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 layer.

In the water-treatment membrane, impurity rejection is used as an important indicator representing membrane performance.

<CIT> and <CIT> disclose a method for manufacturing a selective separation membrane having excellent stain/fouling resistance comprising a step to form a polyamide thin film on a porous support and a step to form a hydrophilic coating film on the polyamide thin film.

<CIT> discloses a method for preparing a polyamide using a composition comprising a nylon salt (<NUM>:<NUM> salt of hexamethylenediamine and adipic acid), tris(hydroxymethyl) aminomethane, adipic acid, demineralized water and an antifoam.

<CIT> and <CIT> disclose a method for preparing a reverse osmosis membrane using an aqueous mPD solution comprising a surfactant.

<CIT> discloses a method for preparing a reverse osmosis membrane using an aqueous mPD solution comprising glucosamine hydrochloride.

<CIT> discloses a method for preparing a reverse osmosis membrane using an aqueous mPD solution comprising glucosamine and a surfactant.

The present invention is directed to providing a method for manufacturing a water-treatment membrane using a composition for interfacial polymerizing polyamide.

The present invention provides a method for manufacturing a water-treatment membrane including preparing a porous support; and forming a polyamide active layer on the porous support by interfacial polymerizing a composition for interfacial polymerizing polyamide and an acyl halide compound,
the composition for interfacial polymerizing polyamide comprising:.

The present invention also provides a water-treatment membrane obtainable from the method mentioned above including a porous support; and a polyamide active layer provided on the porous support and including a structure represented by the following Chemical Formula <NUM> or <NUM>. <CHM>
<CHM>
<CHM>
In Chemical Formulae <NUM> and <NUM>,.

The present invention further provides a water-treatment module including one or more of the water-treatment membranes mentioned above.

Manufacturing a water-treatment membrane using a composition for interfacial polymerizing polyamide according to the method of the present invention is effective in enhancing alcohol rejection and salt rejection since a polyamide active layer includes a number of hydroxyl groups.

<FIG> illustrates a water-treatment membrane according to one embodiment of the present specification.

When preparing a polyamide active layer using the composition for interfacial polymerizing polyamide according to the present disclosure, the composition participates in polyamide formation by having reactivity with a monomer of an organic layer, and therefore, a number of hydroxyl groups are produced in the polyamide active layer. This leads to an increase in the hydrogen bonding energy with alcohols, which leads to not only enhancing alcohol rejection, but also obtaining an effect of increasing salt rejection since the hydroxyl groups are present in the empty space formed during the polyamide active layer forming process.

Specifically, the amino group (-NH<NUM>) may have a chemical bond formed at the hydrogen position, and therefore, may participate in a reaction when forming the polyamide active layer and be present in a form included in the polyamide chain, and, compared to other functional groups, the hydroxyl group bonding to a carbon atoms is highly effective in increasing alcohol rejection by forming a strong hydrogen bond with an alcohol.

In the present specification, the 'chain-type structure' means a structure that does not include a ring, and a chain-type compound may freely rotate compared to a structure including a ring and thereby has a wider radius of functional group movements. Accordingly, an effect of enhancing alcohol rejection is superior compared to a ring-type compound.

In addition, when using the composition for interfacial polymerizing polyamide according to the present disclosure in interfacial polymerization, the additive may be spread over all regions, and a greater effect may be obtained compared to a method of coating the additive on some regions.

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, the alkyl group may be linear or branched, and although not particularly limited thereto, the number of carbon atoms is preferably from <NUM> to <NUM>. Specific examples thereof may include methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, <NUM>-methylbutyl, <NUM>-ethylbutyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, <NUM>-methylpentyl, <NUM>-methylpentyl, <NUM>-methyl-<NUM>-pentyl, <NUM>,<NUM>-dimethylbutyl, <NUM>-ethylbutyl, heptyl, n-heptyl, <NUM>-methylhexyl, cyclopentylmethyl, cyclohexylmethyl, octyl, n-octyl, tert-octyl, <NUM>-methylheptyl, <NUM>-ethylhexyl, <NUM>-propylpentyl, n-nonyl, <NUM>,<NUM>-dimethylheptyl, <NUM>-ethyl-propyl, <NUM>,<NUM>-dimethyl-propyl, isohexyl, <NUM>-methylhexyl, <NUM>-methylhexyl and <NUM>-methylhexyl, but are not limited thereto.

The additive is represented by the following Chemical Formula <NUM> or <NUM>. <CHM>
<CHM>.

In one embodiment of the present specification, m is an integer of <NUM> to <NUM>.

In one embodiment of the present specification, m is <NUM>.

In one embodiment of the present specification, n1 to n3 are each an integer of <NUM> to <NUM>.

In one embodiment of the present specification, n1 to n3 are each <NUM>.

In one embodiment of the present specification, X1 to X3 are each a hydroxyl group.

In one embodiment of the present specification, the additive is one or more types selected from among D-glucamine and tris(hydroxymethyl)aminomethane.

The content of the additive is 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 composition for interfacial polymerizing polyamide.

When the additive content is less than <NUM> wt%, effects obtained by the additive are insignificant, and when the content is greater than <NUM> wt%, the polyamide chain is formed short, which adversely affects active layer formation.

The amine compound is 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).

The content of the amine compound is 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 composition for interfacial polymerizing polyamide.

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

The composition for interfacial polymerizing polyamide further includes 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. According to one embodiment of the present specification, the surfactant may be selected from among sodium lauryl sulphate (SLS); alkyl ether sulphates; alkyl sulphates; 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 sulphate (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.

The content of the surfactant is from <NUM> wt% to <NUM> wt% based on <NUM> wt% of the composition for interfacial polymerizing polyamide.

When the surfactant is included in the above-mentioned range, interfacial energy between the aqueous solution layer and the organic layer including an organic solution decreases increasing reactivity, and an effect of improving coating efficiency is obtained.

In one embodiment of the present specification, the composition for interfacial polymerizing polyamide may include water as a solvent, and the remainder excluding the amine compound, the additive and the surfactant in the composition may all be water.

The method for manufacturing a water-treatment membrane according to the present invention includes preparing a porous support; and forming a polyamide active layer on the porous support by interfacial polymerizing the composition for interfacial polymerizing polyamide and an acyl halide compound.

In one embodiment of the present specification, the preparing of a porous support may be conducted 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 and polyvinylidene fluoride, but are not limited thereto.

In one embodiment of the present specification, the polymer material may be polysulfone.

In one embodiment of the present specification, the forming of a polyamide active layer may include forming an aqueous solution layer including the composition for interfacial polymerizing polyamide 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 including the composition for interfacial polymerizing polyamide, 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.

In one embodiment of the present specification, a method for forming the aqueous solution layer including the composition for interfacial polymerizing polyamide 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.

In one embodiment of the present specification, 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 is too much of the aqueous solution present on the support, and when the aqueous solution is non-uniformly distributed, a non-uniform 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 trimesoyl chloride (TMC) , isophthaloyl chloride, terephthaloyl chloride, or a mixture of two or more types thereof, and preferably, the acyl halide compound may be trimesoyl chloride (TMC).

In one embodiment of the present specification, 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.

The 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 water-treatment membrane according to the present invention includes a porous support; and a polyamide active layer provided on the porous support and including a structure represented by the following Chemical Formula <NUM> or <NUM>. <CHM>
<CHM>.

In one embodiment of the present specification, Chemical Formulae <NUM> and <NUM> may bond to the polyamide polymer to form an - NHCO- type chemical bond.

In one embodiment of the present specification, the water-treatment membrane has isopropyl alcohol (IPA) rejection of <NUM>% or greater, preferably <NUM>% or greater, and more preferably <NUM>% or greater.

The IPA rejection is based on a value measured when applying an aqueous solution containing <NUM> ppm of isopropyl alcohol (IPA) flowing at a flow rate of <NUM>/min on the water-treatment membrane surface with a pressure of <NUM> MPa (<NUM> psi) for <NUM> minutes or longer at <NUM>.

For each constitution of the water-treatment membrane, descriptions on the composition for interfacial polymerizing polyamide and the method for manufacturing a water-treatment membrane described above may apply.

<FIG> illustrates the water-treatment membrane according to one embodiment of the present specification. Specifically, <FIG> illustrates the water-treatment membrane in which a non-woven fabric (<NUM>), a porous support layer (<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 according to one embodiment of the present specification are not limited to the structure of <FIG>, and additional constitutions may be further included.

In one embodiment of the present specification, 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 according to the present invention includes one or more of the water-treatment membranes described above.

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 and a spiral wound module. In addition, as long as the water-treatment module includes the reverse osmosis membrane according to the present invention 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 according to the present invention 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 invention will be described in detail with reference to examples in order to specifically describe the present invention. However, examples according to the present specification may be modified to various different forms. The examples of the present specification are provided in order to more fully describe the present invention to those having average knowledge in the art.

<NUM> wt% of a polysulfone solid was introduced to an N,N-dimethylformamide (DMF) solution 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 having porosity of <NUM>%.

On the support, an aqueous solution layer was formed by coating a composition for interfacial polymerizing polyamide including, based on <NUM> wt% of the composition, <NUM> wt% of m-phenylenediamine (mPD), <NUM> wt% of sodium lauryl sulphate (SLS) as a surfactant, and the remainder of water.

Subsequently, an organic solution including <NUM> wt% of trimesoyl chloride (TMC) and <NUM> wt% of Isopar-G was coated on the aqueous solution layer to form an organic layer, and the result was interfacial polymerized to form a polyamide active layer, and as a result, a water-treatment membrane was manufactured.

A water-treatment membrane was manufactured in the same manner as in Comparative Example <NUM> except that <NUM> wt% of <NUM>,<NUM>-diaminobenzenesulfonic acid was added to the composition for interfacial polymerizing polyamide.

A water-treatment membrane was manufactured in the same manner as in Comparative Example <NUM> except that the <NUM>,<NUM>-diaminobenzenesulfonic acid content was changed to <NUM> wt%.

A water-treatment membrane was manufactured in the same manner as in Comparative Example <NUM> except that <NUM> wt% of <NUM>-aminoresorcinol hydrochloride was added to the composition for interfacial polymerizing polyamide.

A water-treatment membrane was manufactured in the same manner as in Comparative Example <NUM> except that the <NUM>-aminoresorcinol hydrochloride content was changed to <NUM> wt%.

A water-treatment membrane was manufactured in the same manner as in Comparative Example <NUM> except that <NUM> wt% of D-glucamine was added to the composition for interfacial polymerizing polyamide.

A water-treatment membrane was manufactured in the same manner as in Comparative Example <NUM> except that <NUM> wt% of tris(hydroxymethyl)aminomethane was added to the composition for interfacial polymerizing polyamide.

In order to measure IPA rejection and flux (GFD) of the water-treatment membranes manufactured according to the examples and the comparative examples, a water-treatment module formed including a flat-plate permeation cell, a high-pressure pump, a storage tank and a cooling device was used. The flat-plate permeation cell was a cross-flow type and had an effective permeation area of <NUM><NUM>. After installing the water-treatment membrane on the permeation cell, a sufficient preliminary operation was performed for approximately <NUM> hour using tertiary distilled water for device stabilization.

After that, device stabilization was confirmed by operating the device for approximately <NUM> hour with <NUM> ppm of IPA under the condition of <NUM> MPa (<NUM> psi) and a flow rate of <NUM>/min, and then the amount of water permeated for <NUM> minutes at <NUM> was measured, and alcohol concentrations before and after the permeation were analyzed using a conductivity meter to calculate alcohol rejection. The results are as shown in the following Table <NUM>.

After that, device stabilization was confirmed by operating the device for approximately <NUM> hour using <NUM>,<NUM> ppm of an aqueous NaCl solution under the condition of <NUM> MPa (<NUM> psi) and a flow rate of <NUM>/min, and then 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>.

From the results of Table <NUM>, it was identified that Examples <NUM> and <NUM> including the additive according to the present disclosure had salt rejection and IPA rejection enhanced compared to Comparative Examples <NUM> to <NUM> due to a hydroxyl group produced when forming the polyamide active layer.

Specifically, whereas Comparative Examples <NUM> and <NUM> using an additive in which a hydroxyl group bonds to sulfur instead of a carbon atom, and Comparative Examples <NUM> and <NUM> using an additive having a structure including a ring instead of a chain-type structure had salt rejection and IPA rejection decreased compared to even Comparative Example <NUM> that did not include an additive, Examples <NUM> and <NUM> using a chain-type-structured additive including a hydroxyl group bonding to a carbon atom had both salt rejection and IPA rejection increased compared to Comparative Example <NUM> that did not include an additive.

Claim 1:
A method for manufacturing a water-treatment membrane, the method comprising:
preparing a porous support; and
forming a polyamide active layer on the porous support by interfacial polymerizing a composition for interfacial polymerizing polyamide and an acyl halide compound,
the composition for interfacial polymerizing polyamide comprising:
an amine compound;
a chain-type-structured additive containing one or more amino groups and two or more hydroxyl groups bonding to a carbon atom; and
a surfactant,
wherein a content of the amine compound is from <NUM> wt% to <NUM> wt% based on <NUM> wt% of the composition for interfacial polymerizing polyamide,
a content of the additive is from <NUM> wt% to <NUM> wt% based on <NUM> wt% of the composition for interfacial polymerizing polyamide,
a content of the surfactant is from <NUM> wt% to <NUM> wt% based on <NUM> wt% of the composition for interfacial polymerizing polyamide,
the 'chain-type structure' means a structure that does not include a ring,
the polyamide active layer has a number of hydroxyl groups,
the amine compound is 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 a mixture thereof,
the acyl halide compound is trimesoyl chloride (TMC), isophthaloyl chloride, terephthaloyl chloride, or a mixture of two or more types thereof, and
the additive is represented by the following Chemical Formula <NUM> or <NUM>:
<CHM>
<CHM>
in Chemical Formulae <NUM> and <NUM>,
m and n1 to n3 are an integer of <NUM> to <NUM>; and
X1 to X3 are each a hydroxyl group; or an alkyl group, and at least two of X1 to X3 are a hydroxyl group.