KR20150009802A - Reverse osmosis membrane and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a reverse osmosis separation membrane and a manufacturing method thereof, and more specifically, to a reverse osmosis separation membrane which forms a hydrophilic protection layer on the separation membrane and improves salt removal rate and fouling resistant, and to a manufacturing method thereof. To this end, provided is a reverse osmosis separation membrane comprising: a porous supporter; an activation layer formed on the porous supporter; and a hydrophilic protection layer formed on the activation layer, wherein the hydrophilic protection layer comprises a compound represented by chemical formula 1.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reverse osmosis membrane,

The present invention relates to a reverse osmosis membrane and a method of manufacturing the same, and more particularly, to a reverse osmosis membrane having a salt removal ratio and an improvement in contamination resistance by modifying the surface of a separation membrane.

The phenomenon that the solvent moves between the two solutions separated by the semi-permeable membrane through the membrane from the solution with a low solute concentration to the solution with a high solute concentration is called osmotic phenomenon. The pressure acting on the solution side Is called osmotic pressure. However, when an external pressure higher than osmotic pressure is applied, the solvent moves toward the solution having a low solute concentration. This phenomenon is called reverse osmosis. By using the reverse osmosis principle, it is possible to separate various salts or organic substances through the semipermeable membrane using the pressure gradient as a driving force. Reverse osmosis membranes using this reverse osmosis membrane are used for separating molecular-level substances and removing salts from brine or sea water to supply domestic, architectural and industrial water.

Although the cellulose acetate and its derivatives were mainly used in the early stage of development of the reverse osmosis membrane, there were many defects such as chemical resistance, heat resistance, and stain resistance. Accordingly, a polyamide film having superior mechanical strength and separation selectivity than cellulose acetate (CA) based materials is mainly used.

Korean Patent Publication No. 2012-0129811

Reverse osmosis membranes are commercially available and must be highly salt-desorbed for large amounts of dechlorination, and permeate flow characteristics that allow excess water to pass at relatively low pressures. Therefore, it is required to develop a technique for improving the contamination resistance associated with the salt removal rate and the permeation flow rate characteristics of the reverse osmosis membrane.

In order to solve the above problems, the present application relates to a porous support; An active layer formed on the porous support; And a hydrophilic protective layer formed on the active layer, wherein the hydrophilic protective layer comprises a compound represented by the following formula (1).

 [Chemical Formula 1]

In Formula 1,

L is a C ₁ to C ₂₀ alkylene group,

X is a C ₆ to C ₂₀ aryl group substituted with at least one hydrophilic group,

Y is hydrogen or a C ₁ to C ₁₀ alkyl group.

The application also includes forming an active layer on a porous support; And forming a hydrophilic protective layer comprising a compound represented by the following formula (1) on the active layer.

[Chemical Formula 1]

In Formula 1,

L is a C ₁ to C ₂₀ alkylene group,

X is an aryl group substituted with at least one hydrophilic group,

Y is hydrogen or a C ₁ to C ₁₀ alkyl group.

The reverse osmosis membrane of the present application including a hydrophilic protective layer on the active layer has excellent salt removal rate and stain resistance characteristic as compared with the conventional reverse osmosis membrane.

The present application relates to a porous support; An active layer formed on the porous support; And a hydrophilic protective layer formed on the active layer, wherein the hydrophilic protective layer comprises an amide compound having a hydrophilic group.

The amide compound having the hydrophilic group may increase the hydrophilicity of the reverse osmosis membrane to improve the salt removal ratio and improve the contamination resistance property simultaneously.

The amide compound having a hydrophilic group may be represented by the following general formula (1).

 [Chemical Formula 1]

In Formula 1,

L is a C ₁ to C ₂₀ alkylene group,

X is an aryl group substituted with at least one hydrophilic group,

Y is hydrogen or a C ₁ to C ₁₀ alkyl group.

When L is a direct bond, there may be a limit to increase the salt removal rate. In the case of at least one alkylene group, the hydrophilic property and the hydrophobic property are simultaneously given, and the salt removal rate is increased, while the resistance against hydrophilic and / Lt; / RTI >

The aryl group may be selected from the group consisting of phenyl, biphenyl, terphenyl, naphthyl, anthracenyl, phenanthrenyl, pyrenyl, perylenyl, It is not.

The hydrophilic group may be at least one selected from the group consisting of a hydroxyl group, a sulfonic acid group, a carboxy group, an amino group and a phosphoric acid group, but is not limited thereto.

More preferably, the compound represented by Formula 1 may be a compound represented by Formula 2 below.

(2)

In Formula 2,

m is an integer of 1 to 20,

n is an integer of 1 to 5;

If m is less than 1, there may be a limit to increase the salt removal rate, and when m is 1 or more, the hydrophilic property and the hydrophobic property are simultaneously given to increase the salt removal rate, and to resist the hydrophilic and / Lt; / RTI >

When n is less than 1, hydrophilic properties are not added to the polyamide surface, which makes it difficult to improve the permeation flow rate and resistance to the contamination source.

The compound represented by Formula 1 may form a hydrophilic protective layer on the active layer. Preferably, monomers of the compound represented by the formula (1) can be bonded to the surface of the active layer, and clusters formed by the hydrogen bonds between the monomers can be formed to form a hydrophilic protective layer by physical bonding in the form of a polymer.

That is, when bonding with the active layer occurs in the acrylic moiety of the compound represented by the general formula (1), a hydrophilic group is present on the surface of the membrane to form a hydrophilic protective layer. In the case of the chemical formula 2, a hydroxy group (-OH) is present on the surface of the film, and a hydrophilic protective layer can be formed.

Due to the hydrophilic membrane surface property due to the hydrophilic protective layer, not only the permeation flow rate is improved but also the resistance against the contamination source is increased, and the molecular layer is raised, thereby improving the salt removal rate. In addition, the monomer molecules that are not bonded to the active layer form clusters by hydrogen bonding of amide groups in the molecule and are physically adsorbed on the surface of the active layer, thereby contributing to the salt removal rate.

On the other hand, the porous support may be selected from the group consisting of polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetherketone, polypropylene, polymethylpentene, polymethylchloride and polyvinylidene fluoride But is not limited to, at least one selected.

The active layer may include a polyamide-based compound, and the polyamide-based compound may be formed by interfacial polymerization of an amine-based compound and an acyl halide-based compound, but the present invention is not limited thereto.

The amine compound may be at least one compound selected from the group consisting of m-phenylenediamine, p-phenylenediamine, 1,3,6-benzenetriamine, 4-chloro-1,3-phenylenediamine, 6- But are not limited to, at least one selected from the group consisting of 3-chloro-1,4-phenylenediamine and pyrazine.

The acyl halide compound may include, but is not limited to, at least one selected from the group consisting of trimesoyl chloride (TMC), isotaryl chlorite (IPC), and terephthaloyl chloride (TPD) .

The application also includes forming an active layer on a porous support; And forming a hydrophilic protective layer comprising a compound represented by the following formula (1) on the active layer.

[Chemical Formula 1]

In Formula 1,

L is a C ₁ to C ₂₀ alkylene group,

X is an aryl group substituted with at least one hydrophilic group,

Y is hydrogen or a C ₁ to C ₁₀ alkyl group.

The compound represented by Formula 1 may be represented by Formula 2 below.

 (2)

In Formula 2,

m is an integer of 1 to 20,

n is an integer of 1 to 5;

The step of forming the active layer may include forming a polyamide-based film on the porous support by interfacial polymerization of an amine-based compound and an acyl halide-based compound, and activating the polyamide-based film surface.

The step of forming the polyamide-based membrane may be performed by mixing the porous support with at least one member selected from the group consisting of m-phenylenediamine, p-phenylenediamine, 1,3,6-benzenetriamine, 4-chloro-1,3- In an aqueous solution comprising at least one polyfunctional amine selected from the group consisting of 1,3-phenylenediamine, 3-chloro-1,4-phenylenediamine and pyrazine; and

And a solution comprising at least one acyl halide compound selected from the group consisting of trimethoyl chloride (TMC), isophthaloyl chloride (IPC) and terephthaloyl chloride (TPD). It is preferred that the excess organic solution is removed after immersion.

In addition, the step of activating the polyamide-based membrane surface formed may be carried out by immersion, preferably immersed in an aqueous solution containing K ₂ S ₂ O ₈ and Na ₂ S ₂ O ₅ , It is not.

A radical may be formed by activating the surface of the polyamide-based film, and a covalent bond may be formed on the surface of the active layer by reacting with the acrylic functional group of the monomer represented by the general formula (1).

The step of forming the hydrophilic protective layer may be carried out by immersing in an aqueous solution of the compound represented by the formula (1).

The concentration of the aqueous solution of the compound represented by Formula 1 may be 0.1 to 5 wt%, preferably 0.5 to 3 wt%.

 When the concentration of the aqueous solution is less than 0.1 wt%, the bonding reaction by the radical reaction of the hydrophilic protective layer does not occur entirely in the polyamide membrane, so that the hydrophilic protective layer can be partially formed on the membrane. If the concentration of the aqueous solution is more than 5% by weight, the hydrophilic protective layer may be excessively formed on the polyamide membrane or the bonding due to the radical reaction between the monomers may occur, Layer is formed and the flow rate is reduced.

The immersion time is preferably from 1 to 10 minutes, and in the case of less than 1 minute, the hydrophilic material does not completely cover the polyamide film but covers only a part of the hydrophilic material, and if it exceeds 10 minutes, the hydrophilic materials aggregate with each other There is a problem that the film becomes thick and the hydrophilic materials do not rise uniformly on the polyamide film.

The reverse osmosis membrane containing the hydrophilic protective layer manufactured according to the present application may have a salt removal rate and stain resistance as compared with the conventional reverse osmosis membrane due to its hydrophilic property.

Also, various functionalization can be performed by a functional group such as a hydroxyl group (-OH) present in the hydrophilic protective layer, and a remarkable performance improvement of the reverse osmosis membrane can be obtained through formation of a single coating film. Conventionally, different kinds of materials have been used for improving the pollution resistance and the chlorine resistance. In this case, various coating processes have been performed. In the case of such a conventional method, since the coating film is formed in multiple layers, the separation membrane characteristics are deteriorated and the process becomes complicated. The present application is intended to solve such problems, and it is characterized in that a single coating film simultaneously improves the contamination resistance and chlorine resistance. In the case of the reverse osmosis membrane of the present application, since only one coating film is formed, not only the process is simple but also the deterioration of the film performance due to the coating film can be minimized.

Hereinafter, preferred embodiments are presented to facilitate understanding of the present application. However, the following embodiments are intended to illustrate the present application, and the scope of the present application is not limited thereby.

<Examples>

&Lt; Preparation Example > Preparation of polyamide film

A 95 to 100 mu m nonwoven fabric made of polyester was prepared and a polysulfone solid content of 18 wt% (relative to the total solution) was added to DMF (N, N-diethylformamide) solution for casting polysulfone. Melted. When a uniform liquid phase was obtained, 45 to 50 μm of polysulfone was cast on the nonwoven fabric. The prepared porous polysulfone support was immersed in an aqueous solution containing 2% by weight of MDF (m-phenylenediamine) for 2 minutes, then the excess aqueous solution on the support was removed using a 25 psi roller and dried at room temperature for 1 minute. Thereafter, the coated substrate was immersed in a solution containing 0.1 vol% TMC (1,3,5-benzenetricarbonyl trichloride) in an Isol C solvent (SKC Corp.) for 1 minute, and then dried at 60 ° C And dried in an oven for 10 minutes. The separation membrane obtained by the above method is washed with a 0.2 wt% sodium carbonate aqueous solution at room temperature for 2 hours or more, and then washed with distilled water. A polyamide membrane having a thickness of 200 탆 was prepared as described above to obtain a separator.

&Lt; Example 1 >

The polyamide membrane was prepared as in the preparation example, and then immersed in 0.01 wt% K ₂ S ₂ O ₄ and 0.01 wt% Na ₂ S ₂ O ₅ aqueous solution for 10 minutes to activate the membrane surface to form an active layer. The surface-activated membrane was immersed in an aqueous solution of N- (3,4-dihydroxyphenethyl) acrylamide at a concentration of 0.5% by weight for 10 minutes, washed with tertiary distilled water To form a hydrophilic protective layer. The performance of the membrane was measured at a pressure of 800 psi in a 32,000 ppm NaCl aqueous solution after the formation of the hydrophilic protective layer. The results are shown in Table 1 below.

&Lt; Example 2 >

The procedure of Example 1 was repeated except that the concentration of N- (3,4-dihydroxyphenethyl) acrylamide in Example 1 was 1% by weight . The performance was evaluated under the same conditions as described in Example 1, and the physical properties of the membranes performed are shown in Table 1 below.

&Lt; Example 3 >

The procedure of Example 1 was repeated except that the concentration of N- (3,4-dihydroxyphenethyl) acrylamide in Example 1 was 1.5% by weight . The performance was evaluated under the same conditions as described in Example 1, and the physical properties of the membranes performed are shown in Table 1 below.

<Example 4>

The procedure of Example 1 was repeated except that the concentration of N- (3,4-dihydroxyphenethyl) acrylamide in Example 1 was 2% by weight . The performance was evaluated under the same conditions as described in Example 1, and the physical properties of the membranes performed are shown in Table 1 below.

&Lt; Example 5 >

The procedure of Example 1 was repeated except that the concentration of N- (3,4-dihydroxyphenethyl) acrylamide in Example 1 was 2.5% by weight . The performance was evaluated under the same conditions as described in Example 1, and the physical properties of the membranes performed are shown in Table 1 below.

&Lt; Example 6 >

The procedure of Example 1 was repeated except that the concentration of N- (3,4-dihydroxyphenethyl) acrylamide in Example 1 was 3% by weight . The performance was evaluated under the same conditions as described in Example 1, and the physical properties of the membranes performed are shown in Table 1 below.

&Lt; Comparative Example 1 &

A polyamide membrane was prepared as in the preparation example and the membrane performance was evaluated in the same manner as in Example 1 without treatment with N- (3,4-dihydroxyphenethyl) acrylamide (N- (3,4-dihydroxyphenethyl) acrylamide) . The physical properties of the membrane thus obtained are shown in Table 1 below.

&Lt; Experimental Example 1 >

Water contact angle measurements were measured by Contact angle goniometry (PSA 100, KRUSS GmbH). The water contact angle was measured by dropping 3 mu l of water drop on the measurement surface with a micro-injector. Five water droplets were dropped on the measurement surfaces of the membranes prepared in Examples 1 to 6 and Comparative Example 1, and the contact angle was measured with a microscope. The average values of the measured water contact angles are shown in Table 1 below.

Experimental Example 2: Initial salt removal rate and initial permeation flux

The initial salt removal rate and the initial permeate flow rate were measured at a flow rate of 4500 ml / min at a flow rate of 32,000 ppm NaCl at 25 ° C. The reverse osmosis membrane cell apparatus used for the membrane evaluation was composed of a plate type permeation cell, a high pressure pump, Respectively. The structure of the planar type transmissive cell was a cross-flow type with an effective permeation area of 140 cm ² . After the washed membrane was installed in the permeable cell, preliminary operation was performed for about 1 hour by using the third distilled water for stabilization of the evaluation equipment. After that, the equipment was operated for about 1 hour until the pressure and water permeability reached a steady state by replacing with 32,000 ppm NaCl aqueous solution. The amount of water permeated for a certain time was measured to calculate the flow rate. Conductivity meter And the removal rate was calculated by analyzing the salt concentration before and after the permeation.

division Contact angle (°) Early Salt removal rate (%) Initial permeate flux ( GFD ) Example  One 18.1 ± 3.11 99.37 42.11 Example  2 17.4 ± 2.84 99.38 42.07 Example  3 16.9 ± 2.49 99.43 41.80 Example  4 17.1 ± 2.20 99.51 41.09 Example  5 17.2 ± 2.21 99.56 36.17 Example  6 16.5 ± 1.89 99.58 38.47 Comparative Example  One 34.4 ± 5.71 98.48 45.19

The contact angle refers to the angle with respect to the solid surface when drawing a straight line to the liquid surface at the point where the stationary liquid contacts the solid on the solid surface, and the low contact angle shows high hydrophilic and high surface energy.

As shown in Table 1, it can be seen that the contact angle of the reverse osmosis membrane including the hydrophilic protective layer according to the present application is smaller than that of Comparative Example 1 in which the hydrophilic protective layer is not formed. Further, as the concentration of the aqueous solution containing N- (3,4-dihydroxyphenethyl) acrylamide, which forms the hydrophilic protective layer, increases, the contact angle decreases and the deviation decreases Trends can be seen.

That is, it can be seen from Table 1 that the membranes of Examples 1 to 6 have higher hydrophilicity than the membranes of Comparative Example 1. [

As shown in Table 1, in the performance evaluation of the membrane, the reverse osmosis membrane containing the hydrophilic protective layer according to the present application has an improved salt removal rate as compared with Comparative Example 1 in which the hydrophilic protective layer is not formed. Particularly, as shown in the membrane performance evaluation of Example 4, the reverse osmosis membrane was found to contain N- (3,4-dihydroxyphenethyl) acrylamide at a concentration of 2% by weight, It can be seen that when the hydrophilic protective layer is immersed in an aqueous solution, a high salt removal ratio is obtained and the permeation flow rate is reduced within a reasonable range to obtain optimum performance.

&Lt; Experimental Example 3 >

To evaluate the stain resistance, 32,000 ppm of NaCl and 100 ppm of casein aqueous solution were used. After the initial salt removal rate and the flow rate were evaluated, 100ppm casein aqueous solution was added to the evaluator tank, and the salt removal rate and the flow rate were measured after 6 hours. The pollution source used in the evaluation of pollution resistance was casein, which is mostly protein, dissolved in an aqueous solution of pH 11 or higher.

&Lt; Example 7 >

A separator was prepared in the same manner as in Example 1, and the performance of the separator before and after the addition of casein aqueous solution was evaluated at a pressure of 800 psi using 32,000 ppm NaCl aqueous solution and 100 ppm casein mixed aqueous solution. The results are shown in Table 2. In Table 2, the unit of permeate flow is GFD (gallon / ft ² day.

&Lt; Example 8 >

The evaluation was carried out in the same manner as in Example 7, except that a separator was prepared in the same manner as in Example 4, and the results are shown in Table 2.

&Lt; Example 9 >

The evaluation was carried out in the same manner as in Example 7 except that the separation membrane was prepared in the same manner as in Example 6, and the results are shown in Table 2.

&Lt; Comparative Example 2 &

The evaluation was conducted in the same manner as in Example 7, except that the separation membrane as in Comparative Example 1 was used, and the results are shown in Table 2.

division Casein  Before input
Early Salt removal rate
(%) Casein  input
After 6 hours Salt removal rate
(%) Casein  Before input
Initial permeate flux
( GFD ) Casein  input
Permeate flow after 6 hours
( GFD ) Example  7 99.34 99.40 42.37 38.05 Example  8 99.50 99.57 41.87 37.38 Example  9 99.55 99.63 35.17 30.97 Comparative Example  2 98.11 99.20 46.71 35.02

As shown in Table 2, the reverse osmosis membrane including the hydrophilic protective layer according to the present application has a significantly lower decrease in the permeation flow rate after 6 hours of casein injection, as compared with Comparative Example 2 in which the hydrophilic protective layer is not formed have. That is, the reverse osmosis membrane including the hydrophilic protective layer can improve the stain resistance by reducing the contamination degree of the membrane surface by the hydrophilic property.

Claims (16)

A porous support; An active layer formed on the porous support; And a hydrophilic protective layer formed on the active layer, wherein the hydrophilic protective layer comprises a compound represented by the following Formula 1:
[Chemical Formula 1]

In Formula 1,
L is a C ₁ to C ₂₀ alkylene group,
X is an aryl group substituted with at least one hydrophilic group,
Y is hydrogen or a C ₁ to C ₁₀ alkyl group. The method according to claim 1,
Wherein the aryl group is selected from the group consisting of phenyl, biphenyl, terphenyl, naphthyl, anthracenyl, phenanthrenyl, pyrenyl, perylenyl, The method according to claim 1,
Wherein the hydrophilic group is at least one selected from the group consisting of a hydroxyl group, a sulfonic acid group, a carboxy group, an amino group, and a phosphoric acid group. The method according to claim 1,
Wherein the compound represented by the formula (1) is represented by the following formula (2).
(2)

In Formula 2,
m is an integer of 1 to 20,
n is an integer of 1 to 5; The method according to claim 1,
Wherein the porous support is selected from the group consisting of polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetherketone, polypropylene, polymethylpentene, polymethylchloride and polyvinylidene fluoride And at least one reverse osmosis membrane. The method according to claim 1,
Wherein the active layer comprises a polyamide-based compound, and the polyamide-based compound is formed by interfacial polymerization of an amine-based compound and an acyl halide-based compound. The method of claim 6,
The amine compound may be at least one compound selected from the group consisting of m-phenylenediamine, p-phenylenediamine, 1,3,6-benzenetriamine, 4-chloro-1,3-phenylenediamine, 6- 3-chloro-1,4-phenylenediamine, and pyrazine. The method of claim 6,
Wherein the acyl halide compound is at least one selected from the group consisting of trimethoyl chloride (TMC), isotaryl chlorite (IPC), and terephthaloyl chloride (TPD). Forming an active layer on a porous support, and forming a hydrophilic protective layer comprising a compound represented by the following formula (1) on the active layer:
[Chemical Formula 1]

In Formula 1,
L is a C ₁ to C ₂₀ alkylene group,
X is an aryl group substituted with at least one hydrophilic group,
Y is hydrogen or a C ₁ to C ₁₀ alkyl group. The method of claim 9,
Wherein the compound represented by Formula 1 is represented by Formula 2:
(2)

In Formula 2,
m is an integer of 1 to 20,
n is an integer of 1 to 5; The method of claim 9,
Wherein the step of forming the active layer comprises a step of forming a polyamide-based film on a porous support by interfacial polymerization of an amine-based compound and an acyl halide-based compound, and activating the polyamide-based film surface (2). The method of claim 11,
The amine compound may be at least one compound selected from the group consisting of m-phenylenediamine, p-phenylenediamine, 1,3,6-benzenetriamine, 4-chloro-1,3-phenylenediamine, 6- 3-chloro-1,4-phenylenediamine, and pyrazine. The method of claim 11,
Wherein the acyl halide compound is at least one selected from the group consisting of trimesoyl chloride (TMC), isotaryl chlorite (IPC), and terephthaloyl chloride (TPD). The method of claim 11,
Wherein the step of activating the polyamide-based membrane surface comprises the steps of: K ₂ S ₂ O ₈ And Na ₂ S ₂ O ₅ in an aqueous solution containing the polyamide-based membrane. The method of claim 9,
Wherein the hydrophilic protective layer is formed by immersing the hydrophilic protective layer in an aqueous solution of the compound represented by Formula 1. 16. The method of claim 15,
Wherein the concentration of the aqueous solution of the compound represented by Formula 1 is 0.1 to 5 wt%.