Grafted polysulfone membrane

Abstract

To provide an improved membrane capable of filtering a chemical liquid, particularly, a membrane capable of filtering a charged particle from the chemical liquid.SOLUTION: A grafted polysulfone membrane, which has the quantity of water flow equivalent to at least 75% of the quantity of water flow of an ungrafted polysulfone membrane, includes one or more grafted monomers on one or more surfaces of the membrane, and benzophenone. In the grafted polysulfone membrane, the grafted monomer is an anionic or cationic monomer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Related applications This application claims the benefits of U.S. Provisional Patent Application No. 62 / 185222, filed on 26 June 2015. The entire teachings of the above application are incorporated herein by reference with due attribution. [Background technology]

[0002] Chemical liquids are useful in a variety of manufacturing processes. In some applications, such as semiconductor manufacturing, chemical liquids must be filtered to remove particulate impurities. Porous membranes are typically prepared from a chemically compatible and mechanically stable polymer matrix and can have measurable captureability, pore size or pore size distribution, and thickness. The pore size can be selected according to the particle size or type of impurities to be removed in the application, as well as pressure drop and viscosity requirements. In use, porous membranes are generally inserted into a fluid flow and incorporated into equipment adapted to remove particles, microorganisms, or solutes from the process fluid. Particles filtered from the liquid may be neutrally charged, or positively or negatively charged.

[0003] Fluid filtration or purification is typically performed by passing a process fluid through a membrane filter under differential pressure across the membrane, creating a pressure zone upstream of the membrane that is higher than the pressure zone downstream. During filtration, the liquid experiences pressure loss across the porous membrane, and the membrane is subjected to mechanical stress. This pressure difference can also cause dissolved gases to precipitate from the liquid. The liquid upstream of the porous membrane has a higher concentration of dissolved gases than the liquid downstream. This occurs because gases, such as air, have greater solubility in liquids at higher pressures than in liquids at lower pressures. As the liquid passes from upstream to downstream of the porous membrane, dissolved gases can be released from the solution, potentially creating bubbles in the liquid and / or on the surface of the porous membrane. This gas precipitation is commonly referred to as liquid outgassing. [Overview of the project]

[0004] Therefore, there is a need for improved membranes capable of filtering chemical liquids, particularly membranes capable of filtering charged particles from chemical liquids.

[0005] This specification describes a method for producing a grafted polysulfone film. The method includes the steps of contacting a polysulfone film with an alcohol solution containing a type II photoinitiator, contacting the polysulfone film with an aqueous exchange solution, contacting the polysulfone film with an aqueous grafting solution, and exposing the polysulfone film to electromagnetic radiation to produce a grafted polysulfone film. The grafting solution may contain anionic or cationic monomers, sodium sulfate, and sodium persulfate.

[0006] The anionic monomer can be one or more of the following: 2-ethyl acrylic acid, acrylic acid, 2-carboxyethyl acrylate, potassium sulfopropyl acrylate, 2-propyl acrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, sodium 2-methyl-2-propene-1-sulfonate, 1-[2-(methacryloyloxy)ethyl] maleate, potassium sulfopropyl methacrylate, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinylsulfonic acid, and vinylphosphonic acid. In some cases, the anionic monomer is vinylsulfonic acid or sodium vinylsulfonate.

[0007] The cationic monomer can be one or more of the following: 2-(dimethylamino)ethyl acrylate hydrochloride, [2-(acryloyloxy)ethyl]trimethylammonium chloride, 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl) methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyltrimethylammonium chloride, 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl)methacrylamide hydrochloride, N-(3-aminopropyl)methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride, vinylimidazolium hydrochloride, vinylpyridinium hydrochloride, and vinylbenzyltrimethylammonium chloride. In some cases, the cationic monomer is diallyldimethylammonium chloride.

[0008] Alcoholic solutions may contain type II photoinitiators. Benzophenone is an unrestricted example of a type II photoinitiator. While not intended to be theoretically limiting, type II photoinitiators undergo bimolecular reactions such that the excited state of the photoinitiator interacts with a second molecule (e.g., a polysulfone polymer chain) to generate free radicals. Alcoholic solutions may contain isopropyl alcohol. Aqueous exchange solutions may contain chaotropic salts such as sodium sulfate. Aqueous exchange solutions may contain type I photoinitiators. While not intended to be theoretically limiting, type II photoinitiators undergo monomolecular bond cleavage upon UV irradiation, yielding free radicals. Various persulfates, such as sodium persulfate and potassium persulfate, are unrestricted examples of type I photoinitiators. In some cases, aqueous exchange solutions may contain one or more of sodium sulfate and sodium persulfate. In some cases, alcoholic solutions may contain benzophenone and isopropyl alcohol, and aqueous exchange solutions may contain sodium sulfate and sodium persulfate.

[0009] Typically, electromagnetic radiation has wavelengths between approximately 200 nm and 600 nm.

[0010] This specification describes a method for producing a grafted polysulfone film. The method includes the steps of: contacting a polysulfone film with an alcohol solution containing a type II photoinitiator (e.g., benzophenone); contacting the polysulfone film with an aqueous exchange solution; contacting the polysulfone film with an aqueous grafting solution; and exposing the polysulfone film to electromagnetic radiation to produce a grafted polysulfone film. The aqueous grafting solution may contain an anionic or cationic monomer, sodium sulfate, and a type I photoinitiator (e.g., sodium persulfate, potassium persulfate, or ammonium persulfate).

[0011] This specification describes grafted polysulfone membranes. Typically, a grafted polysulfone membrane has one or more anionic or cationic monomers grafted onto one or more surfaces of the membrane, and the grafted polysulfone membrane has a water flow rate that is at least 75% of the water flow rate of a non-grafted polysulfone membrane. In some cases, the grafted polysulfone membrane has a bubble point between about 65 psi and about 75 psi when measured by an HFE 7200 (ethoxy-nonafluorobutane) bubble point test. In some cases, the grafted polysulfone membrane has a water flow rate that is at least 75% of the water flow rate of a non-grafted polysulfone membrane having a bubble point between about 65 psi and about 75 psi when measured by an HFE 7200 (ethoxy-nonafluorobutane) bubble point test.

[0012] In some cases, the monomer is anionic. Anionic monomers can be 2-ethylacrylic acid, acrylic acid, 2-carboxyethyl acrylate, potassium sulfopropyl acrylate, 2-propylacrylic acid, 2-(trifluoromethyl)acrylic acid, methacrylic acid, sodium 2-methyl-2-propene-1-sulfonate, 1-[2-(methacryloyloxy)ethyl] maleate, potassium sulfopropyl methacrylate, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinylsulfonic acid, or vinylphosphonic acid. In some cases, the anionic monomer is diallyldimethylammonium chloride. In some cases, the anionic monomer is vinylsulfonic acid or sodium vinylsulfonate.

[0013] In some cases, the monomer is cationic. Cationic monomers can be 2-(dimethylamino)ethyl acrylate hydrochloride, [2-(acryloyloxy)ethyl]trimethylammonium chloride, 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl) methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyltrimethylammonium chloride, 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl)methacrylamide hydrochloride, N-(3-aminopropyl)methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride, vinylimidazolium hydrochloride, vinylpyridinium hydrochloride, or vinylbenzyltrimethylammonium chloride.

[0014] Each monomer can be provided in the form of a suitable salt. For example, the monomer vinylsulfonic acid can be provided as a sodium vinylsulfonate salt.

[0015] In some cases, the grafted polysulfone film contains approximately 1 μg / cm³ 2 From approximately 5 μg / cm³ 2 Between, or approximately 1 μg / cm³ 2 From approximately 3 μg / cm³ 2 Between, or approximately 2 μg / cm³ 2 From approximately 3 μg / cm³ 2 It has pigment-binding ability that exceeds the range between them.

[0016] In some cases, the longitudinal brittleness of the grafted polysulfone film does not exceed the longitudinal brittleness of the ungrafted polysulfone film by more than 30%. In some cases, the cross-web brittleness of the grafted polysulfone film does not exceed the cross-web brittleness of the ungrafted polysulfone film by more than 30%.

[0017] This specification describes a method for removing impurities from a liquid. The method includes contacting the liquid with a grafted polysulfone film as described herein. The impurities may be negatively charged particles, such as negatively charged gold, or negatively charged ions, such as Ponceau S. The impurities may be positively charged particles, such as positively charged gold, or positively charged ions, such as methylene blue.

[0018] The methods described herein produce membranes with improved filtration properties, particularly for charged particles in solution. Grafting anionic monomers onto a polysulfone membrane yields a negatively charged membrane, improving the filtration of positively charged dyes and particles. Grafting cationic monomers onto a polysulfone membrane yields a positively charged membrane, improving the filtration of negatively charged dyes and particles. Furthermore, the methods produce membranes with high flow rates that retain the strength and integrity of unmodified membranes.

[0019] The above will become clear from the following more detailed description of examples of embodiments of the present invention, where similar reference letters refer to the same parts in the accompanying drawings. The drawings are not necessarily to scale and are intended to illustrate embodiments of the present invention. [Brief explanation of the drawing]

[0020] [Figure 1] Calibration curve showing absorbance of three types of methylene blue dye solutions with known concentrations determined using a Cary spectrophotometer operating at a wavelength of 665 nm (y = 2329.9x). [Figure 2] Calibration curve showing absorbance of four types of ponceau S dye solutions with known concentrations determined using a Cary spectrophotometer operating at a wavelength of 520 nm (y = 498.82x). [Figure 3A-C] SEM images of an asymmetric ungrafted polysulfone membrane. Figure 3A is the dense side (e.g., having smaller pores) magnified 5000 times. Figure 3B is the rough side (e.g., having larger pores) magnified 5000 times. Figure 3C is a cross-sectional view magnified 1400 times, with the upper part being the rough side and the lower part being the dense side. [Figure 4] A series of graphs showing the effects of line speed, monomer, benzophenone, and persulfate concentrations on the average flow-through time of a grafted polysulfone membrane. [Figure 5] A series of graphs showing the effects of line speed, monomer, benzophenone, and persulfate concentrations on the dye-binding ability of a grafted polysulfone membrane.

BEST MODE FOR CARRYING OUT THE INVENTION

[0021] An example of an embodiment of the present invention is described below.

[0022] Before explaining the present composition and method, it should be understood that the specific molecules, compositions, techniques, or protocols described may be changed, and thus the present invention is not limited thereto. Also, the technical terms used in the description are for the purpose of explaining only specific version(s), and should not be understood as limiting the scope of the present invention, which is limited only by the appended claims.

[0023] It should also be noted that, as used herein and in the appended claims, the singular forms "a," "an," and "the" include multiple references unless the context specifically indicates otherwise. For example, a reference to "hole" refers to one or more holes and their equivalents known to those skilled in the art. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art. Any methods and materials similar to or equivalent to those described herein may be used in carrying out or testing versions of the present invention, but non-limiting examples of methods, apparatus, and materials are described herein.

[0024] Monomer grafting onto a membrane Grafting refers to the chemical bonding of a portion, such as a monomer, oligomer, or other molecule, to the surface of a porous polymer membrane, including the inner surface of the pores of the porous membrane. A grafted membrane refers to a membrane having one or more types of monomers grafted onto one or more surfaces of the membrane.

[0025] The invention described in the claims is, in part, based on the discovery that monomers can be grafted onto the surface of a polysulfone film by exposure to electromagnetic radiation, typically in the UV wavelength range. Typically, the monomers are classified as cationic or anionic.

[0026] Suitable cationic monomers include acrylates, methacrylates, acrylamides, methacrylamides, and vinyl types having quaternary ammonium, imidazolium, phosphonium, guanidinium, sulfonium, or pyridinium functional groups. Examples of suitable acrylate monomers include 2-(dimethylamino)ethyl acrylate hydrochloride and [2-(acryloyloxy)ethyl]trimethylammonium chloride. Examples of suitable methacrylate monomers include 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl) methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, and [2-(methacryloyloxy)ethyl]trimethylammonium chloride. Examples of suitable acrylamide monomers include acrylamidopropyltrimethylammonium chloride. Suitable methacrylamide monomers include 2-aminoethylmethacrylamide hydrochloride, N-(2-aminoethyl)methacrylamide hydrochloride, and N-(3-aminopropyl)methacrylamide hydrochloride. Other suitable monomers include diallyldimethylammonium chloride, allylamine hydrochloride, vinylimidazolium hydrochloride, vinylpyridinium hydrochloride, and vinylbenzyltrimethylammonium chloride.

[0027] Suitable anionic monomers include sulfonic acids, carboxylic acids, phosphates, methacrylates, acrylamides, methacrylamides, and vinyl types having phosphate functional groups. Examples of suitable acrylate monomers include 2-ethylacrylic acid, acrylic acid, 2-carboxyethyl acrylate, and potassium 3-sulfopropyl acrylate, 2-propylacrylic acid, and 2-(trifluoromethyl)acrylic acid. Examples of suitable methacrylate monomers include methacrylic acid, sodium 2-methyl-2-propene-1-sulfonate, 1-[2-(methacryloyloxy)ethyl maleate], and potassium 3-sulfopropyl methacrylate. An example of a suitable acrylamide monomer is 2-acrylamido-2-methyl-1-propanesulfonic acid. An example of a suitable methacrylamide monomer is 3-methacrylamidephenylboronic acid. Other suitable monomers include vinyl sulfonic acid and vinyl phosphonic acid.

[0028] An example of a cationic monomer is diallyldimethylammonium chloride (DADMAC). While not intended to be theoretically limited, the double bond portion of the monomer is suitable for radical polymerization. Positively charged groups, such as the quaternary nitrogen atom in DADMAC, lead to electrostatic interactions with negatively charged impurities.

[0029] An example of anionic monomer is vinylsulfonic acid, which can be provided in the form of a suitable salt, such as sodium vinylsulfonate. While not intended to be theoretically limited, the vinyl or allyl moieties of monomers are particularly suitable for radical polymerization in the presence of reducing agents. Negatively charged groups, such as the sulfonate moiety of vinylsulfonic acid, result in electrostatic interactions with positively charged impurities.

[0030] To graft monomers onto a polysulfone film, the film is typically moistened with an alcohol such as isopropyl alcohol (IPA), which may contain a type II photoinitiator such as benzophenone. The film is then placed in an aqueous exchange solution containing a chaotropic salt such as sodium sulfate and a type I photoinitiator such as sodium persulfate. The aqueous exchange solution removes the wetting solution. The film is then placed in a grafting solution containing the monomers and, more typically, the same chaotropic salt and type I photoinitiator used in the aqueous exchange solution. To graft monomers onto the film, the film is then typically exposed to electromagnetic radiation in the ultraviolet region of the spectrum. Typically, a UV light source emits light from about 200 nm to about 600 nm, including UV radiation from about 200 nm to about 350 nm, to excite a type II photoinitiator such as benzophenone.

[0031] As will be explained more fully in Example 13, varying the concentrations of the components can yield films with different properties. Increasing the concentration of benzophenone photoinitiator in the alcohol wetting solution can increase the dye binding ability and decrease the water flow rate. Increasing the concentration of sodium persulfate radical initiator yields a film with a high flow rate and high dye binding ability, indicating that more functional groups were grafted onto the film surface. The line velocity of the film in the UV chamber can also be adjusted. Typically, increasing the line velocity yields a grafted film with a higher flow rate but lower dye binding ability. However, μg / cm 2 The dye-binding capacity, as measured, decreased, indicating that fewer monomers grafted onto the membrane surface, thereby reducing the amount of charge on the membrane. Monomer concentration can also be adjusted. Increasing the monomer concentration increased dye-binding capacity and did not affect the flow rate.

[0032] film Porous membranes are typically polysulfone, polyethersulfone, or polyarylsulfone membranes. These membranes are preferable for filtration applications because they offer higher flow rates at lower differential pressures compared to other membranes (e.g., nylon and PTFE). The pore size of the membranes can range from microporous to nanoporous. Microporous membranes can have an average pore size ranging from approximately 0.01 microns to approximately 50 microns and can be selected according to the particle size or type of impurities to be removed, pressure drop requirements, and viscosity requirements of the application. Nanoporous membranes can have an average pore size ranging from approximately 1 nanometer to approximately 100 nanometers.

[0033] Porous membranes can include a single porous layer, a layer with a pore size gradient, or a multilayer membrane. Porous membranes can take various forms such as lace-like, string-like, and knot-like structures, open-celled, nodular, or other membrane forms. Membranes can have symmetrical or asymmetrical pore structures. Symmetrical membranes have pores of similar size on both sides of the membrane, while asymmetrical membranes have pores of different sizes on both sides of the membrane.

[0034] The film can have any convenient geometric configuration, such as a flat plate, a corrugated plate, or a hollow fiber. The film can be supported or unsupported, isotropic or anisotropic, skinned or unskinned, or a composite film. The film substrate can have a thickness between about 5 microns and about 250 microns, preferably between about 10 microns and about 200 microns, and more preferably between about 100 microns and about 150 microns. In some cases, the film is about 130 microns thick.

[0035] The membrane can be a monolayer membrane having a pore size or pore size distribution that captures classified particles. In some versions, the treated porous membrane may include multiple layers having pores of the same size in various layers, or in yet another version, the porous membrane may include multiple layers having pores of different sizes in various layers. In some versions, the porous membrane may include a filtration layer supported by one or more support layers or layers with different porosities. The layers may support the internal filtration layer, for example, a denser filtration layer with smaller pores may have support layers with larger pore sizes on either side. The layers may be membranes with a skin, membranes without a discernible layer structure, or the membrane may have a pore gradient or pore size distribution. In some versions, the porous membrane may be a nanoporous membrane.

[0036] membrane filtration To evaluate the performance characteristics of grafted polysulfone films, dye binding tests can be performed as shown in Examples 6 and 7. Positively charged dyes, such as methylene blue, can bind to negatively charged films, and the amount of dye that forms a complex with the film correlates with the amount of surface modification during the grafting process. Similarly, negatively charged dyes, such as Ponceau S dye, can bind to positively charged films, and the amount of dye that forms a complex with the film correlates with the amount of surface modification during the grafting process. Dye binding tests are representative examples of complex formation of charged molecules with the surface of grafted polysulfone films.

[0037] To evaluate the effectiveness of grafted polysulfone membranes in filtering charged particles, model solutions of positively or negatively charged gold nanoparticles can be filtered using the membranes, as shown in Examples 8 and 9. Positively charged gold nanoparticles can be filtered using polysulfone membranes grafted with negatively charged monomers, such as vinylsulfonic acid. Similarly, negatively charged gold nanoparticles can be filtered using polysulfone membranes grafted with positively charged monomers, such as diallyldimethylammonium chloride (DADMAC). The pH of the model solution to be filtered can be adjusted so that the solution is acidic (e.g., pH < 7), basic (e.g., pH > 7), or neutral (e.g., pH = 7). The gold nanoparticle filtration test is a representative example demonstrating improved filtration of charged particles by grafted polysulfone membranes.

[0038] Porosimetry Bubble Point The porosimetry bubble point test measures the pressure required to force air through the moist pores of a membrane. The bubble point test is a well-known method for measuring the pore size of a membrane.

[0039] Scanning electron microscopy (SEM) Scanning electron microscopy allows us to observe the surface of the film and confirm whether changes occurred on the film surface during the grafting process. The inventors observed that the bubble points of the film were comparable before and after grafting.

[0040] water flow rate The water flow rate is measured by cutting the membrane into 47 mm discs, wetting them with water, and then placing the discs in a filter holder equipped with a reservoir for a large volume of water. The reservoir is connected to a pressure regulator. Water is flowed through the membrane under a differential pressure of 14.2 psi (pounds per square inch). After equilibrium is reached, the time it takes for 10 ml of water to flow through the membrane is recorded. [Examples]

[0041] Example 1 In this embodiment, the preparation of the wetting solution will be described.

[0042] 0.16 grams of benzophenone (99%, Sigma-Aldrich) was dissolved in 40 ml of isopropyl alcohol (IPA) to obtain a 0.4 wt% benzophenone solution.

[0043] Example 2 This embodiment describes the preparation of an aqueous exchange solution.

[0044] 1.42 g of sodium sulfate (Sigma) and 0.4 g of sodium persulfate (Sigma) were mixed at room temperature for 10 minutes and then dissolved in 40 ml of DI water.

[0045] Example 3 This embodiment describes the preparation of an aqueous grafting solution containing an anionic moiety and a radical initiator.

[0046] A solution was prepared containing 2 g of vinyl sulfonic acid (VS, 25% aqueous solution, Sigma), 1.43 g of sodium sulfate, 0.4 g of sodium persulfate, and 36.17 g of water. After stirring at room temperature for 10 minutes, the solution was completely dissolved.

[0047] Example 4 This embodiment describes the preparation of an aqueous grafting solution containing a cationic moiety and a radical initiator.

[0048] A solution was prepared containing 4 g of diallyldimethylammonium chloride (DADMAC, 65% aqueous solution, Sigma), 1.43 g of sodium sulfate, 0.2 g of sodium persulfate, and 34.37 g of water. After stirring at room temperature for 10 minutes, the solution was completely dissolved.

[0049] Example 5 This embodiment describes surface modification of a polysulfone film to include a cationic or anionic moiety.

[0050] A 47 mm disc of polysulfone membrane (Fuji), evaluated to have a pore size of 30 nm, was moistened for 25 seconds with the 0.4% benzophenone solution described in Example 1. To remove IPA, the polysulfone membrane was rinsed with the replacement solution described in Example 2. The membrane disc was then placed in the grafting solution described in Example 3 or Example 4. The dish was covered and the membrane was immersed in the grafting solution for 2 minutes. The membrane disc was removed and sandwiched between 1 mil polyethylene sheets. A rubber roller was rolled over the polyethylene / membrane disc / polyethylene sandwich on a table to remove excess solution and ensure it was flat. The polyethylene sandwich was then taped to a transport unit that would transport the laminated material into a Fusion Systems broadband UV exposure lab unit emitting wavelengths from 200 nm to 600 nm. The exposure time was controlled by the speed at which the laminated material moved within the UV unit. In this example, the laminated material moved within the UV chamber at 7 feet / minute. After exiting the UV unit, the membrane was removed from the sandwich and immediately placed in deionized (DI) water, where it was washed by stirring for 5 minutes. Next, the treated membrane sample was washed in methanol for 5 minutes. Following this washing procedure, the membrane was dried for 10 minutes on a holder in an oven operating at 50°C.

[0051] The average water flow rates for the three samples tested with DADMAC and VS modified membranes were 82 ml / min and 87 ml / min, respectively. The average water flow rate for the three unmodified membrane samples tested was 104 ml / min.

[0052] Example 6 This example describes the dye-binding ability of a polysulfone film grafted with a grafting solution containing VS monomers. This example further describes how the process of Example 5 yields a negatively charged polysulfone film when carried out using the grafting solution of Example 3.

[0053] The dried 47 mm disc membrane of Example 5 modified with the grafting solution of Example 3 was placed in a beaker containing 0.00075 wt% methylene blue dye (Sigma). The beaker was covered and mixing was continued at room temperature, and the membrane was immersed for 5 minutes. Then, the disc of the membrane was taken out, and the absorbance of the dye solution was measured using a Cary spectrophotometer (Agilent Technologies) operating at 606 nm and compared with the absorbance of the starting solution (before immersing the membrane). The dye is essentially cationic and binds to the negatively charged membrane with an average dye binding capacity of 2.1 μg / cm 2 The absorbance data of the dye solution before and after immersing the membrane were converted to weight % of the dye using the slope of the calibration curve shown in Figure 1. Then, this value was converted to the mass of the bound dye per unit area of the membrane. On the other hand, the unmodified membrane had an average dye binding capacity of 0.2 μg / cm 2 under the same experimental conditions.

[0054] Example 7 In this example, the dye binding capacity of a polysulfone membrane grafted with a grafting solution containing DADMAC monomer is described. In this example, it is further demonstrated that when the process of Example 5 is carried out using the grafting solution of Example 4, a positively charged polysulfone membrane is obtained.

[0055] The dried 47 mm disc membrane of Example 5 modified with the grafting solution of Example 4 was placed in a beaker containing 0.002 wt% Ponceau S dye (Sigma). The beaker was covered and mixing was continued at room temperature, and the membrane was immersed for 5 minutes. Then, the disc of the membrane was taken out, and the absorbance of the dye solution was measured using a Cary spectrophotometer (Agilent Technologies) operating at 512 nm and compared with the absorbance of the starting solution (before immersing the membrane). The dye is essentially anionic and binds to the positively charged membrane with an average dye binding capacity of 3 μg / cm 2 The absorbance data of the dye solution before and after immersing the membrane were converted to weight % of the dye using the slope of the calibration curve shown in Figure 2. Then, this value was converted to the mass of the bound dye per unit area of the membrane. On the other hand, the unmodified membrane had an average dye binding capacity of 0.2 μg / cm 2It possessed an average pigment-binding capacity of [value missing].

[0056] Example 8 This example demonstrates the effectiveness of polysulfone membranes grafted with VS monomers according to Examples 3 and 5 in removing model impurities from model solutions at pH 3, 5, and 10.6.

[0057] A 50 ppb model solution of gold nanoparticles was prepared as follows: 1 ml of stock gold nanoparticles (positively charged 5 nm gold) was added to 2 L of DI water. The pH of the solution was adjusted by adding a few drops of 1 M sodium hydroxide or 1 M hydrochloric acid solution.

[0058] A 96 mm disc of the membrane prepared according to Examples 3 and 5 was immersed in IPA, and then immersed in DI water to replace the IPA. Subsequently, the membrane was placed on a test stand and exposed to 52 ml of a 50 ppb model solution at an inlet pressure of 8-15 psi, maintaining a flow rate of 25 ml / min. The concentration of gold nanoparticles in the filtrate and starting solution was quantified using ICP-MS. The gold nanoparticle removal efficiency of the modified membrane was 100% at pH 3, 5, and 10.6. In comparison, the unmodified polysulfone membrane showed removal efficiencies of 2.2%, 84%, and 38% at pH 3, 5, and 10.6, respectively.

[0059] Example 9 This example demonstrates the effectiveness of the DADMAC monomer-grafted polysulfone membranes according to Examples 4 and 5 in removing model impurities from model solutions at pH 3, 5, and 10.6.

[0060] A 50 ppb model solution of gold nanoparticles was prepared as follows: 1 ml of stock gold nanoparticles (negatively charged 5 nm gold) was added to 2 L of DI water. The pH of the solution was adjusted by adding a few drops of 1 M sodium hydroxide or 1 M hydrochloric acid solution.

[0061] A 96 mm disc of the membrane prepared according to Examples 4 and 5 was immersed in IPA, and then immersed in DI water to replace the IPA. Subsequently, the membrane was placed on a test stand and exposed to 52 ml of a 50 ppb model solution at an inlet pressure of 8-15 psi, maintaining a flow rate of 25 ml / min. The concentration of gold nanoparticles in the filtrate and starting solution was quantified using ICP-MS. The gold nanoparticle removal efficiency of the modified membrane was 100% at pH 3, 5, and 10.6. In comparison, the unmodified polysulfone membrane showed removal efficiencies of 8%, 100%, and 51% at pH 3, 5, and 10.6, respectively.

[0062] Example 10: Bubble Point The porosimetry bubble point test method measures the pressure required to force air through the moist pores in a membrane.

[0063] A 47 mm disc of a dry membrane sample was mounted in a holder with the dense side of the membrane (e.g., with smaller pores in an asymmetrical membrane) facing downwards, and the test was performed. The holder is designed to allow the operator to add a small amount of liquid upstream of the membrane. The dry air flow rate of the membrane is first measured by increasing the air pressure upstream of the membrane to 150 psi. Then, the pressure is released back to atmospheric pressure, and a small amount of ethoxy ICP-MS nonafluorobutane (available as HFE 7200 (3M Specialty Materials (St. Paul, Minnesota, USA))) is added upstream of the membrane to moisten it. Then, the pressure is increased again to 150 psi, and the moist air flow rate is measured. The membrane bubble point is measured from the pressure required to expel HFE from the pores of the membrane moistened with HFE. This critical pressure point is defined as the pressure at which the first nonlinear increase in moist air flow is detected by the flowmeter.

[0064] The bubble point range observed in the film used in this application (65-75 psi). Both the non-grafted and grafted films had an average bubble point of 66 psi.

[0065] Example 11: Scanning Electron Microscopy (SEM) Scanning electron microscopy enables the visualization of surface and cross-sectional properties of films.

[0066] After gold sputtering was performed on the film sample, it was scanned using an FEI Quanta 200 SEM System (available from FEI Company, Hillsboro, Oregon, USA) at an accelerating voltage of 10kV. Cross-sections were obtained by freezing and fracturing the sample in liquid nitrogen.

[0067] Figures 3A-C are SEM images of an asymmetric, non-grafted polysulfone film. Figure 3A is a 5000x magnification image of the dense side (e.g., with smaller pores). Figure 3B is a 5000x magnification image of the rough side (e.g., with larger pores). Figure 3C is a 1400x magnification cross-section with the rough side at the top and the dense side at the bottom.

[0068] Example 12 This example illustrates the influence of disclosed grafting techniques on the mechanical properties of the grafted film.

[0069] In this example, a film grafted according to Example 5 using the grafting solution containing the vinyl sulfonic acid monomer described in Example 3 was used. The effect of the disclosed grafting techniques on the mechanical properties of the film was determined by calculating the film's brittleness, as described in J Mater Sci (2010) 45:242-250.

[0070] Brittleness = 1 / (SE) (where S is the tensile fracture strain and E is the storage modulus measured by dynamic mechanical analysis (DMA)). The tensile fracture strain of the film before and after grafting was evaluated using an Instron® Force Transducer Model 2519-102, an Instron® Model 3342 Compression / Tensile analyzer equipped with a computer and Blue Hill software. The storage modulus E data for the grafted and ungrafted films were collected by dynamic mechanical analysis (DMA) using a strain sweep of 0.05–2.0% at a frequency of 1.0 Hz and a temperature of 30°C.

[0071] Each membrane was tested by continuously tensile testing until it broke, producing three samples in the longitudinal direction and three samples in the cross-web direction. The samples were cut to 1" × 4.5" dimensions using a metal die cutter. DMA analysis revealed that the sample shape was 10 mm in length and 6.5 mm in width.

[0072] Compared to non-grafted films, the brittleness of grafted films improved by 25% in the longitudinal direction and 13% in the cross-web direction, as shown in Table 1. TIFF0007855314000001.tif19170

[0073] Example 13 This example illustrates the influence of disclosed grafting techniques on the mechanical properties of the grafted film.

[0074] Polysulfone membranes were grafted with sodium vinyl sulfonate, and their dye-binding ability was measured using methylene blue. The results are shown in Figures 4 and 5.

[0075] Increasing the concentration of benzophenone photoinitiator in the alcohol humic solution enhances the dye binding capacity and reduces the water flow rate. For example, increasing the concentration of benzophenone photoinitiator in the alcohol humic solution from 0.4% by weight to 0.6% by weight increases the dye binding capacity to 1.3 μg / cm³. 2 From 2.1 μg / cm³ 2As the pressure increased, the water flow rate decreased, as measured by the fact that the time it took to run 500 ml of room-temperature water at a positive pressure of 14.2 psi increased from 370 seconds to 425 seconds.

[0076] Increasing the concentration of sodium persulfate radical initiator resulted in a film with high flow rate and high dye binding ability. This indicated that a greater number of functional groups were grafted onto the film surface.

[0077] The line velocity of the film within the UV chamber can also be adjusted. Typically, a higher line velocity results in a grafted film with a higher flow rate, but with reduced dye binding capacity. In one particular example, increasing the line velocity from 6 feet / min to 8 feet / min resulted in a grafted film with a higher flow rate, indicating less film clogging. However, μg / cm³ 2 The dye-binding capacity, as measured, decreased, which indicates that fewer monomers grafted onto the film surface, thereby reducing the amount of charge on the film.

[0078] The monomer concentration can also be adjusted. Increasing the monomer concentration increased the dye binding ability, but this did not affect the flow rate.

[0079] Equal portions While the present invention has been illustrated and described in relation to one or more embodiments, those skilled in the art will be able to come up with equivalent modifications and alterations by reading and understanding this specification and the accompanying drawings. The present invention includes all such modifications and alterations and is limited only to the scope of the following claims. Furthermore, certain features or aspects of the present invention may be disclosed in relation to only one of several embodiments, such features or aspects may be combined with one or more other features or aspects of other embodiments that may be desirable and advantageous for a given or particular application. Furthermore, where the terms “includes,” “having,” “has,” “with,” or variations thereof are used in any form for carrying out the invention and in the claims, such terms are intended to include all, as is the term “comprising.” Also, the term “exemplary” is intended to mean merely an example, not a best example. Furthermore, it should be understood that the features and / or elements described herein are shown in specific dimensions and / or orientations relative to each other for the sake of simplicity and ease of understanding, and that actual dimensions and / or orientations may differ significantly from those described herein.

[0080] The present invention has been illustrated and described, in particular with reference to exemplary embodiments, and those skilled in the art will understand that various modifications may be made in form and detail without departing from the scope of the invention as encompassed by the appended claims.

Claims

1. A grafted polysulfone film comprising one or more monomers grafted onto one or more surfaces of a film, wherein the monomers are selected from anionic monomers and cationic monomers, (i) a water flow rate such that the grafted polysulfone membrane has at least 75% of the water flow rate of the non-grafted polysulfone membrane, and (ii) 1 μg / cm³ ２ From 5 μg / cm³ ２ It has the ability to bind dyes between them, the dye is methylene blue or Ponceau S, the anionic monomer is one or more of vinyl sulfonic acid or sodium vinyl sulfonate, 2-ethyl acrylic acid, 2-carboxyethyl acrylate, 3-sulfopropyl potassium acrylate, 2-propyl acrylic acid, 2-(trifluoromethyl)acrylic acid, 2-methyl-2-propene-1-sulfonate sodium salt, mono-2-(methacryloyloxy)ethyl maleate, and 3-sulfopropyl potassium methacrylate, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamidophenylboronic acid, vinyl sulfonic acid, and vinylphosphonic acid, and the cationic monomer is 2-(dimethylamino)ethyl acrylate hydrochloride, [2-(acryloyloxy)ethyl] A grafted polysulfone membrane comprising one or more of the following: trimethylammonium chloride, 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl) methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyltrimethylammonium chloride, 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl)methacrylamide hydrochloride, N-(3-aminopropyl)methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride, vinylimidazolium hydrochloride, vinylpyridinium hydrochloride, and vinylbenzyltrimethylammonium chloride.

2. The grafted polysulfone film according to claim 1, wherein one or more monomers are anionic monomers.

3. The grafted polysulfone film according to claim 1, wherein one or more monomers are cationic monomers.

4. A grafted polysulfone film according to claim 1, comprising one or more monomers grafted onto one or more surfaces of the film, The water flow rate is at least 75% of the water flow rate of the non-grafted polysulfone membrane, The grafted polysulfone film according to claim 1, wherein the grafted monomer is a cationic monomer comprising one or more of the following: 2-(dimethylamino)ethyl acrylate hydrochloride, [2-(acryloyloxy)ethyl]trimethylammonium chloride, 2-aminoethyl methacrylate hydrochloride, N-(3-aminopropyl) methacrylate hydrochloride, 2-(dimethylamino)ethyl methacrylate hydrochloride, [3-(methacryloylamino)propyl]trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, acrylamidopropyltrimethylammonium chloride, 2-aminoethyl methacrylamide hydrochloride, N-(2-aminoethyl)methacrylamide hydrochloride, N-(3-aminopropyl)methacrylamide hydrochloride, diallyldimethylammonium chloride, allylamine hydrochloride, vinylimidazolium hydrochloride, vinylpyridinium hydrochloride, and vinylbenzyltrimethylammonium chloride.

5. The grafted polysulfone film according to claim 1 or 4, wherein the longitudinal brittleness does not exceed 30% of the longitudinal, cross-web, or both brittleness of the non-grafted polysulfone film.

6. A grafted polysulfone membrane according to claim 1 or 4, having a bubble point between approximately 65 psi and approximately 75 psi when measured by an ethoxy-nonafluorobutane bubble point test.

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