JP2007125544A - Composite semipermeable membrane and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite semipermeable membrane having a high removal rate when salt is removed from brine water as well as a high permeation flux. <P>SOLUTION: The composite semipermeable membrane is characterized in that a polyamide separation-functional layer is formed on a microporous supporting membrane and low-molecular-weight acyl groups each having two substituted groups in the α position are bonded covalently to each other in a polyamide molecule constituting the polyamide separation-functional layer. It is preferable that the polyamide constituting the polyamide separation-functional layer is cross-linked polyamide obtained by bringing an aqueous solution of polyfunctional amine into contact with an organic solvent containing a polyfunctional acid halide and a predetermined acid halide on the microporous supporting membrane so that the polyfunctional amine and the polyfunctional acid halide/the predetermined acid halide are subjected to a polycondensation reaction on the interface between the aqueous solution and the organic solvent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composite semipermeable membrane useful for selective separation of a liquid mixture and a method for producing the same, and a polyamide on a microporous support membrane that maintains a high salt removal rate against brine and has a high permeation flux. The present invention relates to a composite semipermeable membrane having a separation functional layer and a method for producing the same.

  Many composite semipermeable membranes are known in which a skin layer made of polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a polyfunctional aromatic halide is formed into a support (Patent Document 1). ~ 4).

  Further, as one of the means for improving the salt removal rate of the composite salt-permeable membrane, the addition of a novel reactant in the reactant solution can be mentioned. This method is useful as a simple improvement method because there is no significant change from the conventional manufacturing method.

  For example, in a composite semipermeable membrane, an acid containing a polyamine component having two or more amino groups in the molecule and a linear aliphatic polyacid halide having two or more halogenated carbonyl groups in the molecule as a novel reactant. It is disclosed that a cross-linked polyamide is composed of components (Patent Document 5).

Further, in the composite semipermeable membrane, during the interfacial polycondensation reaction between a compound having two or more reactive amino groups and a polyfunctional acid halide compound having two or more reactive acid halide groups, alcohols, An example of adding ketones, esters, and halogenated hydrocarbons is also disclosed (Patent Document 6).
According to the method, it is described that a composite semipermeable membrane having a high salt removal rate and a high permeation flux and a method for producing the composite semipermeable membrane can be provided. However, the performance is still insufficient, and a composite semipermeable membrane having higher performance is provided. There is a need for permeable membranes.

JP-A-55-147106 JP 62-121603 A JP-A-63-218208 JP-A-2-187135 Japanese Patent No. 3031763 Japanese Patent Laid-Open No. 9-19630

  The object of the present invention is to solve the above-mentioned problems of the prior art and to provide a composite semipermeable membrane that maintains a high salt removal rate and has a high permeation flux even at a low operating pressure.

To achieve the above object, the present invention has the following configuration. That is,
(I) A polyamide separation functional layer is formed on a microporous support membrane, and an acyl group of any one of the following formulas (1) and (2) is bonded to the polyamide separation functional layer. A composite semipermeable membrane.

(In the formula, n represents 0 or 1, X represents O, S, or NR ^6. R ¹ and R ² are both alkyl groups. R ³ and R ⁴ represent a substituent other than a hydrogen atom or a carboxy group. An optionally substituted alkyl group or aromatic group having 1 to 12 carbon atoms, and R ⁵ is an optionally substituted alkyl group or aromatic group having 1 to 12 carbon atoms other than a carboxy group. R ⁶ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.)

(Wherein R ¹ and R ² are as defined above. A represents a hydroxyl group or an amino group in a polyamide molecule).

  (II) A polyamide separation functional layer is formed on a microporous support membrane, and the polyamide constituting the polyamide separation functional layer comprises a polyfunctional amine aqueous solution, a polyfunctional acid halide, the following formula (3), ( 4. The composite according to (I), which is a crosslinked polyamide obtained by bringing an organic solvent solution containing any of the acid halides of 4) into contact with a microporous support membrane and subjecting it to interfacial polycondensation Semipermeable membrane.

(In the formula, n, X and R ^{1 to} R ⁶ are as defined above. Z represents a halogen atom).

  (III) The compound halide according to (II) above, wherein the acid halide of the above formulas (3) and (4) is at least one selected from 2-acetoxyisobutyric acid chloride and dimethylmalonyl chloride. Permeable membrane.

(IV) A salt removal rate of 99.7% or more and a permeation flux of 1.0 m ³ / m ² / d or more under the conditions of a NaCl solution with a pressure of 0.75 MPa, a temperature of 25 ° C., a pH of 6.5, and a feed solution of 500 ppm. The composite semipermeable membrane according to any one of claims (I) to (III).

  (V) a polyfunctional acid halide having at least two acid halide groups after contacting an aqueous polyfunctional amine solution having at least two primary and / or secondary amino groups on the microporous support membrane; and A water-immiscible organic solvent solution containing the acid halide of any one of the above formulas (3) and (4) and containing 5 mol% or more with respect to the polyfunctional acid halide is brought into contact with the interface. The method for producing a composite semipermeable membrane according to any one of (I) to (IV), wherein a separation functional layer containing a crosslinked polyamide is formed on a porous support membrane by polycondensation.

  In the present invention, since the acid halide having a substituent at the α-position with low reactivity can preferably fill the gap between the polymers, the composite semipermeable membrane having a high salt removal rate and a high permeation flux is also provided. Can be provided.

  The composite semipermeable membrane according to the present invention comprises a polyamide separation functional layer formed on a microporous support membrane, and an acyl group of any one of the following formulas (1) and (2) is bonded to the polyamide separation functional layer. It is a composite semipermeable membrane characterized by the above.

（式中、ｎ、Ｘ、Ａ、Ｒ^１〜Ｒ^６は前記記載の定義に従う。）

(In the formula, n, X, A, and R ^{1 to} R ⁶ are as defined above.)

  The separation functional layer polyamide is formed by interfacial polycondensation of a polyfunctional amine, a polyfunctional acid halide, and an acid halide having two substituents at the α-position of the carbonyl group, to form a polyfunctional amine or polyfunctional acid halide. It is preferable that at least one of the components contains a trifunctional or higher functional compound.

  The thickness of the separation functional layer is usually in the range of 0.01 to 1 μm, preferably in the range of 0.1 to 0.5 μm, in order to obtain sufficient separation performance and permeated water amount.

  Here, the polyfunctional amine refers to an amine having at least two primary and / or secondary amino groups in one molecule. For example, two amino groups are any of ortho, meta, and para positions. Aromatic polyfunctional amines such as phenylenediamine, xylylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene and 3,5-diaminobenzoic acid bonded to benzene in the positional relationship of Aliphatic amines such as ethylenediamine and propylenediamine, alicyclic polyfunctional amines such as 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 1,3-bispiperidylpropane and 4-aminomethylpiperazine be able to. Of these, aromatic polyfunctional amines having 2 to 4 primary and / or secondary amino groups in one molecule are preferred in consideration of selective separation, permeability, and heat resistance of the membrane. As the functional aromatic amine, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used. Among these, it is more preferable to use m-phenylenediamine (hereinafter referred to as m-PDA) from the standpoint of availability and ease of handling. These polyfunctional amines may be used alone or in combination.

  The polyfunctional acid halide refers to an acid halide having at least two carbonyl halide groups in one molecule. Examples of trifunctional acid halides include trimesic acid chloride, 1,3,5-cyclohexanetricarboxylic acid trichloride, 1,2,4-cyclobutanetricarboxylic acid trichloride, and bifunctional acid halides include oxalyl chloride. , Aromatic difunctional acid halides such as biphenyl dicarboxylic acid dichloride, azobenzene dicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalene dicarboxylic acid chloride, aliphatic difunctional acid halides such as adipoyl chloride, sebacoyl chloride And cycloaliphatic difunctional acid halides such as cyclopentanedicarboxylic acid dichloride, cyclohexanedicarboxylic acid dichloride, and tetrahydrofurandicarboxylic acid dichloride. Considering the reactivity with the polyfunctional amine, the polyfunctional acid halide is preferably a polyfunctional acid chloride, and considering the selective separation property and heat resistance of the membrane, 2 to 4 per molecule. The polyfunctional aromatic acid chloride having a carbonyl chloride group is preferred. Among them, it is more preferable to use trimesic acid chloride from the viewpoint of easy availability and easy handling. These polyfunctional acid halides may be used alone or in combination.

That is, when forming the polyamide separation functional layer on the microporous support membrane, the polyamide separation functional layer is composed of a polyfunctional amine aqueous solution, a polyfunctional acid halide, and an acid halide of the following formulas (3) and (4). An organic solvent solution containing sulfur may be brought into contact with the microporous support membrane and subjected to interfacial polycondensation. Particularly, the polyamide separation functional layer is brought into contact with a polyfunctional amine aqueous solution and an organic solvent solution containing the polyfunctional acid halide and the acid halide of the following formulas (3) and (4) on the microporous support membrane. The composite semipermeable membrane formed by polycondensation has a salt removal rate of 99.7% or more and a permeation flux of 1. under a pressure of 0.75 MPa, a temperature of 25 ° C., a pH of 6.5, and a feed solution of 500 ppm NaCl solution. It is preferable because it can satisfy 0 m ³ / m ² / d or more and exhibits high salt exclusion performance.

（式中ｎ、Ｘ、Ａ、Ｒ^１〜Ｒ^６は前記記載の定義に従う。Ｚはハロゲン原子を示す。）

(In the formula, n, X, A, and R ^{1 to} R ⁶ are as defined above. Z represents a halogen atom.)

  Examples of the acid halides of the above formulas (3) and (4) include 2-acetoxyisobutyric acid chloride, dimethylmalonyl chloride, 3-methoxy-2,2,3-trimethylbutyryl chloride, 3-methoxy-2,2 -Dimethylbutyryl chloride, 2,2,3-trimethyl-3-methylsulfanylbutyryl chloride, 3-dimethylamino-2,2,3-trimethylbutyryl chloride, and the like. You may use it simultaneously. Among these, 2-acetoxyisobutyric acid chloride and dimethylmalonyl chloride are particularly preferably used because the salt removal rate can be improved without reducing the permeation flux.

  In the present invention, the microporous support membrane is intended to give strength to a separation functional layer that substantially does not have separation performance of ions or the like and has substantial separation performance. The size and distribution of the pores are not particularly limited. For example, the pores have uniform and fine pores or gradually have large pores from the surface on the side where the separation functional layer is formed to the other surface, and the separation functional layer has A support film having a micropore size of 0.1 nm or more and 100 nm or less on the surface to be formed is preferable.

  The material used for the microporous support membrane and the shape thereof are not particularly limited. For example, polysulfone, cellulose acetate, polyvinyl chloride reinforced with a fabric mainly composed of at least one selected from polyester or aromatic polyamide, or those A mixture of these is preferably used. As a material to be used, it is particularly preferable to use polysulfone having high chemical, mechanical and thermal stability.

  Specifically, it is preferable to use polysulfone composed of repeating units represented by the following chemical formula because the pore diameter is easy to control and the dimensional stability is high.

  For example, an N, N-dimethylformamide (DMF) solution of the above polysulfone is cast on a densely woven polyester cloth or non-woven fabric to a certain thickness, and wet coagulated in water, thereby increasing the size of the surface. A microporous support membrane having fine pores with a diameter of several tens of nm or less can be obtained.

  The thickness of the porous support and the substrate affects the strength of the composite semipermeable membrane. In order to obtain sufficient mechanical strength, the thickness is preferably in the range of 50 to 300 μm, more preferably in the range of 100 to 250 μm. Moreover, it is preferable that the thickness of a porous support body exists in the range of 10-200 micrometers, More preferably, it exists in the range of 30-100 micrometers.

  Next, the manufacturing method of the composite semipermeable membrane of this invention is demonstrated.

  The separation functional layer constituting the composite semipermeable membrane is, for example, microporous using an aqueous solution containing the aforementioned polyfunctional amine and an organic solvent solution immiscible with water containing the polyfunctional acid halide. The skeleton can be formed by interfacial polycondensation on the surface of the support membrane.

  Here, the concentration of the polyfunctional amine in the polyfunctional amine aqueous solution is preferably in the range of 0.1 to 20% by weight, and more preferably in the range of 1 to 3% by weight. In this range, sufficient salt removal performance and water permeability can be obtained. As long as the polyfunctional amine aqueous solution does not interfere with the reaction between the polyfunctional amine and the polyfunctional acid halide, a surfactant, an organic solvent, an alkaline compound, an antioxidant, or the like may be contained. The surfactant has the effect of improving the wettability of the porous support membrane surface and reducing the interfacial tension between the aqueous amine solution and the nonpolar solvent, and the organic solvent may act as a catalyst for the interfacial polycondensation reaction. In some cases, the interfacial double reaction can be efficiently performed by adding them.

  In order to perform interfacial polycondensation on the porous support membrane, first, the above-mentioned polyfunctional amine aqueous solution is brought into contact with the porous support membrane. The contact is preferably performed uniformly and continuously on the porous support membrane surface. Specific examples include a method of coating a porous support membrane with a polyfunctional amine aqueous solution and a method of immersing the porous support membrane in a polyfunctional amine aqueous solution. The contact time between the porous support membrane and the polyfunctional amine aqueous solution is preferably in the range of 1 to 10 minutes, and more preferably in the range of 1 to 3 minutes.

  After the polyfunctional amine aqueous solution is brought into contact with the porous support membrane, the solution is sufficiently drained so that no droplets remain on the membrane. By sufficiently draining the liquid, it is possible to prevent the remaining portion of the liquid droplet from becoming a film defect after the film is formed and deteriorating the film performance. The liquid draining method includes a method in which the porous support membrane after the polyfunctional amine aqueous solution contact is vertically gripped to allow the excessive aqueous solution to flow down naturally, or a wind such as nitrogen is blown from an air nozzle to forcibly drain the liquid. Or the like can be used. In addition, after draining, the membrane surface can be dried to remove part of the water in the aqueous solution.

  Next, an organic solvent solution containing a polyfunctional acid halide is brought into contact with the support film after contact with the polyfunctional amine aqueous solution, and a skeleton of a crosslinked polyamide separation functional layer is formed by interfacial polycondensation.

  The concentration of the polyfunctional acid halide in the organic solvent solution is preferably in the range of 0.01 to 10% by weight, and more preferably in the range of 0.02 to 2.0% by weight. Within this range, a sufficient reaction rate can be obtained, and the occurrence of side reactions can be suppressed.

  The organic solvent is desirably immiscible with water, dissolves the acid halide and does not break the microporous support membrane, and may be inert to the amino compound and the acid halide. Preferable examples include hydrocarbon compounds such as n-hexane, n-octane, and n-decane.

  The method for contacting the organic solvent solution of the polyfunctional acid halide with the amino compound aqueous solution phase may be performed in the same manner as the method for coating the microporous support membrane with the polyfunctional amine aqueous solution.

  As described above, after the interface polycondensation is performed by bringing the acid halide organic solvent solution into contact with each other and the separation functional layer containing the crosslinked polyamide is formed on the porous support membrane, the excess solvent may be drained. As a method for draining, for example, a method in which a film is held in a vertical direction and excess organic solvent is allowed to flow down and removed can be used. In this case, the time for gripping in the vertical direction is preferably 1 to 5 minutes, more preferably 1 to 3 minutes. If it is too short, the separation functional layer will not be completely formed, and if it is too long, the organic solvent will be overdried and defects will easily occur and performance will be deteriorated.

  And in the manufacturing method of the composite semipermeable membrane of this invention, the organic solvent solution containing the above-mentioned polyfunctional acid halide and the acid halide of said Formula (3) and (4) is made to contact, for example.

  And the density | concentration of the polyfunctional acid halide in the organic solvent solution in this case is also preferably in the range of 0.01 to 0.2% by weight, and in the range of 0.04 to 0.06% by weight. And more preferred. If it is less than 0.01% by weight, the formation of the separation functional layer as the active layer tends to be insufficient.

  When the acid halide of the above formulas (3) and (4) and the polyfunctional acid halide are mixed in a single organic solvent solution to form a separation functional layer, 5 mol with respect to the polyfunctional acid halide. % Or more is preferable. When it is less than 5 mol%, the salt rejection rate decreases. And even if it uses exceeding 100 mol%, the improvement of a salt exclusion rate is not seen, but since the environmental burden by a large amount of unreacted reagents and the economic burden for a process increase, it is 100 mol% or less. preferable. Among these, in order to obtain a composite semipermeable membrane having both a high salt removal rate and a high permeation flux, the content is more preferably 7.5 to 15 mol%.

  The composite semipermeable membrane thus obtained can be used as it is, but it is preferable to remove unreacted residues by washing before use. It is preferable to wash the membrane with water in the range of 30 to 100 ° C. to remove the remaining amino compound and the like. In addition, the washing can be performed by immersing the support film in water within the above temperature range or spraying water. When the temperature of the water used is less than 30 ° C., the amino compound remains in the composite semipermeable membrane and the permeation flux tends to be low. Further, when washing is performed at a temperature exceeding 100 ° C. with an autoclave or steam, the membrane may cause thermal shrinkage, and the permeation flux tends to be low.

  It is also preferable to increase the salt rejection rate and the permeation flux by, for example, a method of contacting a chlorine-containing aqueous solution within the range of pH 6 to 13 at normal pressure or a method of contacting a nitrous acid-containing aqueous solution at normal pressure.

The composite semipermeable membrane thus obtained had a salt rejection rate of 99.7% or more when a 500 ppm NaCl aqueous solution adjusted to a temperature of 25 ° C. and a pH of 6.5 was evaluated at an operating pressure of 0.75 MPa. Is preferably 1.0 m ³ / m ² · day) or more.

  Measurements in Examples and Comparative Examples were performed as follows.

(Salt removal rate)
The composite semipermeable membrane was determined from the following equation by measuring the permeate concentration when a 500 ppm NaCl aqueous solution adjusted to a temperature of 25 ° C. and pH 6.5 was supplied at an operating pressure of 0.75 MPa.
Salt removal rate = 100 × {1− (salt concentration in permeated water / salt concentration in feed water)}

(Permeation flux)
A 500 ppm NaCl aqueous solution was used as the feed water, and permeation flux (m ³ / m ² · day) was determined from the amount of water per day (cubic meter) per square meter of membrane surface.

(Examples 1 to 5, Comparative Examples 1 and 2)
A 15.7 wt% dimethylformamide (DMF) solution of polysulfone was cast on a polyester nonwoven fabric (air permeability 0.5 to 1 cc / cm ² · sec) at a thickness of 200 μm at room temperature (25 ° C.) A microporous support membrane was prepared by immersing the substrate in the substrate and leaving it for 5 minutes. The microporous support membrane (thickness 210 to 215 μm) thus obtained was placed in an aqueous solution of 1.5% by weight of metaphenylenediamine (hereinafter referred to as mPDA) and 1.5% by weight of epsilon caprolactam (hereinafter referred to as εCL). After dipping for 2 minutes, the support membrane was slowly pulled up in the vertical direction, nitrogen was blown from the air nozzle to remove excess aqueous solution from the surface of the support membrane, 0.06% by weight of trimesic acid chloride (hereinafter referred to as TMC), and a table An n-decane solution containing 7.5 mol% of the acid halide described in 2 (the structural formulas of compounds 1, 2, and 3 are described in Table 1) with respect to TMC was applied so that the surface was completely wetted for 1 minute. Left to stand. Next, in order to remove excess solution from the membrane, the membrane was held vertically for 1 minute to drain the solution.

  Then, after washing with hot water at 90 ° C. for 2 minutes, it was immersed in an aqueous solution of sodium hypochlorite adjusted to pH 7 and a chlorine concentration of 500 mg / l for 2 minutes, and in an aqueous solution having a sodium bisulfite concentration of 1,000 mg / l. By dipping, excess sodium hypochlorite was reduced and removed. When the obtained composite semipermeable membrane was evaluated, the permeation flux and the salt removal rate were values shown in Table 2, respectively.

Claims (5)

A polyamide separation functional layer is formed on a microporous support membrane, and an acyl group of any one of the following formulas (1) and (2) is covalently bonded to a polyamide molecule constituting the polyamide separation functional layer. A composite semipermeable membrane characterized by that.

(In the formula, n represents 0 or 1, X represents O, S, or NR ^6. R ¹ and R ² are both alkyl groups. R ³ and R ⁴ represent a substituent other than a hydrogen atom or a carboxy group. An optionally substituted alkyl group or aromatic group having 1 to 12 carbon atoms, and R ⁵ is an optionally substituted alkyl group or aromatic group having 1 to 12 carbon atoms other than a carboxy group. R ⁶ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.)

(In the formula, R ¹ and R ² are as defined above. A represents a hydroxyl group or an amino group in a polyamide molecule.) A polyamide separation functional layer is formed on a microporous support membrane, and the polyamide constituting the polyamide separation functional layer comprises a polyfunctional amine aqueous solution, a polyfunctional acid halide, and the following formulas (3) and (4): 2. The composite semipermeable membrane according to claim 1, which is a crosslinked polyamide obtained by bringing an organic solvent solution containing any of the acid halides into contact with the microporous support membrane and interfacial polycondensation. .

(In the formula, n, X and R ^{1 to} R ⁶ are as defined above. Z represents a halogen atom.) The composite semipermeable membrane according to claim 2, wherein the acid halide of the formulas (3) and (4) is at least one selected from 2-acetoxyisobutyric acid chloride and dimethylmalonyl chloride. The salt rejection is 99.7% or more and the permeation flux is 1.0 m ³ / m ² / d or more under the conditions of a NaCl solution with a pressure of 0.75 MPa, a temperature of 25 ° C., a pH of 6.5, and a feed solution of 500 ppm. Item 4. The composite semipermeable membrane according to any one of Items 1 to 3. After contacting the polyfunctional amine aqueous solution having at least two primary and / or secondary amino groups on the microporous support membrane, the polyfunctional acid halide having at least two acid halide groups and the above formula ( Porous support by interfacial polycondensation, containing an acid halide of 3) or (4), containing 5 mol% or more of the polyfunctional acid halide in contact with water and an immiscible organic solvent solution The method for producing a composite semipermeable membrane according to any one of claims 1 to 4, wherein a separation functional layer containing a crosslinked polyamide is formed on the membrane.