US2307863A - Spinning of artificial filaments - Google Patents

Description

Jan. 12, 1943. R. SOUKUP SPINNING 0F ARTIFICAL EILAMENTS 2 Sheets-Sheet 1 Filed Dec. 3, 1940 a w a w x uu k m UBG Balh Ymperaiura c.

R0 Souli'u a INVENTOR ATTORNEY Jan. 12,1943. R. SOUKUP SPINNI NG OF ARTIFICAL FILAMENTS Filed Dec. 3, 1940 2 Sheets-Sheet 2 M INVENTOR TTORNEY ?atented Jan. 12, 1943 stares adrenaor ies SPINNING F ARTIFICIAL FEAMENUIS Roy Souknp, Kenmore, N. XL, assignor to E. E. du Pont de Nemonrs & Company, Wilmington, Deb, a corporation of Delaware Application December 3, 1940, Serial No. 368,297

7 Claims,

It is an object of the present invention to provide an improved method for the spinning of viscose rayon yarn.

vated temperature and continuing the coagulation in a second coagulating bath having a lower temperature than said first bath.

As a result of improvements and refinements in the method of spinning viscose rayon; the

maximum permissible spinning speed has been gradually increased from less than 1,000 inches per minute to approximately 3,500 inches per minute. This increase in spinning speed has been made possible by numerous improvements in apparatus and process as well as improvements in raw materials and viscose and coagulating bath compositions. Such improvements have not only made possible an increase in the speed of spinning but they have also operated to yield a yarn of greatly improved physical characteristics. Both factors have contributed greatly to the increased production of. viscose rayon yarn. \1

Despite the above-mentioned improvements, recent attempts to further increase the speed of spinning of viscose rayon yarn have had an adverse efiect on the physical properties of the yarn. Heretofore, spinning speeds above about 3,500 inches per minute .have been considered impractical. It has been found possible by greatly increasing the temperature of the entire coagulating bath to obtain satisfactory yarn at considerably increased spinning speeds. However, the bath temperature in such a case must be raised from the conventional spinning temperature of 40 to 50 C. to a temperature of the order of 80 to 90 C. The additional costs required to effect this change in temperature of spinning more than offset the advantages gained by the increase in spinnings'peed. Furthermore, rapid evaporation of water from the bath at the increased temperature causes the deposition of sulfate crystals from the bath solution upon machine parts, and also within the freshly spun yarn, thus leading to an It is a further object of this invention to provide an improved method for the spinning of viscose rayon yarn having a higher quality than may be produced by processes known heretofore.

It is another object of this invention to provide an economical and practical process for the spinning of viscose rayon yarn of suitable quality at greatly increased spinning speeds.

Other objects of the invention will appear hereinafter.

The objects of the present invention may be accomplished, in general, by extruding a solution of viscose from a spinn'e'ret into a coagulating bath maintained at an elevated temperature (at least 60 C.) and then passing the yarn for.

' further coagulation and regeneration into a improvement in yam quality to be obtained in -accordance with the practice of the present inexcessive number of broken filaments within the yarn and increased maintenancegcost of equipment.

The difficulty of operating the equipment in such a hot bath, and the fact that increased vention.

Figure 2 is a perspective view of spinning apparatus suitable for use in accordance with the present invention.

Figure 3 is a perspective view of a modified form of apparatus suitable for use in accordance with the present invention,

Referring to the graphic illustrations shown in Figure 1 of the drawings, the several curves A, B, C and D illustrate the changes in the "quality factor of viscose rayon yarn spun under varying conditions and at varying speeds and bath temperatures. The compositions of the viscose and the coagulating bath, or baths, were the same in all four curves. I v

Curve A illustrates the change in quality factor when viscose rayon yarn is spun at a spinning speed of 3,300 inches per minute into a coagulating bath having a temperature of 45 C. or greater and subsequently passing the yarn for further coagulation into a coagulating bath having a lower temperature.

Curve '3 illustrates the change in quality through the outlet pipe 6.

factor of a yarn spun at a spinning speed of 3.400 inches per minute into a coagulating bath having a temperature of 35 C. or greater andning speed of 5,300 inches per minute into a coagulating bath having a temperature of 27 C.

or greater and subsequently passing the yarn for further coagulation into a coagulating bath having a lower temperature.

The term quality factor refers to the product of the dry tenacity and dry elongation of a particular yarn. This constitutes a reliable measure of the physical properties of the yarn. A high quality factor indicates a superior yarn due to improved physical properties. It is known that a change in spinning tension will alter the tenacity and the elongation of the yarn in opposite directions and if this change is not too great, the product of the two properties will remain approximately constant; hence, this product of tenacity and elongation is an expression of the total physical properties of the yarn.

The curves of Figure l of the drawings indicate that to duplicate, at a spinning speed of 5,300 inches per minute, the physical properties of a yarn obtained-at 3,400 inches per minute in -a bath at 45 C. (conventional spinning practice), the entire bath must be heated to 85 C.

I On the other hand, the curves show that a yarn of similar physical properties may be obtained at a speed of 5,300 inches per minute by spinning, in accordance with the present invention, in a system wherein that portion of the bath adjacent the spinneret is heated to a temperature of only about 60 to 70 C. while the remainder of the bath is kept at 45 C. When the bath near the spinneret is heated to still higher temperatures, the yarns spun in accordance with this invention are not only better than those spun at 3,400 inches per minute in a 45 0. bath, but are even better than those yarns spun at the lower speed when the entire bath is heated to any temperature.

An apparatus of the type shownin Figure 2 of the accompanying drawings may be satisfactorily used in the spinning of yarn according to the principles of this invention. In this apparatus a small tank 4 fitted with inlet and outlet tubes 5 and 6 is mounted within the coagulating bath trough I. The coagulating bath trough I is fitted with inlet and outlet tubes 2 and 3. In one end of the tank 4, a small restricted opening 1 provides a passage, for the yarn spun in this tank, to the main bath trough. Hot bath is introduced continuously into this small tank through the tube 5 and discharged with the thread into the main trough or is led to drain Additional bath of normal temperature is introduced into the main bath trough I through the inlet pipe 2. Bath is discharged, from this trough through the pipe 3. The viscose solution is introduced into the small tank by means of the spinneret assembly 8. The freshly formed yarn I0 is led through a convergence guide 9 and through the opening I into the main bath trough where it is passed around a guide II and then led from the trough toa collecting device l2.

Spinning apparatus for use in the practice of this invention differs fromthe standard viscose spinning machine only in that it possesses some means of maintaining at an elevated temperature that portion of the coagulating bath that immediately surrounds the spinneret. This means may satisfactorily comprise a small tank fitted within the main bath trough and containing the spinneret assembly as described above. However, it is not necessary that the freshly formed yarn pass directly from the hotter bath into the colder one. A system of rollers of the type shown in Figure 3 and which act to lift the yarn from the first bath and direct it into the second bath may be used. The second bath may, if desired, be provided witha multiple roller setup whereby to obtain a long bath travel. As a further improvement, this small tank may be covered so as to prevent evaporation of the bath constituents.

A further modification contemplates the use of a' hot bath into which only the face of the spinneret protrudes, the rest of the spinneret assembly being positioned in air or in a bath of normal temperature. Such a construction will act to prevent the gradual accumulation of gelled viscose within the spinneret assembly.

Other means may also be used. For instance, a spinning funnel of the type used in the spinning of yarn according to the cuprammonium process may be used in conjunction with a standard viscose spinning machine, the 'hot bath being contained within this funnel. Or, local heating may be supplied by mounting a heating device in the coagulating bath in close proximity to the spinneret.-

With regard to other yarn properties, tests have shown that increasing the spinning speed and maintaining other conditions constant reduces the luster of the yarn slightly. However, the luster of the yarn spun with only that portion of the bath surrounding the spinneret heated, is

equal to or better than the luster of yarn spun with the entire bath heated. The softness of the yarn is improved by the higher speed and still better results are obtained whenthe hot bath is confined to the region of the spinneret.

It is believed that the great improvements resulting from the practice of this invention are the result of a particularly favorable condition of coagulation at and near the face of the spinneret. They are not due simply to heating the viscose, for if the viscose inlet tube is surrounded with a steam coil, and the heated viscose is spun into a bath maintained at 45. C., distinctly adverse results are obtained. Neither are these improvements due only to the heating of the coagulated filaments for if the viscose is spun into an initial bath at C. and the coagulated filaments are then passed into a hot bath, even though the initial 45 bath travel is less than /2 inch, the improvements are not obtained. Hence, it appears that some peculiar and hitherto unobserved effect occurring at the instant of coagulation of the viscose is responsible for the new results obtained by the practice of this invention.

Further evidence pointing toward the existence of such a peculiar type of coagulation in thepractice of the present invention may be obtained from a study of the cuprammonium viscosities of yarns spun according to usual practice and according to the principles of the invention. The cupramtemperature of 33 C degree of degradation of the yarn, an increase in degradation being indicated by a decrease in cuprammonium viscosity. Tests reveal that yarns spun at 5,300 inches per minute and in accordance with the principles of this invention, possess a higher cuprammonium viscosity than do yarns spun from similar viscose into a 45 C. bath and ata normal draw-off speed of 3,200 to 3,400 inches per minute. This result is particularly evident when using viscose solutions of high salt index. Thus, the spinning of yarns by the process contemplated by this invention and at high spinning speeds, inhibits the degradation of the yarn that occurs when spinning at normal speeds and temperatures.

However, the cool (45 C.) portion of the bath does not serve only to cool the yarn passing through it. It also serves to permit the yarn to undergo further necessary chemical and physical reactions beyond the region of the heated spinneret zone. This is illustrated by the data of Tables I and IA which show clearly that a certain minimum length of travel in a cool second bath containing the necessary chemical ingredients is necessary for the production of a sat isfactory yarn. The data in these two tables are for yarn of 150-denier, 60-fi1ament count, spun from cotton 'linters viscose containing 7% cellulose and 6% sodium hydroxide and ripened to a salt index of 5.2.

The data in Table I show the meet on yarn properties of passing the yarn from the heated bath directly into one or more cold baths of various compositions. In all cases, in this table, the

yarn was spun at a speed of 6,810 inches per,

minute and first traveled a distance of 6 /2 inches. through a bath heated to 95 C. and containing 11% sulfuric acid, 19% sodium sulfate, 4% glucose and 0.7% zinc sulfate before being passed through the cold baths and directed to a suitable collecting device.

In test No. 1, the yarn issuing from the hot bath was passed for a distance of 18 /2 inches through a second bath of the same composition as the hot bath, but maintained at a temperature of 45 C. This arrangement is in accordance with the preferred embodiment of the present invention.

In test No. 2, the yarn issuing from the hot bath was first passed for a distance of 28 inches through a second. bath of the same composition as the hot bath but maintained at 45 C. The

.yarn was then further passed for a distance of TABLE I Elonga- 7 Spin Break Tenacity Quality Test 1\ tension tension dr factor Grama 1 Grams Grams denier Per cent The data in Table I-A show the effect on yarn properties of changing the length of yarn travel as the hot bath in all cases, and were main-.

tained at 45 C.

TABLE I-A Hot Cold Tenac- Elonit? bath bath 555.... 235.. i333? travel travel ry) y) Grams per Grams Grams denier Per cent 5 1 16. 2 28. 3 1. 52 22. 5 34. 4 6- 8 30. 0 36. 3 1. 83 21. 7 39. 7 7- 14 31. 0 76. 0 1. 92 22. 1 42.3 8. 43. 5 120. 0 2. 20 20. 9 46. 0 9 0 13. 0 l. 35 19. 0, 25. 7 10...--. 5A 0 26. 0 43. 5 1. 75 19. 2' 33. 7

A further striking fact that is brought out by the data of Tables I and I- -A is the effect of the process contemplated by this invention on the breaking tension of the yarn. The breaking tension of present normal yarns spun at speeds of approximately 3,300 inches per minute in a bathgrams at 68 10 inches per minute spinning speed sodium sulfate, glucose and zinc sulfate,---and maintained at a temperature of 37 C.

In test No. 4, the yarn issuing from the hot Gil and it is raised to 76 grams at 5,400 inches per minute spinning speed, and by increasing the yarn travel in the cool portion of the bath, as indicated in Table I-'A, it is possible to increase the breaking tension of the'yam to grams. This discovery, which further points to the existence of a peculiar type of coagulation in the case of this present process, is of the greatest practical importance. Not only does this improved breaking tension permithigher spinning tensions to be successfully employed in the spinning of yarns of higher tenacities, but, if only present normal spinning tensions are employed,-it serves to promote improved spinning quality with a resultant decrease in the number of broken filaments, etc. because of the thus increased ratio of breaking tension tospinning tension.

The two tables above referred to disclose the improvement of the present invention when applied to the spinning'of yarn at high spinning speeds. The present invention, however, has very distinct advantages in the spinning of yarn at speeds of the order of 3,000 inches per minute. Yarns spun at these speeds, in accordance with the present invention, are found to possess greatly improved physical properties. This is brought out most clearly by Table II below. The data contained in this table indicate the effect on the physical properties of yarns spun at a normal spinning speed of 3,300 inches per minute when the temperature of the bath surrounding thespinneret, and including the first six inches of bath travel is increased, while the temperature of the rest of the bath, or the second bath, is maintained at 45 C, In all cases, the total bath travel is 25 inches and the spinning tension is approximately 25 grams.

TABLE II Bathttmb '1 1. Fl o l t para ure ('naci y ongation ua i y '1 est (spinneret (dry) (dry) factor zone) Grams per 0. denier I er cent By suitable manipulation of the; spinning tension or bath travel, or both, the dry elongations of the yarn spun with the bath in the zone of the spinneret heated to temperatures of 66 C. and

76 C. may be reduced to a value of about 20.9%

and the dry tenacities thereby increased to about 2.16 and 2.24 grams per denier, respectively. The essence of this process comprises spinning a viscous solution in to a hot bath with short Cotton linters viscose an a saltindex of 4.0 and containing 7% cellulose and 6% sodium hydroxide is spun into a bath containing 11% sulfuric acid, 21% sodium sulfate, and 0.7% zinc sulfate, using a total bath travel of 25 to inches at a spinning tension of to 48 grams to give a yarn of 150 denier-60 filaments.

Part A The spinning speed is 3,400 inches per minute and the bath temperature C., giving a dry tenacity of 2.17 grams per denier, a dry elongation of 17.4% and a quality factor of 37.8.

Part B The spinning speed is 5,300 inches per minute and the bath temperature 45 C., giving a dry tenacity of 1.84 grams per denier, a dry elongation of 16.8% and a quality factor of 30.9.

' Part C The spinning speed is 5,300 inches per minute and the bath temperature 85 C'., giving a dry tenacity of 1.98 grams per denier, a dry elongation of 18.3% and a quality factor of-36.2.

Part D The spinning speed is 5,300 inches per minute and the bath temperature for the first five inches of travel is C. and thereafter is 45 C., giving a dry tenacity of 2.13 grams per denier, a dry elongation of 18.9% and a quality factor of 40.3.

Part E The spinning speed is 5,300 inches, the bath temperature for the first five inches of travel is C. and thereafter 45 C., giving a dry tenacity of 2.04 grams per denier, a dry elongation of 20.1% and a quality-factor of 41.0.

EXAMPLE II Wood-pulp viscose at a salt index of 4.0 and containing 7% cellulose and 6% sodium hydroxide is spun in a bath containing 11% sulfuric acid, 19% sodium sulfate, 4% glucose, and 0.7% zinc sulfate, using a total bath travel of 25 to 26 inches to give yarn of denier-60 filaments.

Part A The spinning speed is 3.300 inches per minute, the spinning tension is 30 grams, and the bath temperature is 45 C., giving a dry tenacity of 2.05 grams per denier, a dry elongation of 20.1% and a quality factor of 41.1.

Part B .The spinning speed is 5,400 inches per minute, the spinning tension is 28 grams and the bath temperature is 45 C., giving a dry tenacity of 1.77 grams per denier, a dry elongation of 17.1% and a quality factor of 30.2.

Part C The spinning speed is 5,400 inches per minute, the spinning tension is 39 grams and the bath temperature is 82 C. for the first 5 /2 inches of travel and thereafter 45 C., giving a dry tenacity of 2.03 grams per denier, a dry elongation of 19.4% and a quality factor of 39.3.

EXAMPLE III The viscose, bath and spinning conditions in the respective parts are substantially the same as in Example II, except that the viscose is spun at a salt index of 6.0.

Part A The dry tenacity is 1.87 grams per denier, the dry elongation 20.2% and the quality factor 37.8.

Part B The dry tenacity is 1.60 grams per denier, the dry elongation 17.5% and the quality factor 28.0.

Part C The dry tenacity is 2.01 grams per denier, the dry elongation 21.0% and the quality factor 42.2.

EXAMPLE IV Wood-pulp viscose containing 7% cellulose and 4% sodium hydroxide and ripened to a salt index of 7.3 is spun into a bath containing 9.5% sulfuric acid, 22% sodium sulfate, 4% glucose and 0.7% zinc sulfate to give a yarn of 150 denier- 60 filaments, using a total bath travel of approximately 25 inches.

Part A The spinning speed is 3,300 inches per minute, the spinning tension is 32 grams and the bath temperature is 45 C. The yarn possesses a dry tenacity of 1.63 grams per denier, a dry elongation of 17.4% and a quality factor of 28.4.

Part B The spinning speed is 5,400 inches per minute,

of the travel. grams. The yarn possesses a dry tenacity of and a quality factor of 33.8.

2,307,863 the spinning tension is 29 grams and the bath temperature is 45 C. The yam possesses a dry tenacity of 1.52 grams per denier; a dry elongation of 14.8% and a quality factor of 22.5.

Part C Thespinning speed is'5,400 inches per minute,

the spinning tension is 36 grams and the bath temperature is 83". C. for the first inches of travel and 45 C. for the remainder of the travel. The yarn possesses a dry tenacity of 1.94 grams per denier, a dry elongation of 21.0% and a quality factor of 40.7.

EXAMPLE V Cotton linters viscose containing 7% cellulose and 6% sodium hydroxide ,and ripened to a salt index of 5.2 is spun to give a yarn of 150 denier 60 filaments at a draw-off speed of 8,850 inches per minute, using a total bath travel of 11 inches.

Part A The spinning bath containing 11% sulfuric acid, 19% sodium sulfate, and 0.7% zinc sulfate is maintained at 47 C. It is impossible'to spin yarn under these conditions.

Part B The spinning bath possesses the same compo sition as Part A of Example V. The bath, for the first .5 inches of yarn travel, ismaintained at 98 C., andior the remainder of travel is maineven of the same general type; Preferably, however, the coagulating bath, or baths, employed in accordance with thepresent invention; are of the type conventionally used in the commercial spinning of viscose rayon yarn and may contain, in addition to ,the usual 7% to of sulfuric acid, glucose, ammonium sulfate, sodium sulfate, zinc, nickel or iron sulfate, etc. It is furthermore preferred, due to "operating convenience, that the two baths be of the same composition thereby permitting the small quantity of hot bath immediately surrounding the spinneret to flow into the larger bath trough'to heat the same.

As indicated by the examples contained in this specification, the process contemplated by this invention is not limited to the use of a viscose solution of any specified composition or degree of ripeness. In fact, one of the advantages of the process lies in the fact that it enables yarns tained at 46 0. The spinning tension is about 23 grams. The yarn possesses a dry tenacity of 1.46 grams per denier, a dry 21.5% and a qualityiactor of 31.4.

Part 'C The spinning bath contains 12% sulfuric acid,

19% sodium sulfate and 0.7% zinc sulfate. The bath is maintained at 98 C. for the first 6 inches of yarn travel and at 46 C. for the remainder The spinning tension is about 24 151 grams per denier, a dry elongation of 22.4%

I Exempt: VI Cotton linters viscose containing 7% cellulose index of 5.2 is spun into a bathcontaining 12.5%

sulfuric acid, 19% sodium sulfate; 4% glucose. and 0.7% zinc sulfate at a spinning speedof elongation of of satisfactory and even improved properties to be spun-from .viscose solutions that have been ripened less than a normal time. For example, yarn spun from a wood-pulp viscose of salt index 3.0 at 5,400 inches per minute spinning speed,

with a 5-inch travel at the spinneret in a bath heated to 82? C. and with the main bath at 46 0., possesses a dry tenacity of 2.06 grams per denier and a dry elongation of 16.0% for a quality factor of 33.0. Yam spun under similar conditions but using a viscose solution with a salt index-of 4.1 I

possesses a dry tenacity of 2.09 grams per denier and a dry elongation of 17.6% or a quality factor of 36.8, while yarn spun from a viscose solution with a salt index of 7.1 possesses a quality factor' of 43.0.

. The results obtained in this manner are very striking and are of tremendous importance. It

' and 6% sodium hydroxide and ripened to a salt 9,500 inches per minute to give-a-yarn of 150 denierfilaments, using a total bath travel of 13% inches.

r Part A The entire spinning bath maintained at 45 C. and the spinning tension is about 35 grams. The yarn possesses a dry tenacity of 0.74 gram per denier, a dry elongation of 7.5% and a quality factor of 5.6.

' Part B The spinning bath is maintained at 97 C. for

the first 6% inches of yarn travel and at 45 C. 6

for the remainder of the travel. The spinning tension is about 21 grams. The yarn possesses a'dry tenacity of 1.48 grams per denier, a dry elongationof 19.8% and a quality factor of 29.3.

The present invention is not limited to the use of a coagulating bath of any particular composition. .Its advantages may be obtained with.

various types of baths, such as are well known in the art. Furthermore, it is not necessary that pinning process.

has been suggested inthe past that it should be possible to substantially increase the quality factor of a viscose rayon yarn by the use of a viscose solution of high salt index. The chief difliculty in achieving such an increase in the past has been the inability to obtain a spinning bath which will effect a sufflciently rapid and uniform settingup" of .thegel structure of the yarn early in the The above results indicate clearly that the use of a hot bath in the region of the spinneret provides, for the first time, such. a

desired condition. This process not only permits viscosesolutions of high salt-index to be used in the spinningof yarns of improved properties, but

it has been found possible when operating in accordance with this invention to reduce the tend ency toward bad spinning and plugged spinneretsby increasing the salt index of the viscose solution. I Naturally, when viscose solutions of different compositions 0'! degrees of ripeness are employed, it may e desirable to alter to some extentthe various factors involved in the spinning operation, such as spinnning tension, bath travel, etc.

For instance, it is found, when using a viscose solution possessing a higher than normal salt index, that it is desirable, to increase somewhat the length of travel of the yarn in the heated portion -of the bath. The invention contemplates that the two baths be of the same composition, or

elongation. For the conditions of Example I, Part E, the tenacity is greatest with a short hot bath travel of 1 to 4 inches and decreases rather rapidly with longer travel imtii at 15 inches'hot bath travel, it is only 80% of its maximum value. The elongation has a maximum value at 'I to 12 inches hot bath travel, butlfalls onlyslowly at longer travels. The maximum quality factor is obtained at about inches travel. These effects provide a certain flexibility in the process. If a yarn of maximum tenacity and somewhat reduced elongation is desired, a travel of 2 or 3 inches in the heated bath will be preferred. For yarn of higher elongation and reduced tenacity, a travel of about inches is better. It is also possible to obtain yarn of the maximum quality factor by spinning with a bath travel of 5 inches and adjusting the elongation and tenacity by altering the spinning tension. In general, the travel of the yarn in the hot bath is preferably relatively short and will vary from 1 to 10 inches.

The conditions stated above concerning the considerably greater than the length of travel, in the hot bath. Depending upon the physical characteristics which it is desired to impart to the yarn, the yarn will be passed through the second bath a distance of between 12 to 50011 more inches. i

To obtain the advantages 1 of this invention, the. temperature of the firstbath must be raised to at least 60 C. Even greater advantages accrue if the temperature of this bath is raised to a temperature of 85 C. or 100 C. or even higher. These higher temperatures will be of the greatest importance when spinning at speeds of the order of 7,000 inches per minute or more, and particularly, when spinning at speeds of the order of 10,000 inches per minute or more. In connection with these very high speeds, it may be desirable to add various substances, such as glucose or glycerin, to the bath, so that it may be heated to a sufliciently high temperature.

In this connection, it might be noted that the use of the hot spinning bath reduces the liquid drag on the yarn passing through the bath and on the guide rollers rotating in the bath. The spinning tension specified in Parts A and B, respectively, of Example VI illustrate this effect, which is due to the lowered viscosity of the heated bath. Thus a useful means is provided for at least partially controlling the substantial increase in spinning tension which is encountered with the increased spinning speeds with which this invention is concerned. Because a high spinning tension has an adverse effect on spinning performance and physical properties of the yarn, the reduction in liquid drag made possible by the use of a heated bath is of the utmost importance in the spinning of a satisfactory yarn at high speeds.

In accordance with the principles of this invention, the temperature of the second bath must be lower than that of the first bath and should preferably be of the order of C. or even lower. Temperatures much above 45 C. in the second bath will lead to the disadvantages obtained when the entire bath is heated. The optimum temperature of the second bath will depend upon the exact spinning conditions encountered, in-.

cluding the temperature of the first bath and the relative length of travel of the yarn in the two bathsa However, any reduction in temperature between the first and second baths will be better than the use of a single hot bath. The temperature of this second bath should be maintained at least 10 C. below that of the first bath and should preferably be of the order of 45 C. or even lower.

The examples contained in this specification disclose the spinning of viscose rayon yarn at speeds up to 9,500 inches per minute. However, the advantages of the invention may also be realized at higher speed, such as 12,000 inches per minute or even higher as, for. example, upwards of 15,000 inches per minute.

This invention is not limited by the extent or manner of applying tension during the spinning operation. When spinning yarn in the two-temperature bath system of this invention and maintaining the spinning tension constant, it is found thatan increase in the temperature of the first bath causes a small increase in tenacity and a considerably greater increase in elongation. Hence, the invention contemplates the increase of'the spinning tension by an amount suflicient to increase the tenacity of the yarn in a manner corresponding to the increase in elongation. However, the invention also contemplates the use of other means than an increase in spinning tension to gain this increase in yam tenacity. For example, the invention contemplates subjecting the finished yarn'to a stretching operation in a third bath maintained at an elevated temperature in accordance with the precedure outlined in peratures now employed in commercial invention is most useful when main body of the the 'copending application U. 8. Serial No. 278,403 to Kams, filed June 10, 1939.

The chief advantage of this invention lies in its ability to produce yarn of better physical.

properties than can be obtained either with the entire bath heated to the preferred temperature or with the entire bath maintained at the temspinning processes. The spinning'at high speeds because improvements in physical properties are greatly needed under these conditions. The essential feature of the invention consists in maintaining the spinning bath in the region of the spinneret face and for a distance of from 1 to 10 inches beyond at a temperature above bath at a lower temperature. When contrasted with that process in which the entire bath is maintained at an elevated temperature, the process contemplated by' this in-' vention is found to possess the following advantages: i

1. For the same maximum temperature this invention produces a yarn of superior physical properties. I

2. To obtain equivalent properties, the required maximum temperature is substantially lower.

3.Since the high temperature bath is confined to a small volume through which a rapid fiow may be economically provided, an adequate 60 C. while maintaining the spinning filaments may be utilized to heat the main bath to the desired temperature. Heat losses are consequently not important.

5. The surface of the hot bath is relatively small and may be covered. In this manner, evaporation losses are reduced to a minimum.

6. The major portion of the bath is maintained at lower temperatures and thus the yarn is cooled before it leaves the bath. Hence, the tendency toward crysta1 formation within the yarn is no greater than at the present time. In fact, in-. asmuch as this invention contemplates the use of amain bath at a temperature below 45 0., this tendency toward crystal formation will be greatly reduced over the present standard. This is a very important advantage inasmuch as it ofiers a great decrease in the number of cut'and broken filaments.

7. Except for actually starting the flow of filaments from the spinneret face, all the manipulations of the operators are carried out at normal temperatures. The gross machine parts, the guides, bobbins, etc., and the unavoidable spray and drip from the moving parts are not hot. This is a tremendous advantage from the viewpoint of practical, economical operation and maintenance.

8. The process contemplated by the present invention is operative with any bath that can be used in present normal practice. requires no diiference in composition between the two baths although such a difierence may prove to be desirable for other reasons and is contemplated by the invention.

The process provides a means of adjusting the tenacity and elongation of the product by simply changing the length of travel of the yarn in the hot bath.

The process provides a means whereby undesirably large increases in spinning tension may be avoided as the spinning speed is increased.

The process also provides a means of increasing the breaking tension of the yarn during the spinning operation. This increase is desirable because it not only permits a higher spinning tension to be employed whereby the yarn possesses a greater tenacity, but it also serves to improve the spinning quality when only normal spinning tension is employed, thus reducing the number of broken filaments in the spun yarn.

The process provides a means of producing an improved product by the use of a viscose solution ripened to a degree less than normal.

Cuprammonium viscosity measurements show that yarn produced by this process is degraded to a smaller extent than is yarn produced according to known processes.

Although this discussion of the invention has been limited to the spinning of yarns from a viscose solution, it is obvious that the invention should not be so limited. Its principles can be used successfully in the manufacture of films, tubings and other structures of regenerated cellulose from viscose solutions. Such articles, prepared in accordance with the principles of this invention, will be found highly suitable for use in the art.

Since it is obvious that many changes andmodifications can be made in the details above described without departing from the nature and spirit of the invention, it is to be understood that the present invention is not to be limited to the said details except as set forth in the appended claims. a

I claim:

1. A process of spinning viscose rayon yarn which. comprises extruding the viscose through a spinneret into an acid coagulating bath containing 7% to 15% sulfuric acid and having a temperature of at least 60 C., and passing the resulting yarn, at a speed of at least 5,000 inches per minute, into a second coagulating bath having a lower temperature than the first bath.

2. A process of spinning viscose rayon yarn which comprises extruding the viscose through a spinneret into an acid coagulating bath containing 7% to 15% sulfuric acid and having a temperature of at least 60 C., and passing the resulting yarn, at a speed of at least 5,000 inches per minute, into a second'coagulating bath hav- The process ing a temperature of at least 10 C. lower than the first bath.

3. A process of spinning viscose rayon yarn whic comprises extruding the viscose through a spi eret into an acid coagulating bath containing 7% to 15% sulfuric acid and having a temperature of at least C., and passing the resulting yarn, at a speed of at least 5,000 inches per minute, into a second coagulating bath having a temperature of the order of 45 C.

ing yarn, at a speed of at least 5,000 inches per minute, into a second coagulating bath having a lower temperature than the first bath.

5. A process of spinning viscose rayon yarn which comprises extruding the viscose through a spinneret into an acid coagulating bath containing 7% to 15% sulfuric acid and having a temperature of at least 60 C., moving the resulting yarn through said bath for a distance between 1 and 10 inches, and passing the resultmg yarn, at a speed of at least 5,000 inches per Imnute, into a second coagulating bath having a temperature of at least 10 C. lower than the first bath.

6. A process of spinning viscose rayon yarn as defined in claim 1 in which the composition of the second coagulating bath is substantially the same as the first coagulating bath. 4

7. A process of spinning viscose rayon yarn as defined in claim 2 in which the compositon of the second coagulating bath is substantially the same as the first coagulating bath.

Y nor SOUKUP.

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