JP2000064165A - Hydrophilic nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide nonwoven fabric excellent in mechanical strength, having excellent affinity and liquid absorption to water, an alkali aqueous solution, or the like and esp. suitable for separator for alkaline battery. SOLUTION: This nonwoven fabric includes a block copolymer in its fibers, and the block copolymer comprises (A) a block chain having hydrophilic group and (B) a block chain having hydrophobic group, where the ratio (number of structural monomers combined with hydrophilic groups/number of structural monomers in the block chain A) of >=50%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonwoven fabric containing a hydrophilic group, and more particularly to a hydrophilic nonwoven fabric suitable for use in filters, battery separators and the like.

[0002]

BACKGROUND OF THE INVENTION Nonwoven fabrics based on polymers are chemically stable, have excellent chemical resistance, and have good alkali resistance at high temperatures and high concentrations, but have a large hydrophobicity, and thus are highly resistant to electrolytes such as batteries. Since the hydrophilicity with the above is poor, there is a problem that the electrolyte retaining property is not sufficient. Therefore, non-woven fabrics and the like used as battery separators have been modified or surface-treated by various methods. For example, JP-A-6
4-57568 and the like disclose a method of directly sulfonation of a nonwoven fabric made of a polyolefin resin to impart hydrophilicity. However, this method has a problem that the retention of the electrolytic solution is not sufficient due to the insufficient amount of the sulfonic acid group introduced, or the mechanical strength is lowered due to the introduction of the sulfonic acid group. Further, JP-A-53-62138 and the like disclose a method of introducing a hydrophilic functional group into a nonwoven fabric by subjecting it to corona discharge treatment or plasma treatment. However, when this treatment is carried out, there is a problem that the substrate itself is deteriorated, the mechanical strength is lowered, and the treatment process becomes complicated, which is not practical. Also, Japanese Patent Laid-Open No. 7-138391
Discloses a method of graft-polymerizing a sulfonic acid-based monomer and an acrylic-based monomer on a nonwoven fabric made of polyolefin by ionizing radiation. In this method, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid and the like are disclosed as sulfonic acid monomers. However, there is a problem that the irradiation of ionizing radiation causes deterioration of the non-woven fabric substrate, resulting in a decrease in mechanical strength.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydrophilic non-woven fabric which is excellent in hydrophilicity, ion trapping property and mechanical strength and is suitable for battery separators, filter materials and the like. is there.

[0004]

The present invention is a block copolymer comprising a block chain having a hydrophilic group and a block chain having a hydrophobic group, wherein the hydrophilic group is based on the number of constituent monomer units of the block chain having the hydrophilic group. The present invention provides a hydrophilic non-woven fabric containing a block copolymer in which the ratio of the number of constituent monomer units introduced with is 50% or more.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The hydrophilic non-woven fabric of the present invention uses a fiber containing a block copolymer containing a hydrophobic polymer unit and a hydrophilic polymer unit containing a hydrophilic group. The block copolymer used in the present invention is a block copolymer composed of a block chain having a hydrophilic group and a block chain having a hydrophobic group. The block chain having such a hydrophobic group is a polymer or copolymer unit containing a hydrocarbon monomer as a main component. The unit of the polymer or copolymer containing the hydrocarbon-based monomer as a main component is a (co) polymer containing a diene-based monomer as a main component or an olefin-based monomer such as an aromatic vinyl compound or an olefin. Examples thereof include a (co) polymer mainly composed of a polymer or a unit of a (co) polymer obtained by hydrogenating these.

Examples of the block chain having a hydrophilic group include the above-mentioned hydrophobic polymer unit containing a hydrophilic group. As the hydrophilic group, a sulfonic acid group, a carboxylic acid group (carboxylic acid group), a phosphoric acid group,
Examples thereof include amine group, amide group, and hydroxyl group. Among these, a sulfonic acid group and a carboxylic acid group (carboxyl group) are preferable, and a sulfonic acid group is more preferable. For example, a (co) polymer mainly containing a diene monomer, a (co) polymer mainly containing an olefin monomer such as an aromatic vinyl compound or an olefin, or a hydrogenated (co) polymer thereof. Examples of the unit include a unit of a (co) polymer containing a hydrocarbon-based monomer as a main component such as a unit of 1) and a hydrophilic group such as a sulfonic acid group. Examples of the method for incorporating a sulfonic acid group into a (co) polymer unit containing a hydrocarbon-based monomer as a main component include a method of adding a hydrophilic group such as sulfonation of these (co) polymer units, and a sulfone group. Examples thereof include a method of copolymerizing a monomer having a hydrophilic group such as an acid group. A block copolymer 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 is preferable. This is a method of adding a hydrophilic group to a block copolymer (hereinafter referred to as a base polymer) or a hydrogenated block copolymer thereof.

The diene-based monomer used in the unit of the (co) polymer mainly containing the diene-based monomer is
A diene compound having 4 to 12 carbon atoms is preferable, a diene compound having 4 to 8 carbon atoms is more preferable, and a diene compound having 4 to 6 carbon atoms is particularly preferable. Specific examples of these diene compounds include 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 and the like, various branched or alicyclic dienes having 4 to 7 carbon atoms can be mentioned. These can be used alone or in combination of two or more.
Of these, particularly preferred is 1,3-butadiene,
Isoprene.

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

Further, a (co) polymer mainly containing the diene-based monomer, a (co) polymer mainly containing an olefin-based monomer such as an aromatic vinyl compound or an olefin, or hydrogenated ( In addition to the above monomers, other monomers may be used in combination in the unit of the co) polymer.
Examples of other monomers include (meth) acrylic acid alkyl esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate, (meth) acrylic acid, crotonic acid, and maleic acid. Acid, fumaric acid,
Mono- or dicarboxylic acids such as itaconic acid or anhydrides of dicarboxylic acids, vinyl cyanide compounds such as (meth) acrylonitrile, vinyl chloride, vinylidene chloride, vinyl methyl ethyl ketone, vinyl acetate, (meth) acrylamide, glycidyl (meth) acrylate, hydroxy An unsaturated compound such as (meth) acrylate may be mentioned. These other monomers can be used alone or in combination of two or more. A hydrophilic polymer unit can also be obtained by copolymerizing these.

Further, the main component is a diene monomer (co).
The above-mentioned aromatic vinyl compound or olefin may be copolymerized as the other monomer in the polymer unit in a subordinate amount. The diene-based monomer or olefin may be copolymerized in a subordinate amount in the (co) polymer unit mainly composed of an aromatic vinyl compound. In addition, the diene-based monomer or aromatic vinyl compound may be copolymerized in a subordinate amount as another monomer in the (co) polymer unit mainly containing olefin. When these other monomers are used in combination, the amount of the monomer used is usually 60% or less, preferably 50% by weight or less, and more preferably 30% in each (co) polymer unit.
It is not more than 20% by weight, particularly preferably not more than 20% by weight.

Examples of the monomer having a sulfonic acid group include those obtained by adding a sulfonic acid group to the above diene monomer or olefin 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, sulfonic acid group-containing propylene, and the like. Of these, preferred are sulfonic acid group-containing isoprene and sulfonic acid group-containing styrene. Also,
Examples of other hydrophilic group-containing monomers include (meth) acrylic acid, (meth) acrylate, (meth) acrylamide, hydroxy (meth) acrylate, and glycidyl (meth) acrylate. As a method for adding a hydrophilic group other than sulfonation, known methods such as carboxylation, phosphate esterification, amination, amidation, and hydroxylation can be used.

Production of a base polymer, that is, 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 The contained block copolymer can be produced by (co) polymerizing each monomer by using an initiator and, if necessary, a solvent. Examples of such an initiator include radical polymerization initiators such as hydrogen peroxide, benzoyl peroxide and azobisisobutyronitrile, or n-butyllithium,
Examples thereof include anionic polymerization initiators such as sodium naphthalene and metallic sodium. The polymerization temperature is usually −
The temperature is 100 to 150 ° C, preferably 0 to 130 ° C. As the polymerization method, anionic polymerization is particularly preferably used from the viewpoint of obtaining a block copolymer.

Further, with respect to the above block copolymer, part or all of the remaining double bonds based on the diene monomer can be hydrogenated (hydrogenated) before use. In this case, a known hydrogenation catalyst can be used.
Examples thereof include catalysts and methods described in JP-A-222115. After hydrogenating the block copolymer as the base polymer, a hydrophilic group can be introduced by a method described below, but it may be hydrogenated after introducing the hydrophilic group into the copolymer.

The base polymer used in the present invention is preferably a polymer unit A containing a diene monomer.
And a block copolymer containing a polymer unit B containing an aromatic vinyl monomer or an olefin monomer. The preferred structure of the block copolymer is AB type or A (BA) n type or B (A
B) n type or (AB) m type (where n is preferably 1 to 5, more preferably 1 to 3 and even more preferably 1 to
2, particularly preferably 1, m is preferably 2 to 5, more preferably 2 to 3 and even more preferably 2). Also, a diene block copolymer having the following structure can be used. Bm- (AB) x-An, Am-B- (AB) x-An,
Bm- (AB) x-ABn (where m and n are 2-5, preferably 2-3, more preferably 2, x is 0-3, preferably 0-
2, more preferably 1. The above structure is the same when the hydrophilic polymer unit is A and the hydrophobic polymer unit is B.

Of these, preferred are AB type and A type.
They are BA type and BAB type block copolymers. Specific preferred base polymers include, for example, isoprene-styrene block copolymers, styrene-isoprene-styrene ternary block copolymers, isoprene-styrene-isoprene ternary block copolymers, butadiene-styrene block copolymers. , Styrene-butadiene-
Examples thereof include styrene ternary block copolymers, butadiene-styrene-butadiene ternary block copolymers, and hydrogenated products of these block copolymers. In the block chain of the diene monomer unit, the aromatic monomer or other monomer may be partially copolymerized,
The diene monomer or other monomer may be partially copolymerized in the block chain of the aromatic monomer unit.

The polystyrene-equivalent weight average molecular weight (hereinafter referred to as "Mw") of these base polymers or hydrogenated products thereof is preferably 4,000 to 1,000,000.
0, more preferably 7,000 to 500,000, and particularly preferably 10,000 to 200,000. M
When w is less than 4,000, the block copolymer is easily detached from the hydrophilic non-woven fabric, which may unfavorably decrease the hydrophilicity over time.
If it exceeds 0, there may occur problems such as an excessively high viscosity during the production of the nonwoven fabric, which will be described later.

In the block copolymer, the weight ratio A / B of the polymer unit A containing the diene-based monomer and the polymer unit B containing the olefin-based monomer is the same as that of the non-hydrogenated block copolymer. In this case, it is preferably 1 to 80/99 to 20, more preferably 2 to 7
0/98 to 30, particularly preferably 5 to 50/95 to 50
Is. In the case of a hydrogenated block copolymer, it is preferably 20 to 99/80 to 1, more preferably 30 to 98/70 to 2, and particularly preferably 50 to
95 / 50-5. When the hydrophilic polymer unit is A'and the hydrophobic polymer unit is B ',
The weight ratio of A '/ B' is preferably 1 to 80/99 to 2.
0, more preferably 2 to 70/98 to 30, and particularly preferably 5 to 50/95 to 50.

The degree of polymerization of each polymer unit A and B in the case of a non-hydrogenated block copolymer is preferably A of 10 or more, B of 20 or more, more preferably A of 50 or more, B Is 100 or more, particularly preferably A is 100 or more and B is 200 or more. Also,
In the case of a hydrogenated block copolymer, preferably A
Is 20 or more, B is 10 or more, and more preferably A
Is 100 or more, B is 50 or more, and particularly preferably A
Is 200 or more and B is 100 or more.

The block copolymer having a hydrophilic group of the present invention can be produced by introducing a hydrophilic group into the base polymer comprising the above block copolymer by a method such as addition. As this method, a known method can be used. When introducing a sulfo group, for example, edited by the Japan Society for Science, new experiment course (14, III, p. 1773), or
It can be produced by sulfonation according to the method described in JP-A-2-227403.

That is, when the hydrophilic group-containing block copolymer of the present invention is produced by sulfonation of the block copolymer, the above-mentioned base polymer is used as a double bond moiety based on a diene monomer in the polymer. Alternatively, either one of the aromatic moieties can be prepared by preferentially sulfonation with a sulfonating agent. In addition,
(1) When using a non-hydrogenated base polymer or a base polymer in which the diene unit is partially hydrogenated, it is preferable to preferentially sulfonate the diene unit, while (2) the diene unit In base polymers which are hydrogenated, it is preferred to preferentially sulfonate the aromatic units. When the diene unit is preferentially sulfonated as in (1), the sulfonating agent may be a complex of sulfuric anhydride and an electron-donating compound or a bisulfite salt (Na salt, K salt, Li salt).
It is preferable to use such as salt). Also, (2)
As described above, in order to preferentially sulfonate the aromatic unit, it is preferable to use sulfuric acid anhydride, chlorosulfonic acid, fuming sulfuric acid or the like as the sulfonating agent, 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;
Examples thereof include sulfides such as dimethyl sulfide and diethyl sulfide; nitrile compounds such as acetonitrile, ethyl nitrile and propyl nitrile, and of these, N, N-dimethylformamide and dioxane are preferable.

When a non-hydrogenated base polymer or a partially hydrogenated base polymer is used, the amount of sulfonating agent is 0.5 mol per 1 mol of diene units in the base polymer. It is 1.2 mol or more and preferably 1.2 mol or less, preferably 0.8 mol or more and 1.1 mol or less, and if it is less than 0.5 mol, sufficient hydrophilicity may not be obtained. It is not preferable because the reaction sulfonating agent remains as an impurity. When a hydrogenated base polymer is used, the amount of the sulfonating agent is usually 0.5 mol or more and 1.2 mol or less, preferably 1 mol of the aromatic unit in the base polymer. It is 0.8 mol or more and 1.1 mol or less, and if it is less than 0.5 mol, sufficient hydrophilicity may not be obtained, and if it exceeds 1.2, the unreacted sulfonating agent remains as an impurity.

In this sulfonation, a solvent inert to the sulfonating agent such as sulfuric anhydride or sulfuric acid may be used. Examples of the solvent include halogen such as chloroform, dichloroethane, tetrachloroethane, tetrachloroethylene and dichloromethane. And hydrocarbons; nitro compounds such as nitromethane and nitrobenzene; liquid sulfur dioxide, aliphatic hydrocarbons such as propane, butane, pentane, hexane and cyclohexane, ether solvents such as dioxane and tetrahydrofuran, and water. These solvents can be used as a mixture of two or more kinds as appropriate. The reaction temperature for this sulfonation is usually −
70 to 200 ° C, preferably -30 to 50 ° C,
If the temperature is lower than 70 ° C, the sulfonation reaction becomes slow, which is not economical. On the other hand, if the temperature exceeds 200 ° C, a side reaction may occur to blacken or insolubilize the product.

The sulfonated product of the diene block copolymer used in the hydrophilic polymer composition of the present invention is preferably a product obtained by reacting this sulfonated product with water or a basic compound. 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, lithium carbonate; methyl lithium, ethyl lithium, n-butyl lithium, sec-butyl lithium, amyl lithium, propyl sodium, methyl magnesium chloride, ethyl magnesium bromide, propyl magnesium Iodide, diethyl magnesium,
Organometallic compounds such as diethyl zinc, triethyl aluminum, triisobutyl aluminum; ammonia water,
Examples include amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, pyridine, aniline and piperazine; metal compounds such as sodium, lithium, potassium, calcium and zinc. These basic compounds may 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, and more than 2 mol based on 1 mol of the sulfonating agent used. However, the purity of the polymer decreases. In this reaction, the basic compound may be used in the form of an aqueous solution, or may be used by dissolving it in an organic solvent inert to the basic compound. As the organic solvent, in addition to the above various organic solvents, benzene,
Aromatic hydrocarbon compounds such as toluene and xylene; alcohols such as methanol, ethanol, propanol, isopropanol and ethylene glycol. These solvents can be used as a mixture of two or more kinds as appropriate.

When the basic compound is used as an aqueous solution or an organic solvent solution, the concentration of the basic compound 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 0 to 120 ° C., more preferably +50 to 1
It is carried out at 00 ° C., and can be carried out under normal pressure, reduced pressure or increased pressure. Furthermore, the reaction time is usually 0.1 to 24 hours, preferably 0.5 to 5 hours. When a hydrophilic group other than the sulfonic acid group is introduced, it can be produced, for example, by copolymerizing (meth) acrylic acid, (meth) acrylic phosphate, amino (meth) acrylate, hydroxyalkyl (meth) acrylate and the like. it can.

The content of the polar group in the block copolymer having the hydrophilic group introduced therein is usually preferably 50 mol% or more of the constituent monomer units in the block containing the hydrophilic group, more preferably 70 mol. % Or more. When the amount is 50 mol% or more, sufficient hydrophilicity can be obtained. Further, a block copolymer in which the ratio of the number of hydrophilic monomer units (units) to the number of monomer units (units) of the block chain having a hydrophilic group is 50% or more is preferable, more preferably 70% or more, It is particularly preferably 80% or more.

The content of sulfonic acid (salt) group in the block copolymer is preferably 0.1 to 3.3 mmol /
g, more preferably 0.3 to 2.0 mmol / g, and particularly preferably 1.0 to 1.5 mmol / g. 0.
If it is less than 1 mmol / g, functions such as hydrophilicity are difficult to be exhibited, and if it is too large, it may be difficult to form fibers.

The block copolymer having a hydrophilic group of the present invention is generally preferably used in a solid state such as pellets by being blended with a polymer for a nonwoven fabric described later. In some cases, to the extent that problems do not occur when producing the fibers that make up the nonwoven fabric, emulsified and dispersed in water and used as an emulsion (hereinafter, this emulsification step is also referred to as "re-emulsification"). Also, it is possible to use it by dissolving it in a non-aqueous solvent, or to use an emulsion obtained by emulsifying and dissolving a substance dissolved in a non-aqueous solvent in water.

When the block copolymer is used as an emulsion, the emulsification step is performed by stirring and mixing the block copolymer or an organic solvent solution of the copolymer with water.
After emulsifying, the organic solvent can be removed while leaving water. As the organic solvent used in the emulsification step, for example, an aromatic solvent such as toluene or xylene, an hexane or an aliphatic solvent such as heptane, a ketone solvent such as acetone or methyl ethyl ketone, tetrahydrofuran, an ether such as dioxane. A system solvent, an ester solvent such as ethyl acetate and butyl acetate, an alcohol solvent such as methanol, ethanol and isopropyl alcohol, and an amide solvent such as dimethylformamide are used. These solvents may be used alone or in combination of two or more kinds without any problem. This emulsification step, a general method can be adopted, a method of adding water to the organic solvent solution of the block copolymer while stirring, a method of adding the organic solvent solution of the block copolymer to water while stirring. , A method of adding water and an organic solvent solution of the block copolymer at the same time and stirring,
There is no particular limitation.

A surfactant may be used in combination during the emulsification step. Examples of the surfactant include nonionic surfactants such as polyoxyethylene alkyl ether, polyoxysorbitan ester, and polyoxyethylene alkylamine ether, oleate, laurate, rosinate, dodecylbenzenesulfonate. ,
Examples thereof include anionic surfactants such as polyoxyethylene alkyl ether sulfate salt, and cationic surfactants such as octyltrimethylammonium bromide, dioctyldimethylammonium chloride and dodecylpyridinium chloride. These surfactants may be used alone or in combination of two or more. The above-mentioned surfactant may be dissolved or dispersed in an organic solvent solution of the block copolymer before use, or may be dissolved or dispersed in water before use. The amount of the surfactant used is usually 10 parts by weight or less based on 100 parts by weight of the block copolymer,
Preferably 6 parts by weight or less, more preferably 0.001
~ 5 parts by weight.

In order to adjust the pH in the system, alkali compounds such as sodium hydroxide and lithium hydroxide,
It is also possible to add an inorganic acid such as hydrochloric acid or sulfuric acid. In addition, an organic solvent other than water can be used in combination as long as the amount is small. Further, a defoaming agent or the like can be added. The particle size of the emulsion obtained by emulsifying the component (A) polymer thus obtained is usually preferably 10 to 1,000 nm, more preferably 20 to 500 nm.
The solid content concentration of the obtained emulsion of the component (A) polymer is usually 5 to 50% by weight, preferably 10 to 40% by weight, which depends on the use conditions, storage conditions, etc.
It can be appropriately selected.

The structure of the sulfonated diene block copolymer of the present invention can be confirmed from the absorption of sulfo groups by infrared absorption spectrum, and the composition ratio of these can be known by elemental analysis or the like. The structure can be confirmed by the nuclear magnetic resonance spectrum. It is also possible to use a block polymer containing a group other than a sulfonic acid group as the hydrophilic group. For example, after synthesizing a block copolymer composed of the aromatic monomer and t-butyl methacrylate, the t-butyl group of t-butyl methacrylate is removed by heating to obtain a block copolymer having a carboxylic acid as a hydrophilic group. Can be obtained, and the same effect can be obtained by using it.

Next, a non-woven fabric made of fibers containing the block copolymer having the hydrophilic group will be described. A fiber may be made only from the block copolymer having a hydrophilic group and made into a non-woven fabric, but in view of moldability and strength of the fiber, the block copolymer is used in combination with another polymer. It is preferable.

Specific examples of other polymers used in combination include:
For example, ethylene, propylene, butene-1, pentene-
In addition to olefin homopolymers such as 1, hexene-1,4-methylpentene-1, random or block copolymers of these olefins, polyamides, polyesters, acrylic polymers, ethylene-vinyl alcohol copolymers, etc. Examples of the polymer used for the non-woven fabric include polymers which may be used alone or in combination of two or more. In particular, when used as a battery separator, an olefin (co) polymer such as ethylene or propylene is preferable.

In the total amount of the block copolymer having a hydrophilic group and the other polymer used in these non-woven fabrics, the ratio of the block copolymer having a hydrophilic group is usually 0.5 to 5 in terms of weight. It is 50%, preferably 1 to 40%, more preferably 2 to 30%. If the proportion of the block copolymer having a hydrophilic group exceeds 50% by weight, the mechanical strength and water resistance of the prepared nonwoven fabric are reduced. Further, the ratio of the block copolymer having a hydrophilic group is 0.5%.
If it is less than 1, the hydrophilicity is insufficient.

The block copolymer having a hydrophilic group and the other polymer may be used in combination, for example, by blending and melting them into fibers, by mixing or twisting each fiber into fibers, Examples thereof include a method of blending, a method of bonding and using each fiber, and a method of forming a split fiber composed of both fibers. These hydrophilic group-containing block copolymers and other polymers are used in combination to form fibers, and there is no particular limitation on the method for preparing the nonwoven fabric, and known methods can be adopted, but especially spun lace method, melt blow method,
Those manufactured by a wet papermaking method can be preferably used.

The basis weight of the nonwoven fabric is 10 to 300 g / m ^2.
Is preferable, and the average fiber diameter is 0.1 to 40 μm, especially 1 to
It is preferably 10 μm. The thickness of the nonwoven fabric is usually preferably 50 to 1000 μm. Further, the hydrophilic nonwoven fabric of the present invention may be stretched by an arbitrary method such as a heat roll method or a pin tenter method before use.
Further, when preparing the hydrophilic nonwoven fabric of the present invention, known additives such as antioxidants, antioxidants, lubricants, and ultraviolet absorbers may be used.

The hydrophilic non-woven fabric according to the present invention can be applied to various uses. For example, it shows the action of trapping ammonia, weak bases such as amines, or ionic substances existing in air or water, and is applied to filter materials such as air cleaning filters and water cleaning filters. Further, by using it as a battery separator, it is expected that the affinity with the battery electrolyte is improved and the battery characteristics such as self-discharge characteristics are improved. In particular, it can be suitably used as a separator for alkaline batteries. In addition, for example, water-absorbent nonwoven fabric, nonwoven fabric for wet tissue, nonwoven fabric for sealing material, antifouling material, ion exchange fiber, leukocyte removal filter, pollen allergen removal material, water vapor permeable material, antibacterial material, deodorant fiber, deodorant paint , Deodorant paper, anti-fog materials, humidity control materials such as anti-condensation materials, and sanitary products.

[0040]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, parts and% are based on weight unless otherwise specified.

(1) Ratio of Total Content of Sulfonic Acid Groups and Number of Hydrophilic Groups The synthesized sulfonated product was vacuum dried at 80 ° C. overnight. The dried product was dissolved in a toluene / isopropyl alcohol (95/5 weight ratio) solution. After dissolution, insoluble matters such as sulfate and hydroxide were removed by a filter, and then the solvent was removed to obtain a sample for measuring a sulfonic acid content. The sulfur content in the sample was determined by elemental analysis, and the amount of sulfonic acid groups in the copolymer was calculated. Also, using this value, the ratio of the number of hydrophilic groups to the number of constituent monomer units of the block chain having a hydrophilic group was calculated.

(2) Particle size of re-emulsion LPA-3100 LASER P manufactured by Otsuka Electronics Co., Ltd.
The average particle size of the emulsion was measured using ARTICLE ANALYZER. (3) 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.

(4) Evaluation of hydrophilicity Distilled water and a 30% KOH aqueous solution were dropped on the non-woven fabric, and the degree of soaking into the non-woven fabric was qualitatively observed. A sample with good penetration was evaluated as ◯, and a sample that did not readily penetrate was evaluated as x. (5) Measurement of liquid absorption rate The non-woven fabric of 5 cm square was dipped in a 30% KOH aqueous solution for 10 minutes, and the weight increase rate was measured and calculated by the following formula. Liquid absorption rate (%) = (weight of nonwoven fabric after immersion-weight of nonwoven fabric before immersion) / weight of nonwoven fabric before immersion x 100

(6) Measurement of liquid absorption speed 1 cm of the tip of a strip-shaped nonwoven fabric was immersed in a 30% KOH aqueous solution.
After soaking for 0 minutes, measure the height at which the KOH aqueous solution has penetrated. (7) Mechanical strength measurement of non-woven fabric A strip-shaped sample having a width of 1 cm and a length of 5 cm was prepared,
After fixing both ends of 2.5 cm by a chuck, a tensile test was conducted. The stress at break (kg / 25 mm) and the elongation (%) were evaluated.

Reference Example 1 500 g of dioxane was placed in a glass reaction vessel, and 50 g of sulfuric acid anhydride was added thereto while keeping the internal temperature at 25 ° C.
After stirring for 2 hours, a sulfuric anhydride-dioxane complex was obtained. In a separate glass reactor, add isoprene-styrene AB.
Type block copolymer (styrene / isoprene = 80/2
212.5 g of 0 (weight ratio) and a weight average molecular weight of 150,000 were dissolved in 400 g of dioxane. To this, the total amount of the complex obtained above was added while maintaining the internal temperature at 25 ° C,
The stirring was continued for another 2 hours. After stirring, a solution of 27.5 g of sodium hydroxide dissolved in 200 cc of water and 300 g of methanol were added, and the mixture was stirred under reflux at 80 ° C for 4 hours. After stirring, the solvent was removed under reduced pressure to obtain a block copolymer mainly having isoprene moieties sulfonated. This polymer is referred to as X1.

Reference Example 2 1,2-dichloroethane (500 g) in a glass reaction vessel
Then, 50 g of sulfuric acid was added thereto while keeping the internal temperature at 25 ° C. Add butadiene-styrene AB to another glass reactor.
Hydrogenated block copolymer (butadiene / styrene =
90/10 (weight ratio), weight average molecular weight 180,000, hydrogenation rate of butadiene unit: 99%) 425 g was dissolved in 800 g of 1,2-dichloroethane. The total amount of the complex obtained above was added to this while maintaining the internal temperature at 25 ° C., and stirring was continued for 2 hours. After stirring, a solution of 27.5 g of sodium hydroxide in 200 cc of water and 300 g of methanol were added, and the mixture was refluxed at 80 ° C.
Stir for 4 hours. After stirring, the solvent was removed under reduced pressure to obtain a block copolymer mainly having styrene moieties sulfonated. This polymer is called Y1.

Reference Example 3 Polymer X synthesized above
1,100 g was dissolved in 1000 g of tetrahydrofuran / isopropyl alcohol (90/10 weight ratio). In a flask, 500 g of water and 1 g of an anion / nonionic surfactant [Sanyoto EN manufactured by Sanyo Kasei Co., Ltd.] were placed,
It was stirred for another hour. Then, 1000 g of water was added, and all the solvent and part of the water were removed by azeotropic distillation to obtain a re-emulsified emulsion (re-emulsion). The solid content concentration of this emulsion was 40%. This emulsion is referred to as emulsion X1.

Reference Example 4 Polymer Y synthesized above
1,100 g was dissolved in 1000 g of tetrahydrofuran / isopropyl alcohol (90/10 weight ratio). In a flask, water 500g, dodecylbenzene sulfonic acid N
1 g of a was added, and the mixture was further stirred for 1 hour. Then 100
By adding 0 g of water and removing all the solvent and part of the water by azeotropic distillation, a re-emulsified emulsion (re-emulsion) was obtained. The solid content concentration of this emulsion was 40%. This emulsion is referred to as emulsion Y1.

Reference Example 5 500 g of dehydrated tetrahydrofuran and 0.45 mmol of n-butyllithium were placed in a pressure resistant reactor, and 40 g of dehydrated styrene was added while maintaining the internal temperature at -70 to -60 ° C. After the addition, the mixture was stirred for 30 minutes to proceed with polymerization, and then 10 g of dehydrated t-butyl methacrylate was added at an internal temperature of −70 to −60 ° C.
It was added while keeping. After the addition, the mixture was stirred for 1 hour. The produced polymer was precipitated and purified in methanol, recovered, dissolved in toluene, and refluxed at 110 ° C for 5 hours. By heating, the t-butyl group is removed, and the carboxylic acid group is present,
An AB type block copolymer was produced. The weight average molecular weight was 100,000. The amount of carboxylic acid and the like were determined by neutralization titration. This polymer is referred to as polymer Z1.

Properties of these polymers and emulsions are shown in Table 1.

[0051]

[Table 1] * 1 Ratio of the number of constituent monomer units having a hydrophilic group introduced to the number of constituent monomer units of the block chain having a hydrophilic group

Example 1 As a raw material, polymer X1
The polymer X1 / polypropylene ratio was 20/80 (weight ratio) using (solid matter) and polypropylene (“Noblene” manufactured by Mitsui Toatsu Chemicals, Inc.). The above-mentioned resin was melted by using an ordinary stick-out type melt blown spinning machine as an apparatus, and a melt blown nonwoven fabric having a basis weight of 50 g / m 2 was produced under the conditions of a spinning temperature of 300 ° c and a collecting distance of 20 cm. . The fiber diameter of the obtained non-woven fabric is 5.
The thickness of the nonwoven fabric was 2 microns and the thickness of the nonwoven fabric was 100 microns.

Example 2 A nonwoven fabric was prepared in the same manner as in Example 1 except that the polymer Y1 was used instead of the polymer X1. The basis weight was 50 g / m2, the fiber diameter was 5.0 microns, and the thickness of the nonwoven fabric was 100 microns.

Example 3 In Example 1, the emulsion X1 was used in place of the polymer X1 to obtain an emulsion X1 / polypropylene 10/90 (weight ratio, solid content conversion). A nonwoven fabric was produced in the same manner as in Example 1 while removing water in the emulsion. The basis weight was 53 g / m2, the fiber diameter was 5.2 microns, and the thickness of the nonwoven fabric was 100 microns.

Example 4 In Example 1, emulsion Y1 was used in place of polymer X1 to give emulsion X1 / polypropylene 10/90 (weight ratio, solid content conversion). A nonwoven fabric was produced in the same manner as in Example 1 while removing water in the emulsion. The basis weight was 53 g / m2, the fiber diameter was 5.2 microns, and the thickness of the nonwoven fabric was 100 microns.

Example 5 A nonwoven fabric was prepared in the same manner as in Example 1 except that the polymer Z1 was used instead of the polymer X1. The basis weight is 53 g / m
2. The fiber diameter was 5.2 microns and the thickness of the nonwoven fabric was 100 microns.

Comparative Example 1 A nonwoven fabric was prepared in the same manner as in Example 1 except that only polypropylene was used. The basis weight was 50 g / m2, the fiber diameter was 5.4 microns, and the thickness of the nonwoven fabric was 100 microns.

The performance of each nonwoven fabric is shown in Table 2. It can be seen that the hydrophilic non-woven fabric of the present invention has a small decrease in mechanical strength and is significantly excellent in hydrophilicity, liquid absorbency and the like. Especially K
It can be seen that it is suitable for alkaline battery separators such as Ni-hydrogen batteries because of its high affinity and water absorption for alkaline aqueous solutions such as OH.

[0059]

[Table 2]

[0060]

The hydrophilic nonwoven fabric of the present invention is excellent in mechanical strength and has an affinity for water, alkaline aqueous solution, etc.
Excellent liquid absorption. In particular, it can be suitably used as an alkaline battery separator or the like.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuhiro Ishikawa             2-11-24 Tsukiji, Chuo-ku, Tokyo J             Within SRL Co., Ltd. F-term (reference) 4J026 HA03 HA04 HA05 HA06 HA09                       HA10 HA11 HA12 HA13 HA14                       HA15 HA16 HA22 HA23 HA26                       HA39 HA49 HB03 HB04 HB05                       HB06 HB09 HB10 HB11 HB12                       HB13 HB14 HB15 HB16 HB50                       HC03 HC04 HC05 HC06 HC09                       HC10 HC11 HC12 HC13 HC14                       HC15 HC16 HC47 HC49 HC50                       HE01 HE02 HE05 HE06                 4J100 BA56H CA04 CA31 GC02                       HA03 HA55 HA61 HB02 HB52                       HB53 HC88 JA11 JA43                 4L047 AA14 AA28 AB02 AB07 CA19                       CB01 CB07 CC12                 5H021 CC02 EE04 EE15 EE18 EE20                       EE29 HH01

Claims (5)

[Claims] 1. A block copolymer comprising a block chain having a hydrophilic group and a block chain having a hydrophobic group, wherein the number of constituent monomer units having a hydrophilic group is introduced with respect to the number of constituent monomers of the block chain having a hydrophilic group. A hydrophilic non-woven fabric containing a block copolymer having a ratio of 50% or more in the fiber. 2. The hydrophilic non-woven fabric according to claim 1, wherein the hydrophilic group is a sulfonic acid (salt) group. 3. A block copolymer obtained by sulfonation of a block copolymer containing a polymer unit containing a diene monomer and a polymer unit containing an olefin monomer, or a hydrogenated product thereof. The hydrophilic non-woven fabric according to claim 1, wherein 4. A block copolymer containing a polymer unit A containing a diene monomer and a polymer unit B containing an olefin monomer is AB type or A type.
(BA) n type or B (AB) n type or (AB)
The hydrophilic non-woven fabric according to claim 3, wherein the hydrophilic non-woven fabric is m type (where n is 1 to 3 and m is 2 to 3). 5. A battery separator using the hydrophilic non-woven fabric according to claim 1.