US2046347A - Method of making artificial thread - Google Patents

Description

July 7, 1936. V G. SIGLER 2,046,347

METHOD OF MAKING ARTIFIQIAL THREAD Filed Dec. 15, 1953 2 Sheets-Shet 1 A.YA le/v DR/Eb ON THE BEFORE 771m wl/ve. B. YARN THROW/V GEL 5 TA TE.

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THol/smvo Kano SxE/A/s INS/DE or .SPm CAKE INVENTOR A R NEY July 7, 1936. G. $.GLER f 2,046,341

METHOD OF MAKING ARTIFICIAL THREAD Filed Dec. l5, 1933 2 Sheets-Sheet 2 ORNEY' form shrinkage characteristics.

Patented July 7, 1936 METHOD OF MAKING ARTEFICIAL THREAD George Sigler, Richmond, Va., assig' nor to Du Pont Rayon Company, New Yerk, N. Y., a corporatien of Delaware Application December 15, 1933, Sean No. 702,537

Claims.

This invention relates to the manufacture of artificial threads, filaments or the like. More particularly, the invention relates to the productic-n of' artificial threads having substantially uni- One of the methods of preparing regenerated cellulose threads comprises spinning a viscose solution and, after regeneration of the cellulose, 001- lecting the newly formed thread on a rotating bobbin, commonly termed the spin bobbin, where it is laid down in the form of a cake by means of a traversing mechanism. The thread normally consists of a ribbon-like bundle of parallel filaments. which is subsequently washed acid-freeby any one of a number of procedures, such as,,for example, by forcing water outwardly through the cake. The Washed thread, according to the usual practice, is then dried on the spin bobbin and the driedthread is thrown to another bobbin or spool by means of a throwing machine, whereby the thread is twisted to the desired number, of turns per inch. Alternatively, thendried thread is spo'oled and the spooled yarn twisted in the manner mentioned, The dried, twisted threadis then reeled into skeins and the latter are subjected to the purifying operations, i. e., desulphuring and bleaching. In some instances the dried, twisted thread on the second bobbin is subjected-to the purifying operations. i

It is a well-known fact that, rayon thread shrinks during the drying operation. If, during the initial drying step, the thread is freely suspended, it will shrink at least 5% of its original lengthiand indeed as much as 10% of its original length. However, since in the methods above mentioned the rayon thread is dried against a rigid support, i. e. a spin bobbin, much of the shrinkage is prevented and prevented non-uniformly. As a consequence, the thread, when again wetted and dried in the subsequent operations, additionally shrinks no'nuniformly.

The unevenness of the shrinkage in termsof residual shrinkage throughout a bobbin cake of yarn, when it is dried by the usual method on a rigid body, can be readily illustrated by platting a curve with shrinkage as abscissa and length through the cake as ordinates. Re sidual shrinkage is explained as follows:

A package of yarn is reeled-into 1,000 yard skeins; the'skeins are measured, showered for 60 ininutes with 1.35% caustic solution at 95 Q, washed free from caustic withsoft water and then dried in a freely suspended condition. The

.;length of the skeins is measured. andthe percentage difference between the original and final lengths is termed the residual shrinkage.

Upon reference to a curve plotted as above described it will be noted that the yarn comprising the middle portion of the cake is shrunk to a considerably larger extent, 1. e. has less residual shrinkage than either the innermost'or outermost parts of the cake, so that the residual shrinkage of yarn varies about 4% from maximum to minimum or, in other words, the minimum is less than one-half the maximum. This variation'in shrinkage is highly objectionable, because skeins wound therefrom and subjected to the customary desulphuring and bleaching operations shrink unevenly. vSuch yarn, when back-wound, produces an excessive number of stops and breaks, resulte ing in a large number of broken filaments, an excessiveamount of fluff and, in general, lower quality yarn. This non-uniformity of shrinkage is indicative of uneven dyeing characteristics throughout the cake, and it has been found that the afiinity for direct dyes is sufiiciently diminished by the tension built up during drying to render the yarn unsuitable for its intended purpose.

If in any process wherein the thread is dried in the presence of a rigid support, as on the spin bobbin, the yarn is subsequently reeled into skeins,

wettedand dried freely, the non-uniformity of shrinkage is overcome but only at a great sacrifice to the quality of the resultant skein. A skein produced as just mentioned is customarily referred to as a tight and loose skein. It is extremelydifiicult to handle, because that part of the skein containing thread'which has a high resid ual shrinkage shrinks to a considerably greater extent than that part of the skein which contains lower residual shrinkage thread. This uneven shrinkage means that the loops of thread comprising the skein may be'difierent in diam; eter by one-half inch or more. When such a skein is placed on a swift for unwinding, the tight loops are stretched while the loose loops are slack and tend to tangle and knot as the skein is unwound.

Furthermore, in the normal reeling process, if the and. continuous, and thereafter converting into skeins, and purifying. Specifically, I have found that the desired results can be secured by twistingacid free gel thread, by thethrowing of the same prior to skeining and purifying. In the throwing operation, I have found that during the ballooningof the thread a drying is effected in a convenient space.

It is, therefore, an object of this invention to prepare bobbin spun rayon of substantially uniform shrinkage characteristics.

A still further object is to produce a bobbin 7 spunrayon of improved dyeing characteristics.

' the following. description, appended claims and i Another object of this invention is to produce bobbin spun rayon of superior textile properties and which is free from factors responsible for low quality.

A specificobjectofthis invention is'to provide a method of twisting gel rayon and winding the thread in a dry or semi-dry state, the dryingbeing effected during the ballooning of the thread. Additional objects will become apparent from accompanying drawings forming a part of this specification and. wherein: V

lEigurezl represents curves illustrating. the

shrinkage in terms of percentage residual shrinkage throughout a bobbin cake of yarn, when it is dried by the. usual method'and when itis dried by' the-process constituting this invention. Figure 2designates a schematic sideielevation of; a throwing machine employed in carrying out been dried toless than. 50% moisture based on the instant process. The foregoing objects are secured in accordance with the principles; of this invention by.

twistingfa gel. yarn; i. e. a yarn. that. has never.

the dry' weight. of the yarn, and. winding. the.

twisted yarn on to a take-updevice in a substantially-dry orsemi-dry condition. The yarnlis twisted in such a manner and under such atmospheric. conditions as to maintainatension at all times at a value suitable for the requirements necessary. for uniform shrinkage while the yarn isbeing drawnfrom'the spin bobbin cake. a

In the preferred embodiment of. the. invention, 7

the spin bobbin cakes are washed free. from acid and the yarn thrownon a standard throwing machine. In this procedure, during ballooning, the yarn issuitably dried in a convenient. space so. that the twisted yam may be wound on the take-up device in a dry or semi-dry'state. By

yarn in the semi dry state is meantyarn which 1 has never been dried to equilibrium butcontains less than 50 moisture based on the dry weight of the rayon. During the unwinding and twisting of the'yarnthe yarn remaining on the'spin 1 bobbinis maintained in its originalgel state. 1

' To. secure the best results, I have found that theire is a critical drying zone for the gel yarn, wherein the'yarn must be under a uniform and preferably a low tension. This critical zonemay be defined as that in which the moisture content of the thread isbetween 1.0 times and 0.25 times the dry' weight of the thread. In. order to secure this conditionas soon aspossible in'the preferred embodiment of the invention, theb'ob 'bin spun cakes, after being washed to remove the acid, are centrifuged toremove theexces's waterand reduce the-moisture content to 1.2 to 1 times the weightof the bone-dry yarn. The

looninghtheyarn' dries. The. thread then 'pass'es H) which maybe coveredzby'any smooth, and pnef centrifuged cake is also preferably conditioned under appropriate conditions so as to reduce the moisture content to, for example, 1.0 times, and

preferably from 1.0 to 1.25 times, the weight of .the bone-dry yam. It is, of course, to be understood that it is not essential to utilize a spin bobbin cake-which has been'centrifuged in order l to secure the benefits of the instant invention.

The final amount of moisture above equilibrium moisturewhich may be present in the yarn after t'wisting can 'be removed in any convenient way, such as by conditioning with hot air.

In one embodiment of my invention, I subject the twisted yarn to treatment with steam or with air substantially .saturatedwith' moisture which is followed" by treatment with warm dry air to reduce the moisture contentv of the yarn to that.

desired. r V

The twisted yarn is skeined, with or without prior spooling, and the skeins subjected to the go than the yarnof the prior. art, such as. ya 3.0:;

which: has beendried on the spin bobbin, twisted in" thedryState, skeined" and. purified..;. w I 1 a The present invention,. in so far asit relatesto twisting the gel threadand winding. the or semi-dry twisted. yarn,..may. be successfully'catried out ona standard throwing machine-,-such.-.as

is illustrated: in:..Figure 25-01. the drawings. Rm ferring. new to Figure-2 of the drawings, wherein like reference numerals designate like parts, the

reference numeral L'designates a rigid and preb erably perforated; bobbin on whicha cake 21 of artificial. gel. thread. 4. produced by the. process; has been wound; f After washing free from acid and adhering .bath'liquors. in: anysuit able=mannen,.the spin bobbin l together with the cake 2. thereon, is positioned on a throwing spindle 3. which is. operated at high 'speedsnby an'y suitable; and welleknownmeans notshownin the drawings. The thread 4, as it is unwound'from the. revolving spincake', balloons as indicated gen erally by the: reference numeral. 4- prior tax-the" passage. through a'. guide, such as a pigtail. guide 5; and, thenpasses'oyer a. glass bar B'which-ade justs the tension on the thread. During the balonto: a traversing guide 'lspivotally connected to aj traversing; bar 8. .Thetraversing guide] directs the: threadonto a taker-up bobbin. 9 whichzis: roe tatedin anysuitable manner, such-asiby'a roll erably resilient-like. material, such as gum rubber, corkorthelike a The amount of te ,onput into. thethread, due to the ballooning; depends upon the weight of. the

gel thread and, therefore, its moisture content; 7: If a. soaking wet bobbin is placed on the spindle 3, that. is, immediatelyafter it has been washed 7 without any preliminary centrifuging, the thread from the outside of the bobbin will be'veryheavy' because it contains 200% or more. water.; As the 7.0,;

throwing operation continue, howeverg more p more water isremoved'from the package. 0011- sequent-ly, as=the throwing process proceeds; the weight of the wet gel thread becomes lighter and the tension on the-thread becomes less and less; K

If the cake on the bobbin is centrifuged and conditioned prior to the throwing operation or so that the average moisture content in the gel yarn is reduced to, for example, 1.2 times the dry weight of the yarn, the tension on the thread, due to ballooning under these circumstances, will not change appreciably and the thread may be wound up at substantially constant tensions.

The pivoted traverse guide i in combination with the glass rod 5 imparts to the thread a constant or substantially constant tension, for the angle of contact of the thread therewith does not change appreciably from the beginning to the end of the throwing operation. In place of the glass rod 6, a roller (not shown) may be used. This serves to eliminate frictional tension between the thread and the guide. The roller is especially advantageous when unusually wet spin cakes are utilized.

It is to be understood that the expression uniform tension as used in conjunction with the throwing operation is not intended to define a tension which is uniform throughout the entire process. For instance, the tension on the thread at the start of the throwing operation as it is wound on the take-up bobbin may possibly be 12 grams. As the process proceeds, the tension-may vary as much as 1 or 2 grams from this value.

In order to more clearly explain the instant invention, the following specific illustrative procedure is set forth. It is, of course, to be understood that the invention is not restricted to the precise details and procedure set forth, since they are more for illustrative purposes.

Example.A rigid spin bobbin containing a cake of artificial thread produced from viscose by the bobbin spinning process is washed in any suitable manner, so that the spin cakes are acidfree. These spin cakes are then centrifuged to remove excess water and reduce the moisture content to 1.65 times the weight of the bone-dry yarn and allowed to condition in a room maintained at a relative humidity of 7 5% and a temperature of F. which further reduces the moisture content of the cake to 1.25 to 1.0 times the weight of the bone-dry cake. This may require 20 to 30 hours. The bobbins with the spin cakes thereon are then placed on a throwing machine and thrown at a spindle speed in a range of from 3000 R. P. M. to 6000 R. P. M. in atmospheric conditions of 75% relative humidity and a temperature of 75 F. During the throwing step the yarn dries in the balloon while the spin cake retains most of its moisture. The tension on the yarn during ballooning and drying is low and uniform and, in the case of denier thread, this tension may vary from 6 to 14 grams, depending on the tension device and spindle speed used. The twisted yarn collected on'the take-up bobbin contains 25% moisture or less. The take-up bobbin is preferably perforated and of the same diameter as the spin bobbin. Following the throwing step, the twisted cake is conditioned in a suitable manner to reduce the moisture to about 6% and then allowed to regain the moisture content desired for reeling. The yarn is then skeined and the skeins subjected to the purifying treatments.

An alternative method allows the omission of the conditioning step but in this case, since the yarn is much heavier due to a larger amount of moisture, it is necessary to pay special attention to see that the tension on the yarn is uniform.

Still another method allows the omission of the final conditioning step and permits reeling or otherwise winding from the cake containin 25% or less of moisture.

It is to be understood that while I prefer to operate this process under the conditions of temperature and humidity above specified, in some cases it may be advisable to carry out this process at higher or lower temperatures or at higher or 7 teristics of yarn produced according to the prin- 20" ciples of the instant invention.

Referring to curve A, it will be noted that the yarn comprising the middle portion of the cake is shrunk to a considerably greater extent, i. e., has less residual shrinkage than either the innermost or outermost parts of the cake. This curve shows that the residual shrinkage of the yarn varies about 4% from maximum to minimum. In other words, the minimum is less than onehalf the maximum.

Referring now to curve B, it will be noted that the difference between the maximum and minimum residual shrinkages from all parts of the spin bobbin cake is not more than 1.5%, and it is this shrinkage difference between maximum and minimum residual shrinkages which I term uniform residual shrinkage.

Other advantages of my invention are improved uniformity of affinity for dyes, an improved and economical process for setting the twist, improved high quality yarn having few broken filaments and little fluff and improved skein formation, which enables skeins to be better dyed and otherwise treated and improves the running quality of the yarn, when the skeins are rewound.

Though the process has hereinbefore been described in connection with yarn by the viscose process, it is to be understood that it is applicable to the other processes of producing rayon and other synthetic fibers.

Since it is obvious that various changes may be made in the above description without departing from the nature or spirit thereof, this invention is not restricted thereto except as set forth in the appended claims.

I claim:

1. A method of producing regenerated cellulose thread having improved shrinkage characteristics which comprises removing the acid from a cake of regenerated cellulose thread wound on a bobbin and which has never been dried to equilibrium, reducing the moisture in the said regenerated cellulose thread until it constitutes 1.0 to 1.7 times the weight of the dry yarn, throwing the said regenerated cellulose thread on the spin bobbin at a speed that the thread during ballooning is dried to a moisture content less than 50% based on the weight of the dry thread and wound in such condition, converting into skeins and purifying.

2. A method of producing regenerated cellulose thread having improved shrinkage characteristics which comprises removing the acid from a cake of gel regenerated cellulose thread while Wound on the spin bobbin, reducing the moisthread until it' constitutes less than 50% by weight based on the dry thread, maintaining the thread under conditions permitting shrinkage, winding said thread, converting into skeins and purifying. V

1 3. In a method of producing regenerated cellulose thread having improved shrinkage characteristics, the steps which comprise washing a cake of regenerated cellulose produced by the ,viscose'method to make said cake acid-free, re-

ducing the moisture content of the thread until it is gapproximately 100 to 125% by Weight based on the bone-dry thread, throwing .said thread at a speed that the thread during the ballooning thereof is dried to a moisture content of not more than 25% based on the weight of the bonedry thread and wound insuch condition.

7 4. A method of producing regenerated cellulose 2,046,347 t thread having'improved shrinkage characterise tics which comprises removing the acidfrom a cake of regenerated cellulose wound on a bobbin and which has never been idried to equilibrium,

reducing the moisture; in said regenerated cellulose thread until it constitutes 1.0'to 1.7- times the weight of the, dried yarn and throwing the said regenerated cellulose thread on the, spin bobloinat a speed that the thread, duringballooning is dried to amoisture content less than 5)% based on the weight of the dried thread and Wound in such condition.

5. In a method of producing 'regenerated'cellulose threads having improved shrinkage characteristics, the steps comprisingremoving' them acid from a cake of regenerated cellulose thread 7 t wound on a bobbin, reducing the'moisture inthe.

stitutes 1.0 to 1.7 times the weight of the dry yarn, twisting the said regenerated cellulose thread under conditions that permit drying, to a said regenerated cellulose thread until 'it' coni moisture content less than 50% based on the 7 weight of the dry thread, and winding GEORGE SIGLER. t 5

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