| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a filter material suitable as a filter for toner correction capable of satisfying flame retardant standards though a harmless flame retarder is used without deterioration in its filtering performance. <P>SOLUTION: A nonwoven fabric layer 2 on the upstream side composed of an upper layer 3 and an intermediate layer 4 and also having a fiber density gradient is composed of a heat-fusible fiber with a core-sheath structure using a PP (polypropylene) fiber subjected to flame retardant treatment with a phosphorous or nitrogen based flame retarder as a core and PE (polyethylene) as a sheath part. On the other hand, the lower layer 5 as a nonwoven fabric layer on the downstream side is composed of a heat-fusible fiber with a core-sheath structure using a PET fiber as a core and PE as a sheath part. The respective layers 3, 4, 5 are laminated and integrated with the heat fusion of the heat fusible fibers, to form a filter material 1. Further, the whole of the filter material 1 is subjected to electret treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT |
