Method for producing polyamide resin composition film, polyamide resin composition film, and method for producing porous polyamide film

Abstract

The present invention relates to a method for producing a polyamide resin composition film, a polyamide resin composition film, and a method for producing a porous polyamide film. Provided are: a polyamide resin composition film capable of providing a porous polyamide film having a fine pore diameter and a fine pore shape controlled; a method for producing the polyamide resin composition film; and a method for producing a porous polyamide film having a fine pore diameter and a fine pore shape controlled using the aforementioned polyamide resin composition film. A porous polyamide film is produced by removing inorganic fine particles from a polyamide resin composition film produced by a method comprising: melt-kneading a thermoplastic polyamide resin and a specific amount of spherical inorganic fine particles to obtain a thermoplastic polyamide resin composition in which the inorganic fine particles are dispersed in the thermoplastic polyamide resin; and subjecting the polyamide resin composition to film formation by melt processing to obtain a polyamide resin composition film.

Description

Technical Field

[0001] This invention relates to a method for manufacturing polyamide resin composition membranes, and a method for manufacturing polyamide resin composition membranes and porous polyamide membranes. Background Technology

[0002] Various porous membranes have long been used as filters for separating gases or liquids.

[0003] Filter membranes, which remove impurities from gases or liquids, are generally made of materials such as nylon, polyethylene, polypropylene, and PTFE. For example, filter membranes using materials such as nylon are known (e.g., Patent Document 1).

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 55-008887 Summary of the Invention

[0005] The problem that the invention aims to solve Patent Document 1 describes a polyamide resin porous membrane manufactured using a phase separation method. The phase separation method utilizes external stimuli such as cooling, contact with a non-solvent, solvent evaporation, and polymerization chemical reactions. Therefore, it presents the problem of difficulty in controlling the pore size and shape of the porous membrane.

[0006] The present invention was made in view of the above-mentioned problems, and its object is to provide: a polyamide resin composition membrane capable of supplying a porous polyamide membrane with controllable pore size and pore shape; a method for manufacturing the polyamide resin composition membrane; and a method for manufacturing a porous polyamide membrane using the aforementioned polyamide resin composition membrane with controllable pore size and pore shape.

[0007] Methods for solving problems The inventors of this application have discovered that a porous polyamide membrane can be manufactured by removing inorganic particles from a polyamide resin composition membrane produced using a method comprising: melt-blending a thermoplastic polyamide resin with a specific amount of spherical inorganic particles to obtain a thermoplastic polyamide resin composition in which inorganic particles are dispersed; and film-forming the polyamide resin composition by melt processing to obtain a polyamide resin composition membrane. This solves the aforementioned problems, thus completing the present invention. More specifically, the present invention provides the following methods.

[0008] The first aspect of the present invention is a method for manufacturing a polyamide resin composition film, the method comprising: A thermoplastic polyamide resin and inorganic microparticles are melt-blended to obtain a thermoplastic polyamide resin composition in which inorganic microparticles are dispersed in the thermoplastic polyamide resin; and A polyamide resin composition film is obtained by melt processing to form a film from the polyamide resin composition. Inorganic particles are spherical in shape. The ratio of the mass of inorganic microparticles to the mass of the thermoplastic polyamide resin composition is more than 50% by mass and less than 70% by mass.

[0009] The second aspect of the present invention is a polyamide resin composition film, which is formed from a thermoplastic polyamide resin composition in which inorganic microparticles are dispersed in a thermoplastic polyamide resin. Inorganic particles are spherical in shape. The ratio of the mass of inorganic microparticles to the mass of the thermoplastic polyamide resin composition is more than 50% by mass and less than 70% by mass.

[0010] The third aspect of the present invention is a method for manufacturing a porous polyamide membrane, the aforementioned method comprising: The polyamide resin composition film involved in the first method is obtained; and Remove inorganic particles from polyamide resin composition membranes.

[0011] Invention Effects According to the present invention, it is possible to provide: a polyamide resin composition membrane capable of supplying a porous polyamide membrane with controlled pore size and pore shape; a method for manufacturing the polyamide resin composition membrane; and a method for manufacturing a porous polyamide membrane using the aforementioned polyamide resin composition membrane with controlled pore size and pore shape. Detailed Implementation

[0012] Method for manufacturing polyamide resin composition films A method for manufacturing a polyamide resin composition film includes: A thermoplastic polyamide resin and inorganic microparticles are melt-blended to obtain a thermoplastic polyamide resin composition in which inorganic microparticles are dispersed in the thermoplastic polyamide resin; and A polyamide resin composition film is obtained by melt processing to form a film from a thermoplastic polyamide resin composition.

[0013] Inorganic particles are spherical in shape.

[0014] The ratio of the mass of inorganic microparticles to the mass of the thermoplastic polyamide resin composition is more than 50% by mass and less than 70% by mass.

[0015] Inorganic particles are removed from the polyamide resin composition membrane manufactured by the above method according to the method described later, thereby enabling the manufacture of the porous polyamide membrane described later.

[0016] The porous polyamide membrane has spherical pores, which are the same shape as the spherical inorganic microparticles, as micropores. That is, the shape of the micropores in the porous polyamide membrane is controlled to be spherical by using spherical inorganic microparticles. In addition, the micropore size in the porous polyamide membrane is controlled by appropriately selecting the particle size of the spherical inorganic microparticles.

[0017] Hereinafter, the following process will also be referred to as the melt mixing process: The thermoplastic polyamide resin and inorganic microparticles are melt-mixed to obtain a thermoplastic polyamide resin composition in which inorganic microparticles are dispersed in the thermoplastic polyamide resin.

[0018] The following process is also referred to as the melt film formation process: the thermoplastic polyamide resin composition is film-formed by melt processing to obtain a polyamide resin composition film.

[0019] <Melting and Mixing Process> In the melt blending process, thermoplastic polyamide resin and inorganic microparticles are melt blended to obtain a thermoplastic polyamide resin composition in which inorganic microparticles are dispersed in the thermoplastic polyamide resin.

[0020] Regarding the temperature for melt mixing, it is only necessary to use the melting temperature of thermoplastic polyamide resin; there are no special limitations.

[0021] For example, melt mixing is performed at a temperature 5°C to 100°C higher than the melting point of the thermoplastic polyamide resin. When multiple thermoplastic polyamide resins are used in combination, melt mixing is performed at a temperature 5°C to 100°C higher than the melting point of the thermoplastic polyamide resin with the highest melting point among the multiple thermoplastic polyamide resins.

[0022] Here, the melting point of the polyamide resin is determined using a differential scanning calorimeter (DSC) according to JIS K 7121.

[0023] There are no particular limitations on the method of melt blending thermoplastic polyamide resin and inorganic microparticles. Melt blending is usually carried out using extruders such as single-screw extruders and twin-screw extruders.

[0024] When thermoplastic polyamide resin and inorganic microparticles are melt-blended, plasticizers, release agents, and other additives are sometimes used. However, when the thermoplastic polyamide resin composition is film-formed using the above method, it is preferable not to use plasticizers, release agents, or other additives.

[0025] Porous polyamide membranes, obtained by removing inorganic particles from polyamide resin compositions, can be used for filtering various fluids. However, when using porous polyamide membranes to filter fluids containing organic solvents, there is a concern that plasticizers, mold release agents, and other additives may leach into the filtered fluid if the porous polyamide membrane contains plasticizers, mold release agents, or other additives.

[0026] The form of a thermoplastic polyamide resin composition obtained by melt mixing, in which inorganic microparticles are dispersed in a thermoplastic polyamide resin, is not particularly limited. Examples of the form of the thermoplastic polyamide resin composition include flakes, powders, and granules.

[0027] Typically, a thermoplastic polyamide resin composition, obtained by melt mixing and containing inorganic microparticles dispersed in a thermoplastic polyamide resin, is extruded from an extruder in a wire bundle form. The wire bundle of polyamide resin composition is cured by cooling and cut into desired sizes to form granules.

[0028] [Thermoplastic polyamide resin] As a thermoplastic polyamide resin, any known thermoplastic polyamide resin may be used without particular limitation.

[0029] Thermoplastic polyamide resins can be ring-opening polymers of lactams or condensation polymers of hydroxycarboxylic acids. Both ring-opening polymers of lactams and condensation polymers of hydroxycarboxylic acids can be homopolymers or copolymers.

[0030] In addition, thermoplastic polyamide resins can be condensation polymers formed by the condensation of diamine and dicarboxylic acid components. These condensation polymers can contain two or more structural units derived from the diamine component, or they can contain two or more structural units derived from the dicarboxylic acid component.

[0031] Thermoplastic polyamide resins can be polymers formed by polymerizing lactams and / or hydroxycarboxylic acids, as well as diamine components and dicarboxylic acid components.

[0032] Lactams, hydroxycarboxylic acids, diamines, and dicarboxylic acids can each be used in combination of two or more.

[0033] Specific examples of thermoplastic polyamide resins include aliphatic polyamides such as nylon 6, nylon 7, nylon 9, nylon 11, nylon 12, nylon 26, nylon 46, nylon 66, nylon 610, nylon 612, nylon 86, nylon 108, nylon 6 / 12, nylon 6 / 9, nylon 6 / 66, nylon 12 / 66, nylon 26 / 66, nylon 66 / 610, and nylon 6 / 66 / 610. These nylon names are based on JIS K 6920-1.

[0034] Furthermore, the raw materials for the aforementioned nylon are not particularly limited. For example, nylon 6 is generally manufactured by ring-opening polymerization of caprolactam. However, nylon 6 is not limited to ring-opening polymers of caprolactam; it can also be a condensation polymer of 6-aminohexanoic acid.

[0035] In addition, specific examples of thermoplastic polyamide resins include aromatic polyamides such as polyhexyl isophthalamide, polyhexyl terephthalamide, polyadipoxy-isophthalamide, hexyl isophthalamide / terephthalamide copolymer, poly(p-phenylene terephthalamide) and poly(p-phenylene 3,4'-oxydiphenylene terephthalamide), as well as various amorphous polyamides.

[0036] The thermoplastic polyamide resins described above can accept various known modifications.

[0037] [Inorganic particles] The inorganic microparticles are any material that can be removed from the polyamide resin composition membrane when manufacturing a porous polyamide membrane using the polyamide resin composition membrane; there are no particular limitations.

[0038] Preferred examples of materials that are inorganic microparticles include, for example, metal oxides such as silicon dioxide (SiO2), titanium dioxide and aluminum oxide (Al2O3), as well as metals such as iron and iron-nickel alloys.

[0039] Regarding spherical particles formed from metal, for example, they can be manufactured using the methods described in the Journal of Alloys and Compounds, Volume 480, Issue 2, 8 July 2009, Pages 529-533.

[0040] The inorganic particles are spherical in shape. Here, "spherical" is not limited to a perfect sphere in geometry; it simply means a shape that can be identified as close to a perfect sphere when viewed under a microscope with the naked eye.

[0041] As spherical inorganic microparticles, colloidal silica microparticles are preferred, for example. As colloidal silica, monodisperse spherical silica particles are preferred because uniform pores can be formed in the porous polyamide film.

[0042] Furthermore, regarding the inorganic microparticles, high sphericity and a small particle size distribution index are preferred. Inorganic microparticles possessing these conditions exhibit excellent dispersibility in thermoplastic polyamide resin compositions. The volume average particle size of the inorganic microparticles is preferably 0.03 μm or more and 1.0 μm or less, more preferably 0.05 μm or more and 0.5 μm or less.

[0043] The volume-average particle size of inorganic microparticles is called D50. D50 refers to the particle size at the 50th percentile of the cumulative value in the particle size distribution of a volume-based standard determined by laser diffraction and scattering.

[0044] Inorganic microparticles can be used alone or in combination of two or more.

[0045] The amount of inorganic microparticles used is 50% to 70% by mass and more preferably 55% to 70% by mass and even more preferably 60% to 70% by mass and less than 70% by mass relative to the mass of the thermoplastic polyamide resin composition.

[0046] Therefore, in the polyamide resin composition film, the content of inorganic microparticles is 50% to 70% by mass and less than the mass of the thermoplastic polyamide resin composition, more preferably 55% to 70% by mass and less than the mass, and even more preferably 60% to 70% by mass and less than the mass.

[0047] By using an amount of inorganic microparticles within the above range, a non-brittle and uniform polyamide resin composition can be easily obtained. When a porous polyamide membrane is obtained using the method described later, a porous polyamide membrane with the desired porous structure can be easily obtained.

[0048] [Other ingredients] The thermoplastic polyamide resin composition may, as needed, contain other thermoplastic resins besides thermoplastic polyamide resin and various additives along with thermoplastic polyamide resin and inorganic microparticles.

[0049] When the thermoplastic polyamide resin composition contains other thermoplastic polyamide resins along with the thermoplastic polyamide resin, the ratio of the mass of the other thermoplastic resins to the mass of the resin components contained in the thermoplastic polyamide resin composition is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0050] Examples of additives include colorants, antioxidants, UV absorbers, surfactants, and silane coupling agents.

[0051] When using the above method to film-form a thermoplastic polyamide resin composition, it is preferable not to use the above-mentioned additives.

[0052] Porous polyamide membranes obtained by removing inorganic particles from polyamide resin composition membranes can be used for filtering various fluids. When using porous polyamide membranes to filter fluids containing organic solvents, there is a concern that the aforementioned additives may leach into the filtered fluid if the porous polyamide membrane contains such additives.

[0053] <Melting and Film Process> In the melt film formation process, the thermoplastic polyamide resin composition is film-formed through melt processing to obtain a polyamide resin composition film.

[0054] Examples of melt processing methods for obtaining films include the T-die method, the blown film method, and the calendering method. Among these methods, the T-die method is preferred due to its ease of adjusting film thickness and its excellent film productivity.

[0055] The melt processing temperature used for film formation is appropriately determined by taking into account factors such as the type of melt processing method, the melting point and glass transition temperature of the thermoplastic polyamide, and the thickness of the film.

[0056] The thickness of the polyamide resin composition film is preferably 20 μm or more and 200 μm or less, more preferably 40 μm or more and 150 μm or less, and even more preferably 50 μm or more and 100 μm or less.

[0057] Using the above method, it is possible to obtain a polyamide composition film formed from a thermoplastic polyamide resin composition in which inorganic particles are dispersed.

[0058] Manufacturing Method of Porous Polyamide Membranes The method for manufacturing porous polyamide membranes includes the following steps: A polyamide resin composition film was obtained using the aforementioned method; and Remove inorganic particles from polyamide resin composition membranes.

[0059] The thickness of the porous polyamide membrane obtained by the above method is preferably 20 μm or more and 200 μm or less, more preferably 40 μm or more and 150 μm or less, and even more preferably 50 μm or more and 100 μm or less, just like the thickness of the polyamide resin composition membrane.

[0060] There are no particular limitations on the method for removing inorganic particles from polyamide resin composition films.

[0061] As a method for removing inorganic particles from a polyamide resin composition membrane, it is preferable to contact the polyamide resin composition membrane with a liquid capable of dissolving inorganic particles.

[0062] There are no particular limitations on the method of contacting the polyamide resin composition film with a liquid capable of dissolving inorganic particles, but it is preferable to immerse the polyamide resin composition film in a liquid capable of dissolving inorganic particles.

[0063] For example, when the inorganic particles are silica particles, silica particles can be removed from the polyamide resin composition membrane by contacting it with an aqueous solution of hydrogen fluoride (hydrofluoric acid).

[0064] In addition, when the inorganic particles are metal particles such as iron particles or iron-nickel alloy particles, the metal particles can be removed from the polyamide resin composition film by contacting it with a hydrochloric acid solution.

[0065] The membrane obtained by removing inorganic particles from the polyamide resin composition membrane using the above method is cleaned and dried as needed, thereby obtaining a porous polyamide membrane.

[0066] There are no particular limitations on the cleaning method. Typically, organic solvents such as water, methanol, and ethanol are used for cleaning.

[0067] There are no particular limitations on the drying method. For example, drying can be carried out using methods such as heat-based drying, vacuum drying, or resting in the atmosphere.

[0068] Porous polyamide membranes The porous polyamide membrane obtained by the above method comprises a structure in which spherical pores are interconnected (hereinafter referred to as interconnected pores). The openings in the porous polyamide membrane are the portions of the interconnected pores that open on the surface of the porous polyamide membrane.

[0069] The concept of spherical shape in relation to the shape of a hole includes perfect spheres, and is not necessarily limited to perfect spheres. The term "spherical" simply means that it is substantially perfect spheres. Shapes that can be identified as approximately perfect spheres by visual observation of a magnified image of the hole are also included in the concept of spherical shape.

[0070] Specifically, for a spherical aperture, it is sufficient that the surface defining the aperture is curved and that the curved surface defines a spherical or approximately spherical aperture.

[0071] Typically, each spherical pore is formed by removing individual inorganic particles present in the aforementioned polyamide resin composition film. Conversely, interconnecting pores are formed by removing multiple inorganic particles that are in contact with each other from the polyamide resin composition film. The interconnected portions of the spherical pores originate from the locations where the multiple inorganic particles were in contact with each other before removal.

[0072] The diameter of the opening of a porous polyamide membrane is, for example, in the range of 10 nm to 200 nm. The diameter of the opening of the porous polyamide membrane can be appropriately changed according to the application of the porous polyamide membrane.

[0073] The interconnected pores formed by the connection of spherical holes of the specified diameter allow fluid to pass well within the porous polyamide membrane.

[0074] The porous polyamide membrane has interconnecting pores running through it in the thickness direction, serving as flow paths for fluid. This allows fluid to permeate from one main surface of the porous polyamide membrane to the other.

[0075] Furthermore, the fluid passes through the interior of the porous polyamide membrane while contacting the curved surface that defines each spherical pore. Due to the interconnecting pores formed by the spherical pores, the contact area of ​​the fluid inside the porous polyamide membrane is quite large. Therefore, it is believed that if fluid passes through the porous polyamide membrane, minute substances present in the fluid will easily be adsorbed into the spherical pores within the porous polyamide membrane.

[0076] As stated above, the inventors of this application have provided the following [1] to

[10] .

[0077] [1] A method for manufacturing a polyamide resin composition film, the method comprising: A thermoplastic polyamide resin and inorganic microparticles are melt-blended to obtain a thermoplastic polyamide resin composition in which inorganic microparticles are dispersed in the thermoplastic polyamide resin; and A polyamide resin composition film is obtained by melt processing to form a film from the polyamide resin composition. Inorganic particles are spherical in shape. The ratio of the mass of inorganic microparticles to the mass of the thermoplastic polyamide resin composition is more than 50% by mass and less than 70% by mass.

[0078] [2] The method for manufacturing a polyamide resin composition film as described in [1], wherein the inorganic microparticles are silica microparticles.

[0079] [3] A method for manufacturing a polyamide resin composition film as described in [1] or [2], wherein the volume average particle size of the inorganic microparticles is 0.03 μm or more and 1.0 μm or less.

[0080] [4] A polyamide resin composition film formed from a thermoplastic polyamide resin composition in which inorganic microparticles are dispersed in a thermoplastic polyamide resin. Inorganic particles are spherical in shape. The ratio of the mass of inorganic microparticles to the mass of the thermoplastic polyamide resin composition is more than 50% by mass and less than 70% by mass.

[0081] [5] The polyamide resin composition film as described in [4], wherein the inorganic microparticles are silica microparticles.

[0082] [6] A polyamide resin composition film as described in [4] or [5], wherein the volume average particle size of the inorganic microparticles is 0.03 μm or more and 1.0 μm or less.

[0083] [7] A method for manufacturing a porous polyamide membrane, the method comprising: A polyamide resin composition film was obtained using the method described in [1]; and Remove inorganic particles from polyamide resin composition membranes.

[0084] [8] The method for manufacturing a porous polyamide membrane as described in [7], wherein inorganic particles are removed from the polyamide resin composition membrane by contacting the polyamide resin composition membrane with a solvent capable of dissolving inorganic particles.

[0085] [9] The method for manufacturing a porous polyamide membrane as described in [8], wherein the inorganic particles are silica particles and the solvent is an aqueous solution of hydrogen fluoride.

[0086]

[10] The method for manufacturing a porous polyamide membrane as described in [7] or [8], wherein the volume average particle size of the inorganic microparticles is 0.03 μm or more and 1.0 μm or less.

[0087] Example The present invention will now be described in detail through examples. The scope of the present invention is not limited to these examples.

[0088] [Examples 1-4, Comparative Example 1 and Comparative Example 2] Using a twin-screw extruder (HK-25D, PARKER CORPORATION), the amounts of nylon 6 and spherical silica microparticles listed in Table 1 were melt-blended at a barrel temperature of 270°C and a rotation speed of 200 rpm. The volume average particle size of the spherical silica microparticles is as shown in Table 1. While the polyamide resin composition discharged from the extruder in a bundle shape was cooled and solidified, it was cut into granules to obtain the polyamide resin compositions of each example and Comparative Example 2.

[0089] It should be noted that, regarding Comparative Example 1, due to the excessive amount of silica particles used, the compound became brittle and a polyamide resin composition could not be obtained.

[0090] The weight loss rate of the obtained polyamide resin composition sample was measured by heating it to 500°C using TG-DTA (thermogravimetric-differential thermal analysis). The content of silica particles in the obtained polyamide resin composition was then calculated using the following formula: Silica particle content (wt%) = 100 - weight reduction rate.

[0091] The content of silica particles in the polyamide resin composition is shown in Table 1.

[0092] Using a T-die extrusion apparatus (Labo Plastomill, Toyo Seiki Co., Ltd.), the temperature of the polyamide resin composition was set to 270°C and the die lip temperature was set to 280°C. The polyamide resin compositions of each example and Comparative Example 2 obtained as described above were extruded at a rotation speed of 50 rpm while being film-formed to obtain polyamide resin composition films of each example and each comparative example. The film thickness of the polyamide resin composition film was 100 μm.

[0093] The content of silica particles in the obtained polyamide resin composition film was determined using the same method as the determination of silica particle content in the polyamide resin composition. The content of silica particles in the polyamide resin composition film is shown in Table 1.

[0094] The polyamide resin composition membrane obtained as described above was immersed in hydrofluoric acid with a concentration of 10% by mass for 5 minutes at 25°C (room temperature) to remove silica particles from the polyamide resin composition membrane. After removing the silica particles, the membrane pulled out of the hydrofluoric acid was washed with pure water and then dried to obtain the porous polyamide membranes of each embodiment and Comparative Example 2.

[0095] <Evaluation of Porous Structures> The surface and cross-section of the porous polyamide membrane were observed using a scanning electron microscope (SEM), and evaluated based on the following criteria.

[0096] Good: In porous polyamide membranes, multiple spherical pores from inorganic microparticles are interconnected and can be identified as spherical pores by visual observation.

[0097] Defect: In porous polyamide membranes, there are a large number of independent spherical pores that are not connected to other spherical pores.

[0098] As can be seen from Examples 1 to 4, when the ratio of the mass of inorganic microparticles to the mass of the thermoplastic polyamide resin composition is within the aforementioned specified range, a thermoplastic polyamide resin composition and a polyamide resin composition film that can supply a porous polyamide film with a good porous structure can be obtained.

Claims

1. A method for manufacturing a polyamide resin composition film, the method comprising: Thermoplastic polyamide resin and inorganic microparticles are melt-blended to obtain a thermoplastic polyamide resin composition in which the inorganic microparticles are dispersed in the thermoplastic polyamide resin. and The polyamide resin composition is melt-processed to form a film, thereby obtaining a polyamide resin composition film. The inorganic particles are spherical in shape. The ratio of the mass of the inorganic microparticles to the mass of the thermoplastic polyamide resin composition is more than 50% by mass and less than 70% by mass.

2. The method for manufacturing the polyamide resin composition film according to claim 1, wherein, The inorganic particles are silicon dioxide particles.

3. The method for manufacturing a polyamide resin composition film as described in claim 1 or 2, wherein, The volume average particle size of the inorganic microparticles is above 0.03 μm and below 1.0 μm.

4. A polyamide resin composition film, formed from a thermoplastic polyamide resin composition in which inorganic microparticles are dispersed in a thermoplastic polyamide resin. The inorganic particles are spherical in shape. The ratio of the mass of the inorganic microparticles to the mass of the thermoplastic polyamide resin composition is more than 50% by mass and less than 70% by mass.

5. The polyamide resin composition film according to claim 4, wherein, The inorganic particles are silicon dioxide particles.

6. The polyamide resin composition film according to claim 4 or 5, wherein, The volume average particle size of the inorganic microparticles is above 0.03 μm and below 1.0 μm.

7. A method for manufacturing a porous polyamide membrane, the method comprising: The polyamide resin composition film is obtained using the method of claim 1; and Remove the inorganic particles from the polyamide resin composition film.

8. The method for manufacturing a porous polyamide membrane as described in claim 7, wherein, The inorganic particles are removed from the polyamide resin composition film by contacting it with a solvent capable of dissolving the inorganic particles.

9. The method for manufacturing a porous polyamide membrane as described in claim 8, wherein, The inorganic particles are silicon dioxide particles, and the solvent is an aqueous solution of hydrogen fluoride.

10. The method for manufacturing a porous polyamide membrane according to any one of claims 7 to 9, wherein, The volume average particle size of the inorganic microparticles is above 0.03 μm and below 1.0 μm.

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