Patent ID: 7468335

Claim:
A meltblown web comprising interbonded fibers extruded through a die with multiple orifices and attenuated by gas at a predetermined velocity to an average draw ratio of above 50, up to 250, said fibers including a thermoplastic polyester poly (butylene terephthalate) based copolymer which comprises: A) an aromatic dicarboxylic acid component or derivative thereof, which is selected from group consisting of terephthalic acid and its derivatives; and B) at least two diol components, including: i) 60-99 mol percent diol component of butanediol; and ii) 1-40 mol percent diol component of at least one additional aliphatic diol component selected from the group consisting of C 4 -C 12 aliphatic branched diols, cycloaliphatic diol compounds having from 6-20 carbon atoms in the cyclic moiety, and combinations thereof, with the proviso that if 1,4-cylcohexane dimethanol is used as the cycloaliphatic diol, it is used in combination with another cyclic or branched diol, wherein the copolymer composition is selected and formation of the meltblown web is controlled such that the melt-blown web exhibits at least one of the following attributes: 1) a machine direction (MD) strength index in the range of from 3 to 15; 2) an MD/CD tensile strength ratio in the range of from 0.5 to 1.5; or 3) a mean fiber diameter in the range of from 0.5 to 3.0 μm.