JP2000273236A - Hydrophilic porous membrane - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To provide a hydrophilic porous film having excellent porosity and mechanical strength, excellent in hydrophilicity, and useful for a battery separator and the like. SOLUTION: The (co) polymer containing a sulfonic acid (salt) group as a main component and the (co) polymer containing a sulfonic acid (salt) group is at least one selected from diene monomers and aromatic monomers. Having the above monomer units (co)
A hydrophilic porous membrane which is a polymer obtained by sulfonating a copolymer, a block copolymer or a hydrogenated product thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrophilic porous membrane, and more particularly, to a separator for a battery, a diaphragm for an electrolytic capacitor, various filters, a moisture permeable material, a reverse osmosis membrane, an ultrafiltration membrane, The present invention relates to a hydrophilic porous membrane useful for a microfiltration membrane, an ion exchange membrane, and the like.

[0002]

2. Description of the Related Art As a porous material, for example, a nonwoven fabric or a woven fabric based on a polymer, a porous film, and the like are known. Nonwoven fabrics made of polyolefins are chemically stable, have excellent chemical resistance and good alkali resistance at high temperature and high concentration, but have high hydrophobicity and hydrophilicity with aqueous electrolytes such as alkaline batteries. Poorly, there is a problem that the retention of the electrolyte is not sufficient, and the cycle characteristics and self-discharge property of the battery are poor. For this reason, nonwoven fabrics and the like used as battery separators are subjected to a surface hydrophilization treatment by direct sulfonation or acrylic acid graft treatment. However, there is a problem that the fibers of the nonwoven fabric are chemically degraded by the hydrophilic treatment, and the mechanical strength is reduced. For this reason, the fiber diameter must be kept large to some extent, and there is a limit in making the separator thinner. On the other hand, porous membranes made of polyolefins represented by polyethylene are widely known. These porous membranes are microporous membranes having fine pores and are used as separators for lithium batteries and the like, and can be made as thin as several microns to several tens of microns. This microporous membrane is chemically stable, excellent in chemical resistance and good in alkali resistance under high temperature and high concentration, like polyolefin nonwoven fabric, but has high hydrophobicity and poor hydrophilicity. However, there is a problem that it does not have a function as a separator for an alkaline battery. In recent years, separators are becoming thinner, particularly for the purpose of increasing the capacity of alkaline batteries. It is hoped that separators that can be made thinner, have hydrophilic properties, and have excellent chemical and mechanical stability will appear. It is rare.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a porous membrane having functions such as hydrophilicity, ion trapping property and ionic conductivity, and excellent in chemical stability and mechanical stability. In particular, it is an object of the present invention to provide a porous membrane material effective as a separator for an alkaline battery.

[0004]

SUMMARY OF THE INVENTION The present invention provides a hydrophilic porous membrane containing a (co) polymer containing a sulfonic acid (salt) group as a main component.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A (co) polymer containing a sulfonic acid (salt) group, which is a main component of the porous membrane of the present invention, will be described. As the (co) polymer containing a sulfonic acid (salt) group,
For example, a (co) polymer mainly composed of a diene monomer, a (co) polymer mainly composed of an olefin monomer such as an aromatic vinyl compound or an olefin, or a (co) polymer obtained by hydrogenating the above. And a unit of a (co) polymer having a hydrocarbon monomer as a main component, such as the above unit, containing a sulfonic acid group. Examples of a method for causing a (co) polymer unit containing a hydrocarbon monomer as a main component to contain a sulfonic acid group include a method of sulfonating these (co) polymer units and a method of forming a hydrophilic group such as a sulfonic acid group. And the like. Preferred is a (co) polymer containing a (co) polymer unit mainly containing a diene monomer and a (co) polymer unit mainly containing an olefin monomer such as an aromatic vinyl compound or an olefin. This is a method in which a sulfonic acid group is added to a coalesced (hereinafter referred to as a base polymer) or a hydrogenated (co) polymer thereof.

The diene monomer used in the (co) polymer unit mainly composed of the diene monomer includes:
A diene-based compound having 4 to 12 carbon atoms is preferred, and a diene-based compound having 4 to 8 carbon atoms, particularly preferably 4 to 6 carbon atoms, is more preferred. Specific examples of these diene compounds include, for example, 1,3-butadiene, 1,2-butadiene, 1,2-pentadiene, 1,3-pentadiene, 2,3-pentadiene, isoprene, 1,2-hexadiene, 1,3-hexadiene, 1,4-hexadiene, 1,5-hexadiene, 2,3-hexadiene,
2,4-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,2-
Heptadiene, 1,3-heptadiene, 1,4-heptadiene, 1,5-heptadiene, 1,6-heptadiene, 2,3-heptadiene, 2,5-heptadiene,
In addition to 3,4-heptadiene, 3,5-heptadiene, cyclopentadiene, dicyclopentadiene, ethylidene norbornene, etc., various aliphatic or alicyclic dienes having 4 to 7 carbon atoms which are branched may be mentioned. These can be used alone or in combination of two or more.
Of these, particularly preferred are 1,3-butadiene,
Isoprene.

The (co) polymer unit mainly composed of an olefin monomer is a (co) polymer unit mainly composed of an olefin monomer such as an aromatic vinyl compound or an olefin. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene and the like. Examples of the olefin include ethylene, propylene, and butene.
These monomers may be used alone or in combination of two or more. Of these, aromatic vinyl compounds are preferred, and styrene is particularly preferred.

Further, a (co) polymer mainly composed of the above-mentioned diene monomer, a (co) polymer mainly composed of an olefinic monomer such as an aromatic vinyl compound or an olefin, or a hydrogenated product thereof ( In the unit of the (co) polymer, other monomers can be used in combination with the above monomers.
Other monomers include, for example, alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylic acid, crotonic acid, and maleic acid. Acid, fumaric acid,
Mono- or dicarboxylic acid or anhydride of dicarboxylic acid such as itaconic acid, vinyl cyanide compound such as (meth) acrylonitrile, vinyl chloride, vinylidene chloride, vinyl methyl ethyl ketone, vinyl acetate, (meth) acrylamide, glycidyl (meth) acrylate And unsaturated compounds. These other monomers can be used alone or in combination of two or more.

When these other monomers are used in combination, the amount of the monomers used in each (co) polymer unit is usually at most 60%, preferably at most 50% by weight, more preferably at most 50% by weight. Is 30% by weight or less, particularly preferably 20% by weight
It is as follows.

The sulfonic acid group-containing monomer used for producing a sulfonic acid (salt) group-containing (co) polymer by copolymerizing a sulfonic acid group-containing monomer includes: Examples thereof include those obtained by adding a sulfonic acid group to the diene-based monomer or the olefin-based monomer. Specific examples thereof include sulfonic acid group-containing butadiene, sulfonic acid group-containing isoprene, sulfonic acid group-containing styrene, sulfonic acid group-containing ethylene, and sulfonic acid group-containing propylene. Of these, sulfonic acid group-containing isoprene and sulfonic acid group-containing styrene are preferred.

Production of a base polymer, that is, a (co) polymer unit mainly composed of a diene monomer and a (co) polymer unit mainly composed of an olefin monomer such as an aromatic vinyl compound or an olefin. The contained (co) polymer can be produced by (co) polymerizing each monomer using an initiator and, if necessary, using a solvent. Examples of such an initiator include a radical polymerization initiator such as hydrogen peroxide, benzoyl peroxide, and azobisisobutyronitrile, and an anionic polymerization initiator such as n-butyllithium, sodium naphthalene, and metallic sodium. The polymerization temperature is usually -10.
The temperature is 0 to 150 ° C, preferably 0 to 130 ° C.

In the above (co) polymer, part or all of the remaining double bond based on the diene monomer may be hydrogenated (hereinafter, referred to as hydrogenated) for use. In this case, a known hydrogenation catalyst can be used, for example,
A catalyst and a method as described in JP-A-5-222115 are exemplified. After hydrogenation of the above-mentioned block copolymer as a base polymer, a hydrophilic group can be introduced by a method described later, but after introducing a hydrophilic group into the copolymer, hydrogenation may be carried out.

The base polymer used in the present invention may be a random copolymer or a block copolymer, but a preferred one is a block copolymer. Particularly preferred is a block copolymer containing a polymer unit A containing a diene monomer and a polymer unit B containing an aromatic monomer. Preferred structures of the block copolymer are AB type, A (BA)
n-type, B (AB) n-type or (AB) n-type (however,
n is preferably 1 to 5, more preferably 1 to 3, further preferably 1 to 2, and particularly preferably 1).

Among these, AB type and A type are preferable.
BA-type and BAB-type block copolymers. Specific preferred base polymers include, for example, isoprene-styrene block copolymer, styrene-isoprene-styrene triblock copolymer, isoprene-styrene-isoprene triblock copolymer, butadiene-styrene block copolymer , Styrene-butadiene-
Examples include a styrene triblock copolymer, a butadiene-styrenebutadiene triblock copolymer, and hydrogenated products of these block copolymers. Further, in the block chain of the diene monomer unit, the aromatic monomer or another monomer may be partially copolymerized,
The diene monomer or another monomer may be partially copolymerized in the block chain of the aromatic monomer unit.

The weight average molecular weight (hereinafter referred to as "Mw") of these base polymers or hydrogenated products thereof in terms of polystyrene is preferably 10,000 to 2,000,000.
0, more preferably 2,000 to 1,000,000
0, particularly preferably 100,000 to 5,000,000
It is. If Mw is less than 10,000, the mechanical strength is not sufficient, while if it exceeds 2,000,000,
Problems such as gelation during sulfonation may occur.

In the block copolymer, the ratio A / B of the polymer unit A containing the diene monomer and the polymer unit B containing the aromatic monomer is preferably from 5 to 95/95 to 5. Yes, more preferably 10-9
0 / 90-10, particularly preferably 20-80 / 80-2
0.

The polymerization degree of each of the polymer units A and B is preferably such that A is 10 or more and B is 20 or more, more preferably A is 50 or more and B is 100 or more;
Particularly preferably, A is 100 or more and B is 200 or more.

The sulfonic acid (salt) group of the present invention contains (co)
The polymer can be produced, for example, by sulfonating the base polymer. As such a method, a known method can be used. When a sulfonic acid group is introduced, for example, a new experimental course edited by the Japan Society of Science (Vol. 14, III, 1773)
Page) or sulfonation by a method described in JP-A-2-227403 and the like.

That is, when the (co) polymer containing a sulfonic acid (salt) group of the present invention is produced by sulfonating a base polymer or a hydrogenated product of the base polymer, the base polymer or a hydrogenated product thereof is used. Can be produced by preferentially sulfonating either the double bond portion or the aromatic portion based on the diene monomer in the polymer with a sulfonating agent. In addition, (1) When using a base polymer which is not hydrogenated or a base polymer in which a diene unit is partially hydrogenated, it is preferable to preferentially sulfonate the diene unit.
(2) In a base polymer in which a diene unit is hydrogenated, it is preferable to preferentially sulfonate an aromatic unit. When the diene unit is preferentially sulfonated as in (1) above, the sulfonating agent may be
It is preferable to use a complex of sulfuric anhydride and an electron donating compound, or a bisulfite (Na salt, K salt, Li salt, etc.). Further, in order to sulfonate the aromatic unit preferentially as in (2), it is preferable to use, as the sulfonating agent, sulfuric anhydride, chlorosulfonic acid, fuming sulfuric acid and the like in addition to the complex.

Here, as the electron donating compound, N,
Ethers such as N-dimethylformamide, dioxane, dibutyl ether, tetrahydrofuran, diethyl ether; pyridine, piperazine, trimethylamine,
Amines such as triethylamine and tributylamine;
Sulfides such as dimethyl sulfide and diethyl sulfide; nitrile compounds such as acetonitrile, ethyl nitrile and propyl nitrile; and the like, of which N, N-dimethylformamide and dioxane are preferable.

When an unhydrogenated or partially hydrogenated base polymer is used, the amount of sulfonating agent is usually 0 to 1 mole of total monomer units in the base polymer. 0.01 mol or more and 0.5 mol or less, preferably 0.05 mol or more and 0.1 mol or less.
2 mol or less. When a hydrogenated base polymer is used, the amount of the sulfonating agent is usually 0.01 to 1 mol of all monomer units in the base polymer.
The mole is at least 0.6 mole and at most 0.6 mole, preferably at least 0.05 mole and at most 0.2 mole.

In the sulfonation, a solvent inert to a sulfonating agent such as sulfuric anhydride or sulfuric acid may be used. Examples of the solvent include halogens such as chloroform, dichloroethane, tetrachloroethane, tetrachloroethylene and dichloromethane. Nitrocompounds such as nitromethane and nitrobenzene; aliphatic hydrocarbons such as liquid sulfur dioxide, propane, butane, pentane, hexane and cyclohexane; ether solvents such as dioxane and tetrahydrofuran; and water. These solvents may be used as a mixture of two or more. The reaction temperature of this sulfonation is usually-
70-200 ° C, preferably -30-50 ° C.

The sulfonated product of the base polymer or its hydrogenated product is preferably a product obtained by allowing water or a basic compound to act on the sulfonated product. Examples of the basic compound include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide; sodium methoxide, sodium ethoxide, potassium methoxide, sodium-t-butoxide, potassium-t-butoxide and the like. Alkali metal alkoxides; carbonates such as sodium carbonate, potassium carbonate and lithium carbonate; methyl lithium, ethyl lithium, n-butyl lithium, se
c-butyl lithium, amyl lithium, propyl sodium, methyl magnesium chloride, ethyl magnesium bromide, propyl magnesium iodide,
Organometallic compounds such as diethylmagnesium, diethylzinc, triethylaluminum, and triisobutylaluminum; amines such as aqueous ammonia, trimethylamine, triethylamine, tripropylamine, tributylamine, pyridine, aniline, and piperazine; sodium, lithium, potassium, calcium, Metal compounds such as zinc can be mentioned. These basic compounds can be used alone or in combination of two or more. Among these basic compounds, alkali metal hydroxides and aqueous ammonia are preferable, and sodium hydroxide, lithium hydroxide and potassium hydroxide are particularly preferable.

The amount of the basic compound used is preferably 1.5 mol or less, more preferably 1.2 mol or less, per 1 mol of the sulfonating agent used. In this reaction, the basic compound can be used in the form of an aqueous solution, or can be used by dissolving it in an organic solvent inert to the basic compound. Examples of the organic solvent include the above-mentioned various organic solvents, aromatic hydrocarbon compounds such as benzene, toluene, and xylene; and alcohols such as methanol, ethanol, propanol, isopropanol, and ethylene glycol. These solvents may be used as a mixture of two or more.

When the basic compound is used as an aqueous solution or an organic solvent solution, the basic compound concentration is usually
It is about 1 to 70% by weight, preferably about 10 to 50% by weight. The reaction temperature is usually -30 to 150 ° C,
Preferably it is 0-120 degreeC, More preferably, it is + 50-1.
It is carried out at 00 ° C. and can be carried out under normal pressure, reduced pressure or increased pressure. Further, the reaction time is generally 0.1 to 24 hours, preferably 0.5 to 5 hours.

Also, (co) having a sulfonic acid (salt) group
The sulfonic acid (salt) group content of the polymer is preferably 0.2
~ 3mmol / g, more preferably 0.5 ~ 2.5m
mol / g, particularly preferably 1 to 2 mmol / g. If it is less than 0.2 mmol / g, functions such as hydrophilicity are hardly exhibited, and if it exceeds 3 mmol / g, water resistance may become a problem.

In the present invention, the (fine) porous membrane containing a (co) polymer having a sulfonic acid (salt) group as a main component can be produced, for example, by the following steps (1) to (4). Can be. (1) A step of mixing a (co) polymer having a sulfonic acid (salt) group with an inorganic (fine) powder, an organic substance, an additive and the like. (2) A step of uniformly kneading the mixture obtained in the step (1) and then forming a sheet-like film by extrusion molding or the like. (3) A step of extracting and removing inorganic (fine) powder and organic matter from the sheet-like film obtained in the step (2). (4) A step of stretching the film from which organic and inorganic (fine) powders have been extracted, if necessary.

Next, the method for producing a (fine) porous membrane of the present invention will be described in more detail. In the step (1), the content ratio of each component with respect to the total weight of the (co) polymer having a sulfonic acid (salt) group, the inorganic fine powder, and the organic substance is usually the (co) polymer having the sulfonic acid (salt) group. The combined amount is preferably from 10 to 80% by weight, more preferably from 20 to 70% by weight, particularly preferably from 30 to 60% by weight. The content of the inorganic fine powder is preferably 0 to 70% by weight, more preferably 5 to 60% by weight, and particularly preferably 10 to 5% by weight.
0% by weight. The content of the organic substance is preferably 0.
It is preferably from 70 to 70% by weight, more preferably from 5 to 60% by weight, particularly preferably from 10 to 50% by weight. Further, the total content of the inorganic fine powder and the organic substance is preferably 20 to 9
0% by weight, more preferably 30 to 80% by weight, particularly preferably 40 to 70% by weight. If the proportion of the (co) polymer having a sulfonic acid (salt) group is less than 10% by weight, the mechanical strength is low, and if it exceeds 80% by weight, the fluidity at the time of extrusion molding becomes poor and molding processability becomes difficult. On the other hand, if the proportion of the inorganic fine powder exceeds 70% by weight, the fluidity at the time of extrusion molding deteriorates, and if the proportion of the organic substance exceeds 70% by weight, molding becomes difficult and the mechanical strength becomes weak.

Examples of the inorganic fine powder used for producing the (fine) porous membrane of the present invention include silica, mica, talc, titanium oxide, aluminum oxide, barium sulfate and synthetic zeolite. Species may be used alone or in combination of two or more. Preferably it is silica.

The organic substance used for producing the (fine) porous membrane of the present invention includes phthalic acid esters such as diethyl phthalate, dibutyl phthalate and dioctyl phthalate, sebacic esters such as dioctyl sebacate, and adipine. Adipates such as dioctyl acid, trimellitates such as octyl trimellitate, phosphates such as tributyl phosphate, liquid paraffin (for example, alkylnaphthenes having 10 to 20 carbon atoms, preferably about 12 to 16 carbon atoms. Containing paraffins), aliphatic hydrocarbons (for example, having 10 to 70 carbon atoms, preferably 12 to 5 carbon atoms).
0, more preferably about 14 to 30 n-paraffins;
Paraffin wax (for example, having about 25 to 35 carbon atoms),
Microcrystalline wax (for example, having 40 to 6 carbon atoms)
0), low molecular weight polyethylene wax, low molecular weight polypropylene wax (for example, atactic polypropylene), and hydrocarbon waxes such as α-olefin wax. ), Water-soluble polymers soluble in water (for example, a sulfonic acid polymer having a diene skeleton, a sulfonic acid polymer having an aromatic skeleton, a carboxylic acid-containing polymer, and a hydroxyl group-containing polymer). These organic substances can be used alone or in combination of two or more.

In addition to the sulfonic acid (salt) group-containing copolymer, inorganic fine powder, and organic substances, an antioxidant, an ultraviolet absorber, a lubricant, and the like may be used as long as the effects of the present invention are not significantly impaired. And various additives such as an anti-blocking agent. It is also possible to produce a (fine) porous membrane by replacing a part of the copolymer having a sulfonic acid (salt) group with another polymer. Other polymers include, for example, polyamides; halogen-containing vinyl polymers; polyesters; olefin polymers, the above base polymers and hydrogenated products thereof.

As the polyamide, for example, nylon 6, nylon 66, nylon 610, nylon 612,
Nylon 616 and the like. Examples of the halogen-containing vinyl polymer include polyvinylidene chloride and the like. Examples of the polyester include polyesters such as polyalkylene terephthalate, for example, polyethylene terephthalate and polybutylene terephthalate. Examples of the olefin-based polymer include olefin homopolymers and copolymers containing olefins as constituent units. Examples of the olefin include ethylene,
Propylene, 1-butene, 4-methyl-1-butene, 1
Α-olefins having about 2 to 10 carbon atoms, such as -pentene, 3-methyl-1-pentene and 4-methyl-1-pentene; and other olefins such as isobutene. Preferred olefins include α-olefins having about 2 to 6 carbon atoms. One or more of these olefins can be used.

When a (co) polymer having a sulfonic acid (salt) group, an inorganic fine powder, an organic substance, various additives and other polymers are mixed, a super mixer, a ribbon blender, V A blender such as a blender is used.

In the step (2), the mixture obtained in the step (1) is mixed with an extruder, a Banbury mixer and a double roll mill.
The mixture is kneaded with a melt kneading machine such as a kneader and heated, and the mixture is directly extruded by a T-die method, an inflation method, or an extrusion method using a hollow die. A sheet having a kneading / extrusion function is formed into a sheet-like film.

In the step (3), organic or inorganic (fine) powder is extracted and removed from the sheet-like film obtained in the step (2). When organic matter is blended, to extract and remove it,
The organic matter is dissolved and the polymer having a sulfonic acid (salt) group is extracted and removed using a solvent in which the polymer does not dissolve. Examples of such solvents include alcohols, halogenated hydrocarbons, aliphatic hydrocarbons, water and the like. In addition, when inorganic (fine) powder was blended, in order to remove them, the temperature was raised to about 80 ° C. as necessary using an aqueous alkali solution such as sodium hydroxide or potassium hydroxide. In the state, extract and remove. The semi-extracted membrane from which the extraction of the organic substance and the inorganic (fine) powder has been completed may be subjected to drying and removal of the solvent, removal of the alkali by washing, and the like, as necessary. In the step (4), the above-mentioned microporous membrane from which an organic substance or an inorganic fine powder is extracted is
Stretching can be performed if necessary.

In producing the (fine) porous membrane of the present invention, sulfonic acid (salt)
After mixing and dispersing a (co) polymer having a group, an inorganic fine powder, an organic substance, various additives and other polymers as necessary in a suitable solvent, and evaporating and removing the solvent to obtain a film, Fine powders and organic substances may be extracted and removed by the same treatment as in the step (3) to produce them. Also, Japanese Patent Application Laid-Open No. 10-30625
Using an emulsion of a (co) polymer having a sulfonic acid (salt) group prepared by the method described in
Similarly, a membrane may be manufactured.

The (micro) porous film produced as described above has a porosity of usually 10 to 90% by volume, preferably 20% by volume.
８０80% by volume, particularly preferably 30 to 70% by volume. The average pore size is usually 0.01 to 3 μm, preferably 0.02 to 2 μm. The air permeability is 40
0 sec / 100 cc or less, more preferably 3 sec.
00 seconds / 100 cc or less. Further, the breaking strength of the (fine) porous membrane is preferably 100 kg / cm ² or more, more preferably 200 kg / cm ² or more, and the piercing strength is preferably 300 g or more. The thickness is not particularly limited, but is usually 1 to 1000 μm, preferably 5 to 500 μm. Moreover, when using as a separator for alkaline batteries, 20-100 micrometers is preferable.

The (micro) porous membrane of the present invention can be applied to various uses. In particular, it is suitably used as a separator for alkaline batteries such as nickel-metal hydride batteries and nickel-cadmium batteries, but can also be used as a separator for non-aqueous batteries such as lithium batteries. In addition, various filters such as diaphragm for electrolytic condenser, air purifying filter, water purifying filter, leukocyte removing filter, hay fever allergen removing filter, moisture permeable material, reverse osmosis membrane, ultrafiltration membrane, microfiltration membrane, ion exchange membrane Membrane, water absorption membrane,
It can be used for humidity control materials such as deodorant materials, anti-fog materials, and dew condensation preventive materials.

[0039]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited by these. In the examples, parts and% are by weight unless otherwise specified. Various evaluations and measurements in the examples were performed by the following methods.

(1) Total Content of Sulfonic Acid Groups The polymer containing sulfonic acid (salt) groups was vacuum dried at 80 ° C. overnight. The dried product was dissolved in a toluene / isopropyl alcohol (95/5 weight ratio) solution. After dissolution, sulfate,
After removing insolubles such as hydroxide with a filter, the solvent was removed to obtain a sulfonic acid content measurement sample. The sulfur content in the sample was determined from elemental analysis, and the amount (mmol / g) of sulfonic acid groups in the copolymer was calculated. (2) Base Polymer Weight Average Molecular Weight (Mw) The weight average molecular weight (Mw) of the base polymer was measured by gel permeation chromatography (GPC) using polystyrene as a standard sample.

(3) Film thickness The thickness was measured with a dial gauge having a minimum scale of 1 μm. (4) Porosity A sample having a porosity of 10 cm square was cut out, and the weight of the sample when wet, the weight when completely dried, and the film thickness were measured, and were obtained from the following equation. Porosity = (pore volume / microporous membrane volume) × 100 (%) Pore volume = (water content [g] −absolute weight [g]) / water
<BR> Density [g / cm3] Microporous membrane volume = 100 x film thickness [cm] (5) Air permeability According to JIS P-8117, use a Toyo Seiki B-type Gurley type densometer, and mark the scale mark 0 The time required to １００100 was measured with a stopwatch.

(6) Tensile Elongation at Break Using an autograph, the size of the test piece was 10 mm width ×
100mm length, 50mm distance between chucks, tensile speed 2
A tensile test was performed at 00 mm / min, the amount of elongation from the chart to the break was determined, and calculated by the following equation. Tensile elongation at break = (elongation to break [mm]-50 [m
m]) / 50 [mm] × 100 [%] (7) Average pore diameter It was determined by a half-dry method based on ASTM F-316-70.

(8) Evaluation of Hydrophilicity A petri dish containing distilled water and a petri dish containing a 30% KOH aqueous solution were separately prepared, and the obtained hydrophilic (fine) porous membrane was floated on the water surface. The degree of uniform wetting of the film was qualitatively observed. If the film is uniformly wetted in 1 to 10 seconds after placing the film, ○ is required for 10 seconds to 10 minutes or more,
Those that did not wet uniformly even after more than 10 minutes were evaluated as x.

(9) Measurement of Liquid Absorption Rate A hydrophilic (fine) porous membrane cut into 5 cm × 5 cm was
After immersion in a 0% KOH aqueous solution for 5 minutes, the weight increase rate was measured. Liquid absorption rate (%) = (weight of membrane after immersion−weight of membrane before immersion) / weight of membrane before immersion × 100

Reference Example 1 600 g of dioxane was placed in a glass reaction vessel, and 50 g of sulfuric anhydride was added thereto while maintaining the internal temperature at 25 ° C.
After stirring for 2 hours, a sulfuric anhydride-dioxane complex was obtained. In another glass reaction vessel, a styrene-isoprene-styrene ternary block copolymer (composition: 15/30/15
A solution was prepared by dissolving 425 g (wt ratio, weight average molecular weight: 200,000) in 2000 g of dioxane. The whole amount of the complex obtained above was added thereto while maintaining the internal temperature at 25 ° C., and stirring was further continued for 2 hours. After stirring, a solution prepared by dissolving 28.8 g of sodium hydroxide in 300 cc of water and 300 g of methanol were added.
Stirred for hours. After stirring, the solvent was removed under reduced pressure to obtain a sulfonic acid group-containing polymer. This polymer is called A1. The content of (A) sulfonic acid group in A1 is 1.2 mmol.
/ G.

Reference Example 2 The procedure of Reference Example 1 was repeated, except that the amount of sulfuric anhydride was changed to 100 g and the amount of Na hydroxide was changed to 57 g.
The obtained polymer is called A2. The sulfonic acid group content of A2 was 2.0 mmol / g.

Reference Example 3 600 g of 1,2-dichloroethane was placed in a glass reaction vessel.
, And 50 g of sulfuric anhydride was added thereto while maintaining the internal temperature at 25 ° C. In another glass reaction vessel, a 99% hydrogenated product of styrene butadiene-styrene terpolymer (composition: 20
/ 60/20, weight average molecular weight: 200,000) was prepared by dissolving 425 g in 2,000 g of 1,2-dichloroethane. In this, the solution obtained above was heated to an internal temperature of 2
The mixture was added while maintaining the temperature at 5 ° C., and the stirring was further continued for 2 hours.
After stirring, a solution prepared by dissolving 28.8 g of sodium hydroxide in 300 cc of water and 300 g of methanol were added.
The mixture was stirred at 0 ° C under reflux for 1 hour. After stirring, the solvent was removed under reduced pressure to obtain a sulfonic acid group-containing polymer. This polymer is called B1. The (A) sulfonic acid group content of B1 was 1.0 mmol / g.

Reference Example 4 The procedure of Reference Example 3 was repeated, except that the amount of sulfuric anhydride was changed to 100 g and the amount of Na hydroxide was changed to 57 g.
The obtained polymer is called B2. The sulfonic acid group content of B2 was 1.8 mmol / g.

Example 1 50% by weight of the polymer A1, 18% by weight of finely divided silica and 32% by weight of liquid paraffin were mixed by a mixer, and the mixture was formed into a film having a thickness of 100 μm by a twin-screw extruder. The formed membrane was immersed in hexane for 10 minutes to extract liquid paraffin, dried, and further dried at 60 ° C at 25 ° C.
% Of sodium hydroxide for 60 minutes to extract fine silica powder, followed by drying to obtain a hydrophilic microporous membrane. Table 1 shows the properties of the obtained microporous membrane.

Example 2 50% by weight of the polymer A2, 25% by weight of dioctyl phthalate and 25% by weight of liquid paraffin were mixed by a mixer, and the mixture was formed into a film having a thickness of 100 μm by a twin-screw extruder. The formed membrane was immersed in hexane for 10 minutes to extract dioctyl phthalate and liquid paraffin, and then dried to obtain a hydrophilic microporous membrane. Table 1 shows the properties of the obtained microporous membrane.

Example 3 In Example 1, polymer B1 was used instead of polymer A1.
Example 1 was repeated except that No. 1 was used. Table 1 shows the properties of the obtained microporous membrane.

Example 4 In Example 2, polymer B was used instead of polymer A2.
Example 2 was carried out in the same manner as in Example 2, except that No. 2 was used. Table 1 shows the properties of the obtained microporous membrane.

Comparative Example 1 The procedure of Example 1 was repeated, except that a polyethylene polymer having a weight average molecular weight of 280,000 was used instead of the polymer A1. Table 1 shows the properties of the obtained microporous membrane.

[0054]

[Table 1]

As shown in Table 1, the hydrophilicity (fine) of the present invention was
The porous membrane not only exhibits the same porosity, mechanical strength, air permeability, and pore system as the conventionally known polyethylene microporous membrane, but also exhibits excellent hydrophilicity to water or an alkaline aqueous solution. You can see that. That is, such excellent hydrophilicity with respect to water or an aqueous alkaline solution is an effect that cannot be obtained with a conventional microporous polyethylene membrane.
As described above, the hydrophilic (fine) porous membrane of the present invention exhibits excellent hydrophilicity with respect to an alkaline aqueous solution, and thus is useful as a separator for alkaline batteries such as nickel-metal hydride batteries and nickel-cadmium batteries. In addition, the microporous film can be made as thin as 20 to 100 microns, and an alkaline battery using the same as a separator has a higher self-discharge property, cycle characteristics, and higher performance than a battery using a conventional nonwoven fabric separator. It has excellent rate charge / discharge characteristics and can achieve high capacity. Further, the present invention can be applied to the above-mentioned various uses other than the battery separator.

[0056]

The hydrophilic (fine) porous membrane of the present invention has not only excellent porosity and mechanical strength, but also excellent hydrophilicity. Therefore, it is useful for a battery separator and the like.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01G 9/02 H01G 9/02 301 301 H01M 2/16 P H01M 2/16 H01G 9/00 301C // C08L 101: 02 (72) Inventor Katsuhiro Ishikawa 2-11-24 Tsukiji, Chuo-ku, Tokyo F-term in JSR Corporation 4D006 GA03 GA06 GA07 HA93 MA12 MA22 MA24 MB02 MB03 MB09 MB16 MC74 MC81 MC85 PC01 4F074 AA13A AA13B AA13E AC17 AC30 AC32. CA05 FA03 GC02 HA03 HA61 HB52 HB53 HE14 HG02 HG03 HG04 JA43 5H021 BB09 CC00 EE15 EE18 HH02 HH03

Claims (7)

[Claims] 1. A hydrophilic porous membrane mainly comprising a (co) polymer containing a sulfonic acid (salt) group. 2. The hydrophilic porous membrane according to claim 1, wherein the porosity is 10 to 90%. 3. The hydrophilic porous membrane according to claim 1, wherein the average pore size is 0.02 to 2 μm. 4. The (co) polymer containing a sulfonic acid (salt) group has at least one or more monomer units selected from diene monomers and aromatic monomers.
2. The hydrophilic porous membrane according to claim 1, which is a polymer obtained by sulfonating a copolymer or a hydrogenated product thereof. 5. The (co) polymer containing a sulfonic acid (salt) group is a polymer obtained by sulfonating a block copolymer comprising a diene monomer and an aromatic monomer or a hydrogenated product thereof. The hydrophilic porous membrane according to claim 2, characterized in that: 6. A battery separator comprising the hydrophilic porous membrane according to claim 1. 7. A battery comprising the hydrophilic (fine) porous membrane according to claim 1 as a battery separator.