Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Separator – retainer – spacer or materials for use therewith
Reexamination Certificate
1997-09-25
2001-02-06
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Separator, retainer, spacer or materials for use therewith
C429S249000
Reexamination Certificate
active
06183913
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alkaline battery separator, i.e., a separator for an alkaline battery, and a process for producing the same.
2. Description of the Related Art
An alkaline battery separator composed of a hydro-entangled nonwoven fabric containing fine fibers derived from dividable composite fibers has many fine voids formed between the fine fibers, and accordingly has an excellent electrolyte-holding capacity.
For example, Japanese Unexamined Patent Publication (Kokai) No. 7-147154 discloses an alkaline battery separator prepared by imparting a hydrophilic property to a hydro-entangled nonwoven fabric composed of polyolefin fibers, which are mainly fine fibers, derived from polyolefin dividable composite fibers, and an alkaline battery separator prepared by adhering the hydro-entangled nonwoven fabric with polyolefin heat-sensitive-adhesive fibers having a lower melting point. The alkaline battery separators composed of mainly fine fibers derived from the dividable composite fibers have an excellent electrolyte-holding capacity. Further, the alkaline battery separator adhered with the polyolefin heat-sensitive-adhesive fibers has an excellent tensile strength.
Nevertheless, the breaking strength of the alkaline battery separators disclosed in Japanese Unexamined Patent Publication (Kokai) No. 7-147154 is insufficient. For example, when the alkaline battery separators are rolled together with electrode plates upon assembling an alkaline battery, the separators are easily broken by the edges of the electrode plates. The separators also have the disadvantages of a low yield and an inconsistent battery performance.
Further, Japanese Unexamined Patent Publication (Kokai) No. 7-29561 discloses an alkaline battery separator composed of wet-laid hydro-entangled nonwoven fabric prepared by hydro-entangling (1) 60 to 80% by weight of dividable composite fibers (fiber length=5-15 mm) consisting of polyolefin polymer and ethylene vinyl alcohol polymer, (2) 20 to 30% by weight of heat-sensitive-adhesive fibers, and (3) 10-20% by weight of synthetic fibers (fiber length=5-15 mm) having a denier larger than those of fine fibers derived from the dividable composite fibers and the heat-sensitive-adhesive fibers. The alkaline battery separator has an excellent electrolyte-holding capacity and tensile strength, but the hydrophilic nature of the alkaline battery separator is imparted only by the dividable composite fibers. Therefore, it is necessary to raise the ratio of the dividable composite fibers, and thus, the ratio of the synthetic fibers having a denier larger than those of the fine fibers and heat-sensitive-adhesive fibers is lower. As a result, some alkaline battery separators have an insufficient breaking strength.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide an alkaline battery separator having an excellent breaking strength, as well as practically sufficient tensile strength and electrolyte-holding capacity properties.
Other objects and advantages will be apparent from the following description.
In accordance with the present invention, there is provided an alkaline battery separator comprising a hydrophilic nonwoven fabric obtainable by heat-fusing and hydro-entangling (1) polyolefin dividable composite fibers having an average fiber length of 20 to 60 mm, (2) high-strength fibers having an average fiber length of 30 to 60 mm and a fiber strength (tensile strength of fiber) of 5 g/denier or more, and (3) polyolefin heat-sensitive-adhesive fibers having an average fiber length of 30 to 60 mm, the polyolefin heat-sensitive-adhesive fiber containing a polyolefin adhesive portion having a melting point lower than a melting point of the polyolefin dividable composite fiber and lower than a melting point of the high-strength fiber, to obtain a heat-fused and hydro-entangled nonwoven fabric, and imparting a hydrophilic property to the resulting heat-fused and hydro-entangled nonwoven fabric; the high-strength fibers accounting for 20 to 45 mass % with respect to a total mass of the polyolefin dividable composite fibers, the high-strength fibers and the polyolefin heat-sensitive-adhesive fibers.
Further, in accordance with the present invention, there is provided a process for producing an alkaline battery separator comprising the steps of:
substantially uniformly admixing (1) polyolefin dividable composite fibers having an average fiber length of 20 to 60 mm, (2) high-strength fibers having an average fiber length of 30 to 60 mm and a fiber strength of 5 g/denier or more, and (3) polyolefin heat-sensitive-adhesive fibers having an average fiber length of 30 to 60 mm, the polyolefin heat-sensitive-adhesive fiber containing a polyolefin adhesive portion having a melting point lower than a melting point of the polyolefin dividable composite fiber and lower than a melting point of the high-strength fiber, to form a fiber web, the high-strength fibers accounting for 20 to 45 mass % with respect to a total mass of the polyolefin dividable composite fibers, the high-strength fibers and the polyolefin heat-sensitive-adhesive fibers;
subjecting the resulting fiber web to a heat-fusing treatment and a hydro-entangling treatment to obtain a heat-fused and hydro-entangled nonwoven fabric, a sequence of the treatments being not specified; and then,
imparting a hydrophilic property to the resultant heat-fused and hydro-entangled nonwoven fabric.
REFERENCES:
patent: 5290645 (1994-03-01), Tanaka et al.
patent: 5609976 (1997-03-01), Ueda et al.
patent: 7-029561 (1995-01-01), None
patent: 8-138645 (1996-05-01), None
Patent Abstracts of Japan, vol. 096, No. 009, Sep. 30, 1996 & JP 08 138645 A (Daiwabo Co Ltd), May 31, 1996.
Patent Abstracts of Japan, vol. 095, No. 004, May 31, 1995 & JP 07 029561 A (Daiwabo Co Ltd), Jan. 31, 1995.
Patent Abstracts of Japan, vol. 096, No. 011, Nov. 29, 1996 & JP 08 185848 A (Asahi Chem Ino Co Ltd), Jul. 16, 1996.
Kimura Koji
Tanaka Masanao
Tokutake Nobutoshi
Burgess, Ryan & Wayne
Crepeau Jonathan
Japan Vilene Company Ltd.
Kalafut Stephen
Moran William R.
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