Patent GB-1132135-A (GB)
Title: Method and apparatus for spinning fibers
IPC: D04H13/00
Filed: 1966-06-10
Abstract: 1,132,135. Fibre spinning apparatus. MONSANTO CO. 10 June, 1966 [16 June, 1965 (2)], No. 25973/66. Heading B5B. A method for producing fine fibres from a synthetic organic polymer comprises feeding said polymer in liquid form on to the internal concave face of a rotating conoid surface, adjusting the flow of the said liquid with relation to the speed of rotation of the conoid surface so that a continuous moving film of said liquid is formed and substantially covers said internal concave face, whereby said liquid will be discharged as elongated droplets from the periphery of said surface by the centrifugal force resulting from the rotation of said surface, surrounding the periphery of said surface with an annular gas stream flowing substantially parallel with the axis of rotation of said surface, entraining the discharged elongated droplets in said gas stream, and adjusting the temperature thereof with relation to the rate of flow so that fine fibres of the said polymer are formed in the gas stream and recovering said fibres from said stream. Both solutions and melts of polymers may be so spun. In the apparatus of Fig. 1, which is suitable for solution spinning, a solution of a synthetic organic polymer from source 1 passes via line 2 and pump 3 through tubular feeding means 4 on to the internal concave face of conoid disc 5 through aperture 6. Pump 3 provides constant pressure to the solution, thus allowing it to essentially cover the concave face of disc 5. Disc 5 may be rotated at speeds from 1000 to 7000 r.p.m., preferably from 2000 to 4000 r.p.m. A gas, e.g. air, is forced by pump 10 through heating means 11 and line 12 and out of vaned annular opening 13 into enclosure 14. The polymer solution is discharged from disc 5 by the centrifugal force resulting from its rotation, as elongated droplets which are picked up in the gas stream exiting from opening 13, are carried through enclosure 14 and deposited on gathering means 15, suitably, as shown, a screen. During the passage of the droplets from disc 5 to screen 15, the action of the gas stream removes solvent from polymer solution, thus forming fine fibres which are deposited on screen 15, which is preferably in the form of an endless belt moved by drive means 17 in a direction perpendicular to the axis of rotation of disc 5. As the screen moves out of enclosure 14 the fibrous mat 16 formed thereon is removed and taken up, e.g. on take-up roll 19. Solvent remaining in the gas stream passes through the screen and is directed to solvent collection means 21. It is also possible to remove the fibres in the form of a yarn using the apparatus of Fig. 3, wherein air jets 24 serve to decrease the width of the mat 16 as it passes over roll 19. Fibres are further compacted by passage through guide 25, over roll 26 and through guide 25(a) and the yarn 27 is taken up on bobbin 28. Mixtures of fibres may be spun either by admixing the melts or solutions prior to their introduction through the feeding means, by having a plurality of feeding means through the aperture of the conoid disc, or by providing a plurality of discs on the same shaft. The preferred polymer for use in solution spinning comprises acrylonitrile and copolymers thereof but other polymers which may be solution spun include polycarbonates and polyurethanes. For solution spinning, the gas stream is suitably heated from 100‹ to 350‹ C., preferably 250‹ to 300‹ C., and suitable gas stream velocities are from 1500 ft. per min. to 6000 ft. per min., especially from 2000 ft. per min. to 4000 ft. per min. Fig. 5 shows an apparatus suitable for melt spinning. A synthetic organic polymer from source 29 is passed into chamber 30 where it is melted and forced by screw feeder 31 through tubular feeding means 4 out through orifice 32 and on to the internal concave face of conoid disc 5. Disc 5 has an annular recessed portion 38 located within the aperture and surrounding tubular feeding means 4. This annular recessed portion serves as a reservoir for incoming melt and ensures more even distribution thereof over the internal concave face of disc 5, which is rotated at from 1000 to 7000 r.p.m., preferably from 2000 to 4000 r.p.m. Tubular feeding means 4 is surrounded by heating means 41 which serves to maintain the polymer in the molten state while it passes through the feeding means. Opposite the concave surface of disc 5 are located additional heating means 42, preferably radiant heaters, which serve to maintain the disc temperature above the polymer melting.point. Insulation means 43 surround radiant heaters 42. Behind the convex surface of disc 5 is located annular opening 44, through which atmospheric air is drawn into enclosure 14 by the operation of vacuum means 47. As the melt is introduced through the aperture on to the internal, concave surface of disc 5, the centrifugal force resulting from the rotation of the disc causes the melt to substantially cover the concave surface and to be discharged from the periphery of disc 5 and solidify into fine fibres. The fibre stream then passes through enclosure 14 on to fibre gathering means 15 which is preferably a moving screen in the form of an endless belt mounted on rotating means 48. Between the two sides of the rotating screen is located frame 46 which serves to direct the gas stream into vacuum means 47. The mat of fine fibres 16 is removed from screen 15 and wound up on take-up roll 19. Heating means 42 prevent the solidification of polymer on disc 5. The fibres may alternatively be removed in the form of a yarn as in the case of solution spinning, using the apparatus of Fig. 3. Suitable synthetic organic polymers for melt spinning include polyamides, polyesters, polycarbonates, polyurethanes, polyvinyl chloride, polyvinyl alcohol, and polystyrene. The velocity of the entering atmospheric air should be between 1500 and 6000 ft. per min. Fibres so made range from about five microns to about 0À1 microns diameter with an average diameter of from 1-2 microns.