US2479218A

US2479218A - Process for making rayon filaments

Info

Publication number: US2479218A
Application number: US567898A
Authority: US
Inventors: Rene E Dosne; Charles Frank Roland
Original assignee: International Paper Canada Inc
Current assignee: International Paper Canada Inc
Priority date: 1944-12-12
Filing date: 1944-12-12
Publication date: 1949-08-16
Anticipated expiration: 1966-08-16
Also published as: GB603131A; FR940888A

Description

Patented Aug. 16, 1949 PROCESS FOR MAKING RAYoN FILAMENTS Ren E. Dosne and Frank Roland Charles, Hawkesbury, Ontario, Canada, assignors to Canadian International Paper Compa y,

Montreal, Quebec, Canada, a corporation of Qu c No Drawing.

The present invention relates to the manufacture of artificial filaments and provides a novel process. In particular the invention relates to the manufacture of artificial yarn admirably adapted for use as reinforcement in the manufacture of rubber goods such as automobile tires and especially adapted for use in heavy-duty truck tires and the like.

The yarn produced by the process of the present invention exhibits fatigue Application DecemberlZ, 1944, N Serial No. 567,898 3 Claims. e (Cl. 18-54) 2 teristics to the product and to insure successful spinning.

The usual concentration of analytically determinable cellulose, in the viscose or spinning solution is approximately 7.5%. The usual viscosity of the spinning solution is, as determined for instance bythe time of fall of a /8 steel ball through cm. in a viscosity tube of 1.4 cm. diameter (test made at 0.), about seconds (46.5 poises). In commercial operation the cellulose concentration may be as low as 7% or as high as 8% or 8.5%, and in such instances the It is therefore an object of the present invention to provide a process for the manufacture of artificial filaments of unusually high fatigue resistance.

It is a further object of the present invention to provide a novel process for the manufacture of thread or yarn from purified orrefined chemic wood pulp. 1

It has been thought necessary in the manufacture of artificial filaments suitable for tire cord to use cotton linters as the source of cellulose. The process'of the present invention produces artificial filaments of quality suitable for tirecord manufacture and in said process purified or refined chemical wood pulp, a cheaper raw material than linters, may be used as the source of cellulose. By theuse of said process it is possible to produce a product which exhibits resistance to fatigue greater than that of any wood pulp product or any cotton linters product heretofore available. Thus the present invention not only offers the decided economical advantage of making it possible to use the less expensive wood pulp as a raw material, but it also makes available to the industry a product of improved quality.

In the customary manufacture of artificial filaments from refined chemical wood pulp or from cotton linters or blends of the two, the raw material is usually steeped in a caustic soda-solution of mercerizing strength, normally about 18%, pressed to remove a certain amount of thecaustic soda and shredded preparatory to the'xan'thation step. After shredding, the alkali cellulose is normally aged for a definite period of time in order to establish a desirable spinning viscosity in the spinning solution. The aged or unaged'alkali cellulose is then xanthated'by treatment with carbon disulphide. The xanthated cellulose is then dissolved in dilute caustic soda to form the spinning solution which is ordinarily knownflas viscose. Prior to spinning, the vscose isnormallyripened. and filtered to impart deSiIeQ Oh a aging period of the alkali cellulose must be suitably adjusted to establish the usual spinning viscosity. In the use of any of the usual spinning methods it is not possible to secure successful spinning of viscose solutions having cellulose content below 6.5% because as the cellulose content is lowered the filaments produced become increasingly discontinuous, harsh, brittle and weak. This condition is emphasized if it is attempted to subject the filaments to substantial stretching between godets. Examples will be cited herein of attempts to spin viscose containing less than 6.5% cellulose in accordance with usual spinning methods. A concentration of above 8.5% is not normally used because of the tendency toward high viscosity and the necessity for unduly long aging periods.

'We have discovered that by combining a number of changes over the usual spinning processes we are enabled to produce from refined wood pulp filaments having fatigue resistance as high as, if not higher than, that exhibited by the best artificial filaments heretofore produced, irrespective of the source of the cellulose used, while in the use of cellulose from any particular source our processprovides marked improvement in the fatigue resistance of the resulting filaments. According to our invention such artificial filaments are produced from viscose of very low cellulose concentration, namely in the range from somewhat morethan 3% to about 6.5%, which is adjusted to normal spinning viscosity and is spun under specific conditions to be set forth herein into a special setting bath and is subjected to considerable stretching between godets.

The range of cellulose concentrations within which the advantageous results of our invention spinning within this range. Toward the upper end of our range the unusual characteristics of our yarn become rapidly less apparent, and when cellulose concentrations of the usual rangeof 7% greater very little difference exists. The results on skeined and coned yarn have also been averaged.

..,We havealso shown at the bottom of Table I to 8.5%, are, employed .no unusual. results are characteristic average bend tests upon yarn achieved. Toward the lower end of our range, spun in accordance with our process and under specifically that portion of the range in which the conditions identical with those in the upper porcellulose concentration is below 4%, the unusual tion of the table, except that the viscoses were characteristics of our yarn again beconi less prepared from a raw material comprising 100% apparent, cotton linters.

Table! Test 5'10-:;- 1 2 a 4 5 5 7 8 9 tl 4.0 4.5 4.9 5.1 0 0.5 7.0 7.5 8.3 ge c efii ffln 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Aging Temp, C 20 20 20 20 20 20 20 20 Aging Time, Hrsa 11 19 19 35 40 01 59 07 Viscosity 1 N N N N N N N N N Stretch per cent between g0dets 77 77 77 77 77 77 77 77 77 Tension in grams between godets 434 514 320 424 413 398 389 413 436 Ripening lemp. .0. 19 19 19 19 19 l9 19 19 19 Ripening Time, Hrs. 48 48 48 48 48 48 48 48 48 Ripening Index 10-12 10-12 10-12 10-12 10-12 10-12 10-12 10-12 -10-12 Streng'thdry,g./d 3. 20 3.49 s. 12 a. 42 0.09 3. 41 5.41 3.40 3.55 StrengthWet,g./d 2.22 2.22 2.24 2.44 2.21 2.12 2.15 2.15 2.19 Extensibility-dry, percent 17.6 20.8 .19.3 20:4 21.0 20.3 20.0 20.0 17.2 Tensile-faction 127.4 101.0 154.9 170.3 157.4 140.0 140.0 147.5 103.9 Bend-skeins. 004 850 810 795 735 400 425 440 330 1,284 2,000 1, 599 1,300 1,058 407 420 353 201 944 1,425 1,109 1,047 897 407 422 390 20s Norm-A11 above yarnsiprepared fromwoodpulp.

Average bend test when 1007 Cotton Linters used as raw materiaLi 1,583 1,058 498 1 Normal (averaging seconds, i. e., 46 ois es). Balaczynski Matunmeter, 12.5% NH4 1.

.In Table-Lthere is, set. forth a series. oij nine tests in Whicnwood; pulp viscoses .of normal visposity were vspun intoa setting bath characteriged as above through spinnerets havingopen'ings o f, our. prefer red "0 11 0501 and subjectedto a high, degree of stretch,.- in this instance '77 These nine tests difier from each other only. in the percentage ct cellulose contained in theviscose and; in the aging-period of the alkali cellulose. eThus Table 1 showsthe effect ofvariations in ,cellulose concentration. of. viscose spun under our preferred-conditions which will bemore fully discussed. hereinbelow. It will ,be observed that tests were made with viscoses ranging incellulose concentration, from 8.3% down to 4%. In this {IableII as in .allof the other tables ande rarnples E in this specification, the fatigue resistance is measuredby using. the Sohojpper. bendingtester ,D. P.- 5,. in which the,'yarn, conditioned at 48% relativehumidityand '78? FL, is clanipedbe'tween two jaws and. a weight of 0.375 gram pe'r denier ,applied .directly by lowering a cam supporting the, bottom jaw the yarn being thenben't forwards and backwards through 180", 120 times ,(cycles) per minute until it breaks. The number of cycles automatically registered is the, bend test. Sincethelo'garithmof the bend test is inversely proportional to the load applied to the thread it is understoodthat comparison has to be,,made within thesame denier range with the same number of filaments andwith the same load per denier. Thedenier'range of the: yaljlfiswhose tests, are shown in thesetables. is'betwe en 1150 and 1250, with 480 filaments, and"th'e loa'dper n er s 9:37 1 mt .Bend tests are give for yarn in skeins and yarn wound on cones. lt will be gobs 'erved inTIable :I ,tnatm the lower ranges ofg celli'llose 0 1 501151 1 .tion t e n woun o .c 9211151145 00 .higher fatigue resist ance than .that'in skems, whereas in cellulose concentrationsof 0%"5110 From a consideration 01 Table I it W111 be observed that optimum fatigue resistance is secured n a yarn spun from a-viscose solution of normal s; ih nir1g viscosity containing 4.5% analytically determinable cellulose. It also will be observed that the fatigue resistance of yarn spun under the same conditions from viscoses having cellulose concentrations within the range of 7% to 83% is very much lower than that of yarn spun from viscoses having cellulose concentrations within our new range. It furthermore will be observed that as-the cellulose concentration is lowered progressively to 4.5% there'is a sharply increas'ingr'ate of "improvement in fatigue resist- 5110401 the yarn and that further lowering of cellulose concentration is accompanied by a de- "crease. in fatigue resistance. However, the fatigue resistance of. yarn spun from viscose having cellul'ose concentration of 4%,, for example,'although lower .than that ;of the 4.5% yarn is still very .much' higheixthanthat-of any yarn within the range 017% to 8.3%.

The following. group of specific examples of the .process-, and product of our invention is taken f om T b el E.rample 1. A viscosesolution of normal spinningviscosity of approximately 45 poises is prepared by the usual steps of steeping, shredding, Xanthating and dissolving a chemical wood pulp qorexample, that sulfite wood pulp sold under the, trade name Te'riacellf by Riordon Sales Qorporation Ltd., of 'Montreal, Canada). This .viscdsesolution is so prep'ared that itcontains {1.5 analytically determinable cellulose and 6.5% NaOI-Land in order that normal spinning vislc'os'itvirl'ay be obtainedthe' alkali cellulose is aged "for' 11'hours ata temperature'of 20 C. I The vis cos ity thus established is about 46.5 poises which, as discussed above, is the normalviscosity for cation and in the appending claims the words normal viscosity mean a viscosity of approximately this value. The viscose is ripened for 48 hours at a ripening temperature of 19 C., during which time suitable filtering takes place, and is spun under the following conditions: a spinneret having holes of .0025" diameter is employed and the viscose emerges from the spinneret into a setting bath containing from 8% to 9% sulphuric acid and 4% zinc sulphate, the specific gravity at 20 C. of said setting bath being 1.30. The yarn emerging from the spinning bath is then stretched between godets at elevated temperature in a manner well known in the art. Preferably a high degree of stretch is imparted, and We have found it desirable to stretch the yarn about 77 with a temperature in the intermediate bath of about 87 C. We have also found desirable a 20" immersion in the setting bath and a 17" immersion in the hot water or intermediate bath at a spinning speed at the top godet of 50 m. per minute. The yarn produced in accordance with this specific example exhibits a dry strength of 3.49 grams per denier with an extensibility of 20.8%, a wet strength of 2.22 grams per denier and a tensile factor of 161.0. The tensile factor is a useful empirical value, the product of g./d. dry times g./d. wet times extensibility (dry) in percent. The bend test carried out on the Schopper bending tester aforementioned shows 850 bends required to break the skeined yarn and 2000 bends required to break the coned yarn, and the average of these results is 1425 bends.

The yarn produced in accordance with this specific example spins without difiiculty. Furthermore, there is no evidence of milkiness or milky streaks in yarn if bleached as for textiles. It will be appreciated from the characteristics discussed herein and tabulated in Table I under test No. 2 that this yarn shows Wet and dry strengths and other characteristics of commercially acceptable standard for tire yarn, and that in addition the bend test demonstrates a resistance to fatigue more than four times that of yarn spun under the same conditions from a viscose containing 7.5% cellulose. (See test No. 8 in Table I.) 7

Example 2.A viscose solution is prepared an spun under conditions identical with those in Example 1 except that the cellulose concentration is 4% and the alkali cellulose is aged for only three hours to establish in the viscose of this concentration a normal spinning viscosity. The yarn produced in accordance with this example exhibits characteristics of strength comparable to those of the yarn in Example 1 and exhibits an average bend test of 944, derived from a bend test in skeins of 604 and a bend test in cones of 1284. No difficulty was experienced in achieving continuous spinning under the conditions specified for this specific example.

Example 3.-A viscose solution is prepared and spun under the conditions set forth in Example 1 except that the cellulose concentration of the viscose is 4.9% and the aging time for the alkali cellulose necessary to establish in the viscose of this concentration a normal spinning viscosity is 19 hours. The yarn produced in accordance with this example exhibits strength characteristics fully comparable to those of the preceding examples and exhibits an average bend test of 1109, derived from a bend test of 819 in skeins and 1399 in cones.

Example 4.--A viscose solution is prepared and zinc sulphate is illustrated.

spun under the conditions set forth in Example 1 except that the cellulose concentration of the viscose is 5. and the aging time for the alkali cellulose necessary to establish in the viscose of this concentration a normal spinning viscosity is 19 hours. The yarn produced in accordance with this example exhibits strength characteristics fully comparable to those of the preceding examples and exhibits an average bend test of 1047, derived from a bend test of 795 in skeins and 1300 in cones.

Example 5.--A viscose solution is prepared and spun under the conditions set forth in Example 1 except that the cellulose concentration of the viscose is 6% and the aging time for the alkali cellulose necessary to establish in the viscose of this concentration a normal spinning viscosity is 35 hours. The immersion in the setting bath is 30 in this example and for higher cellulose concentrations in accordance with our finding of slightly improved results with the longer path for concentrations of 6% and higher. The yarn produced in accordance with this example exhibits strength characteristics fully comparable to those of the preceding examples and exhibits an average bend test of 897, derived from a bend test of 735 in skeins and 1058 in cones.

Example 6.-A viscose solution is prepared and spun under the conditions set forth in Example 1 except that the cellulose concentration of the viscose is 6.5% and the aging time for the alkali cellulose necessary to establish in the viscose of this concentration a normal spinning viscosity is 43 hours. The immersion is 30 as in Example 5. The yarn produced in accordance with this example exhibits strength characteristics fully comparable to those of the preceding examples and exhibits an average bend test of 4-67, derived from a bend test of 466 in skeins and 467 in cones.

Example 7 .A viscose solution is prepared and spun as set forth in any of Examples 1 through 6 except that cotton linters is used as the source of cellulose instead of wood pulp. The yarn produced in each instance exhibits slightly higher tensile properties than wood pulp yarn and also slightly higher bend test as can be seen in Tables I and III.

In the preceding examples we have specified the use of a setting bath which we have found to be a practical optimum in so far as the production of yarn of high fatigue resistance is concerned. We have also specified the use of spinnerets having holes of .0025" diameter and the stretching of the yarn about 77% at elevated temperature. Each of these latter factors has also been found by us to be optimum conditions for the production of yarn having the characteristic high bend test of the present invention when they are used in conjunction with the special setting bath and the low cellulose content viscose. In Table II we have set forth four tests in which the difference between a setting bath containing 4% zinc sulphat-e and a normal setting bath containing 1% We have. also illustrated herein the effect of stretching yarns spun into the special setting bath and into a normal setting bath. We have also shown in Table II the effect of spinneret holes of a diameter of .0025" as compared to spinneret holes of .0032, In the four tests included in Table II we have also shown the effect of diifering periods of viscose ripening. In all four of the tests in Table II the viscose has a cellulose concentration of 4.2% and contains 6.5% NaOH.

Table II SttingBath Normal Setting Bath SpecialSetti'ng Bath S; Grav'. M720" 1.300 1.300 Sulphuric Acid." 8% Zinc Sulphate 1% 4% N 0 Stretch Stretch 77% N0 Stretch Stretch 77% 56 hours or more No spinning possible... No spinning possible Good spinning; Gildememiry, Good spinning; GJdenier-dry,

at. 19 C. .239; GJdenier-wet, l-.32;:Per 3.65; G./demer-wet, 2.22; Per

56 to 40 hours at Fair spinning. Yarn very harsh; Tensile No continuous spinning, breaks everyiew m1nsile Eact.,'9;7.

Cent Extensibility, 395; .Ten-

siz le Fact, 124.5; Bend Test,-

5 2. Good spinning; GJdenieHiry;

2.28, GJdenier-nvet, 1.26; 1 Per Cent 'Extensibility,39.2;Tcnsile. Fact; 112.6; Bend Test,

Cent Extensibility, 21:8; Ten sigleFacta 176.6; .Bend Test, 1

Good spinning;- GJclenier-dry, 3.36;. GJdenier-w'et, 2.09; Per Cent Extensibility, .203; Ten.- sile Fact, 142.5; Bend Test,

1699. Good. spinning. Poor spinning with .0032" spinneret at 32 hrs. 'butgoodrwith .002o. GJdenier.-dry,3.50; GJdenier-wet, 2.23;

Would not. spin. continuously,

but better with .oozfi spinneret'than with .0032. G4 denieridry,-2.ll; Gddenier-wet,

1.01; Per Cent Extensibility, Per' Cent Extensibility, 29.41, 3 .5',l.ensilc Fact, 84.2;'-Bend gleansile'llact, 151:4; Bendflest Test, 282.

From a study of Table II it will be apparent that viscose having a cellulose concentration of 42% cannot bespun with any success in a normal setting bath containing 1% zinc sulphate. When theviscose was ripened 56 hours or more at 19 C. nospinning was possible with or without stretchmg.

With shorter ripening periods between 40 and 56 hours fair spinning could be achieved without stretching; but the yarn produced was very harsh and had an unusually low tensile factor. When it is attempted to stretch this yarn no continuous spinning can be achieved. What little yarn is produced is exceedingly harsh and its tensile factor again unusably low.

Witheven shorter ripening periods of 40 hours and less a yarn may be spun without stretching, but it again is very harsh and exhibits again. an unusably low tensile factor. When it is attempted to stretch this yarn spinning becomes very diilicult and such yarn as is produced is very harsh and again exhibits an unusably low tensile factor.

Thus over a very broad range of variations in ripening time it remains a virtual impossibilit to produce yarn by spinning a 4% cellulose, 6.5% NaOI-I viscose into a normal setting bath. None of the yarn produced in the attempt is of a qualit remotely approaching that required for tire yarn.

Table II also shows the results achieved in two tests wherein the only difference over the preceding tests is that the setting bath contained 4% zinc sulphate instead of the 1% zinc sulphate in the normal setting bath. In these tests with 4% zinc sulphate the 4% cellulose, 6.5% NaOII viscose, aged 56 hours or more at 19 C. was spun without diiliculty of any nature, both with and without stretching. The unstretched yarn shows very good strength characteristics and a high tensile factor of 124.5. Its extensibility of 39.5% of course renders it unusable in the manufacture of tire yarn, but this yarn is an interesting, semihigh-tenacity yarn of rather unusual type which should have commercial possibilities. With stretching of '77 between godets the extensibility is brought down to 21.8% and both the dry and wet strength of the yarn is markedly increased. The tensile factor of 176.6 is excellent, and using the Schopper Bending Tester as specified hereinabove a bend test of 1324 is exhibited.

With shorter ripening periods of from'56 hours down to'40 hours at 19 C. no difficulty in spinnina' was noted. with or without stretching. The

strengthcharacteristicsoithe yarn are approximately the same'asthose. of yarn spun in our special settingebath with 56.hours onmorev of ripen.- ing, Whilethe tensile factor-is. somewhatlower in each case it will be observed that. in the case ofthestretched yarn abend test of1'699 was secured. This particular test has led us. tothe conclusion, that a ripening time of somewhat. more than .40 hoursis optimum for the. production, in accordance with our invention, of yarnhaving an unusually high. resistanceto fatigue.

With ripening periodsof abhours and less some spinning difficulty was observed; For example. without stretching and with spinneret;holes of .0032." diameter we could not achieve continuous spinningandwhile we also could not achieve continuousspinning withspinneret'I-holes of 10025" diameter, andwithoutstretching. the results with the smaller. spinneret holes were markedly better. Here again the yarnrproduced without stretching hasa" high extensibility of 39.5% and is not useful as a tire yarn. With stretching we found good spinning with spinneret' holes of .0025 (this wa particularly noticeable in connection with a viscose ripened for 32 hours)v whereas with spinneret holes of .0032 diameter poor spinning "occurred. The yarntthus produced with stretching and 025 spinneret holes shows a high degreeof'strength and'a highden'sile factor and an extensibility of 19.4%. The bond 'test on thisp'artic'ul'ar yarn was 943; which while "considerabiy less than that achieved with yarn rip- 'ene'd for-somewhat longer periods; is still far in excess "of "the bend test achieved in yarnspun from" viscose containing about "I or'more of cellulose (see Table I).

In "each of thespeciflo'examples setforth above we have made useof the special-sett ing bath found by us to be a practical optimum. In Table II we have examined the efl ect of using in connectionwith a 4% cellulose; 6. 5% NaOH viscosea normal setting bath and our optimum special set-- ting bath. W ehavepointed out that'ouroptimnm setting bathscontai-ns i% zinczsulphate 3% sulphuric acid. to do :not wish totbe :limited .to

this specific :setting' :bath .ainasmuch as we -.have found that yarns of extremely high fatigue resistance .may be produced in accordance with our process wherein the 1 setting bath vcontains a little asabout 225. zinc sulphate.- .In Table III we show the results of tests in which several ,ya-rns-- were: spumin. accordance our process 9 and in which the amount of zinc sulphate in the setting bath varied from 1% to 10%.

10 that this range is the limiting range for soft yarn when 6.5% caustic soda is used in the viscose.

Table III Viscose (all tests):

Cellulose 4.2% (derived from Tenacell or cotton linters as indicated) NaOH 6.5%

Spinning bath:

Sulphuric acid 10% 8% 8% 8% Zinc sulphate 1% 2.5% 4% 10% Source of cellulose Linters Tenacell Tenacell Linters Tenacell Tenacell Tensile factors: 7

Ripening time, hours- 40 No spinning. No spinning. 70 169 151 139 48 -do --do 116 182 142 160 56 -(10 .(10 108 186 176 138 Bend Test average:

Ripening time, hours- 40 No spinning. No spinning. 1,151 1. 296 943 1,179 48 do do r 960 1, 400 1,699 1, 727 so do do 1, 294 1, 257 1, 324 1, 471

A study of Table III will reveal that spinning of a 4.2% cellulose, 6.5% NaOI-I viscose was impossible when a'setting bath containing 1% zinc sulphate was used. When the setting bath contained 2.5% zinc sulphate spinning was successful and the yarn produced exhibited excellent bend test as shown in the table. With this 2.5%

zinc sulphate setting bath we found occasional instances of spinning difficulty, and occasional batches of yarn were considerably weaker than others. From this we conclude that our setting bath should not contain substantially less than' the spinning machine.

As the cellulose concentration is increased the tolerance towards variation in acidity also increases, and the general tendency is for slightly better bend test with lower acidity. However, below 90 grams per litre and even with 7.5% cellulose there are spinning troubles which would prevent commercial use. In all our discussions on acidity We refer to tests on the acid entering Figures in the spinning trough would be 5 to 10 grams per liter lower.

Regarding stretching, we have standardized all our experiments on 77% stretch between godets, having in mind low extensibility in the resulting "yarn and yet perfect spinning. We have emphate as set forth in Table III serves to illustrate cal optimum. Nevertheless, for the purposes of achieving the novel results of our invention the special setting bath needs only to be characterized as containing not substantially less than about 2.5% of zinc sulphate.

Table III also shows a comparison of the results of using cotton linters and wood pulp as the source of cellulose. It will be observed that with the spinning bath containing 1% zinc sulphate no spinning was possible with either a linters or wood pulp viscose. When a spinning bath containing 4% zinc sulphate is used excellent spinning is achieved with either form of viscose.

For all our experiments with viscoses containing 6.5% caustic soda we have used 105 to 110 grams per litre acid. We have to emphasize the fact that the range 100 to 115 grams per litre acid is the best range for very low cellulose concentrations, for instance 4.5%. We may also note ployed lower stretch down to 50% and have produced satisfactory high-tenacity yarn with the same relation of bend tests for different percentages of cellulose, but the extensibility of the yarn is too high for easy slashing to tire yarn level. Similarly we have employed higher stretch up to but have not found this to be justified by 7 results.

'With regard to spinning speeds, all our experiments have been made with 50 meters per minute, but our invention is not limited to this speed. The relative improvement in bend test due to low cellulose for higher spinning speed is just as great as with 50 meters per minute, if not greater.

In all of the above examples and tests the viscose solution has contained varying concentrations of cellulose but the concentration of sodium hydroxide has remained constant at 6.5%. It is not critical that the percentage of NaOH be limited to 6.5%. Higher concentrations of NaOH may be used and the results of such use are about those to be expected as a result of experience in varying NaOH concentration in viscoses of the usual cellulose content of about 7.5%. Table IV sets forth the results of a series of tests in which the effect of changing the concentration of NaOH is examined. Table IV is also important to the present disclosure in that it makes a very thorough comparison between the yarn spun from a viscose containing 6% cellulose in accordance with our invention and a yarn spun from 7.5% cellulose viscose under the same conditions. This is of particular importance in that in many manufacturing plants it is possible with existing equipment to lower the cellulose concentration of the viscose t0 6% While it may not'be possible without the installation of larger viscose tanks and the like to lower the concentration below 6%. Thus our invention 11 gives to the art a yarn of tire cord quality which may be manufactured from wood'pulp with existing equipment.

12 It'should be expected that yarn having very high degree of polymerization possesses certain advantages; with regard to mechanical properties.

Table IV Viscous Composition:

6 o .5 7.5 i fiie r g t fju 6.5 8.6 Zn 8.5

itiit it tjjjjjjjjj ":1: 1 33 1 133113. iitfifii $333 Aging Temp., C.- 19 20 19 Aging Time, Hours 3 59 59 Normal Normal Normal Normal iflit$tgng7n1ii 19 19 19 19 Ripening Time, Hours 48 to 40 48': so. =40 4s 56 4o .43. so

13??? Eiiifi2f 12.7 11.6 11.6 11.7 14.9. 14.6 11.4 10.1 13.3 13.7 13.5

gr i f st r et gt fi d r yk fjii fi godetsm 33 3. at ic 3&2 3% g./d.strength-wet 2.23 2.21 2.30 2.35 2.13 2. 3 2.18 2. 21' 2.23 2.27 Per cent Extensibility-dry. 2L4 .19.-9- 20.4 21.17' 20.4: 20.5 20.7 20,9 20,3 2L4 TensileFactor- 145, 160 162 146' 165; 184 143;: 1 1 154 173.

Bend Test, average .927 9 5', 1,304 ,057 980. .452. 460 471 719 4.781 472.

$5321 110 151.7 no 151.7 znsol g./1 52.6 52:8 52.6 -'52.8 1.298 1.317 12% 1.317

Stretch between godets percent 77.5 Temp. of the intermediate bath ..C '87 Immersion 11101185 30 Immersion inhot Wafer [in 17 Spinneret holes d0---- .0025 Spinning speed at top 'g0det. metersper mmute 5V0 Circulation of the bath per spiudle L 5 Circulation of the intermediate bath. 1, 3

From a study of .Table IV it will beapparent However, the advantage of our novel process and that there isa-n enormous increase in fatigue 40 the yarn produced thereby .is not confined to any resistance in'the yarn p pared in accordance advantage, resulting from the higher degree of with our invention from a viscose containing polymerization. This is demonstrated by tests 6% cellulose comparedto-thatoiyarn prepared which :wehave made in whichwe have aged the from 7.5% cellulose viscose. It is also apparent alkali-cellulosc-Ior the same period of time as that the yarn made :in accordance with .our inwould have been involved had webeen preparing vention from 6% cellulose, 8.5% NaOH viscose a- 7.5% viscose. We then prepared viscoses of is somewhat superior to that. made from 6.5% cellulose concentration varyingbetween 6.5% and cellulose. 6.5% .NaOH viscose. The degree of 4%,;which viscoses, of course, had viscosities consuperiority is very obviously smaller than the siderablybelowthenormal spinning viscosity. We Superiority of either of h 16% c l ose Viscose spun-such low cellulose visooses under the condiyarns over the 7.5% cellulose-viscose yarns. It tionsnecessaryinthe carrying out of our invenis thus graphically illustratedathatthe.cellulose tion. and the product was high tenacity yarn concentration is moreimpcrtant than the ratio showin animprovement in bend test of interof cellulose to caustic. mediate degree.

From a consideration :of-the various :tables set It is. known that tire yarn has .tobe slashed or forth above it will be apparent that there. is a strained inorder-to decrease the extensibility to tendency towards higher wet strength in the the -.level:of;10%- required by the tiremanufacyarns spun fromviscoses of low cellulose content. turers- We-had-found that therelative improve- We believe that it should be pointedouthere ment of bend test on slashed yarn when lowering that since with lower cellulose concentrations the'cellulose is. as greatas if not greater than the alkali cellulose is aged a very much shorter that on the unslashediyarn. time, the regeneratedcellulose in the yarnwill From the above disclosure it will be apparent have a correspondingly higher degree of polythatmehave provideda-processand a product merization. In this connection we have been fulfilling theiobjects'of ourinvention. The essenable to relate the degreenf polymerization'to the tial features -of.;ou-r process. are :the spinning of concentration ofcellulose in viscose by the equaa-viscose.-containing from 6.5% to about 3% celtion: D. P.=268.5+48(7C). In this equation luloseandadesirable quantity,say 6.5% -or8.5%, 0 equals cellulose concentrationin percentage. offNaOI-Iinto a spinning bath'containing about Therefore a yarn made with 7.5% cellulose vis- 2.5% or morezino sulphate. Preferablythespincose would'have :a DP. averaging 244 while a 7 'neret. holes have a diameter not substantially yarn made-with 4% cellulose viscose would have greater than .0025. This particular feature is a D. P. averaging .412. It may be:mentionedthat of value throughout our range .oi'cellulose conour figures for D. P. are based on Staudingerfs centrations-and is :of most importance where the 'formula and are lowerthan those based on-more moose-has been ripened for a relatively short recentlydeveloped formulas. period of; say, 32 hours. The yarn isstretched in spinning to a high degree, as for example about 77.5%, at elevated temperatures. The bend test results on yarns made in accordance with our invention are far in excess of those on any yarns with which we are familiar, whether from wood pulp, linters, or blends. In this connection we have tested substantially all of the yarns commercially available and actually in use in the manufacture of tire cords. Such commercial yarns are made from viscose containing a large proportion, and in many instances containing 100%, of cotton linters cellulose. We have never found a commercial yarn exhibiting a bend test above 600 when such bend test is made under the conditions specified herein or corrected for denier, slashing, and the like.

In the above disclosure frequent reference has been made to the value of our process in the manufacture of tire yarn. It is obvious that the benefits of high fatigue resistance which we secure are of value in textile yarn. An additional advantage of our process is that by lowering the cellulose content the very common defect of milkiness and milky streaks in the yarn is progressivey reduced and eliminated. This, of course, refers to comparisons upon viscoses of the same ripeness. This latter benefit is of great importance in textile yarn.

The advantages of our process are clearly of value in the manufacture of staple fibre as well as special types of artificial straw, horse-hair, films, and the like.

Our process, which makes it possible to spin solutions of very low cellulose concentration, has a further value which should not be overlooked. It is much easier to obtain solutions of low cellulose content than solutions of a cellulose content around 7.5%. This applies not only to viscose solutions but to spinning solutions in which cellulose or its esters and others is dissolved in alkaline solutions or in other solvents such as ammonium quaternary compounds, zinc chloride solutions, cuprammonium, cupri-ethylenediamine and the like and also applies to the direct or onestage viscose processes. Indeed, with many solvents it is practically possible to obtain solutions of cellulose only in a concentration around 4%, well outside the range in which spinning heretofore has been commercially practicable.

In certain claims the words bend test value are used. These words define the average number of bends required to break the yarn on the Schopper bending tester D. P. 5 under the conditions specified above and in the denier range specified.

The improvement in bend test, due to low cellulose concentrations, is relatively similar for textile yarns of lower denier, for example 100, 150, 300, 400 and 600 deniers, but of course the absolute value of the bend test at the same load per denier increases as the denier decreases.

From the above disclosure it will be apparent that modifications and variations may be resorted to by those skilled in the art and it is intended that the scope of this invention shall be limited only by the appended claims.

We claim:

1. In a method of producing rayon filaments of the class which when spun as yarn of 1150 to 1250 denier comprising 480 filaments have a bend test value above 1000 the step of projecting a ripened viscose solution having a normal viscosity on the order of 46 poises and having a cellulose concentration of about 4.5% into a spinning bath containing about 4% zinc sulfate and about 8% sulfuric acid.

2. In a method of producing rayon filaments of the class which when spun as yarn of 1150 to 1250 denier comprising 480 filaments have a bend test value above 1000 the steps of projecting a ripened viscose solution having a normal viscosity on the order of 46 posies and having a cellulose concentration of about 4.5% into a spinning bath containing about 4% zinc sulfate and about 8% sulfuric acid and stretching at elevated temperature the filaments leaving said spinning bath to the extent of at least 50% of their original length.

3. In a method of producing rayon filaments of the class which when spun as yarn of 1150 to 1250 denier comprising 480 filaments have a bend test value above 1000 the steps of projecting a ripened viscose solution having a cellulose concentration of about 4.5% into a spinning bath containing about 4% zinc sulfate and about 8% sulfuric acid and stretching at elevated temperature the filaments leaving said setting bath to the extent of about 7.7% of their original length.

RENE E. DOSNE. FRANK ROLAND CHARLES.

REFERENCES CITED 0 The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES High Polymers, vol. V, Cellulose and its Derivatives by Emil Ott. Interscience Publishers, Inc. 1943, pp. 828 to 831.

Glycerol and the Glycols, James W. Lawrie, Chem. Catalog Co. 1928.