Bayer Aktiengesellschaft

Hans K Burghartz

Ulrich Reinehr

Toni Herbertz

Hermann-Josef Jungverdorben

Kurt Bernklau

Rolf-Burkhard Hirsch

Norbert Rink

Joachim Dross

Christian Pieper

A process for the production of acrylonitrile fibers and filaments having a precise cross-sectional profile in which filament-forming synthetic polymers are dry-spun from a solution having a viscosity of at least 120 falling bass seconds, measured at 80.degree. C., or a viscosity of at least 75 falling ball seconds, measured at 100.degree. C. Such solution is dry-spun through one or more nozzles. The nozzle hole are of the profile nozzles being less than 0.2 mm.sup.2 and the lateral width being less than 0.17 mm.

Processes for the production of dry-spun polyacrylonitrile profiled

Extraordinarily low ranges of error, with respect to yarn adhesion and uniformity, in dry spinning yarns are achieved when the spinning gas in the upper part of the shaft blasts the yarns radially from the inside to the outside in an apparatus designed for this purpose, the velocity of the radial flow of gas, dirctly below the spinning nozzle, transverse to the running direction of the yarns and within a spacing of 10 mm from the nozzle, increasing from 0 to at least from 0.2 to 1 m/s.

Process for dry spinning yarns of improved uniformity and reduced

Hollow acrylonitrile fibres and filaments are prepared by dry spinning the spinning dope through a nozzle having loop-shaped nozzle orifices, the solution having a viscosity equivalent to at least 120 falling ball seconds, measured at 80.degree. C., or at least 75 falling ball seconds, measured at 100.degree. C., wherein the nozzle orifice area of the profiling nozzle is smaller than 0.2 mm.sup.2 and the maximum width of the sides of the loop-shaped nozzle is 0.1 mm and the overlap between the two ends of the sides of the loop-shaped nozzle forms an angle of from 10.degree. to 30.degree. measured from the center of the nozzle and wherein the spinning air acts on the filaments in a transverse direction to the filament take-off and the air direction forms an angle of from 80.degree. to 100.degree. with a straight line passing through the opening between the sides.

Process for the production of dry-spun hollow polyacrylonitrile fibers

Hollow polyacrylonitrile fibers having a uniform closed cavity structure are obtained by dry-spinning filament-forming acrylonitrile polymers from a solution through a spinning jet comprising annular jet bores of the type shown in FIG. 1, the solution having a viscosity of at least 120 falling-ball seconds, as measured at 80.degree. C. or of at least 75 falling-ball seconds, as measured at 100.degree. C., the ring of the annular jet bores consisting of three, preferably equally large, ring segments at a distance from one another of at most 0.2 mm, the surface area of the jet bores of the profile jet amounting to less than 0.2 mm.sup.2 and the side width of the ring segments amounting to at most 0.1 mm, the spinning air acting on the filaments transversely of the direction in which they are taken off relative to the center of the spinning jet.

The invention relates to a process for the continuous production of synthetic non-discolored filaments and fibers from a filament forming synthetic polymer being difficultly soluble in an organic polar solvent particularly polyacrylonitrile polymers which process comprises preparing a suspension of said polymer and said solvent at room temperature and subsequently heating the suspension thus formed for at least 3 minutes to at least 130.degree. C., and filtering the clear spinning solution formed without intermediate cooling, homogenizing and spinning it immediately afterwards into filaments.

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Neuss, Germany

Hans K Burghartz