JP6429356B2 - Temperature-responsive microporous membrane and solid polymer electrolyte membrane using the same - Google Patents

Description

  The present invention relates to a temperature-responsive microporous membrane applicable to a separator of a secondary battery, a coating substrate thereof, a filtration filter, a pore filling membrane suitably used as a solid polymer electrolyte membrane of a fuel cell, and the like. The present invention relates to a solid polymer electrolyte membrane.

  In recent years, microporous membranes are generally used in separation membrane materials used for lithium ion secondary battery separators and liquid filtration filters. In these applications, various properties such as heat resistance, strength, and electrolyte retention are required. In recent years, as a method for realizing such required characteristics, a method using a film obtained by coating a porous substrate is becoming mainstream. In such a microporous film for coating, with the diversification of coating materials, the wettability and film physical properties (MD / TD strength balance, pore size distribution, etc.) are required in order to realize uniform coating on the coating surface. Control is important. By realizing uniform coating, it is desired to improve yield, wide product, and improve productivity.

  Under such circumstances, a device for realizing such uniform coating is known. For example, Patent Document 1 discloses a separator in which a nonwoven fabric containing heat-resistant fibers and fibrillated liquid crystalline polymer fibers is subjected to a surface treatment to modify the surface of the nonwoven fabric separator. Certainly, by selecting the most suitable treatment method for coating, uniform coating can be achieved, but since there is only one treatment method (surface energy after treatment is constant), process fluctuations such as temperature fluctuations occur. In this case, coating unevenness such as film thickness fluctuation occurs, and it was necessary to stop and adjust the manufacturing process to eliminate them.

  Further, a temperature responsive membrane material having a property of adjusting the pore diameter in response to temperature is conventionally known. For example, Patent Document 2 discloses a membrane filtration system that aims to increase the amount of treated water to increase the system operation rate, reduce the cost required for chemical cleaning and membrane replacement, and reduce the total running cost. Has been. This temperature-responsive membrane is composed of amphiphilic molecules such as a polymer obtained by copolymerizing acrylic acid, 2-carboxyisopropylacrylamide and 3-carboxy-n-propylacrylamide with N-isopropylacrylamide. In this method, since the pore diameter can be adjusted by the temperature response, it has been devised to cope with the previous process fluctuations, but it is assumed that it is used in a completely wet environment because it is applied to a filtration system. There is a problem that control of properties, MD / TD strength, pore diameter, etc. are not optimized, and the film is not necessarily suitable for coating.

JP 2003-297680 A JP 2007-130532 A

  An object of the present invention is to appropriately utilize the temperature characteristics of a temperature-responsive film material, to control the wettability of the film surface, and to optimize the balance of MD / TD strength, thereby various coatings. An object of the present invention is to provide a highly versatile film material that can appropriately cope with conditions (including process variations such as temperature and humidity).

In order to solve the above problems, a temperature-responsive microporous membrane according to the present invention is a temperature-responsive microporous membrane in which an amphiphilic molecule is disposed on a substrate made of polyolefin, and the amphiphilic molecule The surface free energy measured by the Owens-Wendt method of the base material on which is arranged is 20 mC / m ² or more at 20 ° C., and the surface free energy is 35 mJ / m ² or less at 45 ° C. And Here, the surface free energy is a value of the surface free energy measured by the Owens-Wendt method (two-liquid method) after 25 seconds have elapsed after dropping. The microporous membrane refers to a polymer porous membrane having uniform and fine through-holes made of a polymer material. Furthermore, a temperature-responsive microporous membrane is a membrane in which molecules (amphiphilic molecules) that change the molecular structure by hydration or dehydration accompanying temperature fluctuation are supported on the surface of the previous microporous membrane or inside. Say.

  Such a temperature-responsive microporous membrane of the present invention has a substrate surface that is hydrophilic at room temperature and hydrophobic at 45 ° C., so that the wettability of the membrane surface can be improved by appropriately changing the temperature. Can be controlled. For example, when the temperature-responsive microporous membrane of the present invention is used as a coating separator substrate for a secondary battery, when applying a hydrophilic coating material, the coating is carried out at room temperature or lower, and a hydrophobic coating material When the coating is applied, the coating material is applied at 45 ° C. or higher so that the coating material penetrates into the inside of the microporous membrane, and the adhesion is improved. Appropriate temperature conditions can be selected in accordance with the physical properties of the coating material and the desired film structure, such as preventing penetration of the coating material and preventing deterioration of the air resistance. In addition, when the temperature-responsive microporous membrane of the present invention is used in a liquid filtration filter, the filtration temperature conditions are appropriately controlled according to the physical properties of the solvent during filtration, and the physical properties of the washing liquid during washing. In addition, by properly controlling the washing temperature condition, it is possible to maximize the filtration performance and the washing effect. Furthermore, when the temperature-responsive microporous membrane of the present invention is used as a support for a fuel cell pore filling membrane, an ion (proton) conductive electrolyte solution is introduced into the pores by changing the temperature conditions. Since it can be filled efficiently, a uniform and highly ion conductive film can be formed.

  In the temperature-responsive microporous membrane of the present invention, it is preferable that the substrate is made of two or more kinds of polyolefins having different weight average molecular weights. The polyolefin is preferably a polymer obtained by polymerizing one or more selected from the group consisting of ethylene, propylene, 1-butene, 4-methyl-pentene-1 and 1-hexene, or a mixture thereof. By combining these two or more types of polyolefins, the physical properties of the substrate (tensile strength, air permeability, pore diameter, etc.) can be finely adjusted, and the amphiphilic molecules are excellently supported. The excellent temperature responsiveness possessed by the molecule can be exhibited effectively, and the strength balance suitable for coating can be obtained, and therefore, it can be suitably used for various coating conditions.

  As the amphiphilic molecule in the temperature-responsive microporous membrane of the present invention, for example, a polymer obtained by polymerizing N-isopropylacrylamide, or N-isopropylacrylamide with acrylic acid, 2-carboxyisopropylacrylamide and 3-carboxy-n-propyl A polymer obtained by copolymerizing acrylamide can be used as the amphiphilic molecule. In addition to this, the following polymer materials that reversibly expand / contract at a predetermined temperature described in Patent Document 2 can be used.

· N- Biniruiso acid amide polymer, poly -N- alkyl acrylamide derivative, represented by poly-isopropylacrylamide and polyacrylamide derivatives and polyvinyl derivatives copolymers, N- Biniruiso butyramide such as N- vinyl C _3- Copolymers of ₉ acylamides and N-vinyl C _1-3 acylamides such as N-vinylacetamide, polyacrylamide derivatives, and polymers of monomers composed of poly-N-vinylacylamide and N-isopropylacrylamide And a polymer of monomers composed of N-vinylisobutyric acid amide

In the temperature-responsive microporous membrane of the present invention, it is preferable that the tensile breaking strength in the MD direction is 1000 to 4500 kgf / cm ² and the tensile breaking strength in the TD direction is 1000 to 3000 kgf / cm ² . By setting the tensile breaking strength in the MD direction and the TD direction in such a range, it is possible to secure an optimum tension during coating and to provide a film material having excellent coating properties.

  In addition, a solid polymer electrolyte membrane for a fuel cell can be configured using the temperature-responsive microporous membrane according to the present invention. Such a temperature-responsive microporous membrane can be suitably used as a support for a pore filling membrane for forming a solid electrolyte membrane. The pore filling membrane refers to a polymer obtained by filling a microporous substrate matrix made of polyolefin, Nafion material or the like with an ion conductive electrolyte solution.

  The temperature-responsive microporous membrane according to the present invention can provide a highly versatile membrane material that can control the wettability of the membrane surface by appropriately changing the temperature.

It is a schematic diagram which shows the molecular weight distribution curve of polyolefin. It is a chart which shows the result of the Fourier-transform infrared spectroscopy analysis (FT-IR analysis) (transmission method) of the temperature-responsive microporous film which concerns on one embodiment of this invention.

The temperature-responsive microporous membrane according to the present invention will be described in detail below. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist thereof.
The temperature-responsive microporous membrane according to this embodiment is a polymer obtained by polymerizing N-isopropylacrylamide as an amphiphilic molecule on a polyolefin substrate, or acrylic acid, 2-carboxyisopropylacrylamide on N-isopropylacrylamide. And a temperature-responsive microporous membrane in which a polymer obtained by copolymerizing 3-carboxy-n-propylacrylamide is disposed. In this embodiment, the temperature-responsive microporous membrane is a membrane in which a molecule (amphiphilic molecule) that changes the molecular structure by hydration or dehydration accompanying temperature fluctuation is supported on the surface of the previous microporous membrane. It is.

  Examples of the method for supporting an amphiphilic molecule include spin coating, dip coating, spray coating, graft polymerization to polyolefin, block copolymerization, plasma polymerization, and electron beam crosslinking with an amphiphilic molecule solution.

  The polyolefin constituting the substrate of this embodiment includes polyethylene, polypropylene, poly (4-methyl-pentene-1), ethylene-propylene copolymer, polytetrafluoroethylene, polytrifluoroethylene chloride, polyfluoride. Examples thereof include vinylidene, polyvinylidene chloride, polyvinyl fluoride, polyvinyl chloride, polysulfone, and polycarbonate, and it is preferable to use polyethylene. The polyethylene content is preferably 90% by weight or more, more preferably 95% by weight or more, and particularly preferably 99% by weight or more, based on 100% by weight of the entire polyolefin. Further, when the total polyethylene is 100% by weight, the content of the polyethylene component having a molecular weight of 500,000 or less is preferably 85% by weight or less, and the content of the polyethylene component having a molecular weight of 1 million or more is preferably 15% by weight or more. . By setting the composition ratio of polyethylene within the above range, the strength of the microporous membrane can be improved.

  The molecular weight of polyethylene can be measured, for example, by a GPC (gel permeation chromatography) analysis technique. FIG. 1 shows a schematic diagram of a molecular weight distribution curve of polyethylene obtained by GPC, in which the horizontal axis is a logarithmic value of molecular weight, and the vertical axis is a value obtained by differentiating the concentration fraction of polyethylene by a logarithmic value of molecular weight. In FIG. 1, the region (a) corresponds to “a polyethylene component having a molecular weight of 500,000 or less”, and the region (b) corresponds to “a polyethylene component having a molecular weight of 1 million or more”.

  The content of the polyethylene component having a molecular weight of 500,000 or less is preferably 85% by weight or less, more preferably 65% by weight or less, and 60% by weight or less, based on 100% by weight of the entire polyethylene. Is particularly preferred. When the content of the polyethylene component having a molecular weight of 500,000 or less is 85% by weight or more, a sufficient molecular chain entanglement effect cannot be obtained, and it becomes difficult to ensure the strength of the microporous membrane.

  On the other hand, the content of the polyethylene component having a molecular weight of 1 million or more is preferably 15% by weight or more, and more preferably 25% or more, when the whole polyethylene is taken as 100% by weight. By setting the content of the polyethylene component having a molecular weight of 1,000,000 or more to 20% by weight or more, excellent strength can be obtained, and it is suitable for coating and also improves safety when used as a battery.

  The physical properties such as the film thickness, average pore diameter, porosity, etc. of the temperature-responsive microporous film of this embodiment are not particularly limited, but the film thickness is preferably 1 to 2000 μm, more preferably 2 to 1000 μm. It is. The average pore diameter is preferably 0.005 to 20 μm, more preferably 0.01 to 10 μm, and the porosity is preferably 20 to 70%, more preferably 30 to 60%.

[Film thickness]
The value of the film thickness was measured at a randomly selected MD position using a contact-type thickness meter (manufactured by Mitutoyo, VL-50A). The thickness measurement along the TD was performed five times at a distance of 5 mm over a distance of 30 cm at a point along the TD (width) of the film, and the arithmetic average was adopted as the value of the film thickness.

[Porosity]
In this embodiment, from the viewpoint of film strength, the upper limit of the porosity is preferably 70% or less, more preferably 60% or less. Further, from the viewpoints of permeation performance and electrolytic solution content, the lower limit of the porosity is preferably 20% or more, and more preferably 30% or more. By setting the porosity within the above range, the balance of permeability, strength and electric field liquid content is improved, the non-uniformity of the battery reaction is eliminated, and the generation of dendrites is suppressed. As a result, good safety, strength, and permeability can be obtained when used as a battery separator.

  The value of the porosity is calculated from the mass w1 of the microporous membrane and the mass w2 of the membrane of the same size made of the same polyethylene composition as the microporous membrane, and the porosity (%) = (w2−w1). ) / W2 × 100.

[Air permeability resistance]
In this embodiment, from the viewpoint of ion permeability, the air resistance when the film thickness is 20 μm is preferably 100 to 1000 sec / 100 cc or less, more preferably 100 to 800 sec / 100 cc, -600 sec / 100 cc is particularly preferred. Here, the air resistance when the film thickness is 20 μm means that the air resistance measured according to JIS P 8117 (2009) is P ₁ in a microporous film having a film thickness T ₁ (μm). Is the air permeability resistance P ₂ calculated by the formula: P ₂ = (P ₁ × 20) / T ₁ . In the following description, the term “air permeability resistance” is used to mean “air resistance when the film thickness is 20 μm” unless otherwise specified. When the air permeation resistance exceeds 1000 sec / 100 cc, ion permeability is deteriorated, insulation performance as a separator is increased, and electric resistance is increased, which is not preferable. On the other hand, when the air resistance is less than 100 sec / 100 cc, when the temperature inside the battery rises, there is a possibility that the shutdown before the meltdown is not sufficiently performed.

  The value of the air resistance is measured with an air permeability meter (AGO-1T, manufactured by Asahi Seiko Co., Ltd.) with respect to a microporous film having a thickness of 20 μm.

[Tensile strength]
The tensile strength of the temperature-responsive microporous membrane of this embodiment is the MD direction tensile strength (the tensile breaking strength in the MD direction. Hereinafter, also simply referred to as “MD tensile strength”) is usually 1000 to 4500 kgf / cm. ^2, preferably 1500~4000kgf / cm ^2, more preferably 1500~3000kgf / cm ^2. If the MD tensile strength is weak, there is a risk of film breakage in the battery winding step. Therefore, the MD tensile strength is preferably at least 1000 kgf / cm ² or more. Moreover, when the conveyance tension at the time of coating is considered, it is more preferable that it is 1500 kgf / cm < ² > or more. However, if the MD tensile strength is increased too much, the balance with the tensile strength in the TD direction (the tensile rupture strength in the TD direction; hereinafter simply referred to as “TD tensile strength”) also deteriorates, and the balance of the tension during film formation Will break down and it will be easier to get candy. Further, there is a risk that winding slip or the like may occur at the time of slitting. Therefore, from the viewpoint of balance with TD tensile strength, the upper limit of MD tensile strength is preferably 4500 kgf / cm ² or less.

From the viewpoint of the balance between the MD tensile strength, TD tensile strength is usually 1000~3000kgf / cm ^2, preferably 1000~2000kgf / cm ^2, more preferably 1000~1500kgf / cm ^2. When the TD tensile strength is within the above range, the slit property of the microporous membrane is improved, and the film breakage caused by the inability to withstand the tensile stress in the winding process can be suppressed. The defective rate can be reduced. In addition, when the substrate is not supported at a suitable tension during coating, not only uniform coating becomes difficult, but also heat transfer irregularities occur in the drying process, causing dry wrinkles and peeling of the coating material. There is a risk. Furthermore, the coating film may be peeled off or wound due to internal residual stress of the coating layer due to coating unevenness. By making the TD tensile strength within the above range, the balance between the MD tensile strength and the TD tensile strength is good, the occurrence of wrinkles and sagging is suppressed, and problems such as those described above can be prevented in advance. Can do.

The MD tensile strength _{S MD} and TD tensile strength _{S TD,} using a strip specimen having a width 10 mm, was measured by a method according to ASTM D882.

[Manufacture of polyolefin substrates]
Although the manufacturing method of a polyolefin base material is not restrict | limited to this, It is preferable that the process of following (1)-(5) is included from a viewpoint of MD intensity | strength improvement.

(1) Step of melt kneading after containing a plasticizer in ultra high molecular weight polyethylene and high density polyethylene (2) Stretching the sheet extruded from the die at a stretching temperature of 90 to 115 ° C. and a stretching ratio of 1.1 to 2.0. Step of stretching in MD direction by double (3) Step of simultaneously stretching sheet stretched in MD direction in MD direction and TD direction at stretching temperature of 100 to 120 ° C. (4) Step of washing away plasticizer by washing (5) Heat fixing process

  By carrying out these steps during production, a microporous membrane can be obtained. Moreover, as a manufacturing method with which the same effect is acquired, the process of extending | stretching to MD direction at the extending | stretching temperature of 90 to 115 degreeC and the draw ratio of 1.1 to 2.0 times after (3) omitting (2). You may add, You may add the process of carrying out dry drawing preferentially in MD direction at the drawing temperature of 110-130 degreeC after (5).

  By appropriately adjusting these steps, a microporous film excellent in physical property balance (MD orientation, MD / TD balance) can be obtained, temperature-responsive molecule loading is improved, and wrinkles during coating can be improved. Therefore, the film can be applied uniformly.

[Polyolefin substrate coating]
NIPAm was dissolved at 0.1 and 1 wt% using water as a solvent. A microporous membrane (E09HMS; MD tensile strength 1650 kgf / cm ² : TD tensile strength 1100 kgf / cm ² : air resistance 280 sec / 100 cc / 20 μm: porosity 33%) obtained through the above-described manufacturing process In order to improve the impregnation property of the NIPAm aqueous solution, the NIPAm aqueous solution was applied by dip coating after the microporous membrane was immersed in ethanol. The microporous membrane was dried in a vacuum oven at 70 ° C. for 10 minutes, and NIPAm was supported on the surface.

  FIG. 2 is a chart showing the results of Fourier transform infrared spectroscopy (FT-720, HORIBA) of the temperature-responsive microporous membrane according to this embodiment. From FIG. 2, it can be seen that the microporous membrane has a polyethylene substrate coated with (or supported by) a component containing NIPAm (N-isopropylacrylamide) on or inside thereof.

  Comparing the dip coat film of 0.1 wt and 1 wt aqueous solution, the air permeability was 293 sec / 100 cc / 20 μm before coating and 36948 sec / 100 cc / 20 μm after coating, and the air permeability resistance was remarkably deteriorated at 1 wt%. I closed it). On the other hand, in the dip coat film using 0.1 wt% aqueous solution, the air resistance is 293 sec / 100 cc / 20 μm before coating and 365 sec / 100 cc / 20 μm after coating, and the air resistance is not deteriorated. It was found that it can be suitably used.

[Measurement of surface free energy]
[Example 1]
Using a contact angle measuring device (DM-501 Hi; manufactured by Kyowa Interface Science), a polyethylene microporous membrane coated with amphiphilic molecules (poly N isopropylacrylamide; manufactured by Aldrich) under two temperature conditions of 20 ° C. and 45 ° C. The dynamic contact angle at 25 seconds after dropping of two kinds of solvents (water (polar solvent) and diiodomethane (nonpolar solvent)) at two levels of temperature was measured, and the surface free energy of the substrate was measured by the Owens-Wendt method. Calculated.

When calculating the surface free energy (γ), the calculation method described in paragraphs [0041] to [0046] of JP-A-2006-89327 was used. That is, the surface free energy (γ) is given by the sum of the solid (or liquid) dispersion force (γ ^d ) and the solid (or liquid) polar interaction force (γ ^p ). By substituting the values of the dispersion force (γ _L ^d ), the polar interaction force (γ _L ^p ) and the measured contact angle (θ) for each of the two known liquids, the solid dispersion force (γ _S ^d ) and the polar interaction force (γ _S ^p ) are obtained, and the surface free energy of the solid can be calculated as the sum of these.

[Comparative Example 1]
The same measurement as in Example 1 was performed on a polyethylene microporous membrane not coated with amphiphilic molecules. The measurement results are shown in Table 2.

As shown in Table 2, the distribution of the surface free energy of the temperature-responsive microporous membrane in Example 1 is 46.6 mJ / m ² in total with a polar component 41.8 and a nonpolar component 4.8 at room temperature. As compared with 35.0 mJ / m ^{2 of} 1 (PE microporous membrane), an increase in the polar component was observed, and the surface free energy of water was 72.8 (polarity 51. 0, 21.8 mJ / m ² ), which indicates hydrophilicity. On the other hand, in the 45 ° C. measurement, the distribution of the surface free energy of the temperature-responsive microporous membrane in Example 1 is a polar component 17.2 and a nonpolar component 16.6, a total of 33.8 mJ / m ^2. Since the component value decreases, the nonpolar component increases, and the total value approaches Comparative Example 1 (PE microporous membrane), it is hydrophobic. From this result, it can be seen that the hydrophilic and hydrophobic surfaces can be controlled depending on the temperature, and it works as a temperature-responsive microporous membrane.

  In Example 1, the amphiphilic molecule was applied to the polyethylene microporous membrane, but the amphiphilic molecule may be graft-polymerized to the polyethylene microporous membrane instead.

  Next, the coating liquid was adjusted, the temperature during coating and the drying temperature were controlled, and the wettability and coating property of the temperature-responsive microporous film in each state were evaluated.

[Preparation of coating solution]
Average particle size: 0.5 μm alumina powder (manufactured by Nippon Light Metal Co., Ltd., LS-231 (trade name)) 60 wt%, average particle size: 50 μm, 2.4 μm of two types of alumina powder (LS -22 (trade name)) To the alumina powder mixed with 40 wt%, a dispersant (trade name A-6114, manufactured by Toa Gosei Co., Ltd.) containing pure water and a commercially available ammonium polycarboxylate is added. The slurry concentration was 50 wt%. Thereafter, the solution was finely filtered with a felt type polypropylene filter having a filtration particle size (initial filtration efficiency: 95%) of 10 μm to obtain a coating solution.

[Example 2]
The polyolefin substrate was coated by hand coating, and the aforementioned coating solution was coated on the microporous membrane at room temperature and dried at room temperature for 30 minutes.

[Comparative Example 2]
The polyolefin substrate was coated by hand coating, and the above coating solution was coated on a microporous film on a hot plate at 45 ° C. and dried at room temperature for 30 minutes.

[Comparative Example 3]
The polyolefin substrate was coated by hand coating, and the above coating solution was coated on a microporous film on a 45 ° C. hot plate and dried at 45 ° C. for 30 minutes.

  Since the base material used for coating was excellent in the balance of tensile strength between MD and TD, generation of wrinkles and the like was suppressed during hand coating.

[Wettability]
In Example 2 and Comparative Examples 2-3, the wettability determination at the time of coating was performed by dropping a suitable amount of the coating liquid and visually confirming the state of wetting and spreading on the microporous film. After dropping 5 ml of the coating material, the time until it spreads in the range of 2 cm × 2 cm was measured. Judgment criteria are as follows.

Less than 10 s: good 10 s or more: poor

  In Comparative Examples 2 and 3, there was almost no wetting spread at 45 ° C. coating, and it seemed to be forcibly wet spread at hand coating.

[Coating properties]
For the coating property judgment, a sample with a size of 10 cm x 5 cm is taken at random, and visually checked for the presence of coating unevenness (wrinkles, peeling of the coating material, cracks, etc.) and there are few coating unevenness portions. The coating property was good. Judgment criteria are as follows.

0 to 3 places: Excellent 4 to 10 places: Good 11 places or more: Bad

  Table 3 summarizes the determination results of coatability and wettability. Since it was a hydrophilic coating material, the wettability at room temperature was good in Example 2 (room temperature coating: room temperature drying), and the coating film after drying was also stabilized. On the other hand, in Comparative Example 3 (45 ° C. coating: 45 ° C. drying), wettability and coating property were the worst, and coating unevenness was observed at a plurality of locations. Furthermore, in Comparative Example 2 (45 ° C. coating: room temperature drying), the wettability tends to improve as the temperature decreases during drying (from 45 ° C. to room temperature), and coating unevenness is in Comparative Example 3 (45 ° C. coating). Work: improved at 45 ° C.).

  From this result, it was shown that coating unevenness can be controlled by controlling the surface free energy of the substrate.

  The temperature-responsive microporous membrane and the solid polymer electrolyte membrane using the same according to the present invention are used as a separator (or coating substrate) for a secondary battery, a filtration filter, and a solid polymer membrane for a fuel cell. It can be used as a support for a pore filling membrane.

Claims (6)

A temperature-responsive microporous film in which an amphiphilic molecule is arranged on a polyolefin substrate, and the surface free energy measured by the Owens-Wendt method of the substrate on which the amphiphilic molecule is arranged What der 45 mJ / ^{m 2} or more at 20 ° C., it said substrate surface amphiphilic molecules, which are arranged indicates hydrophilicity, and the surface free energy 35 mJ / ^{m 2} or less der at 45 ° C. A temperature-responsive microporous membrane (except for a temperature-responsive microporous membrane having a hollow fiber shape) , wherein the substrate surface on which the amphiphilic molecules are arranged exhibits hydrophobicity .   The temperature-responsive microporous membrane according to claim 1, wherein the base material is composed of two or more kinds of polyolefins having different weight average molecular weights.   The polyolefin is a polymer obtained by polymerizing at least one selected from the group consisting of ethylene, propylene, 1-butene, 4-methyl-pentene-1 and 1-hexene, or a mixture thereof. 2. A temperature-responsive microporous membrane according to 1.   The amphiphilic molecule is a polymer obtained by polymerizing N-isopropylacrylamide, or a polymer obtained by copolymerizing acrylic acid, 2-carboxyisopropylacrylamide and 3-carboxy-n-propylacrylamide with N-isopropylacrylamide. Item 4. The temperature-responsive microporous membrane according to any one of Items 1 to 3. The temperature-responsive microporous membrane according to any one of claims 1 to 4, having a tensile breaking strength in the MD direction of 1000 to 4500 kgf / cm ² and a tensile breaking strength in the TD direction of 1000 to 3000 kgf / cm ² . A solid polymer electrolyte membrane comprising the temperature-responsive microporous membrane according to claim 1.

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