JP2018169308A - Method for measuring concentration of carbon nano-tube in reverse osmosis membrane and measurement device, and manufacturing method of reverse osmosis composite membrane - Google Patents

Abstract

To provide a measurement method for measuring the concentration of a carbon nano-tube in a reverse osmosis membrane with a simple method by non-destruction.SOLUTION: A measurement method according to the present invention is a method for measuring the concentration of a carbon nano-tube in a reverse osmosis membrane with respect to a reverse osmosis composite membrane provided with the reverse osmosis membrane containing the carbon nano-tube on a porous support. The measurement method includes a calibration curve creation step (S10), an analysis step (S20) and a calculation step (S30). The calibration curve creation step (S10) creates a calibration curve showing a correspondence between concentration of the carbon nano-tube and infrared absorption spectra with respect to the reverse osmosis composite membrane containing the carbon nano-tube with a known concentration. The analysis step (S20) analyzes the infrared absorption spectra with respect to the reverse osmosis composite membrane of the analysis object. The calculation step (S30) calculates the concentration of the carbon nano-tube contained in the reverse osmosis membrane of the analysis object from the infrared absorption spectra obtained in the analysis step (S20) based on the calibration curve.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method and apparatus for measuring the concentration of carbon nanotubes in a reverse osmosis membrane, and a method for producing a reverse osmosis composite membrane.

  A reverse osmosis composite membrane containing carbon nanotubes has been proposed (Patent Document 1). The reverse osmosis composite membrane can be excellent in chlorine resistance because the carbon nanotubes are defibrated. The content of the carbon nanotubes in the reverse osmosis membrane of the reverse osmosis composite membrane is measured using a thermal analyzer using the difference in the thermal decomposition start temperature between polyamide and carbon nanotubes.

  In addition, as a method for examining the concentration of single-walled carbon nanotubes (SWNT) in a carbon soot sample, a method using solid nuclear magnetic resonance (NMR) has been proposed (Patent Document 2).

International Publication No. 2016/158992 JP 2008-534984

  An object of the present invention is to provide a measuring method for measuring the concentration of carbon nanotubes in a reverse osmosis membrane by a simple non-destructive method, a measuring apparatus for the measurement, and production of a reverse osmosis composite membrane in which the concentration of carbon nanotubes is measured It aims to provide a method.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
The measurement method according to this application example is
For a reverse osmosis composite membrane provided with a reverse osmosis membrane containing carbon nanotubes on a porous support, a method for measuring the concentration of the carbon nanotubes in the reverse osmosis membrane,
A sample of a reverse osmosis composite membrane containing carbon nanotubes of a known concentration is irradiated with infrared rays from the reverse osmosis membrane side to analyze in advance the infrared absorption spectrum of the porous support, and the concentration of carbon nanotubes and the infrared absorption spectrum A calibration curve creating process for creating a calibration curve indicating the correspondence between
For the reverse osmosis composite membrane to be analyzed, an analysis step of analyzing the infrared absorption spectrum of the porous support by irradiating infrared rays from the reverse osmosis membrane side;
From the infrared absorption spectrum obtained in the analysis step, based on the calibration curve, a calculation step of calculating the concentration of carbon nanotubes contained in the analysis target reverse osmosis membrane;
It is characterized by including.

[Application Example 2]
In the measurement method according to this application example,
The porous support is polysulfone;
In the calibration curve creating step, the correspondence relationship is the concentration of carbon nanotubes and 1500.
cm ^-1 or 1510 cm ^-1 or less of the intensity of the absorption peak in the absorption peak and 1480 cm ^-1 or 1490cm ^-1 within the range that is within the range ratio and a relationship, and,
In the calculating step, from the infrared absorption spectrum obtained by the analysis step, the absorption peak in the range of the absorption peak and 1480 cm ^-1 or 1490cm ^-1 or less within the range of 1500 cm ^-1 or 1510 cm ^-1 or less And the concentration of the carbon nanotubes can be calculated based on the calibration curve.

[Application Example 3]
In the measurement method according to this application example,
In the calibration curve creation step and the analysis step, an infrared absorption spectrum can be analyzed using a total reflection infrared spectrometer.

[Application Example 4]
In the measurement method according to this application example,
The reverse osmosis membrane may include carbon nanotubes defibrated in a crosslinked polyamide and dispersed throughout the reverse osmosis membrane.

[Application Example 5]
In the measurement method according to this application example,
The concentration of the carbon nanotubes contained in the reverse osmosis membrane may be more than 0% by mass and 30% by mass or less.

[Application Example 6]
The measuring device according to this application example is
A reverse osmosis composite membrane provided with a reverse osmosis membrane containing carbon nanotubes on a porous support, a measuring device for measuring the concentration of the carbon nanotubes in the reverse osmosis membrane,
For a sample of a reverse osmosis composite membrane containing carbon nanotubes of known concentration, the concentration and red of carbon nanotubes obtained by analyzing the infrared absorption spectrum of the porous support in advance by irradiating infrared rays from the reverse osmosis membrane side. A storage unit in which a calibration curve indicating a correspondence relationship with the external absorption spectrum is stored;
For the reverse osmosis composite membrane to be analyzed, an infrared ray is irradiated from the reverse osmosis membrane side, and an analysis unit that analyzes the infrared absorption spectrum of the porous support,
From the infrared absorption spectrum obtained in the analysis unit, based on the calibration curve, a calculation unit for calculating the concentration of carbon nanotubes in the analysis target reverse osmosis membrane;
It is characterized by including.

[Application Example 7]
The manufacturing method of the reverse osmosis composite membrane according to this application example,
Forming a reverse osmosis membrane containing carbon nanotubes on a porous support;
For the reverse osmosis composite membrane in which the reverse osmosis membrane is formed on the porous support, the concentration of the carbon nanotubes in the reverse osmosis membrane is measured by the measurement method described in the application example,
A reverse osmosis composite membrane having a reverse osmosis membrane having a predetermined carbon nanotube concentration is obtained.

  According to the measurement method of the present invention, the concentration of carbon nanotubes in the reverse osmosis membrane can be measured by a simple non-destructive method. Moreover, according to the measuring apparatus of this invention, the density | concentration of the carbon nanotube in a reverse osmosis membrane can be measured by the simple method by nondestructive. Furthermore, according to the manufacturing method of the reverse osmosis composite membrane of this invention, the reverse osmosis composite membrane by which the density | concentration of the carbon nanotube was measured can be manufactured.

FIG. 1 is a longitudinal sectional view schematically showing a reverse osmosis composite membrane. FIG. 2 is a plan view schematically showing a smooth surface of a reverse osmosis membrane observed with a scanning electron microscope. FIG. 3 is a graph showing the distribution of the closest distance of carbon nanotubes. FIG. 4 is a flowchart illustrating a measurement method for measuring the concentration of carbon nanotubes according to an embodiment. FIG. 5 is a block diagram showing the overall configuration of a measurement apparatus for measuring the concentration of carbon nanotubes according to an embodiment. FIG. 6 is a schematic explanatory diagram of attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR). FIG. 7 is a graph showing the dependence of the absorption spectrum obtained by Fourier transform infrared spectroscopy on the concentration of carbon nanotubes. FIG. 8 is a diagram showing the relationship between the concentration of carbon nanotubes and the intensity ratio of absorption peaks.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are essential constituent requirements of the present invention.

  The measurement method according to this embodiment is a method for measuring the concentration of the carbon nanotubes in the reverse osmosis membrane for a reverse osmosis composite membrane in which a reverse osmosis membrane containing carbon nanotubes is provided on a porous support. The sample of the reverse osmosis composite membrane containing carbon nanotubes with a known concentration was irradiated with infrared rays from the reverse osmosis membrane side to analyze in advance the infrared absorption spectrum of the porous support, and the concentration of carbon nanotubes and the infrared absorption spectrum A calibration curve creation process to create a calibration curve showing the correspondence between the reverse osmosis composite membrane and the analysis of analyzing the infrared absorption spectrum of the porous support by irradiating infrared rays from the reverse osmosis membrane side Step, and the concentration of carbon nanotubes contained in the reverse osmosis membrane to be analyzed, based on the calibration curve, from the infrared absorption spectrum obtained in the analysis step A calculation step of calculating to, characterized in that it comprises a.

A. Reverse Osmosis Composite Membrane The reverse osmosis composite membrane 100 will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view schematically showing a reverse osmosis composite membrane 100, FIG. 2 is a plan view schematically showing a smooth surface of a reverse osmosis membrane 104 observed with a scanning electron microscope, and FIG. It is a graph which shows distribution of the closest distance of a carbon nanotube.

  In the reverse osmosis composite membrane 100, a reverse osmosis membrane 104 is provided on a porous support 102. At least one surface of the porous support 102 is covered with the reverse osmosis membrane 104. The reverse osmosis membrane 104 includes a crosslinked polyamide (hereinafter, an example of the crosslinked aromatic polyamide 120 will be described, but is not limited thereto) and a carbon nanotube 110. The entire surface of the reverse osmosis membrane 104 (microscopic observation) is covered with the crosslinked aromatic polyamide 120.

The reverse osmosis membrane 104 includes carbon nanotubes 110 defibrated in a cross-linked aromatic polyamide 120 and dispersed throughout the reverse osmosis membrane 104. The crosslinked aromatic polyamide 120 serves as a matrix, and the space between adjacent defibrated carbon nanotubes 110 is filled with the crosslinked aromatic polyamide 120. Usually, the carbon nanotube raw material is in an aggregated state in contact with each other due to intermolecular force and forms an agglomerate. The carbon nanotubes 110 are cross-linked aromatically by releasing the carbon nanotubes from the agglomerate by a process described later. A defibrated state dispersed in the polyamide 120 is obtained. It is confirmed by the distribution of the closest distance of the carbon nanotubes 110 in the reverse osmosis membrane 104 that the carbon nanotubes 110 are disentangled in the cross-linked aromatic polyamide 120 as disclosed in WO2016 / 1588992. can do.

  The closest distance of the carbon nanotube can be measured by observation with a scanning electron microscope. Specifically, a thin film-like surface is formed by cutting along the surface of the reverse osmosis composite membrane 100 by a cryomicrotome method (for example, cutting at the position of the arrow shown on the left side of FIG. 1) and making the surface of the reverse osmosis membrane 104 a smooth surface. A test piece is cut out, and the smooth surface (reverse osmosis membrane 104) of the test piece is observed with a scanning electron microscope.

  As shown in FIG. 2, when the smooth surface of the reverse osmosis membrane 104 is observed with a scanning electron microscope, cut portions of the carbon nanotubes 110 scattered in the crosslinked aromatic polyamide 120 can be seen. In FIG. 2, the cut portion of the carbon nanotube 110 is indicated by a black dot. In the reverse osmosis membrane 104, the closest distance between the carbon nanotubes is measured not as the distance between the carbon nanotube surfaces but as the distance between the centers of the cut surfaces of the carbon nanotubes.

  A method of measuring the closest distance will be specifically described with reference to FIG.

  First, an image of the smooth surface of the reverse osmosis membrane 104 photographed with a scanning electron microscope as shown in FIG. 2 is taken into a computer.

  Next, the measurer displays this image on a computer screen and cuts a predetermined number (20,000) of carbon nanotubes 110 indicated by black dots in FIG. 2 in a predetermined area (measurement area 441 square micrometers). Get the coordinates on the image for each copy.

  Next, when the coordinates of a predetermined number of adjacent black points are obtained, another black point closest to each black point is found, and the distance between the two points is obtained for each black point. For example, among the plurality of black spots around the carbon nanotube 110a in FIG. 2, the black spot closest to the coordinates of the carbon nanotube 110a is the coordinates of the carbon nanotube 110b, and the distance between the two points is the carbon nanotube 110a. The closest distance L. The operation for obtaining the closest distance L from the distance between the two points is performed for each black point. The operation of finding the coordinates of the other black point closest to the coordinates of the black point in the image, the operation of measuring the distance between the two points, and the operation of obtaining the closest distance L can be automatically analyzed and processed by a computer. Good.

  From this measurement result, the distribution of the closest distance of the carbon nanotube 110 is created as a graph plotted with the horizontal axis as the closest distance (nm) and the vertical axis as the number of measurement points (frequency). The measurement area of the test piece is 441 square micrometers, and the number of measurement points is 20,000. If the measurement area of the test piece is 200 square micrometers or more, the number of measurement points is 10,000 or more, and the adjacent carbon nanotubes 110 are measured without omission, a distribution that can determine whether the carbon nanotubes 110 are defibrated is obtained. However, it is preferable that the measurement area is 400 square micrometers or more and the number of measurement points is 20,000 or more.

  In the present invention, the fact that the carbon nanotubes 110 in the reverse osmosis membrane 104 are defibrated means that the distribution of the closest distance of the carbon nanotubes 110 in the reverse osmosis membrane 104 peaks within the thickness range of the reverse osmosis membrane 104. The half width of the peak is equal to or less than the thickness of the reverse osmosis membrane 104.

The distribution of the closest distance of the carbon nanotube will be described with reference to FIG. FIG. 3 is a graph showing the distribution of the closest distance of carbon nanotubes, which is an example of measuring defibrated carbon nanotubes. A sample (defibration sample) in which the carbon nanotubes used for the measurement were defibrated was a test piece cut out from a reverse osmosis membrane (the content of carbon nanotubes in the crosslinked polyamide was 15.5% by mass) produced by the production method described later. It is. As shown in FIG. 3, the distribution of the closest distance of the carbon nanotubes that have been defibrated has a peak within the range of the thickness of the reverse osmosis membrane (for example, 100 nm) as indicated by a triangle mark. And the half width of this peak is below the thickness of a reverse osmosis membrane. Further, the distribution of the closest distance of the carbon nanotubes that have been defibrated is a normal distribution. When the carbon nanotubes are not sufficiently defibrated and contain aggregates of carbon nanotubes, they do not have a clear peak within the thickness range of the reverse osmosis membrane as shown by the circles in FIG. Nor does it show a normal distribution. In the example shown in FIG. 3, a sample containing unaggregated carbon nanotubes (undefibrated sample) is a second aqueous solution obtained by simply performing ultrasonic treatment without going through the second mixing step described later. It is the test piece produced using it. It should be noted that the interval between carbon nanotubes in the agglomerate (referred to herein as the aggregate having a maximum diameter of 50 nm or more) cannot be measured. This is because, when cut by the cryomicrotome method, the reverse osmosis membrane 104 is cut while avoiding the agglomerates, so that the agglomerates cannot be confirmed on the smooth surface.

  The measurement results in FIG. 3 were obtained by cutting out a thin-film test piece having a smooth surface as the reverse osmosis membrane 104 as shown in FIG. Even if the cross section is measured, the distribution is basically the same. This is because the carbon nanotubes 110 are distributed almost isotropically in three dimensions.

  In reverse osmosis membranes containing defibrated carbon nanotubes, carbon nanotubes are dispersed at a relatively high concentration (high blending ratio), so the closest distance of carbon nanotubes is rarely greater than the thickness of the reverse osmosis membrane. . Since the closest distance of the carbon nanotube is almost equal to or less than the film thickness of the reverse osmosis membrane, the half width of the peak in the distribution of the closest distance is equal to or less than the film thickness of the reverse osmosis membrane, and the peak position is also the thickness of the reverse osmosis membrane. Within range.

  In addition, when the carbon nanotubes are not defibrated, aggregates are formed. Therefore, the concentration of the carbon nanotubes is low and the carbon nanotubes are widely dispersed in the places where there are no aggregates. Therefore, there are many cases where the closest distance is greater than the film thickness of the reverse osmosis membrane, and the distribution is wide like the undefibrated sample in FIG. 3, and the closest distance is less than the film thickness of the reverse osmosis membrane. There are few points.

  The distribution of the closest distance of the carbon nanotubes in the reverse osmosis membrane can be a normal distribution as shown in FIG. This is because when the carbon nanotubes in the reverse osmosis membrane are defibrated, the variation in the distribution of the closest distance becomes small, and the distribution of the closest distance of the carbon nanotube shows a normal distribution. Here, the normal distribution includes a distribution approximate to the normal distribution. Further, the distribution of the closest distance of the carbon nanotubes in the reverse osmosis membrane may be a Poisson distribution or a Lorentz distribution.

  From the experience of measuring the sample of the example, it is known that the sample in which the carbon nanotube has been defibrated exhibits a normal distribution with an average distance of 20 nm to 80 nm and a standard deviation σ of 20 nm to 75 nm.

  The graph showing the distribution of the closest distance of carbon nanotubes as shown in FIG. 3 shows that the peak appears on the left side when the concentration of carbon nanotubes in the reverse osmosis membrane is high, and conversely the peak appears on the right side when the concentration of carbon nanotubes is low. Appear in

The reverse osmosis membrane 104 desirably contains almost no aggregates of the carbon nanotubes 110. If there is an agglomerate in the reverse osmosis membrane 104, the agglomerate part becomes a structural defect and the strength of the membrane is impaired. Further, in the reverse osmosis membrane 104 having a large number of aggregates, a region of only the crosslinked aromatic polyamide in which the carbon nanotube 110 does not exist between the aggregates and the adjacent aggregates, in particular, a crosslinked aromatic polyamide having no molecular orientation. Since there is a wide area, it is easily deteriorated by cleaning with oxidizing chlorine. Furthermore, in the reverse osmosis membrane 104 having a large number of aggregates, the desalting performance is impaired because the crosslinked aromatic polyamide does not enter the interior of the aggregates.

  In the reverse osmosis composite membrane 100 illustrated in FIG. 1, the concentration of the carbon nanotubes 110 included in the reverse osmosis membrane 104 may be more than 0 mass% and 30 mass% or less. Further, the concentration of the carbon nanotubes 110 in the reverse osmosis membrane 104 in the reverse osmosis composite membrane 100 can be 5% by mass to 25% by mass, and particularly 5% by mass to 20% by mass.

  Examples of the type of solution separated by the reverse osmosis composite membrane 100 include high-concentration brine, seawater, concentrated seawater (desalination), and the like.

  The reverse osmosis composite membrane can be used, for example, by incorporating it into a spiral, tubular, or plate-and-frame module, and by bundling hollow fibers into a module.

A-1. Carbon nanotube The carbon nanotube may have an average diameter (fiber diameter) of 5 nm to 30 nm. Since the thickness of the commercially available reverse osmosis composite membrane is 100 nm or more and 500 nm or less, the carbon nanotube is preferably a thin one having a thickness of 30 nm or less, and the carbon nanotube has a thickness of 5 nm or more for ease of handling in the defibration process described later. preferable. The carbon nanotube may have an average length of 1 μm or more and 10 μm or less. This is because if the carbon nanotube is too short, it may protrude from the surface of the reverse osmosis membrane. Commercially available carbon nanotubes having a length of 10 μm or less can be used.

  In the detailed description of the present invention, the average diameter and the average length of the carbon nanotubes are, for example, 5,000 times imaged by an electron microscope (the magnification can be appropriately changed according to the size of the carbon nanotubes), and the diameters and lengths of 200 or more locations. It can be obtained by measuring the thickness and calculating the arithmetic average value.

  The carbon nanotubes can be oxidized, for example, in order to improve the reactivity with the liquid on the surface.

  The carbon nanotube may be a so-called carbon nanotube having a shape formed by winding one surface of graphite (graphene sheet) of carbon hexagonal mesh surface, and is a multi-wall carbon nanotube (MWCNT: multi-wall carbon nanotube). be able to.

  Examples of carbon nanotubes having an average diameter of 5 nm to 30 nm include NC-7000 manufactured by Nanocyl.

  A carbon material partially having a carbon nanotube structure can also be used. In addition to the name “carbon nanotube”, it may be called “graphite fibril nanotube” or “vapor-grown carbon fiber”.

Carbon nanotubes can be obtained by vapor deposition. The vapor phase growth method is also called catalytic chemical vapor deposition (CCVD), and is a method for producing carbon nanotubes by gas phase pyrolysis of a gas such as hydrocarbon in the presence of a metal catalyst. . The vapor phase growth method will be described in more detail. For example, an organic compound such as benzene or toluene is used as a raw material, an organic transition metal compound such as ferrocene or nickelcene is used as a metal catalyst, and these are used together with a carrier gas at a high temperature such as 400 ° C. It is introduced into a reaction furnace set at a reaction temperature of 1000 ° C or lower and floated on a floating state or a floating reaction method for generating carbon nanotubes on the reaction furnace wall, or in advance on ceramics such as alumina and magnesium oxide. A catalyst supported reaction method (Substrate Reaction Method) in which the supported metal-containing particles are brought into contact with a carbon-containing compound at a high temperature to form carbon nanotubes on the substrate can be used.

  Carbon nanotubes having an average diameter of 5 nm to 30 nm can be obtained by a catalyst-supporting reaction method, and carbon nanotubes having an average diameter of more than 30 nm and not more than 110 nm can be obtained by a floating flow reaction method.

The diameter of the carbon nanotube can be adjusted by, for example, the size of the metal-containing particles and the reaction time. Average diameter 30nm or less of the carbon nanotubes than 5nm a nitrogen adsorption specific surface area of 10 m ² / g or more 500 meters ² / g can be less, can be more or less 100 m ² / g or more 350 meters ² / g, In particular, it can be 150 m ² / g or more and 300 m ² / g or less.

A-2. Polyamide The polyamide can be an aromatic polyamide. The polyamide in the reverse osmosis membrane is a crosslinked product.

  The aromatic polyamide contains an aromatic amine component. The aromatic polyamide can be a wholly aromatic polyamide. As aromatic amines, m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene 2,4-diaminoanisole, amidole, xylylenediamine, at least one aromatic polyfunctional amine selected from the group consisting of N-methyl-m-phenylenediamine and N-methyl-p-phenylenediamine, May be used alone or in combination of two or more.

The cross-linked aromatic polyamide can have a functional group selected from the group consisting of COO ⁻ , NH ₄ ⁺ , and COOH.

A-3. Porous Support The porous support 102 shown in FIG. 1 is provided to give the reverse osmosis membrane 104 mechanical strength. The porous support 102 may not substantially have separation performance.

  The porous support 102 has fine pores from the front surface to the back surface. As the porous support 102, polysulfone, cellulose acetate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, polyphenylene sulfide sulfone, or the like can be used. Polysulfone is suitable for the porous support 102 because it has high chemical, mechanical and thermal stability.

B. Measurement Method A measurement method will be described with reference to FIG. FIG. 4 is a flowchart for explaining a measurement method for measuring the concentration of carbon nanotubes according to an embodiment.

As shown in FIG. 4, the measurement method according to this embodiment measures the concentration of carbon nanotubes in a reverse osmosis membrane for a reverse osmosis composite membrane in which a reverse osmosis membrane containing carbon nanotubes is provided on a porous support. A calibration curve creation step S10, an analysis step S20, and a calculation step S30. The measurement method may further include a display step S40. The reverse osmosis composite membrane is desirably dispersed throughout the reverse osmosis membrane in a state where the carbon nanotubes in the reverse osmosis membrane are defibrated. This is because, in infrared spectroscopy, infrared light is transmitted through the reverse osmosis membrane, and therefore accurate measurement cannot be performed if the distribution of carbon nanotubes in the reverse osmosis membrane is uneven.

B-1. Calibration curve creation step In the calibration curve creation step (S10), a sample of a reverse osmosis composite membrane containing carbon nanotubes of a known concentration is irradiated with infrared rays from the reverse osmosis membrane side to obtain an infrared absorption spectrum related to the porous support beforehand. Analyze and create a calibration curve showing the correspondence between the concentration of carbon nanotubes and the infrared absorption spectrum.

  First, the concentration of carbon nanotubes in the reverse osmosis membrane in the sample of the reverse osmosis composite membrane can be measured by the method disclosed in Patent Document 1 (International Publication No. 2016/158992). Specifically, it can be measured using the difference in the thermal decomposition start temperature between polyamide and carbon nanotube using a thermal analyzer. Further, other known methods may be used for the concentration of carbon nanotubes in the sample.

  Next, an infrared absorption spectrum is analyzed for the sample whose carbon nanotube concentration is known by a thermal analyzer. For the analysis of the infrared absorption spectrum, another part of the same sample as that used for the thermal analysis is used. An infrared spectrophotometer can be used for analysis of the infrared absorption spectrum, and in particular, total reflection infrared spectroscopy (IR-ATR method) using a Fourier transform infrared spectrometer (FT-IR) is used. it can.

  In total reflection infrared spectroscopy, an absorption spectrum of a sample is obtained using an evanescent wave generated by bringing a sample into close contact with a prism having a high refractive index and causing infrared light to enter the prism. In total reflection infrared spectroscopy, the depth of light reaching the sample (the depth of light penetration) is considered to be about 0.5 μm to 2 μm. The reverse osmosis membrane side of the reverse osmosis composite membrane as a sample is brought into close contact with the prism, infrared light is irradiated from the reverse osmosis membrane side, and the infrared light is reflected in the porous support. Therefore, the absorption spectrum of the sample obtained by total reflection infrared spectroscopy is an absorption spectrum related to the porous support.

  The present inventors have found that the absorption spectrum of the porous support is closely related to the concentration of carbon nanotubes in the reverse osmosis membrane through which infrared light is transmitted in the spectroscopic method. A calibration curve showing the correspondence between the concentration of carbon nanotubes and the infrared absorption spectrum is created from the absorption spectrum of the porous support.

For example, when the porous support is a polysulfone, correspondence between the calibration curve, the concentration of carbon nanotubes in the reverse osmosis membrane, the absorption peak in the range of 1500 cm ^-1 or 1510 cm ^-1 or less _{(I 1)} and 1480 cm ^-1 or 1490cm ^-1 absorption peak within the range _{(I 2)} and the intensity ratio of the _{(Ia = I 2 / I 1} ), it may be a relationship.

Infrared absorption spectra of polysulfone, appear two peaks and the peak near the peak and 1505cm ^-1 in the vicinity of 1485cm ^-1. The infrared absorption spectrum of the reverse osmosis composite membrane varies depending on the concentration of carbon nanotubes. The reflected light from polysulfone has infrared light reabsorption of carbon nanotubes, and the reabsorption is 2 in polysulfone. It is assumed that there is a difference in absorption at the wave number (cm ⁻¹ ) of one peak.

The calibration curve is obtained by graphing the relationship between the absorption peak intensity ratio (Ia = I ₂ / I ₁ ) obtained by spectroscopy and the concentration of carbon nanotubes (concentration measured in advance by a thermal analyzer) and by the least square method. be able to.

B-2. Analysis Step The analysis step (S20) analyzes the infrared absorption spectrum of the porous support by irradiating infrared rays from the reverse osmosis membrane side with respect to the reverse osmosis composite membrane to be analyzed.

  The infrared absorption spectrum of the sample of the reverse osmosis composite membrane to be analyzed is analyzed by the same method as in the calibration curve creation step (S10). The sample of the reverse osmosis composite membrane to be analyzed is a sample whose carbon nanotube concentration in the reverse osmosis membrane is unknown.

  In the calibration curve creation step (S10) and the analysis step (S20), the infrared absorption spectrum can be analyzed using a total reflection infrared spectroscopic device. As the total reflection infrared spectroscopic apparatus, a commercially available apparatus can be employed, and examples thereof include a Nicolet 6700 FT-IR apparatus manufactured by Thermo Scientific.

B-3. Calculation Step The calculation step (S30) calculates the concentration of carbon nanotubes contained in the reverse osmosis membrane to be analyzed based on the calibration curve from the infrared absorption spectrum obtained in the analysis step (S20).

For example, when the porous support is a polysulfone, the obtained infrared absorption spectrum by the analysis step (S20), the absorption peak in the range of 1500 cm ^-1 or 1510 cm ^-1 or less as _{(I 1)} 1480cm ^-1 The intensity ratio (Ib = I ₂ / I ₁ ) with the absorption peak (I ₂ ) in the range of 1490 cm ⁻¹ or less is obtained, and based on the calibration curve obtained in the calibration curve creation step (S10), carbon The concentration of the nanotube is calculated. That is, if the absorption peak intensity ratio (Ib) to be analyzed is obtained, the concentration of carbon nanotubes corresponding to the absorption peak intensity ratio (Ia) in the calibration curve can be calculated.

B-4. Display Step In the display step (S40), the concentration of carbon nanotubes in the reverse osmosis membrane calculated in the calculation step (S30) is displayed on, for example, a display.

C. Measuring Device A measuring device for measuring the concentration of carbon nanotubes in the reverse osmosis membrane will be described with reference to FIG. FIG. 5 is a block diagram illustrating the overall configuration of the measurement apparatus 1 that measures the concentration of carbon nanotubes according to an embodiment.

  As shown in FIG. 5, the measuring apparatus 1 according to the present embodiment has a concentration of carbon nanotubes in a reverse osmosis membrane for a reverse osmosis composite membrane in which a reverse osmosis membrane containing carbon nanotubes is provided on a porous support. The measuring device 1 for measuring includes an analysis unit 20, a calculation unit 30, and a storage unit 40. As the measuring apparatus 1, a computer capable of executing the processing of each unit can be employed.

  The measuring device 1 may further include an input unit 10. The input unit 10 may include a known input device such as a keyboard.

  The measuring device 1 may further include a display unit 50. The display part 50 can display the analysis result by the analysis part 20, and the calculation result by the calculation part 30, for example. The display unit 50 can employ a known display device such as a display.

  The storage unit 40 is a carbon obtained by previously analyzing an infrared absorption spectrum of a porous support by irradiating infrared rays from the reverse osmosis membrane side with respect to a sample of a reverse osmosis composite membrane containing carbon nanotubes having a known concentration. A calibration curve indicating the correspondence between the concentration of the nanotube and the infrared absorption spectrum is stored.

  The analysis unit 20 irradiates infrared rays from the reverse osmosis membrane side with respect to the analysis target reverse osmosis composite membrane, and analyzes the infrared absorption spectrum of the porous support. The analysis unit 20 may be a part of the spectroscopic device or may analyze based on an output from the spectroscopic device. The analysis unit 20 is, for example, a computer.

  The calculation unit 30 calculates the concentration of carbon nanotubes in the reverse osmosis membrane to be analyzed from the infrared absorption spectrum obtained by the analysis unit 20 based on the calibration curve. The calculation unit 30 may be a computer built in or connected to the spectroscopic device.

D. Method for Producing Reverse Osmosis Composite Membrane A method for producing a reverse osmosis composite membrane according to this embodiment comprises forming a reverse osmosis membrane containing carbon nanotubes on a porous support, and the reverse osmosis membrane on the porous support. A reverse osmosis composite membrane having a reverse osmosis membrane having a predetermined carbon nanotube concentration is measured by measuring the concentration of the carbon nanotube in the reverse osmosis membrane by the measurement method described in B above. It is characterized by obtaining.

  The manufacturing process of a reverse osmosis composite membrane obtains a reverse osmosis composite membrane by making a liquid mixture contact a porous support body, and then carrying out the crosslinking reaction of the amine component in the liquid mixture adhering to the porous support body.

  The step of obtaining a mixed solution includes, for example, a step of mixing a first aqueous solution containing an amine component and a second aqueous solution containing defibrated carbon nanotubes to obtain a third aqueous solution containing the amine component and carbon nanotubes. be able to. Hereinafter, each step will be described.

D-1. Step of obtaining third aqueous solution The first aqueous solution contains water and an amine component. As an amine component, at least 1 sort (s) can be selected from the aromatic amine demonstrated by said A-2.

  The second aqueous solution contains water and carbon nanotubes. The second aqueous solution can exist uniformly dispersed throughout the aqueous solution in a state in which the carbon nanotubes are defibrated. The second aqueous solution is obtained from the first mixing step and the second mixing step.

  In the first mixing step, a predetermined amount of water and carbon nanotubes placed in the container can be stirred manually or by a known stirrer. The aqueous solution obtained in the first mixing step is in a state where carbon nanotubes are individually distributed in the form of particles in water. Since the carbon nanotubes used in conventional reverse osmosis membranes are stirred with an ultrasonic stirrer or the like, they exist as aggregates obtained by subdividing the aggregates in an aqueous solution and are not defibrated. After the first mixing step, the next second mixing step is performed on the aqueous solution.

In the second mixing step, the aqueous solution containing the carbon nanotubes obtained in the first mixing step is pressurized while flowing to compress the aqueous solution, and then the pressure of the aqueous solution is released or reduced to restore the aqueous solution to the original volume. including. The second mixing step is repeated a plurality of times. In the second mixing step, for example, a three roll can be used. The roll interval (nip) of each roll can be 0.001 mm or more and 0.01 mm or less. Although three rolls are used here, the number of rolls is not particularly limited, and a plurality of rolls, for example, two rolls may be used. In that case, kneading is performed at the same roll interval. can do.

  In the second mixing step, the rotation ratio of the roll may be 1.2 or more and 9.0 or less, and may be 3.0 or more and less than 9.0. This is because if the rotation ratio of the roll is large, the shearing force is increased in the aqueous solution and acts as a force for separating the carbon nanotubes. The rotation ratio of a roll here is a rotation ratio of an adjacent roll.

  In the second mixing step, the peripheral speed of the roll can be 0.1 m / s or more and 2.0 m / s or less, and further can be 0.1 m / s or more and 1.5 m / s or less. This is because, if the peripheral speed of the roll is high, kneading utilizing elasticity is possible even in an aqueous solution. The peripheral speed of a roll here is the speed of the surface of a roll.

  The aqueous solution supplied to the roll enters a very narrow nip between the rolls and is pressurized while flowing according to the rotation ratio of the roll, and a predetermined volume is sequentially supplied to the nip and is compressed in the nip to reduce the volume. Thereafter, when the aqueous solution exits the nip, the pressure is released or reduced to restore the original volume. As the volume is restored, the carbon nanotubes flow greatly, and the aggregated carbon nanotubes are loosened. By repeating this series of steps a plurality of times, defibration of the carbon nanotubes in the aqueous solution proceeds and a second aqueous solution can be obtained. The second mixing step can be performed, for example, for 3 minutes to 10 minutes. For example, when the series of steps is performed once, the second mixing step can be performed 10 times or more and 30 times or less.

  Moreover, the 2nd mixing process can be performed in the range of 0 degreeC or more and 60 degrees C or less of the temperature of the aqueous solution obtained at the 1st mixing process, and also the 2nd mixing process was obtained at the 1st mixing process. The temperature of the aqueous solution can be in the range of 15 ° C. or more and 50 ° C. or less. Since the second mixing step is performed using the bulk modulus of water, it is preferable to perform the second mixing step at as low a temperature as possible. The bulk modulus is proportional to the Young's modulus and is the reciprocal of the compressibility. This is because the Young's modulus decreases with increasing temperature and the compressibility increases with increasing temperature, and the bulk modulus also decreases with increasing temperature. Therefore, the temperature of the aqueous solution can be set to 60 ° C. or lower, and can be further set to 50 ° C. or lower. From the viewpoint of productivity, the temperature of the aqueous solution can be 0 ° C. or higher, and can be 15 ° C. or higher. This is because, when the temperature of the roll is low, for example, a problem of condensation in the roll occurs.

  The second mixing step is not limited to kneading by a roll such as a three-roll, but may be any other method as long as it is a kneading method capable of restoring after compressing the volume of the aqueous solution. For example, it is possible to use a dispersion device that compresses an aqueous solution while flowing it to cause cavitation or turbulent flow, and then rapidly reduces the pressure.

  Due to the shearing force obtained in the second mixing step, a high shearing force acts on the water, and the aggregated carbon nanotubes are gradually separated from each other by being repeatedly passed through the roll, and defibrated. Dispersed and excellent in dispersibility and dispersion stability of carbon nanotubes (carbon nanotubes are less likely to reaggregate).

  Further, the second aqueous solution can further contain a surfactant in order to maintain the defibrated state of the carbon nanotubes. Surfactants include ionic surfactants and nonionic surfactants. For example, examples of the ionic anionic surfactant include a sulfate ester type, a phosphate ester type, and a sulfonic acid type, and examples of the cationic surfactant include a quaternary ammonium salt type. Examples of amphoteric surfactants include alkyl betaine type, amide betaine type, and amine oxide type. Further, examples of the nonionic surfactant include fatty acid esters and sorbitan fatty acid esters.

  The third aqueous solution can be obtained by mixing the first aqueous solution and the second aqueous solution containing defibrated carbon nanotubes. The third aqueous solution is adjusted so that the aromatic amine is 1.0 mass% or more and 3.0 mass% or less and the carbon nanotube is 0.11 mass% or more and 1.3 mass% or less. If the aromatic amine in the third aqueous solution is less than 1.0% by mass, the crosslink density is insufficient and it is difficult to obtain a desalting rate, and if it exceeds 3.0% by mass, unreacted residual amine is increased and eluted from the membrane. In this range, it is preferable. In addition, if the carbon nanotubes in the third aqueous solution are less than 0.11% by mass, a three-dimensional structure is not formed on the entire polyamide, so that it becomes difficult to obtain chlorine resistance. This is preferable because the group polyamide film tends to peel off.

D-2. The step of obtaining the reverse osmosis composite membrane The step of obtaining the reverse osmosis composite membrane comprises contacting the third aqueous solution obtained as described above with the porous support, and then in the third aqueous solution attached to the porous support. Aromatic amines are allowed to crosslink.

  The third aqueous solution is applied to a porous support and brought into contact by impregnation. After that, a solution containing a cross-linking agent is further applied on the third aqueous solution, heat-treated to cause a polycondensation reaction at the interface between the two, and cross-linked to form a reverse osmosis membrane. Thus, a reverse osmosis composite membrane in which a reverse osmosis membrane containing carbon nanotubes is formed on the porous support described in the above “A. Reverse osmosis composite membrane” can be produced.

  As the crosslinking agent, for example, an organic solvent solution containing an acid chloride component such as trimesic acid chloride, terephthalic acid chloride, isophthalic acid chloride, or biphenyldicarboxylic acid chloride can be used.

  Next, with respect to the reverse osmosis composite membrane in which the reverse osmosis membrane is formed on the porous support, the concentration of carbon nanotubes in the reverse osmosis membrane is measured according to the measurement method of B above, and the reverse osmosis of the predetermined carbon nanotube concentration is performed. A reverse osmosis composite membrane having a membrane is obtained. For example, using the measurement results, based on the quality control criteria specified in advance, the reverse osmosis composite membrane that does not meet the quality control criteria is excluded, and the reverse osmosis composite membrane that satisfies the quality control criteria is passed (determined as a non-defective product). ). The quality control standard sets, for example, an allowable width for a predetermined carbon nanotube concentration.

  The reverse osmosis composite membrane thus obtained can have a predetermined quality control standard (a predetermined concentration of carbon nanotubes). In particular, since the concentration of carbon nanotubes in the reverse osmosis composite membrane also affects pressure resistance, chlorine resistance, fouling characteristics, etc., it is desirable to satisfy quality control standards. For example, if the concentration of carbon nanotubes in the reverse osmosis membrane is 5% by mass or more, the entire reverse osmosis membrane is reinforced by a three-dimensional structure and has excellent pressure resistance, so that the operating pressure can be increased, and the permeation flux can be increased. Contributes to higher. Moreover, since the cross-linked aromatic polyamide molecularly aligned with the carbon nanotubes is present in almost the entire reverse osmosis membrane, the chlorine resistance (oxidation resistance) is enhanced while maintaining the desalting performance of the cross-linked aromatic polyamide. Therefore, if the concentration of the predetermined carbon nanotube is set to 5% by mass or more, for example, a reverse osmosis composite membrane having a reverse osmosis membrane excellent in pressure resistance and chlorine resistance can be obtained.

  Applications of the reverse osmosis composite membrane include, for example, pretreatment for seawater, irrigation desalting, food washing water sterilization process, industrial water, and domestic water pretreatment sterilization process. Moreover, the use of a reverse osmosis composite membrane includes, for example, food industrial wastewater treatment, industrial process wastewater treatment, and RO pretreatment of activated sludge treated water.

  In the present invention, a part of the configuration may be omitted within a range having the characteristics and effects described in the present application, or each embodiment or modification may be combined.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

(1) Preparation of sample for preparing calibration curve (1-1) Preparation of third aqueous solution The first aqueous solution obtained by adding distilled water to m-phenylenediamine and stirring and mixing using a magnetic stirrer was defibrated. The second aqueous solution containing carbon nanotubes was stirred and mixed using a magnetic stirrer to obtain a third aqueous solution containing m-phenylenediamine and carbon nanotubes.

  Here, the second aqueous solution was prepared through a step of uniformly mixing the carbon nanotubes by applying pressure and reducing pressure while flowing the aqueous solution containing carbon nanotubes. Specifically, the second aqueous solution is prepared by adding a predetermined amount of multi-walled carbon nanotubes (Nanocyl-7000 manufactured by Nanosil Co., Ltd., average diameter of 10 nm (average diameter is 200 or more using scanning electron microscope imaging) to distilled water. (A value obtained by arithmetically averaging the measured values)) was manually stirred (first mixing step), and then a three-roll (EXAKT M-50 I manufactured by Nagase Screen Printing Laboratory Co., Ltd.) having a roll diameter of 50 mm (roll temperature 25). To 40 ° C. or lower) and kneaded (second mixing step) for 3 minutes to 10 minutes. The roll interval was 0.001 mm or more and less than 0.01 mm, the roll speed ratio was V1 = 1, V2 = 1.8, V3 = 3.3, and the roll speed V3 was a peripheral speed of 1.2 m / s.

(1-2) Preparation of reverse osmosis composite membrane After immersing a porous support (polysulfone of DSS GR40PP manufactured by Alfa-Laval Co., whose film thickness is 150 μm) in a third aqueous solution for 2 minutes to 3 hours, AIDEN Co., Ltd. Using a dip coater DC4300 manufactured by the company, the film surface was slowly pulled up at a pulling rate of 0.1 mm / min to 10 mm / min so that the film surface was vertical. When the immersion time of the porous support in the third aqueous solution is less than 2 minutes, the carbon nanotubes are not sufficiently taken into the porous support and it is difficult to obtain anti-fouling properties. There is a tendency for concern about oxidative degradation to increase. When the pulling rate of the dip coater is less than 0.1 mm / min, it takes time to pull the porous support from the third solution, and the amine tends to be oxidized and deteriorated. When the pulling rate exceeds 10 mm / min, there is a tendency that the cross-linked aromatic polyamide film is easily peeled off from the porous support. After drying in the air until the excess aqueous solution disappeared from the surface of the porous support, 5 ml of a 25 ° C. n-hexane solution containing 0.1% by mass of trimesic acid chloride was applied so that the membrane surface was completely wetted. After leaving still for 1 minute, in order to remove excess solution from the film, the film surface was held vertically for 1 minute to drain the liquid. Then, the reverse osmosis membrane composite membrane of Example 1- Example 6 was obtained by wash | cleaning for 2 minutes with 45 degreeC water. In addition, a sample of polyamide alone produced at the same polyamide concentration as the third aqueous solution (not including carbon nanotubes) was also obtained.

(1-3) Measurement of carbon nanotube concentration For measurement of the carbon nanotube concentration in the reverse osmosis membrane, SII EXSTAR 6000 thermal analyzer TG / DTA6200 was used. The reverse osmosis composite membrane was sampled on an alumina pan, and the concentration of carbon nanotubes was evaluated using the difference in the thermal decomposition start temperature between polyamide and carbon nanotubes in a temperature rise rate of 10 ° C./min and in an air atmosphere. The concentration of carbon nanotubes in the reverse osmosis membranes of Samples 1 to 7 was as shown in Table 1. Sample 1 was a sample of a single polyamide not containing carbon nanotubes.

(2) Infrared spectroscopy Infrared spectroscopy was performed using a Nico Scientific 6700 FT-IR apparatus 22 manufactured by Thermo Scientific. FIG. 6 is a schematic explanatory diagram of attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR) in the FT-IR apparatus 22. As shown in FIG. 6, the FT-IR device 22 includes a reflecting prism 23, an infrared laser light source 24, and an infrared detector 25. Samples 1 to 7 of the reverse osmosis composite membrane 100 are closely attached to the diamond prism (reflection prism 23) of the FT-IR device 22, and the infrared beam 26 from the infrared laser light source 24 is irradiated from the reverse osmosis membrane 104 side. The porous substrate 102 was attenuated and totally reflected. The infrared detector 25 received the reflected light from the porous support 102. The diameter of the infrared beam 26 was about 2 mm, and the incident angle was 45 degrees. Measurement wavelength is 650~4500cm ^-1, it was the resolution ^{2 cm -1.} The sample size of the reverse osmosis composite membrane 100 was about 1 cm square.

The result of infrared spectroscopy is shown in FIG. FIG. 7 is a graph showing the dependence of the absorption spectrum obtained by Fourier transform infrared spectroscopy on the concentration of carbon nanotubes. In FIG. 7, the vertical axis represents absorbance (arbitrary unit), and the horizontal axis represents wave number (cm ⁻¹ ). Samples 1 to 7 both showed absorption peaks due to absorption of polysulfone near 1485 ⁻¹ cm and 1505 cm ⁻¹ .

(3) From the results of the calibration curve creation infrared spectroscopy, of each sample in ¹⁴⁸⁵ -1 cm near the peak intensity (maximum value) _{I 2} and 1505cm ^-1 vicinity of the peak intensity (maximum value) _{I 1} ratio (Ia = I ₂ / I ₁ ) was determined. When the absorption peak intensity ratio (Ia) is obtained, the baseline is not subtracted.

  And since the density | concentration of the carbon nanotube of each sample was known by thermal analysis, the relationship shown in FIG. 8 was calculated | required based on peak intensity ratio (Ia). FIG. 8 is a diagram showing the relationship between the concentration of carbon nanotubes and the intensity ratio (Ia) of the absorption peak. In FIG. 8, the vertical axis represents the peak intensity ratio (Ia), and the horizontal axis represents the concentration of carbon nanotubes in the reverse osmosis membrane. A calibration curve (shown by a solid line) was obtained from the graph of FIG. 8 by the least square method.

(4) Measurement of the concentration of carbon nanotubes The peak intensity ratio obtained by performing infrared spectroscopic analysis of a polysulfone porous support on a sample of a reverse osmosis composite membrane in which the concentration of carbon nanotubes is unknown as in Samples 1-7. From (Ib), the concentration of carbon nanotubes can be calculated based on this calibration curve, and the concentration of carbon nanotubes contained in the sample of the reverse osmosis membrane to be analyzed can be measured.

  DESCRIPTION OF SYMBOLS 1 ... Measuring apparatus, 10 ... Input part, 20 ... Analysis part, 22 ... FT-IR apparatus, 23 ... Reflection prism, 24 ... Infrared laser light source, 25 ... Infrared detector, 26 ... Infrared beam, 30 ... Calculation part, 40 DESCRIPTION OF SYMBOLS Memory | storage part, 50 ... Display part, 100 ... Reverse osmosis composite membrane, 102 ... Porous support body, 104 ... Reverse osmosis membrane, 110 ... Carbon nanotube, 120 ... Cross-linked aromatic polyamide

Claims (7)

For a reverse osmosis composite membrane provided with a reverse osmosis membrane containing carbon nanotubes on a porous support, a method for measuring the concentration of the carbon nanotubes in the reverse osmosis membrane,
A sample of a reverse osmosis composite membrane containing carbon nanotubes of a known concentration is irradiated with infrared rays from the reverse osmosis membrane side to analyze in advance the infrared absorption spectrum of the porous support, and the concentration of carbon nanotubes and the infrared absorption spectrum A calibration curve creating process for creating a calibration curve indicating the correspondence between
For the reverse osmosis composite membrane to be analyzed, an analysis step of analyzing the infrared absorption spectrum of the porous support by irradiating infrared rays from the reverse osmosis membrane side;
From the infrared absorption spectrum obtained in the analysis step, based on the calibration curve, a calculation step of calculating the concentration of carbon nanotubes contained in the analysis target reverse osmosis membrane;
A measurement method comprising: The porous support is polysulfone;
In the calibration curve generating step, the correspondence relation, the concentration of the carbon nanotube, and an absorption peak in the range of the absorption peak and 1480 cm ^-1 or 1490cm ^-1 or less within the range of 1500 cm ^-1 or 1510 cm ^-1 or less And the intensity ratio of
In the calculating step, from the infrared absorption spectrum obtained by the analysis step, the absorption peak in the range of the absorption peak and 1480 cm ^-1 or 1490cm ^-1 or less within the range of 1500 cm ^-1 or 1510 cm ^-1 or less The measurement method according to claim 1, wherein the intensity ratio is calculated, and the concentration of the carbon nanotube is calculated based on the calibration curve.   3. The measuring method according to claim 1, wherein in the calibration curve creating step and the analyzing step, an infrared absorption spectrum is analyzed using a total reflection infrared spectroscopic device.   The measurement method according to any one of claims 1 to 3, wherein the reverse osmosis membrane includes carbon nanotubes defibrated in a crosslinked polyamide and dispersed throughout the reverse osmosis membrane. .   5. The measurement method according to claim 1, wherein the concentration of the carbon nanotubes contained in the reverse osmosis membrane is more than 0% by mass and not more than 30% by mass. A reverse osmosis composite membrane provided with a reverse osmosis membrane containing carbon nanotubes on a porous support, a measuring device for measuring the concentration of the carbon nanotubes in the reverse osmosis membrane,
For a sample of a reverse osmosis composite membrane containing carbon nanotubes of known concentration, the concentration and red of carbon nanotubes obtained by analyzing the infrared absorption spectrum of the porous support in advance by irradiating infrared rays from the reverse osmosis membrane side. A storage unit in which a calibration curve indicating a correspondence relationship with the external absorption spectrum is stored;
For the reverse osmosis composite membrane to be analyzed, an infrared ray is irradiated from the reverse osmosis membrane side, and an analysis unit that analyzes the infrared absorption spectrum of the porous support,
From the infrared absorption spectrum obtained in the analysis unit, based on the calibration curve, a calculation unit for calculating the concentration of carbon nanotubes in the analysis target reverse osmosis membrane;
A measuring device comprising: Forming a reverse osmosis membrane containing carbon nanotubes on a porous support;
The measurement method according to any one of claims 1 to 5, wherein a concentration of the carbon nanotube in the reverse osmosis membrane is determined for a reverse osmosis composite membrane in which the reverse osmosis membrane is formed on the porous support. Measured by
A reverse osmosis composite membrane having a reverse osmosis membrane having a predetermined carbon nanotube concentration is obtained.

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