Process for laying fibrous webs from a centrifugal spinning process
View Patent ↗A method for laying down a nanoweb of nanofibers from a centrifugal spinning process by a combination of an air flow field and a charging arrangement. Fibrous streams in the form of fibrils of molten polymer or polymer solution are discharged from a rotating member into an air flow field that is essentially parallel to the direction of discharge of fibrils at the point of discharge of the fibrils. The fibrous streams are attenuated and directed by means of the air flow field onto the surface of a collector to form a nanoweb. The fibrous streams are charged along all or at least a portion of their route from the point of discharge to the surface of the collector.
1. A method for laying down a nanoweb from a centrifugal spinning process comprising the steps of:
(i) ejecting a polymer melt in air or an inert gas from a surface of a rotating member comprising a disk or cup rotating about an axis and located in a spinning head, wherein molten fibrils exit the surface in a direction essentially perpendicular to the axis of rotation of the disc or cup and into an electric field established between a fiber collector and the spinning head; and wherein the fibrils are attenuated by the centrifugal force and cool to form nanofibers that have a number average fiber diameter of less than 1,000 nm;
(ii) applying a charge to the polymer melt, the molten fibrils, the nanofibers, or any combination of these three locations;
(iii) directing the nanofibers with a shaping air flow towards a collector that has a charge opposite to the charge on the fibers in (ii) above;
(iv) collecting the polymeric nanofibers on the collector;
wherein turbulent motion of air located between the spinning head and the collector is suppressed by air jets supplied by nozzles located on the underside of the rotating member, on the surface facing the collector, and wherein a region exists adjacent to and touching the collector where the motion of the fibers is governed by the potential difference between the nanofibers and the collector and is unaffected by the shaping air flow.