| abstract |
Heat-resistant aromatic polyester filaments having heretofore unknown physical properties and a combination of excellent heat resistance and mechanical strength, which (1) is composed of an aromatic polyester in which at least 90 mole % of the structural units are ethylene-2,6-naphthalate units, (2) has a melting point at a constant length (Tm; DEG C.) of at least 287 DEG C., (3) has a density (d)(g/cm3) of at least 1.370, (4) is insoluble in a phenol/orthodichlorobenzene mixed solvent (mixing ratio = 6/4 on the weight basis) at 160 DEG C. and (5) meets the requirements expressed by the following formulae L(Tm - 280) = 400 (I) DELTA n(d - 1.350) = 70 x 10<->3 (II) L = lambda K/(B-b)cos theta (III) and the process for the preparation thereof. |