JP3080675B2 - Alkaline battery separator - 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 comprising a polyamide nonwoven fabric, which is suitable for an alkaline battery using an alkali as an electrolyte.

[0002]

2. Description of the Related Art Conventionally, as a separator for an alkaline battery, a non-woven fabric made of fibers such as polyamide, polypropylene and polysulfide has been used.

[0003] Of these, polyamide-based nonwoven fabrics are excellent in electrolyte retention and water absorption and have a high diffusivity of the electrolyte, so that high-rate discharge is possible. There is a disadvantage that the life of the battery is shortened due to elution of impurities due to alkali decomposition. Also,
Polypropylene-based nonwoven fabrics have excellent alkali resistance, but have low liquid retention due to fibers that are inherently highly hydrophobic. Therefore, if the positive and negative electrodes are brought as close as possible to perform a high-rate discharge, a leak phenomenon occurs and the device cannot be used. Further, the polysulfide-based nonwoven fabric has a slightly better liquid retaining property than the polypropylene-based nonwoven fabric, but still has a disadvantage of causing a leak phenomenon.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and is intended for an alkaline battery which has good electrolyte retention, excellent alkali resistance, and is advantageous in cost. It is intended to provide a separator.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a high-melting polyamide fiber having a relatively low elongation and a specific elongation range, and a specific polyamide as a sheath component. The present inventors have found that a nonwoven fabric composed of the used composite adhesive fiber has extremely excellent properties, and have reached the present invention. That is, the present invention relates to a separator comprising a non-woven fabric comprising a high-melting polyamide fiber having an elongation of 41 to 45% and a polyamide composite adhesive fiber having an elongation of 65% or less. , Sheath melting point 16
It includes a linear aliphatic polyamide having a melting point exceeding 5 ° C. and at least 10 ° C. lower than the melting point of the high melting point polyamide constituting the core component.

Hereinafter, the present invention will be described in detail. First, with the high melting point polyamide fiber of elongation 41-45% according to the present invention,
Nylon 6 (melting point 215 ° C), Nylon 66 (melting point 250
C.), polyamide 46 such as nylon 46 (melting point 290 ° C.) or a mixed fiber thereof. The high melting point polyamide fiber needs to have an elongation of 41 to 45%. If the elongation exceeds 45%, the alkali resistance becomes relatively low, which is not preferable. In order to obtain a product with an elongation of less than 41%, it is necessary to remodel the drawing equipment, or a single yarn is wound around the drawing roller at the time of drawing, the frequency of cutting increases, and the cost decreases. It is not preferable because it becomes an up factor.

The effect of alkali resistance is saturated when the elongation is about 41%, and even if the elongation is less than 41%, the alkali resistance does not improve much. However, when the elongation exceeds 45%, the alkali resistance rapidly decreases. That is, the range of elongation of the high-melting polyamide fiber of 41 to 45% exhibits a very favorable effect from the viewpoint of alkali resistance and cost.

Further, the linear aliphatic polyamide constituting the sheath component of the composite adhesive fiber according to the present invention has a melting point exceeding 165 ° C. and is at least higher than the melting point of the high melting point polyamide constituting the core component.
It has a melting point lower by 10 ° C., for example, mainly composed of nylon 6 itself or nylon 6 and / or nylon 66 to which nylon 610, nylon 11, nylon 12
And copolymers of one or more components selected from the above.

If the difference between the melting point of the linear aliphatic polyamide constituting the sheath component and the melting point of the high melting point polyamide constituting the core component is less than 10 ° C., the melting point of the high melting point polyamide of the core component is too close to that of the core component. In addition, the nonwoven fabric obtained by the heat treatment becomes film-like, and the liquid retention property is unfavorably reduced. The melting point of the linear aliphatic polyamide constituting the sheath component is 16
When the temperature is lower than 5 ° C., the third component to be copolymerized to lower the melting point is expensive, which is not preferable because the cost increases.

When the sheath component of the composite adhesive fiber is, for example, nylon 6, the high-melting polyamide fiber to be the main fiber must be naturally selected from nylon 66, nylon 46 or the like having a higher melting point than nylon 6.

The composite adhesive fiber of the present invention needs to have an elongation of 65% or less. If the elongation exceeds 65%, the alkali resistance becomes relatively low, which is not preferable. The core / sheath weight ratio of the core-sheath composite adhesive fiber is not specified, but is suitably in the range of 20/80 to 80/20. When the weight ratio of the core / sheath is less than 20/80, the obtained nonwoven fabric becomes a film-like film depending on the blending ratio with the high-melting polyamide fiber having an elongation of 41 to 45%, and the liquid retention property is reduced. It may be difficult to control the size of the fine voids between the fibers to be formed, and it may be difficult to evenly penetrate the electrolyte. Further, when the core-sheath weight ratio exceeds 80/20, the high-melting polyamide of the core may be partially exposed on the fiber surface to lower the alkali resistance of the conjugate fiber itself.

The blending degree of the high-melting polyamide fiber and the polyamide composite adhesive fiber may be determined as appropriate, but is approximately 50 to 90% by weight of the high-melting polyamide fiber and 50 to 10% by weight of the polyamide composite adhesive fiber.

When a copolyamide is used as the straight-chain aliphatic polyamide constituting the sheath component of the polyamide composite adhesive fiber in the present invention, the copolyamide may be any other than the above-mentioned components as long as the effects of the present invention are not impaired. The components may be copolymerized, and additives such as a matting agent, a stabilizer and a colorant may be added. However, additives that impair the battery life should be avoided.

Further, the nonwoven fabric used in the present invention is obtained by cutting a high-melting polyamide fiber and a composite adhesive fiber into short fibers, forming a nonwoven fabric-mixed web by a usual card method, an air lay method, a wet papermaking method, and the like. It can be manufactured by heat treatment using a heat treatment device such as a dryer such as a suction drum dryer or a Yankee dryer or a flat calender roll.

[0015]

The polyamide-based nonwoven fabric used for the separator of the present invention inherently has a good electrolyte retaining property. Furthermore, since the high melting point polyamide fiber and the polyamide composite adhesive fiber having relatively low elongation are used as the constituent fiber components, they have excellent alkali resistance.

[0016]

Next, the present invention will be specifically described based on examples. The various characteristic values in the examples were measured by the following methods. Alkali resistance: The ratio (strength retention) of the strength after immersing the fiber in a 40% KOH aqueous solution heated to 80 ° C. for 500 hours to the strength before heat treatment. Retention of electrolyte: Nonwoven fabric test piece cut into a size of 10 cm x 10 cm is immersed in a 40% KOH aqueous solution kept at room temperature for 1 hour, pulled up from the solution, suspended vertically, and tested after 10 minutes Measure the weight of the piece. The liquid retention amount is determined from the difference from the weight of the nonwoven fabric before immersion, and the liquid retention ratio with respect to the weight after immersion is calculated as a measure of liquid retention. Electrolyte water absorption: A 2.5 × 20 cm long and thin sample was cut out from the longitudinal direction of the non-woven fabric, suspended vertically in a 40% aqueous KOH solution kept at room temperature so that the lower end of the sample was 1 cm, soaked in the solution, and after 30 minutes the aqueous KOH solution Measure the height at which it rises. Battery life: The nonwoven fabric is incorporated into a 1000 mAhr alkaline battery as a separator, and charging and discharging are repeated. The number of charge / discharge repetitions (cycles) and the ratio of the dischargeable time after 800 cycles to the initial dischargeable time (dischargeable time maintenance rate) were determined and used as a guide for battery life. The larger the value, the longer the life. Example 1 Nylon 6 fiber (fineness 1.0 denier, cut length 51 mm, strength 5.4 g / d, elongation 42%) 75% by weight, nylon 6 as a core component, nylon 6 / nylon 12 ／ = 70/30 (molar ratio )｝,
The copolyamide having a melting point of 180 ° C is sheathed (core / sheath weight ratio)
50/50) and 25% by weight of a polyamide composite adhesive fiber (1.5 denier, cut length 51 mm, strength 5.5 g / d, elongation 57%) were mixed, and a mixed web was prepared by a roller card method. This mixed web was passed through a flat calender roll heated to 195 ° C. to obtain a nonwoven fabric having a basis weight of 75 g / m ² and a thickness of 0.20 mm. Table 1 shows the alkali resistance of the constituent fibers, the liquid retention and water absorption of the nonwoven fabric, and the life of the battery using the nonwoven fabric as a separator. Examples 2 to 3 and Comparative Example 1 Table 1 shows the results obtained in the same manner as in Example 1 except that nylon 6 fibers having different strength and elongation were used. In Comparative Example 1, the nylon 6 fiber had low alkali resistance, and the battery life was shorter than that of Example. Examples 4 to 5 and Comparative Example 2 Copolymerization of Sheath Component of Polyamide Composite Adhesive Fiber Except that the polymer component of the polyamide was changed to use a sheath component having various melting points, and that the elongation of the composite adhesive fiber was changed. Was carried out in the same manner as in Example 1. In Comparative Example 2, the nonwoven fabric had a low liquid retention property and low water absorption, and a leak phenomenon was observed during use. Also, the battery life was short. Example 6 and Comparative Example 3 In Example 1, nylon 66 was used instead of nylon 6 fiber.
Fiber (1.0 denier, cut length 51mm, strength 5.5g /
d, elongation 41%; Example 6) and nylon 66 fiber (strength)
Table 1 shows the results obtained in the same manner as in Example 1 except for using 5.2 g / d and elongation of 48%; Comparative Example 3). In Comparative Example 3, the nylon 66 fiber had low alkali resistance, and the battery life was shorter than that in Example 6. Comparative Examples 4 and 5 Table 1 shows the results obtained in the same manner as in Example 1 except that nylon 6 fibers having different strengths and elongations were used. Comparative Example 4,
No. 5 had good battery life, but had a problem that the operability at the time of drawing nylon 6 fiber was poor.

[0017]

[Table 1]

Example 7 In Example 1, the core component of the polyamide composite adhesive fiber is nylon 66, and the denier is 1.5 denier, the cut length is 51 mm, the strength is 5.7 g / d, the elongation is 52%, and the alkali resistance is 73%. Except for this, the results obtained in the same manner as in Example 1 are shown in Table 2. The liquid retention of the non-woven fabric was 245%, the water absorption was 15 cm, and the battery life was as good as 74%. Examples 8 to 9 and Comparative Example 4 In Example 7, nylon 66 fibers (denier 1.0 denier,
Table 2 shows the results obtained in the same manner as in Example 7 except that the cut length was 51 mm) and the strength and elongation were changed. Examples 10 to 13 and Comparative Examples 5 to 7 In Example 8, the same as Example 8 except that the polyamide component of the sheath component of the polyamide composite adhesive fiber was changed, and the elongation of the composite adhesive fiber was changed. The results obtained are shown in Table 2. In Comparative Example 5, the nonwoven fabric became film-like, the liquid retention property and water absorption were low, and a leak phenomenon was observed during use. In Comparative Example 6, the alkali resistance of the composite adhesive fiber was insufficient, and the battery life was short. In Comparative Example 7, both the alkali resistance and the battery life were good, but the expensive copolymer component (nylon 12) was used in a large amount and the cost was high.

[0019]

[Table 2]

[0020]

As described above, according to the battery separator of the present invention, the elongation of the high-melting polyamide fiber constituting the non-woven fabric is set to 41 to 45%, and good stretchability during spinning of the fiber is ensured. In addition, the required alkali resistance can be ensured, and the required alkali resistance of the adhesive fiber can be ensured by setting the elongation of the polyamide composite adhesive fiber constituting the nonwoven fabric to 65% or less.
The required alkali resistance can be imparted to all the fibers constituting the nonwoven fabric, and therefore, according to the battery separator of the present invention, it is possible to achieve excellent alkali resistance, high liquid retention, and high water absorption. Therefore, an alkaline battery incorporating this has a long battery life and is capable of highly efficient discharge.

Claims (1)

(57) [Claims] 1. An alkaline battery separator comprising a non-woven fabric comprising a high melting point polyamide fiber having an elongation of 41 to 45% and a polyamide composite adhesive fiber having an elongation of 65% or less, wherein the polyamide composite adhesive fiber has a core. A separator for an alkaline battery comprising a high melting point polyamide and a linear aliphatic polyamide having a melting point at least 10 ° C. lower than the melting point of the high melting point polyamide having a melting point exceeding 165 ° C. and constituting a core component.