Hydrophilic porous film and production method of the same

Abstract

To provide a hydrophilic porous film where the surface is uniformly hydrophilic and high permeability can be obtained when used as a liquid filter.SOLUTION: In a hydrophilic porous film whose main component material is a resin, the resin contains polyolefin as a main component. The resin is provided with a hydrophilic group containing at least one of a hydroxy group and a carboxy group and an amino group.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a hydrophilic porous film and a method for producing the same.

Background Art

[0002] In recent years, with the evolution of electronic devices such as smartphones, the requirements for the production of state-of-the-art semiconductor devices have become increasingly stringent. The technological progress of various wafer defect inspection devices in recent years has also been remarkable, and minute defects that could not be detected until now have come to be detected. Along with this, the role of filters for defect reduction has become even more important.

[0003] Currently, nylon filters are used as filtration filters for photoresists in the lithography process in semiconductor manufacturing. Since nylon filters have hydrophilic groups, they can effectively adsorb and remove poorly soluble components in photoresists. In addition, since they exhibit a positive zeta potential, they have the characteristic of being able to collect anionic fine particles smaller than the pore diameter by electrostatic attraction. However, nylon has a problem in that it is difficult to produce a filter medium having a pore diameter capable of removing minute impurities of about 10 nm. Therefore, the development of a filter medium that can collect finer impurities and satisfy recent high-level requirements in place of nylon filters is expected. On the other hand, polyolefin porous films can be produced into porous films having pores with a low pore diameter capable of removing minute impurities of about 10 nm, in addition to excellent mechanical strength and chemical resistance. Further, since the hydrophilized polyolefin porous film has hydrophilicity and water absorbency, it is expected to be used in devices that perform functions such as water absorption, retention, diffusion, and permeation. As a method for hydrophilizing a polyolefin porous film by introducing a hydrophilic group, for example, a method of exposing the polyolefin porous film in a mixed gas atmosphere of fluorine and oxygen to hydrophilize it is described in Patent Documents 1 and 2.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2021-87919 [Patent Document 2] Japanese Patent Application Laid-Open No. 7-246322 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] However, in the method for hydrophilizing a polyethylene porous film by direct fluorination described in Patent Documents 1 and 2, since the introduction of hydrophilic groups is carried out by moisture in the air, the hydrophilicity of the pore wall surfaces where air hardly contacts is insufficient, and sufficient water permeability cannot be obtained when used as a filtration membrane for liquid filters. Further, in the above hydrophilized polyethylene porous film, since the zeta potential is presumed to be negative, there is a problem that the collection effect of anionic fine particles cannot be obtained.

[0006] Therefore, in view of such problems, the present invention provides a hydrophilic porous film having at least one of a hydroxy group and a carboxy group as a hydrophilic group, the surface and pore wall surfaces of the hydrophilic porous film being hydrophilic, showing sufficient water permeability when used as a filtration membrane for liquid filters, and further having an amino group so that the zeta potential of the film surface becomes positive and having a collection effect on anionic fine particles. [Means for Solving the Problems]

[0007] In order to solve such problems, the present invention has the following features. That is, (1) A hydrophilic porous film whose main constituent material is a resin, the resin containing polyolefin as a main component, the resin being a hydrophilic porous film having a hydrophilic group containing at least one of a hydroxy group and a carboxy group and an amino group. (2) The above hydrophilic porous film preferably has an oxygen atom concentration / carbon atom concentration (O / C), which is the ratio of the oxygen atom concentration to the carbon atom concentration, in the range of 0.05 to 0.20, and a nitrogen atom concentration / carbon atom concentration (N / C), which is the ratio of the nitrogen atom concentration to the carbon atom concentration, in the range of 0.01 to 0.10. (3) The above hydrophilic porous film preferably has an average pore diameter in the range of 0.01 μm or more and 0.1 μm or less. Further, the following method for producing the above hydrophilic porous film is preferably employed. (4) A method for producing a hydrophilic porous film according to any one of (1) to (3), which includes, in this order, step I of exposing a polyolefin porous film to a mixed gas of fluorine and oxygen, step II of exposing the polyolefin porous film to the atmosphere, and step III of immersing the polyolefin porous film in an aqueous solution containing at least one of a compound having one or more functional groups selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group and a quaternary ammonium salt. Further, the above hydrophilic porous film is preferably used for the following. (5) A liquid filtration filter provided with the above hydrophilic porous film.

Advantages of the Invention

[0008] According to the present invention, since the hydrophilic porous film has a hydroxy group and a carboxy group as hydrophilic groups and the surface and pore wall surface of the hydrophilic porous film are hydrophilic, it exhibits sufficient water permeability when used as a filtration membrane for a liquid filter. Further, since it has an amino group, the zeta potential of the film surface becomes positive, and a hydrophilic porous film capable of collecting anionic fine particles when used as a filter can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail.

[0011] The hydrophilic porous film of the present invention has a resin as the main constituent material, the resin contains polyolefin as a main component, and the resin is a hydrophilic porous film having a hydrophilic group containing at least one of a hydroxy group and a carboxy group and an amino group.

[0012] Here, the configuration of the hydrophilic porous film of the present invention will be described with reference to FIG. 1. The hydrophilic porous film (101) has a large number of pores (102), and since the pores are through-holes, gas and liquid can permeate therethrough. That is, it has air permeability and water permeability. Further, since the hydrophilic porous film has at least one of a hydroxy group and a carboxy group in the resin as the main constituent material, the surface portion (103) constituting both surfaces of the hydrophilic porous film and the wall surface (104) of the pores have good hydrophilicity to water. In addition, since it has an amino group in addition to the two functional groups, the zeta potential on the surface of the hydrophilic porous film is strengthened in the positive direction. As a result, the water permeability of the hydrophilic porous film becomes excellent, and when used as a filter, anion fine particles can be collected more efficiently. The resin, which is the main constituent material of the hydrophilic porous film of the present invention, is polyolefin. Since the main constituent material of the hydrophilic porous film is polyolefin, the manufacturing cost is low, and further, since it melts with heat, it is easy to mold and has excellent chemical resistance and water resistance. Examples of the polyolefin used for the hydrophilic porous film include homopolymers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene, copolymers of these olefins, or blends of the above homopolymers and the above copolymers. Further, since high physical strength can be obtained when the chemical resistance and high porosity are achieved with a thin film, the main constituent material is preferably polyethylene.

[0013] It is important that the resin, which is the main constituent material of the hydrophilic porous film of the present invention, has a hydrophilic group containing at least one of a hydroxy group and a carboxy group and an amino group. The hydrophilic group is a general term for a group that ionizes in water to become an ion or a functional group that hydrates by hydrogen bonding without ionization, and in the present invention, mainly refers to a hydroxy group and a carboxy group. By the hydrophilic group containing either one of the hydroxy group and the carboxy group, the resin exhibits high hydrophilicity. Further, in the present invention, the hydrophilic group is a concept that does not include an amino group. Further, by providing an amino group in addition to the above hydrophilic group, the hydrophilicity is further improved, the zeta potential on the surface of the hydrophilic porous film becomes positive, and anion fine particles can be collected, increasing the usefulness of the hydrophilic porous film of the present invention as a liquid filtration filter.

[0014] The hydrophilic porous film of the present invention preferably has an oxygen atom concentration / carbon atom concentration (O / C), which is the ratio of the oxygen atom concentration to the carbon atom concentration, in the range of 0.05 to 0.20, and a nitrogen atom concentration / carbon atom concentration (N / C), which is the ratio of the nitrogen atom concentration to the carbon atom concentration, in the range of 0.01 to 0.10. The atomic concentration is measured by X-ray photoelectron spectroscopy (XPS / ESCA). When the (O / C) and the (N / C) satisfy the above ranges, the hydrophilic porous film has sufficient hydrophilicity not only on the surface but also on the pore wall surface and has sufficient water permeability. In addition, it exhibits high mechanical strength and an efficient anion microparticle collection effect. The preferred range of the (O / C) is 0.07 to 0.18, more preferably 0.09 to 0.16. When the (O / C) is 0.07 or more, the hydrophilicity of the surface and the pore wall surface of the hydrophilic porous film becomes better, and higher water permeability of the hydrophilic porous film can be exhibited. When the (O / C) is 0.18 or less, the cleavage of the main chain of the polyolefin, which is the main component of the hydrophilic porous film, is more suppressed, and the mechanical strength of the hydrophilic porous film can be maintained higher. On the other hand, the preferred range of the (N / C) is 0.03 to 0.09, more preferably 0.05 to 0.08. When the (N / C) is 0.03 or more, the hydrophilicity of the surface and the pore wall surface of the hydrophilic porous film becomes better, higher water permeability of the hydrophilic porous film is exhibited, the zeta potential of the surface of the hydrophilic porous film increases in the positive direction, and anion microparticles can be collected more efficiently. When the (N / C) is 0.09 or less, the cleavage of the main chain of the polyolefin, which is the main component of the hydrophilic porous film, is more suppressed, and the mechanical strength of the hydrophilic porous film can be maintained higher.

[0015] In the hydrophilic porous film of the present invention, the average pore diameter is preferably 0.01 μm or more and 0.10 μm or less, and more preferably 0.02 μm or more and 0.05 μm or less. When the average pore diameter is equal to or greater than the lower limit of the preferred range, the hydrophilic porous film exhibits higher water permeability. On the other hand, when the average pore diameter is equal to or less than the upper limit of the preferred range, when the hydrophilic porous film is used as a liquid filter, finer substances can be collected.

[0016] The method for producing the hydrophilic porous film of the present invention preferably includes a step of exposing a polyolefin porous film to a mixed gas of fluorine and oxygen. By exposing the polyolefin porous film to the mixed gas of fluorine and oxygen, the chemical bonds of the polyolefin are partially broken by the corrosive action of the fluorine gas on the surface portion and the pore wall surfaces of the polyolefin porous film, and other elements and functional groups can be bonded, that is, an active state is achieved. It is preferable to quickly expose the polyolefin porous film in the active state to the atmosphere. By exposing it to the atmosphere, the film surface reacts with water in the atmosphere to generate hydrophilic groups. Further, by immersing the polyolefin porous film after exposure to the atmosphere in an aqueous solution containing at least one of a compound having one or more functional groups selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group and a quaternary ammonium salt, the aqueous solution penetrates into the interior of the pores, and hydrophilic groups and amino groups are mainly generated on the pore wall surfaces. Through these steps, a hydrophilic porous film having hydrophilic surfaces and pore wall surfaces is obtained.

[0017] A method of exposing the above-mentioned mixed gas to a polyolefin porous film will be described below. The partial pressure of fluorine gas in the mixed gas is preferably 0.1 to 0.2 atm, more preferably 0.13 to 0.16 atm. By setting the partial pressure of fluorine gas within the above-mentioned range, the fluorine gas and the polyolefin porous film react sufficiently, and the chemical bonds of the polyolefin are easily broken on the surface portion and the pore wall surface of the polyolefin porous film. Furthermore, by suppressing the excessive progress of the reaction between the polyolefin porous film and the fluorine gas, the mechanical strength of the hydrophilic porous film becomes excellent.

[0018] Also, the partial pressure of oxygen gas in the mixed gas is preferably 0.3 to 0.8 atm, more preferably 0.5 to 0.6 atm. By setting the partial pressure of oxygen gas within the above-mentioned range, it is possible to suppress the bonding of hydrophobic fluorine elements to the sites where the chemical bonds of the polyolefin are broken, and the hydrophilicity of the hydrophilic porous film can be increased.

[0019] In addition to fluorine gas and oxygen gas, the mixed gas may contain an inert gas such as nitrogen gas, carbon dioxide gas, or argon gas.

[0020] Also, the time for exposing the polyolefin porous film to the mixed gas, that is, the treatment time of the polyolefin porous film with the mixed gas, can be appropriately selected according to the use of the hydrophilic porous film. Specifically, the above treatment time is preferably 5 seconds or more and 30 seconds or less, more preferably 15 seconds or more and 30 seconds or less. By setting the above treatment time to 5 seconds or more, the reaction between the polyolefin porous film and the mixed gas becomes sufficient. On the other hand, by setting the above treatment time to 30 seconds or less, in addition to excellent productivity, it is possible to suppress the excessive progress of the reaction between the polyolefin porous film and the mixed gas, and the mechanical strength of the obtained hydrophilic porous film becomes excellent.

[0021] Regarding the timing of exposing the polyolefin porous film to the atmosphere, it is preferable to expose it to the atmosphere as soon as possible after exposing it to the mixed gas. As described above, by exposing the polyolefin porous film exposed to the mixed gas to the atmosphere, the film surface reacts with the moisture in the atmosphere to form hydrophilic groups. However, if the timing of exposing to the atmosphere is late or not exposed, carbon tetrafluoride generated by the fluorine gas treatment or the low-molecular-weight polyolefin adheres to the surface of the polyolefin porous film, preventing the formation of hydrophilic groups.

[0022] Examples of the aqueous solution containing at least one of a compound having one or more functional groups selected from the group consisting of the primary amino group, secondary amino group, and tertiary amino group and a quaternary ammonium salt include acrylic acid, methacrylic acid, vinyl sulfonic acid derivatives containing primary amine, secondary amine, tertiary amine, and quaternary ammonium salt, allylamine, p-vinylbenzyltrimethylammonium chloride, and the like. More specific examples include 3-(dimethylamino)propyl acrylate, 3-(dimethylamino)propyl methacrylate, N-[3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)propyl]methacrylamide, (3-acrylamidopropyl)trimethylammonium chloride, trimethyl[3-(methacryloylamino)propyl]ammonium chloride, and the like. In addition, the aqueous solution may contain a surfactant such as polyoxyethylene alkyl ether for the purpose of enhancing solubility and permeability in addition to the above compounds.

[0023] The total concentration of the compound having one or more functional groups selected from the group consisting of the primary amino group, secondary amino group, and tertiary amino group and the quaternary ammonium salt in the aqueous solution containing at least one of them is preferably 0.10 to 1.00% by mass, more preferably 0.10 to 0.50% by mass. When the concentration of the aqueous solution is equal to or higher than the lower limit of the preferable range, sufficient hydrophilic groups are introduced into the polyolefin porous film, and excellent water permeability is exhibited. Further, by sufficiently introducing amino groups into the polyolefin porous film, the hydrophilic porous film exhibits an excellent anion microparticle collection effect. On the other hand, when the aqueous solution concentration is equal to or lower than the upper limit of the preferable range, for example, when the hydrophilic porous film is used as a liquid filter, it is possible to suppress the mixing of excessive solute components into the filtrate.

[0024] The time for immersing the polyolefin porous film in an aqueous solution containing at least one of a compound having one or more functional groups selected from the group consisting of the primary amino group, secondary amino group, and tertiary amino group and a quaternary ammonium salt is preferably 30 to 180 seconds, more preferably 30 to 60 seconds. When it is equal to or longer than the lower limit of the preferable range, hydrophilic groups are sufficiently bonded to the polyolefin porous film, and as a result, the water permeability becomes excellent. At the same time, the amount of amino groups introduced into the hydrophilic porous film also becomes sufficient, and as a result, the hydrophilic porous film exhibits an excellent anion microparticle collection effect. On the other hand, when it is equal to or shorter than the upper limit of the preferable range, the productivity becomes excellent.

[0025] It is preferable to immerse the polyolefin porous film in an aqueous solution containing at least one of a compound having one or more functional groups selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group and a quaternary ammonium salt, and then wash the polyolefin porous film with pure water. By washing with pure water, it is possible to remove the solute components that adhered excessively in the step of immersing in the aqueous solution containing at least one of a compound having one or more functional groups selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group and a quaternary ammonium salt. The time for washing with pure water is not particularly limited, but from the viewpoint of productivity, it is preferably 180 seconds or less.

[0026] After washing the polyolefin porous film with pure water, it is preferable to remove moisture in a drying step. In this case, the drying temperature needs to be equal to or lower than the melting point of the polyolefin porous film, preferably 80°C or lower, more preferably 60°C or lower. By setting the drying temperature to be equal to or lower than the preferable temperature, it is possible to suppress deformation due to thermal shrinkage of the obtained hydrophilic porous film.

[0027] The base materials used in the production of the hydrophilic porous film of the present invention, that is, the monomer components constituting the polyolefin porous film, include, for example, ethylene, propylene, 1-butene, 1-pentene, 3-methylpentene-1, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 5-ethyl-1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl-2-norbornene, etc. Examples include homopolymers of these, at least two copolymers selected from the group consisting of these monomer components, blends of these homopolymers and copolymers, etc., but are not limited thereto. In addition to the above monomer components, for example, vinyl alcohol, maleic anhydride, etc. may be copolymerized. Particularly in the case of the porous base material, from the viewpoints of adjusting the porosity, pore diameter, etc., film-forming properties, and reducing production costs, the monomer components constituting the above resin are more preferably one or more selected from the group consisting of ethylene and propylene.

[0028] As a method for forming the polyolefin porous film, a known wet method or a known dry method can be adopted.

[0029] The resin constituting the polyolefin porous film may contain various additives such as an antioxidant, a heat stabilizer, a light stabilizer, a neutralizing agent, an antistatic agent, a lubricant composed of organic particles, and further an antiblocking agent, a filler, and an incompatible polymer as long as the effects of the present invention are not impaired.

[0030] In addition, the hydrophilic porous film of the present invention is suitably used for a liquid filtration filter. This liquid filtration filter may use the hydrophilic porous film of the present invention as a membrane filter in a flat state. Further, the hydrophilic porous film of the present invention may be formed into a pleated shape at regular intervals and filled into a hollow cylindrical molded body to be used as a cartridge filter. Further, in any case of the membrane filter and the cartridge filter, in order to suppress the deformation of the hydrophilic porous film due to the pressure during filtration, the hydrophilic porous film and a reinforcing member may be laminated and used. As the reinforcing member, a mesh of a metal or resin material that can exhibit sufficient water permeability during filtration is preferably used. Further, the hydrophilic porous film of the present invention is suitably used for a liquid filtration filter for collecting very fine substances used in pharmaceutical applications, semiconductor manufacturing processes, etc.

Examples

[0031] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by these examples. The measurement methods used in this example are shown below. Unless otherwise specified, when obtaining a numerical value from the measured value, the number of measurements was set to 2 times, and the average value was adopted as the numerical value.

[0032] 〈Measurement method〉 (1) Concentration of oxygen atoms / Concentration of carbon atoms (O / C) The elemental concentration of the hydrophilic porous film was measured using X-ray photoelectron spectroscopy (XPS / ESCA). The measurement was performed on the film cross-section exposed by oblique cutting by the cryomicrotome method for the sample. The measurement conditions of the X-ray photoelectron spectroscopy (XPS / ESCA) are shown below.

[0033] · XPS apparatus: PHI-QuanteraII manufactured by ULVAC-PHI · X-ray source: AlKα monochromator 1486.6 eV, 25W · Analysis area: 100μmΦ · Analyzer: Using a charge neutralization mechanism (electron neutralization gun, ion beam) The concentration of oxygen atoms / the concentration of carbon atoms (O / C) was calculated by calculating the peak areas of C1s and O1s based on the obtained spectrum, considering the photoionization cross-section (with C1s taken as 1), and applying it to the following formula to calculate O / C. O / C = Peak area of O1s / 2.85 / Peak area of C1s.

[0034] (2) Concentration of nitrogen / concentration of carbon atoms (N / C) Measurement was carried out using X-ray photoelectron spectroscopy (XPS / ESCA) in the same procedure as (1) except for calculating the peak areas of C1s and N1s from the obtained spectrum. Then, the obtained measurement results were applied to the following formula to calculate N / C. N / C = Peak area of N1s / 1.77 / Peak area of C1s.

[0035] (3) Types of hydrophilic groups in the resin contained in the hydrophilic porous film Three specimens of hydrophilic porous film samples with an area of 3 mm 2 or more and being square were prepared. For the first specimen, a gas-phase chemical modification method using trifluoroacetic anhydride was carried out to label the hydroxy groups contained in the specimen. The specimen with the labeled hydroxy groups was introduced into the XPS apparatus in the same manner as (1), and peak fitting was performed on the obtained spectrum. The horizontal axis of the spectrum was corrected with the main peak of the C1s spectrum in the hydrocarbon state (284.6 eV). When a peak was detected near 689 eV in the F1s spectrum, it was determined that the hydrophilic porous film contained hydroxy groups.

[0036] For the second specimen, gas-phase chemical modification was carried out using trifluoroethanol to label the carboxy groups contained in the specimen. The specimen with the labeled carboxy groups was introduced into the XPS apparatus in the same manner as (1), and peak fitting was performed in the same way as the first specimen. When a peak was detected near 689 eV in the F1s spectrum, it was determined that the hydrophilic porous film contained carboxy groups.

[0037] For the third specimen, it was introduced into the XPS apparatus in the same manner as (1), and peak fitting was performed in the same manner as for the first and second specimens. When a peak with a peak top at 399 eV in the N1s spectrum was detected, it was determined that the hydrophilic porous film contained amino groups.

[0038] (4) Average pore diameter The average pore diameter was measured by the Wet pressurization / Dry pressurization method using a palm porometer "CFP-1500 (manufactured by PMI)". The measurement conditions were as follows.

[0039] · Test liquid: Galwick (15.9 DYNES / CM) · Measurement pressure: 500 - 2000 kPa (5) Tensile strength The tensile strength was measured in accordance with JIS K7127 (1999) using TENSILON (registered trademark) UCT-100 (manufactured by Orientec). The measurement method was as follows.

[0040] · Shape: Strip shape with a length of 150 mm and a width of 10 mm in the measurement direction · Initial chuck distance: 50 mm · Tensile speed: 200 mm / min (6) Water permeability The hydrophilic porous film was cut into a diameter of 47 mm and set in a stainless steel tank-type filter holder (manufactured by Merck). Then, 100 ml of pure water was filled in the tank, and a pressure of 70 kPa was applied from the upper part of the tank by compressed air. From 1 minute to 6 minutes after the start of pressurization, the pure water that permeated through the hydrophilic porous film was collected in a beaker. The weight of the collected pure water was measured, and the obtained weight was taken as the water permeability (ml / cm 2 · min).

[0041] (7) Zeta potential (mV) The zeta potential of the hydrophilic porous film was measured by the electrophoresis light scattering method using a zeta potential measurement system ELS-Z (manufactured by Otsuka Electronics Co., Ltd.). A hydrophilic porous film was attached to the upper surface of the cell of a cell unit for flat plate samples (manufactured by Otsuka Electronics Co., Ltd.), and the cell was filled with a 10 mM sodium chloride aqueous solution with a pH of 6 to 7 in which monitor particles (manufactured by Otsuka Electronics) were dispersed. The electrophoresis of the monitor particles was carried out, and the electrophoretic mobility of the monitor particles was measured at seven points between the upper and lower surfaces of the cell. The zeta potential of the hydrophilic porous film was calculated by analyzing the obtained electrophoretic mobility data using the Mori-Okamoto equation and the Smoluchowski equation.

[0042] (8) Composition of hydrophilic porous film The composition of the hydrophilic porous film was measured by infrared absorption spectrum using a Fourier transform infrared spectrophotometer "IR Prestige-21 (manufactured by Shimadzu Corporation)". By comparing the obtained infrared absorption spectrum with a commercially available database, the type of polyolefin was identified. For example, if it is polyethylene, typical polyethylene peaks can be confirmed at 2915, 2850, 1465, 720 cm -1 and if it is polypropylene, it can be identified by whether typical polypropylene peaks can be confirmed at 2955, 2920, 2870, 2840, 1465, 1455, 1375, 720 cm -1 . The measurement conditions were as follows.

[0043] · Unit: ATR method unit (MIRacleA) · Measurement wave number: 400 - 4000 cm -1 (Example 1) As the polyolefin porous film, a polyethylene film with a thickness of 12 μm and an average pore diameter of 0.033 μm was prepared.

[0044] The above-mentioned polyethylene porous film was placed in a reaction vessel, and after evacuating the inside of the reaction vessel to create a vacuum, a mixed gas with a partial pressure of oxygen gas (O2) / fluorine gas (F2) / nitrogen gas (N2) = 0.3 / 0.1 / 0.6 atm was introduced into the reaction vessel. Then, the reaction vessel was left at room temperature (23°C) for 30 seconds to expose the polyethylene porous film to the mixed gas. After that, the inside of the reaction vessel was replaced with nitrogen gas, the substrate was taken out from the reaction vessel, and exposed to the atmosphere. Next, the above-mentioned polyolefin porous film was immersed in an aqueous solution having a concentration of 0.1% by mass of polyallylamine (manufactured by Nitto Boseki Co., Ltd., "PAA01" (registered trademark)) containing at least one of a compound having one or more functional groups selected from the group consisting of primary amino groups, secondary amino groups, and tertiary amino groups and a quaternary ammonium salt, and a surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "Neugen LF-40X") as a reaction catalyst at 0.1% by mass for 60 seconds. Then, it was immersed in pure water for 60 seconds and dried in an oven at 60°C for 1 minute to obtain a hydrophilic porous film. The composition of the obtained hydrophilic porous film is shown in Table 1, and the manufacturing conditions are shown in Table 2. Note that the hydrophilic porous film of Example 1 contained a resin having a hydroxy group, a carboxy group, and an amino group.

[0045] (Example 2) A hydrophilic porous film was obtained in the same manner as in Example 1, except that the exposure time to the mixed gas was changed to 15 seconds. The composition of the obtained hydrophilic porous film is shown in Table 1, and the manufacturing conditions are shown in Table 2. Note that the hydrophilic porous film of Example 2 contained a resin having a hydroxy group, a carboxy group, and an amino group.

[0046] (Example 3) A hydrophilic porous film was obtained in the same manner as in Example 1, except that the concentration of the aqueous solution containing polyallylamine was changed to 0.01% by mass. The composition of the obtained hydrophilic porous film is shown in Table 1, and the manufacturing conditions are shown in Table 2. Note that the hydrophilic porous film of Example 3 contained a resin having a hydroxy group, a carboxy group, and an amino group.

[0047] (Example 4) A hydrophilic porous film was obtained in the same manner as in Example 1, except that the immersion time in the aqueous solution containing polyallylamine was changed to 15 seconds. The composition of the obtained hydrophilic porous film is shown in Table 1, and the production conditions are shown in Table 2. Note that the hydrophilic porous film of Example 4 contained a resin having a hydroxy group, a carboxy group, and an amino group.

[0048] (Example 5) A hydrophilic porous film was obtained in the same manner as in Example 1, except that a polyethylene film with a thickness of 16 μm and an average pore diameter of 23 nm was used as the polyolefin porous film. The composition of the obtained hydrophilic porous film is shown in Table 1, and the production conditions are shown in Table 2. Note that the hydrophilic porous film of Example 5 contained a resin having a hydroxy group, a carboxy group, and an amino group.

[0049] (Example 6) A hydrophilic porous film was obtained in the same manner as in Example 1, except that a polypropylene film with a thickness of 20 μm and an average pore diameter of 0.065 μm was used as the polyolefin porous film. The composition of the obtained hydrophilic porous film is shown in Table 1, and the production conditions are shown in Table 2. Note that the hydrophilic porous film of Example 6 contained a resin having a hydroxy group, a carboxy group, and an amino group.

[0050] (Example 7) A hydrophilic porous film was obtained in the same manner as in Example 1, except that no surfactant was mixed when the polyolefin porous film after mixed gas treatment was immersed in the aqueous solution containing polyallylamine. The composition of the obtained hydrophilic porous film is shown in Table 1, and the production conditions are shown in Table 2. Note that the hydrophilic porous film of Example 7 contained a resin having a hydroxy group, a carboxy group, and an amino group.

[0051] (Comparative Example 1) A hydrophilic porous film was obtained in the same manner as in Example 1, except that it was not exposed to the mixed gas. The composition of the obtained hydrophilic porous film is shown in Table 1, and the production conditions are shown in Table 2. Note that the porous film of Comparative Example 1 did not have any of a hydroxy group, a carboxy group, and an amino group.

[0052] (Comparative Example 2) A hydrophilic porous film was obtained in the same manner as in Example 1, except that the step of immersing in an aqueous solution containing polyallylamine was skipped. The composition of the obtained hydrophilic porous film is shown in Table 1, and the production conditions are shown in Table 2. Note that the porous film of Comparative Example 2 had a hydroxy group and a carboxy group, but did not have an amino group.

[0053] (Comparative Example 3) A hydrophilic porous film was obtained in the same manner as in Example 1, except that it was immersed in pure water instead of an aqueous solution containing polyallylamine. The composition of the obtained hydrophilic porous film is shown in Table 1, and the production conditions are shown in Table 2. Note that the porous film of Comparative Example 3 had a hydroxy group and a carboxy group, but did not have an amino group.

[0054] (Comparative Example 4) A hydrophilic porous film was obtained in the same manner as in Example 5, except that it was immersed in pure water instead of an aqueous solution containing polyallylamine. The composition of the obtained hydrophilic porous film is shown in Table 1, and the production conditions are shown in Table 2. Note that the porous film of Comparative Example 4 had a hydroxy group and a carboxy group, but did not have an amino group.

[0055] (Comparative Example 5) A hydrophilic porous film was obtained in the same manner as in Example 7, except that it was immersed in pure water instead of an aqueous solution containing polyallylamine. The composition of the obtained hydrophilic porous film is shown in Table 1, and the production conditions are shown in Table 2. Note that the porous film of Comparative Example 5 had a hydroxy group and a carboxy group, but did not have an amino group.

[0056] Table 3 shows the evaluation results for the hydrophilic porous films of Examples 1 to 7 and Comparative Examples 1 to 5. Each hydrophilic porous film described in Examples 1 to 7 is a hydrophilic porous film whose main constituent material is a resin. The resin contains polyolefin as a main component and has a hydrophilic group containing at least one of a hydroxy group and a carboxy group and an amino group. Therefore, it exhibits high water permeability and high mechanical strength, and since the zeta potential is positive, it is expected to have an anion microparticle collection effect. On the other hand, the hydrophilic porous film described in Comparative Example 1 does not have any functional groups of hydroxy group, carboxy group, or amino group, so it has low water permeability and shows a negative zeta potential. Also, the hydrophilic porous films described in Comparative Examples 2 to 5 have hydroxy groups and carboxy groups but do not have amino groups, so they show a negative zeta potential.

[0057] Examples 1 to 4 exhibit higher water permeability because they have a larger average pore diameter compared to the hydrophilic porous films described in Examples 5 and 6. Also, in Example 7, unlike Examples 1 to 6, a surfactant serving as a catalyst is not added, and there is a considered un-hydrophilized portion, so the water permeability is slightly decreased.

[0058] Example 2 exhibits a higher tensile strength compared to the hydrophilic porous films described in Examples 1, 3, 4, and 7. This is presumably because, in the manufacturing method of the hydrophilic porous film, the treatment time of the fluorine and oxygen mixed gas is short, so the damage suffered by the hydrophilic porous film due to the erosion of the fluorine gas is small.

[0059] Examples 1, 2, 5, and 6 exhibit a higher zeta potential compared to the other examples. This is presumably because the immersion of the porous film in the aqueous solution containing polyallylamine is sufficient, and the amino groups are satisfactorily introduced into the hydrophilic porous film.

[0060]

Table 1

[0061]

Table 2

[0062]

Table 3

Explanation of Symbols

[0063] 101. Hydrophilic Porous Film 102. Pore 103. Surface 104. Wall Surface of Pore

Industrial Applicability

[0064] In addition to the excellent mechanical strength and chemical resistance derived from polyolefin, the hydrophilic porous film of the present invention has water permeability and water absorbency, and thus is useful as a filter filtration material. In addition, since it has an amino group as a hydrophilic group, depending on the type of amino group it has, it can selectively capture anions such as mineral acids such as HCl and H2SO4, salts of weak bases such as NH4Cl, and Cl - and SO4 - It is also expected to have the effect of being able to selectively capture anions such as. The filter filtration material is useful as a filtration filter for water treatment, semiconductor use, membrane bioreactor use, industrial liquid filtration, deaeration, gas dust removal, chemical filter use, and clothing use.

Claims

1. A hydrophilic porous film whose main constituent material is resin, wherein the resin contains polyolefin as a main component, and the resin has a hydrophilic group containing at least one of a hydroxy group and a carboxy group and an amino group, the hydrophilic porous film.

2. The hydrophilic porous film according to Claim 1, wherein the ratio of the concentration of oxygen atoms to the concentration of carbon atoms, which is the ratio of the concentration of oxygen atoms / the concentration of carbon atoms (O / C), is 0.05 to 0.20, and the ratio of the concentration of nitrogen atoms to the concentration of carbon atoms, which is the ratio of the concentration of nitrogen atoms / the concentration of carbon atoms (N / C), is 0.01 to 0.

10.

3. The hydrophilic porous film according to Claim 1, having an average pore diameter of 0.01 μm or more and 0.10 μm or less.

4. A method for producing a hydrophilic porous film according to any one of (1) to (3), comprising, in this order, step I of exposing a polyolefin porous film to a mixed gas of fluorine and oxygen, step II of exposing the polyolefin porous film to the atmosphere, and step III of immersing the polyolefin porous film in an aqueous solution containing at least one of a compound having one or more functional groups selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group and a quaternary ammonium salt.

5. A liquid filtration filter comprising the hydrophilic porous film according to Claim 1.

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