US2369190A

US2369190A - Manufacture of rayon

Info

Publication number: US2369190A
Application number: US259261A
Authority: US
Inventors: Gilbert I Thurmond
Original assignee: American Enka Corp
Current assignee: Akzona Inc
Priority date: 1939-03-01
Filing date: 1939-03-01
Publication date: 1945-02-13
Anticipated expiration: 1962-02-13

Description

Feb. 13, 1945.

G. l. THURMOND MANUFACTURE of' RAYON.

Filed March l, 1939 4 Sheets-Sheetl l TWICE 5779576190?? FMA/mms' can :cria

gime/MM Feb. 13, 1945. 3` T HURMOND 2,369,190

` y MNUFACTURE oF RAYON Filed March l, 1959 4 Sheets-Sheet 2 o. my w ,u d o u. /n N wf M Feb. 13, 1945. G. 1. THURMOND v MANUFACTURE 0F RAYON 4 Sheets-Sheet 3 Feb. 13, 1945. 3.` L THURMOND 2,369,190

MANUFAGTURE oF RAYON l Filed March l, 1959 4 Sheetsv-Sheet 4 A 'llerlf 72101110111 'u MM Patented Feb. 13, A19.45 l

MANUFACTURE F RAYON Gubert I. ramona, Asheville, N. c., assignmto AmericanEnka Corporation, Enka, N. G., a corporation of- Delaware Application Maren 1, '1939, serial No. 259261 (cl. 11s-s) .6 Claims.

'Ihis invention relates to a process of and system for producing a. strong yarn or thread of synthetic filaments and to the treatment of yarn or thread in a manner to preserve the properties thereof when formed into a cable of the type normally used in the manufacture of pneumatic tires,

hose, belting or reinforcements for molded and cast .plastic materials in general of either natural or synthetic origin. More specifically the invention contemplates the formation of improved artificial threads or filaments formed primarily of viscose which have an unusually high4 tenacity and low elongation.

In the manufacture of pneumatic tires and generally similar flexible rubber articles it has long been the custom to utilize cotton cords forl the reinforcement thereof. The substantially universal use of cottonncords in the manufacture of tires has been due primarily to the factthat such cords are not affected by heat and moisture to a prohibitive degree and that when they are formed into strands twisted in a definite manner they have the required degree of resiliency, ilexibility and tenacity. However, during recent years many tests have shown thatcords formed of rayon may be utilized in tires and like constructions With even greater effectiveness than cords produced from cotton. Nevertheless, the substitution of rayon cor-ds or cables for cotton cords in the manufacture of products of the type indicated has been delayed for numerous dimculties In connection with the use of rayon in the production of cables for use as reinforcements in tires, belts and the like, the properties of the individual filaments and of the slightly twisted yarn determine to a substantial degree the final properties of the cables or cords. While the strength per unit weight and elongation of the cable or cord may be markedly impaired by improper twisting at its various stages of formation yet the ratio of corresponding values for filaments and cords will -be very nearly constant for a given were encountered which had to be more fullyl overcome before rayon cords were suitable forv extensive commercial adoption.

In View of the research and other activities of the manufacturers of tires, belts and allied prody ucts there is at present a demand for high quality.' rayon threads and yarns -at a cost somewhat com-l parable with cotton, and this demand will undoubtedly increase rapidly as yarns are produced which have a greater strength and lower elongation and when cables formed therefrom have higher flexing tests and adhere satisfactorily to rubber. Customarily tire cords are formed in three separate twisting operations, the basic threads which are termed yarn comprise a plurality of small filaments twisted together. A plurality of yarns are twisted together or plied to form a structure known as a ply or intermediate strand and plies thus formed are twisted with other plies to form a cord or cable. It has been determined that the properties of the cable are dependent in part upon the degree of vtwist at eachv stage in the formation thereof. Preferably the yarn has a very low degree of twist.

method of twisting. f In the manufacture of pneumatic tires, cord are impregnated with and covered by rubber which is then vulcanized and the strength of the tire walls is dependent to a large extent upon the properties of the cord imbedded therein. It is clear that a strong cord is required for use in tires. However disadvantages other than those naturally resulting from weakness of the fiber arise from the use of inferior cords even when formed of high quality fibers and the reasons therefor are not so readily apparent. If there is any tendency on the part of the cord to alter its length due to its original inferior qualities or because of deterioration or aging,` the bond between adjacent cords and between the cord and rubber may be ruptured to such extent as to render the tires practically useless. Nevertheless, the cord must have\a substantial resiliency in order to withstand the `strains normally imposed by reason of the pneumatic pressure within and of mechanical shocks applied to the exterior of the tire casing. Rayon threads and cables known prior tothis invention do not possess a suitable combination of high tenacity, resilience and low degree of elongation to adapt them for use' in bodies formed from plastic compositions, such as tires, belts, and the like.

This invention contemplates the provision of a superior type 'of artificial filaments and yarn formed thereof, which overcomes the difficulties referred to above and which have a high tenacity and other properties very desirable in the production of cords for the fabrication of pneumatic tires and the like. It has as a further object the provision of a process for the formation of laments and yarns of uniform properties.

Additionally the invention contemplates a process of and al system for producing a strong and extremely low elongation artificial yarn, wherein the freshly formed filaments 4are stretched up to the breaking point, washed, and thereafterin the acid free condition they are stretched up to the breaking point as a result of which treatment a greater stretching of the laments is obtained than has heretofore been considered possible.

It is also an important object of this invention to provide a rayon cord or cable having increased resilience and very little tendency to change in length as a result of alteration in the properties thereof. A

Other objects and advantages of the present invention will be apparent from the following detailed description when considered in connection with the accompanying drawings wherein:

Figure 1 isa flow sheet setting forth the important steps of one complete continuous process conducted in accordance with the invention, which iiow sheet additionally sets forth an alternative interrupted process;

Figure 2 is a diagrammatic view of an apparatus formed in accord-ance with this invention for producing yarn in a continuous manner;

Figure 3 is a diagrammatic view of a modified form of apparatus constructed in accordance with this invention;

Figure 4 is a view taken on line 4 4 of Figure 3 showing the freely rotating stretching rollers arranged in a bath through which the filaments are propelled; i

Figure 5 is a diagrammatic view of an apparatus which includes a twisting device used in one step of the alternative interrupted process of Figure 1; and

Figure 6 is another modification shown diagrammatically of the invention wherein the major stretching operation takes place between driven rollers and during washing.

In referring to the drawings in detail with particular reference 'to Figure 1, it will be seen that the present invention when applied to the production of viscose yarn comprises generally the preparation of a viscose spinning solution of alkali and cellulose, the latter preferably comprising at least of cotton linters. The solution is then aged, filtered and thoroughly deaerated. Such deaeration of the viscose is usually accomplished under vacuum, in which event the deaeration step is preferably practiced by subjecting the viscose solution to pressures abnormally low as compared with known technique 'for an abnormally prolonged period of time. For

example, a vacuum below 20 mm. may be desirable. The spinning solution thus treated is then delivered to spinnerets through corrosion resistant and non-contaminating conduits, spun into a novel coagulating bath and the yarn composed of a number of filaments is thereafter stretched a plurality of times. In the spinning arrangement shown in Figure 6, the yarn is only given a slight stretch between the spinneret and first godet, but by virtue of the Washing action in the second bath which is only slightly acidic, a veryl much greater stretch can be obtained between the two godets than has heretofore been possible. When the yarn is stretched initially up to its breaking point while in acid condition and then is washed and again stretched up to its breaking point while in a moist and substantially acid free condition it will have a very high tensile strength, and a low degree of elongation. However, filaments which are stretched to a lesser degree during either of the stretching steps or both will nevertheless be suited for use in tires and they will have substantially uniform properties throughout their lengths. l

It has also been determined that very ecient results may be had if the filaments are stretched but once providing a high degree of stretch is imparted thereto. This is particularly true if the stretching step is conducted during or subsequent to, the washing of the filaments and while they are still in a plastic state.

More specically as will appear from a consideration of Figure 1 of the drawings very high quality filaments are obtained by the utilization of a viscose solution which contains about 7.4% cellulose by weight and an equal amount of sodium hydroxide. Although the viscose solution employed according to this invention is characterized by a content of cellulose substantially equal to the amount of caustic employed therein, the proportions may be varied within rather wide limits with resultant loss of but some of the benefits of the invention. After the preparation of the viscose solution it is subjected to high vacuum deaeration for a prolonged period. The deaerated solution is then aged or ripened. Preferably it is ripened to or above 111A, ammonium chloride index. During the aging period the viscose solution is ltered in a ltration apparatus composed of materials resistant to attack by components of the solution.` A filter press may be utilized for this purpose, the frames of the press and other parts which come in contact with the solution being formed of, or covered with, nickel or other suitable material which will not contaminate the solution undergoing treatment. After the viscose solution has been properly ripened and it has been filtered it is passed through conduits similarly formed or lined with noncontaminating material and it is delivered to spinnerets through which it is extruded into a spinning or coagulating bath. The spinning or coagulating bath is one of high magnesium content vas it contains according to the preferred embodiment of the invention approximately 10% of magnesium sulphate by weight.

The filaments thus formed are then stretched and further treated to provide a yarn having a high tensile strength, a low degree of elongation particularly suited to the formation of tire cords and one which has substantially uniform properties throughout its length.

y In general the spinning bath is of somewhat conventional nature except as noted with respect to the magnesium content and as hereinafter specified. Ofther components dissolved therein may include sulphuric acid, sodium sulphate, ammonium sulphate, zinc sulphate and other salts when desirable. Such baths, as are known in the art, give considerable diflicultyduring the spinning operation by reason of the fact that when they are used solids tend to accumulate in the spinneret orices and impair the properties of the filaments. -In order to produce a yarn satisfactory for general use frequent cleaning of the spinnerets was found to be necessary and this cleaning operation of the small orifices necessarily involves costly precision work. However, this problem may now be substantially entirely overcome and a great improvement in the properties of the filaments produced will be had by spinning the filaments in the presence of a dissolved material of a cation active nature. Such materials are discussed at length in United States Patent 2,125,031 to Polak, et al. For example, a small quantity (0.04 per cent by weight) of dodecylpyridinium chloride dissolved in the spinning bath eliminates practicallyy all of the irregularities and' diiiiculties of spinning and permits a much longer vspinning time free from the 'frequent interruptions heretofore encountered for cleaning the spinneret.

The contamination of the spinnerets to an exaggerated degree has been encountered when an ordinary viscose solution is extruded through gold-palladium Spinnerets into a spinning bath of the type noted above. The spinnerets become seriously contaminated in a few hours and this incurs interruption of the spinning period with resultant time and production losses. However, the presence of 0.1 per cent of dodecyl triethyl amonium iodide in the spinning solution reduces the tendency toward clogging of the spinneret l orifices to a remarkable extent.

The laments formed by the extrusion step are conducted through the bath and upon being withdrawn therefrom they are given a suitable stretch, such as for example from about 30% up to the breaking point. The filaments are then again stretched while in moist condition from about up to the breaking rpoint. Between the two stretching steps the filaments are ably washed and desulphurized or at least they are partially washed since the intermediate washing step causes the filaments to be stronger and to have a lower elongation than when the step is omitted. It is surprising to note that byfollowing such a procedure considerablyn morev stretch can be imparted to the filaments than has heretofore been possible. Atotal stretch can be obtained that is substantially above 50% and it has even been determined that the filaments vcan be stretched more than l70% of their original length without breaking. Washing and desu]- phurizing of the filaments may be accomplished in several ways and as set'forth in the flow sheet in Figure l of the drawings the process employed may be continuous or it may be interrupted, that is, the coagulated filaments may by the continuous process be stretched, then washed by being drawn 'through a bath and then again stretched while by the interrupted process the filaments are stretched and then wound upon a spool under reduced tension, whereupon the bobbin is washed by the pressure-vacuum method yand the moist filaments are then either twisted and stretched during a rewinding operation or they are merely stretched and not twisted. Cake spun yarn having been twisted during collection has to be stretched only.

The interrupted process permits the winding of a spool of freshly spun yarn under less tension than heretofore utilized and this facilitates easy washing of the yarn while in spool form. During the rewinding the yarn is wound in the usual manner. Ease of washing is an important feature of this phase of the invention. In this connection it should be noted that while the second stretching step may be performed before complete washing, such procedure then involves the washing of a tightly wound bobbin, but this is permissible because the package contains only a small amount of residual acid from the precipitating bath.

In referring to Figs. 2 to 5 inclusive, several systems are illustrated which are constructed in accordance with specific features of this invention. Yarns having the characteristics suitable for use in the manufacture of tires and the like may be readily produced with any one of the systems by the proper preparation and handling of the spinning solution in the bath and by the control of the stretching operation. While artiilcial yarns other than viscose yarns may be pro- ,duced by the methods herein disclosed with satispelled by the godet prefer- Figs. 2 to 4 inclusive are of a continuous nature.

factory results, it will sumce to refer to the apparatus illustrated when `used in connection with the viscose process. In each of the systems referred to, a spinneret I0 is connected to a feed pipe (not shown) through which a viscose solution properly prepared, deaerated and ripened, is delivered thereto. The solution is then extruded through the spinneret into a coagulating bath II of the type referred to above, and the yarn I2 formed of a number of filaments ls'drawn from the bath by a godet wheel I3. The `yarn is pro- I3 at the same speed as the peripheral-speed thereof and the -yarn is led one or more times therearound to avoid slippage upon its surface. Another godet wheel Ill is arranged in spaced relation to godet Wheel I3 and i/t is rotated at a greater peripheral speed than is the first godet' wheel, whereby, when the yarn is passed from the godet wheel I3 and is directed over and around godet wheel It one or more times, it will of necessity be stretched between the two godet wheels, the desired degree of stretching being controlled by the relative speeds of the godet wheels.

y The specific processes intended to be conducted by the utilization of the systems illustrated in In each of these systems a bath I5 is provided beyond godet wheel I4 and the filaments are caused to travel through said bath with a resulti'ng washing, bleaching and/or desulphurizing treatment as may be desired and effected by the proper selection of the bath. Within the bath Iii the filaments are again stretched and they are thereafter conducted to and collected upon a bobbin I6. 1t isof course to be understood that all of the systems illustrated may be modified so that a centrifugal the collecting mechanism, instead of a bobbin,

yArranged within the bath, as illustrated in Fig. 2, are two godet wheels Il and IB respectively, which godet wheels are substantial duplicates o godet wheels I3 and I4. Filaments I2 are-passed from godet wheel I4 to' and around godet wheel I'I one or more times in order to avoid slippage. Godet wheel Il is preferably driven at a peripheral speed substantially the same as that of godet wheely I t. As the filaments are passed between godet wheel Il and to bobbin It they are directed around godet wheel I8 one l .or more times.

The filaments in the passage through the bath are thus subjected to the desired washing or other treatment and during the latter part of their passage within the bath they are given an additional stretch for the reason that while godet wheel I1 has a peripheral speed commensurate to the peripheral speed of godet It, the peripheral speed of godet wheel I8 is greater than that of godet wheels I4 andv I1. The degree of stretching of filaments within the bath I5 is controlled bythe speed at which the godet wheel I8 is driven, and of course this speed may be modified inv accordance with the degree of stretch required. I Filaments I2 are collected on bobbin I6 under the desired tension by means of the peripheral speed'imparted to such bobbin.

The specific stretching mechanism illustrated inI Figs. 3 and 4 which is contained in the bath I5 for the purpose of imparting. the second stretch to the filaments I2 is of the type illustrated in the patent to Hans A. Schrenk, No. 1,968,912, dated August 7, 1934. .Thismechanism involves an idler roller I9 and freely rotatable upper and lower rollers 20 and 2I respectively. The rollers 20 and 2l are driven solely by the filaments and pot or bucket may be used as y are provided with guiding grooves 22 which decrease in depth toward the discharge end thereof so that the respective diameters of the rollers at the bases of the grooves will gradually increase from the first groove in which the filaments I2 are received after they have passed from idler I9 to the last groove contacted by the filaments on the roller 2| from which the filaments are delivered to a driven godet wheel 23. An idler guide 24 is positioned adjacent godet wheel 23 for directing the filaments thereover and an idler 25 is positioned to receive the filaments as they are passed from godet wheel 23. After the filaments are passed around idler 25 they are conducted to bobbin I6 in the manner previously described with respect to the apparatus of Fig. 2. From the `description of Fig. 3 it will be clear that filaments I2 are washed or otherwise treated in bath I5 before and during the second stretch and, due to the arrangement of rollers 20 and 2|, each time that the filaments are passed from one of vthe rollers to the other they are slightly stretched and at the same time subjected to further treatment in the bath. This' each passage of the to the other results gradual stretching during filaments from one roller from the gradual increase base of each succeeding groove 22.

The processes as conducted in the apparatus of both Figs. 2 and 3 are continuous. The laments are rst stretched after being extruded and they are then washed and again stretched. The second stretching may be imparted after the filaments have been passed from the washing or treating bath so long as the filaments are still in a plastic and moist condition.

The system illustrated in Fig. 5 is of a noncontinuous or interrupted type. In the system illustrated in Fig. 5 the laments as they are passed from godet wheel I4 are led to and around idler 26, whereupon they are passed to the temporary bobbin 21 Where they are collected under reduced tension. It will be noted in the system as thus far described only one stretching is imparted to the filaments up to the time of collection on bobbin 21. Bobbin 21 is next subjected to a high-pressure high-vacuum washing operation in a bath 28, which may be of the same genheretofore referred to in connection with Figs. 2 to 4 inclusive of the drawings.. `Bobbin 21 after being treated, and while the filaments are still in a plastic condition, is placed upon a stationary support and the filaments are drawn therefrom and twisted. The filaments pass through l godet wheel 30 one or more times, and they are then passed to and around godet wheel 3|, after which they are delivered to bobbin I6 for col-` lection in the usual and 3| are manner. Godet wheels 30 substantially the same as godet wheels I3 and I4 and the filaments are conducted thereover in a similar manner. In order to effect a second stretching of the filaments as they are passed between godet wheels 30 and 3|,' wheel 3I is driven in such a manner that its peripheral speed is increased to the desired extent above the peripheral speed of godet'wheel 30. In the event that the freshly spun filaments are collected in a centrifugal bucket, the cake is made up of already twisted filaments, in which case it is only necessary to restretch and collect the filaments in a manner also shown in Fig. 5. It

to dry the washed bobbin or cake spun package prior to the re-stretching operation. The dried guide 29 and then around f' in diameter of the vthe second stretch.v

package must then be rewetted before or during 'I'he washed bobbin package 21 may even be satisfactorily restretched without twisting, the twisting step being conducted in a subsequent separate operation. When'the package 21 or 21a is restretched between the godets 30 and 3I, a certain amount o1' drying will result, especially if the twisting is simultaneously effected. If it is desired tocompletely dry the packages either in bobbin or cake form, a drying zone can be `readily interposed between the last godet 3| and the take-up device I6. It has been determined that such treatment will result in yarn having extremely uniform shrinkage properties throughout its length.

Referring sp'ecilcally to Fig. 6, the filaments I2 are extruded through spinneret I0 into a coagulating bath II and thence led one or more times around a godet wheel 32 whereupon the filaments are conducted to an idler roller 33 1ocated in' a wash bath 34. This bath may be very slightly acidic in order to further coagulate the effect a substanspeed than godet wheel 32. 'I'his difference in peripheral speed imparts the desired stretch to the' filaments which taken in conjunction with the initial stretch in bath II, can be considerably greater than was heretofore possible by conventional methods. The filaments are then collected on a bobbin 36 or in a pot after first passing around a second idler roller 31.`

In the interrupted process or' in the process according to Fig. 6 in which a high stretch is only imparted at one stage, the threads may be co1- lected under the desired tension, Washed and dried. An additional stretch may then be simultaneously imparted to a multiplicity of threads after rewetting the same and collecting at a common source such as a slasher or beam and the like. The yarn produced by the utilization of any of the above systems in connection with the process of this invention has, as stated above, important application to the tire and related arts. An important step in the preparation of a tire cord for the purpose of preventing loss of strength due to the twisting of the cord components involves the application of a finishing material to the yarn in at least one stage of the spinning operation. A softening agent which has no deteriorating effect on the yarn is utilized as the finishing material. This is a highly important aspect of the complete process of this invention since it has been found that the employment of the finishing material will improve the final .strength of the cable by from 10 to 50% by preventing substantial loss in strength of the yarn during twisting. Apparently, the employment of the finishing material permits the yarns and plies when twisted to assume a position of least tension and strain and specific flexing tests have been made oh cables formed of yarn twisted as hereinafter specified which show abnormally high flexing tests as compared to yarn otherwise similar but not finished in the same manner. Additionally, cables formed from yarns finished in this manner are smoother and more dense than similar cables formed of untreated yarns and the strength thereof closely approaches the combined strength of the individual yarns. A solution of Monopole Brilliant oil has been found to produce excellent results when used as a finish for the yarn. However, various types of materials can be advantageously used for this purpose and sulphonated olive oil, sulphonated castor oil, emulsiiled glyceridessuch as blown tea-seed oil, and lecithin have been found satisfactory. Sulphonated oils for this purpose may be stabilized by the addition thereto of a small amount of alkali such as soap and an antioxidant. l

The finishing agent may be applied to the yarn as such or as a solution or emulsion with any suitable vehicle. Goodeffects are obtained from the addition of a finish during washing or immediately subsequent to the washing stage. However, application of the treating material to the dried spools of yarn with redrying prior to the twisting of the yarn gives excellent "results, It has been found that 0.3% of monopole oil based on the weight of the dry yarn Will provide one of the best concentrations for most purposes.l Results which have been obtained indicate very clearly that softening agents are much better than lubricating ilnishes in connection with yarns to be plied or plied and cabled and then used in the production of cord, tires and the like. For example, a straight mineral oil finish has little or no effect in conserving the strength of the yarn to give a strong cable, while a softening agent yields 'improvements in strength running as high as 50% over cables formed from yarns not so finished. it would seem that such finishing of the yarn is essential for the production of a smooth, well-formed, compact cable which will have the maximum strength obtainable from a plurality of twisted yarns. l

It is of course desirable that the yarn be lubricated to some extent to prevent breakage or other damage during handlingand if the softening agent does not impart sufficient lubrication thereto, a suitable lubricant may be blended with the softening agent.

Tire cords and reinforcing cables and fabrics used in various bodies formed of plastic material may be prepared from rayonl in the manner noted above with numerous not heretofore obtainable advantages. In addition to the points of superiority already noted, the tendency of rayon cord in tires to grow in service is prevented or minimized by the use of the yarns of low elongation described above. It will be readily seen that the tire structure will be adversely affected or the tire per se enlarges if the yarns used in producing the reinforcing cables becomes permanently elongated during use of the tire.

To better set forth' a comparison of the improvements of the various features of this invention the details of one specic process for producing a rayon cable will be described without the additional stretch but with the conditioning operation and other novel features merely by Way of exemplification. A soaking lye is ilrstv prenormal manner for two hours and is subjected to an' ageing temperature of 21 C. for approximately 56 hours. Viscose having a cellulose content of '7.4% and alkali content of 7.3% is next formed therefrom, and it is permitted to`mature or ripen to 12.3 ammonium chloride index Whereupon the viscosity is approximately 40 seconds.- The viscose is then extruded through a spinneret into a coagulating bath containing sulphuric acid, sodium sulphate, zinc sulphate and approximately 10% of magnesium sulphate. The spinning bath is maintained at a temperature of 43 C. to 45 C., and a higher temperature may be utilized if proper equipment is available to avoid evaporation problems encountered with the likely impairment to the health of the operators. The filaments thus formed are conducted from the bath and lhave a stretch impartedl thereto of 45% by passing the same between two godets, and thence' to a spinning spool that has a takeup speed substantially equal to the peripheral speed of the second godet. This corresponds to the first part of the interrupted process. The spinning speed utilized is 'Il meters per minute, the yarn being of 275 deniers and having filaments. Yarn thus produced is washed acid free and then dried and it is nished by being further dried by the vacuum method. A solution of 0.6% Monopole Brilliant oil is caused to permeate the wound package and the package is subjected to dry vacuum to insure uniform distribution of the finish. The package is 'then additionally dried on the spinning spool. After being dried, the yarn is then twisted four turns per inch. The yarn in this condition is ready for formation into cables and in tests which have been conducted to determine the exibility of cables formed from such yarn, .uve of the thus formed yarns were twisted together to form a ply or intermediate strand and three such strands were then twisted together to form a cable. The herring or fatigue test of such a cable was 35,235 flexes before breaking and a cable similarly produced but in which the viscose was formed entirely from wood pulp without the inclusion of cotton linters and the coagulating bath did not have a high magnesium content, a fiexing test of 24,975 was determined. The same flexing test made with respect to a cable formed of yarns which were not finished with Monopole Brilliant oil or any of the other materials referred to above, had a exing test of only about 900. The fatigue or flexing tests were conducted on a similar principle as that taught in an article by F. B. W. King and R. rIruesdale, published in The Textile Recorder, May 15, 1923. v

The other physical characteristics of the yarn I Y are tabulated below in order to show by way of comparison the improved results obtained.

Yam cable Dry Wet Dry elon- Wet elonstrength strength gation gation Strength Etia- Per cent Per cent Prepared from normal viscose 281 1l 14 13 ,Per cmi; Prepared from normal viscose softening agent-.-. 281 162 11 14 1s 9 4 Prepared according'to above example 318 185 12 l5 19,9 9 Prepared according to above example additional 15% stretch y 340 207 12, 5 23 a 5 pared from 18.3% alkali containing 0.6 or'0.7% hemicellulose. Alkali cellulose is next prepared and at least 25% of cotton linters is utilized with the remainder of the cellulose being derived from The strength of the yarn is given in grams per .100 denier and the strength of the 'cable is given in pounds; in addition, the strength of both the yarn and cable was obtained by conditioning at wood pulp. The alkali cellulose is shredded in a 'I6 65% relative humidity.

Wet strength Wet elon- Dry elongation Dry gation strength Before 2nd stretch.. 5-l0% 2nd stretch. g '20% 2nd stretch..-

The importance of stretching after washing and subsequent proper :finishing to increase the cable strength, to prevent loss of strength during cabling, and to obtain a cable of low elongation is obvious from the preceding examples.

Yarns spun from a mixture of viscose solutions and casein solutions give cables of improved bonding properties with respect to rubber. The proportions of viscose and casein used in producing the yarn may vary from a small proportion up to about 10% depending upon the properties which the yarn is intended to possess but it is preferred that the casein be present in amounts not exceeding by weight of the cellulose in solution or of the finished yarn. Such mixed yarns may be treated with formaldehyde or a suitable tanning agent during spinning or subsequent thereto in order to cause the casein content of the yarn to assume the desired properties. Spinping baths particularly suited for use in methods of preparing strong casein are disclosed at length in the application of J acokes, et al., Serial Number 246,466, led December 17, 1938.

Additionally it has been found -that formaldehyde resin in particular, and other non-thermoplastic materials to some extent, may be added tol the viscose for the purpose of aiding the bond between the rubber of the tire or the like and the reinforcing viscose cable. l

Yarn formed from mixtures of casinand viscose produce a strong yarn suitable for cord construction for tires, belts and the like liiias'much as these proteins cause unusually improved adhesion of the cables to rubber. The cords for these purposes may be constructed from mixtures of casein fibers and viscose bers, yarn spun from a mixed solution of casein and viscose. It has been known to prepare casein-viscose mixtures for spinning to produce a thread suitable for general textile purposes but prior to the present invention it has not been considered possible to prepare a mixed fiber having properties such as high strength, low elongation, fiexibility and resiliency suitable for use in the preparation of cord tires, belts and the like.

The preparation of casein-viscose solutions for the purpose of producing yarns may be carried out in any suitable manner. A preferred method for the production of such solutions is to prepare a viscose solution by soaking sheets of cellulose in alkali, pressing said sheets to remove the excess caustic and the more alkali soluble forms of cellulose, shredding the sheets impregnated with alkali, aging the shredded material to reduce the viscosity thereof, reacting the shredded alkali cellulose with carbon disulphide and dissolving the thus formed xanthate in dilute caustic soda to yield a viscose solution containing a little over rI% cellulose. 'I'he viscose solution as thus pre pared is aged for a suitable period to improve the spinning characteristics and it is then thoroughly mixed with casein, preferably denatured in the manner disclosed in the above noted application and dissolved in dilute alkali. A suitable` spinning composition as finally prepared is composed of:

f Per cent Cellulose A 'I Sodium hydroxidel V7 Casein ,12 Sulphur 2 1 Based on the weight of the cellulose.

It has been found that especially high quality filaments and yarns are obtained with a solution which contains equal Aparts cellulose and sodium hydroxide to thecaustio. After the preparation of the casein-,viscose mixture, it is aged for 24 hours, filtered and deaerated under strong vacuum for a prolonged period similar to the manner of deaerating the viscose solution as set forth in the above specific example. The composition is then extruded into any of the conventional baths used for viscose, particularly when the casein content is comparatively low. Suitable coagulating baths are described above. When the composition being extruded contains a large quantity of casein, the coagulating bath may be modied according'ly.

The viscose-casein filaments formed as above specified are drawn from the bath and they have a suitable stretch imparted thereto, for example, a stretch of 40%, after which they are formed into a cord or cable as in the case of the viscose as above described. To prevent the stripping of the casein from the filament by washing operations prior to cabling, the yarn is given a preliminary washing with a dilute solution of formaldehyde or of other insolubilizing agents and it is then washed with water. The yarn thus washed, and while still moist, is then given an additional stretch before it is dried in any suitable manner.

Relatively small quantities of casein or other protein do not adversely affect the physical strength of the viscoseyarn but they do materially improve its stability and adhesion to rubber. As will appear from the above, the yarn formed of the viscose-casein mixture is subjected to substantially the same treatment and manipulation as the viscose yarn except for such modifications in the treating bathas are necessary.

In the utilization of this invention, it is extremely important that all apparatus, used in the preparation of the yarns, that contact with the substances entering into the vformation thereof, be composed of a material which resists corrosion and which will not contaminate said substances. It has long been known that porcelain, nickel and the like and stainless steel are suitable materials for use in constructing the filter presses, conduits, and the like or as linings or coating therefor.

It is to be understood that while the discussion is generally directed to the preparation of filaments, it is intended to cover threads, yarns, cords, ribbons, foils, sheets or other products usually produced by extrusion or spinning. The invention has been described in detail in order that those skilled in the art may practice the same, but it is obvious that it is not to be restricted to the specific examples set forth.

In using the expression up to the breaking point throughout the specification andl claims, it is, of course, intended to mean that the thread is stretched just short of the breaking point.

What is claimed is:

high tenacity artificial yarn comprising a spinneret for delivering filaments to a coagulating bath, a washing bath, a device for collecting the filaments, rotatable rollers operating at different peripheral speeds intermediate said spinneret and said collecting device for stretching thefilaments, and means intermediate said stretching rollers and said collecting device for again stretching the filaments, said second stretching means comprising rotatable rollers mounted in spaced relation, and operating at different peripheral speeds, at least one of the rollers of the second stretching means being positioned within said washing bath.

2. An apparatus for producing low elongation, high tenacity artificial yarn comprising a spinneret for delivering filaments to a coagulating bath, a device for collecting the laments, rotatable rollers operating at dierent peripheral speeds intermediate said spinneret and said collecting device for stretching the filaments, and means intermediate said stretching rollers and said collecting device for again stretching the filaments, said second stretching means comprising freely rotatable rollers in mounted spaced re'- lation, said rollers having guiding surfaces so arranged that when the filaments are passed alternately from the surface of one roller to the surface of another roller a plurality of times, each succeeding guiding surface in the path of the filaments has a greater diameter than the preceding one, whereby different linear speeds are imparted to the filaments.

3. An apparatus for producing low elongation, high tenacity artificial yarn comprisingy a spinneret for delivering filaments to a coagulating bath, a device for collecting the filaments, ro-

I tatable rollers operating at different peripheral speeds intermediate said spinneret and said collecting device for stretching the filaments, and means intermediate said stretching rollers and said collecting device for again stretching the filaments, said second stretching means comprising freely rotatable rollers in mounted spaced relation within a bath, said rollers having guiding surfaces so arranged that when the laments are passed alternately from the surface of one roller to the surface of another roller a pluralityv of times, each succeeding guiding surface in thev path of the mamentshas agrcater diameter-than the preceding one, whereby different linear speeds are imparted to the filaments. y

4. In the manufactureof high tenacity, low elongation viscose yarn, the steps which comprise extruding a viscose solution into an acid bath that coagulates and partially regenerates th filaments formed therein, withdrawing the filaments from the bath and positively stretching the same to substantially their breaking point prior to contact with a second bath, thereafter passing the filaments through a washing bath and during their said passage imparting a second stretch to said filaments to substantially vtheir breaking point as their regeneration 'conprior to contact with a second bath, thereafter passing the filaments through a washing bath and during their said passage impartinga second stretch to said filaments to-substantiaily their breaking point as their regeneration continues substantially to completion, said second stretch being imparted to said filaments independently of the first mentioned stretch and the summation of the stretches totaling more than 70%.

v6. In the manufacture of high tenacity, -low elongation viscose yarn, the steps which comprise extruding a viscose solution into an acid bath that coagulates and partially regenerates the filaments formed therein, withdrawing the 40 filaments from the bath and positively stretchsubstantially to completion, said second stretch being imparted to said laments yindependently of the rst mentioned stretch, and finally collect ing the laments without releasing the tension thereon.

GILBERT I. THURMOND.