Patent ID: 8747796

Claim:
A method of preparing a carbon substrate for a gas diffusion layer of a polymer electrolyte type fuel cell, the method comprising: forming an oxidized carbon precursor fiber preweb comprising oxidized carbon precursor staple fibers and binder staple fibers; impregnating the oxidized carbon precursor fiber preweb with a slurry including a thermosetting resin and carbonaceous fillers and drying the resulting preweb to obtain an oxidized carbon precursor fiber web; applying heat and pressure to the oxidized carbon precursor fiber web, which has been impregnated with the thermosetting resin and the carbonaceous fillers, to cure the thermosetting resin and press the oxidized carbon precursor fiber web; a carbonization process including heating the oxidized carbon precursor fiber web in an inert atmosphere, thereby stabilizing and carbonizing the oxidized carbon precursor staple fibers to obtain a carbon substrate wherein the step of forming an oxidized carbon precursor fiber preweb comprises: uniformly mixing and loosening lumps of oxidized carbon precursor stale fibers and the lumps of binder staple fibers, and disentangling them; arranging the oxidized carbon precursor staple fibers and the binder staple fibers in parallel and collecting them to form the oxidized carbon precursor fiber preweb in a sheet shape; stacking the oxidized carbon precursor fiber preweb into a plurality of layers to obtain an oxidized carbon precursor fiber preweb with a desired weight; bonding the oxidized carbon precursor staple fibers and the binder staple fibers by allowing them to be mechanically entangled with eachother by needle-punching to bind the oxidized carbon precursor fiber preweb; heat-pressing the oxidized carbon precursor fiber preweb thus-bound by calendaring the preweb; winding the oxidized carbon precursor fiber preweb.