| 摘要 |
PURPOSE:To obtain a filter improved in filtration efficiency by superposing nonwoven fabric having low fiber density on filter paper having high density to form a layer and positioning nonwoven fabric on the inflow side of liquid to be treated. CONSTITUTION:A filter medium 1 is formed into a layer by superposing nonwoven fabric 5 on filter paper 2. In the filter paper 2, fine pores 4 are formed in a base material 3 and the fiber density of filter paper 2 is set comparatively high. On the other hand, in the nonwoven fabric 5, the fiber density is set comparatively low and the whole cross section forms a network. The filter medium 1 is arranged so that nonwoven fabric 5 is positioned on the upstream side of fluid to be filtered and filter paper 2 is positioned on the downstream side. Therefore, this filter medium forms a gradient density type filter medium in which the density is changed from sparse to dense toward the downstream side from the upstream side of the flow of liquid to be filtered and an excellent dust cake layer can be formed. |
