JP2926167B2 - Alkaline battery separator and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator for an alkaline battery and a method for producing the same. More particularly, the present invention relates to an alkaline battery separator having an appropriate air permeability and capable of preventing a dryout phenomenon, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as separators for alkaline batteries, Japanese Patent Publication No. 57-33828 and Japanese Patent Application Laid-Open No. 60-90
No. 56 and JP-A-60-170159. For these separators,
All are excellent in chemical resistance and use a non-woven fabric made of polyolefin-based ultra-fine fibers that are not easily degraded by alkali, and a non-woven fabric made of fibers with a finer size than polyolefin-based ultra-fine fibers is laminated on this non-woven fabric for reinforcement And these were integrated and the separator was comprised.

[0003]

However, the ultrafine polyolefin fibers constituting these separators have high water repellency, and the electrodes adjacent to the separator have a very fine porous structure. The so-called dry-out phenomenon occurs in which the electrolyte held in the inside is sucked up by the adjacent electrode due to the capillary phenomenon, and the electrolyte which should be originally held in the nonwoven fabric made of the polyolefin-based ultrafine fibers decreases, and the battery It had a significant effect on life.

Further, in these separators, since a dense porous structure is made of polyolefin-based ultrafine fibers having high water repellency, as shown in FIG. Since the gap is closed, gas generated in the electrode cannot be sufficiently moved, and a problem has occurred that the internal pressure increases during overcharging or rapid charging.

[0005] In order to solve the problem caused by the high water repellency of the polyolefin-based ultrafine fibers, attempts have been made to attach a surfactant to the polyolefin-based ultrafine fibers to make them hydrophilic. The surfactant adhering to the fiber surface flowed out into the electrolyte with the passage of time, and the effect of attaching the surfactant to make the fiber hydrophilic was obtained only in the initial stage.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an alkaline battery separator which has an appropriate air permeability and can prevent a dry-out phenomenon, and a method of manufacturing the same. Is what you do.

[0007]

In order to achieve the above object, the alkaline battery separator of the present invention has an average fiber diameter obtained by a melt blow method of 1 as shown in FIG. 1 and FIG. A first fiber layer 12 made of 0.5 to 8 μm nylon-based ultrafine fibers 11 and a second fiber layer 14 made of fibers 13 having an average fiber diameter larger than the nylon-based ultrafine fibers 11 are laminated and integrated ; The
The separator has an average pore diameter of 11 to 15 μm .

The alkaline battery separator of the present invention comprises a first
The fiber layer and the second fiber layer are laminated and integrated.
The first fiber layer is composed of ultrafine nylon fibers having an average fiber diameter of 1.5 to 8 μm. Nylon-6, Nylon 66, Nylon 12 or Nylon 6 and Nylon 1 which are rich in hydrophilicity and excellent in air permeability as nylon type ultrafine fibers
Ultrafine fibers having an average fiber diameter of 1.5 to 8 μm, which is a nylon-based fiber such as a copolymer of No. 2 and produced by a melt blow method, are used. The reason for setting the average fiber diameter of the fibers to the above range is that when the average fiber diameter of the fibers is 1.5 μm or less, the air permeability decreases, and when the average fiber diameter of the fibers is 8 μm or more, the liquid retention property decreases. . The first fiber layer can be used in any state of a web in which the above-mentioned nylon-based ultrafine fibers are laminated by a predetermined amount and a nonwoven fabric in which fibers are bonded to each other. In the first fiber layer thus configured, since the fibers constituting the fiber layer are made of hydrophilic nylon-based ultrafine fibers, as shown in FIG. The fine holes 15 are formed in the gaps between the fibers 11. As a result, the first fiber layer is in a state where sufficient liquid retention and air permeability are maintained.

The second fiber layer is composed of fibers having an average fiber diameter larger than the nylon-based ultrafine fibers of the first fiber layer. The fibers constituting the second fiber layer have a larger average fiber diameter than the nylon-based ultrafine fibers of the first fiber layer (specifically, preferably 8 to 30 μm). The type and structure of the fiber are not particularly limited as long as a certain mechanical strength can be imparted against the tensile force sometimes applied to the separator. For example, the same nylon 6, nylon 6 as the first fiber layer
6, nylon 12 or a nylon fiber such as a copolymer of nylon 6 and nylon 12, a polyolefin fiber having high alkali resistance, and a composite fiber comprising a nylon component and a polyolefin component. Also, the second fiber layer contains a heat-adhesive fiber, and the heat-adhesive fiber bonds the fibers of the second fiber layer to each other and bonds the second fiber layer to the first fiber layer. You may do it. The heat-adhesive fibers contained in the second fiber layer preferably include an adhesive component having a melting point lower than the melting point of the nylon-based ultrafine fibers of the first fiber layer. In other words, when the adhesive component in the heat-adhesive fiber has a melting point higher than the melting point of the nylon-based ultrafine fiber, bonding of the second fiber layer to each other and integration of the first fiber layer with the second fiber layer are performed. This is because the ultrafine nylon-based fibers of the first fiber layer are changed by heat before performing the above. Further, the second fiber layer can be used in any state of a web or a non-woven fabric, similarly to the first fiber layer.

The above-mentioned first fiber layer and second fiber layer are laminated and integrated to constitute the alkaline battery separator of the present invention. The weight ratio of the first fiber layer to the second fiber layer is as follows. Is 20/80 to 80/20, preferably 30/7
The range of 0 to 70/30 is good. When the weight of the first fiber layer is smaller than this range and the weight of the second fiber layer is larger, the liquid retaining property is reduced, and a sufficient effect of preventing the dryout phenomenon cannot be obtained. On the other hand, when the weight of the first fiber layer is larger and the weight of the second fiber layer is smaller than this range, a problem occurs in that the air permeability decreases. or,
A method of integrating the first fiber layer and the second fiber layer is to include a thermo-adhesive fiber in the second fiber layer and hot press the first fiber layer and the second fiber layer. A method of bonding the first fiber layer and the second fiber layer with the heat-adhesive fiber, by interposing an adhesive in a dotted or linear manner between the first fiber layer and the second fiber layer, A method of partially bonding the first fiber layer and the second fiber layer to each other, and a method of spraying ultrafine nylon fibers constituting the first fiber layer directly onto the second fiber layer. It is ^40g / ^{m 2 ~100g} / m 2 as a weight per unit area of the thus two fibrous layers which are integrated. If the basis weight is smaller than this, the mechanical strength is reduced and it is impossible to withstand the tensile force applied during the production of the battery. If the basis weight exceeds 100 g / m ² , the thickness of the fiber layer becomes too thick, and When it is wound while being interposed between the shade and the anode, it cannot be wound a predetermined number of times, or the battery becomes large.

The number of fiber layers to be laminated is not limited to the above-mentioned two but may be three or more. For example, the first fiber layer made of nylon-based ultrafine fibers having an average fiber diameter of 1.5 to 8 μm may be used. A three-layer structure in which a second fiber layer made of a fiber having an average fiber diameter larger than that of a nylon-based ultrafine fiber is arranged on each side, and two first fiber layers are laminated, and a second fiber layer is formed on both sides. May have a four-layer structure in which each layer is disposed one by one.

It is useful from the viewpoint of preventing the dry-out phenomenon to further increase the hydrophilicity of the separator by attaching a surfactant to the laminated and integrated fiber layer. As the surfactant, an anionic surfactant or a nonionic surfactant can be used. As anionic surfactants, alkali metal salts of higher fatty acids, alkyl sulfonates,
And sulfosuccinate salts. Examples of the nonionic surfactant include polyoxyethylene alkyl ether and polyoxyethylene alkyl phenol ether.

Next, a method of manufacturing the separator for an alkaline battery according to claim 4 will be described. According to the present invention, the average fiber diameter obtained by the melt blow method is 1.5 to 8
a first fiber layer made of micron nylon-based ultrafine fibers, and a structure
Larger than the average fiber diameter of the fibers is the nylon-based ultra-fine fibers
And 8 to 30 μm fibers, and the nylon type
Adhesive component with melting point close to the crystallization peak temperature of microfiber
A second fiber layer containing a heat-adhesive fiber having
The weight ratio between the fiber layer and the second fiber layer is from 20/80 to 80/2
0, and lamination of the first fiber layer and the second fiber layer
Produced so that the later basis weight is 40 to 100 g / m ² ,
Next, the first fiber layer and the second fiber layer are laminated, and
By hot pressing the adhesive component of the thermoadhesive fiber.
Utilizing the adhesive strength of both nylon and ultrafine nylon fibers.
Adhesion between fibers of the first fiber layer and the second fiber layer, and the first fiber
Layer and the second fiber layer, and the separator is flattened.
The gist of the present invention is a method for producing a separator for an alkaline battery, wherein the pore size is 11 to 15 μm . In the present invention, the crystallization peak temperature is a temperature range in which the crystallization of the non-crystalline portions of the fibers constituting the nonwoven fabric proceeds when the meltblown nonwoven fabric is heated, that is, the crystallization temperature is particularly high. It is a temperature at which the temperature proceeds rapidly, that is, a temperature higher than the glass transition temperature and lower than the melting point, and the temperature at which the temperature difference of the differential heat curve takes the maximum value.
87 ° C. and 238 ° C. for nylon 66.

First, a first fiber layer and a second fiber layer are laminated. The first fiber layer is a web made of nylon-based ultrafine fibers having an average fiber diameter of 1.5 to 8 μm obtained by a melt blow method. On the other hand, the second fiber layer has an average fiber diameter of
A web of fibers constituting 8 to 30 m, this is the second fibrous layer contains thermally bondable fibers having an adhesive component having a melting point of coming close to the crystallization peak temperature of the nylon microfine fibers. The first fiber layer and the second fiber layer may be laminated in a state of a web in advance. However, the fiber web may be sprayed on the second fiber layer by spraying the ultrafine nylon fibers constituting the first fiber layer. May be formed. The first fiber layer and the second fiber layer
The fibrous layers have a weight ratio of 20/80 to
80/20 and the first fiber layer and the second fiber layer
Basis weight after lamination to produce <br/> so that 40 to 100 g / ^{m 2.}

Next, the first fiber layer and the second fiber layer are hot-pressed with a calender roll or the like. In the hot press, heating and pressurization may be performed at the same time, but it is better to press by a calender roll immediately after heating in a constant temperature atmosphere for a predetermined period of time so that heating reaches the inside of the fiber layer. In this case, it is desirable that the heating temperature is equal to or higher than the melting point of the adhesive component of the heat-adhesive fiber, and the temperature of the calender roll is lower than the melting point. Thereby, the heat-adhesive fibers in the second fiber layer are melted, and the fibers of the second fiber layer are bonded to each other.
Further, the first fiber layer and the second fiber layer are also bonded by the heat bonding fiber. On the other hand, since the melting point of the adhesive component of the heat-adhesive fiber is close to the crystallization peak temperature of the nylon-based ultrafine fibers in the first fiber layer, the nylon-based ultrafine fibers are simultaneously bonded to each other by this heating press. .

As described above, according to the production method of the present invention, the bonding between the fibers of the first fiber layer and the second fiber layer is performed by utilizing the adhesive force of both the adhesive component of the heat-bondable fiber and the ultrafine nylon fiber. The first fiber layer and the second fiber layer can be bonded in one step.

[0017]

EXAMPLE 1 Ultrafine fiber web 30 g / m ² of nylon 6 having an average fiber diameter of 5 μm obtained by a melt blowing method, nylon 66 fiber having a denier of 1.5 denier 50% and nylon-based composite fiber having a denier of 2 denier (Copolymer of nylon 6 and nylon 12 having a core of nylon 6 and a sheath of melting point 170 ° C.)
m ^2, and heated at 180 ° C. for 10 seconds to obtain a linear pressure of 1 k.
pressurized by a calender roll under the condition of g / cm,
The fibers of each fiber web were bonded together and between the fiber webs.
Thereafter, a nonionic surfactant was attached at a ratio of 1% to the weight of the two bonded fiber webs, and this was again passed through a calender roll to obtain a 0.15 mm thick alkaline battery separator.

Example 2 40 g / m ² of an ultrafine fiber web made of nylon 6 having an average fiber diameter of 5 μm obtained by a melt blow method, and nylon 66 having a fineness of 1.5 denier
20 g of a fibrous web composed of 50% of fibers and 50% of nylon-based composite fibers having a fineness of 2 denier (a core of nylon 6 and a sheath of a copolymer of nylon 6 and nylon 12 having a melting point of 170 ° C.)
/ M ² and heated at 180 ° C. for 10 seconds to obtain a linear pressure of 1
Pressed by a calender roll under the condition of kg / cm,
The fibers of each fiber web were bonded together and between the fiber webs.
Thereafter, a nonionic surfactant was attached at a ratio of 1% to the weight of the two bonded fiber webs, and this was again passed through a calender roll to obtain a 0.15 mm thick alkaline battery separator.

Example 3 Ultrafine fiber web 20 g / m ² made of nylon 6 having an average fiber diameter of 5 μm obtained by a melt blow method and nylon 66 having a fineness of 1.5 denier
40 g of a fibrous web composed of 50% of fibers and 50% of nylon-based composite fibers having a denier of 2 denier (a core of nylon 6 and a sheath of a copolymer of nylon 6 and nylon 12 having a melting point of 170 ° C.)
/ M ² and heated at 180 ° C. for 10 seconds to obtain a linear pressure of 1
Pressed by a calender roll under the condition of kg / cm,
The fibers of each fiber web were bonded together and between the fiber webs.
Thereafter, a nonionic surfactant was attached at a ratio of 1% to the weight of the two bonded fiber webs, and this was again passed through a calender roll to obtain a 0.15 mm thick alkaline battery separator.

Example 4 A nylon-based composite having a denier of 1.5 denier and 50% of nylon 66 fiber and a denier of 2 denier was provided on both sides of an ultrafine fiber web 30 g / m ² made of nylon 6 having an average fiber length of 5 μm and obtained by a melt blowing method. A fibrous web 158 / m ² composed of 50% of fibers (a core of nylon 6 and a sheath of a copolymer of nylon 6 and nylon 12 having a melting point of 170 ° C.) is laminated to form a three-layer structure, and heated at 180 ° C. for 10 seconds. Pressure was applied by a calender roll under the condition of a linear pressure of 1 kg / cm to bond the fibers of each fiber web to each other and between the fiber webs. Thereafter, a nonionic surfactant was applied at a rate of 1% based on the weight of the three bonded fiber webs, and again passed through a calender roll to a thickness of 0.1%.
A 5 mm alkaline battery separator was obtained.

Comparative Example 1 An ultrafine fiber web 60 g / m ² made of nylon 6 having an average fiber diameter of 5 μm obtained by a melt blowing method was heated at 180 ° C. for 10 seconds, and a linear pressure of 1 k was applied.
Pressure was applied by a calender roll under the condition of g / cm to bond the fibers of the fiber web to each other. After this, the bonded 2
Nonionic surfactant per 1 fiber web weight
%, And again passed through a calender roll to obtain a 0.15 mm thick alkaline battery separator. Comparative Example 2 50% nylon 66 fiber having a fineness of 1.5 denier and a nylon-based composite fiber having a fineness of 2 denier (a nylon 6 core and a nylon 6 sheath having a melting point of 170 ° C. and nylon 1)
2 g) fibrous web consisting of 50%
² was heated at 170 ° C. for 10 seconds and pressed by a calender roll under the condition of a linear pressure of 1 kg / cm to bond the fibers of the fiber web to each other. Thereafter, a nonionic surfactant was applied at a rate of 1% based on the weight of the two bonded fiber webs, and again passed through a calender roll to a thickness of 0.1%.
A 5 mm alkaline battery separator was obtained. Comparative Example 3
An ultrafine fiber web 30 g / m ² made of polypropylene having an average fiber diameter of 5 μm obtained by a melt blow method;
A fibrous web 30 g / m ² made of a polyolefin-based conjugate fiber having a fineness of 1.5 denier (core: polypropylene, sheath: polyethylene) is laminated, heated at 140 ° C. for 10 seconds, and calendered under a linear pressure of 1 kg / cm. And bonded between the fiber webs. Thereafter, a nonionic surfactant was attached at a ratio of 1% to the weight of the two bonded fiber webs, and this was again passed through a calender roll to obtain a 0.15 mm thick alkaline battery separator.

The 5% modulus, air permeability, liquid retention, and average pore size of the alkaline battery separators of Examples 1 to 4 and Comparative Examples 1 to 3 were measured and are shown in Table 1.
In addition, the 5% modulus (kg / 5 cm width) was obtained by collecting three test pieces of 5 × 20 cm from the longitudinal direction of each of the above separators.
For each test piece, according to JIS L1096 (General woven fabric test method), gripping interval 10 cm, tensile speed 300 mm
/ Min was measured one sheet at a time, and the tensile load when the test piece was stretched by 5% was read and expressed as an average value.

The liquid retention rate (%) is obtained by collecting three test pieces (202.5 cm ² ) having the shape shown in FIG. 4 from each separator, and measuring the state of each test piece that has reached water equilibrium up to 1 mg (see FIG. 4). W). Next, the test piece is spread and immersed in a caustic potash solution at a specific temperature of 1.30 (20 ° C.) at room temperature, and is sufficiently absorbed (1 hour or more). W ₁ ) was measured, and the liquid retention was calculated by the following equation. Liquid retention rate = (W ₁ −W) ÷ W × 100

As for the air permeability (cc / cm ² sec), three test pieces having a size of 20 × 20 cm were sampled from the right end, the center, and the left end in the width direction of the separator, and each test piece was subjected to a Frazier-type air permeability tester. Then, the air permeability at a measured differential pressure of 12.7 mmAg was measured and expressed as an average value.

The average pore size (μm) is based on the bubble point method and is based on Coulter Electronics (Coulte Electronics).
The measurement was performed with a porometer (POROMETER), a pore size distribution measuring device manufactured by Electronics (Limited).

[0026]

[Table 1]

From Table 1, the 5% modulus, air permeability, liquid retention rate, and average pore diameter of the separators of Examples 1 to 4 all show satisfactory values, while Comparative Example 1 shows satisfactory values.
The separator of Comparative Example 2 could not obtain sufficient numerical values for both the 5% modulus, the air permeability, and the liquid retention rate, and the separator of Comparative Example 2 had sufficient numerical values for the 5% modulus, the air permeability, and the liquid retention rate. However, it has a structure in which the average pore diameter is large and the dry-out phenomenon easily occurs. Comparative Example 3
It became clear that the liquid retention rate was low in the separator of No. 1.

[0028]

According to the present invention, the above-mentioned structure is provided.
In the alkaline battery separator described, since the hydrophilic nylon-based ultrafine fibers are used, the electrolytic solution permeates not only the fiber surface but also the inside, and the gap between the fibers constituting the separator is Fine holes are formed.
For this reason, in this alkaline battery separator,
The so-called dry-out phenomenon, in which the electrolyte held in the separator is sucked up by the adjacent electrode due to capillary action, can be reliably prevented, and since the proper air permeability is maintained, overcharging is performed. There is no problem that the internal pressure rises during quick charging.

In the separator for an alkaline battery according to the second aspect, the adhesive component of the thermo-adhesive fibers in the second fiber layer has a melting point lower than the melting point of the nylon-based ultrafine fibers in the first fiber layer. Therefore, bonding between fibers and bonding between fiber layers can be reliably performed.

According to the third aspect of the present invention, the weight ratio of the first fiber layer to the second fiber layer is 20%.
Since it is in the range of / 80 to 80/20, sufficient liquid retention is maintained, the dryout phenomenon is reliably prevented, and sufficient air permeability is ensured.

According to a fourth aspect of the present invention, there is provided a method for manufacturing a separator for an alkaline battery, wherein the first fiber layer and the second fiber layer are formed by utilizing the adhesive strength of both the adhesive component of the thermo-adhesive fiber and the ultrafine nylon fiber. Bonding between the fibers and bonding between the first fiber layer and the second fiber layer can be performed in one step, and the manufacturing process can be rationalized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a battery using the alkaline battery separator of the present invention.

FIG. 2 is an enlarged perspective view showing a separator for an alkaline battery of the present invention.

FIG. 3 is a schematic view showing a state of a fiber surface of the alkaline battery separator of the present invention.

FIG. 4 is a plan view showing a test piece for measuring a liquid retention ratio.

FIG. 5 is a schematic diagram showing a state of a fiber surface of a conventional alkaline battery separator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Nylon-based ultrafine fiber 12 First fiber layer 13 Fiber having an average fiber diameter larger than that of nylon-based ultrafine fiber 14 Second fiber layer

Claims (4)

(57) [Claims] 1. A first fiber layer made of a nylon-based ultrafine fiber having an average fiber diameter of 1.5 to 8 μm and obtained by a melt blow method, and a second fiber made of a fiber having an average fiber diameter larger than that of the nylon-based ultrafine fiber. And the layers are laminated and integrated, and the average pore size of the separator is 11 to 15 μm.
A separator for an alkaline battery. 2. The second fiber layer contains a heat-adhesive fiber containing an adhesive component having a melting point lower than the melting point of the nylon-based ultrafine fiber. 2. The separator for an alkaline battery according to claim 1, wherein the two fiber layers are integrated. 3. The weight ratio of the first fiber layer to the second fiber layer is 2
2. The ratio is 0/80 to 80/20.
Or the separator for alkaline batteries according to 2. 4. A first fiber layer made of ultrafine nylon fibers having an average fiber diameter of 1.5 to 8 μm obtained by a melt blow method, and an average fiber diameter of constituent fibers of said nylon.
Consisting of a fiber of 8 to 30 μm larger than the system ultrafine fiber,
And near the crystallization peak temperature of the ultrafine nylon fiber
Fiber containing a thermo-adhesive fiber having an adhesive component having a melting point
The weight ratio between the first fiber layer and the second fiber layer is 2
0/80 to 80/20, and the first fiber layer and
And the basis weight after lamination of the second fiber layer is 40 to 100 g / m ² .
And then the first fiber layer and the second fiber
By laminating fiber layers and hot pressing them,
Bonding of adhesive component of adhesive fiber and ultrafine nylon fiber
The fibers of the first fiber layer and the second fiber layer are
And bonding between the first fiber layer and the second fiber layer,
So that the average pore diameter of the separator is 11 to 15 μm
A method for producing a separator for an alkaline battery, comprising the steps of: