US2267055A - Production of regenerated cellulose yarn - Google Patents

Description

ec. 23, 1941. E. A. TIPPETTS 2,257,955

, PRODUCTION OF REGENERATED CELLULOSE YARN I Filed June 10, 1939 '-;ii a.

' 5222811901? A. ZE'ppeztJ INVENTOR jIWTORNEY Patented Dec. 1941 UNITED STATES PATENT oppmgfl Emerson A. Tippetts, Kenmore, N. Y., assignor to E. L du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware Application June 10, 1939, Serial No. 218,426

V 2Claims.

cellulose yarn is subjected to a stretching operation while in contact with a liquid having an .ele-

vated temperature.

Heretofore, in the production of fine denier filament yarn by the viscose process it has been commercially uneconomical to produce yarns the filaments of which were finerthan about one denier per filament. Furthermore, the previously known processes for the production of such one denier per-filament yarns were attended by difllculty of spinning and very material and objectionable yarn degradation.

It is an object of the present invention to produce, by the viscose process, regenerated cellulose yarn composed of filaments having a denier of less than one.

It is another object of this invention to produce, by the viscose process, regenerated cellulose yarn composed of filaments having a denier of the order of 0.5 to 0.75.

It is a further object of the present invention to provide a process for the production of extremely fine denier filament regenerated cellulose yarn from viscose, which process represents an improvement in efliciency and decreased filament degradation over previously known processes.

It is a. still further object of the present invention to provide a process for the production of extremely fine denier filament regenerated cellulose yam from viscose by subjecting the previously regenerated yarn to a stretching operation while in contact with a liquid having an elevated temperature.

Other objects of the invention will appear hereinafter.

In accordance with the present invention, the

tained when the hot liquid bath is a hot sulfuricacid bath.

It has now been found that regenerated cellulose filaments having a denier of less than one, for example, having a denier of the order of 0.5 to 0.75, can be spun from viscose if the freshly spun filaments, spun under low tension, are removed from the regenerating bathand passed into a' stretching bath having a temperature of between 60 C. and the boiling temperature of the bath liquid, in which they are given a material stretch.

It has been discovered that very materialadvances in economy and material reduction in yarn degradation will be obtained if the freshly precipitated fine denier filament yarns are stretched in a hot sulfuric acid bath, and if the contact-with the said hot sulfuric acid bath is confined to a distance 01.45 inches or less based on spinning speeds of 3000 to 8000 inches per with hot sulfuric acid during the stretching operation is critical, from a standpoint of yarn deg-. radation, when compared with the prior art processes in which it was considered necessary to contact the threads in hot liquids for a distance of 2 to 12 meters (78 to 460 inches) at speeds considerably less than 3000 inches per minute.

The procedure and apparatus by means of which'the process of the present inventionmay be carried out will be clearly apparent from the following description when taken in connection with the accompanying illustration.

The accompanying illustration is a diagrammatic perspective view of one form of apparatus suitable for use in accordance with the present invention.

Referring to the illustration, reference numeral 7 H designates a spinneret which is positioned in tank I! containing a coagulating and regenerating bath l5. A viscose solution is extruded through spinneret ll into bath l 5 for the formation of a multifilament yarn II. The yarn I1 is passed about pin, I! which functions as a convergence guide to bring the several extruded filaments together into .a single yarn. The yarn is then passed about a plurality of roller guides 2|, thence around guide 23. After passing around guide 23 the yarn is drawn from the coagulating and regenerating bath by means of transfer roller 25. The yarn may be looped one or more times about the transfer roller 25 to prevent slippa e'of the yarn thereon. The yarn is then passed around rollers 33 which are submerged in a hot sulfuric acid bath 29 in tank 21. The yarn is drawn from the hot sulfuric acid bath 29 and I pumped into the coagulating and regenerating bath l by means of pump 421 and conduit 39, or the hot acid bath may be drained through conduit 40. Spent coagulating and regenerating liquid may be passed from the coagulating tank l3 through conduit 4 I.

It is to be understood that the illustrated and above-described apparatus is disclosed for illustrative purposes only. Obviously various diiierent forms and modifications of apparatus can be employed equally well.

The number and type of roller guides ii in the coagulating and regenerating bath will be determined by the spinning speed, by the size of the threads or filaments being spun, by the tension to be imposed on the yarn, and by the composition of the coagulating and regenerating bathliquid.

It is necessary to maintain sufiiciently low tension on the yarn during its travel through the passed onto a collecting bobbin 35. The hot acid regenerating bath to allow sufllcient stretch to be from overlapping and chafing each other. The

transfer roller may be rotated by the pull exerted page 69.

To avoid w mer t will be understood to refer to the peripheral velocity of the spin-bobbin in the bobbin process or the feed wheel speed in the bucket process, and the term spinning tension" is the tension on the yarn, measured at a point just ahead of the spin-bobbin or its equivalent, when the spinning containing approximately 7% cellulose and 6% sodium hydroxide is used. Obviously viscose having different characteristics can be employed in the practice of the invention depending upon the type of yarn to be produced. Particularly good results have been obtained by the use of a viscose spinning solution which has been ripened to a point where it has an index materially greater than 4.0, for example an index of 4.5 to 6.0, or even greater, as determined by the-method of Reinthaler and Rowe, fArtificial Silk}! .--1928,

Example! Viscose is passed through a spinneret containing 100 holes, with an average viscose delivery of 7.7 grams per minute, into anaqueousspinning bath containing 9% sulfuric-g'acid, 19%"scdium sulfate, 4% glucose and 0.85%{z'inc suimtegsam bath being maintained ati I-L-1 C. The extruded filaments are. guided through this bath by a plurality of roller guides selected tempos-e a slight tension on th'e'yam' bath' 't'ravei of 26 inches. The yarn is withdrawn'from the bath and passed overa; "yarn drlventransfer roller into a secondary bath which" consistsbf an aqueous solution containing 2% S 111furicacid'and which is maintained at 'a temperature of 90i2 C. The yarn is guided through the secondary thereon by the yarn, or the roller may be posi- 5 tively driven in any desired manner. The collecting bobbin may be of any type well known in the art. The collecting bobbin will, of course, be provided with necessary traverse guides in a manner well known in the art. If desired, the 'yarn may be drawn through the hot acid bath 29 by means of a feed roll or the like and collected ina rotating bucket in accordance with theconventional bucket process for the production of rayon yarn. In any event, the collecting bobbin, or the feed roller when using the bucket process, will be rotated at a peripheral speed sufllciently higher than the peripheral speed of transfer roller 25 to impart a stretch to the yarn as it passes through the hot acid bath 29. The stretch imposed on the yarn in the bath 29 may be as low as 5% or 10%: however, to obtain the greatest benefit from the present invention the stretch imposed should be 30% to 60% or even 100% or more. depending upon the tension imposed in the spinning bath. upon the physical characteristics to be imparted to the yarn, and limited by the stretch the yarn will stand without breaking.

The spent coagulating and regenerating liquid mav be discarded, or it may be renovated, as desired.

For convenience the invention will be described in terms of a spinning process as depicted in the drawing where the yarn is collected on a spinhnbbin.

bath by a plurality of roller'guide's selected so that at a spinning speed of 4500 inches per minute the spin tension will be 29"grams when the peripheral speed of the yarn driven f-transfer roller is 3040 inches per minute. The finished yarn, after washing on thebobbinor'l 'which it has been collected, and twister drying' 'inaccordance with the method'describ'ed 'in- Parker Example II I Viscose is passed through-a spinneret-containlng holes, with an .average'viscosedelivery of 11 grams per minute, into an aqueous spinning bath containing 11% sulfuric acid, 23%,sodiuigi sulfate, 4%- glucose and 0.7% zincsulfatasaid bath being maintained at 45':1 C. ;The,-,extruded filaments are guided-through the bath; by a plurality oi roller guides selected toimpose a tension on the yarnduring a-bath travel of inches. The yarn is then led over a-freelyrotating transfer roller into a secondary bat wheel, whence it is collected .in. a centrifugal 1 bucket rotating at 10,000 R. P. M. in the usual way. The spinning speed (feed wheel speed) is 3600 inches per minute and the roller guides in .the baths are such that a spin tension of 85 grams is obtained when the transfer roll runs at a peripheral speed of 2710 inches per minute.

Thefinishedyarmwashedanddriedinthe cake without bleaching, has a denier of about 100, (one denier per filament) a dry tenacity of 2.96 grams per denier, and a wet tenacity'of 1.95

grams per denier with dry and 'wet elongations of 14.9% and 15.3% respectively;

By reference to the above examples, it will be apparent that yarn of exceptionally fine denier can be produced from viscose with great case even though very highspinning speeds are employed. Yarn produced in accordance with the present invention will have a high tenacity and may therefore be used to greatadvantage in the production of sheer knit goods and light-weight woven fabrics. The quality of the yarn is vastly superior to that of fine denier viscose rayon produced in prior art processes in respect to yarn degradation, yamtenacity and fineness of denier. The reason for this lies in the fact that the yarn denier can be reduced by a stretching operation in which much greater stretch can be secured than when stretching in the spinning bath is relied upon. The amount of stretch given the yarn aifects in large measure the tenacity and denier of the final product; however, the stretch must be imposed on the yarn during a comparatively short period so as to prevent yarn degradation. It material yarn degradation takes place the tenacity of the yarn will be substantially lowered.

The composition of the hot acid stretching bath may bethe same as that of the coagulating and regenerating bath with the attendant advantages of simplified bath make-up systems, use of hot bath overflow tomaintain spinning bath temperature and composition, economical use ultimately as spinning bath, and the like. However,'if high salt concentrations are used, the tendency toward crystallization in the hot acid stretching bath is increased so that it is frequently preferabl to use a difierent hot bath composition. To this end then, compositions containing 2% to 13% sulfuric acid, 0 to sodium sulfate and with or without zinc sulfate or glucose may be used. Inasmuch as the higher temperature of the secondary bath is conducive to carbonization of glucose, a glucose-free bath' the spinning bath controls to a considerable extent the amount of stretch which .can later be given the yarn in the hot acid bath- This relationship is qualitatively expressed in the follow.- ingtable in which the tension ismeasured on the yarn as it leaves the spinning bathz' Tension stretch Per c0255 0.1gramper denier 0.4 grams per denier 35 0.5 grams per denier 28 0.9 grams per denier 19 Thus it is readily apparent. that since a relatively large amount of stretch is essential when fine denier filaments are to be made it is advantageous to keep the tension on the, yarn in the spinning bath at a low level. The tension on the yarn in the spinning bath must be maintained below 1.0 gram per denier, and to obtain full advantage of the present inventionvthe tension in the said spinning bath should not exceed 0.5 gram per denier. V y

.By the process of the present invention it is practical to'spin a yarn of 0.5 to 0.75 denier per filament at high speed while stillkeeping the yarn speed in the coagulating and regenerating bath sufliciently low to' prevent entrance of this bath into the spinneret, which will result in plugged spinneret holes. As a consequencespinnerets of larger hole sizes can be used than ha beenv possible, in prior art processes.

The ratio of spinning speed to average linear spin a 0.5 D/F yarn with such a spinventionwill permitratios of 6 or higher by virtue of a 30%-60% or higher stretch imposed on the may be preferred. Inasmuch as greater stretch temperature of the secondary bath is selected in the range of C. to boiling temperature, and

usually 90-100 C. This preferred range gen-- 'erally yields higher breaking tensions, that is,

subjected the tensionto which athread can be before breaking.

yarn during its passage through the bath by virtue of the hot treatment under tension which in turn allows for slower yarn speeds in the spinning bath than can be possible in the absence of the hot bath treatment.

The advantages'of the foregoing can be appreciated by the following. In spinning fine denier per filament yarn the ratio of yarn speed, at a point, say, 25 inches from the spinneret, to viscose delivery is critical. For producing 1 D/F yarn by a single bath process this ratio is about 2.5 when a spinneret having holes about -0.0025 inch in diameter is used. Any decrease in filament denier without change in hole size will raise this ratio proportionately so that it will be about 5 for a 0.5 D/F yarn. By theprocess of this invention the ratio can be kept well below 5 or in the range 2.9 to about 4. Similarly, for a yarn or 1 D/F, this invention makes it'possible to keep the ratio well below 2.5 or in the range 1.5 to about 2. These lower ratios are valuable in producing higher quality yarns by an economical procedure.

Since it is obvious that manychanges and v I 3 Theamount of tension imposed on the yamin Breaking invention above described, it is to be understood that the invention is not to be limited except as set forth in the appended claims.

I claim: v

l. The process of spinning regenerated cellulose yarn comprising filaments having a denier of less than one which comprises extruding a viscose solution into a coagulating and regenerating bath the dilute acid type (of the order 01' 9% to 11% acid) with a ratio of'yarn speed, at a point 25 inches from the spinneret, to viscose delivery speed 012.9 to 4 (based on a 0.5 denier per filament yarn) to form yarns, maintaining said yarn under tension of lessthan 1 gram per denier during its passage through said coagulating and regenerating bath, removing said yarns from said bath and passing them, for a distance not to exceed 45 inches, based on a spinning speed of 3000 to 8000 inches per minute, through.

a 2% to 13% sulfuric acid bath having a temperature of 60 C. to boiling temperature, and

stretching said yarns at least 30% to materially reduce their denier during their passage through said hot acid bath. c

, 2,207,055 modifications can be made in the details of the 2. The process of spinning regenerated cellulose yarn comprising filaments having a denier denier during its passage through said coagulating and regenerating bath, removing said yarns from said bath and passing them, for a distance not to exceed 45 inches, based on a spinning speed of 3000 to 8000 inches per minute, through a 2% to 13% sulturic acid bath'oi a composition essentially the same as said coagulating and regenerating bath and having a temperature of 60 C. to boiling temperature, and stretching said yarns at least to materially reduce their denier during their passage through said hot acid bath.

' EMERSON A.- TIBPE'I'IS.

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