KR20200111028A - Pressure retarded osmosis membrane and Manufacturing method thereof - Google Patents

Abstract

The present invention relates to a pressure retarded osmosis (PRO) membrane with high water permeability and high power density and a manufacturing method thereof. In order to commercialize a pressure retarded osmosis process, it is essential to develop a pressure retarded osmosis module with high water permeability and high power density. To this end, the present invention relates to a method of manufacturing a separator having high water permeability and high power density.

Description

Pressure retarded osmosis membrane and manufacturing method thereof

The present invention relates to a pressure delayed osmosis membrane and a method of manufacturing the same, and more particularly, to a high water permeability and high power density PRO membrane capable of providing a pressure delayed osmosis module excellent in commerciality, and a method of manufacturing the same.

If a semi-permeable membrane, which has the property of permeating water but hardly permeating solutes (ions and molecules) dissolved in water, is installed between the high concentration solution and the low concentration solution, the solvent of the low concentration solution moves to the high concentration solution and attempts to achieve concentration equilibrium. Natural phenomena occur and are referred to as "osmotic" or "osmotic". The osmotic phenomenon was discovered by the German chemist M. Traube in 1867, and the osmotic pressure caused by the osmotic phenomenon was first measured by Pepper in 1877.

The osmosis phenomenon as described above is the core of desalination technology using seawater, which is one of the methods that can solve the severe water shortage due to climate change caused by global warming, industrial water increase due to industrialization, and water demand increase due to population increase.

However, the seawater desalination process up to now is a highly energy-intensive process, and it still has limitations in terms of economics unless it is a water shortage area such as the Middle East.

Methods for removing and using salts in seawater can be broadly divided into evaporation and reverse osmosis.

The reverse osmosis method is a technology that has been used for the past 30 years, and has a high degree of completion. Recently, the development of a technology focusing on improvement of a reverse osmosis membrane capable of obtaining a high recovery rate even at low pressure has been continued.

On the other hand, with the continuation of technology development as described above, technologies for recovering high-pressure energy from seawater condensed water discharged from the reverse osmosis process have recently emerged, and as the membrane technology has continued to develop rapidly, the osmotic pressure development introduced in 1976. There is increasing interest in

Osmotic power generation means generating electric power by using the osmotic pressure action at the place where two streams with a difference in salinity meet, and 27 bar osmotic pressure at the place where seawater with an osmotic pressure of 27 bar and river or sewage with an osmotic pressure close to zero meet. This can be used for power generation.

The power generation uses a pressure delayed osmosis (PRO) method different from the reverse osmosis method (RO). When the pressure of the high-concentration seawater is applied at a pressure lower than the osmotic pressure using the pressure delayed osmosis method, the flux of water permeating the membrane is reduced by the osmotic pressure, and the osmotic pressure is changed to water pressure, and the generated water pressure is used in the turbine. This is to produce electricity.

Power generation using pressure delayed osmosis as described above can cope with the global warming problem, which is an international issue, and is a renewable energy that can replace current fossil fuel energy, and it is environmentally friendly and generates carbon dioxide because it uses seawater, an infinite energy source. There is an urgent need to develop technology for zero. To this end, it is necessary to simultaneously develop several technologies such as the development of a pressure delayed osmosis membrane, an osmotic module, and a pressure delayed osmosis power plant.

In particular, in the case of using the pressure delayed osmosis (PRO) method, when the high concentration solution and the low concentration solution are separated and moved based on the pressure delayed osmosis membrane, the low concentration solution passes through the support layer and the active layer of the membrane in order and moves to the high concentration solution side by osmotic pressure. However, in order to implement a pressure delayed osmosis membrane having a high power density, it is essential to develop a separator having a high water permeability in which the amount of water passing through the support layer and the active layer is increased.

As a known technology, it relates to a method of manufacturing a high-performance forward osmosis thin film composite separator using a hydrophilic porous support layer. A prepolymerization solution is prepared by mixing polyethylene glycol diacrylate, a photoinitiator and a solvent, and light is applied to the prepolymerization solution. A method of preparing a porous support layer by irradiation and polymerization and forming a selection layer (active layer) on the support layer to prepare a separator having a high water permeability has been known. However, the method of irradiating and polymerizing light in order to manufacture a porous support layer having a high water permeability suggested in the prior art has a problem that it is very complex to be applied in an actual large-capacity separator manufacturing process and is difficult to commercialize due to high cost burden.

Korean Patent Registration No. 10-1731825 (announcement date 2017.05.11)

The present invention has been conceived to solve the above-described problems, and the problem to be solved by the present invention is a method of manufacturing a pressure delayed osmosis (PRO) separator and module that can be commercialized more easily and secures high water permeability and high power density. To provide.

The present invention for solving the above problem relates to a pressure delayed osmosis membrane, comprising a porous support layer, a porous hydrophilic polymer layer, and a composite membrane in which an active layer is sequentially stacked, and the porous hydrophilic polymer layer is a polysulfone resin and It may be formed by coating and phase-separating a polymer crude liquid containing at least one selected from among sulfonated polysulfone resins.

As a preferred embodiment of the present invention, the polysulfone resin may be a copolymer including a repeating unit represented by Formulas 1-1 and 1-2 below.

[Formula 1-1]

[Formula 1-2]

As a preferred embodiment of the present invention, the sulfonated polysulfone resin may be a copolymer including a repeating unit represented by the following Formulas 2-1 and 2-2.

[Formula 2-1]

[Formula 2-2]

In Formulas 2-1 and 2-2, each of R ₁ , R ₂ , R ₃ and R ₄ is independently a hydrogen atom, a straight chain alkyl group of C1 to C5, a branched alkyl group of C3 to C5 or an alkyl of C2 to C4. It's Rengi.

As a preferred embodiment of the present invention, the polysulfone resin may have a weight average molecular weight of 15,000 to 100,000 g/mol, and the sulfonated polysulfone resin may have a weight average molecular weight of 100,000 to 200,000 g/mol.

As a preferred embodiment of the present invention, the polymer crude liquid may contain 4 to 15 parts by weight of the sulfonated polysulfone resin based on 100 parts by weight of the polysulfone resin.

As a preferred embodiment of the present invention, the sulfonation degree of the polysulfone resin may be 5 to 40%.

As a preferred embodiment of the present invention, the polymer crude liquid may have a viscosity of 500 to 3,000 cP (25°C).

As a preferred embodiment of the present invention, the porous support layer may include a fabric made of one or more fibers selected from polyester, polypropylene, nylon, polyethylene, acrylic, rayon, acetate, and cellulose.

As a preferred embodiment of the present invention, the active layer may contain at least one selected from polyamide-based polymer, polypiperazine-based polymer, polyphenylenediamine-based polymer, polychlorophenylenediamine-based polymer, and polybenzidine-based polymer. I can.

In a preferred embodiment of the present invention, the porous support layer may have a thickness of 60 to 80 μm, the porous hydrophilic polymer layer may have a thickness of 30 to 80 μm, and the active layer may have a thickness of 0.1 to 1 μm.

As a preferred embodiment of the present invention, the total thickness of the pressure delayed osmosis membrane of the present invention may be 90.1 μm to 161 μm.

As a preferred embodiment of the present invention, the pressure delayed osmosis (PRO) separator of the present invention is subjected to a pressure delayed osmosis experiment under conditions of a flow rate of 0.5 LPM at 25° C., a pressure of 20 bar and a 70,000 ppm sodium chloride aqueous solution, and the following equation When measuring the water permeability according to 1, the water permeability may be 12 to 40 L/m ² /hr.

[Equation 1]

In Equation 1, J _W is the water permeability, π _draw is the osmotic pressure of the _draw solution, π _feed is the osmotic pressure of the influent solution, A is the water permeation constant of the PRO membrane, B is the salt permeation constant of the PRO membrane, and K _m is 1 /K _R , K _R is the salt diffusion resistance coefficient of the porous hydrophilic polymer layer of the PRO membrane, and ΔP is the pressure.

As a preferred embodiment of the present invention, in Equation 1, the water permeability constant value (A) of the PRO separator is 1 to 3.6 L/m ² /hr/bar, and the salt permeability constant value (B) of the PRO separator is 0.1 to It may be 0.8 L/m ² /hr.

As a preferred embodiment of the present invention, the water permeation constant value and the salt permeation constant value can be obtained based on Equation 2 below through an experiment of a salt removal rate under conditions of 1,000 ppm NaCl aqueous solution and 10 bar.

[Equation 2]

In Equation 2, A is the water permeation constant of the PRO membrane, B is the salt permeation constant of the PRO membrane, R is the salt removal rate, ΔP is the pressure, and Δπ is the difference between the osmotic pressure of the draw solution and the osmotic pressure of the input solution. .

As a preferred embodiment of the present invention, the salt diffusion resistance coefficient (K _R ) of the porous hydrophilic polymer layer of the PRO membrane of Equation 1 and the structural constant (S) of the porous hydrophilic polymer layer of the PRO membrane are derived under a pressure condition of 20 bar. Through a pressure delayed osmosis experiment using 70,000 ppm of NaCl aqueous solution as a solution and distilled water as a feed solution, it can be calculated based on Equation 3 below.

[Equation 3]

In Equation 3, S (mm) is the structural constant of the porous hydrophilic polymer layer of the PRO separator, and D _s is the salt diffusion coefficient.

As a preferred embodiment of the present invention, the PRO separator of the present invention may have a power density of 6 to 25 W/m ² when measured according to Equation 4 below.

[Equation 4]

In Equation 4, PRO is the water permeability (L/m ² /hr), and ΔP is the pressure.

Another object of the present invention is to provide a method for manufacturing a pressure delayed osmosis membrane of the present invention described above, and the pressure delayed osmosis membrane of the present invention comprises at least one selected from polysulfone resin and sulfonated polysulfone resin. 1 step of preparing a polymer crude liquid by mixing a polymer resin and a solvent; A second step of forming a porous hydrophilic polymer layer on the porous support layer by treating the polymer crude liquid on the porous support so that the polymer crude liquid penetrates into the pores of the porous support, and then performing a phase transition of the polymer crude liquid; And it can be prepared by performing a process comprising a; 3 step of forming an active layer on the porous hydrophilic polymer layer.

As a preferred embodiment of the present invention, the polysulfone resin may be a copolymer including a repeating unit represented by Formulas 1-1 and 1-2.

As a preferred embodiment of the present invention, the sulfonated polysulfone resin may be a copolymer including a repeating unit represented by Chemical Formulas 2-1 and 2-2.

Another object of the present invention is to provide a pressure delayed osmosis module provided with the pressure delayed osmosis membrane described above.

The pressure delayed osmosis (PRO) membrane of the present invention can implement a pressure delayed osmosis membrane and module having high water permeability and high power density. In particular, by adding a hydrophilic polymer to the polymer support layer, a high water permeability can be easily achieved, and thus, a pressure delayed osmosis membrane and a manufacturing method of a high power density suitable and practical for a large-capacity separation membrane production process can be provided.

1 is a schematic diagram showing a cross-sectional view of a separator used in RO and PRO processes and a fouling phenomenon thereof.
2 is a schematic cross-sectional view of a pressure delayed osmosis (PRO) separation membrane according to an embodiment of the present invention.
3 is a SEM measurement photograph of a cross section of a PRO separator according to an embodiment of the present invention.
4 is a schematic diagram of a pressure delay osmotic membrane module according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

As described above, the method of manufacturing a high-performance forward osmosis thin film composite separator using a conventional hydrophilic porous support layer is to prepare a prepolymerization solution by mixing polyethylene glycol diacrylate, a photoinitiator and a solvent, and irradiate light to the prepolymerization solution. A method of preparing a porous support layer by polymerization and forming a selection layer on the support layer to prepare a separator having a high water permeability is disclosed. However, the method of irradiating and polymerizing light in order to prepare a porous support layer having a high water permeability proposed in the prior art is very complicated to be applied in an actual large-capacity separator manufacturing process and has a problem that it is difficult to commercialize it due to high cost burden.

As shown in Figure 1, the pressure delayed osmosis (hereinafter referred to as PRO) process differs from the RO (Reverse Osmosis) and FO (Forward Osmosis) processes, and the direction of movement of the flux according to the osmotic gradient is the rear surface of the PRO membrane ( The backing layer) moves to the active layer or the selection layer, and thus there is a problem in that a fouling phenomenon occurs toward the back side of the PRO separator. Such fouling causes the degradation of the PRO separator and shortens the membrane module replacement and CIP cleaning cycle, thereby increasing the maintenance cost of the process.

Accordingly, the present invention is a high water permeability and high power by forming a porous hydrophilic polymer layer 12 on the porous support layer 12 and forming the active layer 13 disposed on the upper surface of the support layer, as shown in the schematic diagram in FIG. It is an invention that can provide a pressure delayed osmosis membrane having a density (hereinafter, PRO membrane, 10) and a manufacturing method that can be easily manufactured and commercialized.

In addition, by using the PRO separation membrane of the present invention, it is possible to provide a pressure delayed osmosis module having a high power density.

The PRO separator of the present invention comprises a first step of preparing a polymer crude liquid by mixing a hydrophilic polymer resin and a solvent; A second step of forming a porous hydrophilic polymer layer on the porous support layer by processing the polymer crude liquid on the porous support so that the polymer crude liquid penetrates into the pores of the porous support, and then phase-transferring the polymer crude liquid; And 3 steps of forming an active layer on the porous hydrophilic polymer layer; by performing a process including, a PRO separator having a structure as in the schematic diagram of FIG. 2 may be manufactured.

In addition, the PRO separation membrane manufacturing method of the present invention may further include a fourth step of washing and drying the laminate having the active layer formed thereon in order to remove the unreacted residue.

In step 1, the hydrophilic polymer resin may include at least one selected from a sulfonated polysulfone resin and a sulfonated polyethersulfone resin, preferably

According to another embodiment of the present invention, the hydrophilic polymer resin may include at least one of polysulfone and sulfonated polysulfone, and the sulfonated polysulfone resin is 4 parts by weight based on 100 parts by weight of the polysulfone resin. In ~ 25 parts by weight, more preferably, based on 100 parts by weight of the polysulfone resin, the sulfonated polysulfone resin may be included in an amount of 5 to 15 parts by weight. At this time, if the amount of the sulfonated polysulfone resin used is less than 4 parts by weight, there may be a problem that the hydrophilicity of the separator may not be expressed, so that the water permeability may be lowered. If it exceeds 25 parts by weight, the structure of the separator is deformed, resulting in low porosity and pressure resistance. There may be a problem with this occurring.

In addition, the polysulfone resin may include a copolymer including a repeating unit represented by Formulas 1-1 and 1-2 below, and the weight average molecular weight of the polysulfone resin is 15,000 to 100,000 g/mol, preferably May be 20,000 to 65,000 g/mol, more preferably 20,000 to 40,000 g/mol. In addition, the degree of sulfonation of the polysulfone resin may be 5 to 40%, preferably 20 to 40%. At this time, when the degree of sulfonation is less than 5%, the degree of hydrophilicity of the separation membrane is reduced, resulting in a decrease in water permeability, and the power density of the pressure-delayed osmosis membrane may be lowered.If the degree of sulfonation exceeds 40%, the pressure resistance of the PRO membrane is low. There may be a problem that the salt removal rate is lowered.

[Formula 1-1]

[Formula 1-2]

In addition, the sulfonated polysulfone resin may include a copolymer including a repeating unit represented by Formulas 2-1 and 2-2 below.

[Formula 2-1]

[Formula 2-2]

In Formulas 2-1 and 2-2, each of R ₁ , R ₂ , R ₃ and R ₄ is independently a hydrogen atom, a straight chain alkyl group of C1 to C5, a branched alkyl group of C3 to C5 or an alkyl of C2 to C4. It is a ren group, and preferably each of R ₁ , R ₂ , R ₃ and R ₄ may be independently a hydrogen atom, a straight chain alkyl group of C1 to C5 or a branched alkyl group of C3 to C5, and more preferably C1 to C3 It may be a straight-chain alkyl group of.

Among the hydrophilic polymer resins, the sulfonated polysulfone resin may have a weight average molecular weight of 100,000 to 200,000 g/mol, preferably 120,000 to 180,000 g/mol, more preferably 130,000 to 165,000 g/mol. At this time, if the weight average molecular weight of the sulfonated polysulfone resin is less than 100,000 g/mol, the structure of the separator may be affected, and the active layer may become unstable, resulting in a decrease in the salt removal rate, and the weight of the sulfonated polysulfone resin If the average molecular weight exceeds 200,000 g/mol, the hydrophilicity of the porous hydrophilic polymer layer may decrease, resulting in a problem of lowering the water permeability.

In addition, the polymer crude liquid used to form the porous hydrophilic polymer layer is prepared by mixing the hydrophilic polymer resin and a solvent, and the polymer crude liquid has a viscosity of 500 to 3,000 cP (25°C), preferably 900 to 2,800 cP (25 ℃), more preferably 1,250 ~ 2,500 cP (25 ℃) is good. At this time, when the viscosity of the polymer crude liquid is less than 500 cP, the water permeability may increase, but the pressure resistance decreases, making it impossible to operate at high pressure. When the viscosity of the polymer crude liquid is more than 3,000 cP, the water permeability decreases and the power density of the pressure delayed osmosis membrane decreases. Due to the high viscosity, the bonding strength between the porous support layer and the porous hydrophilic polymer layer may be weakened, resulting in a desorption phenomenon, and the surface of the porous hydrophilic polymer layer may become unstable, resulting in a low salt removal rate.

In step 1, the porous support layer may be used without limitation, as long as the support layer is generally used for a pressure delayed osmosis membrane support, and preferably polyester, polypropylene, nylon, polyethylene, acrylic, rayon, acetate and It may include a fabric served with one or more fibers selected from cellulose.

In addition, the performance of the separator may be improved depending on the porosity and thickness of the porous support. Since the structure and thickness of the support affects the S value, which is the structural constant of the PRO separator, the power density of the separator may change depending on the selection of the support. For example, when a support having excellent air permeability is used, the S value decreases to implement a pressure delayed osmosis membrane having high water permeability and high power density, and when the thickness of the support is decreased, a high performance pressure delayed osmosis membrane can be manufactured. However, if a support with an air permeability exceeding 700 cc/m ² /sec is used, the polymer support layer is not properly applied on the support, resulting in unstable shape of the separator and affecting the formation of the filtration layer, resulting in a disadvantage of lowering the salt removal rate . Therefore, the porous support is used with an air permeability of 50 to 700 cc/m ² /sec, preferably 80 to 500 cc/m ² /sec, more preferably 90 to 400 cc/cm ² ·sec. good.

Next, step 2 is a process of forming a porous hydrophilic polymer layer on top of the porous support layer.After applying the polymer crude solution prepared in step 1 to one side of the porous support, it is immersed in a coagulation bath containing a non-solvent, and phase separation (phase transition ) To form a porous hydrophilic polymer layer on top of the porous support layer to prepare a two-layered laminate. Here, as the non-solvent, at least one selected from water, ethanol, isopropyl alcohol and methanol may be used, and water and/or isopropyl alcohol may be preferably used.

Next, the third step is a process of forming an active layer on the porous hydrophilic polymer layer of the laminate prepared in step 2, and the second step is 3 in which the laminate is immersed in an aqueous solution containing a polyfunctional amine or an alkylated aliphatic amine. -Level 1; 3-2 step of removing the non-solvent from the surface of the laminate; 3-3 step of performing interfacial polymerization by immersing the laminate from which the non-solvent has been removed in an organic solution containing a polyfunctional acid halogen compound; And 3-4 steps of drying the interfacially polymerized laminate to form an active layer.

The active layer may include at least one selected from polyamide-based polymers, polypiperazine-based polymers, polyphenylenediamine-based polymers, polychlorophenylenediamine-based polymers, and polybenzidine-based polymers, and preferably polyamide-based It may be a layer containing a polymer.

When the active layer in the third step is a polyamide-based active layer composed of a polyamide-based compound, it will be described in detail as follows.

Step 3-1 is the multifunctional amine or alkylation of the layered product in an aqueous solution containing 1.5 to 3.8% by weight of a polyfunctional amine or an alkylated aliphatic amine for 30 seconds to 300 seconds, preferably at a concentration of 2.0 to 3.8% by weight. It is carried out by immersing in an aqueous solution containing a polyfunctional amine or an alkylated aliphatic amine at a concentration of 2.5 to 3.5% by weight for 40 seconds to 200 seconds, more preferably in an aqueous solution containing the aliphatic amine. At this time, if the concentration of the polyfunctional amine or the alkylated aliphatic amine in the aqueous solution is less than 1.5% by weight, there may be a problem in that the interfacial polymerization reaction of 2-3 steps is not sufficiently formed and the active layer is not formed evenly, and the polyfunctionality in the aqueous solution If the concentration of amine or alkylated aliphatic amine exceeds 3.8% by weight, the water permeation constant (L/m ² /hr/bar) of the produced PRO membrane is too low, or the structural constant of the porous hydrophilic polymer layer of the PRO membrane (S ,mm) is too high, there may be a problem that the water permeability and/or power density of the PRO separator is very low.

In addition, the polyfunctional amine is at least one selected from metaphenyldiamine, paraphenyldiamine, orthophenyldiamine, piperazine, and alkylated piperazine, preferably from metaphenyldiamine, paraphenyldiamine and orthophenyldiamine. It may include at least one selected, more preferably at least one selected from metaphenyldiamine and paraphenyldiamine.

In addition, the aqueous solution containing the polyfunctional amine or the alkylated aliphatic amine of step 3-1 is at least one selected from the group consisting of a hydroxyl group, a sulfonated group, a carbonyl group, a trialkoxysilane group, an anionic group, and a tertiary amino group. It may further contain a hydrophilic compound having a hydrophilic functional group.

More specifically, preferred examples of the hydrophilic compound having a hydroxy group include 1,3-diamino-2-propanol, ethanolamine, diethanolamine, 3-amino-1-propanol, 4-amino-1-butanol, It may contain at least one selected from 2-amino-1-butanol.

In addition, the hydrophilic compound having a carbonyl group is 1 selected from aminoacetaldehyde dimethylacetal, α-aminobutylrolactone, 3-aminobenzamide, 4-aminobenzamide and N-(3-aminopropyl)-2-pyrrolidinone It may contain more than one species.

In addition, the hydrophilic compound containing a trialkoxysilane group may include at least one selected from (3-aminopropyl)triethoxysilane or (3-aminopropyl)trimethoxysilane.

In addition, the hydrophilic compounds having an anionic group include glycine, taurine, 3-amino-1-propenesulphonic acid, 4-amino-1-butenesulphonic acid, 2-aminoethyl hydrogen sulfate, and 3-aminobenzenesulphate. Phonic acid, 3-amino-4-hydroxybenzenesulphonic acid, 4-aminobenzenesulphonic acid, 3-aminopropylphosphonic acid, 3-amino-4-hydroxybenzoic acid, 4-amino-3- Including at least one selected from hydroxybenzoic acid, 6-aminohexenoic acid, 3-aminobutanoic acid, 4-amino-2-hydroxybutyric acid, 4-aminobutyric acid, and glutamic acid can do.

In addition, as hydrophilic compounds having a tertiary amino group, 3-(dimethylamino)propylamine, 3-(diethylamino)propylamine, 4-(2-aminoethyl)morpholine, 1-(2-aminoethyl)pipe It may contain at least one selected from ragine, 3,3'-diamino-N-methyldipropylamine, and 1-(3-aminopropyl)imidazole.

The method of removing the non-solvent from the surface of the layered product in step 3-2 may be performed by a general method used in the art, and as a preferred example, the non-solvent may be removed by a compression method.

Step 3-3 is a step of performing interfacial polymerization, in the organic solution from which the non-solvent has been removed, at room temperature (10 to 35°C) for 30 seconds to 300 seconds, preferably 40 seconds to 180 seconds, more preferably 50 seconds to By immersing for about 120 seconds, the polyfunctional amine or the alkylated aliphatic amine present on the surface of the laminate and the polyfunctional acid halogen compound undergo interfacial polymerization to form an active layer including the polyamide compound.

At this time, the organic solution includes a polyfunctional acid halogen compound and an organic solvent, wherein the organic solvent may include at least one selected from hexane, toluene, cyclohexane, and heptane.

In addition, the polyfunctional acid halogen compound may include at least one selected from a polyfunctional acyl halide, a polyfunctional sulfonyl halide, and a polyfunctional isocyanate. More specifically, at least one polyfunctional acyl halide selected from trimesoyl chloride, isophthaloyl chloride and terephthaloyl chloride may be included, and preferably trimesoyl chloride may be included.

In addition, the organic solution may have a concentration of the polyfunctional acid halogen compound of 0.1 to 0.5% by weight, preferably 0.15 to 0.40% by weight, and if the concentration of the polyfunctional acid halogen compound is less than 0.1% by weight, a sufficient interfacial polymerization reaction product Due to the lack of this, the active layer may not be formed well, and if the amount exceeds 0.5% by weight, the active layer may be formed thick and there may be a problem that the water permeability decreases. Therefore, it is preferable to use an organic solution in the above concentration range.

The active layer thus formed can be formed as a dense surface layer of the PRO separator to form a structure with strong pressure resistance, and at the same time, the thin-film hydrophilic selective layer can maintain a uniform size of pores to secure a high salt exclusion rate.

Step 3-4 is a process of forming an active layer by drying the laminate subjected to the interfacial polymerization reaction. In this case, the drying may be performed by a general method used in the art, and a preferred example may be performed by naturally drying for 1 minute to 5 minutes at 15 to 35°C.

The PRO separator of the present invention thus prepared has a form in which a porous support layer, a porous hydrophilic polymer layer, and an active layer are sequentially stacked, and the porous support layer may have a thickness of 60 to 80 μm, preferably 65 to 75 μm. At this time, if the thickness of the porous support layer is less than 60㎛, and if the thickness of the support is less than 60㎛, the pressure resistance is low, so that it cannot be utilized under high pressure operation conditions, so that the function as a PRO separator may not be performed properly. If it exceeds, the S value, which is the structural constant of the PRO membrane, increases and the water permeability decreases, resulting in a problem of lowering the power density.

In addition, the porous hydrophilic polymer layer may have a thickness of 30 to 80 μm, preferably 35 to 75 μm, more preferably 40 to 65 μm. At this time, when the thickness of the porous hydrophilic polymer layer is less than 30 μm, the pressure resistance may be weakened, and when the thickness of the porous hydrophilic polymer layer is less than 80 μm, there may be a problem in that the separator structure constant increases and water permeability decreases.

In addition, the active layer may have a thickness of 0.1 to 1 μm, preferably 0.2 to 0.8 μm, and if the thickness of the active layer is less than 0.1 μm, there may be a problem that the reverse salt transmission constant increases, and the thickness of the active layer is 1 μm. If it is exceeded, there may be a problem that the water permeability decreases.

Such, the PRO separation membrane of the present invention has an overall thickness of 90.1 μm to 161 μm, preferably 95 to 145 μm, more preferably 100 to 140 μm, which is good in terms of proper water permeability and power density.

The PRO separation membrane of the present invention is subjected to a pressure delayed osmosis experiment at 25° C., a pressure of 20 bar and a flow rate of 0.5 LPM for an aqueous solution of 70,000 ppm sodium chloride, and the water permeability (J _W ) is measured according to the following equation The transmittance may be 12 to 40 L/m ² /hr, preferably 14 to 38 L/m ² /hr, more preferably 14.5 to 35 L/m ² /hr.

[Equation 1]

In Equation 1, J _W is the water permeability, π _draw is the osmotic pressure of the _draw solution, π _feed is the osmotic pressure of the influent solution, A is the water permeation constant of the PRO membrane, B is the salt permeation constant of the PRO membrane, and K _m is 1 /K _R , K _R is the salt diffusion resistance coefficient of the porous hydrophilic polymer layer of the PRO membrane, and ΔP is the pressure.

In the actual pressure delayed osmosis process, 1) osmotic pressure loss due to salt permeation, 2) effective osmotic pressure decrease due to disturbance of salt diffusion in the support layer, and 3) dilution of the draw solution in the filter layer can reduce the permeate flow rate. These three effects can be expressed by the diffusion resistance value including the salt permeability constant B, the support layer structure constant S, and the water permeability constant A, which is related to the fluid flow and water permeation amount of the draw solution.

In addition, the PRO separation membrane of the present invention has a water permeability constant value (A) of the PRO separation membrane in Equation 1 from 1 to 3.6 L/m ² /hr/bar, preferably 1.10 to 3.00 L/m ² /hr/bar , More preferably, it may satisfy the range of 1.15 to 2.90 L/m ² /hr/bar. At this time, if the water permeability constant value is less than 1 L/m ² /hr/bar, the water permeability decreases and the power density decreases. If it exceeds 3.6 L/m ² /hr/bar, salt The disadvantage of lowering the removal rate may occur.

In addition, the PRO membrane of the present invention may satisfy a salt permeation constant value (B) of 0.1 to 0.8 L/m ² /hr in Equation 1, preferably 0.200 to 0.600 L/m ² /hr, more preferably In other words, the range of 0.300 to 0.550 L/m ² /hr may be satisfied. At this time, if it is less than 0.1 L/m ² /hr, there may be a disadvantage of decreasing the water permeability, and if it is more than 0.7 L/m ² /hr, the amount of salt permeates backwards. There may be a disadvantage of lowering the power density due to a decrease in the concentration difference between the influent solutions.

In addition, the water permeation constant value and the salt permeation constant value can be obtained based on Equation 2 below through an experiment of a salt removal rate under 1,000 ppm NaCl aqueous solution and 10 bar condition.

[Equation 2]

In Equation 2, A is the water permeation constant of the PRO membrane, B is the salt permeation constant of the PRO membrane, R is the salt removal rate, ΔP is the pressure, and Δπ is the difference between the osmotic pressure of the draw solution and the osmotic pressure of the input solution. .

In addition, the PRO separation membrane of the present invention may satisfy a range in which the S value, which is a structural constant in Equation 1, is 6×10 ^-4 to 3×10 ^-3 m, and preferably 7×10 ^-4 to 2.5×10 ^It can satisfy the range of ^-3 m. At this time, if it is less than 6×10 ^-4 m, the pressure resistance of the separator decreases, so durability at high pressure may be lowered, and the operating period may also be reduced, and if it is 3×10 ^-3 m or more, the resistance inside the separator increases, resulting in water permeability. Reducing disadvantages can occur.

In addition, the salt diffusion resistance coefficient (K _R ) of the porous hydrophilic polymer layer of the PRO separation membrane of Equation 1 and the structural constant (S) of the porous hydrophilic polymer layer of the PRO separation membrane are 70,000 ppm NaCl aqueous solution as a draw solution under pressure of 20 bar. And through a pressure delayed osmosis experiment using distilled water as a feed solution, it can be calculated based on Equation 3 below.

[Equation 3]

In Equation 3, S (mm) is the structural constant of the porous hydrophilic polymer layer of the PRO membrane, and D _s is the salt diffusion coefficient.

The power density is the most important performance indicator in pressure delayed osmosis and can be defined as the amount of power that can be produced per unit area of the separator, and the maximum power density is calculated as the product of the water permeability through the separator and the water pressure difference. In more detail, in the pressure-delayed osmosis process, the low-concentration influent is moved to the high-concentration draw solution by the osmosis phenomenon. At this time, the turbine is operated using the increased flow rate of the draw solution to generate power. In this case, the power density is expressed by using the permeate flow rate through the separation membrane. In addition, the PRO separator of the present invention has a power density of 6 to 25 W/m ² , preferably 7.0 to 22.5 W/m ² , more preferably 8.0 to 22.0 W/m when measured according to Equation 4 below. ^It can be ² .

[Equation 4]

In Equation 4, PRO is the water permeability (L/m ² /hr), and ΔP is the pressure.

Hereinafter, the present invention will be described through the following examples. At this time, the following examples are only presented to illustrate the invention, and the scope of the present invention is not limited by the following examples.

[Example]

Example 1

As a porous support, a fabric with a weft and warp of polyester material in the range of width (2.54 cm) × length (2.54 cm) and in the range of 300 to 310 plain weaves by carpenters was prepared. The fabric has an air permeability of about 100 to 200 cc/cm ² ·sec and has a thickness of about 65 μm.

With respect to 100 parts by weight of the polysulfone resin, 11 parts by weight of a sulfonated polysulfone resin and 444 parts by weight of a dimethylformamide solvent were mixed and stirred to prepare a polymer crude liquid having a viscosity of 2,000 cP (centi poise) at 25°C.

In this case, the polysulfone resin is a copolymer having a weight average molecular weight of 25,000 g/mol including a repeating unit represented by the following Chemical Formulas 1-1 and 1-2, and a sulfonation degree of 30%. In addition, the sulfonated polysulfone resin is a copolymer having a weight average molecular weight of 145,000 g/mol including a repeating unit represented by the following Chemical Formulas 2-1 and 2-2.

[Formula 1-1]

[Formula 1-2]

[Formula 2-1]

[Formula 2-2]

In Formulas 2-1 and 2-2, R ₁ , R ₂ , R ₃ and R ₄ are all methyl groups.

Next, after applying the polymer crude solution to one side of the porous support, it is immersed in a coagulation bath containing water as a non-solvent to induce phase separation (phase transition) to form a porous hydrophilic polymer layer on top of the porous support layer to form a two-layer structure. A laminate was prepared. At this time, the temperature of the coagulation bath solution was maintained at 20°C.

Next, the two-layered laminate was immersed in an aqueous solution containing metaphenylenediamine (MPD) in an amount of 3.5% by weight for 1 minute, and then the non-solvent on the surface was removed by a compression method. Thereafter, it was immersed in an organic solution containing 0.1% by weight of trimesoyl chloride (TMC) in an ISOPAR solvent (Exxon Corp.) for 1 minute, followed by interfacial polymerization, and then naturally dried at room temperature (25°C) for 1 minute and 30 seconds to obtain polyamide. The configured active layer was formed.

Thereafter, in order to remove unreacted residues, a pressure delayed osmosis (PRO) membrane having a total thickness of about 120 μm was prepared by immersing in a 0.2% by weight sodium carbonate solution for 2 hours. At this time, in the pressure delayed osmosis membrane, the thickness of the porous support layer was 65 μm, the thickness of the porous hydrophilic polymer layer was about 55 μm, and the thickness of the active layer was about 0.2 μm.

Example 2

Preparation was carried out in the same manner as in Example 1, but after preparing a polymer crude liquid having 2,500 cP at 25° C. by adjusting the solvent content, a PRO separator was prepared as shown in Table 1 below.

Example 3

Preparation was carried out in the same manner as in Example 1, but a polymer crude solution was prepared using 5.6 parts by weight of a sulfonated polysulfone resin based on 100 parts by weight of a polysulfone resin, and then a PRO separator was prepared as shown in Table 1 below. .

Example 4

Preparation was carried out in the same manner as in Example 1, but a polymer crude solution was prepared using 8.3 parts by weight of a sulfonated polysulfone resin based on 100 parts by weight of a polysulfone resin, and then a PRO separator was prepared as shown in Table 1 below. .

Comparative Example 1

In the same manner as in Example 1, a PRO separation membrane was prepared as shown in Table 2 below, but a PRO separation membrane having a thickness of 135 μm was prepared. In this case, in the pressure delayed osmosis membrane, the thickness of the porous support layer was 65 μm, and the porosity The thickness of the hydrophilic polymer layer was about 70 μm, and the thickness of the active layer was about 0.2 μm.

Comparative Example 2

In the same manner as in Example 1, a PRO separation membrane was prepared as shown in Table 2 below, but a polymer crude solution having 3,200 cP was prepared at 25° C. by using less solvent, and then a PRO separation membrane was prepared using this.

Comparative Example 3

In the same manner as in Example 1, a PRO separator was prepared as shown in Table 2 below, but a PRO separator was prepared using a support having a thickness of 40 μm.

Comparative Example 4

A PRO separation membrane was prepared as shown in Table 2 below by performing the same as in Example 1, but when the active layer was formed, the two-layered laminate was immersed in an aqueous solution containing metaphenylenediamine (MPD) at 4.0% by weight for 1 minute. After that, the non-solvent on the surface was removed by a pressing method. Thereafter, it was immersed in an organic solution containing 0.1% by weight of trimesoyl chloride (TMC) in an ISOPAR solvent (Exxon Corp.) for 1 minute, followed by interfacial polymerization, and then naturally dried at room temperature (25°C) for 1 minute and 30 seconds to obtain polyamide. The configured active layer was formed.

Other procedures were carried out in the same conditions and method as in Example 1 to prepare a PRO separator.

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Polymer
Crude liquid A 100
Parts by weight 100
Parts by weight 100
Parts by weight 100
Parts by weight 100
Parts by weight 100
Parts by weight B 11
Parts by weight 11
Parts by weight 5.6
Parts by weight 8.3
Parts by weight 11
Parts by weight 11
Parts by weight menstruum 444 parts by weight 326
Parts by weight 450
Parts by weight 447
Parts by weight 444
Parts by weight 444
Parts by weight Viscosity
(25℃) 2,000 cP 2,500 cP 1,950 cP 2,010 cP 2,000 cP 2,000 cP Each layer thickness Porous support layer 68 μm 68 μm 68 μm 68 μm 68 μm 68 μm Porous hydrophilic polymer layer 50㎛ 50㎛ 50㎛ 50㎛ 38㎛ 74㎛ Active layer 0.2 μm 0.2 μm 0.2 μm 0.2 μm 0.2 μm 0.2 μm Total thickness of separator
118.2 μm 118.2 μm 118.2 μm 118.2 μm 106.2 μm 142.2 μm A: Polysulfone resin having a weight average molecular weight of 25,000 g/mol
B: Sulfonated polysulfone resin having a weight average molecular weight of 145,000 g/mol

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Polymer
Crude liquid A 100
Parts by weight 100
Parts by weight 100
Parts by weight 100
Parts by weight 100
Parts by weight 100
Parts by weight 100
Parts by weight B 11
Parts by weight 55
Parts by weight 11
Parts by weight 11
Parts by weight 2.5
Parts by weight 11
Parts by weight 11
Parts by weight menstruum 444 parts by weight 400
Parts by weight 444
Parts by weight 444
Parts by weight 444
Parts by weight 444
Parts by weight 444
Parts by weight Viscosity
(25℃) 2,000 cP 3,200 cP 2,000 cP 2,000 cP 1,240 cP 2,000 cP 2,000 cP Each layer thickness Porous support layer 90 μm 68 μm 40 μm 68 μm 68 μm 68 μm 68 μm Porous hydrophilic polymer layer 50㎛ 50㎛ 50㎛ 50㎛ 50㎛ 22㎛ 85㎛ Active layer 0.2 μm 0.2 μm 0.2 μm 0.2 μm 0.2 μm 0.2 μm 0.2 μm Total thickness of separator
140.2 μm 118.2 μm 90.2 μm 118.2 μm 118.2 μm 90.2 μm 153.2 μm A: Polysulfone resin having a weight average molecular weight of 25,000 g/mol
B: Sulfonated polysulfone resin having a weight average molecular weight of 145,000 g/mol

Experimental Example: Measurement of property evaluation of PRO membrane

The water permeability and power density of the PRO separators prepared in the Examples and Comparative Examples were measured, and the results are shown in Table 3 below.

(1) Water permeability measurement and calculation method

The active layer of the PRO separation membrane is mounted in the direction of the draw solution (aqueous sodium chloride solution) (direction in contact with the pressure), and under the conditions of 25℃ temperature, 20bar pressure and 0.5 LPM flow rate, 70,000 ppm NaCl aqueous solution and distilled water as the supply solution Through a pressure delayed osmosis experiment using, the water permeability (J _w , L/m ² /hr) of the PRO membrane was measured, and the water permeability was calculated based on Equation 1 below.

[Equation 1]

In Equation 1, J _W is the water permeability, π _draw is the osmotic pressure of the _draw solution, π _feed is the osmotic pressure of the influent solution, A is the water permeation constant of the PRO membrane, B is the salt permeation constant of the PRO membrane, and K _m is 1 /K _R , K _R is the salt diffusion resistance coefficient of the porous hydrophilic polymer layer of the PRO membrane, and ΔP is the pressure.

In addition, A (L/m ² /hr/bar), the water permeation constant of the PRO membrane and B (L/m ² /hr), the salt permeation constant of the PRO membrane were 1,000 ppm NaCl aqueous solution, and the salt removal rate was tested under 10 bar conditions. Through, it can be obtained based on Equation 2 below.

[Equation 2]

In Equation 2, A is the water permeation constant of the PRO membrane, B is the salt permeation constant of the PRO membrane, R is the salt removal rate, ΔP is the pressure, and Δπ is the difference between the osmotic pressure of the draw solution and the osmotic pressure of the input solution. .

In addition, the salt diffusion resistance coefficient (K _R ) of the porous hydrophilic polymer layer of the PRO separation membrane of Equation 1 and the structural constant (S) of the porous hydrophilic polymer layer of the PRO separation membrane are 70,000 ppm NaCl aqueous solution as a draw solution under a pressure of 20 bar. And through a pressure delayed osmosis experiment using distilled water as a feed solution, it can be calculated based on Equation 3 below.

[Equation 3]

In Equation 3, S (mm) is the structural constant of the porous hydrophilic polymer layer of the PRO separator, and D _s is the salt diffusion coefficient.

(2) power density

The power density (W) of the PRO separator was calculated based on Equation 4 below.

[Equation 4]

In Equation 4, PRO is the water permeability (L/m ² /hr), and ΔP is the pressure.

division Water permeation constant of PRO membrane
(A, L/m ² /hr/bar) Salt permeation constant of PRO membrane (B, L/m ² /hr) Structural constant of the porous hydrophilic polymer layer of the PRO membrane (S,mm) Water permeability
(L/m ² /hr) Power density
(W/m ² ) Example 1 2.85 0.466 0.93 31.4 17.1 Example 2 1.35 0.400 1.19 17.04 9.5 Example 3 1.15 0.337 1.57 16 8.7 Example 4 1.47 0.435 1.51 17 9.3 Example 5 1.90 0.625 1.08 15 7.4 Example 6 1.51 0.481 2.16 12 6.7 Comparative Example 1 1.8 0.714 4.29 6 3.3 Comparative Example 2 1.84 0.707 2.83 9 4.9 Comparative Example 3 Not measurable Comparative Example 4 0.73 0.069 6.12 5.4 2.9 Comparative Example 5 1.4 0.710 2.8 8 4.1 Comparative Example 6 2.1 1.115 2.8 7 3.8 Comparative Example 7 1.7 0.711 4.1 6.5 3.6

Looking at Table 1, it can be seen that the pressure-delayed osmosis membrane prepared in Example 1 has higher water permeability and superior power density than the separation membranes prepared in Examples 2 to 4 and Comparative Examples 1 to 4.

In addition, in the case of Example 2, which has a higher viscosity than Example 1, it can be seen that the water permeability constant A value and the water permeability decreased, and thus the power density was also lowered. It is believed that the thickness of the separator increased as the viscosity of the polymer crude liquid increased.

In the case of Examples 3 to 4, as the amount of sulfonated polysulfone was decreased compared to Example 1, the water permeability of the pressure delayed osmosis membrane showed a tendency to decrease, and thus the power density also showed a tendency to slightly decrease.

And, in the case of Comparative Example 1, it was confirmed that the thickness of the support layer was increased than that of Example 1, so that the S value, which is the separator structural constant, was increased and the water permeability decreased, so that the power density was lowered.In Comparative Example 2, the viscosity was 3,000 cP or more. As the polymer crude solution was applied, the salt permeation constant B value increased to 0.8L/m ² /hr or more, the separator structural constant S value increased, and the power density decreased.

Comparative Example 3 had a problem in that the thickness of the separator was decreased compared to Example 1, and the separator was compressed due to low durability, making it impossible to measure physical properties. In addition, in Comparative Example 4, as the content of metaphenylenediamine (MPD) in the active layer was increased, the salt removal rate was increased, so that the salt permeability constant B value decreased to 0.1 L/m ² /hr or less. It was confirmed that the water permeability decreased and the water permeability constant A value was lowered to 1 L/m ² /hr/bar or less, resulting in a problem of decreasing power density.

10: pressure delayed osmosis membrane 11: porous support layer
12: porous hydrophilic polymer layer 13: active layer
14: back side 20: porous permeated water outlet pipe
21: hole 22: pressure delayed osmosis membrane
30: pressure case

Claims (12)

A porous support layer, a porous hydrophilic polymer layer, and a composite membrane in which an active layer is sequentially stacked,
The porous hydrophilic polymer layer is formed by coating and phase-separating a polymer crude liquid containing at least one selected from polysulfone resin and sulfonated polysulfone resin,
The polysulfone resin is a copolymer including a repeating unit represented by Formulas 1-1 and 1-2,
The sulfonated polysulfone resin is a pressure delayed osmosis membrane, characterized in that it is a copolymer comprising a repeating unit represented by the following formulas 2-1 and 2-2;
[Formula 1-1]

[Formula 1-2]

[Formula 2-1]

[Formula 2-2]

In Formulas 2-1 and 2-2, each of R ₁ , R ₂ , R ₃ and R ₄ is independently a hydrogen atom, a straight chain alkyl group of C1 to C5, a branched alkyl group of C3 to C5 or an alkyl of C2 to C4. It's Rengi.
The pressure delayed osmosis membrane of claim 1, wherein the polysulfone resin has a weight average molecular weight of 15,000 to 100,000 g/mol, and the sulfonated polysulfone resin has a weight average molecular weight of 100,000 to 200,000 g/mol.
The pressure delayed osmosis membrane according to claim 1, wherein the polymer crude liquid comprises 4 to 15 parts by weight of the sulfonated polysulfone resin based on 100 parts by weight of the polysulfone resin.
The pressure delayed osmosis membrane of claim 1, wherein the porous support layer comprises a fabric made of at least one fiber selected from polyester, polypropylene, nylon, polyethylene, acrylic, rayon, acetate, and cellulose.
The method of claim 1, wherein the active layer comprises at least one selected from a polyamide polymer, a polypiperazine polymer, a polyphenylenediamine polymer, a polychlorophenylenediamine polymer, and a polybenzidine polymer. Pressure delayed osmosis membrane.
The pressure-delayed osmosis membrane according to claim 1, wherein the polymer crude liquid has a viscosity of 500 to 3,000 cP (25°C).
The method of claim 1, wherein the porous support layer has a thickness of 60 to 80 μm, the porous hydrophilic polymer layer has a thickness of 30 to 80 μm, the active layer has a thickness of 0.1 to 1 μm, and the total thickness of the pressure delayed osmosis membrane is 90.1 to Pressure delayed osmosis membrane, characterized in that 161㎛.
According to any one of claims 1 to 7, by performing a pressure delayed osmosis experiment under conditions of 25°C, a pressure of 20 bar and a flow rate of 0.5 LPM for an aqueous solution of 70,000 ppm sodium chloride, according to Equation 1 below. When measuring the permeability, the pressure delayed osmosis membrane, characterized in that the water permeability of the pressure delayed osmosis membrane 12 ~ 40 L / m ² /hr;
[Equation 1]

In Equation 1, J _W is the water permeability, π _draw is the osmotic pressure of the _draw solution, π _feed is the osmotic pressure of the influent solution, A is the water permeation constant of the PRO membrane, B is the salt permeation constant of the PRO membrane, and K _m is 1 /K _R , K _R is the salt diffusion resistance coefficient of the porous hydrophilic polymer layer of the PRO membrane, and ΔP is the pressure.
The pressure delayed osmosis membrane according to claim 8, wherein when measured according to Equation 4 below, the power density of the pressure delayed osmosis membrane is 6 to 25 W/m ² ;
[Equation 4]

In Equation 4, PRO is the water permeability (L/m ² /hr), and ΔP is the pressure.
The method of claim 8, wherein the pressure delayed osmosis membrane has a water permeability constant value (A) of 1 to 3.6 L/m ² /hr/bar, and a salt permeability constant value (B) of 0.1 to 0.8 L/m ² /hr, Structural constant (S) is (0.6 ~ 3) ⅹ10 ^-3 m pressure delayed osmosis membrane, characterized in that.
A first step of preparing a polymer crude liquid by mixing a polymer resin containing at least one selected from polysulfone resin and sulfonated polysulfone resin and a solvent;
A second step of forming a porous hydrophilic polymer layer on the porous support layer by processing the polymer crude liquid on the porous support so that the polymer crude liquid penetrates into the pores of the porous support, and then phase-transferring the polymer crude liquid; And
It is prepared by performing a process including; 3 step of forming an active layer on the porous hydrophilic polymer layer,
The polysulfone resin is a copolymer including a repeating unit represented by Formulas 1-1 and 1-2,
The sulfonated polysulfone resin is a method for producing a pressure delayed osmosis membrane, characterized in that the copolymer comprising a repeating unit represented by the following formulas 2-1 and 2-2;
[Formula 1-1]

[Formula 1-2]

[Formula 2-1]

[Formula 2-2]

In Formulas 2-1 and 2-2, each of R ₁ , R ₂ , R ₃ and R ₄ is independently a hydrogen atom, a straight chain alkyl group of C1 to C5, a branched alkyl group of C3 to C5 or an alkyl of C2 to C4. It's Rengi.
A pressure delayed osmosis module having the pressure delayed osmosis membrane of claim 8.

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