Method for manufacturing separation membrane

Abstract

A method for manufacturing a separation membrane according to the present invention includes: preparing a precursor layer that contains Si, O, and C; and carrying out plasma treatment using inductively coupled plasma on a first surface of the precursor layer to obtain the separation function layer. The plasma treatment is, for example, a treatment performed using inductively coupled plasma of a gas that contains at least one selected from the group consisting of argon, oxygen, and nitrogen, said gas being generated by application of high-frequency power to a low-inductance antenna.

Description

Separation membrane manufacturing method

[0001] The present invention relates to a method for producing a separation membrane.

[0002] Currently, there is a demand for a carbon-neutral society, and the development of products with various functions is accelerating. For example, in industries such as semiconductors and alcohol production, large amounts of water are used in the manufacture of products. Therefore, with the aim of water reuse, separation technologies are being developed to separate water from mixed liquids containing water and organic solvents such as alcohol. Furthermore, in relation to the issue of global warming, technology is being developed to separate and capture carbon dioxide from exhaust gases in thermal power plants, cement plants, steelworks blast furnaces, etc.

[0003] Membrane separation methods using separation membranes have been developed as methods for separating target substances from mixed fluids such as mixed liquids and mixed gases. For example, in liquid separation, which separates a target liquid from a mixed liquid, membrane separation methods require less energy than separation by distillation, which requires a heating step, and can also suppress the generation of carbon dioxide. Thus, membrane separation methods are excellent as a separation technology that uses less energy and has a small environmental impact.

[0004] For gas or liquid separation, separation membranes in which the portion having the separation function is made of an organic material such as polyimide are usually used. On the other hand, separation membranes in which the portion having the separation function is made of an inorganic material, such as separation membranes using zeolite and hollow fiber membranes, have been proposed.

[0005] Conventionally, separation membranes of various materials and configurations have been proposed to improve the separation function for separating a target substance from a mixed fluid (e.g., 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 having a specific configuration is formed by subjecting a resin layer precursor containing a compound having a siloxane bond to plasma treatment, and a protective layer containing a silicone resin and a porous layer are further disposed on the resin layer.

[0006] Patent No. 6652575

[0007] There is room for improvement in the separation performance of conventional separation membranes that exhibit separation performance through plasma treatment, such as that disclosed in Patent Document 1. Therefore, the present invention provides a manufacturing method for producing a separation membrane with improved separation performance.

[0008] The present invention provides a method for manufacturing a separation membrane having a separation functional layer containing Si, O, and C, the method including: preparing a precursor layer containing Si, O, and C as a precursor of the separation functional layer; and obtaining the separation functional layer by plasma treating a first main surface of the precursor layer with inductively coupled plasma.

[0009] According to the present invention, a manufacturing method for manufacturing a separation membrane with improved separation performance can be provided.

[0010] 5 is a flowchart showing a method for producing a separation membrane according to one embodiment of the present invention; FIG. 6 is a diagram for explaining a method for producing a separation membrane according to one embodiment of the present invention; FIG. 7 is a cross-sectional view showing a precursor layer supported on a porous support, which is an example of a precursor layer prepared in a method for producing a separation membrane according to one embodiment of the present invention; FIG. 8 is a cross-sectional view showing a modified example of a porous support supporting a precursor layer prepared in a method for producing a separation membrane according to one embodiment of the present invention; FIG. 9 is a schematic configuration diagram showing an example of an apparatus for performing plasma treatment in a method for producing a separation membrane according to one embodiment of the present invention; FIG. 10 is a schematic configuration diagram showing a modified example of an apparatus for performing plasma treatment in a method for producing a separation membrane according to one embodiment of the present invention; FIG. 11 is a perspective view showing the positional relationship between a low inductance antenna and a precursor layer in the plasma treatment chamber shown in FIG. 5; FIG. 12 is a cross-sectional view showing the positional relationship between a low inductance antenna and a precursor layer in the plasma treatment chamber shown in FIG. 5;

[0011] A method for manufacturing a separation membrane according to a first aspect of the present invention is a method for manufacturing a separation membrane having a separation functional layer containing Si, O, and C, the method including: preparing a precursor layer containing Si, O, and C as a precursor of the separation functional layer; and obtaining the separation functional layer by plasma treating a first main surface of the precursor layer with inductively coupled plasma.

[0012] In a second aspect of the present invention, for example, in the manufacturing method according to the first aspect, the plasma treatment is a treatment using inductively coupled plasma of a gas containing at least one selected from the group consisting of argon, oxygen, and nitrogen, which is generated by applying high frequency power to a low inductance antenna.

[0013] In a third aspect of the present invention, for example, in the manufacturing method according to the first or second aspect, the plasma treatment is a treatment using inductively coupled plasma of a gas containing argon, and in the plasma treatment, the intensity I of a maximum emission peak in the wavelength range of 300 nm or more and 900 nm or less in plasma emission is max The wavelength of the light emitted from the light source is set to be in the range of 811 nm or more and 812 nm or less, and the ratio of the intensity I2 of the emission peak in the wavelength range of 603 nm or more and 604 nm or less to the intensity I1 of the emission peak in the wavelength range of 706 nm or more and 707 nm or less is set to be 1.0 or less.

[0014] In a fourth aspect of the present invention, for example, in the manufacturing method according to the first or second aspect, the plasma treatment is a treatment using inductively coupled plasma of a gas containing oxygen, and in the plasma treatment, the ratio of the maximum emission peak intensity I4 within a wavelength range of 555 nm or more and 565 nm or less to the maximum emission peak intensity I3 within a wavelength range of 775 nm or more and 779 nm or less is set to 1.0 or less.

[0015] In a fifth aspect of the present invention, for example, in the manufacturing method according to any one of the first to fourth aspects, the plasma treatment is carried out while cooling or heating the precursor layer.

[0016] In a sixth aspect of the present invention, for example, in the manufacturing method according to any one of the first to fifth aspects, the plasma treatment is carried out while the precursor layer is being transported and cooled or heated by a roller having a temperature control function that is in contact with the precursor layer.

[0017] In a seventh aspect of the present invention, for example, in the manufacturing method according to any one of the first to sixth aspects, the plasma treatment is carried out in a reduced pressure atmosphere in a chamber.

[0018] In an eighth aspect of the present invention, for example, in the manufacturing method according to any one of the first to seventh aspects, the first main surface of the precursor layer contains a compound containing a siloxane bond.

[0019] In a ninth aspect of the present invention, for example, in the production method according to the eighth aspect, the compound is a silicone resin.

[0020] In a tenth aspect of the present invention, for example, in the manufacturing method according to any one of the first to ninth aspects, the precursor layer is supported by a porous support disposed on a second main surface side opposite the first main surface.

[0021] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

[0022] The method for producing a separation membrane of this embodiment is a method for producing a separation membrane having a separation functional layer containing Si, O, and C. As shown in Figures 1 and 2, the production method of this embodiment includes the steps of preparing a precursor layer 1 containing Si, O, and C as a precursor of the separation functional layer (S1), and performing a plasma treatment on a first main surface 1a of the precursor layer 1 using inductively coupled plasma to obtain a separation functional layer 2 (S2).

[0023] According to the manufacturing method of this embodiment, a separation membrane with improved separation performance can be manufactured.

[0024] In the manufacturing method of this embodiment, as described above, the first main surface 1a of the precursor layer 1 is plasma-treated using inductively coupled plasma (ICP). Compared to general plasma treatment, ICP plasma treatment can moderately modify the compounds containing Si, O, and C that make up the first main surface 1a of the precursor layer 1 while preventing excessive damage to the first main surface 1a. This moderate modification can form micropores in the first main surface 1a that are appropriate for molecular sieving, thereby obtaining a separation function layer 2 with improved separation performance, having a first main surface 2a with such pores. The first main surface 2a of the separation function layer 2 corresponds to the first main surface 1a of the precursor layer 1, i.e., the plasma-treated surface. Note that general plasma treatment refers to treatment using capacitively coupled plasma (CCP).

[0025] The step (S1) of preparing precursor layer 1 and the step (S2) of plasma treating precursor layer 1 will be described in detail below.

[0026] (Preparation process of precursor layer) The precursor layer 1 is a precursor of the separation functional layer 2 of the separation membrane and contains Si, O, and C. The process of preparing the precursor layer 1 includes, for example, a process of producing the precursor layer 1. In the process of producing the precursor layer 1, for example, a coating liquid containing a material containing Si, O, and C is prepared, and the coating liquid is applied onto a substrate to produce a coating film, and the coating film is dried. In this way, the precursor layer 1 can be produced. The coating film may be subjected to, for example, a heat treatment, if necessary. The materials constituting the coating liquid are not particularly limited, and may be selected appropriately taking into account the material of the separation functional layer 2 to be produced.

[0027] The precursor layer 1 is made of a material containing Si, O, and C. The material of the precursor layer 1 may further contain H. The material containing Si, O, and C includes, for example, an organosilicon compound containing Si, O, and C. Examples of the organosilicon compound containing Si, O, and C include alkoxysilanes such as alkylsilicon alkoxides, and compounds containing a siloxane bond (Si—O—Si). Examples of alkylsilicon alkoxides include methyltriethoxysilane (MTES), dimethyldiethoxysilane, and the like.

[0028] The first main surface 1a of the precursor layer 1 preferably contains a compound containing a siloxane bond. When the first main surface 1a contains a compound containing a siloxane bond, an organosilica containing, for example, a siloxane bond, a Si—C bond, and a C—O bond can be formed on the first main surface 1a by plasma treatment using ICP. This makes it easier to form pores on the first main surface 1a of the precursor layer 1 that are miniaturized to a size appropriate for a molecular sieve, and the resulting separation function layer 2 can have higher separation performance. The organosilica may further contain a C═O bond and / or a COO bond. The organosilica may also contain, for example, an organosilica having a cyclic structure. The compound containing a siloxane bond may be a silicone resin.

[0029] For example, when preparing a separation functional layer 2 containing a silicone resin, a coating liquid containing a silicone resin composition containing polyorganosiloxane and a curing catalyst may be used, and the coating film may be cured by heat treatment to prepare the precursor layer 1. The silicone resin composition and the curing catalyst are not particularly limited and can be selected appropriately. In this manner, the precursor layer 1 is prepared.

[0030] The thickness of the precursor layer 1 is not particularly limited and may be appropriately determined depending on the thickness of the separation functional layer 2 to be produced. As an example, the thickness of the separation functional layer 2 to be produced is, for example, 200 μm or less, and may be 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 2 may be 0.05 μm or more, or may be 0.1 μm or more.

[0031] The precursor layer 1 may be supported by a substrate. The substrate may be a porous support that supports the separation functional layer 2 in the completed separation membrane. In this case, as shown in FIG. 3 , the precursor layer 1 is supported by a porous support 3 arranged on the second main surface 1b side opposite the first main surface 1a. Note that if the separation membrane to be prepared does not include a porous support and is a free-standing membrane (single-layer membrane) that includes only the separation functional layer 2, the substrate used in preparing the precursor layer 1 may be peeled off from the separation functional layer 2 after the separation functional layer 2 is completed.

[0032] Examples of the porous support 3 as a member supporting the separation function layer 2 include nonwoven fabric, porous polytetrafluoroethylene, aromatic polyamide fiber, porous metal, sintered metal, porous ceramic, porous polyester, porous nylon, activated carbon fiber, latex, silicone, silicone rubber, polyvinyl fluoride, polyvinylidene fluoride (PVDF), polyurethane, polypropylene, polyethylene, polycarbonate, polysulfone, polyether ether ketone, polyacrylonitrile, polyimide, polyolefin, and polyphenylene oxide. 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, mesh screens, etc. The porous support may be a combination of two or more of these.

[0033] The porous support has an average surface pore diameter of 3, for example, 5 to 100 nm. The thickness of the porous support 3 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 3 is, for example, 300 μm or less, preferably 200 μm or less, and more preferably 150 μm or less.

[0034] Fig. 4 is a cross-sectional view showing a modified example of a porous support body 3A. As shown in Fig. 4, the modified porous support body 3A may be, for example, a laminate including a main body portion 4 and a microporous layer 5.

[0035] The main body 4 is 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 4 is a nonwoven fabric made of polyester fiber, for example. The main body 4 has an average pore size of, for example, 1 μm to 50 μm.

[0036] Examples of materials for the microporous layer 5 include fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene, polyarylethersulfones such as polysulfone and polyethersulfone, and polyimides. The microporous layer 5 has an average pore size of, for example, 0.01 μm to 0.4 μm.

[0037] The thickness of the porous support 3 and the porous support 3A 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 3 and the porous support 3A is, for example, 300 μm or less, or may be 200 μm or less.

[0038] (Plasma Treatment Step) The ICP used for plasma treatment of the first main surface 1 a of the precursor layer 1 is preferably an ICP using a low inductance antenna. The plasma treatment method is not particularly limited, but the plasma treatment may be performed while transporting the precursor layer 1 using a roll-to-roll method, or may be performed using a batch method.

[0039] Here, the term "low-inductance antenna" refers to an antenna that has a low inductance of 7.5 μH or less and that can generate inductively coupled plasma by applying high-frequency power. The high-frequency power is power from a high-frequency power source (RF power source) used to excite plasma discharge.

[0040] By performing plasma treatment using an ICP with a low-inductance antenna, the compounds containing Si, O, and C that make up the first main surface 1a can be modified to a more suitable state. Such modification makes it easier to form pores that are miniaturized to a size suitable for the molecular sieve, thereby obtaining a separation functional layer 2 with improved separation performance.

[0041] When the first main surface 1a of the precursor layer 1 contains a compound containing a siloxane bond, plasma treatment by ICP using a low-inductance antenna, compared to general plasma treatment, tends to cleave C-H bonds without cleaving many Si-C bonds, and furthermore tends to generate C-O bonds. By modifying such compounds, it is possible to form, for example, organosilica containing siloxane bonds, Si-C bonds, and C-O bonds as described above, while suppressing excessive damage to the first main surface 1a of the precursor layer 1. The inclusion of such organosilica facilitates the formation of micropores in the first main surface 1a of the precursor layer 1 that are miniaturized to a size appropriate for a molecular sieve. This allows the resulting separation function layer 2 to have higher separation performance. As described above, the organosilica may further contain C=O bonds and / or COO bonds, and may, for example, contain organosilica having a cyclic structure.

[0042] 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 equal to or higher than the lower limit, plasma current density can be increased while stabilizing plasma discharge. When the frequency is equal to or lower than the upper limit, the antenna potential can be suppressed, thereby suppressing plasma damage to the first main surface 1a of the precursor layer 1. Furthermore, 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 equal to or higher than the lower limit, a high-density plasma environment can be formed in the plasma treatment chamber during ICP plasma treatment. When the high-frequency power is equal to or lower than the upper limit, excessive plasma damage to the first main surface 1a of the precursor layer 1 can be suppressed.

[0043] The plasma treatment gas 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 further contains oxygen (i.e., a mixed gas containing argon and oxygen). This effectively modifies the compounds contained in the precursor layer 1, allowing the formation of a separation functional layer 2 with higher separation performance.

[0044] From the above, in order to produce a separation membrane with higher separation performance, it is preferable that the plasma treatment carried out in the manufacturing method of this embodiment is a treatment by ICP of a gas containing at least one selected from the group consisting of argon, oxygen, and nitrogen, which is generated by applying high-frequency power to a low-inductance antenna.

[0045] In the plasma treatment of the first main surface 1a of the precursor 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, particularly preferably 0.3 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 equal to or greater than the above-mentioned lower limit, a plasma environment of sufficient density for surface modification treatment of the first main surface 1a of the precursor layer 1 can be formed in the plasma treatment chamber. When the pressure is equal to or less than the above-mentioned upper limit, thermal damage to the precursor layer 1 caused by excessively high-density plasma and thermal deformation of the precursor layer 1 can be suppressed. The pressure can be adjusted, for example, by the amount of gas supplied into the plasma treatment chamber.

[0046] In the plasma treatment for forming the first main surface 1a of the separation functional layer 2, the plasma treatment time is preferably 5 seconds or more, 10 seconds or more, or 30 seconds or more, more 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-mentioned lower limit, sufficient surface modification can be achieved on the first main surface 1a of the precursor layer 1 for forming the separation functional layer 2 by plasma treatment. When the plasma treatment time is equal to or less than the above-mentioned upper limit, thermal damage to the precursor layer 1 caused by excessively high-density plasma and thermal deformation of the precursor layer 1 can be suppressed.

[0047] The plasma treatment of the first main surface 1 a of the precursor layer 1 may be performed while cooling or heating the precursor layer 1. This makes it possible to cool the precursor layer 1 during the plasma treatment to suppress damage to the precursor layer 1 due to heat, or to heat the precursor layer 1 during the plasma treatment to enhance the effect of the plasma treatment.

[0048] The plasma treatment of the precursor layer 1 may be performed, for example, by a roll-to-roll method under a reduced pressure atmosphere while the precursor layer 1, which is the object to be plasma treated, is being transported. The following details of the plasma treatment will be described in detail using an example in which the plasma treatment is performed by the roll-to-roll method. However, for example, the configuration of the low-inductance antenna provided in the plasma treatment chamber C2 described below, the positional relationship between the low-inductance antenna and the precursor layer, and the treatment conditions of the plasma treatment performed in the plasma treatment chamber C2 are not limited to the roll-to-roll method and can also be applied to plasma treatment by a batch method.

[0049] 5 is an example of an apparatus for performing plasma treatment on the precursor layer 1. The apparatus 50 includes, for example, a feed chamber R1, a winding chamber R2, a connecting chamber C1, a plasma treatment chamber C2, a connecting chamber C3, and a PEM device (not shown).

[0050] The feeding chamber R1 is equipped with a feeding roller 51 for feeding the object to be plasma treated 100 (precursor layer 1). A roll of the long object to be plasma treated 100 is attached to the feeding roller 51. In addition, a predetermined number of guide rollers G for guiding the object to be plasma treated 100 are provided in the feeding chamber R1.

[0051] The winding chamber R2 includes a winding roller 52 for winding up the plasma processing object 100. A predetermined number of guide rollers G for guiding the plasma processing object 100 are provided in the winding chamber R2.

[0052] The connecting chamber C1 is disposed next to the feeding chamber R1 in the traveling direction of the object 100 to be plasma treated, and is disposed before the plasma treatment chamber C2. A predetermined number of guide rollers G for guiding the object 100 to be plasma treated are provided inside the connecting chamber C1. The connecting chamber C1 is connected to a vacuum pump (not shown), and is configured so that the pressure inside the connecting chamber C1 can be adjusted. When the device 50 is in operation, the pressure inside the connecting chamber C1 is maintained at a predetermined pressure between the pressure inside the feeding chamber R1 and the pressure inside the plasma treatment chamber C2. This ensures a pressure difference between the feeding chamber R1 and the plasma treatment chamber C2.

[0053] The plasma processing chamber C2 is disposed between the connecting chamber C1 and the connecting chamber C3 in the traveling direction of the plasma processing object 100. In the plasma processing chamber C2, plasma processing is carried out as described below.

[0054] In this embodiment, the plasma processing chamber C2 is equipped with a plurality of low inductance antennas (LA) 71. In this embodiment, the LAs 71 are disposed inside the plasma processing chamber C2 while being supported by fixtures 72, as shown in Figures 7 and 8. Here, a case where the number of LAs 71 is four is illustrated as an example.

[0055] The multiple LAs 71 are aligned in the travel direction of the plasma processing object 100 and in a direction perpendicular to the travel direction (the width direction of the plasma processing object 100). The fixture 72 is a vacuum flange. As shown in FIG. 8, the LAs 71 are fixed to the fixture 72 via a feedthrough 74. As shown in FIG. 5, the fixture 72 is attached to an opening 75 provided in the wall of the plasma processing chamber C2. Specifically, the fixture 72 is attached to the opening 75 with a seal member (not shown) sandwiched between the wall of the plasma processing chamber C2 and the fixture 72. The LAs 71 are electrically connected to a high-frequency power source (RF power source) outside the plasma processing chamber C2 via an impedance matcher. The LAs 71 are formed of a conductor. Examples of conductors include copper and silver, with copper being preferred. The LAs 71 may be covered with an insulator. Examples of insulators include glass and quartz.

[0056] As shown in FIG. 7 , in this embodiment, the LA 71 has an open loop shape. Having an open loop shape for the LA 71 is advantageous for reducing the inductance of the LA 71. Therefore, the open loop LA 71 can suppress an increase in voltage due to an increase in power applied to the LA 71. This suppresses abnormal discharge during plasma processing, as described below. Suppressing abnormal discharge also suppresses damage to the plasma-processed object 100 being plasma-processed. Specifically, the LA 71 has a U-shape with two free ends. For each LA 71, the two free ends are fixed to the fixture 72 so as to be aligned in the width direction of the plasma-processed object 100. In this embodiment, the LA 71 also has an extension portion 71a on the opposite side from the two free ends. The extension portion 71a extends parallel to the plasma-processed object 100 passing through the plasma processing chamber C2. The extension portion 71a extends in the width direction of the plasma-processed object 100. Each extension 71a may extend in the traveling direction of the plasma processing object 100, and four LAs 71 may be arranged in this manner. The length of the extension 71a is, for example, 50 to 150 mm. Note that FIG. 7 exemplarily illustrates a case where the length of the extension 71a is the same as the maximum length d2 of the LA 71, which will be described later. The LA 71 may have a coil shape instead of an open loop shape.

[0057] The LA 71 extends from the fixture 72 toward the object 100 to be plasma treated. The LA 71 preferably extends perpendicular to the fixture 72. The extension length d1 of the LA 71 from the fixture 72 is, for example, 30 to 150 mm. The maximum length d2 of the LA 71 in the surface direction of the object 100 to be plasma treated is, for example, 50 to 150 mm. The separation distance d3 (shown in FIG. 8) between the LA 71 and the object 100 to be plasma treated is, for example, 50 to 200 mm. The extension length d1 and the separation distance d3 are preferably the same. The ratio (d3 / d1) of the separation distance d3 to the extension length d1 is, for example, 0.5 to 3.5. The number of LAs 71 (number of rows) spaced apart in the traveling direction of the object 100 to be plasma-treated may be one, two, or three, or four or more if necessary, depending on the traveling speed (i.e., plasma processing time) of the object 100 to be plasma-treated. The center-to-center distance d4 between adjacent LAs 71 in the traveling direction of the object 100 to be plasma-treated is, for example, 100 to 500 mm. The center-to-center distance d5 between adjacent LAs 71 in the width direction of the object 100 to be plasma-treated is, for example, 200 to 500 mm. By adjusting the center-to-center distance d5, the uniformity of the plasma density in the width direction of the object 100 to be plasma-treated can be controlled. The center-to-center distances d4 and d5 are preferably the same. The ratio of the center-to-center distance d5 to the center-to-center distance d4 (d5 / d4) is, for example, 0.5 to 2.0. The centers of the extensions 71a of the four LAs 71 preferably form a square with their vertices as vertices. High density plasma with high in-plane uniformity can be generated by using such a set of LAs 71. As the LAs 71, for example, a high frequency antenna for plasma generation described in Japanese Patent Laid-Open No. 2013-258153 may be used.

[0058] In this embodiment, the plasma processing chamber C2 further includes transport rollers 53. The transport rollers 53 are main guide rollers for transporting the object 100 to be plasma-processed within the plasma processing chamber C2. The transport rollers 53 have a temperature control function that can heat or cool the object 100 to be plasma-processed. In other words, the transport rollers 53 are transport rollers with a temperature control function. When the apparatus 50 is in operation, the transport rollers 53 transport the precursor layer 1, which is the object 100 to be plasma-processed, while contacting the precursor layer 1. At this time, the transport rollers 53 contact the second main surface 1b of the precursor layer 1, which faces the first main surface 1a, which is the surface to be plasma-processed of the precursor layer 1. The LA 71 is disposed opposite the transport rollers 53. In the apparatus 50 including the plasma processing chamber C2, during plasma processing, the precursor layer 1 can be plasma-processed while being cooled or heated by the transport rollers 53 with a temperature control function that contacts the precursor layer 1. By controlling the temperature of the precursor layer 1, it is possible to suppress thermal deformation of the precursor layer 1 and also to suppress the influence of the thermal deformation on the transportation of the precursor layer 1.

[0059] By using the transport roller 53 with the temperature control function as described above, it is possible to, for example, cool the precursor layer 1 during plasma treatment to suppress damage to the precursor layer 1 due to heat, or to heat the precursor layer 1 during plasma treatment to enhance the effect of the plasma treatment.

[0060] The PEM device is used to perform plasma emission monitoring (PEM) during plasma processing and includes a device body and an optical fiber for collecting light. One end of the optical fiber is positioned in the plasma processing chamber C2 between the object to be plasma processed 100 and the LA71 in the direction of separation between them. The other end of the optical fiber is connected to the device body. A first line L1 equipped with a flow control valve for introducing gas into the plasma processing chamber C2 is also connected to the plasma processing chamber C2.

[0061] The connecting chamber C3 is disposed next to the plasma processing chamber C2 in the traveling direction of the object 100 to be plasma processed. A predetermined number of guide rollers G for guiding the object 100 to be plasma processed are provided in the connecting chamber C3. The connecting chamber C3 is connected to a vacuum pump (not shown) and is configured to be able to adjust the pressure inside the chamber. When the device 50 is in operation, the pressure inside the connecting chamber C3 is maintained at a predetermined pressure between the pressure inside the plasma processing chamber C2 and the pressure inside the winding chamber R2. This ensures a pressure difference between the plasma processing chamber C2 and the winding chamber R2.

[0062] The above-described apparatus 50 can perform plasma treatment on the precursor layer 1. Specifically, the process is as follows.

[0063] The object to be plasma-treated 100 is unwound from the unwinding chamber R1. After being unwound from the unwinding chamber R1, the object to be plasma-treated 100 passes through the connecting chamber C1, the plasma processing chamber C2, and the connecting chamber C3 in sequence, and is wound up in the winding chamber R2. The traveling speed of the object to be plasma-treated 100 is preferably 0.1 m / min or more, more preferably 0.5 m / min or more, even more preferably 0.7 m / min or more, and particularly preferably 0.9 m / min or more. Furthermore, the traveling speed of the object to be plasma-treated 100 is, for example, 10 m / min or less. When the traveling speed of the object to be plasma-treated 100 is equal to or greater than the above-mentioned lower limit, the production efficiency of the separation membrane can be ensured. When the traveling speed of the object to be plasma-treated 100 is equal to or less than the above-mentioned upper limit, variation in the quality of the separation membrane can be suppressed. Furthermore, the series of lines from the unwinding chamber R1 to the winding chamber R2 is not exposed to the atmosphere along the way, and the process is carried out in this line under a reduced pressure atmosphere. The reduced pressure atmosphere is preferably a vacuum. The term "under vacuum" preferably means a reduced pressure atmosphere of 10 Pa or less.

[0064] In the plasma treatment chamber C2, a plasma treatment is performed. In the plasma treatment, for example, the first main surface 1 a of the precursor layer 1 is plasma-treated in a reduced pressure atmosphere in the plasma treatment chamber C2 (chamber). The plasma treatment may be performed while detecting the plasma emission intensity.

[0065] As an example, a case will be described below in which the plasma processing is an ICP processing of argon-containing gas generated by applying high frequency power to the LA 71.

[0066] During plasma processing, argon is supplied into the plasma processing chamber C2 via the first line L1. Other inert gases besides argon may be supplied into the plasma processing chamber C2. Examples of other inert gases include krypton and xenon. The gas in the plasma processing chamber C2 may also contain other gases besides the inert gas. Examples of other gases include oxygen, nitrogen, hydrogen, and water vapor. The argon concentration (Ar concentration) in the gas (argon-containing gas) in the plasma processing chamber C2 is preferably 50% by volume or more, more preferably 65% ​​by volume or more, even more preferably 80% by volume or more, even more preferably 90% by volume or more, even more preferably 95% by volume or more, and particularly preferably 100% by volume. When the Ar concentration is equal to or greater than the above-mentioned lower limit, high-density argon plasma can be generated.

[0067] The pressure in the plasma treatment chamber C2 during plasma treatment is preferably 0.05 Pa or more, more preferably 0.1 Pa or more, even more preferably 0.2 Pa or more, particularly preferably 0.3 Pa or more, and preferably 10 Pa or less, more preferably 7 Pa or less, even more preferably 5 Pa or less, and particularly preferably 3 Pa or less. When the pressure in the plasma treatment chamber C2 is equal to or greater than the above-mentioned lower limit, a plasma environment of sufficient density for surface modification treatment of the first main surface 1a of the precursor layer 1 can be formed in the plasma treatment chamber C2 during plasma treatment. When the pressure in the plasma treatment chamber C2 is equal to or less than the above-mentioned upper limit, thermal damage to the precursor layer 1 caused by excessively high-density plasma can be suppressed during plasma treatment, and thermal deformation of the precursor layer 1 can also be suppressed. The pressure in the plasma treatment chamber C2 can be adjusted by the amount of argon-containing gas supplied into the plasma treatment chamber C2.

[0068] The frequency of the high-frequency power applied to the LA 71 during plasma processing 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 equal to or higher than the lower limit, plasma current density can be increased while stabilizing plasma discharge. When the frequency is equal to or lower than the upper limit, the antenna potential can be suppressed, thereby suppressing damage to the precursor layer 1 caused by plasma. Furthermore, 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 equal to or higher than the lower limit, a high-density plasma environment can be formed in the plasma processing chamber C2 during plasma processing using inductively coupled plasma. When the high-frequency power is equal to or lower than the upper limit, excessive damage to the precursor layer 1 caused by plasma can be suppressed.

[0069] In the plasma treatment, the plasma emission intensity during the plasma treatment may be monitored by the PEM device. When the gas used is an argon-containing gas, for example, based on the monitoring results, the intensity I of the maximum emission peak in the wavelength range of 300 nm or more and 900 nm or less in the plasma emission may be measured. maxThe wavelength is controlled to be within the range of 811 nm or more and 812 nm or less. Furthermore, the ratio (I2 / I1) of the intensity I2 of the emission peak within the wavelength range of 603 nm or more and 604 nm or less to the intensity I1 of the emission peak within the wavelength range of 706 nm or more and 707 nm or less is controlled to be 1.0 or less, preferably 0.50 or less, more preferably 0.45 or less, even more preferably 0.40 or less, and particularly preferably 0.35 or less. The maximum emission peak within the wavelength range of 300 nm or more and 900 nm or less in the plasma emission is an emission peak attributed to the transition of argon radicals from the ground state of 11.55 eV to the excited state of 13.08 eV. The emission peak within the wavelength range of 706 nm or more and 707 nm or less is an emission peak attributed to the transition of argon radicals from the ground state of 11.55 eV to the excited state of 13.30 eV. The emission peak in the wavelength range of 603 nm or more and 604 nm or less is an emission peak attributed to the transition of argon radicals from the ground state of 13.08 eV to the excited state of 15.13 eV. max The wavelength of the laser beam is within the range of 811 nm or more and 812 nm or less, and the ratio (I2 / I1) is 1.0 or less, indicating that the kinetic energy of argon particles in the plasma is suppressed. Specifically, this is shown in the examples and comparative examples described below. When the ratio (I2 / I1) is equal to or less than the upper limit, excessive increases in the kinetic energy of argon particles in the plasma can be controlled, and damage to the surface of the plasma treatment object can be suppressed. The ratio (I2 / I1) is preferably equal to or more than 0.01, more preferably equal to or more than 0.10, and even more preferably equal to or more than 0.20. When the ratio (I2 / I1) is equal to or more than the lower limit, moderately active movement of argon particles is ensured, and activation of the surface of the plasma treatment object can be promoted. Methods for controlling the plasma emission intensity include, for example, adjusting the amount of argon gas introduced into the plasma treatment chamber C2, adjusting the frequency of the high-frequency power in the high-frequency power supply, and adjusting the magnitude of the applied power.

[0070] When the gas used is an oxygen-containing gas, the ratio (I4 / I3) of the maximum emission peak intensity I4 in the wavelength range of 555 nm to 565 nm to the maximum emission peak intensity I3 in the wavelength range of 775 nm to 779 nm is controlled to, for example, 1.0 or less, preferably 0.50 or less, more preferably 0.45 or less, even more preferably 0.40 or less, and particularly preferably 0.35 or less. The maximum emission peak in the plasma emission wavelength range of 555 nm to 565 nm is considered to be an emission peak attributable to a transition in carbon dioxide gas. The maximum emission peak in the wavelength range of 775 nm to 779 nm is an emission peak attributable to a transition in oxygen radicals from the ground state of 9.15 eV to the excited state of 10.74 eV. A ratio (I4 / I3) of 1.0 or less indicates that the kinetic energy of oxygen particles in the plasma is suppressed. Specific examples are shown in the examples and comparative examples described below. When the ratio (I4 / I3) is equal to or less than the upper limit, excessive increases in the kinetic energy of oxygen particles in the plasma can be controlled, and damage to the surface of the plasma treatment object can be suppressed. The ratio (I4 / I3) is preferably equal to or greater than 0.01, and more preferably equal to or greater than 0.02. When the ratio (I4 / I3) is equal to or greater than the lower limit, it can be confirmed that the oxidative decomposition of the surface of the plasma treatment object is progressing appropriately by such oxygen plasma. Methods for controlling the plasma emission intensity include, for example, adjusting the amount of oxygen gas introduced into the plasma treatment chamber C2, adjusting the frequency of the high-frequency power in the high-frequency power supply, and adjusting the magnitude of the applied power.

[0071] In the plasma treatment, the plasma current density at the intermediate position between the LA 71 and the precursor layer 1 is preferably 1.0 mA / cm 3 More preferably, 2.0 mA / cm 3 More preferably, 3.0 mA / cm 3 or more, and preferably 10 mA / cm 3 Less than or equal to 8 mA / cm 3 More preferably, 4 mA / cm or less 3When the plasma current density is equal to or greater than the lower limit, sufficient plasma particles (e.g., plasma argon particles) can be secured in the plasma processing chamber C2 during plasma processing, and the first main surface 1a of the precursor layer 1 can be appropriately surface-modified. When the plasma current density is equal to or less than the upper limit, damage to the first main surface 1a due to excessively high density plasma particles can be suppressed during plasma processing. Methods for adjusting the plasma current density include, for example, adjusting the amount of gas introduced into the plasma processing chamber C2, adjusting the frequency of high-frequency power in the high-frequency power supply, and adjusting the magnitude of the applied power.

[0072] The apparatus used for plasma processing may be an apparatus 60, as shown in Fig. 6, which includes a plasma processing chamber C2' instead of the plasma processing chamber C2 (see Fig. 5) in the apparatus 50 shown in Fig. 5. The plasma processing chamber C2' differs from the plasma processing chamber C2 in that it does not include the transport rollers 53. In other words, it is also possible to use an apparatus 60 that does not include the transport rollers 53.

[0073] The separation functional layer in the separation membrane manufactured by the manufacturing method of this embodiment can separate a substance to be separated (hereinafter referred to as a "fluid to be separated") from a mixed fluid such as a mixed liquid and a mixed gas. The separation functional layer may be a layer that preferentially allows the fluid to be separated contained in the mixed fluid to permeate, or 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.

[0074] The use of the separation membrane manufactured by the manufacturing method of this embodiment is not particularly limited. The separation membrane manufactured by the manufacturing method of this embodiment can be used for a variety of purposes. Furthermore, the separation method to which the separation membrane manufactured by the manufacturing method of this embodiment is applied is not particularly limited. The separation membrane manufactured by the manufacturing method of this embodiment can be used in various separation methods such as reverse osmosis (RO), nanofiltration (NF), pervaporation (PV), and vapor permeation (VP).

[0075] The separation membrane produced by the production method of this embodiment can be used for both gas separation and liquid separation, and has excellent separation performance.

[0076] For example, when a mixed fluid is a mixed liquid containing water (HO) and an organic solvent and HO is to be separated from the mixed liquid as a liquid to be separated, the separation membrane manufactured by the manufacturing method of this embodiment can separate HO from the mixed liquid by preferentially allowing HO to permeate.

[0077] For example, when the mixed fluid is a mixed gas containing hydrogen (H) and other gases such as carbon dioxide (CO), and H is to be separated from the mixed gas as a target gas for separation, the separation membrane manufactured by the manufacturing method of this embodiment can separate H from the mixed gas by preferentially allowing H to permeate.

[0078] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0079] (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.

[0080] Next, the surface (first main 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 technology, and plasma treatment was performed on the first main surface of the precursor layer using an ICP with a low-inductance antenna. Specifically, an apparatus 50 shown in FIG. 5 was used, which can perform a roll-to-roll process on the laminate. In this example, a roll of general-purpose PET film was set on the payout roller 51 as a carrier film for transporting the laminate. The plasma treatment chamber C2 was equipped with a temperature-controlled transport roller 53 and four low-inductance antennas 71. The positional relationship between the low-inductance antennas and the plasma-treated object in the plasma treatment chamber C2 used in this example was the same as the positional relationship shown in FIGS. 7 and 8. Each low-inductance antenna 71 had an extension 71a parallel to the plasma-treated object 100. The four low-inductance antennas 71 had an extension length d of 88 mm, a maximum length d (length of the extension) of 100 mm, a separation distance d of 112 mm, a center-to-center distance d of 290 mm, and a center-to-center distance d 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 C2.

[0081] The laminate of the porous support and the precursor layer, which was the plasma treatment object 100, was cut to A4 size and attached using tape so that the porous support was in contact with the general-purpose PET film, which was the 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 by a roll-to-roll method, plasma treatment was performed on the first main surface of the precursor layer in plasma treatment chamber C2.

[0082] The plasma treatment conditions were as follows: the ultimate vacuum of the plasma treatment chamber was 1.0×10 -4After evacuating the apparatus to a vacuum of 0.1 Pa, argon (Ar) gas was introduced into the plasma treatment chamber, and the pressure in the plasma treatment chamber was set to 0.12 Pa. A 13.56 MHz high-frequency power source (RF power source) was used to apply 5.0 kW of power to the four low-inductance antennas, thereby forming an inductively coupled plasma of argon gas around the four low-inductance antennas. The running speed of the carrier film was changed according to the treatment time (80 seconds in Example 1). The temperature of the temperature-adjustable transport roller was set to 20°C. Furthermore, the intensity I of the maximum emission peak in the plasma emission was measured. max The wavelength of the light was set to be in the range of 811 nm or more and 812 nm or less, and the ratio (I2 / I1) of the intensity I2 of the emission peak in the wavelength range of 603 nm or more and 604 nm or less to the intensity I1 of the emission peak in the wavelength range of 706 nm or more and 707 nm or less was controlled to be 0.5. Table 1 shows the plasma treatment conditions.

[0083] The first main 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.

[0084] 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 1.

[0085] Example 3 A separation membrane of Example 3 was produced in the same manner as in Example 1, except that the plasma treatment conditions were changed as shown in Table 1.

[0086] Example 4 A 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 1.

[0087] Example 5 A separation membrane of Example 5 was produced in the same manner as in Example 1, except that the plasma treatment conditions were changed as shown in Table 1.

[0088] Example 6 A precursor layer was prepared on a porous support using the same method as in Example 1. The surface (first main surface) of this precursor layer was plasma treated. The same apparatus as used in Example 1 was used for the plasma treatment. The first main surface of the precursor layer was plasma treated while a laminate (plasma treatment target) in which a precursor layer was formed on a porous support was transported using a roll-to-roll method. The plasma treatment was performed on the first main surface of the precursor layer using the same method as in Example 1, except that oxygen gas was used instead of argon gas and the plasma treatment conditions were changed as shown in Table 1. Note that, because oxygen gas was used, the ratio of I / I was controlled to 0.04, not I / I.

[0089] (Example 7) 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.

[0090] Next, the surface (first main surface) of the prepared precursor layer was subjected to plasma treatment in the same manner as in Example 1, except that the plasma treatment conditions were changed as shown in Table 2.

[0091] Example 8 A separation membrane of Example 8 was produced in the same manner as in Example 7, except that the plasma treatment conditions were changed as shown in Table 2.

[0092] Example 9 A separation membrane of Example 9 was produced in the same manner as in Example 7, except that the plasma treatment conditions were changed as shown in Table 2.

[0093] Example 10 A separation membrane of Example 10 was produced in the same manner as in Example 7, except that the plasma treatment conditions were changed as shown in Table 2.

[0094] Example 11 A separation membrane of Example 11 was produced in the same manner as in Example 7, except that the plasma treatment conditions were changed as shown in Table 2.

[0095] Example 12 A separation membrane of Example 12 was produced in the same manner as in Example 7, except that the plasma treatment conditions were changed as shown in Table 2.

[0096] Example 13 A precursor layer was prepared on a porous support using the same method as in Example 7. The surface (first main surface) of this precursor layer was plasma treated. The same apparatus as that used in Example 1 was used for the plasma treatment. The first main surface of the precursor layer was plasma treated while a laminate (plasma treatment target) in which a precursor layer was formed on a porous support was transported using a roll-to-roll method. Plasma treatment was performed on the first main surface of the precursor layer. The plasma treatment was performed using the same method as in Example 1, except that oxygen gas was used instead of argon gas and the plasma treatment conditions were changed as shown in Table 2. Note that, because oxygen gas was used, the ratio of I / I was controlled to 0.04, not I / I.

[0097] Example 14 A separation membrane of Example 14 was produced in the same manner as in Example 13, except that the plasma treatment conditions were changed as shown in Table 2.

[0098] Example 15 A separation membrane of Example 15 was produced in the same manner as in Example 13, except that the plasma treatment conditions were changed as shown in Table 2.

[0099] Example 16 A precursor layer was produced on a porous support using the same method as in Example 7. The surface (first main surface) of this precursor layer was plasma treated. For the plasma treatment, the same apparatus as that used in Example 1 was used. The plasma treatment was carried out on the first main surface of the precursor layer while transporting a laminate (plasma treatment target) in which a precursor layer was formed on a porous support using a roll-to-roll method. The plasma treatment was carried out in the same manner as in Example 1, except that nitrogen gas was used instead of argon gas and the plasma treatment conditions were changed as shown in Table 2.

[0100] Comparative Example 1 A separation membrane of Comparative Example 1 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 performed in Comparative Example 1 was as follows.

[0101] Instead of a plasma treatment chamber equipped with a low-inductance antenna, a cathode electrode and an anode electrode (rectangular electrodes made of SUS304) 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 a laminate (object to be plasma-treated) consisting of a porous support and a precursor layer formed thereon. 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 first main 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 0.4 kW from the high-frequency power supply between the planar electrodes, and treatment was performed. The plane size of each planar electrode facing the laminate was 110 mm x 430 mm.

[0102] 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, a laminate of the porous support and the precursor layer produced in Example 1 was used as a separation membrane of Comparative Example 2.

[0103] Comparative Example 3 A separation membrane of Comparative Example 4 was produced in the same manner as in Example 7, except that the plasma treatment using ICP was changed to plasma treatment using CCP. The plasma treatment using CCP performed in Comparative Example 4 was the same as in Comparative Example 1.

[0104] Comparative Example 4 The precursor layer produced in Example 7 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 7 was used as the separation membrane of Comparative Example 4.

[0105] (Evaluation of Liquid Separation) Liquid separation was evaluated for the separation membranes of Examples 1 to 6 and Comparative Examples 1 and 2. Specifically, the separation coefficient α (α=HO / IPA) of water relative to isopropanol (IPA) was measured by the following method.

[0106] First, the separation membrane was cut into a size of 74 mm in diameter to prepare a flat membrane test piece. This test piece was set 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.

[0107] 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 in the cell. As a result, the mixed liquid permeated the separation membrane, and a gas permeated fluid was obtained.

[0108] The gaseous permeate was cooled and condensed using a cold trap using liquid nitrogen. The composition of the liquid permeate was analyzed using gas chromatography, and the separation factor α was calculated based on the results. The results are shown in Table 1.

[0109] (Evaluation of Gas Separation) Gas separation was evaluated for the separation membranes of Examples 7 to 16 and Comparative Examples 3 and 4. Specifically, the separation factor α of H2 relative to CO2 (α = H2 / CO2) was measured by the following method.

[0110] 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). H gas and CO 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. This allowed the mixed gas to permeate the separation membrane, and permeated gas was obtained.

[0111] The composition of the permeated gas was analyzed using gas chromatography, and the 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. The results are shown in Table 2. Gas separation factor α = H [GPU] / CO [GPU]

[0112]

[0113]

[0114] As shown in Tables 1 and 2, the separation membranes produced by the production methods of the Examples had improved separation performance in both liquid separation and gas separation.

[0115] The separation membrane of this embodiment has improved separation performance and is particularly suitable for separating water from a liquid mixture and hydrogen from a gas mixture.

Claims

1. A method for manufacturing a separation membrane having a separation functional layer containing Si, O, and C, the method comprising: preparing a precursor layer containing Si, O, and C as a precursor of the separation functional layer; and plasma treating a first main surface of the precursor layer with inductively coupled plasma to obtain the separation functional layer.

2. The method for producing a separation membrane according to claim 1, wherein the plasma treatment is a treatment using inductively coupled plasma of a gas containing at least one selected from the group consisting of argon, oxygen, and nitrogen, which is generated by applying high frequency power to a low inductance antenna.

3. The plasma treatment is a treatment using inductively coupled plasma of a gas containing argon, and in the plasma treatment, the maximum emission peak intensity I in the wavelength range of 300 nm or more and 900 nm or less in the plasma emission is max and a ratio of an emission peak intensity I2 within a wavelength range of 603 nm to 604 nm to an emission peak intensity I1 within a wavelength range of 706 nm to 707 nm is 1.0 or less.

4. The method for producing a separation membrane according to claim 1, wherein the plasma treatment is a treatment using inductively coupled plasma of a gas containing oxygen, and the ratio of the intensity I4 of the maximum emission peak in the wavelength range of 555 nm or more and 565 nm or less to the intensity I3 of the maximum emission peak in the wavelength range of 775 nm or more and 779 nm or less in the plasma emission is set to 1.0 or less.

5. The method for producing a separation membrane according to claim 1, wherein the plasma treatment is carried out while the precursor layer is cooled or heated.

6. The method for producing a separation membrane according to claim 1, wherein the plasma treatment is carried out while the precursor layer is being transported and cooled or heated by a roller with a temperature control function that comes into contact with the precursor layer.

7. The method for producing a separation membrane according to claim 1, wherein the plasma treatment is carried out in a reduced pressure atmosphere in a chamber.

8. The method for producing a separation membrane according to claim 1, wherein the first main surface of the precursor layer contains a compound containing a siloxane bond.

9. The method for producing a separation membrane according to claim 8, wherein the compound is a silicone resin.

10. The method for producing a separation membrane according to claim 1, wherein the precursor layer is supported by a porous support disposed on a second main surface side opposite the first main surface.

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