JPH10174852A - Composite reverse osmotic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite reverse osmotic film excellent in salt blocking ratio and water permeability. SOLUTION: In the composite reverse osmotic film obtained by forming a thin film on the surface of a porous supporting body, the thin film is a polyamide thin film formed by the polymerization and condensation reaction of a compound having >=2 reactive amino groups with a polyfunctional acid halide compound having >=2 reactive acid halide groups, the specific surface area (A/B) of the surface area (A) in the liquid feed side of the thin film to the surface area (B) of the porous supporting body of the side in contact with the thin film is >=3 and the thin film is treated by the contact with an acid solution containing at least one of a salt and an organic material and having pH1-5. In such a case, the salt blocking ratio is >=99% and permeated flux is 1.4m<3> /m<2> .D at the time of evaluating the film at 25 deg.C under 7.5kgf/cm<2> operation pressure with an aq. solution containing 500ppm sodium chloride and having pH6.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite reverse osmosis membrane used for selectively separating components in a liquid mixture, and more particularly, to a polyamide thin film (an active layer or a polyamide film) provided on the surface of a porous support. (Sometimes referred to as a system skin layer) having high salt rejection and high permeation flux.

[0002] Composite reverse osmosis membranes are suitably used for producing ultrapure water, desalination of seawater or brackish water, etc. In addition, the composite reverse osmosis membrane is capable of removing pollutants such as dyeing wastewater and electrodeposition paint wastewater which cause pollution. Eliminate and recover contained pollutants or active substances,
In addition, it contributes to the closure of wastewater. Further, this composite reverse osmosis membrane can also be used in advanced processes such as concentration of active ingredients in the food industry and the like, and removal of harmful components in water purification and sewage applications.

[0003]

2. Description of the Related Art Conventionally, as a reverse osmosis membrane having a structure different from that of an asymmetric reverse osmosis membrane, a composite reverse osmosis comprising an active skin layer (thin film) having selective separation ability formed on the surface of a porous support. Films are known. As such a composite reverse osmosis membrane, for example, a membrane in which a polyamide thin film obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide is formed on the surface of a porous support is proposed. (For example, JP-A-55-147106,
JP-A-62-121603, JP-A-63-218
No. 208, Japanese Patent Publication No. 6-73617).

Although the composite reverse osmosis membrane has high desalination performance and water permeation performance, it is necessary to improve water permeability while maintaining higher desalination performance. It is desired from such points. In response to these demands, the use of various additives has been proposed (for example, JP-A-63-12310). But,
Although the use of this additive slightly improves the performance of the composite reverse osmosis membrane, it is still insufficient. In addition, a technique for treating a composite reverse osmosis membrane with an acid solution (for example, see
Although the composite reverse osmosis membrane obtained by this method has the highest permeation flux even at an operation pressure of 15 kgf / cm ² , its salt rejection is 99.2%. And the permeation flux is 1.5 m ³ / m ² / day,
Operating at half pressure, 7.5 kgf / cm ² , also reduces the permeation flux by half and greatly reduces the salt rejection. For this reason, the composite reverse osmosis membrane obtained by this technique cannot be used substantially under low pressure conditions of, for example, 7.5 kgf / cm ² , and, of course, is about 3 kgf / cm ^2, which is the tap water pressure of ordinary households. Under the condition of ultra-low pressure, almost no permeation flux is obtained, and it cannot be used.

[0005]

Accordingly, it is an object of the present invention to provide a composite reverse osmosis membrane having both high salt rejection and water permeation performance.

[0006]

In order to achieve the above object, a composite reverse osmosis membrane according to the present invention is a composite reverse osmosis membrane in which a thin film is formed on the surface of a porous support.
A polyamide thin film formed by a polycondensation reaction between a compound having two or more reactive amino groups and a polyfunctional acid halide having two or more reactive acid halide groups, and a liquid supply of the thin film The specific surface area (A / B) of the surface area (A) of the porous support and the surface area (B) of the porous support in contact with the thin film is 3 or more, and the thin film contains at least one of a salt and an organic substance. It is characterized by being subjected to a contact treatment with an acid solution having a pH of from 1 to 5 contained therein.

[0007] Since the composite reverse osmosis membrane having such a configuration has both a high salt rejection and a high water permeation performance, it can be used even at a low pressure such as the tap water pressure of ordinary households.

The specific surface area can be specifically expressed by the following (Equation 1).

(Equation 1)

The surface area of the thin film on the liquid supply side is, in other words, the surface area of the surface opposite to the surface in contact with the porous support. On the other hand, the surface area of the porous support on the side in contact with the thin film refers to the area of the porous support in contact with the thin film.

The method for determining the surface area and the specific surface area can be determined according to a general method for determining a surface area or a specific surface area, and the method is not particularly limited. For example, a method using a surface area measuring device, a specific surface area measuring device, a scanning electron microscope (SEM, FE-SEM), a transmission electron microscope (TEM) or the like can be used.

The preferred range of the specific surface area is 3
To 1,000, particularly preferably 3 to 500.

[0012] In the composite reverse osmosis membrane of the present invention, specific membrane performance values include sodium chloride at a temperature of 25 ° C.
When the membrane performance was evaluated using an aqueous solution having a pH of 6.5 containing 0 ppm and an operating pressure of 7.5 kgf / cm ² , the salt rejection was 99% or more and the permeation flux was 1.4 m ³ / m ^2.
Days or more.

In the composite reverse osmosis membrane of the present invention, p
As the salts contained in the acid solution of H1 to H5, a mixture of a trialkylamine and an organic acid is preferable, and as the organic substance, a polyhydric alcohol is preferable.

[0014]

Next, the present invention will be described in detail. The composite reverse osmosis membrane of the present invention comprises at least one of a porous support, a compound having two or more reactive amino groups, a polyfunctional acid halide having two or more reactive acid halide groups, a salt, and an organic substance. PH 1 containing the substance
5 is prepared using the acid solution.

In the present invention, the contact treatment with the acid solution is important. The permeation flux of the composite reverse osmosis membrane not treated with the acid solution is high to some extent, but not at the level targeted by the present invention. That is, the salt rejection in membrane performance was 99% or more and the permeation flow rate was 1% when evaluated at a temperature of 25 ° C. and a pH 6.5 aqueous solution containing 500 ppm of sodium chloride at an operating pressure of 7.5 kgf / cm ^2. .4m
^In order to obtain a high performance of ³ / m ² · day or more, the contact treatment with the acid solution is required.

The pH of the acid solution needs to be in the range of 1-5. If the pH is less than 1, problems such as deterioration of the porous support and the like and reduction in the strength of the obtained composite reverse osmosis membrane occur. Conversely, if the pH exceeds 5, the effect of the treatment with the acid solution cannot be obtained. The p
A preferred range for H is 1-4.

The acid solution is, for example, an aqueous solution of an acidic substance. Examples of the acidic substance include phosphoric acid, hydrochloric acid, sulfuric acid, nitric acid and the like.

The acid solution needs to contain at least one of salts and organic substances. this is,
This is because an acid solution containing no salts or the like requires a long processing time to reach a predetermined permeation flux, and on the contrary, the permeation flux may decrease.

In this acid solution, the concentration of at least one of the salt and the organic substance is preferably in the range of 0.5 to 90% by weight of the whole acid solution.

Examples of the salts include normal salts, acidic salts, and basic salts. As mentioned above, among these, a mixture of a trialkylamine and an organic acid is preferred. Examples of the trialkylamine include triethylamine, trimethylamine, tripropylamine and the like. Examples of the organic acid include organic sulfonic acids such as camphorsulfonic acid and benzenesulfonic acid.

Examples of the organic substance include organic substances which dissolve in water in an amount of 0.5% by weight or more and which are adsorbed on the polyamide skin layer and do not reduce the amount of permeated water. As described above, the organic substance is preferably a polyhydric alcohol. Examples of the polyhydric alcohol include propylene glycol, ethylene glycol, diethylene glycol, glycerin and the like.

The compound having two or more reactive amino groups is not particularly limited as long as it is a polyfunctional amine. Examples thereof include an aromatic polyfunctional amine, an aliphatic polyfunctional amine, and an alicyclic polyfunctional amine. Is raised.

Examples of the aromatic polyfunctional amine include m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, and 3,5-diaminobenzo. Acid, 2,4
-Diaminotoluene, 2,4-diaminoanisole, amidole, xylylenediamine and the like.

Examples of the aliphatic polyfunctional amine include ethylenediamine, propylenediamine, and tris (2-diaminoethyl) amine.

Examples of the alicyclic polyfunctional amine include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane,
Piperazine, 2,5-dimethylpiperazine, 4-aminomethylpiperazine and the like.

These polyfunctional amines may be used alone or in combination of two or more.

The polyfunctional acid halide having two or more reactive acid halide groups is not particularly limited, and examples thereof include aromatic polyfunctional acid halides and aliphatic polyfunctional acid halides. And alicyclic polyfunctional acid halides.

Examples of the aromatic polyfunctional acid halide include trimesic acid chloride, terephthalic acid chloride, isophthalic acid chloride, biphenyldicarboxylic acid dichloride, benzenetrisulfonic acid chloride, benzenedisulfonic acid chloride, and chlorosulfonylbenzenedicarboxylic acid chloride. And naphthalenedicarboxylic acid dichloride.

The alicyclic polyfunctional acid halide includes, for example, propanetricarboxylic acid chloride, butanetricarboxylic acid chloride, pentanetricarboxylic acid chloride, glutaryl halide, adipoyl halide and the like.

Examples of the alicyclic polyfunctional acid halide include cyclopropanetricarboxylic acid chloride,
Cyclobutanetetracarboxylic acid chloride, cyclopentanetricarboxylic acid chloride, cyclopentanetetracarboxylic acid chloride, cyclohexanetricarboxylic acid chloride, tetrahydrofurantetracarboxylic acid chloride, cyclobutanedicarboxylic acid chloride, cyclopentanedicarboxylic acid chloride, cyclohexanedicarboxylic acid chloride, tetra Hydrofurandicarboxylic acid chloride and the like.

These acid halides may be used alone or in combination of two or more.

Next, in the present invention, in order to obtain the composite reverse osmosis membrane having the predetermined specific surface area and membrane performance, for example, the compound having two or more reactive amino groups and the two or more Compounds having a solubility parameter of 8 to 14 (cal / cm ³ ) ^1/2 , such as alcohols, ethers and ketones, in a reaction field of interfacial polycondensation with a polyfunctional acid halide compound having a reactive acid halide group. , Esters, halogenated hydrocarbons, sulfur-containing compounds, and the like.

Examples of the alcohols include ethanol, propanol, butanol, 1-pentanol, 2-pentanol, t-amyl alcohol, isoamyl alcohol, isobutyl alcohol, isopropyl alcohol, undecanol, 2-ethylbutanol,
2-ethylhexanol, octanol, cyclohexanol, tetrahydrofurfuryl alcohol, neopentyl glycol, t-butanol, benzyl alcohol, 4-methyl-2-pentanol, 3-methyl-2-
Butanol, allyl alcohol, ethylene glycol,
Examples thereof include diethylene glycol, triethylene glycol, and tetraethylene glycol.

Examples of the ethers include anisole, ethyl isoamyl ether, ethyl-t-butyl ether, ethyl benzyl ether, crown ether, cresyl methyl ether, diisoamyl ether,
Diisopropyl ether, diethyl ether, dioxane, diglycidyl ether, sionell, diphenyl ether, dibutyl ether, dipropyl ether, dibenzyl ether, dimethyl ether, tetrahydropyran, tetrahydrofuran, trioxane, dichloroethyl ether, butylphenyl ether, furan, methyl-t- Butyl ether, monodichlorodiethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, ethylene glycol monomethyl ether,
Examples include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and diethylene chlorohydrin.

Examples of the ketones include ethyl butyl ketone, diacetone alcohol, diisobutyl ketone, cyclohexanone, 2-heptanone, methyl isobutyl ketone, methyl ethyl ketone, methyl cyclohexane and the like.

Examples of the esters include methyl formate, ethyl formate, propyl formate, butyl formate, isobutyl formate, isoamyl formate, methyl acetate, ethyl acetate,
Examples include propyl acetate, isobutyl acetate, butyl acetate, amyl acetate and the like.

The halogenated hydrocarbons include, for example, allyl chloride, amyl chloride, dichloromethane,
Dichloroethane and the like.

The sulfur-containing compounds include, for example, dimethyl sulfoxide, sulfolane, thiolane and the like.

Of these, alcohols and ethers are particularly preferably used. These compounds can be present alone or in combination.

The porous support is not particularly limited as long as it can support a thin film. For example, materials such as polysulfone, polyarylethersulfone such as polyethersulfone, polyimide, and poly (vinylidene fluoride) can be used. Can be given. Among them, a porous support formed of polysulfone or polyaryletherphone is preferable because it is chemically, mechanically and thermally stable. The shape of the porous support is usually a membrane. The thickness of the porous support is
Usually about 25-125 μm, preferably about 40-75 μm
m, but is not necessarily limited to these.

Next, the composite reverse osmosis membrane of the present invention can be produced using the above-mentioned materials, for example, as follows.

That is, first, on the surface of the porous support,
The aqueous solution A of the compound having two or more reactive amino groups is applied to form a layer of a coating film. The concentration of the compound in the aqueous solution A is usually 0.01 to
It is 10% by weight, preferably 0.5 to 5% by weight. Then, a solution B of the polyfunctional acid halide having two or more reactive acid halide groups is applied on this layer.
The concentration of the polyfunctional acid halide in the solution B is usually 0.01 to 5% by weight of the whole solution B, preferably 0.1 to 5% by weight.
0.5 to 1% by weight. Then, the respective solutions A and B
After removing the excess solution of the above layer, the mixture is heat-dried at a temperature of about 20 to 150 ° C., preferably about 70 to 130 ° C., usually for about 1 to 10 minutes, preferably for about 2 to 8 minutes to interfacially polycondensate both compounds. By doing so, a polyamide thin film is formed. The thickness of this thin film is usually in the range of about 0.05-2 μm, preferably about 0.1-1 μm. When the compound having the predetermined solubility parameter is present in the reaction field of the interfacial polycondensation, for example, solutions A and B of both compounds are used.
May be added in advance in at least one of them, or may be added separately when applying the solutions A and B of the above both compounds.
In this way, a polyamide thin film is formed on the surface of the porous support, and a composite film is obtained.

In the aqueous solution A, in order to facilitate membrane formation or to improve the performance of the obtained composite reverse osmosis membrane,
For example, a water-soluble polymer such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrylic acid, and a polyhydric alcohol such as sorbitol and glycerin can be contained.

The aqueous solution A is described in Japanese Patent Application Laid-Open No. 2-187.
No. 135, for example, a tetraalkylammonium halide or a salt of a trialkylamine with an organic acid may be blended. This facilitates film formation, improves the absorbability of the aqueous solution A onto the support, and further promotes the polycondensation reaction.

The aqueous solution A may contain a surfactant such as sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium lauryl sulfate and the like.
These surfactants are effective in improving the wettability of the aqueous solution A onto the porous support.

Further, in order to promote the polycondensation reaction at the interface, sodium hydroxide or trisodium phosphate capable of removing hydrogen halide generated by the interface reaction, or an acylation catalyst or the like as an aqueous solution is used as a catalyst. Mixing with A is also effective.

Examples of the solvent of the solution B include a water-immiscible organic solvent, particularly, hexane, heptane,
Hydrocarbons such as octane, nonane, and cyclohexane, and halogenated hydrocarbons such as carbon tetrachloride, trichlorotrifluoroethane, difluorotetrachloroethane, and hexachloroethane are preferable.

Next, an acid solution C having a pH of 1 to 5 containing at least one of an organic substance and a salt is formed on the composite membrane.
By contacting with, a desired composite reverse osmosis membrane is obtained. This composite reverse osmosis membrane has a specific surface area of 3 or more, a salt rejection in membrane performance under the above conditions of 99% or more, and a permeation flux of 1.4 m ³ / m ² · day or more.

The shape of the composite film when performing the contact treatment with the acid solution C is not particularly limited.
Examples include a flat membrane shape and a spiral element shape.

Examples of the method for treating the composite membrane with the acid solution C include an immersion method under normal pressure, a normal water flow method, and a pressurized water flow method. The pressure in the case of the pressurized water flow method is not particularly limited as long as it is within the range of the resistance of the composite membrane or its member.

[0051]

Next, examples will be described together with comparative examples.

Example 1 m-phenylenediamine
Aqueous solution A containing 0% by weight, 0.15% by weight of sodium lauryl sulfate, 3.0% by weight of triethylamine, 6.0% by weight of camphorsulfonic acid and 5% by weight of isopropyl alcohol at the above-mentioned ratios. (System ultrafiltration membrane) for a few seconds, then remove excess solution A, and place the solution A on the support membrane.
Was formed. Then, an isoparaffinic hydrocarbon oil (IP101) containing 0.20% by weight of trimesic acid chloride and 0.05% by weight of isopropyl alcohol in the above ratio is provided on the surface of the supporting film (on the layer of the solution A).
6, manufactured by Idemitsu Chemical Co., Ltd.)
The resultant was held in a hot air dryer at 3 ° C. for 3 minutes to form a polyamide thin film on the support film, thereby obtaining a composite film.

A part of the obtained composite membrane was washed with water and dried,
The cross section of the composite reverse osmosis membrane was analyzed using a TEM, and the specific surface area was measured. As a result, the specific surface area was 4.3.

Next, phosphoric acid was added to aqueous solution C containing 3.0% by weight of triethylamine and 6.0% by weight of camphorsulfonic acid in the above ratio to adjust the pH to 2, and the remaining aqueous solution C was added to the aqueous solution C. The membrane was immersed at room temperature for 20 hours, then pulled up and washed with water to obtain a target composite reverse osmosis membrane.

The membrane performance of this composite reverse osmosis membrane was evaluated at 25 ° C. at a pressure of 7.5 kgf / cm ² of a saline solution containing 500 ppm of sodium chloride and having a pH of 6.5.
The salt rejection by permeate conductivity was 99.3%, and the permeate flux was 1.5 m ³ / m ² · day. Further, the membrane performance of this composite reverse osmosis membrane was measured using the above-mentioned saline solution at 3 kgf / cm.
^When evaluated at a pressure of ^2, the salt rejection by the permeate conductivity was 99.2%, and the permeation flux was 0.6 m ³ / m ^2.
It was a day. Further, the film performance of the same film was 1
When a salt solution having a pH of 6.5 containing 500 ppm of sodium chloride was used and evaluated at a pressure of 15 kgf / cm ² , the salt rejection by permeate conductivity was 99.3%.
The permeation flux was 2.9 m ³ / m ² · day.

(Comparative Example 1) In Example 1, the aqueous solution A
A composite reverse osmosis membrane was obtained in the same manner as in Example 1, except that isopropyl alcohol was not added to the acid chloride organic solution B. When the specific surface area of the obtained composite reverse osmosis membrane was examined in the same manner as in Example 1, it was 2.2.

When the performance of this composite reverse osmosis membrane was examined in the same manner as in Example 1, 7.5 kg of a saline solution containing 500 ppm of sodium chloride at 25 ° C. and pH 6.5 was used.
a salt rejection of 99.4 when evaluated at a pressure of f / cm ^2.
%, And the permeation flux was 0.66 m ³ / m ² · day.

Example 2 A composite reverse osmosis membrane was obtained in the same manner as in Example 1 except that propylene glycol was added to the aqueous phosphoric acid solution C in place of the salt of triethylamine and camphorsulfonic acid.

Comparative Example 2 A composite reverse osmosis membrane was obtained in the same manner as in Example 1 except that the salt of triethylamine and camphorsulfonic acid was not added to the phosphoric acid aqueous solution C.

Example 3 A composite reverse osmosis membrane was obtained in the same manner as in Example 1, except that the pH of the aqueous solution C was adjusted using hydrochloric acid instead of phosphoric acid.

Comparative Example 3 A composite reverse osmosis membrane was obtained in the same manner as in Example 1, except that the pH was not adjusted with phosphoric acid. The aqueous solution C at this time had a pH of 8
Met.

The membrane performance of the composite reverse osmosis membranes of Examples 2 and 3 and Comparative Examples 2 and 3 thus obtained was evaluated in the same manner as in Example 1. The results are shown in Table 1 below together with the results of Example 1 and Comparative Example 1.

[0063]

[Table 1]

From Table 1, it can be seen that the composite reverse osmosis membrane of the example of the present invention has both high salt rejection and high water permeation performance. In particular, it has been confirmed that the composite reverse osmosis membrane of the example of the present invention can be practically used even under ultra-low pressure conditions of about 3 kgf / cm ² . On the other hand, the composite reverse osmosis membrane of the comparative example had a high salt rejection but a low permeation flux.

[0065]

As described above, the composite reverse osmosis membrane of the present invention is a highly permeable composite reverse osmosis membrane which is excellent in both salt rejection and water permeability. Accordingly, by using the composite reverse osmosis membrane of the present invention, for example, desalination by desalination of seawater, seawater, or the like, production of ultrapure water required for the production of semiconductors, etc., power saving, energy saving, space saving, It can be implemented at low cost. In particular, 3kgf / c which is the water pressure of general households
Even ultra-low pressure conditions of about m ^2, for the composite reverse osmosis membrane of the present invention is practically available, it is manufactured modules using the composite reverse osmosis membrane of the present invention, a particular pump Even if not used, this module can be used as a household water purifier.

Claims (4)

[Claims] 1. A composite reverse osmosis membrane having a thin film formed on the surface of a porous support, wherein the thin film comprises a compound having two or more reactive amino groups and two or more reactive acid halide groups. A thin film made of polyamide formed by a polycondensation reaction with a polyfunctional acid-halogen compound, the surface area of the thin film on the liquid supply side (A) and the surface area of the porous support on the side in contact with the thin film (B) ) And the specific surface area (A / B) is 3
The composite reverse osmosis membrane described above, wherein the thin film is subjected to a contact treatment with an acid solution having a pH of 1 to 5 containing at least one of a salt and an organic substance. 2. 500p of sodium chloride at a temperature of 25 ° C.
operating pressure using an aqueous solution of pH 6.5 containing pm.
Composite reverse osmosis membrane salt rejection is the flux at 99% or more according to claim 1 is 1.4m ³ / m ² · day or more when evaluated film performance under conditions of 5 kgf / cm ^2. 3. The composite reverse osmosis membrane according to claim 1, wherein the salts contained in the acid solution having a pH of 1 to 5 are a mixture of a trialkylamine and an organic acid. 4. The composite reverse osmosis membrane according to claim 1, wherein the organic substance contained in the acid solution having a pH of 1 to 5 is a polyhydric alcohol.