Mitsubishi Chemical Industries Limited

Diafoil Company, Ltd.

Michio Nakata

Seiichi Nozawa

Shigeo Utsumi

A heat-resistant film or sheet produced by melt extruding polyether ketone having an intrinsic viscosity of at least 0.4 dl/g, which is obtained by heat treating an unstretched film or sheet which comprises (i) heat-treating to crystallization being not more than 60%, or (ii) uni- or biaxially stretching under specific conditions to an extent in which a stress at 5% elongation in the stretched direction is at least 13 kg/mm.sup.2 ; an initial elastic modulus in the stretched direction is at least 600 kg/mm.sup.2 ; and thermal shrinkages in a lengthwise direction and its vertical direction are not more than 4%. The film or sheet of the present invention is excellent in such properties as heat resistance, mechanical strength and the like, and is suitable for use as a substrate for magnetic recording or electric insulation.

Heat-resistant film or sheet

A process for producing aromatic polyether ketones and polythioether ketones, which comprises reacting aromatic ethers or thioethers represented by the general formula: ##STR1## where each of R.sup.1 to R.sup.12 is a hydrogen atom, a halogen atom, a hydrocarbon group or an alkoxy group, n is an integer of 0 to 5, and X is an oxygen atom or a sulfur atom, with phosgene in aprotic solvent having a dielectric constant of lower than 20 and a dipole moment of lower than 3.0 in the presence of anhydrous halides of metals of Group III in the periodic table as a catalyst.

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Kanagawa, Japan

Michio Nakata