KR20190081613A - Water separating ultrafiltration membrane using complex of amphiphilic copolymer-metal oxide and method for manufacturing thereof - Google Patents

Abstract

One aspect of the present invention provides a method for manufacturing an ultrafiltration membrane for water treatment, which comprises the steps of: (a) mixing an amphiphilic copolymer, a metal oxide precursor, and a solvent to manufacture a solution; and (b) applying the solution onto a substrate to manufacture an ultrafiltration membrane using a phase transition method.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrafiltration membrane for water treatment using an amphiphilic copolymer-metal oxide complex and a method for producing the same. 2. Description of the Related Art [0002]

TECHNICAL FIELD The present invention relates to an ultrafiltration membrane for water treatment using an amphiphilic copolymer-metal oxide composite and a method for producing the same, and more particularly, to an ultrafiltration membrane for water treatment having improved water permeability and membrane pollution reducing effect, .

The water pollution problem in the world is an inevitable problem as long as wastewater is generated. For this reason, it is becoming an important issue in the water treatment field to discharge as much of the maximum amount of water as possible with the minimum cost. Various materials have been developed for this purpose. Particularly, water treatment films using relatively inexpensive polymers are being studied extensively. Polyvinylidene fluoride (PVDF) and polyetherimide (PEI) It is known as a polymer used for

Among the polymer filtration membranes developed so far, membranes using polyvinyl chloride (PVC) have the advantages of excellent durability and chemical stability, but due to inherent hydrophobicity, excessive membrane contamination occurs during water treatment, There is a problem that the pore formation due to the pores is not easy.

In the case of a filtration membrane using a conventional polymer, surface polymerization is performed mainly or pores are formed on the surface thereof by using a surfactant or the like. This is because when the hydrophilic material is formed of a copolymer in a conventional membrane, the mechanical strength of the membrane becomes insufficient due to expansion of the membrane due to water.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method for producing an ultrafiltration membrane for water treatment having high water permeability and low membrane contamination.

One aspect of the present invention is a process for preparing a solution, comprising: (a) preparing a solution by mixing an amphiphilic copolymer, a metal oxide precursor, and a solvent; And (b) applying the solution to a substrate and then preparing an ultrafiltration membrane using a phase transition method. [7] The present invention also provides a method of manufacturing an ultrafiltration membrane for water treatment.

In one embodiment, the amphiphilic copolymer may be a graft copolymer of a hydrophobic polymer and a hydrophilic polymer.

In one embodiment, the amphiphilic copolymer may be one that has been synthesized by atom transfer radical polymerization.

In one embodiment, the hydrophobic polymer is selected from the group consisting of polyvinyl chloride, polychlorotrifluoroethylene, polydichlorodifluoromethane, polyvinylidene chloride, polyvinylidene fluoride-co-chlorotrifluoroethylene, and 2 And combinations thereof.

In one embodiment, the hydrophilic polymer is selected from the group consisting of polyoxyethylene methacrylate, polyhydroxyethylmethacrylate, polyt-butyl methacrylate, polyacrylamide, poly N-vinylpyrrolidone, polyaminostyrene, polystyrene Sulfonic acid, polymethylpropanesulfonic acid, polysulfopropyl methacrylate, polysulfoethyl methacrylate, polysulfobutyl methacrylate, and a combination of two or more thereof.

In one embodiment, the weight ratio of the hydrophilic polymer to the hydrophobic polymer may be 1: 8-10.

In one embodiment, the metal oxide precursor may be one selected from the group consisting of titanium isopropoxide, titanium butoxide, titanium ethoxide, titanium propoxide, titanium tetrachloride, and combinations of at least two of the foregoing.

In one embodiment, the phase transfer method comprises reacting a non-solvent selected from the group consisting of water, acetonitrile, ethanol, methanol, tetrahydrofuran, and combinations of two or more thereof with N-methylpyrrolidone, dimethylacetamide, Dimethylformamide, triethyl phosphate, and a combination of two or more thereof.

According to another aspect of the present invention, there is provided an ultrafiltration membrane for water treatment manufactured by the method for manufacturing the ultrafiltration membrane for water treatment.

In one embodiment, the water treatment ultrafiltration membrane may have a porosity of 80% to 90% and a bovine serum albumin rejection of 85% to 95%.

According to one aspect of the present invention, water permeability of the ultrafiltration membrane for water treatment can be improved and membrane contamination can be lowered by preparing an ultrafiltration membrane for water treatment using a phase transfer method from a solution containing an amphiphilic copolymer and a metal oxide precursor have.

It should be understood that the effects of the present invention are not limited to the effects described above, but include all effects that can be deduced from the description of the invention or the composition of the invention set forth in the claims.

FIG. 1 is a graph showing the results of analysis of a copolymer synthesized from each of the polymers used in Production Examples and the polymer through an infrared spectroscopy (Fourier transform infrared spectroscopy, FT-IR).
FIG. 2 is a graph showing the results of analysis of the copolymer synthesized in Preparation Example through proton nuclear magnetic resonance spectroscopy ( ¹ H-NMR).
3 is an image (200 nm) showing the result of observation of the hydrophobic polymer used in the production example and the ultrafiltration membrane prepared in Example 1 and Comparative Example 1 by a transmission electron microscopy (TEM) (B) shows a comparative example 1, and (c) shows a first embodiment.
4 is an image (200 nm) showing the results of observing the surfaces of the ultrafiltration membranes prepared in Examples 1 and 2 and Comparative Examples 1 and 2 by scanning electron microscopy (SEM) Example 1, (b) shows Comparative Example 2, (c) shows Example 1, and (d) shows Example 2.
5 is an image (20 μm) showing the cross section of the ultrafiltration membrane prepared in Examples 1 and 2 and Comparative Examples 1 and 2 by SEM, wherein (a) is Comparative Example 1, (b) 2, (c) shows the first embodiment, and (d) shows the second embodiment.
FIG. 6 is a graph showing the results of X-ray photoelectron spectroscopy (XPS) analysis of the ultrafiltration membranes prepared in Examples 1 and 2 and Comparative Examples 1 and 2. FIG. 6 (a) A chlorine atom, and (b) represents titanium and an oxygen atom.
FIG. 7 is a graph showing the results of FT-IR analysis of the ultrafiltration membranes prepared in Examples 1 and 2 and Comparative Examples 1 and 2. FIG.
FIG. 8 is a graph showing the results of analysis of the ultrafiltration membranes prepared in Examples 1 and 2 and Comparative Examples 1 and 2 through cross flow filtration, wherein (a) 1 and Comparative Example 2, and (b) shows Example 2 and Comparative Example 1 which are relatively low in rejection.

The invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Throughout the specification, when an element is referred to as " comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments of the present invention will be described in detail.

A method for preparing an ultrafiltration membrane for water treatment according to one aspect of the present invention comprises the steps of: (a) preparing a solution by mixing an amphiphilic copolymer, a metal oxide precursor, and a solvent; And (b) applying the solution to a substrate and then preparing an ultrafiltration membrane using a phase transfer method.

In the present specification, an amphiphilic copolymer means a polymer having both a hydrophobic region and a hydrophilic region with two or more monomer units as constituent units.

The metal oxide precursor is hydrophilic and selectively interacts with the hydrophilic site of the amphipathic copolymer to form an amphiphilic copolymer-metal oxide complex. This increases the size of the nanostructured unit of the hydrophilic polymer and consequently increases the pore size.

The amphiphilic copolymer may be a graft copolymer of a hydrophobic polymer and a hydrophilic polymer.

The ultrafiltration membrane using only the hydrophobic polymer tends to be contaminated with the membrane, and it is difficult to form a passage through which the non-solvent moves in the phase transition method, thereby obtaining a low surface porosity. Conventional ultrafiltration membranes copolymerized with hydrophilic polymers can increase the water permeability and prevent membrane contamination, but the mechanical strength of the membrane is weakened due to the expansion of the membrane due to water. To solve this problem, it is possible to form a pore by graft copolymerizing a hydrophilic polymer with a hydrophobic polymer.

The amphiphilic copolymer may be synthesized by atomic transfer radical polymerization (ATRP).

Wherein the hydrophobic polymer is selected from the group consisting of polyvinyl chloride, polychlorotrifluoroethylene, polydichloro difluoromethane, polyvinylidene chloride, polyvinylidene fluoride-co-chlorotrifluoroethylene, and a combination of two or more thereof But is not limited thereto.

The hydrophilic polymer may be at least one selected from the group consisting of polyoxyethylene methacrylate, polyhydroxyethylmethacrylate, polyt-butyl methacrylate, polyacrylamide, poly N-vinylpyrrolidone, polyaminostyrene, polystyrenesulfonic acid, But are not limited to, sulfonic acid, polysulfopropyl methacrylate, polysulfoethyl methacrylate, polysulfobutyl methacrylate, and combinations of two or more thereof.

The weight ratio of the hydrophilic polymer to the hydrophobic polymer may be 1: 8 to 10. If the ratio of the hydrophilic polymer is increased, the mechanical strength of the membrane may become insufficient due to expansion of the membrane by water.

The metal oxide precursor may be selected from the group consisting of titanium isopropoxide, titanium butoxide, titanium ethoxide, titanium propoxide, titanium tetrachloride, and combinations of two or more thereof, but is not limited thereto.

The phase transfer method may be carried out by reacting a non-solvent selected from the group consisting of water, acetonitrile, ethanol, methanol, tetrahydrofuran, and combinations of two or more thereof with N, Phosphate, and a solvent selected from the group consisting of a combination of two or more of them. However, the present invention is not limited thereto.

The non-solvent-derived phase transformation method may be performed using water at 70-90 DEG C as non-solvent. When the non-solvent induction phase transfer method is carried out with hot water, the exchange rate of the solvent is influenced and larger pores can be formed.

The ultrafiltration membrane for water treatment according to another aspect of the present invention may be one manufactured by the method for manufacturing the ultrafiltration membrane for water treatment.

The water treatment ultrafiltration membrane may have a porosity of 80% to 90% and a bovine serum albumin rejection of 85% to 95%.

The ultrafiltration membrane for water treatment may include an amphiphilic copolymer represented by the following formula (1).

[Chemical Formula 1]

In the above formula (1), x: y = 1: 8-10, n = 8-10, and preferably x: y = 1: 9 and n = 9.

Hereinafter, embodiments of the present invention will be described in more detail. However, the following experimental results only describe representative experimental results of the above embodiments, and the scope and contents of the present invention can not be construed to be limited or limited by the embodiments and the like. Each effect of the various embodiments of the present invention not expressly set forth below will be specifically described in that section.

Experimental Results The following is a polyvinyl chloride (polyvinyl chloride, PVC) and polyoxyethylene methacrylate amphiphilic copolymer polyvinyl through (polyoxyethylene methacrylate, POEM) chloride-grafted-polyoxyethylene methacrylate (graft polyvinyl chloride- -Polyoxyethylene methacrylate, PVC- g- POEM) was synthesized, and the amphiphilic copolymer was mixed with titanium isopropoxide (TTIP) to prepare a polyvinyl chloride- graft -polyoxyethylene methacrylate / (PVC- g- POEM / TTIP) to make an ultrafiltration membrane for water treatment.

Production example. Amphiphilic Copolymer PVC- g Synthesis of POEM

18 g of PVC was dissolved in 150 mL of N-methylpyrrolidone at 50 DEG C for 6 hours. 12 g of POEM (M _n = 500 g mol ^-1 ) was added to make it homogeneous, and 0.3 g of copper (I) chloride and 0.69 mL of HMTETA (1,1,4,7,10,10-hexamethyltriethylenetetramine) . Thereafter, the reaction was carried out for 24 hours by setting the temperature of the stirrer to 90 占 폚. The reaction-terminated solution was slowly poured into a large amount of methanol to wash the polymer and polymer so that the solvent and remaining POEM were dissolved in methanol. The washed polymer was dried in an oven at 50 ° C for removal of residual solvent and methanol, and then dried in a vacuum oven for 10 hours so that POEM was graft-copolymerized with the side chain of the polymer main chain. 0.3 g of the thus-synthesized PVC- g- POEM was added to a mixed solvent of dimethylformamide: tetrahydrofuran in a volume ratio of 7: 1 in a proportion of 12% by weight and completely dissolved at 50 캜 for 4 hours to obtain PVC- g- POEM Solution.

The copper (I) chloride was used as an initiator and the HMTETA acted as a ligand on the double bond of POEM and chlorine of PVC to produce radicals.

EXAMPLES Example 1 Preparation of PVC- g -POEM / TTIP Ultrafiltration membrane manufacturing

To the PVC- g- POEM solution of the above preparation example, 0.15 mL of the following TTIP inorganic solution was added, followed by stirring overnight. The completed PVC- g- POEM / TTIP solution was spread over a flat glass plate with a thickness of 200 μm by doctor-blade technique, and after 20 seconds, it was immersed in water at room temperature for two hours. The formed film was then separated from the glass plate, and the finished ultrafiltration membrane was stored in distilled water.

The TTIP inorganic solution was prepared by mixing 1 mL of TTIP solution vigorously, 0.312 mL of hydrochloric acid slowly, leaving it for 5 minutes, adding 3 mL of tetrahydrofuran, and stirring for 2 minutes.

Example 2: Preparation of PVC- g -POEM / TTIP Ultrafiltration membrane manufacturing

The glass plate coated with the PVC- g- POEM / TTIP solution in Example 1 was prepared in the same manner except that the glass plate was immersed in water at 80 ° C instead of water at room temperature.

Comparative Example 1. PVC- g -POEM ultrafiltration membrane manufacturing

The PVC- g- POEM solution of the above preparation example was stirred overnight, coated on a flat glass plate by a doctor-blade technique to a thickness of 200 袖 m, and after 20 seconds, it was immersed in water at room temperature for two hours. The formed film was then separated from the glass plate, and the finished ultrafiltration membrane was stored in distilled water.

Comparative Example 2. PVC- g -POEM ultrafiltration membrane manufacturing

Except that a glass plate coated with a PVC- g- POEM solution in Comparative Example 1 was immersed in water at 80 ° C instead of water at room temperature.

Experimental Example 1. Preparation of PVC- g -POEM structure analysis

The copolymer synthesized from each polymer and the polymer used in the above Preparation Examples was analyzed by Fourier transform infrared spectroscopy (FT-IR), Proton nuclear magnetic resonance spectroscopy ( ¹ H-NMR) And analyzed by a transmission electron microscopy (TEM). The results are shown in FIGS. 1, 2 and 3, respectively.

Referring to Figure 1, in the PVC- g- POEM spectrum, 1728 and 1097 cm < ^-1 > peaks that were not present in the PVC spectrum prior to synthesis were newly formed. This was confirmed by the carbonyl functionality (C = O, 1728 cm ^-1 ) and the ether functionality (COC, 1097 cm ^-1 ) in POEM bonded to PVC.

The carbonyl functionality (C = O, 1717 cm ^-1 ) present in the POEM monomer migrated to the 1728 cm ^-1 peak due to the loss of pi-conjugation and structural failure due to side chains as POEM bound to PVC to be.

Also, it was confirmed that the carbon double bond (-C═C-, 1637 cm ^-1 ) peak in the POEM monomer was synthesized and disappeared. This means that the synthesis process of the polymer is almost 100%, and the remaining unreacted POEM monomer is completely dissolved in the methanol washing. The above results confirm that POEM is grafted well to PVC.

Referring to FIG. 2, the signal in the 4.6-4.4 ppm region is the CH ₂ functional group of the PVC main chain and the signal region of 4.4 - 4.3 ppm means the CHCl functional group of the PVC main chain. Also, the 4.0, 3.5, and 3.25 ppm regions refer to the ethylene oxide units of POEM side chains. Through the area of these signals, it was confirmed that about 10% by weight of POEM side chain of PVC- g- POEM was bonded to the PVC main chain.

Referring to FIG. 3, it was confirmed that there was no difference in the electron density in that the PVC single polymer had no structure observed.

In the case of PVC- g- POEM, which is a synthesized copolymer, PVC with high electron density was observed in the dark region due to chlorine atom, and POEM with low electron density was observed in the bright region.

In the case of PVC- g- POEM / TTIP, it was confirmed that the hydrophilic property of the solution became strong and the dark region of PVC was uniformly observed at a smaller size.

Experimental Example 2: SEM analysis

The pore and cross-sectional properties of the ultrafiltration membranes prepared according to Examples 1 and 2 and Comparative Examples 1 and 2 were analyzed by scanning electron microscopy (SEM), and the results are shown in FIGS. 4 and 5, respectively .

Referring to FIG. 4, very small pores were rarely observed when PVC- g- POEM phase-transitions to water at room temperature (Comparative Example 1). It can be interpreted that the PVC- g- POEM polymer properties are swelled and shrunk according to the presence of water, and solvent exchange is performed through the POEM side chain and pores are formed.

When PVC- g- POEM phase transitions to water at 80 캜 (Comparative Example 2), rapid solvent exchange takes place on the surface, and large pores are arbitrarily formed.

When the TTIP inorganic solution was added to the PVC- g- POEM solution and the phase transition to water at room temperature (Example 1), it was confirmed that the pores were clearly visible on the surface. This was confirmed by the fact that TTIP partially fixed the POEM side chain through the dipole attraction Therefore, it can be interpreted that the solvent exchange between dimethylformamide, which is a hydrophilic solvent, and water is more effective than when pure polymer solution is used.

When the TTIP inorganic solution was added to the PVC- g- POEM solution and the phase transition occurred in water at 80 ° C (Example 2), TTIP fixed the side chain and did not cause rapid solvent exchange as in Comparative Example 2, but thermodynamically chain transfer And the rate of solvent exchange was increased to confirm that larger and more pores were formed.

5, it was confirmed that a general asymmetric structure having a selective layer at the top and a finger-shaped lower layer was formed in the other cases except for Comparative Example 2. In the case of Example 2 and Comparative Example 2, It is confirmed that the selective layer has a thicker layer than that of Example 1.

Experimental Example 3. Analysis of TTIP Residue

The ultrafiltration membranes prepared according to Examples 1 and 2 and Comparative Examples 1 and 2 were analyzed by X-ray photoelectron spectroscopy (XPS) and FT-IR. The results are shown in FIGS. 6 and 7 Respectively.

Referring to FIG. 6, it was confirmed that peaks were formed at the same positions in all cases, which means that all the TTIPs were removed during the phase transition.

Referring to FIG. 7, it was confirmed that all cases had the same shape and same peak, which means that all the TTIPs were removed during the phase transition.

Experimental Example 4. Evaluation of water treatment performance of ultrafiltration membrane

The water permeability of the ultrafiltration membrane prepared according to Examples 1 and 2 and Comparative Examples 1 and 2 and the permeability of bovine serum albumin (BSA) were measured. The results are shown in FIG. 8, Table 1 shows the results. Water permeability was analyzed by cross-flow filtration. The BSA rejection ratio was measured by analyzing the permeated BSA solution with a UV-Visible spectrometer in the 278 nm region, and the rejection rate was calculated from the permeability.

Referring to FIG. 8, it was confirmed that Example 1 and Comparative Example 2 had higher BSA elimination rates than Example 2 and Comparative Example 1.

division Comparative Example 1 Comparative Example 2 Example 1 Example 2 Water permeance (LMH) 275 138 338 185 BSA solution permeance (LMH) 46 59 75 117 BSA rejection (%) 74.0 92.6 89.4 47.7 FRR (%) 40.5 64.6 91.9 97.6 Contatct angle ( ^o ) 66.0 ± 0.9 61.7 ± 4.9 69.6 ± 3.6 67.1 ± 1.9 O / C atomic ratio 0.165 0.176 0.160 0.162 Water content
(g / g membrane) 6.26 ± 0.27 2.62 ± 0.01 7.03 0.26 6.00 0.40 Porosity (%) 86.2 ± 0.52 72.4 ± 0.05 87.5 ± 0.39 85.7 ± 0.82

Referring to Table 1, it can be confirmed that the water permeance is highest when phase transition occurs at room temperature by adding an inorganic TTIP solution (Example 1). This is because the passages are well formed through the attraction of the TTIP and POEM side chains and thus have a higher porosity. As a result, it can be seen that Example 1 has the highest water content.

Comparing Example 1 with Comparative Example 1, BSA rejection showed that the exclusion rate was relatively higher due to the more uniform pore formation due to the attraction of TTIP and POEM. When the polymer solution was phase-transformed in water at 80 캜 (Comparative Example 2), pores on the surface formed large pores by sudden solvent exchange, but formed a thicker selective layer in the lower layer, BSA exclusion rate can be interpreted as showing. Example 2: Phase transformation in water at 80 캜 with a polymer solution containing TTIP inorganic solution (Example 2) Although the water permeability was low due to the thick selective layer, it was confirmed that the pore size was large and the BSA elimination rate was lower.

When analyzed for membrane contamination, Examples 1 and 2 showed better performance in terms of membrane contamination. In the case of using the polymer solution (Comparative Examples 1 and 2), the solvent was exchanged mainly through the POEM passage, but at the same time, since a relatively large amount of solvent was exchanged also through the PVC, the FRA reverse). On the other hand, it was confirmed that when the TTIP inorganic solution was added to the polymer solution (Examples 1 and 2), the FRR value was remarkably high.

As a result of checking the contact angle of water and the oxygen / carbon atom ratio, it was confirmed that the surface of the membrane was more hydrophilic when the TTIP inorganic solution was added to the polymer solution (Examples 1 and 2). It is known that when a hydrophilic membrane surface is provided, the contamination of the membrane is reduced. Therefore, it is confirmed that Examples 1 and 2 are excellent in the effect of reducing membrane contamination.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (10)

(a) preparing a solution by mixing an amphipathic copolymer, a metal oxide precursor, and a solvent; And
(b) coating the solution on a substrate and then preparing an ultrafiltration membrane using a phase transfer method. The method according to claim 1,
Wherein the amphiphilic copolymer is graft-copolymerized with a hydrophobic polymer and a hydrophilic polymer. The method according to claim 1,
Wherein the amphiphilic copolymer is synthesized by an atom transfer radical polymerization reaction. 3. The method of claim 2,
Wherein the hydrophobic polymer is selected from the group consisting of polyvinyl chloride, polychlorotrifluoroethylene, polydichloro difluoromethane, polyvinylidene chloride, polyvinylidene fluoride-co-chlorotrifluoroethylene, and a combination of two or more thereof Wherein the ultrafiltration membrane is a selected one. 3. The method of claim 2,
The hydrophilic polymer may be at least one selected from the group consisting of polyoxyethylene methacrylate, polyhydroxyethylmethacrylate, polyt-butyl methacrylate, polyacrylamide, poly N-vinylpyrrolidone, polyaminostyrene, polystyrenesulfonic acid, Wherein the ultrafiltration membrane is one selected from the group consisting of sulfonic acid, polysulfopropyl methacrylate, polysulfoethyl methacrylate, polysulfobutyl methacrylate, and combinations of two or more thereof. 3. The method of claim 2,
Wherein the weight ratio of the hydrophilic polymer to the hydrophobic polymer is 1: 8-10. The method according to claim 1,
Wherein the metal oxide precursor is one selected from the group consisting of titanium isopropoxide, titanium butoxide, titanium ethoxide, titanium propoxide, titanium tetrachloride, and combinations of at least two of them. Way. The method according to claim 1,
The phase transfer method may be carried out by mixing a non-solvent selected from the group consisting of water, acetonitrile, ethanol, methanol, tetrahydrofuran, and combinations of two or more thereof,
Wherein the solvent is selected from the group consisting of N-methylpyrrolidone, dimethylacetamide, dimethylformamide, triethylphosphate, and a combination of two or more thereof. 9. An ultrafiltration membrane for water treatment characterized by being manufactured by the method according to any one of claims 1 to 8. 10. The method of claim 9,
Wherein the water treatment ultrafiltration membrane has a porosity of 80% to 90% and a bovine serum albumin rejection of 85% to 95%.

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