Patent Description:
A phenomenon that a solvent moves from, between two solutions separated by a semi-permeable membrane, a solution with a low solute concentration to a solution with a high solute concentration through the membrane is referred to as an osmosis phenomenon, and herein, a pressure working on the side of the solution with a high solute concentration due to the solvent migration is referred to as an osmotic pressure. However, when applying an external pressure higher than an osmotic pressure, the solvent moves toward the solution with a low solute concentration, and this phenomenon is referred to as reverse osmosis. Using a reverse osmosis principle, various salts or organic substances may be separated through a semi-permeable membrane with a pressure gradient as a driving force. A water-treatment membrane using such a reverse osmosis phenomenon has been used to supply water for household, construction and industry after separating substances at a molecular level and removing salts from salt water or sea water.

Typical examples of such a water-treatment membrane may include a polyamide-based water-treatment membrane, and the polyamide-based water-treatment membrane is manufactured using a method of forming a polyamide active layer on a microporous support. More specifically, the polyamide-based water-treatment membrane is manufactured using a method of forming a polysulfone layer on a non-woven fabric to form a microporous support, dipping this microporous support into an aqueous m-phenylenediamine (hereinafter, mPD) solution to form an mPD layer, and dipping this again into an organic trimesoyl chloride (TMC) solvent, bringing the mPD layer into contact with the TMC, and interfacial polymerizing the result to form a polyamide active layer.

The polyamide active layer has a great effect on salt rejection and flux, indicators representing performance of a polyamide-based water-treatment membrane, and studies thereon have been continuously ongoing.

<CIT> discloses a method of making a reverse osmosis membrane, comprising: (A) providing, on the surface of a porous membrane, a composition comprising a polyamine and a polyfunctional acyl halide, the porous support membrane comprising a polymer matrix and microparticles, nanoparticles, or a combination thereof, dispersed throughout the body of the polymer matrix; and (B) interfacially polymerizing the polyamine and polyfunctional acyl halide on the surface of the porous support membrane to form a revserse osmosis membrane comprising the porous support membrane and a discrimination layer comprising a polyamide. It is also disclosed that various post-treatments can be employed to enhance water-permeability, solute rejection, or fouling resistance of a formed TFC membrane. For example, a membrane can be immersed in an acidic and/or basic solution to remove residual, unreacted acid chlorides and diamines which can improve the flux of the formed composite membrane. A membrane can be also exposed to an oxidant such as chlorine by filtering a solution of sodium hypochlorite through the membrane. Post-chlorination of a fully aromatic polyamide thin film composite forms chloramines as free chlorine reacts with pendant amine functional groups with the polyamide film.

The present specification is directed to providing a method of testing a water-treatment membrane after hypochlorite treatment.

One embodiment of the present specification provides a method of testing a water-treatment membrane after hypochlorite treatment by its discoloration, the water-treatment membrane comprising:
a porous support;
a polyamide active layer provided on the porous support and including chlorine on a surface thereof, wherein CIE L*a*b* color coordinate values after storing for <NUM> days or longer at <NUM> to <NUM> satisfy the following [Equation <NUM>] to [Equation <NUM>] <MAT> <MAT> <MAT>.

There is an advantage in that use of a hypochlorite process can be detected through color coordinate values.

In the present specification, a description of a certain member being placed 'on' another member includes not only a case of the certain member adjoining the another member but a case of still another member being present between the two members.

In the present specification, a description of a certain part 'including' certain constituents means capable of further including other constituents, and does not exclude other constituents unless particularly stated on the contrary.

In the present specification, being measured 'at the beginning' or 'immediately after' means, unless mentioned otherwise, being measured within <NUM> minutes after the corresponding step is completed.

In the present specification, a 'moisture content of water-treatment membrane' measured immediately after a specific step means a moisture content for a sample completed up to the corresponding step. For example, a moisture content of a water-treatment membrane measured immediately after step (a) means a moisture content of a sample completed only up to a process of forming a polyamide active layer on a porous support.

A method for manufacturing a water-treatment membrane includes,.

When pretreating the polyamide active layer with a solution including water; or water and a salt, a swelling effect of the active layer is induced during the pretreatment process, which is effective in enhancing flux.

In addition, when bringing a hypochlorite solution into contact with the pretreated polyamide active layer, chloride ions bond in the active layer ultimately enhancing salt rejection and flux of a water-treatment membrane.

The porous support may be prepared by coating a polymer material on a non-woven fabric, and type, thickness and porosity of the non-woven fabric may diversely vary as necessary.

Examples of the polymer material may include polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethyl chloride, polyvinylidene fluoride and the like, but are not limited thereto.

The polymer material may be polysulfone.

The forming of a polyamide active layer may be conducted by interfacial polymerizing an amine compound and an acyl halide compound, and specifically, may include forming an aqueous solution layer including an amine compound on the porous support; and bringing an organic solution including an acyl halide compound and an organic solvent into contact with the aqueous solution layer thereon.

When bringing the organic solution into contact with the aqueous solution layer, polyamide is produced by interfacial polymerization while the amine compound coated on the porous support surface and the acyl halide compound react, and the polyamide is adsorbed on the microporous support to form a thin film. As a method of the contact, a method of dipping, spraying, or coating may be used.

Coating an additive such as triethylammonium camphorsulfonate (TEACSA) may be further included after preparing a porous support and before the forming of a polyamide active layer on the porous support, that is, before coating an aqueous solution including an amine compound on the support.

A method for forming the aqueous solution layer including an amine compound on the porous support is not particularly limited, and methods capable of forming an aqueous solution layer on a support may be used without limit. Specifically, spraying, coating, dipping, or dropping may be used.

The amine compound is not limited as long as it may be used in polyamide polymerization, however, examples thereof may include m-phenylenediamine (mPD), p-phenylenediamine (PPD), <NUM>,<NUM>,<NUM>-benzenetriamine (TAB), <NUM>-chloro-<NUM>,<NUM>-phenylenediamine, <NUM>-chloro-<NUM>,<NUM>-phenylenediamine, <NUM>-chloro-<NUM>,<NUM>-phenylenediamine or mixtures thereof, and preferably, the amine compound may be m-phenylenediamine (mPD).

A content of the amine compound may be from <NUM> wt% to <NUM> wt%, preferably from <NUM> wt% to <NUM> wt%, and more preferably from <NUM> wt% to <NUM> wt% based on <NUM> wt% of the aqueous solution including an amine compound.

When the amine compound content is in the above-mentioned range, a uniform polyamide active layer may be prepared.

The aqueous solution layer may further go through removing an excess amine compound-including aqueous solution as necessary. The aqueous solution layer formed on the porous support may be non-uniformly distributed when there are too much of the aqueous solution present on the support, and when the aqueous solution is non-uniformly distributed, a nonuniform polyamide active layer may be formed by subsequent interfacial polymerization. Accordingly, the excess aqueous solution is preferably removed after forming the aqueous solution layer on the support. A method of removing the excess aqueous solution is not particularly limited, however, methods using a sponge, an air knife, nitrogen gas blowing, natural drying, or a compression roll may be used.

The acyl halide compound is not limited as long as it may be used in polyamide polymerization, however, an aromatic compound having <NUM> or <NUM> carboxylic acid halides, for example, one type selected from the compound group consisting of trimesoyl chloride (TMC), isophthaloyl chloride and terephthaloyl chloride, or a mixture of two or more types thereof may be preferably used, and preferably, trimesoyl chloride (TMC) may be used.

The organic solvent preferably does not participate in an interfacial polymerization reaction, and an aliphatic hydrocarbon solvent, for example, one or more types selected from among freons, alkane having <NUM> to <NUM> carbon atoms and isoparaffin-based solvents, an alkane mixture material, may be included. Specifically, one or more types selected from among hexane, heptane, octane, nonane, decane, undecane, dodecane, cyclohexane, IsoPar (Exxon), IsoPar G (Exxon), ISOL-C (SK Chem) and ISOL-G (Exxon) may be used, however, the organic solvent is not limited thereto.

A content of the acyl halide compound may be from <NUM> wt% to <NUM> wt%, preferably from <NUM> wt% to <NUM> wt%, and more preferably from <NUM> wt% to <NUM> wt% based on <NUM> wt% of the organic solution.

A uniform polyamide layer may be prepared when the acyl halide compound content is in the above-mentioned range.

The aqueous solution including an amine compound may further include a surfactant.

When interfacial polymerizing the polyamide active layer, polyamide is quickly formed at an interface of an aqueous solution layer and an organic solution layer, and herein, the surfactant makes the layer thin and uniform so that the amine compound present in the aqueous solution layer readily migrates to the organic solution layer to form a uniform polyamide active layer.

The surfactant may be selected from among nonionic, cationic, anionic and amphoteric surfactants. The surfactant may be selected from among sodium lauryl sulfate (SLS); alkyl ether sulfates; alkyl sulfates; olefin sulfonates; alkyl ether carboxylates; sulfosuccinates; aromatic sulfonates; octylphenol ethoxylates; ethoxylated nonylphenols; alkyl poly(ethylene oxide); copolymers of poly(ethylene oxide) and poly(propylene oxide); alkyl polyglucosides such as octyl glucoside and decyl maltoside; aliphatic acid alcohols such as cetyl alcohol, oleyl alcohol, cocamide MEA, cocamide DEA, alkyl hydroxyethyldimethylammonium chloride, cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride; and alkyl betaines. Specifically, the surfactant may be SLS, octylphenol ethoxylates or ethoxylated nonylphenols.

Particularly, when using sodium lauryl sulfate (SLS) as the surfactant, the SLS is highly soluble in water due to its high affinity for water and oil (hydrophile-lipophile balance, HLB), and by having a high critical micelle concentration (CMC), formation of the polyamide active layer is not inhibited even when added in excess.

A content of the surfactant may be from <NUM> wt% to <NUM> wt% based on <NUM> wt% of the aqueous solution including an amine compound.

A moisture content of the water-treatment membrane measured after drying for <NUM> minute to <NUM> minutes at <NUM> to <NUM> immediately after the step (a) may be from <NUM>% to <NUM>% and preferably from <NUM>% to <NUM>%, and a measurement error is ±<NUM>%.

The pretreatment may be conducted through a process of bringing the polyamide active layer prepared in the step (a) into contact with a pretreatment solution including water.

The contact may be conducted using a method such as dipping, spraying or coating, and may be preferably conducted through dipping.

The step (b) may be conducted at <NUM> to <NUM> and preferably at <NUM> to <NUM>, and may be conducted for <NUM> second to <NUM> minutes, preferably for <NUM> second to <NUM> minutes, and more preferably for <NUM> second to <NUM> minute. A higher temperature of the pretreatment solution has advantages of shortening the process time since the rate of removing monomers remaining after forming the polyamide active layer is higher, and increasing the L* value. However, a temperature of higher than <NUM> may cause denaturation of the non-woven fabric.

Forming the pretreatment solution only with water may be advantageous in that the temperature of the solution is readily adjusted, and there is no concern over a secondary reaction caused by constituents other than water and gas generation and the like resulting therefrom.

The pretreatment solution may further include one or more types of acidic salts or basic salts. When the pretreatment solution further includes an acidic salt or a basic salt, osmosis of the polyamide active layer is induced, and the degree of pore shrinkage and expansion may be controlled depending on the concentration, which is advantageous in controlling polyamide active layer performance.

The acidic salt may be sodium sulfate, calcium sulfate, potassium sulfate, sodium phosphate, calcium phosphate or potassium phosphate, and the basic salt is sodium carbonate, calcium carbonate or potassium carbonate.

The salt may be included in <NUM> wt% to <NUM> wt% based on <NUM> wt% of the pretreatment solution.

Through such a pretreatment process, swelling of the polyamide active layer is induced, which may increase flux.

A moisture content of the water-treatment membrane measured immediately after the step (b) may be from <NUM>% to <NUM>% and preferably from <NUM>% to <NUM>%, and a measurement error is ±<NUM>%.

This means that the moisture content greatly increases compared to immediately after the step (a) due to the pretreatment process, and it may be identified whether the pretreatment process is applied or not through measuring a moisture content before hypochlorite treatment of the step (c).

The method for manufacturing a water-treatment membrane may include bringing a hypochlorite solution having a concentration of <NUM> ppm to <NUM> ppm into contact with the polyamide active layer in order to enhance salt rejection and flux.

The contact may be conducted using a method of coating a hypochlorite solution on the polyamide active layer or dipping the polyamide active layer into a hypochlorite solution. Among these, a method of coating a hypochlorite solution on the polyamide active layer is preferred since the treatment condition is readily controlled and uniformity of the hypochlorite effect is excellent.

Particularly, using a slot die coating method has advantages in that a concentration of active chlorine participating on the membrane surface may be maintained uniformly, and a sufficient chlorine treatment effect is obtained with a hypochlorite solution having a low concentration by providing a pressurizing condition.

The hypochlorite solution may be an aqueous sodium hypochlorite (NaOCl) solution.

The hypochlorite solution may have a concentration of <NUM> ppm to <NUM> ppm, preferably <NUM> ppm to <NUM> ppm, and more preferably <NUM> ppm to <NUM> ppm.

When the hypochlorite solution has a concentration of <NUM> ppm or greater, a sufficient hypochlorite effect may be obtained, and when the hypochlorite solution has a concentration of <NUM> ppm or less, a hypochlorite effect may be obtained without reducing durability of the water-treatment membrane.

The contacting of a hypochlorite solution may be conducted using a method of dipping the water-treatment membrane into a hypochlorite solution for <NUM> second to <NUM> minute.

The hypochlorite solution may have a temperature of <NUM> to <NUM>. Preferably, the temperature may be from <NUM> to <NUM>. When the hypochlorite solution temperature is in the above-mentioned range, reactivity of active chlorine is optimized. When the hypochlorite solution has a temperature of lower than <NUM>, an effect of improving performance of the water-treatment membrane is insignificant and managing the solution is difficult as well. When the solution temperature is higher than <NUM>, a structure of the water-treatment membrane is destroyed, which may weaken durability of the membrane.

A moisture content of the water-treatment membrane measured immediately after the step (c) may be from <NUM>% to <NUM>% and preferably from <NUM>% to <NUM>%, and a measurement error is ±<NUM>%.

The method for manufacturing a water-treatment membrane may further include, after the step (c), (d) forming a protective layer by coating an aqueous glycerin solution on the polyamide active layer.

A content of glycerin may be from <NUM> wt% to <NUM> wt%, preferably from <NUM> wt% to <NUM> wt% and more preferably from <NUM> wt% to <NUM> wt% in <NUM> wt% of the aqueous glycerin solution.

A moisture content of the water-treatment membrane measured after drying for <NUM> minute to <NUM> minutes at <NUM> to <NUM> in a dryer immediately after the step (d) may be from <NUM>% to <NUM>% and preferably from <NUM>% to <NUM>%, and a measurement error is ±<NUM>%.

A method for manufacturing a water-treatment module may include,.

The steps (a) to (c) may be conducted in the same manner as in the method for manufacturing a water-treatment membrane described above.

Each constitution of the method for manufacturing a water-treatment module may cite the descriptions on each constitution of the method for manufacturing a water-treatment membrane.

The method for manufacturing a water-treatment module may employ methods commonly used in the art except that the method for manufacturing a water-treatment membrane described above is used. For example, processes of tricoater packaging, membrane prepping, manual rolling, end trimming, fiber reinforced polymer coating (FRP coating) and the like may be consecutively conducted in the manufacture.

A moisture content of the water-treatment membrane measured after dissembling the water-treatment module to the water-treatment membrane after the step (e) may be from <NUM>% to <NUM>% and preferably from <NUM>% to <NUM>%.

The water-treatment membrane may include a porous support; and a polyamide active layer provided on the porous support and including chlorine on a surface thereof, wherein CIE L*a*b* color coordinate values after storing for <NUM> days or longer at <NUM> to <NUM> satisfy the following [Equation <NUM>] to [Equation <NUM>]. <MAT> <MAT> <MAT>.

In the water-treatment membrane, CIE L*a*b* color coordinate values after storing for <NUM> days or longer at <NUM> to <NUM> may satisfy <NUM><L*<<NUM>, -<NUM><a*<<NUM> and -<NUM><b*<<NUM>.

In the water-treatment membrane, CIE L*a*b* color coordinate values after storing for <NUM> days or longer at <NUM> to <NUM> may satisfy <NUM><L*<<NUM>, -<NUM><a*<<NUM> and <NUM><b*<<NUM>.

A storage temperature of the water-treatment membrane is preferably from <NUM> to <NUM>, and more preferably room temperature.

In the water-treatment membrane, CIE L*a*b* color coordinate values after storing for <NUM> days or longer, preferably for <NUM> days or longer and <NUM> days or shorter, and more preferably for <NUM> days satisfy [Equation <NUM>] to [Equation <NUM>].

In one embodiment of the present specification, the 'storing for <NUM> days or longer' may mean storing for <NUM> days or longer from the date of completing a final product after completing manufacture of all components forming the water-treatment membrane.

In one embodiment of the present specification, the 'storing for <NUM> days or longer' may mean storing for <NUM> days or longer from the date of obtaining a commercially available water-treatment membrane.

In examples of the present specification, CIE L*a*b* color coordinate values at the beginning are measured within <NUM> minutes after forming a protective layer, a final step of the water-treatment membrane manufacturing process, and CIE L*a*b* color coordinate values are measured again after storing for <NUM> days from the beginning.

The water-treatment membrane may further include a protective layer including glycerin on the polyamide active layer.

The protective layer may have a thickness of <NUM> to <NUM>, and when the thickness is in the above-mentioned range, there is an advantage of increasing flux without losing rejection.

The protective layer thickness may be measured using an image observed with a scanning electron microscope (SEM). Specifically, after cutting a cross section of a <NUM> membrane sample through a microtome, platinum (Pt) is coated thereon, and the protective layer thickness is measured using a scanning electron microscope (SEM) to calculate an average value.

In the water-treatment membrane, CIE L*a*b* color coordinate values satisfy [Equation <NUM>] to [Equation <NUM>] even after storing for <NUM> days or longer at <NUM> to <NUM>, and this means that the manufactured water-treatment membrane has a small degree of discoloration. When a large amount of unreacted monomers remain during the water-treatment membrane manufacturing process, the degree of discoloration is severe, and in this case, the monomer acts as an impurity declining performance of the water-treatment membrane. In other words, the water-treatment membrane has excellent durability.

In addition, by identifying whether CIE L*a*b* color coordinate values of the water-treatment membrane at the beginning and after storing for <NUM> days satisfy [Equation <NUM>] to [Equation <NUM>], applications of the pretreatment process and the hypochlorite process may be identified.

In one embodiment of the present specification, a chlorine element content when conducting an elemental analysis on the water-treatment membrane surface is greater than <NUM> at% and less than or equal to <NUM> at%, preferably greater than or equal to <NUM> at% and less than or equal to <NUM> at%, and more preferably greater than or equal to <NUM> at% and less than or equal to <NUM> at%.

The elemental analysis in the present specification may be conducted through X-ray photoelectron spectroscopy (XPS) or electron spectroscopy for chemical analysis (ESCA).

<FIG> illustrates the water-treatment membrane. Specifically, <FIG> illustrates the water-treatment membrane in which a non-woven fabric (<NUM>), a porous support (<NUM>) and a polyamide active layer (<NUM>) are consecutively provided, and as raw water including impurities (<NUM>) flows into the polyamide active layer (<NUM>), purified water (<NUM>) is discharged through the non-woven fabric (<NUM>), and concentrated water (<NUM>) is discharged outside failing to pass through the polyamide active layer (<NUM>). However, structures of the water-treatment membrane are not limited to the structure of <FIG>, and additional constitutions may be further included.

The water-treatment membrane may be a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane or a reverse osmosis membrane, and may specifically be a reverse osmosis membrane.

The water-treatment module includes one or more of the water-treatment membranes.

Specific types of the water-treatment module are not particularly limited, and examples thereof may include a plate & frame module, a tubular module, a hollow & fiber module, a spiral wound module or the like. In addition, as long as the water-treatment module includes the water-treatment membrane described above, the water-treatment module is not particularly limited in other constitutions and manufacturing methods, and general means known in the art may be employed without limit.

Meanwhile, the water-treatment module has excellent salt rejection and boron rejection, and therefore, is useful in water-treatment systems such as household/industrial water-purification systems, sewage treatment systems or sea to fresh water treatment systems.

Hereinafter, the present specification will be described in detail with reference to examples in order to specifically describe the present specification. However, examples according to the present specification may be modified to various different forms, and the scope of the present specification is not construed as being limited to the examples described below. The examples of the present specification are provided in order to more fully describe the present specification to those having average knowledge in the art.

<NUM> wt% of a polysulfone solid was introduced to N,N-dimethylformamide (DMF) and dissolved for <NUM> hours or longer at <NUM> to <NUM> to obtain a uniform liquid phase. This solution was casted to a thickness of <NUM> on a non-woven fabric made of a polyester material and having a thickness of <NUM> to <NUM>. Then, the casted non-woven fabric was placed in water to prepare a porous polysulfone support. Herein, the support was prepared to have a width of <NUM>.

On the porous polysulfone support, a solution including <NUM> wt% of triethylammonium camphorsulfonate (TEACSA) with respect to the whole solution and water was coated using a slot die coating method.

After that, an aqueous solution including <NUM> wt% of metaphenylenediamine (mPD) with respect to the whole aqueous solution was coated on the porous polysulfone support using a slot die coating method at a rate of <NUM>/min to form an aqueous solution layer. Furthermore, an extra aqueous solution generated during the coating was removed using an air knife.

On the aqueous solution layer, an organic solution including <NUM> wt% of trimesoyl chloride (TMC) and <NUM> wt% of an organic solvent (IsoPar G) with respect to the whole organic solution was coated using a slot die coating method at a rate of <NUM>/min. Then, the result was dried at <NUM> until all the liquid components evaporated, and then washed with ultrapure distilled water (DIW) to manufacture a water-treatment membrane. Herein, the membrane was prepared to have a width of <NUM>.

After pretreating the water-treatment membrane of the preparation example using a method of dipping into water for <NUM> seconds at room temperature, hypochlorite treatment was conducted using a method of dipping the pretreated water-treatment membrane into a <NUM> ppm hypochlorite solution at <NUM>. After that, a protective layer was formed using a method of coating <NUM> wt% of an aqueous glycerin solution on the hypochlorite treated polyamide active layer to complete a water-treatment membrane.

The completed water-treatment membrane was rolled in multiple layers to manufacture a round-shaped cylindrical water-treatment module having a diameter of <NUM> inches and a length of <NUM> inches.

A water-treatment module was manufactured in the same manner as in Example <NUM> except that the temperature of the water, a pretreatment solution, was adjusted to <NUM> or higher, and the concentration of the hypochlorite solution was changed to <NUM> ppm.

A round-shaped cylindrical water-treatment module having a diameter of <NUM> inches and a length of <NUM> inches was manufactured by rolling the water-treatment membrane of the preparation example in multiple layers.

A water-treatment module was manufactured in the same manner as in Example <NUM> except that the concentration of the hypochlorite solution was changed to <NUM> ppm.

A water-treatment module was manufactured in the same manner as in Example <NUM> except that the pretreatment was not conducted.

A round-shaped cylindrical water-treatment module having a diameter of <NUM> inches and a length of <NUM> inches was manufactured by rolling the water-treatment membrane of the preparation example in multiple layers, and then hypochlorite treatment was conducted on the manufactured water-treatment module under a condition of <NUM>, <NUM> ppm hypochlorite solution and <NUM> psi pressurizing.

For each of the water-treatment modules manufactured according to the examples and the comparative examples, performance was evaluated using a salt water containing <NUM> ppm NaCl.

After device stabilization was confirmed by operating the device for approximately <NUM> hour by passing the salt water with <NUM> psi and a flow rate of <NUM>/min, flux (GFD, gallon/ft<NUM>·day) was calculated by measuring the amount of water permeated for <NUM> minutes at <NUM>, and salt concentrations before and after the permeation were analyzed using a conductivity meter to calculate salt rejection. The results are as shown in the following Table <NUM>.

Through the results of Table <NUM>, it was identified that Examples <NUM> and <NUM> had much higher flux than the comparative examples while salt rejection is either similar to or higher than the comparative examples.

The moisture content in each step of the manufacturing process of the examples and the comparative examples was measured under conditions as follows after drying the sample for <NUM> minute and <NUM> seconds at <NUM> using an IR heater, and through changes in the weight before and after the drying.

The results are described in the following Table <NUM>.

Through the results of Table <NUM>, it was seen that, when the pretreatment process was used as in Examples <NUM> and <NUM> and Comparative Example <NUM>, s moisture content before the hypochlorite treatment was measured to be <NUM>±<NUM>%. In addition, it was identified that the moisture content was measured high at <NUM>±<NUM>% when the hypochlorite treatment was conducted in the module step as in Comparative Example <NUM>, whereas the moisture content was low at <NUM>±<NUM>% after manufacturing the module in Examples <NUM> and <NUM> and Comparative Examples <NUM> to <NUM> conducting the hypochlorite treatment in the membrane step. In other words, through the moisture content in each step, it was identified which process was used in which step.

For each of the water-treatment membranes manufactured in the examples and the comparative examples, the membrane was cut to a <NUM> cmx5 cm size sample before being rolled to a water-treatment module, and using a CM-3600D spectrophotometer of Konica Minolta, Inc. , CIE L*a*b* color coordinate values were measured based on specular component included (SCI).

In addition, after storing the sample for <NUM> days at room temperature, color coordinate values were measured in the same manner, and the results are shown in the following Table <NUM>.

Through the results of Table <NUM>, it was identified that, in the water-treatment membrane according to one embodiment of the present specification, the color coordinate values at the beginning measured within <NUM> minutes after preparing the sample and the color coordinate values measured after storing for <NUM> days all satisfied [Equation <NUM>] to [Equation <NUM>]. It was seen through color coordinate values that the degree of discoloration was severe in the comparative examples, and this means that there are many residual monomers that were not able to be changed to a polymer by participating in the reaction, and means that such residual monomers may act as an impurity afterward declining performance of the membrane.

In addition, it was identified that, in Example <NUM> having a pretreatment solution temperature of <NUM> or higher, the L* value increased after storing for <NUM> days compared to the value at the beginning, whereas, in Example <NUM>, the L* value decreased after storing for <NUM> days compared to the value at the beginning. Through this, it was identified that, when the pretreatment solution temperature was <NUM> or higher, there were no substances subject to an oxidation reaction even when the time of storage increased since monomers remaining after forming the polyamide active layer were quickly removed, and as a result, an effect of maintaining or increasing the L* value of the membrane was obtained.

For each of the water-treatment membranes manufactured in Examples <NUM> and <NUM> and Comparative Example <NUM>, the content of each element obtained through a result of elemental analysis on the surface is shown in the following Table <NUM>. In addition, graphs of elemental analysis results on Example <NUM> and Comparative Example <NUM> are shown in <FIG> and <FIG>.

In the elemental analysis, an optoelectronic spectrometer (XPS or ESCA, model name: K-Alpha, Thermo Fisher Scientific Inc) was used, and while using Al Kα (X-ray spot size: <NUM>) as an X-ray source, analyses were made on <NUM> or more spots per sample, and data were collected by scanning <NUM> or more times per spot.

Claim 1:
A method of testing a water-treatment membrane after hypochlorite treatment by its discoloration, the water-treatment membrane comprising:
a porous support (<NUM>);
a polyamide active layer (<NUM>) provided on the porous support (<NUM>) and including chlorine on a surface thereof,characterized in that CIE L*a*b* color coordinate values after storing for <NUM> days or longer at <NUM> to <NUM> satisfy the following [Equation <NUM>] to [Equation <NUM>] <MAT> <MAT> <MAT>