Mild method for preparing degerming film

Abstract

The invention provides a mild method for preparing a degerming membrane, and belongs to the technical field of degerming membrane.The method comprises the steps that polyether sulfone is dissolved in a solvent, a pore-foaming agent 1 and a pore-foaming agent 2 are added, and a membrane casting solution is obtained after uniform mixing; casting the membrane casting solution on a PET plate with a smooth surface to form a membrane layer; exposing the cast film layer in atmosphere steam with constant temperature and humidity, and performing steam-induced phase splitting to form a primary film; enabling the primary membrane to enter a gel bath, and further performing phase splitting on the membrane casting solution due to the fact that the temperature of the gel bath is higher than the cloud point temperature of the membrane casting solution to form a membrane with a compact pore structure. According to the preparation method, a membrane preparation mode of coupling steam-induced phase separation and anti-thermally induced phase separation is adopted, and the cloud point temperature of a membrane casting solution is changed and the temperature for preparing the membrane casting solution is reduced by adjusting the proportion and components of additives in a formula; the used solvent has less pollution to the environment and can be recycled; the overall energy consumption is low, the requirement on equipment is low, and the membrane casting difficulty is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of antibacterial film preparation, and specifically relates to a mild method for preparing an antibacterial film. Background Art

[0002] Microbial contamination has become an important factor affecting product quality, environmental hygiene and human health. Therefore, the development of efficient and environmentally friendly antibacterial technologies has become the focus of attention in the scientific research and industrial communities. The use of antibacterial films is simple, fast, efficient, and does not change the properties of the filtrate during use. It is widely used in the production of sterile drugs, the filtration of biological products, the production of recombinant proteins, cosmetics and personal care products (to ensure sterility during production), the food and beverage industries (filtering fruit juices, beers, wines, etc. to remove microorganisms and impurities), the purification of drinking water and industrial water in the water treatment industry, the eye drop industry, etc.

[0003] The existing antibacterial film preparation technologies still have the following disadvantages: For the method of preparing antibacterial films by vapor-induced phase separation, the time required for film casting is relatively long, and the temperature, humidity and residence time need to be regulated. Therefore, the preparation process is complex and requires high equipment requirements. For the method of preparing antibacterial films by thermally induced phase separation (TIPS), a relatively high temperature is required during the preparation process to dissolve the polymer system into a uniform casting solution, which increases the energy consumption during the production process, and the diluent is easy to volatilize, resulting in a dense skin layer and poor continuity of micropores. The pore structure of the film prepared by non-solvent induced phase separation is uneven, and the strength of the prepared film is relatively low. The casting solution uses an easily drug-making solvent or a pore-forming agent with a relatively large molecular weight, which has a risk of precipitation during use, affects the quality of the filtrate, and may cause harm to the human body and the environment. Most antibacterial film preparations require relatively extreme temperature and humidity, and have high equipment requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide a mild method for preparing an antibacterial film to solve at least one of the technical problems existing in the above background art.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The present invention provides a mild method for preparing an antibacterial film, including:

[0007] Preparing a casting solution: Dissolve polyethersulfone in a solvent, add pore-forming agent 1 and pore-forming agent 2, and mix evenly to obtain a casting solution;

[0008] Casting into a film: Cast the casting solution on a smooth PET plate to form a film layer;

[0009] Vapor-induced phase separation: Expose the cast film layer to a vapor atmosphere with constant temperature and humidity for vapor-induced phase separation to form a primary film;

[0010] Gel bath treatment: The nascent membrane is immersed in the gel bath. Since the temperature of the gel bath is higher than the cloud point temperature of the casting solution, the casting solution further phase-separates to form a membrane with a dense pore structure.

[0011] Washing and preservation: The membrane after gel bath treatment is washed to remove residual solvents and pore formers, and then preserved.

[0012] Furthermore, based on parts by weight, the components of the casting solution are as follows: 10 - 30 parts of polyethersulfone, 24 - 37 parts of pore former 1, 7 - 18 parts of pore former 2, and 36 - 40 parts of solvent.

[0013] Furthermore, pore former 1 is one or a mixture of two of diethylene glycol or triethylene glycol.

[0014] Furthermore, pore former 2 is one or a mixture of two of PEG200 or PEG400.

[0015] Furthermore, the solvent is one or a mixture of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylformamide, or dimethyl sulfoxide.

[0016] Furthermore, steam-induced phase separation is carried out for 10 - 60 s to form a nascent membrane.

[0017] Furthermore, the nascent membrane is immersed in the gel bath, and the temperature of the gel bath is 40 - 80 °C.

[0018] Furthermore, the composition of the gel bath is pure water.

[0019] Furthermore, the washing method is soaking in water at 80 °C for 3 - 6 min.

[0020] Term explanation: Reverse thermally induced phase separation: Traditional TIPS forms a homogeneous solution at high temperature and then cools down to achieve phase separation, while RTIPS can form a homogeneous solution at a lower temperature and then achieve phase separation by heating. This method combines the characteristics of solvent-induced phase separation (low stirring temperature) and thermally induced phase separation (driving force is heat). Steam-induced phase separation: The casting solution is exposed to non-solvent vapor (usually humid air) to induce phase separation, thereby forming a membrane with a specific morphology. Cloud point temperature: Under specific conditions, the critical temperature at which the casting solution changes from clear to turbid. Bacterial challenge: This test is a key method to prove whether the filter membrane can retain microorganisms. Usually, a solution of Brevundimonas diminuta ATCC19146 is used for the challenge test. The filter membrane needs to reach at least 10 7 log CFU / cm 2Only when the bacteria retention of the filter membrane can be achieved can it be considered a sterilizing-grade filter membrane. Determination of the permeation rate of bovine serum albumin (BSA): Measure the flow rate and pressure during the BSA filtration process to ensure that a specific volume of filtration operation is completed within a predetermined time, and at the same time evaluate the possible blockage situation during the BSA filtration process.

[0021] Advantages of the present invention: A film-forming method that combines vapor-induced phase separation and inverse thermally induced phase separation is adopted. By adjusting the proportion and composition of additives in the formulation, the cloud point temperature of the casting solution is changed, the temperature for preparing the casting solution is reduced, and the preparation difficulty is reduced. Then, sterilizing membranes with different properties are prepared by changing the temperature and humidity in the atmosphere and the residence time in the atmosphere. The combination of the two film-forming methods prepares a sterilizing membrane with high strength, high flux, strong anti-pollution ability, and excellent sterilization effect. A method for preparing a microporous membrane by using a composite phase separation method that combines the inverse thermally induced phase separation method (RTIPS) and vapor-induced phase separation. The vapor and inverse thermally induced phase separation composite method gives more process feasibility to this film-forming method and can better regulate the membrane structure and performance. This method is simple and easy to implement, and significantly shortens the vapor exposure time during the film-forming process. The time for preparing the sterilizing membrane is shortened, and the production efficiency of the sterilizing membrane is improved. The prepared sterilizing membrane has the characteristics of good sterilization effect, high filtration flux, and high film strength. In the middle part of the cross-section of the filter membrane of the prepared sterilizing membrane, a filtration layer with smaller pore size is formed, which plays a role in protecting the filtration layer; the filter membrane has good sterilization effect, high filtration flux, and strong anti-pollution ability. The membrane of the present invention shows excellent permeability to protein aqueous solutions. The formulation of the casting solution of the present invention is simple, the solvent used has less environmental pollution and can be recycled. The temperature required for the preparation process of the casting solution is low, and the temperature and humidity required for the preparation process are also low. The overall energy consumption is low, the requirements for equipment are low, and the casting difficulty is reduced. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 It is a flow chart of a mild method for preparing a sterilizing membrane according to an embodiment of the present invention.

[0024] Figure 2 It is a structural diagram of a bacteria challenge test device according to an embodiment of the present invention.

[0025] Figure 3 It is a SEM photograph of the cross-section of the sterilizing filter membrane prepared in Example 1 of the present invention.

[0026] Figure 4SEM photograph of the lower surface of the sterilizing filter membrane prepared in Example 1 of the present invention.

[0027] Figure 5 SEM photograph of the upper surface of the sterilizing filter membrane prepared in Example 1 of the present invention.

[0028] Figure 6 SEM cross-section photograph of the sterilizing filter membrane prepared in Example 2 of the present invention.

[0029] Figure 7 SEM photograph of the lower surface of the sterilizing filter membrane prepared in Example 2 of the present invention.

[0030] Figure 8 SEM photograph of the upper surface of the sterilizing filter membrane prepared in Example 2 of the present invention.

[0031] Wherein: 1 - bacterial solution; 2 - peristaltic pump; 3 - pressure gauge; 4 - sample filtration assembly; 5 - exhaust valve; 6 - analytical filter membrane filtration assembly; 7 - flowmeter. Detailed implementation manners

[0032] The following details the implementation manners of the present invention. Examples of the implementation manners are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The implementation manners described through the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0033] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention belongs.

[0034] It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art and will not be interpreted with an idealized or overly formal meaning unless defined as herein.

[0035] Those skilled in the art of the present technology can understand that, unless specifically stated, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present invention means the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements and / or their groups.

[0036] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. Without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0037] For the convenience of understanding the present invention, the following will further explain the present invention with specific embodiments in conjunction with the accompanying drawings, and the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0038] Those skilled in the art should understand that the drawings are only schematic diagrams of the embodiments, and the components in the drawings are not necessarily essential for implementing the present invention.

[0039] The present invention proposes a new film casting method, which is a composite phase separation method for preparing microporous membranes by combining the reverse thermally induced phase separation method (RTIPS) and vapor induced phase separation. The sterilization membrane prepared in this way has the characteristics of good sterilization effect, high filtration flux, and high film strength. This method is simple and easy to implement. The vapor and reverse thermally induced phase separation composite method endows this film-making method with more process feasibility and can better regulate the membrane structure and performance. This method significantly shortens the vapor exposure time during the film-making process. It shortens the time for preparing the sterilization membrane and improves the production efficiency of the sterilization membrane. In the middle part of the cross-section of the prepared sterilization membrane filter membrane, a filter layer with smaller pore size is formed, which plays a role in protecting the filter layer; the filter membrane has good sterilization effect, high filtration flux, and strong anti-pollution ability. The membrane of the present invention shows excellent permeability to protein aqueous solutions. The casting solution formula of the present invention is simple, the molecular weight of the pore-forming agent used is small, it is easy to wash out, the solvent used has less environmental pollution, and it can also be recycled. The gel bath used is a water bath, and it can be discharged basically without additional treatment. The temperature required for the preparation process of the casting solution is low, and the temperature and humidity required for the preparation process are also low. The overall energy consumption is low, the requirements for equipment are low, and the film casting difficulty is reduced.

[0040] As Figure 1As shown in the figure, the method for gently preparing a sterilizing membrane provided by the embodiment of the present invention includes the following process steps: Preparing a casting solution: Dissolve polyethersulfone in a solvent, add a pore-forming agent 1 and a pore-forming agent 2, and mix evenly to obtain a casting solution. Casting into a film: Cast the casting solution on a smooth PET plate to form a film layer. Steam-induced phase separation: Expose the cast film layer to a steam atmosphere with constant temperature and humidity for steam-induced phase separation for 10 - 60 s to form a primary film. Gel bath treatment: Immerse the primary film in a gel bath, and the temperature of the gel bath is 40 - 80 °C. Since the temperature of the gel bath is higher than the cloud point temperature of the casting solution, the casting solution further undergoes phase separation to form a film with a dense pore structure. Among them, the composition of the gel bath is pure water. Cleaning and preservation: Clean the film after gel bath treatment to remove residual solvents and pore-forming agents, and then preserve it. The cleaning method is to soak it in water at 80 °C for 3 - 6 min.

[0041] In the present invention, the performance of the sterilizing membrane prepared by the present invention is tested by the bacterial challenge test method and the determination of the filtrate flow rate of bovine serum albumin (BSA) aqueous solution respectively.

[0042] In the present invention, as shown in Figure 2 the figure, a bacterial challenge test device is used to conduct a bacterial challenge test, including: Sterilization: All instruments, equipment, and filter membranes used in the experiment are sterilized by high temperature or ultraviolet light before use; Bacterial liquid 1: The challenging strain is Pseudomonas diminuta (ATCC19146), and the concentration > 10 7 CFU / ml; Filtration: Bacterial liquid 1 passes through a sample filtration assembly 4 and an analytical filter membrane filtration assembly 6 in sequence under the pressure of a peristaltic pump 2. A pressure gauge 3 and an exhaust valve 5 are provided on the pipeline between the sample filtration assembly 4 and the peristaltic pump 2. A pressure gauge 3 and an exhaust valve 5 are also provided on the pipeline between the sample filtration assembly 4 and the analytical filter membrane filtration assembly 6. The analytical aluminum membrane filtration assembly 6 is connected to a flow meter 7. The analytical filter membrane filtration assembly 6 contains a membrane disc with a nominal pore size of 0.45 μm. After putting the filtered sample filter membrane into a culture dish, pour semi-solid medium until it completely solidifies, and place the culture dish in a constant temperature incubator at 30 °C for 3 - 7 days to observe the colony growth status. A negative control group and a positive control group are set for the bacterial challenge test.

[0043] In the present invention, for the determination of the filtrate flow rate of bovine serum albumin (BSA) aqueous solution, a cross-flow laboratory device with a recirculating feed stream is used to measure the filtrate flow rate of BSA aqueous solution. By the membrane to be detected, two approximately 12.56 cm 2Samples were tested. First, the membrane samples were equilibrated in phosphate buffer solution (pH 5, 67 mM), and then placed in a test cell. Initially, the flow rate of the phosphate buffer solution was measured at 0.3 bar for 60 minutes or until a stable value was obtained. Subsequently, the reservoir for the feed stream was filled with a BSA solution (2 g / l, phosphate buffer, pH 5), and the filtrate flow rate through the membrane sample was continuously measured at 0.3 bar for 120 minutes.

[0044] Example 1

[0045] In this Example 1, a method for gently preparing a sterilizing membrane is provided, including the following process steps:

[0046] (1) Preparation of casting solution: Weigh 36.4 parts of N,N-dimethylacetamide, 15 parts of polyethersulfone (BASF 6020), and 24.3 parts of polyethylene glycol 200 into a stirring kettle. After heating and fully dissolving at 60 °C, cool down to 30 °C, and then add 24.3 parts of diethylene glycol (DEG), and continue stirring for 3 - 6 h. The stirred casting solution was left standing for 6 h to remove bubbles;

[0047] (2) The obtained homogeneous casting solution was cast on a 36-μm-thick PET plate using a 270-μm doctor blade to form a liquid film;

[0048] (3) The liquid film was sent into an atmosphere at 35 °C and a relative humidity of 30%, and subjected to vapor-induced phase separation for 40 s to obtain a nascent membrane;

[0049] (4) The nascent membrane was cured into a membrane by a water bath at 80 °C, and then washed to obtain a sterilizing filter membrane.

[0050] According to "GB / T 32361-2015 Test Method for Pore Size of Separation Membranes - Bubble Point and Mean Flow Rate Method", the bubble point pressure (test liquid: deionized water) and flux (test liquid: deionized water) of the filter membrane prepared in Example 1 were detected. The test results showed that the pure water flux was 16000 LMH@1 bar, and the water bubble point was 0.40 - 0.43 Mpa. The removal rate of Stenotrophomonas maltophilia was above 7 logs. When testing the BSA transmembrane flux, the membrane showed high permeability and high fouling load capacity for the BSA solution. After 10 minutes of testing, the BSA flux dropped to about 85% of the initial value.

[0051] As Figure 3 This is the cross-sectional SEM photograph of the sterilizing filter membrane prepared in Example 1, Figure 4 This is the lower surface SEM photograph of the sterilizing filter membrane prepared in Example 1, Figure 5SEM photograph of the upper surface of the sterilizing filter membrane prepared in Example 1. As can be seen from the figure, the pore size of the upper surface (air side) of the filter membrane is smaller, while that of the lower surface (plate side) is larger. The dense layer is located between the upper and lower surfaces, which can protect the dense layer.

[0052] Example 2

[0053] In this Example 2, a method for gently preparing a sterilizing membrane is provided, including the following process steps:

[0054] (1) Preparation of the casting solution: Weigh 37.8 parts of N,N-dimethylacetamide, 15 parts of polysulfone (BASF 6020), and 18.9 parts of polyethylene glycol 200 into a stirring kettle. After heating and fully dissolving at 60 °C, cool down to 30 °C, then add 28.3 parts of diethylene glycol (DEG), and continue stirring for 3 - 6 h. The prepared casting solution is left to stand for 6 h to remove bubbles;

[0055] (2) The obtained homogeneous casting solution is cast on a 36-μm-thick PET plate using a 270-μm doctor blade to form a liquid membrane;

[0056] (3) The liquid membrane is sent into an atmosphere with a temperature of 35 °C and a relative humidity of 40%, and undergoes vapor-induced phase separation for 50 s to obtain a nascent membrane;

[0057] (4) The nascent membrane is cured into a membrane in a 70 °C water bath, and then washed to obtain a sterilizing filter membrane.

[0058] The flux bubble point test method is the same as that in Example 1. The test results show that the pure water flux is 16000 LMH@1 bar, and the water bubble point is 0.39 - 0.42 Mpa. The removal rate of Brevundimonas diminuta is above 7 logs. When testing the BSA transmembrane flux, this membrane shows high permeability and high fouling load capacity for BSA solution. After 10 minutes of testing, the BSA flux drops to about 85% of the initial value.

[0059] Figure 6 SEM cross-section photograph of the sterilizing filter membrane prepared in Example 2 Figure 7 SEM photograph of the lower surface of the sterilizing filter membrane prepared in Example 2 Figure 8 SEM photograph of the upper surface of the sterilizing filter membrane prepared in Example 2. As can be seen from the figure, the pore size of the upper surface (air side) of the filter membrane is smaller, while that of the lower surface (plate side) is larger. The dense layer is located between the upper and lower surfaces, and this structure can protect the dense layer.

[0060] Example 3

[0061] In this Example 3, a method for gently preparing a sterilizing membrane is provided, including the following process steps:

[0062] (1) Preparation of casting solution: Weigh 31.9 parts of N,N-dimethylacetamide, 15 parts of polyethersulfone (BASF 6020), and 21.3 parts of polyethylene glycol 200 into a stirring kettle. Heat and dissolve them fully at 60°C, then cool down to 30°C, and add 31.9 parts of triethylene glycol (TEG). Continue stirring for 3 - 6 h. Let the well-stirred casting solution stand for 6 h to remove bubbles;

[0063] (2) Cast the obtained homogeneous casting solution onto a 36-μm-thick PET plate using a 270-μm doctor blade to form a liquid film;

[0064] (3) Feed the liquid film into an atmosphere with a temperature of 35°C and a relative humidity of 35%, and perform vapor-induced phase separation for 50 s to obtain a nascent membrane;

[0065] (4) Cure the nascent membrane in a 60°C water bath to form a membrane, and then wash it to obtain a sterilizing filter membrane.

[0066] The method for testing flux and bubble point is the same as that in Example 1. The test results show that the pure water flux is 16000 LMH@1 bar, and the water bubble point is 0.39 - 0.42 Mpa.

[0067] Comparative Example 1

[0068] (1) Preparation of casting solution: Weigh 44.16 parts of N,N-dimethylacetamide, 15 parts of polyethersulfone (BASF 6020), and 26 parts of diethylene glycol (DEG) into a stirring kettle. Heat and dissolve them fully at 60°C, then cool down to 30°C, and add 14.84 parts of diethylene glycol. Continue stirring for 3 - 6 h. Let the well-stirred casting solution stand at room temperature for 6 h to remove bubbles. The cloud point temperature of the casting solution is about 35°C.

[0069] (2) Cast the obtained homogeneous casting solution onto a 36-μm PET plate using a 270-μm doctor blade to form a liquid film;

[0070] (3) Feed the liquid film into an atmosphere with a temperature of 37°C and a relative humidity of 6.8%, and perform vapor-induced phase separation for 16 s to obtain a nascent membrane;

[0071] (4) Cure the nascent membrane in a 60°C water bath to form a membrane, and then wash it to obtain a sterilizing filter membrane.

[0072] The method for testing flux and bubble point is the same as that in Example 1. The test results show that the pure water flux is 12000 LMH@1 bar, and the water bubble point is 0.42 - 0.50 Mpa. The result of bacteria retention shows that the removal rate of Brevundimonas diminuta is above 7 logs. The membrane of the present invention has a filtrate flow rate of at least 8000 LMH for an aqueous solution of BSA (bovine serum albumin), which is determined 5 minutes after starting to filter a BSA aqueous solution with a BSA concentration of 2 g / l and a pH value of 5 under a transmembrane pressure of 0.4 bar.

[0073] The membrane of the present invention has a high dirt loading capacity. The filtrate flow rates of the membrane sheet in Example 1 for the BSA aqueous solution were 8000 LMH and 6500 LMH respectively after 5 minutes and 15 minutes. The 10 - minute flux decay was 18.75%. The filtrate flow rate of the BSA aqueous solution was 4000 LMH after 120 minutes.

[0074] Comparative Example 2

[0075] (1) Preparation of casting solution: Weigh 34 parts of N,N - dimethylacetamide, 15 parts of polyethersulfone (BASF 6020), and 30 parts of triethylene glycol (TEG) into a stirring kettle. After heating and fully dissolving at 60 °C, cool down to 30 °C, then add 21 parts of triethylene glycol, and continue stirring for 3 - 6 h. The well - stirred casting solution is left standing for 6 h to remove bubbles;

[0076] (2) The obtained homogeneous casting solution is cast on a 36 - μm - thick PET plate using a 270 - μm doctor blade to form a liquid membrane;

[0077] (3) The liquid membrane is sent into an atmosphere with a temperature of 36 °C and a relative humidity of 10%, and undergoes vapor - induced phase separation for 37 s to obtain a nascent membrane;

[0078] (4) The nascent membrane is cured into a membrane in a 60 °C water bath, and then washed to obtain a sterilizing filter membrane.

[0079] The flux bubble - point test method is the same as that in Example 1. The test results show that the pure - water flux is 12000 LMH@1 bar, and the water bubble - point is 0.40 - 0.44 Mpa. The removal rate of Brevundimonas diminuta is above 7 logs. When testing the BSA transmembrane flux, this membrane shows high permeability and high dirt loading capacity for the BSA solution. After 10 minutes of testing, the BSA flux drops to about 85% of the initial value.

[0080] Comparative Example 3

[0081] (1) Preparation of casting solution: Weigh 44.16 parts of N,N - dimethylacetamide, 15 parts of polyethersulfone (BASF 6020), and 26 parts of diethylene glycol (DEG) into a stirring kettle. After heating and fully dissolving at 60 °C, cool down to 30 °C, then add 14.84 parts of diethylene glycol, and continue stirring for 3 - 6 h. The well - stirred casting solution is left standing at room temperature for 6 h to remove bubbles. The cloud - point temperature of the casting solution is about 35 °C.

[0082] (2) The obtained homogeneous casting solution is cast on a 36 - μm PET plate using a 270 - μm doctor blade to form a liquid membrane;

[0083] (3) The liquid membrane is quickly put into water, and there is basically no vapor - induced phase separation to obtain a nascent membrane;

[0084] (4) The nascent membrane is subjected to a water bath at 60 °C, mainly for reverse thermally induced phase separation to solidify into a membrane, and then it is washed to obtain a sterilizing filter membrane.

[0085] The flux bubble point test method is the same as that in Example 1. The test results show that the pure water flux is 1000 LMH@1 bar, and the water bubble point is 0.50 - 0.55 Mpa.

[0086] The flux of the sterilizing membranes prepared in Examples 1 - 3 is 12000 LMH@1 bar, while the flux of the sterilizing membrane prepared in Comparative Example 1 is only 1000 LMH@1 bar.

[0087] The humidity during the preparation of the sterilizing membranes in Comparative Examples 1 and 2 is lower than that in Examples 1, 2, and 3. The humidity required for the preparation of the sterilizing membranes in Comparative Examples 1 and 2 is 5% - 12%, while the humidity required for the preparation of the sterilizing membranes in Examples 1 - 3 is 30 - 40%. The flux of Comparative Example 3 is less than that of Comparative Examples 1 and 2. There is basically no process of vapor induced phase separation in Comparative Example 3, while there is this process in Comparative Examples 1 and 2, and finally the flux of the prepared sterilizing membrane is higher.

[0088] The bacteria retention tests were carried out on the membranes in Examples 1 - 3 and Comparative Examples 1 and 2 by using the bacteria challenge test method, and each test was carried out 3 times respectively. The test results are shown in Table 1 below. The qualified rates of the bacteria challenge tests of the sterilizing filter membranes prepared in Examples 1 - 3 and Comparative Examples 1 and 2 are all 100%.

[0089] Table 1 Bacteria retention test results

[0090]

[0091] In summary, the mild method for preparing a sterilizing membrane provided by the present invention mainly solves the problems of high requirements for process equipment, high required temperature and humidity for preparation, complex preparation process, high energy consumption, complex casting solution formula, and low production efficiency in the existing methods for preparing sterilizing membranes.

[0092] The present invention mainly protects a mild method for preparing a sterilizing membrane by coupling reverse thermally induced phase separation method (RTIPS) and vapor induced phase separation. The vapor and reverse thermally induced phase separation composite method endows the membrane preparation method with more process feasibility and can better regulate the membrane structure and performance. The casting solution formula for achieving the mild membrane preparation effect is as follows: by weight, 10 - 30 parts of polyethersulfone, 24 - 37 parts of pore former 1, 7 - 18 parts of pore former 2, and 36 - 40 parts of solvent. Pore former 1 can be one or two of diethylene glycol and triethylene glycol, pore former 2 is one or two of PEG200 or PEG400, and the solvent can be one or several of N - methylpyrrolidone, N, N - dimethylformamide, N, N - dimethylacetamide, dimethylformamide, and dimethyl sulfoxide.

[0093] In the present invention, a method for preparing a microporous membrane is provided by using a composite phase separation method combining reverse thermally induced phase separation (RTIPS) and vapor induced phase separation. The vapor and reverse thermally induced phase separation composite method endows the film preparation method with more process feasibility and can better regulate the membrane structure and performance. By adjusting the vapor humidity (30 - 40%) and the gel bath temperature, the membrane pore size (0.15 - 0.4 μm) can be flexibly controlled to adapt to different application scenarios. This method is simple and easy to implement, and significantly shortens the vapor exposure time during the film preparation process. It shortens the time for preparing the sterilization membrane and improves the production efficiency of the sterilization membrane. The prepared sterilization membrane has the characteristics of good sterilization effect, high filtration flux, and high film strength. In the cross-section of the prepared sterilization membrane filter membrane, a filtration layer with a smaller pore size is formed in the middle part, which plays a role in protecting the filtration layer; the filter membrane has a good sterilization effect, high filtration flux, and strong anti-pollution ability. The membrane of the present invention shows excellent permeability to protein aqueous solutions. The casting solution formulation of the present invention is simple, the solvents used have less environmental pollution and can be recycled. Low molecular weight pore-forming agents (PEG200 / 400) and recyclable solvents (such as DMAc) are used to replace traditional easily drug-making solvents (such as butyrolactone). The solvent recovery rate is ≥90%, and the risk of residual pore-forming agent precipitation is reduced by 80%. The temperature required for the preparation of the casting solution is low, and the temperature and humidity required for the preparation process are also low. The overall energy consumption is low, the requirements for equipment are low, and the film casting difficulty is reduced. The temperature for preparing the casting solution is reduced to 30 - 60°C, the vapor exposure time is shortened to 10 - 60 seconds, and the gel bath temperature is only 40 - 80°C. Technical effects: The energy consumption is reduced by 20 - 40%, and the defect of the dense skin layer is avoided.

[0094] Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that based on the technical solutions disclosed in the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts should be covered within the protection scope of the present invention.

Claims

1. A gentle method for preparing a sterilization film, characterized in that: include: Prepare a casting solution: dissolve polyethersulfone in a solvent, add porogen 1 and porogen 2, and mix well to obtain a casting solution; Casting film: Cast the film-casting liquid on a smooth PET plate to form a film layer; Steam-induced phase separation: The cast film layer is exposed to the atmosphere steam with constant temperature and humidity to induce steam phase separation and form a primary film; Gel bath treatment: The primary membrane is placed in a gel bath. Since the gel bath temperature is higher than the cloud point temperature of the casting solution, the casting solution further separates into phases to form a membrane with a dense pore structure. Cleaning and preservation: The membrane treated in the gel bath is cleaned to remove the residual solvent and porogen, and then preserved.

2. The method for preparing a mild sterilization film according to claim 1, characterized in that: The components of the casting solution are calculated by weight: polyethersulfone is 10-30 parts, porogen 1 is 24-37 parts, porogen 2 is 7-18 parts, and solvent is 36-40 parts.

3. The method for preparing a mild sterilization film according to claim 1, characterized in that: The porogen 1 is one of diethylene glycol and triethylene glycol or a mixture of the two.

4. The method for preparing a mild sterilization film according to claim 1, characterized in that: Porogen 2 is PEG200 or PEG400 or a mixture of the two.

5. The method for preparing a mild sterilization film according to claim 1, characterized in that: The solvent is a mixture of one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylformamide or dimethyl sulfoxide.

6. The method for preparing a mild sterilization film according to claim 1, characterized in that: Steam-induced phase separation is performed for 10-60 seconds to form a primary membrane.

7. The method for preparing a mild sterilization film according to claim 1, characterized in that: The nascent membrane is placed in a gel bath at a temperature of 40-80°C.

8. The method for preparing a mild sterilization film according to claim 1 or 7, characterized in that: The gel bath consists of pure water.

9. The method for preparing a mild sterilization film according to claim 1, characterized in that: The cleaning method is to soak in 80℃ water for 3-6 minutes.

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