Patent GB-667147-A (GB)
Title: Improvements in the production of staple fibres and staple fibre products
IPC: D01D10/04
Filed: 1949-11-03
Abstract: <PICT:0667147/IV (a)/1> <PICT:0667147/IV (a)/2> <PICT:0667147/IV (a)/3> High-tenacity regenerated cellulose staple fibres and staple fibre products, such as spun yarns are produced by breaker-drafting a tow of high-tenacity continuous filaments of an organic acid ester of cellulose to convert the filaments into staple fibres, and saponifying the resulting staple fibres to convert the ester into regenerated cellulose.  The high-tenacity can be imparted to the filaments by temporarily plasticizing or softening them, preferably by the application of saturated steam under pressure, or hot water at 100-150 DEG  C., and stretching the filaments while they are in a plasticized state, e.g. by 150-2000 per cent.  On cooling, the steam-softened filaments revert to the unplasticized state and are ready for breaker-drafting.  This may be carried out so as to produce a sliver without interrupting the continuity of the tow, and a twist, e.g. of 0.25 to 1.0 turns per inch may be imparted to the sliver with or without the application of additional draft in order to convert it into a roving.  After saponification, washing and drying the roving can be spun into a yarn.  The continuous filaments may be composed of cellulose butyrate, propionate, acetatebutyrate or acetate-propionate, but preferably of acetone-soluble cellulose acetate.  The tow may contain 1000-15,000 filaments, the denier of each filament may be 2-40 and the total denier of the tow may be 10,000-150,000 before stretching and 1000-15,000 after stretching. The filaments may be plasticized before they are stretched by treating the tow with solvents such as dioxane, diacetone alcohol, diethylene glycol diacetate or glycerol formal.  The draft ratio of the two successive sets of breaker-draft rollers may be 1.5-3.0 or more and the length of the staple fibres is preferably 3-8 inches. The roving obtained from the tow may be saponified either continuously or intermittently with solutions of sodium hydroxide, sodium carbonate or ammonium hydroxide which may contain buffering agents such as sodium acetate, sodium citrate or sodium sulphate.  In the example a tow of cellulose acetate filaments 11 (Fig. 1) is drawn into the compartment 23 of the chamber 12 by means of the positively driven pulleys 29, 31 and 32, and saturated steam at 45 p.s.i. pressure and 130 DEG  C. is admitted into the compartment 26 through a pipe 39 and leaves the compartment through a second pipe 41.  The steam plasticizes the filaments of the tow as it passes through the compartment 26. Simultaneously, water at about 25 DEG  C. is forced into the compartment 23 at 38 p.s.i. pressure through a pipe 42 to limit the flow of steam through the aperture 34.  The water flows from the compartment 23 through the aperture 33 past the tow 11 into the compartment 24.  Water at 25 DEG  C. is also forced into the compartment 27 at 8 p.s.i. pressure through a pipe 44 to control the flow of steam through the aperture 36.  The steam entering the compartment 27 is condensed by the water in this compartment and leaves the compartment together with the water through a pipe 46. The water flowing through the compartment also serves to cool the tow and restore it rapidly to its unplasticized state.  After leaving the chamber 12 the tow passes round the wheel 38 which is driven at a peripheral speed 9.5 times as great as the peripheral speed of the pulleys 29, 31 and 32.  The stretched and deplasticized tow is then passed to the two sets of breaker-draft rollers 47-49 and 51 and 52 (Fig. 2), which are positively driven and spaced about 6 inches apart.  The peripheral speed of the second set of rollers is about 1.6 times that of the first set and the tow 11 is thereby converted into a sliver 53 which passes directly to the fly frame 54, which twists the sliver into a roving 56 having approximately 0.25 turn per inch and winds the roving into a package 57.  The roving 56 is then unwound from the bobbin 57 and saponified by being subjected for two minutes to the action of a saponifying bath at 98 DEG  C. containing 3 per cent sodium hydroxide and 8 per cent sodium acetate.  The roving is then washed and dried.  Two ends of the roving are then doubled and converted to a yarn on a conventional ring spinning frame. The saponification, washing and drying of the roving may be carried out continuously on the apparatus shown in Fig. 3.  In this case the roving 56, after being unwound from the bobbin 57, is passed over a pulley 62 leading it to a pair of positively driven hollow rollers 63.  For a short distance 64 from their feed end, the diameter of the rollers increases rapidly to take up the slack which develops in the roving immediately after the saponifying solution is applied to it.  Over the next portion 66 of their length, the diameter of the rollers decreases slightly to accommodate the slight shrinkage which takes place in the roving as the saponifying agent continues to act thereon. Finally, over the portion 67 at their discharge end, the diameter of the rollers decreases more rapidly to accommodate the shrinkage of the roving during the washing and drying steps.  Positioned above the rollers is a header 68 provided with jets 69 through which saponifying liquid is applied to the roving.  A second header 71 is provided with jets 72 by means of which wash water is applied to the roving.  After acting on the roving, the saponifying liquid and wash water are collected in a drip pan 73 from which they are removed by a drain 74.  The saponified and washed roving is then dried as it passes over the latter part of the portion 67 of the rollers, steam or other heating medium being admitted into the partitioned off compartments 76 through pipes 78 which also serve as bearings upon which the rollers are journalled.  The condensate formed in the compartments 76 is discharged from them through pipes 79 which pass concentrically through the pipes 78.  After being dried, the roving passes over a pulley 81 to a packaging device or spinning frame.