JP2001291504A - Film for alkaline battery separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for an alkaline battery separator in which swelling degree to alkaline water solution is suppressed, and which is superior in the durability so as to be durable for use of a long time. SOLUTION: This is a film for the alkaline battery separator, consisting of vinyl alcohol based polymer composition, and the vinyl alcohol based polymer composition is composed of vinyl alcohol based polymer, and the vinyl alcohol based polymer composition is the composition which contains metal oxides which are obtained by a polycondensation reaction of metal alkoxide or an oligomer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film for a separator used in various alkaline batteries such as an alkaline manganese battery, a silver battery, a mercury battery and a zinc battery. More specifically, the present invention relates to an alkaline battery separator film that prevents internal short circuit of a battery due to contact between an anode active material and a cathode active material and has a low internal resistance.

[0002]

2. Description of the Related Art Alkaline batteries usually use a separator (paper or film) for isolating the active material of both electrodes. As the characteristics required for this separator, it has an effect of preventing short-circuiting due to the contact between the active substances of the two electrodes, and has excellent durability that does not cause shrinkage or alteration to an alkali hydroxide solution or a depolarizer, It is desired that an electrolyte solution sufficient to cause an electromotive reaction be held and that the volume occupied by the electrolyte solution be small when the electrolyte solution is incorporated inside the battery.
Conventional separator paper is a separator paper in which vinyl chloride / vinyl acetate copolymer fiber and rayon fiber are mixed and heat-treated by heat treatment, and the polyvinyl alcohol fiber is mixed with polyvinyl alcohol fiber and cellulose fiber. Partially dissolves with moisture and heat
Mixed papers of synthetic fibers and cellulose fibers, such as fused separator paper, have been used. Further, as separator paper having a dense structure, there have been proposed those using ultrafine fibers having a fineness of 1 denier or less and those having a two-layer structure (JP-A-62-154559). As a film for the separator, polyvinyl alcohol (hereinafter referred to as PV)
A), or a cellophane film is used, but there is a problem that the durability to the electrolyte and the depolarizer is insufficient.

[0003]

The conventional separator paper obtained by blending a synthetic fiber and a cellulose fiber has no problem in practical use in terms of durability and retention of an electrolytic solution. However, the separator paper has a large pore size. However, there is a problem that an internal short circuit due to contact of the bipolar active material cannot be completely prevented. For this reason, separator paper using fibers having a small fineness as described above and separator paper having a two-layer structure have been studied, but the density of the obtained sheet is high, and the degree to which the fibers are heat-sealed or adhered to each other is increased. Is larger, the smaller the denier, the larger the adhesive area,
There was a drawback that the electric resistance increased. Also 2
The separator paper having a layered structure has a problem that the volume of the separator paper occupying the inside of the battery increases, so that the amount of the active substance necessarily decreases and the battery capacity decreases.
Further, if fibers having a small fineness are used, the fibers become expensive, which leads to an increase in the cost of the separator. An object of the present invention is to solve the above-mentioned problems and to provide a separator film for an alkaline battery which is excellent in durability, eliminates internal short-circuits, keeps electric resistance low, and can secure battery capacity.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have found an alkaline battery separator film made of a specific vinyl alcohol-based polymer composition, and have completed the present invention. Reached.

That is, a film for an alkaline battery separator comprising a film comprising a vinyl alcohol-based polymer composition, wherein the vinyl alcohol-based polymer composition comprises a vinyl alcohol-based polymer and a metal alkoxide or oligomer thereof. A separator film for an alkaline battery, which is a composition containing a metal oxide obtained by a condensation reaction.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The vinyl alcohol polymer composition used in the present invention is preferably prepared by a polycondensation reaction of a metal alkoxide or an oligomer thereof and a saponification reaction of a vinyl carboxylate polymer. What is known as synthesis of an inorganic-organic composite by a typical sol-gel method can be applied.

A more preferable method for producing the vinyl alcohol-based polymer composition used in the present invention is to use a solution (sol) containing a metal alkoxide or an oligomer thereof, a vinyl carboxylate-based polymer and an organic solvent to prepare an organic solvent. By performing the polycondensation reaction of the metal alkoxide or the oligomer and the saponification reaction of the vinyl carboxylate polymer in the same reaction system while removing low-boiling substances including A known method for producing a vinyl alcohol-based polymer composition (gel or solid organic / inorganic composite) comprising a vinyl alcohol-based polymer (hereinafter, this method is abbreviated as "in situ saponification sol-gel method"). There is).

The vinyl carboxylate-based polymer used in the present invention is a polymer having a vinyl carboxylate unit, and may be an addition polymer of vinyl carboxylate alone or an addition copolymer of vinyl carboxylate and another comonomer. Include.
As the vinyl carboxylate, vinyl acetate, vinyl propionate, vinyl 2-methylpropionate and the like are preferable, and vinyl acetate is particularly preferable. Examples of the comonomer include α-olefins such as ethylene, propylene and 1-butene; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and t-butyl vinyl ether;
Allyl alcohol; vinyl silane compounds such as vinyl trimethoxy silane and vinyl triethoxy silane; unsaturated carboxylic acids such as itaconic acid, methacrylic acid, acrylic acid, maleic anhydride and itaconic acid and salts thereof, partial or complete esters thereof, Examples thereof include nitriles, amides thereof, anhydrides thereof; unsaturated sulfonic acids and salts thereof; alkylthiols and the like, and α-olefins can be particularly preferably used. Examples of the vinyl carboxylate polymer include polyvinyl carboxylate such as polyvinyl acetate and polyvinyl propionate; and ethylene-vinyl carboxylate such as ethylene-vinyl acetate copolymer and ethylene-vinyl propionate copolymer. Polymers and the like are used, and among them, polyvinyl acetate, ethylene-vinyl acetate copolymer and the like are particularly preferably used.

When polyvinyl carboxylate or ethylene-vinyl carboxylate copolymer is used as the vinyl carboxylate polymer, the content of ethylene units is 0 to 0 based on the total structural units, since the electrical resistance can be reduced. 7
It is preferably in the range of 0 mol%, more preferably in the range of 0 to 30 mol%, even more preferably in the range of 2 to 19 mol%, 10
It is particularly preferred that it is in the range of mol%.

The molecular weight of the vinyl carboxylate polymer used is not particularly limited, and it can be used from low molecular weight to high molecular weight, but the resulting vinyl alcohol polymer composition has a high mechanical strength. Those having a polymerization degree in the range of 300 to 6000 are preferably used because of their excellent points.
Those having a size of from 00 to 3000 are particularly preferably used. Also,
As long as the vinyl carboxylate polymer used is within a range that does not impair the effects of the present invention, it may be modified even if it has been modified with a silyl group or a boronic acid. The amount of modification is 0.1 in that the internal short circuit in the alcohol-based polymer composition can be highly suppressed.
Mol% or less, and preferably 0.01 mol% or less.
It is more preferable to stop at the following, and it is particularly preferable that it is unmodified. Further, the vinyl carboxylate polymer used may be one in which some of the acyloxy groups derived from the vinyl carboxylate units are saponified to hydroxyl groups, but the resulting vinyl alcohol polymer composition From the viewpoint of the retention of the electrolytic solution, the degree of saponification of the vinyl carboxylate polymer is preferably kept at 50 mol% or less, more preferably at 10 mol% or less, and more preferably 1 mol or less. % Is particularly preferred.

In the present invention, a metal alkoxide or an oligomer thereof (hereinafter, “metal alkoxide or oligomer” may be collectively referred to as “metal alkoxide-based component”) is used. In the present invention, the metal alkoxide-based component is selected from the group consisting of silicon alkoxide, metal alkoxide other than silicon alkoxide, oligomer of metal alkoxide having a unit derived from silicon alkoxide, and oligomer of metal alkoxide having no unit derived from silicon alkoxide. At least one component. In the present invention, it is not necessarily limited, and it is possible to use a silicon alkoxide or an oligomer of a metal alkoxide having a unit derived from a silicon alkoxide as at least one component of the metal alkoxide-based component, and obtain a vinyl alcohol-based polymer. This is preferable in that the composition has a high retention of the electrolyte solution and the internal short circuit can be highly suppressed.

The silicon alkoxide preferably has one silicon atom and has a chemical structure in which two, three or four alkoxy groups are bonded to the silicon atom. Here, the number of alkoxy groups is more preferably three or four, and particularly preferably four.
When the number of alkoxy groups is two or three, an alkyl group (eg, a methyl group), an aryl group (eg, a phenyl group), a halogen atom (eg, a chlorine atom), and the like are further bonded to the silicon atom. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group and a butoxy group. Specific examples of silicon alkoxide include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane,
Octyltrimethoxysilane, phenyltrimethoxysilane, chlorotrimethoxysilane and the like can be mentioned.

The metal alkoxide other than the above-mentioned silicon alkoxide has one or more (more preferably trivalent or tetravalent) metal atoms such as titanium, aluminum and zirconium, and has one or more (more than one) Preferably 2
(Preferably 3 or more, particularly preferably 3 or more) compounds having a chemical structure to which an alkoxy group is bonded. Specific examples of the alkoxy group include those exemplified above for the silicon alkoxide. The metal atom may have a substituent other than the alkoxy group, and examples of the substituent include an alkyl group (such as a methyl group), an aryl group (such as a phenyl group), and a halogen atom (such as a chlorine atom). . Specific examples of the metal alkoxide include alkoxytitanium compounds such as tetramethoxytitanium, tetraethoxytitanium, tetraisopropoxytitanium, and methyltriisopropoxytitanium; trimethoxyaluminum, triethoxyaluminum, triisopropoxyaluminum, and methyldiisopropoxy. Alkoxyaluminum compounds such as aluminum, tributoxyaluminum and diethoxyaluminum chloride; and alkoxyzirconium compounds such as tetraethoxyzirconium, tetraisopropoxyzirconium and methyltriisopropoxyzirconium.

The above-mentioned oligomers of metal alkoxides having units derived from silicon alkoxide include oligomers of the above-mentioned silicon alkoxides alone and co-oligomers of the above-mentioned silicon alkoxides with other metal alkoxides. Examples of the other metal alkoxide include titanium, aluminum, zirconium and the like.
One or more (more preferably trivalent or tetravalent) metal atoms
And a compound having a chemical structure in which one or more (more preferably two or more, particularly preferably three or more) alkoxy groups are bonded to the compound. Oligomers of metal alkoxides having units derived from silicon alkoxides can be produced by hydrolyzing / polycondensing a silicon alkoxide alone or in a mixture with other metal alkoxides by a known method, and having a low molecular weight hydroxyl group. It is preferably an oligomer containing. Preferred specific examples of the oligomer of the metal alkoxide having a unit derived from a silicon alkoxide include a silanol group-containing tetramethoxysilane dimer or an oligomer of a trimer or more thereof, a silanol group-containing tetraethoxysilane dimer or a trimer thereof The above oligomers, silanol-terminal-modified oligodimethylsiloxane, and the like can be mentioned. Although the degree of polymerization is not necessarily limited, it is preferably in the range of 2 to 25, and more preferably in the range of 2 to 10.

Examples of the metal alkoxide oligomer having no unit derived from silicon alkoxide include divalent or more (more preferably trivalent or tetravalent) metal atoms such as titanium, aluminum and zirconium.
One or two compounds having a chemical structure in which one or more (excluding silicon atoms) is bonded to one or more (more preferably two or more, particularly preferably three or more) alkoxy groups The above is preferably a low molecular weight hydroxyl group-containing oligomer which can be produced by hydrolysis and polycondensation by a known method. Preferred specific examples of the oligomer of the metal alkoxide having no unit derived from silicon alkoxide include a hydroxyl group-containing tetraisopropoxytitanium dimer or an oligomer of a trimer or more thereof. Although the degree of polymerization is not necessarily limited, it is preferably in the range of 2 to 25, and more preferably in the range of 2 to 10.

In the metal alkoxide component used in the present invention, from the viewpoint of high retention of an electrolytic solution and a high degree of suppression of internal short circuit in the obtained vinyl alcohol polymer composition, all metal atoms Preferably, the content of metal atoms on a standard basis is at least 20 mol%, more preferably at least 50 mol%, and 8
It is particularly preferred that the content be 0 mol% or more.

In the present invention, a metal salt, a metal complex or a layered clay compound can be added to the reaction system, if desired, as long as the effects of the present invention are not impaired. Examples of metal salts or metal complexes include fine powders of metal oxides produced by hydrolyzing / polycondensing the above metal alkoxides in a wet manner; metal oxides prepared by hydrolyzing / polycondensing or burning metal alkoxides in a dry manner Fine powder; carbonate, hydrochloride,
Inorganic acid metal salts such as nitrates; organic acid metal salts such as oxalates; metal complexes such as acetylacetonate metal complexes, cyclopentadienyl metal complexes, and cyano metal complexes. Examples of the above layered clay compound include natural smectite, lipophilic treated smectite, hydrophilic treated smectite, natural mica, lipophilic treated mica,
Talc and the like.

In the known sol-gel method, coupling agents such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane and γ-aminopropyltrimethoxysilane are generally used. Is often used for the purpose of improving the dispersibility of the metal oxide in the obtained composition, but in the present invention, it may hinder the improvement of the retention of the electrolytic solution in the obtained composition. Therefore, not using such a coupling agent often gives better results. However,
When a metal salt, a metal complex, a layered clay compound, or the like as described above is used, the use of a coupling agent may be effective in improving their dispersibility. Therefore, when a coupling agent is used, the amount of the coupling agent is preferably limited to 0.1 mol% or less, and preferably 0.01 mol% or less based on the metal component in the metal alkoxide-based component used. It is more desirable to stop.

In the reaction according to the present invention, the above-described polycondensation reaction of the metal alkoxide-based component and the saponification reaction of the vinyl carboxylate-based polymer proceed in parallel in the same system, and are basically performed in situ. This is a known reaction in the saponification sol-gel method. The polycondensation reaction of the metal alkoxide-based component produces a macromolecularized metal oxide. When a compound containing an alkoxy group or an oligomer containing an alkoxy group is used, such as a metal alkoxide, the alkoxy group is used. The reaction proceeds by a dehydration-condensation reaction via a hydrolysis reaction that changes to a hydroxyl group. However, when an oligomer containing a hydroxyl group is used, the reaction may proceed by a dehydration-condensation reaction alone without a hydrolysis reaction. Either case is applicable to the present invention. On the other hand, the saponification reaction of the vinyl carboxylate polymer generates a vinyl alcohol polymer, and the acyloxy group derived from the vinyl carboxylate unit in the vinyl carboxylate polymer is converted into a hydroxyl group, and at the same time, the carboxylic acid is converted into a hydroxyl group. An acid compound (one or more compounds of a carboxylic acid, a carboxylic acid ester and a carboxylate is usually produced as a by-product, although it differs depending on the type of the organic solvent and the catalyst used). It is assumed that in the vinyl alcohol-based polymer composition obtained by the reaction according to the present invention, a chemical bond may be partially formed between the vinyl alcohol-based polymer and the metal oxide.

In the reaction according to the present invention, the amounts of the vinyl carboxylate-based polymer and the metal alkoxide-based component are determined by converting the metal alkoxide-based component into an acyl group derived from a vinyl carboxylate unit in the vinyl carboxylate-based polymer. It is necessary to use the metal alkoxide-based component in such a ratio that the metal atom in the metal alkoxide-based component is in the range of 0.01 to 100 mol per 100 mol. When the metal atom in the metal alkoxide-based component is 0.01 mol or more based on 100 mol of the acyl group derived from the vinyl carboxylate unit in the vinyl carboxylate polymer, the resulting vinyl alcohol-based polymer composition The retention of the electrolyte is improved.
Further, when the metal atom in the metal alkoxide-based component is 100 mol or less based on 100 mol of the acyl group derived from the vinyl carboxylate unit in the vinyl carboxylate polymer,
The resulting vinyl alcohol-based polymer composition can reduce performance unevenness (difference in electrolyte solution holding performance depending on the position in the composition). In the point that the retention of the electrolytic solution and the smallness of the performance unevenness in the obtained vinyl alcohol-based polymer composition become more advanced, the amount of the metal alkoxide-based component is reduced by the amount of carboxylic acid in the vinyl carboxylate-based polymer. The metal atom in the metal alkoxide component is 0.1 to 100 mol of the acyl group derived from the vinyl unit.
It is preferable to set the ratio to be in the range of 01 to 80 mol, and it is more preferable to set the ratio to be in the range of 0.1 to 60 mol, and in the range of 0.1 to 40 mol. It is more preferable to set the ratio such that

In the reaction according to the present invention, in situ
In addition to the acid catalyst known in the tu saponification sol-gel method, various catalysts known in the general sol-gel method can be used. Catalysts that can be used include hydrochloric acid, sulfuric acid,
acidic catalysts such as p-toluenesulfonic acid, benzoic acid, acetic acid, lactic acid, and carbonic acid; and basic catalysts such as sodium hydroxide, magnesium hydroxide, potassium hydroxide, ammonia, triethylamine, and ethylenediamine. They may be used alone or in combination.
In general, it is preferable to use an acidic catalyst, and it is more preferable to use a combination of an acidic catalyst and a basic catalyst from the viewpoint of the retention of the electrolytic solution in the obtained vinyl alcohol polymer composition. However, when a low molecular weight hydroxyl group-containing oligomer which has been hydrolyzed or polycondensed to some extent in advance is used as the metal alkoxide-based component, it is preferable to use a basic catalyst. The amount of catalyst used is not necessarily strictly limited,
0 to 1 mole of the sum (total mole number) of the mole number of the alkoxy group in the metal alkoxide component used and the mole number of the acyl group derived from the vinyl carboxylate unit of the vinyl carboxylate polymer used. It is preferably in the range of 0.001 to 0.1 gram equivalent, more preferably in the range of 0.01 to 0.05 gram equivalent.

In the reaction according to the present invention, a solution (sol) obtained by dissolving a vinyl carboxylate polymer and a metal alkoxide component in an organic solvent is used. The organic solvent used at this time is not particularly limited as long as it can sufficiently dissolve both the vinyl carboxylate polymer and the metal alkoxide component, and alcohols such as methanol, ethanol, propanol, and butanol are used. Amides such as dimethylformamide and dimethylacetamide; sulfoxides such as dimethylsulfoxide and the like are preferably used alone or in combination of two or more. Among them, methanol, ethanol, dimethylsulfoxide and the like are particularly preferable. The amount of the organic solvent used is not necessarily limited, but is preferably 20 to 2 parts by weight based on 100 parts by weight of the total weight of the vinyl carboxylate-based polymer and the metal alkoxide-based component.
000 parts by weight is preferred, and 100 to 1000 parts by weight.
More preferably, it is in the range of parts by weight. Acyl derived from vinyl carboxylate units in the vinyl carboxylate polymer used in the organic polymer in the reaction system (final target product or an intermediate thereof induced by saponification reaction of the vinyl carboxylate polymer used) When it is desired to reduce the residual ratio of groups, a uniform solvent containing 5% by weight or more of an organic solvent having an affinity for a predetermined vinyl alcohol-based polymer is preferably used.

In the reaction according to the present invention, if necessary, water may be present in the reaction system. For example, when a metal alkoxide having an alkoxy group or an oligomer having an alkoxy group is used as the metal alkoxide-based component, the presence of water is necessary for the hydrolysis reaction of the alkoxy group to proceed. The amount of water to be used is not necessarily limited, and as described above, can be appropriately set in consideration of the metal alkoxide-based component to be used, the type of catalyst, and the like. 1.5 to 4.5 with respect to the alkoxy group in the metal alkoxide-based component.
It is preferably within the range of 0 times mol. When a water-containing component such as hydrochloric acid is used, the amount of water to be used should be determined in consideration of the amount of water introduced by the component.

The reaction according to the present invention is carried out at least at a later stage while removing low-boiling substances outside the system by means such as evaporation. As the low-boiling point substance, an organic solvent, the above-mentioned carboxylic acid-based compound by-produced by saponification of a vinyl carboxylate-based polymer, a by-product (eg, water) by polycondensation of a metal alkoxide-based component, and excess water are added. In this case, excess water and the like are included.

In the reaction according to the present invention, at the beginning of the reaction,
That is, it is derived from the vinyl carboxylate unit in the vinyl carboxylate polymer used in the organic polymer in the reaction system (the final target product or its intermediate derived by the saponification reaction of the vinyl carboxylate polymer used). Before the residual ratio of the acyl group reaches 40 mol%, the dissipation of the organic solvent and the like to the outside of the system is suppressed, and the organic solvent and the carboxylic acid compound are removed to the outside of the system in the second half of the subsequent reaction. It is preferable to carry out the reaction while performing. For this purpose, the evaporation of the organic solvent and the like is suppressed by performing the reaction under normal pressure or under pressure in the early stage of the reaction, and the evaporation of the organic solvent and the carboxylic acid compound is promoted by shifting to the reduced pressure system in the latter stage of the reaction. It may be preferable to do so. In the reaction according to the present invention, the reaction mixture is in a solution state at the beginning of the reaction, but is in a solid state at the end of the reaction.

When the pressure in the reaction system is reduced to remove the carboxylic acid compound from the reaction system, if the pressure is lowered unnecessarily, the organic solvent evaporates too quickly to obtain a homogeneous composition, Since inconvenience may occur such that the composition cannot be obtained in a predetermined shape due to foaming, it is preferable to gradually lower the pressure while observing the state of the reaction system. From these facts, when the pressure reduction condition is adopted, the pressure condition at that time is generally 0.01 to 700 mmHg in absolute pressure.
Is preferably selected from the range of 0.1 to 400.
It is more preferable to select from the range of mmHg.

In the reaction according to the present invention, the obtained vinyl alcohol-based polymer composition is treated with an organic polymer in the reaction system in that the excellent durability and the retention of the electrolyte can be enhanced. It is preferably carried out until the residual ratio of the acyl group derived from the vinyl carboxylate unit in the vinyl carboxylate polymer used in the above reaches 10 mol% or less, preferably 5 mol% or less. More preferably, the reaction is performed up to the stage of 1 mol% or less, and particularly preferably, the reaction is performed up to the stage of 0.1 mol% or less. In order to highly reduce the residual ratio of the acyl group, for example, the water content in the reaction system in the reaction according to the present invention is 3% by weight or less, more preferably 1% by weight or less.
The amount of the solvent used is adjusted so as to be not more than 0.5% by weight, more preferably not more than 0.5% by weight. Within the range, more preferably 40 to
The content is adjusted within the range of 75 mol%, and, as the metal alkoxide-based component, the alkoxy group and the hydroxyl group are mixed at a molar ratio of alkoxy group / hydroxyl group of from 1 / 0.5 to 1 / l.
2.0, more preferably 1 / 0.8 to 1/1.
It is desirable to employ one or more conditions of using a metal alkoxide or an oligomer thereof contained in the range of 25.

In the reaction according to the present invention, although not necessarily limited, if it is desired to obtain a vinyl alcohol-based polymer composition having a good color tone without coloring such as brown or black, an organic compound in the reaction system may be used. The residual ratio X of the acyl group derived from the vinyl carboxylate unit in the vinyl carboxylate polymer in the polymer (the final target product or its intermediate derived by the saponification reaction of the vinyl carboxylate polymer used) is 40. In the range of not more than mol%, the carboxylic acid compound is represented by the following formula:

Y ≦ 0.9X + 5.0 (I)

(In the formula, X represents the residual ratio (unit: mol%) of the above acyl group, and Y represents the initial amount of the acyl group derived from the vinyl carboxylate unit in the vinyl carboxylate polymer used. Relative ratio (unit: mol%) of the amount of the carboxylic acid compound contained in the reaction system on the basis of
Represents It is preferred to carry out the reaction while removing from the reaction system so as to satisfy the above condition. The residual ratio X (mol%) of the acyl group of the organic polymer in the reaction system is based on the organic weight contained in the reaction system based on the initial amount of the acyl group in the vinyl carboxylate polymer used. It is a relative ratio of the amount of the acyl group in the coalescence, and the saponification degree of the organic polymer by only the saponification reaction according to the present invention is represented by Z (mol%),
It can be represented by 00-Z.

The above formula (I) qualitatively indicates that the content of the by-produced carboxylic acid compound in the reaction system must be further reduced as the reaction proceeds, that is, the carboxylic acid This means that removal of the system compound from the reaction system needs to be performed more strictly. For the purpose of satisfying the formula (I), after the point in the middle of the reaction (the point when the residual ratio X of the acyl group in the organic polymer in the reaction system becomes 40 mol% or before), the reaction system It is generally preferable to accelerate the evaporation of the carboxylic acid compound by performing a reaction under reduced pressure conditions controlled based on the quantitative value while quantifying the carboxylic acid compound present in the carboxylic acid compound. However, since the carboxylate salt cannot be removed by evaporation among the carboxylic acid compounds, it is preferable to set conditions so that the formation of the carboxylate salt is suppressed and the carboxylic acid and / or carboxylic acid ester can be preferentially formed.

In the above formula (I), the residual ratio X of the acyl group and the abundance Y of the carboxylic acid compound are each determined at appropriate times during the reaction by quantitative analysis using a small amount of sample collected from the reaction system. be able to. That is, the residual ratio X of the acyl group is, for example, a value obtained by quickly drying a small amount of a sample collected from a liquid (sol), gel or solid reaction system at a temperature of about 40 ° C. under reduced pressure. The composition containing the organic polymer of FT-I
The acyl group (acetyl group, propionyl group, etc.) is quantitatively analyzed by the diffuse reflection method using R, and the analysis value and the acyl group obtained by quantitatively analyzing the vinyl carboxylate polymer used in the same manner. It can be determined based on the value. Further, the abundance Y of the carboxylic acid compound is determined, for example, by dissolving a small amount of a sample collected from a liquid (sol), gel or solid reaction system in deuterated methanol,
^{Using 13} C-NMR, all acyl groups (acetyl group, propionyl group, etc.) of the organic polymer and by-produced carboxylic acid compound in the course of the reaction were quantitatively analyzed. The relative ratio (mol%) based on the analysis value of the acyl group of the vinyl carboxylate polymer obtained by quantitatively analyzing the vinyl polymer in the same manner was calculated, and the relative ratio and the acyl group were calculated. Can be determined by calculating the difference from the residual ratio X of

When the reaction is carried out so as to satisfy the above formula (I) for the purpose of obtaining a vinyl alcohol polymer composition having a good color tone, when the residual ratio X of acyl groups in the organic polymer is 40 mol% or less. In a certain region, it is not always necessary to always determine the residual ratio X and the abundance Y of the carboxylic acid compound, and if it is instantaneous, the condition of the formula (I) may be deviated. Therefore,
Under the above-mentioned purpose, as long as the conditions that can satisfy the above-mentioned formula (I) with a certain margin are adopted, both are quantified at appropriate time intervals, and if necessary, the pressure condition of the reaction system is adjusted. It is practical to control.

The temperature of the reaction system in the reaction according to the present invention is not necessarily limited, but is usually 20 to 1
It is in the range of 00 ° C, preferably in the range of 40-60 ° C. The reaction time varies depending on the reaction conditions such as the amount and type of the catalyst, but is usually in the range of 0.5 to 120 hours, preferably in the range of 1 to 60 hours, and more preferably in the range of 1 to 24 hours. Within range. The atmosphere of the reaction system is not necessarily limited, and conditions such as an air atmosphere and a nitrogen stream can be adopted.

In the reaction according to the present invention, the reaction is carried out using a solution (sol) containing a metal alkoxide-based component, a vinyl carboxylate-based polymer, an organic solvent and, if necessary, other components (catalyst, water, etc.). Although the reaction is started, the reaction is carried out while removing low-boiling substances such as organic solvents and carboxylic acid compounds out of the system, so that the state of the reaction system changes with the elapse of the reaction time. , A gel composition containing a metal oxide and a small amount of an organic solvent is formed, and finally, a solid composition is formed. In addition,
When the reaction system is liquid, stirring may be performed. In addition, heat treatment may be performed at the latter stage of the reaction and / or after the completion of the reaction, and the temperature is preferably in the range of 50 to 250 ° C, more preferably in the range of 60 to 200 ° C. is there.

In the reaction according to the present invention, various kinds of compounds such as polymer compounds other than vinyl carboxylate polymers, plasticizers, antioxidants, ultraviolet absorbers, flame retardants and the like can be used as long as the effects of the present invention are not impaired. May be carried out in the presence of an additive.
As the additive, those which can be dissolved or finely dispersed in the solution at the beginning of the reaction can be used. Examples of the high molecular compound include polyamide, polyolefin, and styrene block copolymer. As the additive, those which can be dissolved or finely dispersed in a reaction solution in the course of preparing the vinyl alcohol polymer composition can be used. Examples of the polymer compound include polyacrylic acid and 2-hydroxy polyacrylate. Acrylic resins such as ethyl; methacrylic resins such as polymethacrylic acid and 2-hydroxyethyl polymethacrylate; starch, cellulose, and salts thereof can be added.

The micro phase separation structure of the vinyl alcohol polymer composition used in the present invention is not necessarily limited, but in many cases, the vinyl alcohol polymer composition formed by saponification of the vinyl carboxylate polymer is used. The polymer and the metal oxide formed by the polycondensation of the metal alkoxide-based component each form a co-continuous structure, or the vinyl alcohol-based polymer and the metal oxide form a sea-island structure, and The component is composed of a vinyl alcohol-based polymer, and the island component has a form of a co-continuous structure in which the vinyl alcohol-based polymer is embedded in metal oxide particles.

For the purpose of imparting water resistance to the vinyl alcohol-based polymer composition used in the present invention, a method of adding a cross-linking agent within a range that does not impair the retention of the electrolytic solution is also used. As a crosslinking agent, epoxy compounds, isocyanate compounds, aldehyde compounds, silica compounds,
An aluminum compound, a zirconium compound, a boron compound and the like can be given. The amount of the crosslinking agent added is usually 10 parts by weight or less, preferably 5 parts by weight or less, more preferably 3 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol-based polymer. If high expression is required, it is preferably not used.

The vinyl alcohol-based polymer composition used in the present invention has excellent electrolyte solution retention properties, and has less unevenness in the excellent electrolyte solution retention properties. For this reason,
The vinyl alcohol-based polymer composition obtained by the reaction according to the present invention is particularly useful as an alkaline battery separator film that requires a high degree of electrolyte solution retention.

As a method for producing the alkaline battery separator film of the present invention, an aqueous solution or aqueous dispersion of the above-mentioned vinyl alcohol-based polymer composition or a solution in the course of the above-mentioned reaction of the vinyl alcohol-based polymer composition is put on a hot roll. A casting film forming method is generally used. Further, as a special method, a vinyl alcohol-based polymer composition which has been heated and melted by adding water, a plasticizer, or the like can be formed into a film by inflation or melt extrusion. The film obtained by film formation is 100
Heat treatment is performed at ~ 180 ° C to adjust the degree of crystallinity in the film to prepare a film having excellent electrolyte solution retention and durability. It is desirable to use the film of the present invention alone, but in some cases, it may be used by laminating with a separator paper obtained by mixing synthetic fibers and cellulose fibers by adhesion or fusion. The vinyl alcohol-based polymer composition of the present invention is prepared alone as a separator film, and in some cases, a plasticizer such as glycerin or polyethylene glycol, a clay,
To prepare a film by blending a filler such as titanium oxide, charcoal or carbon black, a crosslinking agent such as a glyoxal, a polyvalent isocyanate compound, a prepolymer of a urea resin or a melamine resin, etc. with a vinyl alcohol polymer composition. Can also.

Various additives may be added to the alkaline battery separator film of the present invention as long as the effects of the present invention are not impaired. Examples of such additives include an antioxidant, a plasticizer, a heat stabilizer, a flame retardant, an ultraviolet absorber, an antistatic agent, a lubricant, a colorant, and a filler. The above-mentioned thing which can be added to a united composition is mentioned.

The thickness of the alkaline battery separator film of the present invention is not particularly limited.
It is preferably from 3000 to 3000 m, more preferably from 10 to 1000 m. If the thickness is less than 1 μm, sufficient retention of the electrolyte cannot be exhibited, while if it exceeds 1000 μm, the performance unevenness increases.

Preparation of vinyl alcohol polymer composition
At least in the middle of the solution state
If the reaction is pursued after being applied to the
Within the range, a surfactant and a resin
A belling agent, a fungicide, a preservative, and the like may be added. Ma
Further, water is added during the reaction within a range not to impair the present invention.
The addition improves the coatability. Coating solution
The concentration is not particularly limited, but is 0.1% at the total solid concentration.
It is preferable that the content be adjusted within the range of 50% by weight. Dark
If the degree is less than 1% by weight, the drying load becomes large, and 50% by weight.
%, The viscosity of the aqueous solution increases and the coatability decreases.
You. The temperature during the application of the reaction solution system is 20 to 80 ° C.
preferable. Coating method is not particularly limited
But gravure roll coating method, reverse gravure
Coating method, reverse roll coating method,
Yerber coating and spray coating are preferred
Appropriately used. Drying conditions after applying the above coating liquid are also
Important, evaporation rate 2-2000 g / m ^Two・ In min
Drying is preferred, and particularly preferred drying conditions are evaporation.
Speed 50-500g / m^Two・ It is min, but basically
Are the above-mentioned favorable conditions in the preparation of the vinyl alcohol polymer composition.
Most preferably, it conforms to appropriate conditions.

The layer having a vinyl alcohol-based polymer composition is preferably subjected to a heat treatment step and / or a step of irradiating with ultraviolet rays or an electron beam for the purpose of imparting a high degree of retention of the electrolytic solution. Specifically, drying and heat treatment are performed at a temperature of 80 ° C. or higher, preferably in a range of 120 to 200 ° C. When the material to be coated has a low softening point, an ultraviolet ray (250 nm) or an electron beam (0.
Irradiation with ultraviolet rays or electron beams such as 1 to 50 megarads) is suitably selected.

[0046]

EXAMPLES Hereinafter, the laminated film of the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

The measurement or evaluation in the following examples and the like was performed by the following methods (1) to (6).

(1) Amount of acyl group: The vinyl carboxylate polymer used (polyvinyl acetate, polyvinyl propionate, ethylene-vinyl acetate copolymer, etc.) and the corresponding amount in the finally obtained composition For vinyl alcohol-based polymers (polyvinyl alcohol, ethylene-vinyl alcohol copolymer, etc.), an acyl group (acetyl group or propionyl group) is obtained by a diffusion reflection method using FT-IR (“FTIR8200” manufactured by Shimadzu Corporation). ) Was quantitatively analyzed. For the acyl group-containing organic polymer in the course of the reaction, a small amount of a sample is collected from a liquid (sol), gel or solid reaction system, dried quickly at 40 ° C. under reduced pressure, and then, similarly. Was quantitatively analyzed. The residual ratio of acyl groups (unit: mol%) in the organic polymer during the reaction and the final vinyl alcohol-based polymer was calculated based on the amounts of these acyl groups.

(2) Film thickness:
The thickness was measured at five places and the average value was obtained.

(3) Tensile strength: The tensile strength of the film is
After the film is conditioned at 65% RH, the width between chucks is 50
mm, the tensile elongation was measured by an autograph at a tensile speed of 500 mm / min, and the maximum strength was measured.

(4) Swelling degree: The swelling degree of the film was 40%.
The film was immersed in a KOH aqueous solution for 30 minutes, the thickness of the film before and after immersion was measured with a film thickness meter, and the degree of swelling was determined by the following equation. Swelling degree (%) = (thickness after immersion−thickness before immersion) / thickness before immersion × 100 When the swelling degree is less than 5%, “particularly good (（)”, 5%
In the case of not less than 10%, “good (○)”, 10% or more 2
When it was less than 0%, it was evaluated as "slightly poor (△)", and when it was 20% or more, it was evaluated as "bad (x)".

(5) Electric resistance: The electric resistance was measured by inserting a film between platinum electrodes parallel to each other at an interval of 3 mm, and the increase in electric resistance between the electrodes accompanying the insertion was defined as the electric resistance of the film. A 40% KOH aqueous solution was used as an electrode solution, and the electric resistance between the electrodes was measured using an ESR meter at a frequency of 1000 Hz.

(6) Battery discharge characteristics: Using the obtained separator film, an alkaline manganese battery (LR-6) using a zinc mercury-reduced active material was prototyped, and the battery was discharged for 75 days.
A discharge test was performed at Ω for 100 hours, and the discharge voltage of the battery before and after the test was measured.

Example 1 18.5 parts by weight of polyvinyl acetate having a polymerization degree of 1700 was dissolved in 200 parts by weight of methanol, and then 1.26 parts by weight of tetramethoxysilane, 0.5 parts by weight of distilled water and 1N ( (Regulation)-A sol was prepared by adding 1.0 part by weight of hydrochloric acid, and the mixture was reacted at 60 ° C for 4 hours while stirring. The obtained sol was transferred to a flat-bottomed container made of polytetrafluoroethylene ("Teflon" manufactured by DuPont), and the upper open portion of the container was covered with a polyvinylidene chloride film ("Saran Wrap" manufactured by Asahi Kasei Kogyo Co., Ltd.).
The reaction was further performed at 0 ° C. for 4 hours. Thereafter, a hole was formed in the coated film with a needle so that the porosity was 1% based on the area of the coated film, and the reaction was continued at 60 ° C. for 4 hours. Next, when the residual ratio of the acyl group (residual ratio of acetyl group in this example) in the organic polymer in the system reached 60 mol%, the inside of the reaction system was transferred to a reduced pressure system (pressure: 100 mmHg), The reaction was carried out at 60 ° C. while controlling the amount of the carboxylic acid-based compound (acetic acid-based compound in this example) to satisfy the above formula (I). After 4 hours, the pressure was increased to 20
The pressure was changed to mmHg, and the reaction was continued at 40 ° C. for 4 hours. The final acyl group residual ratio was 1 mol% or less. Thus, a colorless and transparent single-layer film composed of the vinyl alcohol-based polymer / silica composite was obtained. The obtained monolayer film was subjected to a heat treatment at 150 ° C. for 10 minutes to prepare a separator film, and the results of evaluating the thickness tensile strength, swelling degree, electric resistance and battery discharge characteristics of the separator film by a predetermined method are shown in the table below. It is shown in FIG.

<Examples 2 to 4> In Example 1, 18.5 parts by weight of polyvinyl acetate and 1.2 parts by weight of tetramethoxysilane were used.
The combination of 6 parts by weight was combined with 17.5 parts by weight of polyvinyl acetate and 2.5 parts by weight of tetramethoxysilane (Example 2), the combination of 17.5 parts by weight of polyvinyl acetate and 3. Combination with 4 parts by weight (Example 3)
And 11.4 parts by weight of an ethylene-vinyl acetate copolymer having an ethylene unit content of 44 mol% and tetramethoxysilane 7.
A colorless and transparent separator film comprising a vinyl alcohol-based polymer / silica composite was prepared by performing the same reaction except that the combination was changed to 6 parts by weight (Example 4). However, the transition of the amount of the carboxylic acid compound during the reaction was as shown in Table 1. Table 1 also shows the results of evaluating the thickness, tensile strength, swelling degree, electric resistance, and battery discharge characteristics of the obtained separator film by a predetermined method.

Comparative Example 1 A commercially available polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name: PVA-117H) was used as an aqueous solution and cast on a hot roll at 70 ° C. to obtain a transparent film. The obtained film is dried in a dryer at 150 ° C. for 1 hour.
Heat treatment was performed for 0 minutes to produce a colorless and transparent film for a separator. Table 1 shows the evaluation results of the obtained separator films in terms of thickness tensile strength, swelling degree, electric resistance and battery discharge characteristics of the separator films by a predetermined method.
Shown in

[0057]

[Table 1]

The "metal alkoxide-based component ratio" in Table 1 means that the amount of metal atoms in a metal alkoxide such as a silicon alkoxide used or an oligomer thereof is determined by using a vinyl carboxylate in a vinyl carboxylate polymer used. It is represented by the number of moles per 100 moles of the acyl group derived from the unit.

According to the above Table 1, the first embodiment according to the present invention is shown.
According to ~ 4, the degree of swelling and the electric resistance are small,
It can be seen that a constant discharge voltage is exhibited even in a time-discharge test, and a separator film having excellent physical properties that does not cause internal short circuit of the battery can be obtained. On the other hand, when a commercially available polyvinyl alcohol was used (Comparative Example 1), the electrical resistance was small but the degree of swelling was very large, and partial degradation of the film occurred in a 100-hour discharge test. The voltage is low. This is considered to be due to internal short circuit of the battery due to deterioration of the film.

[0060]

The separator film for an alkaline battery according to the present invention has a reduced degree of swelling in an alkaline aqueous solution and has a durability that can withstand long-term use. In addition, the separator paper formed by mixing conventional synthetic fibers and cellulose fibers has a problem that the pore diameter between the fibers is large and it is difficult to completely separate the active substances of both electrodes inside the battery, thereby causing an internal short circuit. The film of the present invention has strong film properties even when swelled to some extent by an alkaline aqueous solution, and provides excellent performance without internal short circuit. Further, since the film is a film, the volume inside the battery is small, and the battery capacity can be increased.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C08L 29/04 C08L 29/04 AD 83/02 83/02 85/00 85/00 F-term (reference) 4F071 AA28 AA29 AA66 AA68 AA78 AC05 AC16 AF39 AF57 AH15 BC01 4J002 BE02W BE021 CP02X CQ03X EC076 EX036 GQ01 4J100 AD02P AG04P AG04Q AG06P AG06Q BA03H CA01 CA04 CA05 CA31 HA09 HE00 HE14 EB09H01 EE44 JAH 5H02 EB01

Claims (4)

[Claims] 1. A film for an alkaline battery separator comprising a film comprising a vinyl alcohol-based polymer composition, wherein the vinyl alcohol-based polymer composition is a polycondensation of a vinyl alcohol-based polymer and a metal alkoxide or an oligomer thereof. A film for an alkaline battery separator, which is a composition containing a metal oxide obtained by the reaction. 2. The composition according to claim 1, wherein the vinyl alcohol polymer composition is a composition prepared by a polycondensation reaction of a metal alkoxide or an oligomer thereof and a saponification reaction of a vinyl carboxylate polymer. The alkaline battery separator film according to the above. 3. A vinyl alcohol polymer composition comprising: (1) using a solution containing a metal alkoxide or an oligomer thereof, a vinyl carboxylate polymer and an organic solvent to remove low boiling substances including an organic solvent; A metal oxide and a vinyl alcohol polymer obtained by performing a polycondensation reaction of the metal alkoxide or the oligomer and a saponification reaction of the vinyl carboxylate polymer in the same reaction system in parallel. And (2) the metal alkoxide or the oligomer is prepared such that the metal atom in the metal alkoxide or the oligomer is 0.01 to 100 mol of the acyl group derived from the vinyl carboxylate unit in the vinyl carboxylate-based polymer. The composition according to claim 2, wherein the composition is prepared by using the composition in such a ratio as to be within a range of 100 mol. Alkaline battery separator film. 4. A vinyl alcohol-based polymer composition wherein the residual ratio of acyl groups derived from vinyl carboxylate units in the vinyl carboxylate polymer in the organic polymer in the reaction system is 10 mol% or less. The film for an alkaline battery separator according to claim 2 or 3, wherein the reaction is continued until the reaction reaches.