Patent ID: 8636942

Claim:
A process for production of a nonwoven fabric, which comprises a step wherein a thermoplastic polymer is dissolved in a mixed solvent composed of a volatile good solvent for the polymer and a volatile poor solvent for the polymer, a step wherein the resulting solution is spun by an electrospinning method and a step wherein a nonwoven fabric accumulated on a collecting sheet is obtained, which process yields a nonwoven fabric with a mean fiber size of 0.1-20 μm, wherein the nonwoven fabric is an aggregate of filaments and any given lateral cross-section of said filaments is irregular, and a mean apparent density in the range of 10-95 kg/m 3 , wherein the irregular shape is at least one selected from the group consisting of 0.1-1 μm pits on filament surfaces, 0.1-1 μm protrusions on filament surfaces, pits formed in a linear fashion in the fiber axis direction on filament surfaces, protrusions formed in a linear fashion in the fiber axis direction on filament surfaces and micropores in filament surfaces, formed either alone or present in combinations so long as any given lateral cross-section is irregular, the thermoplastic polymer is polylactic acid or poly(lactic-co-glycolic acid), the volatile good solvent for the polymer is methylene chloride, and the volatile poor solvent for the polymer is ethanol, methanol, isopropanol, acetone, or acetonitrile, wherein the ratio of the volatile poor solvent for the polymer and volatile good solvent for the polymer in said mixed solvent is in the range of (23:77) to (40:60), based on weight.