Polyvinylidene fluoride membrane as well as preparation method and application thereof

Abstract

The invention provides a polyvinylidene fluoride membrane as well as a preparation method and application thereof, and relates to the technical field of materials. The preparation method of the polyvinylidene fluoride membrane provided by the invention comprises the following steps: coating a membrane casting solution on a base material to form a liquid membrane, staying a carrier in an environment of 30-80 DEG C for 1-5 seconds, immersing the carrier into a coagulating bath, curing to form a membrane, and washing with water to obtain the polyvinylidene fluoride membrane. The preparation method is environment-friendly, simple in process and low in cost, and the prepared polyvinylidene fluoride membrane has a dendritic-spherocrystal alternate porous structure and controllable membrane aperture, and can be used for biological application technologies such as western blot, sterilization and 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, the production and application of PVDF protein transfer membranes have the following technical bottlenecks: (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.

[0003] (2) Complex preparation process: Existing patent technologies mostly use vapor-induced phase separation (VIPS) or thermal-induced phase separation (TIPS) methods, which require precise control of temperature, pressure or steam environment, and the process is complicated and the equipment cost is high, which is difficult to scale up production.

[0004] (3) Structural limitations: Traditional PVDF membranes are mostly homogeneous porous structures, with limited specific surface area, resulting in low protein adsorption efficiency, especially for small molecule proteins (<30 kDa) with poor retention effect.

[0005] (4) Environmental protection and cost problems: Some solvents or additives are toxic and difficult to dispose, which does not meet the trend of green chemistry; complex process also increases production cost.

[0006] 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 achieving environmental protection, low cost and easy scale-up production.

[0007] Therefore, the present application is proposed. SUMMARY

[0008] 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.

[0009] The second object of the present application is to provide a polyvinylidene fluoride membrane.

[0010] 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.

[0011] In order to achieve the above objects, the following technical solutions are adopted: In a first aspect, the present application provides a preparation method of a polyvinylidene fluoride membrane, comprising the following steps: casting a casting solution on a substrate to form a liquid film, then placing the carrier in an environment at 30-80℃ for 1-5s, then immersing the carrier in a coagulation bath to solidify into a membrane, and then washing with water to obtain a polyvinylidene fluoride membrane; The casting solution comprises 10-25% of polyvinylidene fluoride by mass percentage, and the rest is an organic solvent; The organic solvent comprises one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), trimethyl phosphate or triethyl phosphate; The coagulation bath is an aqueous solution of alcohol with a mass concentration of 30-100%.

[0012] As a further technical solution, the molecular weight of the polyvinylidene fluoride is 300-800,000 Da.

[0013] As a further technical solution, the casting solution further comprises a non-solvent.

[0014] As a further technical solution, 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%.

[0015] As a further technical solution, the substrate comprises glass, plastic film or non-woven fabric.

[0016] As a further technical solution, a doctor blade is used to coat the substrate into a liquid film; the coating thickness is 300-600 μm.

[0017] As a further technical solution, the alcohol comprises one or more of methanol, ethanol or propanol.

[0018] In a second aspect, the application provides a polyvinylidene fluoride film prepared by the above preparation method.

[0019] As a further technical solution, the pore size of the polyvinylidene fluoride film is 0.1-1.2 μm.

[0020] In a third aspect, the application provides the use of the above preparation method in the preparation of a protein transfer film.

[0021] Compared with the prior art, the application has the following beneficial effects: The polyvinylidene fluoride membrane preparation method provided by the application is prepared by using a polyvinylidene fluoride-organic solvent system through a short-time thermally induced phase separation (TIPS) method and a non-solvent induced phase separation (NIPS) method, the preparation method is environmentally friendly: without adding any additives (such as surfactants, pore-forming agents, etc.), avoiding the interference of chemical residues on the experiment, and reducing environmental pollution; the process is simple: the thermally 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 the casting solution formula), without the need for complex equipment, simple operation, low cost, and suitable for large-scale industrial production; the structure is optimized: by accurately controlling 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

[0022] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0023] Figure 1 The electron microscope results of the polyvinylidene fluoride membrane of Example 1 are shown in the following table: Figure 2 The electron microscope results of the polyvinylidene fluoride membrane of Comparative Example 1 are shown in the following table: Figure 3 The electron microscope results of the polyvinylidene fluoride membrane of Comparative Example 2 are shown in the following table: Figure 4 The electron microscope results of the polyvinylidene fluoride membrane of Comparative Example 3 are shown in the following table: Figure 5 The electron microscope results of the polyvinylidene fluoride membrane of Comparative Example 4 are shown in the following table. DETAILED DESCRIPTION

[0024] The embodiments of the 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 used to illustrate the application and should not be regarded as limiting the scope of the application. Based on the examples in the application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the application. If the specific conditions are not specified, the conventional conditions or the conditions recommended by the manufacturer are used. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased on the market.

[0025] In a first aspect, the present application provides a method for preparing a polyvinylidene fluoride membrane, comprising 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 membrane, and then the polyvinylidene fluoride membrane is prepared after washing with water. The casting solution comprises 10%-25% of polyvinylidene fluoride and the balance of 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%.

[0026] It should be noted that before being immersed in the coagulation bath, the carrier is left in an environment, for example, the temperature of the environment can be, but is not limited to, 30℃, 50℃ or 80℃, 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 carrier is directly immersed in the coagulation bath, instantaneous phase separation will occur. In this scheme, the liquid film is left in an environment at a certain 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.

[0027] 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 (as shown in a of Figure 1 The "crystal ball" in a 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 pore structure; the dendritic fibers dominate the high porosity and connectivity, while the spherulites enhance the mechanical stability of the membrane by connecting with the dendritic fibers; this unique alternating distribution is derived from the competition and synergy of liquid-liquid phase separation (forming dendritic fibers) and crystallization kinetics (forming spherulites) in the short TIPS and NIPS process, finally forming a hierarchical porous structure with high porosity and mechanical strength.

[0028] In some optional embodiments, the molecular weight of the polyvinylidene fluoride is in the range of 300-800 thousand Da.

[0029] In some optional embodiments, the casting solution further comprises a non-solvent.

[0030] The non-solvent is added to regulate the size of the membrane pores.

[0031] In some optional embodiments, the non-solvent includes, but is not limited to, one or more of triethylene glycol, isopropyl alcohol, ethanol or methanol. The mass percentage of the non-solvent may be, for example, but is not limited to, 3%, 10% or 15%.

[0032] In some optional embodiments, the substrate includes, but is not limited to, glass, plastic film or non-woven fabric, or other substrates known to those skilled in the art.

[0033] In some optional embodiments, a doctor blade is used to coat the substrate into a liquid film; the coating thickness may be, for example, but is not limited to, 300 μm, 500 μm or 600 μm.

[0034] In some optional embodiments, the alcohol includes one or more of methanol, ethanol or propanol.

[0035] The present application ensures uniform and stable film structure through synergistic regulation of coating thickness and coagulation bath concentration.

[0036] In a second aspect, the present application provides a polyvinylidene fluoride film prepared by the above preparation method.

[0037] The polyvinylidene fluoride film has a unique dendritic-spherulitic alternating porous structure, significantly improved specific surface area, excellent protein adsorption capacity, and can be used for protein blotting, bacteria removal filtration and other biological application technologies.

[0038] In some optional 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.

[0039] In some optional embodiments, the thickness of the polyvinylidene fluoride film is 100-300 μm.

[0040] In a third aspect, the present application provides the use of the above preparation method in the preparation of a protein transfer film.

[0041] The polyvinylidene fluoride film prepared by the preparation method provided by the present application has controllable pore size, can be adapted to proteins of different molecular weights, and can be used as a transfer film with high transfer efficiency and low background signal.

[0042] The present application will be further described below through specific examples, but it should be understood that these examples are only for more detailed description and should not be understood as limiting the present application in any form.

[0043] In the following examples and comparative examples, "parts" refer to "weight parts".

[0044] Example 1 A polyvinylidene fluoride film, the preparation method thereof comprises: (1) Take 25 parts of polyvinylidene fluoride powder (Mw=30w) in a container, add 70 parts of N,N-dimethylacetamide, 5 parts of isopropanol, stir and dissolve, and let the obtained casting solution stand for 24 hours to degas; (2) The casting solution is uniformly coated on a smooth and clean glass plate with a gap of 500 μm using a doctor blade, and is left in a hot air environment at 80°C for 1 s and immersed in anhydrous ethanol for 2 min; (3) The wet film is rinsed with water and dried at 120°C to obtain a PVDF membrane with a pore size of 0.45 μm.

[0045] After detection, the bubble point pressure is 0.064 MPa, and the water flow rate is 45328 LMH / bar, and the surface and cross-sectional electron micrographs are shown in Figure 1 a and Figure 1 b, respectively.

[0046] Example 2 A polyvinylidene fluoride membrane, the preparation method comprising: (1) Take 18 parts of polyvinylidene fluoride powder (Mw=50w) in a container, add 79 parts of N-methylpyrrolidone and 3 parts of isopropanol, stir and dissolve, and let the obtained casting solution stand for 24 hours to degas; (2) The casting solution is uniformly coated on a smooth and clean glass plate with a gap of 500 μm using a doctor blade, and is left in a hot air environment at 50°C for 3 s and immersed in a 60% isopropanol solution for 2 min; (3) The wet film is rinsed with water and dried at 90°C to obtain a PVDF membrane with a pore size of 0.1 μm.

[0047] After detection, the bubble point pressure is 0.29 MPa, and the water flow rate is 927 LMH / bar.

[0048] Example 3 A polyvinylidene fluoride membrane, the preparation method comprising: (1) Take 10 parts of polyvinylidene fluoride powder (Mw=80w) in a container, add 90 parts of N,N-dimethylformamide, stir and dissolve, and let the obtained casting solution stand for 24 hours to degas; (2) The casting solution is uniformly coated on a smooth and clean glass plate with a gap of 500 μm using a doctor blade, and is left in a hot air environment at 30°C for 5 s and immersed in a 30% ethanol solution for 2 min; (3) The wet film is rinsed with water and dried at 80°C to obtain a PVDF membrane with a pore size of 1.2 μm.

[0049] After detection, the bubble point pressure is 0.026 MPa, and the water flow rate is 93576 LMH / bar.

[0050] Comparative Example 1 A polyvinylidene fluoride membrane, the preparation method comprising: (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; (2) The casting solution was uniformly coated on a smooth and clean glass plate with a gap of 500 μm, and immersed in water for 2 min; (3) The wet film was rinsed with water and dried at 120°C to obtain a PVDF membrane.

[0051] This condition did not undergo short-time TIPS, and water was used as a non-solvent, resulting in no pore formation on the surface, forming a dense skin layer, which resulted in the bubble point pressure and water flow rate being unable to be tested, and finger-like pores appearing near the surface. The electron microscope surface and cross-sectional views are shown in Figure 2 a and Figure 2 b, respectively.

[0052] Comparative Example 2 A polyvinylidene fluoride membrane, the preparation method comprising: (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; (2) The casting solution was uniformly coated on a smooth and clean glass plate with a gap of 500 μm, and immersed in water for 2 min; (3) The wet film was rinsed with water and dried at 120°C to obtain a PVDF membrane.

[0053] This condition did not undergo short-time TIPS, and water was used as a non-solvent, resulting in no pore formation on the surface, forming a dense skin layer, which resulted in the bubble point pressure and water flow rate being unable to be tested, and finger-like pores appearing near the surface. The electron microscope surface and cross-sectional views are shown in Figure 3 a and Figure 3 b, respectively. Upon testing, the bubble point pressure was 0.035 MPa, and the water flow rate was 100430 LMH / bar. Since TIPS was not used to delay phase separation and inhibit the crystallization process, the pore size was larger, and the structure was mainly large spherocrystal, resulting in a lower bubble pressure and a smaller specific surface area of the membrane.

[0054] Comparative Example 3 A polyvinylidene fluoride membrane, the preparation method comprising: (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; (2) Apply the casting solution evenly to a smooth and clean glass plate using a scraper with a gap of 500 μm, and leave it in a hot air environment at 80℃ for 5 min; (3) After rinsing the membrane with water, dry it at 120°C to obtain a PVDF membrane.

[0055] Under these conditions, PVDF films were obtained directly via a long-duration TIPS method. The surface and cross-sectional images under electron microscopy are shown below. Figure 4 a and Figure 4 As shown in b. Because it did not undergo slow pore formation via NIPS, a dense skin layer formed on its surface, making it impossible to test bubble point pressure and water flow rate, and the finger-like pore structure became more pronounced.

[0056] Comparative Example 4 A polyvinylidene fluoride membrane, the preparation method of which includes: (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. (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. (3) After rinsing the wet film with water, dry it at 120°C to obtain a PVDF film.

[0057] 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.

[0058] Comparative Example 5 A polyvinylidene fluoride membrane, the preparation method of which includes: (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. (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. (3) The wet film is rinsed with water and dried at 120°C to obtain a PVDF film.

[0059] The condition causes solidification gel on the surface of the liquid film, forms dense skin layer, and causes the bubble point pressure and water flow rate to be unable to be tested.

[0060] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not limited to them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; 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 preparing a polyvinylidene fluoride (PVDF) membrane, characterized in that, Includes the following steps: The casting solution is coated onto the substrate to form a liquid film. Then, the carrier is kept in an environment of 30-80℃ for 1-5 seconds. After that, the carrier is immersed in a coagulation bath to solidify into a film. After washing with water, a polyvinylidene fluoride film is prepared. The casting solution comprises 10%-25% polyvinylidene fluoride by mass percentage, with the balance being organic solvents; The organic solvent includes 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 preparation method according to claim 1, characterized in that, The molecular weight of the polyvinylidene fluoride is 300,000 to 800,000 Da.

3. The preparation method according to claim 1, characterized in that, The casting solution also includes non-solvents.

4. The preparation method according to claim 3, characterized in that, The non-solvent includes one or more of triethylene glycol, isopropanol, ethanol, or methanol; The non-solvent content is 3%-15% by mass.

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

6. The preparation method according to claim 1, characterized in that, A liquid film is applied to the substrate using a doctor blade; the coating thickness is 300-600 μm.

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

8. A polyvinylidene fluoride membrane, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The polyvinylidene fluoride membrane according to claim 8, characterized in that, The polyvinylidene fluoride membrane has a pore size of 0.1-1.2 μm.

10. The application of the preparation method according to any one of claims 1-7 in the preparation of protein transfer membranes.

Images