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US 4,728,472 AGranted
Cellular fibers via soluble fluid injection
AssigneeE. I. Du Pont de Nemours and Company
InventorWilliam T. Windley
Life of this patent
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Abstract
A fiber having 1/2-50% substantially gas-filled and essentially all closed cells having a diameter of 0.2-25 microns and a length to diameter ratio of greater than 500 is disclosed. The fiber is made by mixing a fluorocarbon blowing agent into molten polymer, shearing the polymer at a high shear rate, extruding the polymer in a spinneret capillary at a low jet velocity and a low capillary entrance pressure and drawing down the polymer at a total extension greater than 1000.
Claims14
A process for making a fiber with cells comprising the steps of:
- (a) mixing a fluorocarbon blowing agent into molten polymer and shearing the molten polymer at greater than about 8,000 reciprocal seconds;
- thereafter
- (b) extruding the molten polymer through a spinneret capillary at a jet velocity of 5-150 cm/min. and a differential capillary pressure of less than 0.5 kg/cm.sup.2 resulting in substantial development of voids within the polymer internally of the spinneret;
- and
- (c) drawing down the polymer extrudate at a total extension of greater than 1000.
2 more elements
Dependencies are inferred from the claim text.