Polyurethane filaments, generically known as spandex, have become important commercially, and have become increasingly important recently in applications utilizing fine deniers, 70 denier or less. In the commercial production, for example by wet spinning, of polyurethane filaments a commercial unit has greater productivity by weight when it is used to produce a heaver denier such as one of 420 denier rather than when it is used to produce a finer denier, 70 denier or less. Also, mechanical handling of the finer deniers, because of their lightness, is more difficult, both as to handling by textile operators and otherwise in their transportation through the process, for example through a dryer. In addition, the energy requirements to operate a spinning line are substantially the same irrespective of the denier produced. As a result the cost per unit weight to produce a fine denier is higher than for a heavier denier.
USPTO Backgrounds
USPTO Backgrounds