| 摘要 |
PURPOSE:To form in high productivity a highly heat-resistant, stiff filter having backwashable cell structure by imparting wavy shape on nonwoven fabric or felt consisting of specific polyimide fibers through preheating, molding and cooling processes followed by cutting and jointing. CONSTITUTION:Nonwoven fabric or felt consisting of highly heatresistant polyimide fibers made up of recurring unit of the formula is introduced into a preheating chamber where said fabric or felt is preheated with a preheating caterpillar-type mold; the fabric or felt is then conveyed into a hot molding chamber where it is imparted, laterally or longitudinally, with wavy form periodically differing in height at regular intervals using a hot molding caterpillar-type mold, and then introduced into a cooling chamber where it is cooled with a cooling caterpillar-type mold; the resultant fabric or felt is cut to a specified dimension, thus obtaining the objective air-permeable wavy-surfaced polyimide fibrous molded form 0.5-1g/cm<2>. These molded forms are then mutually laminated to form a self-standing, stiff, wavy-surfaced filter of specified design. By the way, grooved rolls may be used in place of the above-mentioned respective caterpillar-type molds. |
