KR101114537B1 - Method of preparing a highly durable reverse osmosis membrane - Google Patents

Abstract

The present invention comprises the steps of forming a thin polyamide film on the porous support layer; After forming the polyamide thin film, treating the polyamide thin film surface with a glycol solution to increase the wettability of the polyamide thin film surface; Activating the polyamide thin film surface using an etchant to generate radicals on the wetted polyamide thin film surface; First coating the activated polyamide thin film surface with an aqueous solution of a silane derivative compound; Coating the first coated polyamide thin film surface with an aqueous solution of silane derivative compound, followed by secondary coating with an aqueous solution of glycidyl compound and drying; And it provides a method for producing a durable reverse osmosis membrane comprising the step of washing the dried membrane with a basic aqueous solution and the reverse osmosis membrane prepared accordingly.

Polyamide thin film, silane derivative compound, glycidyl compound, reverse osmosis membrane, durability, fouling resistance, chlorine resistance

Description

Manufacturing method of reverse osmosis membrane improved durability {METHOD OF PREPARING A HIGHLY DURABLE REVERSE OSMOSIS MEMBRANE}

The present invention relates to a method for preparing a reverse osmosis membrane having improved durability, and a reverse osmosis membrane prepared accordingly.

Generally, the materials in the solution can be separated from the solvent using various kinds of selective membranes. Such membranes include microfiltration membranes, ultrafiltration membranes, nano separation membranes, and reverse osmosis membranes. Reverse osmosis membranes are useful for desalination of semi-saline or seawater. Demineralization of semi-saline or seawater using a reverse osmosis membrane is a filtration process in which water is separated from the brine by pressurization so as not to pass salt and other dissolved ions or molecules. Osmotic pressure is inevitably generated in such a filtration process. As the concentration of raw water is higher, a higher osmotic pressure is generated, and thus a higher pressure is required to treat it.

In case of water supplied through tap water, it must go through microbial removal process by chlorine disinfection treatment. In addition, in the case of industrial water and seawater desalination, chlorine disinfection and removal of residual chlorine are essential to prevent contamination of the reverse osmosis membrane by microorganisms. However, there is a lot of difficulty in maintenance because chlorine removal is mainly performed by activated carbon and chemical treatment.

Widely used as a reverse osmosis membrane is a membrane comprising a porous support layer and a polyamide membrane on the support layer. The polyamide membrane can be obtained by interfacial polymerization of a polyfunctional amine and a polyfunctional acyl halide.

US Pat. No. 4,227,344, filed by Cadotte, discloses aromatic polys obtained by interfacial polymerization of an aromatic acyl halide having three or more acyl halide functional groups with an aromatic polyfunctional amine containing two primary amine substituents. Techniques for amide thin films are presented. Although it is true that the membrane of the cadot has excellent flow rate and salt removal rate, various studies have been conducted on increasing the flow rate and improving the salt removal rate of the polyamide reverse osmosis composite membrane.

Tomashke US Pat. No. 4,872,984 discloses (a) an aqueous solution consisting of an aromatic polyamine reactant having two or more amine functional groups and an amine salt of a monomer to form a liquid layer on the microporous support layer. Applying a porous support; (b) contacting the liquid layer with an organic solution comprising an aromatic polyfunctional acyl halide or mixture thereof having an average of about 2.2 or more acyl halides, which are functional groups that react with amines; And (c) drying the product of step (b) to form a permeable membrane. Tomashke's membrane production method is a method of greatly improving the permeate yield by adding a step of adding the amine salt of the monomer to the existing membrane preparation method.

Hirose, U.S. Patent No. 5,614,099, presents a control technique for the structure of a polyamide surface layer. The Hirose patent relates to a process for producing a film having a surface roughness formed at a predetermined level or more, based on Tomashke's film production method, that surface roughness is closely related to flow rate improvement.

However, although the above-mentioned polyamide-based reverse osmosis membrane has excellent separation performance and permeation performance, the membrane surface is adsorbed due to the adsorption of membrane surface by suspended matter or dissolved pollutant in solution, and thus the permeate flow rate is reduced. can not avoid. In addition, there is a serious problem of degradation of the separation performance of polyamide main chains due to residual chlorine generated by membrane cleaning agents such as sodium hypochlorite (NaOCl) used to prevent this.

The techniques used to reduce the contamination of polyamide membranes to date are mainly using a double coating process. However, each of these coatings has a problem of increasing the membrane resistance, thereby showing a low permeation performance compared to the permeation performance of the polyamide composite membrane before coating.

Accordingly, the present inventors have continued to develop a polyamide membrane having improved permeability and durability against chlorine and contamination at the same time. As a result, the chlorine resistance and fouling resistance produced by first coating treatment with an aqueous solution of silane derivative compound having chlorine resistance on the surface of the polyamide membrane and secondary coating treatment with an aqueous solution of glycidyl compound having a fouling resistance group at the same time. It is to develop a method of manufacturing a reverse osmosis membrane with improved durability and a reverse osmosis composite membrane prepared accordingly.

The present invention is to provide a method for producing a reverse osmosis membrane having improved durability having both stain resistance and chlorine resistance by first coating the polyamide membrane surface with an aqueous solution of a silane derivative compound and secondary coating with an aqueous solution of glycidyl compound. It is for.

In addition, the present invention by coating the silane derivative compound on the surface of the activated polyamide film using an etchant to provide a stable chemical bond of the compound and the polyamide film and to coat the glycidyl compound thereon, to prevent contamination and flame It is to provide a method for producing a reverse osmosis membrane having a firing at the same time.

In addition, the present invention is to provide an improved reverse osmosis membrane manufactured by the above method.

In addition, the present invention is to provide a reverse osmosis membrane having excellent permeability.

According to one aspect of the invention, the present invention comprises the steps of forming a polyamide thin film on the porous support layer; After forming the polyamide thin film, treating the polyamide thin film surface with a glycol solution to increase the wettability of the polyamide thin film surface; Activating the polyamide thin film surface using an etchant to generate radicals on the wetted polyamide thin film surface; First coating the activated polyamide thin film surface with an aqueous solution of a silane derivative compound; Coating the first coated polyamide thin film surface with an aqueous solution of silane derivative compound, followed by secondary coating with an aqueous solution of glycidyl compound and drying; And it provides a method for producing a durable reverse osmosis membrane comprising the step of washing the dried membrane with a basic aqueous solution.

According to one embodiment of the present invention, the polyamide thin film formed on the porous support layer is treated with a glycol to increase the wettability of the surface of the polyamide thin film and the etching agent to generate radicals on the surface of the polyamide thin film with increased wettability It is characterized in that the surface treatment through the step of activating the polyamide thin film surface using.

The glycol may be selected from the group consisting of propylene glycol, ethylene glycol, propylene glycol, diethylene glycol, and mixtures thereof, but is not necessarily limited thereto.

The concentration of the glycol solution may be 0.1 to 10% by weight.

The etchant may be selected from the group consisting of potassium hydroxide, sodium hydroxide, sodium ethoxide, potassium persulfate and potassium metabisulfite.

The concentration of the etchant may be 0.001 to 1.0M.

According to an embodiment of the present invention, the silane derivative compound may be an alkoxyalkylsilane compound represented by Formula 1 below:

[Formula 1]

R ¹ is a substituted or unsubstituted C6-C18 alkyl group; Substituted or unsubstituted vinyl group; Substituted or unsubstituted aromatic group; Selected from the group consisting of a substituted or unsubstituted phenyl group, wherein R ² is a C1-C4 alkyl group; And n is an integer equal to 1, 2 or 3.

According to one embodiment of the present invention, the glycidyl compound includes three to four triatomic cyclic epoxy functional groups, and one functional group selected from the group consisting of an ether functional group, a glyceryl functional group and a sorbitol functional group It may be a glycidyl compound containing the above.

According to one embodiment of the present invention, the polyamide thin film may be further coated with a glycidyl compound aqueous solution and dried, followed by hot air drying in a range of 25 to 100 ° C.

The reverse osmosis membrane according to the manufacturing method of the present invention is provided by primary coating treatment with an aqueous solution of a silane derivative compound having flame-resistant plasticity on the surface of a polyamide thin film and secondary coating treatment with an aqueous solution of glycidyl compound having a foul-resistant group. . When the primary coating with the aqueous solution of the compound in the silane induction has an effect of improving the durability of the residual chlorine by the silane functional group, the secondary coating with the aqueous solution of glycidyl compound has the effect of improving the stain resistance at the same time.

In particular, the inclusion of the glycidyl functional group, which is a polar functional group, results in an improvement in the initial flow rate and the cumulative flow rate during the contamination process compared to the membrane coated with only the silane functional group. In addition, the method of the present invention performs the surface treatment step to improve the wettability on the surface of the polyamide film and the step of forming a radical using an etchant to confirm the direct chemical reaction between the silane and the polyamide by XPS analysis. If omitted, it was confirmed that no chemical bonding between the silane and the polyamide polymer occurred (see FIGS. 1 and 2).

According to the production method according to the present invention, the surface treatment step to improve the wettability on the surface of the polyamide film and the step of forming a radical using an etchant has the effect that the silane compound is stably mounted on the surface of the polyamide film.

In another aspect of the present invention, the present invention provides an improved reverse osmosis membrane manufactured by the above-mentioned manufacturing method.

Reverse osmosis membrane according to the production method of the present invention, the first coating treatment with a solution of the silane derivative compound having a flame-resistant plasticity on the surface of the polyamide thin film and a second coating treatment with a glycidyl compound aqueous solution having a fouling-resistant group, Its durability against contamination and contamination is improved at the same time, and its permeation performance is also excellent.

Method for producing a reverse osmosis membrane of the present invention,

After forming the polyamide thin film, treating the polyamide thin film surface with a glycol solution to increase the wettability of the polyamide thin film surface;

Activating the polyamide thin film surface using an etchant to generate radicals on the wetted polyamide thin film surface;

First coating the activated polyamide thin film surface with an aqueous solution of a silane derivative compound;

Coating the first coated polyamide thin film surface with an aqueous solution of silane derivative compound, followed by secondary coating with an aqueous solution of glycidyl compound and drying; And

Washing the dried membrane with an aqueous basic solution.

Hereinafter, the present invention will be described in more detail.

The forming of the polyamide thin film on the porous support layer may use a method known in the art. Generally, a polyfunctional amine solution is applied on a microporous support layer, and the excess aqueous solution is removed, and then, on the surface thereof, an amine reactive compound selected from the group consisting of polyfunctional acyl halide, polyfunctional sulfonyl halide, and polyfunctional isocyanate is applied. It forms through the process of contacting and containing surface-polymerization of the containing organic solution.

The porous support layer refers to a microporous support. There is no particular limitation on the material and the manufacturing method of the porous support layer, any one known in the art can be used. The micropores should be large enough to allow permeate to penetrate and not be large enough to interfere with the crosslinking of the thin film formed on the micropores. The pore size of the porous support layer is preferably 1 to 500 nm, but is not necessarily limited thereto. In the case of using a porous support layer having a pore size exceeding 500 nm, a problem may occur that the film of the surface layer obtained by interfacial polymerization penetrates between the pore diameters of the support layer and thus fails to form a normal flat membrane.

There is no particular limitation on the material that can be used as the microporous support layer, any one used in the art may be used. Preferred examples include polymers such as polysulfone, polyethersulfone, polyimide, polyamide, polyetheramide, polyacrylonitrile, polymethylmethacrylate, polyethylene, polypropylene, polyvinylidene fluoride and the like. The thickness of the microporous layer support layer is also not particularly limited, but is preferably 25 to 130 μm.

There is no particular limitation on the kind of the polyfunctional amine, and any material known in the art may be used, and a single polyfunctional amine group or a mixture thereof may be used. Specific examples thereof include aromatic primary diamines or substituents thereof of methylphenyldiamine or paraphenyldiamine; Analogues having N-alkyl or aryl substituents; Aliphatic ring primary amines such as alkanediamine or cyclohexanediamine, aliphatic ring secondary amines such as piperazine and alkyl derivatives thereof, and aromatic secondary diamines. Substituents of the aromatic primary substituent include an alkyl group, an alkoxy group hydroxyalkyl group or a halogen atom.

The polyfunctional amine is provided in the form of an aqueous solution. The polyfunctional amine may be contained in 0.1 to 30% by weight. The pH of the polyfunctional amine aqueous solution is 7 to 13. In addition, an acid acceptor such as hydroxide, carboxylate, carbonate, borate, alkali metal phosphate, and trialkylamine is added to the aqueous polyfunctional amine solution to neutralize acid (hydrochloric acid, etc.) generated during interfacial polymerization. Sometimes.

The polyfunctional amine solution, that is, an aqueous polyamine solution, may be used alone or in addition to the additives mentioned in the prior art. Polar protic solvents, mixtures of polar protic solvents, mixtures of polar protic solvents and polar aprotic solvents can be used to improve flow rates. Polar protic solvents include alcohols, dialcohols, alcohol-ethers, and the like. Polar aprotic solvents include ether derivatives such as diethylene glycol and di (ethylene glycol) tert-butyl methyl ether, dimethyl sulfoxide and butyl sulfoxide. And sulfoxide derivatives such as tetramethylene sulfoxide. In addition, additives containing an amine salt of the monomer can also be used for improving the flow rate.

The polyfunctional acyl halides used in the interfacial polymerization reaction are aromatic compounds having 2 to 3 carboxylic acid halides, and trimezoyl chloride, isophthaloyl chloride, terephthaloyl chloride and mixtures thereof can be widely used. Aromatic polyfunctional acyl halides may be used alone or in a mixed state. Examples thereof include trimesoyl chloride, mixture of trimesoyl chloride and isophthaloyl chloride, mixture of trimesoyl chloride and terephthaloyl chloride, and the content of the total carboxylic acid halide in the organic solvent may be 0.005 to 5% by weight. .

The present invention comprises forming a polyamide thin film on the porous support layer, and then treating glycol with respect to the polyamide thin film to increase the wettability of the polyamide thin film surface; And activating the polyamide thin film surface using an etchant to generate radicals on the wetted polyamide thin film surface.

Treatment of glycol with the polyamide thin film to increase the wettability of the polyamide thin film surface is important for the reverse osmosis membrane for water treatment. This is to reduce the damage of the film due to deterioration when hot air drying after each of the above-mentioned primary and secondary coating processes. Specifically, if the glycol is not treated, the polyamide polymer network may be damaged in the heat treatment step during the two coating processes, thereby reducing the membrane initial performance.

Treatment of glycol with respect to the polyamide thin film to increase the wettability of the surface of the polyamide thin film may be performed using a glycol represented by the following formula (2).

[Formula 2]

The glycol may be selected from the group consisting of propylene glycol, ethylene glycol, propylene glycol, diethylene glycol, and mixtures thereof, but is not necessarily limited thereto. The glycol treatment is a process in which a polyamide thin film is immersed in a glycol solution for a predetermined time and then dried.

The concentration of the glycol solution is preferably 0.1 to 10% by weight. If the concentration is more than 10% by weight, the thickness of the coating layer may be thickened may cause a problem of less water permeability, and less than 0.1% by weight may cause a problem of poor wettability.

Next, the step of activating the polyamide thin film surface by etching with an etchant to generate radicals on the surface of the polyamide thin film having increased wettability.

를 통하여 화학적으로 안정하게 결합되어 있다. 이러한 안정적 결합이 이루어진 폴리아미드 박막 표면에, 단순히 실란 코팅액을 폴리아미드 박막 표면에 스프레이 방식이나 침 지(dipping) 형태의 코팅 방법을 사용한다 하더라도 아미드 관능기와 실란 화합물간의 화학적 반응이 일어날 수 있는 라디칼이 형성 되어있지 못하므로, 폴리아미드 표면에서 코팅제가 안정하게 결합되기는 어렵고 물리적 결합으로 표면에 층을 형성할 뿐이다.The reason for activating the polyamide thin film surface is to form a chemical bond with the silane compound or the glycidyl compound. Polyamide thin film surface formed after the glycol treatment as described above, the amide group

It is chemically stable through. On the surface of the polyamide thin film formed with such a stable bond, even if a silane coating liquid is simply sprayed or dipping onto the surface of the polyamide thin film, radicals capable of chemical reaction between the amide functional group and the silane compound may occur. Since it is not formed, it is difficult for the coating agent to be stably bonded on the polyamide surface and only a layer is formed on the surface by physical bonding.

Therefore, in the present invention, a chemical bond with the silane compound is performed by etching the polyamide thin film surface using an etchant for chemical bonding with the silane compound, and then forming radicals to activate the polyamide thin film surface before the epoxy silane coating. Enhance the bond by generating bonds.

In the present invention, an etching agent is used to activate a polyamide structure and stably fix a silane compound having a hydrophobic functional group thereto and to coat a compound glycidyl compound having a hydrophilic functional group on the coated surface. To form a structure.

The etchant that can be used in the present invention may be selected from the group consisting of potassium hydroxide, sodium hydroxide, sodium ethoxide, potassium persulfate and potassium metabisulfite, but is not necessarily limited thereto. In particular, potassium persulfate (K ₂ S ₂ O ₈ ) represented by the following Chemical Formula 3 or potassium metabisulfite (K ₂ S ₂ O ₅ ) represented by the following Chemical Formula 4 may be used, but is not necessarily limited thereto.

(3)

[Formula 4]

The concentration of the etchant may be 0.001 to 1.0 M. If the concentration exceeds 1.0 M, there is a risk of damaging the membrane, and if the concentration is less than 0.001 M, there may occur a problem that the radical reaction does not sufficiently occur.

Important in the radical formation process is time, because if the radical formation process is performed for too long, the performance of the film is rather deteriorated. The time for using the etchant to activate the polyamide film is preferably 10 to 60 minutes.

The present invention is to remove the bio-contaminants (bio swarms, moss, etc.) of the surface mainly generated in the reverse osmosis process. In general, sodium hypochlorite is used as a cleaning agent to remove bio-contaminants, which causes damage to the reverse osmosis membrane because dissolved chlorine in the compound breaks the main chain of the polyamide of the reverse osmosis membrane and shortens the lifespan. do. The present invention solves this problem and provides a reverse osmosis composite membrane having improved chlorine resistance and fouling resistance.

In the present invention, after the polyamide thin film is formed, the polyamide thin film surface is first coated with an aqueous solution of a silane derivative compound. As the silane derivative compound, an alkoxyalkylsilane compound represented by Formula 1 may be used:

R ¹ is a substituted or unsubstituted C6-C18 alkyl group; Substituted or unsubstituted vinyl group; Substituted or unsubstituted aromatic group; Selected from the group consisting of a substituted or unsubstituted phenyl group, wherein R ² is a C1-C4 alkyl group; And n is an integer equal to 1, 2 or 3.

As the alkoxyalkylsilane compound used in the present invention, it is preferable to use an alkoxyalkylsilane compound in which R ¹ is a substituted or unsubstituted C8-18 alkyl group in Chemical Formula 1 in terms of durability against chlorine, and R ¹ in Chemical Formula ¹ It is more preferable to use the alkoxyalkylsilane compound which is this substituted or unsubstituted C8 alkyl group.

As the alkoxyalkylsilane compound in the present invention, trialkoxyalkylsilane, dialkoxydialkylsilane, alkoxytrialkylsilane and mixtures thereof may be used.

More preferably, the alkyl group may further include at least one functional group selected from the group consisting of an amine group, an aldehyde group, an acid group, an ether group, a ketone group, an alcohol group, an ester group, a halogen group and an aromatic group.

In the present invention, the alkoxyalkylsilane compound is trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, dimethylethylmethoxysilane, dimethylethylethoxysilane, dimethylethylpropoxysilane, diethylmethylmethoxysilane , Diethylmethylethoxysilane, diethylmethylpropoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, methyltripropoxysilane , Ethyltripropoxysilane, propyltripropoxysilane, pentyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, (trifluoromethyl Trimethoxysilane, (3,3,3, -trifluoropropyl) trimethoxysilane, 3-aminopropyl-methoxy-diethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, phenethyl Trimethock At least one selected from the group consisting of cysilane, vinyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and mixtures thereof can be used.

After preparing an aqueous solution of the silane derivative compound in which 0.1 to 4% by weight of the above-mentioned silane derivative compound and 96 to 99.9% by weight of the coating solvent are prepared, the aqueous solution is first coated by self-assembly on the polyamide thin film surface. It is preferable to use ethanol as the coating solvent, but is not limited thereto. When the content of the silane derivative compound is less than 0.1% by weight, the sol-gel reaction of the silane may be insignificant on the surface of the membrane to cover the entire surface of the polyamide, which may cause problems in that chlorine resistance or fouling resistance may not be properly represented. In addition, when the content of the silane derivative compound is more than 4% by weight, the sol-gel reaction of the silane occurs thick on the surface of the membrane, so that even if the chlorine resistance and fouling resistance effect is obtained, the flow rate decreases, and thus may not be a useful membrane. .

As a result of coating the silane derivative compound aqueous solution on the surface of the polyamide thin film by self-assembly, a non-polar nanostructure is formed on the surface of the polyamide thin film to improve chlorine resistance. More specifically, the aqueous solution of the silane derivative compound is uniformly distributed on the surface of the polyamide activated by the etchant by polymerization in a polymer state through a sol-gel reaction by a self-assembly method. Here, self-assembly means that before the sol-gel polymerization reaction of the n-alkyl silane coupling agent occurs, the monomers are preceded by a thermodynamically stable structure, and then the polymer is polymerized by hydrolysis between adjacent silane monomers. It is said to form. At this time, one alkoxide of the silane is activated to react with a polar atom on the surface of the polyamide thin film in which the radical is generated, thereby enabling polyamide-polysiloxane immobilization. In addition, there is an advantage that the non-polar nanostructures are easily controlled because the non-polar functional groups exist in an arrangement state before the polymerization reaction occurs.

As a result, when the permeation process proceeds through the polyamide thin film, the phenomenon of chlorine radicals and chlorine substituent radicals penetrating the polyamide thin film can be alleviated to improve durability (ie, chlorine resistance) to the chlorine-containing solution.

The method of coating the silane derivative compound aqueous solution on the surface of the polyamide thin film as described above is well known to those skilled in the art to which the present invention pertains, and a detailed description thereof will be omitted.

Next, the polyamide thin film surface is first coated with an aqueous solution of silane derivative compound, and then secondly coated with an aqueous solution of glycidyl compound and dried. The glycidyl compound may include 3 to 4 triatomic cyclic epoxy groups, and may include one or more functional groups selected from the group consisting of an ether group, a glyceryl group, and a jobitol group.

Examples of the glycidyl compound containing the three epoxy groups include glycerol triglycidyl ether, diglycerol triglycidyl ether, pentaerythritol triglycidyl ether, zobitoltriglycidyl ether, and glycerol propoxylate Triglycidyl ether, trimethylolpropanetriglycidyl ether, 1,1,1, -tris (hydroxymethyl) ethanetriglycidyl ether, 1,1,1-tris (hydroxyphenyl) ethanetriglycidyl Dyl ether, trishydroxymethylnitromethanetriglycidyl ether, tris (2,3-epoxypropyl) isocyanurate, fluoroglucinol triglycidyl ether, N, N-diglycidyl-4 Glycidyloxyaniline, epichlorohydrin and 1,3,5-tris (2-hydroxyethyl) cyanuric acid reactant, epichlorohydrin and tris (hydroxymethyl) aminomethane reactant May be used.

Examples of the glycidyl compound containing the four epoxy groups include zobitol tetraglycidyl ether, pentaerythritol tetraglycidyl ether, polyglycerol tetraglycidyl ether and 4,4'-methylenebis ( N, N- diglycidyl aniline) can be used.

In addition, the glycidyl compound may be a water-soluble glycidyl compound, and a glycidyl compound soluble in a mixed solution having a water content of 50% by volume or more in the water-ethanol mixed solution may be used.

Using the glycidyl compound aqueous solution prepared by mixing 0.1 to 4% by weight of the glycidyl compound and 96 to 99.9% by weight of the coating solvent, the second coating on the first coating layer with the aqueous solution of the silane derivative compound. Water is mainly used as the coating solvent, but is not limited thereto.

 As such, the secondary coating of the aqueous glycidyl compound solution on the nanostructure formed by primary coating the aqueous silane derivative compound on the surface of the polyamide thin film serves as a crosslinking function to firmly fix the nanostructure, as well as the secondary The coating allows hydrophilic groups to be placed on the polyamide thin film, reducing contamination at the membrane surface.

As described above, the present invention is the first coating treatment with an aqueous solution of silane derivative compound having chlorine resistance, and the second coating treatment with an aqueous solution of glycidyl compound having a fouling resistance group to satisfy both chlorine resistance and fouling resistance at the same time. It is possible to provide an improved reverse osmosis membrane.

According to one embodiment of the present invention, the present invention preferably is to dry the sample through a hot air drying or drying process. The hot air drying step or drying step is to increase the effective concentration of the substance in which the sol-gel reaction occurs.

Specifically, after the first coating on the surface of the polyamide thin film with an aqueous solution of a silane derivative compound and subsequently the second coating with an aqueous solution of glycidyl compound, it may further comprise the step of hot air drying in the range of 25 ~ 100 ℃. This hot air drying step can effectively fix the first layer and the second layer formed by using the silane derivative compound and the glycidyl compound on the polyamide thin film surface to the polyamide thin film surface. Since the hot air drying process itself is well known in the art, a detailed description thereof will be omitted.

Then, the dried polyamide membrane is washed with a basic aqueous solution. There is no restriction on the kind of the basic aqueous solution, and materials used in the art may be used without limitation. In the present invention, a sodium carbonate solution or a sodium hydroxide solution was used.

In another aspect of the present invention, the present invention provides a reverse osmosis membrane prepared by the above-mentioned manufacturing method. Specifically, the reverse osmosis membrane, the porous support layer; A polyamide thin film formed on the porous support layer; It comprises a silane derivative compound layer and a glycidyl compound layer coated on the polyamide thin film surface.

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

Example

Preparation of Polyamide Membrane

In the present invention, in order to minimize the change in physical properties of the polyamide membrane manufacturing process, the same commercial membrane made as a module was decomposed and used as a substrate. Commercial membrane was selected from reverse osmosis membrane (CPA2-4040) for brackish water of the United States Hydronautics. The porous support layer is a thin film having a thickness of 100-150 μm and a pore size of 0.01 μm cast with a polysulfone on a polyester nonwoven fabric). Specifically, the reverse osmosis membrane used in the present invention is a polyamide-based industrial reverse osmosis membrane, and a polysulfone polymer support of 40-50 μm is cast on a polyester nonwoven fabric reinforcement layer of about 90-95 μm, and the polysulfone polymer support is about Polyamide polymers of less than 2 μm have the structure of a coated membrane.

Initial salt removal rate and initial permeate flow rate measurement

In the present invention, the initial salt removal rate and the initial permeation flux were measured using an aqueous 2,000 ppm NaCl solution. The reverse osmosis membrane cell evaluation device used in this experiment was composed of a flat plate permeation cell, a high pressure pump, a storage tank, and a cooling device. The flat permeation cell has a cross-flow method, and the effective permeation area is 27.01 cm. ² After the washed membrane was installed in the permeation cell, the preliminary operation of the evaluation apparatus was sufficiently performed for 1 hour until the pressure and water permeability reached a normal state, and then the water permeability was calculated by measuring the amount of water permeated every 30 minutes, The removal rate was calculated by analyzing the salt concentration before and after the permeation using a conductivity meter.

Chlorine Resistance Evaluation

Evaluation of chlorine resistance in the present invention was made in a mixed aqueous solution containing 2,000 ppm NaCl and 2,000 ppm NaOCl. In order to exclude the penetration of chlorine and salts through the nonwoven fabric and polysulfone layer, which are porous support layers of the reverse osmosis membrane, the mixed solution is poured in the evaluator for about 10 to 30 seconds and then kept at a stop state so that the salt penetrates only to the polyamide surface. The change in salt removal rate and flow rate were measured with time.

Pollution resistance evaluation

For fouling resistance evaluation, 2,000 ppm of NaCl and 100 ppm of casein solution were used. After evaluating the initial permeation properties, 100 ppm casein aqueous solution was added directly to the evaluator's tank, and the permeability properties were immediately evaluated. The change in water permeability before and after the plot was plotted and the slope of the case was calculated by computer to evaluate the degree of contamination. In the present invention, as a contaminant used as a pollution resistance evaluation experiment, casein, which is mostly protein, was dissolved in an aqueous solution having a pH of 11 or higher. Bio fouling is artificially contaminated on the surface of the membrane to show the contamination characteristics before and after coating in MFI index.

Measurement of Chemical Changes on Polyamide Thin Film Surfaces

Chemical changes of the polyamide thin film surface were confirmed using XPS (X-ray Photoelectron Spectroscopy), a direct analytical method for identifying damage and deformation of the active layer.

Membrane Contamination Index Measurement

Membrane Fouling Index (MFI) is defined by the following equation, and is mainly a membrane contamination index that measures the degree of contamination of a microfiltration membrane.

[Equation]

The membrane fouling index is shown on the premise that the thickness of the cake layer (contamination) formed on the membrane surface is proportional to the amount of filtration. Specifically, the permeate flux is measured and multiplied by the membrane area A to obtain the flow rate Q. By multiplying this value by the filtration time (t), the filtration amount (V) can be calculated, and when the x-axis is represented by the filtration amount (V) and the y-axis is represented by 1 / Q, the slope of the t / V vs. V curve is the MFI value. . The meanings of the symbols in the formula are as follows:

ΔP (intermediate differential pressure) = ΔPm + ΔPp + ΔPc

    ΔPm: pressure drop caused by passing through the membrane itself

    ΔPp: pressure drop due to the concentration polarization layer

    ΔPc: pressure loss due to cake bed

Rm: membrane resistance

A: the area of the membrane

η: absolute viscosity

-Cb: bulk layer concentration / Cc: cake layer concentration

rc: particle radius of the cake

When the MFI is applied to the reverse osmosis membrane process, the decrease in permeation before and after the input of the pollutant can be measured and expressed as a change in the slope to compare the contamination of the reverse osmosis membrane. In other words, according to the MFI definition, the higher the MFI value of the polyamide reverse osmosis membrane, the better the membrane contamination.

Example 1

The surface of the polyamide film (CPA2-4040) mentioned above was washed with distilled water and then immersed in a 5 wt% propylene glycol (PG) solution for 30 minutes and then dried in an oven at 70 ° C. for 5 minutes. Thereafter it was immersed in 0.1 M potassium persulfate solution for 30 minutes. Next, an aqueous solution of octyltriethoxysilane (OcTES) (solvent: ethanol) having a concentration of 1.5% by weight was coated on the surface of the polyamide thin film, followed by hot air drying at 70 ° C. for 10 minutes to obtain a primary coating. Subsequently, a second coating of 1.0 wt% of zobitoltriglycidyl ether (solvent: water) on the surface of the octyltriethoxysilane-polyamide reverse osmosis membrane was carried out by hot air drying at 70 ° C. for 10 minutes, and then for 24 hours. It can be dried at room temperature to obtain a double coating film. After drying the membrane obtained, the surface of the membrane was washed with distilled water, and then immersed in an aqueous NaOH solution at pH 10-11 for 2 hours or more and washed with water to obtain a reverse osmosis membrane.

The separator was subjected to surface analysis using XPS (K-Alpha, Thermo Electron, UK), and the results are shown in FIG. 1. In addition, the secondary coating membrane was measured for the initial permeation performance at a pressure of 225 psi in 2,000 ppm NaCl aqueous solution and the results are shown in Table 1.

For chlorine resistance evaluation, 2,000 ppm NaCl aqueous solution and 2,000 ppm NaOCl aqueous solution were mixed, and durability evaluation for chlorine when the evaluator was operated at a pressure of 225 psi was performed. The performance of the reverse osmosis membrane was measured after the lapse of 6 hours immediately after idling, with the membrane mounted in the permeation cell. Table 2 shows the results of the performance change over time.

For the evaluation of fouling resistance, 2,000 ppm NaCl and 100 ppm casein mixed aqueous solution were used, and the salt removal rate and permeate flow rate of the reverse osmosis membrane were measured immediately after the casein aqueous solution and 2 hours at 225 psi pressure. At this time, the permeate flow rate was converted into MFI index to measure the membrane contamination, and the results are shown in Table 3.

Example 2

Reverse osmosis membranes were prepared in the same manner as in Example 1, except that the coating was performed using polyglycerol triglycidyl ether having a concentration of 1.0 wt%. The secondary coated membrane was measured for performance at a pressure of 225 psi in an aqueous 2,000 ppm NaCl solution. The results are shown in Table 1.

Chlorine resistance evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

Pollution-resistant smoothing was carried out in the same manner as in Example 1. The results and the MFI index are shown in Table 3.

Example 3

Reverse osmosis membranes were prepared in the same manner as in Example 1 except for the second coating using a diglycerol triglycidyl ether having a concentration of 1.0% by weight. The secondary coated membrane was measured for performance at a pressure of 225 psi in an aqueous 2,000 ppm NaCl solution. The results are shown in Table 1.

Chlorine resistance evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

Pollution-resistant smoothing was carried out in the same manner as in Example 1. The results and the MFI index are shown in Table 3.

Comparative Example 1

The surface of the polyamide membrane (CPA2-4040) was immersed in distilled water for at least 1 hour without any treatment, and the performance thereof was measured at a pressure of 225 psi in a 2,000 ppm aqueous NaCl solution by the method of Example 1. The results are shown in Table 1.

Chlorine resistance evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

Pollution resistance evaluation was performed in the same manner as in Example 1. The results and the MFI index are shown in Table 3.

Comparative Example 2

A reverse osmosis membrane was obtained in the same manner as in Example 1 except that the propylene glycol and potassium persulfate (K ₂ S ₂ O ₈ ) solutions were not treated on the surface of the polyamide membrane (CPA2-4040). .

The performance was measured by the method of Example 1 at a pressure of 225 psi in an aqueous 2,000 ppm NaCl solution. The results are shown in Table 1.

Chlorine resistance evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

Pollution-resistant smoothing was carried out in the same manner as in Example 1. The results and the MFI index are shown in Table 3.

Comparative Example 3

A reverse osmosis membrane was obtained in the same manner as in Example 1, except that propylene glycol was not treated on the surface of the polyamide membrane (CPA2-4040).

The performance was measured by the method of Example 1 at a pressure of 225 psi in an aqueous 2,000 ppm NaCl solution. The results are shown in Table 1.

Chlorine resistance evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

Pollution resistance evaluation was performed in the same manner as in Example 1. The results and the MFI index are shown in Table 3.

Comparative Example 4

The surface of the polyamide film (CPA2-4040) mentioned above was washed with distilled water and then immersed in a 5 wt% propylene glycol (PG) solution for 30 minutes and then dried in an oven at 70 ° C. for 5 minutes. After that, it was immersed in 0.1 M potassium persulfate solution for 30 minutes. Next, an aqueous solution of octyltriethoxysilane (OcTES) (solvent: ethanol) having a concentration of 1.5% by weight was coated on the surface of the polyamide thin film, followed by hot air drying at 70 ° C. for 10 minutes to obtain a primary coating. Thereafter, Example 1 except that the second coating was not performed on the octyltriethoxysilane-polyamide reverse osmosis membrane with a concentration of 1.0 wt% of zobitoltriglycidyl ether (solvent: water). The same process as in the dried to obtain a separator consisting of only a silane coating.

The silane coating-only separator thus obtained was measured at an initial permeation performance at a pressure of 225 psi in an aqueous solution of 2,000 ppm NaCl, and the results are shown in Table 1.

Chlorine resistance evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

Pollution resistance evaluation was performed in the same manner as in Example 1. The results and the MFI index are shown in Table 3.

[Table 1]

TABLE 2

[Table 3]

Comparative example  5

The composite membrane obtained in Comparative Example 2 was subjected to surface analysis using XPS (K-Alpha, Thermo Electron, UK) and the results are shown in FIG. 2.

As shown in Table 1 to 3, the reverse osmosis membrane according to the present invention can be seen that the effect is excellent while appearing at the same time chlorine resistance and fouling resistance. Therefore, the reverse osmosis membrane according to the present invention is not only resistant to cleaning agents such as sodium hypochlorite (NaOCl), which is introduced to reduce membrane contamination, but also can reduce the contamination of the membrane surface, so that the reverse osmosis membrane is used for seawater desalination facilities and ultrapure water. It can be applied to manufacturing facilities.

In addition, as shown in Figure 1 XPS analysis results of the reverse osmosis membrane of the present invention, the binding energy peak value is (a) the binding in the form of Si-OC ₆ H ₅ group at 283.92 eV based on C1s; (b) In view of the presence of Si-OC ₆ H ₅ bonds at 532.19 eV based on O1s, it can be seen that the desired silane compound layer was chemically stably formed on the surface of the coating separator.

On the other hand, as shown in FIG. 2, the results of XPS analysis of the polyamide-based separator without the PG and the etchant treatment on the surface of the polyamide thin film, that is, no radical formation (etching process) are as follows. Binding energy peak values are (a) 287.01 eV and 284.06 eV based on C1s; (b) 530.34 eV and 531.5 eV based on O1s, and the combination of CH and C = O and CO of glycidyl compound, a secondary coating agent, can be seen but Since no bond with Si can be confirmed, it can be seen that a crosslink cannot be formed chemically and stably.

1 is a graph showing the results of surface analysis using XPS (X-ray Photoelectron Spectroscopy) for the reverse osmosis membrane prepared in Example 1 of the present invention. 2 is a graph showing the results of surface analysis of the reverse osmosis membrane prepared in Comparative Example 5 of the present invention using XPS (X-ray Photoelectron Spectroscopy).

Claims (18)

Forming a thin polyamide film on the porous support layer; After forming the polyamide thin film, treating the polyamide thin film surface with a glycol solution to increase the wettability of the polyamide thin film surface; Activating the polyamide thin film surface using an etchant to generate radicals on the wetted polyamide thin film surface; First coating the activated polyamide thin film surface with an aqueous solution of a silane derivative compound; Coating the first coated polyamide thin film surface with an aqueous solution of silane derivative compound, followed by secondary coating with an aqueous glycidyl compound solution and drying, followed by hot air drying in a range of 25 to 100 ° C .; And Washing the dried membrane with a basic aqueous solution, The glycidyl compound aqueous solution is prepared by mixing 0.1 to 4% by weight of a soluble glycidyl compound and 96 to 99.9% by weight of a mixed solution having a water content of 50% by volume or more in a water-ethanol mixed solution. Method for producing a reverse osmosis membrane. The method of claim 1, The glycol is a propylene glycol, ethylene glycol, propylene glycol, diethylene glycol and a method for producing a durable reverse osmosis membrane, characterized in that selected from the group consisting of a mixture thereof. The method of claim 1, The concentration of the glycol solution is a method for producing a polyamide reverse osmosis composite membrane, characterized in that 0.1 to 10% by weight. The method of claim 1, The etchant is a method for producing a polyamide reverse osmosis composite membrane, characterized in that selected from the group consisting of potassium hydroxide, sodium hydroxide, sodium ethoxide, potassium persulfate and potassium metabisulfite. The method of claim 1, The concentration of the etchant is a method for producing a polyamide reverse osmosis composite membrane, characterized in that 0.001 to 1.0 M. The method of claim 1, The silane derivative compound aqueous solution is a durable reverse osmosis membrane production method characterized in that the mixture is prepared by mixing 0.1 to 4% by weight of the silane derivative compound and 96 to 99.9% by weight of ethanol. The method of claim 1, The silane derivative compound is a method for producing a durable reverse osmosis membrane, characterized in that the alkoxyalkylsilane compound represented by the formula (1): [Formula 1]

R ¹ is a substituted or unsubstituted C6-C18 alkyl group; Substituted or unsubstituted vinyl group; And a substituted or unsubstituted phenyl group; R ² is a C1-C4 alkyl group; And n is an integer equal to 1, 2 or 3. The method of claim 7, wherein The alkyl group further includes at least one functional group selected from the group consisting of an amine group, an aldehyde group, an acid group, an ether group, a ketone group, an alcohol group, an ester group, a halogen group, and an aromatic group. Manufacturing method. The method of claim 7, wherein The alkoxyalkylsilane compound is a method for producing a durable reverse osmosis membrane, characterized in that selected from the group consisting of trialkoxyalkylsilane, dialkoxydialkylsilane, alkoxytrialkylsilane and mixtures thereof. The method of claim 7, wherein The alkoxyalkylsilane compound is trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, dimethylethylmethoxysilane, dimethylethylethoxysilane, dimethylethylpropoxysilane, diethylmethylmethoxysilane, diethylmethyl Methoxysilane, diethylmethylpropoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, methyltripropoxysilane, ethyltripropoxy Silane, propyltripropoxysilane, pentyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, (trifluoromethyl) trimethoxysilane , (3,3,3, -trifluoropropyl) trimethoxysilane, 3-aminopropyl-methoxy-diethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, phenethyltrimethoxysilane, Vinyl tree Method for producing a silane, 3-aminopropyltrimethoxysilane, 3-amino propyl triethoxysilane, and the first reverse osmosis membrane having improved durability, characterized in that at least member selected from the group consisting of a mixture thereof. delete The method of claim 1, The glycidyl compound includes 3 to 4 triatomic cyclic epoxy groups, and durability improved reverse osmosis comprising at least one functional group selected from the group consisting of an ether group, a glyceryl group and a jobitol group Method for producing a permeation membrane. The method of claim 12, Glycidyl compounds containing the three epoxy groups include glycerol triglycidyl ether, diglycerol triglycidyl ether, pentaerythritol triglycidyl ether, zobitol triglycidyl ether, and glycerol propoxylate triglycol. Cydyl ether, trimethylolpropanetriglycidyl ether, 1,1,1, -tris (hydroxymethyl) ethanetriglycidyl ether, 1,1,1-tris (hydroxyphenyl) ethanetriglycid Dyl ether, trishydroxymethylnitromethanetriglycidyl ether, tris (2,3-epoxypropyl) isocyanurate, fluoroglucinol triglycidyl ether, N, N-diglycidyl-4 -Selected from the group consisting of glycidyloxyaniline, epichlorohydrin and 1,3,5-tris (2-hydroxyethyl) cyanuric acid reactant, epichlorohydrin and tris (hydroxymethyl) aminomethane reactant Improved durability, characterized in that Method for producing a reverse osmosis membrane. The method of claim 12, Glycidyl compounds comprising the four epoxy groups include zobitol tetraglycidyl ether, pentaerythritol tetraglycidyl ether, polyglycerol tetraglycidyl ether and 4,4'-methylenebis (N , N- diglycidyl aniline) method of producing a reverse osmosis membrane with improved durability characterized in that it is selected from the group consisting of. The method of claim 1, The glycidyl compound is a durable reverse osmosis membrane production method characterized in that the water-soluble glycidyl compound. delete delete The reverse osmosis membrane prepared according to any one of claims 1 to 10 and 12 to 15.

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