JP2007246876A - Porous film and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous film having homogeneous micro-pores and excellent film strength. <P>SOLUTION: The porous film includes a number of micro-pores having communicating property. The average pore diameter of the micro-pores is 0.01-10 μm. The average pore diameter A of the micro-pores on one surface side of the porous film and the average pore diameter B of the micro-pores on the other surface side satisfy the relationship of 0.1≤A/B≤10. Furthermore, the porosity is 30-80%, and the tensile strength is 2 MPa or higher. The porous film is composed of, for example, a material based mainly on a polycarbonate resin or a polyarylate resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a porous film having a large number of continuous micropores and having strength, and a method for producing the same.

  Porous films have been applied to membrane separation techniques such as microfiltration and separation / concentration using their pore characteristics. As such a porous film, a film having substantially no skin layer on the surface and a high porosity is preferably used. However, a thin film has a low film strength and is very difficult to handle as a single film. It was. For this reason, the conventional porous film has been devised such as handling in a state of being lined with a reinforcing material, or processing the film into a hollow fiber shape.

  For example, JP-A-49-128371 discloses a method of casting microporous material by casting a mixture of polycarbonate, a solvent, a non-solvent, and an N, N-dialkyl-substituted amide or sulfoxide, and then removing the solvent by drying. A method for obtaining a membrane is disclosed. However, in this method, since the boiling point of N, N-dialkyl-substituted amide or sulfoxide is high and drying is difficult, not only the productivity is inferior, but also the production of a porous membrane having uniform pores on the front and back sides due to uneven drying temperature is possible. Have difficulty. Japanese Patent Application Laid-Open No. 57-52461 discloses a microporous film of a polycondensate of bisphenol A and polyalkylene oxide, 3 to 10% by weight of a polycarbonate resin, and a maximum of 15% (1 to 6%). A technique for casting a non-solvent mixture and treating it in a polar solvent / alcohol mixing tank is disclosed. However, in this method, it is necessary to immerse the membrane in a solvent tank, and not only the process is complicated, but it is difficult to remove the polar solvent from the microporous membrane.

JP-A-49-128371 JP-A-57-52461

An object of the present invention is to provide a porous film having homogeneous micropores and excellent membrane strength.
Another object of the present invention is to provide a method by which the porous film can be easily produced.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have communicability by phase-transforming under specific conditions using a polymer solution mainly composed of a polycarbonate resin or a polyarylate resin. The inventors have found that a porous film having a large number of micropores and excellent film strength can be obtained, and the present invention has been completed.

  That is, in the present invention, there are a large number of micropores having communication properties, the average pore diameter of the micropores is 0.01 to 10 μm, and the average pore diameter A of the micropores on one side of the porous film is Pores having an average pore diameter B of micropores on the other surface side satisfying a relationship of 0.1 ≦ A / B ≦ 10, a porosity of 30 to 80%, and a tensile strength of 2 MPa or more Provide film.

  This porous film includes a porous film made of a material mainly composed of a polycarbonate-based resin or a polyarylate-based resin. Examples of such a porous film include a porous film made of a material mainly composed of a polycarbonate resin or a polyarylate resin containing a structural unit corresponding to bisphenol A as a main structural unit.

  The thickness of the porous film is preferably in the range of about 5 to 200 μm.

  The present invention is also a porous film made of a material mainly composed of a polycarbonate-based resin or a polyarylate-based resin and having a large number of micropores having communication properties, and has a viscosity of 0.00001 to After dropping 1 μl of a 1 Pa · s solution, a porous film having a contact angle within 1000 μsec of 60 ° or less is provided.

Furthermore, the present invention is a porous film made of a material mainly composed of a polycarbonate-based resin or a polyarylate-based resin, and has a large number of communicating micropores, and the surface of the porous film has a viscosity of 0.00001 to 1 μl of a 1 Pa · s solution is dropped to provide a porous film satisfying θ ₁₀₀₀ / θ ₁₀₀ <0.9 when the contact angle θ ₁₀₀ after ₁₀₀ μsec and the contact angle θ ₁₀₀₀ after ₁₀₀₀ μsec are set. The θ ₁₀₀₀ may be 60 ° or less.

  The present invention also casts a polymer solution comprising at least one resin selected from a polycarbonate-based resin and a polyarylate-based resin, a solvent, and a water-soluble polymer onto a substrate in the form of a film having a humidity of 70 to 100%. Provided is a method for producing a porous film that obtains the porous film by conducting phase separation in a phase separation tank for 1 to 600 seconds and then guiding it to a coagulating liquid.

  In this production method, the film guided to the coagulating liquid may be transferred from the substrate onto the support and dried.

  The support is preferably made of a material having coagulation liquid resistance and having a large number of micropores on the surface in contact with the film.

  As a polymer solution, 1 to 40 parts by weight of a water-soluble polymer is added to 100 parts by weight of a solution comprising 5 to 30% by weight of at least one resin selected from polycarbonate resins and polyarylate resins and 70 to 95% by weight of a solvent. A dissolved solution is preferred.

  The weight ratio of at least one resin (a) selected from polycarbonate resin and polyarylate resin contained in the polymer solution to the water-soluble polymer (b) is 0.1 ≦ (b) / (a) ≦ 5 0.0 relationship is preferably satisfied.

  The porous film of the present invention has a fine pore average pore diameter, porosity, and the like within a specific range, has substantially no skin layer on the surface, has uniform and excellent pore characteristics, and is sufficient Since it has membrane strength, it can be used for membrane separation techniques such as microfiltration and separation / concentration, for example, as filter paper. Further, it is easy to fill the pores with a functional material, and it is easy to produce a composite material of a porous film / filling material. Therefore, it can be used as a wide range of substrate materials such as fuel cell separators, fuel cell electrolyte membranes (supports), circuit substrates and the like. The porous film of the present invention can also be used as a printing substrate on which characters and the like are printed by various printing devices such as an ink jet printer, and further, for circuit formation by printing conductive ink. It can also be used. Moreover, since it can be selectively plated by printing a plating catalyst, it can be used for a wiring circuit, an antenna, and the like. According to the method of the present invention, a porous film having both high porosity and excellent film strength can be easily obtained.

  The porous film of the present invention has a large number of micropores having communication properties, the average pore diameter of the micropores is 0.01 to 10 μm, and the average pore diameter of the micropores on one surface side of the porous film A and the average pore diameter B of the micropores on the other surface side satisfy the relationship of 0.1 ≦ A / B ≦ 10, the porosity is 30 to 80%, and the tensile strength is 2 MPa or more. . The material of the porous film is not particularly limited as long as it has the above-mentioned properties, but as a preferable material, a material mainly composed of a polycarbonate resin or a polyarylate resin, for example, at least selected from a polycarbonate resin and a polyarylate resin Examples thereof include a material containing 50% by weight or more of one kind of resin, preferably 80% by weight or more, and particularly preferably substantially 100% by weight. The porous film material can be used alone or in combination of two or more.

  Polycarbonate resins and polyarylate resins as materials are heat resistant, can be thermoformed, and have excellent mechanical strength, water resistance, weather resistance, chemical resistance, and electrical properties. Widely used in various molding materials. A porous film made of such a material is capable of exhibiting sufficient mechanical strength even when a large number of micropores having communication properties are formed and has a high porosity. Property can be remarkably improved. For this reason, it is advantageous in that the application can be expanded and workability can be improved because it can be used as a single film without separately providing a reinforcing material or forming a hollow fiber. The polycarbonate resin and polyarylate resin in the present invention are not particularly limited, and known resins can be used.

  In the present invention, the polycarbonate-based resin and the polyarylate-based resin are preferably polycarbonate-based resins and polyarylate-based resins containing, as main structural units, structural units corresponding to bisphenols such as bisphenol A and bisphenol F. For example, as a polycarbonate-type resin, the polycarbonate-type resin containing the repeating unit represented by following formula (1) can be used conveniently. Moreover, as a polyarylate-type resin, the polyarylate-type resin containing the repeating unit represented by following formula (2) can be used suitably. Such polycarbonate resins and polyarylate resins are preferable because they contain a plurality of aromatic rings per one repeating unit, and can significantly improve the film strength.

(In the formula, Ar represents a divalent group containing an aromatic ring)

Examples of the divalent group containing an aromatic ring in Ar include phenylene, biphenylene, -phenylene-C _n H _2n -phenylene-, -phenylene-O-phenylene-, -phenylene-S-phenylene-,- And phenylene-CO-phenylene-, -phenylene-SO ₂ -phenylene- and the like (n represents an integer of 1 to 10).

  In the present invention, the material of the porous film is not limited to the polycarbonate-based resin and the polyarylate-based resin, but mainly includes a resin containing a structural unit corresponding to bisphenols such as bisphenol A and bisphenol F as a main structural unit. The obtained material is preferable in terms of heat resistance and mechanical strength. In a resin containing a structural unit corresponding to such a bisphenol as a main structural unit, the content of the structural unit corresponding to the bisphenol is preferably 50 mol% or more of the entire structural unit based on the diol component in the resin. It is preferably 80 mol% or more, and it is preferable that the structural unit based on substantially all the diol component is a structural unit based on bisphenols.

  The porous film of the present invention has many micropores having communication properties, and the average pore size of the micropores (= average pore size on the film surface) is 0.01 to 10 μm. The average pore diameter of the micropores is preferably 0.1 to 10 μm, particularly preferably 1.0 to 10 μm. If the size is too small, the permeation performance is inferior, and if it is too large, the separation and concentration efficiency is reduced. In addition, when the porous material is filled with a functional material, it is preferable that the porous material can be filled with submicron to micron resolution, so that the average pore diameter described above is preferable, and if it is too small, the functional material cannot be filled. On the other hand, if it is too large, control in submicron to micron units becomes difficult. The maximum pore diameter on the film surface is preferably 15 μm or less.

  In the porous film of the present invention, the average pore diameter A of the micropores on one surface side and the average pore diameter B of the micropores on the other surface side satisfy the relationship of 0.1 ≦ A / B ≦ 10. When A / B is less than 0.1 or exceeds 10, the balance of the micropores provided on both surfaces of the film is poor, and the permeation performance and separation / concentration efficiency are significantly reduced.

  The porous film of the present invention is usually based on a method in which a polymer solution in which a resin constituting the porous film, for example, a polycarbonate resin or a polyarylate resin is dissolved, is cast into a film on a substrate and then solidified. It is manufactured by the phase change method. The porous film thus obtained has different micropore formation environments on the surface that is not in contact with the substrate (air-side surface) and the surface that is in contact with the substrate (base material-side surface). Often it has different pore characteristics. For the micropores on the surface of the porous film, when A represents the average pore diameter of the air-side surface of the porous film and B represents the average pore diameter of the substrate-side surface, for example, 0.15 ≦ A / B ≦ 8 The range is preferably 0.2 ≦ A / B ≦ 5. The A / B value can be adjusted by appropriately setting the production conditions for the porous film. Specifically, for example, the type of base material on which the polymer solution containing the material constituting the porous film is cast, the surface characteristics of the base material, the atmosphere (temperature, humidity, etc.) at the time of micropore formation are appropriately set. Can be controlled.

  The average open area (porosity) inside the porous film is 30 to 80%, preferably 40 to 80%, and more preferably 45 to 80%. If the porosity is too low, the permeation performance may not be sufficient, or the function may not be exhibited even if a functional material is filled. On the other hand, if the porosity is too high, the mechanical strength may be inferior. Moreover, as a surface area porosity (surface area ratio) of a porous film, it is 30% or more (for example, 30-80%), for example, Preferably it is about 40-60%. If the surface porosity is too low, the transmission performance may not be sufficient, and even if the pores are filled with a functional material, the function may not be fully exerted. If it is too high, the mechanical strength tends to decrease. Become.

  The thickness of the porous film is, for example, 5 to 200 μm, preferably 10 to 100 μm, and more preferably 20 to 80 μm. If the thickness is too thin, the mechanical strength of the film will be insufficient, while if it is too thick, it will be difficult to control the pore size distribution uniformly.

  The tensile strength of the porous film is 2 MPa or more (for example, 2 MPa or more and less than 100 MPa), preferably 4 MPa or more and less than 100 MPa, more preferably 7 MPa or more and less than 100 MPa. If the tensile strength is less than 2 MPa, the rigidity is low and the handling tends to be difficult. On the other hand, the porosity may be too low at 100 MPa or more. The porous film of the present invention has sufficient mechanical strength as described above even when it has the above-described pore characteristics. For this reason, since the handleability of a single film is improved, it can be used for various purposes. The tensile elongation of the porous film is, for example, 5% or more, preferably 7% or more, and more preferably 10% or more. If the tensile elongation is less than 5%, the film strength is low and handling tends to be difficult. The tensile strength and tensile elongation are values obtained in accordance with JIS K 7127 using a test piece type 5 having a width of 6 mm under the conditions of a distance between chucks of 80 mm and a tensile speed of 50 mm / min.

  The connectivity of the micropores present in the film can be indexed by the Gurley value representing the air permeability and the pure water permeation rate. The Gurley value of the porous film is, for example, 0.2 to 2000 seconds / 100 cc, preferably 1 to 1000 seconds / 100 cc, and more preferably 1 to 500 seconds / 100 cc. If the numerical value is too large, the practical permeation performance may not be sufficient, or the functional material may not be sufficiently filled and the function may not be exhibited. On the other hand, if the value is too small, the mechanical strength may be inferior.

  A preferable porous film has a large number of micropores having communication properties, the thickness of the porous film is 5 to 200 μm, the average pore diameter of the micropores is 0.01 to 10 μm, and one surface of the porous film The average pore diameter A of the micropores on the side and the average pore diameter B of the micropores on the other surface side satisfy the relationship of 0.1 ≦ A / B ≦ 10, the porosity is 30 to 80%, and the tensile strength is The porous film which is 2 MPa or more and less than 100 MPa is included.

  Since the porous film of the present invention has homogeneous micropores and excellent membrane strength, the membrane separation technology such as microfiltration and separation / concentration and its pore characteristics are used as they are, or the pores function. By filling with a conductive material, it can be used in a wide range of applications such as battery separators, electrolytic capacitors, circuit substrates, etc., and also for handling single films. The porous film of the present invention can be used as a composite film having at least one surface on a base material, or can be used as a single porous film by peeling off from the base material, transferring to a support and drying. .

  In the composite film having a porous film on at least one side of the above-mentioned base material, it is preferable to form a dense layer as the base material. Examples of the base material include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyimide, liquid crystal polymers (such as wholly aromatic polyesters), polycarbonate, high-density polyethylene, linear low-density polyethylene, polypropylene, Polyolefins such as poly-4-methylpentene-1, polystyrene, polysulfone (PSF), polyethersulfone (PES), polyphenylsulfone (PPSU), polyphenylene sulfide, aramid, poly-p-phenylene terephthalamide, polyamide, polyether Ether ketone, polyacrylate, polyarylate, polyphenylene ether, polyphenylene oxide, polyacetal, polymethyl methacrylate, polyacrylonitrile Polychlorinated ethylene trifluoride, polytetrafluoroethylene, polyparaxylene, polyetherimide, polyimide, polyvinyl chloride, polyurethane, epoxy resin, xylene resin, guanamine resin, diallyl phthalate resin, vinyl ester resin, phenol resin, Examples include plastics such as saturated polyester resin, furan resin, melamine resin and urea resin; metals such as iron, aluminum, copper, titanium, tin and zinc; inorganic materials such as glass, ceramics, concrete and rocks; wood and bamboo The These materials can be used alone or in combination of two or more.

  Such a porous film can be produced, for example, by a phase change method based on solidification after casting a polymer solution containing a polymer as a material constituting the porous film onto a substrate. . The addition of a water-soluble polymer or water to the polymer solution to be cast is effective for making the membrane structure porous like a sponge. Examples of the water-soluble polymer include polyethylene glycol, polyvinyl pyrrolidone, polyethylene oxide, polyvinyl alcohol, polyacrylic acid, polysaccharides, derivatives thereof, and mixtures thereof. Among these, polyvinylpyrrolidone is preferable in that it can suppress the formation of voids inside the film and improve the mechanical strength of the film. These water-soluble polymers can be used alone or in combination of two or more. From the viewpoint of porosity, the molecular weight of the water-soluble polymer is preferably 1000 or more, preferably 5000 or more, particularly preferably 10,000 or more (for example, about 10,000 to 200,000). In the present invention, polyvinyl pyrrolidone having a molecular weight of 1000 or more is particularly preferably used as the water-soluble polymer. The void diameter can be adjusted by adding water. For example, when the amount of water added to the polymer solution is increased, the void diameter can be increased. Examples of good solvents such as polycarbonate resins and polyarylate resins include N, N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide, NMP / xylene mixed solvents, NMP / xylene / methyl ethyl ketone mixed solvent, ethyl alcohol / toluene mixed solvent and the like can be mentioned, and those having solubility can be used according to the chemical skeleton of the polymer used. Of these, N-methyl-2-pyrrolidone (NMP) is preferable in terms of handling because of its high polymer solubility and low volatility.

  As a polymer solution to be cast, 100 parts by weight of a solution consisting of 5 to 30% by weight of a resin (for example, at least one resin selected from polycarbonate resins and polyarylate resins) and 70 to 95% by weight of a solvent is used. A solution in which 1 to 40 parts by weight of a water-soluble polymer is dissolved (regardless of the order of addition, the content of each component may be finally equal to that of the solution) is preferable. According to the polymer solution having the above composition, it is possible to form a porous film in which the mechanical strength is further improved and the handleability of the single film is remarkably improved.

  In the polymer solution, if the concentration of the polymer (polymer component) as the main component of the substrate is too low, the strength of the film becomes weak, and if it is too high, the porosity becomes small. The water-soluble polymer constituting the polymer solution is added to make the inside of the film a homogeneous sponge-like porous structure. If the concentration is too low, a huge void exceeding 10 μm is generated inside the film. The homogeneity is lowered, and if the concentration is too high, the solubility becomes worse. In addition, from the viewpoint of forming homogeneous micropores having a desired porosity with a desired porosity, the use ratio of the resin and the aqueous solution polymer is important. For example, the weight ratio of the resin (for example, at least one resin selected from polycarbonate resin and polyarylate resin) (a) and the water-soluble polymer (b) is, for example, 0.1 ≦ (b) / (a ) ≦ 2.0, preferably 0.3 ≦ (b) / (a) ≦ 1.5, more preferably 0.5 ≦ (b) / (a) ≦ 1.0.

  Examples of substrates on which polymer solutions can be cast include glass plates; polyolefin resins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate (PET); polycarbonate, polyarylate, polyimide, polyethersulfone, polysulfone, and styrene resins. , PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride) and other fluorine-based resins, vinyl chloride resins, plastic sheets made of other resins; stainless steel plates, aluminum plates and other metal plates. In addition, the composite board which combined the surface material and the internal material with a different thing may be sufficient. Either a single plate or a roll-like continuous film can be used.

  Preferred conditions for casting the polymer solution in the form of a film are a relative humidity of 70 to 100% and a temperature of 30 to 80 ° C., and a particularly preferred condition is a relative humidity of about 100% (eg, 95 to 100%). The temperature is 40-70 ° C. When the amount of moisture in the air is less than this, there is a problem that the surface porosity is not sufficient.

  When the polymer solution is cast into a film, the film is kept for 1 to 600 seconds in an atmosphere having a relative humidity of 70 to 100% and a temperature of 15 to 90 ° C. It is desirable to lead to. By setting the film after casting to the above-mentioned conditions, it is possible to improve the hole area ratio on the air side surface of the film. The reason why the open area ratio is improved is considered to be that moisture is infiltrated from the surface of the film into the interior by being placed under humidification, thereby efficiently promoting phase separation of the polymer solution.

  The coagulation liquid used in the phase change method may be any solvent that coagulates the polymer component, and is appropriately selected depending on the type of polymer used as the polymer component. For example, polycarbonate resin, polyarylate resin, etc. Any solvent that coagulates the resin may be used, for example, water; alcohols such as monohydric alcohols such as methanol and ethanol, polyhydric alcohols such as glycerin; water-soluble polymers such as polyethylene glycol, and water-soluble coagulations such as mixtures thereof Liquid etc. can be used. In order to remove the coagulant from the porous film after solidification, a volatile solvent or water is desirable, and a boiling point of, for example, less than 120 ° C. is preferable. Particularly preferred coagulating liquid is water alone or a mixed liquid of water and a volatile solvent (for example, a monohydric alcohol).

  As a preferable embodiment, for example, a total of 100 parts by weight of a resin (for example, at least one resin selected from polycarbonate resins and polyarylate resins) 5 to 30% by weight and a solvent 70 to 95% by weight is soluble in water. When casting a polymer solution in which 1 to 40 parts by weight of a polymer is dissolved, and a polymer solution in which the remainder is a good solvent of the resin, the film is subjected to a relative humidity of 70 to 100% and a temperature of 15 to 90 ° C. For 1 to 600 seconds (preferably 5 to 300 seconds, particularly preferably 30 to 120 seconds) in an atmosphere, and then led (or brought into contact) with a water-soluble coagulating liquid containing a non-solvent of the resin. .

  The film led to the coagulation liquid and deposited can be directly dried on the substrate, but in the present invention, the film led to the coagulation liquid is transferred from the substrate onto the support and dried. It is preferable. According to such a process, since a drying speed is quick compared with the case of the film obtained by drying on a base material, a porous film can be obtained efficiently and it is preferable. The support is made of a material having resistance to coagulation liquid, and has a large number of micropores on the surface that comes into contact with the film, in particular, the permeability that can permeate the coagulation solvent at an appropriate speed. Those having the following are preferred. Such a support has, for example, an air permeability of less than 1000 seconds / 100 cc (preferably less than 100 seconds / 100 cc), a film thickness of 5 to 1000 μm (preferably 50 to 500 μm), and a thickness of 0. The pores of 01 to 10 μm (preferably 0.03 to 1 μm) are dispersed with sufficient density. Specifically, a nonwoven fabric or a porous film made of a polyolefin such as polyester, polyamide, polyethylene, and polypropylene, cellulose, Teflon (registered trademark), or the like can be used. In addition, the composite film | membrane which has a porous film | membrane on the at least single side | surface of the said base material can be obtained by drying the film which was guide | induced to said coagulating liquid and deposited on a base material as it is.

  According to the above method, for example, a resin such as a polycarbonate-based resin or a polyarylate-based resin having a large number of communicating micropores (for example, a resin including a structural unit main structural unit corresponding to bisphenols such as bisphenol A). The average pore diameter of the micropores is 0.01 to 10 μm, and the average pore diameter A of the micropores on one side of the porous film and the micropores on the other side It is possible to produce a porous film in which the average pore diameter B of the pores satisfies the relationship of 0.1 ≦ A / B ≦ 10, the porosity is 30 to 80%, and the tensile strength is 2 MPa or more.

  In addition, the porous film of the present invention has a feature that it has excellent liquid absorbency. In general, it is known that the surface of a porous film excellent in liquid absorbency has a very low contact angle. The porous film of the present invention has, for example, a contact angle within 1000 μsec of 60 ° or less when a change in contact angle is measured by dropping 1 μl of a solution having a viscosity of 0.00001 to 1 Pa · s onto the film surface, Preferably it is 45 degrees or less, More preferably, it is 30 degrees or less.

Further, when the change in the contact angle of the porous film of the present invention was measured according to the same method as described above, when the contact angle θ ₁₀₀ after ₁₀₀ μsec had elapsed and the contact angle θ ₁₀₀₀ after ₁₀₀₀ μsec, θ ₁₀₀₀ / It is preferable that θ ₁₀₀ <0.9. More preferably, θ ₁₀₀₀ / θ ₁₀₀
0.85, especially 0.7 or less. Furthermore, in the porous film of the present invention, θ ₁₀₀₀ / θ ₁₀₀ is preferably less than 0.9, and θ ₁₀₀₀ is preferably 60 ° or less. θ ₁₀₀₀ is preferably 45 ° or less, more preferably 30 ° or less.

  Since the porous film of the present invention has the liquid absorption characteristics as described above, ink and the like are easily absorbed when a conductor wiring is formed on the surface by a printing method. For this reason, it is advantageous in that it has excellent adhesion to the wiring, and ink is diffused on the surface so that the line is less likely to bleed and fine wiring can be easily formed.

  In the present invention, the microporous diameter, porosity, air permeability, openness, and tensile strength of the porous film to be treated are the substrate used, the type and amount of the constituent components of the polymer solution, water, as described above. It is possible to adjust to a desired value by appropriately selecting the amount used, the humidity at the time of casting, the temperature and time, the type of resin constituting the film, and the like.

  The porous film thus obtained may be subjected to heat treatment or film formation treatment as necessary in order to impart desired properties.

  In actual use of the porous film, in addition to being excellent in mechanical strength, finally, heat resistance, chemical resistance, flexibility, hardness, color, ease of manufacture, pore diameter, porosity, There are various requirements such as porous structure, price, strength, chemical properties (hydrophilicity, organophilic solvent property), and all of them must be satisfied in a well-balanced manner. The porous film of the present invention is suitable for a wide range of uses from the above viewpoint. In particular, since the film can be handled alone, workability and productivity can be improved.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. Table 1 shows the results of Examples and Comparative Examples.

[Air permeability]
Measurement was performed according to JIS P8117 using a Gurley's Densometer manufactured by YOSHIMITSU. However, since an apparatus having a measurement area of 1/10 of the standard was used, the standard Gurley value was calculated according to Appendix 1 of JIS P8117.

[Average surface pore size]
From the electron micrograph, the area of any 30 or more holes on the film surface was measured, and the average value was defined as the average hole area Save. Next, it converted into the hole diameter when it assumed that the hole was a perfect circle from the following formula, and the value was made into the average hole diameter. Here, π represents a circumference ratio.
Surface average pore diameter = 2 × (Save / π) ^1/2

[Average surface area porosity]
For the average surface area porosity, an arbitrary 20 × 20 μm area was selected from an electron micrograph of the film surface, and the ratio of the total area of the pores present therein to the whole was calculated. This operation was carried out at any five locations and the average value was determined.

[Porosity]
The porosity of the film was determined by the following formula. Here, V is the volume of the film (cm ³ ), W is the weight (g) of the film, and D is the density (g / cm ³ ) of the film material. For example, from the repeating unit represented by the formula (1) The density of the resulting polycarbonate was 1.2 (g / cm ³ ).
Porosity (%) = 100-100 × W / (V · D)

[Measurement of contact angle]
For the measurement of the contact angle, a contact angle measuring device “Drop Master 700” manufactured by Kyowa Interface Science Co., Ltd. was used. 1 μl of the test solution was dropped on the film surface, and the contact angle and droplet radius of the droplet were measured (see FIG. 1). To the PC porous film (air side surface) obtained in Example 1, (i) distilled water (surface tension 73 dyne / cm), (ii) toluene (surface tension 28.4 dyne / cm), (iii) high viscosity When an aqueous solution [an aqueous solution in which 2.0% by weight of Ernest gum (a carboxymethyl cellulose resin manufactured by Daicel Chemical Industries, Ltd.) was added to distilled water] was dropped, the elapsed time after dropping and the contact angle θ The relationship is shown in FIG. Further, Table 2 shows the physical properties of the liquids (i) to (iii) and the contact angles when 100 μsec and 1000 μsec have elapsed after dropping.

Example 1
A polycarbonate resin (PC) containing a repeating unit represented by the formula (1) [trade name “Caliver 200-3” manufactured by Sumitomo Dow Co., Ltd.] was dissolved in N-methyl-2-pyrrolidone (NMP). A solution having a polycarbonate resin concentration of 20% by weight was obtained. 30 parts by weight of polyvinylpyrrolidone (PVP) (molecular weight 55,000: water-soluble polymer) was added to 100 parts by weight of this solution and dissolved to prepare a polymer solution. The polymer solution was coated (cast) on a polyethylene terephthalate (PET) film substrate with a gap adjusted so that the thickness after drying was about 50 μm using a film applicator.
The cast film was held for 60 seconds in an atmosphere of 25 ° C. and 100% RH, and then immersed in water to be solidified. Next, using a polypropylene (PP) non-woven fabric (support: air permeability of less than 1 sec / 100 cc, film thickness of 260 μm), the film was transferred onto the support, and the whole support was dried to obtain a porous film. .
The obtained film had a tensile strength of 9.8 MPa and a tensile elongation of 10%. When the membrane structure was observed, the average pore diameter A of the micropores on the air side surface was 2.4 μm, the average pore diameter B of the substrate side surface was 3.3 μm, and A / B = 0.73. It was confirmed that it was a film having. Furthermore, when the surface and cross section of the film were observed with an electron microscope (SEM), as shown in FIG. 1, both the air side surface (A) and the substrate side surface (B) of the film had micropores having uniform pore diameters. It was formed in a dispersed manner, the inside (c) was almost homogeneous, and there existed micropores having communication throughout the entire area. The porosity of the film was 70%. Thus, a porous film having high strength and uniform pores was obtained.

Example 2
A polycarbonate resin (similar to Example 1) was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a solution having a polycarbonate resin concentration of 20% by weight. To 100 parts by weight of this solution, 10 parts by weight of polyvinylpyrrolidone (molecular weight 360,000) was added and dissolved to prepare a polymer solution. This polymer solution was cast on a PET film substrate with a gap adjusted so that the thickness after drying was about 50 μm using a film applicator.
The cast film was held at 50 ° C. in a 100% RH atmosphere for 120 seconds, and then immersed in water to be solidified. Subsequently, the film was transferred onto a non-woven fabric made of PP (similar to Example 1), and the whole support was dried to obtain a porous film.
The obtained film had a tensile strength of 11.2 MPa and a tensile elongation of 14%. When the film structure was observed, the average pore diameter A of the pores existing on the surface was 2.3 μm, the back surface (base material side) average pore diameter B was 3.5 μm, and A / B = 0.66, and the front and back surfaces were uniform. It was confirmed that the film had a pore size. The porosity of the film was 68%. Thus, a porous film having high strength and uniform pores was obtained.

Example 3
A polycarbonate resin (similar to Example 1) was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a solution having a polycarbonate resin concentration of 20% by weight. 10 parts by weight of polyvinylpyrrolidone (molecular weight 55,000) was added to 100 parts by weight of this solution and dissolved to prepare a polymer solution. This polymer solution was cast on a PET film substrate with a gap adjusted so that the thickness after drying was about 50 μm using a film applicator.
The cast film was held at 50 ° C. in a 100% RH atmosphere for 120 seconds, and then immersed in water to be solidified. Subsequently, the film was transferred onto a non-woven fabric made of PP (similar to Example 1), and the whole support was dried to obtain a porous film.
The obtained film had a tensile strength of 6.5 MPa and a tensile elongation of 36%. When the film structure was observed, the average pore diameter A of the pores existing on the surface was 0.5 μm, the back surface (base material side) average pore diameter B was 2.7 μm, and A / B = 0.19. It was confirmed that the film had a pore size. The porosity of the film was 75%. Thus, a porous film having high strength and uniform pores was obtained.

Example 4
A polycarbonate resin (similar to Example 1) was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a solution having a polycarbonate resin concentration of 25% by weight. 20 parts by weight of polyvinylpyrrolidone (molecular weight 55,000) was added to 100 parts by weight of this solution and dissolved to prepare a polymer solution. This polymer solution was cast on a PET film substrate with a gap adjusted so that the thickness after drying was about 50 μm using a film applicator.
The cast film was held at 50 ° C. in a 100% RH atmosphere for 60 seconds, and then immersed in water to be solidified. Subsequently, the film was transferred onto a non-woven fabric made of PP (similar to Example 1), and the whole support was dried to obtain a porous film.
The obtained film had a tensile strength of 9.8 MPa and a tensile elongation of 22%. When the film structure was observed, the average pore diameter A of the pores existing on the front surface was 1.6 μm, the back surface (base material side) average pore diameter B was 2.2 μm, and A / B = 0.73. It was confirmed that the film had a pore size. The porosity of the film was 66%. Thus, a porous film having high strength and uniform pores was obtained.

Comparative Example 1
A polycarbonate resin (similar to Example 1) was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a solution having a polycarbonate resin concentration of 20% by weight. This polymer solution was cast on a PET film substrate with a gap adjusted so that the thickness after drying was about 50 μm using a film applicator.
The cast film was held at 50 ° C. in a 100% RH atmosphere for 60 seconds, and then immersed in water to be solidified. Subsequently, the film was transferred onto a non-woven fabric made of PP (similar to Example 1), and the whole support was dried to obtain a porous film.
The film obtained had a tensile strength of 1.6 MPa and a tensile elongation of less than 2%. When the film structure was observed, the average pore diameter A of the pores existing on the surface was 0.9 μm, the back surface (base material side) average pore diameter B was 11.2 μm, and A / B = 0.08, and the front and back surfaces were uniform. It was confirmed that the film had a pore size. The porosity of the film was 57%. Thus, only a film with non-uniform front and back and low strength was obtained.

Comparative Example 2
A polycarbonate resin (similar to Example 1) was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a solution having a polycarbonate resin concentration of 35% by weight. To 100 parts by weight of this solution, 10 parts by weight of polyvinylpyrrolidone (molecular weight 55,000) was added and dissolved, and an attempt was made to prepare a polymer solution. No membrane was obtained.

Comparative Example 3
The same polymer solution as in Example 1 was prepared, and this polymer solution was cast on a PET film as a substrate by adjusting the gap so that the thickness after drying was about 50 μm using a film applicator.
The cast film was held at 50 ° C. and 10% RH for 300 seconds. Thereafter, the film was immersed in water to be solidified, but was dissolved and a film was not obtained.

Comparative Example 4
A polycarbonate resin (similar to Example 1) was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a solution having a polycarbonate resin concentration of 15% by weight. To 100 parts by weight of this solution, 45 parts by weight of polyvinylpyrrolidone (molecular weight 55,000) was added and dissolved to prepare a polymer solution. This polymer solution was cast on a PET film substrate with a gap adjusted so that the thickness after drying was about 50 μm using a film applicator.
The cast film was held at 50 ° C. in a 100% RH atmosphere for 60 seconds. Thereafter, the film was immersed in water to be solidified, but was dissolved and a film was not obtained.

(A) is the air side surface of the porous film obtained in Example 1, (b) is the substrate side surface, and (c) is a cross-sectional electron microscope (SEM) photograph. 2 is an electron microscope (SEM) photograph of a cross section of a porous film obtained in Comparative Example 1. It is explanatory drawing of a contact angle and a droplet radius. It is a graph which shows the relationship between the elapsed time after dripping, and a contact angle at the time of dripping various liquids to the PC porous film surface (air side surface) obtained in Example 1. FIG.

Claims (12)

  There are many micropores having communication properties, the average pore diameter of the micropores is 0.01 to 10 μm, and the average pore diameter A of the micropores on one side of the porous film and the micropores on the other side A porous film having an average pore diameter B of 0.1 ≦ A / B ≦ 10, a porosity of 30 to 80%, and a tensile strength of 2 MPa or more.   2. The porous film according to claim 1, comprising a material mainly composed of a polycarbonate resin or a polyarylate resin.   The porous film according to claim 2, comprising a material mainly composed of a polycarbonate resin or a polyarylate resin containing a structural unit corresponding to bisphenol A as a main structural unit.   The porous film according to claim 1, wherein the porous film has a thickness of 5 to 200 μm.   A porous film made of a material mainly composed of a polycarbonate-based resin or a polyarylate-based resin and having a lot of communicating micropores, and 1 μl of a solution having a viscosity of 0.00001 to 1 Pa · s on the surface of the porous film Is a porous film having a contact angle within 1000 μsec of 60 ° or less. A porous film made of a material mainly composed of a polycarbonate-based resin or a polyarylate-based resin and having a lot of communicating micropores, and 1 μl of a solution having a viscosity of 0.00001 to 1 Pa · s on the surface of the porous film , And a contact angle θ ₁₀₀ after ₁₀₀ μsec and a contact angle θ ₁₀₀₀ after ₁₀₀₀ μsec, θ ₁₀₀₀ / θ ₁₀₀ <0.9. The porous film according to claim 6, wherein θ ₁₀₀₀ is 60 ° or less.   A polymer solution composed of at least one resin selected from a polycarbonate-based resin and a polyarylate-based resin, a solvent, and a water-soluble polymer is cast into a film on a substrate, and is a phase separation tank having a humidity of 70 to 100%. The method for producing a porous film according to any one of claims 1 to 7, wherein the porous film according to any one of claims 1 to 7 is obtained by phase separation for ~ 600 seconds and then guiding to a coagulating liquid.   Furthermore, the manufacturing method of the porous film of Claim 8 which transcribe | transfers the film led to the coagulating liquid from a base material on a support body, and attach | subjects it to drying.   The method for producing a porous film according to claim 9, wherein the support is made of a material having coagulation liquid resistance, and a large number of micropores are present on the surface in contact with the film.   The polymer solution is 1 to 40 parts by weight of a water-soluble polymer in 100 parts by weight of a solution comprising 5 to 30% by weight of at least one resin selected from polycarbonate resins and polyarylate resins and 70 to 95% by weight of a solvent. The method for producing a porous film according to any one of claims 8 to 10, which is a dissolved solution.   The weight ratio of at least one resin (a) selected from polycarbonate resin and polyarylate resin contained in the polymer solution to the water-soluble polymer (b) is 0.1 ≦ (b) / (a) ≦ 5 The method for producing a porous film according to any one of claims 8 to 11, which satisfies a relationship of 0.0.