US 2683072 A
Description (OCR text may contain errors)
July 6, 1954 R. E. CLARK REMOVAL OF cs WITH on. FROM VISCOSE YARN 2 Sheets-Sheet 1 Filed June 16, 1950 FIG].
X Y -i VENT T0 082 RECO VERY SYSTEM OIL BA TH T0 SE PARA T/I."
INVENTOR. ROBERT ELL/S CLARK A T TORNE Y R. E. CLARK REMOVAL OF CS1 WITH OIL FROM VISCOSE YARN 2 Sheets-Sheet 2 July 6, 1954 Filed June 16, 1950 MG QEQRM Ff: 53w
ROBERT ELL/S CLARK BY A TTORNE Y Patented July 6, 1954 REMOVAL OF CS2 WITH OIL FROM VISCOSE YARN Robert Ellis Clark, Midlothian, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Application June 16, 1950, Serial No. 168,573
4 Claims. 1
This invention relates to a method of processing regenerated cellulose rayon yarn during the spinning operation, and relates more particularly to a process for removing carbon bisulfide from freshly spun viscose rayon yarn in the spinning bucket.
Over 80% of the carbon bisulfide used in preparing the alkali cellulose xanthate from which viscose spinning solution is made is released duringcoegulation and regeneration in the spinning room. Of this amount, approximately 30% remains in the yarn when doifed from the machine. Not only is this material remaining in the yarn lost at present, but it is evolved gradually into the spinning room air during transportation to the next process, creating a severe ventilation problem.
In the past, attempts have been made to remove this carbon bisulfide, but have failed because they were either ineffective, too expensive, or caused damage to properties of the yarn. Application of hot dilute spinning bath to the acid yarn in the bucket was effective, but reduced physical properties, especially fatigue resistance.
Application of hot water in the spinning bucket is undesirable for economic reasons, as the bath wrung from the cake is excessively diluted, leading to high bath recovery costs. Removal of carbon bisulfide by evacuation of cakes after dofiing requires expensive additional equipment and increased operating cost. Attempts to remove the carbon bisulfide by passing the acid.
.yarn through a hot oil bath, or by applying hot oil on the Godet wheels, did not effect sufilciently complete removal.
It is an object of this invention to provide an economical method for effectively removing carbon bisulfide from freshly spun viscose rayon yarn without impairing the physical properties of the yarn. A further object of the invention is to provide such a method which requires only simple equipment in addition to that regularly in use in the spinning operations while providing for recovery of the carbon bisulfide for reuse, and which eases the burden on spinning room. ventilating equipment. Other objects of the invention will become apparent from the following description and claims.
The objects of the invention are accomplished by a process which comprises introducing oil into a rotating spinning bucket as freshly spun viscose rayon yarn wet with residual acid bath liquor is being Wound into a cake, providing for rotation of the bucket to centrifuge most of the oil and bath liquor from the cake into the bucket men-t the oil, bath liquor and carbon bisulfide removed from the yarn by the oil. Preferably the oil, bath liquor and carbon bisulfide are recovered for reuse.
Preferably, the oil is added to the spinning bucket through the conventionalyarn traversing funnel, is drained from the bottom of the bucket compartment along with the residual bath liquor, is separated from the bath liquor by gravity in a settling tank, and is then recirculated to be used again. The oil absorbs and removes almost all of the carbon bisulfide in the yarn, which is then vaporized from the oil into the air in the bucket compartment as the oil is spun from the cake. Air is circulated through the bucket compartment to carry away the carbon bisulfide, which can readily berecovered from the air by adsorption on activated carbon, or by other conventional procedures. The flow of air can be regulated to have a high concentration of carbon bisulfide vapor, e. g., in the range of 150 to 300 or more parts per million, so that recovery is facilitated.
The term oil as used herein is intended to refer to any inert oil which is a solvent for car-- bonbisulfide, of mineral, vegetable or animal origin. In view of its function, it is apparent that any inert, normally liquid water immiscible material which is a solvent for carbon bisulfide may be used. Paraffin-base mineral oil is pre ferred because of its excellent absorbent properties for this purpose, except when the residual of paraffin oil left in the yarn would be objectionable in the intended use of the yarn, in which 'cas'ea different type of oil should be used. The temperature of the oil may vary from about room temperature up to C., or even higher. Temperatures below 60 C. are preferred because high temperatures, such as 0., cause some reduction in desirable yarn properties, particularly in fatigue resistance.
The invention will be more easily understood by reference to the accompanying drawing of apparatus suitable for use in performing the process of the present invention, in which,
Fig. 1 is a sectional front elevation of a conventional spinning bucket which has been modifled for use in the present invention, and
Fig. 2 is a flow sheet of the complete process, including carbon bisulfide recovery.
Referring to Fig. l, a freshly spun viscose rayon yarn I0 enters a conventional spinning bucket H through traversing funnel I2, and is formed into a cake l3 by rotation of the bucket. The
r 100 to 400 cc. per minute per cake have been found suitable when spinning 1650 denier yarn. The flow may be varied from cc. per minute for small denier yarn to 600 cc. per minute or more for very heavy denier yarn, as necessary to obtain satisfactory carbon bisulfide removal, without harm to the cake structure.
The centrifugal force resulting from the rotation of the bucket causes most of the oil and the bath liquor carried by the yarn to pass through the cake and out of the bucket through holes [8, provided in the bucket. The mixture of oil and bath liquor is caught by and falls to the bottom 01 the compartment 20, which surrounds the bucket. The mixture then flows out of the bucket compartment through pipe 2| and passes to separating means for recovering the oil for reuse. During its passage through the bucket compartment, the oil is exposed to the air in a thin film and carbon bisulfide removed from the yarn is vaporized. Air laden with this vaporized carbon bisulfide is drawn from the compartment through vent 22 and passed to a suitable recovery system.
Fig. 2 shows suitable recovery systems for the oil and carbon bisulfide. The oil and bath liquor leave the bucket compartment 22 through pipe 21 and flow to a gravity separating tank 25, where they separate into two layers. The oil, which rises to the top, is. drawn off through pipe '28 and returned to the bucket by pump 27 through pipe 28. A suitable flow-meter 2a is provided in this return line as a guide in controlling the pumping rate. The flow-meter is connected to the side-arm it of funnel [2 by means of a flexible tube 38 to allow for the usual up and down traverse movement of the funnel. A temperature control means 3% is also provided in the return line. The bath layer overflows from tank through pipe 34 and is returned to the spinning bath system for reuse.
The air laden with carbon bisulfide vapor is passed from bucket compartment 26 through vent pipe 22 to a carbon bisulfide recovery system shown at the right hand side of Fig. 2. The air and vapor pass through manifold 49 to two or more adsorbers ti containing beds of activated carbon. The carbon bisulfide is adsorbed by the bed and the air is drawn through, passing out of the adsorber to the manifold 42 and being blown to disposal stacks by blower 43. When a bed is saturated, the adsorber is cut out of the airvapor system and steamed to remove the carbon bisulfide. The mixture or steam and carbon bisulfide is passed through manifold to a brinecooled condenser 46. The condensed mixture flows into a gravity separating tank 48 from which the separated carbon bisulfide overflows through pipe ii) to storage for reuse. The water layer overflows to a sewer through pipe 59.
The following examples, in which proportions are by weight unless otherwise specified. are given for illustrative purposes only and are not intended to place any restrictions on the invention described and claimed:
Except for the oil treatment, the general procedure employed in all of the examples was the usual method for preparing 1650 denier, 720 filament yarn of high tenacity suitable for use in tire cord. A normal 7% cellulose-6% caustic viscose solution was spun into a sulfuric acidsodium sulfate bath containing a small amount 4. of zinc sulfate. The filaments formed were hot dipped through a second bath made up of the primary bath diluted with water and stretched. They were then passed through the traversing funnel 12 of the apparatus described above and into the spinning bucket I l. A paraffinic oil was simultaneously flowed into the funnel and bucket through the funnel side-arm [6. The particular oil used was K Absorbent Oil sold by The Atlantic Refining Company. The rate of flow and temperature of the oil difiered in the examples as shown in the table below. After completing the spin cycle, the cakes were washed and wet-creeled through a finish bath to a slasher, slasher-dried at a stretch of about 6 to 8%, and the finished dry yarn was wound up.
Tab-2e Example No 1 2 3 4 5 Oil Flow, cc./n1in 200 400 200 200 Oil Temp, C 39 38 60 9O CS2 in Acid Cake, p e 0. 49 0.25 0.33 0.35 Oil in Yarn after Slashing,
percent 0.35 3.3 4.2 3 3 3.4 Slasher Stretch, percent 8.0 6. 8 6. 3 7. 1 8. 8 Yarn Properties:
Denier 1, 650 l, 650 l, 650 l, 650 l, 650 Dry Tenacity, g. p. Cl 3. 78 3. 90 3. 76 3.81 3. 91 Wet Tenacity, g. p. (1 2. 33 2. 21 2. 28 2. 30 2. 19 Dry Elongation, percent. 9. 5 l0. 4 10. 1 ll. 1 10. 1 Wet Elongation, percent... 20.9 20. 0 l9. 5 20. 0 l9. 2 Cord Properties (2 ply cons tr notion) Conditioned-Denier 3, 747 3, 791 3, 703 3, 756 3, 770 Conditioned'lenacity, g.
p. d 2. 74 2. 83 2. 96 2. 89 2. 68 OonditionedElongation at 15 lbs., percent 9. 5 9. 5 9. 5 9. 5 9. 5 ConditionedElongation at Break, percent l4. 7 15.7 16.4 16.0 14. 2 Oven Dry-Tenacity, g.
p. 3. 31 3. 30 3. 42 3. 36 3.19 Oven DryElongation at 15 lbs, percent 4.8 4. 9 5.1 5. 2 4. 9 Oven Dry-Elongation at Break, percent 11.3 13. 1 13.1 13.3 11.4 Cond. Cord Tenacity/ Yarn Tenacity 0. 73 0.73 0. 79 0. 76 0. 69 Relative Fatigue Values 40 44 45 35 11 From the data of the table it is seen that to of the carbon bisulfide normally remaining in the yarn at the time of doffing the bucket cakes has been removed by oil treatment in accordance with this invention. Furthermore, when the oil was used at temperatures of 60 C. or below there was no deleterious efiect on the yarn, and the physical properties of the yarn and of cord made therefrom were actually improved.
The present invention provides a relatively simple and economical method for removing and recovering carbon bisulfide from freshly spun viscose rayon yarn. Existing equipment can readily be modified for oil treatment of yarn in the spinning bucket, the physical properties of the yarn are not impaired, and the treatment does not interfere with the usual spinningoperations. The additional equipment required for recovering the treating oil, and for recovering the carbon bisulfide removed from the yarn, is read ily adapted from equipment used for similar purposes and is sufficiently simple to be economically justified by the value of the recovered carbon bisulfide.
As different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments disclosed except as defined in the appended claims.
What is claimed is:
1. In the process of spinning viscose rayon yarn in which an aqueous alkali cellulose xanthate solution is extruded in the form of filaments, passed through aqueous coagulating and acid regenerating baths with release of carbon bisulfide, and the resulting filaments carrying carbon bisulfide and acid bath liquor are wound into a yarn cake in a rotating spinning bucket, the improvement of continuously applying to said filaments as the filaments are being wound into said cake a water-immiscible, inert, liquid oil solvent for carbon bisulfide at a temperature of from about room temperature to 60 C., the rate of application of said oil being such that most of the oil passes through the cake, spinning oil and bath liquor from the cake, said oil carrying carbon bisulfide out of the cake and then releasing the carbon bisulfide as vapor, and finally removing the oil, bath liquor and carbon bisulfide vapor from the vicinity of the cake.
2. The process defined in claim 1 in which said rate of application of oil is from 10 cc. per minute for small denier yarn up to 600 cc. per minute for heavy denier yarn.
3. The process defined in claim 1 in which the oil removed from said cake is decanted from said bath liquor and recirculated for application to said filaments.
4. The process defined in claim 1 in which the carbon bisulfide carried out of said cake and vaporized from said 011 is removed from the vicinity of the cake with an air stream and recovered by adsorption from said air.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,350,858 Dow et a1 Aug. 24, 1920 2,042,016 Moritz et a1. May 26, 1936 2,092,203 Brennecke et a1 Sept. 7, 1937 2,101,361 Borzykowski Dec. 7, 1937 2,141,349 Engelhardt Dec. 27, 1938 2,326,150 MacLaurin et a1. Aug. 10, 1943 2,480,974 Seymour et a1 Sept. 6, 1949