Mitsui Petrochemical Industries, Ltd.

Shiro Homma

Masatoshi Kashiwagi

Mutsuhiro Tanaka

Mitsuhiro Tanaka

Hiroyuki Arita

When a hydrophobic thermoplastic resin such as an olefin resin and a water-insoluble or non-water-swelling polymer containing a carboxylic acid salt group are melt-kneaded in the presence of water, phase inversion of forming a dispersion comprising water as the dispersion medium phase and resin particles as the dispersed phase is caused even if the amount of water is very small. If an anionic surfactant, optionally together with a solvent or oil, is made present in the composition to be melt-kneaded, the size of dispersed particles can be greatly reduced in the formed aqueous dispersion even if a resin having a very high molecular weight or a high melt viscosity is used.

Aqueous dispersion and process for preparation thereof

A non-water swelling or a water-insoluble thermoplastic resin, water and an assistant for assisting dispersion of water into the thermoplastic resin are melt-kneaded and the kneaded composition is extruded from an orifice under such conditions that flashing of water is prevented. As the assistant, a water-soluble resin or a water-insoluble resin having a carboxylic acid salt group is used optionally in combination with a surface active agent. The spun product is a fiber bundle in which single filaments having a diameter smaller than 100 .mu.m are gathered in parallel to one another, and this fiber bundle is easily opened.

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Iwakuni, Japan

Shiro Homma