Abstract: The method of producing an islands-in-sea type composite spun fiber having an island component diameter of 1 ?m or less according to the present invention comprises drawing (superdrawing) with a total draw ratio of from 5 to 100 an undrawn islands-in-sea type composite spun fiber having been prepared by spinning at a spinning speed of from 100 to 1,000 m/min, at temperatures higher than the glass transition points of both the polymer forming the sea component and the polymer forming the island components of the composite spun fiber.

Abstract: The method of producing an islands-in-sea type composite spun fiber having an island component diameter of 1 ?m or less according to the present invention comprises drawing (superdrawing) with a total draw ratio of from 5 to 100 an undrawn islands-in-sea type composite spun fiber having been prepared by spinning at a spinning speed of from 100 to 1,000 m/min, at temperatures higher than the glass transition points of both the polymer forming the sea component and the polymer forming the island components of the composite spun fiber.

Abstract: A paper-like polyester sheet having an enhanced filtering property, an excellent mechanical strength and satisfactory touch and appearance, comprises polyester staple fibers and has a coefficient of air flow resistance of 1,000 to 50,000 dyn.s/cm.sup.4 at a volume fraction of the fibers of from 0.01 to 0.24.

Abstract: Polyester binder fibers consisting of a water-dispersible copolymerized polyester, comprising at least one dicarboxylic acid and/or an esterforming derivative thereof, a glycol and an esterforming sulfonic acid alkali metal salt composition, wherein the total glycol component contained in the above mentioned polyester contains from 5 mole percent to 20 mole percent of a composition represented by the formula H--(OCH.sub.2 CH.sub.2).sub.n --OH, wherein n is an integer of from 2 to 13. The binder fibers are useful especially in a papermaking process.