JPH09199100A - Alkaline battery separator and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for an alkaline battery having excellent hydrophilic property, liquid-retainability, and high alkali resistance and to provide a manufacturing method for the separator. SOLUTION: This separator is obtained by carrying out wet paper making process of polyolefin type synthesized pulp containing 1.0-10.0wt.% of polyvinyl alcohol after heating treatment at not lower than 100 deg.C and not higher than the melting point of the synthesized pulp in dry condition or by carrying out wet paper making of the synthesized pulp after heating treatment and mixing a polyolefin type thermally melting fibrous binder, drying, and carrying out a thermally melting and depositing process at not higher than the melting point of the synthesized pulp and not lower than the melting point of the polyolefin type thermally melting fibrous binder.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a separator used in an alkaline battery such as a nickel-cadmium battery or a nickel-hydrogen battery, and a method for producing the same. More specifically, the present invention relates to a hydrophilic material made of a specific synthetic pulp. The present invention relates to an excellent alkaline battery separator and a method for producing the same.

[0002]

2. Description of the Related Art Conventional separators for alkaline batteries have
Nonwoven fabrics of polyamide fibers having excellent hydrophilicity and nonwoven fabrics of polyolefin fibers having excellent alkali resistance are used. However, by repeatedly using polyamide fiber, it decomposes in alkaline electrolyte to generate nitrogen oxides,
It has the drawback of shortening the battery life. Further, since the polyolefin fiber is originally hydrophobic, it has been subjected to a hydrophilic treatment with a surfactant, but the surfactant gradually deteriorates in the electrolytic solution, its performance is lost, and eventually the hydrophilic property is obtained. It has the drawback of disappearing.

Further, in recent years, a non-woven fabric of sulfonated polyolefin fibers having an excellent hydrophilic property, which is a modification of the defects of polyolefin fibers, has been used.

[0004]

However, the above-mentioned sulfonated polyolefin fiber is expensive because concentrated sulfuric acid or fuming sulfuric acid is used in the sulfonation process and the yield is low.

The present inventor has recognized the above-mentioned problems of the prior art, and carried out research for the purpose of improving them, and by using a specific synthetic pulp as a raw material, it can be manufactured at low cost and has hydrophilicity and liquid retention. In addition, an alkaline battery separator having excellent durability was developed and a patent application has been filed as Japanese Patent Application No. 7-329259.

The present inventor, in the process of re-trying the invention and continuing the research, uses another material different from the above invention as the synthetic pulp of the above material, and thus has the same excellent characteristics as the above invention. It was found that a separator for an alkaline battery having the above can be obtained, and the present invention was completed based on this finding.

[0007]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a separator for an alkaline battery, which can be manufactured at low cost, is excellent in hydrophilicity, liquid retention and durability, and a method for manufacturing the same.

[0008]

The present invention has been proposed in order to achieve the above-mentioned object, and is characterized in that a polyolefin synthetic pulp after a specific treatment is used as a raw material. is there.

That is, according to the present invention, a polyolefin synthetic pulp having a polyvinyl alcohol content of 1.0 to 10.0% by weight is heat-treated in a dry state at a temperature of 100 ° C. or higher and a melting point of the synthetic pulp or lower. After that, a separator for an alkaline battery, which is obtained by wet papermaking, is provided.

Further, according to the present invention, a polyolefin synthetic pulp having a polyvinyl alcohol content of 1.0 to 10.0% by weight is heat-treated in a dry state at a temperature of 100 ° C. or higher and a melting point of the synthetic pulp or lower. After mixing 40 to 95% by weight with 5 to 60% by weight of a polyolefin-based heat-sealing fiber binder, wet papermaking and drying,
Provided is a separator for an alkaline battery, which is obtained by heat-sealing at a temperature not higher than the melting point of the synthetic pulp and not lower than the melting point of the polyolefin-based heat-sealing fiber binder.

According to the present invention, there is also provided the above alkaline battery separator, wherein the synthetic pulp is produced by flash spinning an emulsion.

Further, according to the present invention, there is provided the above-mentioned alkaline battery separator in which the surfactant is present before or after the heat treatment.

Further, according to the present invention, said polyolefin
Specific surface area of synthetic pulp is 0.1m ^Two / G or more
An alkaline battery separator is provided.

Further, according to the present invention, there is provided the above alkaline battery separator, wherein the polyolefin synthetic pulp is polyethylene synthetic pulp.

Further, according to the present invention, there is provided a method for producing a separator for an alkaline battery according to claim 1, wherein a polyolefin synthetic pulp heat-treated at a temperature of 100 ° C. or higher and a melting point or lower is subjected to wet papermaking, There is provided a method for producing a separator for an alkaline battery, which comprises drying with hot air at 100 ° C or lower.

According to the present invention, 40 to 95% by weight of the heat-treated polyolefin-based synthetic pulp is mixed with 5 to 60% by weight of a polyolefin-based heat-sealing fiber binder to make paper, and after drying, the polyolefin-based material is used. Provided is a method for producing a separator for an alkaline battery, which is characterized in that the heat treatment is carried out at a temperature not lower than the fusing temperature of the heat fusion fiber binder and not higher than the melting point of the synthetic pulp.

According to the present invention, the alkali is heat treated at a temperature not higher than the melting point of the synthetic pulp and not lower than the fusing temperature of the polyolefin-based heat-sealing fiber binder, and then treated with hot water at 80 to 100 ° C. A method of making a battery separator is provided.

Further, according to the present invention, there is provided a method for producing the above-mentioned alkaline battery separator in which the surfactant is present before or after the heat treatment.

Further, according to the present invention, there is provided a method for producing the above alkaline battery separator in which the specific surface area of the polyolefin is 0.1 m ² / g or more.

Further, according to the present invention, there is provided a method for producing the alkaline battery separator, wherein the polyolefin synthetic pulp is polyethylene synthetic pulp.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a polyolefin synthetic pulp having a polyvinyl alcohol content of 1.0 to 10.0% by weight is heat-treated in a dry state at a temperature of 100 ° C. or higher and a melting point of the synthetic pulp or lower. It has an important feature in that it is formed as a separator for an alkaline battery after the process. By carrying out this treatment, the tackiness can be reduced while maintaining the hydrophilicity of polyvinyl alcohol, and as a result, a sheet having a sufficient porosity can be obtained.

When the content of polyvinyl alcohol is within the above range in the polyolefin-based synthetic pulp, the separator is given sufficient hydrophilicity. If the polyvinyl alcohol content is less than 1.0%, it is difficult to impart sufficient hydrophilicity to the separator, and 10.0%.
When it exceeds, the adhesion between the synthetic pulp fibers becomes large, and there is a tendency that a sufficient space for holding the electrolytic solution cannot be secured. The polyvinyl alcohol attached to the synthetic pulp reduces the hydrophilicity-imparting property and tackiness by heat treatment, but surprisingly, in the wet papermaking process of the synthetic pulp, only the hydrophilicity-imparting property is recovered, and as a separator for an alkaline battery. It becomes a suitable material.

At this time, the synthetic pulp is preferably one prepared by flash spinning a solution or emulsion and having a specific surface area of 0.1 m ² / g or more. Since the synthetic pulp is produced by flash-spinning a solution or emulsion, it is a multi-branched fiber and has a large entanglement with each other, wet papermaking is possible, and the polyvinyl alcohol content is 1. 0
To 10.0% by weight, preferably 1.5 to 10.
By setting the content to 0% by weight, a sheet having sufficient strength can be obtained.

Hereinafter, in order to simplify the description of the present invention,
The polyvinyl alcohol content is 1.0 to 10.
A product obtained by heat-treating 0% by weight of a polyolefin-based synthetic pulp in a dry state at a temperature of 100 ° C. or higher and a melting point of the synthetic pulp or lower may be simply referred to as “heat-treated synthetic pulp”.

The composition of the alkaline battery separator of the present invention may be either synthetic pulp alone or a mixture of synthetic pulp and a polyolefin-based heat-sealing fiber binder. When the separator is made of the heat-treated synthetic pulp alone, at a temperature of 100 ° C. or lower after wet papermaking,
Moreover, drying with hot air is an important feature. Drying using a drum-type or Yankee-type dryer is not preferable because the tightness of the sheet surface increases and the liquid absorbency of the separator decreases. By incorporating a surfactant in the process of producing the separator, it is possible to further improve the properties of the separator such as liquid absorption and liquid retention. The surfactant may be present either before or after the heat treatment.

In the case of the mixed system, the heat-treated synthetic pulp and the polyolefin-based heat-sealing fiber binder are mixed, wet paper-making, dried, and then synthesized at a temperature not lower than the fusing temperature of the polyolefin-based heat-sealing fiber binder. Heat treatment is performed at a temperature below the melting point of pulp. The use of heat-bonded fiber binders increases the strength of the sheet. After the heat treatment, it is treated with hot water at 80 to 100 ° C. By performing this treatment with hot water, the hydrophilicity once reduced by the heat treatment is restored. Examples of the treatment with hot water include a method of immersing in hot water of 80 to 100 ° C. for 10 seconds or more, preferably 30 seconds or more and then drying. Drying is 10
It is performed with hot air at 0 ° C or lower. In the case of incorporating a surfactant in the process of producing the separator, the hot water treatment is not performed.

<Characteristics of the alkaline battery separator of the present invention> The alkaline battery separator of the present invention is inexpensive because it can be manufactured by a usual papermaking method using inexpensive synthetic pulp as a raw material. In addition, it is suitable as a separator for alkaline batteries. Further, since the alkaline battery separator of the present invention uses a polyolefin synthetic pulp having a specific surface area of 0.1 m ² / g or more, it is particularly excellent in liquid retention and has a finished thickness of 0.10 to 0. At 40 mm, it has excellent physical properties such that the liquid retention rate of a 35% by weight potassium hydroxide (KOH) solution is 400% by weight or more.

<Raw material> The synthetic pulp used in the present invention is known per se, and the details of the production method are described in Encyclopedia of Chemical Technology 3rd ed.Vo.
l.19 P420 to 425 for more details. As a preferable method, for example, a method of performing a beating process after performing a solution flash or an emulsion flash is exemplified. Among them, those produced by a method in which polyvinyl alcohol (PVA) is used as a hydrophilizing agent to prepare an emulsion, which is then flashed and then beaten with a refiner are preferably used. In the synthetic pulp prepared by the emulsion flash method, the polyvinyl alcohol and the polyolefin are firmly bound to each other, and the polyvinyl alcohol is not released during the disintegration and papermaking processes.

As the polyolefin, polyethylene,
Olefin homopolymers such as polypropylene and 4-methylpentene-1, ethylene-propylene copolymers, ethylene-1-butene copolymers, ethylene-4-methylpentene-1 copolymers and other ethylene and other α -Copolymers with olefins are exemplified, but among them, polyethylene is preferably used because of its binding property to polyvinyl alcohol.

The average fiber length of the synthetic pulp is 0.1
It is preferably from 10 to 10 mm. If it is 0.1 mm or less, the entanglement between fibers is small and it is difficult to form a sheet substantially, and if it is 10 mm or more, it is difficult to form a homogeneous sheet by wet papermaking. Further, the freeness of the synthetic pulp is 1.0 to 20 seconds / g, especially 2.0 to 10.0.
It is preferably seconds / g. If it is 1.0 second / g or less, sufficient sheet strength cannot be obtained, and if it is 20 seconds / g or more, the sheet tends to be too tight and the liquid retaining property tends to decrease.

In the present invention, 1.0 to 10.0% by weight of polyvinyl alcohol is added to the synthetic pulp for the purpose of imparting hydrophilicity. As the polyvinyl alcohol, ordinary polyvinyl alcohol can be used without any limitation, but among them, those having a saponification degree of 70 mol% or more and a polymerization degree of 1500 or less are preferably used. When the saponification degree is less than 70 mol%, the polyvinyl alcohol tends to deteriorate in the alkaline electrolyte, and when the polymerization degree exceeds 1500, the hydrophilicity of the synthetic pulp tends to be poor. As described above, the synthetic pulp containing polyvinyl alcohol loses or loses its hydrophilicity by heat treatment at 100 ° C. or higher,
The treatment with hot water at ℃ restores the hydrophilicity.

In the emulsion flash method, the addition of polyvinyl alcohol is performed in the emulsion step. In other manufacturing methods, the addition is performed in the beating step or the subsequent steps.

In another embodiment of the present invention, a polyolefin heat fusion fiber binder is used for the purpose of imparting strength to the sheet. The heat-bonding fiber includes a fiber composed of a single component and a composite fiber composed of two or more components. Examples of the single-component fiber include synthetic pulp having the same form as the main material and having a lower melting point than the main material, single fiber obtained by melt-spinning a low-melting resin, and the like. Examples of the form of the composite fiber include a sheath core having a high-melting point resin as a core and a low-melting point resin as a sheath, an eccentric sheath-core type, or a side-by-side type in which both are bonded. Can also be used.

Examples of the high melting point resin include polyethylene,
Homopolymers of olefins such as polypropylene and 4-methylpentene-1 are exemplified, and examples of the low melting point resin include:
Examples thereof include copolymers of ethylene and other α-olefins such as polyethylene, ethylene-propylene copolymer, ethylene-1-butene copolymer, and ethylene-4-methylpentene-1 copolymer. Among them, the composite fiber is preferably used, and among them, the one using polypropylene for the core and low density polyethylene for the sheath is particularly preferably used.

The fiber diameter and fiber length of the single fiber and the composite fiber are not particularly limited, but the fiber diameter is 0.1 to 20 denier,
Fibers having a fiber length of 0.1 to 20 mm are preferably used. The binder fiber is used in an amount of 5 to 60% by weight, preferably 10 to 30% by weight, based on 40 to 95% by weight of the heat-treated synthetic pulp. If it is less than 5% by weight, the strength of the sheet is not sufficiently imparted. It will not be enough.

<Surfactant> In the present invention, in order to compensate for the disappearance or deterioration of the hydrophilicity-imparting ability of polyvinyl alcohol, which is brought about by the heat treatment for fusion-bonding the heat-sealing fibers, and the heat-treated synthetic pulp alone. In the case of use, it is recommended to add a surfactant in order to improve hydrophilicity. As the kind of the surfactant, both ionic and nonionic surfactants can be used. When a nonionic surfactant is used, one having an HLB value of 5 or more is preferably used.

Examples of the anionic surfactant include fatty acid salts such as potassium oleate soap, sodium stearate soap, mixed fatty acid soda soap, sodium lauryl sulfate, triethanolamine lauryl sulfate, alkyl sulfate ester salts such as ammonium lauryl sulfate, and dodecyl. Alkyl benzene sulfonate such as sodium benzene sulfonate,
Alkyl naphthalene sulfonate, alkyl sulfosuccinate, alkyl diphenyl sulfonate, alkyl phosphate, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl allyl sulfate, alkenyl succinate, alkane sulfonate, etc. Is exemplified.

As the nonionic surfactant, polyoxyethylene alkyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene alkyl phenyl ether, oxyethylene / oxypropylene block polymer, sorbitan (mono, di, tri) alkylate. , Polyoxyethylene sorbitan (mono, di, tri) alkylate, glycerol alkylate, glyceride alkylene, polyoxyethylene glycol alkylate, polyoxyethylene alkylate, polyoxyethylene alkylamine and the like.

Examples of the cationic surfactant include alkylamine acetate, alkylamine hydrochloride, alkylamine oleate, alkyltrimethylammonium chloride, alkylbenzyldimethylammonium chloride, alkylbetaine and alkyldimethylamine oxide.

The amount of the surfactant added varies depending on the type and the amount of polyvinyl alcohol in the synthetic pulp as the main material, but is 0.01 to 10% by weight, particularly 0% for the alkaline battery separator. .5 to 5
Preference is given to addition by weight. The surfactant is added to the wet sheet after the drying treatment or after the wet papermaking in the synthetic pulp alone system, but in the mixed system, it is usually after the heat fusion treatment of the heat fusion fiber, or It may be performed on the wet sheet after wet papermaking, or they may be used together.
Further, for the nonionic surfactant, a method of adding and adhering it to the synthetic pulp from the beginning is also adopted.

<Sheating> In the present invention, a sheet is produced by mixing the heat-treated synthetic pulp described above or the heat-treated synthetic pulp with a polyolefin-based heat-sealing fiber binder and then wet-making. In wet papermaking, a wet sheet is made on a wire, and this wet sheet is subjected to suction dehydration only, or suction dehydration and light press dehydration. If the press dehydration is made too strong, the sheet becomes tight and the liquid absorbability decreases.
It is essential to dry the sheet with hot air for the reasons described above. In the case of producing the heat-treated synthetic pulp alone, the drying after the wet papermaking is performed with hot air at 100 ° C. or lower, preferably 40 to 80 ° C. Further, a surfactant is added as necessary, but in this case, the above-mentioned drying temperature is not limited.

In the mixed system of the heat-treated synthetic pulp and the polyolefin-based heat-sealing fiber binder, heat treatment is subsequently performed. The heat treatment is also preferably performed with hot air, and is performed at a temperature not lower than the melting point of the low melting point component or the heat melting component of the heat fusible fiber and not higher than the melting point of the polyolefin synthetic pulp as the main material. Preferably, the heat treatment is performed within a range of 5 ° C or higher from the melting point of the fusion component of the heat-sealing fiber and 5 ° C or lower from the melting point of the polyolefin synthetic pulp. At this time, a surfactant is incorporated, or after the heat treatment, a treatment with hot water at 80 to 100 ° C. is performed.

In the case of hot water treatment, 80 to 1
After being dipped in hot water at 00 ° C. for 10 seconds or longer, preferably 30 seconds or longer, drying is performed. At this time, the drying is performed with hot air at 100 ° C. or lower, preferably 40 to 80 ° C., and usually in a drying oven. The drying time is appropriately determined depending on factors such as air volume, temperature, and basis weight. If the drying temperature exceeds 100 ° C., the hydrophilicity of the sheet will disappear or decrease, which is not preferable. In addition, also in this case, when a drum type dryer is used, the tightness of the sheet surface increases, which leads to a decrease in liquid absorbability, which is not preferable. When the surfactant is added, the drying temperature is not limited.

Examples of paper machines include cylinders, long-mesh, short-mesh,
Inclined wire type, twin wire type paper machines and the like can be mentioned, and any of them can be used, but from the viewpoint of mounting the suction box, it is preferable to use a long wire, short wire or inclined wire type paper machine. .

[0045]

According to the present invention, a polyolefin synthetic pulp having excellent alkali resistance and a large surface area is used as a separator material, and polyvinyl alcohol firmly bonded to the synthetic pulp is used as a hydrophilic agent. Since the hydrophilicity is stably maintained for a long period of time even in the alkaline electrolyte, a separator for an alkaline battery that is excellent in the electrolyte absorbability and the liquid retention is provided. Even when a surfactant is added, the surfactant is added to restore the hydrophilicity of polyvinyl alcohol. Since the amount is smaller than that of the above, it is possible to suppress the adverse effect on the electrode due to the deteriorated product of the surfactant as much as possible. Further, when the polyolefin-based heat-sealing fiber is used as the binder in the heat-treated synthetic pulp, the obtained alkaline battery separator sufficiently retains the strength required during the battery assembly work.

[0046]

The present invention will be specifically described below based on examples and comparative examples. In the examples, each physical property was measured by the following methods.

<Measurement of Specific Surface Area> The specific surface area is measured by the amount of N ₂ gas adsorbed by the BET method.

<Measurement of Freeness> Sheet basis weight is 500 g /
The time required for water discharge is measured in seconds according to the TAPPI-T221 standard, except that the time is changed to m ² . Freeness is expressed in hours per gram of pulp.

<Measurement Method of Electrolytic Solution Retention Rate> Test piece is 1
The size is set to 00 × 100 mm, and one sheet is sampled from the center of each of the three sheets, a total of three sheets. The weight at room temperature is measured up to 1 mg. Next, the test piece is spread and immersed in a 35 wt% potassium hydroxide (KOH) solution at room temperature (25 ± 2 ° C.), left to stand for 30 minutes or more, and then pulled out of the solution to remove one corner of the test piece. Clip and hang 10
The weight of the test piece after the minute was measured, and the liquid retention rate was calculated by the following formula. Where A ₀ : electrolyte retention rate W ₀ : weight of test piece when dry (g) W ₁ : weight of test piece when containing liquid (g)

<Evaluation Method of Liquid Absorption> A test piece having a length of 20 cm and a width of 1.5 cm was sampled, the upper end was fixed to a horizontal bar and hung vertically, and the lower end 5 mm of the test piece was measured at a concentration of 35% by weight. Immerse in potassium hydroxide (KOH) solution, and after 5 minutes K
The height at which the OH solution rose was measured.

<Evaluation Method of Alkali Resistance> A test piece was spread on a 35% by weight potassium hydroxide (KOH) solution,
Immerse at room temperature for 7 days. Then, it was washed with water until the neutralization point was reached, and the liquid absorbency was measured in a dried state.

<Sheet Strength Measuring Method> A test piece is set to have a width of 1
The length was 5 mm and the length was 100 mm, and the strength at break was measured 5 times by pulling in the length direction at a speed of 100 mm / min, and the average value was obtained.

<Example 1> 10 liters of n-hexane (23 ° C), 10 liters of water (23 ° C), in an autoclave with a stirrer and a capacity of 30 liters equipped with a baffle plate,
High-density polyethylene resin 1,000 g, polyvinyl alcohol [PVA, saponification degree: 99%, 4% aqueous solution viscosity (20 ° C.): 4.6 to 6.0 cps, trade name Gohsenol NL-05, Nippon Synthetic Chemical Industry Co., Ltd. )] 50g
Was charged, and the temperature of the mixed solution was raised to 140 ° C. while stirring at 900 rpm. Then, the liquid temperature of the mixed liquid was maintained at 140 ° C., and stirring was further continued for 30 minutes to obtain a suspension.

Then, this suspension was passed through a pipe having a diameter of 3 mm and a length of 20 mm attached to an autoclave, under a nitrogen atmosphere and at -400 mmHg.
A fibrous substance was obtained by jetting (flashing) into the drum under the pressure of.

Next, the fibrous material was made into a water slurry having a concentration of 10 g / liter in a receiver and beaten with a disk type refiner having a diameter of 12 inches to obtain a pulp material. The physical properties of the polyethylene synthetic pulp thus obtained are shown below. Average fiber length 1.5 mm Specific surface area 9.8 m ² / g Freeness 15.0 sec / g PVA content 4.0 wt% Melting point 135 ° C.

The above high density polyethylene synthetic pulp
In the dry state, heat treatment was performed at 125 ° C. for 5 minutes with a circulating hot air dryer. The heat-treated high-density polyethylene synthetic pulp was disaggregated with a JIS type pulper, and paper was made with a 25 × 25 cm square paper machine. The obtained wet sheet was dried with a circulating hot air dryer at 50 ° C. for 1 hour to obtain a sheet. Table 1 shows the physical properties of the obtained sheet.

Example 2 A polyethylene synthetic pulp was obtained in the same manner as in Example 1 except that the amount of polyvinyl alcohol added to the autoclave was 30 g. The physical properties are shown below. Average fiber length 1.2 mm Specific surface area 8.2 m ² / g Freeness 7.5 sec / g PVA content 3.0 wt% Melting point 135 ° C. The above synthetic pulp was placed in a circulating hot air dryer in the same manner as in Example 1. Then, heat treatment was performed at 125 ° C. for 5 minutes. The high-density polyethylene synthetic pulp after heat treatment and the composite fiber having a fiber diameter of 1.5 denier, a fiber length of 5 mm, made of polypropylene, and a sheath made of low-density polyethylene (melting point = 110 ° C.) at a ratio of 80/20. The mixture was mixed, disaggregated with a JIS type pulper, and paper was made with a 25 × 25 cm square paper machine. The wet sheet thus obtained was subjected to 1 at 50 ° C. with a circulating hot air dryer.
It was dried for an hour to obtain a sheet. This sheet was further heat-treated at 125 ° C. for 5 minutes with a circulating hot air dryer. Then, it was immersed in hot water at 90 ° C. for 1 minute and dried again at 50 ° C. for 30 minutes by a circulating hot air dryer to obtain a target sheet. Table 1 shows the physical properties of the obtained sheet.

Example 3 A polyethylene synthetic pulp was obtained in the same manner as in Example 1 except that the amount of polyvinyl alcohol added to the autoclave was 20 g. The physical properties are shown below. Average fiber length 1.2 mm Specific surface area 6.2 m ² / g Freeness 5.0 sec / g PVA content 2.0% by weight Melting point 135 ° C. The above synthetic pulp was circulated hot air dryer in the same manner as in Example 1. Heat treatment was performed at 125 ° C. for 5 minutes. The heat-treated high-density polyethylene synthetic pulp and a composite fiber having a fiber diameter of 1.5 denier, a fiber length of 5 mm, a polypropylene core and a sheath of low-density polyethylene (melting point = 110 ° C.),
The mixture was mixed at a ratio of 80/20, disaggregated with a JIS type pulper, and paper was made with a 25 × 25 cm square paper machine. The wet sheet thus obtained was dried at 50 ° C. for 1 hour with a circulating hot air dryer to obtain a sheet-like material. This sheet was further heat-treated at 125 ° C. for 5 minutes with a circulating hot air dryer. Thereafter, a surfactant (sodium dialkylsulfosuccinate) was added to the sheet in an amount of 1% by weight as an aqueous solution, and the sheet was dried again at 50 ° C. for 30 minutes with a circulating hot air dryer to obtain a target sheet. Table 1 shows the physical properties of the obtained sheet.
Shown in

<Comparative Example 1> The high-density polyethylene synthetic pulp obtained in Example 1 was immediately subjected to JIS without heat treatment.
It was disintegrated with a mold pulper and made into paper with a 25 × 25 cm square paper machine. The obtained wet sheet was dried at 50 ° C. for 1 hour or more with a circulating hot air dryer to obtain a sheet. The physical properties of this sheet are shown in Table-2.

<Comparative Example 2> The high-density polyethylene synthetic pulp obtained in Example 2 was immediately subjected to heat treatment without heat treatment, and the core having a fiber diameter of 1.5 denier and a fiber length of 5 mm was polypropylene and the sheath was a low-density polyethylene. The composite fiber (melting point = 110 ° C.) was mixed at a ratio of 80/20, disaggregated with a JIS type pulper, and paper was made with a 25 × 25 cm square paper machine. A target sheet was obtained in the same manner as in Example 2 below. Table 2 shows the physical properties of the obtained sheet.

<Comparative Example 3> The high-density polyethylene synthetic pulp obtained in Example 3 was immediately subjected to heat treatment without heat treatment, and the core portion having a fiber diameter of 1.5 denier and a fiber length of 5 mm was polypropylene and the sheath portion was low-density polyethylene. The composite fiber (melting point = 110 ° C.) was mixed at a ratio of 80/20, disaggregated with a JIS type pulper, and paper was made with a 25 × 25 cm square paper machine. The target sheet was obtained in the same manner as in Example 3 below. Table 2 shows the physical properties of the obtained sheet.

Comparative Example 4 Example 1 was repeated except that the amount of polyvinyl alcohol added to the autoclave was 4 g.
A polyethylene synthetic pulp was obtained in the same manner as in. The physical properties of the obtained synthetic pulp are shown below. Average fiber length 1.5 mm Specific surface area 5.4 m ² / g Freeness 0.5 sec / g PVA content 0.4% by weight Melting point 135 ° C. The above high-density polyethylene synthetic pulp is dried in a circulating hot air dryer. Then, heat treatment was performed at 125 ° C. for 5 minutes. JIS high density polyethylene synthetic pulp after heat treatment
It was disintegrated with a shape pulper and paper was made with a 25 × 25 cm square paper machine. The obtained wet sheet was dried with a circulating hot air dryer at 50 ° C. for 1 hour to obtain a sheet. Table 2 shows the physical properties of the obtained sheet.

Comparative Example 5 The same performance test was performed on a polypropylene dry type nonwoven fabric (melt spinning type) separator. The results are shown in Table-2.

From the results shown in Tables 1 and 2, the alkaline battery separator of Example 1 has a higher liquid retention and absorption than the alkaline battery separator of Comparative Example 1 used without heat treatment. It is recognized that the liquidity and alkali resistance are remarkably excellent. Further, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3, respectively, use the same synthetic pulp, are heat-treated in the Examples, and are not heat-treated in the Comparative Examples. Even in this case, it is recognized that the example has superior liquid retention, liquid absorption and alkali resistance.

[0065]

[0066]

Claims (12)

[Claims] 1. A polyolefin synthetic pulp having a polyvinyl alcohol content of 1.0 to 10.0% by weight is heat treated in a dry state at a temperature of 100 ° C. or higher and a melting point of the synthetic pulp or lower, and then wet papermaking. A separator for an alkaline battery obtained by the above. 2. A polyolefin-based synthetic pulp having a polyvinyl alcohol content of 1.0 to 10.0% by weight, which is heat-treated in a dry state at a temperature of 100 ° C. or more and a melting point of the synthetic pulp or less, 40 to 95% by weight. % To 5% by weight of polyolefin heat fusion fiber binder
For alkaline batteries, characterized by being obtained by heat-treating at a temperature not higher than the melting point of the synthetic pulp and not lower than the fusion temperature of the polyolefin-based heat-sealing fiber binder after mixing and wet-making paper. separator. 3. The synthetic pulp is produced by flash spinning an emulsion.
The separator for alkaline batteries according to the item. 4. The alkaline battery separator according to claim 1, wherein the surfactant is present before or after the heat treatment. 5. The separator for an alkaline battery according to claim 1, wherein the polyolefin synthetic pulp has a specific surface area of 0.1 m ² / g or more. 6. The synthetic polyolefin pulp according to claim 1, which is a synthetic polyethylene pulp.
The separator for alkaline batteries according to the item. 7. The method for producing a separator for an alkaline battery according to claim 1, wherein the polyolefin synthetic pulp that has been heat-treated at a temperature of 100 ° C. or higher and a melting point or lower is wet-processed in a dry state to obtain hot air at 100 ° C. or lower. A method for producing a separator for an alkaline battery, characterized by being dried by. 8. 40 to 95% by weight of the heat-treated polyolefin synthetic pulp according to claim 7 is mixed with 5 to 60% by weight of a polyolefin heat-sealing fiber binder for wet papermaking, and after drying, the polyolefin-based heat is used. A method for producing a separator for an alkaline battery, which comprises performing a heat treatment at a temperature not lower than a melting temperature of a fusion fiber binder and not higher than a melting point of synthetic pulp. 9. The alkaline battery according to claim 8, which is heat-treated at a temperature below the melting point of the synthetic pulp and above the fusion temperature of the polyolefin-based heat-sealing fiber binder, and then treated with hot water at 80 to 100 ° C. Manufacturing method for the separator. 10. The method for producing a separator for an alkaline battery according to claim 7, wherein the surfactant is present before or after the heat treatment. 11. The specific surface area of the polyolefin is 0.1.
The method for producing the alkaline battery separator according to claim 7, which has a m ² / g or more. 12. The method for manufacturing the alkaline battery separator according to claim 7, wherein the polyolefin synthetic pulp is polyethylene synthetic pulp.