SEPARATOR FOR ALUMINUM ELECTROLYTIC CAPACITOR AND ALUMINUM ELECTROLYTIC CAPACITOR

A separator which is capable of reducing ESR and improving electrostatic capacity while maintaining high short-circuit resistance, a solid electrolytic capacitor using the separator, and a hybrid electrolytic capacitor. To achieve this, the present invention has, for example, the following configuration. This separator which is to be used in an aluminum electrolytic capacitor and which is interposed between a pair of electrodes of a capacitor is such that the separator contains synthetic fiber, for example, polyamide fiber and/or fibrillated polyamide fiber, the droplet elimination times for one surface and for the opposite surface are 10-350 seconds, the ratio of the droplet elimination times is 1.0-2.0, the airtightness is 10-350 sec./100 ml, and the average pore size is 0.1-15.0 μm. Furthermore, the separator is characterized in that the synthetic fiber contains 20-80 mass % of fibrillated polyamide fiber and 20-80 mass % of fibrillated natural cellulose fiber.