JP2021137756A - Separation membrane and method for manufacturing separation membrane - Google Patents

Abstract

To provide a separation film having sufficient separation performance and excellent chemical resistance.SOLUTION: This separation membrane comprises: a porous support; a polyamide-based separation functional layer provided on the porous support; and a coating layer provided on the polyamide-based separation functional layer, wherein a fragment of CN2-(m/z=40) and/or CHN2-(m/z=41) is detected in the analysis of the coating layer by time-of-flight secondary ion mass spectrometry (TOF-SIMS).SELECTED DRAWING: Figure 1

Description

The present invention relates to a separation membrane and a method for producing the separation membrane.

As a separation membrane for desalination treatment used for producing pure water, desalination of seawater, etc., a separation membrane having a separation function layer formed on a porous support membrane is well known (for example, Patent Document 1). Further, it is conventionally known that the separation functional layer is coated with polyvinyl alcohol or the like in order to improve the performance of the separation membrane as described above (for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2000-33243 International Publication No. 97/34686

If the separation membrane is used for a certain period of time, foulants (dirt) may adhere to the surface of the separation membrane. Therefore, the separation membrane is usually washed regularly to remove such foulants. At the time of cleaning, chemicals are used as a cleaning liquid.

However, when a chemical cleaning solution such as acid or alkali is used, the separation membrane may be damaged by the chemical and the separation performance of the membrane may be impaired. Therefore, a separation membrane having sufficient separation performance and high chemical resistance is desired.

One aspect of the present invention is to provide a separation membrane having sufficient separation performance and excellent chemical resistance.

The separation membrane according to one aspect of the present invention includes a porous support, a polyamide-based separation functional layer provided on the porous support, and a coating layer provided on the polyamide-based separation functional layer. (m / z = 40) and / or _CHN ² - - fragments of (m / z = 41) is detected _CN ² in the analysis by the time-of-flight secondary ion mass spectrometry of the coating layer (TOF-SIMS) ..

According to one aspect of the present invention, it is possible to provide a separation membrane having sufficient separation performance and excellent chemical resistance.

A schematic cross-sectional view of the separation membrane according to the embodiment of the present invention is shown.

Hereinafter, embodiments for carrying out the present invention will be described in more detail, but the present invention is not limited to the embodiments described in the present specification. In addition, the description of the content, ratio, and concentration in this specification shall be based on weight unless the unit is specified.

The separation membrane according to one embodiment of the present invention includes a porous support, a polyamide-based separation functional layer provided on the porous support, and a coating layer provided on the separation functional layer, and the coating layer flies. in a time-of secondary ion mass spectrometry (TOF-SIMS) _analysis, ^CN 2 - in which fragment (m / z = 41) is detected - (m / z = 40) and / or _CHN ^2.

Further, the separation membrane according to one embodiment of the present invention includes a porous support, a polyamide-based separation functional layer provided on the porous support, and a coating layer provided on the polyamide-based separation functional layer. The coating layer contains a carbodiimide compound and / or a reactant thereof. The coating layer can be formed by applying a composition containing a carbodiimide compound on the polyamide-based separation functional layer as described later. Further, in the present specification, the reactant of the carbodiimide compound is, for example, a compound formed by reacting the carbodiimide compound with the carboxylic acid of the polyamide-based separation functional layer, and N-acylurea and / or a polymer thereof. include.

Further, one embodiment of the present invention forms a porous support, forms a polyamide-based separation functional layer on the porous support, and contains a carbodiimide compound and / or a reaction product thereof on the polyamide-based separation functional layer. A method for producing a separation membrane, which comprises forming a coating layer.

FIG. 1 schematically shows the structure of the separation membrane 10 according to one embodiment of the present invention. As shown in FIG. 1, the separation membrane 10 includes a porous support 5 and a separation functional layer (also referred to as an active layer or a skin layer) 2 provided on the porous support 5. The separation functional layer 2 in this embodiment may be a separation functional layer mainly containing polyamide. More specifically, the separation functional layer 2 is a layer containing a crosslinked polyamide, preferably a layer made of a crosslinked polyamide.

Further, in the separation membrane 10 according to the present embodiment, the coating layer 1 is provided on the separation function layer 2. The coating layer 1 is a layer constituting the uppermost layer of the separation membrane, and is a layer that comes into direct contact with the water to be treated when the separation membrane is used. The coating layer 1 is a layer that at least partially covers the separation function layer 2. The formation of the coating layer 1 improves the separation function and chemical resistance. It is considered that this is the effect of repairing the fine pores of the crosslinked polyamide by the coating layer 1 and the effect of sealing the end of the crosslinked polyamide by the carbodiimide compound and / or its reaction product contained in the coating layer 1. The porous support 5 may have a base material 4 and a porous support layer 3 provided on the base material 4, and the separation function layer 2 is formed on the porous support layer 3.

The base material used for the porous support may be a fiber planar structure, specifically, a woven fabric, a knitted fabric, a non-woven fabric, or the like, of which a non-woven fabric is preferable. The type of fiber constituting the base material is not limited, but synthetic fiber is preferable. Specific examples of the fiber include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polyglycolic acid (PGA), polylactic acid (PLA), and nylon 6. , Polycaprolactone (PCL), polyethylene adipate (PEA), polyhydroxyalkanoate (PHA), and copolymers thereof. Of these, polyester such as polyethylene terephthalate is preferably used because of its high dimensional stability and moldability and high oil resistance.

Materials for the porous support layer formed on the substrate include polysulfone, polyethersulfone, polycarbonate, polyethylene oxide, polyimide, polyetherimide, polyetheretherketone, polypropylene, polymethylpentene, polymethylchloride, and polyvinylidene fluoride. And so on. The method for forming the porous support layer on the base material is not particularly limited. For example, a solution obtained by dissolving the above material in a solvent is applied to the base material, and microphase separation is performed at a predetermined temperature and a predetermined humidity. Can be obtained by coagulating the polymer after producing.

The separation functional layer formed on the porous support layer may contain polyamide, and is preferably substantially made of polyamide. Further, the above-mentioned polyamide is preferably a crosslinked polyamide.

The method for forming the polyamide separation functional layer is not particularly limited, but for example, the surface of the porous support layer is immersed in a solution of a polyfunctional amine compound, and then the surface of the porous support layer is brought into contact with a solvent solution of an acid halide compound to carry out interfacial polymerization. It can be done by advancing. The thickness of the separating functional layer formed can be 0.01 to 1 μm.

The polyfunctional amine used may be an aromatic polyfunctional amine, an aliphatic polyfunctional amine, or a combination thereof. Aromatic polyfunctional amines include m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene and the like, or N-alkylated products thereof such as N, N'-dimethylm-phenylenediamine, N, It may be N'-diethylm-phenylenediamine, N, N'-dimethylp-phenylenediamine, N, N'-diethylp-phenylenediamine. The aliphatic polyfunctional amine may be piperazine or a derivative thereof. Specific examples of the aliphatic polyfunctional amines include piperazine, 2,5-dimethylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,3,5-trimethylpiperazine, 2,5-diethylpiperazine, 2, Examples thereof include 3,5-triethylpiperazine, 2-n-propylpiperazine, 2,5-di-n-butylpiperazine and ethylenediamine. These polyfunctional amines can be used alone or in combination of two or more.

The acid halide compound is not particularly limited as long as it gives polyamide by the reaction with the polyfunctional amine, but an acid halide having two or more carbonyl halide groups in one molecule is preferable. Acid halide compounds include fatty acids such as oxalic acid, malonic acid, maleic acid, fumaric acid, glutaric acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. Halide compounds, phthalic acid, isophthalic acid, 1,3,5-benzenetricarboxylic acid (trimesic acid), 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, etc. Examples include acid halide compounds of aromatic acids. These acid halide compounds can be used alone or in combination of two or more.

Separation membrane according to the present embodiment, from the surface, i.e. from the surface of the coating layer, time-of-flight secondary ion mass spectrometry (TOF-SIMS) by CN ₂ ^- and / or CHN ₂ ^- of which the fragment ions are detected Is. If the analyte to carbodiimide groups are present, CN ₂ ^- and / or CHN ₂ ^- is a fragment ion can be detected.

Further, in the separation membrane according to this embodiment, the coating layer may contain a carbodiimide compound (or carbodiimide) and / or a reaction product thereof. The carbodiimide compound is not particularly limited as long as it is a compound having a carbodiimide structure (-N = C = N-) in the molecule. In other words, the carbodiimide compound may have a carbodiimide group as a functional group or a cyanamide group which is a tautomeric group thereof in the molecule. The carbodiimide compound may be a monomer or a polymer (oligomer or polymer).

_{Fragment ions of CN 2} ⁻ and / or CHN ₂ ⁻ are detected from the surface of the coating layer of the separation membrane, or the separation membrane according to this embodiment containing a carbodiimide compound in the coating layer has chemical resistance, more specifically acid. And / or excellent resistance to alkalis, especially alkalis. Therefore, the separation membrane is not easily damaged even if it is washed with a chemical, so that the separation performance can be maintained for a long period of time.

When the carbodiimide compound is a monomer, specific examples of the carbodiimide compound include N, N'-dicyclohexylcarbodiimide (DCC), N, N'-diisopropylcarbodiimide (DIC), 1-ethyl-3- (3-dimethylaminopropyl). ) Carbodiimide (EDC), N- [3- (dimethylamino) propyl] -N'-propyl carbodiimide, N-tert-butyl-N'-ethyl carbodiimide and the like. These carbodiimide compounds can be used alone or in combination of two or more.

Further, the carbodiimide compound is preferably a polymer compound, that is, a carbodiimide group-containing polymer (polycarbodiimide) from the viewpoint of improving the performance of the separation membrane, particularly lowering the salt permeability (or increasing the blocking rate). The carbodiimide group-containing polymer preferably contains a carbodiimide group as a repeating unit of the polymer.

The carbodiimide group-containing polymer may be in the form of a linear or branched chain, or may be cyclic. Furthermore, the carbodiimide group-containing polymer may have a three-dimensional crosslinked structure. Further, the carbodiimide group-containing polymer may be a polymer composed of repeating units containing a carbodiimide group, to which a hydrophilic segment or the like is added. When the coating layer contains a carbodiimide group-containing polymer and / or a reaction product thereof, the formed coating layer is less likely to be removed even if it is washed with a chemical agent or the like.

The carbodiimide group equivalent of the carbodiimide group-containing polymer, that is, the mass of the carbodiimide group-containing polymer per mol of the carbodiimide group is preferably 300 or more in consideration of stronger bonding with the separation functional layer.

The weight average molecular weight of the carbodiimide group-containing polymer may be preferably 500 to 10,000, more preferably 1,000 to 5,000.

The carbodiimide group-containing polymer has aromas such as poly (4,4'-diphenylmethanecarbodiimide), poly (p-phenylene carbodiimide), poly (m-phenylene carbodiimide), poly (diisopropylphenylcarbodiimide), and poly (triisopropylphenylcarbodiimide). Group polycarbodiimide; may be an alicyclic polycarbodiimide such as poly (dicyclohexylmethanecarbodiimide), an aliphatic polycarbodiimide such as poly (diisopropylcarbodiimide), or the like.

Commercially available products of carbodiimide group-containing polymers include "carbodilite (registered trademark) V-02", "carbodilite V-04", "carbodilite V-02-L2", "carbodilite SV-02", and "carbodilite SV-02" manufactured by Nisshinbo Chemical Co., Ltd. "SW-12G" and the like.

In the present embodiment, when forming a coating layer containing a carbodiimide compound, the carbodiimide compound can prepare a coating forming liquid in the form of a solution, for example, an aqueous solution or an emulsion, and the coating forming liquid can be brought into contact with the separation functional layer. After contact, with or without heating, the carbodiimide compound dries the solution or emulsion to form a coating layer. The carbodiimide compound may react in the drying step after contact to polymerize and / or crosslink. The thickness of the coating layer can be 0.001 to 1 μm.

The concentration of the carbodiimide compound in the coating forming liquid used for forming the coating layer containing the carbodiimide compound and / or its reaction product is preferably 0.0001 to 1% by weight, more preferably 0.0005 to 0.1. It may be% by weight. By setting the concentration of the carbodiimide compound in the above range, the separation function and chemical resistance of the obtained separation membrane can be improved. In addition, it is possible to prevent the coating layer from becoming excessively thick and hindering the function of the separation function layer.

As described above, in this embodiment, the carbodiimide compound and / or its reaction product is contained in the coating layer formed on the surface of the separation functional layer made of polyamide. Therefore, the separation function and chemical resistance of the separation membrane can be effectively improved by using a small amount of the carbodiimide compound.

The separation membrane according to this embodiment is preferably formed in a flat membrane shape. Further, the flat membrane-shaped separation membrane according to the present embodiment can be suitably used in a spiral-type membrane module configured by spirally winding the composite semipermeable membrane around the outside of the water collecting pipe.

Further, the separation membrane according to this embodiment can be suitably used as a reverse osmosis membrane, that is, a membrane used by applying pressure from the supply liquid side. Since it has excellent salt or ion separation performance and high chemical resistance, it can be used for a long period of time for the production of pure water, desalination of seawater, and the like.

Hereinafter, embodiments of the present invention will be described based on examples, but the present invention is not limited to these examples.

[Preparation of separation membrane]
(Example 1)
Preparation of composite semipermeable membrane An aqueous amine solution containing 3% by weight of m-phenylenediamine, 0.15% by weight of sodium dodecylsulfate, 3% by weight of triethylamine, 0.6% by weight of sodium hydroxide, and 9% by weight of camphorsulfonic acid was prepared. Prepared. This aqueous amine solution was applied onto a porous polysulfone support prepared in advance, and then the excess aqueous amine solution was removed to form an aqueous solution coating layer. Next, the surface of the aqueous solution coating layer was immersed in an acid chloride solution in which 0.2% by weight of trimesic acid trichloride (TMC) was dissolved in a naphthenic solvent (EXXSOL D40, manufactured by Idemitsu Kosan Co., Ltd.) for 10 seconds. Then, the excess solution on the surface of the aqueous solution coating layer was removed, air-dried for 60 seconds, and further kept in a hot air dryer at 120 ° C. for 3 minutes. As a result, a composite semipermeable membrane in which a separation functional layer containing a polyamide resin was formed on the porous polysulfone support was obtained.

Formation of coating layer The surface of the separation function layer of the obtained composite semipermeable membrane was added to an aqueous solution containing 0.004% by weight of a carbodiimide group-containing polymer (Nisshinbo Chemical Co., Ltd., cross-linking agent for carbodilite aqueous resin V-02). Soaked for seconds. Then, it was air-dried for 30 seconds and further held in a hot air dryer at 120 ° C. for 2 minutes to form a coating layer. As a result, a separation film in which a coating layer was formed on the separation function layer of the composite semipermeable membrane was obtained.

(Example 2)
A separation membrane was obtained in the same manner as in Example 1 except that the concentration of the carbodiimide group-containing polymer in the aqueous solution was 0.008% by weight in the formation of the coating layer.

(Example 3)
A separation membrane was obtained in the same manner as in Example 1 except that the concentration of the carbodiimide group-containing polymer in the aqueous solution was 0.020% by weight in the formation of the coating layer.

(Example 4)
Example 1 except that another carbodiimide group-containing polymer (manufactured by Nisshinbo Chemical Co., Ltd., cross-linking agent for carbodilite aqueous resin V-04) was used to form the coating layer, and the concentration in the aqueous solution was 0.008% by weight. A separation membrane was obtained in the same manner as above.

(Example 5)
A separation membrane was obtained in the same manner as in Example 4 except that the concentration of the carbodiimide group-containing polymer in the aqueous solution was 0.020% by weight in the formation of the coating layer.

(Example 6)
In the formation of the coating layer, an aqueous solution containing 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide (EDC) at a concentration of 0.010% by weight was used instead of the aqueous solution of the carbodiimide group-containing polymer. , A separation membrane was obtained in the same manner as in Example 1.

(Example 7)
A separation membrane was obtained in the same manner as in Example 6 except that the concentration of 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide (EDC) was 0.020% by weight.

(Example 8)
In the formation of the coating layer, separation was carried out in the same manner as in Example 1 except that a solution containing a carbodiimide group-containing polymer (crosslinked agent for carbodilite aqueous resin manufactured by Nisshinbo Chemical Co., Ltd.) was used at a concentration of 0.008% by weight. A membrane was obtained.

(Comparative Example 1)
A separation membrane was obtained in the same manner as in Example 1 except that an aqueous solution containing polyvinyl alcohol at a concentration of 0.050% by weight was used instead of the aqueous solution of the carbodiimide polymer in the formation of the coating layer.

(Comparative Example 2)
The composite semipermeable membrane before forming the coating layer in Example 1 was designated as Comparative Example 2.

[evaluation]
The separation membranes obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in Table 1.
<Evaluation of membrane performance (measurement of salt permeability)>
The obtained flat membrane-like separation membrane was cut into a predetermined shape and size and set in a cell for flat membrane evaluation. An aqueous solution containing 2000 mg / L of NaCl and adjusted to pH 6.5 to 7 with NaOH was permeated at 25 ° C. by applying a differential pressure of 1.05 MPa to the supply side and the permeation side of the separation membrane for 30 minutes. .. The conductivity of the permeate obtained by this operation was measured, and the salt permeability (%) was calculated. The salt permeability was calculated by the following formula using the correlation (calibration curve) between the NaCl concentration and the aqueous conductivity.
Salt permeability (%) = {(NaCl concentration in permeate (mg / L)) / (NaCl concentration in feed solution (mg / L))} x 100

Further, in each example, the salt permeability ratio based on the salt permeability of Comparative Example 2 in which the coating layer was not formed was determined. More specifically, the salt permeability ratio (%) = {(salt permeability (%) of each example) / (salt permeability (%) of Comparative Example 2)} × 100 was obtained. The criteria for evaluating the salt permeability ratio were as follows.
A: Less than 65% B: 65% or more and less than 90% C: 90% or more and 100% or less

<Evaluation of chemical resistance>
After the salt permeability was first measured as described above (after the initial salt permeability measurement), the separation membrane was immersed in a washing solution which is an aqueous sodium hydroxide solution having a pH of 12.5 for 3 weeks. After that, the separation membrane was set again in the cell for flat membrane evaluation, the aqueous solution was permeated for 30 minutes under the same conditions as the initial salt permeability measurement, and then the conductivity on the supply side and the permeation side was measured, and the same was performed. The salt permeability was calculated.

Then, the rate of change in the salt permeability before and after washing the separation membrane was determined. More specifically, the rate of change in salt permeability (%) = {(salt permeability after washing (%)) / (salt permeability before washing (%))} × 100 was determined. The criteria for evaluating the rate of change in salt permeability were as follows.
〇: Less than 110% ×: 110% or more

As shown in Table 1, in Examples 1 to 8 in which the carbodiimide compound was used to form the coating layer, the rate of change in the salt permeability before and after washing was close to 100%, and the resistance to the washing liquid was high. I was able to confirm that. Further, it was found that Examples 1 to 5 in which the carbodiimide group-containing polymer was used for forming the coating layer showed a salt permeability of less than 65% and had a particularly excellent separation performance.

<Analysis of separation membrane surface>
The separation membrane of Example 8 was washed by pressurized water flow with an acid and an alkali, and the surface of the coating layer before and after the washing was analyzed. In the analysis, the spectral intensity of the secondary ion was measured using a time-of-flight secondary ion mass spectrometer (TOF.SIMS 5 manufactured by ION-TOF). Time-of-flight secondary ion mass spectrometry ^{Bi3 ++} primary ions, using the Time-OF-flight type mass analyzer to secondary ion detection ^{_{system, CN 2 - (m / z}} : 40) and _CHN ² - (m The ion intensity ratio was calculated by dividing / z: 41) by the negative total ion intensity. Further, the separation film of Comparative Example 2 (the one on which the coating layer was not formed) was also analyzed in the same manner. The calculated ionic strength ratio is shown in Table 2.

As shown in Table 2, from the surface of the separation membrane of Example 8 solution having the coating layer formed by applying a containing carbodiimide compound, CN by a time-of-flight secondary ion mass spectrometry ₂ ^- fragment and CHN ₂ ^- fragment was confirmed to be detected. It was also clarified that the peak intensity of each fragment changed little before and after washing with chemicals.

1 Coating layer 2 Separation function layer 3 Porous support layer 4 Base material 5 Porous support 10 Separation membrane

Claims (6)

With a porous support
The polyamide-based separation functional layer provided on the porous support and
Including a coating layer provided on the polyamide-based separation functional layer,
(M / z = 40) and / or _CHN ² - - fragments of (m / z = 41) is detected _CN ² in the analysis by the time-of-flight secondary ion mass spectrometry of the coating layer (TOF-SIMS) , Separation membrane. With a porous support
The polyamide-based separation functional layer provided on the porous support and
Including a coating layer provided on the polyamide-based separation functional layer,
A separation membrane in which the coating layer contains a carbodiimide compound and / or a reaction product thereof. The separation membrane according to claim 1 or 2, wherein the coating layer contains a carbodiimide group-containing polymer and / or a reaction product thereof. The separation membrane according to claim 3, wherein the carbodiimide group-containing polymer has a weight average molecular weight of 500 to 10,000. Form a porous support,
A polyamide-based separation functional layer is formed on the porous support to form a polyamide-based separation functional layer.
A method for producing a separation membrane, which comprises forming a coating layer containing a carbodiimide compound and / or a reaction product thereof on the polyamide-based separation functional layer. The separation membrane according to claim 5, wherein forming a coating layer containing the carbodiimide compound and / or a reaction product thereof comprises applying a solution containing a carbodiimide group-containing polymer to the polyamide-based separation functional layer. Manufacturing method.

Images