Kuraray Co., Ltd.

Kiyonobu Fujii

Ryuhei Ueeda

Hiroshi Narukawa

Kenji Okuno

Koichi Saito

Akira Kubotsu

Osamu Ohara

Shunji Kaneda

Kotaro Ikeda

Polypropylene sheets of high impact resistance at low temperature and of improved formability characterized by specific parameters are described. Such polypropylene sheets are produced by spreading under pressure polypropylene sheets at a temperature within a very narrow range in the vicinity of the melting point of the propylene-based polymer.

Polypropylene sheet

Incorporation in a thermoplastic resin of a mass of mica flakes having a median shape factor of not less than 0.76, an average particle size of not more than 2,000 .mu.m and an average aspect ratio of not less than 10 followed by molding gives moldings which are high not only in mechanical strength but also in strength at weld parts. Incorporation of said mica flake mass in a thermosetting resin followed by molding affords moldings very high in strength as well as in modulus of elasticity.

Mica flake mass and resin composition with the same incorporated therein

According to the present invention, rolled sheet-like materials having superior mechanical properties, in particular toughness and high-impact properties, as well as superior heat resistance and showing no whitening can be provided. Such rolled sheet-like materials are manufactured by isotropically rolling sheet-like materials, which were obtained by melting, blending and forming the mixture consisting of thermoplastic resin having the degree of crystallinity of 10% or more of 20 to 90% by weight and flaky fillers of 10 to 80% by weight, to orientate a part of crystals after it was melted at the melting point of said sheet-like materials and then recrystallizing the melted crystals under the rolled condition.

Tough thermoplastic resin sheet-like material

A diaphragm for an electro-acoustic transducer comprising a sheet formed from a mixture of a polymer and mica, where the sheet contains (a) 30 to 95% by weight of a polymer selected from among polyolefins, polyesters, and polyamides and (b) 5 to 70% by weight of mica having a weight-average flake diameter not exceeding 500 microns and a weight-average aspect ratio of at least 10. By adding the specified mica, the sheet has a drastically improved dynamic modulus and a substantially unchanged loss tangent.

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Okayama, Japan

Kiyonobu Fujii