JP2019006056A - Composite membrane - Google Patents

Abstract

To provide a composite membrane preventing a part without becoming a membrane from existing, and useful for various industrial applications because of having extremely thin membrane structure part with uniform thickness.SOLUTION: There is provided a composite membrane having a membrane structure part which has a first fiber layer and a second fiber layer, and a membrane constitutional resin existing between constitution fibers of the first fiber layer, average fiber diameter of the fiber constituting the first fiber layer is 3 μm or less, and further a part without becoming a membrane is prevented from existing only when a combination that the first fiber layer has lower hydrophilicity than the second fiber layer is satisfied, and for example a composite membrane having extremely thin membrane structure part having membrane thickness of 10 μm or less with uniform thickness can be provided.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite membrane.

Conventionally, a composite membrane having a membrane structure such as a film is used for an electrochemical element such as a liquid separation membrane such as a water treatment membrane, a gas separation membrane, a polymer electrolyte membrane of a fuel cell, a capacitor, and a primary / secondary battery. It is used in various industrial applications such as separators, medical materials, ion exchange membranes, and dialysis membranes.
And, for the purpose of improving the function when used for various industrial applications, the film structure portion has been studied to be thin.
However, when trying to reduce the thickness of the film structure portion, the strength of the film structure portion is so weak that it is likely to cause dimensional changes or cracks and breaks, for example, an extremely thin film structure portion having a film thickness of 10 μm or less. It was thought that the manufacturing problem that it was difficult to manufacture and the handling problem that the handling property was poor occurred.

For example, the following conventional techniques are known as a composite membrane having a membrane structure portion and a method for manufacturing the composite membrane, which are considered to solve such a problem.
JP-A-2006-182701 (Patent Document 1) discloses a film material produced by applying a thermosetting resin solution to a fiber deposition layer of a laminate having a fiber deposition layer on a substrate. It is disclosed. Since the membrane structure portion of Patent Document 1 is reinforced by the fibers constituting the fiber deposition layer, the above-described problem is unlikely to occur even when the membrane structure portion is thinned.
In addition, in patent document 1, as the specific aspect,
-As the material of the base material, a resin sheet, a paper sheet, a cloth sheet, a glass fiber sheet or the like can be used, and the thickness of the base material is preferably 10 to 100 µm.
The constituent fibers of the fiber accumulation layer are not particularly limited and can be produced using various resins, and when the fiber accumulation layer is produced by an electrospinning method, the resin used is preferably PES,
The average fiber diameter of the fiber accumulation layer is, for example, 1 μm or less, and the thickness of the fiber accumulation layer is preferably 1 to 3 μm.
-The type of thermosetting resin is not particularly limited, and the resin used is preferably an epoxy resin,
-The thickness of the layer formed by the thermosetting resin solution permeating into the voids of the fiber deposition layer in the membrane material is 5 to 100 m.
Is disclosed.

Japanese Unexamined Patent Publication No. 2006-182701

The inventors of the present application have a laminate including a first fiber layer and a second fiber layer, and a film-constituting resin, with reference to the prior art such as Patent Document 1, and the constituent fibers of the first fiber layer The preparation of a composite membrane having a membrane structure portion in which the membrane-constituting resin is present was examined.
However, for example, when trying to provide a composite membrane having a very thin membrane structure portion with a uniform thickness and a thickness of 10 μm or less, the main surface of the prepared composite membrane on the first fiber layer side is formed into a membrane. There were portions that were not (for example, there were portions where the fiber shape was present, or portions where there was an unintended opening).
And as above-mentioned, this problem was easy to arise when it was going to provide a composite film using the laminated body provided with a 1st fiber layer and a 2nd fiber layer, and film | membrane structure resin.

The inventors of the present invention have examined the cause of the problem, and as a result of the fact that the above-mentioned phenomenon has occurred as a result of the insufficient film-forming resin between the constituent fibers of the first fiber layer that can constitute the membrane structure portion. it was thought.
Therefore, as long as the prior art is referred to, it is possible to prevent the presence of a non-filmed portion. For example, by providing a very thin film structure portion having a uniform thickness and a thickness of 10 μm or less, it can be used in various industrial applications. It has been difficult to provide useful composite membranes.

The present invention prevents the presence of a non-filmed portion. For example, by providing an extremely thin film structure portion having a uniform thickness and a film thickness of 10 μm or less, a composite film useful for various industrial applications can be provided. For the purpose of provision.

The invention according to claim 1 of the present invention is
“It has a laminate comprising a first fiber layer and a second fiber layer, and a film-constituting resin,
A composite membrane having a membrane structure portion in which the membrane-constituting resin is present between constituent fibers of the first fiber layer,
The average fiber diameter of the fibers constituting the first fiber layer is 3 μm or less,
The first fiber layer is a composite membrane having a lower hydrophilicity than the second fiber layer. "
It is.
The invention according to claim 2 of the present invention is
“(1) Step of preparing a fiber assembly,
(2) By forming another fiber assembly on one main surface of the fiber assembly, the first fiber layer derived from the other fiber assembly and the second fiber layer derived from the fiber assembly are provided. Preparing a laminate,
(3) A step of applying a hydrophilic resin solution to the main surface where the second fiber layer in the laminate is exposed,
(4) The step of causing the hydrophilic resin to exist between constituent fibers of the second fiber layer by removing the solvent from the imparted hydrophilic resin solution,
(5) A step of applying a film-constituting resin solution to the main surface where the first fiber layer in the laminate is exposed,
(6) A step of forming a membrane structure part in which the membrane constituent resin is present between constituent fibers of the first fiber layer by removing a solvent from the applied membrane constituent resin solution;
(7) A step of removing the hydrophilic resin present between constituent fibers of the second fiber layer using a solvent capable of dissolving the hydrophilic resin,
A method for producing a composite membrane having a membrane structure part in which the membrane-constituting resin is present between constituent fibers of the first fiber layer in the laminate,
The average fiber diameter of the fibers constituting the first fiber layer is 3 μm or less,
The method for producing a composite membrane, wherein the first fiber layer is less hydrophilic than the second fiber layer. "
It is.

The present invention provides a “laminate comprising a first fiber layer and a second fiber layer, and a membrane-constituting resin, wherein the membrane-constituting resin is present between constituent fibers of the first fiber layer. The invention relates to a “composite membrane having a structural portion”.
And, since the average fiber diameter of the fibers constituting the first fiber layer is 3 μm or less, the thickness of the first fiber layer is uniform and thin. The composite membrane provided can be provided.
Furthermore, as a result of continuing investigations to solve the above-mentioned problems, the present inventors have found that the relationship between the first fiber layer and the second fiber layer is “the first fiber layer is more hydrophilic than the second fiber layer. When the combination of “low” is satisfied, it is possible to prevent the presence of a non-filmed portion, and to provide a composite film having a very thin film structure portion having a uniform thickness and a film thickness of 10 μm or less, for example. I found.
As described above, the present invention can provide composite membranes useful for various industrial applications.

In particular, since the composite membrane of the present invention has the above-described configuration, it is useful as a separation membrane for a hydrophilic fluid such as a liquid such as water or a gas such as carbon dioxide, ammonia, water vapor, or hydrogen chloride.
That is, the composite membrane of the present invention is considered to be a composite membrane that exhibits the following functions.
The first fiber layer of the laminate constituting the composite membrane is a component that has low hydrophilicity and hardly undergoes deformation such as dissolution, swelling, or shrinkage due to the hydrophilic fluid. For this reason, the membrane structure part constituting the composite membrane is reinforced by the first fiber layer that is unlikely to be deformed, so that even if the composite membrane is exposed to a hydrophilic fluid, the composite membrane may undergo dimensional changes, cracks or fractures. It is possible to prevent the occurrence of problems such as physical properties, which are likely to occur, and handling problems, such as poor handling.
-Since the 2nd fiber layer is a member comprised with the fiber, it has air permeability and liquid permeability. And the 2nd fiber layer among the laminated bodies which comprise the composite film is a structural member with high hydrophilicity and high affinity with a hydrophilic fluid. For this reason, the second fiber layer easily holds a hydrophilic fluid and easily supplies the fluid to the membrane structure portion.
Furthermore, the second fiber layer is a member that can play a role to reinforce the membrane structure part from the outside, and it is said that the composite membrane is prone to dimensional changes or cracks and breaks, and the handling property is poor. It is possible to prevent problems in handling.

Another aspect of the present invention is a method for manufacturing a composite membrane according to the present invention described above.
This manufacturing method is “(1) a step of preparing a fiber assembly,
(2) By forming another fiber assembly on one main surface of the fiber assembly, the first fiber layer derived from the other fiber assembly and the second fiber layer derived from the fiber assembly are provided. Preparing a laminate,
(3) A step of applying a hydrophilic resin solution to the main surface where the second fiber layer in the laminate is exposed,
(4) The step of causing the hydrophilic resin to exist between constituent fibers of the second fiber layer by removing the solvent from the imparted hydrophilic resin solution,
(5) A step of applying a film-constituting resin solution to the main surface where the first fiber layer in the laminate is exposed,
(6) A step of forming a membrane structure part in which the membrane constituent resin is present between constituent fibers of the first fiber layer by removing a solvent from the applied membrane constituent resin solution;
(7) A step of removing the hydrophilic resin present between constituent fibers of the second fiber layer using a solvent capable of dissolving the hydrophilic resin,
And a manufacturing method of a composite membrane having a membrane structure portion in which the membrane-constituting resin exists between constituent fibers of the first fiber layer in the laminate.
And since the first fiber layer having a uniform and thin thickness can be prepared by “the average fiber diameter of the fibers constituting the first fiber layer is 3 μm or less”, a membrane structure portion having a uniform and thin thickness can be prepared. The composite membrane provided can be provided.
Furthermore, the manufacturing method of the present invention has a manufacturing condition that “the first fiber layer is lower in hydrophilicity than the second fiber layer”, and (3) and ( Since the manufacturing steps of 4) and (7) are provided in the order of the steps described above, it is possible to prevent the presence of a non-filmed portion, for example, an extremely thin film structure having a uniform thickness and a film thickness of 10 μm or less. A composite membrane provided with a portion can be provided.

The reason why the production method of the present invention can produce the composite membrane according to the present invention is not completely clarified, but it is considered that the following effects are exhibited.
That is, in the laminate after the above steps (3) and (4), the hydrophilic resin is present between the constituent fibers of the second fiber layer, so that the membrane-constituting resin solution is the constituent of the second fiber layer. It has a mode in which it cannot easily enter between fibers.
Therefore, in the step (5) of applying the film-constituting resin solution to the main surface where the first fiber layer is exposed in the laminate after the steps (3) and (4) described above, the film-constituting resin solution is the first one. The movement from the one fiber layer to the second fiber layer is prevented, and the applied membrane-constituting resin solution is easily retained between the constituent fibers of the first fiber layer.
In particular, this effect is not limited to the case where a membrane-constituting resin solution having a higher affinity for the first fiber layer than the second fiber layer is employed. For example, this effect is equivalent to both the first fiber layer and the second fiber layer. Even when a membrane-constituting resin solution having affinity or a membrane-constituting resin solution having higher affinity for the second fiber layer than the first fiber layer is employed (in other words, from the first fiber layer to the second fiber Even when a membrane-constituting resin solution that easily moves to the layer is adopted), the membrane-constituting resin solution is prevented from moving from the first fiber layer to the second fiber layer. The effect that the resin solution tends to stay between the constituent fibers of the first fiber layer is exhibited.
Therefore, in the state in which the membrane constituent resin solution is sufficiently and abundant between the constituent fibers of the first fiber layer, the film structure portion is obtained by removing the solvent, which is the next step, from the laminate provided with the membrane constituent resin solution. It can be used for the step (6) of forming. Then, the composite film concerning this invention can be provided by passing through the process (7) which removes the hydrophilic resin which exists between the constituent fibers of a 2nd fiber layer using the solvent which can melt | dissolve hydrophilic resin.
As a result, the film-constituting resin is sufficiently present between the constituent fibers of the first fiber layer to prevent the presence of a non-filmed portion. For example, the thickness is uniform and the film thickness is 10 μm. A composite membrane provided with the following extremely thin membrane structure can be provided.

As described above, the present invention can provide composite membranes useful for various industrial applications.

It is the electron micrograph which image | photographed 1000 times the main surface of the side which provided the film | membrane structure resin solution in the composite film prepared in Example 1. FIG. It is the electron micrograph which image | photographed 1000 times the main surface of the side which provided the film | membrane structure resin solution in the composite film prepared in Example 2. FIG. It is the electron micrograph which image | photographed 1000 times the main surface of the side which provided the film | membrane structure resin solution in the composite film prepared in Example 3. FIG. It is an electron micrograph which image | photographed 1000 times the main surface of the side which provided the film | membrane structure resin solution in the composite film prepared by the comparative example 1. FIG. It is an electron micrograph which image | photographed 1000 times the main surface of the side which provided the film | membrane structure resin solution in the composite film prepared in the comparative example 2. FIG.

  In the present invention, various configurations such as the following configurations can be selected as appropriate.

The composite film of the present invention includes a laminate including a first fiber layer and a second fiber layer, and a film constituent resin.
The first fiber layer and the second fiber layer (hereinafter sometimes referred to as each fiber layer) in the present invention are derived from, for example, a fiber web, a nonwoven fabric, or a sheet-like fabric such as a woven fabric or a knitted fabric. It is a layer made of fibers.

  The method for preparing the fibers constituting each fiber layer can be selected as appropriate. For example, the melt spinning method, the dry spinning method, the wet spinning method, the direct spinning method (melt blow method, spun bond method, spinning by applying an electric field to the spinning solution) Electrospinning method, spinning method using centrifugal force, spinning method using accompanying airflow described in JP2011-012372A, electrostatic method described in JP2005-264374A, etc. A known method such as a neutral spinning method, which is a kind of spinning method, or a method of extracting a fiber having a small fiber diameter by removing one or more kinds of resin components from a composite fiber can be used.

A fiber web can be prepared by subjecting the fiber prepared using the above-described method to, for example, a dry method or a wet method, and a non-woven fabric can be prepared by entanglement and / or integration of constituent fibers of the prepared fiber web.
As a method of entanglement and / or integration of constituent fibers, for example, a method of entanglement with a needle or a water stream, a method of subjecting the fiber to a heat treatment or the like, and bonding or integrating the constituent fibers with a binder or adhesive fiber The method of making it integrated can be mentioned.
The heat treatment method can be appropriately selected. For example, a method of heating and pressurizing with a calender roll, a method of heating with a hot air dryer, a method of heating an organic resin contained by irradiating infrared rays under no pressure, and the like are used. Can do.

Alternatively, a fiber web or a nonwoven fabric may be prepared by spinning using a direct spinning method and collecting fibers.
It is preferable to collect fibers spun using the direct spinning method so that a fiber web or a nonwoven fabric composed of fibers having a small average fiber diameter and a uniform fiber diameter can be prepared. In particular, it is preferable to use an electrospinning method because a fiber web or a nonwoven fabric made of fibers having a smaller average fiber diameter and a more uniform fiber diameter can be prepared.
When the electrostatic spinning method is employed, it is preferable to use a spinning solution having spinnability. Use of a spinning solution having a spinnability is preferable because a fiber having a more uniform and fine fiber diameter can be prepared. Whether the spinning solution has spinnability can be determined by the method described in JP-A-2017-053078.

  A woven fabric or a knitted fabric can be prepared by weaving or knitting the fibers prepared as described above.

  In addition to the fiber web, a non-woven fabric or a fabric such as a woven fabric or a knitted fabric may be used for the above-described method of intertwining and / or integrating the constituent fibers.

The first fiber layer is a member that forms a membrane structure portion together with the film-constituting resin, and the constituent fibers of the first fiber layer are present in the film-constituting resin (in other words, a film between the constituent fibers of the first fiber layer. It is a member that can reinforce the membrane structure part and prevent the above-mentioned various problems that occur when the film structure part is thinned.
The fibers constituting the first fiber layer have an average fiber diameter of 3 μm or less and 2 μm or less so that a non-filmed portion can be prevented and a membrane structure portion having a uniform thickness can be realized. It is preferably 1 μm or less, more preferably 800 nm or less. The lower limit value of the average fiber diameter is appropriately selected, but it is realistic that it is 10 nm or more.

A 2nd fiber layer is a member which comprises the laminated body formed by laminating | stacking with a 1st fiber layer, Comprising: It is a member which can bear the role which reinforces a membrane structure part also from the outside.
The average fiber diameter of the fibers constituting the second fiber layer can be selected as appropriate, and the thinner the average fiber diameter, the easier it is to provide a thin composite membrane. Therefore, the average fiber diameter of the fibers constituting the second fiber layer is 15 μm or less. It is preferably 10 μm or less, preferably 5 μm or less, preferably 3 μm or less, preferably 2 μm or less, preferably 1 μm or less, and 800 nm or less. Is preferred. The lower limit value of the average fiber diameter is appropriately selected, but it is realistic that it is 10 nm or more.

  The “average fiber diameter” as used herein is an arithmetic average of the fiber diameters of 50 fibers measured based on a 5000-fold electron micrograph of a measurement target portion including fibers such as the surface and cross section of the composite membrane. Value. When the cross-sectional shape of the fiber is non-circular, the diameter of a circle having the same area as the cross-sectional area is regarded as the fiber diameter.

The fiber length of the fibers constituting each fiber layer is appropriately selected, but short fibers or long fibers having a specific length, or continuous fiber lengths that are substantially difficult to measure the fiber length. Can be fiber.
The first fiber layer has a continuous length as a constituent fiber because the number of fiber end portions contained in the first fiber layer is small, and it is easy to realize a membrane structure portion with a smooth surface and a uniform thickness. It is preferable that the fiber which has is included, and it is more preferable that the constituent fiber of a 1st fiber layer is only the fiber which has continuous length.
In addition, since the number of fiber end portions contained in the second fiber layer is small, it is easy to provide a composite film having a uniform thickness and a thin thickness. Therefore, the second fiber layer is a fiber having a continuous length as a constituent fiber. It is preferable to include, and it is more preferable that the constituent fibers of the second fiber layer are only fibers having a continuous length.
A fiber having such a continuous length can be prepared by using a direct spinning method (particularly, an electrostatic spinning method).

  The “fiber length” here can be measured based on a 5000 × electron micrograph of the measurement target portion including the fiber such as the surface and cross section of the composite membrane, and the fiber length of the fiber is too long to be measured. In some cases, it can be measured based on an electron micrograph with a magnification lower than 5000 times.

The fibers constituting each fiber layer include, for example, polyolefin resins (polyethylene, polypropylene, polymethylpentene, polyolefin resins having a structure in which a part of hydrocarbon is substituted with a cyano group or a halogen such as fluorine or chlorine), styrene Resin, polyether resin (polyethylene glycol, polypropylene glycol, polyether ether ketone, polyacetal, modified polyphenylene ether, aromatic polyether ketone, etc.), phenol resin, melamine resin, urea resin, epoxy resin, polyester resin Resin (polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, polymilk , Wholly aromatic polyester resins, unsaturated polyester resins, etc.), polyimide resins, polyamideimide resins, polyamide resins (for example, aromatic polyamide resins such as aramid resins, aromatic polyetheramide resins, nylon resins, etc.), urethane Resin, epoxy resin, polysulfone resin (polysulfone, polyethersulfone, sulfonated polyethersulfone, etc.), fluorine resin (polytetrafluoroethylene, polyvinylidene fluoride, perfluorosulfonic acid resin, etc.), polysaccharide (starch) Cellulose resin pullulan, alginic acid, hyaluronic acid, etc.), proteins (gelatin, collagen, etc.), vinyl alcohol resins (polyvinyl alcohol, polyvinyl acetate, etc.), polycaprolactone, polyglycolic acid, Vinylpyrrolidone polybenzimidazole resin, acrylic resin (for example, polyacrylonitrile resin copolymerized with acrylate or methacrylate ester, modacrylic resin copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride, etc.) It may be a fiber provided with a resin, and may be a fiber composed of only one type of resin or a fiber composed of a plurality of types of resins such as a mixed resin.
These resins may be either a linear polymer or a branched polymer, and the resin may be a block copolymer or a random copolymer. The resin may have any three-dimensional structure or crystallinity.

The fibers constituting each fiber layer may be single fibers, fibrillar fibers, or composite fibers. As the composite fiber, for example, a core-sheath type, a sea-island type, a side-by-side type, an orange type, a bimetal type, or the like can be used.
The fibers constituting each fiber layer may have irregular cross-sections in addition to substantially circular fibers and elliptical fibers. As the irregular cross-section fibers, hollow shapes, polygonal shapes such as triangular shapes, alphabetic character shapes such as Y shapes, indeterminate shapes, multi-leaf shapes, symbolic shapes such as asterisk shapes, or a plurality of these shapes Examples thereof include fibers having a fiber cross section such as a bonded shape.

  The types and mixing ratios of the fibers constituting each fiber layer can be selected as appropriate, and may be a fiber layer composed of only one type of fiber or a fiber layer composed of a plurality of types of fibers.

The laminated body as used in the field of this invention points out the structure provided with the 1st fiber layer on one main surface of the 2nd fiber layer.
The lamination mode of the first fiber layer and the second fiber layer can be selected as appropriate, the mode in which the first fiber layer and the second fiber layer are simply overlapped, and the interlayer between the first fiber layer and the second fiber layer is a binder. In an integrated mode, the constituent fibers of the first fiber layer and the second fiber layer are entangled beyond both fiber layers (for example, needle punching, hydroentanglement, first on the main surface of the second fiber layer A mode in which the constituent fibers of the first fiber layer are integrated into the second fiber layer by making up the fibers constituting the one fiber layer, and the constituent fibers are melted by heat melting. An embodiment in which the interlayer between the first fiber layer and the second fiber layer is integrated and an interlayer between the first fiber layer and the second fiber layer is integrated by ultrasonic bonding or the like can be employed. .
In particular, when a fiber is spun using a direct spinning method (particularly, electrostatic spinning method) is collected on one main surface of the second fiber layer to form a first fiber layer to prepare a laminate, Since it is possible to prepare a laminate in which the layers of the first fiber layer and the second fiber layer are integrated without bonding by binder or heat melting of the constituent fibers, physical properties such as air permeability can be obtained by the binder and the molten constituent fibers. It is preferable that the first fiber layer and the second fiber layer can be integrated by preventing unintentional changes.

The membrane-constituting resin referred to in the present invention refers to a resin that can form a membrane structure portion described later together with the constituent fibers of the first fiber layer by being present between the constituent fibers of the first fiber layer in the composite membrane of the present invention.
The type of the membrane-constituting resin can be appropriately selected depending on the characteristics required for the composite membrane and its membrane structure, the structure of the first fiber layer, the affinity with the constituent fibers, and the like. For example, the above-mentioned resins listed as resins capable of constituting each fiber layer can be used as a film-constituting resin by a single resin or a mixed resin. These resins may be either linear polymers or branched polymers, and the resin may be a block copolymer or a random copolymer. Further, the resin may have any three-dimensional structure or crystallinity.

  The membrane structure part as used in the field of this invention means the part which has comprised the membrane | film | coat aspect by film-forming resin existing between the constituent fibers of a 1st fiber layer. In addition, even if the membrane structure portion is an embodiment in which the membrane constituent resin exists only between the constituent fibers of the first fiber layer, the membrane constituent resin is in an embodiment in which the membrane constituent resin exists between the constituent fibers of the first fiber layer. In addition, an embodiment in which a film-constituting resin is present between constituent fibers of the second fiber layer may be employed. Moreover, in addition to the above-mentioned aspect, you may provide the layer which consists only of film structure resin.

Particles or functional materials for improving the membrane performance can be added or filled in the membrane structure portion. The filling method uses a membrane-constituting resin solution after filling the first fiber layer with particles or a functional material, even if the membrane-constituting resin solution containing particles and functional materials is used. You may do it. Although the kind of particle | grain can be selected suitably, For example, a silica particle, a titania particle, a zirconia particle, a yttria stabilized zirconia particle, an alumina particle, a metal organic structure (MOF), and various polymer particles can be utilized. Moreover, the surface of these particles may be modified.
The particle shape can also be selected as appropriate, and can be fibrous, flat, spherical, beaded, rod-shaped, or the like. The particles may be solid particles or hollow particles, and may have a porous particle shape.

It can be judged by the following method whether the film | membrane structure part has comprised the film-like aspect because film | membrane structure resin exists between the structure fibers of a fiber layer.
(Judgment method of whether or not it is in the form of a film (pinhole simple inspection))
(1) The composite membrane is disposed on the mesh substrate with one main surface of the composite membrane as the upper surface.
(2) A 10 mL syringe having a scale for each 1 ml is prepared from a 0 ml scale position to a 10 mL scale position having a circular (diameter: 25 mm) suction portion at the tip. An O-ring is attached to the circumference of the intake part of the syringe.
(3) A force is applied to the syringe piston in a state where the suction part is in close contact with the main surface of the composite membrane with a force of 40 N, and the composite membrane side end of the piston is pulled up from the 0 ml scale position to the 10 mL scale position. .
(4) Release the force acting on the syringe piston.
(5) As a result of performing the above-described steps (1) to (4) on both main surfaces of the composite membrane to be measured, at least one main surface of both main surfaces is allowed to act on the piston of the syringe. When the composite membrane side end portion of the piston returns to the scale range of 0 ml to 1 ml after releasing the force, the composite membrane has a membrane structure portion that forms a membrane shape (in other words, The composite film has a film structure portion that prevents the non-filmed portion from being present).
On the other hand, when the composite membrane side end portion of the piston does not return to the scale range of 0 ml to 1 ml on either of the main surfaces, the composite membrane does not have a membrane structure portion that forms a membrane shape ( In other words, it is determined that the composite film does not have a film structure part that prevents the non-filmed part from existing.

Whether the first fiber layer is less hydrophilic than the second fiber layer can be determined by the following method.
(How to determine hydrophilicity)
(1) Water having a conductivity of 10 μS / cm or less (hereinafter referred to as water) is prepared.
(2) 3 μL of water is dropped on the first fiber layer or the main surface of the fiber assembly constituting the first fiber layer, and the contact angle formed by the liquid droplets after 15 seconds from the installation of the liquid droplets is determined. (DM500, manufactured by Kyowa Interface Science Co., Ltd.) and measured by the θ / 2 method.
(3) The contact angle is measured using the method of item (2) on the main surface of the second fiber layer or the fiber aggregate constituting the second fiber layer, and the measurement results are compared.
In the method described above, the contact angle formed by water with respect to the first fiber layer or the main surface of the fiber assembly constituting the first fiber layer is the main surface of the fiber assembly constituting the second fiber layer or the second fiber layer. On the other hand, when it is larger than the contact angle made by water, the first fiber layer is judged to be less hydrophilic than the second fiber layer.

  Preferably, in the step (2) described above, in the first fiber layer (fiber assembly constituting the first fiber layer) having a contact angle of 80 ° or more after 15 seconds from the installation of the droplet. It is preferable that the first fiber layer is 90 ° or more (fiber assembly constituting the first fiber layer), and the first fiber layer is 100 ° or more (fiber assembly constituting the first fiber layer). Body).

  Further, in the above-described step (3), the second fiber layer (fiber assembly constituting the second fiber layer) having a contact angle of 50 ° or less after 15 seconds from the installation of the droplet is formed. The second fiber layer (fiber assembly constituting the second fiber layer) of 40 ° or less is more preferred, and the second fiber layer (fiber assembly constituting the second fiber layer) of 30 ° or less is more preferred. It is more preferable that

  In addition to the above-described configuration, the composite membrane of the present invention is a composite membrane having a first fiber layer having a higher affinity for the membrane-constituting resin solution than the second fiber layer. For example, it is preferable to provide a composite film provided with an extremely thin film structure portion having a uniform thickness and a film thickness of 10 μm or less.

Whether or not the first fiber layer has higher affinity for the membrane-constituting resin solution than the second fiber layer can be determined by the following method.
(How to determine affinity)
(1) A film-constituting resin solution is prepared by dissolving the film-constituting resin in a solvent capable of dissolving it so as to have a concentration of 1 to 20% by mass.
(2) 3 μL of the membrane-constituting resin solution is dropped on the main surface of the first fiber layer or the fiber assembly constituting the first fiber layer, and the contact angle formed by the liquid droplets after 15 seconds from the installation of the liquid droplets, Using a contact angle device (DM500, manufactured by Kyowa Interface Science Co., Ltd.), measurement is performed by the θ / 2 method.
(3) The contact angle is measured using the method of item (2) on the main surface of the second fiber layer or the fiber aggregate constituting the second fiber layer, and the measurement results are compared.
In the method described above, the contact angle formed by the membrane-constituting resin solution with respect to the first fiber layer or the main surface of the fiber aggregate constituting the first fiber layer is the fiber aggregate constituting the second fiber layer or the second fiber layer. When the contact angle made by the membrane constituent resin solution with respect to the main surface is smaller than that of the second fiber layer, the first fiber layer is judged to have higher affinity with the membrane constituent resin solution.

Preferably, in the above-described step (2), the first fiber layer (fiber aggregate constituting the first fiber layer) having a contact angle of 50 ° or less formed by the liquid droplets after 15 seconds have elapsed after the liquid droplets are placed. It is preferable that the first fiber layer is 40 ° or less (fiber assembly constituting the first fiber layer), and the first fiber layer is 30 ° or less (fiber assembly constituting the first fiber layer). Body).
In particular, the more easily the membrane-constituting resin solution penetrates into the first fiber layer (fiber aggregate constituting the first fiber layer), the more the portion that is not formed into a film is prevented, for example, the film thickness is 10 μm. It is easy to provide a composite membrane provided with the following extremely thin membrane structure. Therefore, in the above-described step (2), the contact angle formed by the liquid droplets after 15 seconds has elapsed after the liquid droplets are set is 0 °. Most preferably, it is the first fiber layer (fiber assembly constituting the first fiber layer) that penetrates and no droplets of the membrane-constituting resin solution exist on the main surface.
Further, the more difficult the membrane-constituting resin solution penetrates into the second fiber layer (fiber aggregate constituting the second fiber layer), the more the portion not formed into a film is prevented, for example, the film thickness is 10 μm. It is easy to provide a composite membrane provided with the following extremely thin membrane structure. Therefore, in the above-mentioned step (3), the contact angle formed by the liquid droplets after 15 seconds from the installation of the liquid droplets is a second fiber layer (fiber aggregate constituting the second fiber layer) having a contact angle of 80 ° or more. More preferably, the second fiber layer is 90 ° or more (fiber assembly constituting the second fiber layer), and the second fiber layer is 100 ° or more (fiber assembly constituting the second fiber layer). Most preferably.

The thickness of the composite film is appropriately selected, but can be 30 μm or less, 20 μm or less, and 15 μm or less. On the other hand, the lower limit of the thickness is adjusted as appropriate, but it is practical that the thickness is 1 μm or more.
The thickness of the membrane structure portion in the composite membrane is appropriately selected, but can be 10 μm or less, 8 μm or less, and 6 μm or less. On the other hand, the lower limit value of the thickness is appropriately adjusted, but it is realistic that the thickness is 0.1 μm or more.
The thickness of the second fiber layer in the composite membrane is appropriately selected, but can be 30 μm or less, 20 μm or less, and 10 μm or less. On the other hand, the lower limit of the thickness is adjusted as appropriate, but it is practical that the thickness is 1 μm or more.

The thickness of the film structure portion in the composite film can be measured using an electron micrograph of a cross section obtained by cutting the composite film in the thickness direction. Specifically, the length of the film structure portion in the thickness direction of the composite film is measured, and this is defined as the thickness of the film structure portion in the composite film.
Further, from the main surface on the opposite side in the composite membrane, the length in the thickness direction of the portion consisting only of the fibers constituting the main surface on the opposite side is measured, and this is the thickness of the second fiber layer in the composite membrane. Say it.
The thickness direction refers to the direction that forms the shortest distance between the opposite main surface against one main surface (the widest surface), and the thickness refers to the length in the thickness direction between the two main surfaces. Say.

  The above-mentioned composite membrane may be used as it is, but may be a composite membrane provided with a member such as a reinforcing layer separately. Further, the composite film may be processed so as to be punched in shape or to have a pleated shape or a wound shape in accordance with the application or usage.

  Next, the manufacturing method of the composite film which concerns on this invention is demonstrated. In addition, description is abbreviate | omitted about the point which is the same as the item demonstrated about the above-mentioned composite film.

The method for producing the composite membrane according to the present invention can be appropriately selected.
(1) preparing a fiber assembly;
(2) By forming another fiber assembly on one main surface of the fiber assembly, the first fiber layer derived from the other fiber assembly and the second fiber layer derived from the fiber assembly are provided. Preparing a laminate,
(3) A step of applying a hydrophilic resin solution to the main surface where the second fiber layer in the laminate is exposed,
(4) The step of causing the hydrophilic resin to exist between constituent fibers of the second fiber layer by removing the solvent from the imparted hydrophilic resin solution,
(5) A step of applying a film-constituting resin solution to the main surface where the first fiber layer in the laminate is exposed,
(6) A step of forming a membrane structure part in which the membrane constituent resin is present between constituent fibers of the first fiber layer by removing a solvent from the applied membrane constituent resin solution;
(7) A step of removing the hydrophilic resin present between constituent fibers of the second fiber layer using a solvent capable of dissolving the hydrophilic resin,
A method for producing a composite membrane having a membrane structure part in which the membrane-constituting resin is present between constituent fibers of the first fiber layer in the laminate,
The average fiber diameter of the fibers constituting the first fiber layer is 3 μm or less,
The said 1st fiber layer can mention the manufacturing method of a composite film whose hydrophilicity is lower than said 2nd fiber layer.

First, (1) the step of preparing a fiber assembly will be described.
The fiber assembly is a member that can constitute the second fiber layer in the laminate, and for example, a sheet-like fabric such as a fiber web, a nonwoven fabric, a woven fabric, or a knitted fabric can be used.
The fiber assembly can be formed using dry entanglement, wet papermaking, or direct spinning, but because the fabric has a smooth surface, it is easy to provide a composite film having a uniform and thin thickness. A fabric formed by wet papermaking or direct spinning is preferable. In particular, a fabric using an electrostatic spinning method as a direct spinning method can be used to prepare a fiber web or a nonwoven fabric made of fibers having a uniform average fiber diameter and a uniform fiber diameter. It is preferable because a film can be easily provided.

  The average fiber diameter of the fibers constituting the fiber assembly can be appropriately selected, but is preferably 15 μm or less, preferably 10 μm or less, preferably 5 μm or less, and preferably 3 μm or less, 2 μm. Is preferably 1 μm or less, and more preferably 800 nm or less. The lower limit value of the average fiber diameter is appropriately selected, but it is realistic that it is 10 nm or more.

Although the basis weight of the fiber aggregate may be appropriately selected and a basis weight is preferably from 0.5 to 20 g / ^{m 2,} it is preferably from 0.8~18g / ^{m 2,} in the range of 1~16g / ^{m 2} Is preferred. In the present invention, the basis weight refers to the mass per 1 m ² area of the main surface.

  Although the thickness of the fiber aggregate can be selected as appropriate, the thickness is preferably 30 μm or less, more preferably 20 μm or less, and preferably 10 μm or less. On the other hand, it is realistic that the thickness is 1 μm or more.

  The porosity of the fiber assembly is appropriately selected, but the porosity is preferably 30% or more, and preferably 35% or more so that the air permeability and liquid permeability in the composite membrane do not deteriorate too much. 40% or more is preferable. On the other hand, it is realistic that the porosity is 98% or less.

  The Gurley permeability of the fiber assembly can be selected as appropriate, but the Gurley permeability is preferably 300 s / 100 mL or less, and 200 s / 100 mL so that the air permeability and liquid permeability in the composite membrane do not deteriorate too much. Or less, preferably 100 s / 100 mL or less.

  The Gurley air permeability referred to in the present invention is a method defined in JIS P 8117: 2009 (paper and paperboard-air permeability test method-Gurley test machine method) for measuring objects such as fiber aggregates, for example. It refers to the air resistance measured by the measurement. In addition, it means that it is excellent in air permeability, so that the Gurley value is low, and the value becomes a value larger than zero.

Next, (2) by forming another fiber assembly on one main surface of the fiber assembly, the first fiber layer derived from the other fiber assembly and the second fiber layer derived from the fiber assembly. The step of preparing a laminate comprising: will be described.
Another fiber assembly is a member that can constitute the first fiber layer in the laminate, and for example, a sheet-like fabric such as a fiber web, a nonwoven fabric, a woven fabric, and a knitted fabric can be used.

A method of forming another fiber assembly on one main surface of the fiber assembly can be appropriately selected,
A method of laminating another fiber assembly separately prepared on at least one main surface of the fiber assembly,
A method of forming a fiber deposition layer (another fiber assembly) on one main surface of the fiber assembly by forming fibers that can form another fiber assembly or by directly spinning the fibers. ,
A laminate can be prepared by a method such as
Among these, when a laminate is prepared by collecting fibers spun using a direct spinning method (particularly, electrostatic spinning method) on one main surface of a fiber assembly, adhesion by a binder or heat of constituent fibers Since it is possible to prepare a laminate in which the layers of a fiber assembly and another fiber assembly are integrated without adhesion by melting, the physical properties such as air permeability change unintentionally depending on the binder and the melted constituent fibers. Therefore, it is preferable that the layers of the fiber assembly and another fiber assembly can be integrated. Further, it is preferable to provide a composite film having a uniform and thin film structure portion.

  The average fiber diameter of fibers constituting another fiber assembly can be selected as appropriate, but the average fiber diameter is 3 μm or less, preferably 2 μm or less, preferably 1 μm or less, and 800 nm or less. preferable. The lower limit value of the average fiber diameter is appropriately selected, but it is realistic that it is 10 nm or more.

The basis weight of another fiber aggregate can be selected as appropriate, but the basis weight is preferably 4 g / m ² or less, more preferably 3 g / m ² or less, and preferably 2 g / m ² or less. On the other hand, the basis weight is practically 0.1 g / m ² or more.

  The thickness of another fiber assembly can be selected as appropriate, but the thickness is preferably 10 μm or less, preferably 8 μm or less, and preferably 6 μm or less. On the other hand, it is realistic that the thickness is 0.4 μm or more.

  The porosity of another fiber assembly is appropriately selected. The porosity is preferably 50% or more, more preferably 60% or more, and preferably 70% or more. On the other hand, it is realistic that the porosity is 98% or less.

In this step, when preparing a laminate comprising a first fiber layer having a higher affinity for the membrane-constituting resin solution than the second fiber layer, it further prevents the presence of a non-filmed portion, A composite film having a very thin film structure portion having a uniform thickness and a film thickness of 10 μm or less is preferable.
Although this reason is not completely clear, it is considered that the following effects are exhibited in the steps (5) and (6) described later.
That is, in the step (5) of applying the film-constituting resin solution to the main surface where the first fiber layer described later is exposed to the laminate including the first fiber layer and the second fiber layer, the second fiber layer In other words, the membrane-constituting resin solution is applied to the first fiber layer having high affinity, and the membrane-constituting resin solution tends to stay on the first fiber layer.
Therefore, in the state in which the membrane-constituting resin solution is sufficiently and abundant between the constituent fibers of the first fiber layer, the step (6) of removing the solvent, which is the next step, from the laminate provided with the membrane-constituting resin solution Can be used.

And (3) a step of applying a hydrophilic resin solution to the main surface of the laminate in which the second fiber layer is exposed, and (4) removing the solvent from the applied hydrophilic resin solution. The step of causing the hydrophilic resin to exist between the constituent fibers of the second fiber layer will be described.
The hydrophilic resin solution is a solution obtained by dissolving a hydrophilic resin in a solvent that can be dissolved. The kind of solvent can be suitably selected according to the kind of hydrophilic resin. In addition, it is preferable that this solvent is a solvent which is hard to melt | dissolve the component contained in a 1st fiber layer or a 2nd fiber layer, and it is more preferable that it is a solvent which does not melt | dissolve this component. Employing such a solvent is preferable because it can prevent unintentional occurrence of shape deformation or functional deterioration of the constituent members and provide a composite membrane. In the present invention, dissolution means that the measurement object is saturated more than 0.5 g and dissolved in 100 g of a solvent at 25 ° C.

The kind and concentration of the hydrophilic resin contained in the hydrophilic resin solution are appropriately selected so that a composite film having a desired film structure portion can be provided.
Specific examples of hydrophilic resins include water-soluble polysaccharides (eg, pullulan, amylose, starch, modified starch, hyaluronic acid, xanthan gum), water-soluble polymer proteins (eg, collagen, gelatin, etc.), polyvinyl alcohol, polyvinyl Employs water-soluble polymers such as pyrrolidone, polyacrylic acid, polyvinylpyrrolidone, poly-N-isopropylacrylamide, water-soluble polyamide, water-soluble polyamideimide, polyethylene glycol, polypropylene glycol, polyvinyl methyl ether, and polyacrylic acid. can do. In the step (7) using a solvent capable of dissolving the hydrophilic resin, which will be described later, the hydrophilic resin has a film structure so that the film-forming resin is prevented from being removed along with the removal of the hydrophilic resin by the solvent. A resin different from the resin is preferable.
The temperature of the hydrophilic resin solution can be selected as appropriate so that the shape deformation and functional deterioration of the constituent members are not easily caused. Specifically, a hydrophilic resin solution at 25 ° C. can be employed.

  The method for applying the hydrophilic resin solution can be selected as appropriate, but spray, spin coating, gravure coating, bar coating, die coating, blade coating, air knife coating, roll coating, lip coating, float coating, comma roll coating, kiss coating, screen printing It is possible to employ a method of spraying or applying a hydrophilic resin solution using inkjet printing, a method of immersing the main surface side where the second fiber layer in the laminate is exposed in the hydrophilic resin solution, or the like. it can.

The amount of the hydrophilic resin solution applied to the second fiber layer is also appropriately selected so that a composite membrane having a desired membrane structure portion can be provided. In addition, when the hydrophilic resin solution is applied to the second fiber layer so that the amount of the hydrophilic resin solution is present between the constituent fibers of the second fiber layer, the hydrophilic resin exists in the entire second fiber layer. This prevents the membrane constituent resin solution from moving from the first fiber layer to the second fiber layer, and can easily exert the effect of retaining the applied membrane constituent resin solution between the constituent fibers of the first fiber layer. preferable.
Thus, a hydrophilic resin solution is made to exist between the constituent fibers of the second fiber layer by absorbing the hydrophilic resin solution from the main surface side of the second fiber layer in the laminate.

  The method for removing the solvent contained in the hydrophilic resin solution can be selected as appropriate. For example, it is supplied to a heating machine such as an oven dryer, far-infrared heater, or dry heat dryer, and heated in a room temperature atmosphere or a reduced pressure atmosphere. It can be removed by evaporating the solvent from the laminate to which the hydrophilic resin solution has been applied, for example by standing still. The heating temperature at the time of removing the solvent is a temperature at which the solvent can be volatilized, and the shape and function of the constituent members (first fiber layer, second fiber layer, hydrophilic resin, etc.) may be unintentionally lowered. Select the upper limit of the heating temperature.

Furthermore, (5) a step of applying a film constituent resin solution to the main surface of the laminate in which the first fiber layer is exposed, and (6) removing the solvent from the applied film constituent resin solution. The step of forming a membrane structure portion in which the membrane-constituting resin is present between constituent fibers of the first fiber layer will be described.
The membrane constituent resin solution is a solution obtained by dissolving the membrane constituent resin in a solvent capable of dissolving. The kind of solvent can be suitably selected according to the kind of film constituent resin. In addition, it is preferable that this solvent is a solvent which is hard to melt | dissolve the component contained in a 1st fiber layer, a 2nd fiber layer, and hydrophilic resin, and it is more preferable that it is a solvent which does not melt | dissolve this component. Employing such a solvent is preferable because it can prevent unintentional occurrence of shape deformation or functional deterioration of the constituent members and provide a composite membrane.

The temperature of the membrane-constituting resin solution can be selected as appropriate so that shape deformation and functional deterioration of the constituent members do not occur unintentionally. Specifically, a film constituent resin solution at 25 ° C. can be employed.
The method of applying the film-constituting resin solution can be selected as appropriate, but spraying, spin coating, gravure coating, bar coating, die coating, blade coating, air knife coating, roll coating, lip coating, float coating, comma roll coating, kiss coating, screen printing It is possible to adopt a method of spraying or applying a film-forming resin solution using inkjet printing, a method of immersing the main surface side where the first fiber layer in the laminate is exposed in the film-forming resin solution, or the like. it can.
In this way, the membrane constituent resin solution is present between the constituent fibers of the first fiber layer by absorbing the membrane constituent resin solution from the main surface side of the first fiber layer in the laminate.

  The kind and concentration of the membrane constituent resin contained in the membrane constituent resin solution are appropriately selected so that a composite membrane having a desired membrane structure portion can be provided. The amount of the membrane-constituting resin solution applied to the first fiber layer is also appropriately selected so that a composite membrane having a desired membrane structure portion can be provided.

  The method for removing the solvent contained in the membrane-constituting resin solution can be selected as appropriate.For example, it is supplied to a heating machine such as an oven dryer, a far-infrared heater, a dry heat dryer, etc. It can be removed by evaporating the solvent from the laminate to which the membrane-constituting resin solution has been applied, for example by standing still. The heating temperature when removing the solvent is a temperature at which the solvent can be volatilized, and the shape and function of the constituent members (first fiber layer, second fiber layer, hydrophilic resin, membrane constituent resin, etc.) are not intended. The upper limit of the heating temperature is selected so as not to decrease.

Finally, (7) the step of removing the hydrophilic resin present between the constituent fibers of the second fiber layer using a solvent capable of dissolving the hydrophilic resin will be described.
The solvent used in this step is not particularly limited as long as it can dissolve the hydrophilic resin, and can be appropriately selected. However, it is preferable to employ the solvent constituting the hydrophilic resin solution used in step (3). As a specific example of the solvent, water having an electric conductivity of 10 μS / cm or less used in the above-described (Hydrophilicity determination method) item can be employed.
The solvent is preferably a solvent that hardly dissolves the components contained in the constituent members of the composite membrane (the first fiber layer, the second fiber layer, the membrane constituent resin, etc.), and is a solvent that does not dissolve the components. More preferably. When such a solvent is used and the hydrophilic resin is removed, it is preferable that the composite member can be provided by preventing the deformation of the constituent members and the deterioration of the function of the component members without intention. As a preferred embodiment, when the solvent is water, it is preferable that the constituent members of the composite membrane are composed only of water-insoluble components.

  The temperature of the solvent used for the removal of the hydrophilic resin can be appropriately selected so that shape deformation and functional deterioration of the constituent members are not generated unintentionally. For example, the solvent having the same temperature as that of the hydrophilic resin solution used in the step (3), or the solvent having a lower or higher temperature than that can be employed. In particular, it is preferable to employ the solvent having a temperature higher than that of the hydrophilic resin solution used in the step (3) because the hydrophilic resin existing between the constituent fibers of the second fiber layer can be efficiently removed. Specifically, the solvent having a temperature higher than 25 ° C. can be employed.

  A method for removing the hydrophilic resin using the solvent can be selected as appropriate, a method of immersing a laminate containing the hydrophilic resin in the solvent, and a solvent flowing through the laminate containing the hydrophilic resin such as running water. , A method of removing the solvent in which the hydrophilic resin is dissolved by a suction device after applying the solvent to the laminate containing the hydrophilic resin, and a laminate containing the hydrophilic resin in the vapor of the solvent A method of removing the hydrophilic resin by bringing the resin into contact with each other can be employed.

The first fiber layer and / or the fabric that can form the first fiber layer may be subjected to a non-hydrophilic processing step such as a water repellent / oil repellent / hydrophobic treatment step. Examples of the water repellency / oil repellency / hydrophobization treatment step include coating of water / oil repellency resins such as polytetrafluoroethylene and silicone, and the use of oil / water repellency agents.
Moreover, you may use the fabric which can comprise a 2nd fiber layer and / or a 2nd fiber layer for hydrophilic treatment processes, such as a hydrophilic treatment process. Examples of the hydrophilic treatment step include sulfonation treatment, fluorine gas treatment, vinyl monomer graft polymerization treatment, surfactant treatment, discharge treatment, and hydrophilic resin application treatment.

  Also, in each step of the method for producing a composite membrane of the present invention, if handling alone is difficult when handling a fiber assembly, laminate or composite membrane, if necessary, a porous material such as a separately prepared mesh or You may use for each process in the state which put the fiber aggregate, the laminated body, or the composite film on the support base materials, such as a film, or was pinched | interposed with support base materials, such as porous bodies, such as a mesh prepared separately.

By using the above manufacturing method, the composite film according to the present invention can be manufactured.
The manufacturing method of the present invention prevents the existence of a non-filmed portion, and for example, it is completely possible to manufacture a composite film having a very thin film structure portion having a uniform thickness and a film thickness of 10 μm or less. Although it is not clear, it is thought that the following effects are being demonstrated.

That is, in the laminate after the above steps (3) and (4), the hydrophilic resin is present between the constituent fibers of the second fiber layer, so that the membrane-constituting resin solution is the constituent of the second fiber layer. It has a mode in which it cannot easily enter between fibers.
Therefore, in the step (5) of applying the film-constituting resin solution to the main surface where the first fiber layer is exposed in the laminate after the steps (3) and (4) described above, the film-constituting resin solution is the first one. The movement from the one fiber layer to the second fiber layer is prevented, and the applied membrane-constituting resin solution is easily retained between the constituent fibers of the first fiber layer.

In particular, this effect is not limited to the case where a membrane-constituting resin solution having a higher affinity for the first fiber layer than the second fiber layer is employed. For example, this effect is equivalent to both the first fiber layer and the second fiber layer. Even when a membrane-constituting resin solution having affinity or a membrane-constituting resin solution having higher affinity for the second fiber layer than the first fiber layer is employed (in other words, from the first fiber layer to the second fiber (Even when a membrane-constituting resin solution that is easy to move to the layer is employed), the membrane-constituting resin solution is prevented from moving to the second fiber layer. The effect of easily staying between the constituent fibers of the fiber layer is exhibited.
Therefore, in the state in which the membrane constituent resin solution is sufficiently and abundant between the constituent fibers of the first fiber layer, the film structure portion is obtained by removing the solvent, which is the next step, from the laminate provided with the membrane constituent resin solution. It can be used for the step (6) of forming. Then, the composite film concerning this invention can be provided by passing through the process (7) which removes the hydrophilic resin which exists between the constituent fibers of a 2nd fiber layer using the solvent which can melt | dissolve hydrophilic resin.

  As a result, the film-constituting resin is sufficiently present between the constituent fibers of the first fiber layer to prevent the presence of a non-filmed portion. For example, the thickness is uniform and the film thickness is 10 μm. A composite membrane provided with the following extremely thin membrane structure can be provided.

Further, the inventors of the present invention have a hydrophilic resin between the constituent fibers of the second fiber layer, which is formed through the steps (3) and (4) described above, in the method for manufacturing a composite membrane described above. It has been found that by adjusting the thickness of the layer, the film thickness of the film structure portion provided in the composite film can be controlled to provide a composite film having a film structure portion having a desired thickness and a uniform thickness. .
For example,
-By using a laminate comprising a first fiber layer having a thickness of 10 µm or less and producing a composite membrane using a laminate in which a hydrophilic resin is present between the constituent fibers of the second fiber layer, Or
-The hydrophilic resin is present between the constituent fibers of the second fiber layer, and the hydrophilic resin is also present on the second fiber layer side of the first fiber layer. By manufacturing a composite film using a laminate including a first fiber layer having a thickness of 10 μm or less,
A composite film provided with an extremely thin film structure portion having a uniform thickness and a film thickness of 10 μm or less can be provided.

  Further, by employing a laminate in which the hydrophilic resin is present between the constituent fibers of the second fiber layer and the layer is thin, a composite membrane having a thicker membrane structure can be provided. . Thus, by adjusting the thickness of the layer in which the hydrophilic resin is present between the constituent fibers of the second fiber layer, the film thickness of the film structure portion provided in the composite film is controlled, and the desired film thickness And a composite film having a film structure portion having a uniform thickness

  Whether the thickness of the film structure portion of the composite film referred to in the present invention is uniform or not is determined by taking a 5000 times electron micrograph of a cross section of the composite film and randomly selecting 10 films of the composite film. It can be evaluated by measuring the thickness of the structural part. That is, the minimum value and the maximum value of each thickness obtained by the measurement are both average values calculated from the thickness of the film structure portion obtained by measurement at the 10 points (the film structure portion When the average thickness is within ± 20%, the composite film provides a film structure portion having a uniform thickness.

  In the above-described method for manufacturing a composite membrane, the shape of the composite membrane can be punched out according to the process, application, and usage, and a pleated shape and a wound shape can be obtained. The manufacturing method of the composite film provided with various secondary processes, such as a process to process, may be sufficient.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but these do not limit the scope of the present invention.

(Method for preparing spinning solution)
A polyvinyl alcohol resin (completely saponified, degree of polymerization: 900 to 1000, manufactured by Wako Pure Chemical Industries, Ltd.) is completely dissolved in water having an electric conductivity of 10 μS / cm or less, whereby an aqueous solution a having a polyvinyl alcohol resin concentration of 15% by mass is obtained. Prepared. Further, by completely dissolving methyl vinyl ether-maleic anhydride copolymer resin (manufactured by ALDRICH) in water having a conductivity of 10 μS / cm or less, an aqueous solution b having a methyl vinyl ether-maleic anhydride copolymer resin concentration of 15% by mass is obtained. Was prepared.
A first spinning solution was prepared by mixing 80 parts by mass of the aqueous solution a and 20 parts by mass of the aqueous solution b.
Further, dodecylamine hydrochloride as a hydrophobizing agent was mixed so that the concentration was 1% by mass with respect to the first spinning solution to prepare a second spinning solution.

(Electrostatic spinning conditions)
-Shape of spinning solution discharge part in metal nozzle (spinning solution discharge part): Circular shape with inner diameter of 0.44 mm-Distance between tip of metal nozzle and drum (fiber collector): 8 cm
・ Voltage applied to spinning solution: 15 to 25 kV
-Spinning liquid discharged from metal nozzle: 1 cc / hour-Atmosphere of electrostatic spinning environment: temperature 25 ° C, humidity 50% RH

Example 1
Electrospinning is performed using the first spinning solution under the above-described electrospinning conditions, and the spun fibers are collected on the main surface of the drum, resulting in a thickness of 10 μm on the main surface of the drum. A fiber aggregate of 2.3 g / m ² was formed.
Next, by performing electrostatic spinning using the second spinning solution under the above-described electrostatic spinning conditions, and collecting the spun fibers on the exposed main surface of the fiber assembly on the drum, Another fiber assembly having a thickness of 1 μm and a basis weight of 0.2 g / m ² was formed on the main surface of the fiber assembly.
As a result of peeling off the laminate including the fiber assembly formed in this way from the drum and providing it to the above-described “hydrophilicity determination method”, it is The contact angle of the fiber assembly was 105 °, the contact angle of the fiber assembly was 0 °, and it was found that the other fiber assembly was less hydrophilic than the fiber assembly.
In addition, the structure of a laminated body is 1 micrometer in thickness of the 1st fiber layer derived from another fiber assembly, 10 micrometers in thickness of the 2nd fiber layer derived from a fiber assembly, and the average of the fiber which comprises a 1st fiber layer The fiber diameter was 0.3 μm, and the average fiber diameter of the fibers constituting the second fiber layer was 0.3 μm.
As a hydrophilic resin solution, an aqueous pullulan solution having a pullulan concentration of 20% by mass was prepared by completely dissolving pullulan (manufactured by Hayashibara Kogyo Co., Ltd.) in water having a conductivity of 10 μS / cm or less.
Using a slit coating device (clearance: 60 μm), an aqueous pullulan solution adjusted to 25 ° C. was applied on one main surface of a glass plate having a smooth surface. And the pullulan aqueous solution was provided to the main surface where the 2nd fiber layer in a laminated body has exposed the main surface which the 2nd fiber layer in a laminated body is made to contact with this pullulan aqueous solution.
The glass plate and the laminated body are left in a laminated state in an atmosphere at 80 ° C. for 30 minutes to remove water that is a solvent of the pullulan aqueous solution, and hydrophilicity between the constituent fibers of the second fiber layer in the laminated body. Pullulan was present as the resin.
Next, with the state in which the glass plate and the laminate are laminated, a slit coating device (clearance: 30 μm) is used on the main surface where the first fiber layer in the laminate is exposed, and the film-constituting resin solution is kept at 25 ° C. The sulfonated polyethersulfone dimethylacetamide solution thus prepared (sulfonated polyethersulfone concentration: 20% by mass) was applied by coating.
And, with the glass plate and the laminate laminated, the laminate coated with the film-forming resin solution is allowed to stand for 30 minutes in a 120 ° C. atmosphere, and then left in a 140 ° C. atmosphere for 30 minutes. Dimethylacetamide, which is a solvent for the membrane constituent resin solution, was removed.
Finally, the laminate after removing the above-mentioned dimethylacetamide is peeled off from the glass plate, and the resulting laminate is immersed in water adjusted to 60 ° C. and having an electric conductivity of 10 μS / cm or less, whereby the second fiber Pullulan present between the constituent fibers of the layer was eluted and removed into water.
After taking out the laminate from the water, the composite film (thickness: 10 μm, between the constituent fibers of the first fiber layer derived from another fiber assembly is removed by leaving it in an 80 ° C. atmosphere for 30 minutes. In the presence of a sulfonated polyethersulfone).

FIG. 1 shows an electron micrograph of the composite film prepared in Example 1, taken at 1000 times the main surface on the side to which the membrane-constituting resin solution was applied.
When the electron micrograph shown in FIG. 1 was confirmed, the main surface on the side of the composite membrane to which the membrane-constituting resin solution was applied had a portion where a fiber shape was present and a portion where an unintended opening was present. The presence of was not recognized.
As a result of subjecting the prepared composite membrane to the above-mentioned “determination method for determining whether or not the membrane-like aspect is formed”, the composite membrane according to Example 1 has a membrane structure portion that forms the membrane-like aspect. It was a thing.
In the composite film of Example 1, the average thickness of the film structure portion was 1.8 μm (maximum thickness of the film structure portion: 2.1 μm, minimum thickness of the film structure portion: 1.6 μm).

(Example 2)
Electrospinning is performed using the first spinning solution under the above-described electrospinning conditions, and the spun fibers are collected on the main surface of the drum, resulting in a thickness of 10 μm on the main surface of the drum. A fiber aggregate of 2.3 g / m ² was formed.
Next, by performing electrostatic spinning using the second spinning solution under the above-described electrostatic spinning conditions, and collecting the spun fibers on the exposed main surface of the fiber assembly on the drum, Another fiber assembly having a thickness of 2 μm and a basis weight of 0.5 g / m ² was formed on the main surface of the fiber assembly.
As a result of peeling off the laminate including the fiber assembly formed in this way from the drum and providing it to the above-described “hydrophilicity determination method”, it is The contact angle of the fiber assembly was 112 °, the contact angle of the fiber assembly was 0 °, and it was found that the other fiber assembly was less hydrophilic than the fiber assembly.
In addition, as for the structure of the laminated body, the thickness of the 1st fiber layer derived from another fiber assembly is 2 micrometers, the thickness of the 2nd fiber layer derived from a fiber assembly is 10 micrometers, and the average of the fiber which comprises a 1st fiber layer The fiber diameter was 0.3 μm, and the average fiber diameter of the fibers constituting the second fiber layer was 0.3 μm.
A composite membrane (thickness: 10 μm, between the constituent fibers of the first fiber layer derived from another fiber assembly was used in the same manner as in Example 1 except that the laminate thus prepared was used. Ether sulfone is present).

FIG. 2 shows an electron micrograph of the composite film prepared in Example 2, taken at 1000 times the main surface on the side to which the membrane-constituting resin solution was applied.
When the electron micrograph shown in FIG. 2 was confirmed, the main surface on the side of the composite membrane to which the membrane-constituting resin solution was applied had a portion where a fiber shape was present and a portion where an unintended opening was present. The presence of was not recognized.
As a result of subjecting the prepared composite film to the above-described “determination method for determining whether or not the film-like aspect is formed”, the composite film according to Example 2 has a film structure portion that forms the film-like aspect. It was a thing.
In the composite film of Example 2, the average thickness of the film structure portion was 3.2 μm (maximum thickness of the film structure portion: 3.6 μm, minimum thickness of the film structure portion: 2.7 μm).

(Example 3)
Electrospinning is performed using the first spinning solution under the above-described electrospinning conditions, and the spun fibers are collected on the main surface of the drum, resulting in a thickness of 10 μm on the main surface of the drum. A fiber aggregate of 2.3 g / m ² was formed.
Next, by performing electrostatic spinning using the second spinning solution under the above-described electrostatic spinning conditions, and collecting the spun fibers on the exposed main surface of the fiber assembly on the drum, Another fiber assembly having a thickness of 4 μm and a basis weight of 1.1 g / m ² was formed on the main surface of the fiber assembly.
As a result of peeling off the laminate including the fiber assembly formed in this way from the drum and providing it to the above-described “hydrophilicity determination method”, it is The contact angle of the fiber assembly was 118 °, the contact angle of the fiber assembly was 0 °, and it was found that the other fiber assembly was less hydrophilic than the fiber assembly.
The laminated body has a structure in which the thickness of the first fiber layer derived from another fiber assembly is 4 μm, the thickness of the second fiber layer derived from the fiber assembly is 10 μm, and the average of the fibers constituting the first fiber layer The fiber diameter was 0.2 μm, and the average fiber diameter of the fibers constituting the second fiber layer was 0.2 μm.
A composite membrane (thickness: 12 μm, sulfonated poly (polystyrene) between constituent fibers of the first fiber layer derived from another fiber assembly) was used in the same manner as in Example 1 except that the laminate thus prepared was used. Ether sulfone is present).

FIG. 3 shows an electron micrograph of the composite film prepared in Example 3, taken at 1000 times the principal surface on the side to which the membrane-constituting resin solution was applied.
When the electron micrograph shown in FIG. 3 was confirmed, the main surface on the side to which the membrane-constituting resin solution was applied in the composite membrane had a portion where a fiber shape was present and a portion where an unintended opening was present. The presence of was not recognized.
As a result of subjecting the prepared composite membrane to the above-described “method for determining whether or not the membrane-like aspect is formed”, the composite membrane according to Example 3 has a membrane structure portion that forms the membrane-like aspect. It was a thing.
In the composite film of Example 3, the average thickness of the film structure portion was 4.8 μm (maximum thickness of the film structure portion: 5.2 μm, minimum thickness of the film structure portion: 4.2 μm).

(Comparative Example 1)
Electrospinning is performed using the second spinning solution under the above-described electrospinning conditions, and the spun fibers are collected on the main surface of the drum, resulting in a thickness of 10 μm on the main surface of the drum. A 2.3 g / m ² fiber assembly was prepared. In addition, the average fiber diameter of the fiber which comprises the fiber layer derived from a fiber assembly was 0.3 micrometer.
As a hydrophilic resin solution, an aqueous pullulan solution having a pullulan concentration of 20% by mass was prepared by completely dissolving pullulan (manufactured by Hayashibara Kogyo Co., Ltd.) in water having a conductivity of 10 μS / cm or less.
Using a slit coating device (clearance: 60 μm), an aqueous pullulan solution adjusted to 25 ° C. was applied on one main surface of a glass plate having a smooth surface. And the pullulan aqueous solution was provided to this one exposed main surface in a fiber assembly by making one exposed main surface in a fiber assembly contact with this pullulan aqueous solution.
While the glass plate and the fiber assembly are laminated, the water is removed from the pullulan aqueous solution by leaving it at 80 ° C. for 30 minutes, and the one exposed main surface of the fiber assembly is removed. Pullulan was present as a hydrophilic resin between the constituent fibers on the side.
Next, in a state where the glass plate and the fiber assembly are laminated, the other exposed main surface of the fiber assembly is subjected to 25 ° C. as a film-forming resin solution using a slit coating device (clearance: 30 μm). The sulfonated polyethersulfone dimethylacetamide solution thus prepared (sulfonated polyethersulfone concentration: 20% by mass) was applied by coating.
And the fiber assembly which apply | coated the membrane constituent resin solution is left still for 30 minutes in 120 degreeC atmosphere with the aspect which laminated | stacked the glass plate and the fiber assembly, and is left still for 30 minutes under 140 degreeC atmosphere after that. Then, dimethylacetamide, which is the solvent of the membrane constituent resin solution, was removed.
Finally, the fiber assembly after removing the above dimethylacetamide is peeled from the glass plate, and the resulting fiber assembly is immersed in water adjusted to 60 ° C. and having a conductivity of 10 μS / cm or less. Pullulan existing between the constituent fibers on the one exposed main surface side of the aggregate was eluted into water and removed.
After taking out the laminate from the water, the composite film (thickness: 9 μm, on the other exposed main surface side of the fiber assembly is removed by leaving it in an atmosphere of 80 ° C. for 30 minutes to remove water. A sulfonated polyethersulfone is present between the constituent fibers).

FIG. 4 shows an electron micrograph of the composite film prepared in Comparative Example 1 taken at 1000 times the principal surface on the side to which the membrane-constituting resin solution was applied.
When the electron micrograph shown in FIG. 4 was confirmed, the main surface of the composite membrane on which the membrane-constituting resin solution was applied had a portion where a fiber shape was present and a portion where an unintended opening was present. The existence of
As a result of subjecting the prepared composite film to the above-described “determination method for determining whether or not the film-like aspect is formed”, the composite film according to Comparative Example 1 does not have a film structure portion that forms the film-like aspect. It was a thing.

(Comparative Example 2)
Electrospinning is performed using the second spinning solution under the above-described electrospinning conditions, and the spun fibers are collected on the main surface of the drum, resulting in a thickness of 10 μm on the main surface of the drum. A fiber assembly of 2.2 g / m ² was prepared.
Next, by performing electrospinning using the first spinning solution under the electrospinning conditions described above, and collecting the spun fibers on the exposed main surface of the fiber assembly on the drum, Another fiber assembly having a thickness of 1 μm and a basis weight of 0.2 g / m ² was formed on the main surface of the fiber assembly.
As a result of peeling off the laminate including the fiber assembly formed in this way from the drum and providing it to the above-described “hydrophilicity determination method”, it is The contact angle of the fiber assembly was 0 °, the contact angle of the fiber assembly was 105 °, and it was found that the other fiber assembly was more hydrophilic than the fiber assembly.
In addition, the structure of a laminated body is 1 micrometer in thickness of the 1st fiber layer derived from another fiber assembly, 10 micrometers in thickness of the 2nd fiber layer derived from a fiber assembly, and the average of the fiber which comprises a 1st fiber layer The fiber diameter was 0.3 μm, and the average fiber diameter of the fibers constituting the second fiber layer was 0.3 μm.

As a hydrophilic resin solution, an aqueous pullulan solution having a pullulan concentration of 20% by mass was prepared by completely dissolving pullulan (manufactured by Hayashibara Kogyo Co., Ltd.) in water having a conductivity of 10 μS / cm or less.
Using a slit coating device (clearance: 60 μm), an aqueous pullulan solution adjusted to 25 ° C. was applied on one main surface of a glass plate having a smooth surface. And the pullulan aqueous solution was provided to the main surface where the 2nd fiber layer in a laminated body has exposed the main surface which the 2nd fiber layer in a laminated body is made to contact with this pullulan aqueous solution.
The water which is the solvent of the pullulan aqueous solution was removed by leaving still at 80 degreeC atmosphere for 30 minutes with the aspect which the glass plate and the laminated body laminated | stacked.
Next, with the state in which the glass plate and the laminate are laminated, a slit coating device (clearance: 30 μm) is used on the main surface where the first fiber layer in the laminate is exposed, and the film-constituting resin solution is kept at 25 ° C. The sulfonated polyethersulfone dimethylacetamide solution thus prepared (sulfonated polyethersulfone concentration: 20% by mass) was applied by coating.
And, with the glass plate and the laminate laminated, the laminate coated with the film-forming resin solution is allowed to stand for 30 minutes in a 120 ° C. atmosphere, and then left in a 140 ° C. atmosphere for 30 minutes. Dimethylacetamide, which is a solvent for the membrane constituent resin solution, was removed.
Finally, the laminate after removing the above-mentioned dimethylacetamide is peeled off from the glass plate, and the resulting laminate is immersed in water adjusted to 60 ° C. and having an electric conductivity of 10 μS / cm or less, whereby the second fiber Pullulan present between the constituent fibers of the layer was eluted and removed into water.
After removing the laminate from the water, it is left to stand in an 80 ° C. atmosphere for 30 minutes to remove the water, and the composite membrane (thickness: 9 μm, between the constituent fibers of the first fiber layer derived from another fiber assembly) In the presence of a sulfonated polyethersulfone).

FIG. 5 shows an electron micrograph of the composite membrane prepared in Comparative Example 2 taken at 1000 times the main surface on the side to which the membrane-constituting resin solution was applied.
When the electron micrograph shown in FIG. 5 was confirmed, the main surface on the side of the composite membrane to which the membrane-constituting resin solution was applied had a portion where a fiber shape was present and a portion where an unintended opening was present. The existence of
As a result of subjecting the prepared composite film to the above-described “determination method for determining whether or not the film-like aspect is formed”, the composite film according to Comparative Example 2 does not have a film structure portion that forms the film-like aspect. It was a thing.

  The composite membranes of the present invention include, for example, liquid separation membranes such as water treatment membranes and gas separation membranes, polymer electrolyte membranes for fuel cells, separators for electrochemical devices such as capacitors and primary / secondary batteries, medical materials, ion exchange It can be used for various industrial applications such as membranes and dialysis membranes.

Claims (2)

Having a laminate comprising a first fiber layer and a second fiber layer, and a membrane-constituting resin;
A composite membrane having a membrane structure portion in which the membrane-constituting resin is present between constituent fibers of the first fiber layer,
The average fiber diameter of the fibers constituting the first fiber layer is 3 μm or less,
The first fiber layer is a composite membrane having a lower hydrophilicity than the second fiber layer.
(1) a step of preparing a fiber assembly;
(2) By forming another fiber assembly on one main surface of the fiber assembly, the first fiber layer derived from the other fiber assembly and the second fiber layer derived from the fiber assembly are provided. Preparing a laminate,
(3) A step of applying a hydrophilic resin solution to the main surface where the second fiber layer in the laminate is exposed,
(4) removing the solvent from the imparted hydrophilic resin solution, thereby allowing the hydrophilic resin to exist between constituent fibers of the second fiber layer;
(5) A step of applying a film-constituting resin solution to the main surface where the first fiber layer in the laminate is exposed,
(6) a step of forming a film structure portion in which the film-constituting resin is present between constituent fibers of the first fiber layer by removing a solvent from the applied film-constituting resin solution;
(7) using a solvent capable of dissolving the hydrophilic resin, removing the hydrophilic resin present between the constituent fibers of the second fiber layer;
A method for producing a composite membrane having a membrane structure part in which the membrane-constituting resin is present between constituent fibers of the first fiber layer in the laminate,
The average fiber diameter of the fibers constituting the first fiber layer is 3 μm or less,
The method for producing a composite membrane, wherein the first fiber layer is less hydrophilic than the second fiber layer.

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