| abstract |
Disclosed is a melt-blowing process for producing a fiber of an extrudable polyurethane having a large amount of hard segment, which comprises supplying a polyurethane comprising the reaction product of: (a) an organic polyisocyanate; (b) an isocyanate-reactive material having an average functionality of at least 1.9, a glass transition temperature (Tg) of less than 20 DEG C., and a molecular weight in the range of 500 to 20,000; and (c) at least one chain extender having a functionality from 2 to 3 and a molecular weight from 50 to 400; which reaction product has up to 25 percent by weight of soft segment derived from the organic polyisocyanate (a) and the isocyanate-reactive material (b) and at least 75 percent by weight of hard segment derived from the organic polyisocyanate (a) and the chain extender (c), in a molten form from at least one orifice of a nozzle into a gas stream supplied to an area adjacent to the orifice which attenuates the molten polymer into fibers. Such microfibers are particularly useful in the field of high temperature filtration, coalescing and insulation. |