| 摘要 |
PROBLEM TO BE SOLVED: To improve the trapping efficiency for dust of a filter medium while maintaining the aerating property and flame-retardant property by forming a coarse layer consisting of hot-melt fibers, crimped fibers or the like containing a flame-retarded resin by a specified proportion, forming a dense layer consisting of hot-melt fibers and other fibers by a specified proportion to incorporate a flame-retarded resin and a fire retardant. SOLUTION: In a filter consisting of a coarse layer and a dense layer, the coarse layer consists of 5-30wt.% hot-melt fibers, 10-70wt.% crimped fiber and 0-85wt.% of other fibers. This layer contains 40-180 pts.wt. of a flame-retarded resin based on 100 pts.wt. of the whole fibers. The dense layer consists of 5-30 pts.wt. of hot-melt fibers and 70-95 pts.wt. of other fibers and contains 0.5-20 pts.wt. of a flame-retarded resin and 5-35 pts.wt. of a fire retardant based on 100 pts.wt. of the whole fibers. In this filter, the max. pore diameter and the average pore diameter of the coarse layer are specified to 40-110μm and 35-80μm, respectively. The max. pore diameter and the average pore diameter of the dense layer are specified to 15-50μm and 4-35μm, respectively.
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