Kuraray Co., Ltd.

Matsushita Electric Industrial Co., Ltd.

Masahiro Satoh

Akio Ohmory

Tomoyuki Sano

Hayami Yoshimochi

Syunpei Naramura

Satoru Kobayashi

Akira Kubotsu

Shinya Inada

Masakazu Nishiyama

Toshiaki Ikimine

Atsuhisa Ogawa

Isao Tokunaga

Hisashi Suemori

Mitsuo Mayahara

Jun-ichi Hikasa

Tadashi Saito

Yosuke Sekiya

A fiber of sea-islands phase separation wherein the sea component comprises a vinyl alcohol based polymer with high orientation and great crystallinity and the islands component comprises a water-insoluble cellulose based polymer with excellent absorptivity of alkaline solutions, thermal resistance and heat fusion resistance, and wherein the size of the islands is 0.03 to 10 .mu.m and the strength is 3 g/d or more, is readily disintegrated into a fibril of a diameter of 0.05 to 8 .mu.m when a mechanical stress is imposed onto the fiber wet in water. From the fibril with good hydrophilicity, high strength, great particle captivity and excellent reinforcing performance, and additionally with good absorptivity of alkaline solutions and great thermal resistance and heat fusion resistance, none of the fiber components therein is solubilized during fibrillation. Neither a beating process nor a beating solution causes foaming or environmental pollution. The fibril is extremely useful for use in separator sheets for alkaline batteries, reinforcing fibers of cement slate plates, reinforcing fibers of frictional materials and the like.

Separator for a battery comprising a fibrillatable fiber

A reinforcing material for incorporation into a kneaded and shaped hydraulic material, comprising a fiber having a fineness of 5 d or more, an aspect ratio of from 10-500, a breaking tenacity of 5 g/d or more, an elongation (A) of from 6-20%, a flexing tenacity utilization factor (B) of 35% or more, and (B).ltoreq.4 (A).

Reinforcing material for kneaded and formed hydraulic material, and

Flame-retardant polyvinyl alcohol base fiber

Readily fibrillatable fiber

Easily fibrillatable fiber

By dissolving a vinyl alcohol polymer (A) and an incompatible vinyl polymer (B), preferably an acrylonitrile polymer in a common solvent to prepare a spinning stock solution of a phase separation structure wherein the polymer (B) is present at particle sizes of 2 to 50 .mu.m, and wet spinning or dry-wet spinning the resulting spinning stock solution in a solidifying bath containing a mixture of an organic solvent capable of solidifying both the polymers (A) and (B) and the solvent of the spinning stock solution at a weight ratio of 25/75 to 85/15, thereby drawing the resulting yarn by 8-fold or more, a fiber is provided; and from the fiber can be produced a fibril with good hydrophilicity, a higher strength, and excellent heat fusion resistance, along with excellent wiping performance, filtering performance, micro-particle capturing properties and reinforcing performance, readily, stably and inexpensively.

Fibrillatable fiber of a sea-islands structure

By mixing a high-melting polyvinyl alcohol type polymer (A) and a low-melting water-soluble polymer (B) in a solvent for the polymer (A) to prepare a spinning solution and then subjecting the solution to low-temperature spinning so that the resulting filaments are solidified uniformly in the cross-sectional direction, there is formed a fiber of sea-islands structure comprising said high-melting polyvinyl alcohol type polymer (A) as the sea component and said low-melting water-soluble polymer (B) as the islands component. In this fiber, at least part of the islands component is present in a fiber zone ranging from the fiber surface to 2 .mu.m inside and the fiber surface contains substantially no islands component. This fiber ordinarily shows the performance of the matrix phase, i.e. the performance of a high-melting polyvinyl alcohol fiber; however, when the fiber is pressurized at high temperatures, the low-melting polymer (the islands component) is pushed out onto the fiber surface and there occurs heat bonding between fibers. Owing to this property of the fiber, a nonwoven fabric can be produced advantageously from the fiber.

Water-soluble heat-press-bonding polyvinyl alcohol binder fiber of a

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Kurashiki, Japan

Masahiro Satoh