JP2019130481A - Hydrophilic porous membrane manufacturing method - Google Patents

Abstract

To provide a method for manufacturing a hydrophilic porous membrane which has a high hydrophilicity and which is hard to be clogged.SOLUTION: A method for manufacturing a hydrophilic porous membrane which includes a porous membrane, and a hydrophilic coating which covers at least a part of an external surface of the porous membrane. The method includes: a step in which the porous membrane is impregnated with a hydrophilic liquid for formation of the hydrophilic coating; and a step in which the porous membrane is subjected to a hardening reaction after the membrane is impregnated with the hydrophilic liquid. The hydrophilic liquid contains a mixed solvent of a polymerizable monomer and a polar organic solvent, and water, a gross mass of the polar organic solvent to a gross mass of the mixed solvent is less than 10% by mass or more than 60% by mass, and the hardening reaction is performed in such a manner that a portion of the porous membrane, which is impregnated with the hydrophilic liquid in an entire thickness direction and of which a mass is 3 to 16 times of a mass before being impregnated with the hydrophilic liquid, is irradiated with light.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a hydrophilic porous membrane.

  Porous membranes made of various polymers such as polysulfone and polyolefin are used as filtration membranes in water purification and blood treatment. Since these materials are generally hydrophobic and difficult to wet with water, they are used after being hydrophilized depending on the application.

  For example, Patent Document 1 discloses a method for imparting hydrophilicity by precipitating a hydrophilicity-imparting substance on a polysulfone porous membrane using a poor solvent, and attaching and holding the substance. Patent Document 2 discloses a method for imparting hydrophilicity to a polysulfone porous membrane using a hydrophilic organic polymer such as polyvinyl alcohol. Specifically, a solution containing a hydrophilic organic polymer such as polyvinyl alcohol is applied to the porous membrane, and then heated and dried to adhere and hold the hydrophilic organic polymer on the pore surfaces of the porous membrane. A method is disclosed.

  On the other hand, Patent Document 3 has a monomer (A) composed of one or more polyfunctional (meth) acrylates and a hydrocarbon residue having 5 to 20 carbon atoms on the surface of at least some of the pores of the polyolefin porous membrane. Disclosed is a heat-resistant hydrophilized porous membrane in which a cross-linked copolymer with a monomer (B) composed of one or more types of monofunctional (meth) acrylate is retained, and further a hydrophilic polymer is retained thereon. Yes. In Patent Document 3, after immersing a polyolefin porous membrane in a solution containing the above monomer, the solvent is volatilized and removed, and then the monomer is polymerized to form a cross-linked copolymer. A polymer is formed.

JP-A-8-131792 JP-A-11-179176 JP-A-5-212256

The hydrophilized polysulfone porous membrane obtained by the method described in Patent Document 1 or 2 has a problem that the hydrophilicity tends to decrease due to washing of the membrane or the like because the adhesion holding power of the hydrophilic organic polymer is low. .
In Patent Document 3, heat resistance and hydrophilicity are realized at the same time by a hydrophilization treatment in which a crosslinked copolymer is formed from a composition permeated into a porous membrane. However, there is room for further improvement in order to use as a filtration membrane that can be used for a long time.
An object of the present invention is to provide a method for producing a hydrophilic porous membrane that has high hydrophilicity and is less likely to be clogged.

  In order to solve the above problems, the inventors of the present invention have repeatedly studied earnestly about the procedure when the hydrophilicity of the porous membrane surface and the surface of the pores in the membrane is carried out by polymerization of hydrophilic monomers on these surfaces, The above problems have been solved.

That is, the present invention provides the following <1> to <16>.
<1> A method for producing a hydrophilic porous membrane,
The hydrophilic porous membrane includes a porous membrane and a hydrophilic coating that covers at least a part of the outer surface of the porous membrane,
The above manufacturing method is
Impregnating the porous membrane with the hydrophilizing liquid for forming the hydrophilizing coating, and subjecting the porous membrane after permeating the hydrophilizing liquid to a curing reaction,
The hydrophilizing liquid contains a polymerizable monomer and a mixed solvent of a polar organic solvent and water,
The total mass of the polar organic solvent is less than 10% by mass or more than 60% by mass with respect to the total mass of the mixed solvent,
In the porous film, the curing reaction is a site where the hydrophilic liquid penetrates in the entire thickness direction, and the mass is 3 to 16 times the mass before the hydrophilic liquid is penetrated. The said manufacturing method performed by irradiating with light.

<2> The production method according to <1>, wherein the permeation is performed by immersing the porous membrane in the hydrophilic liquid.
<3> The production method according to <2>, wherein the porous membrane is pulled up from the hydrophilized liquid after the immersion.
<4> The production according to any one of <1> to <3>, comprising drying the porous membrane after the permeation of the hydrophilizing liquid and before the curing reaction to volatilize a part of the mixed solvent. Method.
<5> The production method according to any one of <1> to <4>, wherein the light irradiation is ultraviolet irradiation.
<6> The production method according to any one of <1> to <5>, wherein the polar organic solvent is an organic solvent miscible with water.
<7> The production method according to <6>, wherein the polar organic solvent contains at least one alcohol having 5 or less carbon atoms.
<8> The production method according to any one of <1> to <7>, wherein the polymerizable monomer is an acrylic monomer.
<9> The production method according to <8>, wherein the acrylic monomer is a trifunctional to hexafunctional monomer.
<10> The method according to <9>, wherein the acrylic monomer has a ClogP value of 2.0 or less.

<11> The production method according to <9> or <10>, wherein the acrylic monomer is (meth) acrylamide.
<12> The production method according to any one of <9> to <11>, wherein the hydrophilizing liquid includes an acrylic monomer having 1 to 2 functional groups.
<13> The mass ratio of the trifunctional to hexafunctional acrylic monomer and the monofunctional to bifunctional acrylic monomer in the hydrophilization liquid is 20:80 to 80:20 in <12>. The manufacturing method as described.
<14> The production method according to <12> or <13>, wherein the acrylic monomer having a functionality of 1 to 2 is (meth) acrylamide.
<15> The production method according to any one of <1> to <14>, wherein the porous membrane contains polysulfone.
<16> The production method according to any one of <1> to <15>, wherein the porous membrane has a pore size distribution.

  The present invention provides a novel method for producing a hydrophilic porous membrane. By the production method of the present invention, it is possible to produce a hydrophilic porous membrane having high hydrophilicity and hardly causing clogging.

Hereinafter, the present invention will be described in detail.
In the present specification, “to” is used in the sense of including the numerical values described before and after it as lower and upper limits.
In this specification, “(meth) acryloyl group” means acryloyl group (H ₂ C═CH—C (═O) —) and methacryloyl group (H ₂ C═C (CH ₃ ) —C (═O) —). Represents one or both of the above. Examples of the “acrylic monomer” include (meth) acrylate and (meth) acrylamide. In the present specification, “(meth) acrylamide” represents one or both of acrylamide and methacrylamide.

<Hydrophilic porous membrane>
In this specification, the hydrophilic porous membrane means a membrane obtained by subjecting a porous membrane serving as a base material to a hydrophilic treatment.
A hydrophilic porous membrane is a membrane having a plurality of pores. The hole can be confirmed by, for example, a scanning electron microscope (SEM) image or a transmission electron microscope (TEM) image of the film cross section.

  The hydrophilic porous membrane of the present invention includes a porous membrane and a hydrophilic coating that covers at least a part of the outer surface of the porous membrane. In this specification, the outer surface of the porous membrane refers to the surface of the porous membrane (the front surface or the back surface of the membrane) and the surface of the porous membrane facing each pore inside the porous membrane (this book In the specification, it is sometimes referred to as “the surface of the pore”. In the hydrophilic porous membrane of the present invention, the surface of at least one of the porous membranes and the surface of the porous membrane facing at least some of the plurality of pores inside the porous membrane are hydrophilized It is preferable that it is covered with a coating, and it is more preferable that substantially all of the outer surface of the porous membrane is covered with a hydrophilic coating.

  When the surface of one of the porous membranes is covered, it is preferable that substantially the entire surface of the membrane is covered. The porous membrane may be coated on either one of the membrane surfaces or on both membrane surfaces, but it is preferable that both membrane surfaces are coated.

  In the hydrophilic porous membrane of the present invention, when the pores covered inside are a part of a plurality of pores inside the porous membrane, the part is, for example, any one of the porous membranes As long as it is in the vicinity of the film surface. The film surface at that time is preferably a coated film surface. As one aspect of the present invention, it is preferable that the surface of the porous membrane facing all the pores of the plurality of pores inside the porous membrane is covered.

The coating with the hydrophilic coating may be performed to such an extent that the hydrophilic porous membrane is not easily peeled off during storage or use. The coating may be carried out by covalent bonding between the compound in the hydrophilic coating and the residue on the outer surface of the porous membrane, but the hydrophilic coating is formed on the membrane surface or by forming a cured product network described later. It is preferably in a state held in the pores.
The hydrophilic coating only needs to be applied to the porous film as the base material in an arbitrary mass in consideration of necessary wettability and water permeability. About 25 to 20% by mass, and preferably about 0.5 to 15% by mass.

<Method for producing hydrophilic porous membrane>
In the present invention, the hydrophilic porous membrane is produced by performing a hydrophilization treatment that forms a hydrophilic coating on the porous membrane as a substrate.
The hydrophilic coating is formed by infiltrating a hydrophilic film containing a polymerizable monomer and a solvent into the porous film, and then subjecting the porous film infiltrated with the hydrophilized liquid to a curing reaction. You may perform a washing process etc. further to the porous membrane in which the hydrophilic coating was formed.
Hereinafter, each process used in the manufacturing method of this invention and each material used for the manufacturing method of this invention is demonstrated.

[Porous membrane]
(Porous membrane structure)
A porous membrane refers to a membrane having a plurality of pores. The pores can be confirmed by, for example, a scanning electron microscope (SEM) image or a transmission electron microscope (TEM) image of the film cross section.

The pore diameter of the pores of the porous membrane may be 0.01 μm to 10 μm, more preferably 0.01 μm to 5 μm, and still more preferably 0.01 μm to 2 μm. What is necessary is just to measure a hole diameter from the photograph of the film | membrane cross section obtained by the electron microscope. The porous membrane is cut with a microtome or the like, and a photograph of the cross section of the porous membrane can be obtained as a slice of a thin film whose cross section can be observed.
The pore size of the pores of the hydrophilic porous membrane may be smaller than the pore size of the porous membrane of the base material as a result of the hydrophilization treatment, but usually approximated to be the same as the pore size of the porous membrane. it can.

  The structure of the porous membrane may be either an asymmetric structure having a pore size distribution in the thickness direction or a homogeneous structure having no pore size distribution in the thickness direction. The same applies to the hydrophilic porous membrane. Examples of asymmetric structures include a structure in which the pore diameter continuously increases in the thickness direction from one membrane surface to the other membrane surface, and has a layered dense portion in which the pore diameter is minimized. Examples include a structure in which the pore diameter continuously increases in the thickness direction from the portion toward the surface of at least one of the porous membranes.

The thickness of the porous membrane is not particularly limited, but may be 10 μm to 1000 μm from the viewpoint of membrane strength, handleability, and filtration performance, preferably 10 μm to 500 μm, and more preferably 30 μm to 300 μm. preferable.
In addition, although the thickness of the hydrophilic porous film may be larger than the thickness of the porous film of the base material as a result of the hydrophilization treatment, it is usually almost the same as the thickness of the porous film.

(Porous membrane composition)
The porous membrane includes a polymer. The porous membrane is preferably composed essentially of a polymer. The polymer preferably has a number average molecular weight (Mn) of 1,000 to 10,000,000, more preferably 5,000 to 1,000,000.

Examples of the polymer include a thermoplastic or thermosetting polymer. Specific examples of the polymer include polysulfone, sulfonated polysulfone, polyethersulfone (PES), sulfonated polyethersulfone, cellulose acylate, nitrocellulose, polyacrylonitrile, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, ethylene- Saponified vinyl acetate copolymer, polyvinyl alcohol, polycarbonate, organosiloxane-polycarbonate copolymer, polyester carbonate, organopolysiloxane, polyphenylene oxide, polyamide, polyimide, polyamideimide, polybenzimidazole, ethylene vinyl alcohol copolymer, polytetrafluoroethylene (PTFE), polyethylene, polypropylene, polyfluoroethylene, polyethylene Terephthalate, polyamide, polyimide, 6,6-nylon, polyvinylidene fluoride (PVDF) or the like. These may be homopolymers, copolymers, polymer blends, or polymer alloys from the viewpoints of solubility, optical physical properties, electrical physical properties, strength, elasticity, and the like.
Of these, polysulfone, polyethersulfone, PVDF, sulfonated polysulfone, sulfonated polyethersulfone, 6,6-nylon, and cellulose acylate are preferable, and polysulfone is more preferable.

The porous membrane may contain components other than the polymer as additives.
Examples of the additives include metal salts of inorganic acids such as sodium chloride, lithium chloride, sodium nitrate, potassium nitrate, sodium sulfate and zinc chloride, metal salts of organic acids such as sodium acetate and sodium formate, polyethylene glycol, polyvinyl pyrrolidone and the like. Examples include molecules, polymer electrolytes such as sodium polystyrene sulfonate and polyvinylbenzyltrimethylammonium chloride, and ionic surfactants such as sodium dioctylsulfosuccinate and sodium alkylmethyl taurate. The additive may act as a swelling agent for the porous structure.

The porous film is preferably a film formed from one composition as a single layer, and preferably not a multi-layer laminated structure.
Regarding the method for producing the porous membrane, reference can be made to JP-A-4-349927, JP-B-4-68966, JP-A-4-351645, JP-A-2010-235808, and the like.
A commercially available product may be used as the porous membrane. For example, Sumilite FS-1300 (manufactured by Sumitomo Bakelite), Micro PES 1FPH (manufactured by Membrana), Durapore (manufactured by Merck Millipore), PSEUH20 (polysulfone membrane, manufactured by Fuji Film Co., Ltd.), 15406 (PES membrane, Sartorius) and the like.

[Hydrophilic liquid]
The hydrophilizing liquid contains a polymerizable monomer and a mixed solvent of a polar organic solvent and water. In the present invention, the total mass of the polar organic solvent is less than 10 mass% or more than 60 mass% with respect to the total mass of the mixed solvent.
The hydrophilization liquid may contain other components such as a polymerization initiator in addition to the polymerizable monomer and the mixed solvent of the polar organic solvent and water.

(Polymerizable monomer)
The polymerizable monomer is a compound having a polymerizable functional group and a molecular weight of about 2500 or less. Examples of the polymerizable monomer include acrylic monomers, styrene monomers, monomers having an epoxy group or monomers having an oxetane group, and acrylic monomers are preferred. “Acrylic monomer” means a monomer having a (meth) acryloyl group.
Examples of the acrylic monomer include (meth) acrylate and (meth) acrylamide. The polymerizable monomer is more preferably (meth) acrylamide.

The polymerizable monomer is preferably polyfunctional, more preferably 2 or more and 6 or less, and still more preferably 3 or more and 4 or less.
The hydrophilization liquid may contain 2 or more types of monomers as a polymerizable monomer. A preferred example of a combination of two or more monomers is a combination of a trifunctional or higher and hexafunctional polymerizable monomer and a bifunctional polymerizable monomer.

It is preferable that the hydrophilization liquid contains a predetermined acrylic monomer described as a “first acrylic monomer” in the present specification as a polymerizable monomer.
The first acrylic monomer is an acrylic monomer having a trifunctional or higher and hexafunctional or lower and a ClogP value of 2.0 or lower.
The first acrylic monomer is preferably trifunctional or higher and tetrafunctional or lower.
In addition, in this specification, the functional number of an acrylic monomer shows the number of (meth) acryloyl groups.

  The ClogP value is a value obtained by calculating the common logarithm logP of the distribution coefficient P between 1-octanol and water. The ClogP value is a hydrophilicity index. Any known method or software may be used to calculate the ClogP value. In the present invention, unless otherwise specified, a ClogP program incorporated in ChemBioDraw Ultra 13.0 of Cambridge software is used. To do. The ClogP value of the first acrylic monomer is 2.0 or less, more preferably 1.0 or less, and further preferably 0.0 or less. The lower limit is preferably −6.0, more preferably −2.0, and even more preferably −1.0. The ClogP value of the first acrylic monomer is, for example, preferably from -6.0 to 2.0, more preferably from -2.0 to 1.0, and from -1.0 to 0 More preferably, it is 0.0 or less.

  Although the preferable example of a 1st acrylic monomer is shown below, a 1st acrylic monomer is not limited to the following examples. The value in parentheses is the ClogP value of each monomer.

  FAM-401 and FAM-301 are product names. FAM-401 and FAM-301 are available from FUJIFILM Corporation. ATM-35E is a product name. ATM-35E is available from Shin-Nakamura Chemical Co., Ltd.

It is preferable that the hydrophilizing liquid containing the first acrylic monomer further contains a second acrylic monomer. The second acrylic monomer is an acrylic monomer having 1 to 2 functional groups.
The ClogP value of the second acrylic monomer is not particularly limited, but is preferably −6.0 or more and 2.0 or less, more preferably −2.0 or more and 1.0 or less, and −1. More preferably, it is 0 or more and 0.0 or less.

  Although the preferable example of a 2nd acrylic monomer is shown below, a 2nd acrylic monomer is not limited to the following examples. The value in parentheses is the ClogP value of each monomer.

  FAM-201 and FAM-101 are product names. FAM-201 and FAM-101 are available from FUJIFILM Corporation. N, N-methylenebisacrylamide is available from, for example, Tokyo Chemical Industry Co., Ltd.

  The mass ratio of the first acrylic monomer to the second acrylic monomer in the hydrophilization liquid is preferably 20:80 to 80:20, and more preferably 30:70 to 70:30.

  The total mass of the polymerizable polymer in the hydrophilic liquid is preferably 0.05 to 10% by mass with respect to the total mass of the hydrophilic liquid. By setting it as 0.05 mass% or more, a hydrophilic component can fully be fixed to a film | membrane. Moreover, by setting it as 10 mass% or less, it can prevent that there are too many hydrophilic components to fix | fix, and a hole will be clogged and water permeability will deteriorate.

(Polymerization initiator)
The hydrophilizing liquid preferably contains a polymerization initiator. The polymerization initiator is not particularly limited, but is preferably soluble in a mixed solvent of water and a polar organic solvent. Moreover, what has absorption in the wavelength of 300 nm or more is preferable. Preferable examples of the polymerization initiator include FAI-101L (manufactured by FUJIFILM Corporation), Irg2959 (manufactured by BASF), TPO-L (manufactured by BASF), L0290 (manufactured by Tokyo Chemical Industry Co., Ltd.), and H1361 (Tokyo Chemical Industry). Kogyo Co., Ltd.), A2735 (Tokyo Kasei Kogyo Co., Ltd.), A3012 (Tokyo Kasei Kogyo Co., Ltd.), QuantureQTX (manufactured by Tront Research Chemicals), Quanture ABQ (manufactured by Tont Research Chemicals), and the like.

  The addition amount of the polymerization initiator is desirably 0.01 to 0.5% by mass with respect to the total mass of the hydrophilizing liquid. By setting the content to 0.01% by mass or more, the polymerization can be started, and by setting the content to 0.5% by mass or less, the polymerization initiator can be prevented from being precipitated and clogged during the drying process.

(solvent)
As the solvent, a mixed solvent of a polar organic solvent and water is used.
In the mixed solvent of water and the polar organic solvent, the polar organic solvent is less than 10% by mass or more than 60% by mass with respect to the total mass of the mixed solvent. The polar organic solvent should just be 0 mass% or more and less than 10 mass% or more than 60 mass% and 100 mass% or less with respect to the total mass of a mixed solvent. Moreover, a preferable range is 0 mass% or more and less than 10 mass%. The inventors of the present invention have found that a hydrophilic porous membrane that is less prone to clogging can be produced by using this range. Because the degree of polymerization is higher as the surface of the porous film is closer to the surface (for example, the surface irradiated with ultraviolet rays in the curing reaction), and the degree of polymerization is lower as the inside of the film becomes less clogged inside the film. Presumed.

  The polar organic solvent may be an organic solvent having a property of being miscible with water. The polar organic solvent preferably contains at least one or more lower alcohols, and more preferably consists of lower alcohols. Examples of the lower alcohol include alcohols having 5 or less carbon atoms such as methanol, ethanol, propanol, isopropanol, butanol, ethylene glycol, propylene glycol, and glycerin. As the lower alcohol, methanol, ethanol and isopropanol are particularly preferable, and ethanol is more preferable.

[Penetration]
The method for penetrating the hydrophilic liquid into the porous membrane is not particularly limited, and examples thereof include a dipping method, a coating method, a transfer method, and a spray method. In order to efficiently permeate the hydrophilized liquid into the porous membrane, a dipping method or a coating method is preferable, and a dipping method is more preferable. The permeation is performed so that the hydrophilization liquid permeates the entire thickness direction of the porous membrane at least at a portion subjected to light irradiation described later.
In the dipping method, the porous film is impregnated with the hydrophilizing liquid by immersing the porous film in the hydrophilizing liquid. What is necessary is just to remove an excess hydrophilization liquid by raising a porous membrane from a hydrophilization liquid after immersion.
Immersion may be performed under pressure. The hydrophilization liquid can be efficiently injected into each pore of the porous membrane by pressurization.

The dipping time or press-fitting time in the dipping treatment or press-fitting treatment is not particularly limited, but is generally about 0.5 seconds to 30 minutes, and preferably about 0.5 seconds to 10 minutes. The immersion time can be shortened by selecting a solvent or the like.
By appropriately selecting the immersion time of the porous membrane in the hydrophilization liquid and the monomer concentration in the hydrophilization liquid, it is possible to appropriately adjust the monomer adhesion amount.

[Dry]
The porous membrane may be dried after the permeation of the hydrophilizing liquid into the porous membrane and before the curing reaction. By drying and removing at least a part of the solvent in the hydrophilized liquid by drying, the pores of the porous membrane are not blocked, and the composition can easily adhere uniformly over the entire pore surface of the porous membrane. Become. Drying may be semi-dry. In the present specification, semi-drying means that the solvent is volatilized and removed to the extent that the solvent that can volatilize remains.
Examples of drying means include heating, wind, reduced pressure, and the like, and are not particularly limited. However, air drying and warm drying are preferable and air drying is more preferable because of the simplicity of the manufacturing process. Drying may be achieved simply by leaving it to stand.

[Curing reaction]
The curing reaction is achieved by monomer polymerization. The polymerization may be photopolymerization, and photopolymerization with ultraviolet rays is preferred.

  As the light source used in the light irradiation for photopolymerization, a light source that emits light having a wavelength with which the polymerization initiator reacts can be arbitrarily selected. For example, a halogen xenon lamp, a metal halide lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a sterilization lamp, a xenon lamp, an LED (Light Emitting Diode) light source lamp, or the like can be used. The light irradiation may be performed from at least one surface of the porous film, but is preferably performed from both surfaces. This is because the curing reaction proceeds on the surfaces of both films and a more hydrophilic film can be obtained. Further, when the curing reaction is carried out using a porous film having a pore size distribution as a base material, it is preferable to perform light irradiation from the membrane surface having a smaller pore size.

The atmosphere at the time of light irradiation is preferably air or an inert gas replacement atmosphere, and more preferably an atmosphere in which air is replaced with nitrogen until the oxygen concentration becomes 1% or less.
Irradiation energy when irradiated with ultraviolet rays as the light irradiation is preferably ^{20mJ / cm 2 ~50J / cm 2} , 50mJ / cm 2 ~1500mJ / cm 2 is more preferable. The illuminance is preferably ^{10mW / cm 2 ~2000mW / cm 2} , more preferably ^{20mW / cm 2 ~1500mW / cm 2} , further preferably ^{40mW / cm 2 ~1000mW / cm 2} .

  Due to the curing reaction of the composition, crosslinking occurs simultaneously with polymerization, and a network of crosslinked polymers is formed on at least a part of the outer surface of the porous membrane. The degree of polymerization of the cross-linked polymer in the hydrophilic coating (including those that are cross-linked) is not particularly limited.

  In the production method of the present invention, the curing reaction is initiated when the porous membrane is semi-dry. Specifically, after the hydrophilic film has permeated the porous film, the porous film retains the hydrophilic liquid so that the mass of the porous film before the hydrophilic film has permeated the hydrophilic film is reduced. The curing reaction starts when the mass is larger than a certain amount. In particular, in the porous membrane, the present inventors are sites where the hydrophilizing liquid penetrates in the entire thickness direction, and the mass is 3 to 16 times the mass before the hydrophilizing liquid is permeated. It was found that a hydrophilic porous film having higher water permeability and higher wettability can be obtained by a curing reaction in which light is irradiated. From the viewpoint of handleability, the mass is preferably 3 to 12 times, and more preferably 3 to 8 times.

  The part to be irradiated with light can be appropriately set according to production conditions, and may be a part or the whole of the entire area of the porous membrane. The entire area of the porous membrane may be subjected to the curing reaction by performing multiple times of light irradiation satisfying the above-mentioned mass conditions at different sites. For example, when a hydrophilic porous membrane is produced by roll-to-roll, the entire region in the TD (transverse direction) direction within a certain distance range in the MD (machine direction) direction of the roll-like porous membrane is defined as the above-mentioned site. The light may be sequentially irradiated in the MD direction. In this case, the permeation process and the drying process described above and the cleaning process described later can also be sequentially performed in the MD direction. Alternatively, the entire porous film (sheet type not in a roll shape) having an area that can be irradiated with light once may be irradiated with light as the portion.

  When the porous membrane is in the form of a roll, it may be difficult to compare the masses of specific parts. In such a case, for example, a part of the porous membrane to be used may be sampled, and the semi-drying conditions for obtaining the above-mentioned mass after permeation of the used hydrophilizing solution may be confirmed in advance. By irradiating the part after semi-drying with the confirmed semi-dry condition, the light irradiation satisfying the above-mentioned mass condition can be performed.

When light irradiation is performed a plurality of times on the same part, at least the first light irradiation may be started when the part is in the above mass range. In any light irradiation, it is preferable that the same part is in the above mass range.
When the hydrophilized liquid penetrates into the porous membrane (for example, when it is pulled up after immersion), the mass of the porous membrane is already 3 to 16 times the total mass of the porous membrane before the hydrophilized liquid is permeated. If it is, it can be subjected to a curing reaction without further removing the solvent by volatilization. When it exceeds 16 times, it can be semi-dried until it becomes 3 to 16 times the total mass of the porous membrane before infiltrating the hydrophilizing liquid and subjected to a curing reaction.

[Washing]
After the crosslinked polymer network is formed by the curing reaction, it is preferable to perform washing using a washing solvent. This is because unreacted monomers and excess cross-linked polymer can be removed. In addition, unnecessary components contained in the raw material porous membrane can be removed by washing. The cleaning method is not particularly limited, but the cleaning solvent may be permeated into the membrane surface and the pore surface of the hydrophilic porous membrane by dipping or press-fitting, and then removed. Examples of the cleaning solvent include the solvents exemplified as the solvent for the hydrophilizing liquid. The washing solvent may be permeated and removed two or more times. At this time, the washing solvent may be the same or different in two or more washings, but is preferably different. The washing solvent used at the end of washing is preferably water. It is particularly preferable to immerse in water. This is to remove organic solvent components such as alcohol.

<Uses of hydrophilic porous membrane>
The hydrophilic porous membrane of the present invention can be processed into a shape according to the application and used for various applications. Examples of the shape of the hydrophilic porous membrane include a flat membrane shape, a tubular shape, a hollow fiber shape, a pleated shape, a fiber shape, a spherical particle shape, a crushed particle shape, and a massive continuous body shape. It may be processed into a shape according to the application before the hydrophilic treatment of the porous membrane, or may be processed into a shape according to the application after the hydrophilic treatment of the porous membrane.

  The hydrophilic porous membrane may be attached to a cartridge that can be easily removed in an apparatus used for various applications. In the cartridge, the hydrophilic porous membrane is preferably held in a form that can function as a filtration membrane. The cartridge holding the hydrophilic porous membrane can be produced in the same manner as a known porous membrane cartridge, and for example, refer to WO2005 / 037413 and JP2012-045524A.

  The hydrophilic porous membrane of the present invention can be used in various applications as a filtration membrane. Filtration membranes are applied to the separation, purification, recovery, concentration, etc. of liquids containing or suspending various polymers, microorganisms, yeasts, and fine particles, especially from liquids containing fine fine particles that require filtration. It can be applied when it is necessary to separate. For example, a filtration membrane can be used when separating fine particles from various suspensions containing fine particles, a fermentation broth, a culture solution, or the like, or a pigment suspension. Specifically, the hydrophilic porous membrane of the present invention is required for the production of drugs in the pharmaceutical industry, the production of alcoholic beverages such as beer in the food industry, the fine processing in the electronics industry, the production of purified water, and the like. It can be used as a microfiltration membrane.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Accordingly, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Production of hydrophilic porous membranes of Examples and Comparative Examples>
[Preparation of hydrophilization solution]
The polymerizable monomer shown in Table 1 (amount to be 0.38% by mass in the hydrophilization solution) and a mixed solvent were mixed and stirred for 30 minutes. Thereafter, a polymerization initiator (Irg2959, manufactured by BASF) was mixed so as to be 0.12% by mass and stirred for 30 minutes to obtain a hydrophilized liquid.

[Penetration and UV irradiation]
As the porous membrane, as shown in Table 1, a polysulfone membrane or a polyvinylidene fluoride membrane was used.
As a polysulfone membrane, PSEUH20 manufactured by FUJIFILM Corporation was used. This polysulfone membrane has an asymmetric structure with a pore diameter of 0.2 μm and a thickness of 130 μm. In the examples, the membrane surface side with a large pore diameter is the primary surface, and the membrane surface side with the small pore diameter is the secondary surface.
As the polyvinylidene fluoride film, Durapore 0.22 manufactured by Merck Millipore was used. This PVDF membrane has a symmetrical structure with a pore diameter of 0.22 μm and a thickness of 125 μm.

The whole porous membrane was immersed in a hydrophilizing solution for 2 minutes, and the porous membrane was pulled up. The porous membrane was suspended, and the porous membrane was dried for 0 to 10 minutes by applying a wind of 0.8 m / sec at 25 ° C. When the film mass after semi-drying became the mass described in Table 1 with respect to the film mass before immersion, the porous film was irradiated with UV. UV irradiation was performed from both membrane surfaces, and UV irradiation was performed on the other surface (secondary surface in the example of the polysulfone film) immediately after UV irradiation on one surface (primary surface in the example of the polysulfone film). All UV irradiations were performed at 200 mW / cm ² and 100 mJ / cm ² using a high pressure mercury lamp (Fusion, lighthammer 10).

[Washing and drying]
After immersing the hydrophilic porous membrane after UV irradiation in an IPA 75% aqueous solution (IPA 75% aqueous solution in which IPA (isopropyl alcohol) and pure water are mixed at a mass ratio of 3: 1) heated to 70 ° C. for 10 minutes. Then, it was immersed in pure water at room temperature for 3 minutes and dried at room temperature. The hydrophilic porous membrane is further immersed in a 30% aqueous ethanol solution of ethanol and pure water mixed at a mass ratio of 3: 7 for 30 minutes, then immersed in pure water for 5 minutes, and finally at a temperature of 70 ° C. and 99%. It was made to dry for 26 hours in a humidity environment.
The hydrophilic porous membrane after washing was used for the following evaluation. In addition, about washing | cleaning tolerance, it evaluated using the hydrophilic porous membrane before and behind the said washing | cleaning process.

<Evaluation of hydrophilic porous membranes of Examples and Comparative Examples>
[Water permeability]
The hydrophilic porous membrane was cut into a 47 mm diameter circle, and set at the bottom of a container (manufactured by Merck Millipore, stainless pressure filter holder XX4004700). Water was introduced from the upper part of the container, and the pressure was increased until a pressure of 100 kpa was applied to the hydrophilic porous membrane. In this state, the water permeability was evaluated by the water flow rate of the water that permeates the porous membrane. A water flow rate [ml / cm ² / min] per unit area was determined from the mass of water that was discharged for 30 seconds after starting to collect water, and evaluated according to the following evaluation criteria. The results are shown in Table 1.
1: Less than 15 ml / cm ² / min 2: 15 ml / cm ² / min or more and less than 25 ml / cm ² / min 3: 25 ml / cm ² / min or more and less than 35 ml / cm ² / min 4: 35 ml / cm ² / min or more Less than 50 ml / cm ² / min 5: 50 ml / cm ² / min or more

[Coffee soup]
The coffee wicking test was conducted according to the following procedure. One end of the hydrophilic porous membrane was immersed for 10 minutes in an aqueous solution in which instant coffee (Gold Blend, Nestle) was dissolved to a concentration of 1.6% by mass. After soaking, the height of the portion where the hydrophilic porous membrane was colored with coffee was measured from the position of the liquid surface dried at room temperature and soaked in coffee. The primary surface and the secondary surface were measured and evaluated according to the following evaluation criteria. The results are shown in Table 1.
1: 1 primary surface / secondary surface, whichever is lower is less than 3 cm. 2: 1: primary surface / secondary surface, whichever is lower, 3 cm or more and less than 4.5 cm. 3: 1 primary surface / secondary. The lower surface has a height of 4.5 cm or more and less than 5.5 4: 1 primary surface / secondary surface, whichever is the lower surface is 5.5 cm or more and less than 6.5 5: 1 primary surface / secondary The height of the lower of the surfaces is 6.5 cm or more

[Wash resistance]
As the washing resistance, the change in the coffee sucking height before and after washing was evaluated. The coffee sucking height was compared with the lower of the primary surface and the secondary surface. P = Qa / Qb was calculated by setting Qb as the suction height before cleaning and Qa as the amount suction height after cleaning, and the cleaning resistance was evaluated according to the following evaluation criteria. The results are shown in Table 1.
1: Less than 0.5 2: 0.5 or more but less than 0.8 3: 0.8 or more but less than 0.9 4: 0.9 or more but less than 0.95 5: 0.95 or more but less than 1.0

The ClogP of the monomer used is as follows.
FAM-401 (-0.1926)
FAM-301 (-0.194)
FAM-201 (-0.403)
FAM-101 (-5.161)
N, N-methylenebisacrylamide (-0.9426)
Pentaerythritol tetraacrylate (3.49)

Claims (16)

A method for producing a hydrophilic porous membrane, comprising:
The hydrophilic porous membrane includes a porous membrane and a hydrophilic coating that covers at least a part of the outer surface of the porous membrane,
The manufacturing method includes:
Impregnating the porous membrane with the hydrophilizing liquid for forming the hydrophilizing coating, and subjecting the porous membrane after permeating the hydrophilizing liquid to a curing reaction,
The hydrophilizing liquid contains a polymerizable monomer and a mixed solvent of a polar organic solvent and water,
The total mass of the polar organic solvent is less than 10% by mass or more than 60% by mass with respect to the total mass of the mixed solvent;
The part where the curing reaction is a part of the porous membrane in which the hydrophilization liquid penetrates in the entire thickness direction, and the mass is 3 to 16 times the mass before the hydrophilization liquid is infiltrated The said manufacturing method performed by irradiating with light. The manufacturing method according to claim 1, wherein the permeation is performed by immersing the porous membrane in the hydrophilic liquid. The manufacturing method according to claim 2, wherein the porous membrane is pulled up from the hydrophilic liquid after the immersion. The manufacturing method as described in any one of Claims 1-3 including drying the said porous film | membrane after infiltration of the said hydrophilization liquid, and before the said hardening reaction, and volatilizing a part of said mixed solvent. The said light irradiation is ultraviolet irradiation, The manufacturing method as described in any one of Claims 1-4. The production method according to claim 1, wherein the polar organic solvent is an organic solvent miscible with water. The production method according to claim 6, wherein the polar organic solvent contains at least one kind of alcohol having 5 or less carbon atoms. The production method according to claim 1, wherein the polymerizable monomer is an acrylic monomer. The production method according to claim 8, wherein the acrylic monomer is a trifunctional to hexafunctional monomer. The production method according to claim 9, wherein the acrylic monomer has a ClogP value of 2.0 or less. The method according to claim 9 or 10, wherein the acrylic monomer is (meth) acrylamide. The manufacturing method as described in any one of Claims 9-11 in which the said hydrophilization liquid contains 1 to 2 functional acrylic monomers. The production according to claim 12, wherein a mass ratio of the trifunctional to hexafunctional acrylic monomer and the monofunctional to bifunctional acrylic monomer in the hydrophilization liquid is 20:80 to 80:20. Method. The method according to claim 12 or 13, wherein the monofunctional to bifunctional acrylic monomer is (meth) acrylamide. The manufacturing method according to claim 1, wherein the porous membrane contains polysulfone. The manufacturing method according to claim 1, wherein the porous membrane has a pore size distribution.