Porous microfiltration membrane and manufacturing method therefor

Abstract

The present invention relates to a porous microfiltration membrane and a manufacturing method therefor. The manufacturing method according to the present invention is a method for manufacturing a microfiltration membrane having excellent permeation flux and is based on use and composition of glycol-based and inorganic salt additives, which are various viscosity-increasing additives. Provided are: a polymer composition comprising a polymer and various viscosity-increasing additives for forming pores on the surface of a membrane; a porous microfiltration membrane obtained by casting the polymer composition, exposing same under appropriate temperature and constant humidity conditions for several minutes, and then immersing same in a non-solvent; and a method for manufacturing the porous microfiltration membrane.

Description

porous microfiltration membrane and method for manufacturing the same

[0001] The present invention relates to a porous microfiltration membrane and a method for manufacturing the same.

[0002] Starting from the indication that microporous membranes could be widely used in fields such as battery separators, electrolyte capacitor separators, various filters, wet-permeable and waterproof clothing, reverse osmosis membranes, ultrafiltration membranes, or microfiltration membranes, research on the full-scale manufacture of separation membranes for water treatment was conducted after Loeb and Sourirajan succeeded in manufacturing an asymmetric membrane using cellulose acetate through a phase transition process in 1963. The aforementioned phase transition process is a nonsolvent-induced phase inversion (NIPI) process, which is a method of obtaining a solid membrane by dissolving a polymer in a suitable solvent to create a polymer solution, casting it thinly, and then immersing it in a nonsolvent.

[0003] Generally, when manufacturing microfiltration-grade membranes, additives other than the base polymer are added and dissolved in a solvent to prepare a polymer solution. Since the type and amount of additives added to the polymer solution significantly alter performance characteristics such as membrane morphology, pore size, and permeability, they are one of the critical factors in membrane manufacturing.

[0004] Korean Patent Publication No. 10-2001-0074363 (published on June 2, 2003) (hereinafter referred to as "prior art") discloses a method for manufacturing a porous polysulfone-based polymer film that exhibits a pure water permeability.

[0005] Looking at the prior art literature regarding the above-mentioned prior art, a polymer separation membrane could be manufactured by a simple method of adding a predetermined amount of a carboxylic acid-based organic acid to a polysulfone-based polymer solution, casting it into a film, and then exposing it for 3 minutes under high humidity conditions of 60 to 99% or higher. However, if exposed to humidity above a certain level, the membrane pores become very small, causing a decrease in water permeation flow rate, or if exposed for a longer period of time, productivity may decrease when considering mass production in the process.

[0006]

[0007] [Prior Art Literature]

[0008] [Patent Literature]

[0009] (Patent Document 1) Republic of Korea Registered Patent Publication No. 10-2001-0074363 (June 2, 2003)

[0010] The present invention has been devised to solve the aforementioned technical problem and provides a polymer composition comprising a solvent, a polymer, and various glycol-based and inorganic salt additives for forming pores on the membrane surface using polyethersulfone, a polymer mainly used in the manufacture of microfiltration-grade separation membranes, and a microfiltration membrane having porosity by casting the composition and then exposing it under appropriate temperature, humidity, and time conditions.

[0011] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art from the description below.

[0012] A manufacturing method according to one embodiment of the present invention for achieving the above objective comprises: a first step of preparing a polymer solution by dissolving one or more of a glycol-based additive and an inorganic salt additive in an organic solvent to increase the permeation flow rate and viscosity; a second step of casting the polymer solution onto a solid substrate to a certain thickness and then exposing the polymer solution cast onto the solid substrate to a humidity condition of 55% to 90%; and a third step of immersing the exposed polymer solution in a non-solvent to obtain porosity. The glycol-based additive comprises one or more combinations selected from the group consisting of DEG (Diethylene glycol), TEG (Triethylene glycol), and PEG (Polyethylene glycol), and the inorganic salt additive comprises one or more combinations selected from the group consisting of CaCl2, LiCl, LiClO4, Mg(ClO4), and ZnCl2, and the TEG content may be 40 to 50 weight%.

[0013] The above polymer solution may contain 10 to 20 weight percent of polyethersulfone (PES) based on the total weight of the polymer volume.

[0014] The glycol-based additive of the first step above may be performed with a TEG content of 40 to 50 weight%.

[0015] The inorganic salt additive of the first step above includes LiClO4, and the ratio of LiClO4 to the polymer solution may be less than 0.50.

[0016] The first step above may further include a surfactant, wherein the surfactant is PE6400, and the PE6400 content may be 3% by weight.

[0017] The above second step can be performed by casting the polymer solution to a thickness of 100 μm to 300 μm.

[0018] The above second step can be cast in water at 10°C to 30°C.

[0019] The above third step may further include a fourth step of washing the porous polymer solution for more than 24 hours.

[0020] The above second step can be performed by exposing the polymer solution to a time condition of 10 to 60 seconds.

[0021] The second step above can be performed by exposing the polymer solution to a temperature condition of 20°C to 30°C.

[0022] A polymer solution prepared by dissolving one or more of a glycol-based additive and an inorganic salt additive in an organic solvent; porosity obtained by casting the polymer solution onto a solid substrate to a uniform thickness, and then immersing the polymer solution cast on the solid substrate in a non-solvent while exposing it to a humidity condition of 55% to 90%; the glycol-based additive comprises one or more combinations selected from the group consisting of DEG (Diethylene glycol), TEG (Triethylene glycol), and PEG (Polyethylene glycol), and the inorganic salt additive comprises one or more combinations selected from the group consisting of CaCl2, LiCl, LiClO4, Mg(ClO4), and ZnCl2, and the porous microfiltration membrane comprises a TEG content of 40 to 50 weight%.

[0023] The above porous microfiltration membrane may be provided with a water permeability of 10,000 LMH / bar to 30,000 LMH / bar.

[0024] The above porous microfiltration membrane may be provided with an average pore size of 0.2 μm to 0.45 μm.

[0025] The above porous microfiltration membrane includes an asymmetric membrane with different pore sizes in the thickness direction.

[0026] The above porous microfiltration membrane may be provided with a pore shape including either a cone or a conical shape.

[0027] The above porous microfiltration membrane comprises one or more flat membranes, and the flat membrane can be achieved by a porous microfiltration membrane having an additional multilayer structure.

[0028] According to the present invention, the microfiltration membrane of the present invention manufactured by the above manufacturing method has significantly superior porosity and flow rate compared to conventional polysulfone-based separation membranes, making it highly suitable for liquid separation in water treatment, semiconductor processes, pharmaceutical processes, and food and beverage processes.

[0029] The group of viscosity-increasing additives intended for application in this invention not only increases viscosity to maintain the strength of the film during the film casting process and facilitate film formation, but also plays a role in facilitating the formation of various pores by increasing the efficiency of exchange with moisture during processes exposed to actual humidity. In other words, they increase viscosity to facilitate film formation and increase the phase transition exchange rate during processes exposed to humidity, thereby ensuring good pore formation. Furthermore, by causing the pore size to vary depending on the exposure time to humidity during this process, they provide the effect of enabling control over pore size.

[0030] Figure 1 is a graph showing the water permeability according to the influence of relative humidity and ambient air exposure time during the formation of a porous microfiltration membrane prepared according to Experimental Example 1.

[0031] Figure 2 is a graph showing the change in water permeability according to the TEG content of a porous microfiltration membrane prepared according to Experimental Example 2.

[0032] Figure 3 is a graph showing the change in water permeability according to membrane thickness and PES content of a porous microfiltration membrane prepared according to Experimental Example 3.

[0033] Figure 4 is a graph showing the change in pore size according to the exposure time to the outside air during membrane formation for different PES content of the porous microfiltration membrane prepared according to Experimental Example 4.

[0034] Figure 5 is a graph showing the change in water permeability according to the external exposure time with respect to PES content during the formation of a porous microfiltration membrane prepared according to Experimental Example 5.

[0035] Figure 6 is a graph showing the change in membrane thickness with respect to the ambient exposure time according to the PES content during membrane formation of the porous microfiltration membrane prepared according to Experimental Example 6.

[0036] Figure 7 is a scanning electron microscope (SEM) image showing a magnified view of the surface of the membrane when the ambient exposure time was 10 seconds in the method for manufacturing the porous microfiltration membrane prepared in Example 5.

[0037] Figure 8 is a figure showing an enlarged SEM image of the surface of the membrane when the ambient exposure time was 20 seconds in the method for manufacturing the porous microfiltration membrane prepared in Example 5.

[0038] Figure 9 is a figure showing an enlarged SEM image of the surface of the membrane when the ambient exposure time was 30 seconds in the method for manufacturing the porous microfiltration membrane prepared in Example 5.

[0039] Figure 10 is a figure showing an enlarged SEM image of the surface of the membrane when the exposure time to the outside air was 10 seconds in the method for manufacturing the porous microfiltration membrane prepared in Example 7.

[0040] Figure 11 is a figure showing an enlarged SEM image of the surface of the membrane when the ambient exposure time was 20 seconds in the method for manufacturing the porous microfiltration membrane prepared in Example 7.

[0041] Figure 12 is a figure showing an enlarged SEM image of the surface of the membrane when the exposure time to the outside air was 30 seconds in the method for manufacturing the porous microfiltration membrane prepared in Example 7.

[0042] Figure 13 is a figure showing an enlarged SEM image of the surface of the membrane when the exposure time to the outside air was 10 seconds in the method for manufacturing the porous microfiltration membrane prepared in Example 8.

[0043] Figure 14 is a figure showing an enlarged SEM image of the surface of the membrane when the exposure time to the outside air was 20 seconds in the method for manufacturing the porous microfiltration membrane prepared in Example 8.

[0044] Figure 15 is a figure showing an enlarged SEM image of the surface of the membrane when the exposure time to the outside air was 30 seconds in the method for manufacturing the porous microfiltration membrane prepared in Example 8.

[0045] Figure 16 is a graph showing the change in water permeability according to the ratio of additives and PES in Experimental Examples 7 to 11.

[0046] Figure 17 is a graph showing the change in viscosity according to the ratio of additives and PES in Experimental Examples 7 to 11.

[0047]

[0048] The embodiments of one embodiment of the present invention relate to the manufacture of a microfiltration membrane with excellent permeation flow rate and a method of manufacture based on the use and composition of various viscosity-increasing additives, such as glycol-based and inorganic salt additives. However, for the sake of a clearer and more concise explanation of this embodiment, parts that overlap with other embodiments are omitted. The omission of such description does not mean that such parts are excluded from the present invention, and the scope of rights thereof should be recognized as being the same as that of other embodiments.

[0049] In describing the present invention, detailed descriptions of known technologies related to the invention are omitted if it is determined that such descriptions may unnecessarily obscure the essence of the invention. Furthermore, the terms described below are defined considering their functions in the present invention, and these definitions may vary depending on the intentions or practices of the user or operator. Therefore, their definitions should be based on the content throughout this specification.

[0050] The technical concept of the present invention is determined by the claims, and the following embodiments are merely a means to efficiently explain the technical concept of the present invention to those skilled in the art to which the present invention belongs.

[0051] Specific embodiments of the present invention will be described below. However, these are merely examples and the present invention is not limited thereto.

[0052]

[0053] A method for manufacturing a porous microfiltration membrane according to one embodiment of the present invention is described as follows.

[0054] To increase permeation flow rate and viscosity, one or more of glycol-based additives and inorganic salt additives are dissolved in an organic solvent. The glycol-based additive may be any one or more combinations selected from the group consisting of DEG (Diethylene glycol), TEG (Triethylene glycol), and PEG (Polyethylene glycol). Additionally, the inorganic salt additive may include any one or more combinations selected from the group consisting of CaCl2, LiCl, LiClO4, Mg(ClO4), and ZnCl2. The organic solvent may be NMP, but is not limited thereto; it may be determined by a person skilled in the art within a range that does not have an effect other than as a solvent on the formation of the microfiltration membrane.

[0055] Subsequently, the polymer solution prepared by the above method is cast onto a solid substrate to a uniform thickness. When casting the polymer solution, it may be cast to a predetermined thickness. The predetermined thickness can be determined by a person skilled in the art.

[0056] The polymer solution cast on the solid substrate can be exposed to a humidity condition of 55% to 90%. By immersing the exposed polymer solution in a non-solvent, the polymer solution can have porosity.

[0057] In one embodiment of the present invention, the TEG content of the glycol-based additive may be 40 to 50 weight percent. In addition, in another embodiment of the present invention, the polymer solution may contain 10 to 20 weight percent of polyethersulfone (PES) based on the total weight.

[0058] To improve the water permeability of the microfiltration membrane, the inorganic salt additive may include LiClO4, and the ratio of LiClO4 to the polymer solution may be less than 0.50.

[0059] In addition, when preparing the polymer solution, a surfactant may be further included, and for example, the surfactant may be PE6400. The PE6400 may be used at 3% by weight of the total weight.

[0060] The polymer solution can be cast to a thickness of 100 μm to 300 μm. The cast polymer solution can be produced by a manufacturing method comprising the step of being exposed under conditions of 10 seconds to 60 seconds and then washing for 24 hours or more.

[0061]

[0062] The microfiltration membrane according to the present invention may comprise a polymer solution prepared by dissolving in an organic solvent one or more of a glycol-based additive comprising one or more combinations selected from the group consisting of DEG (Diethylene glycol), TEG (Triethylene glycol), and PEG (Polyethylene glycol), and an inorganic salt additive comprising one or more combinations selected from the group consisting of CaCl2, LiCl, LiClO4, Mg(ClO4), and ZnCl2. The microfiltration membrane may be imparted with porosity by casting the polymer solution onto a solid substrate to a certain thickness, and then immersing the polymer solution cast on the solid substrate in a non-solvent by exposing it to a humidity condition of 55% to 90%. In one embodiment of the present invention, the microfiltration membrane may be manufactured by including 40 to 50 weight% of the TEG content as an additive.

[0063] The porous microfiltration membrane may be provided with a water permeability of 10,000 LMH / bar to 30,000 LMH / bar, and the average pore size of the porous microfiltration membrane may be provided to be 0.2 μm to 0.45 μm.

[0064] In addition, the porous microfiltration membrane may include an asymmetric membrane having different pore sizes in the thickness direction. The pore shape of the porous microfiltration membrane may include either a cone or a conical shape.

[0065] The porous microfiltration membrane manufactured by the above manufacturing method may include one or more flat membranes, but the flat membrane may have an additional multilayer structure.

[0066] The following will be explained in detail through examples.

[0067]

[0068] Example 1: Preparation of a porous microfiltration membrane comprising 10 wt% polymer PES and TEG as an additive 1

[0069] A polymer solution prepared by dissolving 10 wt% of polymer PES and 0 wt% of TEG in 90 wt% of organic solvent NMP was prepared by exposing it to an ambient temperature of 15 to 30°C and an ambient humidity of 55 to 70% for 30 seconds.

[0070] Example 2: Preparation of a porous microfiltration membrane comprising 10 wt% polymer PES and TEG as an additive 2

[0071] It was prepared in the same manner as in Example 1, except that 20% by weight of TEG and 70% by weight of organic solvent NMP were used.

[0072] Example 3: Preparation of a porous microfiltration membrane comprising 10 wt% polymer PES and TEG as an additive 3

[0073] It was prepared in the same manner as in Example 1, except that 40% by weight of TEG and 50% by weight of organic solvent NMP were used.

[0074] Example 4: Preparation of a porous microfiltration membrane comprising 10 wt% polymer PES and TEG as an additive 4

[0075] It was prepared in the same manner as Example 1, except that 60% by weight of TEG and 30% by weight of organic solvent NMP were used.

[0076] Example 5: Preparation of a porous microfiltration membrane comprising polymer PES and TEG as an additive, and surfactant PE6400 1

[0077] A polymer solution prepared by dissolving 10 wt% of polymer PES and 57 wt% of TEG in 30 wt% of organic solvent NMP was prepared by exposing it to an ambient temperature of 15 to 30°C and an ambient humidity of 55 to 70% for 10, 20, 30, 60, and 120 seconds.

[0078] Example 6: Preparation of a porous microfiltration membrane comprising TEG as a polymer and additive and surfactant PE6400 2

[0079] It was manufactured in the same manner as Example 5, except that it was manufactured by exposing the ambient humidity conditions to 80 to 90%.

[0080] Example 7: Preparation of a porous microfiltration membrane comprising TEG as a polymer and additive and surfactant PE6400 3

[0081] It was prepared in the same manner as in Example 5, except that 11 wt% of polymer PES, 53 wt% of TEG, and 33 wt% of organic solvent NMP were used.

[0082] Example 8: Preparation of a porous microfiltration membrane comprising TEG as a polymer and additive and surfactant PE6400 4

[0083] It was prepared in the same manner as in Example 5, except that 12 wt% of polymer PES, 50 wt% of TEG, and 35 wt% of organic solvent NMP were used.

[0084] Example 9: Preparation of a porous microfiltration membrane containing a polymer and CaCl2 as an additive 1

[0085] It was prepared in the same manner as in Example 1, except that 14.5 wt% of polymer PES, 3.63 wt% of CaCl2, and 81.88 wt% of organic solvent NMP were used.

[0086] Example 10: Preparation of a porous microfiltration membrane containing a polymer and CaCl2 as an additive 2

[0087] It was prepared in the same manner as in Example 1, except that 4.83 wt% of CaCl2 and 80.67 wt% of the organic solvent NMP were used.

[0088] Example 11: Preparation of a porous microfiltration membrane containing a polymer and CaCl2 as an additive 3

[0089] It was prepared in the same manner as in Example 1, except that 7.25 wt% of CaCl2 and 78.25 wt% of the organic solvent NMP were used.

[0090] Example 12: Preparation of a porous microfiltration membrane containing a polymer and CaCl2 as an additive 4

[0091] It was prepared in the same manner as in Example 1, except that 14.50 wt% of CaCl2 and 71.00 wt% of the organic solvent NMP were used.

[0092] Example 13: Preparation of a porous microfiltration membrane containing a polymer and LiCl as an additive 1

[0093] It was prepared in the same manner as in Example 1, except that 2.42 wt% of the additive LiCl and 83.08 wt% of the organic solvent NMP were used.

[0094] Example 14: Preparation of a porous microfiltration membrane containing a polymer and LiCl as an additive 2

[0095] It was prepared in the same manner as in Example 1, except that 2.90 wt% LiCl and 82.60 wt% organic solvent NMP were used.

[0096] Example 15: Preparation of a porous microfiltration membrane containing a polymer and LiCl as an additive 3

[0097] It was prepared in the same manner as in Example 1, except that 3.63 wt% LiCl and 81.88 wt% organic solvent NMP were used.

[0098] Example 16: Preparation of a porous microfiltration membrane containing a polymer and LiCl as an additive 4

[0099] It was prepared in the same manner as in Example 1, except that 4.83 wt% LiCl and 80.67 wt% organic solvent NMP were used.

[0100] Example 17: Preparation of a porous microfiltration membrane containing a polymer and LiClO4 as an additive 1

[0101] It was prepared in the same manner as in Example 1, except that 2.42 wt% of LiClO4 and 83.08 wt% of the organic solvent NMP were used.

[0102] Example 18: Preparation of a porous microfiltration membrane containing a polymer and LiClO4 as an additive 2

[0103] It was prepared in the same manner as in Example 1, except that 2.90 wt% of LiClO4 and 82.60 wt% of the organic solvent NMP were used.

[0104] Example 19: Preparation of a porous microfiltration membrane containing a polymer and LiClO4 as an additive 3

[0105] It was prepared in the same manner as in Example 1, except that 3.63 wt% of LiClO4 and 81.88 wt% of the organic solvent NMP were used.

[0106] Example 20: Preparation of a porous microfiltration membrane containing a polymer and LiClO4 as an additive 4

[0107] It was prepared in the same manner as in Example 1, except that 4.83 wt% of LiClO4 and 80.67 wt% of the organic solvent NMP were used.

[0108] Example 21: Preparation of a porous microfiltration membrane containing a polymer and Mg(ClO4)2 as an additive 1

[0109] It was prepared in the same manner as in Example 1, except that 0.48 wt% of Mg(ClO4)2 and 85.02 wt% of the organic solvent NMP were used.

[0110] Example 22: Preparation of a porous microfiltration membrane containing a polymer and Mg(ClO4)2 as an additive 2

[0111] It was prepared in the same manner as in Example 1, except that 1.21 wt% of Mg(ClO4)2 and 84.29 wt% of the organic solvent NMP were used.

[0112] Example 23: Preparation of a porous microfiltration membrane containing a polymer and Mg(ClO4)2 as an additive 3

[0113] It was prepared in the same manner as in Example 1, except that 2.42 wt% of Mg(ClO4)2 and 83.08 wt% of the organic solvent NMP were used.

[0114] Example 24: Preparation of a porous microfiltration membrane containing a polymer and Mg(ClO4)2 as an additive 4

[0115] It was prepared in the same manner as in Example 1, except that 2.90 wt% of Mg(ClO4)2 and 82.60 wt% of the organic solvent NMP were used.

[0116] Example 25: Preparation of a porous microfiltration membrane containing a polymer and ZnCl2 as an additive 1

[0117] It was prepared in the same manner as in Example 1, except that 3.63 wt% of ZnCl2 and 81.88 wt% of the organic solvent NMP were used.

[0118] Example 26: Preparation of a porous microfiltration membrane containing a polymer and ZnCl2 as an additive 2

[0119] It was prepared in the same manner as in Example 1, except that 4.83 wt% of ZnCl2 and 80.67 wt% of the organic solvent NMP were used.

[0120] Example 26: Preparation of a porous microfiltration membrane containing a polymer and ZnCl2 as an additive 3

[0121] It was prepared in the same manner as in Example 1, except that 7.25 wt% of ZnCl2 and 78.25 wt% of the organic solvent NMP were used.

[0122]

[0123] Example 27: Preparation of a porous microfiltration membrane containing a polymer and ZnCl2 as an additive 4

[0124] It was prepared in the same manner as in Example 1, except that 14.50 wt% of ZnCl2 and 71.00 wt% of the organic solvent NMP were used.

[0125]

[0126] Experimental Example 1

[0127] 1. Experiment on Changes in Water Permeability of a Membrane According to Relative Humidity and Outdoor Exposure Time

[0128] A polymer solution was prepared by dissolving 10 wt% of the polymer solution PES, 57 wt% of the glycol-based additive TEG, and 3 wt% of the surfactant PE6400 in 30 wt% of the organic solvent NMP, and the polymer solution was uniformly cast onto a solid substrate to a thickness of 250 μm.

[0129] Afterward, two groups with temperature conditions of 15 to 70℃ and humidity conditions of 55 to 70% and 80 to 90% were exposed to the outside air for 10 seconds, 20 seconds, 30 seconds, 60 seconds, and 120 seconds, respectively, and then immersed in a non-solvent and dried to produce a film.

[0130] Changes in water permeability according to relative humidity and exposure time to the outside air were measured using the membrane prepared as described above. The experimental group was divided into two groups, and each of the two groups was prepared with sample names #5 to #9 and sample names #10 to #14.

[0131] For both experimental groups, a polymer solution was prepared by dissolving 10 wt% of the polymer solution PES, 57 wt% of the glycol-based additive TEG, and 3 wt% of the surfactant PE6400 in 30 wt% of the organic solvent NMP.

[0132] The above polymer solution was uniformly cast onto a solid substrate to a thickness of 250 μm, and then, after being exposed to the outside air at a temperature of 15 to 30°C, the film was prepared by immersing it in a non-solvent and drying it.

[0133] Samples #5 to #9 were exposed to the outside air under conditions of 55–70% relative humidity, and samples #10 to #14 were exposed to the outside air under conditions of 80–90% relative humidity. Each of the two groups was exposed for 10, 20, 30, 60, and 120 seconds, and the water permeability (LMH / bar) was measured accordingly. Figure 1 graphs the water permeability according to the influence of relative humidity and outside air exposure time during membrane formation, reflecting the values ​​in Table 1 below. The X-axis of Figure 1 represents the outside air exposure time (sec), where a value closer to 0 indicates a shorter exposure time. The Y-axis represents water permeability (LMH / bar), which was measured as the amount of permeate transmitted per unit area of ​​the membrane per unit time. A Y-axis value closer to 0 can be interpreted as indicating a lower amount of permeate per unit area of ​​the membrane per unit time.

[0134]

[0135] As can be seen in Table 1 above, it was confirmed that water permeability increased as the exposure time to the outside air increased for both experimental groups. In addition, among the two experimental groups, samples #5 to #9, which were tested under conditions of 55 to 70% relative humidity, showed higher water permeability with respect to exposure time compared to samples #10 to #14, which were tested under conditions of 80 to 90% relative humidity. Therefore, it can be considered desirable to conduct tests under conditions of 55 to 70% relative humidity to obtain a microfiltration membrane with excellent permeation flow rate.

[0136]

[0137] Experimental Example 2

[0138] 2. Experiment on Changes in Water Permeability According to TEG Content

[0139] The experimental group was sample names #1 to #4, and polymer solutions were prepared by dissolving polymer PES content of 10 wt% and glycol-based additive TEG content of 0 wt%, 20 wt%, 40 wt%, and 60 wt%, respectively, in organic solvent NMP of 90 wt%, 70 wt%, 50 wt%, and 30 wt%, respectively.

[0140] The polymer solutions of the four groups mentioned above were uniformly cast onto a solid substrate to a thickness of 250 μm, and then exposed to the outside air for 30 seconds at a temperature of 15 to 30°C and a humidity of 55 to 70%, after which the film was immersed in a non-solvent and dried to produce a film.

[0141] In Figure 2, the water permeability of the membrane according to the TEG content is graphed, reflecting the values ​​in Table 2 below. The X-axis of Figure 2 represents the TEG concentration, and a value closer to 0 indicates that less TEG was added during membrane formation. The Y-axis represents the water permeability (LMH / bar), which was measured as the amount of permeate passing per unit area of ​​the membrane per unit time. A Y-axis value closer to 0 can be interpreted as indicating a lower amount of permeate passing per unit area of ​​the membrane per unit time. Therefore, it can be assumed that the water permeability of a porous microfiltration membrane manufactured with a TEG content of 40 wt% or more is high.

[0142]

[0143] As can be seen in Table 2 above, it was confirmed that water permeability increases as the TEG concentration increases. In particular, it was confirmed that water permeability tends to increase rapidly around 40% to 60% by weight of TEG. Therefore, in order to obtain a microfiltration membrane with excellent permeation flow rate, it can be considered desirable to maintain the content of TEG, a glycol-based additive, at 40% to 60% by weight of the total polymer solution.

[0144]

[0145] Experimental Example 3

[0146] 3. Experiment on Changes in Water Permeability According to Membrane Thickness and PES Content

[0147] The experimental groups were divided into sample names #5 to #9, #15 to #19, and #20 to #24, and polymer solutions were prepared by dissolving PES content of 10 wt%, 11 wt%, and 12 wt%, respectively, and glycol-based additive TEG content of 57 wt%, 53 wt%, and 50 wt%, respectively, in organic solvent NMP content of 30 wt%, 33 wt%, and 35 wt%, respectively.

[0148] The polymer solutions of the three groups mentioned above were uniformly cast onto a solid substrate to a thickness of 250 μm, and then exposed to the outside air for 10 seconds, 20 seconds, 30 seconds, 60 seconds, and 120 seconds, respectively, at a temperature of 15 to 30°C and a humidity of 55 to 70%, after which the film was immersed in a non-solvent and dried to produce a film.

[0149] In Figure 3, water permeability with respect to membrane thickness according to PEG polymer content is graphed, reflecting the values ​​in Table 3 below. The X-axis of Figure 3 represents membrane thickness (μm), where a value closer to 0 indicates a thinner thickness after drying. The Y-axis represents water permeability (LMH / bar), which is measured as the amount of permeate per unit area of ​​the membrane per unit time. A Y-axis value closer to 0 can be interpreted as indicating a lower amount of permeate per unit area of ​​the membrane per unit time.

[0150]

[0151] As can be seen in Table 3 above, it was confirmed that for the three groups with PES contents of 10 wt%, 11 wt%, and 12 wt%, the water permeability was lower as the PES content increased, and the water permeability decreased as the film thickness increased. It can be considered desirable to obtain a high transmittance when the PES content is low and the film thickness is thin after drying.

[0152]

[0153] Experimental Example 4

[0154] 4. Experiment on Changes in Pore Size According to Outdoor Exposure Time During Film Formation by PES Content

[0155] As with the experimental group of Experimental Example 3 above, the experimental group was divided into three groups named samples #5 to #9, #15 to #19, and #20 to #24, and polymer solutions were prepared by dissolving PES content of 10 wt%, 11 wt%, and 12 wt%, respectively, and glycol-based additive TEG content of 57 wt%, 53 wt%, and 50 wt%, respectively, in organic solvent NMP content of 30 wt%, 33 wt%, and 35 wt%.

[0156] The polymer solutions of the three groups mentioned above were uniformly cast onto a solid substrate to a thickness of 250 μm, and then exposed to the outside air for 10 seconds, 20 seconds, 30 seconds, 60 seconds, and 120 seconds, respectively, at a temperature of 15 to 30°C and a humidity of 55 to 70%, after which the film was immersed in a non-solvent and dried to produce a film.

[0157] In Figure 4, reflecting the values ​​in Table 4 below, the change in pore size according to the ambient air exposure time during film formation for each PES content is graphed. The X-axis of Figure 4 represents the ambient air exposure time (sec), where a value closer to 0 indicates a shorter exposure time. The Y-axis represents the pore size (μm), where a value closer to 0 indicates a smaller pore size.

[0158] FIGS. 7 to 9 are scanning electron microscope (SEM) images showing enlarged views of the surface of the film when the film prepared in Example 5 was exposed to the outside air for 10 seconds, 20 seconds, and 30 seconds, respectively.

[0159] FIGS. 10 to 12 are scanning electron microscope (SEM) images showing enlarged views of the surface of the film prepared in Example 7 when the exposure time to the outside air was 10 seconds, 20 seconds, and 30 seconds, respectively.

[0160] FIGS. 13 to 15 are scanning electron microscope (SEM) images showing enlarged views of the surface of the film prepared in Example 8 when the exposure times to the outside air were 10 seconds, 20 seconds, and 30 seconds, respectively.

[0161] Referring to FIGS. 7 to 9, FIGS. 10 to 12, and FIGS. 13 to 15, it can be seen that the pore size increases as the exposure time to the outside air increases. In addition, under the same exposure time conditions, it was confirmed that the pore size decreases inversely as the PES content increases. If the pore size decreases, the water permeability may also decrease.

[0162] In addition, as the exposure time to the outside air increases, an asymmetric film with different pore sizes in the thickness direction may be formed.

[0163]

[0164] As shown in Table 4 above, for the three groups with PES contents of 10 wt%, 11 wt%, and 12 wt%, it was confirmed that the pore size decreased as the PES content increased, and that the pore size increased proportionally with the ambient air exposure time. Furthermore, while the pore size increased with increasing ambient air exposure time in each group, it was observed that all three groups showed a tendency for a rapid increase in pore size around 20 to 40 seconds. Since the PES content and ambient air exposure time directly affect pore size, it can be considered desirable to control the PES content and ambient air exposure time to regulate pore size. Therefore, to obtain a microfiltration membrane with excellent permeate flow rate

[0165]

[0166] Experimental Example 5

[0167] 5. Experiment on Changes in Water Permeability According to Outdoor Exposure Time and PES Content During Film Formation

[0168] As with the experimental group of Experimental Example 3 above, the experimental group was divided into three groups named samples #5 to #9, #15 to #19, and #20 to #24, and polymer solutions were prepared by dissolving PES content of 10 wt%, 11 wt%, and 12 wt%, respectively, and glycol-based additive TEG content of 57 wt%, 53 wt%, and 50 wt%, respectively, in organic solvent NMP content of 30 wt%, 33 wt%, and 35 wt%.

[0169] The polymer solutions of the three groups mentioned above were uniformly cast onto a solid substrate to a thickness of 250 μm, and then exposed to the outside air for 10 seconds, 20 seconds, 30 seconds, 60 seconds, and 120 seconds, respectively, at a temperature of 15 to 30°C and a humidity of 55 to 70%, after which the film was immersed in a non-solvent and dried to produce a film.

[0170] In Figure 5, reflecting the values ​​in Table 5 below, the change in water permeability according to the ambient air exposure time for each PES content during membrane formation is graphed. The X-axis of Figure 5 represents the ambient air exposure time (sec), and a value closer to 0 indicates a shorter exposure time. The Y-axis represents water permeability (LMH / bar), which was measured as the amount of permeate passing through per unit area of ​​the membrane per unit time. A value closer to 0 on the Y-axis can be interpreted as indicating a lower amount of permeate passing through per unit area of ​​the membrane per unit time.

[0171]

[0172] As can be seen in Table 5 above, it was confirmed that the higher the PES content, the lower the water permeability. In addition, it was confirmed that for PES 10 wt%, 11 wt%, and 12 wt%, the water permeability increased proportionally as the exposure time to the outside air increased.

[0173]

[0174] Experimental Example 6

[0175] 6. Experiment on Change in Film Thickness with Ambient Exposure Time According to PES Content During Film Formation

[0176] As with the experimental group of Experimental Example 3 above, the experimental group was divided into three groups named samples #5 to #9, #15 to #19, and #20 to #24, and polymer solutions were prepared by dissolving PES content of 10 wt%, 11 wt%, and 12 wt%, respectively, and glycol-based additive TEG content of 57 wt%, 53 wt%, and 50 wt%, respectively, in organic solvent NMP content of 30 wt%, 33 wt%, and 35 wt%.

[0177] The polymer solutions of the three groups mentioned above were uniformly cast onto a solid substrate to a thickness of 250 μm, and then exposed to the outside air for 10 seconds, 20 seconds, 30 seconds, 60 seconds, and 120 seconds, respectively, at a temperature of 15 to 30°C and a humidity of 55 to 70%, after which the film was immersed in a non-solvent and dried to produce a film.

[0178] In Figure 6, reflecting the values ​​in Table 6 below, the change in membrane thickness according to the ambient exposure time for each PES content during membrane formation is graphed. The X-axis of Figure 6 represents the ambient exposure time (sec), and a value closer to 0 indicates a shorter exposure time. The Y-axis represents the membrane thickness (μm), which was measured as the amount of permeate transmitted per unit area of ​​the membrane per unit time. A value closer to 0 on the Y-axis can be interpreted as indicating a lower amount of permeate transmitted per unit area of ​​the membrane per unit time.

[0179]

[0180] As can be seen in Table 6 above, it was confirmed that the film thickness decreases as the exposure time to the outside air increases. In addition, it was confirmed that the higher the PES content, the greater the rate of decrease in film thickness with respect to the exposure time to the outside air. Furthermore, it was confirmed that the decrease in film thickness with respect to the exposure time to the outside air occurred rapidly between 20 and 60 seconds.

[0181]

[0182] Experimental Example 7

[0183] 7. Experiment on Changes in Viscosity and Water Permeability According to CaCl2 Ratio

[0184] A polymer solution was prepared by dissolving 14.5 wt% of the polymer solution PES and the additive CaCl2 in amounts of 0.25, 0.33, 0.50, and 1.00, respectively, relative to 1 wt% of PES, in 81.88 wt%, 80.67 wt%, 78.25 wt%, and 71.00 wt% of the organic solvent NMP, respectively.

[0185] The above polymer solution was uniformly cast onto a solid substrate to a thickness of 250 μm.

[0186] Afterwards, the film was prepared by exposing it to the outside air at a temperature of 15 to 30℃, then immersing it in a non-solvent and drying it.

[0187] For the porous microfiltration membrane manufactured by the above manufacturing method, changes in viscosity and water permeability of the microfiltration membrane were measured according to the ratio of additive CaCl2 and polymer PES.

[0188]

[0189] As can be seen in Table 7 above, it was confirmed that as the weight part of additive CaCl2 relative to 1 weight part of polymer solution PES increases, viscosity increases and water permeability increases and then decreases. Consequently, it was confirmed that as the ratio of additive CaCl2 relative to 1 weight part of polymer solution PES approaches 0.25 to 1.00, there is no significant change in water permeability, but it decreases slightly. It can be considered that the weight part of additive CaCl2 relative to 1 weight part of polymer solution PES does not have a significant effect on obtaining a microfiltration membrane with high water permeability.

[0190]

[0191] Experimental Example 8

[0192] 8. Experiment on changes in viscosity and water permeability according to LiCl ratio

[0193] A polymer solution was prepared by dissolving 14.5 wt% of the polymer solution PES and the additive LiCl at 0.17, 0.20, 0.25, and 0.33 wt%, respectively, relative to 1 wt% of PES, in organic solvent NMP at 83.08 wt%, 82.60 wt%, 81.88 wt%, and 80.67 wt%, respectively.

[0194] The above polymer solution was uniformly cast onto a solid substrate to a thickness of 250 μm.

[0195] Afterwards, the film was prepared by exposing it to the outside air at a temperature of 15 to 30℃, then immersing it in a non-solvent and drying it.

[0196] For the porous microfiltration membrane manufactured by the above manufacturing method, changes in viscosity and water permeability of the microfiltration membrane were measured according to the ratio of the additive LiCl and the polymer.

[0197]

[0198] As can be seen in Table 8 above, it was confirmed that the water permeability decreases as the weight part of the additive LiCl relative to 1 weight part of the polymer solution PES increases. To obtain a porous microfiltration membrane with high water permeability, it can be considered effective to have a lower weight part of the additive LiCl relative to 1 weight part of the polymer solution PES.

[0199]

[0200] Experimental Example 9

[0201] 9. Experiment on changes in viscosity and water permeability according to LiClO4 ratio

[0202] A polymer solution was prepared by dissolving 14.5 wt% of the polymer solution PES and the additive LiClO4 at 0.17, 0.20, 0.25, and 0.33 wt%, respectively, relative to 1 wt% of PES, in organic solvent NMP at 83.08 wt%, 82.60 wt%, 81.88 wt%, and 80.67 wt%, respectively.

[0203] The above polymer solution was uniformly cast onto a solid substrate to a thickness of 250 μm.

[0204] Afterwards, the film was prepared by exposing it to the outside air at a temperature of 15 to 30℃, then immersing it in a non-solvent and drying it.

[0205] For the porous microfiltration membrane manufactured by the above manufacturing method, changes in viscosity and water permeability of the microfiltration membrane were measured according to the ratio of the additive LiClO4 and the polymer.

[0206]

[0207] As can be seen in Table 9 above, it was confirmed that the water permeability increases rapidly as the ratio of additive LiClO4 to polymer solution PES increases. When the weight of additive LiCl relative to 1 weight part of polymer solution PES was 0.33, the water permeability was found to be over 1400, and it can be considered that in order to obtain a porous microfiltration membrane with high water permeability, it is more effective to have a higher weight of additive LiCl relative to 1 weight part of polymer solution PES.

[0208]

[0209] Experimental Example 10

[0210] 10. Experiment on changes in viscosity and water permeability according to Mg(ClO4)2 ratio

[0211] A polymer solution was prepared by dissolving 14.5 wt% of the polymer solution PES and the additive Mg(ClO4)2 at 0.03, 0.08, 0.17, and 0.20 parts by weight, respectively, relative to 1 part by weight of PES, in organic solvent NMP at 85.02 wt%, 84.29 wt%, 83.08 wt%, and 82.60 wt%, respectively.

[0212] The above polymer solution was uniformly cast onto a solid substrate to a thickness of 250 μm.

[0213] Afterwards, the film was prepared by exposing it to the outside air at a temperature of 15 to 30℃, then immersing it in a non-solvent and drying it.

[0214] For the porous microfiltration membrane manufactured by the above manufacturing method, changes in viscosity and water permeability of the microfiltration membrane were measured according to the ratio of the additive Mg(ClO4)2 and the polymer.

[0215]

[0216] As can be seen in Table 10 above, it was confirmed that the water permeability increased as the weight part of the additive Mg(ClO4)2 relative to 1 weight part of the polymer solution PES increased, but there was no significant change, and it was confirmed that the water permeability was significantly lower than that of Experimental Example 9 above.

[0217]

[0218] Experimental Example 11

[0219] 11. Experiment on Changes in Viscosity and Water Permeability According to ZnCl2 Ratio

[0220] A polymer solution was prepared by dissolving 14.5 wt% of the polymer solution PES and the additive ZnCl2 in amounts of 0.25, 0.33, 0.50, and 1.00, respectively, relative to 1 wt% of PES, in 81.88 wt%, 80.67 wt%, 78.25 wt%, and 71.00 wt% of the organic solvent NMP, respectively.

[0221] The above polymer solution was uniformly cast onto a solid substrate to a thickness of 250 μm.

[0222] Afterwards, the film was prepared by exposing it to the outside air at a temperature of 15 to 30℃, then immersing it in a non-solvent and drying it.

[0223] For the porous microfiltration membrane manufactured by the above manufacturing method, changes in viscosity and water permeability of the microfiltration membrane were measured according to the ratio of the additive ZnCl2 and the polymer.

[0224]

[0225] As can be seen in Table 11 above, it was confirmed that the water permeability increased as the ratio of additive ZnCl2 to polymer solution PES increased, but it was confirmed that it increased gradually compared to Experimental Example 9, and the water permeability did not exceed 600 even at 1.00 parts by weight of additive ZnCl2 to 1 part by weight of polymer solution PES.

[0226]

[0227] Figure 16 is a graph showing the change in water permeability according to the ratio of additives and PES in the method for manufacturing porous microfiltration membranes prepared in Experimental Examples 7 to 11 above.

[0228] Referring to Fig. 16, it can be seen that the water permeability increases most rapidly at a ratio of 0.25 to 1.00 parts by weight of the inorganic salt additive LiClO4 relative to 1 part by weight of PES. Additionally, it can be seen that the water permeability decreases as the weight ratio of the inorganic salt additive LiCl relative to 1 part by weight of PES increases. Consequently, it can be considered that a water permeability exceeding 1000 LMH / bar can be obtained at a ratio of 0.25 parts by weight or more of LiClO4 relative to 1 part by weight of the polymer solution PES.

[0229] Figure 17 is a graph showing the change in viscosity according to the ratio of additives and PES in the method for manufacturing porous microfiltration membranes prepared in Experimental Examples 7 to 11 above.

[0230] Referring to Fig. 17, it can be seen that the viscosity of LiCl increases most rapidly at less than 0.40 parts by weight of inorganic salt additive relative to 1 part by weight of PES.

[0231]

[0232] The above description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention.

[0233] Accordingly, the embodiments disclosed in this invention are intended to illustrate, not limit, the technical concept of the invention, and the scope of the technical concept of the invention is not limited by these embodiments. The scope of protection of this invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of this invention.

Claims

1. A first step of preparing a polymer solution by dissolving one or more of glycol-based additives and inorganic salt additives in an organic solvent to increase permeation flow rate and viscosity; A second step of casting the polymer solution onto a solid substrate to a uniform thickness, and then exposing the polymer solution cast onto the solid substrate to a humidity condition of 55% to 90%; A third step of obtaining porosity by immersing the above-exposed polymer solution in a non-solvent; and The above glycol-based additive comprises one or more combinations selected from the group consisting of DEG (Diethylene glycol), TEG (Triethylene glycol), and PEG (Polyethylene glycol), and The above inorganic salt additive comprises one or more combinations selected from the group consisting of CaCl2, LiCl, LiClO4, Mg(ClO4), and ZnCl2, and A method for manufacturing a porous microfiltration membrane in which the above TEG content is 40 to 50 weight%.

2. In Paragraph 1, A method for manufacturing a porous microfiltration membrane, wherein the above polymer solution comprises 10 to 20 weight percent of polyethersulfone (PES) based on the total weight of the polymer volume.

3. In Paragraph 1, The inorganic salt additive of the first step above includes LiClO4, and A method for manufacturing a porous microfiltration membrane in which the ratio of the above LiClO4 to the above polymer solution is less than 0.

50.

4. In Paragraph 1, The above first step further includes a surfactant, and The above surfactant is PE6400, and A method for manufacturing a porous microfiltration membrane in which the above PE6400 content is 3% by weight.

5. A method for manufacturing a porous microfiltration membrane according to claim 1, wherein the second step is performed by casting a polymer solution to a thickness of 100 μm to 300 μm.

6. In claim 1, the second step is a method for manufacturing a porous microfiltration membrane by casting in water at 10°C to 30°C.

7. A method for manufacturing a porous microfiltration membrane according to claim 1, further comprising a fourth step of washing the porous polymer solution for 24 hours or more in the third step.

8. A method for manufacturing a porous microfiltration membrane according to claim 1, wherein the second step is performed by exposing the polymer solution to a time condition of 10 to 60 seconds.

9. A method for manufacturing a porous microfiltration membrane according to claim 1, wherein the second step is performed by exposing the polymer solution to a temperature condition of 20°C to 30°C.

10. A polymer solution prepared by dissolving one or more of glycol-based additives and inorganic salt additives in an organic solvent; Porosity imparted by casting the above polymer solution onto a solid substrate to a uniform thickness, and then immersing the polymer solution cast onto the solid substrate in a non-solvent while exposing it to a humidity condition of 55% to 90%; The above glycol-based additive comprises one or more combinations selected from the group consisting of DEG (Diethylene glycol), TEG (Triethylene glycol), and PEG (Polyethylene glycol), and The above inorganic salt additive comprises one or more combinations selected from the group consisting of CaCl2, LiCl, LiClO4, Mg(ClO4), and ZnCl2, and A porous microfiltration membrane containing 40 to 50 weight% of the TEG content.

11. In Paragraph 10, The above porous microfiltration membrane is a porous microfiltration membrane having a water permeability of 10,000 LMH / bar to 30,000 LMH / bar.

12. In Paragraph 10, The above porous microfiltration membrane is a porous microfiltration membrane having an average pore size of 0.2 μm to 0.45 μm.

13. In Paragraph 10, The above porous microfiltration membrane is a porous microfiltration membrane comprising an asymmetric membrane having different pore sizes in the thickness direction.

14. In Paragraph 10, The above porous microfiltration membrane is a porous microfiltration membrane having a pore shape including either a cone or a conical shape.

15. In Paragraph 10, The above porous microfiltration membrane is a porous microfiltration membrane comprising one or more flat membranes.

16. In Paragraph 15, The above flat membrane is a porous microfiltration membrane having an additional multilayer structure.

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