Between, heat treatment time carried out freeze-drying molding at 3-4 hours.
9. the method that a kind of vinylidene fluoride copolymers resin according to claim 1 prepares perforated membrane, which is characterized in that step
The rapid vinylidene fluoride copolymers resin film 3) obtained is perforated membrane, the thickness of film at 20 μm -200 μm, average pore size 0.1 μm -
1.0 μm, vinylidene fluoride copolymers resin at a temperature of being higher than LCST successively by the preparation of twice difference coagulation bath process is porous
Film does not have epidermis compacted zone, and main body is the spongy pore structure of high porosity, near symmetrical, is suitable for membrane distillation application.
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