Unitika Ltd.

Osaka Gas Company Limited

Yoshiaki Iwaya

Yoshiaki Echigo

Keiichi Asami

Isao Tomioka

Hiroshi Yamada

Akira Ito

Yoshiteru Nakagawa

Shoji Okamoto

Hiroyuki Tajiri

Hiroshi Kajimaru

Minoru Saito

Katsuyuki Mukai

Kiyotaka Nakanishi

Minoru Nishinohara

Katsuyuki Touma

Masatoshi Kawanishi

Shinji Okumura

Yoshiharu Tanaka

A PTC element comprising a conductive sheet of a crystalline polyolefin matrix and a conductive filler, having provided on both sides thereof an electrode of a metallic foil, the PTC element having a resistivity at 20.degree. C. (.rho..sub.20) of not more than 1.8 .OMEGA..multidot.cm, a peak resistivity (.rho..sub.p) of not less than 2.0.times.10.sup.6 .OMEGA..multidot.cm, and a temperature difference �T.sub.a (0.degree.C.)-T.sub.b (.degree.C.)! of not greater than 10.degree. C., wherein T.sub.a (.degree.C.) is a temperature at which the resistivity is 10.sup.6 times the resistivity at 20.degree. C. (.rho..sub.20) and T.sub.b (.degree.C.) is a temperature at which the resistivity is 10 times the resistivity at 20.degree. C. (.rho..sub.20). The PTC element is produced by a process comprising mixing a crystalline polyolefin and a conductive filler, molding the mixture into a conductive sheet, press bonding under heat a metallic foil to both sides of the conductive sheet, and repeatedly subjecting the conductive sheet to a heating and cooling cycle consisting of heating at a temperature of not lower than (the melting point of the crystalline polyolefin minus 5.degree. C.) and then cooling to a temperature lower than (the melting point of the crystalline polyolefin minus 5.degree. C.). The PTC elements exhibit an extremely low resistivity at 20.degree. C. and a high resistivity at a peak temperature, showing a very steep increase in resistance in a narrow temperature range.

PTC element and process for producing the same

Fiber-reinforced porous plastic tube

This invention provides a poly(amic acid) solution which does not contain aprotic polar solvents such as DMF, NMP, DMAc, DMSO, as well as a polyimide film obtained therefrom having appropriate flexibility and a small coefficient of linear thermal expansion and a coated material in which the polyimide film is formed on a substrate. More particularly, it provides a poly(amic acid) solution which has an aromatic poly(amic acid) and a tertiary amine as the solute and a water soluble alcohol compound and/or a water soluble ether compound as the solvent and contains substantially no aprotic polar solvent, as well as a polyimide film obtained from the poly(amic acid) solution and a coated material obtained by forming the film on a substrate.

Poly(amic acid) solution and polyimide film or polymide-coated material

A slurry containing a precursor fiber convertible to carbon fiber and/or a carbon fiber and, based on 100 parts by weight of the fiber, 10 to 300 parts by weight of a thermosetting resin, e.g. phenol resin, is processed into a random web. This web may contain a pitch or an organic granular material. The web is hot-pressed between a pair of belts while curing of the resin is inhibited to prepare a prepreg sheet. This sheet is disposed, leaving a clearance, in a mold having ribs on a molding surface and heated over the melting point of the resin for expansion and complete cure to provide a porous composite sheet equipped with grooves. This porous composite sheet is carbonized or graphitized to produce a porous carbonaceous material for use as a fuel cell electrode material and so on. This porous carbonaceous material has high homogeneity, gas permeability, electrical conductivity, heat conductivity and mechanical strength.

Porous carbonaceous material and a method for producing the same

A film forming solution which does not require aprotic polar solvents, a porous film of poly(4,4'-oxydiphenylenepyromellitimide) obtained from the film forming solution which has excellent heat and chemical resistances, which is controllable in terms of porosity and pore size of the film and which has excellent electrical characteristics, and a coated material where the porous film is formed on a base material. Particularly, a film forming solution of a precursor of poly(4,4'-oxydiphenylenepyromellitimide) and a mixture of at least three solvents which are poor solvents for the precursor when each solvent is used alone, a porous film of poly(4,4'-oxydiphenylenepyromellitimide) obtained from the film forming solution and a coated material where the porous film is formed on a base material.

Film forming solution, porous film obtained therefrom and coated

Aliphatic polyesters and method of preparing the same

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Kyoto, Japan

Yoshiaki Iwaya