NONWOVEN FABRIC FOR AN ALKALINE BATTERY SEPARATOR AND METHOD FOR PRODUCING THE SAME

摘要

A nonwoven fabric for an alkaline battery separator that can prevent the movement of active substances while it has a small weight per unit area and which has superior absorbency for electrolyte and liquid retaining properties under pressure and a method for producing the same. The nonwoven fabric is characterized in that it has substantially no through holes and that the average surface roughness at least the central surface of the nonwoven fabric is 13 mu m with a maximun pore size being 50 mu m or less and a pressurized liquid absorbency being 20 g/m<2> or less. In addition, the nonwoven fabric is characterized in that the standard deviation of pore size distribution measured by using a bubble-point method is 20 mu m or less and that pores whose pore sizes are within an average pore size +/- 2 mu m accounts for 35 % or more of the total pores. Furthermore, the same nonwoven fabric is characterized in that the peak area ratio of oxygen element to carbonelement measured at the surface of the nonwoven fabric and an intermediate position in a thicknesswise direction by using the electron spectroscopy for chemical analysis (ESCA) are 0.50 to 1.85 and 0.45 to 1.40, respectively. A method for producing the nonwoven fabric comprises the steps of water-flow-interlacing a web of polyolefine fiber formed by a wet type paper manufacturing or the like by using a columnar water flow jet nozzle having a shape in which a water injecting port is larger than a water inlet port and disposed in an injector of a water flow interlacing device, corona-discharging the interlaced web by using a multi-electrode whose leading end shape is round and thereafter calender finishing the discharged web.