Mitsubishi Rayon Company, Limited

Mitsubishi Chemical Corporation

Yoshihiro Sako

Kazuhiro Sumioka

Jun Nakauchi

Yoshitaka Kageyama

Keiichi Sakashita

Seiji Hayashi

Tetsuya Ikemoto

Shigeru Tanoue

Kenji Mori

Shunsuke Minami

Mioko Uematsu

Provided is a porous electrode substrate having excellent thickness precision, gas permeability and conductivity, handling efficiency, low production costs and a high carbonization rate during carbonization. Also provided are a method for manufacturing such a substrate, a precursor sheet and fibrillar fiber used for forming such a substrate, along with a membrane electrode assembly and a polymer electrolyte fuel cell that contain such a substrate. The method for manufacturing a porous electrode substrate includes step (1) for manufacturing a precursor sheet in which short carbon fibers (A) and carbon fiber precursor (b) are dispersed, and step (2) for carbonizing the precursor sheet, and the volume contraction rate of carbon fiber precursor (b) in step (2) is 83% or lower. The present invention also relates to a porous electrode substrate obtained by such a manufacturing method, a precursor sheet and fibrillar fiber used for forming the substrate, along with a membrane electrode assembly and a polymer electrolyte fuel cell containing the substrate.

Porous electrode substrate, method for manufacturing same, membrane electrode assembly, polymer electrolyte fuel cell, precursor sheet, and fibrillar fibers

A process of producing a porous electrode substrate, including: dispersing first short carbon fibers and producing a first precursor sheet not having a three-dimensional entangled structure of the first short carbon fibers; treating the first precursor sheet such that the first short carbon fibers in the first precursor sheet are entangled and that a second precursor sheet having a three-dimensional entangled structure of the first short carbon fibers is obtained; dispersing second short carbon fibers on the second precursor sheet such that a porous electrode precursor sheet including the second precursor sheet and a third precursor sheet not having a three-dimensional entangled structure of the second short carbon fibers and stacked on the second precursor sheet is obtained; and carbonization treating the porous electrode substrate precursor sheet at a temperature of at least 1000&#xb0; C. to obtain the porous electrode substrate.

Porous electrode substrate and process for production thereof, porous electrode substrate precursor sheet, membrane-electrode assembly, and polymer electrolyte fuel cell

The provision of a porous electrode substrate that has large sheet strength, low production costs, high handling properties, high thickness precision and surface smoothness, and sufficient gas permeability and electrical conductivity. A porous electrode substrate including a three-dimensional entangled structure including short carbon fibers (A) dispersed in a three-dimensional structure, joined together via three-dimensional mesh-like carbon fibers (B). A method for producing a porous electrode substrate, including a step (1) of producing a precursor sheet including short carbon fibers (A), and short carbon fiber precursors (b) and/or fibrillar carbon fiber precursors (b') dispersed in a two-dimensional plane; a step (2) of subjecting the precursor sheet to entanglement treatment; and a step (3) of subjecting this sheet to carbonization treatment at 1000&#xb0; C. or higher. It is preferable to include a step (4) of subjecting the sheet to hot press forming at lower than 200&#xb0; C. between step (2) and step 3), and to further include a step (5) of subjecting the sheet after hot press forming to oxidation treatment at 200&#xb0; C. or higher and lower than 300&#xb0; C. between step (4) and step (3).

Porous electrode substrate, method for producing the same, precursor sheet, membrane electrode assembly, and polymer electrolyte fuel cell

Provided are: a porous electrode substrate which has excellent handling properties and surface smoothness and satisfactory gas permeability and electrical conductivity, and enables the reduction of damage to a polymer electrolyte membrane when integrated into a fuel cell; and a process for producing the porous electrode substrate. Specifically provided are: a porous electrode substrate comprising a three-dimensional structure (Y-) produced by bonding short carbon fibers through carbon and a three-dimensional structure (Y-) produced by bonding short carbon fibers through carbon, wherein the three-dimensional structures (Y-) and (Y-) are layer stacked on and integrated with each other, the short carbon fibers form a three-dimensional entangled structure in the structure (Y-), and the short carbon fibers do not form a three-dimensional entangled structure in the structure (Y-); a process for producing the electrode base material; a precursor sheet for producing the electrode base material; a membrane-electrode assembly which involves the electrode base material; and a polymer electrolyte fuel cell.

Provided is a porous electrode substrate having high mechanical strength, good handling properties, high thickness precision, little undulation, and adequate gas permeability and conductivity. Also provided is a method for producing a porous electrode substrate at low costs. A porous electrode substrate is produced by joining short carbon fibers (A) via mesh-like of carbon fibers (B) having an average diameter of 4 &#x3bc;m or smaller. Further provided are a membrane-electrode assembly and a polymer electrolyte fuel cell that use this porous electrode membrane. A porous electrode substrate is obtained by subjecting a precursor sheet, in which short carbon fibers (A) and short carbon fiber precursors (b) having an average diameter of 5 &#x3bc;m or smaller have been dispersed, to carbonization treatment after optional hot press forming and optional oxidization treatment.

Porous electrode substrate, method for producing the same, membrane electrode assembly, and polymer electrolyte fuel cell

The present invention provides a porous electrode substrate that has low production cost, high mechanical strength, thickness precision, and surface smoothness, and sufficient gas permeability and electrical conductivity, and a method for producing the same. In the present invention, for example, a porous electrode substrate that includes short carbon fibers (A) joined together via three-dimensional mesh-like carbon fibers (B) is produced by a method including a step (1) of dispersing short carbon fibers (A), and short carbon fiber precursors (b) to be fibrillated by beating, to produce a precursor sheet; and a step (2) of subjecting the precursor sheet to carbonization treatment at a temperature of 1000&#xb0; C. or higher.

Porous electrode substrate and method for producing the same

An optically active compound represented by the formula: ##STR1##

Optical active compound and liquid crystal composition

Disclosed is an optically active substance represented by the formula: ##STR1## wherein m is an integer of 1 to 14, Y is ##STR2## R is --C.sub.n H.sub.2n+1, --OC.sub.n H.sub.2n+1, --OCOC.sub.n H.sub.2n+1 or --COOC.sub.n H.sub.2n+1 (in which n is an integer of 1 to 18), each of the asterisked carbon atoms is an asymmetric carbon atom, X a single bond, --CO.sub.2 --, or --OCO--, and A.sub.1 and A.sub.2 is hydrogen, fluorine, chlorine, bromine, cyano or methoxy.

Optically active substance and liquid crystal composition comprising same

Disclosed is an .alpha.-methylcinnamic acid ester derivative represented by the formula: ##STR1## wherein n is an integer of from 5 to 18, R.sub.1 represents an optically active group of the formula ##STR2## in which m is an integer of from 1 to 5 and *C represents an asymmetric carbon atom, and R.sub.2 represents ##STR3##

Growing community of inventors

Hiroshima, Japan

Yoshihiro Sako