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AssigneesCompagnie Francaise de Raffinage, Groupement Europeen de la Cellulose
InventorsJoseph Aboulafia, Richard Le Fustec, Claude Schranz
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A process and apparatus for manufacturing polyolefin fibers from a composition of the said polyolefins dissolved in a diluent, by subjecting the composition to flow at a velocity above a critical value in a tube or bundle of tubes, the temperature of the composition being within the range of critical temperatures of the said composition over at least a portion of the length of the tube or bundle of tubes and separating the fibers from the liquid diluent. The critical temperature range is below the temperature of solution of the polyolefin in the molten state in a diluent and is more specifically the range of temperatures in which the polyolefin remains in dissolved condition when the solution mixture is maintained at rest but precipitates when the mixture is subjected to certain disturbances such as, for instance, shearing. This typically is between 70.degree. and 130.degree. C. The lower limits of the critical velocity and the critical temperature are determined by the appearance of undesired powder co-precipitating with the fibers. In a variation the composition contains fibrous material (e.g. cellulose) insoluble in the diluent, yielding an interlaced fiber mix (useful in paper making, among other things). In a further improvement to avoid formation of "nodules" (i.e. random agglomerations of fibers), said tube(s) is provided with at least one restriction decreasing the cross-section of the tube(s); e.g. by a diaphragm, conical nozzle, very short inner tube, etc.
A process for manufacturing polyethylene or polypropylene fibers from a composition of said polyolefin dissolved in a diluent, which is cyclohexane, hexane, pentane, heptane, or mixtures thereof, at a concentration of about 1 to about 5% by weight, which fibers generally have a length of between 0.1 mm and 2 cm and a diameter of bundles of such fibers of between 5 .mu. and 200 .mu., comprising flowing said composition through at least one elongated zone circumscribed by a stationery boundary having a length of about 40 cm to about 10 m and a diameter of about 1.5 mm to about 4 mm, said composition being brought down to a temperature range such that while in said zone said range is below the temperature of solution of said polyolefin in the molten state and within, but not below, the range of critical temperatures in which said polyolefin would remain dissolved under the given conditions and with the composition at rest but precipitates when subjected to shear;
Dependencies are inferred from the claim text.