Polyvinylidene fluoride film, method for preparing the same, and use thereof

Abstract

This invention provides a polyvinylidene fluoride (PVDF) membrane, its preparation method, and its applications, relating to the field of materials technology. The preparation method of the PVDF membrane provided by this invention includes: coating a casting solution onto a substrate to form a liquid film; then, holding the carrier in an environment of 30-80°C for 1-5 seconds; subsequently, immersing the carrier in a coagulation bath to solidify it into a film; and finally, washing with water to obtain the PVDF membrane. This preparation method is environmentally friendly, simple, and low-cost. The obtained PVDF membrane has a dendritic-spherulitic alternating porous structure with controllable pore size, and can be used in biotechnology applications such as protein imprinting and sterilization filtration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials, in particular to a polyvinylidene fluoride (PVDF) membrane and a preparation method and application thereof. BACKGROUND

[0002] Currently, there are the following technical bottlenecks in the production and application of PVDF protein transfer membranes:

[0003] (1) Additive residue problem: Commercial PVDF membranes often add plasticizers, pore-forming agents and other auxiliary ingredients, which may affect protein binding or introduce background interference, and some additives have biological safety hazards.

[0004] (2) Complex preparation process: The existing patent technologies mostly use vapor-induced phase separation (VIPS) or thermal-induced phase separation (TIPS) methods, which need to accurately control temperature, pressure or vapor environment, and the process is complicated and the equipment cost is high, which is difficult to scale up production.

[0005] (3) Structural limitations: Traditional PVDF membranes are mostly homogeneous porous structures, and the specific surface area is limited, which leads to low protein adsorption efficiency, especially for small molecule proteins (<30kDa) with poor retention effect.

[0006] (4) Environmental protection and cost problems: Some solvents or additives are toxic, and the post-processing is difficult, which does not meet the green chemistry trend; complex process also increases the production cost.

[0007] The present application solves the above problems by using an additive-free formula and a short-time TIPS plus NIPS process, which ensures high performance while realizing environmental protection, low cost and easy scale-up production.

[0008] Therefore, the present application is proposed. SUMMARY

[0009] The first object of the present application is to provide a preparation method of a polyvinylidene fluoride (PVDF) membrane to solve the above technical problems.

[0010] The second object of the present application is to provide a polyvinylidene fluoride membrane.

[0011] The third object of the present application is to provide the application of the above-mentioned preparation method of the polyvinylidene fluoride membrane in the preparation of protein transfer membranes.

[0012] In order to achieve the above objects, the following technical solutions are adopted:

[0013] In the first aspect, the present application provides a preparation method of a polyvinylidene fluoride membrane, comprising the following steps:

[0014] The casting solution is coated on a substrate to form a liquid film, and then the carrier is left in an environment at 30-80 DEG C for 1-5 s, and then the carrier is immersed in a coagulation bath to solidify into a film, and then the polyvinylidene fluoride film is prepared after washing with water.

[0015] The casting solution comprises 10%-25% of polyvinylidene fluoride by mass percentage, and the balance is an organic solvent;

[0016] The organic solvent comprises one or more of N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), trimethyl phosphate or triethyl phosphate;

[0017] The coagulation bath is an aqueous solution of alcohol with a mass concentration of 30%-100%.

[0018] As a further technical solution, the molecular weight of the polyvinylidene fluoride is 300-800,000 Da.

[0019] As a further technical solution, the casting solution further comprises a non-solvent.

[0020] As a further technical solution, the non-solvent comprises one or more of triethylene glycol, isopropyl alcohol, ethanol or methanol;

[0021] The mass percentage of the non-solvent is 3%-15%.

[0022] As a further technical solution, the substrate comprises glass, a plastic film or a non-woven fabric.

[0023] As a further technical solution, a doctor blade is used to coat the casting solution on the substrate to form a liquid film; the coating thickness is 300-600 μm.

[0024] As a further technical solution, the alcohol comprises one or more of methanol, ethanol or propanol.

[0025] In a second aspect, the application provides a polyvinylidene fluoride film prepared by the above preparation method.

[0026] As a further technical solution, the pore size of the polyvinylidene fluoride film is 0.1-1.2 μm.

[0027] In a third aspect, the application provides the use of the above preparation method in the preparation of a protein transfer film.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] The polyvinylidene fluoride membrane preparation method provided by the application is prepared by using a polyvinylidene fluoride-organic solvent system through a short-time thermal induced phase separation (TIPS) method and a non-solvent induced phase separation (NIPS) method, is environmentally friendly: no additives (such as surfactants, pore-forming agents, etc.) are added, chemical residues are avoided to interfere with the experiment, and environmental pollution is reduced; the process is simple: the thermal induced phase separation process does not need precise temperature control, the membrane pores and the membrane structure are controllable (the membrane pores are controlled by regulating the casting solution formula), no complex equipment is needed, the operation is simple, the cost is low, and the method is suitable for large-scale industrial production; the structure is optimized: by accurately regulating the composition of the coagulation bath, a unique dendritic-spherulitic alternating porous structure is formed, the specific surface area is significantly improved, and excellent protein adsorption capacity is obtained; and the polyvinylidene fluoride membrane prepared has wide compatibility: the membrane pore size is controllable (0.1-1.2 μm), is suitable for different molecular weight proteins (10-200 kDa), has high transfer efficiency and low background signal. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0031] Figure 1 The electron microscope result of the polyvinylidene fluoride membrane of Example 1;

[0032] Figure 2 The electron microscope result of the polyvinylidene fluoride membrane of Comparative Example 1;

[0033] Figure 3 The electron microscope result of the polyvinylidene fluoride membrane of Comparative Example 2;

[0034] Figure 4 The electron microscope result of the polyvinylidene fluoride membrane of Comparative Example 3;

[0035] Figure 5 The electron microscope result of the polyvinylidene fluoride membrane of Comparative Example 4. DETAILED DESCRIPTION

[0036] The embodiments of the present application will be described in detail below with reference to the embodiments and examples, but those skilled in the art will understand that the following embodiments and examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present application. If no specific conditions are indicated, the conventional conditions or the conditions recommended by the manufacturer are used. If no manufacturer of the reagent or instrument is indicated, it is a conventional product that can be obtained by commercial purchase.

[0037] In a first aspect, the present application provides a preparation method of a polyvinylidene fluoride membrane, comprising the following steps:

[0038] The casting solution is coated on a substrate to form a liquid film, and then the carrier is left in an environment at 30-80°C for 1-5s, and then the carrier is immersed in a coagulation bath to solidify into a membrane, and then the polyvinylidene fluoride membrane is prepared after water washing;

[0039] The casting solution comprises 10%-25% of polyvinylidene fluoride and the balance of organic solvent in terms of mass percentage;

[0040] The organic solvent comprises one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, trimethyl phosphate or triethyl phosphate;

[0041] The coagulation bath is an aqueous solution of alcohol with a mass concentration of 30%-100%.

[0042] It should be noted that before immersion in the coagulation bath, the carrier is left in the environment, for example, the temperature of the environment can be, but is not limited to, 30°C, 50°C or 80°C, and the time of staying can be, but is not limited to, 1s, 3s or 5s. During the staying process, there is no need for steam or strict control of high temperature and high pressure environment, and the energy consumption is low. Through this process, the phase separation can be delayed and the crystallization can be inhibited (it should be noted that the phase separation delay in this scheme is relative to direct immersion in the coagulation bath. If the coagulation bath is directly immersed, instantaneous phase separation will occur. In this scheme, the liquid film is left at a certain environmental temperature for a period of time, which can avoid direct phase separation), and then after the coagulation bath treatment, a membrane with a dendritic-spherulite alternating porous structure can be obtained.

[0043] It should be noted that the "dendritic-spherulite alternating porous structure" in this scheme refers to the alternating distribution of dendritic fibers and spherulites (radial crystal clusters), in which the spherulites are embedded in the gaps of the dendritic network (such as Figure 1The "crystal ball" is a small ball on the dendritic structure, which connects the dendritic structure together), and the two are interwoven to form a three-dimensional interconnected channel structure; the dendritic fiber dominates the high porosity and connectivity, and the crystal ball enhances the mechanical stability of the film by connecting with the dendritic fiber; this unique alternative distribution is derived from the competition and synergy of liquid-liquid phase separation (forming dendritic fibers) and crystallization kinetics (forming crystal balls) in the short TIPS and NIPS process, and finally forms a hierarchical pore structure with high porosity and mechanical strength.

[0044] In some alternative embodiments, the molecular weight of the polyvinylidene fluoride is in the range of 300-800 million Da.

[0045] In some alternative embodiments, the casting solution further comprises a non-solvent.

[0046] The size of the film pores is regulated by adding a non-solvent.

[0047] In some alternative embodiments, the non-solvent includes, but is not limited to, one or more of triethylene glycol, isopropyl alcohol, ethanol or methanol;

[0048] The mass fraction of the non-solvent may be, for example, but is not limited to, 3%, 10% or 15%.

[0049] In some alternative embodiments, the substrate includes, but is not limited to, glass, plastic film or non-woven fabric, or other substrates described by those skilled in the art.

[0050] In some alternative embodiments, a doctor blade is used to coat the substrate into a liquid film; the thickness of the coating may be, for example, but is not limited to, 300 μm, 500 μm or 600 μm.

[0051] In some alternative embodiments, the alcohol includes one or more of methanol, ethanol or propanol.

[0052] The present application ensures uniform and stable film structure by synergistically regulating the coating thickness and coagulation bath concentration.

[0053] In a second aspect, the present application provides a polyvinylidene fluoride film prepared by the above preparation method.

[0054] The polyvinylidene fluoride film has a unique dendritic-crystal alternating porous structure, a significantly increased specific surface area, excellent protein adsorption capacity, and can be used for protein blotting, bacteria removal filtration and other biological application technologies.

[0055] In some alternative embodiments, the pore size of the polyvinylidene fluoride film may be, for example, but is not limited to, 0.1 μm, 0.6 μm or 1.2 μm.

[0056] In some alternative embodiments, the thickness of the polyvinylidene fluoride membrane is 100-300 μm.

[0057] In a third aspect, the present application provides the use of the above preparation method in the preparation of a protein transfer film.

[0058] The polyvinylidene fluoride membrane prepared by the preparation method provided by the present application has controllable pore size and can be used as a transfer film for proteins with different molecular weights, and has high transfer efficiency and low background signal.

[0059] The present application will be further described below through specific examples, but it should be understood that these examples are only used for more detailed description and should not be understood as limiting the present application in any form.

[0060] In the following examples and comparative examples, "parts" refer to "parts by weight".

[0061] Example 1

[0062] A polyvinylidene fluoride membrane, the preparation method thereof comprises:

[0063] (1) 25 parts of polyvinylidene fluoride powder (Mw=30w) are weighed in a container, 70 parts of N,N-dimethylacetamide and 5 parts of isopropanol are added and stirred to dissolve, and the obtained casting solution is left to stand for 24 hours for defoaming;

[0064] (2) The casting solution is uniformly coated on a smooth and clean glass plate by using a doctor blade with a gap of 500 μm, and is left to stand in an 80℃ hot air environment for 1s and is immersed in anhydrous ethanol for 2min;

[0065] (3) The wet film is rinsed with water and is dried at 120℃ to obtain a PVDF membrane with a pore size of 0.45 μm.

[0066] It is detected that the bubble point pressure is 0.064 MPa and the water flow rate is 45328 LMH / bar, and the surface and cross-sectional electron microscope images are shown in Figure 1 a and Figure 1 b of

[0067] Example 2

[0068] A polyvinylidene fluoride membrane, the preparation method thereof comprises:

[0069] (1) 18 parts of polyvinylidene fluoride powder (Mw=50w) are weighed in a container, 79 parts of N-methylpyrrolidone and 3 parts of isopropanol are added and stirred to dissolve, and the obtained casting solution is left to stand for 24 hours for defoaming;

[0070] (2) The casting solution is uniformly coated on a smooth and clean glass plate with a gap of 500 μm, and is left in a 50°C hot air environment for 3 s and immersed in a 60% isopropanol solution for 2 min;

[0071] (3) The wet film is rinsed with water and dried at 90°C to obtain a PVDF film with a pore size of 0.1 μm.

[0072] It is detected that the bubble point pressure is 0.29 MPa and the water flow rate is 927 LMH / bar.

[0073] Example 3

[0074] A polyvinylidene fluoride film, the preparation method comprising:

[0075] (1) 10 parts of polyvinylidene fluoride powder (Mw=80w) are weighed in a container, 90 parts of N,N-dimethylformamide are added and stirred to dissolve, and the obtained casting solution is left to stand for 24 hours to remove bubbles;

[0076] (2) The casting solution is uniformly coated on a smooth and clean glass plate with a gap of 500 μm, and is left in a 30°C hot air environment for 5 s and immersed in a 30% ethanol solution for 2 min;

[0077] (3) The wet film is rinsed with water and dried at 80°C to obtain a PVDF film with a pore size of 1.2 μm.

[0078] It is detected that the bubble point pressure is 0.026 MPa and the water flow rate is 93576 LMH / bar.

[0079] Comparative Example 1

[0080] A polyvinylidene fluoride film, the preparation method comprising:

[0081] (1) 25 parts of polyvinylidene fluoride powder (Mw=30w) are weighed in a container, 70 parts of N,N-dimethylacetamide and 5 parts of isopropanol are added and stirred to dissolve, and the obtained casting solution is left to stand for 24 hours to remove bubbles;

[0082] (2) The casting solution is uniformly coated on a smooth and clean glass plate with a gap of 500 μm, and is immersed in water for 2 min;

[0083] (3) The wet film is rinsed with water and dried at 120°C to obtain a PVDF film.

[0084] This condition does not undergo short TIPS, and water is used as a non-solvent, resulting in no pores on the surface, forming a dense skin layer, so that the bubble point pressure and water flow rate cannot be tested, and finger-shaped holes appear near the surface. The electron microscope surface and cross-sectional view are respectively as Figure 2 a and Figure 2a and b in FIG. 1.

[0085] Comparative Example 2

[0086] A polyvinylidene fluoride membrane, the preparation method comprising:

[0087] (1) 25 parts of polyvinylidene fluoride powder (Mw=30w) were weighed into a container, 70 parts of N,N-dimethylacetamide, 5 parts of isopropanol were stirred and dissolved, and the obtained casting solution was left to stand for 24 hours to remove bubbles;

[0088] (2) The casting solution was uniformly coated on a smooth and clean glass plate with a gap of 500 μm using a doctor blade, and then immersed in anhydrous ethanol for 2 min;

[0089] (3) The wet film was rinsed with water and dried at 120°C to obtain a PVDF membrane.

[0090] Under this condition, the PVDF membrane was obtained directly by long-time TIPS method, and the electron microscope surface and cross-section diagram thereof were shown in a and b in FIG. 1, respectively. It was detected that the bubble point pressure thereof was 0.035 MPa, and the water flow rate was 100430 LMH / bar. Since the TIPS was not passed to delay the phase separation and inhibit the crystallization process, the pore size was larger, and the structure was mainly large spherocrystal, resulting in the decrease of the bubble pressure of the membrane and the smaller specific surface area. Figure 3 Figure 3 a and b in FIG. 1, respectively. Since the NIPS was not passed to slowly form pores, a dense skin layer was also formed on the surface, resulting in that the bubble point pressure and water flow rate could not be tested, and the finger-like pore structure was more obvious.

[0091] Comparative Example 3

[0092] A polyvinylidene fluoride membrane, the preparation method comprising:

[0093] (1) 25 parts of polyvinylidene fluoride powder (Mw=30w) were weighed into a container, 70 parts of N,N-dimethylacetamide, 5 parts of isopropanol were stirred and dissolved, and the obtained casting solution was left to stand for 24 hours to remove bubbles;

[0094] (2) The casting solution was uniformly coated on a smooth and clean glass plate with a gap of 500 μm using a doctor blade, and then immersed in anhydrous ethanol for 2 min;

[0095] (3) The wet film was rinsed with water and dried at 120°C to obtain a PVDF membrane.

[0096] Under this condition, the PVDF membrane was obtained directly by long-time TIPS method, and the electron microscope surface and cross-section diagram thereof were shown in a and b in FIG. 1, respectively. It was detected that the bubble point pressure thereof was 0.035 MPa, and the water flow rate was 100430 LMH / bar. Since the TIPS was not passed to delay the phase separation and inhibit the crystallization process, the pore size was larger, and the structure was mainly large spherocrystal, resulting in the decrease of the bubble pressure of the membrane and the smaller specific surface area. Figure 4 Figure 4 a and b in FIG. 1, respectively. Since the NIPS was not passed to slowly form pores, a dense skin layer was also formed on the surface, resulting in that the bubble point pressure and water flow rate could not be tested, and the finger-like pore structure was more obvious.

[0097] Comparative Example 4 ​​

[0098] A polyvinylidene fluoride membrane, the preparation method of which includes:

[0099] (1) Weigh 25 parts of polyvinylidene fluoride powder (Mw=30w) into a container, add 70 parts of N,N-dimethylacetamide and 5 parts of isopropanol and stir to dissolve. Let the resulting casting solution stand for 24 hours to remove bubbles.

[0100] (2) Apply the casting solution evenly to a smooth and clean glass plate with a scraper with a gap of 500 μm, and immerse it in boiling anhydrous ethanol for 2 min.

[0101] (3) After rinsing the wet film with water, dry it at 120°C to obtain a PVDF film.

[0102] Under these conditions, the PVDF film was obtained directly using the simultaneous TIPS and NIPS processing method without prior short-time TIPS. The surface and cross-sectional images under electron microscopy are shown below. Figure 5 a and Figure 5 As shown in b in the figure. The bubble point pressure was measured to be 0.038 MPa, and the water flow rate was 102191 LMH / bar. This process did not involve pre-treatment with TIPS to delay phase separation and inhibit crystallization. Even with the TIPS introduced during the NIPS process, the pore size remained larger, and the structure was mainly composed of large spherulites, resulting in a lower bubble pressure and smaller specific surface area, similar to the results in Comparative Example 2.

[0103] Comparative Example 5

[0104] A polyvinylidene fluoride membrane, the preparation method of which includes:

[0105] (1) Weigh 25 parts of polyvinylidene fluoride powder (Mw=30w) into a container, add 70 parts of N,N-dimethylacetamide and 5 parts of isopropanol and stir to dissolve. Let the resulting casting solution stand for 24 hours to remove bubbles.

[0106] (2) The casting solution was evenly coated onto a smooth and clean glass plate with a scraper with a gap of 500 μm, and kept in a hot air environment at 100℃ for 30s, and then immersed in anhydrous ethanol for 2min.

[0107] (3) After rinsing the wet film with water, dry it at 120°C to obtain a PVDF film.

[0108] Under these conditions, the TIPS temperature was too high and the time was too long, causing the liquid film surface to solidify into a gel, forming a dense skin layer, which made it impossible to test the bubble point pressure and water flow rate.

[0109] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for producing a polyvinylidene fluoride film, characterized by, The method comprises the following steps: The casting solution is coated on a substrate to form a liquid film, and then the carrier is left in an environment at 30-80℃ for 1-5s, and then the carrier is immersed in a coagulation bath to solidify into a film, and then the polyvinylidene fluoride film is prepared after washing with water; the polyvinylidene fluoride film is a film with dendritic-spherulite alternating porous structure; The casting solution comprises 10%-25% of polyvinylidene fluoride and the rest is organic solvent by mass percentage; The organic solvent comprises one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, trimethyl phosphate or triethyl phosphate; The coagulation bath is an aqueous solution of alcohol with a mass concentration of 30%-100%.

2. The production method according to claim 1, characterized by, The molecular weight of the polyvinylidene fluoride is 300-800 thousand Da.

3. The preparation method according to claim 1, characterized in that, The casting solution further comprises a non-solvent.

4. The production method according to claim 3, characterized by, The non-solvent comprises one or more of triethylene glycol, isopropyl alcohol, ethanol or methanol; The mass percentage of the non-solvent is 3%-15%.

5. The preparation method according to claim 1, characterized in that, The substrate comprises glass, plastic film or non-woven fabric.

6. The method of claim 1, wherein, A doctor blade is used to coat the casting solution on the substrate to form a liquid film; the coating thickness is 300-600μm.

7. The preparation method according to claim 1, characterized in that, The alcohol comprises one or more of methanol, ethanol or propanol.

8. Use of the preparation method of any one of claims 1-7 in the preparation of a protein transfer film.

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