PROCESS FOR PRODUCING AN ELECTRET, A FILM ELECTRET, AND AN ELECTRET FILTER

摘要

The improved process fro producing an electret includes the step of alternating continuously at least two cycles of applying electric charges to an article of interest and subsequently heating said article. This process may be applied to a drawn or undrawn film to produce a film electret, or it may be applied to a woven or nonwoven fabric to produce a sheet of fiber electret. Also disclosed are a film electret that contains a polar high-molecular weight compound and that provides a TSDC curve having a homocharge peak temperature of at least 95.degree.C and a heterocharge peak temperature of at least 80.degree.C, as well as an electret filter composed of fibers that are obtained by fibrillating said film of resin electret.