US2462927A - Artificial filaments and yarn - Google Patents

Description

Patented Mar. 1, 1949 ARTIFICIAL FILAMENTS AND YARN Rudolph Woodell, Kenmore, N. Y., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application November 6, 1943, Serial No. 509,280

4 Claims.

This invention relates to improvementsv in artificial filaments and yarn, and it is particularly concerned with the manufacture of regenerated cellulose yarn having high extensibility.

Filaments and yarn composed of synthetic linear polyamides; described in Carothers U. S. Patents Nos. 2,071,253 and 2,130,948, are capable of being cold drawn, i. e. permanently elongated at ordinary temperatures and in the dry state to many times their original length. These polyamide yarns possess, in addition, the unique property, when being cold drawn, of necking down during cold drawing. This necking down characteristic is described in detail in Babcock U. S. Patent No. 2,289,232 and consists, as shown in detail in Figure 1 and in the specification of said Babcock patent, in the localizing of the draw-point of the filaments to a very narrow region which, in general, is a portion of the length of the filament having a magnitude in the neighborhood of the diameter of the filament. Although the necking down of polyamide structures is most easily understood by reference to the individual filaments, yarns composed of several filaments possess the same phenomenon.

Regenerated cellulose filaments and yarns produced by previously known processes, are in-' capable of being elongated more than a limited degree, for example, about 5% to of their that in the following discussion the phenomenon of "necking down will include not only the drawing at one point or region but will also include the drawing at two or more points in they zone in which stress is imposed with the proviso, however, that the drawing, as indicated in said Babcock-patent, is effected in very narrow regions.

' It is an object of this invention to produce artificial yarns having the property of being permanently stretched to a dimension greatly in excess of their original length. A further object'of the invention is concerned with the formation of regenerated cellulose filaments which can be permanently elongated to several times their original length and which possess the characteristic ofnecking'down during drawing. A still further object of the invention is concerned with the cold drawing of regenerated cellulose filaments and yarns to several times their original length. Another object relates to a novel procedure for making artificial yarns and filaments possessing the property of neckingdown during drawing and being permanently elongated to a very large degree. An additional object pertains to the treatment of extensible regenerated cellulosefilaments whereby to greatly increase their extensibility. Other objects will appear hereinafter.

iii

The objects of the invention are, in general, accomplished by extruding an aqueous cellulosic solution such as viscosethrough a nozzle'containing one or more holes into a bath which exhibits a rapid coagulating action on the cellulose xanthate dispersion in the viscose while at the same time possessing very little or no tendency under the conditions prevailing during coagulation to convert the cellulose xanthate to regenerated cellulose, the tension imposed on the filaments prior to passing out of the coagulating bath beingof a very low order of magnitude, preferably not in excess of 0.01 gram per denier. The yarn is then regenerated in the relaxed state, that is, substantially free from tension. The resulting regenerated cellulose yarn is then subjected to tion; the parts, proportions and percentages being by weight:

EXAMPLE I 120 holes into a bath having a rapid coagulating action but, under the conditions obtaining, ex-

"hibiting no substantial tendency to convert the cellulose xanthate to regenerated cellulose. The coagulating bath is prepared from an aqueous solution consisting of:

Per cent Monosodium phosphate 19 Disodiumphosphate 5 Sodium sulfat Water 66 sufiicient phosphoric acid being added -to said solution to impart to the solution a pH of 5.0. The coagulating bath is maintained at a temperature of 75 C. The filaments pass from the spinneret through a tubular member open at both ends and submerged in the coagulating bath for a distance of inches, the tubular member having an inner diameter of 18 mm. and being supported horizontally in the bath so that the only flow of bath through the tube is induced by the passage of the filaments, the bath flow therefore being in the direction of passage of the filaments. Qn leaving the tubular member, the yarn is immediately removed from the bath. It is passed about a feed wheel having a peripheral speed of 816 inches per minute, with a total tension on the filaments during the travel in the bath of about 0.004 gram per denier. The yarn at the feed wheel is about 1,000 denier.

The yarn passes one or more times around the feed wheel to eliminate the danger of slippage and is allowed to drop of its own weight onto any suitable receiving surface, for example, a rectangular tray to which is imparted a predetermined oscillatory traverse which effects the building up, without tension, of a suitable package of yarn. The yarn package is wrapped with a cloth cover and is immersed in a regenerating bath for a period of time sufiicient to completely convert the cellulose xanthate to regenerated cellulose, the regenerating bath used having the same composition as the coagulating bath into which the viscose is extruded but being maintained at a boiling temperature. After having been immersed in this bath for a period of 30 minutes during which regeneration is completed, the package is then removed from the bath, is treated with a washing solution, is showered with an aqueous solution or dispersion of a suitable finish, and is dried. During all of these operations, the yarn is substantially free from tension in view of its having been collected in a completely relaxed state.

The dried yarn is then twisted and reeled to skeins, which are immersed without tension in liquid ammonia for a period of approximately 3 minutes. The yarn is then centrifuged to remove excess ammonia, and the remaining ammonia is removed by evaporation, as by drying at room temperature conditions (75 F.).

tenacity of 05 gram per denier, a'dry elongation 4 of about 100%, a wet elongation of about 120%, and can be colddrawn with a permanent elongation of about 100% of its original length while exhibiting no necking down phenomenon. The

5 cold drawn yarn shows a relatively high degree of orientation as evidenced by the X-ray diffraction pattern, which shows distinct, oppositely opposed arcs as comparedwith the X-ray diffraction pattern of the yarn before cold drawing,

10 showing clearly defined concentric rings without arcs. The yarn, after being treated with ammonia and dried, can readily be cold drawn (stretched without'heat in the dry state at 60% relative humidity and 75 F.) without breaking 15 to 3.5 times its original length (250% stretch) \or, after thoroughly wetting with water, can be stretched to more than 4 times its original length. The ammonia treated and dried yarn prior to drawing shows no orientation as evidenced by its 20 X-ray diffraction pattern but, after cold or wet drawing to a high degree, it exhibits very marked orientation as shown in its X-ray diffraction patterns. The ammonia treated and dried yarn, particularly when it contains absorbed moisture, for example when in equilibrium with 60% rela- -tive' humidity and at 75 F., exhibits a very marked V necking down during cold drawing. It also exhibits a very marked necking down during wet drawing. It also possesses a certain degree of thermoplasticity, that is, when the dry, undrawn yarn is placed in contact with a heated metal surface, the tension required to draw or permanently elongate the yarn is greatly reduced.

The viscose solution employed in the manufacture of the yarn preferably contains 9% cellulose and 9% sodium hydroxide and is ripened to a sodium chloride index of about 3.5. However, this is not essential to the invention. Good results can also be obtained by the use of a viscose solution containing 7% cellulose and 6% sodium hydroxide, or other proportions ofthese constituents can be used. Generally speaking, however, the higher the content of cellulose, the more pronounced the necking down characteristics after the liquid ammonia treatment. The solution is preferably prepared from slightly aged alkali cellulose, although this is not critical to the invention. The solution, prior to its extrusion into the coagulating bath, is preferably ripened to a sodium chloride index of from 3.5 to 4.5, but, here again, these values are not to be considered as limiting. The solution is preferably prepared from cotton linters cellulose of high alpha-cellulose content and, if desired, this material can, prior to its conversion to cellulose xanthate, be etherified or esterified to a low degree, producing, for example, glycol cellulose, cellulose glycolic acid, cellulose glycolic acid derivatives, methyl cellulose, benzyl cellulose, etc. Methyl cellulose containing, for example, 0.3 methyl group per glucose unit is illustrative of such lowly etherified or esterified materials which can be 7 used in preparing the spinning solution.

The. coagulating bath used is preferably an aqueous solution containing at least 10% dissolved phosphate, calculated for convenience as trisodium phosphate. Obviously, the phosphate is not necessarily present or even added in the form of trisodium phosphate but, in referring to said percentage, the assumption that the phosphate is trisodium phosphate facilitates the calculation of the preferred amount of phosphate ion. Alkali metal phosphates, such as the phosphates of sodium and potassium, are preferred, although other water-soluble phosphates, such as ammonifuric acid in moderate amounts. In order to have a rapid coagulating action and slow or negative regenerating action, the pH of the coagulatingbath should be maintained between 3.0 and 7.0 and preferably between 4.5 and 5.5. The

broad scope of the invention contemplates the use of other types of baths, for example, slow regenerating baths and any such baths known to the art may be used, for example, ammonium sulfate-sodium sulfate baths and the like. Generally speaking, aqueous baths containing as an 1 The coagulating bath must be used under such essential ingredient alkali metal salts of weak acids, such as phosphoric acid, sulfurous acid, lactic acid and the like, and adiusted to' the proper pH by the addition of the corresponding acid or of a base, serve as excellent coagulating baths.

conditions that substantially no regeneration takes place during the passage of the yarn through the bath. Thus, the temperature of the bath may conveniently be in the neighborhood of 55 C. to 75 C., although it is only necessary to use a temperature at which the bath does not exhibit any substantial regenerating effect.

The water-soluble cellulose xanthate yarn can be regenerated in any suitable type of bath. Thus, baths such as that used in the above example exert a pronounced regenerating effect at elevated temperatures, such as boiling temperature, and regeneration may be effected in the same type of bath, provided the yarn is subjected to the bath for a sufliclent period of time and, where necessary, at asumclently elevated temperature, Although it is preferred that the yarn be regenerated in a bath of the same composition as the coagulating bath, any suitable regenerating bath, such as dilute sulfuric acid-sodium sulfateibath (Mueller baths), may be used, or heated inert liquids such as aqueous salt'solutions or glycerin may be used.

The following Table I presents examples of fast coagulating, slow regenerating spinning baths which maybe used and of the physical properties possessed by yarns produced by the use of these spinning baths:

Table I Bpihnin! ath: A V 1 A s s s spun NH: spun NHs Spun N H:

No. of NH], treatments required to cause neck- 101:5 down 1 1 1 D er 1,100 1,450 1,300 1,941 1,350 1,052 Filaments. 120 120 120 120 120 120 Tenacity:

, Dry, git/den 1.0 0.55 0.75 0.38 0.81 0. 46 Wet, grJden 0.55 0.35 0. 42 0. 16 0.35 0. L00 galden 0. 95 0. 0, 67 0.37 0.78 0.44

Elon t on: J

ry, percent 114 .250 131 100 -ll5 188 Wet, percent-. 128 275 154 260 '110 225 Loop, percent. 100 225 96 167 100 164 1 Spin tension, grJde 0.004 0.002 0.003 Bath travel, inches l6 15 15 s in p i f 1 is...

g" Composition s Noll r0 -1 Nso-"nt.o.if.'..*" is s :4 Nlfl sol -agfillsqs i ,NMBOG u o..- mg'qr gmor-muusol-rmmsoe u It is also preferred that the same magnitude low tension of the spinningnoperation not be exceeded during the subsequent regeneration, puriflcation, drying and after-treatment of the yarn. For example, the yarn leaving the coagulating bath may be formed without tension into a cake package, as in the preferred embodimentof the invention, or the yarn may be collectedfree of tension in the form of overlapping loops and ringlets, as in British Patent No. 379,880 to Topham wherein the yarn is allowed to drop freely onto a slowly moving conveyor belt which advances the yarn under showers of regenerating I and purifying liquids and through a suitable, drying means.

The dried yarn is preferably twisted and wound in skein form before treatment with liquid ammonia. However, this is not necessary,- provided only that the yarn is treated in a substantially tensionless state.

The above description has been generally concerned with the production of highly extensible yam having the characteristic of necking down by the use of the specific procedure set forth, followed by two and preferably a single treatment .with liquid ammonia. It has been found that when a single treatment with liquid ammonia does not produce the necking down property, the latter can be developed by subjecting the yarn to additional treatments with liquid ammonia. When a plurality of treatmentswith liquid ammonia are used, the yarn is immersed in liquid ammonia until the yarn becomesthoro'ughly wet out by the liquid ammonia, theam monia removed and the yarn dried, all these steps being performed while the yarn'is in ajrelaxed state, and this cycle of steps repeated until the necking down property is developed.

Though in the specific procedure set forth the yarn, prior to treatment with liquid ammonia, is produced by the use of fast coagulating, slow regenerating baths, particularly the phosphate bath, it has been found that the property of necking, down can be developed? by treatment with liquid ammonia of yarn produced without the use of i-fastcoagulating baths having little or no regenerating action if the yjarriis spun'under low tension, preferably not inexcess-of 0.01

gram perdenier, and substantially the same magnitude low tension is not exceeded "duringithe subsequent purification, drying andaften'stre'at ment. of the yarn. Thus, for example; yregener ated cellulose yarn spun underja tension not dn excess of 0.01 gram per denier in thes ca ed "Mueller" type baths (aqueous solutions odium sulfate and sulfuric acid, wither without zinc sulfate and other additions) and purified and dried under the same magnitude lbw tensionjcan, if subjected in the relaxed state to continued and consecutive treatments with liquid ammonia, develop the property of necking down. 'Whena single treatment with liquid ammonia does not produce the necking down property, the latter can, be developed by subjecting the yarn to acidi tional treatments with liquid ammonim as preyiously described. I

spinning baths, the physical properties possesed by yarns produced under low tensions by the use of these spinning baths, and the number of treatments with liquid ammonia required to develop j the necking down property:

Table II A n 0 D, a

Spinning bath A A A A A No. of NH; treatments required to cause necking down 2 2 2 2 2 Delllel' 000 1,000 000 1,000 020 1,420 000 1,400 000 1,020 Filaments 120 120 120 120 120 120 120 120 120 120- Tenacity:

Dry, gr./den.... 1. 0. 00 1.10 0. 00 1. 1a 0. 01 1. 10 0.00 0. s1 0. 43 Wet,gr./den 0. 00 0. 0.00 0.20 0. 41' 0 a1 0. 00 0.34 0.40 020 L00 gr./den 0.00 0.00 1.00 0.04 1.00 0 00 1.10 0.00 0.10 0.41 Elongat on:

.Dry, per cent 76 I165 62 152 60 148 60 183 46 163 Wet, per cent 90 216 86 188 68 100 111 247 89 256 Loop, per cent. 62 146 02 140 52 142 61 177 42 143 Spin tcnsion,gr.lden.. 0.003 0.003 0.003 0.003 0.003 Bath travel, inches l5 1B 7 7 7 Spinning 'lemperabath Cmmsmm yarn must be treated with liquid ammonia to de- N 0 H velop the necking down property, and it also com- H0 is 4; 6.0 3 3, 5, ammonia 55 30 pares the number of treatments with liquid am 1 l i nsgl-4 m glsolm 2g monia necessary for regenerated cellulose yarn 3 1 g -z; 55 produced according to standard methods utilizing a bath which possesses both rapid coagulating Where substantial tensions were used during the coagulation in the case of fast coagulating.

Mueller type bath.

Table III Sample A B p O l) E F N o. of NH: treatments required to cause necking own l 5 6 0 6 l0 Spin tension, gr /den 0 01 0. 06 0.10 0. 17 0. 20 0.83

960 l, 277 008 2, 060 072 l, 728 864 2, 100 209 276 1, 058 120 120 120 120 120 120 120. 40 40 120 120 Tenacity:

Dry, grJden. 1. 05 0. 67 1. 77 0. B8 1. 84 0. 62 2. 62 0. 66 1.90 0. 38 3.3 0. 30 Wet, gr./den.. 0. 66 0. 34 0. 9-1 0. 42 1. 00 0. 64 l. 00 0. 60 0. 00 0.30 1. 0 0. 37 Loop, gr.'/den. 0. 98 0. 64 l. 47 0. 50 l 47 0. 50 1. 92 0.40 l. 77 0. 41 2. 5 0. 31 Elongat on: I

Dry, percent 00 33 276 26 86 15 202 23 12 21! Wet, percent..." 119 181 40 227 3b 166 20 151 26 258 18 107 Loop, ercent 78 146 23 161 17 87 0 46 19 165 8.1 188 Bath trave inches 24 80 95 115 18 Bath temperature, C. 75 75 7 75 47 47 Reference (I) (2) (2) (1) (2) (1) (2) (1) (2) (l) (2) Samples A, B, C and D re resent arns spun into a coagulating bath pre ared from an aqueous solution of 18% NaH:P04, 10% NazSO 0 and 72% water, adjusted to a p of 5.2

y the addition of phosphoric acid or tr sodium phosphate;

Sample E represents regenerated cellulose yarn manufactured according to a standard manufacturing method by the use oi a Mueller type bath; and

Sample F represents a high tenacity yarn likewise produced by spinning into a sodium sulfate-sulfuric acid-zine sulfate bath and suitable for use in the manufacture of tire cord.

(l) signifies the yarn before the liquid ammonia treatment;

(2) signifies the yarn after the number of ammonia treatments indicated in the table.

slow regenerating baths, such as phosphate baths, either during the spinning or during the subsequent treatments up to and including drying, it has been found that although the necking down phenomenon may not be present in the yarn after 0 single treatment with liquid ammonia, nevertheless; additional treatments with liquid amf g develop thi property, the additional .T'treatm'ents with liquid ammonia being performed as previously described. Similarly, in treating rayon produced by standard processes as distinct from the use of fast coagulating, slow regenerating baths and where substantial tensions are used during spinning or during the subsequent treatments up to and including drying, a plu- The above Table III also makes reference to the bath travel in inches. since the length of bath 4 travel obviously has an effect on the degree of 1 0 of treatments Wi h q i amm n D when tested by its X-ray diilraction pattern but 9 is definitely crystalline, as shown by the shape of the concentric rings peculiar to its X-ray diffraction pattern.

The ammonia treated yarns of this invention, as stated above, possess the distinctive necking down property never before obtained in cellulose yarns. Instead of cold drawing the filaments at a relative humidity of and a temperature of F., they may be stretched during or after immersion for a short time in an aqueous solution of a soluble phosphate, such as mono-, dior trisodium phosphate. Drawing of the yarn in either a cold or heated stretching bath develops a high orientation along the fiber axis, but drawing of the yarn in a hot stretching bath permits a high degree of stretching than can be obtained when the yarn is drawn in a cold stretching bath.

The following Table IV shows the physical properties of yarns prior to stretching and after stretching in a cold or hot aqueous sodium phosphate solution:

gle than the uncross-linked product and is crushresistant. So far as is known, this is the first time that a cellulosic fiber has been produced which is both crush-resistant and non-brittle and which can be used in textile operations.

Though the invention has been specifically described in connection with the preferred embodiment which utilizes liquid ammonia to develop the necking down property, the invention is not restricted thereto. In general, substances which, when dissolved in water, form free hydroxylions may be used to develop the necking down property.

- EXAMPLE lI In Example I, afterthe dried yarn is twisted and reeled to skeins, its is immersed in liquid ethylamine for a period of approximately 3 minutes, centrifuged to remove excess ethylamine, and the remaining ethylamine then removed and the (l) Yarn spun at low tension in a phosphate bath.

Table IV N] I: treated NH: treated NH; treated yarn yarn yarn 2 gig? gg stretched cold stretched hot stretched hot mam yam to 217% of to 224% of to 291% of its original its original its original length length length Reference (1) (2) (3) (4) (5) Tenacity:

Dry, grJden 0.9 to 1.1 0.6 to 0.6 2.1 2.25 2. 84 Vet, gin/den 0.4 to 0.55 0.3 to 0.4 1. 05 1. 22 1.37 Loop, grJden 0.85 to 1.1 0.5 to 0.6 Y 1. 1. 72 2. 26 Elon tlon: i

ry, per cent r0145 175 to 285 4.3 4. 9 5.4 Wet, per cent to 170 190 to 300 11. 9 11.0 10.4 Loop, per cent 80 to to 280 3.3 2. 7 3. 8 Ratio loop to dry tenacity..... v 0.86 0. 76 0. 80 Orientation high high high Reference:

(2) Yarn oi the type referred to in (1) treated once with liquid ammonia. (3) Yarn stretched at 35 C. bath composed of 19.1% NaH2PO4+lO% NazSOi with pH adjusted to 5.1.

(4) Yarn stretched in bath same as (3) but at temperature (5) Yarn stretched at 100 C. in bath composed of 17.8%

Each of the stretched yarns referred to in Table IV was obtained by passing the designated undrawn yarn through 55 inches travel in the respective bath at the temperature set forth in the table and, while immersed in the bath, stretching to the extent set forth in the table,

removing the yarn from the bath and collecting it under the'stretching tension on a bobbin and, while on the bobbin, washing it free from the bath, finishing with an emulsion of a sulfonated vegetable oil, and drying.

Though a hot aqueous solution of a-soluble phosphate is the preferred stretching bath, satisfactory results are also obtained when a hot aqueous solution-of potassium formate or glycerin stretching bath is used.

The yarn obtained by drawing the ammonia treated yarn in a hot stretching bath and drying under tension possesses a high elastic recovery but loses a substantial part of this elastic recovcry if boiled off, or wet out and dried under low tension. However, if the tension-dried product is cross-linked (chemically combined) with formaldehyde under tension, a major portion of the elastic recovery is retained. The hot drawn ammonia treated yarn, either prior or subsequent to cross-linking with formaldehyde, is substantially non-brittle. This is indeed unusual for a cellulosic yarn, since up to now all evidence points to substantial embrittlement of cellulosic yarns on cross-linking with formaldehyde. The cross-linked product possesses a higher crease anof 85 NaHzPO4+10% NazSOl adjusted to pH of 4.2.

yam dried, all of the steps being performed without any tension on the yarn. This cycle of steps is repeated 3 times.

and reeled to skeins, it is immersed in a 30%" properties to cellulosic Yarns widens-the field of application of yarns of this general type, especially where it is required that the yarn possess a high work factor, i.e. the ability to elongate greatly under conditions of stress.

Although the advantages of the invention are more apparent in the preparation of yarns comprising a number of filaments, it is obvious that the same advantages follow when the invention is applied to the preparation and treatment of menofils.

Since it is obvious that many changes and modifications can be made in the above-described details without departing from the nature and spirit down during drawing, without heat in the dry state at 60% relative humidity and75 F., beyond the elastic limit but before the point of rupture, and showing no orientation as evidenced by its X-ray pattern.

3. A regenerated cellulose filament capable of being stretched at least 100% without heat in the dry state, exhibiting the property of necking down during drawing, without heat in the dry state at 60% relative humidity and 75 F.,

beyond the elastic limit but before the point of rupture, and possessing a degree of thermoplasticity whereby the tension required to elongate the filament in the dry heated state is substantially less than that required to elongate the filament in the dry unheated state.

4. A regenerated cellulose filament capable of being stretched at least 100% without heat in the dry state, showing no orientation as evidenced by its X-ray pattern, and exhibiting the property of necking down during drawing, at 60% relative humidity and 75 F., beyond the elastic limit but before the point of rupture, said filament possessing a degree of thermoplas'ticity whereby that required to elongate the filament in the dry unheated state.

RUDOLPH WOODELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS v Number Name Date 1,651,404 Neldich Dec. 6, 1927 1,724,670 Lilenfeld Aug. 13, 1929 1,930,803 Harrison Oct. 17, 1933 1,998,551 Mahn Apr. 23, 1935 2,004,271 Dreyfus June 11, 1935 2,082,814 Zetzsche et a1. June 8, 1937 2,161,766 Rugeley et a1. June 6, 1939 2,208,632 j Dreyfus July 23, 1940 2,233,402 Cresswell Mar. 4, 1941 2,233,442 Wiley l Mar. 4, 1941 2,249,745 Charon et a1. July 22, 1941 2,289,232 Babcock July 7, 1942 2,312,152 Davis Feb. 23, 1943 2,340,377 Graumann Feb. 1, 1944 FOREIGN PATENTS Number Country Date 335,605 Great Britain Sept. 29, 193( 344,873 Great Britain Mar. 9, 1931 546,673 Great Britain July 24, 1942 OTHER REFERENCES Certificate of Correction Patent N 0. 2,462,927.

March 1, 1949. RUDOLPH WOODELL It is hereby the Word high droxyhons read hydroxyl 'om;

THOMAS F. MURPHY,

Assistant 6'0mmz'ss2'oner of Patents.