Patent GB-827641-A (GB)
Title: Process and apparatus for producing artificial fibers and the fibers produced thereby
IPC: D01H4/28
Filed: 1956-03-26
Abstract: <PICT:0827641/IV (a)/1> <PICT:0827641/IV (a)/2> Artificial staple fibres are formed by expelling a molten synthetic organic linear fibre-forming high polymer, or a solution of the polymer in a volatile organic solvent, through one or more spray nozzles by centrifugal force into a zone of relatively non-turbulent gas to form one or more streams of the sprayed liquid, attenuating and partially setting the stream or streams while in the non-turbulent gas zone, and breaking the attenuated stream or streams into fibres by passing them into a zone of turbulent gas.  As shown in Fig. 1, the liquid to be sprayed is introduced through a conduit 14 into a hollow spindle 12 which is rotated at a high speed about the stuffing-box 15, which forms a running gland.  The liquid passes up the spindle 12 into the chamber 9 located between a disc 1 secured to the spindle 12 and a cover plate 7 secured to the flange 2 of the disc 1.  Due to the centrifugal force generated by the rotation of the chamber 9 the liquid is discharged from the chamber through the spray nozzles 6 to form a number of streams.  Attached to the disc 1 is an impeller comprising a rim 19 provided with vanes 16 (Figs. 1 and 2).  The rim 19 is made of sufficient width so that its radial projection B from the disc is greater than the length A of the nozzles 6 and therefore shields the nozzle tips from the turbulent air stream produced by the vanes 16.  As the liquid streams move outwardly from the tips of the nozzles they pass into the zone C in which the air increases in turbulence towards the outer edges of the blades 16 and are broken up into fibres.  As shown in Fig. 4, the fibre-forming liquid is supplied from the reservoir 30 under gas pressure through the filter 31 and is forced by the pump 32 through the pipe 28, conduit 14 and hollow spindle 12 into the hollow disc 1 secured to the top of the spindle.  The spindle is driven by motor 25, variable-speed gear 26, belt 27 and pulley 24 secured to the spindle.  The disc 1 is mounted within the chamber 22, at the top of which is positioned the endless travelling collecting screen 33 and suction box 34.  The rotation of the disc causes streams of fibre-forming liquid to be discharged from the peripheral nozzles of the disc while at the same time air is drawn into the chamber 22 through the opening 29 in the floor thereof. The air stream created by the impeller carries the fibres upwardly towards the collecting screen 33 to form a mat 35, which is continuously removed from one end of the screen and collected on the rotating roll 36.  The fibres are preferably formed in an electrostatic field, for example by use of a conducting ring positioned above the disc and having a greater diameter than the impeller.  The ring is connected electrically with a source of high potential 38, the disc and the other side of the source of high potential being earthed.  The collecting screen 33 may also be connected electrically to the source of high potential and thus given an electric charge opposite in sign to that induced in the fibres, to aid in the collection of the charged fibres.  The spinning unit may be provided with two or more superimposed disc-shaped chambers, the peripheral wall of each having spraying nozzles and the hollow spindles leading into each chamber being coaxial.  With such apparatus mats consisting of a mixture of fibres may be produced, the fibre-forming liquids supplied to individual chambers differing in composition.  Mats consisting of a mixture of fibres may also be produced by means of a single-chamber spinning unit as described above-combined with the spraying unit described in Specification 794,725.  In another form of apparatus, the hollow spraying disc and the impeller are mounted for independent rotation and may be driven at the same or different rates of revolution and in the same or different directions of rotation.  The hollow spraying disc may be electrically heated (for spraying a molten polymer) by an electric current which is passed through an electrically insulated split ring of a metal of high electrical resistance, which ring constitutes the peripheral wall of the chamber in the disc and the ends of which are connected electrically to two slip rings mounted on the hollow spindle secured to the spraying disc.  Solid granular polymers may be fed downwards into the disc by screw conveyer and gravity.