Patent GB-589038-A (GB)
Title: Improvements in or relating to process and apparatus for producing artificial filaments
IPC: D01D5/20
Filed: 1944-05-22
Abstract: A solution of an organic plastic substance is supplied to a spinneret or similar extrusion orifice from a pressure source such as a pump that feeds the solution at a constant rate and a periodically varied portion of the solution is <PICT:0589038/IV/1> <PICT:0589038/IV/2> byepassed back to the pressure source from a point between the pressure source and the spinneret, so as to produce variations in the pressure at the spinneret with consequent formation of filaments with recurring tapered sections along their length.  The spinneret may be vibrated during extrusion so as to form circumferential ribs around the filament.  The extrusion device may be modified so that a thread of silk, cotton, or other material may be passed through the spinneret and coated with the plastic material so as to produce a thread with recurring tapered portions along its length.  The tapered filaments or threads may be doubled or twisted with other artificial or natural filaments or fibres, or they may be cut at the termination of each tapered section so as to form tapered bristles for brushes. Bristles having a fibre core coated with plastic material are substantially feathered at the thin end.  The plastic material may be a cellulose ester or ether, e.g. cellulose acetate, formate, nitrate, thiocarbamate, or butyrate, or methyl, ethyl, or benzyl cellulose, or a cellulose glycol ether, or it may be a resin such as a polyvinyl acetal, or it may be a polyamide.  The filaments may be produced by dry or wet spinning processes.  For wet spinning there may be used solutions of cellulose acetate, viscose, cuprammonium-cellulose, or cellulose nitrate, and the filaments may be obtained as regenerated cellulose filaments.  As shown in Figs. 1 and 2, a motor 10 drives a horizontal shaft 15 and the drive is transmitted through cone pulleys 21, 24 to shaft 25 and through gearing to the pump shaft 45.  The position of the belt 23 is adjusted by a lever 39.  The pump 50 is of the screw-type.  The pump casing is connected to an inlet conduit 54 and spinning solution supply tank 56.  The outlet 60 from the pump leads to a filter 61 and spinneret 62 from which filaments 64 are extruded.  A byepass conduit 65 is provided with a gate-valve 68. This valve is connected to lever 71 which carries a roller 76 in contact with a cam 78 on shaft 15.  Rotation of cam 78 varies periodically the volume of solution passing to the spinneret. Filaments in which the thickness gradually decreases and then gradually increases, or filaments in which the thickness gradually increases and then abruptly returns to a minimum may be obtained. The spinneret may be vibrated by means of the strip 91 which bears against a gear-wheel 107.  As shown, the spinneret is constructed so that strands of cotton, silk, or other material may be drawn through the rear side through small openings 123 and then passed through the extrusion orifices so that they are coated with the solution of plastic material.  The finished filament with the fibre core therein has substantially the same tapered shape as that imparted when there is no fibre core.