PURPOSE: To form an electret sheet having high surface charge density in spite of a formed resin article and to obtain a filter having low pressure drop and high collection efficiency by using the sheet as the substrate.
CONSTITUTION: A resin composition is produced by compounding a chlorinated polyolefin resin having a chlorine content of ≥50wt.% with ≥0.1wt.% of a functional agent consisting of at least one substance selected from antibacterial agent, antifungal agent, deodorant, perfumery, colorant, insecticide, water- repellent, ultraviolet absorber and heat stabilizer, e.g. a combination of an antibacterial agent and an antifungal agent. The above resin composition is applied by spraying, coating or impregnation to a composite sheet produced by laminating two or more layers of melt-blown polypropylene sheet having a bending resistance of ≥15cm measured by 45°C cantilever method or laminating a cloth to the above melt-blown sheet and the applied resin is dried. The amount of the resin composition is 0.3-10wt.% based on the weight of the fiber. The dried product is subjected to an electret-forming treatment to obtain an electret sheet having a surface charge density of ≥1×10-10 coulomb/cm2.
HIRAIWA SHOGO
TAKI TAKAKAZU
