WO2025183220A1 - Separation membrane, membrane separation device, and separation method - Google Patents

Abstract

A separation membrane 10 according to the present invention is provided with a separation function layer 1 containing Si, O, and C, wherein, in the analysis of the chemical bonding state of C by the C1s spectrum on a first principal surface 1a of the separation function layer 1 using X-ray photoelectron spectroscopy, the ratio of the peak area derived from the C-H bond to the total of the peak areas derived from the C-H, C-O, C=O, and COO bonds is 92 area% or less.

Description

Separation membrane, membrane separation device, and separation method

The present invention relates to a separation membrane, a membrane separation device, and a separation method.

Currently, there is a demand for a carbon-neutral society, and the development of products with a variety of functions is accelerating. For example, in industries such as semiconductors and alcohol production, large amounts of water are used in the manufacture of products. As a result, separation technologies are being developed to separate water from mixed liquids containing water and organic solvents such as alcohol, with the aim of reusing water. Also, in relation to the issue of global warming, technology is being developed to separate and capture carbon dioxide from exhaust gases at thermal power plants, cement plants, steelworks blast furnaces, and other facilities.

Membrane separation, which uses separation membranes, has been developed as a method for separating target substances from mixed fluids such as mixed liquids and mixed gases. For example, when it comes to liquid separation, which separates the target liquid from a mixed liquid, membrane separation requires less energy than separation by distillation, which requires a heating process, and can also reduce the generation of carbon dioxide. In this way, membrane separation is an excellent separation technology that uses less energy and has a smaller environmental impact.

When it comes to gas or liquid separation, separation membranes are typically used in which the part with the separation function is made of an organic material such as polyimide. On the other hand, separation membranes in which the part with the separation function is made of an inorganic material, such as zeolite separation membranes and hollow fiber membranes, have been proposed.

Conventionally, various materials and configurations of separation membranes have been proposed to improve the separation function for separating target substances from mixed fluids (for example, improving fluid permeability or separation selectivity) or to improve mechanical strength such as bending resistance. For example, Patent Document 1 discloses a gas separation membrane with excellent gas permeability, abrasion resistance, and bending resistance. Specifically, the separation membrane disclosed in Patent Document 1 has a configuration in which a resin layer with a specific configuration is formed by performing plasma treatment on a resin layer precursor containing a compound with a siloxane bond, and a protective layer containing a silicone resin and a porous layer are further disposed on top of the resin layer.

Patent No. 6652575

Conventional separation membranes, such as those disclosed in Patent Document 1, which achieve separation performance through plasma treatment, have room for improvement in terms of separation performance. Therefore, the present invention provides a separation membrane with a configuration suitable for improving separation performance. Furthermore, the present invention also provides a membrane separation device equipped with a separation membrane with a configuration suitable for improving separation performance, and a separation method using such a separation membrane.

The present invention provides
A separation functional layer containing Si, O, and C is provided,
In an analysis of the chemical bonding state of C by C1s spectrum of the first main surface of the separation functional layer by X-ray photoelectron spectroscopy, the ratio of the peak area derived from the C-H bond to the total peak area derived from C-H, C-O, C=O, and COO bonds is 92 area% or less.
A separation membrane is provided.

Furthermore, the present invention provides
A device equipped with the above separation membrane
A membrane separation device is provided.

Furthermore, the present invention provides
A separation method using the above separation membrane,
A mixed fluid containing two or more fluids including a fluid to be separated is brought into contact with one side of the separation membrane, and the mixed fluid is separated into a first fluid containing the fluid to be separated and a second fluid.
A separation method is provided.

The present invention provides a separation membrane having a configuration suitable for improving separation performance. Furthermore, the present invention also provides a membrane separation device equipped with a separation membrane having a configuration suitable for improving separation performance, and a separation method using such a separation membrane.

1 is a cross-sectional view schematically showing a separation membrane according to one embodiment of the present invention. FIG. 2 is a structural diagram showing an example of organosilica having a cyclic structure that can be contained in a separation functional layer in a separation membrane according to one embodiment of the present invention. FIG. 2 is a cross-sectional view showing a modified example of a porous support in a separation membrane according to an embodiment of the present invention. 1 is a schematic cross-sectional view of a membrane separation device equipped with a separation membrane of the present invention. FIG. 10 is a perspective view schematically showing a modified example of a membrane separation device provided with a separation membrane of the present invention. FIG. 2 is a perspective view showing the positional relationship between a low-inductance antenna and an object to be plasma processed in a plasma processing chamber used in the examples. FIG. 2 is a cross-sectional view showing the positional relationship between a low-inductance antenna and an object to be plasma processed in a plasma processing chamber used in the examples.

The separation membrane according to the first aspect of the present invention comprises:
A separation functional layer containing Si, O, and C is provided,
In an analysis of the chemical bonding state of C by C1s spectrum on the first main surface of the separation functional layer by X-ray photoelectron spectroscopy, the ratio of the peak area derived from the C-H bond to the total peak area derived from C-H, C-O, C=O, and COO bonds is 92 area% or less.

In the second aspect of the present invention, for example, in the separation membrane according to the first aspect, when the chemical bonding state of C is analyzed by X-ray photoelectron spectroscopy using a C1s spectrum on the first main surface of the separation functional layer, the ratio of the peak area due to the C-O bond to the total peak area due to C-H, C-O, C=O, and COO bonds is 5 area% or more.

In a third aspect of the present invention, for example, in a separation membrane according to the first or second aspect, the ratio of the number of O atoms to the number of Si atoms, O/Si, on the first main surface of the separation functional layer is 1.2 or greater.

In a fourth aspect of the present invention, for example, in a separation membrane according to any one of the first to third aspects, the ratio of the number of C atoms to the total number of C atoms, N atoms, O atoms, and Si atoms on the first main surface of the separation functional layer is 17 at. % or more.

In a fifth aspect of the present invention, for example, in a separation membrane according to any one of the first to fourth aspects, the ratio of the number of O atoms to the total number of C atoms, N atoms, O atoms, and Si atoms on the first main surface of the separation functional layer is 54 at. % or less.

In a sixth aspect of the present invention, for example, a separation membrane according to any one of the first to fifth aspects further comprises a porous support that supports the separation functional layer and is arranged on the second main surface side of the separation functional layer, opposite the first main surface.

In a seventh aspect of the present invention, for example, in a separation membrane according to any one of the first to sixth aspects, the separation functional layer contains a compound containing a siloxane bond.

In an eighth aspect of the present invention, for example, in the separation membrane according to the seventh aspect, the first main surface of the separation functional layer contains organosilica having siloxane bonds, Si-C bonds, and C-O bonds.

In a ninth aspect of the present invention, for example, in a separation membrane according to any one of the first to eighth aspects, the first main surface of the separation functional layer contains a second compound obtained by modifying a first compound constituting the interior of the separation functional layer by plasma treatment.

In a tenth aspect of the present invention, for example, in the separation membrane according to the ninth aspect, the first compound contains a siloxane bond.

In an eleventh aspect of the present invention, for example, in the separation membrane according to the tenth aspect, the first compound is a silicone resin.

In a twelfth aspect of the present invention, for example, in a separation membrane according to the ninth or tenth aspect, the plasma treatment is a treatment using inductively coupled plasma using a low-inductance antenna.

In a thirteenth aspect of the present invention, for example, in a separation membrane according to any one of the first to twelfth aspects, at least a portion of the first main surface of the separation functional layer is exposed on the surface of the separation membrane.

A membrane separation device according to a fourteenth aspect of the present invention comprises:
The separator includes a separation membrane according to any one of the first to thirteenth aspects.

A separation method according to a fifteenth aspect of the present invention comprises:
A separation method using a separation membrane according to any one of the first to thirteenth aspects,
The method includes bringing a mixed fluid containing two or more fluids including a fluid to be separated into a first fluid containing the fluid to be separated and a second fluid into contact with one side of the separation membrane.

In a sixteenth aspect of the present invention, for example, in the separation method according to the fifteenth aspect, the mixed fluid is a mixed gas containing two or more gases including the gas to be separated.

In a seventeenth aspect of the present invention, for example, in the separation method according to the sixteenth aspect, the gas to be separated is H ₂ , and H ₂ of the mixed gas is preferentially allowed to permeate the separation membrane.

In an 18th aspect of the present invention, for example, in the separation method according to the 15th aspect, the mixed fluid is a mixed liquid containing two or more liquids, including the liquid to be separated.

In a nineteenth aspect of the present invention, for example, in the separation method according to the eighteenth aspect, the liquid to be separated is H ₂ O, and H ₂ O in the mixed liquid is preferentially allowed to permeate the separation membrane.

The present invention will be described in detail below, but the following description is not intended to limit the present invention to any particular embodiment.

<Embodiments of Separation Membranes>
As shown in FIG. 1 , the separation membrane 10 of this embodiment includes a separation functional layer 1. The separation functional layer 1 contains Si, O, and C. The separation functional layer 1 further has a specific configuration in which, in an analysis of the chemical bonding state of C by C1s spectrum of the first main surface 1a of the separation functional layer 1 using X-ray photoelectron spectroscopy (XPS), the ratio of the peak area derived from C-H bonds to the total peak area derived from C-H, C-O, C═O, and COO bonds is 92 area% or less. By providing the first main surface 1a with such a specific configuration, the separation functional layer 1 can improve its separation performance. For example, by having the above-described specific configuration, the separation functional layer 1 can have pores on the first main surface 1a that are miniaturized to a size appropriate for a molecular sieve, thereby improving its separation performance.

In analyzing the chemical bonding state of C in the separation functional layer 1 using XPS, the chemical bonding state of C is analyzed by performing waveform analysis on the C1s spectrum obtained by XPS analysis using monochrome AlKα radiation as the X-ray source. At this time, the peak derived from the C-H bond in the C1s spectrum is charge corrected to 284.6 eV.

The separation membrane 10 further includes, for example, a porous support 2. The porous support 2 is arranged on the second main surface 1b side opposite the first main surface 1a of the separation functional layer 1, and supports the separation functional layer 1. The porous support 2 may be arranged in direct contact with the second main surface 1b of the separation functional layer 1, as shown in FIG. 1, or another layer (intermediate layer) may be further provided between the separation functional layer 1 and the porous support 2. In some cases, the separation membrane 10 may not include the porous support 2, and may be a free-standing membrane (single-layer membrane) equipped only with the separation functional layer 1.

At least a portion of the first main surface 1a of the separation function layer 1 may be exposed on the surface of the separation membrane 10. This configuration allows the separation membrane 10 to effectively exhibit the separation performance of the separation function layer 1. Substantially the entire first main surface 1a of the separation function layer 1 may be exposed on the surface of the separation membrane 10. In this case, "substantially the entire first main surface 1a" means 90% or more of the area of the first main surface 1a, and may be 95% or more. The entire first main surface 1a of the separation function layer 1 may be exposed on the surface of the separation membrane 10.

For example, a resin layer that functions as a protective layer may be provided on the first main surface 1a of the separation functional layer 1. It is desirable that such a protective layer does not interfere with the separation performance of the separation functional layer 1 as much as possible, and it is more desirable that it be provided partially on the first main surface 1a in areas where protection is desired. The separation membrane 10 may be installed within the device in a folded or rolled state, for example. Therefore, taking such installation conditions into consideration, a protective layer may be provided only in areas where reinforcement is desired.

(separation functional layer)
The separation functional layer 1 is a layer that separates a substance to be separated (hereinafter referred to as "fluid to be separated") from a mixed fluid such as a mixed liquid and a mixed gas. The separation functional layer 1 may be a layer that preferentially allows the fluid to be separated contained in the mixed fluid to permeate, or may be a layer that does not allow the fluid to be separated to permeate but allows fluids other than the fluid to be separated to permeate.

For example, when the mixed fluid is a mixed liquid containing water (H ₂ O) and an organic solvent, and H ₂ O is to be separated from the mixed liquid as the liquid to be separated, the separation function layer 1 can separate H ₂ O from the mixed liquid by preferentially allowing H ₂ O to permeate.

For example, when the mixed fluid is a mixed gas containing hydrogen (H ₂ ) and other gases such as carbon dioxide (CO ₂ ), and H ₂ is to be separated from the mixed gas as the gas to be separated, the separation functional layer 1 can separate H ₂ from the mixed gas by preferentially allowing H ₂ to permeate.

The separation functional layer 1 contains Si, O, and C, and as described above, in an analysis of the chemical bonding state of C by XPS C1s spectrum of the first main surface 1a, the ratio of the peak area attributable to C-H bonds to the total peak area attributable to C-H, C-O, C=O, and COO bonds is 92 area% or less. Hereinafter, "the ratio of the peak area attributable to C-H bonds to the total peak area attributable to C-H, C-O, C=O, and COO bonds in an analysis of the chemical bonding state of C by XPS C1s spectrum of the first main surface 1a" will be referred to as "C-H ratio on the first main surface 1a of the separation functional layer 1" or simply "C-H ratio." By having this specific configuration, i.e., a first main surface 1a with a specific C-H ratio, the separation functional layer 1 can achieve improved separation performance. To achieve even higher separation performance, the C-H ratio on the first main surface 1a of the separation functional layer 1 is preferably 90 area% or less.

The lower limit of the C-H ratio on the first main surface 1a of the separation functional layer 1 is not particularly limited, but the C-H ratio is, for example, 50 area% or more, or may be 60 area% or more, 70 area% or more, or 75 area% or more.

In analyzing the chemical bonding state of C by XPS C1s spectroscopy of the first main surface 1a of the separation functional layer 1, the ratio of the peak area attributable to C-O bonds to the total peak area attributable to C-H, C-O, C=O, and COO bonds is preferably 5 area% or more. Hereinafter, "the ratio of the peak area attributable to C-O bonds to the total peak area attributable to C-H, C-O, C=O, and COO bonds in analyzing the chemical bonding state of C by XPS C1s spectroscopy of the first main surface 1a" will be referred to as "C-O ratio on the first main surface 1a of the separation functional layer 1" or simply "C-O ratio." By having the first main surface 1a of the separation functional layer 1 satisfy the above-described C-O ratio, the separation functional layer 1 is more likely to have pores that are miniaturized to a size appropriate for molecular sieving, thereby achieving higher separation performance. To achieve higher separation performance, the C-O ratio on the first main surface 1a of the separation functional layer 1 is more preferably 6 area% or more.

The upper limit of the C-O ratio on the first main surface 1a of the separation functional layer 1 is not particularly limited, but the C-O ratio is, for example, 40 area% or less, or may be 30 area% or less, or may be 20 area% or less.

At least one selected from the group consisting of C=O and COO may be present on the first main surface 1a of the separation functional layer 1. In an XPS analysis of the chemical bonding state of C on the first main surface 1a of the separation functional layer 1 using a C1s spectrum, at least one selected from the group consisting of the ratio of the peak area derived from C=O bonds and the ratio of the peak area derived from COO bonds to the total peak area derived from C-H, C-O, C=O, and COO bonds may be 0.1 area% or more, or may be 1 area% or more. Hereinafter, "the ratio of the peak area derived from C=O bonds to the total peak area derived from C-H, C-O, C=O, and COO bonds in an XPS analysis of the chemical bonding state of C on the first main surface 1a using a C1s spectrum" will be referred to as "C=O ratio on the first main surface 1a of the separation functional layer 1" or simply "C=O ratio." Furthermore, "the ratio of the peak area attributable to COO bonds to the total peak area attributable to C-H, C-O, C=O, and COO bonds in an XPS C1s spectrum analysis of the chemical bonding state of C on the first main surface 1a" is referred to as "COO ratio on the first main surface 1a of the separation functional layer 1" or simply "COO ratio." When the first main surface 1a of the separation functional layer 1 satisfies the above-described C=O ratio and/or COO ratio, the separation functional layer 1 is more likely to have pores that are miniaturized to a size appropriate for molecular sieving, for example, thereby achieving higher separation performance.

C=O may be present on the first major surface 1a of the separation functional layer 1. The C=O ratio on the first major surface 1a of the separation functional layer 1 may be 0.1 area% or more, or may be 1 area% or more.

The upper limit of the C=O ratio on the first main surface 1a of the separation functional layer 1 is not particularly limited, but the C=O ratio may be, for example, 20 area% or less, or may be 15 area% or less, or may be 10 area% or less. Furthermore, the upper limit of the COO ratio on the first main surface 1a of the separation functional layer 1 is not particularly limited, but the COO ratio may be, for example, 20 area% or less, or may be 15 area% or less, or may be 10 area% or less, or may be 5 area% or less.

In the separation functional layer 1, in an analysis of the chemical bonding state of Si by XPS using a Si2p spectrum on the first main surface 1a, the ratio of the peak area derived from the Si(-O) ₄ bond to the total peak area derived from the Si(-O) ₂ , Si(-O) ₃ , and Si(-O) ₄ bonds is preferably 3 area% or more, more preferably 5 area% or more, and even more preferably 10 area% or more. Hereinafter, "the ratio of the peak area derived from the Si(-O)4 bond to the total peak area derived from the Si(-O) ₂ , Si(-O) ₃ , and Si(-O) ₄ bonds in an analysis of the chemical bonding state of Si by XPS using a Si2p spectrum on the first main surface _1a " will be referred to as "Si(-O) ₄ ratio on the first main surface 1a of the separation functional layer 1" or simply "Si(-O) ₄ ratio." When the first main surface 1a of the separation function layer 1 satisfies the above-described Si(—O) ₄ ratio, the separation function layer 1 is more likely to have pores that are miniaturized to a size appropriate for a molecular sieve, for example, thereby achieving higher separation performance.

The upper limit of the Si(—O) ₄ ratio in the first main surface 1a of the separation functional layer 1 is not particularly limited, but the Si(—O) ₄ ratio is, for example, 90 area % or less, and may be 80 area % or less.

In analyzing the chemical bonding state of Si in the separation functional layer 1 using XPS, the chemical bonding state of Si is analyzed by performing waveform analysis on the Si2p spectrum obtained by XPS analysis using monochrome AlKα radiation as the X-ray source. At this time, the peak derived from the C-H bond in the C1s spectrum is charge corrected to 284.6 eV.

In the separation functional layer 1, in an analysis of the chemical bonding state of Si by XPS using a Si2p spectrum on the first main surface 1a, the ratio of the peak area derived from the Si(-O) ₃ bond to the total peak area derived from Si(-O) ₂ , Si(-O) ₃ , and Si(-O) ₄ bonds is preferably 15 area% or more, and more preferably 20 area% or more. Hereinafter, "the ratio of the peak area derived from the Si(-O)3 bond to the total peak area derived from the Si(-O) ₂ , Si(-O) ₃ , and Si(-O) ₄ bonds in an analysis of the chemical bonding state of Si by XPS using a Si2p spectrum on the first main surface 1a" will be referred to as "Si(-O) ₃ ratio in the first main surface 1a of the separation functional layer ₁ " or simply "Si(-O) ₃ ratio." When the first main surface 1a of the separation function layer 1 satisfies the above-described Si(—O) ₃ ratio, the separation function layer 1 is more likely to have pores that are miniaturized to a size appropriate for a molecular sieve, for example, thereby achieving higher separation performance.

The upper limit of the Si(—O) ₃ ratio in the first main surface 1a of the separation functional layer 1 is not particularly limited, but the Si(—O) ₃ ratio is, for example, 90 area % or less, and may be 85 area % or less.

In the separation functional layer 1, in an analysis of the chemical bonding state of Si by XPS using a Si2p spectrum on the first main surface 1a, the ratio of the peak area derived from the Si(-O) ₂ bond to the total peak area derived from the Si(-O) ₂ , Si(-O) ₃ , and Si(-O) ₄ bonds is preferably 80 area% or less, more preferably 70 area% or less, and even more preferably 50 area% or less. Hereinafter, "the ratio of the peak area derived from the Si(-O)2 bond to the total peak area derived from the Si(-O) ₂ , Si(-O) ₃ , and Si(-O) ₄ bonds in an analysis of the chemical bonding state of Si by XPS using a Si2p spectrum on the first main surface _1a " will be referred to as "Si(-O) ₂ ratio on the first main surface 1a of the separation functional layer 1" or simply "Si(-O) ₂ ratio." When the first main surface 1a of the separation functional layer 1 satisfies the above-described Si(—O) ₂ ratio, the separation functional layer 1 is more likely to have pores that are miniaturized to a size appropriate for a molecular sieve, for example, thereby achieving higher separation performance.

The lower limit of the Si(—O) ₂ ratio in the first main surface 1a of the separation functional layer 1 is not particularly limited, but the Si(—O) ₂ ratio is, for example, 1 area % or more.

In the separation functional layer 1, in an analysis of the chemical bonding state of Si by XPS using the Si2p spectrum of the first main surface 1a, the ratio of the peak area attributable to the Si(-O) ₄ bond to the sum of the peak areas attributable to the Si(-O) ₂ and Si(-O) ₃ bonds is preferably 0.1 or greater, and more preferably 0.15 or greater. Hereinafter, the "ratio of the peak area attributable to the Si(-O)4 bond to the sum of the peak areas attributable to the Si(-O) ₂ and Si(-O) ₃ bonds in an analysis of the chemical bonding state of Si by XPS using the _Si2p spectrum of the first main surface 1a" will be referred to as the "Si(-O) ₄ ratio at the first main surface 1a of the separation functional layer 1" or simply as the "Si(-O) ₄ ratio." When the first main surface 1a of the separation functional layer 1 satisfies the above-described Si(-O) ₄ ratio, the separation functional layer 1 is more likely to have pores that are miniaturized to a size appropriate for, for example, a molecular sieve, thereby achieving higher separation performance.

The upper limit of the Si(—O) ₄ ratio in the first main surface 1a of the separation functional layer 1 is not particularly limited, but the Si(—O) ₄ ratio is, for example, 30 or less, or may be 5 or less, or may be 4 or less.

The upper limit of the Si(—O) ₂ ratio in the first main surface 1a of the separation functional layer 1 is not particularly limited, but the Si(—O) ₂ ratio is, for example, 5 or less, and may be 4 or less.

On the first main surface 1a of the separation functional layer 1, the ratio of the number of O atoms to the number of Si atoms, O/Si, is preferably 1.2 or greater, more preferably 1.4 or greater, and even more preferably 1.7 or greater. By ensuring that the O/Si value on the first main surface 1a of the separation functional layer 1 satisfies the above range, the separation functional layer 1 can achieve even higher separation performance.

The O/Si value on the first main surface 1a of the separation functional layer 1 can be determined by composition analysis of the first main surface 1a of the separation functional layer 1 using XPS.

The upper limit of the O/Si ratio on the first main surface 1a of the separation functional layer 1 is not particularly limited, but the O/Si ratio is, for example, 3.0 or less, and may be 2.5 or less.

On the first main surface 1a of the separation functional layer 1, the ratio of the number of C atoms to the total number of C atoms, N atoms, O atoms, and Si atoms is preferably 17 at. % or more, and more preferably 20 at. % or more. By ensuring that the ratio of the number of C atoms on the first main surface 1a of the separation functional layer 1 satisfies the above range, the separation functional layer 1 can achieve higher separation performance.

The upper limit of the proportion of the number of C atoms on the first main surface 1a of the separation functional layer 1 is not particularly limited, but may be, for example, 52 at. % or less, or 50 at. % or less.

In the first main surface 1a of the separation functional layer 1, the ratio of the number of O atoms to the total number of C atoms, N atoms, O atoms, and Si atoms is preferably 54 at. % or less. By ensuring that the ratio of the number of O atoms in the first main surface 1a of the separation functional layer 1 satisfies the above range, the separation functional layer 1 can achieve even higher separation performance.

The lower limit of the proportion of O atoms on the first main surface 1a of the separation functional layer 1 is not particularly limited, but may be, for example, 25 at. % or more, 30 at. % or more, or 35 at. % or more.

As described above, the separation functional layer 1 is composed of a material containing Si, O, and C. Materials containing Si, O, and C include, for example, organosilicon compounds containing Si, O, and C. Examples of organosilicon compounds containing Si, O, and C include alkoxysilanes such as alkylsilicon alkoxides, and compounds containing siloxane bonds (Si-O-Si). Examples of alkylsilicon alkoxides include methyltriethoxysilane (MTES) and dimethyldiethoxysilane.

The separation functional layer 1 preferably contains a compound containing a siloxane bond (Si-O-Si).

The first main surface 1a of the separation functional layer 1 may contain organosilica having siloxane bonds, Si-C bonds, and C-O bonds. That is, on the first main surface 1a of the separation functional layer 1, the compound containing the siloxane bonds may be, for example, organosilica having siloxane bonds, Si-C bonds, and C-O bonds. By including the organosilica on the first main surface 1a of the separation functional layer 1, it becomes easier to form pores on the first main surface 1a of the separation functional layer 1 that are miniaturized to a size appropriate for a molecular sieve. This allows the separation functional layer 1 to have higher separation performance.

The organosilica may further have a C=O bond and/or a COO bond. The inclusion of such organosilica makes it easier for pores that have been miniaturized to a size appropriate for molecular sieving to be formed on the first main surface 1a of the separation function layer 1. This allows the separation function layer 1 to have higher separation performance.

The organosilica may include, for example, organosilica having a cyclic structure.

FIG. 2 is a structural diagram showing an example of organosilica having the above-mentioned cyclic structure that can be contained on the first main surface 1a of the separation functional layer 1. However, the structure of the organosilica contained on the first main surface 1a of the separation functional layer 1 is not limited to the structure shown in FIG. 2.

The separation functional layer 1 may contain a silicone resin as a compound containing a siloxane bond in a portion of the separation functional layer 1 excluding the first principal surface 1a or in a portion excluding the first principal surface 1a and the region adjacent to the first principal surface 1a. In this specification, the portion of the separation functional layer 1 excluding the first principal surface 1a or the portion excluding the first principal surface 1a and the region adjacent to the first principal surface 1a is referred to as the interior of the separation functional layer 1. Silicone resins have excellent properties such as heat resistance, water resistance, acid resistance, and flexibility, and can impart these excellent properties to the separation functional layer 1. The silicone resin contained in the separation functional layer 1 is not particularly limited, and various silicone resins can be used. The reaction type of the silicone resin is also not particularly limited, and it may be an addition reaction type silicone resin or a condensation reaction type silicone resin. The organic substituents contained in the silicone resin are also not particularly limited, and a silicone resin having a substituent that can exhibit appropriate properties depending on the application of the separation membrane 10 can be appropriately selected.

The first main surface 1a of the separation functional layer 1 contains, for example, a second compound obtained by modifying a first compound that constitutes the interior of the separation functional layer 1 through plasma treatment. That is, in a precursor layer of the separation functional layer 1 that contains the first compound, the first compound contained in the precursor layer's main surface may be modified by plasma treating the main surface of the precursor layer that corresponds to the first main surface 1a of the separation functional layer 1, and the material of the first main surface 1a of the separation functional layer 1 may be made up of the second compound formed thereby. The plasma treatment here is, for example, treatment using inductively coupled plasma using a low-inductance antenna. Details of treatment using inductively coupled plasma using a low-inductance antenna will be described later.

The first compound may contain a siloxane bond and may be, for example, a silicone resin. When the first compound is a silicone resin, the second compound is a compound formed by modifying the silicone resin through plasma treatment.

The thickness of the separation functional layer 1 is not particularly limited and may be, for example, 200 μm or less, 100 μm or less, 50 μm or less, 10 μm or less, 4 μm or less, 2 μm or less, or even 1.5 μm or less. The thickness of the separation functional layer 1 may be 0.05 μm or more, or 0.1 μm or more.

(Porous support)
The porous support 2 is a member that supports the separation function layer 1. Examples of the porous support 2 include nonwoven fabrics, porous polytetrafluoroethylene, aromatic polyamide fibers, porous metals, sintered metals, porous ceramics, porous polyesters, porous nylons, activated carbon fibers, latex, silicone, silicone rubber, polyvinyl fluoride, polyvinylidene fluoride (PVDF), polyurethane, polypropylene, polyethylene, polycarbonate, polysulfone, polyether ether ketone, polyacrylonitrile, polyimide, polyolefins, and polyphenylene oxides. Permeable (porous) polymers containing at least one selected from the group consisting of metal foams having open or closed cells, polymer foams having open or closed cells, silica, porous glass, and mesh screens. The porous support 2 may be a combination of two or more of these.

The porous support 2 has an average surface pore diameter of, for example, 5 to 100 nm. The thickness of the porous support 2 is not particularly limited, and is, for example, 10 μm or more, preferably 20 μm or more, and more preferably 50 μm or more. The thickness of the porous support 2 is, for example, 300 μm or less, preferably 200 μm or less, and more preferably 150 μm or less.

Figure 3 is a cross-sectional view showing a modified porous support body. As shown in Figure 3, the modified porous support body 2A may be, for example, a laminate including a main body portion 3 and a microporous layer 4.

The main body 3 is, for example, a fiber structure such as a woven fabric or a nonwoven fabric, and is typically a nonwoven fabric. Examples of fibers contained in the fiber structure include natural fibers such as wood pulp, cotton, and hemp (e.g., Manila hemp); and chemical fibers (synthetic fibers) such as polyester fiber, rayon, vinylon, acetate fiber, polyvinyl alcohol (PVA) fiber, polyamide fiber, polyolefin fiber, and polyurethane fiber. The main body 3 is, for example, a nonwoven fabric made of polyester fiber. The main body 3 has an average pore size of, for example, 1 μm to 50 μm.

Examples of materials for the microporous layer 4 include fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene; polyarylethersulfones such as polysulfone and polyethersulfone; and polyimides. The microporous layer 4 has an average pore size of, for example, 0.01 μm to 0.4 μm.

The thickness of the porous support 2 and the porous support 2A is not particularly limited and may be, for example, 10 μm or more, 50 μm or more, or even 100 μm or more. The thickness of the porous support 2 and the porous support 2A may be, for example, 300 μm or less, or 200 μm or less.

(Shape of separation membrane)
In this embodiment, the separation membrane 10 is typically a flat membrane. However, the separation membrane 10 may have a shape other than a flat membrane, for example, a hollow fiber membrane. As an example, the separation membrane 10 as a hollow fiber membrane includes a separation function layer 1 and a porous support 2 (or a porous support 2A).

(Method for producing separation membrane)
The separation membrane 10 can be produced, for example, by the following method.

First, a precursor (precursor layer) of the separation functional layer 1 is prepared. For example, a coating liquid containing a material including Si, O, and C is prepared, and the coating liquid is applied to a substrate to form a coating film, which is then dried. If necessary, this coating film is subjected to, for example, a heat treatment. The materials constituting the coating liquid are not particularly limited; they can be selected appropriately taking into account the material of the separation functional layer 1 to be prepared. For example, when preparing a separation functional layer 1 containing a silicone resin, the precursor layer can be prepared by using a coating liquid containing a silicone resin composition containing polyorganosiloxane and a curing catalyst, and then heat-treating and curing the coating film. The silicone resin composition and curing catalyst are not particularly limited and can be selected appropriately. In this manner, the precursor layer is prepared. When the separation functional layer 1 is supported by a porous support 2 (or porous support 2A), the porous support 2 (or porous support 2A) can be used as the substrate.

Next, the surface of the precursor layer is subjected to plasma treatment. This allows the formation of a separation functional layer 1 having a first main surface 1a. This plasma treatment is, for example, treatment using inductively coupled plasma (ICP). The ICP used is preferably an ICP that uses a low-inductance antenna. In other words, the plasma treatment performed on the surface of the precursor layer is preferably treatment using ICP that is generated by applying high-frequency power to a low-inductance antenna. The method of plasma treatment is not particularly limited, but the plasma treatment may be performed while the precursor layer is being transported using a roll-to-roll method, or may be performed using a batch method.

Here, a low-inductance antenna refers to an antenna that has a low inductance of 7.5 μH or less and is capable of generating inductively coupled plasma by applying high-frequency power. Furthermore, high-frequency power refers to power from a high-frequency power source (RF power source) used to excite plasma discharge.

Inductively coupled plasma treatment using a low-inductance antenna can easily form the specific configuration of the first main surface 1a of the separation functional layer 1, i.e., a first main surface 1a having the above-mentioned configuration in which the C-H ratio is 92 area% or less. Furthermore, ICP plasma treatment using a low-inductance antenna can also achieve the other configurations described above for the first main surface 1a (e.g., C-O ratio range, O/Si value, etc.). For example, if the precursor layer contains a compound with siloxane bonds such as silicone resin, ICP plasma treatment using a low-inductance antenna, compared to general plasma treatment, tends to cleave C-H bonds without cleaving many Si-C bonds, and more likely to generate C-O bonds. By modifying such compounds, organosilica containing siloxane bonds, Si-C bonds, and C-O bonds can be formed as described above while minimizing excessive damage to the first main surface 1a of the separation functional layer 1. Note that general plasma treatment refers to treatment using capacitively coupled plasma (CCP).

The frequency of the high-frequency power applied during plasma treatment is preferably 1 MHz or higher, more preferably 5 MHz or higher, and even more preferably 10 MHz or higher, and preferably 100 MHz or lower, more preferably 80 MHz or lower, and even more preferably 60 MHz or lower. When the frequency is above the lower limit, the plasma current density can be increased while stabilizing the plasma discharge. When the frequency is below the upper limit, the antenna potential can be suppressed, thereby suppressing damage to the separation functional membrane 1 caused by the plasma. The high-frequency power is preferably 0.1 kW or higher, more preferably 0.3 kW or higher, and even more preferably 1.0 kW or higher, and is preferably 10 kW or lower, more preferably 8 kW or lower, and even more preferably 6 kW or lower. When the high-frequency power is above the lower limit, a high-density plasma environment can be formed in the plasma treatment chamber during plasma treatment using ICP. When the high-frequency power is below the upper limit, excessive damage to the separation functional layer 1 caused by the plasma can be suppressed.

The plasma treatment gas used to form the first main surface 1a of the separation functional layer 1 is, for example, at least one selected from the group consisting of argon, oxygen, and nitrogen. The plasma treatment gas preferably contains argon, and more preferably also contains oxygen (i.e., a mixed gas containing argon and oxygen). This effectively modifies the compounds contained in the precursor layer, allowing the formation of a separation functional layer 1 with higher separation performance.

In the plasma treatment for forming the first main surface 1a of the separation functional layer 1, the pressure in the plasma treatment chamber is preferably 0.05 Pa or more, more preferably 0.1 Pa or more, even more preferably 0.2 Pa or more, and preferably 10 Pa or less, more preferably 7 Pa or less, even more preferably 5 Pa or less, particularly preferably 3 Pa or less, and even more preferably 1 Pa or less. When the pressure is above the above lower limit, a plasma environment of sufficient density for surface modification treatment for forming the first main surface 1a of the separation functional layer 1 can be created in the plasma treatment chamber during the plasma treatment. When the pressure is below the above upper limit, thermal damage to the first main surface 1a of the separation functional layer 1 caused by excessively high-density plasma can be suppressed during the plasma treatment, and thermal deformation of the separation functional layer 1 can also be suppressed. The pressure can be adjusted, for example, by the amount of gas supplied to the plasma treatment chamber.

In the plasma treatment for forming the first main surface 1a of the separation functional layer 1, the plasma treatment time is preferably 5 seconds or more, more preferably 10 seconds or more, even more preferably 30 seconds or more, particularly preferably 40 seconds or more, even more preferably 50 seconds or more, and preferably 200 seconds or less, more preferably 150 seconds or less, and even more preferably 120 seconds or less. When the plasma treatment time is equal to or greater than the above lower limit, sufficient surface modification for forming the first main surface 1a of the separation functional layer 1 by plasma treatment can be achieved. When the plasma treatment time is equal to or less than the above upper limit, thermal damage to the first main surface 1a of the separation functional layer 1 caused by excessively high-density plasma can be suppressed during the plasma treatment, and thermal deformation of the separation functional layer 1 can also be suppressed.

(Uses of separation membranes)
The separation membrane 10 of this embodiment is suitable for separating a mixed fluid containing two or more fluids, including a fluid to be separated, into a first fluid containing the fluid to be separated and a second fluid. The fluid may be a liquid or a gas. The separation method to which the separation membrane 10 is applied is not particularly limited. The separation membrane 10 can be used in various separation methods, such as reverse osmosis (RO), nanofiltration (NF), pervaporation (PV), and vapor permeation (VP).

(Separation method using a separation membrane)
A separation method using the separation membrane 10 includes, for example, contacting a mixed fluid containing two or more fluids including a fluid to be separated with one surface of the separation membrane 10 (for example, the surface of the separation membrane 10 on the first main surface 1a side of the separation functional layer 1 (the first main surface of the separation membrane 10)), and separating the mixed fluid into a first fluid containing the fluid to be separated and a second fluid. The first fluid may consist only of the fluid to be separated. The second fluid may also contain a small amount of the fluid to be separated. The mixed fluid is separated into a first fluid containing a larger amount of the fluid to be separated, or a first fluid consisting of the fluid to be separated, and a second fluid having a small content of the fluid to be separated, or a second fluid not containing the fluid to be separated. The first fluid may be a fluid that has permeated the separation membrane 10, and the second fluid may not have permeated the separation membrane 10, or the first fluid may not have permeated the separation membrane 10, and the second fluid may be a fluid that has permeated the separation membrane 10.

When the separation membrane 10 is used for gas separation, the mixed fluid is a mixed gas containing two or more gases including a gas to be separated. For example, when the gas to be separated is H ₂ , the H ₂ in the mixed gas is preferentially permeated through the separation membrane 10. This allows H ₂ to be separated from the mixed gas. In this way, the separation membrane 10 of this embodiment can separate H ₂ from a mixed gas of H ₂ and another gas (e.g., CO ₂ ), for example.

When the separation membrane 10 is used for liquid separation, the mixed fluid is a mixed liquid containing two or more liquids including a liquid to be separated. For example, when the liquid to be separated is H ₂ O, the H ₂ O in the mixed liquid is preferentially permeated through the separation membrane 10. This allows H ₂ O to be separated from the mixed liquid. In this way, the separation membrane 10 of this embodiment can separate H ₂ O from, for example, a mixed liquid of H ₂ O and another liquid (e.g., an organic solvent such as alcohol).

<Embodiment of Membrane Separation Device>
As shown in Figure 4, the membrane separation apparatus 100 of this embodiment includes a separation membrane 10 and a tank 20. The tank 20 includes a first chamber 21 and a second chamber 22. The first chamber 21 functions as a supply space to which a supply fluid L (i.e., a mixed fluid L containing two or more fluids including a fluid to be separated) is supplied. The second chamber 22 functions as a permeation space to which a permeated fluid L1 is supplied. The permeated fluid L1 is obtained by the permeation of the mixed fluid L through the separation membrane 10.

The separation membrane 10 is disposed inside the tank 20. Inside the tank 20, the separation membrane 10 separates the first chamber 21 and the second chamber 22. The separation membrane 10 extends from one to the other of a pair of walls of the tank 20.

The first chamber 21 has an inlet 21a and an outlet 21b. The second chamber 22 has an outlet 22a. The inlet 21a is an opening for supplying the mixed fluid L to the supply space (first chamber 21). The outlet 22a is an opening for discharging the permeated fluid L1 from the permeated space (second chamber 22). The outlet 21b is an opening for discharging the mixed fluid L (non-permeated fluid L2) that has not permeated the separation membrane 10 from the supply space (first chamber 21). The inlet 21a, outlet 21b, and outlet 22a are each formed, for example, on the wall surface of the tank 20.

The membrane separation device 100 is suitable for flow-through (continuous) membrane separation methods. However, the membrane separation device 100 may also be used for batch-type membrane separation methods.

(Method of operating a membrane separation device)
The membrane separation device 100 is operated, for example, as follows: First, the mixed fluid L is supplied to the first chamber 21 of the membrane separation device 100 through the inlet 21 a. This allows the mixed fluid L to come into contact with one surface of the separation membrane 10 (for example, the first main surface of the separation membrane 10).

The temperature of the mixed fluid L is, for example, 25°C or higher, preferably 40°C or higher, and more preferably 60°C or higher. The temperature of the mixed fluid L may be 75°C or lower.

Next, with the mixed fluid L in contact with one surface of the separation membrane 10, the space adjacent to the other surface of the separation membrane 10 (e.g., the second main surface of the separation membrane 10) is depressurized. Specifically, the pressure inside the second chamber 22 is reduced through the outlet 22a. The membrane separation device 100 may further include a pump (not shown) for reducing the pressure inside the second chamber 22. The second chamber 22 is depressurized so that the pressure inside the second chamber 22 is, for example, 10 kPa or more, preferably 50 kPa or more, and more preferably 100 kPa or more lower than the atmospheric pressure in the measurement environment.

By reducing the pressure inside the second chamber 22, permeated fluid L1 can be obtained on the other side of the separation membrane 10. In other words, permeated fluid L1 is supplied to the second chamber 22. Permeated fluid L1 is discharged to the outside of the membrane separation device 100 through the outlet 22a.

Meanwhile, the mixed fluid L (non-permeated fluid L2) treated in the first chamber 21 is discharged outside the membrane separation device 100 through the outlet 21b.

<Modification of Membrane Separation Device>
The membrane separation device 100 may be a spiral-wound membrane element, a hollow fiber membrane element, a disk-tube membrane element in which multiple separation membranes are stacked, a plate-and-frame membrane element, or the like. Fig. 5 shows a spiral-wound membrane element. The membrane separation device 110 in Fig. 5 includes a central tube 41 and a stack 42. The stack 42 includes separation membranes 10.

The central tube 41 has a cylindrical shape. A plurality of holes or slits are formed on the surface of the central tube 41 to allow the permeating fluid L1 to flow into the interior of the central tube 41. Examples of materials for the central tube 41 include resins such as acrylonitrile butadiene styrene copolymer resin (ABS resin), polyphenylene ether resin (PPE resin), and polysulfone resin (PSF resin); and metals such as stainless steel and titanium. The inner diameter of the central tube 41 is, for example, in the range of 20 to 100 mm.

In addition to the separation membrane 10, the laminate 42 further includes a feed-side flow path material 43 and a permeate-side flow path material 44. The laminate 42 is wound around the central tube 41. The membrane separation device 110 may further include an exterior material (not shown).

The feed-side flow path material 43 and the permeate-side flow path material 44 can be, for example, a resin net made of polyethylene, polypropylene, polyethylene terephthalate (PET), polyphenylene sulfide (PPS), or ethylene-chlorotrifluoroethylene copolymer (ECTFE).

The membrane separation device 110 can be operated, for example, in the following manner. First, mixed fluid L is supplied to one end of the wound stack 42, and the space inside the central tube 41 is depressurized. As a result, permeated fluid L1 that has permeated the separation membrane 10 of the stack 42 moves into the interior of the central tube 41. Permeated fluid L1 is discharged to the outside through the central tube 41. The mixed fluid L (non-permeated fluid L2) that has been treated in the membrane separation device 110 is discharged to the outside from the other end of the wound stack 42.

The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to these.

(Preparation of separation membrane)
Example 1
First, RS-50 (a laminate of a PVDF microporous layer and a PET nonwoven fabric) manufactured by Nitto Denko Corporation was prepared as a porous support. Next, 2 g of a curing catalyst (SRX212 manufactured by Dow Toray) was added to 100 g of a silicone resin composition (LTC-1051L manufactured by Dow Toray) to prepare an addition reaction type silicone resin composition as a coating liquid. This coating liquid was a solventless type that did not contain a solvent. Next, a coating film was obtained by applying the coating liquid onto the microporous layer of the porous support. Next, the coating film was heated at 150°C for 10 minutes and cured to prepare a precursor layer, which is a precursor of the separation functional layer. At this time, the precursor layer was prepared so that its dry thickness was 15 μm or less.

Next, the surface of the prepared precursor layer was plasma-treated. In this example, a laminate (plasma-treated object) in which a precursor layer was formed on a porous support was transported by roll-to-roll, while a plasma treatment was performed on the surface of the precursor layer by ICP using a low-inductance antenna. Specifically, an apparatus capable of performing a roll-to-roll process on the laminate was used. The apparatus included a payout chamber, a plasma treatment chamber, and a winding chamber, which were arranged in this order and connected to each other. The payout chamber was equipped with a payout roller. A roll of general-purpose PET film was set on the payout roller as a carrier film for transporting the laminate. The plasma treatment chamber was equipped with a temperature-adjustable transport roller and four low-inductance antennas. Figure 6 is a perspective view showing the positional relationship between the low-inductance antenna and the plasma-treated object in the plasma treatment chamber used in this example. Figure 7 is a cross-sectional view showing the positional relationship between the low-inductance antenna and the plasma-treated object in the plasma treatment chamber used in this example. Each low-inductance antenna 71 had an extension 71a parallel to the object 70 to be plasma processed. The four low-inductance antennas 71 had an extension length _d1 of 88 mm, a maximum length _d2 (length of the extension) of 100 mm, a separation distance _d3 of 112 mm, a center-to-center distance _d4 of 290 mm, and a center-to-center distance _d5 of 280 mm. Each low-inductance antenna 71 was electrically connected to a high-frequency power source (RF power source, frequency 13.56 MHz) via an impedance matching box outside the plasma processing chamber. In FIGS. 6 and 7, 72 denotes a fixture, 74 denotes a field-through, and the low-inductance antenna 71 was fixed to the fixture 72 via the field-through 74.

The laminate of the porous support and precursor layer, which was the object to be plasma treated, was cut to A4 size and attached using tape so that the porous support was in contact with the general-purpose PET film carrier film. This raw roll was set in the unwinding chamber, and while the carrier film was transported from the unwinding chamber to the winding chamber using the roll-to-roll method, the surface of the precursor layer was plasma treated in the plasma treatment chamber.

The plasma treatment conditions were as follows: The apparatus was evacuated until the ultimate vacuum of the plasma treatment chamber reached 1.0 × 10 ^-4 Pa, and then argon (Ar) gas was introduced into the plasma treatment chamber, setting the pressure inside the plasma treatment chamber to 0.2 Pa. An inductively coupled plasma of argon-containing gas was formed around the four low-inductance antennas by applying 5.0 kW of power to the four low-inductance antennas using a 13.56 MHz high-frequency power source (RF power source). The running speed of the carrier film was changed according to the treatment time (80 seconds in Example 1). The temperature of the temperature-controlled transport roller was set to 20°C. Table 2 shows the plasma treatment conditions.

The surface of the precursor layer that had been subjected to the above plasma treatment became the first main surface of the separation functional layer, and the separation membrane of Example 1 was produced.

Example 2
A separation membrane of Example 2 was produced in the same manner as in Example 1, except that the plasma treatment conditions were changed as shown in Table 2.

Example 3
First, a Nitto Denko SWC (a laminate of a polysulfone microporous layer and a PET nonwoven fabric) was prepared as a porous support and dried overnight in a draft. Next, 30 g of a silicone resin composition (Wacker DEHESIVE (registered trademark) 944) was added with 3 g of a crosslinker (Wacker CROSSLINKER V 24) and 0.6 g of a curing catalyst (Wacker CATALYST OL), and dissolved in 100 mL of a hydrocarbon solvent (Wacker EXXSOL D40) and stirred for 30 minutes to prepare a condensation reaction type silicone resin composition as a coating liquid. Next, the coating liquid was applied onto the microporous layer of the porous support to obtain a coating film. After drying the coating film for 2 hours in a draft, the coating liquid was again applied onto the microporous layer of the porous support. Next, the coating film was dried overnight in a draft and then heated at 100° C. for 30 minutes to be cured, thereby producing a precursor layer, which is a precursor of the separation functional layer. At this time, the precursor layer was produced so that its dry thickness was 15 μm or less.

The plasma treatment of the precursor layer surface was carried out in the same manner as in Example 1, except that the plasma treatment conditions were changed as shown in Table 2.

The separation membrane of Example 3 was produced using the above method.

Example 4
The separation membrane of Example 4 was produced in the same manner as in Example 1, except that the plasma treatment conditions were changed as shown in Table 2. In Example 4, a mixed gas of argon gas and oxygen gas was used, and the flow rates of the argon gas and oxygen gas were adjusted so that the volume ratio of the argon gas to the oxygen gas was 1:1.

Example 5
A separation membrane of Example 5 was produced in the same manner as in Example 3, except that the plasma treatment conditions were changed as shown in Table 2.

Example 6
A separation membrane of Example 6 was produced in the same manner as in Example 3, except that the plasma treatment conditions were changed as shown in Table 2.

Example 7
A separation membrane of Example 6 was produced in the same manner as in Example 3, except that the plasma treatment conditions were changed as shown in Table 2.

(Comparative Example 1)
The precursor layer produced in Example 3 was used as a separation functional layer without being subjected to plasma treatment. That is, the laminate of the porous support and the precursor layer produced in Example 3 was used as the separation membrane of Comparative Example 1.

(Comparative Example 2)
The precursor layer produced in Example 1 was used as a separation functional layer without being subjected to plasma treatment. That is, the laminate of the porous support and the precursor layer produced in Example 1 was used as the separation membrane of Comparative Example 2.

(Comparative Example 3)
A separation membrane of Comparative Example 3 was produced in the same manner as in Example 1, except that the plasma treatment using ICP was changed to plasma treatment using CCP. The plasma treatment using CCP carried out in Comparative Example 3 was as follows.

Instead of a plasma treatment chamber equipped with a low-inductance antenna, a cathode electrode and an anode electrode (rectangular electrodes made of SUS304 stainless steel) were installed as flat plate electrodes and used as a plasma treatment chamber. The pair of planar electrodes were spaced 50 mm apart and positioned parallel to the laminate (object to be plasma-treated), which was a porous support on which a precursor layer was formed. The anode electrode was positioned 35 mm away from the laminate and grounded outside the plasma treatment chamber. The cathode electrode was positioned facing the surface of the precursor layer, which was the plasma treatment surface, and was electrically connected to an RF power supply (high-frequency power supply, 13.56 MHz) via an impedance matcher. Argon gas was introduced into the plasma treatment chamber, and the flow rate was adjusted to a pressure of 0.5 Pa. CCP was generated by applying 0.2 kW from the high-frequency power supply between the planar electrodes, and treatment was performed. The surface size of each planar electrode facing the laminate was 110 mm x 430 mm.

(Analysis of the first principal surface of the separation functional layer)
For the separation membranes of Examples 1 to 7 and Comparative Examples 1 to 3, XPS analysis was performed on the first main surface of the separation functional layer. Wide scan measurement was performed on the first main surface of the separation functional layer, i.e., the outermost surface of the separation functional layer, and qualitative analysis was performed. Narrow scan measurement was performed on each element, and the element ratio (atomic%) was calculated. The chemical bond state was analyzed by performing waveform analysis on the Si2p and C1s spectra. At this time, the peak derived from the C-H bond in the C1s spectrum was charge corrected to 284.6 eV (see Table 1). The apparatus used was a "Quantera SXM" manufactured by ULVAC-PHI, and a monochromatic AlKα was used as the X-ray source. The results of the XPS analysis of the first main surface of the separation functional layer are shown in Tables 3 and 4.

(Evaluation of liquid separation)
Liquid separation was evaluated for the separation membranes of Examples 1 to 4 and Comparative Examples 1 to 3. Specifically, the separation coefficient α (α=H ₂ O/IPA) of water relative to isopropanol (IPA) was measured by the following method.

First, the separation membrane was cut into a size of 74 mm in diameter to create a flat membrane test piece. This test piece was placed in a batch-type membrane separation device (cell). A mixed liquid consisting of IPA and water was supplied to the supply space of this cell. The IPA content in the mixed liquid was 50% by mass.

Next, the cell was immersed in a water bath and the temperature of the mixed liquid was adjusted to 40°C. Next, the pressure in the permeation space was reduced to 15 hPa while stirring the mixed liquid using a stirrer placed inside the cell. This allowed the mixed liquid to permeate the separation membrane, yielding a gaseous permeation fluid.

The gaseous permeating fluid was cooled and condensed using a cold trap using liquid nitrogen. The composition of the liquid permeating fluid was analyzed using gas chromatography, and the separation factor α was calculated based on the results. The results are shown in Table 3.

(Gas Separation Evaluation)
Gas separation was evaluated for the separation membranes of Examples 3 to 7 and Comparative Examples 1 to 3. Specifically, the separation factor α of H ₂ relative to CO ₂ (α=H ₂ /CO ₂ ) was measured by the following method.

First, the separation membrane was cut into a size of 64 mm in diameter to prepare a flat membrane-shaped test piece. This test piece was set in a batch-type membrane separation device (cell). _H2 gas and _CO2 gas were simultaneously supplied to the supply space of this cell. Next, the cell was set in an oven chamber, and the temperature was adjusted to 150 ° C. As a result, the mixed gas permeated the separation membrane, and a permeated gas was obtained.

The composition of the permeated gas was analyzed using gas chromatography, and the gas permeation rate [GPU] of each gas was determined based on the results obtained. The gas separation factor α was calculated from the permeation rate [GPU] of each gas using the following formula.
Gas separation factor α=H ₂ [GPU]/CO ₂ [GPU]

As shown in Tables 3 and 4, the separation membranes of the examples showed improved separation performance in both liquid and gas separation.

The separation membrane of this embodiment has improved separation performance and is particularly suitable for separating water from mixed liquids and hydrogen from mixed gases.

Claims (19)

A separation functional layer containing Si, O, and C is provided,
In an analysis of the chemical bonding state of C by C1s spectrum of the first main surface of the separation functional layer by X-ray photoelectron spectroscopy, the ratio of the peak area derived from the C-H bond to the total peak area derived from C-H, C-O, C=O, and COO bonds is 92 area% or less.
Separation membrane. In an analysis of the chemical bonding state of C by C1s spectrum of the first main surface of the separation functional layer by X-ray photoelectron spectroscopy, the ratio of the peak area derived from the C-O bond to the total peak area derived from C-H, C-O, C=O, and COO bonds is 5 area% or more.
The separation membrane according to claim 1 . In the first main surface of the separation functional layer, the ratio of the number of O atoms to the number of Si atoms, O/Si, is 1.2 or more.
The separation membrane according to claim 1 . In the first main surface of the separation functional layer, the ratio of the number of C atoms to the total number of C atoms, N atoms, O atoms, and Si atoms is 17 at. % or more.
The separation membrane according to claim 1 . In the first main surface of the separation functional layer, the ratio of the number of O atoms to the total number of C atoms, N atoms, O atoms, and Si atoms is 54 at. % or less.
The separation membrane according to claim 1 . The porous support member further includes a porous support member for supporting the separation functional layer, the porous support member being arranged on a second main surface side opposite to the first main surface of the separation functional layer.
The separation membrane according to claim 1 . The separation functional layer contains a compound containing a siloxane bond.
The separation membrane according to claim 1 . the first main surface of the separation functional layer contains organosilica having a siloxane bond, a Si—C bond, and a C—O bond;
The separation membrane according to claim 7. the first main surface of the separation functional layer contains a second compound obtained by modifying a first compound constituting the interior of the separation functional layer by plasma treatment;
The separation membrane according to claim 1 . the first compound contains a siloxane bond;
The separation membrane according to claim 9. The first compound is a silicone resin.
The separation membrane according to claim 10. The plasma treatment is an inductively coupled plasma treatment using a low inductance antenna.
The separation membrane according to claim 9. At least a portion of the first main surface of the separation functional layer is exposed on the surface of the separation membrane.
The separation membrane according to claim 1 . A separation membrane according to any one of claims 1 to 13,
Membrane separation equipment. A separation method using the separation membrane according to any one of claims 1 to 13,
A mixed fluid containing two or more fluids including a fluid to be separated is brought into contact with one side of the separation membrane, and the mixed fluid is separated into a first fluid containing the fluid to be separated and a second fluid.
Separation method. The mixed fluid is a mixed gas containing two or more gases including a gas to be separated.
The separation method according to claim 15. The gas to be separated is H ₂ , and H ₂ of the mixed gas is preferentially permeated through the separation membrane.
The separation method according to claim 16. The mixed fluid is a mixed liquid containing two or more liquids including a liquid to be separated.
The separation method according to claim 15. the liquid to be separated is H ₂ O, and H ₂ O in the mixed liquid is preferentially allowed to permeate the separation membrane;
The separation method according to claim 18.