KR20180136609A - Gas separation membrane and method for fabricating thereof - Google Patents

Abstract

Disclosed are a gas separation membrane and a production method thereof. According to one embodiment of the present invention, the gas separation membrane contains a support, and a coating layer coated thereon, wherein the coating layer comprises a polymer having a structure in which the monomers represented by chemical formula 1 are repeatedly linked. In the chemical formula 1, p is a real number greater than 0 and less than 1, and A is N-alkoxymethyl.

Description

TECHNICAL FIELD [0001] The present invention relates to gas separation membranes,

The present invention relates to a gas separation membrane and a method of manufacturing the same, and more particularly, to a gas separation membrane and a method of manufacturing the same, which comprises a modified PEBAX in which hydrogen in an amide block of polyether block amide (PEBAX) is substituted with N-alkoxymethyl And more particularly, to a gas separation membrane having a coating layer and a method of manufacturing the same.

The gas separation membrane is a polymer separation membrane for selective separation of gas. It is used for various purposes such as recovery and purification of hydrogen, recovery and purification of carbon dioxide gas, separation of oxygen and nitrogen in the air, .

Membrane process technology that selectively separates the desired gas using the gas separation membrane is evaluated as an environmentally friendly technology because it is very advantageous in terms of energy consumption compared with other gas separation technologies. In addition, there is also an advantage that it is easy to use because it can flexibly change the scale of expansion or reduction of the scale of the facility.

As a gas separation membrane, a hollow fiber membrane is generally used. The hollow fiber membrane is a thin, threadlike membrane with an inner hollow, which selectively separates the desired gas through the inner and outer skin layers, and is more important than other types of gas separation membranes because of its high surface area.

Two indicators are commonly used to determine the separation efficiency of the gas separation membrane used to separate the gas mixture: permeability and selectivity. In a typical permeation mechanism, the permeability is determined by the solubility and diffusivity And the selectivity is inversely proportional to the value of the transmittance.

Many studies are underway to improve the trade-off phenomenon between transmittance and selectivity, and they are still ongoing issues.

In order to improve the separation performance of the gas separation membrane, there is a method of applying a thin coating layer on the support of the separation membrane. According to this method, since the coating layer itself exhibits a high separation rate, it is advantageous in terms of selectivity but has disadvantageous results in terms of transparency.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art described above, and its main object is to provide a gas separation membrane that satisfies both selectivity and transparency.

The present invention provides a gas separation membrane comprising a support and a coating layer coated thereon, wherein the coating layer comprises a polymer having a structure in which the monomers of formula (1) are repeatedly linked.

[Chemical Formula 1]

In Formula 1, p is a real number greater than 0 and less than 1, and A is N-alkoxymethyl.

The N-alkoxymethyl may be methoxymethyl, ethoxymethyl, propoxymethyl, or butoxymethyl. The term " alkoxymethyl "

The thickness of the coating layer may be 0.1 to 2.0 탆.

The support may be a polymeric support made of any one of polyetherimide, polysulfone, polyethersulfone, polyvinylidene fluoride, and polyimide, a metal porous support, or a ceramic porous support.

The gas separation membrane may be a hollow fiber membrane.

The present invention also provides a hollow fiber membrane, comprising: a plurality of hollow fiber membranes; And a housing having a plurality of hollow fibers arranged therein, an inlet provided at one end of the inner channel, a first outlet provided at the other end of the inner channel, and a second outlet provided at a side of the inner channel, The hollow fiber membrane module according to any one of the above-described embodiments, wherein the hollow fiber membrane is provided with a gas separation membrane according to any one of the above embodiments.

The present invention also provides a method of manufacturing a semiconductor device, comprising: (a) providing a support; (b) providing a coating liquid; (c) coating the coating liquid on the surface of the support; And (d) drying the gas separation membrane, wherein the coating solution comprises a polymer in which the unit represented by the general formula (1) is repeatedly connected.

[Chemical Formula 1]

In Formula 1, p is a real number greater than 0 and less than 1, and A is N-alkoxymethyl.

The step (b) includes the steps of: (b1) generating the polymer; And (b2) mixing the polymer with a solvent to prepare the coating solution.

As the solvent, water may be used.

The N-alkoxymethyl may be methoxymethyl.

The step (b1) may include the steps of: (b11) dissolving a polymer having a structure in which a unit of formula (2) is repeatedly linked in a formic acid to form a polymer solution;

(2)

(b12) introducing hemiacetal into the polymer solution so that the hydrogen in the amide block of the unit is substituted with methoxymethyl; And (b13) injecting a precipitation inducing agent into the polymer solution to precipitate the polymer in the polymer solution. In the formula (2), p is a real number greater than 0 and smaller than 1.

According to the present invention, by forming a coating layer of a gas separation membrane with a PABEX polymer modified so that hydrogen in the amide block is substituted with N-alkoxymethyl, a gas separation performance can be obtained, It is possible to provide a gas separation membrane with improved permeability.

Since the modified PABEX polymer according to the present invention has greatly improved solubility as compared with the pre-modified polymer, it is possible to use a single solvent such as water as a solvent for preparing a coating solution. Therefore, when a conventional mixed solvent is used, And thus the coating layer is formed thinly and densely, so that the gas permeability of the separation membrane can be greatly improved.

1 is a schematic view of a hollow fiber membrane module according to an embodiment of the present invention.
2 is a conceptual view showing an example of a gas separation mechanism by the hollow fiber membrane module of FIG.
Figure 3 is a graph showing the results of FT-IR analysis of PEBAX-1657 and modified PEBAX samples.
FIG. 4 is a schematic view showing a hollow fiber membrane (separator I) consisting of a PEI support alone, a hollow fiber membrane (membrane II) comprising a PEI support and a PEBAX coating layer, a hollow fiber membrane (membrane III) comprising a PEI support and a modified PEBAX coating layer, It shows the result of shooting a cross-sectional photograph.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for further illustrating the present invention, and the scope of the present invention is not limited to these examples.

1. Gas separation membrane

A gas separation membrane according to the present invention is a membrane used for selective separation of a gas, which comprises a support and a coating layer coated thereon. The gas separation membrane of the present invention is generally provided in the form of a hollow fiber membrane, but is not necessarily limited thereto.

(1.1) Support

The support has a porous structure for selective permeation of gas as a part of the body of the gas separation membrane.

The support may be made of a polymer. By way of example, the support may be made of polyetherimide, polyvinylidene fluoride, polyethersulfone, polysulfone, or polyimide.

Alternatively, the support may be made of a metallic material or a ceramic material. That is, the support may be a metal porous support or a ceramic porous support.

In the case where the gas separation membrane according to the present invention is a hollow fiber membrane, the support body has a long thread-like shape and has a hollow centered in the longitudinal direction.

(1.2) Coating layer

The coating layer is a layer which is thinly coated on the support to improve the separation efficiency of the gas separation membrane, and the thickness thereof can be selected in the range of 0.1 to 2.0 탆.

The coating layer according to the present invention is composed of a polymer having a structure in which a unit represented by the following formula (1) is repeatedly linked. In formula (1), p is a real number greater than 0 and less than 1, and A is N-alkoxymethyl.

The N-alkoxymethyl may be methoxymethyl, ethoxymethyl, propoxymethyl, or butoxymethyl.

[Chemical Formula 1]

In the present invention, the polymer forming the coating layer may be prepared by modifying a polyether block amide (PEBAX).

PEBAX is a polymer having a structure in which a unit represented by the following formula (2) is repeatedly linked. In the formula (2), p is a real number larger than 0 and smaller than 1. For example, PEBAX-1657 has a p value of 0.4.

(2)

More specifically, in the present invention, modification of PEBAX for providing a polymer constituting the coating layer is performed by substituting N-alkoxymethyl for hydrogen in the amide block constituting the PEBAX monomer unit as in the following Substitution Formula 1 ≪ / RTI >

[Substitution formula 1]

When N-alkoxymethyl is methoxymethyl, the substitution reaction is as shown in Substitution Formula 2 below.

[Substituent 2]

When N-alkoxymethyl is ethoxymethyl, the substitution reaction is as shown in Substitution Formula 3 below.

[Substituent 3]

When N-alkoxymethyl is propoxymethyl, the substitution reaction is as shown in Substitution Formula 4 below.

[Substitution formula 4]

When N-alkoxymethyl is butoxymethyl, the substitution reaction is as shown in Substitution Formula 5 below.

[Substitution formula 5]

In the polymer (modified PEBAX) obtained through the modification of PEBAX described above, the number of hydrogen bonds in the polymer is greatly reduced by replacing the hydrogen bonded to the nitrogen of the amide group with N-alkoxymethyl.

Therefore, the modified PEBAX exhibits improved gas permeability and solubility as a result of decreasing the crystallinity due to the action of the amide block, compared to that before the modification.

By applying such a coating layer made of modified PEBAX, the gas separation membrane according to the present invention exhibits improved gas separation performance as compared with the conventional separation membranes.

2. Application example of gas separation membrane (hollow fiber membrane module)

The gas separation membrane of the present invention can be applied to various kinds of gas separation apparatuses. As a typical application example, a hollow fiber membrane module 10 as shown in FIG. 1 is introduced.

The hollow fiber membrane module 10 of FIG. 1 according to the present invention includes a plurality of hollow fiber membranes 20 and a housing 30.

The housing 30 has a long cylindrical inner channel, and a plurality of hollow fiber membranes 20 are closely arranged in the hollow space. The housing 30 has an inlet 31 and a first outlet 32 connected to both ends of the inner channel and a second outlet 33 connected to the side of the inner channel.

When a certain gas flows into the hollow fiber membrane module 10 through the inlet 31, a part of the gas is discharged through the first outlet 32 and a part of the gas is discharged through the second outlet 33. In the hollow fiber membrane 20, The ratio of the discharge amount discharged through the first discharge port 32 and the discharge port 33 differs depending on the permeation speed of the gas. The permeation rate varies depending on the type of gas. The gas having a small permeation rate is discharged at a high rate through the first outlet 32, and the gas having a large permeation rate is discharged through the second outlet 33 There are many.

Referring to the example shown in Figure 2, the hollow fiber membrane module 10, the nitrogen in (N ₂₎ and carbon dioxide (CO ₂₎ gas mixture is a relatively membrane is small permeation rate of nitrogen when the inlet of the (N ₂₎ is the equivalent A portion of the carbon dioxide (CO ₂ ) is discharged to the first discharge port 32 and a relatively large portion of the carbon dioxide (CO ₂ ) having a relatively high film permeation rate is discharged to the second discharge port 33. Therefore, highly concentrated nitrogen can be obtained from the first outlet 32.

3. Gas separation membrane manufacturing method

Hereinafter, a method of manufacturing the gas separation membrane will be described.

(3.1) Production of support

First, a homogeneous polymer solution is prepared by mixing a polymer as a raw material of a support and a solvent.

Here, the polymer as a raw material of the support may be any one of polyetherimide, polyvinylidene fluoride, polyethersulfone, polysulfone, and polyimide.

As a solvent, a mixed solution of 1-methyl-2-pyrrolidone (NMP) and tetrahydrofuran (THF) may be used. Alternatively, dimethylformamide (DMF), dimethylacetamide (DMAc) or dimethyl sulfoxide (DMSO) may be used as the solvent.

The additive may be added during the mixing of the polymer and the solvent. Ethanol may be added as an additive. Alternatively, acetone, methanol, ethanol, n-propanol or n-butanol may be used.

Next, bubbles and foreign substances in the polymer solution are removed, and the polymer solution is spin coagulated to form the shape of the support. This process can be carried out by spinning at room temperature using a deionized deionized water at room temperature through a double nozzle.

Next, the continuously polymerized polymer membrane is cut to an appropriate size, and then the remaining solvent and additives are removed by washing.

Finally, the polymer membrane is dried in air to remove pores or bonds to complete the support membrane. Before the drying step, the polymer membrane may be immersed in a dipping solution (for example, ethanol) to replace the residues present in the polymer membrane.

(3.2) Preparation of coating liquid

First, a polymer (modified PEBAX) as a raw material of the coating layer is produced.

The process for producing the modified PEBAX is a step of preparing a polymer solution by mixing the PEBAX having the units of Formula 2 with the solvent (Step 1), adding a substituent to the polymer solution to convert the hydrogen in the amide block of PEBAX into N- (Step 2), precipitating a polymer comprising the units of formula (1) (step 3) by mixing the polymer solution with a precipitating inducing agent, and adding a dialysis tube (Step 4) of removing the residue from the precipitated polymer.

As the solvent in the first step, formic acid may be used. The N-alkoxymethyl may be methoxymethyl, ethoxymethyl, propoxymethyl or butoxymethyl. When the N-alkoxymethyl is methoxymethyl, the substituent in the second step may be hemiacetal, Can be used. As the precipitation inducing agent in the third step, diethyl ether may be used.

Next, the polymer (modified PEBAX) produced through the above process is mixed with a solvent to form a coating solution.

As the solvent, water may be used. As described above, the modified PEBAX is greatly reduced in crystallinity as compared with that before reforming because of the substitution of N-alkoxymethyl for hydrogen which provided hydrogen bonding, and thus it is sufficiently dissolved in water as a single solvent.

(3.3) Coating and drying

The prepared coating solution is coated on the surface of the prepared support and dried, thereby completing the gas separation membrane. The coating of the coating liquid may be carried out by impregnation of a hollow fiber membrane or a spraying method, and the drying process may be carried out at a temperature higher than room temperature (for example, 60 DEG C) for about 24 hours.

4. Experimental Example

Experiments were conducted to verify the gas separation performance of the gas separation membrane of the present invention using a coating layer made of modified PEBAX. In this experiment, a gas separation membrane (a comparative example) to which a coating layer made by modifying PEBAX-1657 (Example of the present invention) and a coating layer made of PEBAX-1657 (Comparative Example) as a comparative example were manufactured and their characteristics were compared. This will be described in detail below.

(4.1) Production of support

Polyetherimide (PEI) was used as a polymeric raw material for the support. Thus, 30 wt% of PEI was slowly added to a mixture of 65 wt% 1-methyl-2 pyrrolidone (NMP) and tetrahydrofuran (THF) while 5 wt% of ethanol was added as an additive , And mixed to prepare a homogeneous solution.

Then, the bubbles in the mixed solution were removed at room temperature and reduced pressure for 24 hours, and foreign substances were removed by using a filter.

The mixed solution was spun through a double nozzle at room temperature using deionized water at room temperature as a coagulating solution. The air gap was fixed at 10 cm.

Then, after the spin-coagulated hollow fiber support was wound up and cut, it was washed in flowing water for more than 24 hours to remove remaining solvent and additives.

Subsequently, the support was immersed in ethanol for 1 day to replace the residues present in the support, and dried in air at room temperature for 3 days to remove pores or defects, thereby completing the support preparation.

(4.2) PEBAX  Modification

10 wt% of PEBAX-1657 was added to formic acid and dissolved at 60 ° C for 2 hours.

Then, hemiacetal was added as a substituent to the PEBAX-1657 solution, and the solution was maintained at 60 ° C for 4 hours, so that the hydrogen (H) in the amide block of PEBAX-1657 was reacted with methoxymethyl ( methoxymethyl).

[Reaction Scheme 1]

After the substitution reaction, the PEBAX-1657 solution was cooled at room temperature, and the precipitation reaction of PEBAX-1657 (modified PEBAX) substituted with diethyl ether was induced as a precipitation inducing agent, and a dialysis tube The residue was removed from the precipitated polymer.

(4.3) PEBAX  coating

The PEI support prepared above was coated with PEBAX-1657 and modified PEBAX.

In the coating process of PEBAX-1657, 2 wt% of PEBAX-1657 was stirred at 60 ° C for 6 hours or more in a mixed solvent of 70 wt% of ethanol and 30 wt% of water to prepare a coating solution. In the coating process, 2 wt% modified PEBAX was mixed with a single solvent consisting of water, and the coating solution was prepared by using the same conditions.

Two contact times (30 seconds and 150 seconds) were applied while coating the PEBAX-1657 coating solution on the PEI support, and two contact times (30 seconds and 150 seconds) were similarly applied to the modified PEBAX coating solution.

Through this process, two gas barrier membranes coated with PEBAX-1657 (comparative example) and two gas barrier membranes coated with modified PEBAX (embodiment of the present invention) were prepared.

(4.4) Gas permeation experiment

Four hollow fiber membrane modules having the same structure as shown in FIG. 1 were manufactured by applying the four gas separation membranes of the hollow fiber membrane type described above. 300 hollow fiber membranes were arranged in each hollow fiber membrane module.

Then, 99.9% of carbon dioxide and nitrogen were applied to four hollow fiber membrane modules under a predetermined pressure, respectively, to measure the permeability and selectivity to oxygen and nitrogen.

The gas permeability was measured using a mass flow meter and converted to gas permeation unit (GPU, 10 ^-6 cm ³ / cm ² sec cmHg).

(4.5) Test result 1: Solubility evaluation

In order to evaluate the solubility of the modified PEBAX (modified PEBAX) according to the substituent change, PEBAX-1657 and modified PEBAX were dissolved in an ethanol / water mixed solvent (ratio 70:30), water single solvent and ethanol single solvent to prepare 2 wt% Polymer solutions were prepared, and the solubility was evaluated at three temperature conditions (25, 60 and 80 ° C). The results are shown in Table 1.

Referring to Table 1, the modified PEBAX-1657 before the modification is dissolved in the ethanol / water mixed solvent at a temperature of 60 ° C or higher and is not dissolved in the water single solvent and the single solvent of the water, It was confirmed that the reaction mixture was soluble not only in ethanol / water mixed solvent but also in water single solvent and ethanol single solvent.

The reason for the increased solubility of the modified PEBAX is that the number of hydrogen bonds in the polymer is decreased by the modification as described above.

According to the modified PEBAX according to the present invention, since the solubility is improved compared with that before the modification, a single solvent can be applied at the time of preparing the coating liquid, so that the process for preparing the coating liquid is simplified and, at the time of application of the mixed solvent, Can be prevented from being generated.

(4.6) Experimental result 2: PEBAX  Evaluation of reforming characteristics

FT-IR (Fourier Transform Infrared Spectroscopy) analysis was performed on the PEBAX-1657 sample and the modified PEBAX sample to confirm the modification of the modified PEBAX. The analysis result is shown in FIG.

The main band of PEBAX-1657 (band) at 1105 cm ^-1 stretching vibrations CO, 1370 cm ^-1 in the CN, at 1638 cm ^-1 in ^{C = O, 1641 cm -1 amide} group, 2880 cm -1 and 2940 cm ^-1 it is NH in CH, 3370 cm ^-1.

As shown in FIG. 3, the PEBAX-1657 exhibited a band similar to that of PEBAX-1657 after replacing the band. Thus, it can be seen that the basic chemical structure of PEBAX-1657 has not changed. It was confirmed that the NH group was eliminated after the substitution and the peak at 1370 cm ^-1 indicating the CN functional group was increased.

Table 2 below shows the comparison ratios obtained by integrating bands.

In Table 2, the N-H values for C = O are 3.50 for PEBAX and 2.46 for modified PEBAX. From this, it can be confirmed that N-H is decreased by the modification.

The C-N for C = O is 2.34 for PEBAX and 2.33 for modified PEBAX. This can be explained by the fact that the N-H bond was significantly reduced in modified PEBAX without changing the amide group bond of PEBAX before and after the modification.

Finally, the N-H values for C-N are 1.5 for PEBAX and 1.06 for modified PEBAX. This comparison also confirms that the N-H has decreased by the modification.

(4.7) Experimental result 3: Hollow fiber  Membrane structure analysis

FE-SEM cross-sectional photographs of a hollow fiber membrane (membrane Ⅰ) composed of a PEI support alone, a hollow fiber membrane (membrane Ⅱ) comprising a PEI support and a PEBAX coating layer, a hollow fiber membrane (membrane Ⅲ) comprising a PEI support and a modified PEBAX coating layer .

FIG. 4 shows cross-sectional photographs obtained by FE-SEM imaging of the membranes I, II, and III.

The PEBAX coating layer of the membrane II and the modified PEBAX coating layer of the membrane III were formed to a thickness in the range of about 0.3 to 1.4 탆 and the coating thickness was increased as the contact time between the support and the coating solution was increased.

And the PEBAX coating layer of the membrane II was formed thicker than the modified PEBAX coating layer of the membrane III under the same conditions of the contact time (d1 > d2 in FIG. 4).

The reason why the coating layer of the membrane II is formed to be relatively thick is that the ethanol / water mixed solvent is used in the preparation of the membrane II, and as a result, the coating solution penetrates into the PEI support by the action of the ethanol contained in the mixed solvent during the contact between the PEI support and the coating solution As a result.

On the other hand, in the case of the separator III according to the present invention, water used as a single solvent in the production process is difficult to penetrate the surface of the PEI support having hydrophobic characteristics, so that the phenomenon of permeation of the coating solution into the PEI support is suppressed, It is analyzed that it is formed densely.

As described above, since the separator III according to the present invention has a thin and dense coating layer as compared with the separator II, it can exhibit relatively superior performance in terms of gas permeability.

(4.8) Experimental Result 4: Analysis of Gas Permeation Characteristics

The hollow fiber membrane (membrane Ⅲ) composed of the PEI support and the PEBAX coating layer (membrane Ⅱ), the PEI support and the modified PEBAX coating layer was applied to the hollow fiber membrane module shown in Fig. 1 to evaluate gas permeation characteristics , And the results are shown in Table 3 below.

The carbon dioxide / nitrogen selectivity (P _CO2 / _N2 ) was higher than 40 in both membrane II and membrane III, indicating that both membranes II and III exhibited a high carbon dioxide separation rate.

On the other hand, nitrogen permeability (P _N2 ) and carbon dioxide permeability (P _CO2 ) were much higher in membrane III than membrane II.

The relatively high gas permeability of the separator III according to the present invention is due to the decrease in crystallinity due to the modification of the polymer for reduction of the number of hydrogen bonds and the decrease in the thickness of the coating layer due to the suppression of penetration of the coating solution into the support.

10: Hollow Fiber Membrane Module
20: hollow fiber membrane
30: Housing

Claims (11)

1. A gas separation membrane comprising a support and a coating layer coated thereon,
Wherein the coating layer comprises a polymer having a structure in which the monomers of formula (1) are repeatedly linked,
[Chemical Formula 1]

In Formula 1, p is a real number greater than 0 and less than 1, and A is N-alkoxymethyl.
The method according to claim 1,
The N-alkoxymethyl may be methoxymethyl, ethoxymethyl, propoxymethyl, or butoxymethyl, and the like.
Gas separation membrane.
The method according to claim 1,
Wherein the coating layer has a thickness of 0.1 to 2.0 탆,
Gas separation membrane.
The method according to claim 1,
The support may be a polymeric support made of any one of polyetherimide, polysulfone, polyethersulfone, polyvinylidene fluoride and polyimide, a metal porous support, a ceramic porous support,
Gas separation membrane.
The method according to any one of claims 1 to 4,
The gas separation membrane may be a hollow fiber membrane,
Gas separation membrane.
A plurality of hollow fiber membranes; And
A housing having an inner channel in which the plurality of hollow fiber membranes are arranged, an inlet provided at one end of the inner channel, a first outlet provided at the other end of the inner channel, and a second outlet provided at a side of the inner channel; / RTI >
Wherein the hollow fiber membrane is a gas separation membrane according to any one of claims 1 to 4,
Hollow Fiber Membrane Module.
A method for producing a gas separation membrane,
(a) providing a support;
(b) providing a coating liquid;
(c) coating the coating liquid on the surface of the support; And
(d) drying the gas separation membrane,
Wherein the coating solution comprises a polymer in which the unit represented by the formula (1) is repeatedly attached,
[Chemical Formula 1]

In Formula 1, p is a real number greater than 0 and less than 1, and A is N-alkoxymethyl.
The method of claim 7,
The step (b)
(b1) generating the polymer; And
(b2) mixing the polymer with a solvent to prepare the coating solution.
A method for producing a gas separation membrane.
The method of claim 8,
Wherein water is used as said solvent,
A method for producing a gas separation membrane.
The method of claim 8,
Wherein said N-alkoxymethyl is methoxymethyl,
A method for producing a gas separation membrane.
The method of claim 10,
The step (b1)
(b11) dissolving a polymer having a structure in which a unit of formula (2) is repeatedly linked in a formic acid to form a polymer solution;
(2)

(b12) introducing hemiacetal into the polymer solution so that the hydrogen in the amide block of the unit is substituted with methoxymethyl; And
(b13) introducing a precipitation inducing agent into the polymer solution to precipitate a polymer in the polymer solution,
Wherein p is a real number larger than 0 and smaller than 1,
A method for producing a gas separation membrane.

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