Patent GB-652845-A (GB)
Title: Improvements in and relating to the production of cellulose acetate staple fibres
IPC: D01F2/28
Filed: 1948-11-24
Abstract: <PICT:0652845/IV (a)/1> <PICT:0652845/IV (a)/2> <PICT:0652845/IV (a)/3> Staple fibres of cellulose acetate are obtained by extruding, into an aqueous coagulant bath, an aqueous acetic acid solution of cellulose acetate obtained directly by esterification of cellulose, through one or more jets having at least 1500 holes, collecting the filaments so produced to form a tow of substantially parallel filaments, cutting the wet tow into staple lengths and drying the cut fibres in bulk.  The fibres may be washed free from the coagulant liquid at any stage in the process, e.g. immediately before cutting, or after cutting, or both before and after cutting.  Preferably there are at least 3000 holes at each spinning position.  Jets with 7500 or more holes may be used. Two or more jets, each having at least 1500 holes, may be provided at each spinning position.  The holes may have diameters of 0.002-0.003 inch.  The freshly extruded and incompletely coagulated filaments may be collected into a tow of parallel filaments and led on to a thread-advancing device which may consist of a pair of rollers, the axes of which are skewed with respect to each other.  Alternatively, the thread advancing device may take the form of a reel.  The filaments may be stretched 10-45 per cent while on the thread-advancing device or immediately after leaving it so that the stretching tension does not extend back to the spinning jet. The thread-advancing device may dip into the coagulant bath or it may be sprayed with coagulant liquid.  The filaments are preferably led on to the thread-advancing device with a minimum deflection, e.g. by means of a single guide having a wide concave guiding surface.  The coagulant may be caused to flow in the same general direction in the bath as that of the filaments.  The coagulant bath preferably contains potassium acetate with or without acetic acid.  By cutting the wet tow and then drying the fibres in bulk, the fibres shrink and when dry possess sufficient crimp to enable them to be used directly in textile spinning machines.  The tow may be subjected to a stretching treatment in hot or boiling water prior to the cutting operation.  This treatment reduces the degree of shrinkage on drying and improves the handle and opening properties of the fibres.  the spinning solution may be heated to a temperature higher than that of the coagulant bath.  Before the drying operation the fibres may be impregnated with softening agents such as turkey red oil, sodium oleate, triethanolamine salts of fatty acids, condensation products of fatty acids with mixtures of diethylene triamine and triethylene tetramine, or condensation products of fatty acids with ethanolamines and polyglycols or ethylene oxide.  The softening agents may be applied as aqueous dispersions.  The dried fibres may be treated with an antistatic finish consisting of triethanolamine salts of fatty acids.  A fugitive dye may be incorporated in the antistatic finish. As shown in Fig. 1, an aqueous acetic acid solution of cellulose acetate obtained directly by esterification of cellulose is extruded through nozzle 1 and the filaments formed in the aqueous bath 2 are withdrawn as a tow 3.  The nozzle has 3000 holes.  The tow is lapped round godet 4 and guide 5 and then passed to a pair of thread advancing rollers 6, 7, stretching taking place between godet 4 and roller 6.  After passing several times round rollers 6, 7, the tow is passed through washing baths 9-11 as shown in Fig. 2.  The washing liquid flows in countercurrent to the tow.  The tow is then stretched between two thread-advancing roller pairs, 12, 13 and 15, 16, stretching being assisted by passing the tow through a bath 17 of hot or boiling water.  The wet tow is then fed to a rotary cutter 20. The mass of fibres 21 obtained is centrifuged and treated with an aqueous solution of a compound obtained by condensing stearic acid with monoethanolamine and further condensing with triethylene glycol. The fibres are dried in bulk and then treated with an aqueous solution of triethanolamine caprate and triethanolamine sebacate, together with Azo Geranine as fugitive dye.  Instead of the godet 4 (Fig. 1) there may be provided a pair of skewed thread-advancing rollers 23, 24 as shown in Fig. 3, the filaments being brought together by means of the concave guide 22.  If desired, stretching of the tow may be effected by means of conical thread-advancing rollers or by means of a thread advancing reel with flared bars. The spinning solution may contain titanium dioxide or other pigments.  The cellulose acetate staple fibres may be carded alone or in admixture with wool, cotton, or viscose rayon staple fibres. They may then be formed into slivers and spun into yarns. Specifications 289,028, [Class 120 (iii)], 341,009, 341,148, 357,565, 413,413, 413,414, [Group IX], and 652,844 are referred to.ALSO:Condensation products are obtained (a) from long-chain fatty acids and mixtures of diethylene triamine and triethylene tetramine, and (b) from long-chain fatty acids, ethanolamines, and polyglycols or ethylene oxide.  The long-chain fatty acid may be oleic acid, ricinoleic acid, or an acid of the formula CnH2n + 1COOH, where n is an integer from 9 to 21.  The longchain fatty acid may be heated for 4-6 hours at 140-180 DEG  C. with a mixture of diethylene triamine and triethylene tetramine in an amount which is substantially the equimolecular equivalent of the acid.  Condensation products of the type (b) may be obtained by heating 1 molar quantity of the acid with excess of ethanolamine, removing unreacted ethanolamine, e.g. by distillation in vacuo, adding 1 molar quantity of ethylene oxide of a polyglycol, together with a condensing agent such as p-toluene sulphonic acid, and heating at 160-180 DEG  C.  The reactions are preferably effected in an inert atmosphere, e.g. of nitrogen or carbon dioxide.  The products may be used in aqueous solution for imparting a soft finish to cellulose acetate staple fibre.ALSO:Cellulose acetate staple fibres are impregnated with softening agents such as turkey red oil, sodium oleate, triethanolamine salts of fatty acids, condensation products of fatty acids with mixtures of diethylene triamine and triethylene tetramine, or condensation products of fatty acids with ethanolamines and polyglycols or ethylene oxide.  The fatty acid may be oleic or ricinoleic acid, or an acid of the formula CnH2n+1COOH, where n is an integer from 9 to 21.  The softening agents may be applied as aqueous dispersions.  The fibres may also be treated with an antistatic finish consisting of a triethanolamine salt of a fatty acid, if desired together with a fugitive dye, e.g. with an aqueous solution of triethanolamine caprate and triethanolamine sebacate, containing Azo Geranine.