A polyester with ultra-high flowability and good stability over time is provided. The polyester can be polybutylene terephthalate (PBT) or another aliphatic polyester, whose intrinsic viscosity (IV) is less than 0.6 dL/g and a carboxylic end group (CEG) content is 15 meq/kg or less, and characterized by having a melt volume rate (MVR) of greater than 400 cm3/10 min at 250° C. A resin composition of this polyester is provided, which can be meltblown into microfibers of a uniform diameter and a concentrated diameter distribution, forming a fabric with a uniform small pore size.
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