Polymer electrolyte membrane and method for producing the same

Abstract

One aspect of the present invention provides a polymer electrolyte membrane and a method for producing the same, which comprises: a porous substrate including a first part including a first polyolefin modified with a halogen-based compound and a second part including a second polyolefin; and a halogen-based polymer electrolyte impregnated into pores of the porous substrate, wherein the first part and the second part constitute a discontinuous phase and a continuous phase, respectively, in the porous substrate; and the content of the halogen-based compound in the porous substrate is 0.5 to 10 wt %.

Description

[Technical Field]

[0001] The present invention relates to a polymer electrolyte membrane and a manufacturing method thereof, and more particularly to a polymer electrolyte membrane in which a polymer electrolyte is impregnated into a porous substrate, in which the affinity between the polymer electrolyte and the porous substrate and the resulting physical properties are improved, and a manufacturing method thereof. [Background technology]

[0002] Polymer electrolyte membranes increase ionic conductivity, reduce resistance, and increase energy conversion efficiency in electrochemical processes. Such polymer electrolyte membranes, consisting of polymers with ion-exchange functional groups, i.e., single membranes made of only polymer electrolytes, are used in a variety of fields, including fuel cells, redox flow batteries, electrodialysis, water electrolysis, water treatment, and seawater desalination.

[0003] However, the ion-exchange functional groups of the polymer electrolyte constituting such a single membrane have a high affinity for water, which causes the volume of the polymer electrolyte to expand, reducing the mechanical strength and resistance to degradation of the membrane. To address this issue, attempts have been made to introduce hydrophobic substances or structures that can improve the mechanical strength of the polymer electrolyte or to increase the thickness of the membrane, but these methods result in a loss of resistance and a decrease in the overall efficiency of the system.

[0004] To solve these problems, thin-film reinforced composite membranes have been proposed, which can reduce and suppress swelling and resistance loss of the polymer electrolyte by using a hydrophobic substrate (or support) to fix and support the polymer electrolyte while providing sufficient ion exchange capacity to the polymer electrolyte itself. This allows the membrane to be made thinner overall depending on the thickness of the hydrophobic substrate, and ensures sufficient tensile strength compared to conventional single membranes, thereby improving durability and process efficiency.

[0005] However, since the hydrophobic substrate and polymer electrolyte have different material properties and have very low affinity with each other, there is a problem that the polymer electrolyte impregnated and fixed in the hydrophobic substrate can randomly separate, peel off, or detach. The randomly formed water bubbles and / or air bubbles can hinder the movement of substances, resulting in problems such as an increase in voltage and a decrease in current efficiency. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an improved polymer electrolyte membrane and a method for producing the same, which increases the affinity between a hydrophobic substrate and a polymer electrolyte, thereby achieving a well-balanced impregnation and adhesion of the polymer electrolyte to the hydrophobic substrate and the resulting physical properties. [Means for solving the problem]

[0007] One aspect of the present invention provides a polymer electrolyte membrane comprising: a porous substrate including a first part including a first polyolefin modified with a halogen-based compound and a second part including a second polyolefin; and a halogen-based polymer electrolyte impregnated into pores of the porous substrate, wherein the first part and the second part constitute a discontinuous phase and a continuous phase, respectively, in the porous substrate; and the content of the halogen-based compound in the porous substrate is 0.5 to 10 wt %.

[0008] In one embodiment, the halogen-based compound and the halogen-based polymer electrolyte may contain at least one common element.

[0009] In one embodiment, the common element may be fluorine (F).

[0010] In one embodiment, the halogen-based compound may be an alkene-based fluorocarbon.

[0011] In one embodiment, the halogen-based polymer electrolyte may be a perfluorinated sulfonic acid-based polymer.

[0012] In one embodiment, the weight average molecular weight (Mw) of each of the first and second polyolefins may be 200,000 to 1,000,000.

[0013] In one embodiment, the weight average molecular weight (Mw) of the first polyolefin may be 30,000 to 100,000, and the weight average molecular weight (Mw) of the second polyolefin may be 200,000 to 1,000,000.

[0014] In one embodiment, the first and second polyolefins may each include one selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, and combinations of two or more thereof.

[0015] In one embodiment, the polymer electrolyte membrane can satisfy at least one of the following conditions (i) to (v): (i) Ion exchange capacity (A) 0.95-1.50 meq / g, (ii) Ionic conductivity (B) 0.10-0.15 S·cm -1 (iii) Water uptake: 25-35%; (iv) Ratio of ionic conductivity to ion exchange capacity (B / A): 0.095-0.150 S·cm -1 meq -1 ·g, (v) thickness 50 μm or less.

[0016] Another aspect of the present invention provides a method for producing a polymer electrolyte membrane, the method comprising: (a) preparing a porous substrate including a first part containing a first polyolefin modified with a halogen-based compound and a second part containing a second polyolefin; (b) preparing an electrolyte solution by dissolving a halogen-based polymer electrolyte in a solvent; and (c) impregnating the porous substrate with the electrolyte solution.

[0017] In one embodiment, the step (a) may include the steps of: (a1) reacting the halogen-based compound with the first polyolefin in the presence of an initiator to produce a masterbatch; and (a2) processing a composition containing the masterbatch, the second polyolefin, and a pore-forming agent to produce the porous substrate.

[0018] In one embodiment, the step (a) may include the steps of: (a1') reacting a polyolefin, a halogen-based compound, an initiator, and a pore-forming agent in situ while mixing them to produce a composition containing the first polyolefin modified with the halogen-based compound as a portion of the polyolefin, and a second polyolefin as the remainder of the polyolefin; and (a2') processing the composition to produce the porous substrate. [Effects of the Invention]

[0019] A polymer electrolyte membrane according to one embodiment of the present invention includes a porous substrate including a first part including a first polyolefin modified with a halogen-based compound and a second part including a second polyolefin, and a halogen-based polymer electrolyte impregnated into the pores of the porous substrate, wherein the first part and the second part constitute a discontinuous phase and a continuous phase, respectively, in the porous substrate. By adjusting the content of the halogen-based compound in the porous substrate to 0.5 to 10 wt %, the affinity between the porous substrate and the polymer electrolyte is increased, and the impregnation and adhesion of the polymer electrolyte to the porous substrate and the resulting physical properties can be balanced and improved.

[0020] It should be understood that the effects of the present invention are not limited to the effects described above, but include all effects that can be inferred from the configuration of the invention described in the detailed description of the present invention or the claims. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0022] Throughout the specification, when a part is said to be "connected" to another part, this includes not only "directly connected" but also "indirectly connected" through an intervening member. Furthermore, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further comprise other components, unless otherwise specified.

[0023] One aspect of the present invention provides a polymer electrolyte membrane comprising: a porous substrate including a first part including a first polyolefin modified with a halogen-based compound and a second part including a second polyolefin; and a halogen-based polymer electrolyte impregnated into pores of the porous substrate, wherein the first part and the second part constitute a discontinuous phase and a continuous phase, respectively, in the porous substrate; and the content of the halogen-based compound in the porous substrate is 0.5 to 10 wt %.

[0024] Conventionally, porous substrates made solely of polyolefins have the same hydrophobicity as fluorocarbons, or have incompatible hydrophobic side chains, making it difficult to ensure compatibility with fluorocarbons. In contrast, incorporating a certain amount of a halogen-based compound into the polyolefin during the preparation of the porous substrate can impart a desired affinity for the halogen-based polymer electrolyte to the porous substrate. For example, by determining, adjusting, and combining the weight-average molecular weights (Mw) of the first and second polyolefins, the dispersibility of the first and second moieties in the porous substrate, the content of the halogen-based compound in the porous substrate, and the type of the halogen-based compound, it is possible to achieve a good balance between the productivity of the process for incorporating the halogen-based compound into the porous substrate, the affinity of the porous substrate with the halogen-based polymer electrolyte, and the resulting impregnation ability.

[0025] In the porous substrate, the first part and the second part can constitute a continuous phase and a discontinuous phase, respectively. In the porous substrate, the first part is uniformly dispersed in a matrix composed of the second part, and can impart a substantially uniform affinity for the polymer electrolyte to the entire region along the area and / or thickness direction of the porous substrate, thereby improving the impregnation of the polymer electrolyte into the porous substrate.

[0026] The term "matrix" as used herein refers to a component that constitutes a continuous phase in a porous substrate containing two or more components. That is, in the porous substrate, the second region containing the second polyolefin may exist as a continuous phase, and the first region containing the first polyolefin modified with the halogen-based compound may exist dispersedly within the second region as a discontinuous phase.

[0027] The content of the halogen-based compound introduced by the first polyolefin in the porous substrate may be 0.5 to 10 wt%, preferably 1 to 10 wt%, and more preferably 1 to 5 wt%. If the content of the halogen-based compound is less than 0.5 wt%, impregnation of the polymer electrolyte may be insufficient. If the content is greater than 10 wt%, impregnation may be further improved, but the mechanical properties and heat resistance of the porous substrate achieved through the second polyolefin may be reduced. Furthermore, if the content of the halogen-based compound is greater than 10 wt%, the dispersibility of the first moiety may decrease, increasing the number of surface defects on the surface of the porous substrate that have a different brightness from the surrounding area, degrading the appearance quality. Furthermore, there may be a sudden change in resistance at sites and / or regions where the first moiety randomly aggregates on the surface and / or inside of the porous substrate, which may adversely affect the electrochemical properties.

[0028] The halogen-based compound and the halogen-based polymer electrolyte may contain at least one common element. As used herein, the term "common element" means that at least one element contained in the halogen-based compound and at least one element contained in the halogen-based polymer electrolyte are the same. The common element may be at least one of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), preferably fluorine (F).

[0029] The halogen-based compound may be a fluorine-based compound (monomer) and / or a perfluorinated compound (monomer) having a fluorocarbon chain, preferably an alkene-based fluorocarbon, more preferably an alkene-based perfluorocarbon such as (perfluoropropyl)ethylene, (perfluorobutyl)ethylene, or (perfluorohexyl)ethylene, but is not limited thereto.

[0030] The halogen-based polymer electrolyte may be a perfluorinated sulfonic acid-based polymer (or a perfluorinated sulfonic acid-based ionomer). Various types of commercially available perfluorinated sulfonic acid-based polymers (or perfluorinated sulfonic acid-based ionomers) may be used.

[0031] The first and second polyolefins may be derived from the same type and quality of polyolefins, and in this case, the weight-average molecular weight (Mw) of each of the first and second polyolefins may be 200,000 to 1,000,000. In a method for producing a polymer electrolyte membrane according to an embodiment described below, the first polyolefin may be a product obtained by in-situ reaction of a polyolefin, a halogen-based compound, an initiator, and a pore-forming agent while mixing them, with the polyolefin being partially modified with the halogen-based compound, and the second polyolefin may be the remainder of the polyolefin remaining unreacted after the reaction.

[0032] If the weight average molecular weight (Mw) of the polyolefin is less than 200,000, the melt viscosity becomes too low, which significantly reduces the dispersibility of the pore-forming agent, and in particular, phase separation or layer separation may occur between the polyolefin and the pore-forming agent. If the weight average molecular weight (Mw) is more than 1,000,000 g / mol, the melt viscosity becomes too high, which reduces processability and may cause non-uniform mixing during melt mixing.

[0033] The first and second polyolefins may be derived from different polyolefins and / or different materials, and in this case, the weight-average molecular weight (Mw) of the first polyolefin may be 30,000 to 100,000, preferably 50,000 to 100,000, and the weight-average molecular weight (Mw) of the second polyolefin may be 200,000 to 1,000,000. In another embodiment of the method for producing a polymer electrolyte membrane described below, the first polyolefin may be used to prepare a masterbatch for introducing the halogen-based compound into the porous substrate, and the second polyolefin may be mixed with the masterbatch to serve as a dispersion medium for uniformly dispersing the masterbatch and the halogen-based compound contained therein.

[0034] If the weight-average molecular weight of the first polyolefin is less than 30,000 g / mol, it is difficult to obtain the masterbatch used to manufacture the porous substrate in the form of pellets due to the low molecular weight. If the weight-average molecular weight is greater than 100,000 g / mol, excessive loads may be applied to equipment used to manufacture the porous substrate, such as a mixer, extruder, or T-die, resulting in reduced processability. Side reactions between the first and second polyolefins may also occur, resulting in reduced surface quality of the porous substrate. These problems may impede ion mobility and reduce electrochemical properties.

[0035] Furthermore, if the weight average molecular weight (Mw) of the second polyolefin is less than 200,000, the melt viscosity becomes too low, which reduces the dispersibility of the pore-forming agent, and in particular, phase separation or layer separation may occur between the second polyolefin and the pore-forming agent. If the Mw is more than 1,000,000 g / mol, the melt viscosity becomes too high, which reduces processability and may cause non-uniform mixing during melt mixing.

[0036] The ratio of the weight average molecular weight (Mw) of the first polyolefin to the weight average molecular weight (Mw) of the second polyolefin may be 0.001 to 0.2, preferably 0.01 to 0.2, and more preferably 0.1 to 0.2. If the ratio of the weight average molecular weight (Mw) of the first polyolefin to the weight average molecular weight (Mw) of the second polyolefin is outside the above range, the compatibility and dispersibility of the first and second parts may decrease, and the deviation in mechanical properties between regions of the porous substrate may increase, significantly reducing product reliability and reproducibility.

[0037] The molecular weight distribution (Mw / Mn) of each of the first and second polyolefins may be 3 to 7. If the molecular weight distribution of the first and second polyolefins is less than 3, the dispersibility with the pore-forming agent may be reduced, and the uniformity of the porous substrate may be reduced. If the molecular weight distribution is greater than 7, the mechanical strength of the porous substrate and the polymer electrolyte membrane including the porous substrate may be reduced.

[0038] The first and second polyolefins may each include one selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, and a combination of two or more thereof, preferably at least one of polyethylene and polypropylene, and more preferably polyethylene, but are not limited thereto.

[0039] The polymer electrolyte membrane can satisfy at least one of the following conditions (i) to (v): (i) an ion exchange capacity (A) of 0.95 to 1.50 meq / g, preferably 0.95 to 1.30 meq / g, and more preferably 0.95 to 1.10 meq / g; (ii) an ionic conductivity (B) of 0.10 to 0.15 S·cm; -1 , preferably 0.11 to 0.14 S cm -1 , and more preferably 0.11 to 0.13 S·cm -1 (iii) water uptake of 25 to 35%, preferably 25 to 32%, and more preferably 25 to 30%; (iv) ratio of ionic conductivity to ion exchange capacity (B / A) of 0.095 to 0.150 S·cm; -1 meq -1 ·g, preferably 0.100 to 0.130 S·cm -1 meq -1 ·g, more preferably 0.110 to 0.130 S·cm -1 meq -1 ·g, (v) thickness of 50 μm or less, preferably 30 μm or less, and more preferably 5 to 30 μm.

[0040] In particular, the ratio of ionic conductivity to ion exchange capacity (B / A) according to the condition (iv) means the ionic conductivity per ion exchange capacity. Conventionally, various attempts have been made to independently measure and analyze the ion exchange capacity and ionic conductivity of polymer electrolyte membranes (or ion exchange membranes), and to independently improve each of these. While these attempts were effective for thick-film polymer electrolyte membranes with a thickness of 50 μm or more, the effectiveness of such measurements and analyses has diminished for recently developed thin-film polymer electrolyte membranes with a thickness of 50 μm or less, preferably 30 μm or less, and more preferably 5 to 30 μm.

[0041] In contrast, the ratio of ionic conductivity to ion exchange capacity (B / A) according to the condition (iv) can be an effective index for determining the electrochemical properties of a thin-film polymer electrolyte membrane based on the relationship and balance between the ion exchange capacity and ionic conductivity.

[0042] Another aspect of the present invention provides a method for producing a polymer electrolyte membrane, the method comprising: (a) preparing a porous substrate including a first part containing a first polyolefin modified with a halogen-based compound and a second part containing a second polyolefin; (b) preparing an electrolyte solution by dissolving a halogen-based polymer electrolyte in a solvent; and (c) impregnating the porous substrate with the electrolyte solution.

[0043] In the step (a), a porous substrate can be produced that includes a first part containing a first polyolefin modified with a halogen-based compound and a second part containing a second polyolefin.

[0044] The step (a) may include: (a1) reacting the halogen-based compound with the first polyolefin in the presence of an initiator to produce a masterbatch; and (a2) processing a composition containing the masterbatch, the second polyolefin, and a pore-forming agent to produce the porous substrate.

[0045] In step (a1), the halogen-based compound and the first polyolefin are reacted in the presence of an initiator to produce a masterbatch containing a polymer in which the halogen-based compound is grafted onto the first polyolefin, and the amounts and ratios of the reactants used can be adjusted so that the content of the halogen-based compound in the porous substrate produced in the subsequent step is 0.5 to 10 wt %.

[0046] The initiator may be one selected from the group consisting of potassium persulfate, ammonium persulfate, acetylacetone peroxide, benzoyl peroxide, dicumyl peroxide, methane hydroperoxide, 2,4-dichlorobenzoyl peroxide, di-t-butyl peroxide, t-butyl peracetate, hydrogen peroxide, and combinations of two or more thereof, preferably a peroxide-based compound, more preferably benzoyl peroxide, but is not limited thereto.

[0047] In step (a2), the porous substrate can be produced by processing a composition containing the masterbatch, the second polyolefin, and a pore-forming agent. Specifically, the composition is melted and kneaded, then pressurized to produce a base sheet having a predetermined thickness. The base sheet is then stretched to produce a film, and the pore-forming agent is extracted and removed from the film to obtain the porous substrate. The composition may contain 10 to 40 wt % of the masterbatch produced in step (a1), 10 to 40 wt % of the second polyolefin, and 40 to 80 wt % of the pore-forming agent.

[0048] The pore-forming agent may be one selected from the group consisting of paraffin oil, paraffin wax, mineral oil, solid paraffin, soybean oil, rapeseed oil, palm oil, coconut oil, di-2-ethylhexyl phthalate, dibutyl phthalate, diisononyl phthalate, diisodecyl phthalate, bis(2-propylheptyl) phthalate, naphthenic oil, and combinations of two or more thereof, preferably paraffin oil, and more preferably paraffin oil having a kinematic viscosity of 50 to 100 cSt at 40°C, but is not limited thereto.

[0049] The stretching can be carried out by a known method such as uniaxial stretching or biaxial stretching (sequential or simultaneous biaxial stretching). In the case of sequential biaxial stretching, the stretching ratio may be 4 to 20 times in each of the transverse direction (MD) and the longitudinal direction (TD), and the resulting areal stretching ratio may be 16 to 400 times.

[0050] The step (a) may include the steps of (a1') mixing and reacting a polyolefin, a halogen-based compound, an initiator, and a pore-forming agent in situ to produce a composition containing the first polyolefin modified with the halogen-based compound as a part of the polyolefin and a second polyolefin as the remainder of the polyolefin, and (a2') processing the composition to produce the porous substrate.

[0051] In the step (a1'), a polyolefin, a halogen-based compound, and a pore-forming agent are melted and kneaded in the presence of an initiator at 150 to 300°C and 50 to 300 rpm, while simultaneously reacting a portion of the polyolefin with the halogen-based compound, to produce a composition comprising the first polyolefin to which the halogen-based compound has been grafted as part of the polyolefin, and a second polyolefin as the remainder of the polyolefin, and the amounts and ratios of the reactants used can be adjusted so that the content of the halogen-based compound in the porous substrate produced in the subsequent step is 0.5 to 10 wt %.

[0052] Unlike conventional methods, the reaction process of the raw material and the initiator and the melting and kneading process are not separated. Instead, the raw material and the initiator are melted and kneaded under predetermined conditions, and the polyolefin and the halogen-based compound contained in the raw material are grafted through a free radical reaction, i.e., in-situ grafting of the polyolefin and the halogen-based compound can be induced.

[0053] In step (a2'), the composition can be processed to produce the porous substrate. Specifically, the composition is melted, kneaded, and then pressed to produce a base sheet having a predetermined thickness, and the base sheet is stretched to produce a film. The pore-forming agent is extracted and removed from the film to obtain the porous substrate.

[0054] In the step (b), the halogen-based polymer electrolyte can be dissolved in a solvent to produce an electrolyte solution.

[0055] The content of the halogen-based polymer electrolyte in the electrolyte solution may be 10 to 60 wt %. If the content of the halogen-based polymer electrolyte is less than 10 wt %, the amount of electrolyte impregnated into the pores of the porous substrate is small, which may reduce the ionic conductivity of the polymer electrolyte membrane and make it difficult to increase the thickness of the polymer electrolyte membrane. If the content is more than 60 wt %, the solubility of the electrolyte is reduced, which makes it difficult for the electrolyte to penetrate into the pores of the porous substrate, which reduces the flowability of the electrolyte solution and makes it difficult to achieve a uniform thickness of the polymer electrolyte membrane.

[0056] The solvent of the electrolyte solution may be one selected from the group consisting of esters, ethers, alcohols, ketones, amides, sulfones, carbonates, aliphatic hydrocarbons, aromatic hydrocarbons, and combinations of two or more thereof, preferably an amide solvent, and more preferably dimethylacetamide.

[0057] Examples of the amide solvent include, but are not limited to, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methylformamide, dimethylformamide, and dimethylacetamide.

[0058] Examples of the ester solvents include, but are not limited to, methyl acetate, ethyl acetate, n-butyl acetate, cellosolve acetate, propylene glycol monomethyl acetate, 3-methoxybutyl acetate, methyl butyrate, ethyl butyrate, propyl propionate, etc. Examples of the ether solvents include, but are not limited to, diethyl ether, dipropyl ether, dibutyl ether, butyl ethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, octyl ether, hexyl ether, etc.

[0059] Examples of the alcohol-based solvent include, but are not limited to, methanol, ethanol, propanol, isopropanol, n-butanol, amyl alcohol, cyclohexanol, octyl alcohol, decanol, etc. Examples of the ketone-based solvent include, but are not limited to, acetone, cyclohexanone, methyl amyl ketone, diisobutyl ketone, methyl ethyl ketone, methyl isobutyl ketone, etc. Examples of the carbonate-based solvent include, but are not limited to, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, dibutyl carbonate, etc.

[0060] Examples of the sulfone solvent include, but are not limited to, dimethyl sulfoxide, diethyl sulfoxide, diethyl sulfone, tetramethylene sulfone, etc. Examples of the aliphatic hydrocarbon solvent include, but are not limited to, pentane, hexane, heptane, octane, nonane, decane, dodecane, tetradecane, hexadecane, etc. Examples of the aromatic hydrocarbon solvent include, but are not limited to, benzene, ethylbenzene, chlorobenzene, toluene, xylene, etc.

[0061] In step (c), the porous substrate is impregnated with the electrolyte solution and then dried to obtain a polymer electrolyte membrane. The impregnation (and / or coating) can be performed by (i) immersing the porous substrate in an impregnation bath filled with the electrolyte solution for a certain period of time, (ii) coating the porous substrate with a coating device for delivering the electrolyte solution, such as a roll coater or a bar coater, or a combination of (i) and (ii).

[0062] Hereinafter, examples of the present invention will be described in detail. Manufacturing Example 1 90 parts by weight of high-density polyethylene with a weight-average molecular weight (Mw) of 50,000, 10 parts by weight of (perfluorohexyl)ethylene, and 0.3 parts by weight of benzoyl peroxide were mixed in a beaker at room temperature, and then added to a rheomixer preheated to 190°C and kneaded at 60 rpm for 4 minutes to produce a melt. The melt was formed into a sheet using a roll press at 60°C and pelletized to produce masterbatch (MB1).

[0063] Manufacturing Example 2 A masterbatch (MB2) was prepared in the same manner as in Preparation Example 1, except that the amounts of the high-density polyethylene and the (perfluorohexyl)ethylene added were changed to 70 parts by weight and 30 parts by weight, respectively.

[0064] Manufacturing Example 3 A masterbatch (MB3) was prepared in the same manner as in Preparation Example 1, except that the amounts of the high-density polyethylene and the (perfluorohexyl)ethylene added were changed to 80 parts by weight and 20 parts by weight, respectively.

[0065] Production Example 4 A masterbatch (MB4) was prepared in the same manner as in Preparation Example 1, except that the amounts of the high-density polyethylene and the (perfluorohexyl)ethylene added were changed to 95 parts by weight and 5 parts by weight, respectively.

[0066] Manufacturing Example 5 A masterbatch (MB5) was prepared in the same manner as in Preparation Example 1, except that the amounts of the high-density polyethylene and the (perfluorohexyl)ethylene added were changed to 97 parts by weight and 3 parts by weight, respectively.

[0067] Manufacturing Example 6 A masterbatch (MB6) was prepared in the same manner as in Preparation Example 1, except that the weight average molecular weight (Mw) of the high density polyethylene was changed to 70,000.

[0068] Manufacturing Example 7 A masterbatch (MB7) was prepared in the same manner as in Preparation Example 1, except that the weight average molecular weight (Mw) of the high density polyethylene was changed to 100,000.

[0069] Comparative Manufacturing Example 1 A masterbatch (MB8) was prepared in the same manner as in Preparation Example 1, except that the amounts of the high-density polyethylene and the (perfluorohexyl)ethylene added were changed to 65 parts by weight and 35 parts by weight, respectively.

[0070] Comparative Manufacturing Example 2 A masterbatch (MB9) was prepared in the same manner as in Preparation Example 1, except that the amounts of the high-density polyethylene and the (perfluorohexyl)ethylene added were changed to 99 parts by weight and 1 part by weight, respectively.

[0071] Example 1 20 parts by weight of high-density polyethylene with a weight-average molecular weight (Mw) of 600,000, 70 parts by weight of paraffin oil with a kinematic viscosity of 70 cSt at 40°C, and 10 parts by weight of MB1 from Preparation Example 1 were placed in a beaker and mixed at room temperature, then placed in a rheomixer preheated to 190°C and kneaded at 60 rpm for 4 minutes to produce a melt. The melt was passed through a casting roll at 60°C to produce a base sheet.

[0072] The base sheet was stretched 8 times in the machine direction (MD) using a roll stretcher at 123°C, and then stretched 8 times in the transverse direction (TD) using a tenter stretcher at 123°C to produce a film. The film was immersed in a dichloromethane leaching bath at 25°C to extract and remove paraffin oil for 1 minute, and then dried at room temperature for 5 minutes to produce a porous substrate.

[0073] A perfluorinated sulfonic acid polymer (equivalent weight, EW 700 or more) was dissolved in dimethylacetamide to prepare an electrolyte solution with a perfluorinated sulfonic acid polymer concentration of 30 wt %. The electrolyte solution was impregnated into the porous substrate, and the solvent was evaporated at 100°C for 10 minutes. The substrate was then dried at 120°C for 10 minutes to prepare an electrolyte membrane with a thickness of 30±2 μm. The thickness of the electrolyte membrane was measured using a microthickness gauge.

[0074] Example 2 An electrolyte membrane was prepared in the same manner as in Example 1, except that the masterbatch used to prepare the porous substrate was changed from MB1 to MB2 prepared in Preparation Example 2.

[0075] Example 3 An electrolyte membrane was prepared in the same manner as in Example 1, except that the masterbatch used to prepare the porous substrate was changed from MB1 to MB3 prepared in Preparation Example 3.

[0076] Example 4 An electrolyte membrane was prepared in the same manner as in Example 1, except that the masterbatch used to prepare the porous substrate was changed from MB1 to MB4 prepared in Preparation Example 4.

[0077] Example 5 An electrolyte membrane was prepared in the same manner as in Example 1, except that the masterbatch used to prepare the porous substrate was changed from MB1 to MB5 prepared in Preparation Example 5.

[0078] Example 6 An electrolyte membrane was prepared in the same manner as in Example 1, except that the masterbatch used to prepare the porous substrate was changed from MB1 to MB6 prepared in Preparation Example 6.

[0079] Example 7 An electrolyte membrane was prepared in the same manner as in Example 1, except that the masterbatch used to prepare the porous substrate was changed from MB1 to MB7 prepared in Preparation Example 7.

[0080] Example 8 28.7 parts by weight of high-density polyethylene with a weight-average molecular weight (Mw) of 600,000, 1 part by weight of (perfluorohexyl)ethylene, 0.3 parts by weight of benzoyl peroxide, and 70 parts by weight of paraffin oil with a kinematic viscosity of 70 cSt at 40°C were placed in a beaker and mixed at room temperature, then placed in a rheomixer preheated to 190°C and kneaded at 60 rpm for 4 minutes to produce a melt. The melt was passed through a casting roll at 60°C to produce a base sheet.

[0081] The base sheet was stretched 8 times in the machine direction (MD) using a roll stretcher at 123°C, and then stretched 8 times in the transverse direction (TD) using a tenter stretcher at 123°C to produce a film. The film was immersed in a dichloromethane leaching bath at 25°C to extract and remove paraffin oil for 1 minute, and then dried at room temperature for 5 minutes to produce a porous substrate.

[0082] A perfluorinated sulfonic acid polymer (equivalent weight, EW 700 or more) was dissolved in dimethylacetamide to prepare an electrolyte solution with a perfluorinated sulfonic acid polymer concentration of 30 wt %. The electrolyte solution was impregnated into the porous substrate, and the solvent was evaporated at 100°C for 10 minutes, followed by drying at 120°C for 10 minutes to prepare an electrolyte membrane with a thickness of 30±2 μm.

[0083] Comparative Example 1 An electrolyte membrane was prepared in the same manner as in Example 1, except that the masterbatch used to prepare the porous substrate was changed from MB1 to MB8 of Comparative Preparation Example 1.

[0084] Comparative Example 2 An electrolyte membrane was prepared in the same manner as in Example 1, except that the masterbatch used to prepare the porous substrate was changed from MB1 to MB9 of Comparative Preparation Example 2.

[0085] Comparative Example 3 30 parts by weight of high-density polyethylene with a weight-average molecular weight (Mw) of 600,000 and 70 parts by weight of paraffin oil with a kinematic viscosity of 70 cSt at 40°C were placed in a beaker and mixed at room temperature, then placed in a rheomixer preheated to 190°C and kneaded at 60 rpm for 4 minutes to produce a melt. The melt was passed through a casting roll at 60°C to produce a base sheet.

[0086] The base sheet was stretched 8 times in the machine direction (MD) using a roll stretcher at 123°C, and then stretched 8 times in the transverse direction (TD) using a tenter stretcher at 123°C to produce a film. The film was immersed in a dichloromethane leaching bath at 25°C to extract and remove paraffin oil for 1 minute, and then dried at room temperature for 5 minutes to produce a porous substrate.

[0087] A perfluorinated sulfonic acid polymer (equivalent weight, EW 700 or more) was dissolved in dimethylacetamide to prepare an electrolyte solution with a perfluorinated sulfonic acid polymer concentration of 30 wt %. The electrolyte solution was impregnated into the porous substrate, and the solvent was evaporated at 100°C for 10 minutes, followed by drying at 120°C for 10 minutes to prepare an electrolyte membrane with a thickness of 30±2 μm.

[0088] Experimental Example 1 The air permeability of the porous substrates according to the examples and comparative examples was measured by the following method, and the results are shown in Table 1 below.

[0089] - Air permeability (Gurley, sec / 100cc): Using Asahi Seiko's Gurley Densometer EGO2-5 model, the time it takes for 100ml of air to pass through a porous substrate test piece with a diameter of 29.8mm was measured at a measurement pressure of 0.025MPa.

[0090] [Table 1]

[0091] Experimental Example 2 The physical properties of the electrolyte membranes according to the examples and comparative examples were measured by the following methods, and the results are shown in Table 2 below.

[0092] (1) Ion exchange capacity The electrolyte membrane was immersed in a 1.5M H2SO4 aqueous solution for 24 hours to convert the counter ions of the electrolyte membrane into H + After the substitution with the cation group, the membrane was washed with ultrapure water, dried in a vacuum oven at 80°C for 24 hours, and weighed. The dried membrane was immersed in a 3M NaCl aqueous solution to convert the counter ions of the membrane to Na + and some H + A 3M NaCl aqueous solution containing the compound was titrated with a 0.01M NaOH solution, and then the ion exchange capacity was calculated using the following formula 1. <Equation 1> Ion exchange capacity (meq / g dry )=(V NaOH ×C NaOH ) / W dry In Equation 1, W dry is the weight of the dry electrolyte membrane, and V NaOH is the volume of NaOH solution used in the titration, and C NaOH is the concentration of the NaOH solution.

[0093] (2) Ionic conductivity The electrolyte membrane was cut into 1 cm x 3 cm pieces and then placed in a conductivity measurement cell equipped with platinum electrodes. The measurement cell was immersed in ultrapure water at 25°C, and the resistance of the electrolyte membrane was measured at 100% relative humidity (RH) using a measuring instrument (Bio-Logic VSP300 equipped with an impedance module). The ionic conductivity was calculated using the following equation 2. Equation 2: Ionic conductivity (S cm -1 )=t / (R×A) In Equation 2, R (Ω) is the resistance of the electrolyte membrane, and A (cm 2) is the area of ​​the electrode and t (cm) is the thickness of the electrolyte membrane.

[0094] (3) Water uptake The electrolyte membrane was cut into 2 cm x 2 cm pieces and dried in a vacuum oven at 80°C for 24 hours, and the weight of the dry electrolyte membrane was measured using a balance.The electrolyte membrane was immersed in ultrapure water and allowed to swell for 24 hours to remove moisture from the surface of the electrolyte membrane.The weight of the wet electrolyte membrane was measured, and the water absorption rate was calculated using the following equation 3. <Formula 3> WU (%) = (W wet -W dry ) / (W dry ) x 100 In Equation 3, W dry is the weight of the electrolyte membrane in a dry state, and W wet is the weight of the electrolyte membrane in a wet state.

[0095] [Table 2]

[0096] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention may be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not restrictive. For example, each component described as a single component may be implemented in a distributed form, and similarly, each component described as a distributed component may be implemented in a combined form.

[0097] The scope of the present invention is defined by the following claims, and it should be understood that all modifications and variations derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.

Claims

1. a porous substrate comprising a first part containing a first polyolefin modified with a halogen-based compound and a second part containing a second polyolefin; a halogen-based polymer electrolyte impregnated in the pores of the porous substrate; In the porous substrate, the first portion and the second portion constitute a discontinuous phase and a continuous phase, respectively; A polymer electrolyte membrane, wherein the content of the halogen-based compound in the porous substrate is 0.5 to 10% by weight.

2. The polymer electrolyte membrane of claim 1 , wherein the halogen-based compound and the halogen-based polymer electrolyte contain at least one common element.

3. The polymer electrolyte membrane according to claim 2 , wherein the common element is fluorine (F).

4. The polymer electrolyte membrane according to claim 3 , wherein the halogen-based compound is an alkene-based fluorocarbon.

5. The polymer electrolyte membrane according to claim 3 , wherein the halogen-based polymer electrolyte is a perfluorinated sulfonic acid-based polymer.

6. 2. The polymer electrolyte membrane according to claim 1, wherein the weight average molecular weight (Mw) of each of the first and second polyolefins is 200,000 to 1,000,000.

7. The weight average molecular weight (Mw) of the first polyolefin is 30,000 to 100,000; 2. The polymer electrolyte membrane according to claim 1, wherein the weight average molecular weight (Mw) of the second polyolefin is 200,000 to 1,000,000.

8. 2. The polymer electrolyte membrane of claim 1, wherein the first and second polyolefins each comprise one selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, and combinations of two or more thereof.

9. The polymer electrolyte membrane according to claim 1, which satisfies at least one of the following conditions (i) to (v): (i) Ion exchange capacity (A) 0.95 to 1.50 meq / g (ii) Ion conductivity (B) 0.10 to 0.15 S cm －１ (iii) Water absorption rate (water uptake) 25-35% (iv) Ratio of ionic conductivity to ion exchange capacity (B / A) of 0.095 to 0.150 S cm －１ ・meq －１ ・g (v) Thickness: 50 μm or less

10. The method for producing a polymer electrolyte membrane according to any one of claims 1 to 9, (a) producing a porous substrate comprising a first part comprising a first polyolefin modified with a halogen-based compound and a second part comprising a second polyolefin; (b) dissolving a halogen-based polymer electrolyte in a solvent to produce an electrolyte solution; (c) impregnating the porous substrate with the electrolyte solution.

11. The step (a) comprises: (a1) reacting the halogen-based compound with the first polyolefin in the presence of an initiator to produce a masterbatch; (a2) processing a composition containing the masterbatch, the second polyolefin, and a pore-forming agent to produce the porous substrate.

12. The step (a) comprises: (a1') reacting a polyolefin, a halogen-based compound, an initiator, and a pore-forming agent in situ while mixing them to prepare a composition comprising the first polyolefin modified with the halogen-based compound as a portion of the polyolefin, and a second polyolefin as the remainder of the polyolefin; (a2') processing the composition to produce the porous substrate.

Images