WO2020075713A1

WO2020075713A1 - Coating composition for hydrophilization of microporous film, and hydrophilic microporous film

Info

Publication number: WO2020075713A1
Application number: PCT/JP2019/039659
Authority: WO
Inventors: 竜児松元; 直長迫; 隆行岩▲崎▼
Original assignee: Jnc株式会社
Priority date: 2018-10-09
Filing date: 2019-10-08
Publication date: 2020-04-16

Abstract

The purpose of the present invention is to provide a microporous film having permanent hydrophilicity but free of clogging of fine pores caused during hydrophilization of the microporous film. A means was discovered for hydrophilization of a microporous film without hindering the water permeability of the microporous film, and the means involves coating a microporous film with a hydrophilic monomer and a crosslinking-agent monomer as a combination or each singly. The present invention provides: a coating composition that is for hydrophilization of a microporous film and that contains a trifunctional acrylate compound and a salt of an acrylamide monomer compound: and a hydrophilic microporous film coated with a polymer derived from said coating composition.

Description

Coating composition for making microporous membrane hydrophilic and hydrophilic microporous membrane

The present invention relates to a microporous membrane hydrophilized with a coating composition.

Microporous membranes made of fluorine-based resins such as polyvinylidene fluoride (PVDF) -based resins and polytetrafluoroethylene (PTFE) -based resins have excellent chemical resistance and heat resistance, and are therefore suitable for air filters, bag filters, and liquid filtration. Widely used for filters and the like (see Patent Document 1).
However, the microporous film made of a fluororesin is generally hydrophobic. Therefore, for example, when a microporous membrane made of PVDF resin (hereinafter referred to as PVDF microporous membrane or PVDF membrane) is used for filtration of an aqueous solution, the surface of the PVDF membrane is polyvinyl alcohol (PVA). ) Or the like, or a method of substituting with alcohol such as ethanol, etc. However, the hydrophilicity of the hydrophilized PVDF membrane obtained by these methods has a poor sustainability of the effect. Therefore, if the alcohol used for hydrophilization becomes dry, it must be treated with alcohol again for hydrophilization. Further, PVA or ethanol used for hydrophilization elutes from the surface of the PVDF membrane along with filtration, so that the hydrophilization effect of the PVDF membrane disappears. In addition, there are problems that PVA and ethanol used for hydrophilization are mixed in the filtrate, and pores are clogged with PVA.

International publication 2014/054658 pamphlet

The conventional method for hydrophilizing a microporous membrane made of a fluorine resin such as PVDF resin or PTFE resin has the above problems. Therefore, an object of the present invention is to provide a coating composition for hydrophilizing a hydrophobic microporous film, particularly a microporous film made of a fluororesin. Furthermore, it is an object of the present invention to provide a microporous membrane having permanent hydrophilicity without clogging of pores when the microporous membrane is made hydrophilic.

The present inventors have proceeded with the development for the purpose of providing a microporous membrane that is hydrophilized even in a dry state and can be used for filtering an aqueous solution.

As a result, the inventors have found a means for coating a microporous membrane with a combination of a hydrophilic monomer and a crosslinkable monomer, thereby making the microporous membrane hydrophilic without impairing the water permeability of the microporous membrane, and completed the present invention.

When a crosslinking monomer is used as a coating agent, a trifunctional compound is more likely to clog the microporous membrane than a bifunctional compound, but even if a trifunctional compound is used, The present invention has been completed by finding that the porous membrane can be made hydrophilic without clogging.

That is, the configuration of the present invention is as follows.

[1] A coating composition for rendering a microporous membrane hydrophilic, which comprises a salt of an acrylamide monomer compound represented by the following formula (I) and a trifunctional acrylate compound represented by the formula (II).

... (I)

... (II)
(In the formula, l + m + n is 9.)
[2] The coating composition according to [1], wherein the microporous film is a polyvinylidene fluoride-based resin or a polytetrafluoroethylene-based resin microporous film.
[3] A hydrophilic microporous membrane coated with a polymer derived from a salt of an acrylamide monomer compound represented by the following formula (I) and a trifunctional acrylate compound represented by the formula (II).

... (I)

... (II)
(In the formula, l + m + n is 9.)
[4] The microporous membrane according to [3], wherein the microporous membrane is a polyvinylidene fluoride resin or a polytetrafluoroethylene resin.
[5] A method for making a microporous membrane hydrophilic,
Immersing the microporous membrane in a solution of a coating composition containing a salt of an acrylamide monomer compound represented by the following formula (I) and a trifunctional acrylate compound represented by the formula (II);
A step of deoxidizing the immersed microporous membrane,
The deoxygenated microporous membrane is irradiated with ultraviolet rays to form a polymer derived from the salt of the acrylamide monomer compound represented by the formula (I) and the trifunctional acrylate compound represented by the formula (II). Coating the membrane,
Including, methods.

... (I)

... (II)
(In the formula, l + m + n is 9.)
[6] The method according to [5], wherein the microporous film is a polyvinylidene fluoride-based resin or a polytetrafluoroethylene-based resin microporous film.

According to the present invention, by coating the microporous membrane with a combination of a hydrophilic monomer and a crosslinkable monomer, the microporous membrane can be hydrophilized without impeding the water permeability of the microporous membrane.

FIG. 1 is a diagram showing an example of a process for producing the hydrophilic microporous membrane of the present invention.

The coating composition of the present invention for hydrophilizing a microporous membrane comprises a salt of an acrylamide monomer compound represented by formula (I) and a trifunctional acrylate compound represented by formula (II). In the formula (II), l + m + n is 9.

... (I)

... (II)

The microporous membrane is also called a microporous or microporous membrane and is a membrane having a large number of micropores inside, and these micropores have a connected structure, and one surface to the other surface. A membrane that allows gas or liquid to pass through. The microporous membrane is particularly preferably a membrane having minute pores with a pore diameter of about 0.01 to 10 μm, which is less likely to cause uneven liquid permeability and is less likely to cause clogging.

The salt of the acrylamide monomer compound represented by the formula (I) is (3-acrylamidopropyl) trimethylammonium chloride (APTAC), which is available, for example, from Tokyo Chemical Industry Co., Ltd.

The trifunctional acrylate compound represented by the formula (II) is an ethoxylated glycerin triacrylate, and is available, for example, from Shin-Nakamura Chemical Co., Ltd.

In the coating composition of the present invention, the salt of the acrylamide monomer compound represented by formula (I) and the trifunctional acrylate compound represented by formula (II) coat the surface of the microporous membrane when polymerized. Although it can be made hydrophilic, it is adjusted to a concentration at which polymerization is performed to the extent that it does not block the pores of the microporous membrane and hinder the water permeability of the microporous membrane.

In the coating composition of the present invention, the salt of the acrylamide monomer compound represented by the formula (I) can be, for example, 0.5 to 5% by mass in the coating composition of the present invention, preferably 0.75. It is from 3 to 3% by mass, more preferably from 1.0 to 1.5% by mass. The trifunctional acrylate compound represented by the formula (II) can be contained in the coating composition of the present invention in an amount of 0.25 to 2.5% by mass, preferably 0.5 to 1.50% by mass. %, And more preferably 0.75 to 1.25 mass%.

It is possible to use any solvent capable of dissolving the salt of the acrylamide monomer compound represented by the formula (I) and the trifunctional acrylate compound represented by the formula (II) and not inhibiting the polymerization reaction of both compounds. it can. The solvent is preferably water such as ultrapure water and alcohol such as isopropyl alcohol (IPA), methanol and ethanol. As the solvent, an aqueous solution containing alcohol in an arbitrary ratio can be used, and for example, it can be 10 to 100% by volume, preferably 15 to 80% by volume, more preferably 20 to 60% by volume. Is.

Specifically, the coating composition of the present invention comprises 0.75 to 1.5% by mass of a salt of the acrylamide monomer compound represented by the formula (I) and 0. The trifunctional acrylate compound represented by the formula (II) may be contained in an amount of 75 to 1.5% by mass.

The coating composition of the present invention may further contain a polymerization initiator. The polymerization initiator is not particularly limited, but examples thereof include a photopolymerization initiator and a thermal polymerization initiator. As the photopolymerization initiator, an IRGACURE (registered trademark) series initiator available from BASF can be used. For example, as the photopolymerization initiator, an alkylphenone-based photopolymerization initiator such as the product “IRGACURE 2959” can be used.

The coating composition of the present invention may further contain additives such as antioxidants and stabilizers. These additives can be contained in the concentrations usually used in the art.

The coating composition of the present invention can be prepared by mixing the salt of the acrylamide monomer compound, the trifunctional acrylate compound, the solvent, the polymerization initiator, and any additive in any method and order. For example, the coating composition of the present invention is prepared by adding a polymerization initiator and optionally an additive to a salt of an acrylamide monomer compound and a trifunctional acrylate compound dissolved in a solvent at a temperature of 15 to 35 ° C. and mixing them by stirring. It can be prepared by

Specifically, the coating composition of the present invention comprises 0.75 to 1.5% by mass of a salt of the acrylamide monomer compound represented by the formula (I) in an amount of 15 to 30% by volume of isopropyl alcohol aqueous solution. It may contain 75 to 1.5% by mass of a trifunctional acrylate compound represented by the formula (II), and a photopolymerization initiator.

The present invention also provides a hydrophilic microporous membrane coated with a polymer derived from the above coating composition. The microporous film used for the hydrophilic microporous film of the present invention is not particularly limited, and examples thereof include a microporous film of a fluorine-based resin such as PVDF-based resin and PTFE-based resin. The microporous film of a fluororesin is a microporous film derived from a fluororesin called a fluoropolymer, and is a microporous film manufactured using a fluororesin as a material. Further, the PVDF-based microporous membrane and the PTFE-based microporous membrane refer to microporous membranes made of PVDF-based resin and PTFE-based resin, respectively, but may be made of only the respective resins, or other The component may be included.

The fluororesin used in the present invention is a homopolymer of fluororesin and a copolymer of fluororesin. Examples of the fluorine resin include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinyl fluoride (PVF), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA). ), Tetrafluoroethylene / hexafluororopropylene copolymer (FEP), tetrafluoroethylene / ethylene copolymer (ETFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), and the like. Not limited.

The polyvinylidene fluoride resin is a resin containing a vinylidene fluoride homopolymer and / or a vinylidene fluoride copolymer. The polyvinylidene fluoride resin may contain plural kinds of vinylidene fluoride homopolymers having different physical properties (viscosity, molecular weight, etc.). Further, the polyvinylidene fluoride resin may be a resin containing plural kinds of vinylidene fluoride copolymers. The vinylidene fluoride copolymer is a polymer having a vinylidene fluoride residue structure, and is typically a copolymer of vinylidene fluoride monomer and other fluorine-based monomer, such as vinyl fluoride and tetrafluoro It is a copolymer of one or more fluorine-based monomers selected from ethylene, hexafluoropropylene and ethylene trifluoride chloride and vinylidene fluoride monomer, but is not limited thereto.

The polytetrafluoroethylene-based resin is a resin containing a polytetrafluoroethylene homopolymer and / or a polytetrafluoroethylene copolymer. The polytetrafluoroethylene-based resin may contain a plurality of types of polytetrafluoroethylene homopolymers having different physical properties (viscosity, molecular weight, etc.). Further, the polytetrafluoroethylene-based resin may be a resin containing a plurality of types of vinylidene fluoride copolymers.

The fine multi-layered film derived from a fluorine-based resin such as polyvinylidene fluoride-based resin used in the present invention is not limited to the above-mentioned fluorine-based resin alone, and may further include other components. For example, the microporous membrane including the fluororesin used in the present invention may be a microporous membrane composed of a composite material including the fluororesin and another material. For example, the microporous membrane used in the present invention may be a PVDF-based microporous membrane having an asymmetric three-dimensional structure developed by the applicant. This microporous membrane can be manufactured by the procedure described in, for example, WO 2014/054658 and WO 2015/0133364. As an example, briefly, the product “Kyner (trade name) HSV900” manufactured by Arkema as a PVDF resin, dimethylacetamide as a solvent, polyethylene glycol having a weight average molecular weight of 400 as a porosifying agent, and ultrapure water are uniformly added. A raw material liquid is manufactured by mixing. Then, a spunbond nonwoven fabric (“Eltus (trade name) P03050” manufactured by Asahi Kasei) is used as a base film, the base film is placed on a flat glass plate, and the above raw materials are placed on the base film surface using a baker applicator. The solution is applied to a thickness of 250 μm. Next, the above-mentioned film is put into a solidification tank containing ultrapure water, and the whole film is immersed in water and allowed to stand in the film solidification tank to proceed and complete the solidification of the raw material liquid adhering to the substrate film. Then, a PVDF-based microporous membrane having an asymmetric three-dimensional structure can be obtained through drying and washing steps.

The microporous membrane used in the present invention may be a commercially available product. The microporous membrane derived from a fluororesin is, for example, a PVDF membrane available from Merck Millipore as a hydrophobic durapore (type: GVHP04700) or from Membrane Solutions as an MS PVDF hydrophobic membrane, or a W.D. L. For example, a PTFE membrane available from Gore and Associates can be used.

The coating composition of the present invention can make the microporous membrane hydrophilic by being coated on the surface of the microporous membrane. The coating composition of the present invention is brought into contact with or immersed in the microporous membrane in a batch system or a continuous system to uniformly adhere the coating composition to the surface of the microporous membrane. For example, the coating composition of the present invention can be coated on the surface of a microporous film which is a substrate by the following procedure.

First, infiltrate the microporous membrane with an alcohol such as isopropyl alcohol. Next, the microporous membrane is immersed in ultrapure water to replace isopropyl alcohol with ultrapure water. Here, the alcohol is not particularly limited as long as it can infiltrate the microporous membrane. When an aqueous alcohol solution capable of infiltrating the microporous membrane is used in the coating composition for hydrophilizing the microporous membrane, the infiltration and ultrapure water substitution steps can be omitted.

Next, the microporous membrane is immersed in the coating composition for hydrophilizing the microporous membrane of the present invention. For example, the coating composition of the present invention is placed in a sealable bag such as Unipack and the microporous membrane is dipped. Immerse the coating composition in the microporous membrane until it has fully infiltrated. For example, when the solvent of the coating composition is ultrapure water, the microporous membrane is immersed in the coating composition for several tens of minutes, so that the coating composition sufficiently infiltrates the microporous membrane. In addition, when the solvent of the coating composition contains an appropriate amount of isopropyl alcohol, the microporous membrane can be instantly infiltrated.

Next, take out the immersed microporous membrane and start the polymerization of the coating composition. When the coating composition contains a photopolymerization initiator and polymerization is initiated by ultraviolet irradiation (UV irradiation) or the like, nitrogen substitution may be performed in advance to remove oxygen that may inhibit the polymerization reaction.

When the coating composition contains a photopolymerization initiator, UV irradiation can initiate the polymerization of the salt of the acrylamide monomer compound of formula (I) and the trifunctional acrylate compound of formula (II). . When the coating composition contains a thermal polymerization initiator, the polymerization is initiated by heating.

Next, the microporous membrane is washed to remove unreacted materials. The washing can be performed with warm water, warm ethanol, or the like. Moreover, you may dry by natural drying.

By the above procedure, a microporous membrane coated with a polymer derived from the salt of the acrylamide monomer compound represented by the formula (I) and the trifunctional acrylate compound represented by the formula (II) can be obtained.

The present invention further provides a method of rendering a microporous membrane hydrophilic.
The method comprises the steps of immersing a microporous membrane in a solution of a coating composition containing a salt of an acrylamide monomer compound of formula (I) below and a trifunctional acrylate compound of formula (II):
A step of deoxidizing the immersed microporous membrane,
Irradiating the deoxidized microporous membrane with ultraviolet rays. In the formula (II), l + m + n is 9.

... (I)

... (II)

The step of immersing in the solution of the coating composition can be performed by the same procedure as the above-mentioned coating of the microporous membrane.

The step of deoxidizing the immersed microporous membrane can be deoxidized by any method. In the step of deoxidizing, for example, the microporous film is allowed to stand in a nitrogen atmosphere and replaced with oxygen. The substituting step can be performed, for example, in a batch system or a continuous system. In the batch method, the microporous membrane is impregnated with the coating composition and then held by a support. Specifically, in a closed container having a transparent lid, a microporous membrane impregnated with the above coating composition was laid on a flat support (on the side of the lid), and then the laminate was left to stand. In the state, the inside of the closed container is replaced with nitrogen.

The step of irradiating the deoxygenated microporous membrane with ultraviolet rays is performed by irradiating the deoxygenated microporous membrane with ultraviolet rays to obtain a salt of the acrylamide monomer compound represented by the formula (I) and the formula (II). The microporous membrane is coated with a polymer derived from a trifunctional acrylate compound. This step can also be carried out batchwise or continuously as in the step of substituting nitrogen. In the batch method, the surface of the microporous membrane is irradiated with ultraviolet rays from the outside of the container through a transparent lid in a state where the closed container is filled with nitrogen to complete the polymerization and crosslinking reaction of the polymerizable monomer. In the continuous method, ultraviolet rays are applied to a long microporous membrane infiltrated with the coating composition. Specifically, the microporous film carried out from the container of the coating composition is carried into the ultraviolet irradiation area and moved within this area for a certain period of time. By the time the microporous film is carried out from the ultraviolet irradiation area, the polymerization and crosslinking reaction of the polymerizable monomer is completed on the surface of the microporous film.

Next, the microporous membrane whose surface is coated with a polymer is dried and washed to remove excess components. This step can also be carried out batchwise or continuously.

Furthermore, the method can further include a step of treating the obtained hydrophilic microporous membrane with an alkaline solution such as NaOH. The alkaline solution treatment is carried out by immersing it in a 0.1 M NaOH solution for 2 hours. The hydrophilic microporous membrane of the present invention has alkali resistance, and the contact angle of water does not increase even when treated with 0.1 M NaOH. That is, the hydrophilicity does not decrease.

By the above steps, a hydrophilized microporous membrane can be obtained. This microporous membrane can be dried, wound, cut and packaged according to a standard method and, if necessary.

Examples 1-8
(Production of PVDF microporous membrane)
In the present invention, the PVDF microporous membrane used as the base material is a PVDF membrane manufactured through the following steps.

(Process 1) Arkema product “Kyner HSV900” as PVDF resin, dimethylacetamide as solvent, polyethylene glycol having a weight average molecular weight of 400 as a porosifying agent, and ultrapure water are shown in Table 1 in proportions (raw materials). The raw material liquid was manufactured by uniformly mixing the mixture with the total amount of the liquid (% by mass).

(Step 2) As the base film, a spunbond nonwoven fabric (Asahi Kasei “Eltas P03050”) cut into a square of 20 cm × 20 cm was used. This substrate film was placed on a flat glass plate, and the above raw material liquid was applied to the surface of the substrate film using a baker applicator so as to have a thickness of 250 μm. The raw material liquid was applied to the number of substrate films corresponding to the number of times of quantification under the above-mentioned conditions so that the amount of residual components described later could be quantified.

(Step 3) A stainless steel vat containing 2 liters of ultrapure water was used as the solidification tank. Into this solidification tank, the film obtained in step 2 was placed so that the water surface was not ruffled, and the entire film was soaked in water, and allowed to stand in the film solidification tank for 2 minutes to adhere to the substrate film. Solidification was completed and completed.

(Step 4-1) 2.5 liters of ultrapure water was placed in a beaker with a ceramic air stone diffuser tube inserted, and dry air was supplied to the diffuser tube from an external tank to evenly dry it in ultrapure water. Bubbling air bubbles. This was used for the first washing tank. The film subjected to the step 3 was put in this first cleaning tank. The film was washed for 6 minutes while the entire surface of the film was uniformly in contact with water bubbles.

(Step 4-2) 2.5 liters of isopropanol was placed in a beaker with a ceramic air stone diffuser tube inserted, and dry air was supplied to the diffuser tube from an external tank to evenly dry air bubbles in the isopropanol. I made it gush out. This was used for the second washing tank. The film obtained in step 4-1 was put into this second cleaning tank, and the film was washed in a state where the entire surface of the film was in uniform contact with isopropanol and air bubbles. After this the film was air dried.

The pore size of the PVDF microporous membrane thus obtained was measured by the gas permeation method. A PMI palm porometer supplied by Seika Digital Image Co., Ltd. was used as a measuring instrument. Table 1 shows the mode (mode) of the pore diameter of the obtained PVDF-based microporous membrane: Lm (μm) and the proportion (%) of the pores having the pore diameter within Lm ± 15%.

(Production of hydrophilic PVDF microporous membrane)
1. Production of Coating Composition The salt of the acrylamide monomer compound represented by the formula (I) ((3-acrylamidopropyl) trimethylammonium chloride (APTAC)) was obtained from Tokyo Chemical Industry Co., Ltd.

The trifunctional acrylate compound represented by the formula (II) (ethoxylated glycerin triacrylate) was obtained from Shin Nakamura Chemical Co., Ltd. as “NK Ester (registered trademark) A-GLY-9E”.

IRGACURE 2959 obtained from BASF Japan Ltd. was used as a photopolymerization initiator.

The coating composition was prepared as shown in Table 2 below to obtain a coating composition.

2. Production of Hydrophilic Microporous Membrane Using the coating composition produced on the surface of the PVDF microporous membrane (base material) produced in the above steps 1 to 4-2 in the proportions shown in Table 2, Coated by method.

(Step 5) The PVDF-based microporous membrane that had been subjected to Step 4-2 was immersed in isopropyl alcohol, replaced with ultrapure water, and immersed in the coating composition. A non-woven fabric support and a PVDF-based microporous membrane impregnated with a coating composition were stacked in this order on the bottom surface of a stainless steel mesh of a nitrogen gas replacement box with a lid made of quartz glass. Nitrogen gas was circulated in the box for 2 minutes to fill the inside of the box with nitrogen gas. The box was kept closed after filling.

(Step 6) Ultraviolet rays were irradiated from a light source (Light Hammer 10 (product name)) outside the box through the box lid to cure the coating composition.

(Step 7) The PVDF microporous membrane was taken out from the box, washed, and dried.

(Step 8) Furthermore, as an optional step, the hydrophilic PVDF microporous membrane was immersed in a 0.1 M NaOH aqueous solution for 2 hours, washed, and dried.

The following performances were measured for the hydrophilized PVDF-based microporous membrane thus obtained (before NaOH treatment and after 0.1 M NaOH treatment).

(Water contact angle)
In order to confirm the hydrophilization effect, the water contact angle (°) on the surface of the obtained hydrophilized PVDF-based microporous membrane was measured. Approximately 2.0 μL of water droplets were deposited, and the contact angle (°) after 0.5 seconds was measured as the water contact angle.

(Initial water permeability)
A circular sheet having a diameter of 25 mm was cut out from the obtained microporous membrane. This sheet was set in a filter sheet holder having an effective filtration area of 3.5 cm ² . 5 mL of ultrapure water was passed through the set sheet at a filtration pressure of 50 kPa, and the time from the start to the end of passage of ultrapure water was measured. The water permeability was determined by the following formula.
The water permeability of the non-hydrophilic PVDF-based microporous membrane of the substrate used was the value measured after wetting with alcohol. The larger the water permeability, the lower the degree of pore clogging and the higher the liquid filtration efficiency.
Water permeability (10 ⁻⁹ m ³ / m ² / Pa / sec) = water flow rate (m ³ ) / effective filtration area (m ² ) ÷ filtration pressure (Pa) ÷ time (sec).

The results are shown in Table 2. The left column shows the coating state of the microporous membrane, the substrate (PVDF membrane used in Example 1) shows the membrane not treated with the coating composition, and the columns in which each composition is described are: Figure 3 shows a film polymerized with the stated proportions of coating composition.

Before the NaOH treatment, the base material (PVDF membrane used in Example 1) had an initial water permeability of about 160. In addition, the water-permeability of each of the substrates made hydrophilic with the coating composition of each amount ratio did not significantly change. On the other hand, the contact angle was 119.2 ° in the base material, but the base material made hydrophilic with the coating composition decreased to 3.9 to 67.4 °, and the hydrophilicity increased in both cases. It was shown that.

After the NaOH treatment, the water permeability of the base material made hydrophilic with the coating composition did not decrease. Also, the contact angle was not increased by NaOH treatment in any coating, but rather decreased.

Examples 9-12
(Production of hydrophilic PVDF microporous membrane using IPA as solvent)
In Example 1, the coating composition was mixed with ultrapure water as a solvent to prepare a total amount of 100 (mass%) to obtain a coating composition. This eliminates the step of immersing the microporous membrane with isopropyl alcohol.
In Examples 9 to 12, coating compositions were prepared by adjusting the composition as shown in Table 2 below. The surface of the PVDF-based microporous membrane (base material) produced in Example 1 was coated with the coating composition produced in the proportions shown in Table 3. The PVDF microporous membrane (base material) was coated on the surface in the same procedure as in Example 1.

The results are shown in Table 2. The left column shows the coating state of the membrane, the substrate (PVDF membrane used in Example 1) column shows the membrane not treated with the coating composition, and the column describing each reaction solution is the description. 3 shows a film obtained by polymerizing a coating composition of the solvent thus prepared on a substrate.

Before the NaOH treatment, the base material (PVDF membrane used in Example 1) had an initial water permeability of about 160. Further, the base material made hydrophilic with a coating composition using 20 vol% and 30 vol% isopropyl alcohol aqueous solution as a solvent has water permeability of 155.1, 136.9, 148.0 and 140.5, respectively. The water permeability was higher than that when ultrapure water was used as the solvent. On the other hand, the contact angle was 119.2 ° for the substrate (PVDF membrane used in Example 1), but the substrate made hydrophilic with the coating composition decreased to 42.2-46.2 °. It was shown that the hydrophilicity was increased in all cases.

Example 13
(Production of hydrophilic PVDF porous membrane using PVDF membrane manufactured by Membrane Solutions)
In Example 13, the PVDF membrane of MS PVDF hydrophobic membrane available from Membrane Solutions was used as the substrate.
In Example 13, the composition was adjusted as shown in Table 3 below to prepare a coating composition. The surface of a PVDF membrane from Membrane Solutions was coated with the coating composition. The PVDF membrane was coated on the surface by the same procedure as in Example 2.

The results are shown in Table 3. The left column shows the coating state of the membrane, the substrate (Membrane Solutions) column shows the membrane not treated with the coating composition, and the MS-hydrophobic membrane hydrophilization column shows the coating composition. Figure 3 shows a film polymerized on a substrate.

Before the NaOH treatment, the base material (Membrane Solutions) had an initial water permeability of 44.7. The water permeability of the substrate made hydrophilic with the coating composition was 40.9. On the other hand, the contact angle was 113.9 ° in the base material (Membrane Solutions), but the base material made hydrophilic with the coating composition decreased to 46.5 °, and the hydrophilicity is increased. Was shown.

After the NaOH treatment, the water permeability of the substrate made hydrophilic with the coating composition did not decrease. It was also shown that the contact angle was not affected by the NaOH treatment.

Example 14
(Production of hydrophilic PVDF porous membrane using PVDF membrane manufactured by Merck Millipore)
In Example 14, a PVDF membrane of hydrophobic Durapore (type: GVHP04700) available from Merck Millipore was used as a substrate.
In Example 14, a coating composition was prepared by adjusting the composition as shown in Table 4 below. The surface of the PVDF membrane from Merck Millipore was coated with the coating composition. The PVDF membrane was coated on the surface by the same procedure as in Example 1.

The results are shown in Table 4. The left column shows the coating state of the membrane, the substrate (Merck Millipore) column shows the membrane not treated with the coating composition, and the hydrophilization column of M company-hydrophobic membrane shows the coating composition. Figure 3 shows a film polymerized on a substrate.

Before the NaOH treatment, the base material (Merck Millipore) had an initial water permeability of 37.0. The substrate made hydrophilic with the coating composition had a water permeability of 15.6. On the other hand, the contact angle was 118.9 ° in the base material (Membrane Solutions), but the base material made hydrophilic with the coating composition decreased to 56.5 °, and the hydrophilicity was increased. Was shown.

Example 15
(Manufacture of hydrophilic PTFE porous membrane using PTFE membrane manufactured by Sumitomo Electric Industries, Ltd.)
In Example 15, a PTFE membrane available from Sumitomo Electric Industries, Ltd. was used as the base material.
In Example 15, a coating composition was prepared by adjusting the composition as shown in Table 5 below. The surface of the Sumitomo Electric Industries, Ltd. PTFE membrane was coated with the coating composition. The procedure of Example 1 was followed to coat the surface of the PTFE membrane.

The results are shown in Table 5. The left column shows the coating state of the membrane, the HP-020-30 column shows the membrane not treated with the coating composition, and the HPW-020-30 hydrophilization column shows the coating composition as the base material. Shows a film polymerized to.

Before the NaOH treatment, the base material (HP-020-30) had an initial water permeability of 37.0. The water permeability of the substrate made hydrophilic with the coating composition was 22.7. On the other hand, the contact angle could not be measured on the base material (HP-020-30), but the base material made hydrophilic with the coating composition was 123.8 °, showing that the hydrophilicity was increased. It was

The hydrophilic microporous membrane of the present invention can be widely used as an air filter, a bag filter, a liquid filtration filter, and the like.

Claims

A coating composition for rendering a microporous membrane hydrophilic, comprising a salt of an acrylamide monomer compound represented by the following formula (I) and a trifunctional acrylate compound represented by the following formula (II).

... (I)

... (II)
(In the formula, l + m + n is 9.)
The coating composition according to claim 1, wherein the microporous membrane is a polyvinylidene fluoride-based resin or a polytetrafluoroethylene-based resin microporous membrane.
A hydrophilic microporous membrane coated with a polymer derived from a salt of an acrylamide monomer compound represented by the following formula (I) and a trifunctional acrylate compound represented by the following formula (II).

... (I)

... (II)
(In the formula, l + m + n is 9.)
The microporous film according to claim 3, wherein the microporous film is a polyvinylidene fluoride resin or a polytetrafluoroethylene resin.
A method for making a microporous membrane hydrophilic,
Immersing the microporous membrane in a solution of a coating composition containing a salt of an acrylamide monomer compound represented by the following formula (I) and a trifunctional acrylate compound represented by the formula (II);
A step of deoxidizing the immersed microporous membrane,
The deoxygenated microporous membrane is irradiated with ultraviolet rays to form a polymer derived from the salt of the acrylamide monomer compound represented by the formula (I) and the trifunctional acrylate compound represented by the formula (II). Coating the membrane,
Including, methods.

... (I)

... (II)
(In the formula, l + m + n is 9.)
The method according to claim 5, wherein the microporous membrane is a polyvinylidene fluoride-based resin or a polytetrafluoroethylene-based resin microporous membrane.