| 摘要 |
PURPOSE:To obtain a density gradient type nonwoven fabric filter material which has excellent strength and of which the filter material passing apparent velocity is almost same to that of filter paper, by using a spun bond type fiber aggregate comprising a hydrophobic thermoplastic fiber having high rigidity and a hydrophilic fiber aggregate. CONSTITUTION:As the base cloth fiber layer forming the upper layer 1 in an air inflow side, a spun bond type fiber layer comprising a polypropylene or polyester fiber with a fiber diameter of 0.7-3 denier, a void ratio of about 88% and a basis wt. of 25g/cm<2> is used. The fiber layer forming an intermediate layer 2 comprises a fiber mixture layer with a basis wt. of 40g/cm<2> consisting of 50wt% of a rayon fiber with a fiber diameter of 1 denier, 35wt% of a polyester fiber with a fiber diameter of 1.25 denier and the remainder of a polyolefine fiber with a fiber diameter of 1.5 denier and, as a lower layer, a fiber mixture layer with a basis wt. of 50g/cm<2> consisting of 50wt% of a rayon fiber with a fiber diameter of 1 denier and the remainder of a polyester fiber with a fiber diameter of 1.25 denier is used. These layers are bonded by a needle punching method and impregnated with a binder.
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