DEPTH FILTER

PROBLEM TO BE SOLVED: To provide a depth filter which has a low pressure loss, a long filtration life, and further has a small maximum passage particle diameter.SOLUTION: A depth filter comprising a filter medium which is formed into a cylindrical shape by winding of a fiber sheet. The filter medium includes at least two layers of a pre-filtration layer and a precision filtration layer, and the pre-filtration layer and the precision filtration layer are joined in this order with respect to a filtration direction. The pre-filtration layer is made of a melt-blown non-woven fabric, and the precision filtration layer includes a fine fiber layer. The fine fiber layer comprises fibers each containing a resin which can be spined by electrical field spinning method and having a fiber diameter of at least 20 nm and less than 1000 nm, and a thickness of the filter medium is 5 mm or more.SELECTED DRAWING: None 【課題】 圧力損失が低く、濾過寿命が長く、さらに最大通過粒径が小さいデプスフィルターを提供すること。【解決手段】 繊維シートが巻回されて円筒状に形成された濾材からなり、該濾材は、前濾過層および精密濾過層の少なくとも２層を含み、濾過方向に対して、前濾過層、精密濾過層の順に接合されており、該前濾過層は、メルトブロー不織布であり、該精密濾過層は、微細繊維層を含み、該微細繊維層は、電界紡糸法で紡糸可能な樹脂を含有する２０ｎｍ以上、１０００ｎｍ未満の繊維径を有する繊維であり、濾材の厚みが５ｍｍ以上であるデプスフィルターによる。【選択図】なし