JP2018199303A - Composite membrane - Google Patents

Abstract

To provide a composite membrane useful for various industrial applications by preventing presence of a part which is not made as a membrane, and providing an extremely thin membrane structure part with membrane thickness of for example 10 μm or less.SOLUTION: There is provided a composite membrane having a membrane structure part, which has a laminate with a first fiber layer and a second fiber layer, and a membrane constitutional resin, and is constituted by the membrane constitutional resin existing between the constitutional fibers of the first fiber layer, in which average fiber diameter of fibers constituting the first fiber layer is 3 μm or less and the first fiber layer has higher compatibility with the membrane structure resin solution than the second fiber layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite membrane.

Conventionally, composite membranes having a membrane structure include, for example, liquid separation membranes such as water treatment membranes and gas separation membranes, polymer electrolyte membranes for fuel cells, separators for electrochemical elements such as capacitors and primary / secondary batteries, medical treatment, etc. It is used in various industrial applications such as industrial 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 technology disclosed in 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 having a thickness of 10 μm or less, the main surface on the first fiber layer side in the prepared composite membrane (for example, a portion that is not filmed) In other words, there is a part where the fiber shape is present and a part where the pores are unintentionally present), and it has not been possible to provide a composite membrane having a membrane structure part.
As described above, this problem is likely to occur when a composite film is provided using a material composed of a fiber assembly and a film-constituting resin.

When the inventors of the present invention examined the cause of the problem, it was considered that the above-mentioned phenomenon occurred because the film-constituting resin was not sufficiently present between the fibers that could constitute the film structure portion.
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 film thickness of 10 μm or less, thereby making a composite film useful for various industrial applications. It was difficult to provide.

  An object of the present invention is to provide a composite film useful for various industrial applications by preventing the existence of a non-filmed portion and providing an extremely thin film structure portion having a film thickness of 10 μm or less, for example. .

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 higher affinity for the membrane-constituting resin solution 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 (A),
(2) A step of forming a laminate by forming another fiber assembly (B) on at least one main surface of the fiber assembly (A),
(3) A step of applying a film-constituting resin solution to the main surface where the other fiber aggregate (B) in the laminate is exposed,
(4) A step of removing the solvent from the applied film-constituting resin solution,
Comprising a membrane structure portion in which the membrane-constituting resin is present between constituent fibers of the another fiber assembly (B),
The average fiber diameter of the fibers constituting the another fiber assembly (B) is 3 μm or less,
The method for producing a composite membrane, wherein the another fiber assembly (B) has a higher affinity for the membrane-constituting resin solution than the fiber assembly (A). "
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 becomes uniform and thin. The composite membrane provided can be provided.
Furthermore, as a result of continuing the study to solve the above-mentioned problems, the inventors of the present application have a relationship between the first fiber layer, the second fiber layer, and the membrane constituent resin solution obtained by dissolving the membrane constituent resin in a solvent. , When satisfying the combination of “the first fiber layer has a higher affinity with the membrane-constituting resin solution than the second fiber layer”, for the first time, it is possible to prevent the presence of a non-membrane portion, The present inventors have found that a composite film provided with an extremely thin film structure portion having a film thickness of 10 μm or less can be provided.
As described above, the present invention can provide composite membranes useful for various industrial applications.

Another aspect of the present invention is a method for manufacturing a composite membrane according to the present invention described above.
This production method is described as follows: “(1) Step of preparing a fiber assembly (A), (2) Forming another fiber assembly (B) on at least one main surface of the fiber assembly (A). A step of preparing a laminate, (3) a step of applying a film-constituting resin solution to the main surface of the laminate where the other fiber assembly (B) is exposed, and (4) the applied membrane. A process for removing the solvent from the constituent resin solution, comprising a membrane structure portion in which the membrane constituent resin is present between constituent fibers of the another fiber assembly (B). It is an invention.
And since the first fiber layer having a uniform thickness can be produced by “the average fiber diameter of the fibers constituting another fiber assembly (B) is 3 μm or less”, a film having a uniform and thin thickness A composite membrane having a structural portion can be provided.
Furthermore, the manufacturing method of the present invention has a manufacturing condition that “the other fiber assembly (B) has a higher affinity for the membrane-constituting resin solution than the fiber assembly (A)”, so that the membrane For example, it is possible to provide a composite film provided with an extremely thin film structure part having a film thickness of 10 μm or less.
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 step of applying the membrane-constituting resin solution to the main surface where the other fiber assembly (B) is exposed to the laminate including the fiber assembly (A) and another fiber assembly (B), The membrane-constituting resin solution is applied to another fiber aggregate (B) having higher affinity than the fiber aggregate (A), and the membrane-constituting resin solution tends to stay in the other fiber aggregate (B). .
Therefore, the solvent which is the next step is removed from the laminated body to which the membrane constituent resin solution is applied in a state where the membrane constituent resin solution is sufficiently and abundant between the constituent fibers of another fiber assembly (B). It can be used for the process.
As a result, since the film-constituting resin is sufficiently present between the constituent fibers of another fiber assembly (B), it is possible to prevent the presence of a non-filmed portion, for example, the film thickness is 10 μm or less. A composite membrane provided with an 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 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. 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 3. 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 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 4. 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 5. 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 6. 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 part together with the membrane constituent resin, and the constituent fibers of the first fiber layer exist in the membrane constituent resin (the membrane constituent resin exists between the constituent fibers of the first fiber layer. This is a member that can reinforce the membrane structure and prevent the above-described various problems that occur when the membrane structure 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” herein refers to an arithmetic average value of the fiber diameters of 50 fibers measured based on a 5000-fold electron micrograph of the surface and cross section of the composite membrane. Moreover, when the fiber diameter is too thin and measurement is difficult, it can be measured based on an electron micrograph having a magnification higher than 5000 times. 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” as used herein can be measured based on a 5000 × electron micrograph of the surface and cross section of the composite membrane. When the fiber length of the fiber is too long and measurement is difficult, it can be measured based on an electron micrograph having 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. The irregular cross-section fibers include hollow shapes, polygonal shapes such as triangular shapes, alphabetic character shapes such as Y shapes, irregular 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 the integrated mode, the constituent fibers of the first fiber layer and the second fiber layer are entangled across both fiber layers (for example, needle punching, hydroentanglement, fibers on the main surface of the second fiber layer) A method in which the constituent fibers of the first fiber layer are integrated into the second fiber layer, etc.), and the interfiber bonding is achieved by the thermal melting of the constituent fibers. An embodiment in which the layers between the layer and the second fiber layer are integrated, an embodiment in which the layers between the first fiber layer and the second fiber layer are integrated by ultrasonic bonding, or the like can be used.
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 with a binder or heat melting of the constituent fibers, the air permeability is intended by the binder or the molten constituent fibers. It is preferable that the first fiber layer and the second fiber layer can be integrated with each other.

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 resin described above as a resin capable of constituting each fiber layer can be used as a film structure 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 because film | membrane constituent resin exists between the constituent fibers of a fiber layer. In addition, even if the membrane structure portion is a mode in which the membrane-constituting resin exists only between the constituent fibers of the first fiber layer, the configuration of the second fiber layer other than between the constituent fibers of the first fiber layer in the composite membrane An embodiment in which a film-constituting resin exists between the fibers may also be used. 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 determined by the following method whether or not a film-like (non-film-formed portion) is formed due to the presence of the membrane-constituting resin between the constituent fibers of the 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 circular (diameter: 25 mm) suction portion at the tip is prepared. 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 applied force, it is determined that the composite membrane has a membrane structure portion that forms a membrane shape.
On the other hand, if the composite membrane side end portion of the piston does not return to the scale range of 0 ml to 1 ml on both the main surfaces, the composite membrane does not have a membrane structure portion that forms a membrane shape. to decide.

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 made by the membrane-constituting resin solution with respect to the main surface of the fiber aggregate (first fiber layer) constituting the first fiber layer is the fiber aggregate (second fiber) constituting the second fiber layer. The first fiber layer (fiber assembly constituting the first fiber layer) is the second fiber layer (fibers constituting the second fiber layer) when the contact angle made by the membrane-constituting resin solution with respect to the main surface of the layer) is smaller It is determined that the affinity to the membrane-constituting resin solution is higher than that of the aggregate.

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 a first fiber layer (a fiber aggregate constituting the first fiber layer) that permeates and the membrane-constituting resin solution does not 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 process (2) described above, 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 an 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.

In addition, 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 to the main surface on the side where the membrane structure portion in the composite membrane exists, the length of the portion consisting only of the fibers constituting the opposite main surface is measured, and this is the composite membrane The thickness of the second fiber layer in FIG.

  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 the fiber assembly (A),
(2) A step of forming a laminate by forming another fiber assembly (B) on at least one main surface of the fiber assembly (A),
(3) A step of applying a film-constituting resin solution to the main surface where the other fiber aggregate (B) in the laminate is exposed,
(4) A step of removing the solvent from the applied film-constituting resin solution,
Comprising a membrane structure portion in which the membrane-constituting resin is present between constituent fibers of the another fiber assembly (B),
The average fiber diameter of the fibers constituting the another fiber assembly (B) is 3 μm or less,
The another fiber assembly (B) can be exemplified by a method for producing a composite membrane having a higher affinity for the membrane-constituting resin solution than the fiber assembly (A).

First, (1) the step of preparing the fiber assembly (A) will be described.
The fiber assembly (A) is a member that can constitute the second fiber layer, 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 second fiber layer 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 cloth made by wet papermaking or direct spinning is preferred. 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 (A) can be selected as appropriate, but is preferably 15 μm or less, preferably 10 μm or less, preferably 5 μm or less, and 3 μm or less. Preferably, it is 2 μm or less, preferably 1 μm or less, and 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 (A) can be appropriately selected, and the basis weight is preferably from 0.5 to 20 g / ^{m 2,} it is preferably from ^{0.8~18g / m 2, 1~16g / m} 2 Is preferred. In the present invention, the weight per unit area refers to the mass per 1 m ² area on the widest surface (main surface).
The thickness of the fiber assembly (A) can be appropriately selected. The thickness is preferably 30 μm, more preferably 20 μm, and preferably 10 μm. On the other hand, it is realistic that the thickness is 1 μm or more.
The porosity of the fiber assembly (A) is appropriately selected, but the porosity is preferably 30% or more and 35% or more so that the air permeability and liquid permeability in the composite membrane do not deteriorate too much. And is preferably 40% or more. On the other hand, it is realistic that the porosity is 98% or less.
The Gurley permeability of the fiber assembly (A) can be selected as appropriate, but the Gurley permeability is preferably 300 s / 100 mL or less so that the air permeability and liquid permeability in the composite membrane do not decrease too much. It is preferably 200 s / 100 mL or less, and 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) the step of forming another fiber assembly (B) on at least one main surface of the fiber assembly (A) to prepare a laminate will be described.
Another fiber assembly (B) is a member that can constitute the first fiber layer, 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 (B) can be selected as appropriate,
A method of laminating another fiber assembly (B) separately prepared on at least one main surface of the fiber assembly (A),
-On one main surface of the fiber assembly (A), fibers capable of forming another fiber assembly (B) are deposited by paper making or directly spinning, and a deposited layer of the fiber (another fiber assembly) Body (B)),
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, an electrostatic spinning method) on one main surface of the fiber assembly (A), adhesion and configuration by a binder Since it is possible to prepare a laminate in which the layers of the fiber assembly (A) and another fiber assembly (B) are integrated without bonding by heat melting of the fibers, the air permeability etc. is a binder or melted constituent fiber Therefore, it is possible to prevent the unintended change and to integrate the layers of the fiber assembly (A) and another fiber assembly (B). Further, it is preferable to provide a composite film having a uniform and thin film structure portion.

The average fiber diameter of the fibers constituting the other fiber aggregate (B) can be appropriately selected, 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. Preferably there is. 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 the other fiber aggregate (B) can be appropriately selected, but the basis weight is preferably 4 g / m ² or less, 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 the other fiber assembly (B) can be appropriately selected, 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 (B) is appropriately selected, but 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.

And (3) The process of providing a film | membrane structure resin solution to the main surface where the said another fiber assembly (B) in the said laminated body is exposed is demonstrated.
The application method 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, inkjet printing, etc. A method of spraying or coating a film-constituting resin solution by using a film, a method of immersing the main surface of another laminate (B) side of the laminate in the film-constituting resin solution, or the like can be employed.
The application amount of the membrane-constituting resin solution is appropriately selected so that a composite membrane having a desired membrane structure portion can be provided.
In this way, the membrane-constituting resin solution is absorbed between constituent fibers of another fiber assembly (B) by absorbing the membrane-constituting resin solution from the main surface side of another fiber assembly (B) in the laminate. Make it exist.

Further, (4) the step of removing the solvent from the applied film-constituting resin solution will be described.
The method for removing the solvent can be selected as appropriate.For example, the film structure is prepared by heating to a heater such as an oven dryer, a far infrared heater, a dry heat dryer, or by leaving it in a room temperature atmosphere or a reduced pressure atmosphere. It can be removed by evaporating the solvent from the laminate provided with the resin solution. 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, membrane constituent resin, etc.) may be unintentionally lowered. Select the upper limit of the heating temperature.

In addition, you may use for the process processes, such as a hydrophilization process process, the fabric, laminated body, and composite film which can comprise a 1st fiber layer and / or a 2nd fiber layer. 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.
Further, the fabric, laminate, and composite film that can constitute the first fiber layer and / or the second fiber layer may be subjected to processing steps such as a water repellency / oil repellency / hydrophobization 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.

  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 part, and for example, the reason why a composite film having a very thin film structure part having a film thickness of 10 μm or less can be manufactured is not completely clarified. However, this is thought to be due to the following effects.
That is, in the step of applying the membrane-constituting resin solution to the main surface where the other fiber assembly (B) is exposed to the laminate including the fiber assembly (A) and another fiber assembly (B), The membrane-constituting resin solution is applied to another fiber assembly (B) having a higher affinity than the fiber assembly (A), and the membrane-constituting resin solution tends to stay in another fiber assembly (B). In addition, even when there is a membrane-constituting resin solution that has passed through another fiber assembly (B) and moved to the fiber assembly (A), the membrane-constituting resin solution is more compatible from the fiber assembly (A). It is easy to move to another high fiber assembly (B).
Therefore, the solvent which is the next step is removed from the laminated body to which the membrane constituent resin solution is applied in a state where the membrane constituent resin solution is sufficiently and abundant between the constituent fibers of another fiber assembly (B). It can be used for the process.
As a result, since the film-constituting resin is sufficiently present between the constituent fibers of another fiber assembly (B), it is possible to prevent the presence of a non-filmed portion, for example, the film thickness is 10 μm or less. A composite membrane provided with an extremely thin membrane structure can be provided.

  Furthermore, the inventors of the present invention control the film thickness and uniformity of the membrane structure part included in the composite membrane by adjusting the thickness of another fiber assembly (B) in the above-described composite membrane manufacturing method. The present inventors have found that a composite film having a desired thickness and a film structure portion having a uniform thickness can be provided. For example, by using a laminate including another fiber assembly (B, first fiber layer) having a thickness of 10 μm or less, for example, a membrane structure portion having a very thin film thickness of 10 μm or less and a uniform thickness can be obtained. A composite membrane can be provided.

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 difference between the minimum value and the maximum value among the thicknesses obtained by measurement is an average value (film structure) calculated from the thickness of the film structure portion obtained by measurement at the 10 points. The composite film provides a film structure portion having a uniform thickness when it falls within ± 20% of the (average thickness of the portion).
In addition, by using a laminate including another fiber assembly (B, first fiber layer) having a thickness greater than 10 μm, for example, a film structure portion having a thickness greater than 10 μm and a uniform thickness can be obtained. Provided composite membranes can also be provided.

  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 of the aqueous solution a and 20 parts 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.

Subsequently, a polyvinyl alcohol resin concentration (17.5% by mass) is obtained by completely dissolving a polyvinyl alcohol resin (complete saponification, degree of polymerization: 900 to 1000, manufactured by Wako Pure Chemical Industries, Ltd.) in water having a conductivity of 10 μS / cm or less. An aqueous solution c was prepared. Further, the methyl vinyl ether-maleic anhydride copolymer resin (manufactured by ALDRICH) is completely dissolved in water having a conductivity of 10 μS / cm or less, so that the concentration of methyl vinyl ether-maleic anhydride copolymer resin is 17.5% by mass. Aqueous solution d was prepared.
A third spinning solution was prepared by mixing 80 parts of the aqueous solution c and 20 parts of the aqueous solution d.
In addition, a fourth spinning solution was prepared by mixing dodecylamine hydrochloride, which is a hydrophobizing agent, with a concentration of 1% by mass with respect to the third spinning solution.

Furthermore, the polyvinyl alcohol resin concentration is 12.5% by mass by completely dissolving the polyvinyl alcohol resin (completely saponified, degree of polymerization: 900 to 1000, manufactured by Wako Pure Chemical Industries, Ltd.) in water having a conductivity of 10 μS / cm or less. An aqueous solution e was prepared. Further, by completely dissolving methyl vinyl ether-maleic anhydride copolymer resin (manufactured by ALDRICH) in water having an electric conductivity of 10 μS / cm or less, the concentration of methyl vinyl ether-maleic anhydride copolymer resin is 12.5% by mass. An aqueous solution f was prepared.
After mixing 80 parts of the aqueous solution e and 20 parts of the aqueous solution f, dodecylamine hydrochloride as a hydrophobizing agent was mixed so that the concentration became 1% by mass with respect to the solute, thereby preparing a fifth 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 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 aggregate of 2.3 g / m ² was formed.
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 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 subjecting the laminate including the fiber assembly formed in this way to another fiber assembly to the above-described “affinity determination method”, another fiber assembly after 15 seconds has elapsed since the droplet was placed. The contact angle of the fiber assembly was 0 °, and the contact angle of the fiber assembly was 108 °. It was found that the other fiber assembly had a higher affinity for the first spinning solution used as the membrane-constituting resin solution than the fiber assembly. did.
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.
It was provided by applying the first spinning solution as a membrane-constituting resin solution to the main surface of the laminated body from which another fiber assembly was exposed, using a slit coating device (clearance: 50 μm).
Then, the laminated body coated with the first spinning solution is allowed to stand for 30 minutes in an 80 ° C. atmosphere, and then left for 30 minutes in a 180 ° C. atmosphere to remove water that is the solvent of the first spinning solution. Thus, a composite membrane (thickness: 14 μm, and the resin constituting the first spinning solution is present between constituent fibers derived from another fiber assembly) was prepared.

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 6.0 μm (maximum thickness of the film structure portion: 7.1 μm, minimum thickness of the film structure portion: 5.4 μm).

(Comparative 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 2.4 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 1.0 g / m ² was formed on the main surface of the fiber assembly.
As a result of subjecting the laminate comprising the fiber assembly formed in this way to another fiber assembly to the above-described “affinity determination method”, the contact of the fiber assembly after 15 seconds has elapsed since the droplet was placed. The angle is 0 °, the contact angle of another fiber assembly is 121 °, and the fiber assembly is found to have higher affinity to the first spinning solution used as the membrane-constituting resin solution than the other fiber assembly. did.
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.
It was provided by applying the first spinning solution as a membrane-constituting resin solution to the main surface of the laminated body from which another fiber assembly was exposed, using a slit coating device (clearance: 50 μm).
Then, the laminated body coated with the first spinning solution is allowed to stand for 30 minutes in an 80 ° C. atmosphere, and then left for 30 minutes in a 180 ° C. atmosphere to remove water that is the solvent of the first spinning solution. A composite membrane (thickness: 13 μm) was prepared.

The electron micrograph which image | photographed 1000 times of main surfaces of the composite film prepared in Comparative Example 1 on the side to which the membrane-constituting resin solution was applied is shown in FIG.
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 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 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 2.4 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 0.2 micrometer.
By using a slit coating device (clearance: 50 μm) on one exposed main surface of the fiber assembly, the first spinning solution was applied as a membrane-constituting resin solution.
Then, the laminated body coated with the first spinning solution is allowed to stand for 30 minutes in an 80 ° C. atmosphere, and then left for 30 minutes in a 180 ° C. atmosphere to remove water that is the solvent of the first spinning solution. A composite membrane (thickness: 9 μm) was prepared.

FIG. 3 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. 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 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.

(Comparative Example 3)
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 0.2 micrometer.
A composite membrane (thickness: 9 μm) was prepared in the same manner as in Comparative Example 2 except that the fiber assembly thus prepared was used.

FIG. 4 shows an electron micrograph of the composite film prepared in Comparative Example 3 taken at 1000 times the main surface on 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 3 does not have a film structure portion that forms the film-like aspect. It was a thing.

(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 aggregate of 2.3 g / m ² was formed.
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 0.5 μm and a basis weight of 0.1 g / m ² was formed on the main surface of the fiber assembly.
As a result of subjecting the laminate including the fiber assembly formed in this way to another fiber assembly to the above-described “affinity determination method”, another fiber assembly after 15 seconds has elapsed since the droplet was placed. The contact angle of the fiber assembly is 0 °, the contact angle of the fiber assembly is 121 °, and the other fiber assembly is found to have higher affinity to the first spinning solution used as the membrane-constituting resin solution than the fiber assembly. did.
In addition, the structure of a laminated body is the fiber which comprises the 1st fiber layer from which the thickness of the 1st fiber layer derived from another fiber assembly is 0.5 micrometer, the thickness of the 2nd fiber layer derived from a fiber assembly is 10 micrometers The average fiber diameter was 0.2 μm, and the average fiber diameter of the fibers constituting the second fiber layer was 0.2 μm.
It was provided by applying the first spinning solution as a membrane-constituting resin solution to the main surface of the laminated body from which another fiber assembly was exposed, using a slit coating device (clearance: 20 μm).
The laminated body coated with the first spinning solution is allowed to stand in an 80 ° C. atmosphere for 30 minutes, and then left in a 180 ° C. atmosphere for 30 minutes to remove water that is the solvent of the first spinning solution, A composite membrane (thickness: 11 μm, and the resin constituting the first spinning solution is present between constituent fibers derived from another fiber assembly) was prepared.

FIG. 5 shows an electron micrograph of the composite film prepared in Example 2, 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. 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 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 0.8 μm (maximum thickness of the film structure portion: 0.88 μm, minimum thickness of the film structure portion: 0.71 μm).

Example 3
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, thereby having a thickness of 5 μm on the main surface of the drum. A fiber aggregate of 1.2 g / m ² was formed.
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 0.3 g / m ² was formed on the main surface of the fiber assembly.
As a result of subjecting the laminate including the fiber assembly formed in this way to another fiber assembly to the above-described “affinity determination method”, another fiber assembly after 15 seconds has elapsed since the droplet was placed. The contact angle of the fiber assembly is 0 °, the contact angle of the fiber assembly is 114 °, and the other fiber assembly is found to have higher affinity to the first spinning solution used as the membrane-constituting resin solution than the fiber assembly. did.
In addition, as for the structure of the laminated body, the thickness of the first fiber layer derived from another fiber assembly is 1 μm, the thickness of the second fiber layer derived from the fiber assembly is 5 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.
It was provided by applying the first spinning solution as a membrane-constituting resin solution to the main surface of the laminated body from which another fiber assembly was exposed, using a slit coating device (clearance: 20 μm).
The laminated body coated with the first spinning solution is allowed to stand in an 80 ° C. atmosphere for 30 minutes, and then left in a 180 ° C. atmosphere for 30 minutes to remove water that is the solvent of the first spinning solution, A composite membrane (thickness: 5 μm, resin containing the first spinning solution is present between constituent fibers derived from another fiber assembly) was prepared.

FIG. 6 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. 6 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-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 2.0 μm (maximum thickness of the film structure portion: 2.2 μm, minimum thickness of the film structure portion: 1.7 μm).

(Example 4)
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, thereby having a thickness of 5 μm on the main surface of the drum. A fiber assembly of 1.1 g / m ² was formed.
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 0.3 g / m ² was formed on the main surface of the fiber assembly.
As a result of subjecting the laminate including the fiber assembly formed in this way to another fiber assembly to the above-described “affinity determination method”, another fiber assembly after 15 seconds has elapsed since the droplet was placed. The contact angle of the fiber assembly was 0 °, and the contact angle of the fiber assembly was 124 °. It was found that the other fiber assembly had a higher affinity for the pullulan aqueous solution described later used as the membrane-constituting resin solution than the fiber assembly. did.
In addition, as for the structure of the laminated body, the thickness of the first fiber layer derived from another fiber assembly is 1 μm, the thickness of the second fiber layer derived from the fiber assembly is 5 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 pullulan aqueous solution having a pullulan concentration of 15% 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.
And it applied | provided by apply | coating the pullulan aqueous solution to the main surface which another fiber assembly in a laminated body has exposed using the slit coating device (clearance: 20 micrometers).
The laminated body to which the aqueous solution of pullulan is applied is allowed to stand in an 80 ° C. atmosphere for 30 minutes, and then left in a 180 ° C. atmosphere for 30 minutes to remove water, which is a solvent for the film-constituting resin solution. (Thickness: 5 μm, a film-constituting resin is present between constituent fibers derived from different fiber aggregates).

FIG. 7 shows an electron micrograph of the composite film prepared in Example 4 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. 7 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 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 4 has a film structure portion that forms the film-like aspect. It was a thing.
In the composite film of Example 4, the average thickness of the film structure portion was 1.0 μm (maximum thickness of the film structure portion: 1.2 μm, minimum thickness of the film structure portion: 0.9 μm).

(Example 5)
Electrospinning is performed using the fourth 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 6 μm on the main surface of the drum. A fiber aggregate of 1.2 g / m ² was formed.
Next, by performing electrostatic spinning using the third 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 subjecting the laminate including the fiber assembly formed in this way to another fiber assembly to the above-described “affinity determination method”, another fiber assembly after 15 seconds has elapsed since the droplet was placed. The contact angle of the fiber assembly was 0 °, and the contact angle of the fiber assembly was 118 °. The other fiber assembly was found to have a higher affinity than the fiber assembly for the pullulan aqueous solution described later used as the membrane-constituting resin solution. did.
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 6 micrometers, and the average of the fiber which comprises a 1st fiber layer The fiber diameter was 0.5 μm, and the average fiber diameter of the fibers constituting the second fiber layer was 0.5 μm.
A pullulan aqueous solution having a pullulan concentration of 15% 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.
And it applied | provided by apply | coating the pullulan aqueous solution to the main surface which another fiber assembly in a laminated body has exposed using the slit coating device (clearance: 20 micrometers).
The laminated body to which the aqueous solution of pullulan is applied is allowed to stand in an 80 ° C. atmosphere for 30 minutes, and then left in a 180 ° C. atmosphere for 30 minutes to remove water, which is a solvent for the film-constituting resin solution. (Thickness: 6 μm, a film-constituting resin is present between constituent fibers derived from other fiber aggregates).

FIG. 8 shows an electron micrograph of the composite film prepared in Example 5, 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. 8 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 unintentional 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 5 has a membrane structure portion that forms the membrane-like aspect. It was a thing.
In the composite film of Example 5, the average thickness of the film structure portion was 2.0 μm (maximum thickness of the film structure portion: 2.2 μm, minimum thickness of the film structure portion: 1.7 μm).

(Example 6)
Electrospinning is performed using the fifth 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 6 μm on the main surface of the drum. A fiber aggregate of 1.2 g / m ² was formed.
Next, by performing electrostatic spinning using the third 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 0.5 μm and a basis weight of 0.1 g / m ² was formed on the main surface of the fiber assembly.
As a result of subjecting the laminate including the fiber assembly formed in this way to another fiber assembly to the above-described “affinity determination method”, another fiber assembly after 15 seconds has elapsed since the droplet was placed. The contact angle of the fiber assembly is 0 °, the contact angle of the fiber assembly is 89 °, and the other fiber assembly is found to have higher affinity to the pullulan aqueous solution described later used as the membrane-constituting resin solution than the fiber assembly. did.
In addition, the structure of a laminated body is the fiber which comprises the thickness of the 1st fiber layer derived from another fiber assembly, the thickness of the 2nd fiber layer derived from a fiber assembly is 6 micrometers, and a 1st fiber layer The average fiber diameter was 0.1 μm, and the average fiber diameter of the fibers constituting the second fiber layer was 0.5 μm.
A pullulan aqueous solution having a pullulan concentration of 15% 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.
And it applied | provided by apply | coating the pullulan aqueous solution to the main surface which another fiber assembly in a laminated body has exposed using the slit coating device (clearance: 20 micrometers).
The laminated body to which the aqueous solution of pullulan is applied is allowed to stand in an 80 ° C. atmosphere for 30 minutes, and then left in a 180 ° C. atmosphere for 30 minutes to remove water, which is a solvent for the film-constituting resin solution. (Thickness: 5 μm, a film-constituting resin is present between constituent fibers derived from different fiber aggregates).

FIG. 9 shows an electron micrograph of the composite film prepared in Example 6, taken at 1000 times the principal surface on the side to which the membrane-constituting resin solution was applied.
As a result of confirming the electron micrograph shown in FIG. 9, the main surface of the composite membrane on which the membrane-constituting resin solution is applied has a portion where a fiber shape is present and a portion where an unintended opening is present. The presence of was not recognized.
As a result of subjecting the prepared composite membrane to the above-described “determination method for determining whether or not the membrane-like aspect is formed”, the composite membrane according to Example 6 has a membrane structure portion that forms the membrane-like aspect. It was a thing.
In the composite film of Example 6, the average thickness of the film structure portion was 0.8 μm (maximum thickness of the film structure portion: 0.94 μm, minimum thickness of the film structure portion: 0.69 μm).

  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 higher affinity for the membrane-constituting resin solution than the second fiber layer.
(1) a step of preparing a fiber assembly (A),
(2) On the at least one main surface of the fiber assembly (A), another fiber assembly (B) is formed to prepare a laminate,
(3) A step of applying a film-constituting resin solution to the main surface where the other fiber assembly (B) in the laminate is exposed,
(4) a step of removing the solvent from the applied film-constituting resin solution,
Comprising a membrane structure portion in which the membrane-constituting resin is present between constituent fibers of the another fiber assembly (B),
The average fiber diameter of the fibers constituting the other fiber assembly (B) is 3 μm or less,
The method for producing a composite membrane, wherein the another fiber assembly (B) has a higher affinity for the membrane-constituting resin solution than the fiber assembly (A).

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