JP2006026484A - Production method for composite reverse osmosis membrane with high salt suppression ratio - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite reverse osmosis membrane having a high salt suppression ratio and excellent separation performance of a non-electrolytic organic substance such as IPA and a non-dissociation substance in a usual pH area such as boron, and to provide its production method. <P>SOLUTION: The method for producing the composite reverse osmosis membrane comprising a polyamide-based skin layer and a fine porous support for supporting the layer is characterized in that the fine porous support is covered with an aqueous solution A containing a compound having two or more of reactive amino groups to form a covering layer and a solution B containing a multi-functional acid halide having two or more of reactive acid halide groups is subsequently brought into contact with the covering layer in an organic solvent containing cycloparaffin (C<SB>n</SB>H<SB>2n</SB>) having 7 or more of carbon numbers. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a composite reverse osmosis membrane for selectively separating components of a liquid mixture, and more specifically, a skin layer called an active layer or a thin film mainly composed of polyamide on a microporous support. The present invention relates to a composite reverse osmosis membrane production method and a composite reverse osmosis membrane having both high salt rejection and high permeability.

  Composite reverse osmosis membranes are widely used for the production of ultrapure water, brine or seawater desalination. It also contributes to the closure of wastewater by removing and collecting pollution sources or effective substances contained in it from stains that cause pollution, such as dye wastewater and electrodeposition paint wastewater. Furthermore, it is also used for the concentration of active ingredients in food applications.

  Conventionally, a composite reverse osmosis membrane is known in which an active skin layer (thin film) having a substantially selective separation property is formed on a porous support. Currently, many reverse osmosis membranes are known in which a skin layer made of polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional aromatic acid halide is formed on a support (for example, And see Patent Documents 1-4).

  Also proposed is a skin layer made of polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional alicyclic acid halide on a support (for example, see Patent Document 5). ). The composite reverse osmosis membrane has high desalting performance and water permeation performance, but for the purpose of improving the higher desalting performance and water permeation performance, the solvent of the solution containing the polyfunctional acid halide is saturated hydrocarbon. There has also been proposed a method in which interfacial polymerization is carried out using, for example, unsaturated hydrocarbon or halogenated hydrocarbon (see, for example, Patent Documents 6-9).

Conventional composite reverse osmosis membranes are excellent in desalting performance, water permeation performance and ionic substance separation performance, but dissociated in non-electrolytic organic substances such as isopropyl alcohol (IPA) and in the pH range where they are normally used. The blocking performance of substances that do not (e.g., boron) was not sufficient. IPA is a substance widely used in semiconductor factories and the like, and causes TOC to rise mainly in the process of producing ultrapure water. In addition, boron has toxicity such as causing onset of neuropathy and growth inhibition to human bodies and animals and plants, but since it is contained in seawater, boron removal is important in seawater desalination. Therefore, it has been desired to develop a composite reverse osmosis membrane capable of separating such harmful substances with a high rejection.
JP-A-55-147106 JP 62-121603 A JP-A-63-218208 JP-A-2-187135 JP-A-61-42308 JP-A-5-92130 JP-A-9-225278 Japanese Patent Laid-Open No. 5-76740 JP-A-5-137984

  An object of the present invention is to provide a composite reverse osmosis membrane having a high salt rejection and excellent in separation performance of non-electrolytic organic substances such as IPA and non-dissociating substances in a normal pH region such as boron, and a method for producing the same. It is in.

  As a result of intensive studies to solve the above problems, the present inventors have found that the formation of a polyamide skin layer by interfacial polymerization using a specific solvent is closely related to the performance of the composite reverse osmosis membrane. The invention has been completed.

That is, the method for producing a composite reverse osmosis membrane of the present invention is a method for producing a composite reverse osmosis membrane comprising a polyamide-based skin layer and a microporous support that supports the polyamide skin layer. A coating layer is formed by coating an aqueous solution A containing a compound having the following formula on a microporous support, and then, in an organic solvent containing cycloparaffin (C _n H _2n ) having 7 or more carbon atoms. A solution B comprising a polyfunctional acid halide having one or more reactive acid halide groups is brought into contact with the coating layer.

The cycloparaffin preferably has a boiling point of 90 to 250 ° C. Moreover, it is preferable that content of the cycloparaffin in the said organic solvent is 5 to 100 weight%.
The composite reverse osmosis membrane of the present invention is obtained by the above production method.

  The composite reverse osmosis membrane has a isopropyl alcohol rejection rate of 99% or more when a isopropyl alcohol aqueous solution having a temperature of 25 ° C., a pH of 6.5, and a concentration of 0.15% by weight is subjected to a permeation test under an operating pressure of 1.5 MPa. It is preferable.

  The composite reverse osmosis membrane has a boron rejection when a permeation test is performed at a temperature of 25 ° C., a pH of 6.5, and a 3.2 wt% saline solution containing 5 ppm of boron at an operating pressure of 5.5 MPa. Is 90% or more, and the salt rejection is preferably 99% or more.

  Furthermore, the composite reverse osmosis membrane has a isopropyl alcohol rejection of 99% or more when a permeation test is performed on an aqueous isopropyl alcohol solution at a temperature of 25 ° C., pH 6.5, and a concentration of 0.15 wt% under an operating pressure of 1.5 MPa. And a boron rejection rate of 90% or more when a permeation test of a saline solution having a temperature of 25 ° C., a pH of 6.5, and a boron concentration of 5 ppm containing 3.2 ppm by weight at an operating pressure of 5.5 MPa is performed. It is preferable that the salt rejection is 99% or more.

  According to the production method of the present invention, a polyamide skin layer having desired characteristics can be formed by selecting cycloparaffin as an organic solvent used for interfacial polymerization, maintaining high water permeability and combining high salt rejection. The composite reverse osmosis membrane can be easily produced. By selecting the cycloparaffin from those having a boiling point of 90 to 250 ° C., and selecting the content thereof in the organic solvent from 5 to 100% by weight, the water permeability and non-electrolyte organic substance blocking rate according to the application are selected. In addition, a composite reverse osmosis membrane having an excellent balance of salt rejection and boron rejection can be easily produced.

  Since the composite reverse osmosis membrane of the present invention is obtained by this production method, it maintains high water permeability, has a high salt rejection, non-electrolyte organic rejection, boron, etc. It has an excellent non-dissociation blocking rate and can be suitably used for desalination by desalting such as brine and seawater and for the production of ultrapure water required for semiconductor production.

The method for producing a composite reverse osmosis membrane of the present invention is a method for producing a composite reverse osmosis membrane comprising a polyamide skin layer and a microporous support that supports the polyamide skin layer. An aqueous solution A containing a compound having a reactive amino group is coated on a microporous support to form a coating layer, and then contains a cycloparaffin (C _n H _2n ) having 7 or more carbon atoms. A solution B comprising a polyfunctional acid halide having two or more reactive acid halide groups in an organic solvent is formed by contacting with the coating layer. That is, a polyamide-based skin layer containing a crosslinked polyamide as a main component is formed on a microporous support by interfacial polymerization of a compound having a polyfunctional amino group and a polyfunctional acid halide.

The cycloparaffin used in the present invention has 7 or more carbon atoms and is not particularly limited as long as it is an alicyclic hydrocarbon compound represented by the general formula: C _n H _2n , but has a boiling point (1013 hPa) of 90 to 250 ° C. It is preferable that it is 170-250 degreeC. When the boiling point is less than 90 ° C., such a compound has a high evaporation rate, and a sufficient interfacial polymerization reaction may not be performed. When the boiling point exceeds 250 ° C., it is difficult to evaporate from the surface of the formed polyamide skin layer, and it is difficult to remove it.

  Examples of the cycloparaffin include cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, cyclotridecane, and cyclotetradecane.

  The organic solvent contained in the solution B may be one kind of the cycloparaffin or a mixture of two or more kinds of the cycloparaffins. Furthermore, the cycloparaffin alone or a mixture thereof and another organic solvent may be used. A mixture may be used. In this case, the content of the cycloparaffin in the organic solvent is preferably 5 to 100% by weight, more preferably 30 to 100% by weight, and still more preferably 50 to 100% in order to exert the solvent effect of the cycloparaffin. % By weight.

  Examples of the other organic solvents include water-immiscible organic solvents such as aliphatic hydrocarbons such as hexane, heptane, octane, nonane, cyclohexane, carbon tetrachloride, trichlorotrifluoroethane, hexachloroethane. Halogenated hydrocarbons such as are preferably used.

  The polyfunctional acid halide having two or more reactive acid halide groups contained in the solution B used in the present invention is not particularly limited, and examples thereof include aromatic, aliphatic or alicyclic polyfunctional acid halides. It is done. These polyfunctional acid halides may be used alone or as a mixture.

  Examples of the aromatic polyfunctional acid halide include trimesic acid chloride, terephthalic acid chloride, isophthalic acid chloride, biphenyl dicarboxylic acid chloride, naphthalene dicarboxylic acid dichloride, benzene trisulfonic acid chloride, benzene disulfonic acid chloride, and chlorosulfonylbenzene dicarboxylic acid. Such as chloride.

  Examples of the aliphatic polyfunctional acid halide include propanetricarboxylic acid chloride, butanetricarboxylic acid chloride, pentanetricarboxylic acid chloride, glutaryl halide, adipoyl halide, and the like.

  Examples of the alicyclic polyfunctional acid halide include cyclopropane tricarboxylic acid chloride, cyclobutane tetracarboxylic acid chloride, cyclopentane tricarboxylic acid chloride, cyclopentane tetracarboxylic acid chloride, cyclohexane tricarboxylic acid chloride, and tetrahydrofuran tetracarboxylic acid. Examples include chloride, cyclopentane dicarboxylic acid chloride, cyclobutane dicarboxylic acid chloride, cyclohexane dicarboxylic acid chloride, and tetrahydrofurandicarboxylic acid chloride.

  The compound having two or more reactive amino groups contained in the aqueous solution A used in the present invention is not particularly limited as long as it is a polyfunctional amine, and an aromatic, aliphatic, or alicyclic polyfunctional amine is can give. The polyfunctional amines may be used alone or as a mixture.

  Examples of the aromatic polyfunctional amine include m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2 , 4-diaminotoluene, 2,6-diaminotoluene, 2,4-diaminoanisole, amidol, xylylenediamine and the like.

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

  Examples of the alicyclic polyfunctional amine include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, and 4-aminomethyl. Examples include piperazine.

  The aqueous solution A containing the polyfunctional amine is used to facilitate film formation or improve the performance of the obtained composite reverse osmosis membrane, for example, a polymer such as polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, sorbitol, A polyhydric alcohol such as glycerin can also be contained in water.

  In addition, tetraalkylammonium halides and salts of trialkylammonium and organic acids described in JP-A-2-187135 also improve the absorbability of the aqueous amine solution to the microporous support in order to facilitate film formation. Therefore, it is preferably used in terms of promoting the condensation reaction.

  Further, a surfactant such as sodium dodecylbenzenesulfonate and sodium dodecylsulfate (sodium laurylsulfate) can be contained in the aqueous solution A. These surfactants are effective in improving the wettability of the aqueous amine solution to the microporous 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 is used, or an acylation catalyst or the like is used as an aqueous solution A as a catalyst. It is also beneficial to contain it.

In order to increase the permeation flux, a compound having a solubility parameter of 8 to 14 (cal / cm ³ ) ^1/2 described in JP-A-8-224452 can also be added to the aqueous solution A.

  The concentration of the polyfunctional acid halide and polyfunctional amine contained in the solution B and the aqueous solution A is not particularly limited, but the polyfunctional acid halide is usually 0.01 to 5% by weight, preferably Is 0.05 to 1% by weight, and the polyfunctional amine is usually 0.1 to 10% by weight, preferably 0.5 to 5% by weight.

  In the present invention, the microporous support for supporting the skin layer is not particularly limited as long as it can support the skin layer. Usually, an ultrafiltration membrane having micropores with an average pore diameter of about 10 to 500 mm is preferably used. . Examples of the material for forming the microporous support may include various materials such as polysulfone and polyarylethersulfone such as polyethersulfone, polyimide, and polyvinylidene fluoride. From the viewpoint of stability, a microporous support made of polysulfone or polyarylethersulfone is preferably used. Such a microporous support usually has a thickness of about 25 to 125 μm, preferably about 40 to 75 μm, but is not necessarily limited thereto.

  First, the aqueous solution A containing the polyfunctional amine is coated on the microporous support, and then the excess aqueous solution is removed to form a coating layer.

  Next, the solution B containing the polyfunctional acid halide is brought into contact with the coating layer. After the excess solution is removed, condensation polymerization is performed at the interface generated by the contact. In the present invention, it is usually dried at about 20 to 180 ° C., preferably about 50 to 150 ° C., more preferably about 80 to 130 ° C. for about 1 to 10 minutes, preferably about 2 to 8 minutes. A polyamide-based skin layer is formed on the microporous support membrane.

  The thickness of the formed skin layer is usually about 0.05 to 2 μm, preferably about 0.1 to 1 μm.

  The composite reverse osmosis membrane of the present invention thus obtained maintains high water permeability and has a high salt rejection, and further in a non-electrolytic organic substance such as IPA and a normal pH region such as boron. It has excellent separation performance for non-dissociated substances, and is suitably used for desalination by the desalting of brine or seawater and for the production of ultrapure water.

  The composite reverse osmosis membrane of the present invention has a isopropyl alcohol blocking rate of 99% or more when a isopropyl alcohol aqueous solution having a temperature of 25 ° C., pH 6.5, and a concentration of 0.15 wt% is subjected to a permeation test under an operating pressure of 1.5 MPa. It is preferable that it is 99.3% or more.

  In addition, the composite reverse osmosis membrane of the present invention has a boron content when a permeation test is performed at a temperature of 25 ° C., a pH of 6.5, and a 3.2 wt% saline solution containing 5 ppm of boron at an operating pressure of 5.5 MPa. The rejection is preferably 90% or more, more preferably 92%.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In this example, a polysulfone ultrafiltration membrane was used as the microporous support.

Example 1
An aqueous solution A containing 3.0% by weight of m-phenylenediamine, 0.15% by weight of sodium lauryl sulfate, 2.0% by weight of triethylamine, and 4.0% by weight of camphorsulfonic acid was brought into contact with the porous polysulfone support membrane for several seconds. Thereafter, the excess aqueous solution was removed, and a coating layer composed of the aqueous solution A was formed on the support film. Next, a solution B containing 0.10% by weight of trimesic acid chloride and 0.15% by weight of isophthalic acid chloride was brought into contact with the surface of the support membrane. Cyclododecane (boiling point 200 ° C.) was used as the organic solvent in the solution B. Then, it hold | maintained for 3 minutes in a 120 degreeC hot air dryer, the skin layer was formed on the support membrane, and the composite reverse osmosis membrane was obtained. When the performance of the obtained composite reverse osmosis membrane was evaluated by the following evaluation test, the rejection rate of IPA was 99.5%, the rejection rate of boron was 93.7%, the rejection rate of NaCl was 99.9%, and the permeation flow The bundle was 0.58 m ³ / (m ² · day).

[Evaluation test]
The performances of the composite reverse osmosis membranes obtained in the examples and comparative examples were as follows. The composite reverse osmosis membrane had an isopropyl alcohol (IPA) concentration of 0.15 wt% at an operating pressure of 1.5 MPa, a temperature of 25 ° C., and a pH of 6.5. After allowing the aqueous solution to permeate for 30 minutes, the IPA rejection was measured. The IPA rejection was measured by using the GC analyzer and the concentration of the feed solution and the permeate was measured, and the measurement result was calculated by the following formula.
<IPA rejection rate>
Blocking rate (%) = (1− (IPA concentration in membrane permeate / IPA concentration in feed solution)) × 100

Further, after allowing an aqueous solution containing 3.2% by weight of sodium chloride and 5 ppm of boron (29 ppm of boric acid) to permeate through the composite reverse osmosis membrane at an operating pressure of 5.5 MPa, a temperature of 25 ° C. and a pH of 6.5, for 1 hour. Sodium chloride rejection, boron rejection and permeation flux were measured. The sodium chloride rejection was measured by ordinary conductivity measurement, and the boron rejection was measured by concentration measurement with an ICP analyzer, and calculated from the measurement results by the following formulas.
<NaCl rejection>
Blocking rate (%) = (1− (NaCl concentration in membrane permeate / NaCl concentration in feed solution)) × 100
<Boron rejection>
Blocking rate (%) = (1− (boron concentration in membrane permeate / boron concentration in feed solution)) × 100

Example 2
In Example 1, the organic solvent of the solution B was combined as in Example 1 except that the mixed solvent was 40% by weight of cyclododecane, 40% by weight of cyclononane (boiling point 171 ° C.), and 20% by weight of isooctane. A reverse osmosis membrane was obtained. The results of the evaluation test are shown in Table 1.

Example 3
A composite reverse osmosis membrane was obtained in the same manner as in Example 1 except that the organic solvent of the solution B was a mixed solvent consisting of 70% by weight of cyclododecane and 30% by weight of isooctane. The results of the evaluation test are shown in Table 1.

Example 4
A composite reverse osmosis membrane was obtained in the same manner as in Example 1, except that the organic solvent of the solution B was a mixed solvent composed of 30% by weight of cyclododecane and 70% by weight of isoundecane. The results of the evaluation test are shown in Table 1.

Example 5
A composite reverse osmosis membrane was obtained in the same manner as in Example 1 except that the organic solvent of the solution B was a mixed solvent composed of 70% by weight of cyclododecane and 30% by weight of isoundecane. The results of the evaluation test are shown in Table 1.

Comparative Example 1
In Example 1, a composite reverse osmosis membrane was obtained in the same manner as in Example 1 except that the organic solvent of Solution B was isooctane. The results of the evaluation test are shown in Table 1.

Comparative Example 2
In Example 1, a composite reverse osmosis membrane was obtained in the same manner as in Example 1 except that the organic solvent of the solution B was isoundecane. The results of the evaluation test are shown in Table 1.

Comparative Example 3
A composite reverse osmosis membrane was obtained in the same manner as in Example 1 except that the organic solvent of the solution B was cyclohexane (boiling point 81 ° C.). The results of the evaluation test are shown in Table 1.

表１より明らかなように、多官能アミンと多官能酸ハロゲン化物の組合せを一定にして本発明の範囲内でシクロパラフィンを含有する有機溶媒を変えるだけで、用途に応じたバランスのとれた膜性能を有する複合逆浸透膜を得ることができる。実施例で得られた複合逆浸透膜は、イソパラフィンを含有する有機溶媒で得られたポリアミド系複合逆浸透膜（比較例１、２）と比べて、高い塩阻止率を維持したままＩＰＡ阻止率及びホウ素阻止率が向上しており、特に半導体の製造に必要とされる超純水の製造や、海水の淡水化の用途に適したものが得られたことがわかる。

As can be seen from Table 1, a balanced film according to the application can be obtained simply by changing the organic solvent containing cycloparaffin within the scope of the present invention while keeping the combination of the polyfunctional amine and polyfunctional acid halide constant. A composite reverse osmosis membrane having performance can be obtained. The composite reverse osmosis membranes obtained in the examples were compared with the polyamide-based composite reverse osmosis membranes (Comparative Examples 1 and 2) obtained with an organic solvent containing isoparaffin, while maintaining a high salt rejection rate. In addition, the boron rejection is improved, and it can be seen that a product suitable for the production of ultrapure water particularly required for the production of semiconductors and the desalination of seawater has been obtained.

Claims (6)

In a method for producing a composite reverse osmosis membrane comprising a polyamide-based skin layer and a microporous support for supporting the same, an aqueous solution A containing a compound having two or more reactive amino groups is microporously supported. A polyfunctional acid halogen having two or more reactive acid halide groups in an organic solvent containing a cycloparaffin having 7 or more carbon atoms (C _n H _2n ) A method for producing a composite reverse osmosis membrane, comprising bringing solution B containing a chemical into contact with the coating layer. The method according to claim 1, wherein the cycloparaffin has a boiling point of 90 to 250 ° C. The production method according to claim 1 or 2, wherein the content of cycloparaffin in the organic solvent is 5 to 100% by weight. A composite reverse osmosis membrane obtained by the production method according to claim 1. The composite inverse according to claim 4, wherein when the aqueous isopropyl alcohol solution having a temperature of 25 ° C, pH 6.5, and a concentration of 0.15% by weight is subjected to a permeation test under an operating pressure of 1.5 MPa, the isopropyl alcohol rejection is 99% or more. Osmosis membrane. Boron rejection is 90% or more when a permeation test is performed at a temperature of 25 ° C., pH 6.5, and 3.2 wt% boron containing 5 ppm of boron at an operating pressure of 5.5 MPa. The composite reverse osmosis membrane according to claim 4 or 5, wherein the rate is 99% or more.